Adipokines: A Rainbow of Proteins with Metabolic and Endocrine Functions

Obesity represents one of the most important health problems worldwide with increasing morbidity and mortality. Widespread prevalence of this disease justifies its actual definition of a "global epidemic". Adipose tissue is nowadays considered a complex organ with lots of endocrine and metabolic functions. In addition to fulfilling its task for energy storage and thermal regulation, by virtue of its constituent white and brown cells, adipose tissue represents, considering its size, the biggest endocrine gland in the body. Both adipocytes and surrounding resident cells (macrophages, endothelial cells and others) produce a huge number of molecules, or adipokines, with endocrine or paracrine functions, that regulate various aspects of metabolism whose clinical relevance is emerging. By balancing pro-inflammatory and anti-inflammatory effects, the adipokines control insulin sensitivity and related glucose metabolism changes, lipid accumulation in the liver and other organs, and finally gonadal function. Collectively, literature data remains cloudy because of still conflicting results of pre-clinical and clinical studies. The aim of this review was to summarize scientific evidence about adipokines' effects on human metabolism, by focusing on their role on either Metabolic Syndrome and NAFLD, or insulin-resistance in pregnancy, or finally, reproductive function disorders.