The kidney in diabetes: dynamic pathways of injury and repair. The Camillo Golgi Lecture 2007

Urotensin II system in chronic kidney disease

Chronic kidney disease (CKD) is a progressive and long-term condition marked by a gradual decline in kidney function. CKD is prevalent among those with conditions such as diabetes mellitus, hypertension, and glomerulonephritis. Affecting over 10% of the global population, CKD stands as a significant cause of morbidity and mortality. Despite substantial advances in understanding CKD pathophysiology and management, there is still a need to explore novel mechanisms and potential therapeutic targets. Urotensin II (UII), a potent vasoactive peptide, has garnered attention for its possible role in the development and progression of CKD. The UII system consists of endogenous ligands UII and UII-related peptide (URP) and their receptor, UT. URP pathophysiology is understudied, but alterations in tissue expression levels of UII and UT and blood or urinary UII concentrations have been linked to cardiovascular and kidney dysfunctions, including systemic hypertension, chronic heart failure, glomerulonephritis, and diabetes. UII gene polymorphisms are associated with increased risk of diabetes. Pharmacological inhibition or genetic ablation of UT mitigated kidney and cardiovascular disease in rodents, making the UII system a potential target for slowing CKD progression. However, a deeper understanding of the UII system's cellular mechanisms in renal and extrarenal organs is essential for comprehending its role in CKD pathophysiology. This review explores the evolving connections between the UII system and CKD, addressing potential mechanisms, therapeutic implications, controversies, and unexplored concepts.

The relationship between serum γ-glutamyltransferase (GGT) and diabetic nephropathy in patients with type 2 diabetes mellitus: a cross-sectional study

The relationship between serum γ-glutamyltransferase (GGT) and renal dysfunction is controversial. In this study, we examined the relationship of serum GGT to diabetic nephropathy (DN) in patients with type 2 diabetes mellitus (T2DM). A total of 577 patients with T2DM were enrolled and their basic information and laboratory data were collected and analyzed. The prevalence of DN increased with the elevated serum GGT tertiles. The level of serum GGT in the DN group was higher than in the non-DN groups. Multivariate logistic analysis showed that high GGT was independent risks for DN (OR = 1.041, 95% CIs 1.023-1.059). And the OR of log-transformed serum GGT for DN was 6.190 (95% CIs 4.248-9.021). The OR of DN across increasing tertiles of serum GGT were 1.00, 3.288 (1.851-5.840), and 5.059 (2.620-9.769) (P for trend < 0.001). Stratified receiver operating characteristic (ROC) analysis by gender showed that the area under ROC curve (AUC) value for GGT was 0.781 (0.732-0.825, P < 0.05) in male and was 0.817 (0.761-0.864, P < 0.05) in female. Compared with female, GGT in male showed lower sensitivity (52.86% vs. 82.05%) and higher specificity (90.32% vs. 55.26%). And the AUC value for GGT was greater than creatinine (Cr) and estimated glomerular filtration rate (eGFR) in male and smaller than Cr and eGFR in female, respectively. In Conclusion, there was an independently positive relationship between serum GGT levels and DN, which suggested that elevated GGT was a potential indicator for risk of DN. There were gender differences in the predictive property of GGT for DN.

Presence of Non-Diabetic Kidney Diseases in Biopsy Specimens of Diabetic Patients' Single Center Experience

The complications of type 2 diabetes mellitus (T2DM) are well known and one of them is diabetic chronic kidney disease (DCKD). Over time, it has become clear that patients with T2DM can have nondiabetic chronic kidney diseases (NDCKD), especially those that affect the glomeruli. Clinical indicators for identifying DCKD from NDCKD with high sensitivity and specificity have not yet been identified. Therefore, kidney biopsy remains the golden standard for DCKD diagnosis in patients with T2DM. Despite some indications for kidney biopsy, criteria for a biopsy differ between countries, regions, and doctors. The aim of the study was to analyze the biopsy findings in our T2DM population and the justification of the biopsy according to widely accepted criteria. This single center retrospective study analyzed data from 74 patients with T2DM who underwent kidney biopsy from January 2014 to January 2021. According to the biopsy data, we categorized31 patients in the DN group, patients with typical diabetic glomerulopathy, 11 patients in the mixed group, patients who had pathohistological elements for both DN and non-DN glomerulopathy, and 32 patients in the non-DN group, patients with primary glomerulopathy not linked with DM. In the non-DN and mixed groups, the most frequent glomerulopathy was mesangioproliferative glomerulonephritis, including IgA and non-IgA forms, found in 10 patients, and membranous nephropathy (MN) in 10 patients. We analyzed several parameters and only the amount of proteinuria was found to be significantly linked to biopsy findings related to DN. With the existing criteria for kidney biopsy, we managed to detect changes in the kidneys in about half of our patients with T2DM. These patients required specific treatment, different from that which we use for DCKD patients.

