Anti-appetite Molecule Released by Fiber May Help Overcome Obesity

 Diet  

Researchers have found that small amounts of the short-chain fatty acid acetate, released as a result of the fermentation of dietary fiber in the gut, accumulates within certain neurons in the hypothalamus, a part of the brain that helps regulate hunger.

A
 study led by Imperial College London and the Medical Research Council (MRC), an international team of researchers identified an anti-appetite molecule called acetate that is naturally released when we digest fiber in the gut. Once released, the acetate is transported to the brain where it produces a signal to tell us to stop eating.

Researchers have long realized that consuming a fiber-rich diet will suppress appetite and reduce food intake in both mice and humans, a phenomenon previously attributed to the release hormones in the gut.

"Our research has shown that the release of acetate is central to how fiber suppresses our appetite and this could help scientists to tackle overeating."

This work is the first to establish a link between fermentation in the colon with activity in the brain.

The research, published in Nature Communications, confirms the natural benefits of increasing the amount of fiber in our diets to control over-eating and could also help develop methods to reduce appetite.

The study found that acetate reduces appetite when directly applied into the bloodstream, the colon or the brain.  fiber is found in most plants and vegetables but tends to be at low levels in processed food. When fiber is digested by bacteria in our colon, it ferments and releases large amounts of acetate as a waste product. The study tracked the pathway of acetate from the colon to the brain and identified some of the mechanisms that enable it to influence appetite.

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“The average diet in Europe today contains about 15 g of fiber per day,” said lead author of the study Professor Gary Frost, from the Department of Medicine at Imperial College London. “In stone-age times we ate about 100g per day but now we favor low-fiber ready-made meals over vegetables, pulses and other sources of fiber. Unfortunately our digestive system has not yet evolved to deal with this modern diet and this mismatch contributes to the current obesity epidemic. Our research has shown that the release of acetate is central to how fiber suppresses our appetite and this could help scientists to tackle overeating.”

The study analysed the effects of a form of dietary fiber called inulin which comes from chicory and sugar beets and is also added to cereal bars. Using a mouse model, researchers demonstrated that mice fed on a high fat diet with added inulin ate less and gained less weight than mice fed on a high fat diet with no inulin. Further analysis showed that the mice fed on a diet containing inulin had a high level of acetate in their guts.

Using positron emission tomography (PET) scans, the researchers tracked the acetate through the body from the colon to the liver and the heart and showed that it eventually ended up in the hypothalamus region of the brain, which controls hunger.

Frost commented, “The major challenge is to develop an approach that will deliver the amount of acetate needed to supress appetite but in a form that is acceptable and safe for humans. Acetate is only active for a short amount of time in the body so if we focussed on a purely acetate-based product we would need to find a way to drip-feed it and mimic its slow release in the gut. Another option is to focus on the fiber and manipulate it so that it produces more acetate than normal and less fiber is needed to have the same effect, providing a more palatable and comfortable option than massively increasing the amount of fiber in our diet. Developing these approaches will be difficult but it’s a good challenge to have and we’re looking forward to researching possible ways of using acetate to address health issues around weight gain.”

The research team is now working to determine whether targeted delivery of acetate could be a viable therapeutic option for conditions like obesity down the line.


SOURCE  Imperial College London

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