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Smokers Show Changes in Skeletal Muscles

Type I fiber atrophy, increased lactate dehydrogenase found, even without chronic obstructive pulmonary disease

FRIDAY, Jan. 11 (HealthDay News) -- Changes in skeletal muscle in smokers indicate that tobacco smoke may impair the normal process of nitric oxide generation, according to research published in the January issue of the journal Chest.

Maria Montes de Oca, M.D., Ph.D., of the Hospital Universitario de Caracas in Venezuela, and colleagues analyzed data from 14 smokers without chronic obstructive pulmonary disease and 20 healthy controls. All underwent vastus lateralis muscle biopsy.

The smoking group showed a decrease in cross-sectional area of type I muscle fibers, and a trend toward a similar effect in type IIa fibers. Smokers had increased lactate dehydrogenase and percentage of fibers with low oxidative and high glycolytic capacity. However, their neuronal nitric oxide synthase and endothelial nitric oxide synthase were lower. Also, researchers didn't find evidence of local inflammation in the muscle.

"Interesting additional questions arise: Is exercise capacity affected by the changes observed? Are the changes reversible on cessation of smoking? Even if smoking continues, can endurance training reverse the changes? Why is fiber atrophy apparent in smokers but absent in patients with severe chronic obstructive pulmonary disease (studied by the same investigators)? And perhaps most of all, why did the lungs -- ground zero in these subjects -- escape the effects of smoking, yet distant organs (in this case the muscles) had substantial structural changes? As is so often the case, one question answered gives rise to so many more," writes Peter D. Wagner, M.D., of the University of California San Diego, in an accompanying editorial.

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