title: Inhibition of muscle insulin-like growth factor I expression by tumor necrosis factor-alpha.
abstract: The role of TNF-alpha in muscle catabolism is well established, but little is known about the mechanisms of its catabolic action. One possibility could be that TNF-alpha impairs the production of local growth factors like IGF-I. The aim of this study was to investigate whether TNF-alpha can directly inhibit IGF-I gene and protein expression in muscle. First, we investigated whether the acute inflammation induced by endotoxin injection changes IGF-I and TNF-alpha mRNA in rat tibialis anterior muscle. Endotoxin rapidly increased TNF-alpha mRNA (7-fold at 1 h, P < 0.001) and later decreased IGF-I mRNA (-73% at 12 h, P < 0.001). Furthermore, in a model of C2C12 myotubes, TNF-alpha strongly inhibited IGF-I mRNA and protein (-73 and -47% after 72 h, P < 0.001 and P < 0.01, respectively). Other proinflammatory cytokines failed to inhibit IGF-I mRNA. The effect of TNF-alpha on IGF-I mRNA was not mediated by nitric oxide, and the activation of NF-kappaB was insufficient to inhibit IGF-I expression. Taken together, our data suggest that TNF-alpha induced in muscle after LPS injection can locally inhibit IGF-I expression. The inhibition of muscle IGF-I production could contribute to the catabolic effect of TNF-alpha.
authors.affiliation: Unité de Diabétologie et Nutrition, Université catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Laura
authors.initials: L
authors.lastname: Fernández-Celemín
authors.forename: Nevi
authors.initials: N
authors.lastname: Pasko
authors.forename: Valerie
authors.initials: V
authors.lastname: Blomart
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Thissen
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects*; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007334:Insulin-Like Growth Factor I; D007371:Interferon-gamma