Impaired insulin secretion and insulin resistance are thought to be two major causes of type 2 diabetes mellitus. There are two kinds of diabetic model mice: one is a K
ATP channel knockout (Kir6.2KO) mouse which is defective in glucose-induced insulin secretion, and the other is a transgenic mouse expressing the tyrosine kinase-deficient (dominant-negative form of) human insulin receptor (hIR
KMTG), and which has insulin resistance in muscle and fat. However, all of these mice have no evidence of overt diabetes. To determine if the double mutant Kir6.2KO/hIR
KMTG mice would have diabetes, we generated mutant mice by crossbreeding, which would show both impaired glucose-induced insulin secretion and insulin resistance in muscle and fat. We report here that: 1) blood glucose levels of randomly fed and 6 h fasted double mutant (Kir6.2KO/hIR
KMTG) mice were comparable with those of wild type mice; 2) in intraperitoneal glucose tolerance test (ipGTT), Kir6.2KO/hIR
KMTG mice had an impaired glucose tolerance; and 3) during ipGTT, insulin secretion was not induced in either Kir6.2KO/hIR
KMTG or Kir6.2KO mice, while the hIR
KMTG mice showed a more prolonged insulin secretion than did wild type mice; 4) hyperinsulinemic euglycemic clamp test revealed that Kir6.2KO, Kir6.2KO/hIR
KMTG and hIR
KMTG mice, showed decreased whole-body glucose disposal compared with wild type mice; 5) Kir6.2KO, but not Kir6.2KO/hIR
KMTG mice had some obesity and hyperleptinemia compared with wild type mice. Thus, the defects in glucose-induced insulin secretion (Kir6.2KO) and an insulin resistance in muscle and fat (hIR
KMTG) were not sufficient to lead to overt diabetes.
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