Novel insights into the relationship between glomerular pathology and progressive kidney disease

Podocytes from hypertensive and obese mice acquire an inflammatory, senescent, and aged phenotype

Patients with hypertension or obesity can develop glomerular dysfunction characterized by injury and depletion of podocytes. To better understand the molecular processes involved, young mice were treated with either deoxycorticosterone acetate (DOCA) or fed a high-fat diet (HFD) to induce hypertension or obesity, respectively. The transcriptional changes associated with these phenotypes were measured by unbiased bulk mRNA sequencing of isolated podocytes from experimental models and their respective controls. Key findings were validated by immunostaining. In addition to a decrease in canonical proteins and reduced podocyte number, podocytes from both hypertensive and obese mice exhibited a sterile inflammatory phenotype characterized by increases in NLR family pyrin domain containing 3 (NLRP3) inflammasome, protein cell death-1, and Toll-like receptor pathways. Finally, although the mice were young, podocytes in both models exhibited increased expression of senescence and aging genes, including genes consistent with a senescence-associated secretory phenotype. However, there were differences between the hypertension- and obesity-associated senescence phenotypes. Both show stress-induced podocyte senescence characterized by increased p21 and p53. Moreover, in hypertensive mice, this is superimposed upon age-associated podocyte senescence characterized by increased p16 and p19. These results suggest that senescence, aging, and inflammation are critical aspects of the podocyte phenotype in experimental hypertension and obesity in mice.NEW & NOTEWORTHY Hypertension and obesity can lead to glomerular dysfunction in patients, causing podocyte injury and depletion. Here, young mice given deoxycorticosterone acetate or a high-fat diet to induce hypertension or obesity, respectively. mRNA sequencing of isolated podocytes showed transcriptional changes consistent with senescence, a senescent-associated secretory phenotype, and aging, which was confirmed by immunostaining. Ongoing studies are determining the mechanistic roles of the accelerated aging podocyte phenotype in experimental hypertension and obesity.

Biomarkers and signaling pathways of diabetic nephropathy and peripheral neuropathy: possible therapeutic intervention of rutin and quercetin

Diabetic nephropathy and peripheral neuropathy are the two main complications of chronic diabetes that contribute to high morbidity and mortality. These conditions are characterized by the dysregulation of multiple molecular signaling pathways and the presence of specific biomarkers such as inflammatory cytokines, indicators of oxidative stress, and components of the renin-angiotensin system. In this review, we systematically collected and collated the relevant information from MEDLINE, EMBASE, ELSEVIER, PUBMED, GOOGLE, WEB OF SCIENCE, and SCOPUS databases. This review was conceived with primary objective of revealing the functions of these biomarkers and signaling pathways in the initiation and progression of diabetic nephropathy and peripheral neuropathy. We also highlighted the potential therapeutic effectiveness of rutin and quercetin, two plant-derived flavonoids known for their antioxidant and anti-inflammatory properties. The findings of our study demonstrated that both flavonoids can regulate important disease-promoting systems, such as inflammation, oxidative stress, and dysregulation of the renin-angiotensin system. Importantly, rutin and quercetin have shown protective benefits against nephropathy and neuropathy in diabetic animal models, suggesting them as potential therapeutic agents. These findings provide a solid foundation for further comprehensive investigations and clinical trials to evaluate the potential of rutin and quercetin in the management of diabetic nephropathy and peripheral neuropathy. This may contribute to the development of more efficient and comprehensive treatment approaches for diabetes-associated complications.

Nicotinamide riboside activates renal metabolism and protects the kidney in a model of Alport syndrome

Chronic kidney disease (CKD) is associated with renal metabolic disturbances, including impaired fatty acid oxidation (FAO). Nicotinamide adenine dinucleotide (NAD + ) is a small molecule that participates in hundreds of metabolism-related reactions. NAD + levels are decreased in CKD, and NAD + supplementation is protective. However, both the mechanism of how NAD + supplementation protects from CKD, as well as the cell types most responsible, are poorly understood. Using a mouse model of Alport syndrome, we show that nicotinamide riboside (NR), an NAD + precursor, stimulates renal peroxisome proliferator-activated receptor α signaling and restores FAO in the proximal tubules, thereby protecting from CKD in both sexes. Bulk RNA-sequencing shows that renal metabolic pathways are impaired in Alport mice and dramatically activated by NR in both sexes. These transcriptional changes are confirmed by orthogonal imaging techniques and biochemical assays. Single nuclei RNA-sequencing and spatial transcriptomics, both the first of their kind from Alport mice, show that NAD + supplementation restores FAO in the proximal tubules with minimal effects on the podocytes. Finally, we also report, for the first time, sex differences at the transcriptional level in this Alport model. Male Alport mice had more severe inflammation and fibrosis than female mice at the transcriptional level. In summary, the data herein identify both the protective mechanism and location of NAD + supplementation in this model of CKD.

Screening candidate diagnostic biomarkers for diabetic kidney disease

BACKGROUND

There are big differences in treatments and prognosis between diabetic kidney disease (DKD) and non-diabetic renal disease (NDRD). However, DKD patients couldn't be diagnosed early due to lack of special biomarkers. Urine is an ideal non-invasive sample for screening DKD biomarkers. This study aims to explore DKD special biomarkers by urinary proteomics.

MATERIALS AND METHODS

According to the result of renal biopsy, 142 type 2 diabetes mellitus (T2DM) patients were divided into 2 groups: DKD (n = 83) and NDRD (n = 59). Ten patients were selected from each group to define urinary protein profiles by label-free quantitative proteomics. The candidate proteins were further verifyied by parallel reaction monitoring (PRM) methods (n = 40). Proteins which perform the same trend both in PRM and proteomics were verified by enzyme-linked immunosorbent assays (ELISA) with expanding the sample size (n = 82). The area under the receiver operating characteristic curve (AUC) was used to evaluate the accuracy of diagnostic biomarkers.

RESULTS

We identified 417 peptides in urinary proteins showing significant difference between DKD and NDRD. PRM verification identified C7, SERPINA4, IGHG1, SEMG2, PGLS, GGT1, CDH2, CDH1 was consistent with the proteomic results and p < 0.05. Three potential biomarkers for DKD, C7, SERPINA4, and gGT1, were verified by ELISA. The combinatied SERPINA4/Ucr and gGT1/Ucr (AUC = 0.758, p = 0.001) displayed higher diagnostic efficiency than C7/Ucr (AUC = 0.632, p = 0.048), SERPINA4/Ucr (AUC = 0.661, p = 0.032), and gGT1/Ucr (AUC = 0.661, p = 0.029) respectively.

CONCLUSIONS

The combined index SERPINA4/Ucr and gGT1/Ucr can be considered as candidate biomarkers for diabetic nephropathy after adjusting by urine creatinine.

Novel Biomarkers of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a highly prevalent condition worldwide. It represents one of the most common complications arising from diabetes mellitus (DM) and is the leading cause of end-stage kidney disease (ESKD). Its development involves three fundamental components: the hemodynamic, metabolic, and inflammatory axes. Clinically, persistent albuminuria in association with a progressive decline in glomerular filtration rate (GFR) defines this disease. However, as these alterations are not specific to DKD, there is a need to discuss novel biomarkers arising from its pathogenesis which may aid in the diagnosis, follow-up, therapeutic response, and prognosis of the disease.

Urinary Epidermal Growth Factor: A Promising "Next Generation" Biomarker in Kidney Disease

BACKGROUND

The epidermal growth factor (EGF) is a globular protein that is generated in the kidney, especially in the loop of Henle and the distal convoluted tubule. While EGF is nonexistent or hardly detectable in plasma, it is present in normal people's urine. Until now, risk stratification and chronic kidney disease (CKD) diagnosis have relied on estimated glomerular filtration rate (eGFR) and urine albumin/creatinine ratio (uACR), both of which reflect glomerular function or impairment. Tubular dysfunction, on the other hand, may also be associated with renal failure.

SUMMARY

Because decreased urine EGF (uEGF) indicates tubular atrophy and interstitial fibrosis, this biomarker, together with eGFR and uACR, may be employed in the general population for risk assessment and diagnosis of CKD. uEGF levels have been shown to correlate with intrarenal EGF mRNA expression and have been found to decrease in a variety of glomerular and non-glomerular kidney disorders.

KEY MESSAGE

uEGF, uEGF/creatinine, or uEGF/monocyte chemotactic peptide-1 are possible "new generation" biomarkers linked to a variety of kidney diseases that deserve further investigation as a single biomarker or as part of a multi-biomarker panel.

Urinary IgG, serum CX3CL1 and miRNA-152-3p: as predictors of nephropathy in Egyptian type 2 diabetic patients

The purpose of this study was to assess the role of urinary IgG, serum CX3CL1 and miRNA 152-3p levels as predictors of nephropathy in type 2 Egyptian diabetic patients. Sixty type 2 diabetic patients and twenty healthy controls were enrolled in a cross-sectional study. Then they were grouped into: three groups based upon urine albumin excretion (UAE). The expression of miRNA 152-3p in serum was measured using quantitative polymerase chain reaction (RTq-PCR). Serum CX3CL1 and urinary IgG concentrations were measured by ELISA. RTq-PCR revealed that serum miRNA-152-3p levels in patients were significantly higher than in controls. There was significant differences between group with normoalbuminuria and groups with diabetic nephropathy DN as regard to age, duration of nephropathy, Albumin/Creatinine ratio (A/C ratio), creatinine, urine IgG, CX3CL1 and HbA1c. In diabetic patients, there was a significant positive correlation between miRNA-152-3p levels and disease duration only as well as significant positive correlations between urinary IgG levels and age, disease duration, serum creatinine, A/C ratio, and urea. Positive correlation between serum fractalkine CX3CL1 level and age, duration of disease, urea, creatinine, A/C ratio, HbA1C and IgG in patient with DN. Serum CX3CL1 level, urinary IgG were significantly increased with the progress of nephropathy so these integrated biomarkers could be used as good predictors for early identification of nephropathy. But miRNA- 152-3p has inadequate prognostic indicator for ESRD progression.

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 Neutrophil Gelatinase-Associated Lipocalin versus Conventional Biomarkers in Predicting Response to Treatment of Active Lupus Nephritis

Introduction

Lupus nephritis (LN) affects almost two-thirds of systemic lupus erythematosus (SLE) patients. Despite initial aggressive therapy, up to 25% of patients with LN will progress to permanent renal damage. Conventional serum markers for LN lack the sensitivity of an ideal biomarker. Urinary neutrophil gelatinase-associated lipocalin (UNGAL) is an excellent biomarker for early diagnosis of acute kidney injury and predicting renal outcomes.

Objective

To measure UNGAL among LN patients to correlate its levels with renal disease activity and to investigate its predictive performance in response to induction therapy. Patients and Methods. 40 SLE patients with biopsy-proven LN class III, IV, or V were randomly selected. The study was conducted in the internal medicine department and outpatient clinic in Ain Shams University Hospitals and completed after six months. UNGAL was measured at baseline, three-month follow-up, and after complete induction therapy.

Results

In LN patients at baseline, the mean serum creatinine was 2.57 ± 0.96 mg/dL and the mean UNGAL was 33.50 ± 18.34 ng/dL. Mean UNGAL levels of complete response, partial response, and nonresponse groups were 14.48 ± 2.99 ng/mL, 34.49 ± 4.09 ng/mL, and 62.07 ± 14.44 ng/mL, respectively. Based on the ROC curve, we found a better performance of baseline UNGAL to discriminate the complete response group from partial and nonresponse groups to predict response to induction, outperforming conventional biomarkers. The area under the curve was 0.943, and the best cutoff level was 26.5 ng/mL (92.31% sensitivity and 88.89% specificity).

Conclusion

UNGAL performed better than conventional biomarkers in predicting response to treatment of active LN.

Electrophoretic analysis (sds-page) of canine urinary proteins according to the stage of chronic kidney disease

ABSTRACT Glomerular proteinuria is characterized by the loss of high-molecular-weight proteins (HMWPs), while tubulointerstitial proteinuria is characterized by the loss of low-molecular-weight proteins (LMWPs). The objective was to assess the molecular weight of urinary proteins (MWUP) in dogs with naturally acquired CKD and determine the proportion of HMWPs and LMWPs according to CKD stage. Twenty-eight dogs with CKD were recruited and divided into 4 groups based on serum creatinine (Cr) levels (group1: Cr<1,4, n=8; group2: 1,4<Cr<2,0, n=6; group3: 2,1<Cr<5, n=9; group4: Cr>5,0, n=5). The control group consisted of 5 healthy dogs. The MWUP was determined by SDS-PAGE. The urinary protein-to-creatinine ratio (UP/C) was used to quantitatively assess proteinuria. The electrophoresis pattern revealed a proportionally greater loss of HMWPthan of LMWP in all groups with CKD and an increased loss of LMWP in group 4 (P<0.05). These results suggest a predominance of glomerular injuries throughout all stages of CKD in these dogs and an increase in tubulointerstitial injury towards the end-stage of the disease. The results of the present study support the recommendation of SDS-PAGE as an effective technique for the qualitative assessment of proteinuria, as well as a method for assessing the severity and location of renal injury.

Assessment of two novel renal tubular proteins in type 2 diabetic patients with nephropathy

Nephropathy is a common health issue associated with type 2 diabetes mellitus (T2DM). Treatment of diabetic nephropathy (DN) in an early stage can effectively inhibit its progression. Albuminuria is the currently accepted marker for detection of DN.This study aims to evaluate the urinary level of two novel renal tubular proteins (cyclophilin A and periostin) in patients with T2DM and among different nephropathy stages and also to validate the diagnostic accuracy of both cyclophilin A and periostin as potential markers for early prediction of DN relative to albuminuria.This cross-sectional study recruited 137 patients with T2DM, and they were divided based on their urinary albumin:creatinine ratio into T2DM with normoalbuminuria (group II), incipient T2DN with microalbuminuria (group III) and overt T2DN with macroalbuminuria (group IV) beside 41 healthy subjects as group I Cyclophilin A and periostin were measured in the urine using ELISA. Diagnostic accuracy of both markers was determined for prediction of DN via receiver operating characteristic curve analyses.Urinary cyclophilin A and periostin levels were significantly higher in DN groups when compared with T2DM with normoalbuminuria group. For prediction of incipient and overt DN, areas under the curve (AUCs) of periostin were 0.954, 0.997 and cyclophilin A were 0.914, 0.937, respectively. AUCs of periostin were higher than that for cyclophilin A with a significant AUC difference (p=0.022) in overt DN stage.Periostin and cyclophilin A could be regarded as a potential urinary biomarker for early prediction of DN. Periostin exhibits a higher diagnostic accuracy than urinary cyclophilin A specifically in overt DN stage.

Exposure to environmental pollutants and a marker of early kidney injury in the general population: Results of a nationally representative cross-sectional study based on the Korean National Environmental Health Survey (KoNEHS) 2012-2014

Exposure to environmental pollutants may lead to early kidney injury, chronic kidney disease (CKD) and end-stage renal disease (ESRD). This study investigated the early renal effects associated with exposure to endocrine-disrupting chemicals (EDCs) and heavy metals using general Korean population data. We used data from the Second Korean National Environmental Health Survey (2012-2014). As exposure markers, the concentrations of EDCs, such as triclosan (TCS), bisphenol A (BPA) and phthalate metabolites (DEHP, MnBP and MBzP), and heavy metals, such as cadmium, lead and mercury were analyzed. As an early kidney injury marker, the urinary concentration of β₂-microglobulin (β₂M) was measured. Multiple linear regression was used to analyze the relationship between environmental pollutants and β₂M. A total of 5489 people (male: 2538, female: 2951) aged 19 years and older were enrolled. The geometric mean (GM) concentration of β₂M in the total population was 1.88 μg/g creatinine (95% confidence interval (CI) 1.85-1.91). The β₂M concentrations were significantly higher in cases of female, old age, low income, and presence of a history of diabetes mellitus or hypertension. The GM concentrations of urinary TCS and cadmium were 1.16 μg/g creatinine (95% CI 1.11-1.21) and 0.57 μg/g creatinine (95% CI 0.57-0.59), respectively. TCS, DEHP, cadmium, lead, and mercury exposure was significantly positively related to urinary β₂M in the multiple regression analysis. β₂M levels increased significantly with increases in the cadmium, mercury, and lead levels (p for trend <0.0001). The higher the DEHP, MnBP, and TCS concentrations, the higher the β₂M level (p for trend <0.01). Environmental pollutants exposure significantly increased urinary β₂M levels in the general Korean population. To prevent the development of early kidney injury and CKD, it is important to reduce environmental pollutants exposure through regulatory measures, and cooperation between related bodies in both developing and developed countries.

Urinary biomarkers of tubular injury to predict renal progression and end stage renal disease in type 2 diabetes mellitus with advanced nephropathy: A prospective cohort study

BACKGROUND

Novel potential tubular biomarkers in diabetic nephropathy could improve risk stratification and prediction. The study aimed to evaluate the association of tubular damage markers with rapid renal progression and incidence of end stage renal disease (ESRD) in type 2 diabetes (T2DM).

METHODS

A prospective cohort study, involving a total of 257 patients with T2DM, was included. The baseline values of urine albumin, cystatin-C, angiotensinogen, kidney injury molecule-1 (KIM-1) and neutrophil-gelatinase associated lipocalin (NGAL) were measured. The composite outcomes included a rapid glomerular filtration rate (GFR) decline or incident of ESRD at 3-year follow-up.

MAIN FINDINGS

The composite outcomes were noted in 26.1%. Using univariate followed by multivariate COX proportional hazard regression analysis, the patients with highest quartiles of urine cystatin-C (HR 2.96, 95% CI, 1.38-6.35), urine angiotensinogen (HR 2.93, 95% CI, 1.40- 6.13) urine KIM-1 (HR 2.77, 95% CI, 1.27-6.05) and urine NGAL (HR 2.53, 95% CI, 1.11-5.76) were significantly associated with rapid renal progression when compared with the patients with the lowest quartiles of all tubular biomarkers.

CONCLUSIONS

Patients with T2DM with high levels of baseline urine tubular biomarkers (cystatin-C, angiotensinogen, KIM-1 and NGAL) had a greater incidence of ESRD and rapid GFR decline.

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.

Morphology and Evaluation of Renal Fibrosis

With continuing damage, both the indigenous cells of the cortex and medulla, and inflammatory cells are involved in the formation and development of renal fibrosis. Furthermore, interactions among the glomerular, tubular, and interstitial cells contribute to the process by excessive synthesis and decreased degradation of extracellular matrix. The morphology of kidney is different from pathological stages of diseases and changes with various causes. At the end stage of the disease, the kidneys are symmetrically contracted with diffuse granules. Most glomeruli show diffuse fibrosis and hyaline degeneration, and intervening tubules become atrophied. Renal interstitium shows obvious hyperplasia of fibrous tissues with marked infiltration of lymphocytes, mononuclear cells, and plasma cells. The renal arterioles are wall thickening frequently because of hyaline degeneration. Morphologic analysis based on Masson staining of the kidney tissues has been regarded as the golden standard to evaluate the visual fibrosis. However, the present studies have found that the evaluation system has poor repeatability. Several computer-aided image analysis techniques have been used to assess interstitial fibrosis. It is possible that the evaluation of renal fibrosis is carried out by the artificial intelligence renal biopsy pathological diagnosis system in the near future.

Tubulointerstitial Biomarkers for Diabetic Nephropathy

Patients with diabetic nephropathy have a higher risk of mortality, mostly from cardiovascular complications. Standard biomarkers including serum creatinine, estimated glomerular filtration rate, and albuminuria are imprecise, do not directly measure renal tissue injury, and are relatively insensitive to small changes in renal function. Thus, availability of novel biomarkers that are sensitive, specific, and precise as well as able to detect kidney injury and predict clinically significant outcomes would be widely useful in diabetic nephropathy. Novel biomarkers of the processes that induce tubulointerstitial changes may ultimately prove to better predict renal progression and prognosis in type 2 diabetes. Recently, certain biomarkers, which were initially identified in acute kidney injury, also have been reported to confer value in evaluating patients with chronic kidney disease. Biomarkers such as cystatin C, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), angiotensinogen, periostin, and monocyte chemoattractant protein-1 (MCP-1) reflect tubular injury. In this article, we focused on the potential applications of these biomarkers in diabetic nephropathy.

Urine neutrophil gelatinase-associated lipocalin to predict renal response after induction therapy in active lupus nephritis

Background

Tubulointerstitial injury is important to predict the progression of lupus nephritis (LN). Urine neutrophil gelatinase-associated lipocalin (NGAL) has been reported to detect worsening LN disease activity. Thus, urine NGAL may predict renal outcomes among lupus patients.

Methods

We conducted a prospective multi-center study among active LN patients with biopsy-proven. All patients provided urine samples for NGAL measurement by ELISA collected from all patients at baseline and at 6-month follow-up after induction therapy.

Results

In all, 68 active LN patients were enrolled (mean age 31.7 ± 10.0 years, median UPCR 4.8 g/g creatinine level with interquartile range (IQR) 2.5 to 6.9 and mean estimated glomerular filtration rate (GFR) 89.6 ± 33.7 mL/min/1.73 m²). At baseline measurement, median urinary NGAL in complete response, partial response and nonresponse groups was 10.86 (IQR; 6.16, 22.4), 19.91 (IQR; 9.05, 41.91) and 65.5 (IQR; 18.3, 103) ng/mL, respectively (p = 0.006). Urinary NGAL (ng/mL) correlated positively with proteinuria and blood pressure, and correlated negatively with serum complement C3 level and estimated GFR. Based on ROC analysis, urinary NGAL (AUC; 0.724, 95%CI 0.491–0.957) outperformed conventional biomarkers (serum creatinine, urine protein, and GFR) in differentiating complete and partial response groups from the nonresponse group. The urine NGAL cut-off value in the ROC curve, 28.08 ng/mL, discriminated nonresponse with 72.7% sensitivity and 68.4% specificity.

Conclusion

Urine NGAL at baseline performed better than conventional markers in predicting a clinical response to treatment of active LN except serum complement C3 level. It may have the potential to predict poor response after induction therapy.

Urinary heme oxygenase-1 as a potential biomarker for early diabetic nephropathy

BACKGROUND

Our previous study showed that increases of urinary heme oxygenase-1 (uHO-1) could be a potential biomarker indicating evaluating intrarenal oxidative damage in obstructive nephropathy. Activation of oxidative stress is an important mediator of diabetic nephropathy (DN). The aim of this study was to investigate the clinical implications of uHO-1 levels in patients with type 2 diabetes.

METHODS

Eighty-four type 2 diabetic patients with normoalbuminuria (n=28), microalbuminuria (n=28), and macroalbuminuria (n=28) were included in this study. Control samples were collected from healthy volunteers (n=28) who had normal albuminuria and renal function. Urine HO-1 levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Urinary HO-1/creatinine (cr.) levels were significantly elevated in diabetic patients with microalbuminuria and macroalbuminuria compared to those in diabetic patients with normoalbuminuria (P<0.001) and control subjects (all P<0.001). In diabetic patients with normoalbuminuria, uHO-1/cr. levels were also higher than those in controls (P<0.001). Multivariate regression analyses revealed that uHO-1/cr. levels were positively correlated to urinary albumin/creatinine ratio and inversely correlated to glomerular filtration rate. Receiver operating characteristic (ROC) curve analysis of uHO-1/cr. levels for early diagnosis and detection of DN revealed that the cut-off value of uHO-1/cr. was 4.59 ng/mg (sensitivity 75%, specificity 78.6%).

CONCLUSIONS

The findings of this study indicate that increases of urine HO-1 levels can be detected in patients with type 2 diabetes before the onset of significant albuminuria, and associated with renal derangement in patients with established diabetic nephropathy. Urinary HO-1 may be used as an early biomarker for diabetic renal injury.

Mechanistic insight of diabetic nephropathy and its pharmacotherapeutic targets: An update

Diabetic nephropathy (DN), a chronic complication of diabetes, is charecterized by glomerular hypertrophy, proteinuria, decreased glomerular filtration, and renal fibrosis resulting in the loss of renal function. Although the exact cause of DN remains unclear, several mechanisms have been postulated, such as hyperglycemia-induced renal hyper filtration and renal injury, AGEs-induced increased oxidative stress, activated PKC-induced increased production of cytokines, chemokines, and different inflammatory and apoptotic signals. Among various factors, oxidative stress has been suggested to play a major role underlying the onset and propagation of DN. It triggers several signaling pathways involved in DN, like AGEs, PKC cascade, JAK/STAT signaling, MAPK, mTOR, and SMAD. Oxidative stress-induced activation of both inflammatory and apoptotic signals are two major problems in the pathogenesis of DN. The FDA approved pharmacotherapeutic agents affecting against polyol pathway principally include anti-oxidants, like α-lipoic acid, vitamin E, and vitamin C. Kremezin and benfotiamine are the FDA approved AGEs inhibitors, another therapeutic target against DN. Ruboxistaurin, telmizartan, rapamycin, fenofibrate, aliskiren, and manidipine are some FDA approved pharmacotherapeutics effective against DN via diverse mechanisms. Beside this, some therapeutic agents are still waiting for FDA approval and few drugs without FDA approval are also prescribed in some countries for the management of DN. Despite the medications available in the market to treat DN, the involvement of multiple mechanisms makes it difficult to choose an optimum therapeutic agent. Therefore, much research is required to find out new therapeutic agent/strategies for an adequate pharmacotherapy of DN.

A previously unrecognized role of C3a in proteinuric progressive nephropathy

Podocyte loss is the initial event in the development of glomerulosclerosis, the structural hallmark of progressive proteinuric nephropathies. Understanding mechanisms underlying glomerular injury is the key challenge for identifying novel therapeutic targets. In mice with protein-overload induced by bovine serum albumin (BSA), we evaluated whether the alternative pathway (AP) of complement mediated podocyte depletion and podocyte-dependent parietal epithelial cell (PEC) activation causing glomerulosclerosis. Factor H (Cfh^−/−) or factor B-deficient mice were studied in comparison with wild-type (WT) littermates. WT+BSA mice showed podocyte depletion accompanied by glomerular complement C3 and C3a deposits, PEC migration to capillary tuft, proliferation, and glomerulosclerosis. These changes were more prominent in Cfh^−/− +BSA mice. The pathogenic role of AP was documented by data that factor B deficiency preserved glomerular integrity. In protein-overload mice, PEC dysregulation was associated with upregulation of CXCR4 and GDNF/c-Ret axis. In vitro studies provided additional evidence of a direct action of C3a on proliferation and CXCR4-related migration of PECs. These effects were enhanced by podocyte-derived GDNF. In patients with proteinuric nephropathy, glomerular C3/C3a paralleled PEC activation, CXCR4 and GDNF upregulation. These results indicate that mechanistically uncontrolled AP complement activation is not dispensable for podocyte-dependent PEC activation resulting in glomerulosclerosis.

Independent associations of urine neutrophil gelatinase-associated lipocalin and serum uric acid with interstitial fibrosis and tubular atrophy in primary glomerulonephritis

The degree of interstitial fibrosis and tubular atrophy (IFTA) is one of the strongest prognostic factors in glomerulonephritis (GN). In experimental models, high serum uric acid (UA) could contribute to IFTA through direct effects on the renal tubules, but the significance of this process has not been evaluated in patients. Urine neutrophil gelatinase–associated lipocalin (NGAL) is produced by renal tubules following acute or chronic damage. We investigated the relationship between UA and NGAL excretion in primary GN and tested whether these biomarkers are independently associated with IFTA. Urine and blood were collected from patients on the day of kidney biopsy. IFTA was assessed semi-quantitatively. Fifty-one patients with primary GN were enrolled. NGAL/creatinine correlated significantly with proteinuria but not with glomerular filtration rate (GFR). By contrast, UA correlated with GFR but not with proteinuria. NGAL/creatinine did not correlate with UA. Both NGAL/creatinine and UA increased with the severity of IFTA. By multivariate analysis, GFR, NGAL/creatinine, and UA were independently associated with moderate-to-severe IFTA. Combining UA and NGAL/creatinine with classical predictors (proteinuria and GFR) tended to improve discrimination for moderate-to-severe IFTA. Findings that UA was unrelated to urinary NGAL excretion suggest that the two biomarkers reflect different pathways related to the development of IFTA in primary GN. Both NGAL/creatinine and UA were independently associated with moderate-to-severe IFTA.

Novel Tubular Biomarkers Predict Renal Progression in Type 2 Diabetes Mellitus: A Prospective Cohort Study

Background. Tubulointerstitial injury is both a key feature of diabetic nephropathy and an important predictor of renal dysfunction. Novel tubular biomarkers related to renal injury in diabetic nephropathy could improve risk stratification and prediction. Methods. A total of 303 type 2 diabetic patients were followed up. The baseline urine values of cystatin-C to creatinine ratio (UCCR), angiotensinogen to creatinine ratio (UANG), NGAL to creatinine ratio (UNGAL), and KIM-1 to creatinine ratio (UKIM-1) were measured. The primary outcome was a decline in estimated GFR of ≥25% yearly from baseline. Results. Urine tubular biomarkers of UCCR, UANG, UNGAL, and UKIM-1 were significantly higher according to the degree of albuminuria and all were significantly higher among patients with rapid decline in estimated GFR of ≥25% yearly from baseline. All biomarkers predicted primary outcomes with ROC for UCCR of 0.72; 95% CI 0.64-0.79, for UANG of 0.71; 95% CI 0.63-0.79, for UNGAL of 0.64; 95% CI 0.56-0.72, and for UKIM-1 of 0.71; 95% CI 0.63-0.79. Using multivariate Cox regression analysis, the number of patients with rapid renal progression was higher among those in the upper quartiles of all biomarkers than in those in the lower quartiles. Conclusions. Type 2 diabetic patients with high levels of urine tubular biomarkers had a more rapid decline in renal function.

Performance of the estimated glomerular filtration rate creatinine and cystatin C based equations in Thai patients with chronic glomerulonephritis

Background

Glomerular filtration rate (GFR) is considered the indicator of overall kidney function, and therefore, its assessment has become an important clinical tool in the daily care of chronic glomerulonephritis (CGN) patients. Currently, practical guidelines recommend using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations to assess GFR in CKD patients.

Methods

A cross-sectional study was performed in CGN patients. Standard GFR was measured using 24-hour urine creatinine clearance. GFR was estimated using the Cockcroft-Gault, Modification of Diet in Renal Disease, CKD-EPI equation based creatinine, cystatin C, and combined creatinine and cystatin C. The performance of GFR estimation equations were examined using bias, precision and accuracy and agreement between standard GFR and estimated GFR by calculating Cohen’s k.

Results

A total of 125 patients (74 male, 59.2%) with mean age 56.1±18.1 years were included. Mean standard GFR was 51.6±32.2 mL/min per 1.73 m². A significant correlation was found between standard GFR and all estimated GFRs (r=0.573 to 0.660, P<0.001). CKD-EPI-creatinine-cystatin C equation had the smallest absolute bias and the significantly highest accuracy, although it was not significantly different from CKD-EPI-cystatin C equation (P=0.523). CKD-EPI-creatinine-cystatin C equation had the highest accuracy to classify CKD staging (Cohen’s k=0.345), but it underestimated GFR in 32% and overestimated GFR in 18% of the CGN patients.

Conclusion

CKD-EPI-creatinine-cystatin C equation estimated GFR with little bias, and the highest accuracy among CGN patients. This equation gave a better estimate of GFR than the equation based on serum creatinine.

