Background: The deficit of 25-hydroxyvitamin D (25OHD) associated with secondary hyperparathyroidism (SHPT) is a frequent finding in chronic kidney disease (CKD) patients on haemodialysis (HD). These events are associated with increased morbidity and mortality rates of cardiovascular (CV) origin. Adequate 25OHD serum levels as well as the use of selective vitamin D receptor activators (VDRA) have been shown to have beneficial and independent effects on bone mineral metabolism and cardiovascular risk. Currently, there is still controversy regarding the type of supplementation needed by CKD patients on HD.
Objective: The aim of our study was to evaluate whether there is a benefit of combination therapy with 25OHD, calcifediol and a VDRA, oral paricalcitol, on bone-mineral metabolism and inflammatory markers, compared to single treatment with each of these in a group of patients on HD.
Material and method: We performed a prospective study of 6 months, involving 26 patients in our HD unit. We randomised patients into two groups: group 1 (G1) received oral paricalcitol treatment at doses of 1 mcg/day. Group 2 (G2) was treated with 1 ampoule calcifediol/wk (0.266 mg/wk=16 000U) orally. After 3 months of treatment, calcifediol and paricalcitol were added to the G1 and G2 respectively at the same doses, keeping these treatments together for 3 months to complete the 6 months of follow-up. Laboratory tests were performed at months 0, 3 and 6, measuring in all patients serum markers of 25OHD, calcium (Ca), phosphorus (P) and PTH. Bone turnover markers measured were: alkaline phosphatase (AP), aminoterminal propeptide of procollagen type 1 (Pinp1) and carboxyl-terminal telopeptide of type I collagen (CrossLaps), and inflammatory markers: IL-8. We also collected data on levels of insulin, glucose, haemoglobin, erythropoiesis-stimulating agents (ESAs) and rates of resistance to EPO and HOMA (homeostasis model assessment).
Results: We detected a deficit of 25-hydroxyvitamin D in all patients studied, with a mean of 13.67 ± 4.81 ng/ml. Supplementation with oral calcifediol significantly corrects this deficit without evidence of toxicity (35.36 ± 33.68 ng/ml in G1 at 6 months and 59.21 ± 26.50 ng/ml in G2 at 3 months). Paricalcitol treatment significantly reduces PTH levels in G1 at 3 months (P<.039). We also noted a decrease in bone marker Pinp1 with paricalcitol, pointing to a possible direct effect on bone cells (P<.001). Both treatment with paricalcitol and with calcifediol produced a significant decrease in levels of IL-8 (P<.001), a known inflammatory marker, drawing attention to a trend towards better response to erythropoiesis-stimulating agents (ESAs), possibly related to the decrease in inflammation. The HOMA index did not change significantly.
Conclusion: Based on our results, we cannot conclude that the association of calcifediol and paricalcitol produces advantages over the effect of each drug separately. In addition, Paricalcitol by itself appears to have a direct effect on cellular bone remodelling.