Certain gut bacteria, viruses may increase type 2 diabetes risk, study finds

• Of the approximately 530 million adults worldwide who have diabetes, about 98% have type 2 diabetes.
• Several factors can increase a person’s type 2 diabetes risk.
• Recently, scientists have been examining the gut microbiome as a possible link to heightened risk for type 2 diabetes.
• Researchers from Brigham and Women’s Hospital have identified specific bacterial strains and viruses that can cause functional changes to the gut microbiome that are correlated with heightened type 2 diabetes risk.

Of the about 530 million adults around the world living with diabetes , approximately 98% have type 2 diabetes — a condition where the body develops resistance to insulin which is needed to process blood glucose properly. Insulin resistance can cause a person’s blood sugar levels to remain high.

Several factors play a role in whether a person develops type 2 diabetes or not, including age , family history , and ethnicity , as well as modifiable risk factors such as obesity and sedentary lifestyle .

Recently, scientists have been examining what role the gut microbiome may play in increasing a person’s risk for type 2 diabetes.

One such set of researchers hails Brigham and Women’s Hospital in Boston, MA, where their recently published study in Nature Medicine identified specific bacterial strains and viruses that can cause functional changes to the gut microbiome that are correlated with heightened type 2 diabetes risk.

Gut microbial strains and type 2 diabetes

For this study, researchers analyzed data from the Microbiome and Cardiometabolic Disease Consortium (MicroCardio) that included 8,117 gut microbiome metagenomes from ethnically and geographically diverse participants, including the U.S., China, Israel, and Germany.

“Although research over the past decade has linked changes in the gut microbiome to the development of type 2 diabetes, earlier studies have been too small and varied in design to provide solid conclusions,” said Daniel (Dong) Wang, MD, ScD , assistant professor of medicine in the Channing Division of Network Medicine at Brigham and Women’s Hospital and Harvard Medical School, associate member at the Broad Institute of MIT and Harvard, assistant professor in the Department of Nutrition at Harvard T.H. Chan School of Public Health, and co-corresponding author of this study.

“There’s still a significant gap in understanding the mechanisms, especially the biological pathways encoded by specific microbial strains, that underlie the connection between the gut microbiome and type 2 diabetes,” Wang told Medical News Today .

“Moreover, previous research has focused on microbial species, but it’s actually the strains that are the relevant targets for potential interventions,” Wang continued. “To address these gaps, we initiated this study with a large, diverse, and international population to search for more definitive answers.”

Increased Prevotella copri in the type 2 diabetes gut

At the study’s conclusion, Wang and his team reported finding several microbial species, as well as their functions within the gut microbiome, linked to the development of type 2 diabetes.

For example, researchers identified a strain of the gut microbe Prevotella copri (P.copri), which is able to produce large amounts of branched-chain amino acids (BCAAs) , that was more commonly seen in the gut microbiome of people with type 2 diabetes.

“The discrete genetic structure and population-specific distributions of different strains of P. copri are well-documented in the microbiome field. However, the implication of these strain distributions in human health remains unexplored, so study on this topic is significant because P. copri is one of the most abundant microbial species in the human gut, and our previous research demonstrated that it can predict individual responses to a healthy diet.

For the first time, this current study found that the individuals’ carriage of different P. copri strains can explain between-individual differences in type 2 diabetes risk.”

– Daniel (Dong) Wang, MD, ScD

“Additionally, we discovered that P. copri strains linked to a higher risk of type 2 diabetes have an increased ability to produce branched-chain amino acids, metabolites that could potentially lead to type 2 diabetes, which provide a functional explanation to why individuals carrying certain strains have higher risk of type 2 diabetes,” he added.

Bacteriophages viruses may increase diabetes risk

Wang and his team also discovered evidence suggesting that bacteriophages — viruses that only infect bacterial cells — might also be driving changes to specific bacterial strains in the gut microbiome, driving increased type 2 diabetes risk.

“Few studies have studied the role of bacteriophages in chronic diseases like type 2 diabetes; most previous research focused on their role in infectious diseases,” Wang explained. “Our study is novel because we discovered that bacteria infected by bacteriophages can have different functions related to type 2 diabetes pathology. This infection could be a significant driving force in the evolution of different microbial strains.”

“Our study is the first project from this international consortium on the human microbiome and cardiometabolic health that my group is leading (MicroCardio Consortium). We’ve demonstrated the significant potential of combining a large, diverse population with novel analytical methods to generate new biological insights. We plan to maintain and expand this consortium, extending our research to other disease areas.”

– Daniel (Dong) Wang, MD, ScD

“Additionally, we will go deeper into mechanisms, such as comprehensively studying bacteriophages and horizontal gene transfers in all gut bacteria and their implications in modifying inflammation response and insulin resistance at the local level — gut environment — and systematically,” Wang added.

Future research on gut microbiome

After reviewing this study, Rudolph Bedford, MD , a board-certified gastroenterologist at Providence Saint John’s Health Center in Santa Monica, CA, told MNT that researchers have been investigating the gut microbiome and how it may affect or cause diabetes for some time now.

“My take on it is that there is likely something to it and that insulin sensitivity may be regulated dependent upon the type of bacteria that is within the gut, considering that these bacteria are what are used to process many of the foods and byproducts, such as fatty acids, may certainly affect insulin sensitivity, so to speak,” Bedford explained.

Bedford said it is important for researchers to continue to look for factors that may increase a person’s risk of developing type 2 diabetes, such as changes within the gut microbiome.

“We might be able to modulate their bacterial flora with certain things such as probiotics , possibly dietary modifiers, in terms of regulating the gut microbiome in certain positive ways,” he continued. “I’d like to see the effect of probiotics on the development of insulin sensitivity as it pertains to the bacterial flora of the gut and to see whether or not utilizing probiotics maybe we might be able to alter the course of some patients who are prediabetic and see whether or not we do have an effect on their insulin sensitivity.”