SERPINE1 and chronic kidney disease: To demonstrate this, we quantified a number of biomarkers that have been implicated in the pathology of CVD and CKD: full length osteopontin (flOPN), c-terminal fibroblast growth factor-23 (FGF-23), and plasminogen activator inhibitor-1 (PAI-1), to assess the effects of Vit D repletion after 12 weeks on these established indicators of vascular and kidney function.