title: Myristic acid potentiates palmitic acid-induced lipotoxicity and steatohepatitis associated with lipodystrophy by sustaning de novo ceramide synthesis.
abstract: Palmitic acid (PA) induces hepatocyte apoptosis and fuels de novo ceramide synthesis in the endoplasmic reticulum (ER). Myristic acid (MA), a free fatty acid highly abundant in copra/palmist oils, is a predictor of nonalcoholic steatohepatitis (NASH) and stimulates ceramide synthesis. Here we investigated the synergism between MA and PA in ceramide synthesis, ER stress, lipotoxicity and NASH. Unlike PA, MA is not lipotoxic but potentiated PA-mediated lipoapoptosis, ER stress, caspase-3 activation and cytochrome c release in primary mouse hepatocytes (PMH). Moreover, MA kinetically sustained PA-induced total ceramide content by stimulating dehydroceramide desaturase and switched the ceramide profile from decreased to increased ceramide 14:0/ceramide16:0, without changing medium and long-chain ceramide species. PMH were more sensitive to equimolar ceramide14:0/ceramide16:0 exposure, which mimics the outcome of PA plus MA treatment on ceramide homeostasis, than to either ceramide alone. Treatment with myriocin to inhibit ceramide synthesis and tauroursodeoxycholic acid to prevent ER stress ameliorated PA plus MA induced apoptosis, similar to the protection afforded by the antioxidant BHA, the pan-caspase inhibitor z-VAD-Fmk and JNK inhibition. Moreover, ruthenium red protected PMH against PA and MA-induced cell death. Recapitulating in vitro findings, mice fed a diet enriched in PA plus MA exhibited lipodystrophy, hepatosplenomegaly, increased liver ceramide content and cholesterol levels, ER stress, liver damage, inflammation and fibrosis compared to mice fed diets enriched in PA or MA alone. The deleterious effects of PA plus MA-enriched diet were largely prevented by in vivo myriocin treatment. These findings indicate a causal link between ceramide synthesis and ER stress in lipotoxicity, and imply that the consumption of diets enriched in MA and PA can cause NASH associated with lipodystrophy.
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Martínez
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Torres
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Baulies
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Alarcón-Vila
authors.affiliation: Biomedic Diagnosis Center, Hospital Clinic i Provincial de Barcelona, IDIBAPS, Barcelona, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Elena
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departament de Química Orgànica Biològica, Institut d'Investigacions Químiques i Ambientals de Barcelona, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Fabriàs
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departament de Química Orgànica Biològica, Institut d'Investigacions Químiques i Ambientals de Barcelona, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
authors.forename: Josefina
authors.initials: J
authors.lastname: Casas
authors.affiliation: Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Caballeria
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.|Research Center for ALPD, Keck School of Medicine, Univerisity of Southern California, Los Angeles, CA, USA.
authors.forename: Jose C
authors.initials: JC
authors.lastname: Fernandez-Checa
authors.affiliation: Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain.|Liver Unit, Hospital Clinic I Provincial de Barcelona, IDIBAPS and CIBERehd, Barcelona, Spain.|Research Center for ALPD, Keck School of Medicine, Univerisity of Southern California, Los Angeles, CA, USA.
authors.forename: Carmen
authors.initials: C
authors.lastname: García-Ruiz
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis; D002518:Ceramides / Q000096:biosynthesis*; D002784:Cholesterol / Q000378:metabolism; D004195:Disease Models, Animal; D059865:Endoplasmic Reticulum Stress; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008060:Lipodystrophy / Q000139:chemically induced* / Q000201:enzymology / Q000378:metabolism / Q000517:prevention & control; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008930:Mitochondria, Liver / Q000378:metabolism; D019814:Myristic Acid; D065626:Non-alcoholic Fatty Liver Disease / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D019308:Palmitic Acid; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D051049:Sphingosine N-Acyltransferase / Q000172:deficiency / Q000235:genetics; D013997:Time Factors
chemical_list: D000873:Anthracenes; D002518:Ceramides; D005229:Fatty Acids, Monounsaturated; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D019814:Myristic Acid; D012430:Ruthenium Red; C432165:pyrazolanthrone; D019308:Palmitic Acid; D002784:Cholesterol; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; C580723:Cers2 protein, mouse; D051049:Sphingosine N-Acyltransferase; D048031:JNK Mitogen-Activated Protein Kinases; C001996:thermozymocidin
keywords: FFA; NAFLD; Pathology Section; endoplasmic reticulum; hepatocyte; sphingolipid