Department of Nutrition, Food and Exercise Sciences, The Florida State University, Tallahassee, FL, USA.
J Int Soc Sports Nutr. 2012 Apr 18;9(1):18. doi: 10.1186/1550-2783-9-18.
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.
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.
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.
HMB may blunt age-related losses of strength and myofiber dimensions, possibly through attenuating the rise in protein breakdown.
确定β-羟基-β-甲基丁酸（HMB）给药 16 周对年龄相关功能变化的影响，并通过弥散张量成像（DTI）确定肌纤维尺寸。
12 只年轻（44 周）、6 只中年（60 周）、10 只老年（86 周）和 5 只非常老年（102 周）雄性 Fisher-344 大鼠在基线时评估身体成分和握力。随后，处死 6 只年轻、6 只中年、5 只老年和 5 只非常老年大鼠，以测量比目鱼肌（SOL）和腓肠肌（GAS）的基线肌纤维尺寸和基因转录因子表达。其余 6 只年轻和 5 只老年大鼠给予 HMB 16 周，然后处死。
中年对照组的脂肪量增加（+49%），但中年 HMB 组没有增加。此外，老年 HMB 组的脂肪量减少（-56%），而老年对照组没有减少。从 44 周到 60 周，对照组和 HMB 组的归一化强度分别下降和保持，仅在 HMB 组，从 86 周到 102 周，强度增加（+23%）（p<0.05）。在对照组中，所有肌肉的肌纤维大小从 44 周到 102 周均减少（-10%至-15%），但 HMB 组没有减少。与所有其他条件相比，SOL 和 GAS 肌肉中的 atrogin-1mRNA 表达在 102 周的对照组中更高：SOL（+45%）和 GAS（+100%）。这种升高在 102 周的 SOL 中被 HMB 减弱。在 SOL 中，myogenin 存在条件效应，仅在 102 周的 HMB 组相对于 44 周的组显著增加（+40%）。
HMB 可能通过减弱蛋白分解的增加来缓冲与年龄相关的力量和肌纤维尺寸的丧失。
