A Randomized Study on the Effect of Vitamin D3 Supplementation on Skeletal Muscle Morphology and Vitamin D Receptor Concentration in Older Women

• Published in: The journal of clinical endocrinology and metabolism 2013-12, Vol.98 (12), p.E1927-E1935
• Main Authors: Ceglia, Lisa, Niramitmahapanya, Sathit, da Silva Morais, Mauricio, Rivas, Donato A, Harris, Susan S, Bischoff-Ferrari, Heike, Fielding, Roger A, Dawson-Hughes, Bess
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Aging; Anatomy, Cross-Sectional; Calcifediol - blood; Cholecalciferol - metabolism; Cholecalciferol - therapeutic use; Cohort Studies; Dietary Supplements; Double-Blind Method; Female; Geriatric Assessment; Hot Topics in Translational Endocrinology; Humans; Mobility Limitation; Muscle Development; Muscle Fibers, Fast-Twitch - metabolism; Muscle Fibers, Fast-Twitch - pathology; Muscle Fibers, Slow-Twitch - metabolism; Muscle Fibers, Slow-Twitch - pathology; Muscle Strength; Pilot Projects; Quadriceps Muscle - metabolism; Quadriceps Muscle - pathology; Receptors, Calcitriol - agonists; Receptors, Calcitriol - metabolism; Up-Regulation; Vitamin D Deficiency - blood; Vitamin D Deficiency - diet therapy; Vitamin D Deficiency - metabolism; Vitamin D Deficiency - pathology
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2013-2820

Context: Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor (VDR) concentration are lacking. Objective: Our objective was to determine whether vitamin D3 4000 IU/d alters muscle fiber cross-sectional area (FCSA) and intramyonuclear VDR concentration over 4 months. Design and Setting: This was a randomized, double-blind, placebo-controlled study in a single center. Participants: Participants were 21 mobility-limited women (aged ≥65 years) with serum 25-hydroxyvitamin D (25OHD) levels of 22.5 to 60 nmol/L. Main Outcome Measures: Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type (I/IIa/IIx) and VDR using immunofluorescence. Results: At baseline, mean (±SD) age was 78 ± 5 years; body mass index was 27 ± 5 kg/m2, 25OHD was 46.3 ± 9.5 nmol/L, and a short physical performance battery score was 7.95 ± 1.57 out of 12. At 4 months, 25OHD level was 52.5 ± 17.1 (placebo) vs 80.0 ± 11.5 nmol/L (vitamin D [VD]; P < .01), and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group (r = 0.87, P < .001). By treatment group, percent change in intramyonuclear VDR concentration was 7.8% ± 18.2% (placebo) vs 29.7% ± 11.7% (VD; P = .03) with a more pronounced group difference in type II vs I fibers. Percent change in total (type I/II) FCSA was −7.4% ± 18.9% (placebo) vs 10.6% ± 20.0% (VD; P = .048). Conclusion: Vitamin D3 supplementation increased intramyonuclear VDR concentration by 30% and increased muscle fiber size by 10% in older, mobility-limited, vitamin D-insufficient women. Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved.