Propionate and butyrate counteract renal damage and progression to chronic kidney disease.

BACKGROUND: Short-chain fatty acids (SCFAs), mainly acetate, propionate and butyrate, are produced by gut microbiota through fermentation of complex carbohydrates that cannot be digested by the human host. They affect gut health and can contribute at the distal level to the pathophysiology of several diseases, including renal pathologies. METHODS: SCFA levels were measured in chronic kidney disease (CKD) patients (n = 54) at different stages of the disease and associations with renal function and inflammation parameters were examined. The impact of propionate and butyrate in pathways triggered in tubular cells under inflammatory conditions was analysed using genome-wide expression assays. Finally, a pre-clinical mouse model of folic acid-induced transition from acute kidney injury to CKD was used to analyse the preventive and therapeutic potential of these microbial metabolites in the development of CKD. RESULTS: Faecal levels of propionate and butyrate in CKD patients gradually reduce as the disease progresses, and do so in close association with established clinical parameters for serum creatinine, blood urea nitrogen and the estimated glomerular filtration rate. Propionate and butyrate jointly downregulated the expression of 103 genes related to inflammatory processes and immune system activation triggered by TNF-α in tubular cells. In vivo, the administration of propionate and butyrate, either before or soon after injury, respectively prevented and slowed the progression of damage. This was indicated by a decrease in renal injury markers, the expression of pro-inflammatory and pro-fibrotic markers, and recovery of renal function over the long term. CONCLUSIONS: Propionate and butyrate levels are associated with a progressive loss of renal function in CKD patients. Early administration of these SCFAs prevents disease advancement in a pre-clinical model of acute renal damage, demonstrating their therapeutic potential independently of the gut microbiota.

Recovery of kidney function in patients treated with maintenance dialysis-a report from the ERA-EDTA Registry.

BACKGROUND: Literature on recovery of kidney function (RKF) in patients with end-stage kidney disease treated with maintenance dialysis (i.e. >90 days) is limited. We assessed the incidence of RKF and its associated characteristics in a European cohort of dialysis patients. METHODS: We included adult patients from the European Renal Association-European Dialysis and Transplant Association Registry who started maintenance dialysis in 1997-2016. Sustained RKF was defined as permanent discontinuation of dialysis. Temporary discontinuation of ≥30 days (non-sustained RKF) was also evaluated. Factors associated with RKF adjusted for potential confounders were studied using Cox regression analyses. RESULTS: RKF occurred in 7657 (1.8%) of 440 996 patients, of whom 71% experienced sustained RKF. Approximately 90% of all recoveries occurred within the first 2 years after Day 91 of dialysis. Of patients with non-sustained RKF, 39% restarted kidney replacement therapy within 1 year. Sustained RKF was strongly associated with the following underlying kidney diseases (as registered by the treating physician): tubular necrosis (irreversible) or cortical necrosis {adjusted hazard ratio [aHR] 20.4 [95% confidence interval (CI) 17.9-23.1]}, systemic sclerosis [aHR 18.5 (95% CI 13.8-24.7)] and haemolytic uremic syndrome [aHR 17.3 (95% CI 13.9-21.6)]. Weaker associations were found for haemodialysis as a first dialysis modality [aHR 1.5 (95% CI 1.4-1.6)] and dialysis initiation at an older age [aHR 1.8 (95% CI 1.6-2.0)] or in a more recent time period [aHR 2.4 (95% CI 2.1-2.7)]. CONCLUSIONS: Definitive discontinuation of maintenance dialysis is a rare and not necessarily an early event. Certain clinical characteristics, but mostly the type of underlying kidney disease, are associated with a higher likelihood of RKF.

The APOB polymorphism rs1801701 A/G (p.R3638Q) is an independent risk factor for early-onset coronary artery disease: Data from a Spanish cohort.

