title: HMB attenuates muscle loss during sustained energy deficit induced by calorie restriction and endurance exercise.
abstract: OBJECTIVE
  To investigate the efficacy and underlying mechanisms of β-hydroxy-β-methylbutyrate (HMB) on body composition, muscle mass and physical performance under catabolic versus normal training conditions.
  
  
  METHODS
  Mice were divided into four groups (n=10/group): (1) ALT=ad libitum+trained (1 h/d for 3 d/wk); (2) ALTH=ALT+HMB (0.5 g/kg BW/d); (3) C=calorie restricted (-30%)+trained (6 h/d, 6 d/wk); and (4) CH=C+HMB. Repeated in vivo assessments included body composition, grip strength and sensorimotor coordination before and after the experimental protocol, while in vitro analyses included muscle wet weights, expression of selected genes and proteins regulating muscle mass, and myofiber cross-sectional area. ANOVAs were used with significance set at p<0.05.
  
  
  RESULTS
  ALTH had greater lean mass than ALT and sensorimotor function increased in ALTH, but decreased in ALT under normal training conditions. Grip strength decreased only in C, but was maintained in CH. Gastrocnemius mass and myofiber CSA were greater in CH than C following catabolic conditions. Gastrocnemius atrogin-1 mRNA expression was elevated in C but not in CH compared to all other groups whereas atrogin-1 protein levels showed no significant changes.
  
  
  CONCLUSIONS
  HMB improves body composition and sensorimotor function during normal training and attenuates muscle mass and strength loss during catabolic conditions.
authors.affiliation: Department of Nutrition, Food, and Exercise Sciences, College of Human Sciences, The Florida State University, Tallahassee, FL, USA.
authors.forename: Bong-Sup
authors.initials: BS
authors.lastname: Park
authors.forename: Paul C
authors.initials: PC
authors.lastname: Henning
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Grant
authors.forename: Won Jun
authors.initials: WJ
authors.lastname: Lee
authors.forename: Sang-Rok
authors.initials: SR
authors.lastname: Lee
authors.forename: Bahram H
authors.initials: BH
authors.lastname: Arjmandi
authors.forename: Jeong-Su
authors.initials: JS
authors.lastname: Kim
mesh_terms: D019412:Anatomy, Cross-Sectional; D000818:Animals; D015153:Blotting, Western; D001823:Body Composition / Q000502:physiology; D031204:Caloric Restriction; D004032:Diet; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D009929:Organ Size / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D014631:Valerates / Q000494:pharmacology*
chemical_list: D009124:Muscle Proteins; D000070584:Tripartite Motif Proteins; D014631:Valerates; C004961:beta-hydroxyisovaleric acid; C486692:Fbxo32 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; C499084:Trim63 protein, mouse; D044767:Ubiquitin-Protein Ligases
keywords: ALT; ALTH; B; BH; Body composition; C; CH; CSA; Catabolic; DXA; Dual Energy X-ray Absorptiometry; Functionality; GAPDH; HMB; LBM; Mice; NHMFL; National High Magnetic Field Laboratory; Protein degradation; RT-PCR; Reverse Transcription Polymerase Chain Reaction; SUSOPS; TB; ad libitum-trained; ad libitum-trained+HMB; baseline; baseline+HMB; caloric restricted+trained; caloric restricted+trained+HMB; cross-sectional area; glyceraldehydes 3-phosphate dehydrogenase; lean body mass; sustained operations; true baseline; β-hydroxy-β-methylbutyrate