Magnesemia in renal transplant recipients: relation with immunosuppression and posttransplant diabetes.

Hypomagnesemia, a frequent disorder in renal transplant patients related to the use of calcineurin inhibitors (CNIs), plays a causal role in insulin resistance and type 2 diabetes. Recently, hypomagnesemia has been identified as an independent predictor of new-onset diabetes after transplant (NODAT). The objective of this study was to investigate the influence of various immunosuppressive regimens on magnesemia in relation to the development of NODAT. We performed a retrospective study in 589 nondiabetic subjects who underwent serum magnesium measurements (mg/dL) on days 7 and 15 as well as at 1, 2, 3, 6, 9, and 12 months after transplantation. NODAT was diagnosed during the first year using American Diabetes Association criteria. The overall mean magnesemia was lower among CNI compared with non-CNI patients (1.73±0.25 vs 1.98±0.23; P=.000) and in patients on tacrolimus versus cyclosporine (1.72±0.24 vs 1.80±0.26; P=.007). It was higher in patients who received anti-CD25 antibodies with delayed CNI introduction (1.83±0.28 vs 1.71±0.23; P=.000). The use of CNIs and delayed CNI introduction were identified as independent factors related to magnesemia. No differences in magnesemia were observed among patients who developed NODAT versus the non-NODAT cohort. The incidence of NODAT was higher among patients on tacrolimus versus cyclosporine (26.8% vs 18.1%; P=.026), but no differences were found between the serum Mg tertiles at any time during the study or between mean magenesemia tertiles. In conclusion, despite the fact that CNI patients showed lower magnesemia and the group of tacrolimus, the lowest magnesemia and the highest incidence of NODAT, our study did not demonstrate a relationship between the Mg levels and the occurrence of NODAT. Patients treated with anti-CD25 antibodies and delayed CNI introduction maintained higher magnesemia during the first year after transplant.