Periostin: a novel tissue biomarker correlates with chronicity index and renal function in lupus nephritis patients

Lupus nephritis (LN) is one of the most serious complications in patients with systemic lupus erythematosus (SLE). At present, there is no specific biomarker with high sensitivity and renal pathology involvement in use in clinical practice. Periostin is an extracellular matrix protein involved in kidney development and kidney injury. We performed immunohistochemical analysis for periostin and routine staining of 42 kidney tissues from LN patients compared with controlled kidney tissues. Activity index, chronicity index and periostin staining were evaluated and scored by a renal pathologist. Periglomerular staining of periostin was the most predominant finding. Positive periostin staining was also observed in areas with fibrosis such as sclerosed glomeruli, interstitial fibrosis and fibrous vessels. Moreover, the tubules seemed to be the main location for periostin staining. There was a statistically different level of periostin staining score between patient and control tissues. Periostin staining score also correlated with the chronicity index score of renal pathology ( r = 0.594, p < 0.001). Periostin was also correlated with worsening renal outcomes including serum creatinine, blood urea nitrogen and estimated glomerular filtration rate (eGFR). Subgroup analysis within patients with low activity index score or low chronicity index score found that there was a statistical difference in serum creatinine and eGFR between groups with low and high periostin staining scores. We concluded that periostin staining score correlated with chronicity index score and renal function in patients with lupus nephritis.

Prevalence and Management of Diabetic Nephropathy in Western Countries

BACKGROUND

Diabetic nephropathy (DN) often results in end-stage renal disease, and this is the most common reason for initiation of dialysis in the United States. Complications of diabetes, particularly renal disease, substantially increase the risk of subsequent severe illness and death. The prevalence of DN is still rising dramatically, with concomitant increases in associated mortality and cardiovascular complications.

SUMMARY

Renal involvement in type 1 and type 2 diabetes reflects a complex pathogenesis. Various genetic and environmental factors determine the susceptibility and progression to advanced stages of the disease. DN should be considered in patients who have had type 1 diabetes for at least 10 years with microalbuminuria and diabetic retinopathy, as well as in patients with type 1 or type 2 diabetes with macroalbuminuria in whom other causes for proteinuria are absent. The glomerular characteristic features include mesangial expansion, thickened glomerular basement membrane, and hyalinosis of arterioles. The optimal therapy of DN continues to evolve. For all diabetic patients, practical management including blood glucose and blood pressure control with renin-angiotensin-aldosterone blockade combined with lipid control, dietary salt restriction, lowering the dietary protein intake, increased physical activity, weight reduction, and smoking cessation can reduce the rate of progression of nephropathy and cardiovascular disease.

KEY MESSAGE

DN is a complex disease linking hemodynamic and metabolic pathways with oxidative stress, and systemic inflammation. We summarize the current evidence of epidemiology, clinical diagnosis, and the current management of DN in Western countries.

FACTS FROM EAST AND WEST

The prevalence of DN is increasing in Asia and Western countries alike. The deletion (D) allele of the angiotensin-converting enzyme gene is associated with progression to end-stage renal disease in Asian patients with DN, but this association is uncertain in Europeans. An association between DN and polymorphism of the gene coding for acetyl coenzyme A carboxylase β has been reported in Asian and Western populations. Both in Japan and the US, criteria for diagnosis are a 5-year history of diabetes and persistent albuminuria. Renal biopsy should be done in patients with severe hematuria, cellular casts and - in the US - hepatitis and HIV to rule out other pathologies. Diabetic retinopathy is considered a key criterion in Japan, but the absence of it does not rule out DN in the US. Enlargement of the kidney is observed as a diagnostic criterion in Japan. The differential use of renal biopsy as diagnostic tool might account for a different prevalence between Asian countries. Some Japanese diabetic patients show typical histological alterations for DN with a normal ACR and GFR. The clinical classification is similar between Japan and the US including five stages based on ACR and GFR. The Japanese guidelines do not include blood pressure values for the classification of DN. Guidelines for DN treatment are evolving quickly both in Asia and Western countries based on the numerous clinical trials performed worldwide. Targeting the angiotensin system for its hemodynamic and nonhemodynamic effects is a common approach. DPP-4 inhibitors are widely used in Japan and might have a higher glucose-lowering effect in Asian patients due to their specific diet. A randomized, double-blind placebo-controlled study has been launched to assess the efficacy of the Chinese herbal tea extract Shenyan Kangfu in DN.

Periostin as a tissue and urinary biomarker of renal injury in type 2 diabetes mellitus

BACKGROUND

Improving the early detection of diabetic nephropathy remains a great challenge in disease management. Periostin is a marker of renal tubular injury and related to progressive kidney injury in animal models of chronic kidney disease. The clinical implications of urinary periostin activities in patients with type 2 diabetes have not been evaluated.

METHODS

Urine samples were obtained from 30 healthy volunteers and 328 type 2 diabetic patients with normoalbuminuria (n=114), microalbuminuria (n=100) and macroalbuminuria (n=114). The excretion levels of urinary periostin were quantified with enzyme-linked immunosorbent assay. Immunohistochemical periostin expression was determined in kidney tissues from overt diabetic nephropathy.

