Uremic Toxin Development in Living Kidney Donors: A Longitudinal Study

Trimethylamine-N-oxide (TMAO) and predicted risk of cardiovascular events after partial nephrectomy

INTRODUCTION

Emerging evidence suggests that uremic toxins, in particular trimethylamine-N-oxide(TMAO), indoxyl-sulfate(IS), and p-cresyl-sulfate(PCS), may associate with increased risk of cardiovascular events(CVe). However, whether uremic toxins increase after partial nephrectomy(PN) and their correlation with risk for CVe remains unknown.

METHODS

100 patients managed with PN were retrospectively reviewed. TMAO/IS/PCS levels were examined by liquid chromatography-mass-spectrometry. Renal-parenchymal-volume-preservation(RPVP) was estimated from CT scans. Predicted risks for CVe were obtained using the Framingham score. Linear regression assessed association between uremic toxins, GFR and risk of CVe. Logistic regression evaluated factors associated with post-PN TMAO.

RESULTS

TMAO, IS and PCS increased from 1.7, 3.7 and 3.5 μmol/L before PN to 3.6, 5.4 and 7.4 μmol/L at latest follow-up, respectively, while GFR declined from 102 to 93 ml/min/1.73 m2 (all p<0.001). TMAO, IS and PCS levels all negatively correlated with GFR(all p<0.001). Predicted 10-year risk of CVe increased from 1.1% pre-PN to 1.7% post-PN(p<0.001), primarily due to increased age(p<0.001), blood pressure(p = 0.002) and total cholesterol(p = 0.003). TMAO(β = 0.038) and GFR (β = -0.02) were independent predictors for predicted 10-year CVe risk on multivariable-analysis. Increased TMAO was an early and sustained finding maintained through 5 years, unlike IS, PCS and eGFR. On multivariable analysis, increased pre-PN TMAO(OR = 2.79) and decreased RPVP(OR = 3.23) were identified as independent risk factors for higher post-PN TMAO, while ischemia type/duration failed to correlate.

CONCLUSION

Uremic toxin levels increased after PN correlating with reduced GFR. Higher TMAO independently associated with greater predicted 10-year CVe risk. Parenchymal mass preserved rather than ischemia time or type associated with increased TMAO.

Tryptophan Metabolites Regulate Neuropentraxin 1 Expression in Endothelial Cells

In patients with chronic kidney disease (CKD) and in animal models of CKD, the transcription factor Aryl Hydrocabon Receptor (AhR) is overactivated. In addition to the canonical AhR targets constituting the AhR signature, numerous other genes are regulated by this factor. We identified neuronal pentraxin 1 (NPTX1) as a new AhR target. Belonging to the inflammatory protein family, NPTX1 seems of prime interest regarding the inflammatory state observed in CKD. Endothelial cells were exposed to tryptophan-derived toxins, indoxyl sulfate (IS) and indole-3-acetic acid (IAA). The adenine mouse model of CKD was used to analyze NPTX1 expression in the burden of uremia. NPTX1 expression was quantified by RT-PCR and western blot. AhR involvement was analyzed using silencing RNA. We found that IS and IAA upregulated NPTX1 expression in an AhR-dependent way. Furthermore, this effect was not restricted to uremic indolic toxins since the dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and the tryptophan photoproduct 6-formylindolo[3,2-b]carbazole (FICZ) do the same. In CKD mice, NPTX1 expression was increased in the aorta. Therefore, NPTX1 is a new target of AhR and further work is necessary to elucidate its exact role during CKD.

Effects of living kidney donation on arterial stiffness: a systematic review protocol

INTRODUCTION

Kidney donors have been reported to have accelerated progression of aortic stiffness and decreased glomerular filtration compared with healthy non-donors. This is a concern because increased aortic stiffness is an independent predictor of overall cardiovascular disease and all-cause mortality in the general population. To confirm if arterial stiffness increases after donation, we will systematically review all studies that evaluated indices of arterial stiffness in healthy individuals who underwent unilateral nephrectomy for kidney donation compared with age-matched healthy non-nephrectomised controls.

METHODS/ANALYSIS

We will comprehensively search for studies published between 1 January 1960 and 15 March 2021 in MEDLINE, EMBASE, Cochrane Central, OVID and EBM reviews. All prospective (cohort, case-control, case series and before-and-after studies) and retrospective non-randomised studies reporting indices of arterial stiffness in nephrectomised and non-nephrectomised healthy participants will be included. Primary outcome will be the difference in the functional metrics of arterial stiffness between donors and non-donors. Secondary outcomes will be the differences in systolic/diastolic blood pressures, serum creatinine, glomerular filtration, carotid artery intima-media thickness and vascular calcification. Study screening, selection and data extraction will be performed by two independent reviewers. Risk of bias will be independently assessed with the ROBINS-I tool and confidence in evidence by the Grading of Recommendations Assessment, Development and Evaluation recommendations. Qualitative and quantitative data syntheses as well as clinical and statistical heterogeneity (Forest plots, I2 and Cochran's Q statistics) will be evaluated. If clinical and statistical heterogeneity are acceptable, inverse variance-weighted effects will be analysed by random effect models.

ETHICS AND DISSEMINATION

No ethical approval is necessary. Our results will be disseminated through peer-review publication and presentations to guide stakeholders on the evaluation and follow-up care of kidney donors.

PROSPERO REGISTRATION NUMBER

CRD42020185551.

Indoxyl Sulfate, a Uremic Endotheliotoxin

Chronic kidney disease (CKD) is associated with a high prevalence of cardiovascular diseases. During CKD, the uremic toxin indoxyl sulfate (IS)—derived from tryptophan metabolism—accumulates. IS is involved in the pathophysiology of cardiovascular complications. IS can be described as an endotheliotoxin: IS induces endothelial dysfunction implicated in cardiovascular morbidity and mortality during CKD. In this review, we describe clinical and experimental evidence for IS endothelial toxicity and focus on the various molecular pathways implicated. In patients with CKD, plasma concentrations of IS correlate with cardiovascular events and mortality, with vascular calcification and atherosclerotic markers. Moreover, IS induces a prothrombotic state and impaired neovascularization. IS reduction by AST-120 reverse these abnormalities. In vitro, IS induces endothelial aryl hydrocarbon receptor (AhR) activation and proinflammatory transcription factors as NF-κB or AP-1. IS has a prooxidant effect with reduction of nitric oxide (NO) bioavailability. Finally, IS alters endothelial cell and endothelial progenitor cell migration, regeneration and control vascular smooth muscle cells proliferation. Reducing IS endothelial toxicity appears to be necessary to improve cardiovascular health in CKD patients.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

Impact of Remote Ischemic Preconditioning Conducted in Living Kidney Donors on Renal Function in Donors and Recipients Following Living Donor Kidney Transplantation: A Randomized Clinical Trial

Although remote ischemic preconditioning (RIPC) has been shown to have renoprotective effects, few studies have assessed the effects of RIPC on renal function in living kidney donors. This study investigated whether RIPC performed in living kidney donors could improve residual renal function in donors and outcomes in recipients following kidney transplantation. The donors were randomized into a control group (n = 85) and a RIPC group (n = 85). The recipients were included according to the matched donors. Serum creatinine (sCr) concentrations and estimated glomerular filtration rate (eGFR) were compared between control and RIPC groups in donors and recipients. Delayed graft function, acute rejection, and graft failure within one year after transplantation were evaluated in recipients. sCr was significantly increased in the control group (mean, 1.13; 95% confidence interval (CI), 1.07–1.18) than the RIPC group (1.01; 95% CI, 0.95–1.07) (p = 0.003) at discharge. Donors with serum creatinine >1.4 mg/dL at discharge had higher prevalence of chronic kidney disease (n = 6, 26.1%) than donors with a normal serum creatinine level (n = 8, 5.4%) (p = 0.003) after one year. sCr concentrations and eGFR were similar in the RIPC and control groups of recipients over the one-year follow-up period. Among recipients, no outcome variables differed significantly in the RIPC and control groups. RIPC was effective in improving early renal function in kidney donors but did not improve renal function in recipients.

