Daily b-hydroxy-b-methylbutyrate (HMB) Intake Prevents A Loss of Lean/Total Body Mass Ratio during Senescence

Abstract

The leucine metabolite b-hydroxy-b-methylbutyrate (HMB) has been shown to improve body composition in the elderly. PURPOSE: To determine the effects of 16-wk HMB intake on body composition during senescence in male rats. METHODS: Body composition was assessed using dual X-ray absorptiometry (DXA) at 60, 86, and 102 wks of age in Fisher 344 male rats (N=15). At 86 wks, 5 rats were sacrificed for baseline muscle while the other 5 were administered HMB (0.46 g/kg/d, similar to 6 g/d in humans) for 16 wks prior to being sacrificed. An additional 5 rats were scanned and sacrificed at 102 wks to serve as a Non-HMB group. RESULTS: There was a time effect (p<0.01) in lean body mass (LBM, g), indicating declines in LBM from 60 to 86 wks (-12%) and to 102 wks (-8%). The LBM decline from 60 to 102 wks was only observed in the Non-HMB group (p<0.05). There was a main group x time effect (p<0.01) in the lean/total body mass (LBM/TBM) ratio, indicating an improved ratio only in the HMB group between 86 and 102 wks (+35%). A group x time effect in fat mass (FM, g) revealed a significant loss in FM (-55%) only in the HMB group between 86 and 102 wks (p<0.01). The HMB intervention, however, had no effect on bone density and content. CONCLUSION: Sarcopenia was observed in our aging animals. Daily HMB intake appears to prevent LBM decrements while improving the LBM/TBM ratio during senescence. Intriguingly, this improved ratio seems to be driven primarily by a marked reduction in FM after HMB intake during senescence. Future research is needed to elucidate the underlying mechanisms of these responses. Study partly funded by Metabolic Technologies Inc. and The Florida State University