Telomere length and type 2 diabetes: Mendelian randomization study and polygenic risk score analysis.

Recent epidemiological studies suggest an association between shorter telomere length and higher risk for type 2 diabetes (T2D). However, results from observational studies are susceptible to confounding and reverse causation, and it is not clear whether there is a causal association between telomere length and T2D. Using Mendelian randomization (MR) and polygenic risk score (PRS) approaches, we had evaluated the causal effect of telomere length on T2D in the Chinese Han population. Using 8 telomere-length associated genetic variants as instrumental variables, an analysis of genetically predicted telomere length and T2D risk was performed in the MR study based on data from a T2D genome-wide association study (GWAS) in 2632 individuals (1318 cases and 1314 controls). We also applied a PRS approach to investigate the causal relationship using Chinese GWAS data. The inverse-variance weighted, MR-Egger regression, simple median, and weighted median methods yielded no evidence of association between genetically predicted longer telomere length and risk of T2D (OR = 0.78, 95% CI: 0.36 ~ 1.68, P = 0.522; OR = 0.23, 95% CI: 0.01 ~ 7.64, P = 0.412; OR = 0.60, 95% CI: 0.28 ~ 1.28, P = 0.185; OR = 0.64, 95% CI: 0.31 ~ 1.33,P = 0.233; respectively). Further, PRS analysis did not produce consistent genetic overlap between telomere length and T2D. Accordingly, this study found no evidence supporting a causal association between telomere length and T2D. Further studies with larger cohorts could yield more reliable results and conclusions.