East Carolina University : Research and Creative Achievement Week 2012
Vitamin D receptor expression with aging and exercise in skeletal muscle, Brittanny C. Matthews1, Rengfei Shi2, Hoke B. Whitworth2, William T. Mixon2, Scott E. Gordon2, Terry E. Jones1, 1 Department of Physical Therapy, 2 Department of Kinesiology, East Carolina University, Greenville, NC 27858 Vitamin D insufficiency/deficiency is commonly associated with falls in the elderly and has been related to type 2 muscle atrophy. It has been reported that older individuals have less vitamin D receptors (VDR) in their skeletal muscle. The combination of inadequate serum vitamin D levels and potentially reduced availability of VDR contributes to the increase in falls among elderly individuals. Progressive resistance exercise has proven to be effective in reducing risk for falls in the elderly. It has not been investigated whether resistance exercise increases VDR expression in skeletal muscle which would further enhance the effects of vitamin D. We investigated VDR expression in two parts. First, VDR expression was studied with respect to aging and exercise. We hypothesized that VDR expression would decrease with age, and would be altered with exercise in young and aged rats. Second, we studied the effect of increased cytosolic calcium on VDR expression. We hypothesized that the increased cytosolic calcium would alter the expression of VDR. For the first part of our investigation, an Achilles tenotomy of the gastrocnemius muscle was performed in the left hind limb of 32 week and 8 week old rats, placing an overload on the plantaris and soleus muscles. A sham operation was performed on the right hind limb. The plantaris muscle from the right hind limb served as the control. After one week of overload, the plantaris muscles were excised and homogenized. To analyze the effects of increased cytosolic calcium on VDR, L6 myotubes were treated with caffeine. After harvest, myotubes were homogenized. Both the homogenized animal tissues and L6 myotubes were analyzed using Western blotting techniques. A paired Student s t-Test was used to analyze differences between groups (P d 0.05). We found that expression of VDR was not significantly different in plantaris muscle between young and aged rats, or overloaded versus non-overloaded plantaris muscle. There was no difference in VDR expression in caffeine treated versus non-caffeine treated L6 myotubes.
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