The tumor secretory factor ZAG promotes white adipose tissue browning and energy wasting

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Abstract

<p class="first" id="d5002792e139">Cachexia is a complex tissue-wasting syndrome characterized by inflammation, hypermetabolism, increased energy expenditure, and anorexia. Browning of white adipose tissue (WAT) is one of the significant factors that contribute to energy wasting in cachexia. By utilizing a cell implantation model, we demonstrate here that the lipid mobilizing factor zinc-α <sub>2</sub>-glycoprotein (ZAG) induces WAT browning in mice. Increased circulating levels of ZAG not only induced lipolysis in adipose tissues but also caused robust browning in WAT. Stimulating WAT progenitors with ZAG recombinant protein or expression of ZAG in mouse embryonic fibroblasts (MEFs) strongly enhanced brown-like differentiation. At the molecular level, ZAG stimulated peroxisome proliferator–activated receptor γ (PPARγ) and early B cell factor 2 expression and promoted their recruitment to the PR/SET domain 16 (Prdm16) promoter, leading to enhanced expression of Prdm16, which determines brown cell fate. In brown adipose tissue, ZAG stimulated the expression of PPARγ and PPARγ coactivator 1α and promoted recruitment of PPARγ to the uncoupling protein 1 (Ucp1) promoter, leading to increased expression of Ucp1. Overall, our results reveal a novel function of ZAG in WAT browning and highlight the targeting of ZAG as a potential therapeutic application in humans with cachexia.—Elattar, S., Dimri, M., Satyanarayana, A. The tumor secretory factor ZAG promotes white adipose tissue browning and energy wasting. </p>

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Most cited references 29

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Cancer cachexia: mediators, signaling, and metabolic pathways.

Kenneth C.H. Fearon, David J. Glass, Denis C. Guttridge (2012)

Cancer cachexia is characterized by a significant reduction in body weight resulting predominantly from loss of adipose tissue and skeletal muscle. Cachexia causes reduced cancer treatment tolerance and reduced quality and length of life, and remains an unmet medical need. Therapeutic progress has been impeded, in part, by the marked heterogeneity of mediators, signaling, and metabolic pathways both within and between model systems and the clinical syndrome. Recent progress in understanding conserved, molecular mechanisms of skeletal muscle atrophy/hypertrophy has provided a downstream platform for circumventing the variations and redundancy in upstream mediators and may ultimately translate into new targeted therapies. Copyright © 2012 Elsevier Inc. All rights reserved.

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Transcriptional control of brown fat determination by PRDM16.

Patrick Seale, Shingo Kajimura, Wenli Yang … (2007)

Brown fat cells are specialized to dissipate energy and can counteract obesity; however, the transcriptional basis of their determination is largely unknown. We show here that the zinc-finger protein PRDM16 is highly enriched in brown fat cells compared to white fat cells. When expressed in white fat cell progenitors, PRDM16 activates a robust brown fat phenotype including induction of PGC-1alpha, UCP1, and type 2 deiodinase (Dio2) expression and a remarkable increase in uncoupled respiration. Transgenic expression of PRDM16 at physiological levels in white fat depots stimulates the formation of brown fat cells. Depletion of PRDM16 through shRNA expression in brown fat cells causes a near total loss of the brown characteristics. PRDM16 activates brown fat cell identity at least in part by simultaneously activating PGC-1alpha and PGC-1beta through direct protein binding. These data indicate that PRDM16 can control the determination of brown fat fate.

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PPARγ agonists induce a white-to-brown fat conversion through stabilization of PRDM16 protein.

Haruya Ohno, Kosaku Shinoda, Bruce M. Spiegelman … (2012)

Brown adipose tissue dissipates energy through heat and functions as a defense against cold and obesity. PPARγ ligands have been shown to induce the browning of white adipocytes; however, the underlying mechanisms remain unclear. Here, we show that PPARγ ligands require full agonism to induce a brown fat gene program preferentially in subcutaneous white adipose. These effects require expression of PRDM16, a factor that controls the development of classical brown fat. Depletion of PRDM16 blunts the effects of the PPARγ agonist rosiglitazone on the induced brown fat gene program. Conversely, PRDM16 and rosiglitazone synergistically activate the brown fat gene program in vivo. This synergy is tightly associated with an increased accumulation of PRDM16 protein, due in large measure to an increase in the half-life of the protein in agonist treated cells. Identifying compounds that stabilize PRDM16 protein may represent a plausible therapeutic pathway for the treatment of obesity and diabetes. Copyright Â© 2012 Elsevier Inc. All rights reserved.