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A7693 - Smoking Cessation Reverses Acute Cigarette Smoke Induced Muscle Derangement in Animal Model
Author Block: S. Ngai1, K. Cheung1, J. C. Mak2, S. Cheung1, T. K. Fung1, B. W. Lau1; 1Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, Hong Kong, 2Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
Background: Cigarette-smoke (CS) exposure is one major risk factor for Chronic obstructive pulmonary disease (COPD). Increasing evidence suggest that CS and COPD may exert extra-pulmonary manifestation further contributing to reduction in physical functions. Our previous animal study demonstrated that CS, even at short-term 7-day exposure, induced significant changes in muscle fibers distribution. With the plasticity nature of muscle, it is possible that CS-induced acute changes on muscle fibers is reversible. Thus, this study aims to examine the potential reversibility of muscle derangement upon smoking cessation. Method Two-month old male Sprague-Dawley rats (n=24) were randomly allocated into 4 groups: 1) CSd7 - Exposure to CS for 7 days; 2) SAd7 - Exposure to sham air for 7 days; 3) CSd21 - Exposure to CS for 7 days followed by 14-day smoking cessation; 4) SAd21 - Exposure to sham air for 7 days with no further treatment for 14 days. Proportions of muscle fiber Type I, IIa and hybrid of soleus were examined by immunofluorescent staining. Physical functions such as voluntary physical activity and motor coordination were assessed by number of revolutions in voluntary wheel and time stayed on rotarod respectively. Results One-way ANOVA showed that significant between-group differences were found in the proportion of muscle fiber Type I (p=0.023) and Type IIa (p=0.004). Post-hoc analysis revealed that, comparing to SAd7 (Type I: 82.6±2.9% and Type IIa: 14.1±2.8%), CSd7 demonstrated a significantly lower proportion of Type I (72.4±1.5%, p=0.028) and higher proportion of Type IIa (24.2±1.3%, p=0.012) muscle fiber while no significant difference was found in other group comparisons. However, no significant between group differences in physical activity and motor coordination was found in rotarod and voluntary wheel-running tests. Conclusion These data suggests that CS exposure induces a short-term significant impact on the redistribution of muscle fiber type in the main locomotor muscle and that the differences become minimal after 14 days of smoking cessation, indicating the potential reversibility of muscle fibers upon smoking cessation. However, no direct influence on physical functions such as level of physical activity and motor coordination were observed. Further studies investigating the effect of smoking cessation on long-term CS induced skeletal muscle derangement is warranted. Funding support: The study was supported by The Hong Kong Polytechnic University (1-ZVFM) and Hong Kong Lung Foundation (5-ZH1N)