Ski proto-oncogene regulates body composition and suppresses lipogenesis

• Published in: International Journal of Obesity Vol. 34; no. 3; pp. 524 - 536
• Main Authors: Leong, G.M, Kee, A.J, Millard, S.M, Martel, N, Eriksson, N, Turner, N, Cooney, G.J, Hardeman, E.C, Muscat, G.E.O
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2010; Nature Publishing Group
• Subjects: Adipose tissue; animal models; Animals; Biological and medical sciences; Body composition; Body Composition - genetics; Body Composition - physiology; Body fat; cell differentiation; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Enzymatic activity; enzyme activity; Epidemiology; Fatty acids; Fatty Acids - metabolism; Gene expression; Gene Silencing; genes; Genetic aspects; Growth - physiology; growth and development; Health Promotion and Disease Prevention; Insulin-like growth factors; Internal Medicine; Kinases; lean body mass; Lipid metabolism; lipid peroxidation; lipogenesis; Lipogenesis - genetics; lipogenic gene expression; Medical research; Medical sciences; Medicine; Medicine & Public Health; Metabolic Diseases; Metabolic disorders; Metabolism; Mice; Mice, Transgenic; Muscle, Skeletal - physiology; Musculoskeletal system; myocytes; Myogenesis; myogenic gene expression; Myostatin - metabolism; Obesity; Oncogenes; original-article; Oxidation; palmitic acid; phenotype; Physiological aspects; Proteins; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - physiology; proto-oncogenes; Public Health; RNA, Messenger - genetics; RNA, Messenger - metabolism; Signal transduction; skeletal muscle; Sterol Regulatory Element Binding Protein 1 - metabolism; Thinness - genetics; Thinness - metabolism; Transcription factors; Australia; Queensland Australia; New South Wales Australia; Ski; nuclear receptors; SREBP1c; metabolism; adipogenesis; skeletal muscle; Obesity; Nuclear receptor; Nutrition; Skiing; Nutrition disorder; Metabolic diseases; Striated muscle; Metabolism; Body composition; Sport; Regulation(control); C-Onc gene; Lipogenesis; Nutritional status; Protooncogene
• ISSN: 0307-0565; 1476-5497
• DOI: 10.1038/ijo.2009.265

Objective: The Ski gene regulates skeletal muscle differentiation in vitro and and in vivo. In the c-Ski overexpression mouse model there occurs marked skeletal muscle hypertrophy with decreased adipose tissue mass. In this study, we have investigated the underlying molecular mechanisms responsible for the increased skeletal muscle and decreased adipose tissue mass in the c-Ski mouse. Approach: Growth and body composition analysis (tissue weights and dual energy X-ray absorptiometry) coupled with skeletal muscle and white adipose gene expression and metabolic phenotyping in c-Ski mice and wild-type (WT) littermate controls was performed. Results: The growth and body composition studies confirmed the early onset of accelerated body growth, with increased lean mass and decreased fat mass in the c-Ski mice. Gene expression analysis in skeletal muscle from c-Ski mice compared with WT mice showed significant differences in myogenic and lipogenic gene expressions that are consistent with the body composition phenotype. Skeletal muscle of c-Ski mice had significantly repressed Smad1, 4, 7 and myostatin gene expression and elevated myogenin, myocyte enhancer factor 2, insulin-like growth factor-1 receptor and insulin-like growth factor-2 expression. Strikingly, expression of the mRNAs encoding the master lipogenic regulators, sterol-regulatory enhancer binding protein 1c (SREBP1c), and the nuclear receptor liver X-receptor-α, and their downstream target genes, SCD-1 and FAS, were suppressed in skeletal muscle of c-Ski mice, as were the expressions of other nuclear receptors involved in adipogenesis and metabolism, such as peroxisome proliferator-activated receptor-γ, glucocorticoid receptor and retinoic acid receptor-related orphan receptor-α. Transfection analysis demonstrated Ski repressed the SREBP1c promoter. Moreover, palmitate oxidation and oxidative enzyme activity was increased in skeletal muscle of c-Ski mice. These results suggest that the Ski phenotype involves attenuated lipogenesis, decreased myostatin signalling, coupled to increased myogenesis and fatty acid oxidation. Conclusion: Ski regulates several genetic programs and signalling pathways that regulate skeletal muscle and adipose mass to influence body composition development, suggesting that Ski may have a role in risk for obesity and metabolic disease.