Zinc alpha 2 glycoprotein
- 01-22-2005, 10:20 PM
Zinc alpha 2 glycoprotein
This isn't a supplement, but I hope it becomes one soon (doubtful though):
Zinc-alpha2-glycoprotein, a lipid mobilizing factor, is expressed in adipocytes and is up-regulated in mice with cancer cachexia.
Bing C, Bao Y, Jenkins J, Sanders P, Manieri M, Cinti S, Tisdale MJ, Trayhurn P.
Neuroendocrine and Obesity Biology Unit, Department of Medicine, University Clinical Departments, University of Liverpool, Liverpool L69 3GA, UK.
Zinc-alpha2-glycoprotein (ZAG), a 43-kDa protein, is overexpressed in certain human malignant tumors and acts as a lipid-mobilizing factor to stimulate lipolysis in adipocytes leading to cachexia in mice implanted with ZAG-producing tumors. Because white adipose tissue (WAT) is an endocrine organ secreting a wide range of protein factors, including those involved in lipid metabolism, we have investigated whether ZAG is produced locally by adipocytes. ZAG mRNA was detected by RT-PCR in the mouse WAT depots examined (epididymal, perirenal, s.c., and mammary gland) and in interscapular brown fat. In WAT, ZAG gene expression was evident in mature adipocytes and in stromal-vascular cells. Using a ZAG Ab, ZAG protein was located in WAT by Western blotting and immunohistochemistry. Mice bearing the MAC16-tumor displayed substantial losses of body weight and fat mass, which was accompanied by major increases in ZAG mRNA and protein levels in WAT and brown fat. ZAG mRNA was detected in 3T3-L1 cells, before and after the induction of differentiation, with the level increasing progressively after differentiation with a peak at days 8-10. Both dexamethasone and a beta3 agonist, BRL 37344, increased ZAG mRNA levels in 3T3-L1 adipocytes. ZAG gene expression and protein were also detected in human adipose tissue (visceral and s.c.). It is suggested that ZAG is a new adipose tissue protein factor, which may be involved in the modulation of lipolysis in adipocytes. Overexpression in WAT of tumor-bearing mice suggests a local role for adipocyte-derived ZAG in the substantial reduction of adiposity of cancer cachexia.
PMID: 14983038 [PubMed - indexed for MEDLINE]
Induction of lipolysis in vitro and loss of body fat in vivo by zinc-alpha2-glycoprotein.
Russell ST, Zimmerman TP, Domin BA, Tisdale MJ.
Pharmaceutical Sciences Research Institute, Aston University, Birmingham 7ET, UK.
Loss of adipose tissue in cancer cachexia has been associated with tumour production of a lipid-mobilizing factor (LMF) which has been shown to be homologous with the plasma protein zinc-alpha(2)-glycoprotein (ZAG). The aim of this study was to compare the ability of human ZAG with LMF to stimulate lipolysis in vitro and induce loss of body fat in vivo, and to determine the mechanisms involved. ZAG was purified from human plasma using a combination of Q Sepharose and Superdex 75 chromatography, and was shown to stimulate glycerol release from isolated murine epididymal adipocytes in a dose-dependent manner. The effect was by the cyclic AMP phosphodiesterase inhibitor Ro20-1724, and attenuated by freeze/thawing and the specific beta3-adrenoreceptor antagonist SR59230A. In vivo ZAG caused highly significant, time-dependent, decreases in body weight without a reduction in food and water intake. Body composition analysis showed that loss of body weight could be attributed entirely to the loss of body fat. Loss of adipose tissue may have been due to the lipolytic effect of ZAG coupled with an increase in energy expenditure, since there was a dose-dependent increase in expression of uncoupling protein-1 (UCP-1) in brown adipose tissue. These results suggest that ZAG may be effective in the treatment of obesity.
PMID: 14984739 [PubMed - indexed for MEDLINE]
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