Gut microbes controlling our genes

26 November 2016
Posted by Kerstin Göpfrich.

The microbes in our gut turn our genes on and off - and the healthier we eat, the more they do so, a new study finds.

Trillions of mMicrobiomeicrobes - bacteria, fungi and viruses -  reside in the human gut. They play a crucial role for our health by helping the immune system and the process of digesting food. It has been known for some time that diet influences the balance of microbes in our bodies. But until this week, it was unclear until now how exactly this can affect us.

A team at University of Wisconsin-Madison led by Prof. John Denu found that small molecules secreted by microbes alter the so-called epigenome, the chemical information on the DNA which determines whether or not a certain gene is active.

In the paper published in Molecular Cell, the researchers compared the epigenome of germ-free mice with mice that had an active gut microbiome and were either fed a high-fat, high-sugar Western-type diet or a more healthy diet rich in fruits and vegetables.

"The poor diet was suppressing the communication between the gut microbiome and the host epigenome," says Denu.

A Western diet does not provide a good nutritional source for the microbes, reducing their metabolic activity and hence their impact on their host's epigenome.

In particular, an active microbiome helps regulate genes related to diabetes, metabolism and the immune system.

The researchers identified three fatty acid molecules produced during the metabolism of the gut microbes which were responsible for the altered gene activity - acetate, propionate, and butyrate.

If these molecules were fed to mice without active gut microbes, similar epigenetic alteration were observed as for the mice consuming a healthy diet.

But Denu does not advocate supplementing the diet with short-chain fatty acids as a way around eating healthily, as there are many more benefits to good food.

It remains to be clarified to what extend these findings hold true in humans.

"Obviously that's a complex task," Denu says. "But we know that human microbial communities also generate these short-chain fatty acids, and that you find them in the plasma in humans, so we speculate the same things are going on."

The researchers found that the chemical communication between the microbiome and host cells even reaches tissue that is located far away from the gut.

"We're starting to understand the mechanism of how and why diet and the microbiome matter."

Let's feed the good guys in the gut!

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