The diet that raises the risk of disease

There has been a rapid increase in recent decades in the prevalence of incidents colon cancer and even in people under the age of 50, with scientists trying to discover the causes behind this development. The ever-increasing obesitywhich arises as a result of modern dietary patterns, and the drafts, highly processed foods seem to have an important role in the emergence of new cancer cases.

Now, researchers from the Salk Institute and UC San Diego have discovered by studying mice how one high fat diet it can alter gut bacteria, altering bile acids and thus increasing the risk of developing colon cancer. The related work was published in Cell Reports.

The research team found increased levels of specific gut bacteria in mice fed high-fat diets. These gut bacteria have been shown to alter bile acid composition, causing inflammation and affecting the speed of intestinal stem cell replenishment.

Bile acids are produced by liver and are used by intestine for digesting food and absorbing cholesterol, fats and nutrients. In 2019, the team of Professor Ronald Evans, director of Salk’s Gene Expression Laboratory, conducted a study in mice, the results of which showed that high-fat diets boosted total bile acid levels. Shifting bile acids turned off the Farnesoid X receptor (FXR), a key gut protein, increasing the prevalence of cancer.

In the new research, the team of Dr. Evans collaborated with the labs of Rob Knight and Pieter Dorrestein at UC San Diego to examine the microbiomes and metabolomas -collections of dietary and microbial-derived micromolecules- in the digestive tracts of animals fed high-fat diets. The mice in this study had a genetic mutation which made them more susceptible to developing tumors in the colon.

The scientists discovered that although mice fed high-fat diets had more bile acids, this concentration was characterized by a reduced diversity, but also an increased prevalence of modified bile acids, which reduced the proliferation of stem cells in the intestines. When these cells are not replenished frequently, they may accumulate mutations, which favors the development of cancer.

Striking differences were also noted in the microbiome of mice fed high-fat diets: The gut bacterial collections in the digestive tracts were less diverse and contained different bacteria than the microbiomes of mice not fed high-fat diets. Two of these bacteria, Ileibacterium valens and Ruminococcus gnavus, were behind the production of the modified bile acids.

To the surprise of experts, a high-fat diet actually had a greater impact on the microbiome and altered bile acids than the genetic mutation that made the mice more prone to cancer.

“THE microbial balance in the gut is ensured by diet. We are now discovering that changes in the gut microbiome may favor the development of cancer. “We identified how a high-fat diet affects the gut microbiome and remodels the bile acid pool, pushing the gut into a disease-associated inflammatory state.” says editor Ting Fu, associate dr. Evans.

Researchers believe that high-fat diets alter the composition of the microbiome, encouraging the growth of bacteria such as I. valens and R. gnavus, which in turn boosts levels of modified bile acids. This interaction follows a vicious cycle path, creating a more inflammatory environment, which can further alter the bacterial composition of the gut.

“THE this discovery opens new avenues of interventions for cancer prevention. By knowing what the problem is, we have a much better idea of ​​how to prevent it“, concludes Dr. Evans.