Long-term Low-Intensity Endurance Exercise along with Blood-Flow Restriction Improves Muscle Mass and Neuromuscular Junction Compartments in Old Rats

Abstract

Background: During the aging process, muscle atrophy and neuromuscular junction remodeling are inevitable. The present study aimed to clarify whether low-intensity aerobic exercise along with limb blood-flow restriction (BFR) could improve aging-induced muscle atrophy and nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction.

Methods: Forty-eight male Wistar rats, aged 23-24 months, were randomly divided into control, sham (Sh: subjected to surgery without BFR), BFR (subjected to BFR), exercise (Ex: subjected to 10 weeks of low-intensity exercise), Sh+Ex, and BFR+Ex groups. Forty-eight hours after the last training session, the animals were sacrificed and their soleus and extensor digitorum longus (EDL) muscles were removed. The hypertrophy index was calculated, and molecular parameters were measured using western blotting. Statistical analysis was done with ANOVA using SPSS (version 20), with a P<0.05 as the level of significance.

Results: The control and Sh groups showed weight gain (P=0.001), whereas the Ex, Sh+Ex, and BFR+Ex groups had significant weight loss (P<0.001). The hypertrophy index of the soleus was significantly higher in the BFR+Ex group than in the control, Sh, and BFR groups (P<0.001). BFR+Ex induced significant hypertrophic effects on the EDL (P<0.001 vs. the control, Sh, Ex, and Sh+Ex groups, and P=0.006 vs. the BFR group). BFR+Ex also increased nAChRs in the soleus (P=0.02 vs. the control and Sh groups) and the EDL (P=0.008 vs. the control and Sh groups).

Conclusion: BFR plus mild exercise is a safe method with potential beneficial effects in protecting and augmenting muscle mass and nAChR clustering at the neuromuscular junction in old rats.

Keywords: Aging; Blood-flow restriction; Exercise; Neuromuscular junction; Nicotinic acetylcholine receptors.

Figure 1

Soleus muscle hypertrophy index in the different experimental groups at the end of the study. Values are presented as means±SEMs. Numbers and abbreviations regarding the animal groups are presented in the legend to table 1. •P<0.001 in comparison with the CTL, Sh, and BFR groups

Figure 2

Extensor digitorum longus (EDL) muscle hypertrophy index in the different experimental groups at the end of the study. Values are presented as means±SEMs. Numbers and abbreviations regarding the animal groups are presented in the legend to table 1. *P=0.02 vs. the CTL and Sh groups; •P<0.001 vs. the CTL, Sh, Ex, and Sh+Ex groups; †P=0.006 vs. the BFR group

Figure 3

Shows expression of nicotinic acetylcholine receptors (AChRs) in the soleus muscle using the western blot method. Values are means±SEMs. Numbers and abbreviations regarding the animal groups are presented in the legend to table 1. *P=0.02 vs. the CTL and Sh groups

Figure 4

Shows expression of nicotinic acetylcholine receptors (AChRs) in the extensor digitorum longus (EDL) muscle using the western blot method. Values are means±SEMs. Numbers and abbreviations regarding the animal groups are presented in the legend to table 1. **P=0.008 vs. the CTL and Sh groups