Chronic kidney disease as a cardiovascular risk factor: lessons from kidney donors

Chronic kidney disease (CKD) is a major risk factor for cardiovascular disease but is often associated with other risks such as diabetes and hypertension and can be both a cause and an effect of cardiovascular disease. Although epidemiologic data of an independent association of reduced glomerular filtration rate with cardiovascular risk are strong, causative mechanisms are unclear.

Living kidney donors provide a useful model for assessing the “pure” effects of reduced kidney function on the cardiovascular system. After nephrectomy, the glomerular filtration rate ultimately falls by about one-third so many can be classified as having chronic kidney disease stages 2 or 3. This prompts concern based on the data showing an elevated cardiovascular risk with these stages of chronic kidney disease. However, initial data suggested no increase in adverse cardiovascular effects compared with control populations. Recent reports have shown a possible late increase in cardiovascular event rates and an early increase in left ventricular mass and markers of risk such as urate and albuminuria. The long-term significance of these small changes is unknown. More detailed and long-term research is needed to determine the natural history of these changes and their clinical significance.

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Subjects with chronic kidney disease (CKD) have an elevated risk of cardiovascular disease.

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Kidney donors have a reduced glomerular filtration rate and biochemical changes similar to CKD subjects.

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Most studies of donors have not shown an elevated risk of death or cardiac disease.

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Donors have structural and functional cardiovascular changes similar to early CKD.

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The clinical significance of these changes is currently unknown.

Live donor study - implications of kidney donation on cardiovascular risk with a focus on lipid parameters including lipoprotein a

In this prospective observational cohort study, we evaluate the change in cardiovascular risk parameters, with a focus on lipids, in live kidney donors 1 year post donation. Body mass index, systolic/diastolic blood pressure, kidney function (chromium-51 ethylenediaminetetraacetic acid estimated glomerular filtration) and lipid parameters were measured at baseline and 1 year. Data on 87 live kidney donors were collected. Body mass index increased from 26.5 ± 2.7 pre to 27.4 ± 3.0 kg/m(2) post donation (p < 0.0001). Chromium-51 ethylenediaminetetraacetic acid estimated glomerular filtration decreased from 111.8 ± 20.0 pre to 72.1 ± 13.1 mL/min/1.73 m(2) post donation (p < 0.0001). Serum triglyceride levels increased from 0.8 (interquartile range 0.6-1.3) pre to 1.0 mmol/L (interquartile range 0.7-1.6) post donation (p = 0.0004). Statin use increased from 11.5% pre to 21% post donation (p < 0.005). Low-density lipoprotein remained stable, and other lipids (high-density lipoprotein, apolipoprotein B and lipoprotein a) did not change post donation.

Cystatin-C is associated with partial recovery of kidney function and progression to chronic kidney disease in living kidney donors: Observational study