BACKGROUND AND AIMS: Apoliprotein B (ApoB) has been associated with hypercholesterolemia and ischemic coronary disease. This study was aimed to determine the effect of two APOB gene variants in the risk of developing early-onset coronary artery disease (EO-CAD) in a Spanish population. The association of these polymorphisms with hypercholesterolemia was also analysed. METHODS AND RESULTS: The study involved a total of 889 healthy population controls (397 male) and 790 EO-CAD cases (636 male; EO-CAD was defined as male <60 years and women <65 years). All the patients had at least one vessel with angiography documented atherosclerotic lesion. Patients and controls were genotyped for the APOB variants rs1801701 A/G (p.R3638Q) and rs1367117 C/T (p.T98I). Allele and genotype frequencies were compared between the groups (patients vs. controls, hyper-vs. normo-cholesterolemia) by logistic regression. The rs1801701 was significantly associated with EO-CAD in male (OR = 1.44, 95%CI = 1.05-1.99) and female (OR = 2.22, 95%CI = 1.58-3.14). This SNP was significantly associated with hypercholesterolemia in female, with a trend in male. The association with EO-CAD was independent of hypercholesterolemia (multiple logistic regression). CONCLUSION: A common APOB polymorphism (rs1801701) was an independent risk factor for EO-CAD in our population. The risk-effect was more significant in female than in male.

IL17RA in early-onset coronary artery disease: Total leukocyte transcript analysis and promoter polymorphism (rs4819554) association.

BACKGROUND AND AIMS: The interleukin-17 (IL-17) pathway would play an important role in the pathogenesis of atherosclerosis and coronary-artery disease (CAD). The IL-17 inflammatory mediators are expressed by Th17 cells, a group of CD4 + leukocytes that infiltrate the vascular milieu and are pivotal in the origin, progression, stability and rupture of the atherosclerotic lesion. Cigarette smoke compounds stimulated the expression of IL-17 and IL-17-receptors. In atherogenic mice models the deficiency of IL-17RA resulted in a reduction of the atherosclerotic lesion size and leukocyte infiltrate. We hypothesised that common the IL-17RA transcript might be differential expressed in the leukocytes from CAD patients and healthy individuals. METHODS: The relative amount of the IL-17RA to ACTB transcript was determined in total leukocytes of 55 patients and 50 controls, all smokers. We genotyped the IL-17RA rs48195554 promoter polymorphisms in 390 healthy controls and 450 early-onset CAD patients. RESULTS: Patients showed significantly higher mean IL-17RA normalised transcript value than controls (p < 0.001). For the IL-17RA rs48195554 promoter polymorphisms, IL-17RA G-carriers showed higher transcript values. However, allele and genotype frequencies did not differ between patients and controls and we thus excluded a significant association with CAD. CONCLUSIONS: The higher levels of the IL-17RA transcript among CAD-patients was in agreement with a role for the IL-17 pathway in the pathogenesis of coronary atherosclerosis.

The DESCARTES-Nantes survey of kidney transplant recipients displaying clinical operational tolerance identifies 35 new tolerant patients and 34 almost tolerant patients.

BACKGROUND: Kidney recipients maintaining a prolonged allograft survival in the absence of immunosuppressive drugs and without evidence of rejection are supposed to be exceptional. The ERA-EDTA-DESCARTES working group together with Nantes University launched a European-wide survey to identify new patients, describe them and estimate their frequency for the first time. METHODS: Seventeen coordinators distributed a questionnaire in 256 transplant centres and 28 countries in order to report as many 'operationally tolerant' patients (TOL; defined as having a serum creatinine <1.7 mg/dL and proteinuria <1 g/day or g/g creatinine despite at least 1 year without any immunosuppressive drug) and 'almost tolerant' patients (minimally immunosuppressed patients (MIS) receiving low-dose steroids) as possible. We reported their number and the total number of kidney transplants performed at each centre to calculate their frequency. RESULTS: One hundred and forty-seven questionnaires were returned and we identified 66 TOL (61 with complete data) and 34 MIS patients. Of the 61 TOL patients, 26 were previously described by the Nantes group and 35 new patients are presented here. Most of them were noncompliant patients. At data collection, 31/35 patients were alive and 22/31 still operationally tolerant. For the remaining 9/31, 2 were restarted on immunosuppressive drugs and 7 had rising creatinine of whom 3 resumed dialysis. Considering all patients, 10-year death-censored graft survival post-immunosuppression weaning reached 85% in TOL patients and 100% in MIS patients. With 218 913 kidney recipients surveyed, cumulative incidences of operational tolerance and almost tolerance were estimated at 3 and 1.5 per 10 000 kidney recipients, respectively. CONCLUSIONS: In kidney transplantation, operational tolerance and almost tolerance are infrequent findings associated with excellent long-term death-censored graft survival.

