Non-albumin proteinuria as a parameter of tubulointerstitial inflammation in lupus nephritis

Urinary non-albumin protein-creatinine ratio is an independent predictor of mortality in patients with type 2 diabetes: a retrospective cohort study

Albuminuria is a well-known predictor of chronic kidney disease in patients with type 2 diabetes mellitus (DM). However, proteinuria is associated with chronic complications in patients without albuminuria. In this retrospective cohort study, we explored whether non-albumin proteinuria is associated with all-cause mortality and compared the effects of non-albumin proteinuria on all-cause mortality between patients with and without albuminuria. We retrospectively collected data from patients with type 2 DM for whom we had obtained measurements of both urinary albumin-to-creatinine ratio (UACR) and urinary protein-to-creatinine ratio (UPCR) from the same spot urine specimen. Urinary non-albumin protein-creatinine ratio (UNAPCR) was defined as UPCR-UACR. Of the 1809 enrolled subjects, 695 (38.4%) patients died over a median follow-up of 6.4 years. The cohort was separated into four subgroups according to UACR (30 mg/g) and UNAPCR (120 mg/g) to examine whether these indices are associated with all-cause mortality. Compared with the low UACR and low UNAPCR subgroup as the reference group, multivariable Cox regression analyses indicated no significant difference in mortality in the high UACR and low UNAPCR subgroup (hazard ratio [HR] 1.189, 95% confidence interval [CI] 0.889-1.589, P = 0.243), but mortality risks were significantly higher in the low UACR and high UNAPCR subgroup (HR 2.204, 95% CI 1.448-3.356, P < 0.001) and in the high UACR with high UNAPCR subgroup (HR 1.796, 95% CI 1.451-2.221, P < 0.001). In the multivariable Cox regression model with inclusion of both UACR and UNAPCR, UNAPCR ≥ 120 mg/g was significantly associated with an increased mortality risk (HR 1.655, 95% CI 1.324-2.070, P < 0.001), but UACR ≥ 30 mg/g was not significantly associated with mortality risk (HR 1.046, 95% CI 0.820-1.334, P = 0.717). In conclusion, UNAPCR is an independent predictor of all-cause mortality in patients with type 2 DM.

Renal Dysfunction Phenotypes in Patients Undergoing Obesity Surgery

Obesity surgery candidates are at an increased risk of kidney injury, but pre-operative evaluation usually neglects kidney function assessment. This study aimed to identify renal dysfunction in candidates for bariatric surgery. To reduce the sources of bias, subjects with diabetes, prediabetes under metformin treatment, neoplastic or inflammatory diseases were excluded. Patients' (n = 192) average body mass index was 41.7 ± 5.4 kg/m². Among these, 51% (n = 94) had creatinine clearance over 140 mL/min, 22.4% (n = 43) had proteinuria over 150 mg/day and 14.6% (n = 28) albuminuria over 30 mg/day. A creatinine clearance higher than 140 mL/min was associated with higher levels of proteinuria and albuminuria. Univariate analysis identified sex, glycated hemoglobin, uric acid, HDL and VLDL cholesterol as being associated with albuminuria, but not with proteinuria. On multivariate analysis, glycated hemoglobin and creatinine clearance as continuous variables were significantly associated with albuminuria. In summary, in our patient population prediabetes, lipid abnormalities and hyperuricemia were associated with albuminuria, but not with proteinuria, suggesting different disease mechanisms might be implicated. Data suggest that in obesity-associated kidney disease, tubulointerstitial injury precedes glomerulopathy. A significant proportion of obesity surgery candidates present clinically relevant albuminuria and proteinuria along with renal hyperfiltration, suggesting that routine pre-operative assessment of these parameters should be considered.

Urinary Sediments as Predictors of the Histopathology of Lupus Nephritis

Lupus nephritis (LN) is a major risk factor for morbidity and mortality in systemic lupus erythematosus (SLE). Urinalysis has an invaluable role in the diagnosis of various renal and urological diseases. Examinations of the urinary sediment using phase contrast microscopy (PCM) may add more information to help earlier diagnoses of LN. This cross-sectional study aimed to assess the possible role of the components of urinary sediment examined using PCM in discriminating the proliferative classes of LN (III and IV ± V) from the non-proliferative classes (I, II, and V), and to detect the correlation between the components of urinary sediment and indices of both activity and chronicity found by the renal biopsy. The study was conducted on 40 SLE patients for whom a renal biopsy was indicated. Clinical, demographic, and laboratory data and the results of the histopathological renal biopsy were collected. The morning before the renal biopsy; urine samples were collected from every patient and examined by PCM. Receiver operating characteristic curves were used to detect the area under the curve to predict proliferative LN. The correlations of counts of leukocytes, erythrocytes, all dysmorphic erythrocytes, acanthocytes, and stomatocytes with the indices of activity and chronicity were significant (activity: P = 0.027, P = 0.015, P = 0.033, P = 0.040, and P <0.001*; chronicity: P = 0.035, P = 0.009, P = 0.027, P = 0.010, and P <0.001, respectively). For patients with SLE, urinary sediment examinations can suggest a renal biopsy for the histopathology of LN.

