One type of bacteria found in the gut may contribute to the development of Type 2 diabetes, while another may protect from the disease, according to a study published in the journal Diabetes.
The study found people with higher levels of a bacterium called Coprococcus tended to have higher insulin sensitivity, while those whose microbiomes had higher levels of the bacterium Flavonifractor tended to have lower insulin sensitivity.
Studies of the gut microbiome 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.
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.
“The big question we’re hoping to address is: Did the microbiome differences cause the diabetes, or did the diabetes cause the microbiome differences?” said Goodarzi, who is the senior author of the study and principal investigator of the Microbiome and Insulin Longitudinal Evaluation Study (MILES).
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. For the present study, investigators analysed data from 352 people without known diabetes.
Study participants were asked to attend three clinic visits and collect stool samples prior to the visits. Investigators analysed 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 ability to process glucose.
Investigators found 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 analysed associations between 36 butyrate-producing bacteria found in the stool samples and a person’s ability to maintain normal levels of insulin. They controlled for factors that could also contribute to a person’s diabetes risk, such as age, sex, body mass index and race. 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.
Investigators are continuing to study samples from patients who participated in this study to learn how insulin production and the composition of the microbiome change over time. They also plan to study how diet may affect the bacterial balance of the microbiome.
Goodarzi emphasised, however, that it is too early to know how people can change their microbiome to reduce their diabetes risk.
“As far as the idea of taking probiotics, that would really be somewhat experimental,” said Goodarzi, who is also the Eris M. Field Chair in Diabetes Research at Cedars-Sinai. “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.”
Source: Cedars-Sinai Medical Center
