Aug. 12 (UPI) -- That a high-fat diet increases a person's risk for heart disease has long been known, but researchers now think they understand the process behind this link.
A high-fat diet disrupts the biology of the gut's inner lining and the bacteria that help break down food, producing a substance that, while involved in the digestive process, may contribute to the development of heart disease, a study published Thursday by the journal Science found.
Experiments in animals as part of the research revealed that the intestines and gut microbiome, or the bacteria lining the walls of the intestines, play a key role, study co-author Mariana Byndloss said in a press release.
"Right now, roughly 40% of the U.S. population is obese, and that percentage is predicted to climb," said Byndloss, an assistant professor of pathology, microbiology and immunology at Vanderbilt University Medical Center in Nashville.
"Our research has revealed ... how diet and obesity can increase risk of cardiovascular disease by affecting the relationship between our intestines and the microbes that live in our gut," she said.
Epithelial cells lining the intestines and gut microbes have a mutually beneficial relationship that promotes a healthy gut environment, according to a study authored by Byndloss and her colleague Andreas Bäumler that was published in January by the journal mBio.
These changes may also affect immune health, according to research published in June by the journal Nutrients.
For this new study, they explored whether obesity affects this relationship using animal models.
They found that a high-fat diet causes inflammation and damages intestinal epithelial cells, impairing the function of energy-generating mitochondria.
Impairing the function of mitochondria, the part of cells that produce energy, causes intestinal cells to produce more oxygen and nitrates, researchers said.
This process, in turn, stimulates the growth of harmful microbes such as E. coli, and boosts bacterial production of a metabolite called trimethylamine, or TMA, according to the researchers.
The liver converts TMA to trimethylamine-N-oxide, TMAO, which has been linked with the development of atherosclerosis, or the build up of fatty plaques in the arteries, the researchers said.
Atherosclerosis is a leading cause of heart disease, they said.
"It was known that exposure to a high-fat diet causes dysbiosis -- an imbalance in the microbiota favoring harmful microbes, but we didn't know why or how this was happening," Byndloss said. "We show one way that diet directly affects the host and promotes the growth of bad microbes."
A drug called 5-aminosalicylic acid, which is currently approved for treatment of inflammatory bowel disease, restored the function of intestinal epithelial cells and limited the increase of TMAO in the animals used in the study, the researchers said.
Using the drug in combination with probiotics, or healthy micro-organisms found in foods such as yogurts and dietary supplements that restore gut bacteria, may help preserve healthy intestinal environment and reduce heart disease risk.
"This is evidence that it's possible to prevent the negative outcomes associated with a high-fat diet," Byndloss said.
"Only by fully understanding the relationship between the host -- us -- and gut microbes during health and disease are we going to be able to design therapies that will be effective in controlling obesity and obesity-associated outcomes like cardiovascular disease," she said.
