Author(s): Dr. Syed Shahab Ahmad and Neha Patel

Abstract: Muscle wasting is caused by vitamin D insufficiency in both humans and animals. Sprague Dawley male rats were used to generate a model of vitamin D deficiency in rats. When compared to controls, the deficient group had higher proteasomal enzyme activity, E2 Ubiquitin conjugating enzyme expression, and ubiquitin conjugates. Lysosomal and calpain activities, on the other hand, were unaffected. When compared to control muscle, the deficient muscle had a lower Type II fibre area, a sign of atrophy in the muscle. In D-deficient muscle, proteasomal subunit and muscle atrophy marker genes were up-regulated, while myogenic genes were down-regulated. Increased muscle protein breakdown has been associated to vitamin D deficiency. It seems that the main pathway for vitamin D deficiency-induced muscle protein breakdown is the ubiquitin proteasome pathway, and calcium supplementation alone in the absence of vitamin D only partially reverses the alterations. It does not appear that the lysosomal or calpain proteolytic mechanisms are at play.

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