Adiponectin protects against myocardial ischaemia-reperfusion injury via AMP-activated protein kinase, Akt, and nitric oxide

Aims Cardiovascular disease and type 2 diabetes mellitus are associated with low plasma concentration of adiponectin. The aim of this study was to investigate whether adiponectin exerts cardioprotective effects during myocardial ischaemia-reperfusion and whether this effect is related to the production of nitric oxide (NO). Methods and results Isolated rat hearts were subjected to 30 min of either global or local ischaemia followed by 60 min of reperfusion. The hearts received vehicle, adiponectin (3 mu g/mL), the NO-synthase inhibitor nitro-L-arginine (L-NNA) (0.1 mM), or a combination of adiponectin and L-NNA at the onset of ischaemia. Haemodynamics, infarct size, and expression of endothelial NO-synthase (eNOS), AMP-activated protein kinase (AMPK), and Akt were determined. Adiponectin significantly increased left ventricular function and coronary flow during reperfusion in comparison with the vehicle group. Co-administration of L-NNA abrogated the improvement in myocardial function induced by adiponectin. Infarct size following local ischaemia-reperfusion was 40 +/- 6% of the area at risk in the vehicle group. Adiponectin reduced infarct size to 19 +/- 2% (P < 0.01). L-NNA did not affect infarct size per se but abolished the protective effect of adiponectin (infarct size 40 +/- 5%). Phosphorylation of eNOS Ser(177), AMPK Thr(172), and Akt Ser(473) was increased in the adiponectin group (P < 0.05). Conclusion Adiponectin protects from myocardial contractile dysfunction and limits infarct size following ischaemia and reperfusion by a mechanism involving activation of AMPK and production of NO.