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Hydrogen sulfide (H2S), produced from metabolism of dietary sulfur-containing amino acids, is allegedly a renoprotective compound. Twenty-four-hour urinary sulfate excretion (USE) may reflect H2S bioavailability. We aimed to investigate the association of USE with graft failure in a large prospective cohort of renal transplant recipients (RTR). We included 704 stable RTR, recruited at least 1 year after transplantation. We applied log-rank testing and Cox regression analyses to study association of USE, measured from baseline 24 h urine samples, with graft failure. Median age was 55 [45–63] years (57% male, eGFR was 45 ± 19 ml/min/1.73 m2). Median USE was 17.1 [13.1–21.1] mmol/24 h. Over median follow-up of 5.3 [4.5–6.0] years, 84 RTR experienced graft failure. RTR in the lowest sex-specific tertile of USE experienced a higher rate of graft failure during follow-up than RTR in the middle and highest sex-specific tertiles (18%, 13%, and 5%, respectively, log-rank P 2S bioavailability as a novel, potentially modifiable factor for prevention of graft failure in RTR.

Impaired endogenous nitric oxide (NO) production may contribute to graft failure and premature mortality in kidney transplant recipients (KTR). We investigated potential associations of 24-h urinary NOx (NO3- + NO2-) excretion (uNOx) with long-term outcomes. uNOx was determined by HPLC and GC-MS in 698 KTR and in 132 kidney donors before and after donation. Additionally, we measured urinary nitroso species (RXNO) by gas-phase chemiluminescence. Median uNOx was lower in KTR compared to kidney donors (688 [393-1076] vs. 1301 [868-1863] before donation and 1312 [982-1853] μmol/24 h after donation, P < 0.001). During median follow-up of 5.4 [4.8-6.1] years, 150 KTR died (61 due to cardiovascular disease) and 83 experienced graft failure. uNOx was inversely associated with all-cause mortality (HR per doubling of uNOx: 0.84 [95% CI 0.75-0.93], P < 0.001) and cardiovascular mortality (HR 0.78 [95% CI 0.67-0.92], P = 0.002). The association of uNOx with graft failure was lost when adjusted for renal function (HR per doubling of uNOx: 0.89 [95% CI 0.76-1.05], P = 0.17). There were no significant associations of urinary RXNO with outcomes. Our study suggests that KTR have lower NO production than healthy subjects and that lower uNOx is associated with a higher risk of all-cause and cardiovascular mortality.

Cardiovascular disease (CVD) is the leading cause of death in renal transplant recipients (RTR). Elevated plasma asymmetric dimethylarginine (pADMA), an endogenous nitric oxide synthase inhibitor produced from the turnover of methylated arginine moieties in proteins, is a risk factor for CVD and mortality. It is unknown how urinary ADMA excretion (uADMA), one of the main ADMA elimination routes, is associated with long-term survival. Furthermore, the association of pADMA and uADMA with markers for turnover of arginine-methylated proteins is unknown. We analyzed ADMA using a validated GC–MS/MS method in plasma and 24-h urine samples of 685 RTR, included ≥ 1 year after transplantation. We also analyzed urine symmetric dimethylarginine (uSDMA) using the same method. Urinary creatinine and urea excretions were used as markers for turnover of muscle protein and amino acids, respectively. We applied Cox regression analyses to study associations of pADMA, uADMA, and uSDMA with all-cause and CVD mortality. Mean pADMA was 0.61 ± 0.12 µM, uADMA was 31 ± 13 µmol/24 h, and uSDMA was 52 ± 19 µmol/24 h. Over median follow-up of 5.4 [4.9–6.1] years, 147 RTR died, of which 58 (39%) from CVD. High pADMA was associated with high all-cause mortality (HR per SD [95% CI]: 1.45 [1.26–1.67], P < 0.001), while high uADMA was associated with low all-cause and CVD mortality (HR per SD [95% CI]: 0.57 [0.47–0.69], P < 0.001, and 0.55 [0.40–0.74], P < 0.001, respectively). The associations were independent of adjustment for potential confounders. Creatinine excretion was associated with both pADMA (st. β:− 0.21, P = 0.003) and uADMA (st. β: 0.49, P < 0.001), and urea excretion was associated with uADMA (st. β: 0.56, P < 0.001). Associations of uSDMA with outcomes and with creatinine excretion and urea excretion were comparable to those of uADMA. The associations of pADMA, uADMA and uSDMA with mortality were strongly affected by adjustment for creatinine excretion and urea excretion. We found for the first time that high uADMA and high uSDMA are associated with less risk of all-cause and CVD mortality. The links of uADMA and uSDMA with markers of muscle protein and amino acid turnover may serve to further understand ADMA and SDMA homeostasis and their clinical implications.

Asymmetric dimethylarginine (ADMA) is a methylated form of arginine and an endogenous nitric oxide synthase inhibitor. Renal function decline is associated with increase of plasma ADMA in chronic kidney disease populations. It is yet unknown how isolated renal function impairment affects ADMA homeostasis in healthy humans. Here, we measured plasma concentrations and urinary excretion of ADMA using GC-MS/MS in 130 living kidney donors before and at 1.6 (1.6-1.9) months after donation. We additionally analyzed 201 stable renal transplant recipients (RTR) that were included > 1 year after transplantation, as a model for kidney disease in the context of single kidney state. We measured true glomerular filtration rate (mGFR) using 125I-iothalamate. To study enzymatic metabolism of ADMA, we also measured L-citrulline as primary metabolite. Mean age was 52 ± 10 years in donors and 54 ± 12 years in RTR. Renal function was significantly reduced from pre- to post-donation (mGFR: 104 ± 17 vs. 66 ± 10 ml/min per 1.73 m2 BSA, - 36 ± 7%, P

Carnosine affords protection against oxidative and carbonyl stress, yet high concentrations of the carnosinase-1 enzyme may limit this. We recently reported that high urinary carnosinase-1 is associated with kidney function decline and albuminuria in patients with chronic kidney disease. We prospectively investigated whether urinary carnosinase-1 is associated with a high risk for development of late graft failure in kidney transplant recipients (KTRs). Carnosine and carnosinase-1 were measured in 24 h urine in a longitudinal cohort of 703 stable KTRs and 257 healthy controls. Cox regression was used to analyze the prospective data. Urinary carnosine excretions were significantly decreased in KTRs (26.5 [IQR 21.4–33.3] µmol/24 h versus 34.8 [IQR 25.6–46.8] µmol/24 h, p &lt, 0.001). In KTRs, high urinary carnosinase-1 concentrations were associated with increased risk of undetectable urinary carnosine (OR 1.24, 95%CI [1.06–1.45], p = 0.007). During median follow-up for 5.3 [4.5–6.0] years, 84 (12%) KTRs developed graft failure. In Cox regression analyses, high urinary carnosinase-1 excretions were associated with increased risk of graft failure (HR 1.73, 95%CI [1.44–2.08], 0.001) independent of potential confounders. Since urinary carnosine is depleted and urinary carnosinase-1 imparts a higher risk for graft failure in KTRs, future studies determining the potential of carnosine supplementation in these patients are warranted.

Background: Leucine is an essential amino acid and a potent stimulator of muscle protein synthesis. Since muscle wasting is a major risk factor for mortality in kidney transplant recipients (KTR), dietary leucine intake might be linked to long-term mortality. Urinary 3-hydroxyisovaleryl carnitine (3-HIC) excretion, a functional marker of marginal biotin deficiency, may also serve as a marker for dietary leucine intake.Objective: In this study we aimed to investigate the cross-sectional determinants of urinary 3-HIC excretion and to prospectively investigate the association of urinary 3-HIC excretion with all-cause mortality in KTR.Design: Urinary 3-HIC excretion and plasma biotin were measured in a longitudinal cohort of 694 stable KTR. Cross-sectional and prospective analyses were performed using ordinary least squares linear regression analyses and Cox regression analyses, respectively.Results: In KTR (57% male, 53 +/- 13 years, estimated glomerular filtration rate 45 +/- 19 mL/min/1.73 m(2)), urinary 3-HIC excretion (0.80 [0.57-1.16] mu mol/24 h) was significantly associated with plasma biotin (std. beta = -0.17; P < 0.001). Subsequent adjustment for potential covariates revealed urinary creatinine excretion (std. beta = 0.24; P < 0.001) and urinary urea excretion (std. beta = 0.53; P < 0.001) as the primary determinant of urinary 3-HIC excretion. Whereas plasma biotin explained only 1% of the variance in urinary 3-HIC excretion, urinary urea excretion explained >45%. During median follow-up for 5.4 [4.8-6.1] years, 150 (22%) patients died. Log(2)-transformed urinary 3-HIC excretion was inversely associated with all-cause mortality (HR: 0.52 [0.43-0.63]; P < 0.001). This association was independent of potential confounders.Conclusions: Urinary 3-HIC excretion more strongly serves as a marker of leucine intake than of biotin status. A higher urinary 3-HIC excretion is associated with a lower risk of all-cause mortality. Future studies are warranted to explore the underlying mechanism. (C) 2020 The Authors. Published by Elsevier Ltd.