The donor ABCB1 (MDR-1) C3435T polymorphism is a determinant of the graft glomerular filtration rate among tacrolimus treated kidney transplanted patients.

The ABCB1 gene encodes the P-glycoprotein (P-gp) that drives the transmembrane efflux of many drugs. The donor ABCB1 polymorphisms have been related with chronic histological damage and long-term renal function among kidney transplanted patients who received cyclosporine A and tacrolimus (Tac). The aim of our study was to determine whether the donor ABCB1 3435 C/T genotype was related with renal function among Tac-treated renal transplanted patients. Kidney donors (n=65) and recipients (n=90) were genotyped for the ABCB1 rs1045642 (c.3435 C/T) and CYP3A5 rs776746 single-nucleotide polymorphisms. The estimated glomerular filtration rate (eGFR) was calculated with the modification of diet in renal disease formulae at five post-transplant times (2 weeks and 1, 3, 6 and 12 months). The recipient ABCB1 and CYP3A5 genotypes had no significant effect on the eGFR at all the post-transplant times. We found significantly lower eGFR values among patients who received a kidney from ABCB1 3435 T carriers (P<0.01). In conclusion, our study confirmed the potential impact of the donor ABCB1 3435 genotype on the post-transplant renal function among patients treated with Tac.

ABCB1 (MDR-1) pharmacogenetics of tacrolimus in renal transplanted patients: a Next Generation Sequencing approach.

BACKGROUND: A CYP3A5 gene polymorphism is the main determinant of Tacrolimus (Tac) dose requirements among renal transplanted patients. In spite of the utility of CYP3A5 genotyping to predict the Tac-dose, many patients exhibit an out of range blood Tac level and it is thus likely that other genes/polymorphisms contribute to define Tac bioavailability. To address this issue we searched for coding sequence variants in the ABCB1/MDR1 gene in renal transplanted patients treated with Tac and who had out of the range blood levels. METHODS: We studied 100 renal transplanted patients treated with Tac, 60 of whom had Tac blood levels below (n=39) and above (n=21) the target range (10-15 ng/mL) at 1 week post-transplant. The DNA was subjected to multiplex amplification followed by massive parallel semiconductor sequencing in the Ion Torrent personal genome machine. RESULTS: We found four missense changes, all reported and present in cases above and below the blood Tac target. In addition, we did not find differences in the allele and genotype frequencies for the common rs1045642 polymorphism (p.I1145I) between the groups. CONCLUSIONS: Our results suggested that the ABCB1 variants had no effect on the risk of showing out of range Tac blood levels among renal transplanted patients.

Next generation sequencing search for uromodulin gene variants related with impaired renal function.

Uromodulin gene (UMOD) mutations have been linked to rare forms of mendelian dominant medullary cystic kidney disease and familial hyperuricemia. In addition, common single nucleotide polymorphisms in the UMOD promoter have been associated with the risk for impaired renal function and chronic kidney disease. Our main purpose was to identify UMOD variants related with impaired renal function in an elderly population. The UMOD gene was next generation sequenced in a total of 100 healthy individuals with normal or reduced renal function [measured as the rate of estimated glomerular filtration (eGFR)]. The identified missense changes and the common promoter rs12917707 polymorphism were determined in individuals with reduced (n = 88) and normal (n = 442) eGFR values. Allele and genotype frequencies were compared between the groups. We only identified a rare UMOD misense change, p.V458L, and the rare leu allele was significantly more frequent in a cohort of individuals with reduced (eGFR < 60) compared to normal eGFR (P = 0.02). The common rs12917707 polymorphism previously linked to renal function and kidney disease was not associated with impaired filtration rate in our cohort. We found a significant effect of the rare p.V458L variant on the value of estimated glomerular filtration. This finding deserves further validation in larger cohorts.

