Urinary β2-Microglobulin Is a Good Indicator of Proximal Tubule Injury: A Correlative Study with Renal Biopsies

α-Mangostin reduces hypertension in spontaneously hypertensive rats and inhibits EMT and fibrosis in Ang II-induced HK-2 cells

Hypertension affects a large number of individuals globally and is a common cause of nephropathy, stroke, ischaemic heart disease and other vascular diseases. While many anti-hypertensive medications are used safely and effectively in clinic practice, controlling hypertensive complications solely by reducing blood pressure (BP) can be challenging. α-Mangostin, a xanthone molecule extracted from the pericarp of Garcinia mangostana L., has shown various beneficial effects such as anti-tumor, anti-hyperuricemia, and anti-inflammatory properties. However, the effects of α-Mangostin on hypertension remain unknown. In this study, we observed that α-Mangostin significantly decreased systolic and diastolic blood pressure in spontaneously hypertensive rats (SHR), possibly through the down-regulation of angiotensin II (Ang II). We also identified early markers of hypertensive nephropathy, including urinary N-acetyl-β-D-glucosaminidase (NAG) and β2-microglobulin (β2-MG), which were reduced by α-Mangostin treatment. Mechanistic studies suggested that α-Mangostin may inhibit renal tubular epithelial-to-mesenchymal transformation (EMT) by down-regulating the TGF-β signaling pathway, thus potentially offering a new therapeutic approach for hypertension and hypertensive nephropathy.

Acute hyperbilirubinemia determines an early subclinical renal damage: Evaluation of tubular biomarkers in cholemic nephropathy

BACKGROUND AND AIMS

Cholemic nephropathy is a cause of acute kidney injury occurring in patients with jaundice. The aim of this study was to evaluate early renal function impairment in patients with mild acute hyperbilirubinemia in the absence of alterations of the common parameters used in clinical practice (serum creatinine or urea) and with normal renal morphology. We studied urinary biomarkers of tubular damage urinary neutrophil gelatinase-associated lipocalin (u-NGAL), urinary beta-2-microglobulin (u-B2M), urinary osteopontin (u-OPN), urinary trefoil factor 3 (u-TFF3) and urinary Cystatin C (u-Cys).

METHODS

This is a case-control study investigating the following urinary biomarkers of tubular damage: u-NGAL, u-B2M, u-OPN, u-TFF3 and u-Cys, in patients with mild acute hyperbilirubinemia. Seventy-four patients were included in this study: 36 patients with jaundice and 38 patients without jaundice.

RESULTS

Subjects with jaundice (total bilirubin 12.4 ± 7.3 mg/dL) showed higher u-NGAL, u-B2M, u-OPN, u-TFF3 and u-Cys compared with controls. After logistic regression analyses, including the following independent variables: age, estimated Glomerular Filtration Rate (eGFR), haemoglobin, diabetes, hypertension and jaundice, we observed a higher risk of elevated u-NGAL values (OR = 3.8, 95% CI 1.07-13.5, p = .03) and u-B2M (OR = 9.4, 95% CI 2.3-38.9, p = .0018) in jaundiced subjects. Moreover, urinary biomarkers had a direct correlation with serum cholestasis indexes.

CONCLUSIONS

This study demonstrated increased urinary biomarkers of tubular damage (u-NGAL, u-B2M, u-OPN, u-TFF3, and u-Cys) in patients with mild hyperbilirubinemia in comparison with a control group. These findings suggest early renal tubular damage in the absence of alterations of the normal parameters used in clinical practice (eGFR, serum urea and renal morphology).

The impact of tubular dysfunction and its relationship with acute kidney injury in children

BACKGROUND

Tubular dysfunction can cause electrolyte disturbances with potentially serious consequences. We studied the epidemiology and outcomes of electrolyte disturbances and tubular dysfunction among critically ill children and evaluated their relationships with acute kidney injury (AKI).

METHODS

We conducted a prospective cohort study recruiting children aged 1 month to ≤ 18 years old admitted to the pediatric intensive care unit (PICU) from 6/2020 to 6/2021. The serum levels of sodium, potassium, calcium, phosphate, and magnesium were reviewed and simultaneous urinary investigations for tubular function were performed among children with electrolyte disturbances.

RESULTS

Altogether there were 253 episodes of admission. The median (interquartile) age was 4.9 (1.3-11.0) years and 58.1% were male. The median number of electrolyte disorders was 3 (2-4) types. Hypophosphatemia (74.2%), hypocalcemia (70.3%) and hypermagnesemia (52.9%) were the three commonest types of disturbances. Urinary electrolyte wasting was commonly observed among children with hypomagnesemia (70.6%), hypophosphatemia (67.4%) and hypokalemia (28.6%). Tubular dysfunction was detected in 82.6% of patients and urinary β2-microglobulin level significantly correlated with the severity of tubular dysfunction (p < 0.001). The development of tubular dysfunction was independent of AKI status. Tubular dysfunction was associated with mortality (p < 0.001) and was an independent predictor of PICU length of stay (LOS) (p < 0.001). The incorporation of the tubular dysfunction severity into the AKI staging system improved the prediction of PICU LOS.

CONCLUSIONS

Tubular dysfunction was associated with both morbidity and mortality in critically ill children and its assessment may help to capture a more comprehensive picture of acute kidney insult.

A systematic review and meta-analysis of mortality and kidney function in uranium-exposed individuals

BACKGROUND

Humans are exposed to uranium (U) in a variety of applications. Both animal and observational human studies support an associated U nephrotoxicity. Few statistical syntheses of the human data have been performed and these analyses are limited in the types of exposures considered.

OBJECTIVES

This study aims to evaluate the state of current evidence and to expand on existing meta-analyses by systematically evaluating kidney-associated causes of mortality in multiple U-exposed populations. This study also aims to evaluate the effect of U exposure on kidney function and biomarkers of kidney injury.

METHODS

The published and grey literature were systematically reviewed for studies that reported Standardized Mortality Ratios (SMR) for kidney cancer, chronic nephritis/nephrosis, all-cause mortality, diabetes, all circulatory/heart disease, and/or ischemic heart disease in U-exposed humans. Studies that reported kidney biomarker measures for U-exposed versus control subjects were identified separately.

RESULTS

36 studies were included. The studies were parsed into subgroups based on setting of exposure. Analysis of kidney cancer and chronic nephritis/nephrosis mortality demonstrated an SMR of 0.93 (95CI: 0.82-1.05) and 0.82 (95CI: 0.70-0.96), respectively. The other clinical outcomes evaluated also demonstrated mortality deficits in exposed relative to unexposed individuals. Subgroup analyses demonstrated similar mortality deficits. Conversely, biomarker analyses suggested better kidney function in the controls, but none of these differences reached significance.

DISCUSSION

Given that most of the included mortality studies were conducted in occupational populations, the mortality deficits observed in our analyses were likely due to the healthy-worker effect. Additionally, our analyses of kidney biomarkers were severely limited by low precision due to a low number of available studies and small study-size. Future work needs to evaluate the progression of chronic and to end-stage kidney disease in community-based populations to better assess the full impact of prolonged chronic U exposure on kidney outcomes.

Establishment of Sensitive Sandwich-Type Chemiluminescence Immunoassay for Interleukin-18 in Urinary Samples

Interleukin-18 (IL-18), a member of IL-1 cytokine superfamily, is deemed as an important indicator of the kidney disease. Herein a sandwich chemiluminescence immunoassay integrated with magnetic beads was conducted to detect IL-18 in kidney disease. The detection limit and linear range were 0.0044 ng/mL and 0.01-2.7 ng/mL, respectively. Satisfactory recoveries were ranged from 91.70 to 101.18% with the relative standard deviation below 10%; interference bias of most biomarkers were within allowable deviation range (± 15%). In summary, the whole study was successfully applied to detect IL-18 levels in urine samples for patients with kidney disease. The results showed that chemiluminescence immunoassay for IL-18 detection could be used in the clinical application.

Free triiodothyronine predicts the risk of developing diabetic kidney disease

BACKGROUND

Low levels of Free Triiodothyronine (FT3) are associated with poor survival in chronic kidney disease, and the aim of this study was to further assess the relationship between changes in FT3 levels and renal damage in patients with type 2 diabetes based on glomerular and tubular markers.

METHODS

We retrospectively studied 452 type 2 diabetic patients, measured glomerular damage markers (UACR, eGFR) and tubular damage markers (NAG/Cr,β2-MG), analyzed the relationship between FT3 and renal damage by logistic regression models, and plotted restrictive cubic splines.

RESULTS

41.6% of subjects had diabetic kidney disease (DKD), and the prevalence of DKD decreased progressively with increasing FT3 levels in the third quartile. Spearman correlation analysis showed that FT3 was negatively associated with UACR, NAG/Cr and β2-MG, while eGFR was positively associated with FT3. Multifactorial analysis, after adjusting for relevant confounders, revealed that compared with the lowest quartile of FT3, the highest quartile reduced the risk of developing urinary albumin (OR = 0.499,95% CI:0.289-0.856), moderate to severe impairment of glomerular filtration rate (OR = 0.106,95% CI:0.032-0.354), renal tubular marker β2 -MG positive (OR = 0.516,95% CI:0.299 to 0.883) and the risk of DKD occurrence (OR = 0.450,95% CI:0.260 to 0.774). In the sample model, FT3 levels below 4.39 pmol/L were associated with an increased risk of glomerular tubule injury and DKD occurrence.

CONCLUSIONS

FT3 is closely associated with glomerular tubular injury and is a protective factor. As FT3 levels (< 4.39 pmol/L) decrease, the risk of developing DKD becomes higher, and FT3 can be used as an independent predictor of developing DKD.

Biomarkers for Kidney-Transplant Rejection: A Short Review Study

Kidney transplantation is the preferred treatment for end-stage renal failure, but the limited availability of donors and the risk of immune rejection pose significant challenges. Early detection of acute renal rejection is a critical step to increasing the lifespan of the transplanted kidney. Investigating the clinical, genetic, and histopathological markers correlated to acute renal rejection, as well as finding noninvasive markers for early detection, is urgently needed. It is also crucial to identify which markers are associated with different types of acute renal rejection to manage treatment effectively. This short review summarizes recent studies that investigated various markers, including genomics, histopathology, and clinical markers, to differentiate between different types of acute kidney rejection. Our review identifies the markers that can aid in the early detection of acute renal rejection, potentially leading to better treatment and prognosis for renal-transplant patients.

