Possible Influence of Vitamin D Receptor Gene Polymorphisms on Recombinant Human Erythropoietin Requirements in Dialysis Patients

Abstract

Background Vitamin D receptor (VDR) gene polymorphisms have been widely studied, especially to analyze their effects on calcium-phosphorus metabolism and secondary hyperparathyroidism in patients on dialysis. In this study, we sought to investigate the possible effects of these polymorphisms on the anemia of renal failure and recombinant human erythropoietin (rHuEPO) responses among patients receiving hemodialysis. Methods One hundred twenty-eight patients (52 females/76 males) underwent genotyping for the insertion/deletion Bsml (B→b, restriction site, exon VIII→IX) and Tagl (T→t, 352 exon IX) VDR gene polymorphisms. The mean value of the last 6 months’ monthly evaluated laboratory values (C-reactive protein, hemoglobin, iron indices, PTH, and albumin) and clinical findings (rHuEPO requirement, cumulative iron supplementation doses, and body weight) were analyzed retrospectively excluding patients with chronic inflammation, hemolytic anemia, or active blood loss such as gastrointestinal bleeding. Results Mean age and dialysis durations were 41.5 ± 11.8 years and 91.8 ± 45.3 months, respectively. Polymorphism percentages were as follows: Bsml; BB/Bb/bb: 32.2/63.6/4.2 and Tagl; TT/Tt/tt: 40.5/55.4/4.1%, respectively. BB variant of Bsml gene was related to lower rHuEPO needs ( P < .05) and also higher hemoglobin levels ( P < .005) when compared with the Bb/bb variant. Considering Tagl variants, transferrin saturation levels were lower ( P < .03) among patients with the Tt/tt variant, but there was no other significant difference in the mean values of other data between TT and Tt/tt variants. Conclusion The BB variant of Bsml was related to decreased rHuEPO requirements to achieve higher hemoglobin levels among maintenance hemodialysis patients without chronic inflammation.