Type 2 diabetes is a common and growing metabolic disease in which the body struggles to regulate blood sugar, raising the risk of serious complications such as heart disease and vision loss. Now, researchers have found that certain gut microbes and microbial functions measured years before diagnosis are linked to later diabetes risk.

The findings, published in Cell Reports Medicine, suggest that the microbiota may help predict diabetes risk before disease develops.

Previous studies connecting the gut microbiota to type 2 diabetes have mostly looked at people after they already had the disease, which makes it hard to know whether gut bacteria contributed to diabetes risk or changed because of diabetes, diet, or medications such as metformin. 

Gaël Toubon at Chalmers University of Technology in Gothenburg, Sweden, and his colleagues set out to analyze the gut microbiota of 4,685 older Swedish adults who did not have type 2 diabetes at the start of the study.

Altered microbiota

The researchers used data from the Swedish SIMPLER cohort, a population study with health, diet, lifestyle, and stool-sample data. Over about five years, 383 study participants developed type 2 diabetes. 

Having a more or less diverse gut microbiota was not clearly linked to future diabetes risk, the researchers found. However, six bacterial species were linked to higher future diabetes risk: Desulfovibrio piger, Alistipes communis, Alistipes finegoldii, Akkermansia muciniphila, Ruminococcus gnavus, and one Lachnospiraceae species. Three species were linked to lower risk: an Erysipelotrichaceae bacterium, Coprococcus catus, and one Clostridia species.

The researchers also looked at sets of microbial genes that suggest what chemical tasks the microbiome can perform. Three microbial functions were linked to diabetes risk, they found.

Risk prediction 

Higher levels of A. muciniphila were linked to increased diabetes risk, especially among people with the lowest fiber intake. When dietary fiber is low, A. muciniphila may rely more on the gut’s mucus layer as a food source, weakening the gut barrier and contributing to inflammation, according to the authors. 

This result indicates that diabetes prevention needs to account for diet-microbiota interactions, because some gut microbes appear to predict diabetes risk differently depending on fiber intake.

Although the findings do not prove that gut microbes cause type 2 diabetes, they support the idea that the microbiota may be involved in the development of the condition, the authors say. “These prospective findings offer insights into [type 2 diabetes] etiology and may support microbiome-informed strategies for risk prediction and prevention.”