Chronic vitamin D insufficiency impairs physical performance in C57BL/6J mice.

Vitamin D insufficiency (serum 25-OH vitamin D < 30 ng/ml) affects 70-80% of the general population, yet the long-term impacts on physical performance and the progression of sarcopenia are poorly understood. We therefore followed 6-month-old male C57BL/6J mice (n=6) consuming either sufficient (STD, 1000IU) or insufficient (LOW, 125 IU) vitamin D3/kg chow for 12 months (equivalent to 20-30 human years). LOW supplemented mice exhibited a rapid decline of serum 25-OH vitamin D levels by two weeks that remained between 11-15 ng/mL for all time points thereafter. After 12 months LOW mice displayed worse grip endurance (34.6 +/- 14.1 versus 147.5 +/- 50.6 seconds, p=0.001), uphill sprint speed (16.0 +/- 1.0 versus 21.8 +/- 2.4 meters/min, p=0.0007), and stride length (4.4 +/- 0.3 versus 5.1 +/- 0.3, p=0.002). LOW mice also showed less lean body mass after 8 months (57.5% 5.1% versus 64.5% 4.0%, p=0.023), but not after 12 months of supplementation, as well as greater protein expression of atrophy pathway gene atrogin-1. Additionally, microRNA sequencing revealed differential expression of mIR-26a in muscle tissue of LOW mice. These data suggest chronic vitamin D insufficiency may be an important factor contributing to functional decline and sarcopenia.