adiponektin

Adiponectin, also known as adipocyte complement-related protein of 30 kDa (ACRP30), is a hormone-like protein produced primarily by adipose tissue. It circulates in blood in several multimeric forms and plays a key role in regulating glucose and lipid metabolism. The ADIPOQ gene encodes adiponectin and is located on chromosome 3 in humans.

Biochemically, adiponectin exists as trimers, hexamers, and higher-order oligomers, with the high-molecular-weight form most strongly linked to insulin sensitivity. A truncated form known as globular adiponectin can be generated by proteolysis. The protein contains a signal peptide, a collagen-like domain, and a C1q-like C-terminal domain; post-translational modifications, including hydroxylation and glycosylation, are required for multimerization and stability.

Adiponectin exerts metabolic effects by binding to its receptors AdipoR1 and AdipoR2, which mediate activation of AMPK and PPAR-α signaling, respectively, leading to increased fatty acid oxidation and reduced hepatic gluconeogenesis. A third molecule, T-cadherin, can bind hexameric and high-molecular-weight adiponectin and may influence its tissue distribution, but does not signal via conventional pathways.

Circulating adiponectin levels are inversely related to adiposity; they are typically reduced in obesity, metabolic syndrome, and type 2 diabetes and rise with weight loss and physical activity. Genetic variants in the ADIPOQ gene can affect adiponectin levels and metabolic risk. Because of its insulin-sensitizing and anti-inflammatory properties, adiponectin is a focus of research into therapies for diabetes and cardiovascular disease, including adiponectin receptor agonists and mimetics studied in preclinical models.

Assays such as ELISA are used to quantify adiponectin in plasma or serum for research and, in some settings, clinical evaluation of metabolic health.