Serum and urine profiling by high-throughput TMT-based proteomics for the investigation of renal dysfunction in canine babesiosis

Canine babesiosis is a tick-borne disease caused by Babesia canis, with acute kidney injury as one of the common complications. In the study 8 healthy control dogs and 22 dogs with naturally occurring babesiosis were enrolled, with the aim to analyse differences in serum and urinary proteomes between healthy dogs and dogs with different degree of renal dysfunction in babesiosis using a label-based high-throughput quantitative proteomic approach. In serum, 58 proteins were found differentially abundant between healthy controls and groups of dogs with different degrees of renal dysfunction in babesiosis, while in urine there were 259 differentially abundant proteins. In addition, altered biological pathways were detected in the diseased dogs using bioinformatics tools and validation of several candidate biomarkers was performed. SIGNIFICANCE: The main aim of this comprehensive study was to perform analyses of serum and urinary proteomes of dogs with renal dysfunction in babesiosis compared to healthy dogs using, for the first time, a high-throughput proteomic method and functional enrichment analyses. Serum and urine samples of the same dogs were investigated in order to gain a more complete picture of pathologic changes taking place in renal dysfunction in babesiosis. We highlighted two putative biomarkers validated herein which could be of importance for early diagnosis of renal dysfunction in canine babesiosis, as they are easily accessible from urine and their concentration rises before the appearance of azotaemia: urinary neutrophil gelatinase-associated lipocalin (NGAL) and urinary liver-type fatty acid-binding protein (L-FABP).

Clinical Risk Factors For Kidney Tubule Biomarker Abnormalities Among Hypertensive Adults With Reduced eGFR in the SPRINT Trial

BACKGROUND

Urine biomarkers of kidney tubule health may distinguish aspects of kidney damage that cannot be captured by current glomerular measures. Associations of clinical risk factors with specific kidney tubule biomarkers have not been evaluated in detail.

METHODS

We performed a cross-sectional study in the Systolic Blood Pressure Intervention Trial among 2,436 participants with a baseline estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2. Associations between demographic and clinical characteristics with urine biomarkers of kidney tubule health were evaluated using simultaneous multivariable linear regression of selected variables.

RESULTS

Each standard deviation higher age (9 years) was associated with 13% higher levels of chitinase-3-like protein-1 (YKL-40), indicating higher levels of tubulointerstitial inflammation and repair. Men had 31% higher levels of alpha-1 microglobulin and 16% higher levels of beta-2 microglobulin, reflecting worse tubule resorptive function. Black race was associated with significantly higher levels of neutrophil gelatinase-associated lipocalin (12%) and lower kidney injury molecule-1 (26%) and uromodulin (22%). Each standard deviation (SD) higher systolic blood pressure (SBP) (16 mmHg) was associated with 10% higher beta-2 microglobulin and 10% higher alpha-1 microglobulin, reflecting lower tubule resorptive function.

CONCLUSIONS

Clinical and demographic characteristics, such as race, sex, and elevated SBP, are associated with unique profiles of tubular damage, which could reflect under-recognized patterns of kidney tubule disease among persons with decreased eGFR.

Subclinical Acute Kidney Injury in COVID-19: Possible Mechanisms and Future Perspectives

Since the outbreak of COVID-19 disease, a bidirectional interaction between kidney disease and the progression of COVID-19 has been demonstrated. Kidney disease is an independent risk factor for mortality of patients with COVID-19 as well as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leading to the development of acute kidney injury (AKI) and chronic kidney disease (CKD) in patients with COVID-19. However, the detection of kidney damage in patients with COVID-19 may not occur until an advanced stage based on the current clinical blood and urinary examinations. Some studies have pointed out the development of subclinical acute kidney injury (subAKI) syndrome with COVID-19. This syndrome is characterized by significant tubule interstitial injury without changes in the estimated glomerular filtration rate. Despite the complexity of the mechanism(s) underlying the development of subAKI, the involvement of changes in the protein endocytosis machinery in proximal tubule (PT) epithelial cells (PTECs) has been proposed. This paper focuses on the data relating to subAKI and COVID-19 and the role of PTECs and their protein endocytosis machinery in its pathogenesis.

Increased urinary B2-microglobulin is associated with poor prognosis of upper tract urothelial carcinoma

Background

Kidney tubular damage markers are biomarkers of acute or chronic kidney injury. Hypothetically, upper tract urothelial cancer (UTUC), which induces obstructive uropathy or direct invasion of the renal parenchyma, may also induce increased excretion of urinary tubular damage proteins. Therefore, this study aimed to investigate the use of tubular damage biomarker as prognostic markers for UTUC.

Methods

The records of 417 surgically resected patients with UTUC were obtained from the Seoul National University Prospectively Enrolled Registry for urothelial cancer-upper tract urothelial cancer (SUPER-UC-UTUC) between January 2016 and December 2020. Patients with non-urothelial cancer or without urinary tubular injury marker measurement were excluded, and finally, 296 patients were finally included. B2-microglobulin (B2-MG) was an injury marker, and a value higher than 0.3 was considered abnormally elevated, according to previous studies.

