title: Oleate dose-dependently regulates palmitate metabolism and insulin signaling in C2C12 myotubes.
abstract: Because the protective effect of oleate against palmitate-induced insulin resistance may be lessened in skeletal muscle once cell metabolism is overloaded by fatty acids (FAs), we examined the impact of varying amounts of oleate on palmitate metabolic channeling and insulin signaling in C2C12 myotubes. Cells were exposed to 0.5mM of palmitate and to increasing doses of oleate (0.05, 0.25 and 0.5mM). Impacts of FA treatments on radio-labelled FA fluxes, on cellular content in diacylglycerols (DAG), triacylglycerols (TAG), ceramides, acylcarnitines, on PKCθ, MAPKs (ERK1/2, p38) and NF-ΚB activation, and on insulin-dependent Akt phosphorylation were examined. Low dose of oleate (0.05mM) was sufficient to improve palmitate complete oxidation to CO2(+29%, P<0.05) and to alter the cellular acylcarnitine profile. Insulin-induced Akt phosphorylation was 48% higher in that condition vs. palmitate alone (p<0.01). Although DAG and ceramide contents were significantly decreased with 0.05mM of oleate vs. palmitate alone (-47 and -28%, respectively, p<0.01), 0.25mM of oleate was required to decrease p38 MAPK and PKCθ phosphorylation, thus further improving the insulin signaling (+32%, p<0.05). By contrast, increasing oleate concentration from 0.25 to 0.5mM, thus increasing total amount of FA from 0.75 to 1mM, deteriorated the insulin signaling pathway (-30%, p<0.01). This was observed despite low contents in DAG and ceramides, and enhanced palmitate incorporation into TAG (+27%, p<0.05). This was associated with increased incomplete FA β-oxidation and impairment of acylcarnitine profile. In conclusion, these combined data place mitochondrial β-oxidation at the center of the regulation of muscle insulin sensitivity, besides p38 MAPK and PKCθ.
authors.affiliation: INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France. Electronic address: frederic.capel@clermont.inra.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Capel
authors.affiliation: INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France. Electronic address: naoufel.cheraiti@hotmail.ca.
authors.forename: Naoufel
authors.initials: N
authors.lastname: Cheraiti
authors.affiliation: Service Maladies Héréditaires du Métabolisme, Centre de Biologie et Pathologie Est, CHU de Lyon, France. Electronic address: cecile.acquaviva-bourdain@chu-lyon.fr.
authors.forename: Cécile
authors.initials: C
authors.lastname: Acquaviva
authors.affiliation: Institut Cochin, Département d'Endocrinologie, Métabolisme and Diabète, INSERM U1016/CNRS UMR8104/UMR-S8104, Bâtiment Faculté, 24 rue du faubourg Saint Jacques, 75014 Paris, France. Electronic address: carole.henique@inserm.fr.
authors.forename: Carole
authors.initials: C
authors.lastname: Hénique
authors.affiliation: MetaToul-Lipidomic, MetaboHUB, INSERM UMR 1048, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France University of Toulouse, UMR1048, Paul Sabatier University, France. Electronic address: justine.bertrand-michel@inserm.fr.
authors.forename: Justine
authors.initials: J
authors.lastname: Bertrand-Michel
authors.affiliation: Service Maladies Héréditaires du Métabolisme, Centre de Biologie et Pathologie Est, CHU de Lyon, France. Electronic address: christine.saban@chu-lyon.fr.
authors.forename: Christine
authors.initials: C
authors.lastname: Vianey-Saban
authors.affiliation: Institut Cochin, Département d'Endocrinologie, Métabolisme and Diabète, INSERM U1016/CNRS UMR8104/UMR-S8104, Bâtiment Faculté, 24 rue du faubourg Saint Jacques, 75014 Paris, France. Electronic address: carina.prip-buus@inserm.fr.
authors.forename: Carina
authors.initials: C
authors.lastname: Prip-Buus
authors.affiliation: INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France; INRA UMR1397, Laboratoire CarMeN, Inserm UMR1060, Université Lyon 1, INSA de Lyon, Faculté de Médecine Lyon Sud, BP 12, 165 Chemin du Grand Revoyet, 69921 Oullins Cedex, France. Electronic address: beatrice.morio@lyon.inra.fr.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Morio
mesh_terms: D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives / Q000378:metabolism; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010168:Palmitates / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014280:Triglycerides / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002518:Ceramides; D004075:Diglycerides; D005227:Fatty Acids; D007328:Insulin; D016328:NF-kappa B; D010168:Palmitates; D014280:Triglycerides; C116917:acylcarnitine; D019301:Oleic Acid; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D002331:Carnitine
keywords: Insulin signaling; Lipid metabolism; Lipotoxicity; Skeletal muscle; Substrate partitioning