Adiponectin

Adiponectin belongs to the family of fatty tissue hormones (adipokines). Adiponectin is a larger peptide consisting of 244 amino acids. It is mainly produced in adipocytes (fat tissue cells), but also in skeletal muscle cells (Liu Y et al. 2014). Adiponectin is encoded by ADIPOQ gene located on chromosome 3q27. Various gene polymorphisms are associated with an increased risk of diabetes and obesity.

Adiponectin unfolds its effect via the receptors, AdipoR1 (in skeletal muscle) and AdipoR2 (in the liver). It has a strong insulin-sensitive, anti-inflammatory and antidiabetic effect via various signaling pathways (Liu M et al. 2014).

Its main function is to control glucose homeostasis. Hepatic gluconeogenesis is inhibited, fatty acid oxidation is increased. Adiponectin thus induces processes that reduce the risk of type 2 diabetes, obesity and arteriosclerosis (Lim S et al. 2014). Various genetic variants are associated with an increased risk of diabetes.

Low fat reserves lead to an increased expression of adiponectin. Full fat reserves reduce the formation of the peptide.

Adiponectin levels are reduced in obesity, insulin resistance, type 2 diabetes, hypertension; in high fasting glucose, elevated LDL and total cholesterol. The blood level is already reduced in the stage of prediabetes. It can therefore serve as a prognostic marker for an increased risk of type 2 diabetes. The adiponectin level correlates positively with the HDL cholesterol level.

Adiponectin promotes fat storage in adipocytes and counteracts the development of insulin resistance. It reduces the risk of developing type 2 diabetes. Adiponectin also has a vasoprotective effect, reducing the risk of developing arteriosclerosis. Adiponectin modulates the function of heart muscle cells, endothelial cells and smooth muscle cells of blood vessels, thus counteracting pathological processes (cardiomyopathy, angiopathy).

Overweight and obese people with metabolic syndrome were found to have significantly lower blood concentrations of adiponectin and IL-6 than those without metabolic syndrome.

Adiponectin is able to suppress cellular inflammatory signals. Thus, UV-irradiated keratinocytes express significantly higher amounts of hBD2. Adiponectin is able to suppress this hBD2 overexpression (Kim M et al. 2016).

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