Results

The mean age was 70.9 years, and the male sex was predominant (n = 211, 71.3%). The incidences of renal pelvis and ureter cancer were similar (50.7% vs. 49.3%). Most patients had high-grade diseases (n = 254, 88.8%). The high urine B2-MG group was older, had decreased renal function, and had a higher pathologic T stage than did the low group. Multivariate Cox regression analysis of disease-free survival (DFS), open surgical method (Hazard ratio (HR) 1.52, p = 0.027), large tumor size (HR 1.06, p = 0.017), tumor multifocality (HR 1.90, p = 0.038), lymphovascular invasion (HR 2.19, p < 0.001), and high urine B2-MG (HR 1.57, p = 0.021) were significantly associated with shortened metastasis-free survival (MFS). Kaplan–Meier curve analysis revealed short DFS (median survival 15.5 months vs. unattained, log-rank p = 0.001) and MFS (unattained median survival in both groups, log-rank p = 0.003) for the high urine B2-MG group compared to the low urine B2-MG group.

Conclusion

Patients with UTUC presenting with increased pre-operative urine B2-MG levels were associated with disease recurrence and metastasis. This biomarker may aid in performing pre-operative risk stratification and in assessing the individual prognosis of patients with UTUC.

Nephrotoxic Biomarkers with Specific Indications for Metallic Pollutants: Implications for Environmental Health

Environmental and occupational exposure to heavy metals and metalloids is a major global health risk. The kidney is often a site of early damage. Nephrotoxicity is both a major consequence of heavy metal exposure and potentially an early warning of greater damage. A paradigm shift occurred at the beginning of the 21st century in the field of renal medicine. The medical model of kidney failure and treatment began to give way to a social model of risk factors and prevention with important implications for environmental health. This development threw into focus the need for better biomarkers: markers of exposure to known nephrotoxins; markers of early damage for diagnosis and prevention; markers of disease development for intervention and choice of therapy. Constituents of electronic waste, e-waste or e-pollution, such as cadmium (Cd), lead (Pb), mercury (HG), arsenic (As) and silica (SiO₂) are all potential nephrotoxins; they target the renal proximal tubules through distinct pathways. Different nephrotoxic biomarkers offer the possibility of identifying exposure to individual pollutants. In this review, a selection of prominent urinary markers of tubule damage is considered as potential tools for identifying environmental exposure to some key metallic pollutants.

Dehydration Status Aggravates Early Renal Impairment in Children: A Longitudinal Study

Dehydration is common in children for physiological and behavioral reasons. The objective of this study was to assess changes in hydration status and renal impairment across school weekdays. We conducted a longitudinal study of three repeated measures of urinalysis within one week in November 2019 in a child cohort in Beijing, China. We measured urine specific gravity (USG) to determine the dehydration status, and the concentration of β₂-microglobulin (β₂-MG) and microalbumin (MA) to assess renal function impairment among 1885 children with a mean age of 7.7 years old. The prevalence of dehydration was 61.9%, which was significantly higher in boys (64.3%). Using chi-square tests and linear mixed-effects regression models, we documented the trends of the renal indicators’ change over time among different hydration statuses. Compared to Mondays, there were apparent increases of β₂-MG concentrations on Wednesdays (β = 0.029, p < 0.001) and Fridays (β = 0.035, p < 0.001) in the dehydrated group, but not in the euhydrated group. As for the MA concentrations, only the decrease on Fridays (β = −1.822, p = 0.01) was significant in the euhydrated group. An increased trend of elevated β₂-MG concentration was shown in both the euhydrated group (Z = −3.33, p < 0.001) and the dehydrated group (Z = −8.82, p < 0.001). By contrast, there was a decreased trend of elevated MA concentrations in the euhydrated group (Z = 3.59, p < 0.001) but not in the dehydrated group. A new indicator ratio, β₂-MG/MA, validated the consistent trends of renal function impairment in children with dehydration. Renal impairment trends worsened as a function of school days during the week and the dehydration status aggravated renal impairment during childhood across school weekdays, especially tubular abnormalities in children.

The Use of 'Omics for Diagnosing and Predicting Progression of Chronic Kidney Disease: A Scoping Review

Globally, chronic kidney disease (CKD) contributes substantial morbidity and mortality. Recently, various ‘omics platforms have provided insight into the molecular basis of kidney dysfunction. This scoping review is a synthesis of the current literature on the use of different ‘omics platforms to identify biomarkers that could be used to detect early-stage CKD, predict disease progression, and identify pathways leading to CKD. This review includes 123 articles published from January 2007 to May 2021, following a structured selection process. The most common type of ‘omic platform was proteomics, appearing in 55 of the studies and two of these included a metabolomics component. Most studies (n = 91) reported on CKD associated with diabetes mellitus. Thirteen studies that provided information on the biomarkers associated with CKD and explored potential pathways involved in CKD are discussed. The biomarkers that are associated with risk or early detection of CKD are SNPs in the MYH9/APOL1 and UMOD genes, the proteomic CKD273 biomarker panel and metabolite pantothenic acid. Pantothenic acid and the CKD273 biomarker panel were also involved in predicting CKD progression. Retinoic acid pathway genes, UMOD, and pantothenic acid provided insight into potential pathways leading to CKD. The biomarkers were mainly used to detect CKD and predict progression in high-income, European ancestry populations, highlighting the need for representative ‘omics research in other populations with disparate socio-economic strata, including Africans, since disease etiologies may differ across ethnic groups. To assess the transferability of findings, it is essential to do research in diverse populations.

