title: Beta-hydroxy-beta-methyl-butyrate blunts negative age-related changes in body composition, functionality and myofiber dimensions in rats.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Nutrition, Food and Exercise Sciences, The Florida State University, Tallahassee, FL, USA. jkim6@fsu.edu.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Wilson
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Grant
authors.forename: Sang-Rok
authors.initials: SR
authors.lastname: Lee
authors.forename: Ihssan S
authors.initials: IS
authors.lastname: Masad
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Park
authors.forename: Paul C
authors.initials: PC
authors.lastname: Henning
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Stout
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Loenneke
authors.forename: Bahram H
authors.initials: BH
authors.lastname: Arjmandi
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Panton
authors.forename: Jeong-Su
authors.initials: JS
authors.lastname: Kim