title: NADPH oxidase-derived reactive oxygen species increases expression of monocyte chemotactic factor genes in cultured adipocytes.
abstract: Excess glucose and free fatty acids delivered to adipose tissue causes local inflammation, which contributes to insulin resistance. Glucose and palmitate generate reactive oxygen species (ROS) in adipocytes, leading to monocyte chemotactic factor gene expression. Docosahexaenoate (DHA) has the opposite effect. In this study, we evaluated the potential sources of ROS in the presence of excess nutrients. Differentiated 3T3-L1 adipocytes were exposed to palmitate and DHA (250 μM) in either 5 or 25 mM glucose to evaluate the relative roles of mitochondrial electron transport and NADPH oxidases (NOX) as sources of ROS. Excess glucose and palmitate did not increase mitochondrial oxidative phosphorylation. However, glucose exposure increased glycolysis. Of the NOX family members, only NOX4 was expressed in adipocytes. Moreover, its activity was increased by excess glucose and palmitate and decreased by DHA. Silencing NOX4 inhibited palmitate- and glucose-stimulated ROS generation and monocyte chemotactic factor gene expression. NADPH, a substrate for NOX, and pentose phosphate pathway activity increased with glucose but not palmitate and decreased with DHA exposure. Inhibition of the pentose phosphate pathway by glucose-6-phosphate dehydrogenase inhibitors and siRNA suppressed ROS generation and monocyte chemotactic factor gene expression induced by both glucose and palmitate. Finally, both high glucose and palmitate induced NOX4 translocation into lipid rafts, effects that were blocked by DHA. Excess glucose and palmitate generate ROS via NOX4 rather than by mitochondrial oxidation in cultured adipocytes. NOX4 is regulated by both NADPH generated in the PPP and translocation of NOX4 into lipid rafts, leading to expression of monocyte chemotactic factors.
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Chang Yeop
authors.initials: CY
authors.lastname: Han
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Tomio
authors.initials: T
authors.lastname: Umemoto
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Omer
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Den Hartigh
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Chiba
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Renee
authors.initials: R
authors.lastname: LeBoeuf
authors.affiliation: Division of Nephrology, Department of Medicine, University of Michigan, Ann Arbor, Michigan 48105.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Buller
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sweet
authors.affiliation: Division of Nephrology, Department of Medicine, University of Michigan, Ann Arbor, Michigan 48105.
authors.forename: Subramaniam
authors.initials: S
authors.lastname: Pennathur
authors.affiliation: Division of Endocrinology, Metabolism and Diabetes and the Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, Utah 84112, and.
authors.forename: E Dale
authors.initials: ED
authors.lastname: Abel
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington, Seattle, Washington 98195-6426; Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington 98195-6426,. Electronic address: achait@u.washington.edu.
authors.forename: Alan
authors.initials: A
authors.lastname: Chait
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D004281:Docosahexaenoic Acids / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D021962:Membrane Microdomains / Q000201:enzymology* / Q000235:genetics; D051379:Mice; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D018945:Monocyte Chemoattractant Proteins / Q000096:biosynthesis* / Q000235:genetics; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D019308:Palmitic Acid / Q000494:pharmacology; D010427:Pentose Phosphate Pathway / Q000187:drug effects / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013549:Sweetening Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D018945:Monocyte Chemoattractant Proteins; D017382:Reactive Oxygen Species; D013549:Sweetening Agents; D004281:Docosahexaenoic Acids; D019308:Palmitic Acid; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse; D005947:Glucose