Peter Attia MD281 ‒ Longevity drugs, aging biomarkers, and updated findings from the Interventions Testing Program
EVERY SPOKEN WORD
135 min read · 26,747 words- 0:00 – 0:50
Intro
- RMRichard Miller
To make me happy, it has to be an anti-aging drug, and the evidence has to be effects on many different age-sensitive properties. But we have great evidence now for at least three mutants and the calorie restriction diet and the methionine restriction diet, and we're getting there for rapamycin and several of the other drugs that came along, you know, five years, eight years after that. So I think there will be a very strong case that these drugs are acting by slowing the aging process and delaying maybe not quite all, but maybe all of the, um, aspects of aging that make people unhappy about getting older.
- PAPeter Attia
[upbeat music] Hey, everyone. Welcome to The Drive podcast. I'm your host, Peter Attia. Hey, Rich. Great to, uh, sit down with you again.
- 0:50 – 8:51
An overview of the Interventions Testing Program (ITP)
- PAPeter Attia
Uh, I don't remember exactly when we did this before, but I know I enjoyed it thoroughly, and it's actually one of the few podcasts I've gone back and listened to. I don't often, for obvious reasons, go back and listen to podcasts that I've recorded 'cause I already heard them. But there was so much in that one that I've, I've at times gone back and listened to, to parts of it. So excited to sit down and, and chat with you again. Um, but, uh, a- assuming that maybe people who listened to us in the past or maybe even haven't, aren't familiar with the ITP, I think it's always great to start with sort of an overview of what the Interventions Testing Program is. I certainly refer to it a lot in both, um, podcasts and, and even in things I write.
- RMRichard Miller
Uh, sure. It was, uh, developed by the National Aging Institute under the leadership of Huber Warner about 20 years ago. We are just now finishing our 20th year, and, uh, we've sent in applications. So if the peer reviewers like it, we may get five more years of funding. It represents work being done, uh, by three different research laboratories, mine at the University of Michigan, Randy Strong's at the University of Texas Health Science Center at San Antonio, and a program at The Jackson Labs where David Harrison was in charge. Uh, David will be stepping down, uh, next April, and he will be replaced by Ron Korstanje, uh, a- as the, the first, uh, uh, n- new appointment for the ITP leadership at The Jackson Labs. What we try to do is, uh, quite simple. We try to find drugs that will slow aging and extend mouse lifespan. Um, we have a national announcement every year, i- internationally. Anyone who wants to suggest a drug sends us an application, and they tell us why they think we should test their drug and why they think it will be good and not hurt the mice. We have a committee that evaluates those, and then, uh, we pick five or six or seven each year to see if indeed giving them to the mice will give them a, a lifespan extension. Um, we've had four published significant hits and another two or three that are significant, but really small, and another two that are in press, uh, that should be, I hope, accepted soon. So this gives us, um, a range of successful drugs, and we can then, and we do, uh, try again. We give them to mice at varying doses to see if it's dose sensitive. We look at the pathology. We make tissues that we can give away to other investigators for collaborative studies. And we try to reason, uh, about mechanisms of aging and control points for aging based upon which drugs work and which drugs don't work. A lot of people see this, and I can understand that, I agree with this, as a stalking horse for the important goal of finding drugs that would extend lifespan by slowing aging in people. And that, uh, that is an important element, but there are many steps between a, a mouse drug and a human drug. The other major things that our program does is it really gives us a lot of insight into the biology of aging, which, um, in the moderate term, should give us many clues as to what to look at that may be successful.
- PAPeter Attia
There's a lot in there that I wanna kind of talk about, Rich. So, uh, [clears throat] I think I'll start with just a couple of simple questions. First, um, in a given year, how many candidates do you typically get nominated?
- RMRichard Miller
It varies a lot from year to year. Um, this year was our, our winner. We had 28 suggestions [chuckles] and we only have enough money to do five or six or seven of them. Uh, in a typical year, it's, uh, uh, 10 to 15 from which we pick, uh, uh, about, about six annually. Sometimes-
- PAPeter Attia
And the-
- RMRichard Miller
... we fill up those slots with things that we want to do. For instance, we found, uh, a couple years ago that a, a drug, captopril, which is FDA approved in, in people for blood pressure, kind of to my surprise, gave a really small increase in lifespan in mice. Mice don't die of hypertension. They don't get strokes, et cetera. So I was betting against that, but it was a really small effect. So we decided in the current year, try captopril again, but at a higher dose. Maybe it'll work, give us a nice big effect if we use a higher dose. Some of those slots each year then are taken up with other doses, other dosage forms. Often, if a drug works when you give it to young adults, we say, "Okay, great. Now let's test it in middle-aged mice."
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
Everyone would like to know, as we would, of course, whether a drug would only work if you give it to young adults. We would love to find drugs that work in middle age as well. So that's often fills up one of those available slots.
- PAPeter Attia
Well, we'll, we'll definitely talk about a couple of those drugs. Um, tell me what the budget is. What does the NIA provide to the three laboratories?
- RMRichard Miller
They give $1 million a year to each of the three sites in direct costs. The actual cost to the taxpayer is probably about 50% more than that because each university will also receive, um, indirect costs to pay for the building and the heat and the police force and the library and the president and all of that stuff.
- PAPeter Attia
But it's basically sub $5 million a year.
- RMRichard Miller
About four and a half million total per year-
- PAPeter Attia
Yep
- RMRichard Miller
... of which three million actually goes-
- PAPeter Attia
Into direct cost, yeah
- RMRichard Miller
... a million dollars per year of direct cost to each lab, yeah.
- PAPeter Attia
Yeah. So a- again, r- a relatively paltry sum of money, um, when you consider the insights that I think come out of the ITP. So maybe that's my way of lobbying for the budget being increased
- RMRichard Miller
I agree. I do not think we get too little money. [laughs]
- PAPeter Attia
Yeah.
- RMRichard Miller
We, the orig- the first 10 years, we had half a million dollars, and the NIA, uh, thought of us, I'm pleased to say, as something that was really working well and doing good stuff. So 10 years ago, they doubled our budget, um, which I, I think is a sign of their endorsement and their ability to recognize good stuff, and it certainly made us feel good.
- PAPeter Attia
Uh, what's the, uh, and there are obviously 17 institute- or 17 kind of divisions within NIH, of which NIA is one. Um, what is the NIA's annual intramural, uh, and extramural budget?
- RMRichard Miller
Yeah, I don't know. I'd have to look that up. It's, uh, actually one of the larger institutes now. It didn't used to be. But in, and that's misleading because more than half of their budget goes to Alzheimer's disease. They have, um, through a variety of negotiations been designated sort of the lead agency for Alzheimer's. There are good reasons for wanting to spend money on Alzheimer's research, and all of that goes through the National Institute on Aging. So their budget is big, but their budget for biology all put together is only one-sixth of the NIA budget.
- PAPeter Attia
Mm.
- RMRichard Miller
And for the kind of biology I care about, it's much, much less than that. Uh, a lot of the good biology is what happens to bone aging, what happens to eye aging, what happens to, uh, aging of the immune system. That's interesting research, but the, of course, the kind of stuff I care most about is aging as a global phenomenon. What can you do to slow aging, and how is it that aging, uh, increases your risk basically of almost everything that you don't want to happen to you? That part of the NIA budget is small.
- PAPeter Attia
One last question on budgeting. Um, is there an opportunity for philanthropic, uh, giving to plus up the NIA contributions? In other words, the three million in direct costs or the million to each site, is there an opportunity for those numbers to go up with donations?
- RMRichard Miller
I don't believe that NIA accepts donations. However, a philanthropist, should he or she be listening to this podcast, can certainly set up independent arrangements. For instance, if they wish to have, uh, support for all three sites in the ITP, um, one can imagine a situation in which a foundation makes awards to each of those three. The universities do have the flexibility to take gifts and target them to specific research groups or specific research projects, either independently or as a
- 8:51 – 17:11
How the mice used by the ITP are superior for research relative to mouse models used in most research
- RMRichard Miller
consortium.
- PAPeter Attia
Great. Okay, let's talk a little bit about mice and men, or I guess let's just talk about mice actually. So one of the hallmarks of the ITP is the mouse model that is used and how it differs from some of the more typical mouse models that, um, shall we say, run rampant in biomedical research. Um-
- RMRichard Miller
Yeah
- PAPeter Attia
... maybe tell us a little bit about what the standard off-the-shelf mouse model is, where it came from, and maybe some of the problems or limitations associated with that.
- RMRichard Miller
97%, the last time I checked, of requests for aged mice to the National Aging Institute were for the same kind of inbred mouse. Its formal name is C57 Black 6, and everybody calls it the B6 mouse. So, um, these are the standard mouse, and it's a really bad thing for science, [laughs] not just aging science, but science in generally that relies on an inbred mouse. There are several problems. One is that it's a single genotype, uh, and it has been shown, uh, many times now that if you have a drug that works in Black 6 mice, it might work in another kind of mouse. It might not work. It might have the opposite effect in another kind of mouse. There are good, strong, um, uh, papers on those issues. So people study the Black 6 mice in the mistaken belief that it's sort of like mice in general, despite the now really quite convincing evidence that it isn't. So the ITP, from the word go, made a decision. It was, it, it was controversial, but in retrospect was a really good decision instead to use a genetically heterogeneous mouse. The particular kind of mice we use is called UM-Het3. UM 'cause that's where it was first derived, and Het is for heterogeneous. These are mice, um, essentially which h- have the same set of grandparents. So, um, any two mice in our population have, share half of their genes, just like you would share half of your genes with a brother or sister, but it's a random half. So if we have, uh, two mice, we don't know which genes they'll share, though we know it'll be half of them, and half of the genes will be different. The advantage of the system is you can make as many of these mice as you want anywhere in the world at any time, and you'll get the s- year after year after year, you'll get the same population characteristics. No two mice are identical, but all populations of UM-Het3 genetically are identical with one another. So it's a form of reproducible heterogeneity. And this way, if we, if we had by chance tested a drug that worked in Black 6 and only tested in Black 6, we really wouldn't know whether it would work in any other stock. And if we had tested a drug that failed to work in Black 6, we would have fooled ourselves into thinking that it was a loser drug. Since there are thousands, tens of thousands, hundreds of thousands of genotypes, um, available in the UM-Het3 population, it's really unlikely that one weird genotype would either trick us into believing something to be true when it really isn't or, uh, trick us by missing a, a good response. The other sort of, um, ancillary benefit is you can map genes. There's a set of collaborators, including Rob Williams at Tennessee and Johann Auwerx in Switzerland, uh, which have taken these mice. We've given them at this point, something like 12,000 tails, 12,000 DNA samples from mice that have a known lifespan. And they have already published a paper. It came out last year in Science, and there's another one in the pipeline now that says, "Oh, look, here's a gene that tells you how long the females will live. Here's a gene that tells you how long males and females will live. Here's a gene that tells you how long you'll live, but it only counts if you've made it past the midpoint. It only works on the oldest half of the mice." All that is very cool science. There are hints to human genetics lying within that, and it gives you new tools for thinking about and then working out ideas about the ways in which your inheritance modifies your aging and maybe even your response to drugs.
- PAPeter Attia
Rich, I want to make sure that listeners who maybe aren't as familiar with genetics understand the significance of the UM-Het3 mouse relative to the Black 6. So let's again talk about what it means when you have a Black 6 model. They are all identical, correct?
- RMRichard Miller
Absolutely correct. But it's even worse than that. Not only are they identical, they are homozygous. That means that the gene they got from their mother is identical-
- PAPeter Attia
I know, the gene from the mom and the gene from the father are the same. So it's like an inbred form-
- RMRichard Miller
Exactly. Yes
- PAPeter Attia
... of homozygosity that we can't-- We don't even have a human phenotype that is that inbred.
- RMRichard Miller
Right. People avoid inbreeding because it turns out that when you inbreed people, you get very sick people, a lot of deaths, a lot of deformities, a lot of, uh, mental, uh, disabilities. And that's true of inbred mice as well. Inbred mice almost always have something terribly wrong with them. Nearly every kind of mouse that's used in aging research is fully deaf by one year of age. Many of them-
- PAPeter Attia
Wow
- RMRichard Miller
... are blind. Many of them get a single disease which is not representative of mice in general.
- PAPeter Attia
Yeah, so it's alm- it's almost like a thought experiment where you take a small population of people and you make them breed and breed and breed and breed and breed-
- RMRichard Miller
Yeah
- PAPeter Attia
... until they all become one person. And, and then there's-
- RMRichard Miller
Yeah
- PAPeter Attia
... two issues. One is the probability that that person is healthy is zero. And then secondly, even if you accept that fact and-
- RMRichard Miller
Yeah
- PAPeter Attia
... do all of your testing, what is the likelihood-
- RMRichard Miller
Yeah
- PAPeter Attia
... that what you learn is relevant to people who are not inbred?
