A Novel Serum Protein Similar to C1q, Produced Exclusively in Adipocytes

Abstract

We describe a novel 30-kDa secretory protein, Acrp30 (adipocyte complement-related protein of 30 kDa), that is made exclusively in adipocytes and whose mRNA is induced over 100-fold during adipocyte differentiation. Acrp30 is structurally similar to complement factor C1q and to a hibernation-specific protein isolated from the plasma of Siberian chipmunks; it forms large homo-oligomers that undergo a series of post-translational modifications. Like adipsin, secretion of Acrp30 is enhanced by insulin, and Acrp30 is an abundant serum protein. Acrp30 may be a factor that participates in the delicately balanced system of energy homeostasis involving food intake and carbohydrate and lipid catabolism. Our experiments also further corroborate the existence of an insulin-regulated secretory pathway in adipocytes.

Adipose Tissue as an Endocrine Organ

“…Adiponectin was independently characterized in 1995 and 1996 by four groups using different methods, hence its alternative names of apM1 (adipose most abundant gene transcript 1), Acrp30 (adipocyte complement-related protein of 30 kDa), adipoQ, and GBP28 (gelatin binding protein of 28 kDa) (43)(44)(45)(46). Adiponectin is highly and specifically expressed in differentiated adipocytes and circulates at high levels in the bloodstream (47).…”

Globular adiponectin increases GLUT4 translocation and glucose uptake but reduces glycogen synthesis in rat skeletal muscle cells

“…Adiponectin (Acrp30) [1] is a 30-M r adipose-derived factor that can directly affect glucose homeostasis and regulate peripheral insulin sensitivity [2][3][4][5]. Injection of adiponectin into rodents has been shown to decrease resting blood glucose levels and protect animals with dietinduced obesity from developing insulin resistance [6][7][8][9].…”

Associations of adiponectin with metabolic and vascular risk parameters in the British Regional Heart Study reveal stronger links to insulin resistance-related than to coronory heart disease risk-related parameters

“…1,2 Adiponectin is exclusively produced by adipocytes and unlike other adipocyte hormones (adipokines), adiponectin concentrations are decreased in obesity, insulin resistance and type 2 diabetes. [2][3][4] Furthermore, evidence (largely from animal models and experimental studies) suggests that adiponectin has potential antiatherogenic and anti-inflammatory properties.…”