title: Nitric oxide-induced downregulation of leptin production by 3T3-L1 adipocytes.
abstract: Leptin secreted mainly by adipocytes plays an important role in insulin sensitivity in metabolic syndrome. Inducible nitric oxide synthase (iNOS) in 3T3-L1 adipocytes is induced by lipopolysaccharide (LPS) and several proinflammatory cytokines such as tumor necrosis factor-alpha and interferon-gamma (IFN-gamma). Because the role of iNOS-derived nitric oxide (NO) in adipocyte function has not been fully clarified, the question that we addressed in the present study was whether iNOS-derived NO is involved in regulation of leptin secretion by adipocytes. Incubation of 3T3-L1 adipocytes for 12h with a mixture of IFN-gamma and LPS caused not only a 55% reduction in leptin secretion and a 52% reduction in leptin mRNA, but also significant induction of iNOS at both protein and mRNA levels. Inhibition of leptin secretion that had been induced by the IFN-gamma-LPS mixture was completely nullified by NOS inhibitors such as Nomega-monomethyl-L-arginine and aminoguanidine. Treatment of adipocytes with NO donors such as an NONOate and S-nitrosoglutathione produced an effect on leptin secretion similar to that of the IFN-gamma-LPS mixture. It is likely therefore that NO mediates downregulation of leptin caused by the IFN-gamma-LPS mixture in 3T3-L1 adipocytes, which suggests an important role for NO in adipocyte functions.
authors.affiliation: Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Unno
authors.forename: Teruo
authors.initials: T
authors.lastname: Akuta
authors.forename: Yu-ichiro
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Seikoh
authors.initials: S
authors.lastname: Horiuchi
authors.forename: Takaaki
authors.initials: T
authors.lastname: Akaike
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D020738:Leptin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D020738:Leptin; D008070:Lipopolysaccharides; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D019335:Nitroarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II