Long-term clinical characteristics and renal prognosis of children with tubulointerstitial nephritis and uveitis syndrome

BACKGROUND

Tubulointerstitial nephritis and uveitis (TINU) syndrome is a rare disease, especially in children. Owing to the short-term observational period and the small number of patients analyzed in previous reports, the long-term clinical and laboratory characteristics and renal prognosis of children with TINU syndrome remain unclear.

METHODS

In this retrospective observational study, we enrolled 29 children with TINU syndrome from February 1990 to February 2019.

RESULTS

During the median follow-up duration of 38 months, the kidney function, urinary β2 microglobulin-creatinine ratio (U-β2MG/Cr), and uveitis in the patients had significantly improved at 24, 6, and 36 months after diagnosis. Higher U-β2MG/Cr was associated with longer duration of kidney function normalization. Half of the patients required uveitis treatment for 5 years after the diagnosis.

CONCLUSIONS

Patients with severe low-molecular weight proteinuria at diagnosis needed a longer duration to achieve improvements in kidney function. Uveitis has a much longer treatment period than tubulointerstitial nephritis. This study demonstrates the good prognosis of children with TINU syndrome in terms of their long-term clinical and laboratory characteristics.

First-week urine beta-2 microglobulin levels in term healthy neonates

BACKGROUND

Beta-2 microglobulin (β2mG) is a low-molecular-weight protein that is almost exclusively eliminated through the kidneys. It is freely filtered in the glomeruli and almost completely reabsorbed and degraded in the proximal tubules. Normal urinary β2mG levels are very low (between 0.04 and 0.22 mg/L). No reference values are known in infants and young children.

METHODS

Urinary β2mG levels were measured in 103 healthy term neonates during the first week of life by nephelometric technology.

RESULTS

The average level of urinary β2mG was 0.65 mg/L (95% confidence interval between 0 and 10.8 mg/L). There was a minor difference between male and female neonates but it did not reach statistical significance. There was no effect of the gestational week, birth weight, or weight loss in the first week of life, on urinary β2mG levels.

CONCLUSIONS

First-week urinary β2mG levels in healthy term infants were higher than adult levels. Incomplete maturation of kidney tubules in neonates could be a possible explanation. These can now be used in clinical practice and further studies that assess the degree of proximal tubular function in health and disease. Graphical abstract.

Molecular and functional profiling of apical versus basolateral small extracellular vesicles derived from primary human proximal tubular epithelial cells under inflammatory conditions

Proximal tubular epithelial cells (PTEC) are central players in inflammatory kidney diseases. However, the complex signalling mechanism/s via which polarized PTEC mediate disease progression are poorly understood. Small extracellular vesicles (sEV), including exosomes, are recognized as fundamental components of cellular communication and signalling courtesy of their molecular cargo (lipids, microRNA, proteins). In this study, we examined the molecular content and function of sEV secreted from the apical versus basolateral surfaces of polarized human primary PTEC under inflammatory diseased conditions. PTEC were cultured under normal and inflammatory conditions on Transwell inserts to enable separate collection and isolation of apical/basolateral sEV. Significantly increased numbers of apical and basolateral sEV were secreted under inflammatory conditions compared with equivalent normal conditions. Multi‐omics analysis revealed distinct molecular profiles (lipids, microRNA, proteins) between inflammatory and normal conditions for both apical and basolateral sEV. Biological pathway analyses of significantly differentially expressed molecules associated apical inflammatory sEV with processes of cell survival and immunological disease, while basolateral inflammatory sEV were linked to pathways of immune cell trafficking and cell‐to‐cell signalling. In line with this mechanistic concept, functional assays demonstrated significantly increased production of chemokines (monocyte chemoattractant protein‐1, interleukin‐8) and immuno‐regulatory cytokine interleukin‐10 by peripheral blood mononuclear cells activated with basolateral sEV derived from inflammatory PTEC. We propose that the distinct molecular composition of sEV released from the apical versus basolateral membranes of human inflammatory PTEC may reflect specialized functional roles, with basolateral‐derived sEV pivotal in modulating tubulointerstitial inflammatory responses observed in many immune‐mediated kidney diseases. These findings provide a rationale to further evaluate these sEV‐mediated inflammatory pathways as targets for biomarker and therapeutic development.

