HEALTH NEWS

Study Title:

Vitamin D deficiency impairs skeletal muscle function in a smoking mouse model.

Study Abstract

Chronic obstructive pulmonary disease (COPD) is associated with skeletal muscle dysfunction. Vitamin D plays an important role in muscle strength and performance in healthy individuals. In COPD, vitamin D deficiency is highly prevalent but its role in skeletal muscle dysfunction is unclear. We examined the time-course effect of vitamin D deficiency on limb muscle function in mice with normal or deficient vitamin D serum levels exposed to air or cigarette smoke for 6, 12 or 18 weeks. When combined with smoking, vitamin D deficiency resulted in increased lung inflammation and lung compliance from 6 weeks on with highest emphysema scores at 18 weeks. Smoking reduced body and muscle mass of the soleus and extensor digitorum longus (EDL) but did not affect contractility, despite type II atrophy. Vitamin D deficiency did not alter muscle mass but reduced muscle force over time, downregulated vitamin D receptor expression, increased muscle lipid peroxidation but did not alter actin and myosin expression, fiber dimensions or twitch relaxation time. When combined with smoking, vitamin D deficiency did not further deteriorate muscle function but worsened soleus mass loss and EDL fiber atrophy at 18 weeks. We conclude that, in contrast to the synergy of smoking and vitamin D deficiency on lung disease, smoking and vitamin D deficiency had different, independent but important noxious effects on skeletal muscles in a mouse model of mild COPD.