Glucokinase is required for high‐starch diet‐induced β‐cell mass expansion in mice

AIMS/INTRODUCTION: We aimed to determine whether glucokinase is required for β‐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 β‐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. β‐Cell mass was significantly larger in HSTD‐fed Gck(+/+) mice than that in NC‐fed Gck(+/+) mice. In contrast, the β‐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 β‐cell mass and insulin secretion in Gck(+/+) , but not Gck(+/−) mice. This observation implies that glucokinase in β‐cells would be required for the increase in β‐cell mass induced by HSTD feeding.