Complement Properdin Regulates the Metabolo-Inflammatory Response to a High Fat Diet

Background and objectives: Overnutrition leads to a metabolic and inflammatory response that includes the activation of Complement. Properdin is the only amplifier of complement activation and increases the provision of complement activation products. Its absence has previously been shown to lead to increased obesity in mice on a high fat diet. The aim of this study was to determine ways in which properdin contributes to a less pronounced obese phenotype. Materials and Methods: Wild type (WT) and properdin deficient mice (KO) were fed a high-fat diet (HFD) for up to 12 weeks. Results: There was a significant increase in liver triglyceride content in the KO HFD group compared to WT on HFD. WT developed steatosis. KO had an additional inflammatory component (steatohepatitis). Analysis of AKT signalling by phosphorylation array supported a decrease in insulin sensitivity which was greater for KO than WT in liver and kidney. There was a significant decrease of C5L2 in the fat membranes of the KO HFD group compared to the WT HFD group. Circulating microparticles in KO HFD group showed lower presence of C5L2. Expression of the fatty acid transporter CD36 in adipose tissue was increased in KO on HFD and was also significantly increased in plasma of KO HFD mice compared to WT on HFD. CD36 was elevated on microparticles from KO on HFD. Ultrastructural changes consistent with obesity-associated glomerulopathy were observed for both HFD fed genotypes, but tubular strain was greater in KO. Conclusion: Our work demonstrates that complement properdin is a dominant factor in limiting the severity of obesity-associated conditions that impact on liver and kidney. The two receptors, C5L2 and CD36, are downstream of the activity exerted by properdin.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

Serial Quantification of Urinary Protein Biomarkers to Predict Drug-induced Acute Kidney Injury

BACKGROUND

Drug-induced Acute Kidney Injury (AKI) develops in 10-15% of patients who receive nephrotoxic medications. Urinary biomarkers of renal tubular dysfunction may detect nephrotoxicity early and predict AKI.

METHODS

We prospectively studied patients who received aminoglycosides, vancomycin, amphotericin, or calcineurin inhibitors, and collected their serial urine while on therapy. Patients who developed drug-induced AKI (fulfilling KDIGO criteria) were matched with non-AKI controls in a 1:2 ratio. Their urine samples were batch-analyzed at time-intervals leading up to AKI onset; the latter benchmarked against the final day of nephrotoxic therapy in non- AKI controls. Biomarkers examined include clusterin, beta-2-microglobulin, KIM1, MCP1, cystatin-C, trefoil-factor- 3, NGAL, interleukin-18, GST-Pi, calbindin, and osteopontin; biomarkers were normalized with corresponding urine creatinine.

RESULTS

Nine of 84 (11%) patients developed drug-induced AKI. Biomarkers from 7 AKI cases with pre-AKI samples were compared with those from 14 non-AKI controls. Corresponding mean ages were 55(±17) and 52(±16) years; baseline eGFR were 99(±21) and 101(±24) mL/min/1.73m2 (all p=NS). Most biomarker levels peaked before the onset of AKI. Median levels of 5 biomarkers were significantly higher in AKI cases than controls at 1-3 days before AKI onset (all µg/mmol): clusterin [58(8-411) versus 7(3-17)], beta-2-microglobulin [1632(913-3823) versus 253(61-791)], KIM1 [0.16(0.13-0.76) versus 0.07(0.05-0.15)], MCP1 [0.40(0.16-1.90) versus 0.07(0.04-0.17)], and cystatin-C [33(27-2990) versus 11(7-19)], all p<0.05; their AUROC for AKI prediction were >0.80 (confidence intervals >0.50), with average accuracy highest for clusterin (86%), followed by beta-2-microglobulin, cystatin-C, MCP1, and KIM1 (57%) after cross-validation.

CONCLUSION

Serial surveillance of these biomarkers could improve the lead time for nephrotoxicity detection by days.

Length of gestation and birth weight are associated with indices of combined kidney biomarkers in early childhood

Infants born prematurely or with low birth weights are more susceptible to kidney dysfunction throughout their lives. Multiple proteins measured in urine are noninvasive biomarkers of subclinical kidney damage, but few studies have examined the joint effects of multiple biomarkers. We conducted an exploratory study of 103 children in the Programing Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) longitudinal birth cohort, and measured nine proteins selected a priori in banked spot urine samples collected at ages 4-6. The goal of our study was to explore the combined effects of kidney damage biomarkers previously associated with birth outcomes. To do this, we generated kidney biomarker indices using weighted quantile sum regression and assessed associations with length of gestation or birth weight. A decile increase in each kidney biomarker index was associated with 2-day shorter gestations (β = -2.0, 95% CI: -3.2, -0.9) and 59-gram lower birth weights (β = -58.5, 95% CI: -98.3, -18.7), respectively. Weights highlighting the contributions showed neutrophil gelatinase-associated lipocalin (NGAL) (60%) and osteopontin (19%) contributed most to the index derived for gestational age. NGAL (66%) and beta-2-microglobulin (10%) contributed most to the index derived for birth weight. Joint analyses of multiple kidney biomarkers can provide integrated measures of kidney dysfunction and improved statistical assessments compared to biomarkers assessed individually. Additionally, shorter gestations and lower birth weights may contribute to subclinical kidney damage measurable in childhood.

Heavy Metals and Pesticides in Chronic Kidney Disease - Results from a Matched Case-Control Study from a Rural Population in Shivamogga District in South India

INTRODUCTION

There is a high prevalence of chronic kidney disease (CKD) in the rural agrarian population of South India and it often appears unrelated to major known causes such as diabetes or glomerulonephritis.

