J. M. Wilson; S. C. Grant; S. R. Lee; I. S. Masad; Y. M. Park; P. C. Henning; J. R. Stout; J. P. Loenneke; B. H. Arjmandi; L. B. Panton;J. S. Kim


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Abbreviated Journal Title

J. Int. Soc. Sport Nutr.


Beta-hydroxy-beta-methylbutyrate; Aging; Fat-free mass; Strength; Sarcopenia; HUMAN SKELETAL-MUSCLE; FED AD-LIBITUM; METHYLBUTYRATE HMB; PROTEIN-SYNTHESIS; UBIQUITIN LIGASES; AMINO-ACIDS; STRENGTH; YOUNG; MEN; SUPPLEMENTATION; Nutrition & Dietetics; Sport Sciences


Purpose: To determine the effects of 16 wk. of beta-hydroxy-beta-methylbutyrate (HMB) administration on age-related changes in functionality and diffusion tensor imaging (DTI) determined myofiber dimensions. Methods: Twelve young (44 wk.), 6 middle-aged (60 wk.), 10 old (86 wk.), and 5 very old (102 wk.) male Fisher-344 rat's body composition and grip strength were assessed at baseline. Following, 6 young, 6 middle-aged, 5 old and 5 very old rats were sacrificed for baseline myofiber dimensions and gene transcript factor expression in the soleus (SOL) and gastrocnemius (GAS). The remaining 6 young and 5 old rats were given HMB for 16 wk. and then sacrificed. Results: Fat mass increased in the middle-aged control condition (+49%) but not the middle-aged HMB condition. In addition, fat mass declined (-56%) in the old HMB condition but not the old control condition. Normalized strength declined and maintained respectively in the control and HMB conditions from 44 to 60 wk. and increased (+23%) (p < 0.05) from 86 to 102 wk. in only the HMB condition. Declines occurred in myofiber size in all muscles from 44 to 102 wk. in the control condition(-10 to -15%), but not HMB condition. Atrogin-1 mRNA expression in the SOL and GAS muscles was greater in the 102-wk control condition than all other conditions: SOL (+45%) and GAS (+100%). This elevation was blunted by HMB in the 102 wk. old SOL. There was a condition effect in the SOL for myogenin, which significantly increased (+40%) only in the 102-wk. HMB group relative to the 44-wk. group. Conclusions: HMB may blunt age-related losses of strength and myofiber dimensions, possibly through attenuating the rise in protein breakdown.

Journal Title

Journal of the International Society of Sports Nutrition



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