Donor nephrectomy in living-donor kidney transplantation may result in hyperfiltration injury in remnant kidney; however, its clinical implication in partial recovery of kidney function (PRKF) in remnant kidney and chronic kidney disease (CKD) progression remains unclear. Thus, we investigated the effect of PRKF on CKD development in the residual kidney and the utility of cystatin-C (Cys-C) in evaluating renal function in living-donor kidney transplantation donors.The electronic medical records and laboratory results of 1648 kidney transplant (KT) donors and 13,834 healthy nondonors between January 2006 and November 2014 were reviewed. The predictors of PRKF and CKD diagnosed by Kidney Disease: Improving Global Outcomes (KDIGO) criteria were evaluated by multivariate analysis. CKD risk was compared between KT donors and healthy nondonors using Cox proportional hazard regression analysis following propensity score matching (PSM).The incidence of PRKF for KT donors was 49.3% (813). CKD incidence was 24.8% (408) in KT donors and 2.0% (277) in healthy nondonors. The predictors of PRKF were, male sex (odds ratio [OR], 17.32; 95% confidence interval [CI] 9.16-32.77), age (OR, 1.02; 95% CI, 1.00-1.04; P < 0.001), Cys-C concentration (OR, 1.02; 95% CI, 1.00-1.04; P = 0.02), and preoperative albumin level (OR, 0.49; 95% CI, 0.27-0.89; P = 0.02). The predictors of CKD were age (hazards ratio [HR], 1.04; 95% CI, 1.02-1.05; P < 0.001), Cys-C concentration (HR, 1.024; 95% CI, 1.012-1.037; P < 0.001), and PRKF (HR, 1.41; 95% CI, 1.04-1.92; P = 0.03). After PSM, the risk of progression to CKD was higher in KT donors than in healthy nondonors (HR, 58.4; 95% CI, 34.2-99.8; P < 0.001).Donor nephrectomy is associated with PRKF and progression to CKD. Cys-C is a useful early marker for detecting PRKF and CKD.

The influence of mutant lactobacilli on serum creatinine and urea nitrogen concentrations and renal pathology in 5/6 nephrectomized rats

OBJECTIVES

To explore the capacity of mutant lactobacilli to remove creatinine (Cr) and urea nitrogen (UN) via the gastrointestinal tract and its effects on renal pathology in the 5/6 nephrectomized rat model of chronic renal failure.

METHODS

Sixty Sprague-Dawley rats were randomly divided into a Sham group, a Model group, a wide-type Lactobacilli group (L.B group), and a Mutant Lactobacilli group (Mut-L.B group). The rats in the Model, LB and Mut-L.B groups underwent 5/6 nephrectomy. Eight weeks after administration, 24-h urine, orbital blood and digestive secretions were collected to analyze Cr and UN levels. Pathological changes in nephridial tissues were observed by hematoxylin and eosin and Masson trichrome staining, and the expression of TGF-β1 and FN was detected by immunohistochemistry.

RESULTS

There were no significant differences in urinary Cr and UN levels among the Sham, L.B and Mut-L.B groups (p > .05), while serum and digestive Cr and UN levels were significantly decreased in the Mut-L.B group (p < .01). Furthermore, renal tubular injury and interstitial fibrosis were significantly reduced and TGF-β1 and FN expression was decreased (p < .05) in the Mut-L.B group.

CONCLUSION

Mutant lactobacilli decreased serum Cr and UN levels, reduced the expression of TGF-β1 and FN in renal tissues and alleviated renal interstitial injury and fibrosis in a rat model of chronic renal failure in a mechanism that may involve decomposition and not just excretion of small molecule toxins in the gastrointestinal tract.

Gout after living kidney donation: correlations with demographic traits and renal complications

BACKGROUND

The demographic and clinical correlates of gout after living kidney donation are not well described.

METHODS

Using a unique database that integrates national registry identifiers of U.S. living kidney donors (1987-2007) with billing claims from a private health insurer (2000-2007), we identified post-donation gout based on medical diagnosis codes or pharmacy fills for gout therapies. The frequencies and demographic correlates of gout after donation were estimated by Cox regression with left- and right-censoring. We also compared the rates of renal diagnoses among donors with and without gout, matched in the ratio 1:3 by age, sex, and race.

RESULTS

The study sample of 4,650 donors included 13.1% African Americans. By seven years, African Americans were almost twice as likely to develop gout as Caucasian donors (4.4 vs. 2.4%; adjusted hazard ratio, aHR, 1.8; 95% confidence interval (CI) 1.0-3.2). Post-donation gout risk also increased with older age at donation (aHR per year 1.05) and was higher in men (aHR 2.80). Gout rates were similar in donors and age- and sex-matched general non-donors (rate ratio 0.86; 95% CI 0.66-1.13). Compared to matched donors without gout, donors with gout had more frequent renal diagnoses, reaching significance for acute kidney failure (rate ratio 12.5; 95% CI 1.5-107.0), chronic kidney disease (rate ratio 5.0; 95% CI 2.1-11.7), and other disorders of the kidney (rate ratio 2.2; 95% CI 1.2-4.2).

