A common variant (E23K; rs5219) in KCNJ11 (which encodes the Kir6.2 subunit of the KATP-channel) is associated with enhanced T2D risk (Gloyn et al., 2003), increased KATP-channel activity (Schwanstecher et al., 2002), and impaired glucose-induced suppression of glucagon secretion in vivo (Tschritter et al., 2002). Here, GCG is linked to type 2 diabetes mellitus.