BET inhibitor nanotherapy halts kidney damage and reduces chronic kidney disease progression after ischemia-reperfusion injury.

Targeting epigenetic mechanisms has emerged as a potential therapeutic approach for the treatment of kidney diseases. Specifically, inhibiting the bromodomain and extra-terminal (BET) domain proteins using the small molecule inhibitor JQ1 has shown promise in preclinical models of acute kidney injury (AKI) and chronic kidney disease (CKD). However, its clinical translation faces challenges due to issues with poor pharmacokinetics and side effects. Here, we developed engineered liposomes loaded with JQ1 with the aim of enhancing kidney drug delivery and reducing the required minimum effective dose by leveraging cargo protection. These liposomes efficiently encapsulated JQ1 in both the membrane and core, demonstrating superior therapeutic efficacy compared to freely delivered JQ1 in a mouse model of kidney ischemia-reperfusion injury. JQ1-loaded liposomes (JQ1-NPs) effectively targeted the kidneys and only one administration, one-hour after injury, was enough to decrease the immune cell (neutrophils and monocytes) infiltration to the kidney-an early and pivotal step to prevent damage progression. By inhibiting BRD4, JQ1-NPs suppress the transcription of pro-inflammatory genes, such as cytokines (il-6) and chemokines (ccl2, ccl5). This success not only improved early the kidney function, as evidenced by decreased serum levels of BUN and creatinine in JQ1-NPs-treated mice, along with reduced tissue expression of the damage marker, NGAL, but also halted the production of extracellular matrix proteins (Fsp-1, Fn-1, α-SMA and Col1a1) and the fibrosis development. In summary, this work presents a promising nanotherapeutic strategy for AKI treatment and its progression and provides new insights into renal drug delivery.

Inhibition of BRD4 Attenuates ER Stress-induced Renal Ischemic-Reperfusion Injury.

Renal ischemia-reperfusion injury (IRI) leads to endoplasmic reticulum (ER) stress, thereby initiating the unfolded protein response (UPR). When sustained, this response may trigger the inflammation and tubular cell death that acts to aggravate the damage. Here, we show that knockdown of the BET epigenetic reader BRD4 reduces the expression of ATF4 and XBP1 transcription factors under ER stress activation. BRD4 is recruited to the promoter of these highly acetylated genes, initiating gene transcription. Administration of the BET protein inhibitor, JQ1, one hour after renal damage induced by bilateral IRI, reveals reduced expression of ATF4 and XBP1 genes, low KIM-1 and NGAL levels and recovery of the serum creatinine and blood urea nitrogen levels. To determine the molecular pathways regulated by ATF4 and XBP1, we performed stable knockout of both transcription factors using CRISPR-Cas9 and RNA sequencing. The pathways triggered under ER stress were mainly XBP1-dependent, associated with an adaptive UPR, and partially regulated by JQ1. Meanwhile, treatment with JQ1 downmodulated most of the pathways regulated by ATF4 and related to the pathological processes during exacerbated UPR activation. Thus, BRD4 inhibition could be useful for curbing the maladaptive UPR activation mechanisms, thereby ameliorating the progression of renal disease.

A search for new CYP3A4 variants as determinants of tacrolimus dose requirements in renal-transplanted patients.

The CYP3A5*3 and CYP3A4*1B alleles have been related with tacrolimus (Tac) dose requirements. The rare CYP3A4*22 variant has also been associated with a significantly lower Tac dose. We genotyped the three single-nucleotide polymorphisms in 206 kidney-transplanted patients who received Tac as the primary immunosuppressor. CYP3A5*1 and CYP3A4*1B allele carriers received a significantly higher Tac dose (P<0.01) compared with wild-type homozygotes. We did not find significant differences between the CYP3A4*22 genotypes, either nominally or according to the CYP3A5 genotype (expressers vs. nonexpressers). Sequencing of CYP3A4 coding exons in a total of 15 patients revealed only one nonreported missense change (p.P227>T) in one patient. We concluded that CYP3A5*3 and CYP3A4*1B were the main determinants of the Tac dose-adjusted blood concentration in our cohort of renal-transplanted patients.

