Circulating short-chain and branched short-chain fatty acids and the risk of incident type 2 diabetes: findings from the 4C study

Previous studies suggested that fecal short-chain fatty acids (SCFAs) and branched short-chain fatty acids (BCFAs) are associated with glucose regulation. However, the potential relationship between circulating SCFAs and BCFAs with incident diabetes risk in both men and women remains unidentified in prospective cohort studies. In this study, we examined a panel of nine serum SCFAs and BCFAs in 3414 subjects with incident diabetes, and matched normoglycemic controls from the China Cardiometabolic Disease and Cancer Cohort study. In fully adjusted conditional logistic regression models, total SCFAs, total BCFAs, and isovaleric acid were significantly associated with incident type 2 diabetes mellitus (T2DM) (P < 0.05). Interestingly, gender-specific analysis showed that per standard deviation (SD) increment of SCFAs were positively associated with incident T2DM among women, with the odds ratio (95% confidence interval) of 1.16 (1.05-1.29) for total SCFAs and 1.18 (1.07-1.31) for propionate, respectively (P < 0.05, false discovery rate (FDR) < 0.05). No significant associations were observed in men. A significant interaction was detected between men and women for propionate (P-interaction < 0.001, FDR < 0.01). After further adjustment of insulin measurements, the associations of serum propionate with diabetes remained significant (P < 0.05, FDR < 0.05). Meanwhile, the associations of total BCFAs and isovaleric acid with diabetes were partially mediated by triglycerides, insulin resistance, and beta-cell function in mediation analysis. These findings, for the first time in a large prospective cohort, provide evidence for an association between circulating SCFAs and BCFAs with T2DM risk, and support the potential role of circulating propionate with gender disparities in the early pathogenesis of diabetes.