- RMRichard Miller
Yeah, you can see it in the form of a clinical trial. Let's say you have a drug, you want to test it to see if it, uh, prevents cancer in people or something, and you decide your test population will be a set of identical triplets, Jim, Josh, and John. They're identical triplets, and you've decided you're going to test it in them. People would laugh at you. [chuckles] That's not a good design. If you want to see if your drug works, you sort of have to test it on people who are not identical genetically to one another. Yet that sort of thing, which is so obvious in, you know, human analogies, is ignored by nearly all mouse scientists.
- PAPeter Attia
Yeah, I guess I, I hate asking people to sort of speculate on the, the, the motivations of others, but why does the Black 6 model still exist? Why is biomedical research being done in this model, um, if, if we have-- if we want to have any interest in some translational insight?
- RMRichard Miller
You're a scientist. You're setting up your own lab. Your mentor in her lab, she used Black 6. And so all your preliminary data is in Black 6, and so you do Black 6. If you are aware of these controversies, you just might say, "Oh, I want to test it in some other kinds of mice." But then you say, "No, no, no, my money is limited. I only-- I can only afford one kind of mouse. I'm going to take the kind I'm familiar with." It's like lemmings. You follow the lemming in front of you because that's just how lemmings do it. They don't look at a roadmap or think about the optimal path to take. They just follow the person who trained them, who's following the person who trained them, et cetera, et cetera. Inbred mice are good for two things. Um, they're almost always sick. And if you want to study some kind of sickness, bingo, you've got it. If you want to study lymphoma, you've got some inbred mice that get lymphoma or get blind or get hereditary deafness or something. Studying inbred mice is great for that. The other thing that they're critical for is for transplantation. There are a lot of experimental designs where you have to take cells from one kind of mouse, stick it into another kind of mouse. For, for that to work, both mice have to have the same genotype. Inbreds are still bad for that. The right ones you want to do are the children of two different kinds of inbred mice. That's called an F1 mouse. They're better because they live longer, they're less sick. But that's what inbred mice are good for. You can use them to construct real mice like the Het3 mice. They're good building blocks like Lego blocks.
- PAPeter Attia
[chuckles]
- RMRichard Miller
But to do science on them is almost always a mistake.
- 17:11 – 29:00
Design of ITP studies, outcomes tested, and metrics of interest
- PAPeter Attia
All right, let's talk about the, um, the way in which, uh, a study is conducted. So let's not necessarily even focus on a given molecule, but there's a candidate molecule that's been nominated. The board has reviewed it and decided there's enough biologic, uh, plausibility that we're going to test this.
- RMRichard Miller
Right.
- PAPeter Attia
Um, let's talk about the metrics of interest. Let's talk about median lifespan, maximal lifespan. What do those things mean? Are those always the primary outcomes? What are some of the other outcomes you consider?
- RMRichard Miller
The primary outcomes, the things that we do our statistics on, are, uh, the proportional hazard, that is the risk of death over the whole lifespan, which i- i-- to re-- to-- The closest easily understood term is the median lifespan. It's not quite correct statistically, but nearly always it's a good shortcut to say, "See, this extended the median lifespan by twenty percent or five percent or whatever." The median lifespan is the age at which half the mice have died and half are still alive. So if, um, half of the mice in the normal group, um, died by eight hundred days and in the drug-treated group, half of the mice We're still alive on day 880, that's 80 days later, then that's a 10% increase in lifespan. That, that's a, that's a, a nice big jump. We also always calculate, um, some measure of maximum lifespan. The actual maximum lifespan, the age at death of the last mouse t- to die, is statistically not very useful, not valid, 'cause it, it varies so much depending on the population size and just the luck of the draw. What we do is a better way, which was worked out by David Allison about 20 years ago. Um, the test statistic we use is we wait until 90% of the mice are dead in both populations, the control and the treated population, and then on the date when the 90th percent mouse dies, we say what fraction of the mice are in the treated group of the ones that are alive, and what fraction of the mice are in the control group. If, if we're lucky, if we have a good drug, um, we might have, of the mice in that pool population, if 80% of them are treated and only 20% are control, we know that we have a drug that will ex- uh, give you a much better chance of being alive when you're really, really old. That's the closest we can come to a statistical test for maximum lifespan.
- PAPeter Attia
Sorry, let's make sure I understand that again. So you have to wait until in both groups there's only 10% or less remaining? 'Cause that's obviously gonna occur at a different time.
- RMRichard Miller
Yes. What you do is you, you make your list of all the ages of death in both groups.
- PAPeter Attia
Yep.
- RMRichard Miller
Then you figure out what age is the age at which 10% are still alive-
- PAPeter Attia
Yeah, I see
- RMRichard Miller
... in the pool together and 90% have died in both groups.
- PAPeter Attia
Ah, in the total pool. I'm sorry. Yep.
- RMRichard Miller
Smoosh, smoosh together.
- PAPeter Attia
Yeah, yeah.
- RMRichard Miller
Yes, there's only one age-
- PAPeter Attia
Yep. Yeah, got it. Okay
- RMRichard Miller
... where 10% of the pool is still alive. Then you look at the pool and say, "Okay, well, what fraction of those were in the treated group?" If it's a 50/50 mix, you've lost. [laughs]
- PAPeter Attia
Yep.
- RMRichard Miller
If it's 80% treated and 20% untreated, you've got a winner.
- PAPeter Attia
Yep. Uh, was there ever a test that looked at, like, the 95th percentile for each group and compared those time horizons as a surrogate or proxy for maximal lifespan? Am I making that up? It's possible I am.
- RMRichard Miller
You can... No, you can, you can do that. You can do the 99th percentile. The, there are a couple of pr- of concerns, and they're technical ones. One is that the further you push it up, 95, 99, 99.9, the fewer mice you have to work with. And so after a while, the statistical power drops. It, it, you'll miss a lot of stuff if you only have, like, one or two mice alive at that age. We've picked the 90th percentile because there'll still be a few dozen mice alive at that age at the 90th percentile. The other thing you want to be really careful of is defining your test, uh, uh, and then picking the test that looks best. We could have some groups, [clears throat] excuse me, actually do this, though it's sort of unethical. They look at the 80th percentile, the 85th, the 90th, the 95th, and then they say, "Oh, it looks best at the 90th. Let's pick the 90th." That's not a good thing. You will fool yourself. You'll get false positives. And so we define arbitrarily, 90th. We're gonna do it at the 90th percentile all the time.
- PAPeter Attia
Yeah. Uh, so in other words, it's sort of pre-specified.
- RMRichard Miller
Yeah, yeah. Oh, yep, that's right. It's pre-specified. It's written down before we do any test. In fact, it was written down 20 years ago.
- PAPeter Attia
Do you come up with a new power analysis for each experiment, or do you generally power them the same and therefore have the same number of mice in each ITP?
- RMRichard Miller
Yeah, we use the same number of mice in the control group and the same number of mice in the treated group each and every year. Um, before we start, of course, we don't know whether it'll be a good year or a bad year. Some years, the mice live 5% longer or shorter than in previous years. And we also don't know which drugs will work, and the ones that do work, we don't know how big an effect they'll have. So what we've done is, um, with the assistance of two professional statisticians, and again, this was 21 years ago, we worked out the number of mice we want to have in each group, and our criterion is we wanted to have at least an 80% chance of picking up a significant result, even if one of the three sites had a di- disaster, like an air conditioning failure or a viral infection. So far, we've only had something like that happen once. But, um, we said, "Let's be ultra-conservative. We want to have an 80% chance of picking up an effect that's at least a 12% effect, up or down, a two-sided test, even if only two sites survive." Um, so that, uh, we use that amount to determine how many mice we're using. Now, in practice, almost always we can combine all three sites together. We almost never have a site-specific disaster, and that means, in practice, that we have 80% power to detect drugs will give us, like, an 8% increase or a 10% increase. 12%-
- PAPeter Attia
Mm-hmm
- RMRichard Miller
... was kind of conservative.
- PAPeter Attia
And what does that amount to in total mice usage, typically, for a, for a given drug?
- RMRichard Miller
So at each site, we are using 100 male controls and 100 female controls. So pooling, that's 300 males and 300 females in the control group each year. And for each drug, we use 50 males and 50 females, that is half as many as the controls, again, at each site. So for any one drug, 50 times three is 150. We have 150 male mice distributed across three sites and 150 female mice distributed across three sites. We oversample the controls as we double the size of the control group because we're gonna compare controls to drug A, controls to drug B, controls to drug C. So in a sense, we're reusing. We're getting the, our, our best mileage out of the controls since, uh, we can increase statistical power for every one of those pairwise comparisons by adding extra mice to the control group. So we do it that way.
- PAPeter Attia
In other words, if you're doing a five-drug trial, there will be-
- RMRichard Miller
Yes
- 29:00 – 36:11
The process and challenges of drug formulation for mice
- PAPeter Attia
much complexity is there year after year, drug after drug, to create a good formulation of the drug to give the mice? How are you thinking about the dosing frequency, the dose itself, and how to ensure that the animals indeed get the amount that you want?
- RMRichard Miller
Yeah, that's a, a very good question, and we've put a lot of effort both in planning it and then executing it. The University of Texas, uh, is led by Randy Strong, who's a pharmacologist, and he has a, a colleague, it used to be Marty, uh, Javors, and now, uh, Bret Ginsberg has taken over that role, who is a, uh, devotes a lot of his time to asking exactly that sort of question. So for example, we, before we give any food to mice, we make a batch of food with drug in it, and Bret's lab takes it and measures the amount of drug in the food. And if it's 5% of what we thought it would be, something has gone wrong, and so we try to work out, and this, again, Bret is an expert at this, should we dissolve it first in alcohol? Should we incorporate it in the form of a corn oil suspension? What's the best way to get it into the food? So once Bret, with the, uh, involvement of Peter Reifsnider, who's, uh, who, who runs the lab at the Jackson Labs, once Bret and Prie- Peter have shown that they can make food with the stuff in it and is at the right dose, we then give it to mice for eight weeks. And tissues from these mice then go back to Bret. So Bret can say, "Yep, the tissue of the drug-treated mice has this amount of drug in the liver and this amount of drug in the plasma." So it's only at that point that we actually press the button to say, "Yes, we are going to use this drug in a lifespan experiment." Those pilot mice, my lab gets their liver, and we look at a batch of mRNAs 'cause we wanna at least satisfy ourself that the drug did something. We've picked RNAs in the liver that we know are almost always sensitive to drugs. And if the drug was given to the mice and nothing happened in the liver, we start to get worried. Maybe the drug was excreted quickly and didn't have any biological effect whatsoever. And we've run into problems. I mean, the famous one, the early one, was rapamycin. About 90% of the rapamycin that was given to mice in the food never made it into the mouse because it's, uh, digested in the stomach. In the acid conditions of the stomach, it gets de- deg- degraded. And so Randy, with colleagues of his, uh, worked out a way to encapsulate the rapamycin in a capsule, a plastic capsule, that makes it through the stomach and dissolves in the more alkaline conditions of the small intestine. So that was a way of tricking the body into getting the rapamycin to the portion of the, of the GI tract where it could be absorbed. And, uh, it's not uncommon for Bret to have to say, "Well, you know, this is not gonna work unless we dissolve it in a little bit of alcohol before we mix it into the food." So we do test for that. These are all important issues. The other thing that the, uh, the data on blood concentrations, they can alert us to potential problems. Um, for instance, many of our papers we've published, I think 12 papers now on rapamycin, and almost always rapamycin has been giving a larger percentage increase in females than in males. Well, um, the Texas group showed that the blood concentrations are threefold higher in females than in males. We haven't proven that that's why the females live longer or have a greater percentage increase, but it's certainly very plausible. We've stumbled onto a similar situation with canagliflozin. Um, canagliflozin, we found, gave a terrif-- This was published a few years ago, lovely lifespan increase, but it was in males only, not in females, which is really weird 'cause it's a, a great drug for diabetes in male-- in men and women without sex differentiation. We thought it would work great in both sexes. Well, it, it turns out that the blood concentration in female mice is three times higher than in males. And as they get older and older and older, it, the, the blood concentration in the old females is 10 times the concentration of young males, and it's probably toxic. Um, we, we now are going back to say, "Okay. Well, let's give it to females at a much lower dose. Maybe that'll work."
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
Or, "Let's give it to females, but stop when they're middle-aged so it won't ever reach the really high toxic concentrations." All of these assessments of drug levels allow us to be on the alert for problems of that sort and to come up with ideas, uh, for how we might solve them.
- PAPeter Attia
Rich, I assume it's the case that every candidate drug must be administered in the food. You're not testing intravenous drugs, intramuscular drugs?
- RMRichard Miller
Yes. This is correct. Well, uh, there's a footnote, which I'll get to. [chuckles] Uh, and we could give a, a drug in water if there was some reason in which it wouldn't get into the food, but you could give it in the water. This would be compatible with our protocol. We can't give it to animals intravenously or intramuscularly 'cause it's so much work to give... We have, you know, 150 males and 150 females. Giving 300 shots a day or a week or a month would be a mess, in addition to which we'd have to have a separate control group that got a saline shot, and we couldn't use regular old mice as our control. We'd have to have a separate control group to do that. You can imagine a specific situation if someone said, "I've got a, an antibody or something. All you really have to do is give it to them once, and it will flip their immune system forever into a good configuration. Please give my drug. It has to be given by injection, but only one time." We could consider that. [chuckles]
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
We might need a separate once-only sham group also, but I think that's the only exception to the rule that we would think seriously about.
