Mechanism linking altered gut microbes with obesity uncovered


There have been many findings from researchers to elucidate the association of gut microbes to obesity. The exact mechanism, however, remains smudged. In a recent study published in the journal Nature, a team lead by Yale University researchers identified a pathway leading to obesity that is linked with altered microbial flora in the gut.

 Photo: Joanna Servaes, Wikipedia
Photo: Joanna Servaes, Wikipedia

In an earlier study, Dr. Gerald I. Shulman, the George R. Cowgill Professor of Medicine, observed that a short chain fatty acid – acetate – stimulated the secretion of insulin in rodents. In the current study, Dr. Shulman with his team of researchers at Yale University experimented on rodents as experimental model to know more about the acetate’s role in obesity.

Dr. Shulman is also an investigator at Howard Hughes Medical Institute.

The initial experiments were to compare the levels of acetate to other short-fatty acid chains in animals. His team found higher amounts of acetate  in animals that consumed high fat in their diet. The acetate also stimulated insulin secretions in beta cells of pancreas. The mechanism of this stimulation was still unfounded.

Hereafter, they injected acetate directly into brain and figured out that insulin secretion was triggered by activating parasympathetic nervous system. It was also reported that it  leads to secretion of hormones gastrin and ghrelin, which in turn lead to an increase in food intake.

Finally, the researchers opted to establish a causal relationship between the gut bacteria and high levels of insulin. Upon transferring faecal matter from one group of rodents to the other, similar effects were seen on gut microbiota, acetate levels, and insulin. There was an increased acetate production which led to increased food uptake. This sets up a positive feedback loop that drives obesity and insulin resistance.

“Taken together these experiments demonstrate a causal link between alterations in the gut microbiota in response to changes in the diet and increased acetate production,” said Shulman.

The team believes that this positive feedback loop has served an important role in evolution, prompting animals towards obesity when they encountered high fat food in times of general food scarcity.

“Alterations in the gut microbiota are associated with obesity and the metabolic syndrome in both humans and rodents,” infers Schulman.

Read press release at Eureka Alert