Adiponectin

Adiponectin is a classical adipokine and was among the first factors secreted from adipose tissue found to promote metabolic function. ^[1] Adiponectin is an important adipokine because of its beneficial effects on glucose and lipid metabolism, and low levels are associated with disease states such as diabetes and cardiovascular disease. ^[2]

Functional signal transduction of adiponectin requires at least one of the receptors AdipoR1 or AdipoR2, and additionally the glycosylphosphatidylinositol-anchored molecule T-cadherin. ^[3] High-molecular-weight adiponectin is thought to be the most biologically active isoform and promotes glucose uptake, insulin sensitivity, and fatty acid oxidation, while in obesity isoform formation is disrupted. ^[4] Adiponectin is associated with the metabolism of high-density lipoprotein and triglycerides, appearing to increase serum HDL and to lower triglycerides through enhanced catabolism of triglyceride-rich lipoproteins. ^[5] Upon binding to its receptors AdipoR1 and AdipoR2, adiponectin initiates signal transduction that includes phosphorylation of AMPK, driving fatty acid oxidation and improved energy homeostasis ^[6]. Adiponectin has insulin-sensitizing effects, and its reduction plays a central role in obesity-related insulin resistance and type 2 diabetes ^[7]. Adiponectin improves insulin sensitivity and lipid metabolism, and factors derived from altered adipose tissue play critical roles in the development of metabolic syndrome ^[8].