VDR and vitamin D deficiency: Also, the study on chronic obstructive pulmonary disease mice model shows that VDR expression in both EDL (extensor digitorum longus) and soleus muscles was reduced in vitamin D-deficient mice as compared with mice with normal vitamin D levels and that the reduction in VDR expression with vitamin D deficiency was more pronounced in the soleus muscle (− 57%) compared with the EDL muscle (− 37%) (Cielen et al. 2016).