title: Vitamin D deficiency associates with γ-tocopherol and quadriceps weakness but not inflammatory cytokines in subjects with knee osteoarthritis.
abstract: 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.
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Barker
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA ; The Orthopedic Specialty Clinic, Murray, UT 84107, USA.
authors.forename: Vanessa T
authors.initials: VT
authors.lastname: Henriksen
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA.
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Rogers
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA.
authors.forename: Dale
authors.initials: D
authors.lastname: Aguirre
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA ; The Orthopedic Specialty Clinic, Murray, UT 84107, USA.
authors.forename: Roy H
authors.initials: RH
authors.lastname: Trawick
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA ; The Orthopedic Specialty Clinic, Murray, UT 84107, USA.
authors.forename: G
authors.initials: G
authors.lastname: Lynn Rasmussen
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S., Fashion Blvd., Murray, UT 84107, USA ; The Orthopedic Specialty Clinic, Murray, UT 84107, USA.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Momberger
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000276:immunology / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D014807:Vitamin D / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications / Q000276:immunology / Q000503:physiopathology*; D024504:gamma-Tocopherol / Q000097:blood*
chemical_list: C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; D014807:Vitamin D; D024504:gamma-Tocopherol
keywords: Cytokines; Muscle strength; Vitamin D; Vitamin E