MiR-139-5p is a causal biomarker for type 2 diabetes; Results from genome-wide microRNA profiling and Mendelian randomization analysis in a population-based study

MicroRNAs (miRNAs) have emerged as key regulators of gene expression. Differential expression of miRNAs has been linked to diabetes, but underlying pathways remain poorly understood. We performed genome-wide miRNAs profiling and tested the causal associations between miRNAs and type 2 diabetes in the general population. Subsequently, we investigated target genes and metabolites of miRNAs to provide insight into the metabolic disturbances that emerge with type 2 diabetes. Between 2002 and 2005, plasma levels of 2083 circulatory miRNAs were profiled in 1900 participants (mean age 71.4 years) of the population-based Rotterdam Study cohort. The associations of 591 well-expressed miRNAs with prevalent and incident type 2 diabetes were examined until 2015. Two-sample Mendelian Randomization (MR) was conducted to investigate the causal associations and miRNA-target genes and metabolites were studied in relation to type 2 diabetes. At baseline, higher plasma levels of miR-139-5p and miR-193a-5p were associated (FDR 9.0 years, 209 participants developed type 2 diabetes. Plasma levels of miR-99a-5p, miR-4664-3p, miR-29a-3p, miR-122-5p, and miR-125b-5p were significantly associated with incident type 2 diabetes (n=209). Two-sample MR confirmed a causal effect for miR-139-5p (MR-IWV-beta=0.10, p=3.51x10-4) on type 2 diabetes. We found several target genes and metabolites that could link miR-139-5p to pathways underlying type 2 diabetes. Our study indicates a causal relationship between miR-139-5p and type 2 diabetes and suggests this miRNA as a plasma biomarker of type 2 diabetes.