The adipose organ

Abstract

Mammals are provided with the adipose organ, a multi-depot organ made up by adipocytes, i.e. cells whose distinctive structure allows storing large amount of lipids. White adipocytes store lipids for release as free fatty acids during fasting periods; brown adipocytes burn glucose and lipids to perform thermogenesis; pink adipocytes produce milk for pup nourishment. A range of metabolic and environmental challenges highlights the plasticity of the adipose organ. Cold induces an increase in the “brown” component of the organ to maintain the body temperature constant; during positive energy balance, the “white” component expands to store excess nutrients; finally, the “pink” component only develops in subcutaneous depots during pregnancy and lactation to ensure litter feeding. At cellular level, plasticity is due to a significant extent by direct and reversible transdifferentiation of mature adipocytes. The adipose organ secretes, and is targeted by, numerous hormones, peptides and nutrients through which interacts with the brain and other organs involved in energy balance regulation. This poses the adipose organ at a crucial point of a novel mammalian system, the nutritional system, devoted to the careful storage and use of energy to meet metabolic and behavioral challenges.