Transcription
Hello, welcome to a Physionic detailed study analysis. Today, we're going to be going over the effects that glycine supplementation has on longevity. We will focus our attention on a pretty popular study that was released by The Interventions Testing Program (ITP). I won't bore you with too many background details for the time being, but we'll get into the mechanisms, the actual results, and a bunch of other things as well.
If you're not familiar with who I am, my name is Nicholas Verhoeven. I'm a PhD candidate in molecular medicine, and this is what I do: I translate studies into more understandable terms for the public. So, with that introduction out of the way, let's go ahead and jump into this. Let me pull up the data here.
Okay, so what are we doing? We're going over the mechanisms of action, which there is a little bit of fuzziness when it comes to that. I'm going to give you what the researchers point out, but I'm sure that there's probably more than what they mention. Of course, we're going to be answering the main question: does glycine supplementation actually lead to increases in lifespan?
Now, if you're one of the Physionic Insiders and you're interested in joining the Physionic Insiders for the full version of this video, then we'll also be going over whether glycine's effects—whatever effects that we see—are weight dependent. Does weight loss cause these effects, or are they independent of weight loss? The study actually goes over, and the researchers mention, a number of other molecules as well that may or may not have longevity effects, so we're going to cover those. If you're interested in having access to the full version, as well as all my other full study analyses and much more content, including the Physionic podcast, seminars, and all that good stuff, then certainly hop on over to the Insider version of this content. But otherwise, let's go ahead and move forward.
Alright, so mechanisms of action—let's touch on that. Here we have the actual molecular structure of glycine as an amino acid. However, we're going to be using this as our representation for looking at the mechanisms because it's a lot easier than looking at nitrogenous bases, oxygen, and hydroxy groups and stuff like that.
The idea behind glycine really comes down to at least one of the proposed mechanisms of action for glycine. Again, we're not necessarily confirming that glycine works; we're just talking about the mechanisms that have been proposed. It is actually dependent on another amino acid called methionine. The idea being that if you have high methionine levels, they actually activate an enzyme, a master protein called mTOR (mammalian Target of rapamycin). This mTOR molecule, or this protein, has wide-reaching effects on all kinds of other molecules and proteins. The main effect that it has is that it stimulates protein synthesis. Usually, that's a good thing, but there's a good amount of data that says that if you inhibit mTOR specifically, then you're able to have some sort of longevity benefit from that.
Now, there's certainly a lot more nuance to it than what I'm describing here, but other studies have described that methionine restriction leads to reduced mTOR activity, which has also been linked to greater longevity. So, in this context, methionine activates mTOR, leading to greater cell growth and division. In a healthy body, that's perfectly fine, but you may be compensating and eliminating a little bit of that longevity benefit if you're only focused on growth and division. Additionally, in pathological situations—specifically, I really have to emphasize this—cell growth and division and high activity of mTOR is clearly not a great thing because what is a disease that leads to mass cell growth and division? You're right: cancer.
I'm not saying that if you have high methionine, you're going to have cancer; that's not what I'm saying. If you have cancer, then obviously high mTOR activity can be seen as a negative. Anyway, the point being that if you have high methionine, you have high activity of mTOR, and you have high cell growth and division, among many other things—I'm certainly simplifying here—which then is linked to reduced longevity, or you're not getting that benefit to longevity.
So, where does glycine fit in here? Well, glycine can be dimethylated, meaning that methionine, instead of acting on mTOR, can interact with glycine and give up some of its methyl groups. Essentially, if we go back here, some of the structure of methionine then changes; the chemical structure of the molecule changes, and it donates these methyl groups to glycine. In doing so, it typically goes through a number of other reactions—again, I'm oversimplifying here—but methionine, according to the researchers, can then be extruded or released out of the cell, which means that you have less activity of mTOR. This is the opposite of what we were just talking about, therefore potentially conferring some level of a longevity benefit. Again, a lot of this is speculation; there's a little bit of data on it that the researchers point out, but I think that when it comes to glycine's mechanisms of action, there's still a good amount that needs to be discovered.
I'll cover more mechanisms in the future, but this is one of the mechanisms that's proposed by the paper that we go over. Another mechanism is related to inflammation. Chronic inflammation is certainly not wanted; it's not something that lends itself well to long-term survival. If we take an immune cell here, for any immunology nerds out there, we're looking at a granulocyte. The reason we know that is because there are a bunch of granules inside the cell—could be a neutrophil, for example. Anyway, we have these granulocytes, which are immune cells, and if we were to zoom into the membrane of this granulocyte, we have the cell membrane here, the inside of the cell, and the cytosol, which is all the watery liquid that makes up the inside of the cell. It's separated from the extracellular matrix or the outside of the cell, the extracellular fluid.