Prevalence of Diabetic Kidney Disease with Different Subtypes in Hospitalized Patients with Diabetes and Correlation Between eGFR and LncRNA XIST Expression in PBMCs

INTRODUCTION

Diabetic kidney disease (DKD) has become the leading cause of end-stage kidney disease (ESKD) in most countries. Recently, long noncoding RNA XIST has been found involved in the development of DKD.

METHODS

A total of 1184 hospitalized patients with diabetes were included and divided into four groups based on their estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR): normal control group (nDKD), DKD with normoalbuminuric and reduced eGFR (NA-DKD), DKD with albuminuria but without reduced eGFR (A-DKD), and DKD with albuminuria and reduced eGFR (Mixed), and then their clinical characteristics were analyzed. Peripheral blood mononuclear cells (PBMCs) of patients with DKD were isolated, and lncRNA XIST expression was detected by real-time quantitative PCR.

RESULTS

The prevalence of DKD in hospitalized patients with diabetes mellutus (DM) was 39.9%, and the prevalence of albuminuria and decreased eGFR was 36.6% and 16.2%, respectively. NA-DKD, A-DKD, and Mixed groups accounted for 23.7%, 3.3%, and 12.9%, respectively. Women with DKD had considerably lower levels of lncRNA XIST expression in their PBMCs compared to nDKD. There was a significant correlation between eGFR level and lncRNA XIST expression (R = 0.390, P = 0.036) as well as a negative correlation between HbA1c and lncRNA XIST expression (R = - 0.425, P = 0.027) in female patients with DKD.

CONCLUSIONS

Our study revealed that 39.9% of DM inpatients who were admitted to the hospital had DKD. Importantly, lncRNA XIST expression in PBMCs of female patients with DKD was significantly correlated with eGFR and HbA1c.

The Role of Tubulointerstitial Markers in Differential Diagnosis and Prognosis in Patients with Type 2 Diabetes and Biopsy Proven Diabetic Kidney Disease

OBJECTIVE

To evaluate the potential application of tubularinterstitial biomarkers in the differential diagnosis of diabetic kidney disease (DKD) from non-diabetic kidney disease (NDKD), as well as investigate key clinical and pathological parameters to help improve the stratification of patients according to end-stage renal disease risk.

METHODS

132 type 2 diabetic patients with chronic kidney disease were enrolled. Patients were categorized into 2 groups according to the renal biopsy results: DKD (n=61) and NDKD (n=71).The independent factors of the occurrence of DKD and the diagnostic implications of tubular biomarkers were explored by logistic regression and receiver-operating characteristic curve analysis. Furthermore, predictors were analyzed by least absolute shrinkage and selection operator regression, and constructed a new model for predicting the unfavorable renal outcomes through Cox proportional hazard regression analysis.

RESULTS

Serum neutrophil gelatinase-associated lipocalin (sNGAL) (OR= 1.007; 95%CI = [1.003, 1.012], p = 0.001) was identified as an independent risk factor for the occurrence of DKD in diabetic patients with CKD. Tubular biomarkers including sNGAL, N-acetyl-β-D-glucosaminidase and β2 microglobulin (β2-MG) could complement albuminuria for DKD detection (AUC = 0.926, specificity = 90.14%, sensitivity = 80.33%).Moreover, among of the 47 variables, 4 predictors such as sNGAL, interstitial fibrosis and tubular atrophy (IFTA)score, β2-MG and estimated glomerular filtration rate were selected to construct a new model for predicting the unfavorable renal outcomes through regression analysis. sNGAL (HR = 1.004; 95%CI = [1.001, 1.007], p = 0.013), IFTA score of 2 (HR = 4.283; 95%CI = [1.086, 16.881], p = 0.038), and IFTA score of 3 (HR = 6.855; 95%CI = [1.766, 26.610], p = 0.005) were considered to be independent risk factors for unfavorable renal outcomes.

CONCLUSIONS

Tubulointerstitial injury in DKD is independently associated with renal function decline and routinely detected tubular biomarkers are able to enhance the level of non-invasive diagnosis of DKD beyond traditional factors.

