Vitamin D: a new player in kidney transplantation?

Abstract

Vitamin D is a hormone with pleiotropic effects. It mainly regulates calcium and phosphate metabolism through interactions with FGF23 and its receptor klotho. In addition, it has been shown that Vitamin D also regulates the immune response and has protective effects from cardiovascular disease, cancer and infections. Most renal transplant recipients have overt Vitamin D deficiency, a condition that may be associated with a decline in graft function and other complications. After kidney transplantation, elevated levels of FGF23 may predict increased risks of death and allograft loss. Theoretically, an optimal Vitamin D supplementation might favor operational tolerance and protect transplant recipients from the triad cardiovascular disease-cancer-infection. However, more solid data are needed to confirm this and to set the optimal level of serum Vitamin D supplementation in order to attain the best clinical outcome.

Keywords::

• cardiovascular disease
• immunosuppression
• rejection
• renal transplantation
• vitamin D
• vitamin and hormone

Financial & competing interests disclosure

In the last 2 years C Ponticelli received honoraria for lectures from Novartis and Janssen-Cilag. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Vitamin D deficiency is a frequent complication of advanced renal failure.

• In spite of the resulting better renal function, kidney transplantation does not usually correct vitamin D deficiency.

• Experimental studies pointed out that vitamin D may favor immunological tolerance by switching from Th1 to Th2 phenotypes, favoring the production of graft-tolerant T regulators and interfering with maturation and differentiation of graft-rejecting dendritic cells.

• A number of clinical studies pointed out that vitamin D:

  • – May exert protective effect against cardiovascular disease;

  • – Stimulates the production of antimicrobial peptides thus protecting against infections;

  • – May exert anti-carcinogenetic effects, particularly on colorectal and breast cancers.

• Despite a general practice of supplement transplanted patients with vitamin D, there is no clear evidence yet that this can reduce the risk or the severity of cardiovascular events, infections, graft loss or malignancy.

• In view of the possible advantages of vitamin D supplementation in such patients, controlled trials in kidney transplantation that could provide the optimal supplementation regimen are strongly encouraged.