title: Palmitate-mediated downregulation of peroxisome proliferator-activated receptor-gamma coactivator 1alpha in skeletal muscle cells involves MEK1/2 and nuclear factor-kappaB activation.
abstract: The mechanisms by which elevated levels of free fatty acids cause insulin resistance are not well understood. Previous studies have reported that insulin-resistant states are characterized by a reduction in the expression of peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1, a transcriptional activator that promotes oxidative capacity in skeletal muscle cells. However, little is known about the factors responsible for reduced PGC-1 expression. The expression of PGC-1 mRNA levels was assessed in C2C12 skeletal muscle cells exposed to palmitate either in the presence or in the absence of several inhibitors to study the biochemical pathways involved. We report that exposure of C2C12 skeletal muscle cells to 0.75 mmol/l palmitate, but not oleate, reduced PGC-1alpha mRNA levels (66%; P < 0.001), whereas PGC-1beta expression was not affected. Palmitate led to mitogen-activated protein kinase (MAPK)-extracellular signal-related kinase (ERK) 1/2 (MEK1/2) activation. In addition, pharmacological inhibition of this pathway by coincubation of the palmitate-exposed cells with the MEK1/2 inhibitors PD98059 and U0126 prevented the downregulation of PGC-1alpha. Furthermore, nuclear factor-kappaB (NF-kappaB) activation was also involved in palmitate-mediated PGC-1alpha downregulation, since the NF-kappaB inhibitor parthenolide prevented a decrease in PGC-1alpha expression. These findings indicate that palmitate reduces PGC-1alpha expression in skeletal muscle cells through a mechanism involving MAPK-ERK and NF-kappaB activation.
authors.affiliation: Pharmacology Unit, Department of Pharmacology and Therapeutic Chemistry, University of Barcelona, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Coll
authors.forename: Mireia
authors.initials: M
authors.lastname: Jové
authors.forename: Ricardo
authors.initials: R
authors.lastname: Rodríguez-Calvo
authors.forename: Elena
authors.initials: E
authors.lastname: Eyre
authors.forename: Xavier
authors.initials: X
authors.lastname: Palomer
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Sánchez
authors.forename: Manuel
authors.initials: M
authors.lastname: Merlos
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Laguna
authors.forename: Manuel
authors.initials: M
authors.lastname: Vázquez-Carrera
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D015536:Down-Regulation; D004789:Enzyme Activation; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D048730:MAP Kinase Kinase Kinase 2 / Q000378:metabolism*; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D019301:Oleic Acid / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology*; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D016328:NF-kappa B; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D019301:Oleic Acid; D019308:Palmitic Acid; D048730:MAP Kinase Kinase Kinase 2; C482619:Map3k2 protein, mouse; D048369:MAP Kinase Kinase 1