Iron metabolism in kidney allograft recipients: still a mystery?

All living organisms have evolved sophisticated mechanisms to maintain appropriate iron levels in their cells and within their body. Recently our understanding of iron metabolism has dramatically increased. Overt labile plasma iron (LPI) represents a component of non-transferrin-bound iron (NTBI) that is both redox active and chelatable, capable of permeating into organs and inducing tissue iron overload. LPI measures the iron-specific capacity of a given sample to produce reactive oxygen species. We studied NTBI correlations with markers of iron status and inflammation in prevalent kidney allograft recipients.

Complete blood count, urea, creatinine, serum lipids, fasting glucose, ferritin, serum iron, and total iron-binding capacity (TIBC) were studied by standard laboratory method in the hospital central laboratory. NTBI was assessed by FeROS eLPI kit by Aferrix Ltd (Tel Aviv, Israel). A test result of 0.6 U of LPI or more indicated a potential for iron-mediated production of reactive oxygen species in the sample.

In kidney transplant recipients NTBI was correlated with TIBC (r=.46, P<.001) and ferritin (r=.31, P<.05), with tendencies to correlate with C-reactive protein. Patients with LPI units≥0.6 showed higher serum iron (P<.05), TIBC (P<.05), ferritin (P<.001) and mean corpuscular volume. High ferritin values together with elevated NTBI content were observed among patients undergoing multiple transfusions before and/or after transplantation.

Elevated NTBI as well as ferritin levels in kidney transplant patients may be due to disturbed iron metabolism, since the human body has no possibility to remove an iron excess. NTBI could be responsible for excessive synthesis of reactive oxygen species. Therefore, it may be linked to complications such as atherosclerosis, which is frequently encountered among this population.