A high-fat diet was found to induce obesity and trigger a shift in the gut microbiota, with increases in Streptococcus mitis observed in the distal jejunum and increases in Proteus mirabilis, Lactobacillus animalis, and Enterococcus faecalis recorded in the caecum, according to data presented last week at the 23rd annual meeting of the Society for the Study of Ingestive Behavior in Denver.
These bacteria were also found to damage neurons, thereby affecting their ability to signal, report researchers from the University of Georgia, Washington State University, Binghamton University
“When we switch to a high-fat diet, we reorganize our brain circuits,” explained study co-author Krzysztof Czaja, an associate professor of neuroanatomy in the University of Georgia College of Veterinary Medicine, in a press release.
“We change our brain circuits by eating unbalanced foods, and we also induce the inflammation in brain regions responsible for feeding behavior. Those reorganized circuits and inflammation may alter satiety signaling.”
The study deepens our understanding of the gut-brain axis, and the association between the gut microbiota and weight.
“We should be aware that on a high-fat (and high-carbohydrate) diet, balance in the intestinal microbiota and gut-brain communication—which was developing over thousands and thousands of years in humans and animals—has been interrupted by the introduction of modified foods,” said Czaja. “This leads to the confused brain and inappropriate satiety feedback and results in obesity.”
The researchers used Sprague Dawley rats and randomly divided them into two groups: One was fed a regular rodent diet with 6.4% fat, while the other group ate a high fat diet with 34.9% fat.
Results showed that the high fat diet induced obesity and this was associated with a shift in the intestinal microbiota.
“In the regular physiological state, many different strains of bacteria live in a balanced environment in our intestinal tract,” said Dr Czaja. “When we start introducing a different diet, there is an immediate effect. Suddenly, different nutrients are changing the microenvironment in the gut, and some bacteria begin to overpopulate. Some sensitive bacteria begin to die, and some populations may even vanish. So, introducing a significant change in the gut microenvironment triggers a cascade of events that leads to this population switch.”
All of these changes result in a damage of gut-brain neural connections reflected by an inflammation and miscommunication between the gut and the brain, he added. Additional research will address if this damage is permanent or reversible, he said.
Dr Czaja told us that the conference abstract will be published in Appetite, and a full paper will submitted for publication by the end of this year.
The research was supported by the National Institute on Deafness and Other Communication Disorders.
Source: 23rd annual meeting of the Society for the Study of Ingestive Behavior
July 7-11 in Denver
“Diet-induced obesity is associated with a change in intestinal microbiota, activation of microglia, and reorganization of the nucleus of the solitary tract”
Authors: E.M. Cooper, A.C. Vaughn, P.M. Di Lorenzo, J.L. O'Loughlin, M.E. Konkel, J.H. Peters, K. Czaja