METHODS

In a matched case-control study conducted in a rural population in Shivamogga district in South India, the association of heavy metals - lead (Pb), arsenic (As), cadmium (Cd) - and pesticides in CKD was studied. Blood and spot urine samples were tested quantitatively for heavy metals and qualitatively for pesticides.

RESULTS

In all, 69 matched pairs (40 female, 58%) were recruited. The mean estimated glomerular filtration rate (mL/min/1.73 m2) was 60.1 (14.2) in cases and 83.4 (13.4) in controls. Elevated blood lead level >5 μg/dL was seen in 15 cases and 25 controls, respectively [P = 0.035, matched odds ratio (MOR) 0.5, 95% confidence interval (CI) 0.22-1.05]. Urinary Pb was elevated in 16 cases and 13 controls, respectively (P = 0.28, MOR 1.25, 95% CI 0.58-2.73). There was no significant association with As and Cd, while pesticide residues were undetectable in cases as well as controls. These results did not change even after excluding CKD cases with diabetes, stage 2 hypertension, and significant proteinuria.

CONCLUSIONS

There was no statistical significant association between any of the studied heavy metals and CKD, although there was a significant burden of heavy metals in the studied subjects.

Potential Prognostic Markers of Acute Kidney Injury in the Early Phase of Acute Pancreatitis

Acute kidney injury (AKI) is a serious complication of acute pancreatitis (AP), which occurs in up to 70% of patients with severe AP and significantly increases the risk of mortality. At present, AKI is diagnosed based on dynamic increase in serum creatinine and decreased urine output; however, there is a need for earlier and more accurate biomarkers. The aim of the study was to review current evidence on the laboratory tests that were studied as the potential biomarkers of AKI in AP. We also briefly summarized the knowledge coming from the studies including sepsis or ICU patients since severe acute pancreatitis is associated with systemic inflammation and organ failure. Serum cystatin C and serum or urine NGAL have been shown to predict or diagnose AKI in AP; however, this evidence come from the single center studies of low number of patients. Other markers, such as urinary kidney injury molecule-1, cell cycle arrest biomarkers (tissue inhibitor metalloproteinase-2 and urine insulin-like growth factor-binding protein 7), interleukin-18, liver-type fatty acid-binding protein, or calprotectin have been studied in other populations suffering from systemic inflammatory states. In AP, the potential markers of AKI may be significantly influenced by either dehydration or inflammation, and the impact of these factors may be difficult to distinguish from kidney injury. The subject of AKI complicating AP is understudied. More studies are needed, for both exploratory (to choose the best markers) and clinical (to evaluate the diagnostic accuracy of the chosen markers in real clinical settings).

Urinary Cell Adhesion Molecule 1 Is a Novel Biomarker That Links Tubulointerstitial Damage to Glomerular Filtration Rates in Chronic Kidney Disease

Cell adhesion molecule 1 (CADM1) is an immunoglobulin superfamily member strongly expressed on renal tubular epithelia in the urinary tract. Enzymatic cleavage of its ectodomain increases in chronic kidney disease (CKD), and is assumed to contribute to tubulointerstitial lesion formation. Because the cleaved ectodomain fragments are likely to be released into the urine, a sandwich enzyme-linked immunosorbent assay (ELISA) system for urinary CADM1 was developed using two anti-ectodomain antibodies. Urinary CADM1 concentrations in patients with CKD based on various forms of glomerulonephritis and nephropathy (n = 127) were measured. A total of 44 patients (35%) had elevated CADM1 concentrations over the normal upper limit (362 pg/mL), with a mean of 1,727 pg/mL. Renal biopsy specimens of all patients were pathologically scored for tubulointerstitial lesions using epithelial degeneration, interstitial inflammation, and fibrosis. There were no correlations between urinary CADM1 concentrations and pathological scores or any widely used renal markers, including glomerular filtration rate (GFR), but there was a weak inverse correlation between pathological scores and GFR (R² = 0.292). Notably, this correlation gradually increased in patients with increasing CADM1 concentrations, and reached a maximum R² (0.899) at a cutoff of 1,569 pg/mL. The results of this study suggest that urinary CADM1 is a useful marker indicating tubulointerstitial damage from elevated GFR levels in CKD.

Biochemical evaluation of kidney disease

Different biochemical markers exist in both blood and urine for assessing renal function. Most of these biomarkers have advantages and limitations associated with their use, which is important to consider when ordering and utilising them in the clinical setting. The ideal marker should be able to detect acute kidney injury (AKI) at the onset and be used for the diagnosis and ongoing monitoring and management of kidney disease. The search for such a marker is ongoing, as all potential candidates thus far are associated with certain limitations. This article will attempt to compare and contrast established and emerging kidney disease markers.

