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Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy
Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, 55 Claverick Street, Providence, RI 02903, USA
Department of Neurology, Rhode Island Hospital, Alpert Medical School of Brown University, 593 Eddy Street, Providence, RI 02903, USA
Department of Pathology, Division of Perinatal Pathology, Women and Infants Hospital of Rhode Island, Alpert Medical School of Brown University, 55 Claverick Street, Providence, RI 02903, USA
Departments of Neuropathology/Pathology, Neurology, Neurosurgery, and Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, 55 Claverick Street, Providence, RI 02903, USA
* Author to whom correspondence should be addressed.
Received: 3 July 2012; in revised form: 7 August 2012 / Accepted: 13 August 2012 / Published: 20 August 2012
Abstract: Alcohol-related myopathy (Alc-M) is highly prevalent among heavy drinkers, although its pathogenesis is not well understood. We hypothesize that Alc-M is mediated by combined effects of insulin/IGF resistance and oxidative stress, similar to the effects of ethanol on liver and brain. We tested this hypothesis using an established model in which adult rats were pair-fed for 8 weeks with isocaloric diets containing 0% (N = 8) or 35.5% (N = 13) ethanol by caloric content. Gastrocnemius muscles were examined by histology, morphometrics, qRT-PCR analysis, and ELISAs. Chronic ethanol feeding reduced myofiber size and mRNA expression of IGF-1 polypeptide, insulin, IGF-1, and IGF-2 receptors, IRS-1, and IRS-2. Multiplex ELISAs demonstrated ethanol-associated inhibition of insulin, IRS-1, Akt, and p70S6K signaling, and increased activation of GSK-3β. In addition, ethanol-exposed muscles had increased 4-hydroxy-2-nonenal immunoreactivity, reflecting lipid peroxidation, and reduced levels of mitochondrial Complex IV, Complex V, and acetylcholinesterase. These results demonstrate that experimental Alc-M is associated with inhibition of insulin/IGF/IRS and downstream signaling that mediates metabolism and cell survival, similar to findings in alcoholic liver and brain degeneration. Moreover, the increased oxidative stress, which could be mediated by mitochondrial dysfunction, may have led to inhibition of acetylcholinesterase, which itself is sufficient to cause myofiber atrophy and degeneration.
Keywords: alcohol; myopathy; insulin resistance; signal transduction; experimental model; multiplex ELISA; Akt pathway; gene expression; acetylcholine; oxidative stress; mitochondrial dysfunction
MDPI and ACS Style
Nguyen, V.A.; Le, T.; Tong, M.; Silbermann, E.; Gundogan, F.; de la Monte, S.M. Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy. Nutrients 2012, 4, 1058-1075.
Nguyen VA, Le T, Tong M, Silbermann E, Gundogan F, de la Monte SM. Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy. Nutrients. 2012; 4(8):1058-1075.
Nguyen, Van Anh; Le, Tran; Tong, Ming; Silbermann, Elizabeth; Gundogan, Fusun; de la Monte, Suzanne M. 2012. "Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy." Nutrients 4, no. 8: 1058-1075.