Hyperglycemia
is a potent regulator of endogenous glucose production (EGP). Loss of this
‘glucose effectiveness’ is a major contributor to elevated plasma glucose
concentrations in type 2 diabetes (T2D). ATP-sensitive potassium channels (K<sub>ATP</sub>
channels) in the central nervous system (CNS) have been shown to regulate EGP
in humans and rodents. We examined the contribution of central K<sub>ATP</sub>
channels to glucose effectiveness. Under fixed hormonal conditions (‘pancreatic
clamp’ studies), hyperglycemia suppressed EGP by ~50% in both non-diabetic
humans and normal Sprague Dawley rats. By contrast, antagonism of K<sub>ATP</sub>
channels with glyburide significantly reduced the EGP-lowering effect of
hyperglycemia in both humans and rats. Furthermore, the effects of glyburide on
EGP and gluconeogenic enzymes in rats were abolished by intracerebroventricular
(ICV) administration of the KATP channel agonist diazoxide. These findings
indicate that about half of EGP suppression by hyperglycemia is mediated by
central K<sub>ATP</sub> channels. These central mechanisms may offer a novel
therapeutic target for improving glycemic control in T2D.
Functional roles of KATP channel subunits in metabolic inhibition
