Mounting evidence has presented nitric oxide (NO) and vitamin D (vitD) as having independently complex roles in osteoarthritis (OA). However, a mechanistic or an observational connection between them has never been investigated in the disease. This study investigates the correlation between circulating 25-hydroxyvitamin D [25(OH)D] and total NO as nitrate/nitrite (NO x ) in patients with knee OA.
The recruited subjects comprised 36 post-menopausal women with knee OA, ages 50-60 years, as well as 10 healthy males, 20-30 years of age. 25(OH)D and NO x levels were determined using high-performance liquid chromatography and spectrophotometrically using Griess reaction, respectively.
The mean (SEM) 25(OH)D and NO x concentrations of OA patients were 25.0 (1.6) ng/mL and 32.45 (2.18) μM, respectively, and 35.4 (2.1) ng/mL and 25.49 (2.23) μM, respectively, for controls. Comparison of mean 25(OH)D and NO x concentrations of OA patients and controls yielded significant results (P = 0.001 and 0.034, respectively). NO notably decreased with decreasing 25(OH)D concentration in patients. However, significant results in terms of mean NO x concentration were observed in the comparison of normal and deficient vitD OA groups (P = 0.048).
Results suggest that vitD increases NO production and inducible NO synthase expression in osteoarthritic chondrocytes possibly leading to a protective effect.