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ENDOCRINE PHYSIOLOGY AND METABOLISM

Hypothalamic AMP-activated protein kinase activation with AICAR amplifies counterregulatory responses to hypoglycemia in a rodent model of type 1 diabetes

Department of Internal Medicine and Endocrinology, Yale University, New Haven, Connecticut

Submitted 15 July 2008 ; accepted in final form 27 March 2009

In nondiabetic rodents, AMP-activated protein kinase (AMPK) plays a role in the glucose-sensing mechanism used by the ventromedial hypothalamus (VMH), a key brain region involved in the detection of hypoglycemia. However, AMPK is regulated by both hyper- and hypoglycemia, so whether AMPK plays a similar role in type 1 diabetes (T1DM) is unknown. To address this issue, we used four groups of chronically catheterized male diabetic BB rats, a rodent model of autoimmune T1DM with established insulin—requiring diabetes (40 ± 4 pmol/l basal c-peptide). Two groups were subjected to 3 days of recurrent hypoglycemia (RH), while the other two groups were kept hyperglycemic [chronic hyperglycemia (CH)]. All groups subsequently underwent hyperinsulinemic hypoglycemic clamp studies on day 4 in conjunction with VMH microinjection with either saline (control) or AICAR (5-aminoimidazole-4-carboxamide) to activate AMPK. Compared with controls, local VMH application of AICAR during hypoglycemia amplified both glucagon [means ± SE, area under the curve over time (AUC/t) 144 ± 43 vs. 50 ± 11 ng·l^–1·min^–1; P < 0.05] and epinephrine [4.27 ± 0.96 vs. 1.06 ± 0.26 nmol·l^–1·min^–1; P < 0.05] responses in RH-BB rats, and amplified the glucagon [151 ± 22 vs. 85 ± 22 ng·l^–1·min^–1; P < 0.05] response in CH-BB rats. We conclude that VMH AMPK also plays a role in glucose-sensing during hypoglycemia in a rodent model of T1DM. Moreover, our data suggest that it may be possible to partially restore the hypoglycemia-specific glucagon secretory defect characteristic of T1DM through manipulation of VMH AMPK.

epinephrine; glucagon; ventromedial hypothalamus; adeno-associated viral vector