title: Defective leptin-AMP-dependent kinase pathway induces nitric oxide release and contributes to mitochondrial dysfunction and obesity in ob/ob mice.
abstract: OBJECTIVE
  Obesity arises on defective neuroendocrine pathways that increase energy intake and reduce mitochondrial metabolism. In the metabolic syndrome, mitochondrial dysfunction accomplishes defects in fatty acid oxidation and reciprocal increase in triglyceride content with insulin resistance and hyperglycemia. Mitochondrial inhibition is attributed to reduced biogenesis, excessive fission, and low adipokine-AMP-activated protein kinase (AMPK) level, but lateness of the respiratory chain contributes to perturbations. Considering that nitric oxide (NO) binds cytochrome oxidase and inhibits respiration, we explored NO as a direct effector of mitochondrial dysfunction in the leptin-deficient ob/ob mice.
  
  
  RESULTS
  A remarkable three- to fourfold increase in neuronal nitric oxide synthase (nNOS) expression and activity was detected by western blot, citrulline assay, electronic and confocal microscopy, flow cytometry, and NO electrode sensor in mitochondria from ob/ob mice. High NO reduced oxygen uptake in ob/ob mitochondria by inhibition of complex IV and nitration of complex I. Low metabolic status restricted β-oxidation in obese mitochondria and displaced acetyl-CoA to fat synthesis; instead, small interference RNA nNOS caused a phenotype change with fat reduction in ob/ob adipocytes.
  
  
  METHODS
  We evidenced that leptin increases mitochondrial respiration and fat utilization by potentially inhibiting NO release. Accordingly, leptin administration to ob/ob mice prevented nNOS overexpression and mitochondrial dysfunction in vivo and rescued leptin-dependent effects by matrix NO reduction, whereas leptin-Ob-Rb disruption increased the formation of mitochondrial NO in control adipocytes. We demonstrated that in ob/ob, hypoleptinemia is associated with critically low mitochondrial p-AMPK and that, oppositely to p-Akt2, p-AMPK is a negative modulator of nNOS.
  
  
  CONCLUSIONS
  Thereby, defective leptin-AMPK pathway links mitochondrial NO to obesity with complex I syndrome and dysfunctional mitochondria.
authors.affiliation: Laboratory of Oxygen Metabolism, University Hospital, University of Buenos Aires, Argentina. pfinocchietto@hotmail.com
authors.forename: Paola V
authors.initials: PV
authors.lastname: Finocchietto
authors.forename: Silvia
authors.initials: S
authors.lastname: Holod
authors.forename: Fernando
authors.initials: F
authors.lastname: Barreyro
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Peralta
authors.forename: Yael
authors.initials: Y
authors.lastname: Alippe
authors.forename: Andrés
authors.initials: A
authors.lastname: Giovambattista
authors.forename: María C
authors.initials: MC
authors.lastname: Carreras
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Poderoso
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D005227:Fatty Acids / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D009765:Obesity / Q000378:metabolism*; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D005227:Fatty Acids; D020738:Leptin; D034741:RNA, Small Interfering; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D000263:Adenylate Kinase