Metformin and Canagliflozin Are Equally Renoprotective in Diabetic Kidney Disease but Have No Synergistic Effect

Diabetic Kidney Disease (DKD) is a major microvascular complication for diabetic patients and is the most common cause of chronic kidney disease (CKD) and end-stage renal disease. Antidiabetic drugs, such as metformin and canagliflozin, have been shown to exert renoprotective effects. Additionally, quercetin recently showed promising results for the treatment of DKD. However, the molecular pathways through which these drugs exert their renoprotective effects remain partly unknown. The current study compares the renoprotective potential of metformin, canagliflozin, metformin + canagliflozin, and quercetin in a preclinical rat model of DKD. By combining streptozotocin (STZ) and nicotinamide (NAD) with daily oral N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) administration, DKD was induced in male Wistar Rats. After two weeks, rats were assigned to five treatment groups, receiving vehicle, metformin, canagliflozin, metformin + canagliflozin, or quercetin for a period of 12 weeks by daily oral gavage. Non-diabetic vehicle-treated control rats were also included in this study. All rats in which diabetes was induced developed hyperglycemia, hyperfiltration, proteinuria, hypertension, renal tubular injury and interstitial fibrosis, confirming DKD. Metformin and canagliflozin, alone or together, exerted similar renoprotective actions and similar reductions in tubular injury and collagen accumulation. Renoprotective actions of canagliflozin correlated with reduced hyperglycemia, while metformin was able to exert these effects even in the absence of proper glycemic control. Gene expression revealed that the renoprotective pathways may be traced back to the NF-κB pathway. No protective effect was seen with quercetin. In this experimental model of DKD, metformin and canagliflozin were able to protect the kidney against DKD progression, albeit in a non-synergistic way. These renoprotective effects may be attributable to the inhibition of the NF-κB pathway.

Inhibition of notch signalling and mesangial expansion by combined glucagon like peptide-1 agonist and crocin therapy in animal model of diabetic nephropathy

Diabetic nephropathy (DN) is one of the devastating complications in diabetes mellitus (DM). Glucagon-like peptide-1 (GLP-1) is one of the incretins secreted from L cells in the intestine. Crocin (a carotenoid component of saffron) has antioxidants properties. We investigated the renal effects of Exendin-4 as a GLP-1 agonist and Crocin in DN.Thirty male rats were divided into five groups: control, type II DM, type II DM + Exendin-4, type II DM + Crocin ‏ and type II DM + Exendine-4 + Crocin. At the end of the experimental period, systolic and diastolic blood pressures were measured, and GFR was calculated. Blood and urine samples were collected for biochemical analysis. Tissue samples were collected from the kidney for histological examination and biochemical measurements of protein expression.Treatment with GLP-1 agonist or Crocin caused a significant improvement in renal function. Better results were achieved with simultaneous administration of both drugs with inhibition of notch signalling pathway and the related proteins.

Metabolic dysfunction-associated fatty liver disease can significantly increase the risk of chronic kidney disease in adults with type 2 diabetes

AIMS

This study is to explore the relationship between metabolic dysfunction-associated fatty liver disease (MAFLD) and chronic kidney disease (CKD) among populations with type 2 diabetes through longitudinal cohort study.

METHODS

3,627 subjects who had received at least three health examinations between 2008 and 2015 were included. CKD was stated as subjects with an eGFR < 60 mL/min per 1·73 m2 or the occurrence of 2 or more proteinuria during their follow-up.

RESULTS

After median of 10·0 years follow up, 837 (23·1%) developed CKD (244·7 per 10,000 person-years; 95 % CI, 228.4 - 261·8). MAFLD ([HR] 1·46; 95 % CI 1·26-1·70, P < 0.001) acts as an important risk factor of developing CKD. After adjusting for confounding factors, this association was consistent (HR 1·30; 95 % CI 1·11-1·53, P < 0.001). In stratified analysis, subjects aged < 60 years were likely to have greater risk of MAFLD-related CKD (HR 1·58 and 1·03; 95 % CI 1·28-1·95 and 0·79-1·33, P < 0.001 in both cases, respectively).

CONCLUSIONS

The risk of developing CKD in type 2 diabetes adults with MAFLD was higher, especially if they are below 60 years old. This study underscores the importance of early prevention strategies for MAFLD to reduce the occurrence of CKD in type 2 diabetes adults.

