Excess gut bacteria may lead to obesity and diabetes, researchers reveal

An overgrowth of bacteria in the stomach could change the way the liver processes fat, which may lead to the development of metabolic syndrome, according to researchers.

Metabolic syndrome refers to a group of conditions including obesity, type 2 diabetes, high blood pressure, high blood sugar and excess body fat around the waist, the team from Penn State University (PSU), says. Those who suffer from three or more of these risk factors are considered to have metabolic syndrome and are vulnerable to liver and heart diseases.

While most studies recommend the intake of high-fiber rich diets to improve many aspects of health, the new research reveals that in a certain segment of the population, this advice could be doing more harm than good.

During a mice experiment, the researchers found that overconsumption of dietary fiber may have adverse consequences when there’s excess in gut bacterial and compromised function of toll-like receptor 5 (TLR5).

TLR5 is part of one’s immune system that maintains gut-bacteria homeostasis, which prevents the overgrowth of bacteria in the stomach. Approximately 10 per cent of the human population has a genetic mutation in TLR5, which results to a weakened immune system. People with weak immune systems condition have a higher risk of developing metabolic syndrome, says Matam Vijay-Kumar, assistant professor of nutritional sciences and medicine at Penn State.

According to the PSU team, a human’s gut bacteria can ferment the plant-derived fibres and release them as energy-rich short-chain fatty acids, such as acetic acid. Once they reach the liver, these compounds convert into lipids and add to fat deposits that could potentially lead to the development of metabolic syndrome, especially in those who lack TLR5.

“Our present study suggests that bacterial fermentation of dietary fiber and the production of short-chain fatty acids contribute to deposition of fat in the liver,” Vijay-Kumar says.

He says short-chain fatty acids may be beneficial to health, but could be unfavorable in certain individuals, when their gut bacteria generate uncontrolled short-chain fatty acids for a prolonged period of time.

The researchers found that the combination of unchecked bacterial fermentation, short-chain fatty acids and increased liver lipids can cause non-alcoholic fatty liver disease, leading to liver damage.

For their next steps, the team hopes to analyse the long-term effects of short-chain fatty acids, specifically in experimental models of type 2 diabetes. They believe that their studies would lead to personalized cautioned dietary intake of plant-derived fiber in individuals with compromised immune systems.

In Australia, more than 35 per sccent of adults have metabolic syndrome, while non-alcoholic fatty liver disease is reported to affect up to one-third of the adult population and is increasingly becoming common in children.

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