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.

Regulatory role and mechanisms of myeloid TLR4 in anti-GBM glomerulonephritis

Myeloid cells and TLR4 play a critical role in acute kidney injury. This study investigated the regulatory role and mechanisms of myeloid TLR4 in experimental anti-glomerular basement membrane (GBM) glomerulonephritis (GN). Anti-GBM GN was induced in tlr4flox/flox and tlr4flox/flox−lysM−cre mice by intravenous injection of the sheep anti-mouse GBM antibody. Compared to control mice, conditional disruption of tlr4 from myeloid cells, largely macrophages (> 85%), suppressed glomerular crescent formation and attenuated progressive renal injury by lowering serum creatinine and 24-h urine protein excretion while improving creatinine clearance. Mechanistically, deletion of myeloid tlr4 markedly inhibited renal infiltration of macrophages and T cells and resulted in a shift of infiltrating macrophages from F4/80+iNOS+ M1 to F4/80+CD206+ M2 phenotype and inhibited the upregulation of renal proinflammatory cytokines IL-1β and MCP-1. Importantly, deletion of myeloid tlr4 suppressed T cell-mediated immune injury by shifting Th1 (CD4+IFNγ+) and Th17 (CD4+IL-17a+) to Treg (CD4+CD25+FoxP3+) immune responses. Transcriptome analysis also revealed that disrupted myeloid TLR4 largely downregulated genes involving immune and cytokine-related pathways. Thus, myeloid TLR4 plays a pivotal role in anti-GBM GN by immunological switching from M1 to M2 and from Th1/Th17 to Treg and targeting myeloid TLR4 may be a novel therapeutic strategy for immune-mediated kidney diseases.

Comparative study of 24-hour urinary protein and spot urine protein creatinine ratio in pre-eclamptic women

Background: The aim of the study was to evaluate the ability of the random urine P/C ratio to predict significant proteinuria, as well as to introduce a diagnostic test for pre-eclampsia which will avoid the inconvenience and time consumption of 24-hour urine protein collection. The objective of this study was to compare spot urine protein- creatinine ratio with 24-hour urine protein for estimation of proteinuria in pre-eclampsia.Methods: A total of 50 pregnant women with pre-eclampsia were prospectively studied for proteinuria in Rajarajeswari medical college and Hospital Bangalore for a period of 9 months from September 2018 to May 2019. Spot urine specimens for measuring P/C ratio were obtained immediately before 24-hour urine collection. The correlation between the spot urine P/C ratio and urinary protein excretion in the 24-hour collections was examined using the Spearman correlation test.Results: PCR at a cut off value 0.15 g/mmol had sensitivity and specificity of 96.6% and 55% respectively. In prediction of proteinuria of 300 mg/24 hr positive predictive value and negative predictive value 76.3% and 91.6% respectively.Conclusions: We found that there was a strong correlation between 24-hour urine protein excretion and spot urine protein creatinine ratio in pre-eclamptic women. Spot PCR can be used as a reasonable alternative to 24-hour urine protein test which is a cumbersome.

Total Nephron Number and Single-Nephron Parameters in Patients with IgA Nephropathy

Background: Single nephron dynamics in progressive IgA nephropathy (IgAN) have not been studied. We applied novel methodology to explore single nephron parameters in IgAN. Methods: Non-globally sclerotic glomeruli (NSG) and globally sclerotic glomeruli (GSG) per kidney were estimated using cortical volume assessment via unenhanced computed tomography and biopsy-based stereology. Estimated single-nephron GFR (eSNGFR) and urine protein excretion (SNUPE) were calculated by dividing eGFR and UPE by the number of NSG. Associations with CKD stage and clinicopathologic findings were cross-sectionally investigated. Results: This study included 245 IgAN patients (mean age 43 y, 62% male, 45% on renin-angiotensin aldosterone system [RAAS] inhibitors pre-biopsy) evaluated at kidney biopsy. CKD stages were 10% CKD1, 43% CKD2, 19% CKD3a, 14% CKD3b and 14% CKD4-5. With advancing CKD stage, NSG decreased from mean 992,000 to 300,000 per kidney whereas GSG increased from median 64,000 to 202,000 per kidney. In multivariable models, advancing CKD stage associated with lower numbers of NSG, higher numbers of GSG, and lower numbers of GSG+NSG, indicating potential resorption of sclerosed glomeruli. In contrast to the higher mean glomerular volume and markedly elevated SNUPE in advanced CKD, the eSNGFR was largely unaffected by CKD stage. Lower SNGFR associated with Oxford scores for endocapillary hypercellularity and crescents whereas higher SNUPE associated with segmental glomerulosclerosis and tubulointerstitial scarring. Conclusions: SNUPE emerged as a sensitive biomarker of advancing IgAN. The failure of eSNGFR to increase in response to reduced number of functioning nephrons suggests limited capacity for compensatory hyperfiltration by diseased glomeruli with intrinsic lesions.

