Gut Microbes Alter Host Gene Expression

New research has found that changes in diet affect our gut microbe population and in particular our health. More evidence has shown the important role bacteria plays in our gut and how they alter gene expression depending on diet preferences. Researchers discovered that western diets poor in whole plant food rich in fiber do not provide nourishment for the microbes. The number of microbes in our guts can reach in the trillions and weigh as much as 2 kilograms (4 or 5 pounds). Through fermentation, they help to digest food and produce compounds called metabolites that help the immune system and act as a barrier to infections. The report was published in the journal Molecular Cell by a team of researchers from the University of Wisconsin-Madison.

Metabolites Found to Communicate with the Epigenome

In our DNA are genes which make up the code that makes life possible. However, genes can be altered by many environmental factors which switch some genes on or off. The complete set of genes that make up our entire DNA is called the genome, and molecules called epigenome communicate with the genome.

In the study, researchers used lab mice in two groups with different diets:

• one group was fed plant food high in carbohydrates to mimic a human diet rich in fiber
• the other group was fed a diet of sugar and fat to mimic a typical western diet

After the tests, they found small levels of molecules which were communicating with cells of the mice through the epigenome. UW-Madison  Professor John M. Denu suggests that metabolites (compounds created by gut microbes) and possibly many other compounds were communicating with the epigenome.

The team then compared the mice fed the western-style diet to those fed the plant food diet, and discovered the western diet deterred many epigenetic changes that occur naturally with the plant diet. The researchers then supplemented the diet of the mice that were fed fats and sugars with metabolites. This supplementation restored the proper epigenetic changes seen in the group of mice fed plant food.

Western Diets Deemed Unhealthy for Gut Microbes

Professor Denu and his colleagues suggest the study helped to prove that metabolites that are produced by microbes in the gut when fed a plant-based diet are the major communicators to the epigenome. They call the microbe functions "microbial metabolism." It turns out that food rich in sugar or fat are easily digested but are not a good source of nutrients for the gut bacteria. When the microbes are starved under this diet, the result is a less diverse microbiome with poorer communication with the epigenome.

A surprising result of the study was the discovery that these complex communications in the gut microbiome are not confined to the colon but also between liver cells and fatty tissue inside the gut. This study has profound implications for future studies of the complex interactions between different diets and a healthy gut microbiota.

Scientists are beginning to understand the mechanisms of the bacteria in the microbiome. This study has revealed that gut microbes which are fed a fiber-rich diet of fruits and vegetables produce metabolites that can positively affect our health. But the underlying mechanisms are still poorly understood, and further research in this area could give scientists the tools to create microbiota supplements. This would be a breakthrough for people who eat a western style diet because microbes in the gut help digest excess food thus helping to maintain a healthy weight.