IRA FLATOW: This is Science Friday. I’m Ira Flatow. I have something to confess. I am not a kid. Surprise, surprise. More of the Medicare age and I think we’ve all had the experience of seeing how aging can look different on two different people.

There are some 80-year-olds that exercise regularly that can play rounds of pickleball easily, but others really struggle at this age and aren’t able to maintain a quality of life they’ve had in the past. There’s a growing field of medicine dedicated to better understanding how we age and why two people may age very differently, and recent research pinpoints certain metabolites that could hold the answer. Joining me now to talk about this is my guest, Dr. Aditi Gurkar, assistant professor of geriatric medicine at the University of Pittsburgh School of Medicine in Pittsburgh, PA. Welcome to Science Friday.

ADITI GURKAR: Thank you so much for having me on the show, Ira.

IRA FLATOW: It’s nice to have you. Now I understand that you got into this topic of biological aging by watching your grandparents age. Is that right?

ADITI GURKAR: In India, we grew up in a joint family, so my grandparents actually stayed home with us, which was great. I loved having my grandparents around, but as they were getting older, it was very easy to tell that my grandfather, who aged very gracefully and naturally did almost everything functionally ’til the end of life, did my homework with me, told me grandpa jokes basically. And on the other hand, my grandmother, her last 15 years of her life, she could really not make it out of bed. She had dementia, really could not even remember who I was. So at a very young age, I started wondering why two people in the same household that seemed to age very differently, and that’s what captured my interest very early on.

IRA FLATOW: Well, is there a common definition of what aging or getting old is?

ADITI GURKAR: That’s the million dollar question I guess. We all look at chronological age, which serves as a conventional marker, of course. That’s the age that we have on our license and on our passports.

However, just like you captured it in your introduction, no two people age the same, and so biological age is what we think could capture health and so how healthy we are, how much wear and tear our bodies have gone through, basically telling us about how we feel. And it does so by capturing the interplay of multiple factors including our genetics, our environment, what did we eat last night, or did we even get some exercise during the day.

IRA FLATOW: So biological aging is like a quality of life thing.

ADITI GURKAR: Correct. Correct. But much more difficult to measure.

IRA FLATOW: Yeah. And it’s not something that you can determine by just looking at a person.

ADITI GURKAR: Unfortunately, not. Maybe we can when a person’s 70, 75 maybe. But the goal would be to capture biological age very early on so that we can predict whether one’s going to be a healthy ager or a rapid ager so that we can take the right steps to change that.

IRA FLATOW: Now you recently made a breakthrough in biological markers to determine aging. Tell us what you found there.

ADITI GURKAR: Well, thank you first of all for calling it a breakthrough. As a scientist, I’m always looking at my work, and I think there’s so much to do. But, yes, we are really excited about this new study that we did. Some of us in the field including our lab but many others had identified that as we age, we all accumulate certain cells, dysregulated cells in our body that in popular literature get called zombie cells, and in science, they call it senescent cells. So these cells accumulate in all of us and seem to be playing a major role in disease.

IRA FLATOW: Really?

ADITI GURKAR: Yeah. And when I was a postdoc– seems like ages ago now– we had worked with multiple teams including the Mayo Clinic and the Scripps Research Institute to look for drugs that could eliminate such dysfunctional cells at least in animal models. And what was really exciting was when we could get rid of these zombie cells, at least the mice did much better. They aged much more healthy, and that was like, oh, wow, can we start a process where we can delay biological aging.

So in this study, what we did was we looked at markers of this senescence, but we also integrated it with another marker called metabolites. Our body releases unique small molecules, chemical fingerprints, if you will, all the time, and these are substrates, intermediates, and byproducts of our everyday metabolism. What’s great about metabolites are they are circulating in all of us and can really tell us about how we feel. They tell us about our physical state, our functionality. So in this study for the first time, we have integrated two very important things, metabolites as well as markers of senescence, together in order to capture biological age.

IRA FLATOW: And so how do you judge what biological age is based on these markers?

ADITI GURKAR: Great. Great. So what we started out was with this cohort where we really looked at functional capacity mostly by doing a walk test or a gait speed. The reason we decided to look at gait speed for our initial study was that the gait speed has been linked to hospital readmissions, linked to how we feel, and it really captures multiple things going on in our bodies including pain, how we are feeling on a specific day. So all of these things together go into gait speed and walking ability.

So that’s what we captured in our first study was we call biological age as healthy agers who could walk for about six minutes without taking many rest and felt really good doing so. There was a part of the cohort that could not walk for the six minutes continuously and needed to take breaks, and so that’s what we call rapid agers. Now mind you, all of these people in this cohort were about the age of 65, and we set off this chronological age setup or threshold to really capture what’s happening with age rather than comparing someone who’s 25 with a 65-year-old.

IRA FLATOW: So did you find more markers?

ADITI GURKAR: Yeah!

IRA FLATOW: In a certain group of people who– what did– tell me about that.

ADITI GURKAR: Yeah. So what was exciting was by looking at about 1,400 metabolites that are circulating in one’s blood, we could come up with a marker of 25 metabolites that could distinguish between healthy agers and rapid agers. Now what are these metabolites? Some of these are lipids. Some of these are basically byproducts of plants, fruits, and vegetables that people eat, and together these 25 metabolites could tell us who is a healthy ager versus someone who could be an early or rapid ager.

IRA FLATOW: So this sounds like aging risk factors.

ADITI GURKAR: Well, in this case, that’s actually a good point, and that’s where we have now done some more work into looking at causal factors that could really drive biological aging. And we have come up with two things that we think are really exciting, and we want to follow through. One is how well are one’s mitochondria functions. Mitochondria are these organelles in all of us, most popularly called the powerhouse of the cell. This is an organelle which is very important for metabolism, breaks down fatty acids, and gives us energy basically.