- PAPeter Attia
Okay. Final question on that. Um, again, just so folks understand, how are you regulating the actual dose? In other words, how are you monitoring the amount of chow that's consumed, since the amount of chow that's consumed is proportional to the drug that's consumed?
- RMRichard Miller
We have no idea how much food any one mouse eats, and therefore, we have no measurement on a mouse-by-mouse basis on how much of the drug they've consumed. We know, of course, that smaller mice eat less food than larger mice, and so they will get less drug per mouse, but probably about the same amount of drug per gram of lean body mass or something like that. Um, there's no way to control that other than by putting individual mice in individual cages, which has its own major problems. The, the mice are very social creatures, and they don't like isolation cages any more than people do.
- PAPeter Attia
[chuckles]
- RMRichard Miller
And, uh, in addition, monitoring the actual amount of food a mouse eats is a fiction. No one can really do it. Um, they, they can put a number down and get it into the paper, but it's, it's a fictitious number. And the reason is that mice chew their food and leave a lot on the cage, on the floor of the cage. So you don't know how much food the mouse has actually gotten into itself [chuckles] because you haven't measured little crumbs on the cage
- 36:11 – 43:32
Four drugs identified by the ITP that extends the lifespan of mice
- RMRichard Miller
floor.
- PAPeter Attia
[chuckles] In total, how many drugs have been, uh, run through the protocol in the last 20 years?
- RMRichard Miller
Oh, uh, I would have to go to our recent review article and then add some more drugs to it. It's about 100.
- PAPeter Attia
Yeah. And of course, many of those, you've already alluded to this, have been run through multiple times, so that it, there, there-
- RMRichard Miller
Yeah
- PAPeter Attia
... there are many more experiments than 100. Um, but to the point you made at the outset, there really are some notable successes. I wanna talk about those. I also would like to talk about some notable failures. Um-
- RMRichard Miller
Yeah
- PAPeter Attia
... but let's, let's start with the successes. So what was the first, uh, exogenous molecule that proved a lifespan extension success for the ITP?
- RMRichard Miller
Yeah, well rapamycin, uh, in, in our 2009 paper had a really big effect. Uh, at-- We picked a dose, um, that seemed like it, it might work, [chuckles] and it did. Uh, it's not the optimal dose. It's less than the optimal dose. But at the dose we chose, both males and females had a significant lifespan extension. To put this into perspective, these drugs are giving, like, 15 to-- at, at the mid-middle dose, 15 to 20% increase in median lifespan. To, to give a sense of what that means, if you had a cure for cancer in people, no one over the age of 50 ever got cancer again, median lifespan of humans would go up by 3%. And the same is true if you had a drug that abolished heart attacks. No one over the age of 50 ever got a heart attack again. Uh, median lifespan for people would go up by less than 3%. That's work done by Jay Olshansky and Bruce Carnes and published in Science in 1990. So the drugs that we consider, you know, we have four of these now, that give more than a 10% increase in lifespan in terms of proportional change of healthy lifespan are doing about three times better than some hypothetical drug that abolished cancer in people or abolished heart attacks in people. So there-- that's a really significant chunk of additional, uh, healthy lifespan. Rapamycin, um, in that first paper was also the first drug, I believe, where anyone had showed, we, we found that it works quite well even if you start in really old mice. Some of the mice that were exposed in that paper didn't start until 20 months of age, where the median survival is about 24 for males and 26 for females. It took me very much by surprise. We thought only drugs-- If a drug was gonna slow aging, you really do have to start it when you're young, because a lot of aging is what happens between the ages of 20 and 60 or something like that, as everyone knows. So it was stunning that a drug could start as late as that and still have a full lifespan benefit. That really was news scientifically, and I think that's one of the reasons why the editors of Nature were interested in it. But that turns out not to be a fluke. Um, 17⍺-estradiol, which is male specific, works just great if you start it at 16 or 20 months of age in the males. Acarbose, which is significant in males and females, though better for males, if you start it in middle age, it still works. It's only about half as good. Starting early is smart for acarbose, but even if you start it at, uh, 16 to 20 months of age, it still works just fine. And, um, canagliflozin, our data in, in that group, um, haven't been published yet. Um, for males, it's still terrific. For females, as I mentioned, it actually isn't good, but we suspect it's because the f- the drug dose, the drug concentrations in the blood of females may be toxic. So we really want to do that again, but with lower concentrations of the drug.
- PAPeter Attia
Do you have a sense of why rapamycin and canagliflozin are being more concentrated in females? And are you seeing that with any of the other successful candidate drugs such as, uh, cana-- uh, such as acarbose, for example, or 17, uh, beta-estradiol-- 17⍺-estradiol, sorry?
- RMRichard Miller
That we don't know the answers for any one of those drugs. It wouldn't be too hard to find out. You know, a pharmacologist could look at how quickly it's absorbed, how quick is it conjugated, how quickly is it excreted, does it go out in the urine, does it go out in the feces, all of that. There's very standard 50-year-old methods for answering that question. And, you know, it's, I think, would be important to address. There's a generic answer which is really quite firmly established. The enzymes that the liver uses to deal with foreign drugs, these are called enzymes of xenometa- xenobiotic metabolism. Xenobiotic metabolizing enzymes are radically different-
- PAPeter Attia
Hmm
- RMRichard Miller
... between men and women and between male and female mice. Most of them, not all, but most of them are a lot higher in females, but some are a lot higher in males, and this is also true for people. So the pace at which drugs are conjugated, put into the bile, or put into the urine, or excreted in the feces, or excreted in the urine very often are sex specific. Um, it, it's would not-- it's not-- It doesn't surprise anyone to find that the blood concentrations may be different in men and women or different between, uh, male and female mice. The details on a drug-by-drug basis we haven't looked at yet. The, the one thing I w- I would want to, um, add here as a footnote is for acarbose, it has nothing to do with that. Acarbose, nearly all of it stays in the gut. It doesn't get absorbed-
- PAPeter Attia
Right
- RMRichard Miller
... into the body, so excretion is not the key issue. Um, why the acarbose has such a big effect in males and a small, significant, but small effect in females is unknown. It presumably has to do with males being more sensitive to high glucose levels. Acarbose probably works by limiting very high glucose levels, maybe for unknown reasons, that triggers something horrible in the males and not so much in females.
- PAPeter Attia
R-Rich, when you talk about the difference in the pharmacokinetics between male and female mice, we can only extrapolate and say that our, you know, cytochrome P450 system as humans must have sex differences.
- RMRichard Miller
Oh, yeah. That's well documented. Absolutely.
- PAPeter Attia
But what I can't tell you for the life of me, Rich, is one drug that I'm aware of that we really differentially dose in males and females beyond a weight difference. In other words, we don't seem to take into account that difference when we give a person an antibiotic or a statin or a chemotherapy. They're all based on either weight or nothing at all. And yet if-- I guess what I'm saying is I'm-- This is kind of remarkable to me that we don't have a better set of the pharmacokinetics of these drugs and their differences in human sex and how that maybe should factor into how we think about dosing them.
- RMRichard Miller
I would love to see you have on your show a real pharmacologist who knows the answers to that question. I would love to talk to a real pharmacologist and ask him or her, "Hey, aren't there differences between men and women in the rate at which drugs are excreted? And why isn't that informing our recommendations for drug doses in people?" I think it's a really good question, but I don't know the answer.
- PAPeter Attia
Okay. Well, let's-- That's something we're going to have to dig into a little bit because it seems like, um, an enormous missed opportunity to get that level of granularity.
- 43:32 – 51:49
The success of rapamycin and what it tells us about the biology of aging
- PAPeter Attia
Um-
- RMRichard Miller
Yeah
- PAPeter Attia
... you've rattled off a bunch of the successes. I think it's worth a bit of a double-click on each. We can take them chronologically. So again, people who listen to, uh, this podcast are, are very familiar with rapamycin. Recently had David Sabatini and Matt Kaeberlein on together, so we did a pretty good deep dive on, on rapa. Um, but again, just on the off chance that someone's coming to this as their first exposure to rapamycin, uh, do you remember who made that nomination for the tw- 2009 paper?
- RMRichard Miller
Dave Sharp.
- PAPeter Attia
Okay. So it came in-house almost. Um, and the, um-- Obviously, the, the logic at the time was what? I mean, it, it was a, you know-- Ten years earlier, the drug had been approved, uh, by the FDA for tr- uh, solid organ transplants. And-
- RMRichard Miller
Yeah
- PAPeter Attia
... um, so it was a known immune suppressant. Um, what was the logical step that took it to, "But we also think it could boost longevity"?
- RMRichard Miller
People had just begun to make invertebrates, that is worms and flies, with genetic modulation of the TOR pathway. TOR is the target of rapamycin, the enzyme that rapamycin inhibits. And you know, they were long-lived. And in fact, when you studied some of the yeast stuff that Matt Kaeberlein was, was in on this early on with Brian Kennedy, many of the, um, things that seemed to influence yeast lifespan were also related to the TOR pathway. So Dave said, "I wonder whether if you inhibited TOR in mice, they would also live longer." It really didn't have to do with the notion of immune suppression. It had more to do with control of growth and following up on the genetic data in the invertebrates. Now, in retrospect, 20-some years later, um, we understand that the notion of rapamycin as an immune suppressant, um, is the sort of tip of the iceberg. There are some immune functions which it increases. There are some that it decreases. It's dose dependent and context dependent. By an interesting coincidence, uh, the same year that our lifespan paper appeared, there was another paper where rapa-- also from Michigan, though not my lab at all, uh, in which they gave rapamycin to some old mice and shown that their influenza vaccine response was terrific if they'd had rapamycin. What rapamycin appears to do in their model is it increases the production of B cells from the bone marrow. So the mice would respond to influenza vaccine, and then they were exposed to live virus, and they survive, whereas the un- untreated controls did not survive. So in some circumstances, at least, it's actually immunoboosting.
- PAPeter Attia
And that was also demonstrated by Joan Manick and Lloyd Klickstein six years later, um, using everolimus.
- RMRichard Miller
Yeah, it, it improves-- That's right.
- PAPeter Attia
Yeah.
- RMRichard Miller
In humans, it also improves, uh, vaccine responses in some circumstances to influenza and vaccination in humans.
- PAPeter Attia
Yeah. So you've already alluded to this, but I think it's, again, just worth making sure folks understand this. You had a little bit of a challenge getting the rapamycin formulated. Uh, why did you decide not to abort the study? When you finally got the food formulation done, you've got these geriatric mice. You finally get to start feeding them rapa. I mean, obviously, chance favors the prepared mind, according to someone famous. Um, you elected to take a chance. Uh, w- do you remember the, the decision? I mean, the odds were long, right?
- RMRichard Miller
Well, there are two, there are two decisions.
- PAPeter Attia
Yeah.
- RMRichard Miller
Step one was Randy Strong saying, "I'll bet we can get this into mice. I've got buddies who do encapsulation. Let's encapsulate it and see if that stuff works." So Randy's initiative and creativity were a, a, the first important step. Now we have a batch of mice. They're, uh, 20 months of age. They were originally going to get rapamycin when they were four months of age. We could either, A, throw them out, or B, give them the rapamycin. So we picked B. We were sure it wouldn't work. Now we were wrong. So when Randy finally, with his colleagues, figured out how to make the protected version, the encapsulated version of rapamycin, we actually used it twice, the same batches. Some of it went to the mice that were already 20 months of age, so we wouldn't have to throw them out. And then we executed-- we gave the rest to the young mice that had been produced in, uh, the following year, um, expecting that the old mice, it would fail, the young mice, it might work. And as, as you know, it worked well in both ages.
- PAPeter Attia
What was the difference between the, uh, male females in the 20-month onset versus the four-month onset, both by sex?
- RMRichard Miller
Scott Pletcher actually did that analysis. When you compare within sex, so you're comparing older females-
- PAPeter Attia
Yep
- RMRichard Miller
... to younger females, there's no difference, surprisingly.
- PAPeter Attia
Hmm.
- RMRichard Miller
The b- b- benefit you get starting in old age and the benefit you get starting in young mice is statistically insignificant in females, and it's statistically insignificant in males. In both sexes, starting as late as 20 months of age does not diminish the, um, uh, ability of the drug to extend lifespan.
- PAPeter Attia
This is just really remarkable. What, what do you-- I mean, let's, let's try to philosophize a little bit about what that tells us about the biology of aging. Or does it tell us more about-
- RMRichard Miller
Yeah
- PAPeter Attia
... does it tell us more about aging, or does it tell us more about the drug?
