Respective predictive role of urinary albumin excretion and nonalbumin proteinuria on graft loss and death in renal transplant recipients

Mineralocorticoid receptor antagonists in kidney transplantation

BACKGROUND

The fundamental role of the renin-angiotensin-aldosterone system in the pathophysiology of chronic kidney disease, congestive heart failure, hypertension and proteinuria is well established in pre-clinical and clinical studies. Mineralocorticoid receptor antagonists are among the primary options for renin-angiotensin-aldosterone system blockage, along with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

METHODS

In this narrative review, we aim to evaluate the efficiency and safety of mineralocorticoid receptor antagonists in kidney transplant recipients, including the potential underlying pathophysiology.

RESULTS

The efficiency and safety of mineralocorticoid receptor antagonists in managing chronic kidney disease and proteinuria, either non-nephrotic or nephrotic range, have been demonstrated among nontransplanted patients, though studies investigating the role of mineralocorticoid receptor antagonists among kidney transplant recipients are scarce. Nevertheless, promising results have been reported in pre-clinical and clinical studies among kidney transplant recipients regarding the role of mineralocorticoid receptor antagonists in terms of ischaemia-reperfusion injury, proteinuria, or calcineurin inhibitor-mediated nephrotoxicity without considerable adverse events such as hypotension, hyperkalaemia or worsening renal functions.

CONCLUSION

Even though initial results regarding the role of mineralocorticoid receptor antagonist therapy for kidney transplant recipients are promising, there is clear need for large-scale randomized clinical trials with long-term follow-up data.

Consequences of Nephrotic Proteinuria and Nephrotic Syndrome after Kidney Transplant

Proteinuria is the main predictor of kidney graft loss. However, there is little information regarding the consequences of nephrotic proteinuria (NP) and nephrotic syndrome (NS) after a kidney transplant. We aimed to describe the clinical and histopathological characteristics of kidney recipients with nephrotic-range proteinuria and compare the graft surveillance between those who developed NS and those who did not. A total of 204 patients (18.6% of kidney transplants in the study period) developed NP, and 68.1% of them had NS. Of the 110 patients who underwent a graft biopsy, 47.3% exhibited ABMR, 21.8% the recurrence of glomerulonephritis, 9.1% IFTA, and 7.3% de novo glomerulonephritis. After a median follow-up of 97.5 months, 64.1% experienced graft loss. The graft survival after the onset of NP declined from 75.8% at 12 months to 38% at 5 years, without significant differences between those with and those without NS. Patients who developed NS fewer than 3 months after the onset of NP exhibited a significantly higher risk of death-censored graft loss (HR: 1.711, 95% CI: 1.147-2.553) than those without NS or those with late NS. In conclusion, NP and NS are frequent conditions after a kidney transplant, and they imply extremely poor graft outcomes. The time from the onset of NP to the development of NS is related to graft survival.

Spot Urine Protein Excretion in the First Year Following Kidney Transplantation Associates With Allograft Rejection Phenotype at 1-Year Surveillance Biopsies: An Observational National-Cohort Study

Introduction: Urine protein excretion is routinely measured to assess kidney allograft injury, but the diagnostic value of this measurement for kidney transplant pathology remains unclear. Here we investigated whether spot urine protein excretion in the first year following transplantation associates with allograft rejection phenotype at 1-year surveillance biopsies and de-novo occurrence of donor-specific antibodies (DSA). Patients and Methods: This prospective, observational national-cohort study included 139 non-sensitized patients who received a deceased donor kidney transplant between December 2014 and 2018. All patients received basiliximab induction and tacrolimus-based immunosuppression. Estimated protein excretion rate (ePER) was calculated monthly from spot urine protein-to-creatinine ratios. At 1-year, all recipients underwent surveillance graft biopsy and were screened for de-novo DSA. Screening-positive sera were subjected to single antigen bead (SAB) testing. The occurrence of de-novo DSA was determined based on SAB reactivity patterns using a mean fluorescence intensity threshold >1,000. Results: Among the 139 study patients, 27 patients (19%) had histologic evidence of T cell-mediated rejection (TCMR), and 9 patients (7%) had histologic evidence of antibody-mediated rejection (AMR) at 1-year surveillance biopsy. One year after transplant, 19 patients (14%) developed de-novo DSA. Compared with patients without rejection and no de-novo DSA, mixed-effects linear regression analysis showed a significant difference in slope of ePER during the first year in patients with AMR and de-novo DSA at 1-year (46, 95% CI 25-68 mg/day/1.73 m² per month and 34, 95% CI 20-49 mg/day/1.73 m² per month, respectively). Patients with vascular TCMR also showed a significant difference in ePER slope over time compared with patients with non-rejection findings (31, 95% CI 9-52 mg/day/1.73 m² per month). The discriminatory power of ePER for intragraft rejection processes was better in patients with AMR (AUC 0.95, 95% CI 0.90-0.99; P < 0.001) than in those with TCMR (AUC 0.68, 95% CI 0.59-0.79; P = 0.002), with 89% sensitivity and 93% specificity for proteinuria >550 mg/day/1.73m². Conclusions: An increase in ePER in the first year following kidney transplantation associates with AMR, vascular TCMR and de-novo DSA at 1-year and may be used as a non-invasive clinical marker of intragraft endothelial cell injury.

Clinicopathologic Features and Risk Factors of Proteinuria in Transplant Glomerulopathy

Background: Transplant glomerulopathy (TG) is one of the main causes of post-transplant proteinuria (PU). The features and possible risk factors for proteinuria in TG patients are uncertain.

Methods: We investigated all patients who had biopsy-proven TG from 2000 to 2018 in our center. The clinical and histological data were compared between two groups with or without PU (cut-off = 0.3 g/day). Spearman correlation analysis was used to evaluate the relationship between PU and pathological changes. The risk factors for PU in TG patients were determined by multivariable logistic regression analysis.

Results: One hundred and twenty-five (75.76%) of all enrolled 165 TG patients had proteinuria ≥0.3 g/day at the time of biopsy. TG patients' PU level was significantly correlated with Banff lesion score cg (ρ = 0.247, P = 0.003), and mm (ρ = 0.257, P = 0.012). Systolic blood pressure ≥140 mmHg (OR 2.72, 95% CI 1.04–7.10, P = 0.041), diastolic blood pressure ≥90 mmHg (OR 4.84, 95% CI 1.39–16.82, P = 0.013), peak PRA ≥5% (OR 6.47, 95% CI 1.67–25.01, P = 0.007), positive C4d staining (OR 4.55, 95% CI 1.29–16.11, 0.019), tacrolimus-based regimen (OR 3.5, 95% CI 1.28–9.54, P = 0.014), and calcium channel blocker usage (OR 4.38, 95% CI 1.59–12.09, P = 0.004) were independent risk factors for PU.

Conclusions: Proteinuria is common in TG patients. systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, peak PRA ≥5%, positive C4d staining, tacrolimus-based regimen, and calcium channel blocker usage are associated with proteinuria in TG patients.

