Diet affects epigenome through gut microbiota

Diet affects epigenome through gut microbiota


Excerpt: "You are what you eat, the old saying goes, but why is that so? Researchers have known for some time that diet affects the balance of microbes in our bodies, but how that translates into an effect on the host has not been understood. Now, research in mice is showing that microbes communicate with their hosts by sending out metabolites that act on histones—thus influencing gene transcription not only in the colon but also in tissues in other parts of the body. The findings publish November 23 in Molecular Cell.

In the study, the researchers first compared germ-free mice with those that have active gut microbes and discovered that gut microbiota alter the host's epigenome in several tissues. Next, they compared mice that were fed a normal chow diet to mice fed a Western-type diet—one that was low in complex carbohydrates and fiber and high in fat and simple sugars. Consistent with previous studies from other researchers, they found that the  of mice fed the normal chow diet differed from those fed the Western-type diet.

"When the host consumes a diet that's rich in complex plant polysaccharides (such as fiber), there's more food available for microbes in the gut, because unlike , our human cells cannot use them," explains Federico Rey, an assistant professor of bacteriology at UW-Madison and the study's other senior author.
Furthermore, they found that mice given a Western diet didn't produce certain metabolites at the same levels as mice who ate the healthier diet. "We thought that those metabolites—the short-chain  acetate, propionate, and butyrate, which are mostly produced by microbial fermentation of fiber—may be important for driving some of the epigenetic effects that we observed in mouse tissues," Denu says.
The next step was to connect changes in metabolite production to . When they looked at tissues in the mice, they found differences in global histone acetylation and methylation based on which diet the mice consumed. "Our findings suggest a fairly profound effect on the host at the level of chromatin alteration," Denu explains. "This mechanism affects host health through differential gene expression."

"Fruits and vegetables are a lot more than complex polysaccharides," Rey says. "They have many other components, including polyphenols, that are also metabolized in the gut and can potentially affect chromatin in the  in ways that we don't yet understand. Short-chain fatty acids are the tip of the iceberg, but they're not the whole story."

My comment: Diet is the most significant factor causing changes in the genome. There are several mechanisms known how nutrients impact the epigenome but microbiota mediated gene regulation is one of the most interesting types. This discovery provides a perfect example of cause and effect, signal and response, laws that organisms use within ecological adaptation. These mechanisms have nothing to do with random mutations or natural selection. A couple of living examples: