Tubular kidney injury molecule-1 (KIM-1) in human renal disease

Early kidney injury in immunoglobulin A vasculitis: Role of renal biomarkers

BACKGROUND

We aimed to determine whether urine kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) can be used as early noninvasive biomarkers of kidney injury in immunoglobulin A vasculitis.

METHODS

Patients who were diagnosed with immunoglobulin A vasculitis were included in the study. Urine samples were collected for determination of urine KIM-1 and NGAL levels. The control group consisted of age-matched healthy children.

RESULTS

Sixty-one patients who were diagnosed with immunoglobulin A vasculitis were included in the study; 37.7% of these patients were determined to have renal involvement. Median KIM-1 was found to be significantly higher in the patient group (69.59 pg/mL) than the control group (40.84 pg/mL) (P = 0.001). Median NGAL was determined to be statistically significantly higher in the patient group (59.87 ng/mL) compared with the control group (44.87 ng/mL) (P = 0.013). In 23.6% of the patients without renal involvement at admission renal involvement developed within the following 6 months. When median KIM-1 and NGAL at admission of these patients were compared with the control group, they were determined to be statistically significantly higher (P = 0.001, P = 0.003).

CONCLUSIONS

The fact that our patients with late-term nephropathy had no hematuria and / or proteinuria and that KIM-1 and NGAL levels were determined to be high indicates that these biomarkers might be potentially reliable, noninvasive and early determinants of kidney injury.

Impact of high salt diets on CHOP-mediated apoptosis and renal fibrosis in a rat model

BACKGROUND

Prolonged and excessive salt intake accelerates oxidative stress in kidney tissues, which brings about ER stress. The PERK/ATF4/CHOP/BCL-2 signaling pathway has an essential role in ER stress-induced apoptosis. The present study aimed to investigate the effect of high salt diets on the development of renal fibrosis through CHOP-mediated apoptosis.

METHODS AND RESULTS

Twenty-five male Wistar rats were randomly divided into five groups (n = 5 each). Groups 1-5 were treated with 0%, 0.5%, 1%, 1.2%, 1.5% of NaCl dissolved in distilled water, respectively, for 8 weeks. To detect the degree of renal tubular damage, urinary KIM-1 was measured. The slides of renal tissues were stained via Masson's Trichrome staining methods for fibrosis detection. The relative gene expression of ATF4, CHOP, and BCl-2 in renal tissues were analyzed using the qRT-PCR method. The results revealed no significant difference between the urea, creatinine, and urine flow rate of the rats receiving different concentrations of NaCl (groups 2-5) and those of the control group (group 1). The rats treated with 1.5% NaCl (group 5) showed significant elevations in urinary KIM-1 and the mRNA level of CHOP compared to the control group. Mild renal fibrosis was also observed in group 5.

CONCLUSIONS

Excessive salt intake leads to fibrosis as it induces the PERK/ATF4/CHOP/BCL-2 signaling pathway in renal tissues. KIM-1 is detectable in urine before the impairment of renal function which can be used as a diagnostic marker to prevent the development of progressive renal failure.

Biomarkers of acute kidney injury in patients with nephrotic syndrome

Introduction:

Emergence of acute kidney injury (AKI) in patients with nephrotic syndrome (NS) requires prompt diagnosis and differentiation between acute tubular necrosis (ATN) and proliferative glomerulonephritis. We studied the potential use of commercial urinary biomarkers' tests in the diagnosis of AKI in patients with NS.

Methods:

A cross sectional estimate of urinary concentrations of KIM-1 and NGAL was performed in 40 patients with NS: 9 with proliferative glomerulopathy, being 4 with AKI and 31 without proliferative glomerulopathy, being 15 with AKI. AKI was defined using the KDIGO criteria.

Results:

The mean age was 35 ± 16 years. The main diagnoses were focal and segmental glomerulosclerosis (10, 25%), membranous glomerulopathy (10, 25%), minimal change disease (7, 18%), lupus nephritis (6, 15%), and proliferative glomerulonephritis (3, 8%). Patients with ATN had higher levels of urinary KIM-1 (P = 0.0157) and NGAL (P = 0.023) than patients without ATN. The urinary concentrations of KIM-1 (P= 0.009) and NGAL (P= 0.002) were higher in patients with AKI than in patients without AKI. Urinary NGAL and KIM-1 levels were significantly higher in patients with ATN without proliferative glomerulonephritis than in patients with proliferative glomerulonephritis (P = 0.003 and P=0.024, respectively).

Conclusions:

Neutrophil gelatinase associated lipocalin (NGAL) and kidney injury molecule 1 (KIM-1) estimates correlated with histological signs of ATN and were able to discriminate patients with AKI even in conditions of NS. Furthermore, urinary levels of NGAL and KIM-1 may be useful in the differential diagnosis of acute tubular necrosis and exudative glomerulonephritis in patients with nephrotic syndrome.

N-acetyl-ß-D-glucosaminidase is predictive of mortality in chronic heart failure: a 10-year follow-up

Aim: The study focused on biomarkers of kidney injury as predictors of mortality in patients with chronic heart failure (CHF) in a long-term follow-up (median 104 months). Methods/results: KIM-1, NAG and NGAL were assessed from urine, NT-proBNP from blood samples. 149 patients (age 62 ± 12 years) with CHF (mean EF 30% [IQR 24-40%]) were enrolled. 79 (53%) patients died. Cox regression analysis revealed Log2NAG (HR: 1.46, CI: 1.12-1.89), Log2KIM-1 (HR: 1.23, CI: 1.02-1.49) and Log2NT-proBNP (HR: 1.50, CI: 1.32-1.72) as significant predictors of all-cause mortality as opposed to Log2NGAL (HR: 1.04, CI: 0.90-1.20). Log2NAG remained a significant predictor of all-cause mortality in a multivariate Cox regression model but lost its predictive value in combination with Log2NT-proBNP. Conclusion: The 10-year follow-up suggests NAG as a predictive tubular marker in CHF patients.

Ganoderma lucidum ameliorates the diabetic nephropathy via down-regulatory effect on TGFβ-1 and TLR-4/NFκB signalling pathways

OBJECTIVES

Diabetic nephropathy (DN) is one of the most important complications of diabetes mellitus and it is considered as a principal cause for end-stage renal failure. Ganoderma lucidum (GL) has been studied for its reno-protective effect against different kidney injury models. The aim of our study is to investigate the mechanisms by which GL can improve kidney injury and consequent renal inflammation and fibrosis.

METHODS

GL either in a low dose (250 mg/kg, i.p.) or high dose (500 mg/kg, i.p.) was administered to DN rat model, and nephropathy indices were investigated.

KEY FINDINGS

GL treatment significantly down-regulated kidney injury molecule-1 (KIM-1) gene expression and inhibited TLR-4 (Toll-like receptor-4)/NFκB (nuclear factor kappa B) signalling pathway. As well, GL treatment significantly decreased the pro-inflammatory mediator; IL-1β (interleukin-1 beta) level and fibrosis-associated growth factors; FGF-23 (fibroblast growth factor-23) and TGFβ-1 (transforming growth factor beta-1) levels. In addition, GL remarkably inhibited (Bax) the pro-apoptotic protein and induced (Bcl-2) the anti-apoptotic protein expression in kidneys. Moreover, GL treatment significantly alleviates kidney injury indicated by correcting the deteriorated kidney function and improving oxidative stress status in DN rats.

CONCLUSIONS

GL significantly improved renal function indices through dose-dependent kidney function restoration, oxidative stress reduction, down-regulation of gene expression of KIM-1 and TLR4/NFκB signalling pathway blockage with subsequent alleviation of renal inflammation and fibrosis.

Kidney Injury Molecule-1 Is Associated with Contrast-Induced Nephropathy in Elderly Patients with Non-STEMI

BACKGROUND

Contrast-induced nephropathy (CIN) is associated with an increased risk of major adverse cardiovascular events (MACE), and the association between CIN and oxidative mechanisms is well documented.

OBJECTIVE

This study aimed to evaluate the relationship between serum levels of kidney injury molecule-1 (KIM-1) and CIN in elderly patients with non-ST-segment elevation myocardial infarction (NSTEMI).

METHODS

This study included a total of 758 patients with NSTEMI, who underwent percutaneous coronary intervention (PCI); 15 developed CIN after PCI, and another 104 were the control group, matched for age > 65 years. Baseline to 48-to-72-hour laboratory values and clinical outcomes were recorded. Patients were followed during one year. P values of < 0.05 were considered significant.

RESULTS

CIN was observed in 12.60% of the patients. Serum KIM-1 was significantly higher in the CIN group than in the non-CIN group (14.02 [9.53 - 19.90] vs. 5.41 [3.41 - 9.03], p < 0.001). The Mehran score was significantly higher in the CIN group than in the non-CIN group (14 [5 - 22] vs. 5 [2 - 7], p = 0.001). MACE were significantly higher in the CIN group than in the non-CIN group (7 [46.70%] vs. 12 [11.50%], p = 0.001). Multivariate logistic regression analysis showed that baseline KIM-1 level (OR = 1.652, 95% CI: 1.20 - 2.27, p = 0.002) and Mehran score (OR = 1.457, 95% CI: 1.01 - 2.08, p = 0.039) were independent predictors of CIN in elderly patients with NSTEMI.

CONCLUSION

Baseline serum KIM-1 concentration and Mehran score are independent predictors of CIN in elderly patients with NSTEMI. Additionally, all-cause mortality, cardiovascular death, myocardial reinfarction, stroke, and MACE were significantly higher in the CIN group at one-year follow-up. (Arq Bras Cardiol. 2021; [online].ahead print, PP.0-0).

KIM-1 mediates fatty acid uptake by renal tubular cells to promote progressive diabetic kidney disease

Tubulointerstitial abnormalities are predictive of the progression of diabetic kidney disease (DKD), and their targeting may be an effective means for prevention. Proximal tubular (PT) expression of kidney injury molecule (KIM)-1, as well as blood and urinary levels, are increased early in human diabetes and can predict the rate of disease progression. Here, we report that KIM-1 mediates PT uptake of palmitic acid (PA)-bound albumin, leading to enhanced tubule injury with DNA damage, PT cell-cycle arrest, interstitial inflammation and fibrosis, and secondary glomerulosclerosis. Such injury can be ameliorated by genetic ablation of the KIM-1 mucin domain in a high-fat-fed streptozotocin mouse model of DKD. We also identified TW-37 as a small molecule inhibitor of KIM-1-mediated PA-albumin uptake and showed in vivo in a kidney injury model in mice that it ameliorates renal inflammation and fibrosis. Together, our findings support KIM-1 as a new therapeutic target for DKD.

Pathomechanisms in the Kidneys in Selected Protozoan Parasitic Infections

Leishmaniasis, malaria, toxoplasmosis, and acanthamoebiasis are protozoan parasitic infections. They remain important contributors to the development of kidney disease, which is associated with increased patients' morbidity and mortality. Kidney injury mechanisms are not fully understood in protozoan parasitic diseases, bringing major difficulties to specific therapeutic interventions. The aim of this review is to present the biochemical and molecular mechanisms in kidneys infected with Leishmania spp., Plasmodium spp., Toxoplasma gondii, and Acanthamoeba spp. We present available mechanisms of an immune response, oxidative stress, apoptosis process, hypoxia, biomarkers of renal injury in the serum or urine, and the histopathological changes of kidneys infected with the selected parasites. Pathomechanisms of Leishmania spp. and Plasmodium spp. infections have been deeply investigated, while Toxoplasma gondii and Acanthamoeba spp. infections in the kidneys are not well known yet. Deeper knowledge of kidney involvement in leishmaniasis and malaria by presenting their mechanisms provides insight into how to create novel and effective treatments. Additionally, the presented work shows gaps in the pathophysiology of renal toxoplasmosis and acanthamoebiasis, which need further research.

Kidney Injury Molecule-1 and Periostin Urinary Excretion and Tissue Expression Levels and Association with Glomerular Disease Outcomes

Introductions

Kidney injury molecule-1 (KIM-1) and periostin (POSTN) are proximal and distal tubule injury biomarkers. We tested whether baseline urine KIM-1/creatinine (uKIM-1/cr) and/or uPOSTN/cr correlated with disease severity or improved a remission prediction model.

Methods

Baseline uKIM1/cr and uPOSTN/cr were measured on spot urine samples from immunosuppression-free patients enrolled in Nephrotic Syndrome Study Network until December 15, 2014. Urine protein/creatinine (UPCR) and albumin/creatinine (UACR) were measured at baseline, 4 months, and until last follow-up. Glomerular and tubulointerstitial (TI) expression arrays were analyzed from a baseline research renal biopsy core collected during a clinically indicated biopsy.Renal diagnoses were centrally confirmed, sections scanned, and measured morphometrically. Correlations between baseline uKIM-1/cr and uPOSTN/cr and UPCR, UACR, histopathologic features, glomerular and TI KIM-1 and POSTN expression levels, and renal outcomes were assessed.

Results

Baseline uKIM-1/cr correlated with UPCR and UACR, and were associated with complete remission after adjustment for proteinuria, histopathologic diagnosis, and treatment. Baseline uKIM-1/cr also correlated with degree of foot process effacement and acute tubular injury. Glomerular and TI KIM-1 expression levels correlated with UPCR and UACR. Higher TI KIM-1 expression levels correlated with interstitial fibrosis, tubular atrophy, and global glomerulosclerosis, while glomerular KIM-1 expression correlated with time to remission. Findings for POSTN were of lesser statistical strength.

Discussion/Conclusion

Lower baseline uKIM-1/cr values were associated with more rapid time to complete remission after adjusting for proteinuria, histopathologic diagnosis, and treatment. Increased TI KIM-1 expression levels in proteinuric states were associated with chronic morphological injury; lower glomerular expression levels were associated with a greater potential for proteinuria reversibility.

Outcomes in Coronary No-Reflow Phenomenon Patients and the Relationship between Kidney Injury Molecule-1 and Coronary No-Reflow Phenomenon

Fundamento

O fenômeno de no-reflow coronário (CNP, do inglês Coronary no-reflow phenomenon) está associado a um risco aumentado de eventos cardiovasculares adversos maiores (ECAM).

Objetivo

Este estudo teve como objetivo avaliar a relação entre os níveis séricos da Molécula-1 de lesão renal (KIM-1) e o CNP em pacientes com infarto agudo do miocárdio com supradesnivelamento do segmento ST (IAMCSST).

Métodos

Este estudo incluiu um total de 160 pacientes (113 homens e 47 mulheres; média de idade: 61,65 ± 12,14 anos) com diagnóstico de IAMCSST. Os pacientes foram divididos em dois grupos, o grupo reflow (GR) (n = 140) e o grupo no-reflow (GNR) (n = 20). Os pacientes foram acompanhados durante um ano. Um valor de p<0,05 foi considerado significativo.

Resultados

O CNP foi observado em 12,50% dos pacientes. O nível de KIM-1 sérico foi significativamente maior no GNR do que no GR (20,26 ± 7,32 vs. 13,45 ± 6,40, p<0,001). O índice de massa corporal (IMC) foi significativamente maior no GNR do que no GR (29,41 (28,48-31,23) vs. 27,56 (25,44-31,03), p=0,047). A frequência cardíaca (FC) foi significativamente menor no GNR do que no GR (61,6 ± 8,04 vs. 80,37 ± 14,61, p<0,001). O escore do European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) foi significativamente maior no GNR do que no GR (3,06 ± 2,22 vs. 2,36 ± 2,85, p=0,016). A incidência de AVC foi significativamente maior no GNR do que no GR (15% vs. 2,90%, p=0,013). O nível basal de KIM-1 (OR = 1,19, IC 95%: 1,07-1,34, p=0,002) e HR (OR = 0,784, IC 95%: 0,69-0,88, p<0,001) foram os preditores independentes de CNP.

Conclusão

Em conclusão, os níveis séricos basais de KIM-1 e a FC mais baixa estão independentemente associados com CNP em pacientes com IAMCSST, e o acidente vascular cerebral foi significativamente maior no GNR em um ano de seguimento. (Arq Bras Cardiol. 2021; 116(2):238-247)

Kidney Injury Molecule-1 in the detection of early kidney injury in dogs with leptospirosis

Renal damage, a common feature in canine leptospirosis, ranges from a subclinical affection to kidney dysfunction and death. Chances of recovery can be improved by early intervention. However, traditional biomarkers (serum urea and creatinine) have limited relevance for precocity. Kidney Injury Molecule-1 (KIM-1) is a transmembrane protein upregulated in early stages of tubular injury. This study evaluated the use of urinary KIM-1 to detect early renal injury in naturally occurring canine leptospirosis. This exploratory research included 30 dogs divided into two groups: (1) dogs with leptospirosis (n = 25) and (2) healthy dogs (n = 5). Leptospira sp. infection was diagnosed through urine PCR and/or direct bacteriologic culture and/or serology (single MAT titters ≥800). Additionally, stage of infection was further characterized in acute and subacute phases based on the onset of clinical symptoms from 3 to 7 days. Urinary KIM-1 (uKIM-1) concentrations were measured in both groups with a commercial canine ELISA kit. uKIM-1 levels were statistically different (P < 0.01) between the studied groups, especially in non-azotemic dogs (P = 0.0042). The biomarker showed 88 % sensibility to diagnosis of kidney injury at> 1.49 ng/mL cut-off. Urine KIM-1 was negatively correlated with urine specific gravity (USG) but accompanied histopathological evidence of renal degeneration, necrosis and regeneration processes, extending information on kidney health. Measurement of KIM-1 in the urine of canine patients was able to detect naturally occurring acute and subacute leptospirosis accompanied by tubular injury in early non-azotemic infections.

Effect of high intake of cod or salmon on serum total neopterin concentration: a randomised clinical trial

Purpose

Primarily, to investigate the effect of high intake of cod (lean fish) or salmon (fatty fish) on serum concentration of total neopterin, a marker of cellular immune activation that is associated with cardiovascular disease. Second, to investigate effects of high cod/salmon intake on antioxidant vitamins and elements essential for activity of antioxidant enzymes.

Methods

In this randomised clinical trial, 63 participants with overweight/obesity consumed 750 g/week of either Atlantic cod (N = 22) or Atlantic salmon (N = 22) or were instructed to continue their normal eating habits but avoid fish intake (Control group, N = 19) for 8 weeks. Food intake was recorded, and fasting serum were collected at baseline and endpoint.

Results

Serum total neopterin concentration was reduced in the Cod group (median change − 2.65 (25th, 75th percentiles − 3.68, − 0.45) nmol/l, P = 0.018) but not in the Salmon group (median change 0.00 (25th, 75th percentiles − 4.15, 3.05) nmol/l, P = 0.59) when compared with the Control group after 8 weeks. The estimated daily intake of selenium, iron, magnesium and zinc were similar between all groups. Increased serum concentration of selenium was observed only after cod intake when compared to the Control group (P = 0.017). Changes in serum concentrations of copper, iron, magnesium, all-trans retinol, α-tocopherol and γ-tocopherol were similar between the groups.

Conclusion

A high intake of cod, but not of salmon, lowered serum total neopterin concentration when compared to the Control group.

Clinical trial registration

This trial was registered at clinicaltrials.gov as NCT02350595

A Review of Specific Biomarkers of Chronic Renal Injury and Their Potential Application in Nonclinical Safety Assessment Studies

A host of novel renal biomarkers have been developed over the past few decades which have enhanced monitoring of renal disease and drug-induced kidney injury in both preclinical studies and in humans. Since chronic kidney disease (CKD) and acute kidney injury (AKI) share similar underlying mechanisms and the tubulointerstitial compartment has a functional role in the progression of CKD, urinary biomarkers of AKI may provide predictive information in chronic renal disease. Numerous studies have explored whether the recent AKI biomarkers could improve upon the standard clinical biomarkers, estimated glomerular filtration rate (eGFR), and urinary albumin to creatinine ratio, for predicting outcomes in CKD patients. This review is an introduction to alternative assays that can be utilized in chronic (>3 months duration) nonclinical safety studies to provide information on renal dysfunction and to demonstrate specific situations where these assays could be utilized in nonclinical drug development. Novel biomarkers such as symmetrical dimethyl arginine, dickkopf homolog 3, and cystatin C predict chronic renal injury in animals, act as surrogates for GFR, and may predict changes in GFR in patients over time, ultimately providing a bridge from preclinical to clinical renal monitoring.

Effects of Angiotensin II Type 1A Receptor on ACE2, Neprilysin and KIM-1 in Two Kidney One Clip (2K1C) Model of Renovascular Hypertension

Activation of the renin angiotensin system plays a pivotal role in the regulation of blood pressure, which is mainly attributed to the formation of angiotensin-II (Ang II). The actions of Ang II are mediated through binding to the Ang-II type 1 receptor (AT1R) which leads to increased blood pressure, fluid retention, and aldosterone secretion. In addition, Ang II is also involved in cell injury, vascular remodeling, and inflammation. The actions of Ang II could be antagonized by its conversion to the vasodilator peptide Ang (1-7), partly generated by the action of angiotensin converting enzyme 2 (ACE2) and/or neprilysin (NEP). Previous studies demonstrated increased urinary ACE2 shedding in the db/db mouse model of diabetic kidney disease. The aim of the study was to investigate whether renal and urinary ACE2 and NEP are altered in the 2K1C Goldblatt hypertensive mice. Since AT1R is highly expressed in the kidney, we also researched the effect of global deletion of AT1R on renal and urinary ACE2, NEP, and kidney injury marker (KIM-1). Hypertension and albuminuria were induced in AT1R knock out (AT1RKO) and WT mice by unilateral constriction of the renal artery of one kidney. The 24 h mean arterial blood pressure (MAP) was measured using radio-telemetry. Two weeks after 2K1C surgery, MAP and albuminuria were significantly increased in WT mice compared to AT1RKO mice. Results demonstrated a correlation between MAP and albuminuria. Unlike db/db diabetic mice, ACE2 and NEP expression and activities were significantly decreased in the clipped kidney of WT and AT1RKO compared with the contralateral kidney and sham control (p < 0.05). There was no detectable urinary ACE2 and NEP expression and activity in 2K1C mice. KIM-1 was significantly increased in the clipped kidney of WT and AT1KO (p < 0.05). Deletion of AT1R has no effect on the increased urinary KIM-1 excretion detected in 2K1C mice. In conclusion, renal injury in 2K1C Goldblatt mouse model is associated with loss of renal ACE2 and NEP expression and activity. Urinary KIM-1 could serve as an early indicator of acute kidney injury. Deletion of AT1R attenuates albuminuria and hypertension without affecting renal ACE2, NEP, and KIM-1 expression.

Immunophenotypical Characterization of M1/M2 Macrophages and Lymphocytes in Cisplatin-Induced Rat Progressive Renal Fibrosis

Renal fibrosis is regarded as the common final pathway leading to chronic kidney diseases; macrophages and myofibroblasts play important roles in the development of fibrosis. F344 rats were injected once with cisplatin (CDDP; 6 mg/kg BW) for renal lesions. Here, immunophenotypical characteristics of macrophages and lymphocytes in CDDP-induced rat renal lesions were investigated histopathologically; the CDDP-induced renal lesions consisted of tissue damage at the early-stage, worsen the damage and commencement of interstitial fibrosis at the mid-stage, and progressive fibrosis at the late stage; the KIM-1 expression and α-SMA+ myofibroblast area reflected renal tubular damage/abnormal regeneration and renal interstitial fibrosis, respectively. CD68+ M1 macrophages began to increase at the mid-stage, with increased mRNA expressions of M1-related cytokines (INF-γ, TNF-α and IL-6), and then slightly decreased at the late-stage. CD163+ M2 macrophages showed a gradually increased number at the mid- and late-stages, accompanied by increased TGF-β1 mRNA expression (a fibrogenic factor). Double immunofluorescence using fibrotic samples at the late-stage revealed that 62.0-78.0% of CD68+ M1 macrophages co-expressed CD163, indicating that M1/M2 macrophages may contribute to progressive renal fibrosis in cooperation; further, MHC class II-expressing macrophages had a tendency towards M1 polarization, whereas CD204-expressing macrophages towards M2 polarization. In addition, CD4+ and CD8+ T cells were increased at the late-stage. Collectively, progressive renal interstitial fibrosis may be developed by complicated mechanisms that arose via interaction of M1/M2 macrophages (inflammatory for M1 and anti-inflammatory for M2) and T cells reacting to CD4 (for helper) and CD8 (for cytotoxicity). This study would provide some information on the pathogenesis of renal fibrosis based on inflammatory cells.

Current Challenges and Future Perspectives of Renal Tubular Dysfunction in Diabetic Kidney Disease

Over decades, substantial progress has been achieved in understanding the pathogenesis of proteinuria in diabetic kidney disease (DKD), biomarkers for DKD screening, diagnosis, and prognosis, as well as novel hypoglycemia agents in clinical trials, thereby rendering more attention focused on the role of renal tubules in DKD. Previous studies have demonstrated that morphological and functional changes in renal tubules are highly involved in the occurrence and development of DKD. Novel tubular biomarkers have shown some clinical importance. However, there are many challenges to transition into personalized diagnosis and guidance for individual therapy in clinical practice. Large-scale clinical trials suggested the clinical relevance of increased proximal reabsorption and hyperfiltration by sodium-glucose cotransporter-2 (SGLT2) to improve renal outcomes in patients with diabetes, further promoting the emergence of renal tubulocentric research. Therefore, this review summarized the recent progress in the pathophysiology associated with involved mechanisms of renal tubules, potential tubular biomarkers with clinical application, and renal tubular factors in DKD management. The mechanism of kidney protection and impressive results from clinical trials of SGLT2 inhibitors were summarized and discussed, offering a comprehensive update on therapeutic strategies targeting renal tubules.

Value of urinary kidney injury molecule-1 levels in predicting acute kidney injury in very low birth weight preterm infants

Objective

This study aimed to evaluate the significance of urinary kidney injury molecule-1 (uKIM-1) levels in predicting acute kidney injury (AKI) and mortality in very low birth weight (VLBW) preterm infants.

Methods

This prospective, observational cohort study was conducted on 39 VLBW preterm infants. Serum creatinine (SCr) and uKIM-1 levels were measured in the first 24 and 48 to 72 hours of life. The estimated glomerular filtration rate (eGFR) was calculated. Levels of uKIM-1 were measured with an enzyme-linked immunosorbent assay.

Results

Among 39 VLBW infants, 9 (23%) developed AKI. The mortality rate was 17.9% (n = 7 neonates). There was no significant difference in SCr levels, uKIM-1 levels, or the eGFR obtained in the first 24 hours in the AKI group compared with controls. However, significant differences were found in SCr and uKIM-1 levels, and the eGFR rate at 48 to 72 hours between the groups. Levels of uKIM-1 were significantly higher in non-survivors than in survivors in the first 24 and 48 to 72 hours of life.

Conclusion

The level of uKIM-1 can be used as a simple noninvasive diagnostic method for predicting AKI and mortality, especially within 48 to 72 hours of life.

Clinical trial registration: We do not have a clinical trial registration ID. In Turkey, clinical trial registration is not required for non-drug, noninvasive, clinical studies.

Environmental circadian disruption suppresses rhythms in kidney function and accelerates excretion of renal injury markers in urine of male hypertensive rats

Nontraditional work schedules, such as shift work, have been associated with numerous health issues, including cardiovascular and metabolic disease. These work schedules can chronically misalign environmental timing cues with internal circadian clock systems in the brain and in peripheral organs, leading to dysfunction of those systems and their associated biological processes. Environmental circadian disruption in the kidney may be an important factor in the increased incidence of hypertension and adverse health outcomes in human shift workers. The relationship between renal rhythmicity and injury resilience is not well understood, especially in the context of environmental, rather than genetic, manipulations of the circadian system. We conducted a longitudinal study to determine whether chronic shifting of the light cycle that mimics shift work schedules would disrupt output rhythms of the kidney and accelerate kidney injury in salt-loaded male spontaneously hypertensive, stroke-prone rats. We observed that chronic shifting of the light-dark (LD) cycle misaligned and decreased the amplitude of urinary volume rhythms as the kidney phase-shifted to match each new lighting cycle. This schedule also accelerated glomerular and tubular injury marker excretion, as quantified by nephrin and KIM-1 compared with rats kept in a static LD cycle. These data suggest that disrupted rhythms in the kidney may decrease resilience and contribute to disease development in systems dependent on renal and cardiovascular functions.

Oleanolic Acid Improves the Symptom of Renal Ischemia Reperfusion Injury via the PI3K/AKT Pathway

PURPOSE

The aim of this study was to investigate the therapeutic effect of oleanolic acid (OA) on the renal ischemia reperfusion injury (RIRI) and the possible mechanism.

METHODS

The RIRI model was successfully established in rats. OA, LY294002 (a PI3K inhibitor), and OA combined with LY294002 were dosed to rats in 3 therapeutic groups, respectively. The blood was collected to detect the concentration of Cr and BUN by ELISA. The kidney of each rat was collected to detect the concentration of renal injury factor (Kim-1) and the HE staining was performed. Western blot was used to detect the expression level of PI3K, p-AKT, AKT, PDK1, Skp2, and p27 in the renal tissue homogenate.

RESULTS

The symptom of vacuolar degeneration and interstitial edema was greatly improved in the rat kidney from the 3 therapeutic groups, compared with that from the RIRI model group. No significant difference was observed among the 3 therapeutic groups. The concentration of Cr in the 3 therapeutic groups was greatly lower than that in the RIRI model group. The expression level of p-AKT/AKT, PI3K, PDK1, Skp2, and p27 in OA group, LY294002 group, and OA combined with LY294002 group was significantly lower than that in the RIRI model group, respectively.

CONCLUSION

OA could improve the symptom of RIRI, possibly by inhibiting PI3K/AKT signal pathway.

Mapping and functional characterization of murine kidney injury molecule-1 proteolytic cleavage site

Kidney injury molecule-1 (KIM-1), also known as T cell immunoglobulin and mucin domain 1 (TIM-1), is a transmembrane glycoprotein expressed on proximal tubule epithelia during acute kidney injury (AKI). Extracellular domain of KIM-1 undergoes spontaneous and activated ectodomain shedding into urine and blood via metalloproteases. Soluble KIM-1 (blood and urinary) is a reliable clinical biomarker of proximal tubular injury, but the biological significance of shedding remains unknown. The aim of this study was to identify the specific shedding enzyme and the proteolytic cleavage site of murine KIM-1, followed by the characterization of its functional relevance. In this regard, isoleucine (I) I202 was identified as the potential cleavage site. Mutation of isoleucine I202 to glutamine (I202Q) or alanine (I202A) significantly reduced both constitutive and induced KIM-1 shedding and ultimately efferocytosis. It was also uncovered that ADAM10 is the major sheddase that mediates the proteolytic cleavage of murine KIM-1. In addition, ADAM10-induced KIM-1 shedding was required for efficient phagocytic clearance of apoptotic cells. Importantly, the findings that the addition of exogenous shed KIM-1 rescued the phagocytic impairment suggest that shed KIM-1 is capable of modulating efferocytosis of apoptotic bodies and could represent a potential functional role of the soluble ectodomain KIM-1 during AKI.

The Network of Inflammatory Mechanisms in Lupus Nephritis

Several signaling pathways are involved in the progression of kidney disease in humans and in animal models, and kidney disease is usually due to the sustained activation of these pathways. Some of the best understood pathways are specific proinflammatory cytokine and protein kinase pathways (e.g., protein kinase C and mitogen-activated kinase pathways, which cause cell proliferation and fibrosis and are associated with angiotensin II) and transforming growth factor-beta (TGF-β) signaling pathways (e.g., the TGF-β signaling pathway, which leads to increased fibrosis and kidney scarring. It is thus necessary to continue to advance our knowledge of the pathogenesis and molecular biology of kidney disease and to develop new treatments. This review provides an update of important findings about kidney diseases (including diabetic nephropathy, lupus nephritis, and vasculitis, i.e., vasculitis with antineutrophilic cytoplasmic antibodies). New disease targets, potential pathological pathways, and promising therapeutic approaches from basic science to clinical practice are presented, and the blocking of JAK/STAT and TIM-1/TIM-4 signaling pathways as potential novel therapeutic agents in lupus nephritis is discussed.

Biomarkers in Progressive Chronic Kidney Disease. Still a Long Way to Go

The traditional chronic kidney disease (CKD) biomarkers (eGFR based on serum creatinine, sex and age and albuminuria) cannot predict a patient's individual risk for developing progressive CKD. For this reason, it is necessary to identify novel CKD biomarkers that will be able to predict which patients are prone to develop progressive disease and discriminate between disease processes in different parts of the nephron (glomeruli or tubules). A good biomarker should change before or simultaneously with lesion development and its changes should correlate strongly with lesion development. Also, there should be a close relationship between severity of injury and amount of detectable biomarker and its levels should decrease with diminishing injury. Among the large number of molecules under investigation, we have reviewed the most promising ones: NGAL and KIM-1, MCP-1, MMP-9, clusterin, MMP-9, TIMP-1, Procollagen I alpha 1 and suPAR. All these, have been studied as biomarkers for prediction of CKD progression in cohorts of patients with chronic kidney disease of different stages and various aetiologies (proteinuric and non-proteinuric, glomerulonephritides, diabetic, hypertensive and polycystic kidney disease). There is evidence that these molecules could be useful as biomarkers for progressive chronic kidney disease, however, the available data are not enough to draw final conclusions. Further studies with large cohorts and long follow-up are required to identify appropriate biomarkers, that will be able to accurately and reliably define the risk for progressive chronic kidney disease.

Kidney injury molecule-1/creatinine as a urinary biomarker of acute kidney injury in critically ill neonates

INTRODUCTION

Acute kidney injury (AKI) is a complex disorder, means acute deterioration of renal function generally occurring over hours to days. Serum creatinine (SCr) is a suboptimal biomarker in neonates as the creatinine concentration reflects the maternal level for up to 72 h after birth, to improve the ability for early prediction of AKI and improve clinical outcomes, there has been a significant amount of research to identify novel biomarkers of damage to allow for the earlier identification of neonates with AKI.

OBJECTIVE

This study aimed to study the effectiveness of urinary kidney injury molecule-1/creatinine (uKIM-1/cr) in the diagnosis of AKI in critically ill neonates.

STUDY DESIGN

The patients' group included 50 critically ill full-term septic neonates (39 of them developed AKI according to guidelines of AKI diagnosis), and control group including 50 healthy neonates. Full history taking, clinical assessment and laboratory testing of the renal functions (urea & creatinine), eGFR, uKIM-1 by ELISA technique and uKIM-1/cr ratio on admission, and on day 3 of admission.

RESULTS

Urea, serum creatinine increased, whereas, eGFR decreased significantly in the second sample when compared to the first sample of the AKI group. uKIM-1 and uKIM-1/cr were high in the first sample, uKIM-1 concentration and uKIM-1/creatinine were higher in second sample (2.2 ± 0.6 ng/ml & 7.1 ± 2.1 ng/mg) when compared to first sample (0.6 ± 0.1 ng/ml & 2.6 ± 0.9 ng/mg) in critically ill neonates with AKI. Serum creatinine, uKIM-1 and uKIM-1/cr ratio were significantly associated with higher KDIGO stages. Applying the ROC curve at the first sample for discrimination between critically ill neonatal patients with and without AKI, uKIM-1/cr AUC was significantly higher when compared to AUCs of creatinine, eGFR, uKIM-1. Regression analysis revealed that high uKIM-1 & uKIM-1/cr are independent predictors for AKI within critically ill neonates. So, uKIM-1 & uKIM-1/cr are early biomarkers as their level increased before creatinine increases.

CONCLUSIONS

uKIM-1 and uKIM-1/cr are good early indicators for AKI in neonates suffering from a critical illness.

Myrcene Attenuates Renal Inflammation and Oxidative Stress in the Adrenalectomized Rat Model

Physiological Glucocorticoids are important regulators of the immune system. Pharmacological GCs are in widespread use to treat inflammatory diseases. Adrenalectomy (ADX) has been shown to exacerbate renal injury through inflammation and oxidative stress that results in renal impairment due to depletion of GCs. In this study, the effect of myrcene to attenuate renal inflammation and oxidative stress was evaluated in the adrenalectomized rat model. Rats were adrenalectomized bilaterally or the adrenals were not removed after surgery (sham). Myrcene (50 mg/kg body weight, orally) was administered post ADX. Myrcene treatment resulted in significant downregulation of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) compared to untreated ADX rats. In addition, myrcene resulted in significant downregulation of immunomodulatory factors (IFNγ and NF-κB) and anti-inflammatory markers (IL-4 and IL-10) in treated ADX compared to untreated ADX. Myrcene significantly increased the antioxidant molecules (CAT, GSH, and SOD) and decreased MDA levels in treated ADX compared to untreated. Moreover, myrcene treatment reduced the expression of COX-2, iNOS, KIM-1, and kidney functional molecules (UREA, LDH, total protein, and creatinine) in ADX treated compared to ADX untreated. These results suggest that myrcene could be further developed as a therapeutic drug for treatment of kidney inflammation and injury.

Ameliorative role of curcumin on copper oxide nanoparticles-mediated renal toxicity in rats: An investigation of molecular mechanisms

The increasing role of copper oxide nanoparticles (CuO NPs) in many industries and their broad range of applications increase its potential toxic effects. Curcumin possesses a wide range of health benefits. This study aimed to evaluate the role of curcumin in attenuating CuO NPs toxicity in rat kidney. Thirty six animals were divided into five groups; control groups (I, II), curcumin group orally received curcumin 200 mg/kg bw, CuO NPs group orally gavaged 250 mg/kg bw CuO NPs and combined group orally gavaged curcumin and CuO NPs. Treatment was given for 3 months. Administration of CuO NPs revealed elevation in serum creatinine and blood urea nitrogen levels, elevated kidney and urine levels of kidney injury molecule-1, decreased catalase, superoxide dismutase activities, total sulfhydryl, reduced glutathione content, increased serum reactive oxygen species, tissue total oxidant status, lipid hydroperoxides, protein carbonyl, malondialdehyde, nitric oxide levels, increased interleukin-1β, tumor necrosis factor-α, nuclear factor (NF-κB), and decreased heme oxygenase-1 (HO-1) and γ-glutamylcysteine synthetase (γ-GCS) genes expression. Moreover, histopathological alteration in kidney structure was detected. Immunohistochemical-stained sections by caspase-3 reaction revealed apoptosis. Pretreatment with curcumin improved most of the adverse effects in rats treated with CuO NPs regarding oxidative stress and inflammatory indices in kidney, and kept histopathological- and immunohistochemical-stained sections near to normal. This study shows that curcumin administration attenuates the toxicity in the kidney of CuO NPs-treated rats through its antioxidant, anti-inflammatory, and antiapoptotic effects.

Dietary sodium restriction decreases urinary NGAL in older adults with moderately elevated systolic blood pressure free from chronic kidney disease

Increased aortic stiffness may contribute to kidney damage by transferring excessive flow pulsatility to susceptible renal microvasculature, leading to constriction or vessel loss. We previously demonstrated that 5 weeks of dietary sodium restriction (DSR) reduces large-elastic artery stiffness as well as blood pressure in healthy middle-aged/older adults with moderately elevated systolic blood pressure (SBP) who are free from chronic kidney disease (CKD). We hypothesized that DSR in this cohort would also reduce urinary concentrations of renal tubular injury biomarkers, which predict incident CKD in the general population. We performed a post hoc analysis using stored 24 hours urine samples collected in 13 participants as part of a randomized, double-blind, crossover clinical trial of DSR (low sodium (LS) target: 50 mmol/day; normal sodium (NS) target: 150 mmol/day). Participants were 61±2 (mean±SEM) years (8 M/5 F) with a baseline blood pressure of 139±2/82±2 mm Hg and an estimated glomerular filtration rate of 79±3 mL/min/1.73 m² Twenty-four hour urinary sodium excretion was reduced from 149±7 to 66±8 mmol/day during week 5. Despite having preserved kidney function, participants had a 31% reduction in urinary neutrophil gelatinase-associated lipocalin concentrations with just 5 weeks of DSR (LS: 2.8±0.6 vs NS: 4.2±0.8 ng/mL, p<0.05). Results were similar when normalized to urinary creatinine (urinary creatinine did not change between conditions). Concentrations of another kidney tubular injury biomarker, kidney injury molecule-1, were below the detectable limit in all but one sample. In conclusion, DSR reduces an established clinical biomarker of kidney tubular damage in adults with moderately elevated SBP who are free from prevalent kidney disease.

KIM-1 and Kidney Disease Progression in Autosomal Dominant Polycystic Kidney Disease: HALT-PKD Results

BACKGROUND

Cyst compression of renal tubules plays a role in the progression of autosomal dominant polycystic kidney disease (ADPKD) and may induce expression of kidney injury molecule-1 (KIM-1). Whether urinary KIM-1 indexed for creatinine (uKIM-1/Cr) is a prognostic marker of disease progression in ADPKD is unknown.In this secondary analysis of a prospective cohort study, we sought to determine whether patients with high as opposed to low uKIM-1/CR at baseline had greater rates of eGFR loss and height-adjusted total kidney volume (HtTKV) increase.

METHODS

Baseline uKIM-1/Cr values were obtained from 754 participants in Halt Progression of Polycystic Kidney Disease (HALT-PKD) studies A (early ADPKD) and B (late ADPKD). The predictor was uKIM-1/Cr, which was dichotomized by a median value of 0.2417 pg/g, and the primary outcomes were measured longitudinally over time. Mixed-effects linear models were used in the analysis to calculate the annual slope of change in eGFR and HtTKV.

RESULTS

Patients with high uKIM-1/Cr (above the median) had an annual decline in eGFR that was 0.47 mL/min greater than that in those with low uKIM-1/Cr (p = 0.0015) after adjustment for all considered covariates. This association was seen in study B patients alone (0.45 mL/min; p = 0.009), but not in study A patients alone (0.42 mL/min; p = 0.06). High baseline uKIM-1/Cr was associated with higher HtTKV in the baseline cross-sectional analysis compared to low uKIM-1/Cr (p = 0.02), but there was no difference between the groups in the mixed-effects model annual slopes.

CONCLUSION

Elevated baseline uKIM-1/Cr is associated with a greater decline in eGFR over time. Further research is needed to determine whether uKIM-1/Cr improves risk stratification in patients with ADPKD.

Substitution of high-dose sucrose with fructose in high-fat diets resulted in higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine and phenylalanine, and higher urine concentrations of arginine and citrulline

High fructose intake has been shown to increase circulating alanine transaminase in humans, which could reflect damage to the liver by fructose but could also be linked to higher level of transamination of amino acids in liver. Therefore, we hypothesized that a diet with high content of fructose would affect the amino acid composition in rat plasma and urine differently from a diet with high sucrose content. Because high intake of sucrose and fructose is often accompanied with high intake of saturated fat in the Western-style diet, we wanted to compare the effects of high fructose/sucrose in diets with normal or high content of coconut oil on individual free amino acids plasma and urine. Male Wistar rats were fed diets with normal (10 wt%) or high (40 wt%) content of sucrose or fructose, with normal or high fat content (7 or 22 wt%) and 20 wt% protein (casein). Rats fed high-fructose high-fat diet had higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine, and phenylalanine and higher urine concentrations of arginine and citrulline when compared to rats fed high-sucrose high-fat diet. Substituting normal content of sucrose with fructose in the diets had little impact on amino acids in plasma and urine. Serum concentrations of alanine transaminase, aspartate transaminase, and creatinine, and urine cystatin C and T cell immunoglobulin mucin-1 concentrations were comparable between the groups and within normal ranges. To conclude, substituting high-dose sucrose with high-dose fructose in high-fat diets affected amino acid compositions in plasma and urine.

Mechanisms and pharmacokinetic/pharmacodynamic profiles underlying the low nephrotoxicity and ototoxicity of etimicin

Etimicin (ETM), a fourth-generation aminoglycosides (AGs), is now widely clinically used in China due to its high efficacy and low toxicity. However, the mechanisms underlying its low nephrotoxicity and ototoxicity remain unclear. In the present study we compared the antibacterial and toxicity profiles of etimicin, gentamicin (GM, a second-generation AG), and amikacin (AMK, a third-generation AG), and investigated their pharmacokinetic properties in the toxicity target organs (kidney and inner ear) and subcellular compartments. We first demonstrated that ETM exhibited superior antibacterial activities against clinical isolates to GM and AMK, and it exerted minimal nephrotoxicity and ototoxicity in rats following multi-dose administration. Then, we conducted pharmacokinetic studies in rats, showed that the three AGs accumulated in the kidney and inner ear with ETM being distributed to a lesser degree in the two toxicity target organs as compared with GM and AMK high-dose groups. Furthermore, we conducted in vitro experiments in NRK-52E rat renal tubular epithelial cells and HEI-OC1 cochlear hair cells, and revealed that all the three AGs were distributed predominantly in the mitochondria with ETM showing minimal accumulation; they not only directly inhibited the activity of mitochondrial complexes IV and V but also inhibited mitochondrial function and its related PGC-1α-NRF1-TFAM pathway; ETM caused minimal damage to the mitochondrial complex and mitochondrial biogenesis. Our results demonstrate that the minimal otonephrotoxicity of ETM results from its lesser accumulation in mitochondria of target cells and subsequently lesser inhibition of mitochondrial function. These results provide a new strategy for discovering novel AGs with high efficacy and low toxicity.

Effects of intact and hydrolysed blue whiting proteins on blood pressure and markers of kidney function in obese Zucker fa/fa rats

PURPOSE

To investigate the effects of diets containing intact or hydrolysed proteins from blue whiting (Micromesistius poutassou) on the development of high blood pressure and markers of kidney function in obese Zucker fa/fa rats which are prone to develop hypertension and renal failure.

METHODS

Male rats were fed isocaloric diets containing either intact blue whiting whole meal (BW-WM), blue whiting protein hydrolysate prepared with Alcalase^® (BW-HA) or blue whiting protein hydrolysate prepared with Protamex^® (BW-HP) as 1/3 of total protein with the remaining 2/3 as casein, or casein as sole protein source (control group). Blood pressure was measured at Day 0 and Day 32. Rats were housed in metabolic cages for 24 h for collection of urine in week 4. After 5 weeks, rats were euthanized and blood was drawn from the heart. The renin and angiotensin-converting enzyme (ACE) inhibition capacities for casein and blue whiting proteins were measured in vitro.

RESULTS

The blood pressure increase was lower in rats fed diets containing blue whiting proteins when compared to the control group, whereas markers of kidney function were similar between all groups. The three blue whiting proteins inhibited renin activity in vitro, whereas casein had no effect. The in vitro ACE inhibition was similar for casein, BW-WM and BW-HP proteins, whereas BW-HA protein was less potent.

CONCLUSION

Blue whiting protein feeding attenuated the blood pressure increase in obese Zucker fa/fa rats, possibly mediated through the renin-angiotensin system and without affecting markers of kidney function.

The Marker of Tubular Injury, Kidney Injury Molecule-1 (KIM-1), in Acute Kidney Injury Complicating Acute Pancreatitis: A Preliminary Study

Acute pancreatitis (AP) may be associated with severe inflammation and hypovolemia leading to organ complications including acute kidney injury (AKI). According to current guidelines, AKI diagnosis is based on dynamic increase in serum creatinine, however, creatinine increase may be influenced by nonrenal factor and appears late following kidney injury. Kidney injury molecule-1 (KIM-1) is a promising marker of renal tubular injury and it has not been studied in AP. Our aim was to assess if urinary KIM-1 may be used to diagnose AKI complicating the early stage of AP. We recruited 69 patients with mild to severe AP admitted to a secondary care hospital during the first 24 h from initial symptoms of AP. KIM-1 was measured in urine samples collected on the day of admission and two subsequent days of hospital stay. AKI was diagnosed based on creatinine increase according to Kidney Disease: Improving Global Outcomes 2012 guidelines. Urinary KIM-1 on study days 1 to 3 was not significantly higher in 10 patients who developed AKI as compared to those without AKI and did not correlate with serum creatinine or urea. On days 2 and 3, urinary KIM-1 correlated positively with urinary liver-type fatty acid-binding protein, another marker of tubular injury. On days 2 and 3, urinary KIM-1 was higher among patients with systemic inflammatory response syndrome, and several correlations between KIM-1 and inflammatory markers (procalcitonin, urokinase-type plasminogen activator receptor, C-reactive protein) were observed on days 1 to 3. With a limited number of patients, our study cannot exclude the diagnostic utility of KIM-1 in AP, however, our results do not support it. We hypothesize that the increase of KIM-1 in AKI complicating AP lasts a short time, and it may only be observed with more frequent monitoring of the marker. Moreover, urinary KIM-1 concentrations in AP are associated with inflammation severity.

Empagliflozin attenuates acute kidney injury after myocardial infarction in diabetic rats

Acute kidney injury (AKI) predicts poor prognosis in patients with acute myocardial infarction (MI) and diabetes mellitus (DM) is an independent risk factor of AKI. Recent clinical studies have shown the beneficial effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on cardiovascular and renal outcomes in patients with DM. We recently reported that canagliflozin normalized susceptibility of diabetic rats to AKI after acute MI via β-hydroxybutyrate-mediated suppression of NOX expression. Here we examined whether the same renoprotective effect is shared by empagliflozin. Serum creatinine levels were not changed by MI induced by coronary artery occlusion in LETO, non-diabetic control rats, and OLETF, obese type 2 diabetic rats. However, immunohistochemistry revealed that MI increased renal expression of NGAL and KIM-1, early markers of tubular injury, by 3.2-fold and 2.6-fold, respectively, in OLETF. These increases in injury markers were not observed in LETO. Pretreatment with empagliflozin of OLETF for 2 weeks improved hyperglycemia, increased blood β-hydroxybutyrate level, and suppressed MI-induced expression of NGAL and KIM-1. Empagliflozin suppressed upregulation of NOX2 and NOX4 in the kidney of OLETF. Taken together with the results of our previous study, it was concluded that treatment with the SGLT2 inhibitor protects the diabetic kidney from MI-induced AKI.

A combination of monosodium glutamate and high-fat and high-fructose diets increases the risk of kidney injury, gut dysbiosis and host-microbial co-metabolism

Consumption of either monosodium glutamate (MSG) or high-fat and high-fructose (HFF) diets changes the gut microbiome and hence contributes to development of several diseases. In this study, with an emphasis on kidney injury, hamsters were divided into 4 groups as follows: (1) hamsters fed with standard diet (control); (2) hamsters fed with standard diet and MSG in drinking water (MSG); (3) hamsters fed with high-fat and high-fructose diets (HFF), and (4) animals fed MSG+HFF. After 8 months, the animals were used for the study. Despite showing normal kidney function, hamsters fed with MSG+HFF exhibited signs of kidney damage as demonstrated by the highest expression levels of high-mobility group box-1 and kidney injury molecule-1 in kidney tissues, while slight changes of histopathological features in H&E-stained sections and normal levels of creatinine were observed, indicating possible early stages of kidney injury. Sequencing of the microbial 16S rRNA gene revealed that animals fed with the MSG+HFF diet had a higher ratio of gut Firmicutes/Bacteroidetes along with marked changes in abundance and diversity of gut microbiome compared to hamsters fed with MSG or HFF alone. In addition, ¹H Nuclear magnetic resonance spectroscopy showed an elevation of urine p-cresol sulfate levels in the MSG+HFF group. These results indicate that consumption of both MSG and HFF increases the risk of kidney injury, induces gut dysbiosis and an increase in the amount of p-cresol sulfate in hamsters.

The association of renal tubular inflammatory and injury markers with uric acid excretion in chronic kidney disease patients

AIM

To investigate the correlation of renal tubular inflammatory and injury markers with renal uric acid excretion in chronic kidney disease (CKD) patients.

METHODS

Seventy-three patients with CKD were enrolled. Fasting blood and morning urine sample were collected for routine laboratory measurements. At the same time, 24 h of urine was collected for urine biochemistry analyses, and 10 ml was extracted from the 24-h urine sample to further detect renal tubular inflammatory and injury markers, including interleukin-18 (IL-18), interleukin 1β (IL-1β), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). The patients were divided into three tertile groups according to their 24-h urinary uric acid (24-h UUA) levels (UUA1: 24-h UUA ≤ 393.12 mg; UUA2: 393.12 < 24-h UUA ≤ 515.76 mg; UUA3: 24-h UUA > 515.76 mg). The general clinical and biochemical indexes were compared. Multivariable linear regression models were used to test the association of IL-18/Urinary creatinine concentration (IL-18/CR), IL-1β/CR, NGAL/CR and KIM-1/CR with renal uric acid excretion indicators.

RESULTS

All of tested renal tubular inflammation- and injury-related urinary markers were negatively associated with 24-h UUA and UEUA, and the negative correlation still persisted after adjusting for multiple influencing factors including urinary protein and eGFR. Further group analyses showed that these makers were significantly higher in the UUA1 than in the UUA3 group.

CONCLUSIONS

Our findings suggest that markers of urinary interstitial inflammation and injury in CKD patients are significantly correlated with 24-h UUA and Urinary excretion of uric acid (UEUA), and those with high 24-h UUA have lower levels of these markers. Renal uric acid excretion may also reflect the inflammation and injury of renal tubules under certain conditions.

Inhibition of Inflammatory Cytokine Expression Prevents High-Fat Diet-Induced Kidney Injury: Role of Lingonberry Supplementation

Chronic low-grade inflammation is a major stimulus for progression of chronic kidney disease (CKD) in individuals consuming high-fat diet. Currently, there are limited treatment options for CKD other than controlling the progression rate and its associated complications. Lingonberry (Vaccinium vitis-idaea L.) is rich in anthocyanins with demonstrated anti-inflammatory effect. In the current study, we investigated the potential renal protective effect of lingonberry and its anthocyanin (cyanidin-3-glucoside) in high-fat diet fed obese mice and in human proximal tubular cells. Prolonged consumption of high-fat diets is strongly associated with obesity, abnormal lipid and glucose metabolism. Mice (C57BL/6J) fed a high-fat diet (62% kcal fat) for 12 weeks developed renal injury as indicated by an elevation of blood urea nitrogen (BUN) level as well as an increase in renal kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and renin expression. Those mice displayed an activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and increased expression of inflammatory cytokines-monocyte chemoattractant-1 (MCP-1), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) in the kidneys. Mice fed a high-fat diet also had a significant elevation of inflammatory cytokine levels in the plasma. Dietary supplementation of lingonberry for 12 weeks not only attenuated high-fat diet-induced renal inflammatory response but also reduced kidney injury. Such a treatment improved plasma lipid and glucose profiles, reduced plasma inflammatory cytokine levels but did not affect body weight gain induced by high-fat diet feeding. Lingonberry extract or its active component cyanidin-3-glucoside effectively inhibited palmitic acid-induced NF-κB activation and inflammatory cytokine expression in proximal tubular cells. These results suggest that lingonberry supplementation can reduce inflammatory response and prevent chronic kidney injury. Such a renal protective effect by lingonberry and its active component may be mediated, in part, through NF-κB signaling pathway.

The role of phosphatidylserine recognition receptors in multiple biological functions

Apoptotic cells are rapidly engulfed and degraded by phagocytes through efferocytosis. Efferocytosis is a highly regulated process. It is triggered upon the activation of caspase-dependent apoptosis, which in turn promotes the expression of "eat me" signals on the surface of dying cells and the release of soluble "find me" signals for the recruitment of phagocytes. To date, many "eat me" signals have been recognized, including phosphatidylserine (PS), intercellular adhesion molecule-3, carbohydrates (e.g., amino sugars, mannose) and calreticulin. Among them, PS is the most studied one. PS recognition receptors are different functionally active receptors expressed by phagocytes. Various PS recognition receptors with different structure, cell type expression, and ability to bind to PS have been recognized. Although PS recognition receptors do not fall into a single classification or family of proteins due to their structural differences, they all share the common ability to activate downstream signaling pathways leading to the production of anti-inflammatory mediators. In this review, available evidence regarding molecular mechanisms underlying PS recognition receptor-regulated clearance of apoptotic cells is discussed. In addition, some efferocytosis-independent biological functions of PS recognition receptors are reviewed.

Renoprotective Effects of Alpha Lipoic Acid on Iron Overload-Induced Kidney Injury in Rats by Suppressing NADPH Oxidase 4 and p38 MAPK Signaling

We aimed to investigate the protective effect of alpha lipoic acid (ALA), a powerful antioxidant, against oxidative kidney damage induced by iron overload in rats. Male Wistar albino rats were separated into groups: control (n = 7), ALA (100 mg/kg (n = 7), iron sucrose (IS) (40 mg/kg) (n = 7), and IS + ALA (40 mg/kg IS administration followed by 100 mg/kg ALA) (n = 7). IS and ALA were injected weekly for 4 weeks via the tail vein. Blood and kidneys were collected at sacrification on day 29. Serum creatinine and iron levels were analyzed. Tubular injury and iron deposits were evaluated histopathologically. Additionally, iron, malondialdehyde (MDA), superoxide dismutase (SOD), catalase, and glutathione (GSH) levels and mRNA expressions of the subunits of NADPH oxidase, known as NOX4 and p22^phox, tumor necrosis factor (TNF)-α, kidney injury molecule-1 (KIM-1), and also p38 MAPK signaling in the kidneys, were evaluated biochemically. In the IS group, serum creatinine and iron level, tubular dilation, and loss of brush border in the kidneys were significantly higher than those of the control. Although those changes were reduced by ALA, the differences were not statistically significant. However, ALA reduced significantly MDA level and increased SOD activity in the kidney during IS administration. ALA also significantly reduced mRNA expressions of NOX4 and p22^phox induced by IS, which was parallel to significant decreases of TNF-α and KIM-1 mRNA expressions. Moreover, ALA could suppress the activation of p38 MAPK during IS administration. In conclusion, ALA may be an effective strategy to attenuate in IS-induced oxidative kidney injury.

A Multi-omic Association Study of Trimethylamine N-Oxide

Trimethylamine N-oxide (TMAO) is a circulating metabolite that has been implicated in the development of atherosclerosis and cardiovascular disease (CVD). In this paper, we identify blood markers, metabolites, proteins, gut microbiota patterns, and diets that are significantly associated with levels of plasma TMAO. We find that kidney markers are strongly associated with TMAO and identify CVD-related proteins that are positively correlated with TMAO. We show that metabolites derived by the gut microbiota are strongly correlated with TMAO and that the magnitude of this correlation varies with kidney function. Moreover, we identify diet-associated patterns in the microbiome that are correlated with TMAO. These findings suggest that both the process of TMAO accumulation and the mechanism by which TMAO promotes atherosclerosis are a complex interplay between diet and the microbiome on one hand and other system-level factors such as circulating proteins, metabolites, and kidney function.

Potential Role and Excretion Level of Urinary Transferrin, KIM-1, RBP, MCP-1 and NGAL Markers in Diabetic Nephropathy

BACKGROUND

Analyzing urinary biomarkers may provide better insight into pathophysiological mechanisms of diabetic kidney diseases. The study aimed to analyze the pattern of selected excreted urinary biomarkers and its correlation with albuminuria and estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

METHODS

A total of 185 patients with type 2 diabetes were categorized according to KDIGO guideline based on albuminuria and eGFR. The urinary markers (transferrin, KIM-1, RBP, MCP-1 and NGAL) were measured by ELISA.

RESULTS

The urinary markers were associated with eGFR (total protein/Cr, p=0.001; RBP/Cr, p=0.007; MCP-1/Cr, p=0.023; NGAL/Cr, p=0.011) and albuminuria (total protein/Cr, p<0.001; transferrin, p<0.001; RBP/Cr, p<0.001; MCP-1/Cr, p<0.001; NGAL/Cr, p=0.002).

CONCLUSION

The urinary marker levels (total protein, RBP, MCP-1, and NGAL) are elevated with severity of kidney damage and expressed more in progressive renal impairment.

Preventive effects of fraxin on ischemia/reperfusion-induced acute kidney injury in rats

AIM

Kidney ischemia reperfusion (IR) injury is an important health problem resulting in acute kidney failure. The oxidative stress and inflammatory process are the underlying mechanisms of IR injury. It has been purposed in this study to research the possible protective effects of fraxin on kidney injury induced by IR.

MATERIAL AND METHODS

32 Sprague Dawley male rats were divided into 4 groups. The groups were organized as follows; sham, IR, IR + fraxin 10 mg/kg, and IR + 50 mg/kg fraxin groups. Some oxidant, antioxidant and inflammatory parameters were evaluated in kidney tissues removed at the end of our experimental study.

KEY FINDINGS

It was detected that the oxidant and proinflammatory markers increased and antioxidant parameters decreased in IR group but the results significantly reversed in treatment groups compared to IR group. And also, 8-OHdG, NF-κB, HAVCR1 immunopositivities were at severe levels and these results attenuated in IR fraxin + 10 mg/kg, and IR + fraxin 50 mg/kg groups.

SIGNIFICANCE

These presented results have shown that fraxin performed protective effects against kidney injury induced by IR.

Baseline tubular biomarkers in young adults with congenital heart disease as compared to healthy young adults: Detecting subclinical kidney injury

BACKGROUND

There are significant implications for kidney disease in young adults with congenital heart disease. Prior investigations have not focused on the use of urinary tubular biomarkers for the early identification of kidney disease in this growing patient group.

OBJECTIVE

Determine if young adults with congenital heart disease have differences in the baseline concentration of urinary tubular biomarkers when compared to healthy young adults.

DESIGN/METHODS

In a pilot case control study, 30 patients from 18 to 35 years of age with congenital heart disease and a normal serum creatinine were recruited during a routine follow-up visit. In the same age group, 30 control subjects without history of heart or kidney disease were recruited. Urine samples were obtained to measure beta 2-microglobin, alpha 1-microglobin, N-acetyl-B-D-glucosaminidase, liver fatty acid binding protein, kidney injury molecule-1, insulin-like growth factor binding protein 7, and tissue inhibitor of metalloproteinases-2. Comparisons were done using Wilcoxon rank-sum or Fisher's exact test.

RESULTS

No study participants had proteinuria on urine dipstick. Median concentrations of kidney injury molecule-1 were higher (P = .01) and concentrations of insulin-like growth factor binding protein 7 (P = .001) and tissue inhibitor of metalloproteinases-2 (P = .009) were lower in the subjects with congenital heart disease when compared to the control subjects. There were no significant differences between the groups with respect to the other biomarkers.

CONCLUSION

Our data suggest that young adults with congenital heart disease may have subclinical kidney dysfunction. Lower levels of insulin-like growth factor binding protein 7 and tissue inhibitor of metalloproteinases-2 may indicate an impaired ability to respond to injury, while higher levels of kidney injury molecule-1 may reflect early tubular injury.

A specific immunoassay for detection of feline kidney injury molecule 1

OBJECTIVES

The aim of this study was to design and carry out a preliminary evaluation of a urine point-of-care test for kidney injury molecule 1 (KIM-1) in healthy and diseased cats.

METHODS

Part of the feline KIM-1 gene was amplified, ligated into a plasmid with a signal peptide and monomeric human IgGFc, and transfected into a mammalian cell line. Supernatant was purified and tested for the fusion protein by gel electrophoresis and Western blot. Mice were immunized three times with purified proteins, and hybridomas were generated from splenocytes. Antibodies were tested by ELISA for detection of recombinant KIM-1 and naturally occurring KIM-1 in disease-state urine. Next, a lateral flow assay (LFA) with capture and detection antibodies was constructed, and tested with 34 urine samples from healthy and diseased cats. Antibodies were also tested for reactivity with formalin-fixed paraffin-embedded kidney tissue.

RESULTS

Three antibodies were assessed. Antibodies detected between 0.4 and 60 ng/ml feline KIM-1 fusion protein in the LFA. Urine samples from healthy cats yielded faint bands in the LFA corresponding to optical density (OD) values of 4.8-8.8. Samples from cats with suspected or confirmed acute kidney injury (AKI) had OD values ranging from 1.6-20.5. Urine KIM-1 varied over multiple days in cats with sepsis or urethral obstruction despite normalizing serum creatinine concentration. In tissue sections, KIM-1 antibodies labeled tubular cells with morphological features of injury.

CONCLUSIONS AND RELEVANCE

A practical patient-side assay for detection of KIM-1 in feline urine has been developed. Preliminary results show marked though transient increases in cats with sepsis and urethral obstruction-associated AKI, and expression in injured tubules. Although initial data indicating that the LFA is sensitive and specific for KIM-1 in cats with AKI are promising, values associated with different types of injury, urine collection, urine storage and specific gravity need to be investigated.

Ligustrazine suppresses renal NMDAR1 and caspase-3 expressions in a mouse model of sepsis-associated acute kidney injury

Sepsis-associated acute kidney injury (AKI) is a life threatening condition with high morbidity and mortality. The pathogenesis of AKI is associated with apoptosis. In this study, we investigated the effects of ligustrazine (LGZ) on experimental sepsis-associated AKI in mice. Sepsis-associated AKI was induced in a mice model using cecal ligation and puncture (CLP) method. Mice were administered LGZ (10, 30, and 60 mg/kg) via tail vein injection 0.5 h before CLP surgery. Mice survival was evaluated. Renal water content was detected. Urine samples were collected for ELISA of Kim1. Kidneys were collected for nucleic acid analysis and histological examination. Pathological assessment was used to determine the effect of LGZ on sepsis-associated AKI. Caspase-3 expression in kidney was assessed by immunohistochemistry. Renal NMDAR1 level was also determined. Treatment of LGZ improved mice survival rate; the effect was significant when administered at a high LGZ dose (60 mg/kg). Renal water content of mice undergoing CLP was significantly reduced by LGZ treatment. Both middle-dose and high-dose LGZ treatments reduced urine Kim1 level in sepsis-associated AKI mice. The severity of AKI in septic mice was reduced by middle-dose and high-dose LGZ administration. Immunohistochemical analysis revealed decreased caspase-3 and NMDAR1 levels in the kidney following middle-dose and high-dose LGZ treatments. RT-PCR assay showed a significant reduction in NMDAR1 mRNA expression in the kidney of middle-dose and high-dose LGZ-treated mice. LGZ exhibited protective effects against sepsis-associated AKI in mice, possibly via downregulation of renal NMDAR1 expression and its anti-apoptotic action by inhibiting caspase-3.

Promising therapeutic effect of thapsigargin nanoparticles on chronic kidney disease through the activation of Nrf2 and FoxO1

Pathophysiological states cause misfolded protein accumulation in the endoplasmic reticulum (ER). Then, ER stress and the unfolded protein response (UPR) are activated. Targeting ER stress may enhance the adaptive UPR and then protect the cell against pathogenic environments. In the present study, we utilized nanotechnology to synthesize thapsigargin nanoparticles (TG NPs) which induced ER stress and the UPR pathway, to study the role of ER stress and autophagy in chronic kidney disease (CKD). We found that the mRNA levels of ER stress- and autophagy-related molecules were elevated in the renal tissue of CKD patients compared to those of healthy individuals. Furthermore, TG NPs induced the UPR pathway and autophagy in HK-2 human kidney tubular epithelial cells. TG NPs protected HK-2 cells against oxidative stress-induced cell death through the activation of Nrf2 and FoxO1. The siRNA-mediated inhibition of Nrf2 or FoxO1 resulted in enhanced oxidative stress-induced cytotoxicity in HK-2 cells. In a mouse model of adenine diet-induced CKD, TG NPs and KIM-1-TG NPs ameliorated renal injury through the stimulation of ER stress and its downstream pathways. Our findings suggest that the induction of ER stress using pharmacological agents may offer a promising therapeutic strategy for preventing or interfering with CKD progression.

Blocking Complement Factor B Activation Reduces Renal Injury and Inflammation in a Rat Brain Death Model

Introduction: The majority of kidneys used for transplantation are retrieved from brain-dead organ donors. In brain death, the irreversible loss of brain functions results in hemodynamic instability, hormonal changes and immunological activation. Recently, brain death has been shown to cause activation of the complement system, which is adversely associated with renal allograft outcome in recipients. Modulation of the complement system in the brain-dead donor might be a promising strategy to improve organ quality before transplantation. This study investigated the effect of an inhibitory antibody against complement factor B on brain death-induced renal inflammation and injury. Method: Brain death was induced in male Fischer rats by inflating a balloon catheter in the epidural space. Anti-factor B (anti-FB) or saline was administered intravenously 20 min before the induction of brain death (n = 8/group). Sham-operated rats served as controls (n = 4). After 4 h of brain death, renal function, renal injury, and inflammation were assessed. Results: Pretreatment with anti-FB resulted in significantly less systemic and local complement activation than in saline-treated rats after brain death. Moreover, anti-FB treatment preserved renal function, reflected by significantly reduced serum creatinine levels compared to saline-treated rats after 4 h of brain death. Furthermore, anti-FB significantly attenuated histological injury, as seen by reduced tubular injury scores, lower renal gene expression levels (>75%) and renal deposition of kidney injury marker-1. In addition, anti-FB treatment significantly prevented renal macrophage influx and reduced systemic IL-6 levels compared to saline-treated rats after brain death. Lastly, renal gene expression of IL-6, MCP-1, and VCAM-1 were significantly reduced in rats treated with anti-FB. Conclusion: This study shows that donor pretreatment with anti-FB preserved renal function, reduced renal damage and inflammation prior to transplantation. Therefore, inhibition of factor B in organ donors might be a promising strategy to reduce brain death-induced renal injury and inflammation.

The Predictive Role of the Biomarker Kidney Molecule-1 (KIM-1) in Acute Kidney Injury (AKI) Cisplatin-Induced Nephrotoxicity

Acute kidney injury (AKI) following platinum-based chemotherapeutics is a frequently reported serious side-effect. However, there are no approved biomarkers that can properly identify proximal tubular injury while routine assessments such as serum creatinine lack sensitivity. Kidney-injury-molecule 1 (KIM-1) is showing promise in identifying cisplatin-induced renal injury both in vitro and in vivo studies. In this review, we focus on describing the mechanisms of renal tubular cells cisplatin-induced apoptosis, the associated inflammatory response and oxidative stress and the role of KIM-1 as a possible biomarker used to predict cisplatin associated AKI.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.