First and second morning spot urine protein measurements for the assessment of proteinuria: a diagnostic accuracy study in kidney transplant recipients

BACKGROUND

Quantification of proteinuria in kidney transplant recipients is important for diagnostic and prognostic purposes. Apart from correlation tests, there have been few evaluations of spot urine protein measurements in kidney transplantation.

METHODS

In this cross-sectional study involving 151 transplanted patients, we investigated measures of agreement (bias and accuracy) between the estimated protein excretion rate (ePER), determined from the protein-to-creatinine ratio in the first and second morning urine, and 24-h proteinuria and studied their performance at different levels of proteinuria. Measures of agreement were reanalyzed in relation to allograft histology in 76 patients with kidney biopsies performed for cause before enrolment in the study.

RESULTS

For ePER in the first morning urine, percent bias ranged from 1 to 28% and accuracy (within 30% of 24-h collection) ranged from 56 to 73%. For the second morning urine, percent bias ranged from 2 to 11%, and accuracy ranged from 71 to 78%. The accuracy of ePER (within 30%) in first and second morning urine progressively increased from 56 and 71% for low-grade proteinuria (150-299 mg/day) to 60 and 74% for moderate proteinuria (300-999 mg/day), and to 73 and 78% for high-grade proteinuria (≥1000 mg/day). Measures of agreement were similar across histologic phenotypes of allograft injury.

CONCLUSIONS

The ability of ePER to accurately predict 24-h proteinuria in kidney transplant recipients is modest. However, accuracy improves with an increase in proteinuria. Given the similar accuracy of ePER measurements in first and second morning urine, second morning urine can be used to monitor protein excretion.

Microalbuminuria After Kidney Transplantation Predicts Cardiovascular Morbidity

Background: Microalbuminuria is a well-characterized marker of kidney malfunction, both in diabetic and non-diabetic populations, and is used as a prognostic marker for cardiovascular morbidity and mortality. A few studies implied that it has the same value in kidney transplanted patients, but the information relies on spot or dipstick urine protein evaluations, rather than the gold standard of timed urine collection.

Methods: We revisited a cohort of 286 kidney transplanted patients, several years after completing a meticulously timed urine collection and assessed the prevalence of major cardiovascular adverse events (MACE) in relation to albuminuria.

Results: During a median follow up of 8.3 years (IQR 6.4–9.1) 144 outcome events occurred in 101 patients. By Kaplan-Meier analysis microalbuminuria was associated with increased rate of CV outcome or death (p = 0.03), and this was still significant after stratification according to propensity score quartiles (p = 0.048). Time dependent Cox proportional hazard analysis showed independent association between microalbuminuria and CV outcomes 2 years following microalbuminuria detection (HR 1.83, 95% CI 1.07–2.96).

Conclusions: Two years after documenting microalbuminuria in kidney transplanted patients, their CVD risk was increased. There is need for primary prevention strategies in this population and future studies should address the topic.

Non-Albumin Proteinuria (NAP) as a Complementary Marker for Diabetic Kidney Disease (DKD)

Diabetic kidney disease (DKD) is one of the most common forms of chronic kidney disease. Its pathogenic mechanism is complex, and it can affect entire structures of the kidney. However, conventional approaches to early stage DKD have focused on changes to the glomerulus. Current standard screening tools for DKD, albuminuria, and estimated glomerular filtration rate are insufficient to reflect early tubular injury. Therefore, many tubular biomarkers have been suggested. Non-albumin proteinuria (NAP) contains a wide range of tubular biomarkers and is convenient to measure. We reviewed the clinical meanings of NAP and its significance as a marker for early stage DKD.

Hepatic fibrosis is associated with total proteinuria in Korean patients with type 2 diabetes

The association between non-alcoholic fatty liver disease (NAFLD) and diabetic kidney disease assessed using either albuminuria or proteinuria remains controversial. This study aimed to investigate the association between hepatic steatosis or fibrosis and albuminuria or proteinuria in Korean patients with type 2 diabetes mellitus (T2D).We enrolled 1108 patients with T2D and categorized as 3 groups; non-proteinuria (NP), isolated non-albumin proteinuria (iNAP), and albuminuria. Urinary albumin and protein levels were assessed as urinary albumin-to-creatinine ratio (uACR) and urinary protein-to-creatinine ratio (uPCR), respectively. Hepatic steatosis and fibrotic burden were assessed using the NAFLD liver fat score, Fibrosis-4 calculator (FIB-4) index, and NAFLD fibrosis score (NFS).The prevalence of significant steatosis was similar among groups (NP: 74.6% vs iNAP: 70.3% vs albuminuria: 79.9%, P = .085). The prevalence of significant fibrosis was significantly higher in the iNAP (18.7%) and albuminuria (16.5%) groups than in the NP group (9.5%, P = .001). Both uPCR and uACR showed a correlation with NFS (uPCR: r = 0.123, P < .001; uACR: r = 0.064, P = .033). In multivariate logistic regression analysis, uPCR ≥150 mg/g was found to have a stronger association with hepatic fibrosis than uACR ≥30 mg/g (adjusted odds ratio 1.55 [95% CI 1.03-2.33] vs adjusted odds ratio 1.16 [95% CI, 0.72-1.87]).In conclusion, patients with iNAP and albuminuria had a higher prevalence of hepatic fibrosis than those without proteinuria. Total proteinuria was associated with advanced liver fibrosis, whereas albuminuria was related to hepatic steatosis.

Association of urinary non-albumin protein with the different urinary marker for glomerular and tubular damage in patients with type 2 diabetes

BACKGROUND/AIM

In recent years, the diagnostic utility of urinary protein levels has been demonstrated for the early detection and progression of kidney disease. This study aimed to evaluate the associations of the non-albumin protein (NAP) with different urinary marker for tubular and glomerular damage in patients with type 2 diabetes (T2D).

METHODS

In this observational cross-sectional study, 424 patients with T2D duration > 10 years were classified into two groups according to estimated glomerular filtration rate (eGFR). The ratios of different urinary markers (albumin, NAP, total protein, transferrin, retinol-binding protein (RBP), and neutrophil gelatinase-associated lipocalin (NGAL) to creatinine were analyzed.

RESULTS

The levels of urinary biomarkers increased significantly with decrease in eGFR levels. In the group with moderately decreased eGFR, the albumin to-creatinine ratio (ACR), non-albumin protein-to-creatinine ratio (NAPCR), and total protein-to-creatinine ratio (PCR) were independently associated with all urinary markers after being adjusted for risk factors. The area under the receiver operating characteristics (ROC) curve for ACR and PCR had a better diagnostic value than other urinary biomarkers. Comparing ROC curve of NAPCR with other urinary biomarkers, it was significantly better than NGAL/Cr (p = 0.033).

