Muscle IGF-1-induced skeletal muscle hypertrophy evokes higher insulin sensitivity and carbohydrate use as preferential energy substrate

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BioMed Research International
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Christoffolete M.A.
Silva W.J.
Ramos G.V.
Bento M.R.
Costa M.O.
Ribeiro M.O.
Okamoto M.M.
Lohmann T.H.
Machado U.F.
Musaro A.
Moriscot A.S.
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© 2015 Marcelo Augusto Christoffolete et al.We characterized the metabolic profile of transgenic mice exhibiting enhanced muscle mass driven by increased mIGF-1 expression (MLC/mIGF-1). As expected, 6-month-old MLC/mIGF-1 mice were heavier than age-matched wild type (WT) mice (37.4 ± 0.3 versus 31.8 ± 0.6 g, resp.). MLC/mIGF-1 mice had higher respiratory quotient when compared to WT (0.9 ± 0.03 versus 0.74 ± 0.02, resp.) suggesting a preference for carbohydrate as the major fuel source. MLC/mIGF-1 mice had a higher rate of glucose disposal when compared to WT (3.25 ± 0.14 versus 2.39 ± 0.03%/min, resp.). The higher disposal rate correlated to ~2-fold higher GLUT4 content in the extensor digitorum longus (EDL) muscle. Analysis of mRNA content for the glycolysis-related gene PFK-1 showed ~3-fold upregulation in MLC/mIGF-1 animals. We also found a 50% downregulation of PGC1α mRNA levels in MLC/mIGF-1 mouse EDL muscle, suggesting less abundant mitochondria in this tissue. We found no difference in the expression of PPARα and PPARβ/δ, suggesting no modulation of key elements in oxidative metabolism. These data together suggest a shift in metabolism towards higher carbohydrate utilization, and that could explain the increased insulin sensitivity of hypertrophied skeletal muscle in MLC/mIGF-1 mice.
Assuntos Scopus
Animals , Carbohydrate Metabolism , Glucose Transporter Type 4 , Hypertrophy , Insulin , Insulin Resistance , Insulin-Like Growth Factor I , Mice , Mice, Transgenic , Mitochondria , Muscle Proteins , Muscle, Skeletal , Peroxisome Proliferator-Activated Receptors , RNA, Messenger , Transcription Factors
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