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ENDOCRINE PHYSIOLOGY AND METABOLISM

The PPAR agonist rosiglitazone enhances rat brown adipose tissue lipogenesis from glucose without altering glucose uptake

¹Laval Hospital Research Center and Department of Anatomy and Physiology, Faculty of Medicine, Laval University, Quebec; and ²Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada

Submitted 15 December 2008 ; accepted in final form 9 February 2009

We investigated the mechanisms whereby peroxisome proliferator-activated receptor- (PPAR) agonism affects glucose and lipid metabolism in brown adipose tissue (BAT) by studying the impact of PPAR activation on BAT glucose uptake and metabolism, lipogenesis, and mRNA levels plus activities of enzymes involved in triacylglycerol (TAG) synthesis. Interscapular BAT of rats treated or not with rosiglitazone (15 mg·kg^–1·day^–1, 7 days) was evaluated in vivo for glucose uptake and lipogenesis and in vitro for glucose metabolism, gene expression, and activities of glycerolphosphate acyltransferase (GPAT), phosphatidate phosphatase-1 (PAP or lipin-1), and diacylglycerol acyltransferase (DGAT). Rosiglitazone increased BAT mass without affecting whole tissue glucose uptake. BAT glycogen content (–80%), its synthesis from glucose (–50%), and mRNA levels of UDP-glucose pyrophosphorylase (–40%), which generates UDP-linked glucose for glycogen synthesis, were all reduced by rosiglitazone. In contrast, BAT TAG-glycerol synthesis in vivo and glucose incorporation into TAG-glycerol in vitro were stimulated by the agonist along with the activities and mRNA levels of glycerol 3-phosphate-generating phosphoenolpyruvate carboxykinase and glycerokinase. Furthermore, rosiglitazone markedly increased the activities of GPAT and DGAT but not those of lipin-1-mediated PAP-1, enzymes involved in the sequential acylation of glycerol 3-phosphate and TAG synthesis. Because an adequate supply of fatty acids is essential for BAT nonshivering thermogenesis, the enhanced ability of BAT to synthesize TAG under PPAR activation may constitute an important mechanism by which lipid substrates are stored in preparation for an eventual thermogenic activation.

glycogen; glycerokinase; phosphoenolpyruvate carboxykinase; glycerolphosphate acyltransferase; lipin; diacylglycerol acyltransferase; peroxisome proliferator-activated receptor-

This article has been cited by other articles:

				J. L. Grobe, M. Venegas-Pont, C. D. Sigmund, and M. J. Ryan PPAR{gamma} differentially regulates energy substrate handling in brown vs. white adipose: focus on "The PPAR{gamma} agonist rosiglitazone enhances rat brown adipose tissue lipogenesis from glucose without altering glucose uptake" Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2009; 296(5): R1325 - R1326. [Full Text] [PDF]