CONCLUSION

Donor subgroups at increased risk of gout include African Americans, older donors, and men. Donors with gout have a higher burden of renal complications after demographic adjustment.

A prospective controlled study of living kidney donors: three-year follow-up

BACKGROUND

There have been few prospective controlled studies of kidney donors. Understanding the pathophysiologic effects of kidney donation is important for judging donor safety and improving our understanding of the consequences of reduced kidney function in chronic kidney disease.

STUDY DESIGN

Prospective, controlled, observational cohort study.

SETTING & PARTICIPANTS

3-year follow-up of kidney donors and paired controls suitable for donation at their donor's center.

PREDICTOR

Kidney donation.

OUTCOMES

Medical history, vital signs, glomerular filtration rate, and other measurements at 6, 12, 24, and 36 months after donation.

RESULTS

At 36 months, 182 of 203 (89.7%) original donors and 173 of 201 (86.1%) original controls continue to participate in follow-up visits. The linear slope of the glomerular filtration rate measured by plasma iohexol clearance declined 0.36±7.55mL/min per year in 194 controls, but increased 1.47±5.02mL/min per year in 198 donors (P=0.005) between 6 and 36 months. Blood pressure was not different between donors and controls at any visit, and at 36 months, all 24-hour ambulatory blood pressure parameters were similar in 126 controls and 135 donors (mean systolic blood pressure, 120.0±11.2 [SD] vs 120.7±9.7mmHg [P=0.6]; mean diastolic blood pressure, 73.4±7.0 vs 74.5±6.5mmHg [P=0.2]). Mean arterial pressure nocturnal dipping was manifest in 11.2% ± 6.6% of controls and 11.3% ± 6.1% of donors (P=0.9). Urinary protein-creatinine and albumin-creatinine ratios were not increased in donors compared with controls. From 6 to 36 months postdonation, serum parathyroid hormone, uric acid, homocysteine, and potassium levels were higher, whereas hemoglobin levels were lower, in donors compared with controls.

LIMITATIONS

Possible bias resulting from an inability to select controls screened to be as healthy as donors, short follow-up duration, and dropouts.

CONCLUSIONS

Kidney donors manifest several of the findings of mild chronic kidney disease. However, at 36 months after donation, kidney function continues to improve in donors, whereas controls have expected age-related declines in function.

Detection of cystatin C biomarker for clinical measurement of renal disease by developed ELISA diagnostic kits

Background

Human cystatin C (HCC) is a potential biomarker for tubular damage and impaired renal function. It is difficult to obtain efficient paired monoclonal antibodies against HCC with low molecular to meet the requirements for clinical application The present study was to establish a stable and repeatable measurement for HCC with self-made monoclonal antibodies (McAbs) and Variable domain of heavy chain of heavy-chain antibody (VHHs) increase the sensitivity.

Methods

With hybridoma technology and phage display technology: R-HCC as a screening antigen and N-HCC as the detector for antigens to obtain the specific antibody and established an enzyme-linked immunosorbent assay for human cystatin C using self-made McAbs and VHHs.

Results

We have successfully obtained three McAbs; 5 F2, 4E4, 1E11 and four VHHs; 3-2, 3-24, 3-33 and 4-5 which were specific for HCC. The measurement of HCC was established with the self-made monoclonal antibodies and VHHs with a high sensitivity the lower limit of detection at 0.5 ng/ml and the detection range at 0.5 ~ 31.3 ng/ml.

Conclusion

Our data provides a new approach for paired antibody screening and testing of the small molecular biomarker with a single dominant epitope, with the important biological and clinical significance.