脂滴是胞质器，存储三酸甘油脂和胆固醇等脂质。在营养缺乏条件下，三酸甘油脂液滴被水解产生自由脂肪酸，后者被氧化以提供能量。对于饥饿的第二个细胞反应是细胞自吞，在这个过程中细胞消化自己的组成部分来提供营养。
Singh等人介绍了细胞自吞在调控脂质代谢中的一个新功能，他们将这种功能称之为“macrolipophagy”。在这一过程中，脂滴和自吞组分在饥饿期间结合在一起，而细胞自吞的抑制则会增加脂滴中的脂质存储。自吞作用通过将脂滴释放给溶酶体去降解来促进脂质水解和自由脂肪酸的生成。这项工作发现了自吞在调控脂质代谢中的一个关键作用，可能为防止疾病中的脂质积累提供一个新途径。(生物谷Bioon.com)
生物谷推荐原始出处：
Nature 458, 1131-1135 (30 April 2009) | doi:10.1038/nature07976
Autophagy regulates lipid metabolism
Rajat Singh1,2,7, Susmita Kaushik1,2,3,4,7, Yongjun Wang1,2, Youqing Xiang1,2, Inna Novak2,5, Masaaki Komatsu6, Keiji Tanaka6, Ana Maria Cuervo1,2,3,4 & Mark J. Czaja1,2
1 Department of Medicine,
2 The Marion Bessin Liver Research Center,
3 Department of Developmental and Molecular Biology,
4 Institute for Aging Studies,
5 Department of Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
6 Laboratory of Frontier Science, Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
7 These authors contributed equally to this work.
The intracellular storage and utilization of lipids are critical to maintain cellular energy homeostasis. During nutrient deprivation, cellular lipids stored as triglycerides in lipid droplets are hydrolysed into fatty acids for energy. A second cellular response to starvation is the induction of autophagy, which delivers intracellular proteins and organelles sequestered in double-membrane vesicles (autophagosomes) to lysosomes for degradation and use as an energy source. Lipolysis and autophagy share similarities in regulation and function but are not known to be interrelated. Here we show a previously unknown function for autophagy in regulating intracellular lipid stores (macrolipophagy). Lipid droplets and autophagic components associated during nutrient deprivation, and inhibition of autophagy in cultured hepatocytes and mouse liver increased triglyceride storage in lipid droplets. This study identifies a critical function for autophagy in lipid metabolism that could have important implications for human diseases with lipid over-accumulation such as those that comprise the metabolic syndrome.
