title: Amelioration of palmitate-induced metabolic dysfunction in L6 muscle cells expressing low levels of receptor-interacting protein 140.
abstract: We have shown that reduced expression of receptor-interacting protein 140 (RIP140) alters the regulation of fatty-acid (FA) oxidation in muscle. To determine whether a high level of FA availability alters the effects of RIP140 on metabolic regulation, L6 myotubes were transfected with or without RNA interference oligonucleotide sequences to reduce RIP140 expression, and then incubated with high levels of palmitic acid, with or without insulin. High levels of palmitate reduced basal (53%-58%) and insulin-treated (24%-44%) FA uptake and oxidation, and increased basal glucose uptake (88%). In cells incubated with high levels of palmitate, low RIP140 increased basal FA uptake and insulin-treated FA oxidation and glucose uptake, and decreased basal glucose uptake and insulin-treated FA uptake. Under basal conditions, low RIP140 increased the mRNA content of FAT/CD36 (159%) and COX4 (61%), as well as the protein content of Nur77 (68%), whereas the mRNA expression of FGF21 (50%) was decreased, as was the protein content of CPT1b (35%) and FGF21 (44%). Under insulin-treated conditions, low RIP140 expression increased the mRNA content of MCAD (84%) and Nur77 (84%), as well as the protein content of Nur77 (23%). Thus, a low level of RIP140 restores the rates of FA uptake in the basal state, in part via a reduction in upstream insulin signaling. Our data also indicate that the protein expression of Nur77 may be modulated by RIP140 when muscle cells are metabolically challenged by high levels of palmitate.
authors.affiliation: b Department of Math and Science, Marymount California University, Rancho Palos Verdes, California, USA.
authors.forename: Silvana
authors.initials: S
authors.lastname: Constantinescu
authors.affiliation: a Department of Biological Sciences, Human and Evolutionary Biology, Dana and David Dornsife College of Letters, Arts and Sciences, University of Southern California, 3560 Watt Way, PED 107, Los Angeles, CA 90089-0652, USA.
authors.forename: Lorraine P
authors.initials: LP
authors.lastname: Turcotte
mesh_terms: D000818:Animals; D002460:Cell Line; D005227:Fatty Acids / Q000378:metabolism; D005786:Gene Expression Regulation; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism*; D056971:Nuclear Receptor Co-Repressor 1 / Q000096:biosynthesis*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000096:biosynthesis*; D019308:Palmitic Acid / Q000633:toxicity*; D051381:Rats
chemical_list: D005227:Fatty Acids; C539820:Nr4a1 protein, rat; D056971:Nuclear Receptor Co-Repressor 1; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D019308:Palmitic Acid
keywords: NGFI-B; NRIP1; captation du glucose; déshydrogénase des acyl-CoA à chaine moyenne; facteur de croissance fibroblastique 21; fatty acid oxidation; fibroblast growth factor-21; glucose uptake; medium chain acyl-CoA dehydrogenase; nerve growth-factor-inducible B; nuclear receptor-interacting protein 1; oxydation des acides gras; protein kinase B; protéine kinase B