Update of the recommendations on the management of the SARS-CoV-2 coronavirus pandemic (COVID-19) in kidney transplant patients.

SARS-CoV-2 infection (COVID-19) has had a significant impact on transplant activity in our country. Mortality and the risk of complications associated with COVID-19 in kidney transplant recipients (KT) were expected to be higher due to their immunosuppressed condition and the frequent associated comorbidities. Since the beginning of the pandemic in March 2020 we have rapidly improved our knowledge about the epidemiology, clinical features and management of COVID-19 post-transplant, resulting in a better prognosis for our patients. KT units have been able to adapt their programs to this new reality, normalizing both donation and transplantation activity in our country. This manuscript presents a proposal to update the general recommendations for the prevention and treatment of infection in this highly vulnerable population such as KT.

Association between a common KCNJ11 polymorphism (rs5219) and new-onset posttransplant diabetes in patients treated with Tacrolimus.

KCNJ11 polymorphisms have been linked to the risk of developing type 2 diabetes. Our aim was to define the contribution of KCNJ11 to new-onset diabetes after transplantation (NODAT) among patients treated with Tacrolimus (Tac). A total of 115 NODAT and 205 non-NODAT were genotyped for rs5219 (p.E23K). AA+AG genotypes were significantly associated with NODAT-risk (p=0.004; OR=2.10). The reported effect of this KCNJ11 polymorphism on insulin release by beta cells could explain this association.

Incidence of Lymphoproliferative Disorders After Renal Transplantation is Down, but the Poor Prognosis Remains. Multicenter 32-Year Cohort Study.

BACKGROUND: Post-transplant lymphoproliferative disorders represent rare but serious complications of kidney transplantation. METHODS: We assessed incidence, risk factors, and outcomes in 21,546 patients receiving grafts between 1990 and 2009. Data were compared by decade of transplant (1990-1999 vs 2000-2009). Patients were followed for at least 12 years over a 32-year study period. RESULTS: In total, 331 patients (1.5%) developed PTLD: 189 of 9740 transplanted in the first decade, and 142 of 11,806 in the second. Incidence decreased significantly (19.40 vs12.02 cases/1000 patients; P < .001). Mean age at diagnosis was 50.2 years (standard deviation 14.7), and the median time from transplant to PTLD diagnosis was 48 months (interquartile range, 14.7-77.5), with no difference between cohorts. The origin of PTLD was mostly (86%) B-cell proliferation. No classical risk factors were reported in 31.7% of affected patients. Compared with 2000 to 2009, in 1990 to 1999 there was a higher frequency of induction therapy (P = .023) and detection of the Epstein-Barr virus in lymphoproliferative tissue (71.3% vs 52.7% P = .019). After diagnosis, 1- and 5-year patient survival was 51% and 38%. Graft survival was 48% and 33%. Survival was stable throughout the study period. CONCLUSION: Post-transplant lymphoproliferative disorders have a low and decreasing incidence, but the poor prognosis has not changed.

[Update of the recommendations on the management of the SARS-CoV-2 coronavirus pandemic (COVID-19) in kidney transplant patients.] / Actualización de las recomendaciones en el manejo de la pandemia por coronavirus SARS-CoV-2 (COVID-19) en pacientes con trasplante renal.

SARS-CoV-2 infection (COVID-19) has had a significant impact on transplant activity in our country. Mortality and the risk of complications associated with COVID-19 in kidney transplant recipients (KT) were expected to be higher due to their immunosuppressed condition and the frequent associated comorbidities. Since the beginning of the pandemic in March 2020 we have rapidly improved our knowledge about the epidemiology, clinical features and management of COVID-19 post-transplant, resulting in a better prognosis for our patients. KT units have been able to adapt their programs to this new reality, normalizing both donation and transplantation activity in our country.This manuscript presents a proposal to update the general recommendations for the prevention and treatment of infection in this highly vulnerable population such as KT.

Live donor kidney transplantation. Situation analysis and roadmap.

