Vitamins A and E, retinol binding protein and zinc in rheumatoid arthritis.

Serum vitamins A (2.0 +/- 0.7 mumol/l; p less than 0.05) and E (17.7 +/- 8.2 mumol; p less than 0.001) levels were lower in patients with rheumatoid arthritis (RA) than in healthy controls (2.3 +/- 0.6 mumol/l and 25.3 +/- 5.4 mumol/l, respectively). Low vitamin A and E levels together with a marginally lowered selenium concentration may lead to a markedly decreased antioxidant capacity and enhanced eicosanoid production in RA. Univariate linear regression analysis showed a positive correlation (r = 0.383; p less than 0.005) between serum levels of vitamin A and zinc, and between serum retinol binding protein (RBP) and zinc (r = 0.440, p less than 0.02). These findings suggest that hypovitaminosis A in RA may be mediated by decreased vitamin A transport from the liver to the blood, caused by the low level of zinc dependent hepatic retinol binding protein synthesis. In multiple linear regression analysis, the serum zinc level emerged as the most significant variable and had an independent predictive value of 15.2% for vitamin A. Variations in the serum vitamin E levels were only explained by seropositivity (predictive value of 14.2%), a finding which suggests that the decreased level of vitamin E is a constant feature in RA rather than part of the acute phase response.