β-Hydroxy-β-Methylbutyrate Did Not Enhance High Intensity Resistance Training-Induced Improvements in Myofiber Dimensions and Myogenic Capacity in Aged Female Rats

Abstract

Older women exhibit blunted skeletal muscle hypertrophy 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 β-hydroxy-β-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 significance 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 gastrocnemius 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.

Effect of conjugated linoleic acids and omega‐3 fatty acids with or without resistance training on muscle mass in high‐fat diet‐fed middle‐aged mice

“…This test of sensorimotor coordination required the mice to maintain their body position for 5 s on an inclined plane while the angle of the surface was changed from 20 to 60 deg at 2 deg intervals (Kim et al . ; Park et al . ; Lee et al .…”

“…The animals’ forelimbs were placed on a tension bar while they were restrained manually by the scruff of the neck and base of the tail (Kim et al . ; Park et al . ; Lee et al .…”

“…All isolated tissues were stored at −80°C for later analyses (Kim et al . ; Park et al . ; Lee et al .…”

Validation of Reference Genes for qPCR Analysis of Resistance Training and Androgenic Anabolic Steroids on Hypothalamus, Adrenal Gland and Fat Tissue

“…Two groups used only the 18s gene [13,28], five used only Actb gene [29][30][31][32][33]. Other authors used the Cyclophilin gene [15,31] and eight authors used Gapdh as a reference gene in their studies [12,14,[34][35][36][37][38][39][40].…”

“…Furthermore, physiological and psychological benefits of REx are considered important in physical rehabilitation and treatment programs [11]. Therefore, a number of gene expression and molecular biological studies has been conducted in Rex training and steroids models, including ladder exercise models [12][13][14][15]. There is a methodological gap, in which there is a lack of studies that identify the best reference gene in these areas of knowledge.…”