Effects of gut microbiome on type 1 diabetes susceptibility and complications: A large-scale bidirectional Mendelian...

To assess and verify the effect of the gut microbiome on the susceptibility and complications of type 1 diabetes (T1D).

To achieve this aim, a two-sample and reverse Mendelian randomization (MR) analysis was conducted. In addition, an external validation study was performed using individual microbiome data of patients with T1D from the gutMEGA datasets and the National Clinical Research Center for Metabolic Diseases. The circulating metabolites facilitated two-sample MR analysis, mediation and multivariable MR analysis to evaluate the direct relationship between the gut microbiome and T1D complications.

The MR analysis results from the discovery and validation phases confirmed that Veillonellaceae can potentially reduce the susceptibility of T1D. In the gutMEGA dataset, the average relative abundance of Veillonellaceae in patients with T1D was 0.66%, compared with 1.09% in the controls. Furthermore, the external validation, which included 60 patients with T1D and 30 matched healthy controls, found that the median relative abundance of Veillonellaceae was also lower than controls at 1.10% (95% CI 0.50%-1.80%). Specifically, the Eubacterium coprostanoligenes group, known for its ability to regulate cholesterol, was significantly associated with a lower risk of developing renal, neurological and ophthalmic complications in T1D. Moreover, high cholesterol in small high-density lipoprotein and cholesteryl esters in high-density lipoprotein were associated with a reduced risk of T1D renal and ophthalmic complications. The mediation and multivariable MR analysis combining cholesterol indicated that the E. coprostanoligenes group is the most dominant factor influencing T1D complications.

Our findings supported the potential causal effect of gut microbiota on the susceptibility and complications of T1D.