- RMRichard Miller
Well, I think it tells you something about both, about the drug and its interaction with the aging process. The, the sort of inevitable conclusion, which I would have bet a lot of money against, is that by the time you're 20 months of age in a mouse, which is sort of like 55 or 60 years old in a person, something like that, not yet at the median survival, but getting pretty close, that s- damage will have occurred that's irreversible. Collagen cross-linking, and death of some brain cells, and, uh, a clogging of the arteries or whatever's going to get you, it started already by the time you're in your 50s and 60s, or f- for a mouse, by the time you're in your 20th or 21st month. But apparently there's still some further stages of that process that occur afterwards, after we started to administer the drug at 20 months of age, which are dependent on aging and the drug inhibits. So that's the news that we would not have known if we, uh, hadn't done an experiment starting in late middle age. Now, what those processes are, whether they are same processes as affected by many different drugs, that's unknown. Um, if we have time at some point to talk about these new aging rate indicators, uh, that has come out of the ITP program, we can begin to ask questions about whether the aging rate indicators are effective in the old mice or the middle-aged mice or the young mice. Um, clearly we've got a lot to learn now about what is happening that is drug sensitive, even in middle-aged mice. The fact that acarbose works half as well in middle-aged mice, canagliflozin works at least in males quite well in middle-aged mice, which is unpublished, and that 17 alpha estradiol works great even in middle-aged male mice suggests that it's a general phenomenon. It's not rapamycin only, uh, but it applies to a, a lot of phenomena. Mike Garrett, when he was in my lab, he's, he's now set up his own lab, uh, in New Zealand, but he took a lot of mice and he put them on, um, 17 alpha estradiol or acarbose in middle age, and he found, and this is all published, that their grip strength is great, much better than untreated old mice, and their ability to stay on a rotating rod, which is a complex phenomenon having to do with balance and muscle strength and motivation, that is much better even if they started the 17 alpha estradiol or acarbose in middle age. It's not just a matter of the things that are going to kill you. These mice don't die of dizziness or loss of grip strength or something. But a whole batch of stuff, uh, that is re- is age sensitive is slowed by these mice.
- 51:49 – 59:18
Other measures of healthspan evaluated by the ITP in stage 2 studies
- RMRichard Miller
The next frontier that I really want our lab and other labs in the ITP to dive into is cognition.
- PAPeter Attia
Mm.
- RMRichard Miller
Uh, Michigan has just recruited a, an absolutely top-notch mouse neurobiologist, a woman named Katherine Kaczorowski, and we already have several studies planned or underway in which we're going to be treating mice with these drugs and in addition to looking at their lifespan, test them for cognition. The obvious hypothesis is that the drugs that s- extend lifespan will also postpone loss of cognitive function. For complicated reasons, Katherine thinks that will be untrue, and I think it is true. So we'll see which of us is correct.
- PAPeter Attia
What other measures of healthspan are you capturing? Obviously, cognition is a piece of healthspan, but you already mentioned grip strength and then some complex motor tasks and some complex stamina tasks. Um, do you look at, for example, muscle mass at the time of demise in these mice? Though it's, you know, not a direct, uh, driver of healthspan, it's a highly correlated driver of healthspan. I mean, what, what else can you say about these mice and their health beyond just the elongation of life?
- RMRichard Miller
Right. So we, we have, um, uh, stage 1 and stage 2 studies. In a stage 1 study, which we do for every new drug, lifespan is the only thing we measure in addition to body weight at four ages. We could throw in other tests, but it's really expensive to do that, and to standardize it so that all three labs get the same numbers proved to be really tricky. So i- if we did devote lots of our efforts to looking at these sub- secondary measures of health in addition to lifespan, we would test-
- PAPeter Attia
Sure
- RMRichard Miller
... only three drugs a year.
- PAPeter Attia
Yeah, yeah, of course.
- RMRichard Miller
Maybe four drugs a year.
- PAPeter Attia
Yep. But once you've got candidates-
- RMRichard Miller
So what we do is-
- PAPeter Attia
I mean, yeah
- RMRichard Miller
Once we've got candidates, yes, then we go into stage 2. Every drug that makes it to stage 2, we develop a, a protocol that takes advantage of the strengths and weaknesses and interests of each site. So, uh, Dave Harrison, for instance, had many tests of visual acuity, hearing acuity-
- PAPeter Attia
Mm
- RMRichard Miller
... uh, strength, uh, body temperature regulation. So the stage 2 experiments at the Jackson Labs incorporated many of those tests.
- PAPeter Attia
Mm.
- RMRichard Miller
Randy Strong and his colleagues were interested in glucose control and glucose homeostasis, so the stage 2 stuff that was done at Texas always had some taste of that. My lab is interested in pathology, so we would take a lot of these stage 2 mice, euthanize them at 22 months of age, send them to a veterinary pathologist, and come back with a long list of, "Here's what's happening in the liver, but look, it didn't happen in the drug-treated mice. Here's what's happening in the gut, but look, it didn't happen in the drug-treated mice." So our other hope, of course, is that once we have a winner, the laboratories that have a specific interest in aging of the aorta and aging of the heart and aging of the lung and who know what they're doing will just ask us for tissues. Um, either they can buy the drug and treat their own mice, hopefully not Black 6.
- PAPeter Attia
Yep.
- RMRichard Miller
But they could treat some mice [chuckles] by Ket3 mice with the drug and test their organ-specific, uh, uh, functional or pathological outcome tests. Or if we have tissues in our freezer, they can ask us for tissues. Um, we've-- since 2015, every drug, whether it's a winner or a loser, we've been putting aside 20 or 30 or 40 mice to be euthanized at age, uh, 22 months and frozen. And anyone-- this is changing next year. I'll get to that in a minute. But anyone who wants those tissues just writes us a note saying, "Here's what I want. Uh, this is the tissue I need. Here's what I'm going to do with it. Uh, here's my power analysis." And we just send them the tissue. Uh, it's clearly a national or international resource. We've sent tissues overseas to other labs, um, to make use of tissues that have tons of useful information in them. But, um, we can't study everything. We can hopefully attract the interest of people who can study everything. This, uh, program, which we call CIP, the Collaborative Interactions Program, unfortunately, I think, is going away next year. The National Aging Institute has decided that instead they want to replace it with a new program, which they're calling the, um, [lip smack] uh, uh, Interventional Biogerontology Repository, in which the, the h-tissues will not be requested from us. They'll be requested directly from the National Aging Institute. And the National Aging Institute will make all decisions as to who gets the tissues, who doesn't get the tissues, how much tissue they get. Um, I'm not so sure that's a grand idea, but the worst thing is that they will have only once a year, uh, call. When people send us a note, we generally can make a decision within two or three weeks.
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
And they can generally get the tissue within a month or two. Uh, adding an extra year of time for the NIA staff to sort of figure out who gets the tissue or not is not going to speed things up. So I, I view that as a step backwards, but it-- I'm not in charge of it.
- PAPeter Attia
Rich, based on these, um, tissue blocks, what have you learned, if anything, through collaborations with people looking at epigenetic changes in the treated versus untreated mice? I mean, we have to imagine that there's some difference in gene expression, and that would be at least one way to look at it, correct?
- RMRichard Miller
Yes, that is one way to look at it. Um, and we have indeed-- You know, there are some labs. Steve Horvath, I think, is, is well established and does lovely work. Um, Steve has asked for tissues, and we have sent him tissues. And we've explained to anybody else who is working on some aspect of either global or localized tissue-specific epigenetic change, we'd be delighted to send them tissues, uh, to, to-
- PAPeter Attia
Has, has that, has that been done?
- RMRichard Miller
... look at with whatever. I know Steve has done some of that work. I think some of our, uh, drug-treated mice have gone to him. Um, Vadim Gladyshev has gotten lots of-- at Harvard, has gotten lots of tissues from us and has published metabolomic assays, for instance. I don't think any of his epigenetic stuff has come out yet, though I'm not certain of that. The paper that Johan Auwerx just published with Rob Williams and, uh, Maroun Bou- Sleiman in Science has some epigenetic materials in it. The problem is that no one at this point knows enough to know what tissue to look at. So, um, it may be that a particular drug is working because it sensitizes the liver to high glucose levels or something. So you'd want to then look at liver tissue or pancreas tissue or islet tissue or fat tissue or, quite plausibly, tissue of some obscure cell type in the hypothalamus, which regulates, uh, uh, uh, uh, the, uh, um, hormones that make you hungry or not hungry. And sort of doing, "I'm, I'm gonna guess that I'm-- the liver is important."
- PAPeter Attia
Correct.
- RMRichard Miller
"I'm gonna look at all the epigenetic changes in the liver," is a very crude way of addressing that. I-in my view, the progress will come when someone says, "Hey, look, this drug works by hitting this enzyme in this set of hypothalamic neurons. Now let's look at the epigenetic change in those neurons."
- PAPeter Attia
Yeah.
- RMRichard Miller
But we're, we're not there yet.
- 59:18 – 1:01:16
Distinguishing aging rate indicators from biomarkers of aging
- PAPeter Attia
So you've already alluded to the aging rate indicators. Uh, say a little bit more about that and, and how that's factoring into the work.
- RMRichard Miller
Everybody is familiar with the idea of concept of biomarkers of aging. And by analogy, it's sort of like the odometer in your car. Your odometer tells you how far the car has been driven, and a biomarker of aging, in a crude sense, tells you how far your body has been driven. If you are a seventy-year-old per-
- PAPeter Attia
But what, what, what would you say they are, Rich? I mean, like, what, what biomarkers do you think we really have of aging? What, what are the odometers?
- RMRichard Miller
Yeah, that's a whole separate complicated issue. I pers-personally don't think we have very many at all.
- PAPeter Attia
Yeah. I, I, I-
- RMRichard Miller
There are certainly a lot of things-
- PAPeter Attia
I, I would agree with that. I don't, I don't even think we have-
- RMRichard Miller
Yeah
- PAPeter Attia
... the odometer. So I'm, I'm-- But-
- RMRichard Miller
Yeah. They're, they're-- I agree with you.
- PAPeter Attia
Yeah.
- RMRichard Miller
But conceptually, um, you can imagine if someone comes into your test facility and they've got a lot of high-affinity antibody and their vision is terrific and they've got no cataracts and they're great at hearing and they can do a hundred pushups and they're great at running up and down a hill and their skin is smooth, et cetera, et cetera, all ten or twenty domains, they sort of look like they're forty. You can say, "Okay, they are biologically young." That's a-
- PAPeter Attia
Yeah, yeah. Although, although it's a bit s-- I mean, y-you know, I put that in the realm of function, right? So I agree. We have-
- RMRichard Miller
Yeah
- PAPeter Attia
... lots of functional tests that give you-
- RMRichard Miller
Yeah, yeah
- PAPeter Attia
... odometer-like insights. Um-
- RMRichard Miller
Yeah
- PAPeter Attia
... but when you th- when you think about a biomarker that is assay based, I think we're both saying the same thing.
- RMRichard Miller
I share that skepticism.
- PAPeter Attia
There's, there's nothing there.
- RMRichard Miller
Yeah.
- PAPeter Attia
Yeah.
- RMRichard Miller
Yeah. I wasn't, I wasn't, um, attempting to, to praise, uh, um, biomarkers of aging. I'm-- wanted to set that up as a familiar concept-
- PAPeter Attia
Sure
- RMRichard Miller
... you know, because I mostly wanted to say that aging rate indicators are not that. Um-
- PAPeter Attia
Yep. Sure
- RMRichard Miller
... aging rate indicators by this analogy are the speedometer. They tell you how quickly you're aging and not how far you've
- 1:01:16 – 1:15:36
Aging rate indicators identified through the examination of slow-aging mice
- RMRichard Miller
gone. So what we were looking for, and I'll-- in a moment, I'll tell you the evidence that we think suggests this is a good idea. We were looking for things that always change in the same direction in every kind of slow-aging mouse. That would distinguish not how old they were, but how rapidly they were going to be aging.
- PAPeter Attia
Hmm.
- RMRichard Miller
So, um, we have nine published and one unpublished slow-aging mice. We have four genetic mutants, the Snell, the growth hormone receptor knockout, the Ames dwarf, and the PAP/A. We have a famous diet, calorie restriction.
- PAPeter Attia
Hmm.
- RMRichard Miller
And we have at least four well-vetted drugs, uh, acarbose, canagliflozin, 17⍺-estradiol, and rapamycin. So we, we said, "Let's find something that is changed in the same direction in all nine kinds of mice." And this is true for a 10th kind, P10 overexpressers, though we've just submitted that for publication. So the next time we talk, we'll have at least 10 mice for which these things are true. And the pleasant surprise is that we now have 13 things that always change in the same direction in all 10 kinds of slow-aging mice, even when they are young adults, and that's the crucial thing. The biomarkers are useless until the animal or the person gets old. They've got to have a certain amount of aging behind them to see if they are young-like in comparison to control untreated people or people with a different gene. You have to wait. The aging rate indicators, because they are measures of speed, you can look even when the animal is young and hypothetically when a human is, uh, a young adult. So most of the work, um, that we've done on the mutant mice was done on animals that were s- four to six months of age, and the work on the drug-treated mice was on animals that were only 12 months of age. There are changes that are f- in famous molecules, molecules whose connection to disease is not just fanciful. One of these is UCP1, uncoupling protein one. It's a mitochondrial protein that allows your mitochondria to burn fat without doing a lot of work. It just turns the fat into heat. It's involved in thermogenesis. And it's long been known that having a lot of UCP1, um, is something happens when you do exercise. Exercise increases UCP1, and mice that have a lot of UCP1 live a long time. So it's, uh, thought to play a major role in protecting you from obesity, from diabetes, from metabolic syndrome, from some sorts of inflammation. Well, every one of our slow-aging mice has a lot of UCP1 in the white fat under the, um, skin, in the white fat, uh, in the abdomen, and also in the, um, the brown fat between, uh, the scapulae. All three of these fat depots have elevated UCP1.