The ratio and difference of urine protein-to-creatinine ratio and albumin-to-creatinine ratio facilitate risk prediction of all-cause mortality

The role of the difference and ratio of albuminuria (urine albumin-to-creatinine ratio, uACR) and proteinuria (urine protein-to-creatinine ratio, uPCR) has not been systematically evaluated with all-cause mortality. We retrospectively analyzed 2904 patients with concurrently measured uACR and uPCR from the same urine specimen in a tertiary hospital in Taiwan. The urinary albumin-to-protein ratio (uAPR) was derived by dividing uACR by uPCR, whereas urinary non-albumin protein (uNAP) was calculated by subtracting uACR from uPCR. Conventional severity categories of uACR and uPCR were also used to establish a concordance matrix and develop a corresponding risk matrix. The median age at enrollment was 58.6 years (interquartile range 45.4-70.8). During the 12,391 person-years of follow-up, 657 deaths occurred. For each doubling increase in uPCR, uACR, and uNAP, the adjusted hazard ratios (aHRs) of all-cause mortality were 1.29 (95% confidence interval [CI] 1.24-1.35), 1.12 (1.09-1.16), and 1.41 (1.34-1.49), respectively. For each 10% increase in uAPR, it was 1.02 (95% CI 0.98-1.06). The linear dose-response association with all-cause mortality was only observed with uPCR and uNAP. The 3 × 3 risk matrices revealed that patients with severe proteinuria and normal albuminuria had the highest risk of all-cause mortality (aHR 5.25, 95% CI 1.88, 14.63). uNAP significantly improved the discriminative performance compared to that of uPCR (c statistics: 0.834 vs. 0.828, p-value = 0.032). Our study findings advocate for simultaneous measurements of uPCR and uACR in daily practice to derive uAPR and uNAP, which can provide a better mortality prognostic assessment.

Sub-chronic microcystin-LR renal toxicity in rats fed a high fat/high cholesterol diet

Microcystin-LR (MCLR) is a liver and kidney toxin produced by cyanobacteria. Recently, it was demonstrated that MCLR exposure drives the progression of high fat/high cholesterol (HFHC) induced nonalcoholic fatty liver disease (NAFLD) to a more severe state. NAFLD is also a risk factor for chronic kidney disease (CKD), and the current study investigated MCLR renal toxicity in the context of an HFHC diet. Sprague Dawley rats were fed either a control diet or an HFHC diet for 10 weeks. After 6 weeks of diet, animals were administered either vehicle, 10 μg/kg, or 30 μg/kg MCLR via intraperitoneal injection every other day for 4 weeks. HFHC diet alone increased the renal glomerular change histopathology score, and 30 μg/kg MCLR exposure increased this score in both the control group and the HFHC group. In contrast, 30 μg/kg MCLR caused greater proteinuria and cast formation and decreased protein phosphatase 1 and 2A protein expression in the HFHC group. Urinary excretion of KIM-1 increased, but albumin and tamm-horsfall protein did not change after MCLR exposure. The general concordance between KIM-1, polyuria, proteinuria, and renal casts after MCLR exposure suggests that proximal tubule cell damage contributed to these connected pathologies. The control group adapted to repeated MCLR exposure by increasing the urinary elimination of MCLR and its metabolites, whereas this adaptation was blunted in the HFHC group. These data suggest an HFHC diet may increase the severity of certain MCLR-elicited renal toxicities.

The NLRP3 Inflammasome Role in the Pathogenesis of Pregnancy Induced Hypertension and Preeclampsia

Pregnancy-induced hypertension and preeclampsia are associated with significant maternal and fetal mortality. A better understanding of these diseases, delineation of molecular pathomechanism, and efficient treatment development are some of the most urgent tasks in obstetrics and gynecology. Recent findings indicate the crucial role of inflammation in the development of hypertension and preeclampsia. Although the mechanism is very complex and needs further explanation, it appears that high levels of cholesterol, urate, and glucose activates NLRP3 inflammasome, which produces IL-1β, IL-18, and gasdermin D. Production of these proinflammatory chemokines is the beginning of a local and general inflammation, which results in sympathetic outflow, angiotensin II production, proteinuria, hemolysis, liver damage, immunothrombosis, and coagulopathy. The NLRP3 inflammasome is a critical complex in the mediation of the inflammatory response, which makes it crucial for the development of pregnancy-induced hypertension and preeclampsia, as well as its complications, such as placental abruption and HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome. Herein, the presented article delineates molecular mechanisms of these processes, indicating directions of future advance.

