IL6 and chronic kidney disease: Based upon these studies, we investigated a possible association between deficiency of 25(OH)D and some inflammatory (interleukin 6 [IL-6], leptin, adiponectin, FGF-23 and isoprostane) and oxidative stress (total radical antioxidant parameter [TRAP], lipid hydroperoxide dose [CL-LOOHs], serum concentration of nitric oxide metabolites [NOx], and advanced oxidation protein products [AOPP]) biomarkers in pre-dialysis CKD patients.