CONCLUSIONS

The findings of the present study confirm that ACR and PCR are diagnostic biomarkers in T2D patients with decreased eGFR. NAPCR in these patients diagnostically only outperformed NGAL/Cr.

Transgenic expression of human CD47 reduces phagocytosis of porcine endothelial cells and podocytes by baboon and human macrophages

BACKGROUND

Our initial studies utilizing a galactosyl-α1-3-galactosyltransferase gene knockout (GalTKO) pig-to-baboon renal transplant model demonstrated that the early development of nephrotic syndrome has been a significant obstacle to the long-term survival of baboon recipients. We have recently documented that sphingomyelin phosphodiesterase-3 (SMPDL3b) and CD80 expressed on podocytes in porcine kidney grafts contribute to this complication. We have hypothesized that one regulator of immune function is CD47 and that incompatibilities in CD47 between pig and baboon could potentially affect macrophage function, increasing the susceptibility of the kidney grafts to immunologically induced injury.

METHODS

In order to address this hypothesis in vitro, we isolated and cultured porcine podocytes and ECs from GalTKO alone, human CD47 (hCD47)/hCD55 expressing transgenic (Tg) GalTKO swine, and GalTKO hCD46/hCD55 Tg swine along with baboon or human macrophages.

RESULTS

We found that baboon macrophages phagocytosed porcine ECs in a similar manner to human macrophages, and this response was significantly reduced when porcine ECs and podocytes expressed hCD47/hCD55 but not hCD46/hCD55 without hCD47. Furthermore, masking hCD47 by anti-hCD47 antibody on hCD47/hCD55Tg ECs restored phagocytosis. These results are consistent with the hypothesis that CD47 incompatibility plays an important role in promoting macrophage phagocytosis of endogenous cells from the transplanted kidney.

CONCLUSIONS

The similar levels of phagocytosis of porcine cells by baboon and human macrophages suggest that the expression of hCD47Tg on glomerular cells in donor porcine kidneys may prove to be a key strategy for preventing proteinuria following kidney xenotransplantation in a pig-to-human as well as a pig-to-baboon model.

Glucometabolic characteristics and higher vascular complication risk in Korean patients with type 2 diabetes with non-albumin proteinuria

OBJECTIVE

We investigated the clinical relevance of non-albumin proteinuria (NAP) in Korean patients with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

We enrolled 883 T2D patients who had both their urinary albumin-to-creatinine ratio (uACR) and protein-to-creatinine ratio (uPCR) measured. We classified the patients into non-proteinuria (NP; uPCR <150 mg/g and uACR <30 mg/g), isolated NAP (iNAP; uPCR ≥150 mg/g and uACR <30 mg/g), and albuminuria (uACR ≥30 mg/g) groups. The associations between uPCR, uACR, and several indices of glucose metabolism were investigated.

RESULTS

The glucometabolic pathophysiology of iNAP (96 [10.9%]) group was more associated with a decrease in homeostatic model assessment (HOMA)-beta value (aOR 1.89 [95% CI, 1.21-2,96]) than with an increase in HOMA-insulin resistance (aOR 1.29 [95% CI, 0.83-2.01]). uPCR ≥150 mg/g was also found to have more consistent and stronger association with vascular complications than uACR ≥30 mg/g (aOR 1.44 [95% CI, 1.03-2.02] vs. 1.26 [95% CI, 0.89-1.79]).

CONCLUSIONS

The nephropathy of iNAP may be mainly attributed to decreased beta cell function. Furthermore, uPCR might be a more sensitive urinary biomarker than uACR for the detection of vascular complications in T2D patients.

Modeling graft loss in patients with donor-specific antibody at baseline using the Birmingham-Mayo (BirMay) predictor: Implications for clinical trials

Predicting which renal allografts will fail and the likely cause of failure is important in clinical trial design to either enrich patient populations to be or as surrogate efficacy endpoints for trials aimed at improving long-term graft survival. This study tests our previous Birmingham-Mayo model (termed the BirMay Predictor) developed in a low-risk kidney transplant population in order to predict the outcome of patients with donor specific alloantibody (DSA) at the time of transplantation and identify new factors to improve graft loss prediction in DSA+ patients. We wanted define ways to enrich the population for future therapeutic intervention trials. The discovery set included 147 patients from Mayo Cohort and the validation set included 111 patients from the Paris Cohort-all of whom had DSA at the time of transplantation. The BirMay predictor performed well predicting 5-year outcome well in DSA+ patients (Mayo C statistic = 0.784 and Paris C statistic = 0.860). Developing a new model did not improve on this performance. A high negative predictive value of greater than 90% in both cohorts excluded allografts not destined to fail within 5 years. We conclude that graft-survival models including histology predict graft loss well, both in DSA+ cohorts as well as DSA- patients.

Cold Storage Increases Albumin and Advanced Glycation-End Product-Albumin Levels in Kidney Transplants: A Possible Cause for Exacerbated Renal Damage

Prolonged cold storage (CS) of kidneys is associated with poor renal outcome after transplantation (Tx). We recently showed that in rats (Lewis), proteasome and renal function were severely compromised in kidney transplants subjected to CS (CS/Tx) as compared with those without CS exposure (autotransplanted [ATx]).

Association between nonalbumin proteinuria and renal tubular damage of N-acetyl-β-d-glucosaminidase and its clinical relevance in patients with type 2 diabetes without albuminuria

AIM

Although albuminuria and urinary N-acetyl-β-d-glucosaminidase (uNAG) are known as progression markers of diabetic kidney disease, there is limited information regarding the association between urinary nonalbumin proteinuria (NAP) and uNAG and the clinical relevance thereof in patients without albuminuria.

METHODS

This cross-sectional study included samples from 244 consecutive patients with type 2 diabetes mellitus (T2D) without albuminuria. Proteinuria and albuminuria were defined according to protein-to-creatinine ratio (uPCR) and albumin-to-creatinine ratio (uACR), respectively. NAP was indirectly calculated by the difference between uPCR and uACR.

RESULTS

NAP and uNAG excretion were significantly correlated (r = 0.525, P < 0.001). Individuals whose NAP levels were in the highest tertile had a longer duration of diabetes, uncontrolled hyperglycemia, and impaired insulin stimulation (all P < 0.05), although more patients in the highest NAP tertile were prescribed insulin and sulfonylurea. Multiple linear regression analyses revealed associations among uNAG, diabetes duration, and waist circumference.

CONCLUSIONS

T2D patients without albuminuria excrete proteinuria and that presence of the protein in urine is associated with uNAG. NAP was positively correlated with T2D duration and waist circumference, but negatively correlated with body mass index. Lean, but centrally obese, T2D patients in late diabetes experience more tubular damage, regardless of the presence of albuminuria.

Composite Health Outcomes in Pediatric and Young Adult Kidney Transplant Recipients

OBJECTIVE

To assess composite health outcomes in pediatric and young adult kidney transplant recipients following kidney transplantation.

