Key role for AMP-activated protein kinase in the ventromedial hypothalamus in regulating counterregulatory hormone responses to acute hypoglycemia.

Abstract

To examine in vivo in a rodent model the potential role of AMP-activated protein kinase (AMPK) within the ventromedial hypothalamus (VMH) in glucose sensing during hypoglycemia. Using gene silencing technology to selectively downregulate AMPK in the VMH, a key hypothalamic glucose-sensing region, we demonstrate a key role for AMPK in the detection of hypoglycemia. In vivo hyperinsulinemic-hypoglycemic (50 mg dl(-1)) clamp studies were performed in awake, chronically catheterized Sprague-Dawley rats that had been microinjected bilaterally to the VMH with an adeno-associated viral (AAV) vector expressing a short hairpin RNA for AMPKalpha. In comparison with control studies, VMH AMPK downregulation resulted in suppressed glucagon ( approximately 60%) and epinephrine (approximately 40%) responses to acute hypoglycemia. Rats with VMH AMPK downregulation also required more exogenous glucose to maintain the hypoglycemia plateau and showed significant reductions in endogenous glucose production and whole-body glucose uptake. We conclude that AMPK in the VMH plays a key role in the detection of acute hypoglycemia and initiation of the glucose counterregulatory response.