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[h=1]Protective Effects of Clenbuterol against Dexamethasone-Induced Masseter MuscleAtrophy and Myosin Heavy Chain Transition.[/h]Umeki D1, Ohnuki Y2, Mototani Y2, Shiozawa K2, Suita K3, Fujita T3, Nakamura Y4, Saeki Y2, Okumura S5.
[h=3]Author information[/h]
[h=3]Abstract[/h][h=4]BACKGROUND:[/h]<abstracttext label="BACKGROUND" nlmcategory="BACKGROUND">Glucocorticoid has a direct catabolic effect on skeletal muscle, leading to muscle atrophy, but no effective pharmacotherapy is available. We reported that clenbuterol (CB) induced masseter muscle hypertrophy and slow-to-fast myosin heavy chain (MHC) isoform transition through direct muscle β2-adrenergic receptor stimulation. Thus, we hypothesized that CB would antagonize glucocorticoid (dexamethasone; DEX)-induced muscle atrophy and fast-to-slow MHC isoform transition.</abstracttext>
[h=4]METHODOLOGY:[/h]<abstracttext label="METHODOLOGY" nlmcategory="METHODS">We examined the effect of CB on DEX-induced masseter muscle atrophy by measuring massetermuscle weight, fiber diameter, cross-sectional area, and myosin heavy chain (MHC) composition. To elucidate the mechanisms involved, we used immunoblotting to study the effects of CB on muscle hypertrophic signaling (insulin growth factor 1 (IGF1) expression, Akt/mammalian target of rapamycin (mTOR) pathway, and calcineurin pathway) and atrophic signaling (Akt/Forkhead box-O (FOXO) pathway and myostatin expression) in masseter muscle of rats treated with DEX and/or CB.</abstracttext>
[h=4]RESULTS AND CONCLUSION:[/h]<abstracttext label="RESULTS AND CONCLUSION" nlmcategory="CONCLUSIONS">Masseter muscle weight in the DEX-treated group was significantly lower than that in the Control group, as expected, but co-treatment with CB suppressed the DEX-induced masseter muscle atrophy, concomitantly with inhibition of fast-to-slow MHC isoforms transition. Activation of the Akt/mTOR pathway in masseter muscle of the DEX-treated group was significantly inhibited compared to that of the Control group, and CB suppressed this inhibition. DEX also suppressed expression of IGF1 (positive regulator of muscle growth), and CB attenuated this inhibition. Myostatin protein expression was unchanged. CB had no effect on activation of the Akt/FOXO pathway. These results indicate that CB antagonizes DEX-induced muscle atrophy and fast-to-slow MHC isoform transition via modulation of Akt/mTOR activity and IGF1 expression. CB might be a useful pharmacological agent for treatment of glucocorticoid-induced muscle atrophy.</abstracttext>
<dl class="rprtid" style="margin-right: 15px; margin-left: 0px; font-size: 0.8465em; line-height: 1.4em; display: inline;"><dt style="display: inline; padding: 0px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px !important; white-space: nowrap;">PMID:</dt> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">26053620</dd> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">[PubMed - indexed for MEDLINE] </dd><dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;"></dd><dt style="display: inline; padding: 0px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.5em !important; white-space: nowrap;">PMCID:</dt> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">PMC4460071</dd><dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;"></dd> </dl>
[h=3]Author information[/h]
[h=3]Abstract[/h][h=4]BACKGROUND:[/h]<abstracttext label="BACKGROUND" nlmcategory="BACKGROUND">Glucocorticoid has a direct catabolic effect on skeletal muscle, leading to muscle atrophy, but no effective pharmacotherapy is available. We reported that clenbuterol (CB) induced masseter muscle hypertrophy and slow-to-fast myosin heavy chain (MHC) isoform transition through direct muscle β2-adrenergic receptor stimulation. Thus, we hypothesized that CB would antagonize glucocorticoid (dexamethasone; DEX)-induced muscle atrophy and fast-to-slow MHC isoform transition.</abstracttext>
[h=4]METHODOLOGY:[/h]<abstracttext label="METHODOLOGY" nlmcategory="METHODS">We examined the effect of CB on DEX-induced masseter muscle atrophy by measuring massetermuscle weight, fiber diameter, cross-sectional area, and myosin heavy chain (MHC) composition. To elucidate the mechanisms involved, we used immunoblotting to study the effects of CB on muscle hypertrophic signaling (insulin growth factor 1 (IGF1) expression, Akt/mammalian target of rapamycin (mTOR) pathway, and calcineurin pathway) and atrophic signaling (Akt/Forkhead box-O (FOXO) pathway and myostatin expression) in masseter muscle of rats treated with DEX and/or CB.</abstracttext>
[h=4]RESULTS AND CONCLUSION:[/h]<abstracttext label="RESULTS AND CONCLUSION" nlmcategory="CONCLUSIONS">Masseter muscle weight in the DEX-treated group was significantly lower than that in the Control group, as expected, but co-treatment with CB suppressed the DEX-induced masseter muscle atrophy, concomitantly with inhibition of fast-to-slow MHC isoforms transition. Activation of the Akt/mTOR pathway in masseter muscle of the DEX-treated group was significantly inhibited compared to that of the Control group, and CB suppressed this inhibition. DEX also suppressed expression of IGF1 (positive regulator of muscle growth), and CB attenuated this inhibition. Myostatin protein expression was unchanged. CB had no effect on activation of the Akt/FOXO pathway. These results indicate that CB antagonizes DEX-induced muscle atrophy and fast-to-slow MHC isoform transition via modulation of Akt/mTOR activity and IGF1 expression. CB might be a useful pharmacological agent for treatment of glucocorticoid-induced muscle atrophy.</abstracttext>
<dl class="rprtid" style="margin-right: 15px; margin-left: 0px; font-size: 0.8465em; line-height: 1.4em; display: inline;"><dt style="display: inline; padding: 0px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px !important; white-space: nowrap;">PMID:</dt> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">26053620</dd> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">[PubMed - indexed for MEDLINE] </dd><dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;"></dd><dt style="display: inline; padding: 0px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.5em !important; white-space: nowrap;">PMCID:</dt> <dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;">PMC4460071</dd><dd style="margin: 0px; display: inline; padding: 0px; white-space: nowrap;"></dd> </dl>