Inside, embedded in this membrane, are chloride channels or channels in general that control the flux of, in this specific situation, an ion called chloride. So, why do we care about that? We care about that because generally, outside of the cell, there are more positive ions, meaning that relative to the outside of the cell, the inside of the cell is a lot more negative because there are fewer of these positive ions. If you have fewer positive ions here and more positive ions outside, that means this is more negative than it is outside.
So, why does that matter? When you activate a cell—this can be a neuron, a muscle cell, or any cell—in this case, we're talking about an immune cell, so greater activity of a potentially pro-inflammatory cell means it needs to become more positive. It has to go through a procedure called depolarization to become activated. The way that happens is through the influx of these positive ions into the more negative section of the cell, the cytosol, which then obviously means that the actual inside of the cell becomes more positive.
That's called depolarization, and then the cell goes through a process called repolarization and hyperpolarization. I'm not going to go into that. The point being that you have this activation of the cells. In the context of a pro-inflammatory cell—a cell that is essentially quiescent, just kind of moving through your system, and then it gets activated to become more pro-inflammatory—this means they'll start releasing different pro-inflammatory molecules, which recruit more immune cells and can potentially lead to more oxidative stress and more immune damage to particular tissues of other cells. You typically don't want to be in this chronic state of these cells constantly being activated.
According to these researchers—I'll show you the paper that we're going to be going over—one of the proposed mechanisms is that when you have this activation through these ions entering into the inflammatory cell, it leads to this activation to a pro-inflammatory state. So, where does chloride come in here, and where does glycine come in? Well, glycine can bind to the chloride channel and somehow stabilize it, having some form of effect. I think it's a little unclear on exactly how—if it leads to conformational change, which means that the chloride channel changes its shape in some way, or if it's just through what's known as allosteric regulation, which means that glycine will then bind to the channel and lead to its activity or greater activity or reduced activity.
The point being that glycine somehow interacts with the chloride channel, which then allows more chloride into the cell. Now, we were talking about all these positive ions; chloride, however, is a negative ion. So, remember, we're trying to keep this as negative as possible inside the cytosol, inside the cell itself. If you input more negative ions, that would then reduce the membrane potential, making the cytosol more negative relative to the outside. If you're taking up more negative ions, that's the general idea.
Now, again, a lot of this is still speculation. I'm not saying that they're pulling this out of thin air; they have some data to back this up. But I still think that, for example, there are certain things that you have to keep in mind, like what's the concentration of chloride compared to these positive ions, which are typically sodium and potassium, especially sodium? So, what's the concentration? My understanding is that chloride is actually a pretty small percentage compared to the rest of the ions. So, how much of this actually makes a difference? I'm relying on the researchers to have some idea and have adjusted for some of this stuff, but there's certainly room for a lot of investigation on glycine's direct effects.
But anyway, this is one mechanism by which it's been thought to have an anti-inflammatory effect, which then, of course, is going to affect longevity because you're reducing chronic inflammation as a whole. Okay, so those are the mechanisms. Again, there's a lot of room for improvement, and maybe I can get into that as more research comes out specifically looking at glycine. I know that there's been research on GLX (glycine plus N-acetylcysteine), and that has effects on glutathione and antioxidant ability and whatnot. But for the time being, let's just focus on glycine alone.
So, the next question is: does glycine actually lead to a lifespan effect? I mean, it's great that we just looked at two kind of minor mechanisms that may or may not be the reason why, but what does it actually have an effect on? Okay, so let's find out. We're going to be relying on this study right here, which is study 297. It is publicly funded. If you want to know about the funding as well as conflicts of interest and whatnot, there is one conflict of interest. I think there's one author that is affiliated with a glycine-selling company. If that makes a big difference for you, then certainly understand. The rest of the authors, however, do not have any conflicts of interest, and the study is publicly funded. If you want more details on that, then download the document that I'll have; it's freely available for you and has more details on the study, including the conflicts of interest and where the public funding came from.
Okay, so how did they go about this? People are already screaming because they're seeing mice. The bottom line is, if you want to do lifespan types of studies, you have to use animals that live less long than humans. Otherwise, you're going to be waiting around your entire life to have a study in humans that lasts 60 years or 70 years or whatever to determine some sort of lifespan effect. We can do that, but controlling for those kinds of studies is basically impossible. That's why we rely on associative studies. But then people scream, "Oh, well, we shouldn't be using associative studies." I could go on a rant about how I completely disagree with that. You just have to balance the context of each type of study and understand the weaknesses and strengths.
