Lipolysis of lipid droplets. (a) Schematic representation of the main lipid and protein components of lipid droplets (LDs) and mechanisms of lipid mobilization (lipolysis) by cytosolic lipases. (b) Lipolysis by lipophagy. Schematic representation of the formation of autophagic vacuoles at the surface of an LD. PLIN: perilipin; Atg: autophagy-related protein; FFA: free fatty acids.