Description
Adiponectin, also referred as Acrp30, AdipoQ, apM1, and gelatin binding protein of 28 kD (GBP-28), is encoded by the ADIPOQ gene in humans. Adiponectin contains 244 amino acids with a collagen-like domain at the N-terminal and a globular domain at the C-terminal. The globular domain can be proteolytically truncated forming the globular adiponectin (gAdiponectin). This globular domain resembles the structure of the complement C1q and the TNF-α superfamily. Adiponectin exists in a wide range of homo-oligomers: a low-molecular weight (LMW) trimer, a medium molecular weight (MMW) hexamer, and a high molecular weight (HMW) multimer with little or no interconversion between the forms. Females generally have higher HMW than males in proportion and absolute amounts. Adiponectin has two receptors (adipoRs)-1 and -2. AdipoR1 mRNA is detectable in skeletal muscle, spleen, lung, heart, kidney, and liver. AdipoR2 is expressed in liver, but is also detectable in heart, lung, skeletal muscle, and kidney. Adiponectin plays an important role in carbohydrate and lipid metabolism. It promotes insulin-sensitivity and protects cells from inflammation and apoptosis. It is also hypothesized to have anti-atherogenic activity. Normal circulating adiponectin level ranges from 4-30 µg/mL. Adiponectin levels are inversely correlated with body mass index (BMI). Low serum level of adiponectin is found in obesity, type 2 diabetes and those with coronary artery disease. Therefore, adiponectin serves as an important clinical biomarker for metabolic syndromes.