STUDY DESIGN

We conducted a cross-sectional study of all recipients at our center who had a 1-, 3-, 5-, and/or 10-year transplant anniversary visit between October 2008 and February 2015. The kidney transplant recipients were assessed at each time point according to an outcome measure consisting of 15 pass/fail criteria in 5 domains: allograft health, rejection and immunology, infection, cardiovascular health, and growth.

RESULTS

We analyzed 148 patients at 231 transplantation anniversary visit time points; 52 of 82 (63%) patients assessed at 1 year had an ideal outcome, meeting at least 13 of the 15 criteria. This decreased to 37% at year 3, 40% at year 5, and 26% at year 10 (P < .01). The most common failures across all time points occurred in the domains of growth (43%-52% passing) and cardiovascular health (33%-51% passing). Allograft health declined significantly, decreasing from 74% at year 1 to 33% at year 10 (P < .01). The percentage of patients with graft failure increased from 2.4% at 1 year to 39.5% at 10 years (P < .01), and patient deaths increased from 0 to 11% (P < .01) in the same time frame.

CONCLUSIONS

Ideal outcomes for pediatric kidney transplant recipients decrease over time with growth, cardiovascular health, and allograft health as the primary failure modes. Understanding the composite health of young recipients will allow primary care providers and nephrologists alike to evaluate the overall health of kidney transplant recipients and focus clinical care on the most common sequelae.

The Risk Factors of mTORi-Associated Posttransplant Proteinuria

Treatment with mammalian target of rapamycin inhibitors (mTORi) has been associated with an increased incidence of proteinuria after kidney transplantation as compared to other immunosuppressive agents. Proteinuria after mTORi use may occur in different clinical conditions and the precise mechanism remains unclear. The objective of this study was to investigate the related risk factors for proteinuria after mTORi treatment in kidney transplant recipients. This retrospective observational study population consisted of kidney transplant recipients followed up in a medical center in Southern Taiwan from January 1999 to April 2016. The baseline characteristics and transplantation-related profiles were collected at the time of enrollment. We examined risk factors for mTORi-associated proteinuria using a multivariate logistic regression analysis. P < .05 was considered as statistically significant. Hyperlipidemia and obesity at the initiation of mTORi treatment were strong predictors for proteinuria. Earlier identification of these risk factors may assist physicians in deciding the best candidate for mTORi conversion in order to optimize transplantation outcomes.

Proteinuria in children with autosomal dominant polycystic kidney disease

BACKGROUND

Proteinuria is a common complication in adults with autosomal dominant polycystic kidney disease (ADPKD) and serves as a risk factor for progression. However, proteinuria has rarely been examined in children with ADPKD and the type of proteinuria has not yet been investigated. The aim of the study was to assess the prevalence and to analyse the types of proteinuria in children with ADPKD.

METHODS

Children with ADPKD followed-up in our tertiary centres during the years 2012-2013 were investigated in a cross-sectional study. Morning urine was tested for total protein (PROT), albumin (ALB) and alpha-1-microglobulin (AMG). Renal function was assessed from serum creatinine as estimated glomerular filtration rate.

RESULTS

Thirty-seven children of median age 11.2 (2.0-18.0) years were investigated. Median (range) PROT, ALB and AMG (in mg/mmol creatinine) were 15.1 (6.2-64.8), 2.54 (0.54-37.25) and 3.22 (0.04-10.16), respectively. Pathological total proteinuria (>22) was found in 30% of children, albuminuria (>2.2) in 49% of children and alpha-1-microglobulinuria (>0.55) in 65% of children. No correlation was found between PROT, ALB or AMG and office blood pressure, kidney size or estimated glomerular filtration rate.

CONCLUSIONS

Proteinuria in children with ADPKD is a frequent finding, the most common type is tubular proteinuria. It should be measured in all ADPKD children.

Paricalcitol versus placebo for reduction of proteinuria in kidney transplant recipients: a double-blind, randomized controlled trial

Proteinuria after kidney transplantation is accompanied by an increased risk of graft failure. In this single-center, placebo-controlled, double-blind trial we studied whether vitamin D receptor activator paricalcitol might reduce proteinuria. Patients with urinary protein-to-creatinine ratio (UPCR) ≥20 mg/mmol despite optimization of the renin angiotensin aldosterone system (RAAS) blockade were randomly assigned to receive 24 weeks' treatment with 2 μg/day paricalcitol or placebo. Primary endpoint was change in UPCR, and main secondary endpoints were change in urinary albumin-to-creatinine ratio (UACR) and 24-h proteinuria. Analysis was by intention to treat. One hundred and sixty-eight patients undergo randomization, and 83 were allocated to paricalcitol, and 85 to placebo. Compared with baseline, UPCR declined in the paricalcitol group (-39%, 95% CI -45 to -31) but not in the placebo group (21%, 95% CI 9 to 35), with a between group difference of -49% (95% CI -57 to -41; P < 0.001). UACR and 24-h proteinuria decreased only on paricalcitol therapy and significantly differed between groups at end-of-treatment (P < 0.001). Paricalcitol was well tolerated but incidence of mild hypercalcemia was higher than in placebo. In conclusion, addition of 2 μg/day paricalcitol lowers residual proteinuria in kidney transplant recipients. Long-term studies are needed to determine if the reduction in proteinuria improves transplant outcomes (ClinicalTrials.gov, number NCT01436747).

Nonalbumin proteinuria is a simple and practical predictor of the progression of early-stage type 2 diabetic nephropathy

AIMS

Multiple biomarkers have emerged as a reliable predictor of the progression of diabetic nephropathy. The aim of this study was to pursue a more simple and practical predictor that can be applied in clinical practice.

METHODS

The urine albumin-to-creatinine ratio (ACR), the nonalbumin protein-to-creatinine ratio (NAPCR), and the levels of six biomarkers were measured in 73 patients with type 2 diabetes and estimated glomerular filtration rates (eGFRs)≥60mL/min/1.73m². The renal outcomes were the annual decline in eGFR and the development of chronic kidney disease (CKD) of stage 3 or greater.

RESULTS

The average rate of eGFR decline over a median of 50months of follow-up was -2.48mL/min/1.73m²/year. After adjusting for nine clinical parameters, only the NAPCR showed a significant association with the annual eGFR decline (adjusted R²=0.139, P=0.042). The NAPCR predicted a higher probability of the development of CKD of stage 3 or greater and was more effective than any of the six urinary biomarkers in this respect (C-index 82.7, sensitivity 92.3, specificity 81.7).

CONCLUSIONS

The NAPCR is a better and more practical predictor of the development and progression of CKD than are other urinary biomarkers in patients with early-stage type 2 diabetic nephropathy.

Addition of nonalbumin proteinuria to albuminuria improves prediction of type 2 diabetic nephropathy progression

BACKGROUND

Albuminuria is generally accepted as a sensitive marker of diabetic nephropathy but has limitations in predicting its progression. The aim of this study was to evaluate the use of nonalbumin proteinuria in addition to albuminuria for predicting the progression of type 2 diabetic nephropathy.