Stellenwert der Nierenbiopsie bei Lupusnephritis

Bei systemischem Lupus erythematodes (SLE) findet sich häufig eine renale Mitbeteiligung, der verschiedene pathogenetische Mechanismen zugrunde liegen. Die Nierenbeteiligung hat einen negativen Einfluss auf die Prognose des SLE, insbesondere bei progredienter Niereninsuffizienz. Eine Nierenbiopsie ist aufgrund der Heterogenität der Nierenbeteiligung und der damit verbundenen therapeutischen Konsequenzen unabdingbar. Sie kann durch nicht-invasive Untersuchungen wie die Urindiagnostik oder Serologie nicht ersetzt werden, da das Ausmaß der Proteinurie oder der Mikrohämaturie keine sicheren Rückschlüsse auf den Schweregrad, die Pathogenese und die Prognose der Nierenbeteiligung erlauben. Die Nierenbiopsie gibt neben der korrekten Klassifikation der Lupusnephritis (LN) Informationen über die Mitbeteiligung des Niereninterstitium, der intrarenalen Gefäße und der Aktivität sowie Chronizität der Nephritis. Auch kann der Pathologe die Frage beantworten, inwieweit mit einer Besserung der Nierenfunktion unter Therapie gerechnet werden kann. Der folgende Beitrag gibt einen Überblick über den Stellenwert der Nierenbiopsie bei SLE, der revidierten Klassifikation der LN von 2018 einschließlich Sonderformen der LN und über die Implikationen des Biopsie-Ergebnisses für die Therapie.

Lupus nephritis: challenges and progress

PURPOSE OF REVIEW

The management of lupus nephritis remains unsatisfactory due to insufficiently effective treatment regimens and the dearth of reliable predictors of disease onset or progression to guide individualized therapeutic decisions. This review summarizes new findings related to lupus nephritis over the last 18 months and discusses clinical needs that should be considered to advance trials of mechanism-based therapeutic strategies.

RECENT FINDINGS

Collaborative teams are addressing how to improve disease definitions and are developing predictive models for disease onset, disease response and risk of flare in individual patients. More attention is being paid to clinical trial design. Advanced technologic approaches are allowing the analysis of small amounts of human tissue and urine in unprecedented detail so as to discover new pathogenic mechanisms and identify disease biomarkers. Novel therapies continue to be tested in disease models and include new strategies to protect renal tissue from cell damage and fibrosis.

SUMMARY

The collaborative efforts of patients, clinical and translational researchers, the pharmaceutical industry and funding sources are needed to advance therapies for lupus nephritis. Specialized clinical centers can then deliver optimal and more personalized patient care that will improve patient outcomes.

Immunoglobulin Binding Protein 1 as a Potential Urine Biomarker in Patients with Lupus Nephritis

We evaluated the role of immunoglobulin binding protein 1 (IGBP1), a phosphoprotein associated with the B cell receptor (BCR) complex, as a urine biomarker in lupus nephritis (LN). The IGBP1 concentrations in plasma and urine of patients with LN, systemic lupus erythematosus (SLE) without nephritis and healthy controls were estimated by ELISA. IGBP1 expression in the kidneys of LN patients and transplantation donors was detected by immunohistochemistry. Microarray-based global gene expression profile of HK-2 cells with IGBP1 knock-down and fluorescence-activated cell sorting (FACS) for intracellular IGBP1 expression in human peripheral blood mononuclear cells (PBMCs) was performed. Urine IGBP1 levels were elevated significantly in LN patients, and it correlated with the clinical activity indices (complement 3 (C3) level, anti-dsDNA antibodies titer, SLE Disease Activity Index-2000 (SLEDAI-2K) and histological activity index. IGBP1 expression was increased in LN patients as compared to the donors and was detected mainly in the tubules by histopathology. In microarray analysis, several genes related to SLE pathogenesis (PPME1, ROCK2, VTCN1, IL-17R, NEU1, HLA-DM, and PTX3) responded to siRNA-mediated IGBP1 silencing. In FACS, IGBP1 was expressed mainly in the CD14⁺ cells. The overall expression of IGBP1 in PBMCs was higher in LN patients as compared with that in SLE patients without nephritis. Conclusively, urinary IGBP1 may be a novel biomarker reflecting the clinical and histological activities in LN.