Protective effects of anthocyanins from bilberry extract in rats exposed to nephrotoxic effects of carbon tetrachloride

This study examined the nephroprotective effects of 15 different anthocyanins from the bilberry extract on the acute kidney injury caused by CCl₄. The acute nephrotoxicity in rats was induced 24 h after the treatment with a single dose of CCl₄ (3 mL/kg, i.p.).The nephroprotective effects of the anthocyanins were examined in the animals that had been given the bilberry extract in a single dose of 200 mg of anthocyanins/kg daily, 7 days orally, while on the seventh day, 3 h after the last dose of anthocyanins, the animals received a single dose of CCl₄ (3 mL/kg, i.p.) and were sacrificed 24 h later. When the nephrotoxicant alone was administered, it resulted in a substantial increase of the pro-oxidative (TBARS, CD, H₂O₂, XO, and GSSG) and pro-inflammatory markers (TNF-α, NO, and MPO), as well as a noticeable reduction of the antioxidant enzymes (CAT, SOD, POD, GPx, GST, GR) and GSH when compared to the results of the control group. Moreover, the application of CCl₄ significantly influenced a reduction of the renal function, as well as an increase in the sensitive and specific injury indicators of the kidney epithelial cells (β₂-microglobulin, NGAL, KIM1/TIM1) in the serum and urine of rats. The pretreatment of the animals poisoned with CCl₄ with the anthocyanins from the bilberry extract led to a noticeable reduction in the pro-oxidative and pro-inflammatory markers with reduced consumption of the antioxidant defence kidney capacity, compared to the animals exposed to CCl₄ alone. Anthocyanins have been protective for the kidney parenchyma, with an apparent absence of the tubular and periglomerular necrosis, severe degenerative changes, inflammatory mononuclear infiltrates and dilatation of proximal and distal tubules, in contrast to the CCl₄-intoxicated animals. The nephroprotective effects of anthocyanins can be explained by strong antioxidant and anti-inflammatory effects achieved through the stabilization and neutralization of highly reactive and unstable toxic CCl₄ metabolites.

Short-term Changes in Urine Beta 2 Microglobulin Following Recovery of Acute Kidney Injury Resulting From Snake Envenomation

Introduction

Urine β2 microglobulin (β2m) is a validated marker to diagnose sepsis and toxin-related acute kidney injury (AKI). In the current study, we used urine β2m as a potential marker to identify persistent tubular dysfunction following a clinical recovery from snake venom–related AKI.

Methods

A total of 42 patients who developed AKI following hemotoxic envenomation were followed up for a period of 6 months. Urine albumin excretion, estimated glomerular filtration rate (eGFR), and urine β2m levels were measured at 2 weeks, 3 months, and 6 months following discharge.

Results

At the end of 6 months of follow-up, 6 patients (14.3 %) progressed to chronic kidney disease (CKD) (eGFR < 60 ml and/or urine albumin excretion > 30 mg/d). The urine β2m levels were 1590 μg/l (interquartile range [IQR] 425–5260), 610 μg/l (IQR 210–1850), 850 μg/l (IQR 270–2780) at 2 weeks, 3 months, and 6 months, respectively (P = 0.020). The levels of urine β2m in the study population at the end of 6 months remained significantly higher compared with the levels in healthy control population (850 μg/l [IQR 270–2780] vs. 210 μg/l [IQR 150–480]; P = 0.001). The proportion of patients with urine β2m levels exceeding the 95th percentile of control population (>644 µg/l) during the 3 follow-up visits were 70.7% (n = 29), 48.8 % (n = 20), and 51.2% (n = 21). Similar trends were noticed in a sensitivity analysis, after excluding patients with CKD.

Conclusions

Urine β2m levels remain persistently elevated in approximately half of the individuals who recover from AKI due to snake envenomation.

Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases

There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β₂M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β₂M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β₂M function arise as a result of altered binding of β₂M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β₂M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β₂M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β₂M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β₂M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β₂M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β₂M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.

Associations of Low Environmental Exposure to Multiple Metals with Renal Tubular Impairment in Korean Adults

Recently several studies reported that the renal toxicity of lead (Pb) and cadmium (Cd) may exist in even a low level exposure. In terms of the deterioration of tubular function, it affects the loss of divalent metals and leads to other complications, so renal tubular effect of heavy metals should be well managed. Considering the exposure to heavy metals in reality, it is hard to find the case that human is exposed to only one heavy metal. We designed a cross-sectional study using Korean Research Project on the Integrated Exposure Assessment (KRIEFS) data to investigate the renal effects of multiple metal exposure in general population. We used blood Pb and urinary Cd as exposure measures, and urinary N-acetyl-β-D-glucosaminidase (NAG) and β₂-microglobulin (β₂-MG) as renal tubular impairment outcome. We conducted linear regression to identify the association between each heavy metal and urinary NAG and β₂-MG. And then, we conducted linear regression including the interaction term. Of 1953 adults in KRIEFS (2010~2011), the geometric mean of blood Pb and urinary Cd concentration was 2.21 μg/dL (geometric SD = 1.49 μg/dL) and 1.08 μg/g cr (geometric SD = 1.98 μg/g cr), respectively. In urinary Cd, the strength of the association was also high after adjusting (urinary NAG: β = 0.44, p < 0.001; urinary β₂-MG: β = 0.13, p = 0.002). Finally, we identified the positive interactions for the two renal biomarkers. The interaction effect of the two heavy metals of β₂-MG was greater than that of NAG. It is very important in public health perspective if the low level exposure to multiple heavy metals has an interaction effect on kidney. More epidemiological studies for the interaction and toxicological studies on the mechanism are needed.