Failure of successful renal transplant to produce appropriate levels of 1,25-dihydroxyvitamin D

Vitamin D Levels After Kidney Transplantation and the Risk of Cytomegalovirus Infection

Background:

Some studies reported an association between low levels of vitamin D and the risk of infections, especially viral infections. Kidney transplant patients are at risk of opportunistic infections; however, no study has been conducted on the association between vitamin D levels and the risk of CMV infection.

Objectives:

The aim of this study was to compare the level of vitamin D in two groups of patients with and without CMV infection within four months after the transplantation. Moreover, we aimed to find a relation between vitamin D level, before and after transplantation in each group.

Patients and Methods:

This prospective cohort study was conducted in Baqiyatallah hospital in Tehran in 2013. A total of 82 kidney transplant patients were enrolled and vitamin D levels were measured in them before transplantation. The kidney transplant patients had been followed up for four months and monitored for the presence of cytomegalovirus antigen (CMV Ag) in their blood. In patients with positive CMV Ag, vitamin D level was measured again when they became positive but in other patients it was measured at the end of follow-up; at the end, characteristics of patients and vitamin D levels were compared between the two groups.

Results:

Of all, 40 patients were CMV Ag positive and 42 patients were negative. In most patients transplanted organs were taken from cadaver (66%) and the most common type of dialysis was hemodialysis (92%). Most participants did not undergo antithymocyte globulin therapy (69%) and pulse corticosteroid therapy (83%). Vitamin D level before transplantation was 17.2 ± 11.6 ng/mL. In patients with positive results or at the end of follow-up in patients without CMV Ag, vitamin D level was 16.3 ± 11.4 ng/mL. Only 11% of kidney transplant patients, within four months after transplantation, had a normal level of vitamin D (> 30 ng/mL). There was no significant difference between the two groups for patients’ characteristics (P > 0.05). Vitamin D levels, before transplantation and at the time of detecting CMV Ag or at the end of follow-up period in patients without CMV, were not significantly different between the two groups (P > 0.05). However, vitamin D levels decreased in patients with CMV, while it increased in CMV Ag negative patients, which was statistically significant (P = 0.037).

Conclusions:

Only 11% of kidney transplant patients, even with a successful transplantation of the kidney and with an acceptable performance of the transplanted kidney, had an adequate level of vitamin D. Although, we did not find any significant association between vitamin D levels and CMV infection during a 4-month follow-up after kidney transplantation. It was observed that, compared with the time before transplantation, vitamin D levels decreased in patients with CMV, while it increased in CMV negative patients.

Metabolic bone diseases in kidney transplant recipients

Metabolic bone disease after kidney transplantation has a complex pathophysiology and heterogeneous histology. Pre-existing renal osteodystrophy may not resolve completely, but continue or evolve into a different osteodystrophy. Rapid bone loss immediately after transplant can persist, at a lower rate, for years to come. These greatly increase the risk of bone fracture and vertebral collapse. Each patient may have multiple risk factors of bone loss, such as steroids usage, hypogonadism, persistent hyperparathyroidism (HPT), poor allograft function, metabolic acidosis, hypophosphatemia, vitamin D deficiency, aging, immobility and chronic disease. Clinical management requires a comprehensive approach to address the underlying and ongoing disease processes. Successful prevention of bone loss has been shown with vitamin D, bisphosphonates, calcitonin as well as treatment of hypogonadism and HPT. Novel approach to restore the normal bone remodeling and improve the bone quality may be needed in order to effectively decrease bone fracture rate in kidney transplant recipients.

