Kids With Chronic Kidney Disease Often Vitamin D Deficient – MedPage Today
About two-thirds of children and adolescents with chronic kidney disease treated at European nephrology centers had vitamin D deficiency, according to a new study, and vitamin D deficiency was related to a certain gene variant and to kidney disease-related factors.
Researchers studied 500 patients with chronic kidney disease across 12 countries in Europe and found that glomerulopathy, albuminuria, and being female were associated with lower levels, and single-nucleotide polymorphisms (SNPs) in a gene that binds vitamin D were associated with lower vitamin D and with higher levels of the inactive metabolite 24,25-dihydroxy-vitamin D.
Patients taking vitamin D supplements had 25-hydroxy-vitamin D concentrations that were twice as high as those not on supplements (21.6 versus 10.4 ng/mL; P<0.001), reported Anke Doyon, MD, at the University of Heidelberg in Germany, in the Clinical Journal of the American Society of Nephrology.
“This study provides a comprehensive analysis of modifiable and non-modifiable correlates of the vitamin D status of children with chronic kidney disease,” the authors concluded.
After the authors adjusted for genetic, environmental, and supplementation variables, renal function was not associated with vitamin D levels, leading the authors to hypothesize that some factors beside estimated glomerular filtration rate (eGFR) contributes to the higher prevalence of vitamin D deficiency among patients with chronic kidney disease.
The average age of the patients was 12 and all were 6-18 years of age. All of them had stage 3-5 of chronic kidney disease; data were drawn from the nephrology centers that the patients visited. Only those with known vitamin D status and genetic information were included. Medical history and other relevant factors were also included in the analysis. Nearly all of the patients were white.
Renal hypodysplasia was diagnosed in 69% of patients, glomerulopathy in 7.6%, tubolointerstitial and metabolic disorders in 12%, and chronic kidney disease after acute kidney injury in 7%. Almost all of the patients (94.2%) had insufficient vitamin D levels (below 30 ng/mL), and 24,25-dihydroxy-vitamin D levels were associated with 25-hydroxy-vitamin D and 1,25-dihydroxy-vitamin D (r=0.87 and r=0.55; both P<0.001).
About 11% of the patients were taking vitamin D supplements — a number that was “inappropriately low” according to Doyon and colleagues — and supplementation prevalence increased as eGFR declined, from 5.4% in chronic kidney disease stage 3a to 22.2% in stage 5. Vitamin D levels varied by season, unsurprisingly, and by region. Turkish children consistently had lower vitamin D concentrations than others, independent of supplementation and disease-related factors.
Genome-wide association studies of vitamin D have found that vitamin D levels are associated with proteins that play a part in the synthesis, metabolism, and transport of a handful of enzymes, and several SNPs have been linked to vitamin D deficiency in the general population.
In a univariate analysis, vitamin D and 24,25(OH)2D were both negatively associated with intact parathyroid hormone (r=-0.24 and -0.3, respectively; both P<0.001), but they weren’t associated with c-terminal fibroblast growth factor 23.
The results are limited because they might not be generalizable to other patient populations with chronic kidney disease. Only a few patients were taking supplements and the causal relationships of supplementation and other outcomes are unclear. Vitamin D deficiency is associated with a host of poor outcomes, but supplementation has shown to be ineffective in terms of outcomes for many of those problems.
The authors disclosed no relationships with industry.