CTRP-9, C1q-TNF-related protein-9

The C1q TNF-related proteins (CTRPs) are a newly discovered highly conserved family of adiponectin paralogs, containing 15 members (CTRP1 to CTRP15). Although structurally related, the CTRP family members are functionally diverse. C1q-TNF-related protein-9 (CTRP9) is increasingly recognized as a promising cardioprotective adipocytokine, which regulates biological processes like vascular relaxation, proliferation, apoptosis, and inflammation. CTRP9 is the closest adiponectin paralog, and is predominantly expressed in adipose tissue. It also forms heterotrimers with adiponectin, and similarly to mouse adiponectin, reduces serum glucose. While many of CTRP9’s metabolic roles overlap those of adiponectin, CTRP9 is also being studied for its beneficial cardiovascular effects, especially related to atherosclerosis. For instance, in aortic vascular rings, CTRP9 caused significant vasorelaxation, and the vasoactive potency of CTRP9 exceeded that of adiponectin by 3-fold. This effect was endothelium-dependent and nitric oxide-mediated. Furthermore, CTRP9 modulates neointimal hyperplasia and vascular smooth muscle cell proliferation in vivo and in vitro. Moreover, a recent study found that CTRP9 attenuated adverse cardiac remodeling after ischemia-perfusion injury in mice. Thus, CTRP9 is likely to be involved in the regulation of vascular function, more specifically atherosclerosis, in both rodents and humans (Jung CH et al.,J Clin Endocrinol Metab. 2014 Dec;99(12):E2477-84).