The vitamin D receptor expression in skeletal muscle of women with distal radius fracture

Abstract

We evaluated the vitamin D receptor (VDR) expression in the forearm flexor muscle of women with distal radius fracture. High VDR expression was associated with low appendicular lean mass index. Introduction We aimed to evaluate the relationship between the VDR expression in the muscle cell and the muscle mass in women with a distal radius fracture (DRF). Methods We prospectively recruited 45 women over 50 years of age (mean age, 66 years) with DRF and acquired biopsy of the forearm flexor muscle. The muscle cross-sectional area (CSA) and VDR expression were measured using immunohistochemistry staining. The clinical parameters including grip strength, gait speed, body mass index (BMI), bone mineral density (BMD), and serum vitamin D levels were compared between patients grouped by appendicular lean mass index and were correlated with the VDR expression. Results Twelve patients (27%) showed a decreased appendicular lean mass index, less than the cut-off value of 5.4 kg/m² which was suggested by the Asian Working Group for Sarcopenia. Patients with a low appendicular lean mass index had significantly lower muscle CSA (p = 0.037), but a higher VDR expression (p = 0.045) than those with higher indices. VDR expression was negatively correlated with BMI (r = -0.417, p = 0.004) and appendicular lean mass index (r = -0.316, p = 0.044). Conclusions DRF patients with low appendicular lean mass index presented high VDR expression and low CSA in forearm muscle cells. This suggests that the VDR expression might be upregulated in the attempt to compensate for the decreasing muscle mass. Further studies are necessary to explore the role of VDR in the progression of sarcopenia.