Objective: To verify that adiponectin and tumor necrosis factor (TNF)-α reciprocally regulate their expression, thereby synergistically affecting both coronary and aortic endothelial dysfunction in type 2 diabetic mice.
Methods and results: We examined endothelium-dependent and endothelium-independent vasodilation/vasorelaxation of coronary arterioles and aortas in control mice, diabetic mice (Lepr(db)), and Lepr(db) treated with adiponectin or neutralizing antibody to TNF-α (anti-TNF-α). Endothelium-dependent vasodilation to acetylcholine in both coronary arterioles and aortas was blunted in Lepr(db) compared with control mice. Endothelium-independent vasodilation to sodium nitroprusside was comparable. Adiponectin and anti-TNF-α improved acetylcholine-induced vasodilation of coronary arterioles and aortas in Lepr(db) without affecting dilator response to sodium nitroprusside. Adiponectin protein expression was significantly reduced, and TNF-α protein expression was significantly greater, in coronary arterioles and aortas of Lepr(db) compared with control mice. Immunofluorescence staining results indicate that adiponectin was colocalized with endothelial cells. Anti-TNF-α treatment upregulated adiponectin protein expression in Lepr(db) coronary arterioles and aortas. Adiponectin administration reduced TNF-α protein expression in Lepr(db). Although adiponectin receptor 1 protein expression in coronary arterioles and aortas was similar between control and diabetic mice, adiponectin receptor 2 protein expression was significantly reduced in Lepr(db). Both adiponectin and anti-TNF-α inhibited IκBα phosphorylation and nuclear factor κB protein expression in Lepr(db), suggesting that adiponectin and TNF-α signaling may converge on nuclear factor κB to reciprocally regulate their expression.
Conclusions: A reciprocal suppression occurs between adiponectin and TNF-α that fundamentally affects the regulation of coronary and aortic endothelial function in type 2 diabetic mice.