Vitamin D deficiency associates with γ-tocopherol and quadriceps weakness but not inflammatory cytokines in subjects with knee osteoarthritis

• Published in: Redox biology Vol. 2; no. C; pp. 466 - 474
• Main Authors: Barker, Tyler, Henriksen, Vanessa T., Rogers, Victoria E., Aguirre, Dale, Trawick, Roy H., Lynn Rasmussen, G., Momberger, Nathan G.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier 01.01.2014
• Subjects: Adult; Cytokines; Female; gamma-Tocopherol - blood; Humans; Male; Middle Aged; Muscle strength; Muscle Weakness - physiopathology; Osteoarthritis, Knee - complications; Osteoarthritis, Knee - immunology; Osteoarthritis, Knee - physiopathology; Quadriceps Muscle - physiopathology; Research Paper; Tumor Necrosis Factor-alpha - blood; Vitamin D; Vitamin D - blood; Vitamin D Deficiency - complications; Vitamin D Deficiency - immunology; Vitamin D Deficiency - physiopathology; Vitamin E; Muscle strength; Cytokines; Vitamin D; Vitamin E
• ISSN: 2213-2317; 2213-2317
• DOI: 10.1016/j.redox.2014.01.024

Knee osteoarthritis (OA) is a degenerative joint condition and a leading cause of physical disability in the United States. Quadriceps weakness and inflammatory cytokines contribute to the pathogenesis of knee OA, and both of which, increase with vitamin D deficiency. Other micronutrients, such as vitamins C and E and β-carotene, modulate inflammatory cytokines and decrease during inflammation. The purpose of this study was to test the hypothesis that vitamin D deficiency associates with quadriceps weakness, an increase in serum cytokines, and a decrease in circulating micronutrients in subjects with knee OA. Subjects (age, 48±1 y; serum 25(OH)D, 25.8±1.1 ng/mL) with knee OA were categorized as vitamin D deficient (n=17; serum 25(OH)D≤20 ng/mL), insufficient (n=21; serum 25(OH)D 20-29 ng/mL), or sufficient (n=18; serum 25(OH)D≥30 ng/mL). Single-leg strength (concentric knee extension-flexion contraction cycles at 60 °/s) and blood cytokine, carotene (α and β), ascorbic acid, and tocopherol (α and γ) concentrations were measured. Quadriceps peak torque, average power, total work, and deceleration were significantly (all p<0.05) impaired with vitamin D deficiency. Serum γ-tocopherol concentrations were significantly (p<0.05) increased with vitamin D deficiency. In the vitamin D sufficient group, γ-tocopherol inversely correlated (r=-0.47, p<0.05) with TNF-α, suggesting a pro-inflammatory increase with a γ-tocopherol decrease despite a sufficient serum 25(OH)D concentration. We conclude that vitamin D deficiency is detrimental to quadriceps function, and in subjects with vitamin D sufficiency, γ-tocopherol could have an important anti-inflammatory role in a pathophysiological condition mediated by inflammation.