METHODS

In this retrospective observational study, the urine albumin-to-creatinine ratio (ACR) and the nonalbumin protein-to-creatinine ratio (NAPCR) were measured in 325 patients with type 2 diabetes and estimated glomerular filtration rates (eGFR) ≥30 mL/min/1.73 m². The patients were divided into four groups based on the cutoff points for the urinary ACR (30 mg/g) and NAPCR (120 mg/g). The renal outcomes were chronic kidney disease (CKD) progression and accelerated eGFR decline.

RESULTS

During the 4.3-year follow-up period, 25 (7.7%) patients showed CKD progression and 69 (21.2%) patients showed accelerated eGFR decline. After adjusting for nine clinical parameters, the group with a NAPCR greater than 120 mg/g exhibited higher cumulative incidences of CKD progression (hazard ratio 6.84; P = 0.001) and accelerated eGFR decline (hazard ratio 1.95; P = 0.011) than the group with a NAPCR < 120 mg/g. In patients with normoalbuminuria, the group with NAPCR levels greater than 120 mg/g also exhibited a higher cumulative incidence than that with NAPCR levels <120 mg/g of CKD progression (hazard ratio 21.82; P = 0.005). The addition of NAPCR to ACR improved the model fit for CKD progression and accelerated eGFR decline.

CONCLUSION

Nonalbumin proteinuria showed additional value over and above that of albuminuria for predicting the progression of CKD in patients with type 2 diabetes.

Reduced human transitional B cell T1/T2 ratio is associated with subsequent deterioration in renal allograft function

Human transitional B cells express relatively high IL-10 and low TNF-α levels, which correlate with B regulatory activity in vitro. Herein, we aim to further define B regulatory phenotype and determine whether B regulatory activity can serve as a prognostic marker for renal allograft dysfunction (graft loss or 2-fold fall in estimated glomerular filtration rate). Transitional B cells can be divided into T1 and T2 subsets based on surface phenotype. T1 cells express a significantly higher ratio of IL-10 to TNF-α than T2 cells or other B subsets. When analyzed in 45 kidney transplant recipients at the time of late for-cause biopsy, the T1/T2 ratio was independently associated with allograft dysfunction over the next 5 years. Next, the T1/T2 ratio was examined in an independent set of 97 clinically stable kidney transplant recipients 2 years after transplant. Again, the T1/T2 ratio was strongly and independently associated with allograft dysfunction over the ensuing 5 years. In these clinically quiescent patients, a low T1/T2 ratio identified a 41-patient subgroup in which 35% developed allograft dysfunction, with 25% losing their allografts. However, none of the 56 patients with a high ratio developed graft dysfunction. In both the initial study and validation groups, the T1/T2 ratio was a much stronger predictor of graft dysfunction than donor-specific antibodies or the estimated glomerular filtration rate. Thus, the T1/T2 ratio, a relative measure of expressing an anti-inflammatory cytokine profile, is a novel prognostic marker that might inform individualized immunosuppression.

Decreased Kidney Graft Survival in Low Immunological Risk Patients Showing Inflammation in Normal Protocol Biopsies

INTRODUCTION

The pros and cons for implementing protocol biopsies (PB) after kidney transplantation are still a matter of debate. We aimed to address the frequency of pathological findings in PB, to analyze their impact on long-term graft survival (GS) and to analyze the risk factors predicting an abnormal histology.

METHODS

We analyzed 946 kidney PB obtained at a median time of 6.5 (±2.9) months after transplantation. Statistics included comparison between groups, Kaplan-Meier and multinomial logistic regression analysis.

RESULTS AND DISCUSSION

PB diagnosis were: 53.4% normal; 46% IFTA; 12.3% borderline and 4.9% had subclinical acute rejection (SCAR). Inflammation had the strongest negative impact on GS. Therefore we split the cases into: "normal without inflammation", "normal with inflammation", "IFTA without inflammation", "IFTA with inflammation" and "rejection" (including SCAR and borderline). 15-year GS in PB diagnosed normal with inflammation was significantly decreased in a similar fashion as in rejection cases. Among normal biopsies, inflammation increased significantly the risk of 15-y graft loss (P = 0.01). Variables that predicted an abnormal biopsy were proteinuria, previous AR and DR-mismatch.

CONCLUSION

We conclude that inflammation in normal PB is associated with a significantly lower 15-y GS, comparable to rejection or IFTA with inflammation.

Current Challenges in Diabetic Nephropathy: Early Diagnosis and Ways to Improve Outcomes

Diabetes is often associated with chronic kidney disease (CKD) and is the primary cause of kidney failure in half of patients who receive dialysis therapy. Given the increasing prevalence of diabetes and its high morbidity and mortality, diabetic nephropathy is a serious drawback in individual patients and a tremendous socioeconomic burden on society. Despite growing concern for the management of diabetic nephropathy, the prevalence of CKD with diabetes is the same today as it was 20 years ago. The current strategy to manage diabetic nephropathy, including the control of hyperglycemia, dyslipidemia, and blood pressure and the wide-spread use of renin-angiotensin-aldosterone system inhibitors, is well established to be beneficial in the early stages of diabetic nephropathy. However, the effects are uncertain in patients with relatively progressed CKD. Therefore, early diagnosis or risk verification is extremely important in order to reduce the individual and socioeconomic burdens associated with diabetic nephropathy by providing appropriate management to prevent the development and progression of this condition. This review focuses on recent research and guidelines regarding risk assessment, advances in medical treatment, and challenges of and future treatments for diabetic nephropathy.

Predicting Individual Renal Allograft Outcomes Using Risk Models with 1-Year Surveillance Biopsy and Alloantibody Data

The ability to predict outcomes for individual patients would be a significant advance for not only counseling, but also identifying those for whom interventions may be needed. The goals of this study were to validate an existing risk prediction score that incorporates easily obtainable clinical factors and determine if histologic findings at 1-year surveillance biopsy and/or serum donor-specific alloantibody status could improve predictability of graft loss by 5 years. We retrospectively studied 1465 adults who received a solitary kidney transplant between January of 1999 and December of 2008 and had sufficiently detailed 5-year follow-up data for modeling. In this cohort, the Birmingham risk model (incorporating recipient factors at 1 year, including age, sex, ethnicity, renal function, proteinuria, and prior acute rejection) predicted death-censored and overall graft survival (c statistics =0.84 and 0.78, respectively). The presence of glomerulitis or chronic interstitial fibrosis (g and ci scores by Banff, respectively) on 1-year biopsy specimens independently correlated with graft loss by 5 years. Adding these variables to the model for death-censored graft loss increased predictability (c statistic =0.90), improved calibration (ability to stratify risk from high to low), and reclassified risk of failure in 29% of patients. Adding the presence of donor-specific alloantibody at 1 year did not improve predictability or reclassification but did improve calibration marginally. We conclude that, at 1 year after kidney transplant, a risk model of graft survival that incorporates clinical factors and histologic findings at surveillance biopsy is highly predictive of individual risk and well calibrated.

