title: Lipotoxic Palmitate Impairs the Rate of β-Oxidation and Citric Acid Cycle Flux in Rat Neonatal Cardiomyocytes.
abstract: OBJECTIVE
  Diabetic hearts exhibit intracellular lipid accumulation. This suggests that the degree of fatty acid oxidation (FAO) in these hearts is insufficient to handle the elevated lipid uptake. We previously showed that palmitate impaired the rate of FAO in primary rat neonatal cardiomyocytes. Here we were interested in characterizing the site of FAO impairment induced by palmitate since it may shed light on the metabolic dysfunction that leads to lipid accumulation in diabetic hearts.
  
  
  METHODS
  We measured fatty acid oxidation, acetyl-CoA oxidation, and carnitine palmitoyl transferase (Cpt1b) activity. We measured both forward and reverse aconitase activity, as well as NAD+ dependent isocitrate dehydrogenase activity. We also measured reactive oxygen species using the 2', 7'-Dichlorofluorescin Diacetate (DCFDA) assay. Finally we used thin layer chromatography to assess diacylglycerol (DAG) levels.
  
  
  RESULTS
  We found that palmitate significantly impaired mitochondrial β-oxidation as well as citric acid cycle flux, but not Cpt1b activity. Palmitate negatively affected net aconitase activity and isocitrate dehydrogenase activity. The impaired enzyme activities were not due to oxidative stress but may be due to DAG mediated PKC activation.
  
  
  CONCLUSIONS
  This work demonstrates that palmitate, a highly abundant fatty acid in human diets, causes impaired β-oxidation and citric acid cycle flux in primary neonatal cardiomyocytes. This metabolic defect occurs prior to cell death suggesting that it is a cause, rather than a consequence of palmitate mediated lipotoxicity. This impaired mitochondrial metabolism can have important implications for metabolic diseases such as diabetes and obesity.
authors.affiliation: Montreal Heart Institute, Montréal, Canada.
authors.forename: Taha
authors.initials: T
authors.lastname: Haffar
authors.forename: Ali
authors.initials: A
authors.lastname: Akoumi
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bousette
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002478:Cells, Cultured; D002952:Citric Acid Cycle / Q000187:drug effects*; D004075:Diglycerides / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D019301:Oleic Acid / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010168:Palmitates / Q000633:toxicity*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: C011439:1,2-diacylglycerol; D004075:Diglycerides; D010168:Palmitates; D017382:Reactive Oxygen Species; D019301:Oleic Acid; D002334:Carnitine O-Palmitoyltransferase