Background: It is unknown whether meat intake is beneficial for long-term patient and graft survival in kidney transplant recipients (KTR).Objectives: We first investigated the association of the previously described meat intake biomarkers 1-methylhistidine and 3-methylbistidine with intake of white and red meat as estimated from a validated food frequency questionnaire (FFQ). Second, we investigated the association of the meat intake biomarkers with longterm outcomes in KTR.Methods: We measured 24-h urinary excretion of 1-methylhistidine and 3-methylhistidine by validated assays in a cohort of 678 clinically stable KTR. Cross-sectional associations were assessed by linear regression. We used Cox regression analyses to prospectively study associations of log`-transformed biomarkers with mortality and graft failure.Results: Urinary 1-methylhistidine and 3-methylhistidine excretion values were median: 282; interquartile range (IQR): 132-598 mu mol/24 h and median: 231; IQR: 175-306 mu mol/24 h, respectively. Urinary 1-methylhistidine was associated with white meat intake (standardized beta (st beta): 0.20; 95% CI: 0.12, 0.28; P < 0.001], whereas urinary 3-methylhistidine was associated with red meat intake (st beta: 0.30; 95% CI: 0.23, 0.38; P < 0.001). During median follow-up for 5.4 (IQR: 4.9-6.1) y, 145 (21%) died and 83 (12%) developed graft failure. Urinary 3-methylhistidine was inversely associated with mortality independently of potential confounders (HR per doubling: 0.55; 95% CI: 0.42.0.72; P < 0.001). Both urinary 1-methylhistidine and urinary 3-methylhistidine were inversely associated with graft failure independent of potential confounders (HR per doubling: 0.84; 95% CI: 0.73. 0.96; P = 0.01; and 0.59; 95% CI: 0.41, 0.85; P = 0.004, respectively).Conclusions: High urinary 3-methylhistidine, reflecting higher red meat intake, is independently associated with lower risk of mortality. High urinary concentrations of both 1- and 3-methylhistidine, of which the former reflects higher white meat intake, are independently associated with lower risk of graft failure in KTR. Future intervention studies are warranted to study the effect of high meat intake on mortality and graft failure in KTR. using these biomarkers.

Background. End-stage kidney disease and dialysis vintage are characterized by accelerated atherosclerosis, volume overload, and progressive left ventricular hypertrophy, leading to elevated N-terminal probrain natriuretic peptide (NT-proBNP) levels. Pretransplant dialysis vintage is associated with excess mortality after transplantation. We want to study whether pretransplant NT-proBNP is associated with posttransplantation mortality and if it explains the association of dialysis vintage with posttransplantation mortality in kidney transplant recipients (KTR). Methods. We measured plasma NT-proBNP on arrival at the hospital before kidney transplantation in 658 KTR between January 1995 and December 2005 in our center. Multivariable Cox regression analyses, adjusted for potential confounders, were used to prospectively study the associations of dialysis vintage and NT-proBNP with all-cause mortality. Results. During median 12.7 (7.8-15.6) years of follow-up after transplantation, 248 (37.7%) KTR died. Dialysis vintage was associated with an increased risk of posttransplant mortality in the fully adjusted model (hazard ratio [HR], 1.22; 95% confidence interval [CI], 1.03-1.43; P = 0.02), independent of potential confounders. The association weakened materially and lost significance after further adjustment for NT-proBNP (HR, 1.14; 0.96-1.34; P = 0.14). NT-proBNP was independently associated with all-cause mortality in the fully adjusted model (HR, 1.34; 1.16-1.55; P < 0.001). The association remained independent of adjustment for dialysis vintage (HR, 1.31; 1.13-1.52; P < 0.001). Conclusions. Our study shows that longer dialysis vintage is associated with a higher mortality risk in KTR, and this association might be explained for a considerable part by variation in pretransplant NT-proBNP at the time of transplantation.

