In the total analysis, the eNOS 4b/4a was associated with a substantially lower T2DM risk (ab vs. aa: OR = 0.71, 95% CI = 0.52–0.96; bb vs. aa: OR = 0.55, 95% CI = 0.38–0.79; ab + bb vs. aa: OR = 0.58, 95% CI = 0.40–0.82; bb vs. aa + ab: OR = 0.77, 95% CI = 0.66–0.89; b vs. a: OR = 0.76, 95% CI = 0.65–0.87, Table 6; Figure 2). Here, NOS3 is linked to type 2 diabetes mellitus.