Brain GLP-1 Signaling Regulates Femoral Artery Blood Flow and Insulin Sensitivity Through Hypothalamic PKC-δ

OBJECTIVE-Glucagon-like peptide 1 (GLP-1) is a gut-brain hormone that regulates food intake, energy metabolism, and cardiovascular functions. In the brain, through a currently unknown molecular mechanism, it simultaneously reduces femoral artery blood flow and muscle glucose uptake. By analogy to pancreatic beta-cells where GLP-1 activates protein kinase C (PKC) to stimulate insulin secretion, we postulated that PKC enzymes would be molecular targets of brain GLP-1 signaling that regulate metabolic and vascular function. RESEARCH DESIGN AND METHODS-We used both genetic and pharmacological approaches to investigate the role of PKC isoforms in brain GLP-1 signaling in the conscious, free-moving mouse simultaneous with metabolic and vascular measurements. RESULTS-In normal wild-type (WT) mouse brain, the GLP-1 receptor (GLP-1R) agonist exendin-4 selectively promotes translocation of PKC-delta (but not -beta II, -alpha, or -epsilon) to the plasma membrane. This translocation is blocked in Glp1r(-1-) mice and in WT mice infused in the brain with exendin-9, an antagonist of the GLP-1R. This mechanism coordinates both blood flow in the femoral artery and whole-body insulin sensitivity. Consequently, in hyperglycemic, high-fat diet-fed diabetic mice, hypothalamic PKC-delta activity was increased and its pharmacological inhibition improved both insulin-sensitive metabolic and vascular phenotypes. CONCLUSIONS-Our studies show that brain GLP-1 signaling activates hypothalamic glucose-dependent PKC-delta to regulate femoral artery blood flow and insulin sensitivity. This mechanism is attenuated during the development of experimental hyperglycemia and may contribute to the pathophysiology of type 2 diabetes. Diabetes 60:2245-2256, 2011