Important adipokine involved in the control of fat metabolism and insulin sensitivity, with direct anti-diabetic, anti-atherogenic and anti-inflammatory activities. Stimulates AMPK phosphorylation and activation in the liver and the skeletal muscle, enhancing glucose utilization and fatty-acid combustion. Antagonizes TNF-alpha by negatively regulating its expression in various tissues such as liver and macrophages, and also by counteracting its effects. Inhibits endothelial NF-kappa-B signaling through a cAMP-dependent pathway. May play a role in cell growth, angiogenesis and tissue remodeling by binding and sequestering various growth factors with distinct binding affinities, depending on the type of complex, LMW, MMW or HMW. Homomultimer. Forms trimers, hexamers and 12- to 18-mers. The trimers (low molecular weight complexes / LMW) are assembled via non-covalent interactions of the collagen-like domains in a triple helix and hydrophobic interactions within the globular C1q domain. Several trimers can associate to form disulfide-linked hexamers (middle molecular weight complexes / MMW) and larger complexes (higher molecular weight / HMW). The HMW-complex assembly may rely aditionally on lysine hydroxylation and glycosylation. LMW, MMW and HMW complexes bind to HBEGF, MMW and HMW complexes bind to PDGFB, and HMW complex binds to FGF2. Interacts with CTRP9A via the C1q domain (heterotrimeric complex). Synthesized exclusively by adipocytes and secreted into plasma. Note: This description may include information from UniProtKB.
Protein type: Secreted; Endoplasmic reticulum; Secreted, signal peptide; Hormone