Fiber-fermenting bacteria improve health of type 2 diabetes patients


This is gut bacteria in culture. Credit: Tao Liu and Xiaoyan Pang/Shanghai Jiao Tong University

Dietary fibers promote gut bacteria that benefit blood glucose control

The fight against type 2 diabetes may soon improve thanks to a pioneering high-fiber diet study led by a Rutgers University-New Brunswick professor.

Promotion of a select group of gut bacteria by a diet high in diverse fibers led to better blood glucose control, greater weight loss and better lipid levels in people with type 2 diabetes, according to research published today in Science.

The study, underway for six years, provides evidence that eating more of the right dietary fibers may rebalance the gut microbiota, or the ecosystem of bacteria in the gastrointestinal tract that help digest food and are important for overall human health.

“Our study lays the foundation and opens the possibility that fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment,” said Liping Zhao, the study’s lead author and a professor in the Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences at Rutgers University-New Brunswick.

Type 2 diabetes, one of the most common debilitating diseases, develops when the pancreas makes too little insulin — a hormone that helps glucose enter cells for use as energy — or the body doesn’t use insulin well.

In the gut, many bacteria break down carbohydrates, such as dietary fibers, and produce short-chain fatty acids that nourish our gut lining cells, reduce inflammation and help control appetite. A shortage of short-chain fatty acids has been associated with type 2 diabetes and other diseases. Many clinical studies also show that increasing dietary fiber intake could alleviate type 2 diabetes, but the effectiveness can vary due to the lack of understanding of the mechanisms, according to Zhao, who works in New Jersey Institute for Food, Nutrition, and Health at Rutgers-New Brunswick.

In research based in China, Zhao and scientists from Shanghai Jiao Tong University and Yan Lam, a research assistant professor in Zhao’s lab at Rutgers, randomized patients with type 2 diabetes into two groups. The control group received standard patient education and dietary recommendations. The treatment group was given a large amount of many types of dietary fibers while ingesting a similar diet for energy and major nutrients. Both groups took the drug acarbose to help control blood glucose.

The high-fiber diet included whole grains, traditional Chinese medicinal foods rich in dietary fibers and prebiotics, which promote growth of short-chain fatty acid-producing gut bacteria. After 12 weeks, patients on the high-fiber diet had greater reduction in a three-month average of blood glucose levels. Their fasting blood glucose levels also dropped faster and they lost more weight.

Surprisingly, of the 141 strains of short-chain fatty acid-producing gut bacteria identified by next-generation sequencing, only 15 are promoted by consuming more fibers and thus are likely to be the key drivers of better health. Bolstered by the high-fiber diet, they became the dominant strains in the gut after they boosted levels of the short-chain fatty acids butyrate and acetate. These acids created a mildly acidic gut environment that reduced populations of detrimental bacteria and led to increased insulin production and better blood glucose control.

The study supports establishing a healthy gut microbiota as a new nutritional approach for preventing and managing type 2 diabetes.


Gut bacteria found to trigger gene that protects against type 1 diabetes


Researchers have discovered that a powerful guardian gene known to protect against a variety of autoimmune diseases, including type 1 diabetes, is triggered by the bacteria in our gut. This finding offers a clue to the complex interaction between our genes, immune system and gut microbiota.

Scientists at the Harvard Medical School set out to investigate what factors influence the activity of a powerful gene complex known as the human leukocyte antigen (HLA). It has been known for some time that specific variants of HLA genes in humans and major histocompatibility complexes (MHC) in mice can protect against diseases such as type 1 diabetes, but how that influence is exerted has been a mystery.

The team focused on gut bacteria as being a potential catalyst for modulating the genes’ activity. In a series of experiments, non-obese diabetic (NOD) mice engineered to carry a guardian gene were treated with gut bacteria killing antibiotics at various times in their development.

The mice treated with antibiotics during the first six weeks of life were found to subsequently develop symptoms of early stage type 1 diabetes despite holding the protective guardian gene. On the other hand, when treated with antibiotics at between six and 10 weeks of age, the mice still displayed signs of genetic diabetic resistance.

These results imply that early-life formation of gut microbiota has a significant effect on gene modulation influencing immune system behavior. The experiment also delivered antibiotics to mother mice in the 10 days before giving birth and discovered this also disrupted their offspring’s genetic protections. This particularly highlights the influence of a mother’s microbiota on her offspring.

Exactly how the bacteria in the gut affects gene activity is still unknown, but the researchers suggest that this offers clear evidence of how disrupting the early development of an individual’s gut microbiome can usurp any genetic predisposition and alter proper immune function.

“Our findings need to be borne out in further experiments,” says co-lead of the study Diane Mathis. “However, our results powerfully illustrate the notion that early antibiotic exposure can modulate disease risk and that avoiding or at least minimizing antibiotic treatment in infants and pregnant women during critical periods of development may be a good idea.”

The last experiment the team conducted involved fecal transplants from mice with the guardian gene to mice without that genetic protection. The mice receiving the fecal transplant displayed a reduction in pancreatic cell inflammation, the general marker signaling the onset of type 1 diabetes. This solidifies the role gut bacteria plays in regulating our immune system and suggests future treatments for autoimmune diseases could be targeted at the gut microbiome.

The new research was published in the journal Proceedings of the National Academy of Sciences.

Source: Harvard Medical School

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