Objective Reduced plasma adiponectin (APN) in diabetic patients is associated with endothelial dysfunction. However, APN knockout animals manifest modest systemic dysfunction unless metabolically challenged. The protein family CTRPs (C1q/TNF-related proteins) has recently been identified as APN paralogs and some CTRP members share APN’s metabolic regulatory function. However, the vasoactive properties of CTRPs remain completely unknown. Methods and Results The vasoactivity of currently identified murine CTRP members was assessed in aortic vascular rings and underlying molecular mechanisms was elucidated in HUVECs. Of eight CTRPs, CTRPs 3, 5, and 9 caused significant vasorelaxation. The vasoactive potency of CTRP9 exceeded that of APN (3-fold), and is endothelium-dependent and nitric oxide (NO) mediated. Mechanistically, CTRP9 increased AMPK/Akt/eNOS phosphorylation and increased NO production. AMPK knockdown completely blocked CTRP9-induced Akt/eNOS phosphorylation and NO production. Akt knockdown had no significant effect upon CTRP9-induced AMPK phosphorylation, but blocked eNOS phosphorylation and NO production. Adiponectin receptor 1 (AdipoR1), but not receptor 2, knockdown blocked CTRP9-induced AMPK/Akt/eNOS phosphorylation and NO production. Finally, pre-incubating vascular rings with an AMPK-inhibitor abolished CTRP9-induced vasorelaxive effects. Conclusion We have provided the first evidence that CTRP9 is a novel vasorelaxive adipocytokine which may exert vasculoprotective effects via the AdipoR1/AMPK/eNOS dependent/NO mediated signaling pathway.

Background Obesity/diabetes adversely affects post-ischemic heart remodeling via incompletely understood underlying mechanisms. C1q/TNF-related protein-3 (CTRP3) is a newly identified adipokine exerting beneficial metabolic regulation, similar to adiponectin. The current study determined whether CTRP3 may regulate post-ischemic cardiac remodeling and cardiac dysfunction, and, if so, sought to elucidate the involved underlying mechanisms. Methods and Results Male adult mice were subjected to myocardial infarction (MI) via left anterior descending (LAD) coronary artery occlusion. Both the effect of MI upon endogenous CTRP3 expression/production and the effect of exogenous CTRP3 (adenovirus or recombinant CTRP3) replenishment upon MI injury were investigated. MI significantly inhibited adipocyte CTRP3 expression and reduced plasma CTRP3 level, reaching nadir 3 days post-MI. CTRP3 replenishment improved survival rate (P<0.05), restored cardiac function, attenuated cardiomyocyte apoptosis, increased revascularization, and dramatically reduced interstitial fibrosis (P values all <0.01). CTRP3 replenishment had no significant effect upon cardiac AMP-activated protein kinase (AMPK) phosphorylation, but significantly increased Akt phosphorylation and expression of hypoxia inducing factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). Surprisingly, treatment of human umbilical vascular endothelial cells (HUVECs) with CTRP3 did not directly affect NO production or tube formation. However, pre-conditioned medium from CTRP3-treated cardiomyocytes significantly enhanced HUVEC tube formation, an effect blocked by either pre-treatment of cardiomyocytes with a PI3K inhibitor, or pre-treatment of HUVECs with a VEGF inhibitor. Finally, pre-conditioned medium from CTRP3-knockdown 3T3 cells significantly enhanced hypoxia-induced cardiomyocyte injury. Conclusions CTRP3 is a novel anti-apoptotic, pro-angiogenic, and cardioprotective adipokine, whose expression is significantly inhibited following MI.