The strengths of a study like this are that because mice only live about two years—maybe a little bit beyond—you can actually do these studies and figure out if there's a lifespan effect. The next best thing might be monkeys, for example, which certainly live much longer than mice, which also makes them a lot more expensive for these kinds of studies. But that's also extremely rare to get those kinds of studies.
There are some unique aspects about the study. At the very beginning, in the introduction, I did mention that this is done in the ITP, the Interventions Testing Program. Why is that important? For two reasons: one reason is that this is done in heterogeneous mice. A lot of studies that have been done in mice are done in a more homogeneous mouse population. Think of humans: we are humans, right? You wouldn't disagree. If you saw another human, you'd be like, "Oh, that's a human." Not that you'd sit there and be like, "Hello, human," but you would subconsciously understand this is a human being, as opposed to when you interact with a dog. You're like, "This is a dog." You're not going to be like, "Let's discuss the philosophies of Immanuel Kant or something like that with a dog," but you might with a human, depending on their education level. They will understand at least the words that you're saying to them.
So, you understand this is a human being. The reason is that they have a genetic profile; they have a genome that is very similar to yours, and it's basically identical, except that there are some teeny tiny nuances that make them a specific subcategory of human. They may have red hair, or they may have blue eyes, or they may have whatever. There are different little differences between you as a human and them as a human. That's what creates heterogeneity—there are little differences between all humans, although we are all humans. The same is true for mice.
A lot of the studies that have been done have been done in these mice called C57BL/6 mice. It's not necessarily a problem with that, except that the liability, if you want to apply this, is that if all the mice have pretty much a very similar genetic background, then how do you know that this actually applies to not even humans, but does it actually even apply to other types of mice? In this situation, what the ITP does is they specifically focus on heterogeneous mice—mice that are very different from one another genetically, but they are still mice, just like people are still people. They're just very different types of people within the grand category of people. That's what allows them to distinguish if there's an effect of a molecule like glycine and whether it applies to a wide range of mice.
So, that's one big advantage of this study over other mouse studies. The second big advantage is that in the ITP, they have three different labs. One of the main critiques of science is that can we reproduce the data? The beauty of the ITP is that they're essentially reproducing the data within the same study. They have a population of mice that are given glycine by completely independent researchers in Michigan. They have another group of mice that are by an independent group of researchers at the University of Texas, and then the last one is at Jackson Laboratory.
Jackson Laboratories is the laboratory that's most well-known for having massive strains of mice, and that's where a lot of researchers get their mice. They ask, "Hey, Jackson Laboratories, can we have X amount of these types of mice?" and they pay for them. They pay a certain amount of money, and then they get shipped to these different installations, different universities. Jackson Laboratories is well-known for having mice and robust facilities for this kind of stuff. They also have their own researchers, and they do the exact same thing.
Now, you have three independent labs that are conducting everything independently of one another, and then they pull the data together. We still have the data independently, and then we can pull the data together to see if there's an overall effect. Now, we're talking about this being really expensive—this is hundreds of mice that are being used for these experiments. We're not talking about like four mice at Jackson and three mice at Michigan; we're talking hundreds of mice, which creates so much data that they can pull together. If you have many different mice that you're measuring, then you're getting more and more data, which really creates supreme sensitivity in the ability to come to a conclusion, which is what we're going to hopefully be able to do.
So, that's a huge advantage of the ITP. Okay, that said, what's the study design? It's really simple. They just used different groups of mice, and they either gave them the regular mouse food—just let them live for their entire lives, grow up from 8 weeks old all the way to 20-something weeks old. They live for a long time, about 2 years, maybe a little bit more. They're given their normal food, or they're put into a different group where they're given their normal food plus supplemented with glycine.
So, what happens when they supplement with glycine? Okay, we can look at this data right here. First of all, here we've got female mice, here we've got male mice, and here we've got all both sexes put together—pooled data. This is from all three labs; all their data has been pulled. In the next slide, we're going to break apart the labs and look in more detail at each lab.
So, the control mice are the ones that are fed just chow—no glycine—and the female mice with glycine are obviously the ones supplemented with glycine. Here we've got the lines or the different dots that make up the overall line, and that is the mice that are still alive at this point. So, at 200 days, 100% of the mice are alive. At 400 days, I don't know, we'll say like 98% of the mice are still alive, and so on and so forth. You have the days of age over on the horizontal axis (the x-axis), and you have survival. The lower it goes, then that means that you have more and more mice that have died. This is survival, so once you reach down here and you're at zero, that means all the mice have died. What you're looking for is a shift to the right. Does one line shift more to the right than the other line, or are they basically superimposed on one another?
