How Gut Bacteria Affects Aging

How Gut Bacteria Affects Aging 

Huang, Y., Chen, X., Ye, J. et al. Causal effect of gut microbiota on DNA methylation phenotypic age acceleration: a two-sample Mendelian randomization study. Sci Rep 13, 18830 (2023). https://doi.org/10.1038/s41598-023-46308-4

Introduction

In our digestive system, there's a big and diverse group of bacteria known as the gut microbiota. It's made up of about 1000 to 1150 different types of bacteria. Recently, scientists have been studying it a lot because it's closely linked to how our immune system works, how we process food, and the development of diseases. This group of bacteria changes as we grow up and get older. So, understanding how it's connected to aging is crucial for finding ways to slow down aging and prevent age-related diseases. 

The epigenetic clock, a tool created in 2018, uses gene changes to estimate how old someone's body is, which can be different from their actual age. It's better at telling us about a person's real aging and how long they might live compared to just looking at their birthday. We know that the bacteria in the gut (GM) are linked to aging and some diseases, but we're still not sure if they directly speed up how our genes change with age. 

Mendelian randomization (MR) is a scientific method used in research to figure out if one thing causes another. It uses certain genes as clues to see if there's a cause-and-effect relationship between things, like a health factor and an outcome. It's become popular in medical research because it helps to deal with tricky issues like other factors messing up the results. This study is all about using MR to see if the bacteria in the gut affect how our genes change with age 

Methods

The researchers ran two tests to make sure the connection between gut bacteria (GM) and how our genes change with age is reliable.

The first test, called the heterogeneity test, checks if different genetic markers (SNPs) linked to GM show similar results. If they don't, it suggests that the link between GM and aging might not be strong or consistent.

The second test, called the horizontal pleiotropy test, looks for any hidden factors that might be messing up the results. If they find such factors, it could mean that something other than GM is influencing how our genes change with age.

Out of the 12 GM species they studied, the ones that passed both of these tests were considered to be the most likely to affect how our genes age. Some of them seemed to speed up the aging process, while others seemed to slow it down. They used a heatmap, which is like a visual chart, to show how these 12 GM species affect the aging of our genes.

Results

Many studies have shown that changes in gut bacteria (GM) are linked to the aging process, but there's still uncertainty about whether one causes the other in most of these studies. In healthy adults, specific types of bacteria like Bacteroidetes and Firmicutes are usually more common in the gut, while Actinobacteria and Proteobacteria are less common. However, as people age, the levels of Bacteroidetes and Proteobacteria tend to go up, and the overall variety of GM decreases. Because GM is incredibly diverse and complicated, finding the exact GM changes related to aging is tricky. So, this study aimed to use a special analysis method to figure out if GM directly affects how our genes change with age, focusing on epigenetic clocks.

We discovered that some types of bacteria in our gut can either make our bodies age faster or slower. It's like having different travel companions on our journey through life, and these companions can affect the pace of our journey, which is how our genes age. We found that seven of these bacteria made our genes age a bit faster, while five of them slowed down the aging process. It's not a straightforward relationship because different bacteria have different effects. Some can speed up the aging process, and some can slow it down. Our findings match what other studies have found – for example, one study showed that a certain bacterium could slow down aging in animals, which is similar to our results. Another study found that a specific group of bacteria was linked to longer life, which supports our findings. In a nutshell, our research shows that the influence of these bacteria on how our genes age is quite complex and fascinating.

Researchers have been exploring the idea of using fecal microbiota transplantation (FMT) as a way to promote longevity by transferring the gut bacteria of healthy and long-lived individuals to others. This could potentially slow down the aging process. While some studies have hinted at a connection between gut bacteria (GM) and aging, the results from different studies don't always match up. So, more research is needed to really understand how different types of GM affect how our genes change with age. 

There are a couple of things to keep in mind with this study. First, most of the data we used came from people in Europe, so it might not apply to other places or ethnic groups. Second, we didn't look at exactly how different types of gut bacteria affect the aging process. To get a better understanding, we need more data from a larger group of people and some experiments in the lab.

Conclusion

The findings of this research shed light on the complex relationship between gut microbiota and the aging process. While our study points to the potential influence of specific gut bacteria on how our genes change with age, it's clear that this is a multifaceted puzzle. We've uncovered valuable insights that could have implications for clinical applications like fecal microbiota transplantation and personalized treatments. However, there's still much more to explore, particularly regarding the mechanisms involved and the potential variations among different populations. As we continue to unravel the mysteries of aging and gut bacteria, this study serves as a stepping stone for further investigation, which may ultimately lead to innovative approaches to enhance longevity and overall well-being.