Vitamin D in organ transplantation

Vitamin D deficiency is prevalent among patients with end-stage organ failure awaiting transplant. Low serum 25-hydroxyvitamin D (25-OHD) levels in these patients may be related to many disease-specific factors, as well as decreased sunlight exposure and limited intake of foods containing vitamin D. Low serum 25-OHD levels are also extremely common following solid organ transplantation, both during the immediate postoperative period and in long-term graft recipients. Demographic and lifestyle factors are important in determining D status in transplant recipients. Worse vitamin D status is associated with poorer general health, lower albumin, and even decreased survival among these patients. Although several studies have demonstrated that active forms of vitamin D and its analogues prevent bone loss following transplantation, the data do not show consistent benefit. These therapies may have particular utility after renal transplantation. However, given the narrow therapeutic window with respect to hypercalcemia and hypercalciuria, and the demonstrated efficacy of bisphosphonates to prevent post-transplantation bone loss, we regard these agents as adjunctive rather than primary therapy for transplantation osteoporosis. The effects of 1,25(OH)(2)D on the immune system, which are still being elucidated, may have potential for reducing infections and preventing allograft rejection after transplantation.

1,25-dihydroxyvitamin D deficiency predicts poorer outcome after renal transplantation

OBJECTIVE

To assess 1,25-dihydroxyvitamin D status and the effect of vitamin concentration on transplantation outcome in renal allograft recipients.

PATIENTS AND METHODS

Ninety patients underwent renal transplantation between 2002 and 2005. All received alfacalcidol supplementation before surgery. 1,25-Dihydroxyvitamin D concentration was determined on day 3 posttransplantation and at 1-, 6-, 12-, 18-, and 24-month follow-up.

RESULTS

Severe 1,25-dihydroxyvitamin D deficiency was noted in 83% of patients immediately posttransplantation. From 1 to 12 months thereafter, concentrations increased almost 3-fold, and remained constant to 24 months. In 50% of patients, the 1,25-dihydroxyvitamin D concentration reached a concentration of more than 30 pg/mL, similar to that in healthy volunteers; in the other 50%, the concentration reached 17.2 pg/mL. A high incidence of delayed graft function was observed in patients with 1,25-dihydroxyvitamin D deficiency (44% vs 6%). There was a negative correlation between the initial 1,25-dihydroxyvitamin D and serum creatinine concentrations at day 3 and month 6 (P < .03). Similarly, the 1,25-dihydroxyvitamin D concentration at 1 month was negatively correlated with creatinine concentration at months 1 through 24 (P < .01). Poor outcome was observed primarily in patients with 1,25-dihydroxyvitamin D deficiency; 2 patients developed cancer, 5 grafts were lost, and 4 patients died of cardiovascular events.

CONCLUSIONS

1,25-Dihydroxyvitamin D deficiency is highly prevalent in renal allograft recipients. Patients with 1,25-dihydroxyvitamin D deficiency are at greater risk of delayed graft function, and the graft is more likely to be lost. These findings suggest the necessity of adequate vitamin D supplementation both before and after transplantation.

Bone disease after renal transplantation

In light of greatly improved long-term patient and graft survival after renal transplantation, improving other clinical outcomes such as risk of fracture and cardiovascular disease is of paramount importance. After renal transplantation, a large percentage of patients lose bone. This loss of bone results from a combination of factors that include pre-existing renal osteodystrophy, immunosuppressive therapy, and the effects of chronically reduced renal function after transplantation. In addition to low bone volume, histological abnormalities include decreased bone turnover and defective mineralization. Low bone volume and low bone turnover were recently shown to be associated with cardiovascular calcifications, highlighting specific challenges for medical therapy and the need to prevent low bone turnover in the pretransplant patient. This Review discusses changes in bone histology and mineral metabolism that are associated with renal transplantation and the effects of these changes on clinical outcomes such as fractures and cardiovascular calcifications. Therapeutic modalities are evaluated based on our understanding of bone histology.

Vitamin effects on the immune system: vitamins A and D take centre stage

Vitamins are essential constituents of our diet that have long been known to influence the immune system. Vitamins A and D have received particular attention in recent years as these vitamins have been shown to have an unexpected and crucial effect on the immune response. We present and discuss our current understanding of the essential roles of vitamins in modulating a broad range of immune processes, such as lymphocyte activation and proliferation, T-helper-cell differentiation, tissue-specific lymphocyte homing, the production of specific antibody isotypes and regulation of the immune response. Finally, we discuss the clinical potential of vitamin A and D metabolites for modulating tissue-specific immune responses and for preventing and/or treating inflammation and autoimmunity.