The influence of dairy on the gut microbiome has not been studied extensively. We performed a randomized cross-over study to analyze the effect of high dairy intake on the gut microbiome. Subjects were randomly assigned to a high-dairy diet (HDD) (5&ndash, 6 dairy portions per day) and a low-dairy diet (LDD) (&le, 1 dairy portion per day) for 6 weeks with a washout period of 4 weeks in between both diets. The gut microbiome was assessed using 16S rRNA gene sequencing. Compositionality and functionality of the gut microbiome was assessed using Quantitative Insights Into Microbial Ecology (QIIME) and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Stool consistency was evaluated using the Bristol stool chart. In total, 46 healthy overweight subjects (BMI range 25&ndash, 30 kg/m2) completed both intervention periods. During the HDD, there was a significantly higher abundance of the genera Streptococcus, Leuconostoc, and Lactococcus, and the species Streptococcus thermophilus, Erysipelatoclostridium ramosum and Leuconostoc mesenteroides (pFDR &lt, 0.10). Furthermore, during the HDD, there was a significantly lower abundance of the genera Faecalibacterium and Bilophila, and the species Faecalibacterium prausnitzii, Clostridium aldenense, Acetivibrio ethanolgignens, Bilophila wadsworthia and Lactococcus lactis (pFDR &lt, 0.10). There were eight subjects who became constipated during the HDD and these subjects all had a lower abundance of F. prausnitzii. This is the first cross-over study in which the effect of an HDD compared to an LDD on the gut microbiome has been studied. An HDD led to a significantly different composition of the gut microbiome, with a particularly lower abundance of F. prausnitzii and a higher abundance of S. thermophilus. Constipation was observed in several subjects during the HDD. Predicted metabolic pathways were not significantly altered due to an HDD.

Epidemiologic studies have linked urinary oxalate excretion to risk of chronic kidney disease (CKD) progression and end-stage renal disease. We aimed to investigate whether urinary oxalate, in stable kidney transplant recipients (KTR), is prospectively associated with risk of graft failure. In secondary analyses we evaluated the association with post-transplantation diabetes mellitus, all-cause mortality and specific causes of death. Oxalate excretion was measured in 24-h urine collection samples in a cohort of 683 KTR with a functioning allograft &ge, 1 year. Mean eGFR was 52 &plusmn, 20 mL/min/1.73 m2. Median (interquartile range) urinary oxalate excretion was 505 (347&ndash, 732) &micro, mol/24-h in women and 519 (396&ndash, 736) &micro, mol/24-h in men (p = 0.08), with 302 patients (44% of the study population) above normal limits (hyperoxaluria). A consistent and independent inverse association was found with all-cause mortality (HR 0.77, 95% CI 0.63&ndash, 0.94, p = 0.01). Cause-specific survival analyses showed that this association was mainly driven by an inverse association with mortality due to infection (HR 0.56, 95% CI 0.38&ndash, 0.83, p = 0.004), which remained materially unchanged after performing sensitivity analyses. Twenty-four-hour urinary oxalate excretion did not associate with risk of graft failure, post-transplant diabetes mellitus, cardiovascular mortality, mortality due to malignancies or mortality due to miscellaneous causes. In conclusion, in KTR, 24-h urinary oxalate excretion is elevated in 44% of KTR and inversely associated with mortality due to infectious causes.

