Do gut bacteria play a role in diabetes?

Researchers have tried to figure out whether different gut bacteria participate in the development of diabetes in human bodies in a recent study.

Hyderabad: According to a study published in the journal Diabetes, people with higher levels of 'Coprococcus', a bacterium, tend to have higher insulin sensitivity, while those with higher levels of the bacterium, Flavonifractor tend to have lower insulin sensitivity.

Researchers have tried to understand why people develop diabetes by studying the composition of the microbiome (a collection of micro-organisms that include fungi, bacteria and viruses living in the digestive tract). The microbiome affects medications and diets. Studies suggest that people who cannot process insulin properly have lower levels of a certain type of bacteria which produces a type of fatty acid called Butyrate.

"The big question we're hoping to address is: Did the microbiome differences cause the diabetes, or did the diabetes cause the microbiome differences?" says Mark Goodarzi, MD, PhD, the director of the Endocrine Genetics Laboratory at Cedars-Sinai, is leading an ongoing study that is following and observing people at risk for diabetes to learn whether those with lower levels of these bacteria develop the disease, and also the senior author of the study and principal investigator of the multicenter study called Microbiome and Insulin Longitudinal Evaluation Study (MILES).

Researchers 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 cesarean section is associated with a higher risk of developing prediabetes and diabetes. For the most recent study to come out of this ongoing trial, investigators analyzed data from 352 people without known diabetes who were recruited from the Wake Forest Baptist Health System in Winston-Salem, North Carolina.

The study participants were asked to attend three clinic visits and collect stool samples before their visits. Researchers analyzed data collected at the first visit. They conducted genetic sequencing on the stool samples, for example, to study the participants' microbiomes, and specifically look for bacteria that earlier studies have found to be associated with insulin resistance.

Each participant also filled out a diet questionnaire and took an oral glucose tolerance test, which was used to determine the ability to process glucose. Investigators found that 28 people had oral glucose tolerance results that met the criteria for diabetes. They also found that 135 people had prediabetes, a condition in which a person's blood sugar levels are higher than normal but not high enough to meet the definition of diabetes.

The research team analyzed associations between 36 butyrate-producing bacteria found in the stool samples and a person's ability to maintain normal levels of insulin. They controlled the factors that could also contribute to a person's diabetes risk, such as age, sex, body mass index and race. Coprococcus and related bacteria form 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 has found higher levels of Flavonifractor in the stool of people with diabetes.