Central K Channels Modulate Glucose Effectiveness in Humans and Rodents.

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). K channels in the central nervous system have been shown to regulate EGP in humans and rodents. We examined the contribution of central K channels to glucose effectiveness. Under fixed hormonal conditions (studies using a pancreatic clamp), hyperglycemia suppressed EGP by ∼50% in both humans without diabetes and normal Sprague-Dawley rats. By contrast, antagonism of K 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 were abolished in rats by intracerebroventricular administration of the K channel agonist diazoxide. These findings indicate that about half of the suppression of EGP by hyperglycemia is mediated by central K channels. These central mechanisms may offer a novel therapeutic target for improving glycemic control in subjects with T2D.