Gut bacteria could be blamed for obesity and diabetes

October 29, 2015, Pennsylvania State University

An excess of bacteria in the gut can change the way the liver processes fat and could lead to the development of metabolic syndrome, according to health researchers.

Metabolic syndrome is a group of conditions including obesity, type 2 diabetes, , and excess body fat around the waist. People experiencing three or more of these conditions are considered to have and are vulnerable to liver and heart diseases. Approximately 20 to 25 percent of adult Americans have the syndrome, according to the American Heart Association.

Research supported by the National Institutes of Health has recommended that Americans add more fiber to their diets because higher fiber diets have been found to improve many aspects of health. However in a certain segment of the population, this advice could be doing more harm than good.

"It is a common misconception that plant-derived dietary fiber contains zero calories," said Matam Vijay-Kumar, assistant professor of nutritional sciences and medicine at Penn State.

While it's true that neither people nor mice can digest plant-derived fiber, their gut bacteria can readily ferment the fibers and then 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 people and mice lacking toll-like receptor 5 (TLR5).

TLR5 is a receptor for bacterial flagellin and is part of the innate immune system that maintains gut-bacteria homeostasis, keeping gut bacteria from over-proliferating. Approximately 10 percent of the human population has a genetic mutation in TLR5, resulting in a complete lack of its function, according to Vijay-Kumar. These individuals have a weakened immune system that may increase the risk of developing metabolic syndrome.

"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," said Vijay-Kumar, adding that it may be detrimental to the liver if these processes become dysregulated, especially in individuals with excess gut bacteria commonly associated with intestinal and liver disorders.

Short-chain fatty acids may be beneficial to the host's health, but could be unfavorable in certain contexts where dysregulated generate uncontrolled short-chain fatty acids for a prolonged period of time.

In the current study, published today (Oct. 29) in the journal Cell Metabolism, the researchers found a link between unchecked bacterial fermentation, short-chain fatty acids and increased liver lipids—which can cause non-alcoholic fatty liver disease, leading to damage. They also found that overconsumption of may have adverse consequences in mice with compromised TLR5 function and gut bacterial overgrowth.

"Most of the observations describing the beneficial effects of short-chain fatty acids in metabolic disorders are from short-term studies and primarily from healthy subjects and experimental animals," said Vishal Singh, postdoctoral fellow in nutritional sciences, Penn State. "Our next goal is to analyze the long-term effects of short-chain , specifically in experimental models of type 2 diabetes and/or metabolic syndrome. We envision that our studies would drive the field towards 'personalized' cautioned dietary intake of plant-derived fiber in immunocompromised individuals."

Explore further: Dietary fat impacts autoimmune flare-ups in mice

Related Stories

Dietary fat impacts autoimmune flare-ups in mice

October 20, 2015
Dietary fat may impact the severity and duration of autoimmune flare-ups, suggests a study published on October 20 in the journal Immunity. Adjusting the length of fatty acids consumed by mice altered the function of T helper ...

Study reveals a key role your gut bacteria play in body's self-defense

October 19, 2015
Chalk up another reason why your gut bacteria are so critical to your health—and why these microorganisms could be the key to preventing a host of diseases. Scientists in Sweden have discovered that human intestinal flora ...

Intestinal worms 'talk' to gut bacteria to boost immune system

October 27, 2015
EPFL researchers have discovered how intestinal worm infections cross-talk with gut bacteria to help the immune system.

High dietary fiber intake linked to health promoting short chain fatty acids

September 28, 2015
Eating a lot of fibre-rich foods, such as fruit, vegetables, and legumes—typical of a Mediterranean diet—is linked to a rise in health promoting short chain fatty acids, finds research published online in the journal ...

Short-chain fatty acids in diet stimulate fat utilization

March 6, 2015
(HealthDay)—Short-chain fatty acids (SCFAs), the main products of dietary fiber fermentation, induce a peroxisome proliferator-activated receptor (PPAR) γ-dependent switch from lipid synthesis to lipid utilization, according ...

Boosting chemical by-product of dietary fiber fermentation in gut slims and trims

December 10, 2014
Boosting levels of a naturally produced by-product of dietary fiber fermentation in the bowel can help trim the waistline and stave off weight gain, reveals a small study published online in the journal Gut.

Recommended for you

Scientists solve the case of the missing subplate, with wide implications for brain science

June 21, 2018
The disappearance of an entire brain region should be cause for concern. Yet, for decades scientists have calmly maintained that one brain area, the subplate, simply vanishes during the course of human development. Recently, ...

LincRNAs identified in human fat tissue

June 21, 2018
A large team of researchers from the U.S. and China has succeeded in identifying a number of RNA fragments found in human fat tissue. In their paper published in the journal Science Translational Medicine the group describes ...

Key molecule of aging discovered

June 21, 2018
Every cell and every organism ages sooner or later. But why is this so? Scientists at the German Cancer Research Center in Heidelberg have now discovered for the first time a protein that represents a central switching point ...

Compound made inside human body stops viruses from replicating

June 20, 2018
The newest antiviral drugs could take advantage of a compound made not by humans, but inside them. A team of researchers has identified the mode of action of viperin, a naturally occurring enzyme in humans and other mammals ...

Research reveals zero proof probiotics can ease your anxiety

June 20, 2018
If you're expecting probiotics to reduce your anxiety, it might be time to put down that yogurt spoon—or supplement bottle—and call a professional instead.

Long-term estrogen therapy changes microbial activity in the gut, study finds

June 20, 2018
Long-term therapy with estrogen and bazedoxifene alters the microbial composition and activity in the gut, affecting how estrogen is metabolized, a new study in mice found.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.