Introduction
renal anemia, CKD, chronic kidney disease, hypoxia, Anemia
HYPOXIA, RENAL ANEMIA, ANEMIA, POSITIVE
Anemia is a frequent finding in chronic kidney disease (CKD) and it is associated with increased mortality and morbidity rates [Hepcidin, the central regulator of iron homeostasis, is considered to play a key role in the development of functional ID in CKD [The bioactive isoform of hepcidin is hepcidin-25 (HEP-25). Positive regulators of hepcidin expression comprise tissue iron levels, iron availability, and inflammatory activity whereas erythropoietic activity and hypoxia decrease its synthesis [Hepcidin is to large extent filtered freely by the glomeruli and clearance occurs by degradation in the proximal tubuli in addition to cellular endocytosis at its site of action [However, in patients with The strong influence of iron reserves on hepcidin expression, shown in healthy individuals as well as in patients with CKD [Based on its described mode of action, animal experiments demonstrating improvements of renal anemia with hepcidin ablation, in addition to supportive epidemiological data, hepcidin has gained interest as a potentially modifiable target for alleviating renal anemia [A recently identified suppressor of hepcidin expression is vitamin D (VD), which through its downstream metabolites 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)Only a limited number of interventional studies evaluating the suppressive effect of nutritional VD on serum levels of HEP-25 in non-dialysis CKD patients have been undertaken. Apart from a trial in pediatric CKD patients (stage G2-G5) that was unable to demonstrate a suppressive effect on serum levels of HEP-25 after 12 weeks of VD supplementation, studies in the adult CKD population evaluating nutritional VD as a potential modifier of serum HEP-25 in a placebo (PBO) controlled manner is scarce [