Mol. Cells 2012; 34(5): 439-448
Published online November 6, 2012
https://doi.org/10.1007/s10059-012-0196-x
© The Korean Society for Molecular and Cellular Biology
Correspondence to : *Correspondence: jkim6@fsu.edu
Older women exhibit blunted skeletal muscle hypertro-phy following resistance training (RT) compared to other age and gender cohorts that is partially due to an impaired regenerative capacity. In the present study, we examined whether ?-hydroxy-?-methylbutyrate (HMB) provision to aged female rodents would enhance regenerative mechanisms and facilitate RT-induced myofiber growth. Nineteen-month old female Sprague-Dawley rats were randomly divided into three groups: HMB (0.48 g/kg/d; n = 6), non-HMB (n = 6), and control (n = 4). HMB and non-HMB groups underwent RT every third day for 10 weeks using a ladder climbing apparatus. Whole body strength, grip strength, and body composition was evaluated before and after RT. The gastrocnemius and soleus muscles were analyzed using magnetic resonance diffusion tensor imaging, RT-PCR, and immunohistochemistry to determine myofiber dimensions, transcript expression, and satellite cells/myonuclei, respectively. ANOVAs were used with sig-nificance set at p < 0.05. There were significant time effects (pre vs. post) for whole body strength (+262%), grip strength (+17%), lean mass (+20%), and fat mass (-19%). Both RT groups exhibited significant increases in the mean myofiber cross-sectional area (CSA) in the gas-trocnemius and soleus (+8-22%) compared to control. Moreover, both groups demonstrated significant increases in the numbers of satellite cells (+100-108%) and myonuclei (+32%) in the soleus but not the gastrocnemius. A significant IGF-I mRNA elevation was only observed in soleus of the HMB group (+33%) whereas MGF and myogenin increased significantly in both groups (+32-40%). Our findings suggest that HMB did not further enhance intense RT-mediated myogenic mechanisms and myofiber CSA in aged female rats.
Keywords aging, HMB, ladder climbing, magnetic resonance, satellite cell, sarcopenia
Mol. Cells 2012; 34(5): 439-448
Published online November 30, 2012 https://doi.org/10.1007/s10059-012-0196-x
Copyright © The Korean Society for Molecular and Cellular Biology.
Jeong-Su Kim1,2,*, Young-Min Park1, Sang-Rok Lee1, Ihssan S. Masad3, Andy V. Khamoui1,2, Edward Jo1,2, Bong-Sup Park1, Bahram H. Arjmandi1,2, Lynn B. Panton1,2, Won Jun Lee1,4, and Samuel C. Grant2,3
1Department of Nutrition, Food, and Exercise Sciences, The Florida State University, Tallahassee, FL, USA, 2The Center for Advancing Exercise and Nutrition Research on Aging, The Florida State University, Tallahassee, FL, USA, 3The National High Magnetic Field Laboratory and Department of Chemical and Biomedical Engineering, The Florida State University, Tallahassee, FL, USA, 4Department of Exercise Science, Ewha Womans University, Seoul 120-749, Korea
Correspondence to:*Correspondence: jkim6@fsu.edu
Older women exhibit blunted skeletal muscle hypertro-phy following resistance training (RT) compared to other age and gender cohorts that is partially due to an impaired regenerative capacity. In the present study, we examined whether ?-hydroxy-?-methylbutyrate (HMB) provision to aged female rodents would enhance regenerative mechanisms and facilitate RT-induced myofiber growth. Nineteen-month old female Sprague-Dawley rats were randomly divided into three groups: HMB (0.48 g/kg/d; n = 6), non-HMB (n = 6), and control (n = 4). HMB and non-HMB groups underwent RT every third day for 10 weeks using a ladder climbing apparatus. Whole body strength, grip strength, and body composition was evaluated before and after RT. The gastrocnemius and soleus muscles were analyzed using magnetic resonance diffusion tensor imaging, RT-PCR, and immunohistochemistry to determine myofiber dimensions, transcript expression, and satellite cells/myonuclei, respectively. ANOVAs were used with sig-nificance set at p < 0.05. There were significant time effects (pre vs. post) for whole body strength (+262%), grip strength (+17%), lean mass (+20%), and fat mass (-19%). Both RT groups exhibited significant increases in the mean myofiber cross-sectional area (CSA) in the gas-trocnemius and soleus (+8-22%) compared to control. Moreover, both groups demonstrated significant increases in the numbers of satellite cells (+100-108%) and myonuclei (+32%) in the soleus but not the gastrocnemius. A significant IGF-I mRNA elevation was only observed in soleus of the HMB group (+33%) whereas MGF and myogenin increased significantly in both groups (+32-40%). Our findings suggest that HMB did not further enhance intense RT-mediated myogenic mechanisms and myofiber CSA in aged female rats.
Keywords: aging, HMB, ladder climbing, magnetic resonance, satellite cell, sarcopenia
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