title: β-Hydroxy-β-methylbutyrate reduces myonuclear apoptosis during recovery from hind limb suspension-induced muscle fiber atrophy in aged rats.
abstract: β-Hydroxy-β-methylbutyrate (HMB) is a leucine metabolite shown to reduce protein catabolism in disease states and promote skeletal muscle hypertrophy in response to loading exercise. In this study, we evaluated the efficacy of HMB to reduce muscle wasting and promote muscle recovery following disuse in aged animals. Fisher 344×Brown Norway rats, 34 mo of age, were randomly assigned to receive either Ca-HMB (340 mg/kg body wt) or the water vehicle by gavage (n = 32/group). The animals received either 14 days of hindlimb suspension (HS, n = 8/diet group) or 14 days of unloading followed by 14 days of reloading (R; n = 8/diet group). Nonsuspended control animals were compared with suspended animals after 14 days of HS (n = 8) or after R (n = 8). HMB treatment prevented the decline in maximal in vivo isometric force output after 2 wk of recovery from hindlimb unloading. The HMB-treated animals had significantly greater plantaris and soleus fiber cross-sectional area compared with the vehicle-treated animals. HMB decreased the amount of TUNEL-positive nuclei in reloaded plantaris muscles (5.1% vs. 1.6%, P < 0.05) and soleus muscles (3.9% vs. 1.8%, P < 0.05). Although HMB did not significantly alter Bcl-2 protein abundance compared with vehicle treatment, HMB decreased Bax protein abundance following R, by 40% and 14% (P < 0.05) in plantaris and soleus muscles, respectively. Cleaved caspase-3 was reduced by 12% and 9% (P < 0.05) in HMB-treated reloaded plantaris and soleus muscles, compared with vehicle-treated animals. HMB reduced cleaved caspase-9 by 14% and 30% (P < 0.05) in reloaded plantaris and soleus muscles, respectively, compared with vehicle-treated animals. Although, HMB was unable to prevent unloading-induced atrophy, it attenuated the decrease in fiber area in fast and slow muscles after HS and R. HMB's ability to protect against muscle loss may be due in part to putative inhibition of myonuclear apoptosis via regulation of mitochondrial-associated caspase signaling.
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Division of Exercise Physiology,West Virginia University School of Medicine, Morgantown, WV 26506, USA.
authors.forename: Yanlei
authors.initials: Y
authors.lastname: Hao
authors.forename: Janna R
authors.initials: JR
authors.lastname: Jackson
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Neile
authors.initials: N
authors.lastname: Edens
authors.forename: Suzette L
authors.initials: SL
authors.lastname: Pereira
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Alway
mesh_terms: D000375:Aging; D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D016009:Chi-Square Distribution; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D019417:Hindlimb Suspension; D020287:In Situ Nick-End Labeling; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000473:pathology; D053580:Muscle Strength / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D009133:Muscular Atrophy / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D009929:Organ Size / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D020127:Recovery of Function; D014631:Valerates / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494828:Bax protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D014631:Valerates; D051028:bcl-2-Associated X Protein; C004961:beta-hydroxyisovaleric acid