Proteinuria in Severe Hypothyroidism: A Prospective Study

Context Hypothyroidism is associated with reversible decline in kidney function as measured by estimated glomerular filtration rate (eGFR). eGFR and proteinuria are the most important markers for clinical assessment of kidney function. Though hypothyroidism is associated with proteinuria in cross-sectional data, the impact of treatment on proteinuria is unknown. Objective This study explores the effect of thyroid hormone replacement therapy on eGFR and 24-hour urine protein excretion in patients with severe primary hypothyroidism. Design and Participants This study was a prospective, observational cohort study in adults with severe primary hypothyroidism (serum thyrotropin [TSH] > 50 µIU/mL). Individuals with preexisting or past kidney disease, kidney or urinary tract abnormalities, calculi or surgery, diabetes mellitus, or hypertension were excluded. The participants received thyroid hormone replacement therapy. Thyroid functions, eGFR, 24-hour urine protein excretion, and biochemical parameters were measured at baseline and 3 months. Setting This study took place at a single center, a tertiary care referral and teaching hospital. Results Of 44 enrolled participants, 43 completed 3 months of follow-up. At 3 months, serum TSH levels decreased and thyroxine levels increased (P < .001 for both). Significant increases in eGFR (mean difference, 18.25 ± 19.49 mL/min/1.73 m2; 95% CI, 12.25 to 24.25, P < .001) and declines in 24-hour urine protein excretion (mean difference, –68.39 ± 125.89 mg/day; 95% CI, –107.14 to –29.65, P = .001) were observed. Serum cholesterol and low-density lipoprotein levels also significantly decreased (P < .001). Conclusions Thyroid hormone replacement therapy in patients with severe primary hypothyroidism improves eGFR and decreases 24-hour urine protein excretion, thereby suggesting reversible alterations.

Leflunomide Plus Low-dose Prednisone in Patients with Progressive IgA Nephropathy: A Multicenter, Prospective, Randomized, Open-labelled and Controlled Trial

Background: This trial was designed to assess the efficacy and safety of Leflunomide (LEF) plus low-dose prednisone for the treatment of progressive IgA nephropathy (IgAN). Methods: We did a prospective, randomized, open-labelled, multicenter, controlled trial, comprised of 3-month run-in, 12-month treatment and 12-month follow-up phases. After 3-month run-in phase, patients with biopsy-confirmed IgAN at a risk of progression were randomly allocated to LEF plus low-dose prednisone (LEF group) or conventionally accepted-dose prednisone (prednisone group). Our primary outcome was 24h urine protein excretion(UPE) and secondary outcomes were serum albumin(sALB), serum creatinine(Scr), and eGFR. Safety was evaluated in all patients who received the trial medications. Results:108 patients (59 in LEF group, 49 in prednisone group) were enrolled and finished their treatment and follow-up periods. The difference in baseline data between the two groups was comparable. Compared with baseline, both groups showed significant decrease in 24h UPE(p<0.01) and increase in sALB (p<0.01), with stable Scr and eGFR throughout the 12-month treatment period. What’s more, these effects sustained through the 12-month follow-up period. However, there was no difference in 24h UPE, sALB, Scr and eGFR between the two groups (P>0.05). At 12 months, difference of overall response rate, relapsing rate and incidence of adverse events between the two groups was not significant. Conclusions: The efficacy and safety of LEF plus low-dose prednisone and conventionally accepted-dose prednisone in treatment of progressive IgAN are comparable. Trial registration: The trial is registered at isrctn.org with the ISRCTN97636235 on July 28, 2006.

Estimation of 24-hour urine protein excretion using urine albumin-to-creatinine ratio

Background There is still a lack of quantitative description of the relationship between urine albumin-to-creatinine ratio (ACR) and 24-hour urine protein excretion (24h UPE). We aimed to study the correlation between 24h UPE and urine ACR and develop a prediction model for 24h UPE employing urine ACR. Methods This was a retrospective and observational study. All individuals with same-day urine ACR and 24h UPE tests in Sichuan Provincial People’s Hospital from September 1, 2018 to December 31, 2019 were enrolled in the study. Correlation and agreement between urine ACR and 24h UPE were evaluated. A prediction model of 24h UPE was developed and validated. Results 671 subjects were identified. Urine ACR correlated well with 24h UPE (Pearson’s coefficient after natural logarithm transformation = 0.908; p<0.001) and the agreement was consistently good (overall ICC = 0.938; 95% CI: 0.928-0.947; p<0.001). Our multivariable transform model had good performance (R 2 =0.869) and high accuracy (RMSE=0.690) to estimate 24h UPE less than 10 g/day. Conclusions Urine ACR correlates well with 24h UPE in a general population. Our prediction model is an useful tool for estimating 24h UPE less than 10 g/day, however, 24h UPE is still mandatory in situation when the majority of proteinuria is of tubular origin.