The Tacrolimus Metabolism Rate Influences Renal Function after Kidney Transplantation

The effective calcineurin inhibitor (CNI) tacrolimus (Tac) is an integral part of the standard immunosuppressive regimen after renal transplantation (RTx). However, as a potent CNI it has nephrotoxic potential leading to impaired renal function in some cases. Therefore, it is of high clinical impact to identify factors which can predict who is endangered to develop CNI toxicity. We hypothesized that the Tac metabolism rate expressed as the blood concentration normalized by the dose (C/D ratio) is such a simple predictor. Therefore, we analyzed the impact of the C/D ratio on kidney function after RTx. Renal function was analyzed 1, 2, 3, 6, 12 and 24 months after RTx in 248 patients with an immunosuppressive regimen including basiliximab, tacrolimus, mycophenolate mofetil and prednisolone. According to keep the approach simple, patients were split into three C/D groups: fast, intermediate and slow metabolizers. Notably, compared with slow metabolizers fast metabolizers of Tac showed significantly lower estimated glomerular filtration rate (eGFR) values at all the time points analyzed. Moreover, fast metabolizers underwent more indication renal biopsies (p = 0.006) which revealed a higher incidence of CNI nephrotoxicity (p = 0.015) and BK nephropathy (p = 0.024) in this group. We herein identified the C/D ratio as an easy calculable risk factor for the development of CNI nephrotoxicity and BK nephropathy after RTx. We propose that the simple C/D ratio should be taken into account early in patient’s risk management strategies.</p

Bone marrow-derived cells and their conditioned medium induce microvascular repair in uremic rats by stimulation of endogenous repair mechanisms

The reduced number of circulating stem/progenitor cells that is found in chronic kidney disease (CKD) patients may contribute to impaired angiogenic repair and decreased capillary density in the heart. Cell therapy with bone marrow-derived cells (BMDCs) has been shown to induce positive effects on the microvasculature and cardiac function, most likely due to secretion of growth factors and cytokines, all of which are present in the conditioned medium (CM); however, this is controversial. Here we showed that treatment with BMDC or CM restored vascular density and decreased the extent of fibrosis in a rat model of CKD, the 5/6 nephrectomy. Engraftment and differentiation of exogenous BMDCs could not be detected. Yet CM led to the mobilization and infiltration of endogenous circulating cells into the heart. Cell recruitment was facilitated by the local expression of pro-inflammatory factors such as the macrophage chemoattractant protein-1, interleukin-6, and endothelial adhesion molecules. Consistently, in vitro assays showed that CM increased endothelial adhesiveness to circulating cells by upregulating the expression of adhesion molecules, and stimulated angiogenesis/endothelial tube formation. Overall, our results suggest that both treatments exert vasculoprotective effects on the heart of uremic rats by stimulating endogenous repair mechanisms.</p

Tacrolimus concentration/dose ratio influences renal functions after liver transplantation

BACKGROUND: The calcineurin inhibitor (CNI) tacrolimus (Tac) is an effective immunosuppressant used after liver transplantation (LTx), but is often associated with CNI nephrotoxicity. Currently, there is no simple clinical predictor for CNI nephrotoxicity after LTx. We hypothesized that the Tac metabolism rate – defined as the blood concentration normalized by its daily dose (the C/D ratio) – is associated with post-LTx renal impairment. MATERIAL AND METHODS: We analyzed the relationship between the C/D ratio and post-transplant renal function in 179 patients who underwent LTx between 2000 and 2012 and were initially immunosuppressed with Tac, mycophenolate mofetil, and prednisolone. Six months after LTx, 115 patients were categorized into 1 of 2 groups based on their Tac C/D ratio (<1.09 or ≥1.09): fast (n=58) or slow (n=57) metabolizers. The renal function was determined 36 months after LTx using the estimated glomerular filtration rate (eGFR) as described by Cockcroft and Gault. RESULTS: At the time of LTx there was no statistically significant difference between the eGFR of fast and slow metabolizers. Six months (P=0.016), 12 months (P=0.001), and 36 months (P=0.018) after LTx, fast Tac metabolizers had significantly more impaired renal function than slow metabolizers. Because of a presumption of CNI nephrotoxicity, 32.8% of fast metabolizers and 14.0% of slow metabolizers were switched from Tac to other immunosuppressants (P=0.027). CONCLUSIONS: In this study, the Tac metabolism rate appears to influence renal function after LTx, suggesting that a C/D ratio of <1.09 is associated with increased CNI nephrotoxicity in LTx recipients.</p