And so we find that healthy agers seem to have better mitochondria, more functional mitochondria compared to rapid agers. So that’s exciting, and we think that rapid agers instead, because they cannot use their mitochondria, seem to break down their fat in other places such as another organelle called the endoplasmic reticulum or the ER. And here we get these byproducts that might end up being more toxic to health. So that’s the first thing we are following through.

The other exciting part was– and this is more I guess proof that my mom was right because my mom always told me to eat more vegetables. And one of the metabolites that we found in our study really comes from fruits and vegetables, and this really correlates well with healthy agers. So I think, again, everybody, your moms were right. Please eat your fruits and vegetables.

IRA FLATOW: Well, it sounds like you were investigating the rapid aging people at 65. What about the normal, quote unquote, aging people?

ADITI GURKAR: Right.

IRA FLATOW: Was there a difference there, and then I’m going to move on to the older people who are still, as I say, playing pickleball at 80.

ADITI GURKAR: Correct. Correct. So in this cohort, we had 200 people that were hundreds of them were healthy ages, what you called normal aging. So these are the people who could play pickleball. They didn’t need to rest for five minutes. They could walk fairly well. We had also captured many other things including their memory scores, how fast they can get in and get out of a chair, things like that.

And these people did really well in these functional tests. So just like you said, people who can do great even in their 80s, and then we compared them with the rapid agers. So comparing these two is what gave us this index of healthy aging.

IRA FLATOW: I see. I see. So what about genetics because there are some people like my mom lived to just about almost 100.

ADITI GURKAR: Wow.

IRA FLATOW: Yes, thank goodness. And you come up with people who– and we’re having an aging population that’s living a lot older for some people, aren’t they?

ADITI GURKAR: Absolutely

IRA FLATOW: Is there something useful you can take out of your study for that cohort?

ADITI GURKAR: Absolutely. I think this is why we need to look at aging right now. We are all surviving to much older ages than we did 40, 50 years ago. So our population demographics are changing completely.

Now does genetics play a role in biological aging? Absolutely. There is no question about it. However, we think– and several studies have looked at this before where they’ve compared even twins so having very similar genetics and looked at how they age, and other factors can control how one’s aging. Even in these twin studies, their environment, their lifestyle choices, all of these made an impact on how they were aging, not just their genetics. And so that’s why we decided to look at metabolomics because it can arise from capturing all of these factors including genetics and lifestyle choices.

IRA FLATOW: So what are the implications of your findings? Are you talking about a possible test you can take at the doctor’s office and look at your metabolites and say, oh, you’re not eating– not eating enough vegetables or something like that?

ADITI GURKAR: Yeah. The hope is that, you know, we are at very early stages in our study. What I’m really looking for in the future is, yes, when we do our annual exam, can we just do a simple blood test and that can tell us although our chronological age is 40 like I am but my biological age is only 30 or whether you’re heading in the opposite way. And– by catching your risk to be an early ager, we can perhaps personalize these interventions. Maybe someone has a lot more of these senescent cells, and so maybe there’s an intervention of giving senolytics or seno-therapeutics, the small molecules that can eliminate senescent cells.

IRA FLATOW: I see. Now on the other hand, some medical tests are based on how old you are. For example, colonoscopies for cancer are not prescribed for people 75 or older because the risk outweighs the benefits, but if your biological age is let’s say 65 and though your chronology is 75, shouldn’t you still be getting those tests?

ADITI GURKAR: Correct. Exactly. That’s the thing is we know that and– especially now I’m sure you’ve realized this as well– in the last few years, a lot of people in the middle age also have started becoming susceptible to other cancers.

IRA FLATOW: Yes. Yes, absolutely.

ADITI GURKAR: And so we will have to change policies on when we have to start testing probably soon, and for something like that, we need to dig deeper into what one’s biological age is.

IRA FLATOW: So when might we see your test, your panel, so to speak, be available to doctors to use?

ADITI GURKAR: Great question. As a scientist, I’m always very careful about making sure that our test is going to be sensitive, it’s really going to pick up biological aging, and it’s reliable and confident. Saying that, I think there are two main things we need to do. One is hopefully do a study where we can look at already known interventions for aging, for example, exercise. It’s the best known intervention, at least that we have currently. So we are hoping that we can look at a cohort where before and after exercise do we see any changes in their biological age based on our metabolites.

And then the second thing we need to do is figure out how early on can we tell a person is biologically aging. Is it in their 30s? Is it in their 50s? Or really we have to wait until their 70s, and then it doesn’t really serve a purpose or maybe much of a purpose.

So I think those two things are important questions to address, and we’re really working towards both of these currently. And if we can get that to go, then I think– I’m really looking forward to having this test a few years from now.

IRA FLATOW: So what you’re saying is it’s very important to determine your biological age possibly even early in life and then keep up with it, keep determining it as you get older because it’s got a great impact?

ADITI GURKAR: Absolutely. Absolutely. Because I think what we are doing in medicine now is only taking care of the symptoms. Once we have a disease, that’s what we are treating. But if we can think of aging as the underlying factor that drives all of these diseases and if we can really intervene early on in life, then hope is we don’t have to treat one disease at a time. We can just have a healthier life for a longer period of time.

IRA FLATOW: A lot of what you said is really interesting and makes a lot of sense. I want to thank you for taking time to be with us today.

ADITI GURKAR: Thank you so much for having me again, Ira. Dr. Aditi Gurkar, assistant professor of geriatric medicine at the University of Pittsburgh School of Medicine in Pittsburgh, Pennsylvania.