Association Between Vitamin D System And Prognosis Of Hospital-acquired Acute Kidney Injury

Background. Low circulating vitamin D status was suggested to possibly contribute to acute complications in critically ill patients due to its pleiotropic effects in various tissues. However, the evidence was not powerful enough as the sample sizes of the previous studies, so it is still wondered whether vitamin D deficiency is a potentially important contributor to worse early outcomes in critically ill patients. We aimed to investigate the vitamin D status in AKI patients and the possible association of the low vitamin D status and the polymorphisms of vitamin D receptor with the90-day overall mortality.Methods. We conducted a prospective single-center cohort study of200AKI patients, defined by the RIFLE staging criteria. Healthy subjects and critically ill patients with similar SOFA score without AKI were served as control subjects matched in age and gender. Serum vitamin D concentration (25-hydroxyvitamin D and1,25-dihydroxyvitamin D) were measured in the three groups and the AKI patients were followed up for90days grouped by the median value of serum vitamin D concentration. The vitamin D receptor polymorphisms (BsmI and FokI) were measured in patients with AKI and the AKI patients were also followed up grouped by the mutation of VDR gene.Results. Lower serum1,25-dihydroxyvitamin D was detected in patients with AKI compared with healthy subjects and critically ill patients without AKI (59.56+53.00vs86.15+35.34vs98.76+39.69pmol/L, ANOVA p=0.005) and the concentration of1,25-dihydroxyvitamin D stratified by risk, injury and failure is72.55±69.42,53.69±32.68and42.27±29.29pmol/L, decreasing with the severity of AKI (ANOVA p=0.042). No significant finding was found in25-hydrovitamin D. According to the Kaplan-Meier plots, the90-day survival curves of those patients with high concentration of serum25-hydroxyvitamin D or high1,25-dihydroxyvitamin D show no significant difference with those with low concentration.(25-hydroxyvitamin D:log rank p=0.554;1,25-dihydroxyvitamin D: log rank p=0.147) and the survival curves of those patients with BB/Bb or FF/Ff also show no significant difference between those with bb or ff (Bsml:log rank p=0.955; Fokl:log rank p=0.173).Conclusions. Patients with AKI manifest a marked decrease in1,25-dihydroxylvitamin D and the degree of1,25-dihydroxyvitamin D deficiency increased with the severity of AKI. No association between serum1,25-dihydroxyvitamin D status as well as Fokl and BsmI polymorphisms and90-day all-cause mortality was found.