Circulating interleukin-6 is not altered while γ-tocopherol is increased in subjects scheduled for knee surgery with low vitamin D

The purpose of this study was to identify if circulating interleukin (IL)-6 and γ-tocopherol (γT) fluctuate with vitamin D status in subjects with an underlying knee joint injury or disease. We hypothesized that low vitamin D associates with an increase in plasma γT while serum IL-6 remains unchanged in subjects with an underlying knee joint trauma or disease. Fifty-four subjects scheduled to undergo primary, unilateral anterior cruciate ligament reconstructive surgery (ACL; n = 27) or total knee arthroplasty (TKA; n = 27) were studied. Circulating γT, α-tocopherol (αT), lipids (cholesterol and triglycerides), IL-6, and 25-hydroxyvitamin D (25(OH)D) were measured in fasting blood samples obtained prior to surgery. Subjects were classified as vitamin D deficient, insufficient, or sufficient if they had a serum 25(OH)D concentration <50, 50-75, or >75 nM, respectively. The majority (57%) of the subjects possessed a serum 25(OH)D less than 50 nM. Circulating cholesterol, triglycerides, and IL-6 were not significantly (all p > 0.05) different between vitamin D status groups. However, lipid corrected αT was significantly (p < 0.05) decreased and both lipid- and non-lipid-corrected plasma γT concentrations were significantly (both p < 0.05) increased with low serum 25(OH)D (i.e., <50 nM). A significant (p < 0.05) multi-variate analysis revealed that an increase in plasma γT per lipids was significantly (p < 0.05) predicted by a decrease in serum 25(OH)D but not by a decrease in plasma αT per lipids. We conclude that low vitamin D associates with an increase in plasma γT but not IL-6 in subjects with an underlying joint injury or disease.