Fatty acids are the most efficient substrates for energy production in vertebrates and are essential components of the lipids that form biological membranes. Synthesis of triacylglycerols from non-esterified free fatty acids (FFAs) combined with triacylglycerol storage represents a highly efficient strategy to stockpile FFAs in cells and prevent FFA-induced lipotoxicity. Although essentially all vertebrate cells have some capacity to store and utilize triacylglycerols, white adipose tissue is by far the largest triacylglycerol depot and is uniquely able to supply FFAs to other tissues. The release of FFAs from triacylglycerols requires their enzymatic hydrolysis by a process called lipolysis. Recent discoveries thoroughly altered and extended our understanding of lipolysis. This Review discusses how cytosolic 'neutral' lipolysis and lipophagy, which utilizes 'acid' lipolysis in lysosomes, degrade cellular triacylglycerols as well as how these pathways communicate, how they affect lipid metabolism and energy homeostasis and how their dysfunction affects the pathogenesis of metabolic diseases. Answers to these questions will likely uncover novel strategies for the treatment of prevalent metabolic diseases.

脂肪酸是脊椎动物中产生能量最有效的底物，并且是形成生物膜的脂质的必需成分。由未酯化的游离脂肪酸（FFA）结合三酰甘油的储存来合成三酰甘油代表了将FFA储存在细胞中并防止FFA诱导的脂毒性的高效策略。尽管基本上所有脊椎动物细胞都具有一定的储存和利用三酰甘油的能力，但是白色脂肪组织是迄今为止最大的三酰甘油贮库，并且独特地能够向其他组织提供FFA。从三酰基甘油释放FFA需要通过称为脂解的过程将其酶促水解。最近的发现彻底改变并扩展了我们对脂肪分解的理解。这篇评论讨论了胞质如何“中性” 在溶酶体中利用“酸性”脂解作用的脂解作用和脂吞噬作用会降解细胞三酰甘油，以及这些途径如何通讯，它们如何影响脂质代谢和能量稳态以及它们的功能障碍如何影响代谢性疾病的发病机理。这些问题的答案可能会发现治疗流行性代谢疾病的新策略。