Glucose regulation of adipocyte differentiation 1 Glucose availability controls adipogenesis in mouse 3T3-L1 adipocytes via upregulation of nicotinamide metabolism

Expansion of adipose tissue in response to a positive energy balance underlies obesity and occurs through both hypertrophy of existing cells and increased differentiation of adipocyte precursors (hyperplasia). To better understand the nutrient signals that promote adipocyte differentiation, we investigated the role of glucose availability in regulating adipocyte differentiation and maturation. 3T3-L1 preadipocytes were grown and differentiated in media containing a standard differentiation hormone cocktail and either 4 or 25mM glucose. Adipocyte maturation at day 9 postdifferentiation was determined by key adipocyte markers, including glucose transporter 4 (GLUT4) and adiponectin expression, and Oil Red O staining of neutral lipids. We found that adipocyte differentiation and maturation required a pulse of 25mM glucose only during the first 3 days of differentiation. Importantly, fatty acids were unable to substitute for the 25mM glucose pulse during this period. The 25mM glucose pulse increased adiponectin and GLUT4 expression, and accumulation of neutral lipids via distinct mechanisms. Adiponectin expression and other early markers of differentiation required an increase in the intracellular pool of total NAD/P. In contrast, GLUT4 protein expression was only partially restored by increased NAD/P levels. Furthermore, GLUT4 mRNA expression was mediated by glucose-dependent activation of GLUT4 gene transcription through the cis-acting GLUT4-LXRE promoter element. In summary, this study supports the conclusion that high glucose promotes adipocyte differentiation via distinct metabolic pathways and independently of fatty acids. This may partly explain the mechanism underlying adipocyte hyperplasia that occurs much later than adipoctye hypertrophy in the development of obesity. http://www.jbc.org/cgi/doi/10.1074/jbc.M117.791970 The latest version is at JBC Papers in Press. Published on September 15, 2017 as Manuscript M117.791970 Copyright 2017 by The American Society for Biochemistry and Molecular Biology, Inc. by gest on M arch 8, 2018 hp://w w w .jb.org/ D ow nladed from Glucose regulation of adipocyte differentiation