Estimating glomerular filtration rate in kidney transplantation: Still searching for the best marker

Kidney transplantation is the treatment of choice for end-stage renal disease. The evaluation of graft function is mandatory in the management of renal transplant recipients. Glomerular filtration rate (GFR), is generally considered the best index of graft function and also a predictor of graft and patient survival. However GFR measurement using inulin clearance, the gold standard for its measurement and exogenous markers such as radiolabeled isotopes ((51)Cr EDTA, (99m)Tc DTPA or (125)I Iothalamate) and non-radioactive contrast agents (Iothalamate or Iohexol), is laborious as well as expensive, being rarely used in clinical practice. Therefore, endogenous markers, such as serum creatinine or cystatin C, are used to estimate kidney function, and equations using these markers adjusted to other variables, mainly demographic, are an attempt to improve accuracy in estimation of GFR (eGFR). Nevertheless, there is some concern about the inability of the available eGFR equations to accurately identify changes in GFR, in kidney transplant recipients. This article will review and discuss the performance and limitations of these endogenous markers and their equations as estimators of GFR in the kidney transplant recipients, and their ability in predicting significant clinical outcomes.

Management of proteinuria in the transplanted patient

Proteinuria is a relatively frequent complication in children after renal transplantation (40-80 %). It is usually mild and non-nephrotic in nature and predominantly tubular in origin. The major causes of post-transplant proteinuria are recurrence of primary glomerulonephritis [mostly focal segmental glomerulosclerosis (FSGS)], rejection (acute and chronic), mTOR inhibitors or hypertension. Proteinuria is a risk factor for graft loss and patient death in adults, and even a mild proteinuria (0.1-0.2 g/day) is associated with impaired graft and patient survival. In children, proteinuria seems to be associated with graft but not patient survival. Proteinuria (protein/creatinine ratio) should be assessed regularly in all children. In children with prior chronic kidney disease due to idiopathic FSGS, proteinuria should be assessed daily during the first month after transplantation to enable early diagnosis of recurrence. The cause of proteinuria should be identified, and graft biopsy should be considered in children with unexplained proteinuria, especially with new onset proteinuria or deterioration of previously mild proteinuria. Treatment must be primarily targeted at the cause of proteinuria, and in normotensive children symptomatic antiproteinuric therapy with angiotensin-converting enzyme inhibitors/angiotensin II receptor antagonists should also be initiated. Other antihypertensive drugs should be used to achieve target blood pressure of <75th percentile. Target proteinuria should be <20 mg/mmol creatinine.

The need for minimization strategies: current problems of immunosuppression

New immunosuppressants and the better use of immunosuppressant combination therapy have led to significant improvements in renal allograft outcomes over the last decades. Yet, despite dramatic reduction in rejection rates and improvement in 1-year graft survival, long-term graft attrition rates remained rather constant. Current immunosuppressant combinations are frequently leading to overimmunosuppression and are increasing cardiovascular risk. Importantly, calcineurin inhibitors are nephrotoxic, contribute to cardiovascular risk and chronic allograft dysfunction. Furthermore, immunosuppressant-associated toxicities aggravate immune-mediated nephron injury and side effects lead to nonadherence, an identified important reason for late acute and chronic antibody-mediated rejections. The frequent development of a chronic humoral response indicates rather insufficient immunosuppression of current combinations than simple under-immunosuppression. While there is no evidence that increasing immunosuppressive doses will improve outcomes or reduce de novo HLA-antibody formation, there is clear evidence that adequate minimization strategies will reduce side effect burden. Because of low rejection risk, but frequent side effects, drug minimization is particularly relevant for the many maintenance patients. In summary, new therapeutic strategies need to be developed from adequately powered clinical trials for reduction of the many side effects of immunosuppressants. Such evidence-based and time-dependent immunosuppressive minimization strategies are needed to achieve better long-term outcomes in the future.

Resolution of low-grade proteinuria is associated with improved outcomes after renal transplantation-a retrospective longitudinal study

Low-grade proteinuria and systolic hypertension (SHT) are risk factors for allograft failure. Both are dynamic variables and their relationship is not independent. We have simultaneously analyzed the effects of proteinuria and SHT on graft outcomes in 805 adult Kidney Transplant Recipients and impact of their changes over time. Proteinuria and systolic blood pressure (SBP) were recorded for years 1 and 3 posttransplantation. Subjects with proteinuria >1 g/day were excluded. Patients were divided into groups based on proteinuria (Absent(A) <150 mg/day or low-grade(P)150 mg-1 g/day) and blood pressure (Normotensive-SBP <140 mmHg or hypertensive-SBP ≥ 140 mmHg). Graft survival was assessed in all four groups over 10 years by multivariate analysis. At the three annual time points (Year 1, 2 and 3) hypertensive patients with proteinuria had the worst graft survival. Patients with persistent proteinuria between years 1-2 and 2-3 had the poorest graft survival with an improvement if proteinuria regressed (P-A), especially in the Hypertensive group. The impact of proteinuria was highest in persistently hypertensive patients between years 1-3. Thus both proteinuria and SHT were associated with poor graft survival and the combination of the two led to the worst outcomes. Importantly, SHT was associated with significantly worse outcomes in patients with proteinuria. Patient cohort with SHT and low-grade proteinuria represent a selective group that might benefit from intervention.

Nonalbuminuric proteinuria as a biomarker for tubular damage in early development of nephropathy with type 2 diabetic patients

AIM

The aim of this study was to evaluate the association between urinary nonalbumin protein (NAP) and urinary tubular markers in early diabetic nephropathy.

METHODS

Urinary NAP was measured in 118 patients with type 2 diabetes with estimated glomerular filtration rates (eGFR) ≥60 mL/min/1.73 m². Urine levels of tubular markers [kidney injury molecule (KIM)-1, neutrophil gelatinase-assoicated lipocalin (NGAL) and liver-type fatty acid-binding protein (L-FABP)] were measured by using an Enzyme-linked immunosorbent assay (ELISA). Patients were divided into three groups according to urinary NAP values.

RESULTS

The urine levels of KIM-1, NGAL and L-FABP were significantly higher in the third tertile group than in the first tertile group (all p < 0.001). There was a significant positive correlation between NAP and each tubular marker (KIM-1, NGAL and L-FABP) in univariate analysis (all p < 0.001). Urinary NAP was positively correlated with all urinary tubular markers after adjustment for age, duration of diabetes, systolic blood pressure, eGFR, low-density lipoprotein cholesterol, HbA1c and albumin-to-creatinine ratio (KIM-1 r = 0.170, p < 0.001; NGAL r = 0.142, p < 0.015 and L-FABP r = 0.262, p < 0.001). In normoalbuminuric patients (n = 58), urinary NAP was also significantly correlated with NGAL and L-FABP in multivariate regression analyses (r = 0.302, p = 0.030 and r = 0.430, p = 0.001).