Taurine is a sulfur containing nutrient that has been shown to protect against oxidative stress, which has been implicated in the pathophysiology leading to late graft failure after renal transplantation. We prospectively investigated whether high urinary taurine excretion, reflecting high taurine intake, is associated with low risk for development of late graft failure in renal transplant recipients (RTR). Urinary taurine excretion was measured in a longitudinal cohort of 678 stable RTR. Prospective associations were assessed using Cox regression analyses. Graft failure was defined as the start of dialysis or re-transplantation. In RTR (58% male, 53 &plusmn, 13 years old, estimated glomerular filtration rate (eGFR) 45 &plusmn, 19 mL/min/1.73 m2), urinary taurine excretion (533 (210&ndash, 946) &micro, mol/24 h) was significantly associated with serum free sulfhydryl groups (&beta, = 0.126, P = 0.001). During median follow-up for 5.3 (4.5&ndash, 6.0) years, 83 (12%) patients developed graft failure. In Cox regression analyses, urinary taurine excretion was inversely associated with graft failure (hazard ratio: 0.74 (0.67&ndash, 0.82), P &lt, 0.001). This association remained significant independent of potential confounders. High urinary taurine excretion is associated with low risk of late graft failure in RTR. Therefore, increasing taurine intake may potentially support graft survival in RTR. Further studies are warranted to determine the underlying mechanisms and the potential of taurine supplementation.

Long-term data on cardiovascular (CV) outcome of renal transplant recipients (RTR) on mTOR-i (mammalian Target Of Rapamycin-inhibitors) are scarce. In a sub-study of the MECANO trial we investigated changes in intima media thickness (IMT), CV risk profile, Major Adverse CV Events (MACE) and survival in RTR on a mTORi versus CNI based regimen. Patients (enrolled 361) were treated with (basiliximab) and triple IS (CsA-Cyclosporine A-(C), MPS(M), prednisolone(P)). At M6 patients were randomized (n=224) to the CsA group (C, P, N=89), MPS group (M, P, N=39) EVL group (Everolimus, P, N=96). At week 2, M6 and M 24, IMT measurements of the Common Carotid Artery were performed. Cardiovascular risk factors were assessed at baseline, 6 and 24 months of follow-up. Seven years survival and MACE -free survival probability were calculated by the Cardiovascular Risk Calculator for RTR. After seven years of follow-up incidence of cardiovascular events and patient survival were assessed. Mean IMT at baseline, (N=192), was 0.64±0.14 mm. At M6 (N=158), 0.66±0.15, M24 IMT was 0.68±0.15 (N=95).CONCLUSION: No significant differences between groups concerning IMT, true CV events and mortality, CV risk profile, predicted MACE / Mortality were found between mTORi and CNI-based regimen after 7 years of follow-up. This article is protected by copyright. All rights reserved.

BACKGROUND: Little is known about optimal protein intake after transplantation. The aim of this study was to prospectively investigate associations of urinary urea excretion, a marker for protein intake, with graft failure and mortality in renal transplant recipients (RTR) and potential effect modification by body mass index (BMI) and estimated glomerular filtration rate (eGFR).METHODS: Urinary urea excretion was measured in repeated 24-hr urine collections between 6 and 18 months after transplantation.RESULTS: In total, 940 RTR were included. During 4.4 (2.3-7.8) years of follow-up for graft failure and 4.8 (2.5-8.3) years for all-cause mortality, 78 RTR developed graft failure and 158 RTR died. Urinary urea excretion was not associated with graft failure in the overall population, but was inversely associated with graft failure in RTR with BMI less than 25 kg/m (hazard ratio [HR], 0.64 [0.28-1.50] and 0.27 [0.09-0.83] for the second and third tertiles, respectively, P < 0.001), and in RTR with eGFR of 45 mL per min per 1.73 m or higher (HR, 0.34 [0.15-0.79], P = 0.015 and HR, 0.31 [0.11-0.86], P = 0.025 for the second and third tertiles, respectively), both independent of potential confounders. Compared to the first tertile, RTR in the second and third tertiles of urinary urea excretion were at a lower risk of all-cause mortality (HR, 0.47 [0.32-0.69]; P < 0.001 and HR, 0.42 [0.26-0.68]; P < 0.001, respectively), independent of potential confounders. Body mass index and eGFR did not influence this association.CONCLUSION: Urinary urea excretion, a marker for protein intake, was inversely related to graft failure in RTR with BMI less than 25 kg/m and in RTR with an eGFR of 45 mL per min per 1.73 m or higher. In addition, urinary urea excretion was inversely related to mortality.