Globular adiponectin controls insulin-mediated vasoreactivity in muscle through AMPKα2

Decreased tissue perfusion increases the risk of developing insulin resistance and cardiovascular disease in obesity, and decreased levels of globular adiponectin (gAdn) have been proposed to contribute to this risk. We hypothesized that gAdn controls insulin's vasoactive effects through AMP-activated protein kinase (AMPK), specifically its alpha 2 subunit, and studied the mechanisms involved. In healthy volunteers, we found that decreased plasma gAdn levels in obese subjects associate with insulin resistance and reduced capillary perfusion during hyperinsulinemia. In cultured human microvascular endothelial cells (HMEC), gAdn increased AMPK activity. In isolated muscle resistance arteries gAdn uncovered insulin-induced vasodilation by selectively inhibiting insulin-induced activation of ERK1/2, and the AMPK inhibitor compound C as well as genetic deletion of AMPK alpha 2 blunted insulin-induced vasodilation. In HMEC deletion of AMPK alpha 2 abolished insulin-induced Ser(1177) phosphorylation of eNOS. In mice we confirmed that AMPK alpha 2 deficiency decreases insulin sensitivity, and this was accompanied by decreased muscle microvascular blood volume during hyperinsulinemia in vivo. This impairment was accompanied by a decrease in arterial Ser(1177) phosphorylation of eNOS, which closely related to AMPK activity. In conclusion, globular adiponectin controls muscle perfusion during hyperinsulinemia through AMPK alpha 2, which determines the balance between NO and ET-1 activity in muscle resistance arteries. Our findings provide a novel mechanism linking reduced gAdn-AMPK signaling to insulin resistance and impaired organ perfusion. (C) 2015 Elsevier Inc. All rights reserved.