The acute effects of cigarette smoke exposure on muscle fiber type dynamics in rats

Abstract

Reduced exercise capacity is common in people with chronic obstructive pulmonary diseases (COPD) and chronic smokers and is suggested to be related to skeletal muscle dysfunction. Previous studies using human muscle biopsies have shown fiber-type shifting in chronic smokers particularly those with COPD. These results, however, are confounded with aging effects because people with COPD tend to be older. In the present study, we implemented an acute 7-day cigarette smoke-exposed model using Sprague-Dawley rats to evaluate early effects of cigarette smoking on soleus muscles. Rats (n = 5 per group) were randomly assigned to either a sham air (SA) or cigarette smoking (CS) groups of three different concentrations of total particulate matters (TPM) (CS TPM2.5 , CS TPM5 , CS TPM10 ). Significantly lower percentages of type I and higher type IIa fiber were detected in the soleus muscle in CS groups when compared with SA group. Of these, only CS TMP10 group exhibited significantly lower citrate synthase activity and higher muscle tumor necrosis factor-α level than that of SA group. Tumor necrosis factor-α level was correlated with the percentage of type I and IIa fibers. However, no significant between-group differences were found in fiber cross-sectional area, physical activities, or lung function assessments. In conclusion, acute smoking may directly trigger the onset of glycolytic fiber type shift in skeletal muscle independent of aging.

NMR Spectroscopy Identifies Chemicals in Cigarette Smoke Condensate That Impair Skeletal Muscle Mitochondrial Function

“…Furthermore, the same study demonstrated that acutely treating healthy soleus muscles with cigarette smoke extract impaired mitochondrial respiration [ 16 ]. Additional work in rats reported a reduction in muscle citrate synthase activity, a marker of mitochondrial content, following only 7-days of cigarette smoke exposure [ 17 ]. Therefore, these studies demonstrate that active smoking acutely impairs muscle mitochondrial health, which can be recovered upon smoking cessation, suggesting that tobacco smoke contains chemicals that are toxic to muscle mitochondria.…”

Moderate Treadmill Training Induces Limited Effects on Quadriceps Muscle Hypertrophy in Mice Exposed to Cigarette Smoke Involving Metalloproteinase 2

“…The extra-pulmonary changes inherent to CS could also reduce muscle endurance and strength, ultimately leading to diminished exercise capacity and regenerative response. 11 Curiously, the speed and time running did not differ significantly between mice nonsmokers and smokers, which could be partially explained by similar body weight between groups and substantial metabolic adjustments. Optimal body weight maintenance may compensate the skeletal muscle energy metabolism during exercise to maintain exercise capacity and tolerance.…”

“…The heterogeneity of fiber size in the present study is consistent with previous reports on human 33 and rodent skeletal muscle after CS exposure. 11 Such heterogeneous fiber size distribution is believed to be associated with the redistribution of muscle fiber types observed in CS exposure, shifting from type I oxidative muscle fibers to type II glycolytic muscle fibers. 11 A non-uniform atrophy response can be a considerable adaptation to the CS condition, generally related to physiological character.…”

“…32 Collectively, these studies suggest that the harmful effects of CS on CSA with a predominance of type II fibers, such as quadriceps, It is possible to assume that fibers are not all the same size and might respond to stress or mechanical stimuli differently. 11 So, the use of frequency histograms according to diameter provides a more detailed and accurate quantitative analysis of fibers size distribution than reliance on mean size, which is influenced by the size and the relative number of cells with any given diameter. The heterogeneity of fiber size in the present study is consistent with previous reports on human 33 and rodent skeletal muscle after CS exposure.…”

“… 5 CS has several toxins with immunomodulatory effects that might impair fatigue resistance, exercise tolerance, and functional disability, culminating in fiber atrophy and skeletal muscle abnormalities. 6 , 11 Such dysfunction is believed to be associated with impairment of muscle structure (ie, cross-sectional area, fiber-type distribution, capillary density), 6 metabolic capacity, and cellular damage. 12 However, the changes in muscle extracellular matrix (ECM) remain largely unknown in CS conditions.…”