Can some gut bacteria cause diabetes? Can probiotics help in controlling them?

“This is an interesting study,” says Dr V Mohan, Chairman, Mohan Diabetes Speciality Centre, Chennai, “but it’s early days yet.” Besides, many studies have attempted to firm up a link between diabetes and the gut microbiome or the fungi, bacteria and viruses that live in the digestive tract. Many researchers have found that people who don’t process insulin properly have lower levels of a certain type of bacteria that produce a type of fatty acid called butyrate. “We have ourselves helmed a large Indo-Danish study, backed by the Department of Biotechnology, on the impact of gut microbiota on insulin sensitivity. We assessed the gut microbes among three categories of people, those without diabetes, those with prediabetes and diabetics. We found a great difference between the gut microbiota of Indians and the Danes. That was because our food patterns are different; we are a high carb-eating people. That was a racial difference. But within the same race, the difference in gut microbiota between normal and those with prediabetes and diabetes were minor at best and not noticeable enough. One or two bacteria were more or less in the study groups but their presence or absence was not significant enough to make a differential diagnosis based on microbiota. Even this study is based on early observations and detailed research is needed to identify a pattern,” says Dr Mohan.

As for the growing currency of the theory that probiotics help diabetics, no study has shown conclusive evidence, he insists. “Probiotics are useful for smooth gut function among the elderly with constipation. You need them every time you have antibiotics. But their role in diabetes is not proven and definitely not applicable to Indians,” says Dr Mohan. At best, they are good for suppressing inflammation markers.

Besides, there is another dilemma. Mark Goodarzi, MD, PhD, the director of the Endocrine Genetics Laboratory at Cedars-Sinai, was quoted as saying, “The big question we’re hoping to address is: Did the microbiome differences cause the diabetes, or did the diabetes cause the microbiome differences?”

Investigators involved in MILES have been collecting information from participating Black and non-Hispanic white adults between 40 and 80 years of age since 2018. An earlier cohort study from the MILES trial found that birth by Caesarean section is associated with a higher risk for developing prediabetes and diabetes.

This time investigators analysed data from 352 people without known diabetes. Study participants were asked to attend three clinic visits and collect stool samples before they reached the venue. Investigators did a genetic sequencing on the stool samples to specifically look for bacteria that earlier studies have found to be associated with insulin resistance.

The research team analysed associations between 36 butyrate-producing bacteria found in the stool samples and a person’s ability to maintain normal levels of insulin. According to the findings, “Coprococcus and related bacteria formed a network of bacteria with beneficial effects on insulin sensitivity. Despite being a producer of butyrate, Flavonifractor was associated with insulin resistance; prior work by others have found higher levels of Flavonifractor in the stool of people with diabetes.”

“We need more research to identify the specific bacteria that we need to be modulating to prevent or treat diabetes, but it’s coming, probably in the next five to 10 years,” say researchers.