CONCLUSIONS

These findings suggest that urinary NAP reflects tubular damage in the early-stage type 2 diabetic nephropathy (eGFR ≥ 60 mL/min/1.73 m²). We suggest that urinary NAP could be used as a biomarker for tubular damage in clinical practice.

Rituximab treatment prevents the early development of proteinuria following pig-to-baboon xeno-kidney transplantation

We previously reported life-supporting α1,3-galactosyltransferase knockout (GalTKO) thymokidney xenograft survival of >2 months in baboons. However, despite otherwise normal renal function, recipients developed proteinuria with morphologic changes (podocyte effacement), a condition that presents a major obstacle to long-term studies in this model. A recent clinical study showed that rituximab therapy after allogeneic transplant prevented proteinuria possibly associated with loss of sphingomyelin phosphodiesterase acid-like 3b (SMPDL-3b). Here, we demonstrate that rituximab prevents the disruption of pig podocytes in an SMPDL-3b-dependent manner in vitro and the early development of proteinuria after xenogeneic kidney transplantation in baboons. Immunofluorescence showed SMPDL-3b expression in pig glomerular epithelium; immunoprecipitation demonstrated rituximab binding to SMPDL-3b in glomeruli. Culture of isolated pig podocytes with naive baboon sera, which has preformed antipig natural antibodies, reduced SMPDL-3b expression, disrupted podocyte morphology, and decreased podocyte proliferation, whereas pretreatment with rituximab prevented these effects. Six baboons received rituximab before transplantation to deplete B cells and again in the peri-transplant period; 18 baboons treated only before transplantation served as historical controls. The onset of post-transplant proteinuria was significantly delayed in a B cell-independent manner in the animals that received peri-transplant rituximab treatment. Although further optimization of this protocol is required, these data provide intriguing clues to the mechanisms of post-transplant proteinuria in xenogeneic kidney transplantation and a potential strategy for its prevention.

Urinary retinol binding protein is a marker of the extent of interstitial kidney fibrosis

Currently, a non-invasive method to estimate the degree of interstitial fibrosis (IF) in chronic kidney disease is not available in routine. The aim of our study was to evaluate the diagnostic performance of the measurement of urinary low molecular weight (LMW) protein concentrations as a method to determine the extent of IF. The urines specimen from 162 consecutive patients who underwent renal biopsy were used in the analysis. Numerical quantification software based on the colorimetric analysis of fibrous areas was used to assess the percentage IF. Total proteinuria, albuminuria, and the urinary levels of retinol binding protein (RBP), alpha1-microglobulin (α1MG), beta 2-microglobulin (β2MG), transferrin, and IgG immunoglobulins were measured. There was a significant correlation between the degree of IF and the RBP/creatinine (creat) ratio (R2: 0.11, p<0.0001). IF was associated to a lesser extent with urinary β2MG and α1MG; however, there was no association with total proteinuria or high molecular weight (HMW) proteinuria. The correlation between IF and RBP/creat remained significant after adjustment to the estimated glomerular filtration rate, age, body mass index, α1MG, and β2MG. The specificity of the test for diagnosing a fibrosis score of >25% of the parenchyma was 95% when using a threshold of 20 mg/g creat. In conclusion, RBP appears to be a quantitative and non-invasive marker for the independent prediction of the extent of kidney IF. Because methods for the measurement of urinary RBP are available in most clinical chemistry departments, RBP measurement is appealing for implementation in the routine care of patients with chronic kidney disease.

Predicting 5-year risk of kidney transplant failure: a prediction instrument using data available at 1 year posttransplantation

BACKGROUND

Accurate prediction of kidney transplant failure remains imperfect. The objective of this study was to develop and validate risk scores predicting 5-year transplant failure, based on data available 12 months posttransplantation.

STUDY DESIGN

Development and then independent multicenter validation of risk scores predicting death-censored and overall transplant failure.

SETTING & PARTICIPANTS

Outcomes of kidney transplant recipients (n=651) alive with transplant function 12 months posttransplantation in Birmingham, United Kingdom, were used to develop models predicting transplant failure risk 5 years posttransplantation. The resulting risk scores were evaluated for prognostic utility (discrimination, calibration, and risk reclassification) in independent cohorts from Tours, France (n=736); Leeds, United Kingdom (n=787); and Halifax, Canada (n=475).

PREDICTORS

Weighted regression coefficients for baseline and 12-month demographic and clinical predictor characteristics.

OUTCOMES

Death-censored and overall transplant failure 5 years posttransplantation.

MEASUREMENTS

Baseline data and time to transplant failure.

RESULTS

Following model development, variables included in separate scores for death-censored and overall transplant failure included recipient age, sex, and race; acute rejection; transplant function; serum albumin level; and proteinuria. In the validation cohorts, these scores showed good to excellent discrimination for death-censored transplant failure (C statistics, 0.78-0.90) and moderate to good discrimination for overall transplant failure (C statistics, 0.75-0.81). Both scores demonstrated good calibration (Hosmer-Lemeshow P>0.05 in all cohorts). Compared with estimated glomerular filtration rate in isolation, application of the scores resulted in statistically significant and clinically relevant risk reclassification for death-censored transplant failure (net reclassification improvement [NRI], 36.1%-83.0%; all P<0.001) and overall transplant failure (NRI, 38.7%-53.5%; all P<0.001). Compared with the previously described US Renal Data System-based risk calculator, significant and relevant risk reclassification for overall transplant failure was seen (NRI, 30.0%; P<0.001).

LIMITATIONS

Validation is required in further populations.

CONCLUSIONS

These validated risk scores may be of prognostic utility in kidney transplantation, accurately identifying at-risk transplants, and informing clinicians and patients.

Clinicopathological findings in non-human primate recipients of porcine renal xenografts: quantitative and qualitative evaluation of proteinuria

BACKGROUND

Immunological and histopathological features in pig-to-primate renal xenotransplantation are widely studied. Only limited data have been reported about clinicopathological findings in primate recipients of life-supporting renal xenografts. In human medicine, proteinuria represents a common complication in kidney transplantation and is associated with impaired graft survival. The detection of low molecular weight proteins of tubular origin is considered an early method for predicting potential graft rejection. In this study, the presence and the significance of quantitative and qualitative proteinuria were evaluated in xenotransplanted non-human primates in which kidney function was supported only by the transplanted organ.

METHODS

Eight bilaterally nephrectomized cynomolgus monkeys (Macaca fascicularis) were transplanted with a single kidney from α1,3-galactosyltransferase gene-knockout (GTKO) pigs transgenic for human CD39, CD55, CD59, and α1,2-fucosyltransferase. In addition to hematological and biochemical analyses, quantitative and qualitative analysis of proteinuria was evaluated by urinary protein-to-creatinine ratio (UPC ratio) and sodium dodecyl sulfate-agarose gel electrophoresis (SDS-AGE), respectively.

