GCKR and type 2 diabetes mellitus: Two studies investigated the association of GCKR rs780094 and T2DM: one in 2009 in Beijing showed that the G allele was a risk factor of T2DM, and the A allele may increase β-cell function [29]; the other study, in 2011 in Shanghai, found no association of the G allele and T2DM, but the authors did not check β-cell function and insulin resistance [27].