Adipositas & Bewegung / Obesity & Physical Activity

Abstract

Most of white and brown adipocytes, in spite of their different functions storing energy and thermogenesisare contained together in subcutaneous and visceral depots. The reason for this mixture liesin the fact that adipocytes have plastic properties allowing eachto convert to theother: under chronic cold exposure,white convert into brown to support the need for thermogenesis and under obesogenic diet, brown convert into white to satisfy the need for energy storing. The white-brown transdifferentiation is of medical interest because the browning is associated with obesity resistance and drugs inducing the browning phenomenon curb obesity and related disorders. Type2 diabetes is the most common disorder associated withvisceral obesity. Macrophages infiltrating the obese adipose organ are responsible for the low-grade chronic inflammation dealing to insulin resistance and T2 diabetes. Macrophages form characteristic histopathology figures: crown-like structures (CLS) due to the need forremoval of debris deriving from the death of adipocytes. Death of adipocytes is related to their hypertrophy up to the critical death size. Visceral adipocytes have a smaller critical death size, thus offering an explanation for the higher inflammation and morbidity of visceral fat. Physical exercise induces both useful changes of adipose organ: size reduction of adipocytes and browning. Exercise-induced browning is due to several mechanisms including increased density of noradrenergic fibres in white adipose tissue and to factors produced by skeletal muscles and adipose tissue.KEY WORDS: Adipose Organ, White Adipose Tissue, Brown Adipose Tissue, Adipocyte, Transdifferentiation, Physical Exercise