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Sci Rep. 2016 Mar 14;6:23043. doi: 10.1038/srep23043.

Metabolic Reprogramming by Hexosamine Biosynthetic and Golgi N-Glycan Branching Pathways.

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Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Ave., Toronto ON M5G 1X5, Canada.
Department of Molecular Genetics, University of Toronto, Toronto ON M5S 1A8, Canada.
Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa ON K1H 8M5, Canada.
CAS Key Lab of Separation Sciences for Analytical Chemistry, National Chromatographic Research and Analysis Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
Department of Genetics, Research Center, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Kingdom of Saudi Arabia.
Centre for the Analysis of Genome Evolution &Function, University of Toronto, Toronto ON M5S 3B2, Canada.
Department of Chemistry, Faculty of Science, University of Ottawa, Ottawa ON K1N 6N5, Canada.
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto ON M5S 1A8, Canada.


De novo uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc) biosynthesis requires glucose, glutamine, acetyl-CoA and uridine, however GlcNAc salvaged from glycoconjugate turnover and dietary sources also makes a significant contribution to the intracellular pool. Herein we ask whether dietary GlcNAc regulates nutrient transport and intermediate metabolism in C57BL/6 mice by increasing UDP-GlcNAc and in turn Golgi N-glycan branching. GlcNAc added to the drinking water showed a dose-dependent increase in growth of young mice, while in mature adult mice fat and body-weight increased without affecting calorie-intake, activity, energy expenditure, or the microbiome. Oral GlcNAc increased hepatic UDP-GlcNAc and N-glycan branching on hepatic glycoproteins. Glucose homeostasis, hepatic glycogen, lipid metabolism and response to fasting were altered with GlcNAc treatment. In cultured cells GlcNAc enhanced uptake of glucose, glutamine and fatty-acids, and enhanced lipid synthesis, while inhibition of Golgi N-glycan branching blocked GlcNAc-dependent lipid accumulation. The N-acetylglucosaminyltransferase enzymes of the N-glycan branching pathway (Mgat1,2,4,5) display multistep ultrasensitivity to UDP-GlcNAc, as well as branching-dependent compensation. Indeed, oral GlcNAc rescued fat accumulation in lean Mgat5(-/-) mice and in cultured Mgat5(-/-) hepatocytes, consistent with N-glycan branching compensation. Our results suggest GlcNAc reprograms cellular metabolism by enhancing nutrient uptake and lipid storage through the UDP-GlcNAc supply to N-glycan branching pathway.

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