Glucokinase is required for high-starch diet-induced beta-cell mass expansion in mice

Aims/Introduction We aimed to determine whether glucokinase is required for beta-cell mass expansion induced by high-starch diet (HSTD)-feeding, as has been shown in its high-fat diet-induced expansion. Materials and Methods Eight-week-old male wild-type (Gck(+/+)) or glucokinase haploinsufficient (Gck(+/-)) mice were fed either a normal chow (NC) or an HSTD for 15 weeks. The bodyweight, glucose tolerance, insulin sensitivity, insulin secretion and beta-cell mass were assessed. Results Both HSTD-fed Gck(+/+) and Gck(+/-) mice had significantly higher bodyweight than NC-fed mice. Insulin and oral glucose tolerance tests revealed that HSTD feeding did not affect insulin sensitivity nor glucose tolerance in either the Gck(+/+) or Gck(+/-) mice. However, during the oral glucose tolerance test, the 15-min plasma insulin concentration after glucose loading was significantly higher in the HSTD group than that in the NC group for Gck(+/+), but not for Gck(+/-) mice. beta-Cell mass was significantly larger in HSTD-fed Gck(+/+) mice than that in NC-fed Gck(+/+) mice. In contrast, the beta-cell mass of the HSTD-fed Gck(+/-) mice was not different from that of the NC-fed Gck(+/-) mice. Conclusions The results showed that HSTD feeding would increase pancreatic beta-cell mass and insulin secretion in Gck(+/+), but not Gck(+/-) mice. This observation implies that glucokinase in beta-cells would be required for the increase in beta-cell mass induced by HSTD feeding