Serum total bile acids associate with risk of incident type 2 diabetes and longitudinal changes in glucose-related metabolic traits.

BACKGROUND: Bile acids have been found to be related to changes in gut microbiota and multiple metabolic disorders, including type 2 diabetes (T2D). We aimed to prospectively investigate associations of serum total bile acids (TBAs) with risk of incident T2D and longitudinal changes in glycemic traits. METHODS: A community-based study was conducted at baseline in 2010, including 4968 nondiabetic participants aged ≥40 years followed up for an average of 4.3 years. Incident T2D was defined by using the 1999 WHO criteria based on 75-g oral glucose tolerance tests. Multivariate Cox proportional hazards regression was used to examine the association of serum TBAs with incident T2D. Fasting plasma glucose (FPG), 2-hour postload plasma glucose (2-h PPG), and fasting serum insulin (FSI) were measured at baseline and follow-up. RESULTS: During 21 653.7 person-years of follow-up, 605 cases of incident diabetes were identified (incidence rate 2.8%). Comparing to quartile 1 of serum TBAs, quartile 2, 3, and 4 were significantly associated with a 14.2%, 15.0%, and 31.4% higher risk of incident T2D (P = .029). Each one unit of log-TBAs was associated with an increase of 0.034 mmol/L in FPG, 0.111 mmol/L in 2-h PPG, 0.023 in log-FSI, and 0.012 in log-HOMA-IR (homeostasis model assessment of insulin resistance) (all P ≤ .024). The association was attenuated after further adjustment for HOMA-IR. Mediation analysis showed that insulin resistance indicated by HOMA-IR might mediate 28.5% of indirect effect on the association of TBAs with T2D (P = .0004). CONCLUSIONS: Baseline serum TBAs were significantly associated with incident T2D and longitudinal changes in glycemic traits. Insulin resistance might partially mediate the association of TBAs and T2D.