The Relationship Between Vitamin D Status and Graft Function in Renal Transplant Recipients

Abstract

C hronic kidney disease (CKD), which has a high morbidity and mortality rate, negatively affects the quality of life. The incidence of the disease has increased significantly in recent years [1]. Renal replacement therapies, such as dialysis and renal transplantation, are implemented for patients with CKD. In renal transplantation patients, survival and quality of life is improved markedly compared with dialysis patients, and less cardiovascular disease is observed [2]. However, there is still a high risk for acute rejection and chronic allograft nephropathy in renal transplantation [3,4]. Due to the increasing importance of the renal transplantation, it is very important to reduce major risk factors involved in graft failure. Vitamin D, which plays an important role in the regulation of calcium, phosphorus, and bone metabolism, is a steroid hormone. It is obtained through nutrition and solar radiation. Two hydroxylation steps are required to convert it to the physiologically active form of vitamin D (1,25-dihydroxyvitamin D, calcitriol). The first step occurs in the liver, producing 25-hydroxyvitamin D3 , and plasma 1,25(OH)2D3 levels were measured. In addition, the urine protein/creatinine (P/C) ratio was calculated. The plasma 1,25(OH)2D3 level was determined using liquid chromatography-tandem mass spectrometry. Results: The posttransplant level of serum phosphorus, PTH, creatinine, BUN and ALP was found to be significantly decreased (p=0.0001; p=0.011 for ALP). Although the plasma 1,25(OH)2D3 level had significantly increased (p=0.0001) after transplantation, no significant difference in the serum 25(OH)D level was observed. The urine P/C ratio was found to be significantly decreased after transplantation (p=0.007). A deficiency of vitamin D was observed frequently both before (87%) and after (73%) transplantation. Conclusion: Persistent vitamin D deficiency was detected in the recipients even after transplantation, although the serum PTH level decreased. Some studies published to date draw a direct link between serum vitamin D level and graft function; however, evidence for this link was not observed in the present study. Long-term monitoring may be needed to evaluate the correlation between vitamin D level and graft function. Keywords: 1,25-dihydroxyvitamin D3, graft function, liquid chromatography-tandem mass spectrometry, protein/creatinine ratio, renal transplantation, vitamin D Research ArticleThe relationship between vitamin D status and graft function in renal transplant recipients