Gut microbiome changes can signal future type 2 diabetes risk

The presence of certain bacteria in the gut microbiota, and fluctuations in a person's metabolism, can be seen in people who go on to develop type 2 diabetes years later. This has been shown in a large Swedish study led by researchers at Chalmers University of Technology. The discovery paves the way for identifying people at risk of developing type 2 diabetes at an early stage, enabling preventive measures to be introduced.

"Our study was able to show changes in the gut microbiota several years before the disease developed. This could indicate that the composition of the microbiome plays a role in the development of diabetes, and not the other way round," says Gaël Toubon, a postdoctoral researcher in food science at Chalmers' Department of Life Sciences.

The number of adults with diabetes has more than doubled since the 1990s, according to the World Health Organisation (WHO). Today, 800 million people are living with the disease, and more than 90 per cent of cases are type 2 diabetes. Studies of the human gut microbiome, namely the bacteria and other microorganisms that live in our intestinal tract, have shown that certain changes in the gut microbiota can be seen in people with type 2 diabetes.

Common denominators among diabetes patients

Now, a comprehensive study has shown that changes in the bacteria found in the gut microbiota can be seen several years before the disease develops, and could therefore predict who will go on to develop it. As part of the EU project HealthFerm, the Chalmers researchers led a large epidemiological study involving 4,685 Swedish adults, whose microbiomes were examined in stool samples. Of all the participants in the study, 383 developed diabetes after an average follow-up period of five years, and early common denominators were observed in their gut microbiota.

"We observed nine bacteria in the microbiome that are associated with the risk of developing the disease. One very interesting finding is that an individual's dietary habits appear to play a role, determining whether certain bacteria in the gut are beneficial or harmful," says Gaël Toubon.

Fiber intake is important

What surprised the researchers was that those who developed diabetes had high levels of the bacterium Akkermansia muciniphila in their gut microbiota. This bacterium is usually associated with health benefits.

"Under favourable conditions, this bacterium feeds on the fibre we get from our diet. But when our fibre intake is too low, it instead starts to break down the gut's protective mucus layer. This can lead to other bacteria coming into contact with the intestinal lining, causing inflammation and other metabolic disruptions linked to insulin resistance and type 2 diabetes," says Gaël Toubon.

One type of bacterium, Coprococcus catus, could be linked to diabetes when the bacterium was present only in very small quantities in the gut microbiota. Above a certain level, this risk was not observed.

"Research into the gut microbiota has made great strides in recent years, but the new knowledge has so far had little impact on clinical practice. In future, these bacteria could be used as biomarkers to identify people at risk of developing type 2 diabetes. Risk factors such as obesity, heredity and blood glucose levels could be supplemented with a stool sample to better predict the risk of developing the disease and enable preventive measures to be introduced, " says Gaël Toubon.

The microbiome could become a target for treatment

The Chalmers researchers' findings need to be validated in further large studies. If the role of the gut microbiota in the development of diabetes is confirmed, our microbiome could become a target for personalised preventive strategies, as the gut microbiota, unlike our genes, can be modified through lifestyle and diet.

"We cannot yet give that kind of dietary advice, but, at a general level, the study's findings support current recommendations to eat foods rich in fibre from fruit, vegetables, legumes and wholegrains. Our results emphasise the importance of studying the gut microbiome together with other lifestyle factors, as together they may influence the risk of developing type 2 diabetes," says Rikard Landberg, Professor at the Department of Life Sciences and lead author of the study.