GCK and diabetes mellitus: In the overall estimate (Figure 2), the minor A-allele of GCK rs1799884 was significantly associated with increased risk of diabetes (OR, 1.04; 95%CI, 1.01–1.08; p = 0.006), with moderate heterogeneity (Q = 40.09; I2 = 42.6%; p = 0.015).