A study from Finland has identified some bacterial species in the gut microbiome as being predictive of development of type 2 diabetes. The study of more than 5000 people has been published in the journal Diabetes Care

In this study, researchers collected fecal samples from 5572 study subjects from the FINRISK 2002 cohort. More than half of them were women (54.1%) and their mean age was 48.7 years. Persons with diagnosed diabetes at baseline, including those being treated with antidiabetic drugs such as metformin were not included in the trial. They were followed up for nearly 16 years, till December 2017 with an objective to explore any association between the composition of gut microbiome and new onset type 2 diabetes. The taxa examined were then clustered. The study population was derived from two geographically different areas of Finland: western Finland and eastern Finland. The two areas differ with regards to genetics, lifestyle including morbidity and mortality. Data from eastern Finland group was used to determine the associations, which were then validated in the participants from western Finland.

During the follow-up period, 432 (7.8%) cases of incident diabetes were documented. A significant association was noted between four species and two clusters of bacteria in the gut microbiome of healthy adults at baseline and incident type 2 diabetes in participants from western Finland. These included Clostridium citroniae (hazard ratio 1.21), C. bolteae (HR 1.20), Tyzzerella nexilis (HR 1.17) and Ruminococcus gnavus (HR 1.17) were found to be associated with new onset diabetes and this association persisted all through the duration of the study. These associations were almost similar to those in eastern Finland.

A similar association was also noted for two clusters, which mostly consisted of these same species. The hazard ratio for this association was 1.18. Cluster 1 contained C. citroniae, C. boltae, and R. gnavus along with Eggerthella lenta. While Cluster 5 contained T. nexilis with C. symbiosum and C. glycyrrhizinilyticum. No association with type 2 diabetes was seen for C. symbiosum, C. glycyrrhizinilyticum and E. lenta in the two clusters.

The authors hypothesize that the association of these bacterial species with type 2 diabetes is due to their correlation with dietary quality and with other metabolic diseases. C. citroniae has been linked with trimethylamine N-oxide (TMAO) produced in the body from red meat, which is known to increase the risk of type 2 diabetes. TMAO also causes inflammation in the adipose tissue and obstructs the insulin signaling pathway in the liver leading to a state of insulin resistance.  Likewise, R. gnavus synthesizes an inflammatory polysaccharide, which induces proinflammatory cytokines. It has also been shown to be associated with obesity.

“We are what we eat”. And what we eat directly influences the quality of the intestinal microbiome, which is an important defense against pathogens and also enhances immunity. Gut dysbiosis has been implicated in many diseases including type 2 diabetes.

 This long-term follow-up study has demonstrated that the gut microbiome is predictive of new onset of type 2 diabetes in healthy adults. Some bacterial species are associated with greater risk of future diabetes. Even though these findings may not find immediate clinical application and further studies are needed, the authors write, “The current study thus serves as a stepping stone toward the goal of improved prediction and the development of effective treatments for type 2 diabetes through modification of the gut microbiome.”

Reference

1. Ruuskanen MO, et al. Gut microbiome composition is predictive of incident type 2 diabetes in a population cohort of 5,572 Finnish adults. Diabetes Care. 2022 Jan 31;dc212358. doi: 10.2337/dc21-2358.