PON1 and metabolic syndrome: Systemic treatment with methotrexate for weeks alleviated dyslipidemia, i.e., a notable reduction in total cholesterol, LDL and HDL was seen (p < 0.05), however it did not influence oxidative stress levels, as similar pre- versus post-therapy concentrations of serum paraoxonase-1, total antioxidant status, total oxidant status, and oxidative stress index were registered (p > 0.05).