We also have the p-value here to indicate the statistical significance of this effect, so we're not just basing things off of our eye. The blue is the controls, and the yellowish is the glycine-given mice. We've got males over here, and we've got the pooled data. What we see is that in the pooled females, we see that it shifts to the right, indicating that the glycine-supplemented mice do live longer. Their overall average lifespan seems to be longer, and we're going to look at the actual numbers in just a little bit.
Then, when we look at the male mice, it seems like pretty consistently that it's also the case—statistically significant. The male mice also have this statistical effect, and then, of course, if you have two statistically significant effects and you're increasing the sample because now you're combining the female mice plus the male data altogether, then we have the pooled data, which also indicates it's statistically significant. So, this data alone already indicates yes, glycine does have a longevity benefit. But how much of a longevity benefit?
Okay, before you freak out, this is really easy to read. I'm going to walk you through it, but this is all the data—all of this data is what came out of this. But now we're looking at the actual numbers themselves. Here we've got pooled data across both sides, or I guess I should say all three sites. We've got the Jackson Laboratory data here, we've got the University of Michigan right here, and we've got the University of Texas data right here.
Before I go into this, I just want to let you know that I actually have a course to teach you how to read studies for yourself so you can make decisions more easily. Usually, it focuses more on randomized control trials and meta-analyses because that's what I think most people should be focused on. So, if you're interested in accessing that, then certainly check it out; it's in the description box, and I'd love for you to join and learn how to read studies just like I am right here today.
But that said, let's actually get into the data itself. Okay, so here we've got female control. I'm going to focus on the pooled data, but I am going to point out a few things about the individual data, and all this applies across the board. So, if we focus on the pooled data, we've got the control female (non-glycine supplemented), glycine supplemented female, control male, and glycine male, and then both combined together. Here we've got the p-value for the actual effect and the actual data over here.
So, the median number of days that they survive—what you're doing here is comparing the control female versus the glycine supplemented female and the control male versus the glycine supplemented male. You don't have to do the calculation in your head because they actually have the relative percentage right here. So, how much of an increase in lifespan is there in the female mice? About a 3.7% increase in median lifespan. For males, it's a bit higher—about a 6.2% increase in median lifespan. Now, another statistic that they do—and of course, these are both statistically significant—now another statistic that they do is they look at the P90, which indicates—and let me look at my notes here to just make sure that I represent this absolutely correctly—P90 is the number of days at which 90% of the mice have died, so just the remaining 10% are around.
The oldest mice—do they get an additional longevity benefit? If we look at that, what they do for this, just to be clear, is they use a Wang-Allison test. This Wang-Allison test is attributed to this P90 statistic. So, here you don't fully need to understand that; just know that this is the p-value for the P90 measure here. We've got 1.8% for the oldest female mice versus the control mice, and we've got a 4.5% increase for the oldest male mice versus the control mice. We've got a p-value here for the male mice, but we don't have that p-value here for the female mice.
So, the oldest male mice still experience a benefit, but the oldest female mice do not experience a benefit. However, they still experience a benefit on the median, so the males get both benefits, and the females get some benefit just in a different way. Okay, so that's how you would apply this data—these data right here—to the rest of this over here.
Now, I'd like to point out one thing here. The one thing I'd really like to point out is that for the Jackson Laboratory, there's basically no effect when we're looking at median lifespan for the males. That doesn't mean that they lose their longevity; it just means that there's no effect. I know that says minus one, so you would think they lose 1% of their life, but it's not statistically significant. Therefore, the true interpretation would be that we don't have statistical significance; therefore, there's likely no effect.
Now, we still see the effect for females, but the majority of the male effect is occurring at the University of Texas, with 9% here and 10% here. So, is this maybe site-specific and mainly driving most of this effect? That's a possibility, but we do see a little bit of an effect in Michigan, and we still see an effect when we're looking at the P90 for the Jackson Laboratories. I just wanted to point out that the most robust effects—I'll put it that way—are found at the University of Texas. There is some repeatability that is also seen in the other two laboratories, but still, I just wanted to point that out.
So, overall, however, these data indicate that glycine does have a lifespan extension effect.
Okay, so the midpoint conclusion at this point—unless you're going to be continuing on with the Insider version of this—is that glycine supplementation extends lifespan in heterogeneous mice across three different laboratories. If you're interested in continuing on, we're going to go over the weight-dependent glycine effects, as well as some other longevity molecules that were tested and some of the ones that were mentioned by the researchers. But if you're not interested in continuing on, then let me just say thank you for joining me up to this point.
If you'd like to learn how to analyze studies for yourself—go from absolute beginner to being able to be proficient and bring studies to your doctor and have conversations with your doctor—then certainly consider joining my course, which I put a lot of work into, and I'll certainly be continuing to add more content to it and try to improve as much as possible.
With that said, thanks for joining, and I'll catch you in the next one. Bye!