RESULTS

The main hematological and biochemical changes recorded after transplantation were a progressive anemia and a severe and progressive decrease in total proteins. In urine samples, the UPC ratio was low before transplantation and increased after transplantation. Similarly, SDS-AGE was negative before transplantation, but bands consistent with mixed (i.e., tubular and glomerular) proteinuria were observed in all samples collected post-transplantation.

CONCLUSIONS

The study of clinicopathological changes in cynomolgus monkey renal xenograft recipients provides a valid help in monitoring the health conditions in the post-transplant period. Moreover, the evaluation of UPC ratio and the use of SDS-AGE technique in urine samples of cynomolgus monkey renal xenograft recipients may be considered a valid, inexpensive, and less time-consuming method than more sophisticated techniques in monitoring proteinuria. Proteinuria and presence of low molecular weight (LMW) proteins were consistently found in urine after transplantation, independent of fluctuations in renal function.

Urine high and low molecular weight proteins one-year post-kidney transplant: relationship to histology and graft survival

Increased urinary protein excretion is common after renal transplantation and portends worse outcome. In this study we assessed the prognostic contribution of several urinary proteins. Urinary total protein, albumin, retinol binding protein (RBP), α-1-microglobulin, IgG and IgM were measured in banked urine samples from 221 individuals 1 year after renal transplantation (age 52 ± 13 years, 55% male, 93% Caucasian and 82% living donor). Levels of all proteins measured were higher than in normal nontransplant populations. Patients with glomerular lesions had higher urinary albumin than those with normal histology, while those with interstitial fibrosis and tubular atrophy plus inflammation (ci>0, cg = 0, i>0) had higher levels of IgG, IgM, α-1-microglobulin and RBP. Concomitant normal levels of urinary albumin, IgM and RBP identified normal histology (specificity 91%, sensitivity 15%,). Urinary levels of the specific proteins were highly correlated, could not differentiate among the histologic groups, and appeared to result from tubulointerstitial damage. Increased urinary excretion of the low molecular weight protein RBP was a sensitive marker of allografts at risk, predicting long-term graft loss independent of histology and urinary albumin. This study highlights the prognostic importance of tubulointerstitial disease for long-term graft loss.

Urinary cystatin C and tubular proteinuria predict progression of diabetic nephropathy

OBJECTIVE

The aim of this study was to evaluate the association of urinary cystatin C, a tubular damage marker, with the progression of type 2 diabetic nephropathy. RESERCH DESIGN AND METHODS: The baseline values of serum and urinary cystatin C were measured as primary parameters and those of urinary nonalbumin protein (NAP) were measured as secondary parameters. In this prospective observational study, a total of 237 type 2 diabetic patients were followed up for 29 months (13-44 months).

RESULTS

Both the urinary cystatin C-to-creatinine ratio (CCR) and NAP-to-creatinine ratio (NAPCR) were significantly different according to the degree of albuminuria. Both markers had strongly positive correlations at baseline. After adjusting for several clinical factors, both urinary CCR and NAPCR had significant associations with the decline of the estimated glomerular filtration rate (eGFR) (r = 0.160, P = 0.021; r = 0.412, P < 0.001, respectively). Urinary CCR had positive correlations with the decline of eGFR in the subpopulation of patients with eGFR ≥60 mL/min/1.73 m(2). In patients with eGFR ≥60 mL/min/1.73 m(2) and normoalbuminuria, only urinary NAPCR showed a significant association with the decline of eGFR; urinary CCR did not. In multivariate regression analysis, the number of patients who progressed to chronic kidney disease stage 3 or greater was higher in those in the upper tertiles of both the urinary levels of cystatin C and NAP than in those in the lower tertiles.

CONCLUSIONS

The results of this study suggest that urinary cystatin C and NAP may be predictors of the progression of type 2 diabetic nephropathy.

Early association of low-grade albuminuria and allograft dysfunction predicts renal transplant outcomes

BACKGROUND

Data on the combined associations of albuminuria and estimated glomerular filtration rate (eGFR) with renal transplant outcomes are limited. Our objective was to explore how renal transplant outcomes could be predicted by a combined variable of early low-grade albuminuria and allograft dysfunction.

METHODS

We studied a cohort of adult deceased-donor kidney transplant recipients who were subdivided into four groups according to median albuminuria (100 mg/day, interquartile range, 0-470 mg/day) and median eGFR (60 mL/min/1.73 m(2); interquartile range, 30-73 mL/min/1.73 m(2)) at third month posttransplantation as follows: group I (albuminuria <100 and eGFR >60, n=238); group II (albuminuria ≥100 and eGFR >60, n=151); group III (albuminuria <100 and eGFR ≤60; n=167); and group IV (albuminuria ≥100 and eGFR ≤60, n=228).

RESULTS

Death-censored graft survival was significantly lower in group IV compared with the rest (P<0.0001). Multivariate Cox regression analysis using fixed and time-dependent covariates showed that the combination of low-grade albuminuria and lower eGFR was associated with graft failure (hazard ratio, 2.2, 95% confidence interval, 1.3-3.7; P=0.003). Likewise, but to a lesser extent, the risk of mortality was increased for group IV (hazard ratio, 1.7, 95% confidence interval, 1.01-2.8; P=0.042).

CONCLUSIONS

Early association of low-grade albuminuria and allograft dysfunction represents an important risk factor of graft failure and mortality. This additive effect should be considered to identify individuals at risk for adverse kidney transplantation outcomes.

Renal resistive index as a new independent risk factor for new-onset diabetes mellitus after kidney transplantation

Pulse pressure and urinary albumin excretion were recently identified as risk factors of new-onset diabetes after renal transplantation (NODAT), suggesting that microvascular injury may be implicated in NODAT. However, the relationship between of microvascular injury and NODAT is unknown. In the present long-term (median follow-up: 5.7years; observation period: 4908 patient-years) retrospective study in 656 renal transplant recipients, the association between baseline renal resistance index (RI, used as a marker of widespread microvascular damage) and the incidence of NODAT was assessed. The incidence of NODAT was 11.2% and 14.6% at 5 and 10years, respectively, after transplantation. RI at 3months was a risk factor for NODAT [hazard ratio (HR) per 0.1: 2.19 (1.55-3.09), P<0.0001]. RI >0.75 (vs. 0≤0.75) was a potent a predictor of NODAT [HR: 3.29 (1.91-5.67), P<0.0001], even after adjustments [HR: 3.29 (1.50-7.24), P=0.0030] on age, weight, glucose, nephropathy, and arterial pressure. Similar results were observed when RI was measured at 1month [HR per 0.1:1.74 (1.33-2.27), P<0.0001] and 12months [HR per 0.1:1.74 (1.33-2.27), P<0.0001] after transplantation. High RI early after renal transplantation is a long-term risk factor for NODAT, and could be used to refine the individual risk of NODAT.