MTNR1B and type 2 diabetes mellitus: HbA1c-associated variants located at the ANK1, CDKAL1, G6PC2/ABCB11, GCK, MTNR1B, SLC30A8, and TCF7L2 loci confer an increased risk for type 2 diabetes (T2D) and/or are associated with 1 or more glycaemic traits, including FPG, 2-hour glucose, and fasting proinsulin16.