RESULTS

Increased periostin expression in glomeruli and tubular epithelium in diabetic renal pathology was observed. Urinary periostin levels were significantly elevated in the patients of the normoalbuminuria [3.06 (IQR: 1.12, 6.77) ng/mgCr], microalbuminuria [8.71 (IQR: 5.09, 19.29) ng/mgCr] and macroalbuminuria [13.58 (IQR: 3.99, 16.19) ng/mgCr] compared with healthy controls [1.15 (IQR: 0.60, 1.63) ng/mgCr] (P<0.01).Increased urine periostin level significantly correlated with aging, high albuminuria and decline of GFR. Urine periostin ELISA also demonstrated high performance for the diagnosis of established normoalbuminuric, microalbuminuric and macroalbuminuric type 2 diabetes (AUC 0.78 (95%CI, 0.71 to 0.86), 0.99 (95%CI, 0.98 to 1.00) and 0.95 (95%CI, 0.91 to 0.98), respectively).

CONCLUSION

The study indicates that increased urine periostin levels can be detected in patients with type 2 diabetes before the onset of significant albuminuria. Urinary periostin is an associated renal derangement in patients with established diabetic nephropathy and it may be used as an early marker of diabetic renal injury.

Urine periostin as a biomarker of renal injury in chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) represents the main cause of renal allograft failure after transplantation. Noninvasive CAN testing is required. Periostin promotes the expression of a mesenchymal phenotype in renal tubules and is a promising urine biomarker for progressive renal injury. Information regarding periostin expression in the setting of CAN remains scarce.

METHODS

Subjects were recruited from our outpatient transplantation clinic. Random urine samples were collected from CAN patients (n = 24) and renal transplant patients with normal renal function (transplant controls, n = 18). Control samples were collected from healthy volunteers (n = 18) who had normal renal function. Urine periostin was measured by enzyme-linked immunosorbent assay.

RESULTS

The median urine periostin in CAN patients was significantly higher than in transplant and healthy controls (1.74 vs 0.00 vs 0.14 ng/mg creatinine, respectively; P < .001). Urine periostin enzyme-linked immunosorbent assay at a cutoff value of 0.152 ng/mg creatinine demonstrated the sensitivity, specificity, and accuracy for distinguishing CAN patients from transplant patients with normal renal function (91.7%, 77.8%, and 85.7%, respectively). In addition, urine periostin levels correlated directly with urine protein creatinine ratio (R = 0.566, P < .001) and serum creatinine (R = 0.522; P < .001), whereas inverse significant correlations were evidenced with estimated glomerular filtration rate (R = -0.431; P < .001).

CONCLUSION

The appearance of urine periostin in CAN patients but not in healthy and transplant controls underscores its value as a potential biomarker for chronic progressive renal injury in transplant recipients.

Effect of sulodexide on urinary biomarkers of kidney injury in normoalbuminuric type 2 diabetes: a randomized controlled trial

Glycosaminoglycans or sulodexide has shown benefits in early experimental diabetic nephropathy (DN) models, but its efficacy in patients with early stage of DN is unknown. Methods. Twenty patients were randomly assigned to the placebo group and another 20 patients were randomly assigned to receive sulodexide 100 mg/day for 14 weeks. Primary outcome was a change of urinary TGF-beta1, albuminuria, and glomerular filtration rate (GFR). All patients had stable metabolic profiles for at least 90 days before randomization. Results. Urinary TGF-beta1 increased significantly in the placebo group but did not change significantly in the sulodexide group. Additionally, the mean change of urine TGF-beta1 in the placebo group was significantly higher than that in the sulodexide group (8.44 ± 9.21 versus 2.17 ± 6.96 pg/mg Cr, P = 0.02). Mean changes of urinary albumin were 15.05 ± 30.09 μg/mg Cr (P = 0.038) in the placebo group and 13.89 ± 32.25 μg/mg Cr (P = 0.069) in the sulodexide group. No consistent patterns of side effects were observed. Conclusion. In this 14-week trial, benefits of sulodexide in preventing the increase of urinary TGF-beta1 were observed in patients with normoalbuminuric type 2 diabetes. The study suggests that sulodexide treatment may provide additional renoprotection in early stage DN. This trial is registered with TCTR20140806001.

Comprehensive approach to diabetic nephropathy

Diabetic nephropathy (DN) is a leading cause of mortality and morbidity in patients with diabetes. This complication reflects a complex pathophysiology, whereby various genetic and environmental factors determine susceptibility and progression to end-stage renal disease. DN should be considered in patients with type 1 diabetes for at least 10 years who have microalbuminuria and diabetic retinopathy, as well as in patients with type 1 or type 2 diabetes with macroalbuminuria in whom other causes for proteinuria are absent. DN may also present as a falling estimated glomerular filtration rate with albuminuria as a minor presenting feature, especially in patients taking renin-angiotensin-aldosterone system inhibitors (RAASi). The pathological characteristic features of disease are three major lesions: diffuse mesangial expansion, diffuse thickened glomerular basement membrane, and hyalinosis of arterioles. Functionally, however, the pathophysiology is reflected in dysfunction of the mesangium, the glomerular capillary wall, the tubulointerstitium, and the vasculature. For all diabetic patients, a comprehensive approach to management including glycemic and hypertensive control with RAASi combined with lipid control, dietary salt restriction, lowering of protein intake, increased physical activity, weight reduction, and smoking cessation can reduce the rate of progression of nephropathy and minimize the risk for cardiovascular events. This review focuses on the latest published data dealing with the mechanisms, diagnosis, and current treatment of DN.