The lipid droplet proteins FSP27, Cidea, and perilipin are regulated by PPARγ and play a role in lipid droplet biogenesis and dynamics. These lipid droplet proteins inhibit lipolysis (red inhibitory symbol). Thus, depletion of these lipid droplet proteins enhances adipocyte lipolysis, releasing glycerol and FFAs. According to this model, FFAs released during lipolysis induced by depletion of FSP27, Cidea, or perilipin may act as ligands for PPARs that further regulate the transcriptional coactivator PGC-1α as well as genes that encode proteins that promote mitochondrial biogenesis and fatty acid oxidation. Similarly, FFAs released during lipolysis have been shown to activate AMPK, which functions to stimulate fatty acid oxidation, by increasing fatty acid transport into mitochondria and perhaps by regulating the transcription of genes that encode proteins that promote fatty acid oxidation. Thus, the increased mitochondrial oxidation of fatty acids in white adipocytes of FSP27-KO mice may result in part from activation of AMPK. In addition, fragmentation of lipid droplets in FSP27-KO mice may enhance access of mitochondria to the resulting increased surface area of lipid droplets, further augmenting fatty acid oxidation (data not shown, see text for details). COXI, subunit I of cytochrome c oxidase; CPT-1, carnitine palmitoyltransferase-1; LCAD, long-chain acyl–coenzyme A dehydrogenase; MCAD, medium-chain acyl–coenzyme A dehydrogenase; PGC-1α, PPARγ-coactivator 1α; TG, triglyceride; VLCAD, very LCAD.