GK and type 2 diabetes mellitus: Genetically-proxied GK activation was associated with reduced risk of T2D (OR 0.31 per 1 mmol/L lower FPG, 95% CI 0.17–0.56, P = 9.88 × 10−5) and higher plasma insulin level (β 0.84 per 1 mmol/L lower FPG, 95% CI − 0.01 to 1.69, P = 0.051) (Tables 1 and 2).