Gut Microbial Mix Linked to Various Stages of Glucose Tolerance

Gut Microbial Mix Linked to Various Stages of Glucose Tolerance
Gut Microbial Mix Linked to Various Stages of Glucose Tolerance
The composition of gut microbiota may change over time in unhealthy ways in African American men with prediabetes.

SAN DIEGO — The composition of gut microbiota may change over time in unhealthy ways in African American (AA) men with prediabetes, according to new data presented at ENDO 2015.

However, researchers report that it may be possible to make simple dietary changes and lower the risk for developing type 2 diabetes.

Researchers previously found that the gut microbiota can affect human health in many ways and that the mix of this community of microscopic organisms differs in patients with type 2 diabetes compared with healthy individuals.

In their current investigation, they examined the relationship between microbiota and changes in the glycemic control of African American men with prediabetes. They collected stool samples from African American men participating in a randomized controlled trial of D Vitamin Intervention at VA (DIVA) clinical trial.

“I believe that microbiota is a significant contributor to pathogenesis,” said senior investigator Elena Barengolts, MD, who is a professor of medicine in the University of Illinois College of Medicine and section chief of endocrinology at the Jesse Brown Veterans Affairs (VA) Medical Center in Chicago. 

“Our study has suggested a new explanation for why high fat in the diet is not good. It promotes growth of unhealthy bacteria that make people gain weight and develop diabetes.”

She said a patient’s gut bacteria could predict their risk for diabetes. Unlike other studies that evaluated gut microbes at one time point in people with diabetes, this current study analyzed the microbiota composition over 1 year in adults with varying blood glucose and insulin levels.

The study included 116 African American men aged 45 to 75 years (mean age, 60 years). The men were divided into 4 groups based on changes in their glycemic control as demonstrated by the oral glucose tolerance test, between the start and end of the 1-year study. The four glycemic control groups were: stable (unchanged) normal (1), stable impaired (2), worsened (3) and improved (4).

The researchers found that men whose blood sugar control stayed normal over the year had more gut bacteria that are considered beneficial for metabolic health. Conversely, the men who still had prediabetes had fewer beneficial bacteria and more harmful bacteria.

In addition, the group whose glycemic control improved (group 4) had a trend for even more abundant Akkermansia (healthy bacteria) than the group who maintained normal blood sugar control throughout the year.

Dr. Barengolts said this information may be highly beneficial to practicing endocrinologists.

“Empower your patients by explaining to them that gut bacteria can promote weight gain and worsen diabetes control. If the patient sticks to the diet long enough, gut bacteria would change and the vicious cycle could be broken,” Dr. Barengolts told Endocrinology Advisor

“Patients frequently complain to me that despite eating small amount of the right foods they are unable to lose weight or improve their blood sugar. Knowledge of microbiota contribution to both weight and glucose control helps me as a doctor understand and teach the patient that indeed the same number of consumed calories can be converted into different number of digested calories that would be converted into pounds of flesh because bacteria have different harvesting capacity and different influence on glucose control.”

Although the study found connections between composition of the gut microbiota and glycemic states, Dr. Barengolts emphasized that these are pilot data in a relatively small number of participants. She also emphasized that this study suggests association only and further research is warranted to evaluate whether certain intestinal bacteria cause type 2 diabetes. 

Clinicians now have additional reasons to recommend foods, such as probiotics, which improve the growth and activity of helpful gut bacteria, she said.

The study also showed for the first time an association between vitamin D levels and gut microbiota. Dr. Barengolts said both vitamin D and bacteria are involved in inflammation and immunity and it is well established that inflammation is a contributor to the development of diabetes development.

The DIVA trial results will be published in June 2015 issue of Endocrine Practice.


  1. Ciubotaru I et al. Abstract FRI-587. Presented at: The Endocrine Society’s 97th Annual Meeting & Expo (ENDO 2015); March 5-8, 2015; San Diego.