- PAPeter Attia
Hmm.
- RMRichard Miller
The exception to that rule is very informative. You remember two of those drugs, canagliflozin and 17⍺-estradiol, extend lifespan in males only, and UCP1 goes up in males only for those two drugs, which is a, a strong indication that whatever process [lip smacks] is making the drugs slow the, uh, uh, mortality rate and increase longevity is the same process, at least in its sex specificity, as the, uh, UCP1 story.
- PAPeter Attia
And, and tell me, UCP1, you are measuring that how? Uh, how much-
- RMRichard Miller
We take the fat, and we look at the-
- PAPeter Attia
Yeah
- RMRichard Miller
... protein by Western blot.
- PAPeter Attia
Okay. How much biologic noise do you think exists in that on a day-to-day basis in-- So, so let's now talk about a normal mouse, a control mouse on the control diet. If you sample his fat every day for a month, and some days you put him on a treadmill, uh, a wheel, some days you don't, some days he doesn't eat that much, some days he does. In other words, he replicates for short bursts of time some of the activities-
- RMRichard Miller
Yeah
- PAPeter Attia
... that might either be associated with a longer life and/or associated with a behavior that increases the protein of interest. It would be-
- RMRichard Miller
Yeah
- PAPeter Attia
... really troublesome, even if everything you said were true, it would be really troublesome if UCP1 spiked on those days, because then it-
- RMRichard Miller
Yeah
- PAPeter Attia
... wouldn't really be a useful odometer or-
- RMRichard Miller
Yeah
- PAPeter Attia
... rather, speedometer.
- RMRichard Miller
So you brought up three separate interesting issues, and they need to be treated separately. The first, uh, is in a normal mouse where you're not making them exercise and you're not feeding them, uh, foie gras, uh, if hypothetically you get a little bit of fat from that same mouse every single day or every hour over the day, would there be much change in UCP1? That experiment, of course, can't be done. Uh, uh, but it doesn't invalidate our findings because even if that would introduce some noise, the consistent difference between the mutant mice or drug-treated mice and the controls, the noise is already built in, uh, budgeted into that. If there was a lot of noise, too much noise, we wouldn't see a significant effect of the drug or the diet or the genetic intervention. The second point you raised is could one perturb this by getting an animal to exercise? And people have done that. UCP1 is changed by chronic exercise. Um, and that's one of the-- it's one of the reasons why it's thought to be amongst the mediators of the health benefits that, uh, attribute in people and in mice to, to exercise. The third point you asked about-
- PAPeter Attia
I'm sorry. I was asking a slightly different question on that, Rich, although that's good to know.
- RMRichard Miller
Okay, great.
- PAPeter Attia
The question I was asking was if you took an otherwise sedentary mouse and exercised-
- RMRichard Miller
Yeah
- PAPeter Attia
... the hell out of him for a day and checked it then-
- RMRichard Miller
Oh
- PAPeter Attia
... would you be fooled-
- RMRichard Miller
Yeah
- PAPeter Attia
... by an elevated level? And y- in other words-
- 1:15:36 – 1:25:30
Why proteomics are essential to understand changes in the cell
- PAPeter Attia
And tying this back to what we said earlier, this is an example of where, for example, the epigenome might not matter as much because that presumably would have a greater impact on transcription, and here you're saying, "Actually, this seems kind of independent of transcription. This is a purely translational phenomenon."
- RMRichard Miller
Yeah, let me, let me agree with that about 90%. So the, the 90% I agree with, um, many, many labs just look at RNA levels. Transcriptome biology is relatively easy, and now you can follow it up with epigenetic exploration of what control trans-
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
Most of the published omics information is lists of RNAs that go up or down. However, uh, RNA is very poorly correlated with protein, and it's the protein that counts. There's a lovely pair of studies from the Jackson Labs. Ron Constanda was involved in one of these. They measured, um... A lot of this is Gary Churchill's work. They took mice of four different age groups, black six, but what can you do? And they, uh, measured the changes in proteins. They made a long list of proteins that change with age. Good. They did it in two tissues. Then they looked at the same mice, a long list of RNAs that change with age in the same mice, in the same tissues. It turns out that the correlation between the RNA and the protein was 30%. That is-
- PAPeter Attia
Hmm
- RMRichard Miller
... only 30% of the age effect on protein level could be blamed on, attributed to changes in the underlying transcription data. So if all you've got is the transcription data, which is what most people have, you have sort of blinded yourself to the 70-- to s- other 70% of what is controlling protein levels, and it's the proteins that actually do stuff, uh, in, in the cell. Um, I think, uh, un- until people come to grips with that discontinuity, um, they won't really be motivated to look at the proteins, which are harder to study, but doable, and I think it is the proteomic data collection that will be valuable. Our lab has shown that, um, the proteins can be modified, we're not the first to show this, both by differential RNA translation, this cap-independent translation, and Joe Endicott has found that there's also differential degradation, subsets of proteins that are degraded by the lysosomes through chaperone-mediated autophagy. They mold the proteome in ways that are completely independent of the mRNA for the underlying proteins. I think that's a big part of the story which people are just gradually waking up to.
- PAPeter Attia
Yeah, I think this is so important. I'm gonna just slow you down, and I wanna make sure-
- RMRichard Miller
Okay
- PAPeter Attia
... we, we go through this again in some detail. Uh, I understand what you're saying. I wanna make sure everybody does because I hadn't actually known that fact about the poor correlation between, uh, protein translation and mRNA transcription. That's a very big deal.
- RMRichard Miller
Yeah.
- PAPeter Attia
I would have guessed that to be a much higher number. Um-
- RMRichard Miller
Me too.
- PAPeter Attia
So c- can, can you just go back and give everybody the sort of Bio 101 explanation for how we turn DNA into mRNA into tRNA and protein, where that's occurring in the cell, and, uh, you know... So, so people-- I want people to understand the point that you just made, which I think I wrote down, it's so vital, um, which is without the proteomic assessment, the story is incomplete. That, that's to me the takeaway from what you just said.
- RMRichard Miller
Not only incomplete, but Mostly wrong.
- PAPeter Attia
[laughs]
- RMRichard Miller
Uh, so yeah, sure. I mean, um, uh, y- you learn nowadays, I guess in, in, uh, high school that, um, the, uh, the DNA can be transcribed into messenger RNA. It has the same sequence more or less and, uh, encodes proteins. That's where epigenetic control comes in. They're... The cells that are made only by, uh, proteins made only by the liver are in large part because the liver has turned some transcripts on and others off. The same is true for the eye and the brain, et cetera. So now each cell has its own complement of RNAs. Now they-
- PAPeter Attia
Right. Let, let's, let's make sure people see that point again, right? The liver and the eye and the muscle have the same DNA. Why does the-
- RMRichard Miller
Yeah
- PAPeter Attia
... hepatocyte make a protein that the liver needs, whereas the neuron makes a protein that it needs? This is where turning on and off the gene, the epigenome matters. Okay, so.
- RMRichard Miller
It certainly does matter. People used to think it was the only thing that mattered.
- PAPeter Attia
Yep.
- RMRichard Miller
And I think that's probably wrong, but it's certainly an important thing. Many of the differences between the neurons and the skin cells and the blood cells and the liver cells are because they express different messenger RNAs from the same DNA template. It's just like if you have a library of, of, uh, books and someone decides to, uh, read the Trollope and somebody else wants to read Emily Dickinson. They, they have different experiences even though they have the same library, uh, to work with.
- PAPeter Attia
[laughs]
- RMRichard Miller
So now you've got a batch of RNAs that you've transcribed selectively depending on the cell. Now you have to make them into proteins, so the ribosome will generally bind to them and churn out protein, and the sequence of the protein will be based upon the sequence of the bases in the messenger RNA. Most ribosomes start this by binding to the very end of the message at a place called the cap, the five-prime cap. That's not where the translation starts. That's the sort of start here signal. Then the ribosome bumbles its way down to the place where it's going to start, and then it starts making proteins. So most translation is cap dependent. The ribosome can only find and get working on that messenger RNA by binding to the cap, bumbling down to the start site, and then making the protein. So the default presumption, which turns out to be wrong, is that once you've got those RNAs out there because of transcription into the mRNA, the rest is automated. They just churn out proteins based upon the RNA that they've got. So there are now many studies, and I quoted my favorite ones because they come from friends of mine [laughs] and because it's related to aging. There are now lots of studies that say the idea that the set of proteins depends only on what mRNAs you've got is really a poor approximation.
- PAPeter Attia
[laughs]
- RMRichard Miller
What Gary Churchill and Ron Corstanje and their buddies, uh, accomplished was they actually looked at this in the context of aging in a systematic way. They looked at a tissue like kidney, which is Ron's special favorite tissue. They looked at kidneys of 6, 12, 18, 24-month-old mice, and they made a long list of which genes change at the RNA level as aging progressed. And now they did the same thing but at the protein level. Same tissue, same age, same genetic stock, the same mice as far as I know. And so now they have two parallel lists. And the old-fashioned default assumption would be that if you are on the winner list for age sensitivity for the mRNA, you're gonna be on the winner list for the proteins encoded by that messenger RNA, and that was right 30%-
- PAPeter Attia
Hm
- RMRichard Miller
... of the time. Not 100%, but 30%. There were big differences with age in the kidney and one other tissue. I for- don't remember what other tissue they looked at. There were big differences in proteins as aging went on, but only 30% of those changes were, uh, corresponded to the same change, uh, same amount, same direction in the messenger RNA. The rest came in somewhere else. So this could in principle-
- PAPeter Attia
And, and by the way, is it post-translational? How much of that is-
- RMRichard Miller
Good question, and that's-
- 1:25:30 – 1:31:54
Unraveling aging rate indicators: dose-effect, duration, and future frontiers
- PAPeter Attia
Well, I mean, that's-- there's at least five. I lost count, right? At least five, uh, plausible explanations, and none of them are mutually exclusive, so you could al-
- RMRichard Miller
Right
- PAPeter Attia
... obviously have hybrids of these, um-
- RMRichard Miller
Absolutely
- PAPeter Attia
... as to all the places where you can, quote-unquote, "go wrong" between transcription and the final protein output. Um, this-
- RMRichard Miller
Or go right. I mean, it, you mold it. Whether it's-
- PAPeter Attia
Fair
- RMRichard Miller
... bad for you or good for you-
- PAPeter Attia
Yeah
- RMRichard Miller
... is interesting.
- PAPeter Attia
Um, let's go back to the speedometer, the aging speedometer. Obviously, one of the... So, so you, so you used these 10 known cases of slower aging, right? So four-
- RMRichard Miller
Yeah
- PAPeter Attia
... genetic mutations that result in slower aging, the tried and true caloric restriction, and then five drugs-
- RMRichard Miller
It's actually four, four drugs and-
- PAPeter Attia
Four, but one-
- RMRichard Miller
'Cause the, the newest-
- PAPeter Attia
One on the way
- RMRichard Miller
... unpublished one is actually another mutant.
- PAPeter Attia
Okay. Oh, I see. Got it.
- RMRichard Miller
Yeah.
- PAPeter Attia
So four drugs. Um, so you've got these 10 slowly aging phenotypes, and now-
- RMRichard Miller
Right
- PAPeter Attia
... you've identified consistent, very consistent, even down to sex-specific, uh, differences.
- RMRichard Miller
Yeah.
- PAPeter Attia
Is there a dose effect that you're seeing? Because presumably, these t- nine or 10 phenotypes technically have slightly different lifespans, and therefore are slightly, uh, differentially aging.
- RMRichard Miller
Yeah. So let, let me... I'll, I'll address that question in the context of a battery of things we don't know, want to know, and could find out in the next few years, uh, if, if we're given the opportunity. Um, one of the things we would really like to know is what about the next three drugs? Do they do the same things to the same aging rate indicators? That's a test of our hypothesis. If the answer is yes, yes, and yes, that is great. If the answer is no, no, and no, something has gone wrong, and we need to reconsider the whole foundational idea. Another important area which is getting closer to what you were just asking is, if you give a drug to a mouse, how long does it take for the aging rate indicators to switch?
- PAPeter Attia
Mm-hmm.