Living donor kidney transplantation (LDKT) is the best treatment option for end stage renal disease in terms of both patient and graft survival. However, figures on LDKT in Spain that had been continuously growing from 2005 to 2014, have experienced a continuous decrease in the last five years. One possible explanation for this decrease is that the significant increase in the number of deceased donors in Spain during the last years, both brain death and controlled circulatory death donors, might have generated the false idea that we have coped with the transplant needs. Moreover, a greater number of deceased donor kidney transplants have caused a heavy workload for the transplant teams. Furthermore, the transplant teams could have moved on to a more conservative approach to the information and assessment of patients and families considering the potential long-term risks for donors in recent papers. However, there is a significant variability in the LDKT rate among transplant centers and regions in Spain independent of their deceased donor rates. This fact and the fact that LDKT is usually a preemptive option for patients with advanced chronic renal failure, as time on dialysis is a negative independent factor for transplant outcomes, lead us to conclude that the decrease in LDKT depends on other factors. Thus, in the kidney transplant annual meeting held at ONT site in 2018, a working group was created to identify other causes for the decrease of LDKT in Spain and its relationship with the different steps of the process. The group was formed by transplant teams, a representative of the transplant group of the Spanish Society of Nephrology (SENTRA), a representative of the Spanish Society of Transplants (SET) and representatives of the Spanish National Transplant Organization (ONT). A self-evaluation survey that contains requests about the phases of the LDKT processes (information, donor work out, informed consent, surgeries, follow-up and human resources) were developed and sent to 33 LDKT teams. All the centers answered the questionnaire. The analysis of the answers has resulted in the creation of a national analysis of strengths, weaknesses, opportunities, threats (SWOT) of the LDKT program in Spain and the development of recommendations targeted to improve every step of the donation process. The work performed, the conclusions and recommendations provided, have been reflected in the following report: Spanish living donor kidney transplant program assessment: recommendations for optimization. This document has also been reviewed by a panel of experts, representatives of the scientific societies (Spanish Society of Urology (AEU), Spanish Society of Nephrology Nursery (SEDEN), Spanish Society of Immunology (SEI/GETH)) and the patient association ALCER. Finally, the report has been submitted to public consultation, reaching ample consensus. In addition, the transplant competent authorities of the different regions in Spainhave adopted the report at institutional level. The work done and the recommendations to optimize LDKT are summarized in the present manuscript, organized by the different phases of the donation process.

KCNQ1 gene variants and risk of new-onset diabetes in tacrolimus-treated renal-transplanted patients.

Recent genome-wide association studies identified single-nucleotide polymorphisms (SNPs) in the gene encoding the pore-forming subunit of the voltage-gated K+ channel (KCNQ1) as a risk factor for type 2 diabetes. Tacrolimus (Tac) increased the risk of new-onset diabetes after transplantation (NODAT). The aim of this study was to analyze the association between KCNQ1 variants and the risk for NODAT in kidney-transplanted patients who received Tac as primary immunosuppressor. We genotyped three common KCNQ1 SNPs in 145 Spanish patients who received a cadaveric kidney graft and developed NODAT in the first-year post-transplant (the NODAT group), and 260 patients who remained non-diabetics (non-NODAT). In addition, we searched for DNA variants in the whole KCNQ1 coding exons in these patients. SNP rs2237895 (genotype CC) was associated with an increased risk for NODAT in our population (p = 0.008; OR = 1.83, 95% CI = 1.14-2.93), independently of other risk factors as body mass index, recipient age, or tacrolimus dosage. Other KCNQ1 variants were not associated with NODAT in our patients. Our work supported a role for KCNQ1 gene variants as determinants of the risk of developing NODAT among Tac-treated patients.

Pharmacogenetics of tacrolimus after renal transplantation: analysis of polymorphisms in genes encoding 16 drug metabolizing enzymes.

