title: Characterising the inhibitory actions of ceramide upon insulin signaling in different skeletal muscle cell models: a mechanistic insight.
abstract: Ceramides are known to promote insulin resistance in a number of metabolically important tissues including skeletal muscle, the predominant site of insulin-stimulated glucose disposal. Depending on cell type, these lipid intermediates have been shown to inhibit protein kinase B (PKB/Akt), a key mediator of the metabolic actions of insulin, via two distinct pathways: one involving the action of atypical protein kinase C (aPKC) isoforms, and the second dependent on protein phosphatase-2A (PP2A). The main aim of this study was to explore the mechanisms by which ceramide inhibits PKB/Akt in three different skeletal muscle-derived cell culture models; rat L6 myotubes, mouse C2C12 myotubes and primary human skeletal muscle cells. Our findings indicate that the mechanism by which ceramide acts to repress PKB/Akt is related to the myocellular abundance of caveolin-enriched domains (CEM) present at the plasma membrane. Here, we show that ceramide-enriched-CEMs are markedly more abundant in L6 myotubes compared to C2C12 myotubes, consistent with their previously reported role in coordinating aPKC-directed repression of PKB/Akt in L6 muscle cells. In contrast, a PP2A-dependent pathway predominantly mediates ceramide-induced inhibition of PKB/Akt in C2C12 myotubes. In addition, we demonstrate for the first time that ceramide engages an aPKC-dependent pathway to suppress insulin-induced PKB/Akt activation in palmitate-treated cultured human muscle cells as well as in muscle cells from diabetic patients. Collectively, this work identifies key mechanistic differences, which may be linked to variations in plasma membrane composition, underlying the insulin-desensitising effects of ceramide in different skeletal muscle cell models that are extensively used in signal transduction and metabolic studies.
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France.
authors: Rana
authors: R
authors: Mahfouz
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France.
authors: Rhéa
authors: R
authors: Khoury
authors: Department of Physiology, Medical University of Bialystok, Bialystok, Poland.
authors: Agnieszka
authors: A
authors: Blachnio-Zabielska
authors: Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
authors: Sophie
authors: S
authors: Turban
authors: INRA, UMR1331 Toxalim, Research Centre in Food Toxicology, Toulouse, France.
authors: Nicolas
authors: N
authors: Loiseau
authors: Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
authors: Christopher
authors: C
authors: Lipina
authors: Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
authors: Clare
authors: C
authors: Stretton
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France; Département de Diabétologie et Maladies métaboliques, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France.
authors: Olivier
authors: O
authors: Bourron
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France.
authors: Pascal
authors: P
authors: Ferré
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France.
authors: Fabienne
authors: F
authors: Foufelle
authors: Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
authors: Harinder S
authors: HS
authors: Hundal
authors: INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie - Paris 6, UMR-S 1138, Paris, France; Université Paris Descartes, UMR-S 1138, Paris, France.
authors: Eric
authors: E
authors: Hajduch
mesh_terms: D000818:Animals; D022461:Caveolins / Q000235:genetics / Q000378:metabolism; D002518:Ceramides / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D061251:Primary Cell Culture; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D022461:Caveolins; D002518:Ceramides; D007328:Insulin; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D054648:Protein Phosphatase 2