- RMRichard Miller
If it takes a few months, that is terrific, because that means we can take 100 drugs and test all 100 of them, not for lifespan, which is really expensive, but test all 100 of them for the ability to switch aging rate indicators. If we test 100 drugs off the shelf or that some, some colleague suggests to us, and five of them switch all of the aging rate indicators, those are the five that are most likely, we think, to be winners for the lifespan experiment. So we could use these as a s- a screen to try to identify drugs that are more likely than not to work in the context of a lifespan experiment. We also don't know how long they stay switched. So let's say-
- PAPeter Attia
Mm-hmm
- RMRichard Miller
... we give a mouse rapamycin or 17⍺-estradiol or mystery drugs A, B, and C, and yes, all the aging rate indicators, eight weeks later, they're at the slow aging level. Okay. Now we remove the drugs. Will they stay, the aging rate indicators, will they stay where they are? We don't know that for drugs. We do know it, however, because of a great experiment that, uh, we did with Andrzej Bartke. He was the inventor of the Ames dwarf mouse. He's the first person who showed they were long-lived. Andrzej had found that if you, you take these Ames dwarf mice, they're mice that have very low growth hormone, very low IGF-1, and they live 40% longer. He's found, he published this 10 years ago, if you give them growth hormone shots when they're a little baby, just starting at two weeks of age, and only for six weeks, so we stop giving them shots when they're eight weeks old, that's enough to turn off the whole anti-aging program. They are no longer long-lived. We found that they no longer have stress-resistant cells, and we found they no longer have low inflammation in the brain. They go back to normal. So what we did was we got from, from Andrzej Bartke some 20-month-old mice that were treated, but only when they were babies. So any epigenetic change that happened to them, they'd have to do it in that growth hormone treatment period and remember it for 20 more months. And the answer is that the changes in all the aging rate indicators, easily seen in the 20-month-old mutant mice, they all went away in the mice that had gotten the growth hormone shots in the juvenile period. So the exposure to growth hormone shots by injection for a brief period of time in youth was sufficient to lead to lifelong reversion of the aging rate indicators to the normal, that is, away from the slow aging position. What we want to do now is the inverse of that. We want to give them something good for them and see if we turn them on, that is, to slow aging, and then it stays up forever. That's what we're hoping to see, of course. We can also use these for people. That's the sort of next frontier. If you give these drugs to people, do the people change the aging rate indicators? If the answer there is yes, that opens up, of course, uh, a massively productive frontier for aging research in people.
- 1:31:54 – 1:44:32
A closer look at aging rate indicators: bridging the gap from mice to humans
- PAPeter Attia
the biomarkers, uh, BDNF, DCSF, you're measuring-- DCX, I'm sorry. You're measuring those directly in sections of the brain. You're measuring those in CSF. Where are you getting that?
- RMRichard Miller
We take, uh, bits and pieces of the hippocampus, uh, make a suspension of the proteins, and do a Western blot. It's just measuring the amount of protein right in the brain.
- PAPeter Attia
Okay. As you think about the application of bringing this to humans, what would, what would it look like to bridge that gap? In other words, if, if, if you wanted to know if this type of exercise routine versus that type of exercise routine, this type of diet versus that type of diet, or your home brew of rapamycin versus not is having a benefit, at some level, we will need to get this out of plasma. It will be very difficult to do this out of CSF or even fat biopsies. Uh, how difficult a bridge is that?
- RMRichard Miller
I'll tell you about, uh, two steps we're taking. Uh, one of them is a collaboration with Stephen Cummings and Teresa Mou and their colleagues. They have a project at UCSF called SOMA, S-O-M-A. They have a collection of several hundred human volunteers, all in their 70s, in good health. These people took a lot of functional tests. How good are they at thinking? How fast are they? How strong are they? And then they allowed tiny, tiny muscle biopsies and tiny fat biopsies. So we have requested, and I think are likely to receive, tiny bits of muscle and fat from these brave volunteers, and we will test. Do those that have a lot of the muscle-specific change, which is a protein called FNDC5, and the fat-specific change, like UCP1, for instance. Our prediction is that amongst the 70-year-olds, the really fit ones will be the ones that look as though they have always had, uh, youthful aging rate indicators. So that will be one way in humans-- And we'll have plasma from these same people as well. So that'll be one way in humans of beginning to test internal tissues to compare with plasma. But pr- that's impractical for clinical use, so what we really need now is ways of extending our results to plasma. Two of the things that we can measure, uh, we have measured and published in plasma, it turns out that irisin, which is the product of G-- of, uh, FNDC5, the thing that goes from muscle to fat, that's in plasma, and in fact, it goes up in all of our slow-aging mice. And the other is GPLD1, which I was talking about previously. GPLD1 is also in plasma, and it also goes up in all of our slow-aging mice. So we'll be able to evaluate that in human plasma samples. But we really want more than that. So one of the studies that we will be doing in the next few years, um, with Catherine Kaczorowski and with a colleague named Kostas Lysiotis at Michigan, he's a metabolomics expert. We will take a batch of mice, healthy, young UM-Het3 mice, the same kind that the ITP uses. We'll take blood samples from them. We will measure the aging rate indicators in the blood, but also in the muscle, fat, liver, and brain of all these mice, and Kostas will measure, um, several hundred metabolites in the blood of the same mice. And our goal will be to ask which two or ten or 20 or 100 metabolites correlate, plasma metabolites, correlate with the plasma and the internal tissue-
- PAPeter Attia
Mm-hmm
- RMRichard Miller
... ARIs. If we can derive from this exploratory exercise a list of five or 10 things you can measure in mouse and human plasma that tell you where the ARIs would be internally, that's great. We think it can be done in principle. There's a, a terrific, uh, scholar, younger scholar named Hamilton Oh working at Stanford with Tony Wyss-Coray. Hamilton has been able to deconvolute plasma signals by saying these represent changes in the pancreas. These represent changes in the liver. These represent changes in the brain. He's not working in, in, in mice yet. I'm trying to twist his arm to get him to do it. But in principle, it, it can be done. You will be able, we hope, to detect plasma molecules which correlate with tissue-specific levels of ARIs. That will be the bridge to human studies.
- PAPeter Attia
Now, is he doing that by looking at cell-free DNA?
- RMRichard Miller
I can't tell you for two reasons. A, I don't understand it, and B, it was at a Gordon conference, and I'm not allowed to talk about it. But you could call Hamilton. His last name is spelled O-H. Or Tony Wyss-Coray, who runs the lab, and maybe they'll tell you.
- PAPeter Attia
Going back to, um, irisin or irisin, that is the product from what protein?
- RMRichard Miller
Well, um, it is a cleavage product of a muscle protein called FNDC5. So we do two things. We measure FNDC5 as a protein in muscle, and we measure irisin as a peptide or protein in the plasma. And they always, in our hands, go up and down together. All the slow-aging mice have more of the protein in the muscle and more of the irisin in their blood.
- PAPeter Attia
There was, um A study in Nature, God, I, I, I want to say it was about 2011, maybe 2012, that made all this promise that, um, uh, it was basically, I think, identifying that irisin concentrations were high in people post-exercise. And the, the, the, the, the promise of the paper was we now have the exercise drug, right? It was, we're gonna, we're gonna just give people irisin, and that's-- you're giving them an exercise pill. Um, uh, the temptation, I suspect, for any of these things is the same, right? Presumably, uh, uh, GPLD1 in a pill is, is something that someone's going to think, "Hey, that's got to be a good thing." Uh, do you think that's a good thing? And if not, why not? And by good thing, I mean, do you think it's going to have efficacy? Let's not-- let's take a moral judgment out of that and just talk about sort of clinical efficacy.
- RMRichard Miller
Right. Irisin has had a checkered past history. The original papers that said what you just said turned out to be using an assay for irisin that was highly inaccurate in the sense that they overestimated the actual concentration of irisin by a factor of about 100. Not subtle.
- PAPeter Attia
That's a problem. [chuckles]
- RMRichard Miller
Okay. And, and people who were skeptical of the original results, they actually worked out a mass spec-based assay for irisin, gold standard, and proved that the original antibodies were not specific enough to be useful-
- PAPeter Attia
Mm-hmm
- RMRichard Miller
... to actually measure irisin levels. And so many people who had felt those original papers were highly promising, as indeed they were, sort of discounted the whole system. But I-- it now looks as though they were throwing out the proverbial baby with the bathwater. Now, there are good antibodies that are sensitive enough to detect irisin at actual levels. When-
- PAPeter Attia
Mm
- RMRichard Miller
... Zhenna Li brought me her irisin data, I said, "Oh, okay, I sort of believe it, but, you know, irisin antibodies have a terrible reputation. Let's look at the precursor protein, FNDC5, in the muscle." And, uh, we decided not to publish it until we had both the irisin in plasma and the FNDC5 by Western blot in muscle. And they were s- they were paralleling one another so very well that I believed that-- I believe both of them now because they always came out the same.
- PAPeter Attia
And, and why not just do the mass spec on the irisin in that situation and avoid the antibody?
- RMRichard Miller
Oh, we're no good at mass spec, and we know how to do Western blots.
- PAPeter Attia
Okay. Um, so back to the point, do we think that these molecules-
- RMRichard Miller
Yeah
- PAPeter Attia
... are merely biomarkers of all of the myriad good things that these behaviors, drugs, or exercises do?
- RMRichard Miller
I, I will bet you-- I don't have any secret inside dope. I will bet you that, that pharmaceutical companies thrilled with what Ozempic and its competitors are doing have devoted tons of money to figuring out whether they can get something like irisin into you in a way that doesn't hurt you and does you some good. Uh, uh, you-- neither you nor I is the first person to have thought of this idea. I'll bet the pharm- pharm companies have devoted tons of money into looking at that. I think it's a highly promising area of research, although I imagine a lot of it currently is proprietary. GPLD1 is, um, a protein, and swallowing a pill might not work 'cause it might be digested in the stomach, just like every, every bit of meat you eat is digested-
- PAPeter Attia
But the same is, the same is true with irisin as well. It's also a peptide, isn't it?
- RMRichard Miller
Yeah. Yeah, yeah.
- PAPeter Attia
Yeah. So these are gonna need-
- RMRichard Miller
Yeah. These-
- PAPeter Attia
... to be injectables, presumably.
- RMRichard Miller
Yes, un- unless you can come up with a s- a small, a small factor that turns on FNDC5 in your muscles. That's what we want to get.
- 1:44:32 – 1:48:09
What do laboratory mice die from?
- PAPeter Attia
We've already s- talked a lot about why the Black 6 mouse has a lot of problems. You've also alluded to the fact that they're basically genetically programmed to die of cancer. What is the, uh, natural history of your mice, and how does the, uh, natural death of the mice in the control group by cause -- We've already obviously talked about l- length of life. Uh, but what is the cause of death in the controls typically versus the treateds in the success cases?
- RMRichard Miller
Yeah, two, two very good questions. Um, the context that's necessary here is that nearly all of the mice that are available throughout the world for medical experimentation, um, come from the Jackson Laboratory, which for 30 or 40 years was mostly interested in cancer. So whenever a mouse got cancer, they kept it. So most of the strains that became the world famous inbreds for-
- PAPeter Attia
They were positively selected for cancer.
- RMRichard Miller
Yeah.
- PAPeter Attia
Yeah.
- RMRichard Miller
They were selected for getting a lot of cancer. So the UM had three mice, had four different grandparents, and cancer is the cause of death in about 80% of our mice, but it's varied. Uh, some sort of lymphoid or leukemia cancer, maybe 30 or 35% of the deaths. Uh, in the males, pulmonary cancer, liver cancer, uh, are both prominent. In the female, it's, uh, um, not pulmonary so much, but breast cancer, liver cancer again, hemangiosarcoma. And then maybe 30% of the mice, if both sexes die of... You know, 1% will die of this kind of cancer, 2% will die of this kind of cancer-
- PAPeter Attia
Mm
- RMRichard Miller
... 3% of that kind of cancer. So it's... 80% of the time, it's some sort of neoplasia that is the, the lethal, uh, injury. Um, and that's why one could make initially a case that, "Oh, all these drugs are doing is slowing down every single kind of cancer." That's why we have to look at a lot of things that are not cancer. The second part of your question is, does the proportion of c- different kinds of cancers or causes of death change in these different mice? And that's a hard question to answer because when we do a necropsy series at the end of life, which is... You have to do it at the end of life to see what they died of. The n- we usually have only about 60 mice in the treated group and about 60 mice in the control group. So if, if a particular kind of cancer, let's say liver cancer, kills 10% of the mice, you only have six cases. [chuckles] And-
- PAPeter Attia
Yeah
- RMRichard Miller
... if that goes up to nine or goes down to three, that would answer your question with a yes, but statistically, we just don't have enough cases to be confident. Only once did we come across a statistically significant alteration, and could have been a fluke. We had a drug that was extending lifespan in males and females, but it did not increase the age at death of the females dying of breast cancer. So one could have made a case that breast cancer is caused by something that is not related to this drug's anti-aging mode. That's something we're always on the lookout for, but the number of autopsy cases is almost always too small to really have a good grip on it.
