Gut bacteria may play a role in diabetes

Early results from an ongoing prospective study suggest that one type of bacteria found in the gut may contribute to the development of type 2 diabetes, while another may prevent the disease
.
The study was led
by researchers at Cedar Sinai.

The study, published in the peer-reviewed journal Diabetes, found that higher levels of Coprococcus bacteria in the body were associated with higher insulin sensitivity, while those with higher levels of flavonoids ifractor bacteria had lower
insulin sensitivity.

For years, researchers have tried to understand why people develop diabetes by studying the composition of the microbiome, a collection of microbes that live in the digestive tract, including fungi, bacteria and viruses
.
The microbiota is thought to be influenced
by drugs and diet.
Studies have also found that people who can't process insulin properly have lower levels of a type of bacteria that produce a fatty acid
called butyrate.

Mark Goodarzi, MD, director of the Sinai Endocrine Genetics Laboratory, is leading an ongoing study to track and observe people at risk for diabetes to see if people with lower levels of these bacteria develop diabetes
.

"The biggest question we want to solve is: Does the difference in the microbiome cause diabetes, or does diabetes cause the difference in the microbiome?" Goodarzi, who is the study's senior author and principal investigator
of the multicenter study Microbiome and Insulin Longitudinal Evaluation Study (MILES).

Since 2018, investigators participating in MILES have been collecting information
on black and non-Hispanic white adults ages 40 to 80.
An early cohort study from the MILES trial found that caesarean section was associated with
a higher risk of prediabetes and diabetes.

For the latest study of this ongoing trial, researchers analyzed data from 352 people without diabetes recruited from the Wake Forest Baptist Health System in Winston-Salem, North Carolina
.

Study participants were asked to attend three clinic visits and collect stool samples
prior to the visits.
The investigators analyzed the data collected during the
first visit.
For example, they genetically sequenced stool samples to study the participants' microbiomes and specifically looked for bacteria
that earlier found to be involved in insulin resistance.
Each participant also filled out a dietary questionnaire and underwent an oral glucose tolerance test to determine the ability to
process glucose.

The researchers found that oral glucose tolerance results in 28 people met the criteria for
diabetes.
They also found that 135 people had prediabetes, a person whose blood sugar levels were higher than normal but not enough to meet the definition of
diabetes.

The team analyzed the relationship
between the 36 butyrate-producing bacteria found in stool samples and a person's ability to maintain normal insulin levels.
They controlled for factors that could contribute to diabetes risk, such as age, gender, body mass index, and ethnicity
.
Staphylococcus faecalis and related bacteria form a network
of bacteria that have a beneficial effect on insulin sensitivity.
Although flavonolytic factors are producers of butyrate, they are associated with insulin resistance; Previous studies by others have found that the feces of people with diabetes contain higher levels of flavonoid-breaking factors
.

The researchers are continuing to study samples from patients involved in the study to understand how insulin production and the composition of the microbiome change over time
.
They also plan to study how diet affects the bacterial balance
of the microbiome.

However, Goodarzi stressed that it's too early
to know how people can change their microbiome to reduce diabetes risk.

"In terms of the idea of taking probiotics, it's really experimental in a way," said Goodez, who is also the Eris M.
Field Chair
in Diabetes Research at Cedars-Sinai University.
"We need more research to identify the specific bacteria we need to modulate to prevent or treat diabetes, but it's coming, probably in the next 5 to 10 years
.
"