BACKGROUND: Tacrolimus (Tac) is an immunosuppressive drug used to prevent post-transplant (PT) organ rejection. Continuous Tac monitoring is necessary to adjust the dose and prevent toxicity or rejection. Tac is metabolized by cytochrome-P450 (CYP) enzymes, and variation at the CYP and other drug metabolizing enzymes could influence Tac bio-availability and dose requirements. Our aim was to define the effect of DNA variants at 16 drug metabolising enzymes on Tac dose in patients with kidney transplants. METHODS: The REDINREN Pharmacogenetics Project was a multicenter study designed to evaluate the effect of DNA polymorphisms on Tac dose requirements. A total of 200 patients who received a first cadaveric kidney and Tac as primary immunosuppressive drug were genotyped for 96 DNA polymorphisms on 16 genes. Significant associations were further replicated in a second group of 200 patients. The Tac daily dose was adjusted to achieve a blood concentration of 10-15 ng/mL in the period 0-3 months PT, and 5-10 ng/mL thereafter. The dose of tacrolimus dose and blood concentrations were compared between genotypes at 1 week, 6 months, and 1 year PT. RESULTS: The CYP3A5 genotype (SNP rs776746) was the strongest predictor of Tac dose requirements. Patients who were CYP3A5*3*3 (CYP3A5 non-expressors) received significantly higher Tac dose at 1 week, 6 months, and 1 year PT (p<0.0001). At 1 week, 41% of the CYP3A5 non-expressors achieved target blood concentrations compared to 26% of the CYP3A5 expressors (p=0.007). We also found a significant effect of CYP3A4 genotype (SNP rs2740574) on Tac dose requirements in patients who were CYP3A5 non-expressors. None of the other polymorphisms were related to Tac dose requirements or modified the effect of the CYP3A5 genotype. CONCLUSIONS: rs776746 (CYP3A5) and rs2740574 (CYP3A4) were the only SNPs associated with Tac dosage. The genotyping of these polymorphisms could be a useful pharmacogenetic tool to determine the Tac dose immediately after transplantation.

Defining a Methylation Signature Associated With Operational Tolerance in Kidney Transplant Recipients.

Operational tolerance after kidney transplantation is defined as stable graft acceptance without the need for immunosuppression therapy. However, it is not clear which cellular and molecular pathways are driving tolerance in these patients. We performed genome-wide analysis of DNA methylation in peripheral blood mononuclear cells from kidney transplant recipients with chronic rejection and operational tolerance from the Genetic Analysis of Molecular Biomarkers of Immunological Tolerance (GAMBIT) study. Our results showed that both clinical stages diverge in 2737 genes, indicating that each one has a specific methylation signature associated with transplant outcome. We also observed that tolerance is associated with demethylation in genes involved in immune function, including B and T cell activation and Th17 differentiation, while in chronic rejection it is associated with intracellular signaling and ubiquitination pathways. Using co-expression network analysis, we selected 12 genomic regions that are specifically hypomethylated or hypermethylated in tolerant patients. Analysis of these genes in transplanted patients with low dose of steroids showed that these have a similar methylation signature to that of tolerant recipients. Overall, these results demonstrate that methylation analysis can mirror the immune status associated with transplant outcome and provides a starting point for understanding the epigenetic mechanisms associated with tolerance.

A Current Review of the Etiology, Clinical Features, and Diagnosis of Urinary Tract Infection in Renal Transplant Patients.

Urinary tract infection (UTI) represents the most common infection after kidney transplantation and remains a major cause of morbidity and mortality in kidney transplant (KT) recipients, with a potential impact on graft survival. UTIs after KT are usually caused by Gram-negative microorganisms. Other pathogens which are uncommon in the general population should be considered in KT patients, especially BK virus since an early diagnosis is necessary to improve the prognosis. UTIs following kidney transplantation are classified into acute simple cystitis, acute pyelonephritis/complicated UTI, and recurrent UTI, due to their different clinical presentation, prognosis, and management. Asymptomatic bacteriuria (ASB) represents a frequent finding after kidney transplantation, but ASB is considered to be a separate entity apart from UTI since it is not necessarily a disease state. In fact, current guidelines do not recommend routine screening and treatment of ASB in KT patients, since a beneficial effect has not been shown. Harmful effects such as the development of multidrug-resistant (MDR) bacteria and a higher incidence of Clostridium difficile diarrhea have been associated with the antibiotic treatment of ASB.