- PAPeter Attia
Well, that's why I think it makes it very interesting that we're going to see your colleague coming on board who specializes in the neuroscience and the neurology-
- RMRichard Miller
Yeah
- PAPeter Attia
... of the mice, because I think to make this truly exciting, we wanna continue to see functional improvements. And-
- RMRichard Miller
Yeah
- PAPeter Attia
... functional improvements in both strength, uh, and cognition would go a long way. And by the
- 1:48:09 – 1:48:48
Distinguishing between a drug that improves an age-sensitive outcome and a drug that improves all aspects of aging
- PAPeter Attia
way, it also is worth, I guess, asking. I, I haven't asked you this, but do you know if there are cases of drugs that do not improve lifespan but do improve, say, grip strength and treadmill time? Um, in other words, are there, are there drugs that are improving healthspan without lifespan in the ITP that you've documented?
- RMRichard Miller
Yeah, this is, this is a chestnut that always comes up, and the Aging Institute in particular is passionately interested in the notion that maybe a drug will make you healthy, and then you'll drop dead right on schedule. Um, I, I myself... The, the answer to your question is no one has looked for it, and that's because
- 1:48:48 – 1:58:34
The ITP study of 17⍺-estradiol: mechanisms of life extension and surprising sex differences
- RMRichard Miller
in our phase one assays, we-
- PAPeter Attia
Yeah, it's too much work. Yeah.
- RMRichard Miller
Um-
- PAPeter Attia
You can't do it.
- RMRichard Miller
We, we don't do it.
- PAPeter Attia
Yeah.
- RMRichard Miller
We only l- do those detailed studies on things that extended lifespan.
- PAPeter Attia
So, yeah.
- RMRichard Miller
The reason that things extend lifespan is basically it postpones all the bad stuff that, that lead to death. So-
- PAPeter Attia
Yeah
- RMRichard Miller
... to do it the... We, we could screen a lot of drugs for age-sensitive variables in the hopes that we would find one that made age-sensitive variables go away but didn't have any effect on lifespan. I'm not so sure that we would find any. The... You know, it's trivially easy to do that. Um, if you teach a mouse to do push-ups, you will postpone age-associated changes in muscle mass and muscle strength And if you tra- teach them they won't get food until they solve a maze, they're gonna get pretty darn good at solving that maze. So system-specific postponement of, uh, age-sensitive outcomes is not too hard to achieve. It's not really relevant, I think, to the issue of what you can do to postpone all the aspects of aging together.
- PAPeter Attia
Let's pivot and talk about, um, one of the successes of the ITP that still somewhat perplexes me. You've already alluded to it several times, which is 17⍺-estradiol. So, um, I, I, [chuckles] I'm pretty s- sure I asked you this question last time, but I will ask you again. Remind me the difference between 17⍺-estradiol and 17-
- RMRichard Miller
Yep
- PAPeter Attia
... beta-estradiol, which is the estradiol that is the dominant form in both males and females. Like, we're rolling around with lots of 17-beta.
- RMRichard Miller
Traditionally called estrogen. Yeah. [laughs] So the-
- PAPeter Attia
Yes
- RMRichard Miller
... 17⍺-estradiol is just the same chemically as the 17-beta except for one of the bonds, instead of pointing up out of the plane, points down in the opposite direction. So it's a stereoisomer. Same chemical formula, all the atoms are attached in the same place, it's just that two of them are pointing up instead of pointing down. And because of that manipulation, it doesn't bind very well to the traditional es- famous estrogen receptors.
- PAPeter Attia
Mm.
- RMRichard Miller
So it's doing something. It's gotta be binding to something [laughs] , but it, it probably is not the traditional estrogen receptors, or it might be that plus something else to get, um, an effect on estrogen sensitive tissues. You can do it with 17⍺-estradiol. You just have to use a lot more, I think tenfold more is what Jim Nelson found when he, when he did that titration.
- PAPeter Attia
And what was the rationale when this was proposed to the ITP? What was the-
- RMRichard Miller
Yeah
- PAPeter Attia
... scientific rationale for why this would be a, a, a geroprotector?
- RMRichard Miller
Jim Simpkins recommended it. He's a steroid physiologist, neuroendocrinologist. He reasoned, and a lot of this was wrong, but it... this is the rationale. Estrogens are good for you. That's why females live longer than males. Let's find an estrogen we can give to males.
- PAPeter Attia
Mm.
- RMRichard Miller
We don't wanna give them 17-beta-estradiol because they'll turn into girls, and they won't like that.
- PAPeter Attia
[laughs]
- RMRichard Miller
No one wants to be a girl. So let's use 17⍺-estradiol because they won't turn into girls. It does not turn on secondary sexual characteristics. Maybe it will do all the good stuff that estrogen 17-beta actually does. That was Jim's argument. Very plausible. Now, it turns out that if you give 17⍺-estradiol to male mice, it pushes their lifespan way beyond females. [laughs] It's not merely mimicking the good stuff-
- PAPeter Attia
Mm
- RMRichard Miller
... if, if there is good stuff, that estrogen 17-beta does in females. If so, it wouldn't go much further-
- PAPeter Attia
Yep
- 1:58:34 – 2:09:13
Unsuccessful drugs studied by the ITP: resveratrol, metformin, and nicotinamide riboside
- PAPeter Attia
What is the-- Let's talk about a couple notable failures in the ITP, i.e., drugs-
- RMRichard Miller
Yeah
- PAPeter Attia
... that everybody thought were home runs that didn't pan out. I guess the-
- RMRichard Miller
Yeah
- PAPeter Attia
... three that come to my mind are resveratrol, metformin, nicotinamide riboside. Uh, any others-
- RMRichard Miller
Yeah
- PAPeter Attia
... that should be on that list?
- RMRichard Miller
Most people who suggest a drug think their drug is going to work. But I think the three you've pointed out are the ones that have gotten the largest numbers of notices in AARP bulletins and on social media and at, uh, the conventions where people, uh, want to mingle with, uh, snake oil salesmen. So, um, uh, they are certainly the most, the most famous. And they-- I think there's a different level of enthusiasm for each one of them. Metformin, I think, [lip smack] has been very sensibly proposed as a potential anti-aging drug in people. I d- I don't know enough about its benefits and side effects. I know that you yourself have, uh, you know, ten times more information about this than I do. But a case has been made because it's so very safe, uh, in people that it could be used in people to postpone aspects of aging. I can see reasons not to believe that, but at least you can make a case for that. It doesn't seem to work in mice. Um, the ITP showed that it didn't work in mice, and now several other groups have confirmed that result. Rafa de Cabo at one point claimed that it worked in mice, but he used a very weird statistical test, and I suspect that if you had-- if he had used the standard statistical test, it would have failed in his lab as well. I haven't seen the data, so I'm not sure of that, but that's my guess. Resveratrol was, was hyped, um, for, uh, many years. People, often with commercial interests or who had a grant or who wanted to get a lot of money for a clinical trial, would start their talk with a beautiful bottle of red wine and then say, "Resveratrol is in red wine, and sirtuins are, uh, uh, important, and resveratrol influences sirtuins, and just take some of my resveratrol or sirtuin activating agent and you'll live forever." None of that was right. I mean, it's been shown very clearly now that the amount of resveratrol in red wine, uh, is, uh, to get enough of it, you need to, uh, drink 30 bottles a day. Its status as a sirtuin activator has been questioned by very s- serious and skilled biochemists. The original data on worms has been disconfirmed by a couple of very good labs. Uh, so it was mostly hype. Uh, people made a lot of money by selling companies that had an interest in sirtuin activators. We tested it, um, because, um, the director of the National Aging Institute, Richard Hodes, for the first and last time said, "You will test-
- PAPeter Attia
[chuckles]
- RMRichard Miller
... resveratrol or you will not [chuckles] get any money this year." We said, "Yes, sir. Yes, sir." So we, we tested it. We used-- We checked with David Sinclair and asked David, "What is the concentration we ought to use?" He said, "Use this concentration and this concentration." We said, "Sure. We'll do it your way. Let's find out." And it didn't work. And subsequently, many groups now, including groups that Dr. Sinclair is associated with, have shown that it doesn't work to extend lifespan of regular mice. The- Famous paper was one in which the mice were poisoned with a 60% coconut oil diet, and they weren't dying of aging. They were dying because their liver swelled up to the point that it crushed their lungs and they couldn't inhale. Uh, they couldn't breathe. Th-this is not, I believe, an, a pretty good model for the aging response. So I think the evidence that resveratrol by itself should have been tested was quite weak, and the fact the evidence that it works is, uh, very bad. It, it almost certainly doesn't do anything, at least in mice, in terms of, uh, a- uh, aging. An anecdote-
- PAPeter Attia
Does it surprise you how ubiquitous resveratrol supplements are still on the internet?
- RMRichard Miller
No, people are easy-
- PAPeter Attia
I mean, you go to Amazon-
- RMRichard Miller
I'm sorry to be cynical.
- PAPeter Attia
Yeah.
- RMRichard Miller
People are very easy to fool. [laughs] It's easy to come up with eight or 10 things that people believe because they read them on the internet-
- PAPeter Attia
Yeah
- RMRichard Miller
... or they watch them on Fox News or whatever, and they're strong about this. But they're very... People are very, very gullible. The, the anecdote about resveratrol that I think is, um, gives you a sense of what that time was like. I had a, a friend, a neurologist at Michigan, who had been given a huge grant to give resveratrol to Alzheimer's patients or pa- or at the early stage to see if it would slow Alzheimer's. Tons of money. And he came around to a meeting of resveratrol biologists. I was attending it. And he asked people what dose to use. And the range of suggested doses as milligrams of drug per person per day, uh, ranged over a million fold.
- PAPeter Attia
[laughs]
- RMRichard Miller
That is among the, the, the experts, the world's experts on resveratrol. The consensus ranged from one to a million as to what dose was the most logical one. So this is a sign of a field that is making it up as it goes along. NR is the last of the three drugs that you mentioned.
- PAPeter Attia
Yeah, yeah. [laughs]
- RMRichard Miller
I had high hopes.
- PAPeter Attia
So e- e- probably more hype with NR than resveratrol, truthfully, on some level. Um-
- RMRichard Miller
Somebody's making a lot of money.
- PAPeter Attia
Yeah, many people are.
- RMRichard Miller
Yeah.
- PAPeter Attia
Um, so tell us about, uh, tell us about the, the findings and what it tells us or doesn't tell us.
- RMRichard Miller
Well, well, we tested it and it didn't, didn't work. Um, that is, it didn't extend mouse lifespan. Some people said, "Oh, well, you have to use NMN, a metabolite that would have a more bioavailability and better profiles." And this is reasonable. And, um, if someone makes a good case that we should test NMN and we could afford it, the commercial sources are expensive, um, we would probably test that as well. I think the notion that-
- PAPeter Attia
I, I would have to imagine that some commercial party would donate the, the, the drug at this point, right?
- RMRichard Miller
We are in negotiations with one such company. Yes, I'm hoping you're right. [laughs] I hope we could-
- 2:09:13 – 2:16:00
Over-the-counter successes in the ITP: meclizine and astaxanthin
- PAPeter Attia
So Rich, I don't know if you know this about me, but, oh, I don't know, 15 to 20 years ago, I used to spend an awful lot of time on boats. Now, these-
- RMRichard Miller
Yeah
- PAPeter Attia
... these weren't big boats. These are typically small boats. So these are kinda 30-foot boats where you're out in really, really, really rough water. Um-
- RMRichard Miller
Yeah
- PAPeter Attia
... so hours and hours. I don't know how many hours of my life I've spent out in, you know, 30, 40 miles off the coast of California, uh, getting thrown around like crazy. And, um, I was pretty lucky. I'm-- I've only been seasick once in my life, which when you consider the amount of time I've spent out there, I, I consider pretty, pretty fortunate. But, but most of the people I, uh, I, I, I spent time with out there got seasick a lot more. And, um-
- RMRichard Miller
Yep
- PAPeter Attia
... one of the drugs that people used to take care of their seasickness was an over-the-counter-
- RMRichard Miller
Yep
- PAPeter Attia
... uh, drug called meclizine.
- RMRichard Miller
Yeah.
- PAPeter Attia
So, um, I would occasionally take it. I didn't take it that often 'cause again, I, I almost never got seasick. But sometimes just to be safe, I would say, "You know what? The, the water looks unbelievably rough today. Uh-"
- RMRichard Miller
Yep.
- PAPeter Attia
"... I'm gonna take my, my meclizine." Over the counter. Uh, Bonine I think is the brand name. B-O-N-N-
- RMRichard Miller
B-O-N-I-N-E. Bonine.
- PAPeter Attia
B- Bonine.
- RMRichard Miller
Yep.
- PAPeter Attia
Yeah. So, um, why am I telling you this story, Rick? I'm sure the listener is wondering, "Why is Peter bringing this up?"
- RMRichard Miller
Oh, that's... I have a, I have an answer for you.
