MTNR1B and type 2 diabetes mellitus: The MTNR1B gene, which encodes melatonin receptor 1B, is robustly associated with various glycemic traits, such as increased fasting glucose, aggravated insulin resistance and attenuated β-cell function according to a genome-wide association (GWA) and replicated cohort studies, with T2DM risk most strongly linked to the rs10830963 G allele [28–30].