Grönke S, Müller G, Hirsch J, Fellert S, Andreou A, Haase T, Jäckle H, Kühnlein RP. Dual lipolytic control of body fat storage and mobilization in Drosophila.
PLoS Biol 2007;
5:e137. [PMID:
17488184 PMCID:
PMC1865564 DOI:
10.1371/journal.pbio.0050137]
[Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Accepted: 03/13/2007] [Indexed: 01/07/2023] Open
Abstract
Energy homeostasis is a fundamental property of animal life, providing a genetically fixed balance between fat storage and mobilization. The importance of body fat regulation is emphasized by dysfunctions resulting in obesity and lipodystrophy in humans. Packaging of storage fat in intracellular lipid droplets, and the various molecules and mechanisms guiding storage-fat mobilization, are conserved between mammals and insects. We generated a Drosophila mutant lacking the receptor (AKHR) of the adipokinetic hormone signaling pathway, an insect lipolytic pathway related to ß-adrenergic signaling in mammals. Combined genetic, physiological, and biochemical analyses provide in vivo evidence that AKHR is as important for chronic accumulation and acute mobilization of storage fat as is the Brummer lipase, the homolog of mammalian adipose triglyceride lipase (ATGL). Simultaneous loss of Brummer and AKHR causes extreme obesity and blocks acute storage-fat mobilization in flies. Our data demonstrate that storage-fat mobilization in the fly is coordinated by two lipocatabolic systems, which are essential to adjust normal body fat content and ensure lifelong fat-storage homeostasis.
The amount of body fat that an animal stores is a critical parameter for its survival. Although under-storage of fat creates risk during periods of famine, over-storage also impairs fitness—obesity in humans is associated with severe health threats, such as cardiovascular disease, type II diabetes, and cancer. A delicate balance between two antagonistic processes adjusts body fat storage: lipogenesis produces fat stores, and lipolysis mobilizes fat. It is unclear, however, how many regulatory systems orchestrate lipolysis in animals, whether these systems are evolutionarily conserved, and to what extent impaired lipolytic regulation contributes to excessive body fat accumulation. We show that in the fruit fly Drosophila, lipolysis is under dual control. Inactivation of either of the two control pathways generates flies with excessive fat accumulation and limited fat-mobilization capability. Mutant flies simultaneously lacking key genes of both lipolytic systems, however, are extremely obese and completely blocked in body fat mobilization even when fully food deprived. Interestingly, our study reveals that key components and regulatory mechanisms of lipolysis are evolutionarily conserved between insects and mammals, making the fruit fly a valuable model system for research on lipid metabolism.
Simultaneous loss of the receptor for adipokinetic hormone and the Brummer triglyceride lipase causes extreme obesity and blocks acute storage fat mobilization in flies.
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