- PAPeter Attia
[laughs]
- RMRichard Miller
I'm spending two weeks in December in a small boat actually off the coast of Chile. We're going to go up and down the archipelago, uh, doing photography, and the seas there can be very choppy, and we've been told to take, um, meclizine, uh, or some other, uh, anti seasickness remedy so that we'll be able to photograph to our heart's content without feeling ill. And meclizine is also included in the latest paper for the ITP, which, which also makes it of interest. The, the paper that we've just submitted, it hasn't been accepted yet, but, uh, again, because it's complete, I'm allowed to, to present it at meetings and in t- talks like this. There are two drugs. Uh, one is meclizine, one is astaxanthin, which, uh, in males led to a significant increase, about 10%, in the lifespan of the males. Um, meclizine was suggested to us by Gino Cortopassi. Um, he knew that rapamycin was good as an anti-aging drug, and it was a TOR inhibitor. So he took, um, several thousand FDA-approved drugs, and in a tissue culture assay, he said, "Which of these inhibit TOR?" Maybe a safe drug that inhibits TOR could find a place as an anti-aging remedy. And at the top of his list, to everyone's surprise, certainly his, was meclizine. It was famous as an antihistamine and also has mysterious CNS effects, which is why it's so good for seasickness. It wasn't, I believe, known as a TOR inhibitor, but Gino found that it was, and so he suggested that we test it, and, uh, it does indeed lead to, at the dose we used, a significant increase, about 10%, in, uh, lifespan of the male mice. Uh, it did not affect females, so we're gonna try it again at higher concentrations and see if we can get that to go. We haven't proven that the effect is mediated by TOR inhibition. It has a lot of CNS effects, and maybe the good stuff that it's doing to the male mice is unrelated to TOR. Maybe it has to do with changes in, um, serotonin or histamine production at, in some critical nucleus in, in the brain. We need to now look at that. But that, that's the, the cool news. The other thing that same paper has, um, the two points of interest. One is astaxanthin. Astaxanthin is also available over the counter. You can buy it in your, your local drugstore. It, it is alleged to have health benefits, but they're all over the map, and I can't assess the strength of the evidence for health benefits. It's also alleged to have m- many different physiological effects like an antihistamine or, uh, uh, an anti-inflammatory or an antioxidant. It's been alleged to do a little bit of everything. But there's a company in-
- PAPeter Attia
And it's a food dye, isn't it?
- RMRichard Miller
Uh, yeah, it's fam- We eat it all the time. It's famous because it's what's turned salmon pink. The reason... If you wanna make your farm, farm-grown salmon pink, you dump tons, I mean tons, you know, dump truck loads of astaxanthin into the water, and the salmon turn pink. It's not that you dip the salmon into astaxanthin. The natural salmon eat a lot of, uh, crustaceans which have the stuff in their shells, and you can mimic that effect in farm-grown, uh, salmon by giving them synthetic or naturally derived astaxanthin. In any case, there's a company in Hawaii that believes it might have health benefits, and they asked us to test it, and we did test it, and that also has a significant effect. And also it's males only. So this paper hopefully will be accepted soon and out for people to judge the strengths of the evidence. Neither of these led to a change in our measurement of maximum lifespan, this test of percentage of live mice at the 90th percentile. It's possible that at a higher or maybe even a lower dose, it might have done that. We're gonna need to go back and do a more complete dose response curves. The, the reason this paper is, I think, likely to be of particular interest to the general public, uh, is that it is the first time we've gotten winners that you can buy without a prescription, over the counter. They're not as strong in terms of lifespan benefit as the four drugs we were talking about earlier on in our discussion. But, um, uh-- And of course, we don't know if they will work in humans at all. But, um, the, uh, position of the FDA that you can't test a drug claiming it has an anti-aging effect will be of less relevance if some of the, uh, over-the-counter non-prescription medicines actually slow aging, first in mice and then maybe also eventually in people. Um, I think that's an interesting political and legal question. In terms of the science, we now need to figure out what is astaxanthin doing, and is meclizine acting through TOR or through some other target? It opens up... As, as any new drug does, it opens up, um, new possibilities for mechanistic exploration. You can bet we're gonna be looking at the aging rate indicators in tissues from meclizine-treated and astaxanthin-treated mice.
- 2:16:00 – 2:22:30
A senolytic drug, fisetin, fails to extend lifespan
- PAPeter Attia
Well, you know, Rich, that-
- RMRichard Miller
Oh, and the last thing in the paper-- So the last thing in the paper that many people will be interested to know is we've tested fisetin. Um, this was suggested to us by Paul Robbins and Jim Kirkland and Tamara Arshakonia and their colleagues. Um, fisetin is undergoing a lot of human trials because of claims that it is a, a senolytic drug. There are some people, though I am not in that group, who think that there's such a thing as a senescent cell, and that you get a lot of them when you get old, and that they're bad for you, and that a drug that removes senescent cells therefore will be good for you. I'm not convinced, but this is a very popular line of thought. So fisetin was given to us as a drug to test the hypothesis that if you remove senescent cells from mice by giving them fisetin, they would live longer. A very-- I thought it wouldn't work, but it was a very reasonable and important thing to do. So we gave fisetin, uh, two different dose regimes suggested by Dr. Kirkland. He had found in his lab with his kind of mice that they did work at this dose, so that was good news. We thought we were trying to replicate his stuff in our mice at much larger scale, and the take-home messages were two. First, it had no effect whatsoever on lifespan of male or female mice using either of the dosage regimes that, that, uh, Dr. Kirkland recommended. However, that is not dispositive because it turns out it didn't remove any senescent cells either [laughs] . Um, what we can do is you can-- There are quite a number of surface markers like p16 that the senescent cell gurus say, "This will tell you whether you've got senescent cells." They do go up with age. They go up with age in-- We looked at three different tissues. That is, um, Paul Robbins' lab and Jim Kirkland's lab. We, we sent them tissue. It was blind, so they wouldn't know which ones were controls and which ones were treated. They sent us back this number of beta-galactosidase positive cells, this number of p16 positive cells, this number, this amount of p21. And when we, uh, unblinded it, there was no effect of fisetin on brain, on liver, on muscle, on kidney, um, at either lab for any marker that we looked at. So we thought we were testing the notion that removing senescent cells would be good for you, and it turned out we were testing the notion that fisetin removes senescent cells. Now, maybe it works in people. This is not my area. But, uh, we-- Our colleagues were disappointed, and I can understand why they were disappointed in this, in both results.
- PAPeter Attia
Rich, say more about your lack of belief around the role of senescent cells. I, y-y-you, you made it sound like you don't believe in senescent cells. I assume what you meant-- Was that actually what you meant, or did you mean you don't believe that senescent cells drive aging or that you don't believe removal of senescent cells slows or reverses an aging phenotype? Let-- Say, say a bit more on that whole thing.
- RMRichard Miller
I'm in a slightly awkward position because to tell you the details of why... All that is true [laughs] . Uh, uh, and the details require, you know-
- PAPeter Attia
Just don't say you'll have to kill me if you tell me
- RMRichard Miller
... half an hour or something like that.
- PAPeter Attia
That's the only thing I don't want to hear [laughs] .
- RMRichard Miller
No, no, no, no, no. I, I don't do that. Um, it, it, it's a, it's a long, long story. But let me give you an analogy. If, if someone says, "Do you believe in stress?" The answer is, sure, I believe in stress, right? But that doesn't end the conversation because there's the stress of being about to undergo a tense podcast discussion or the tension of having to give a talk before the National Aging Institute's committee or the stress of dental work. I hate dental work. Or the chronic stress of being locked into a marriage or a job that you really hate or getting a diagnosis of cancer. All of the-- Or dropping a bit of, uh, of a poison into your GI tract. All of those produce stress, but they're radically different things. They produce different physiological effects. And to say Do you believe in stress or is this caused by stress is a way of blinding yourself accidentally to the critically important distinctions. So do I believe that there is such a thing as a senescent cell? Yeah. If you take cells in-- human cells in culture, they stop dividing, and those have been called senescent cells. They exist, no question about it, and they're caused by telomere shortening. Now, if you take another kind of cell and you zap it with X-rays, you get a different kind of cell. They make different proteins. They don't have telomere problems. People have referred to those as senescent cells. If you have cells that when you get older, they have p16 on them, people have referred to those as senescent cells. And by saying that this drug removes senescent cells, they are hoping you won't begin to think about what sen-- the vague definition of what a senescent cell is. In laboratory A, these proteins are called the senescence secreted proteins. In lab B, it's two of those plus seven more. In lab C, well, they don't see those, but they do see changes in the nucleolus, which they view as senescent. So I believe that there certainly are cells that accumulate in mice and in people when you get old that do stuff that's bad for you. Some of them might make this set of cytokines. Some of them, maybe they can't divide anymore, and that's bad for you. Some of them may even have, uh, two of these problems together.
- PAPeter Attia
Hmm.
- RMRichard Miller
Maybe some of that is changed because Ras has been mutated or DNA has been damaged or something. And exploring what causes those things, how they become bad for you, whether removing that cell type is good, I think that's wonderful. Now, if you say, "Oh, these are senescent cells. I've got a drug that removes senescent cells," you are skipping all the interesting stuff. That's my view.
- PAPeter Attia
Got it. So it, it's as, it's as much a lack of nuance and a, um, semantics issue as it is potentially or even more so than a biology problem. And when people talk about senolytics, uh, you're saying, "Hey, we can't really talk about senolytics without understanding which senescent cell you're targeting or which secretory product of senescent cells you're targeting."
- RMRichard Miller
That's
- 2:22:30 – 2:31:19
Optimism about future findings
- RMRichard Miller
a, that's a part of it, although the problem is much deeper than that. Let me, let me tell you a, a story. The, the-- There's this famous paper. Judy Campisi was the key author.
- PAPeter Attia
Yes, of course.
- RMRichard Miller
Uh, she measured the number of senescent cells. This is the paper that introduced beta-galactosidase as the way to count senescent cells. And she looked at the skin of a lot of people, young and old people. And she counted the number of senescent cells and proved that it went up a lot with age. That was a very influential paper. If you look at the paper-
- PAPeter Attia
She's at the-
- RMRichard Miller
... the number of cells that-
- PAPeter Attia
She's at the Buck Institute, correct, if I'm not mistaken?
- RMRichard Miller
Dr. Campisi? Yeah, Judy is-
- PAPeter Attia
Yeah, yeah
- RMRichard Miller
... I believe, at the Buck Institute. Yeah.
- PAPeter Attia
Yeah.
- RMRichard Miller
Um, so in this original paper, which was many years ago, the scores were one plus, two plus, three plus, and four plus, not actually a percentage of cells that were beta-gal positive in the skin sections. And only one person was four positive. It was a 90-some-year-old grandmother. Well, the, the actual cell counting was done by a friend of mine, Monica Peacock, who is a dermatopathologist. We were all at BU at that time. So I called Monica, and I said, "Okay, Monica, so four plus. How many cells do you have to get to be four plus?" And she said, "Yeah, that's 10 to the minus fourth." That is, the, the, the skin section that had the highest number of beta-gal positive cells had only one positive cell-
- PAPeter Attia
Per 1,000
- RMRichard Miller
... in 10,000.
- PAPeter Attia
Or to per 10,000, yeah.
- RMRichard Miller
One in 10 to the fourth cells. Everybody else, all the 70s, 60s, 50s, all of those people had, um, fewer than one cell in 10,000. So the statement is literally true. Senescent cells go up with age. These people wouldn't make up the data. But they didn't emphasize the fact that even in the very oldest sections, the, the oldest people, the number of actual senescent cells was, was really quite small.
- PAPeter Attia
By the way, what was the difference between the 10 to the threes, 10 to the... Or sorry, the one plus, two plus, three plus, 'cause it-- clearly those aren't-- those numbers don't refer to log differences, so w-
- RMRichard Miller
I don't know.
- PAPeter Attia
That would be worth knowing.
- RMRichard Miller
I don't know.
- PAPeter Attia
Right? I mean, 'cause if it goes from-
- RMRichard Miller
Pathologists-
- PAPeter Attia
Yeah, if it goes from one in 100,000 to one... If, if there's a 10-- if there's a log full jump between every group-
- RMRichard Miller
Yeah
- PAPeter Attia
... you could argue maybe there's something interesting. But then at that point, it's pretty hard to count.
- RMRichard Miller
That was the high limit. I mean, all, uh-
- PAPeter Attia
Yeah, yeah
- RMRichard Miller
... the, the take home message here is that senescent cells, at least as indicated by that one marker, beta-galactosidase, are so rare that they're virtually absent from the skin of people of any age. That is virtually absent, I would consider 10 to the minus fourth and, and-
- PAPeter Attia
Yeah
- RMRichard Miller
... lower. Um, but it's been a very influential, I believe, much overly emphasized, over-influential concept. So I was hoping we would show that fisetin would remove senescent cells from mice, and it would have no lifespan effect. That was what I was betting on. But, uh, in fact, that didn't seem to actually remove p16 or p21 positive cells from any of the tissues that we evaluated, so we're, we're back at square one.
- PAPeter Attia
So we're still back... We-- What we have learned is that fisetin doesn't do jack. What we haven't learned is if removing senescent cells is or is not beneficial.
Episode duration: 2:31:20
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