PLVAP as an Early Marker of Glomerular Endothelial Damage in Mice with Diabetic Kidney Disease

Plasmalemma vesicle-associated protein (PLVAP) is the main component of endothelial diaphragms in fenestrae, caveolae, and transendothelial channels. PLVAP is expressed in the adult kidney glomerulus upon injury. Glomerular endothelial injury is associated with progressive loss of kidney function in diabetic kidney disease (DKD). This study aimed to investigate whether PLVAP could serve as a marker for glomerular endothelial damage in DKD. Glomerular PLVAP expression was analyzed in different mouse models of DKD and their respective healthy control animals using automatic digital quantification of histological whole kidney sections. Transgenic mice expressing a dominant-negative GIP receptor (GIPR^dn) in pancreatic beta-cells as a model for diabetes mellitus (DM) type 1 and black and tan brachyuric (BTBR) ob/ob mice, as a model for DM type 2, were used. Distinct PLVAP induction was observed in all diabetic models studied. Traces of glomerular PLVAP expression could be identified in the healthy control kidneys using automated quantification. Stainings for other endothelial injury markers such as CD31 or the erythroblast transformation-specific related gene (ERG) displayed no differences between diabetic and healthy groups at the time points when PLVAP was induced. The same was also true for the mesangial cells marker α8Integrin, while the podocyte marker nephrin appeared to be diminished only in BTBR ob/ob mice. Glomerular hypertrophy, which is one of the initial morphological signs of diabetic kidney damage, was observed in both diabetic models. These findings suggest that PLVAP is an early marker of glomerular endothelial injury in diabetes-induced kidney damage in mice.

Youth versus adult-onset type 2 diabetic kidney disease: Insights into currently known structural differences and the potential underlying mechanisms

Type 2 diabetes (T2D) is a global health pandemic with significant humanitarian, economic, and societal implications, particularly for youth and young adults who are experiencing an exponential rise in incident disease. Youth-onset T2D has a more aggressive phenotype than adult-onset T2D, and this translates to important differences in rates of progression of diabetic kidney disease (DKD). We hypothesize that youth-onset DKD due to T2D may exhibit morphometric, metabolic, and molecular characteristics that are distinct from adult-onset T2D and develop secondary to inherent differences in renal energy expenditure and substrate metabolism, resulting in a central metabolic imbalance. Kidney structural changes that are evident at the onset of puberty also serve to exacerbate the organ’s baseline high rates of energy expenditure. Additionally, the physiologic state of insulin resistance seen during puberty increases the risk for kidney disease and is exacerbated by both concurrent diabetes and obesity. A metabolic mismatch in renal energetics may represent a novel target for pharmacologic intervention, both for prevention and treatment of DKD. Further investigation into the underlying molecular mechanisms resulting in DKD in youth-onset T2D using metabolomics and RNA sequencing of kidney tissue obtained at biopsy is necessary to expand our understanding of early DKD and potential targets for therapeutic intervention. Furthermore, large-scale clinical trials evaluating the duration of kidney protective effects of pharmacologic interventions that target a metabolic mismatch in kidney energy expenditure are needed to help mitigate the risk of DKD in youth-onset T2D.

Diabetic Kidney Disease Back in Focus: Management Field Guide for Health Care Professionals in the 21st Century

Chronic kidney disease due to diabetes, or diabetic kidney disease (DKD), is a worldwide leading cause of chronic kidney disease and kidney failure and an increasingly important global public health issue. It is associated with poor quality of life, high burden of chronic diseases, and increased risk of premature death. Until recently, people with DKD had limited therapeutic options. Treatments have focused largely on glycemic and blood pressure control and renin-angiotensin system blockade, leaving patients with significant residual risk for progression of DKD. The availability of newer classes of glucose-lowering agents, namely, sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists, has changed the therapeutic landscape for these patients. These therapies have offered unprecedented opportunities to reduce the risk for progression of kidney disease and the risk of death that have led to recent updates to clinical guidelines. As such, the American Diabetes Association, the Kidney Disease: Improving Global Outcomes, and the European Association for the Study of Diabetes now recommend the use of sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists for patients with DKD to provide both kidney and cardiovascular protective benefits. This review highlights the importance of early detection of DKD and summarizes the latest recommendations in the clinical guidelines on management of patients with DKD with hope of facilitating their uptake into everyday clinical practice. An integrated approach to patient care with a multidisciplinary focus can help achieve the necessary shift in clinical care of patients with DKD.

Elevated ACE Levels Indicate Diabetic Nephropathy Progression or Companied Retina Impaired

Objectives

Renin-angiotensin-aldosterone system plays important roles in the development of diabetic nephropathy (DN), and angiotensin converting enzyme (ACE) is the key factor in the process from angiotensin I to angiotensin II, but the variation and roles of serum ACE in DN patients are still unclear.

Methods

Forty-four type 2 diabetes mellitus (T2DM) patients, 75 DN patients, and 36 age-gender-matched healthy volunteers were recruited who attended Xiangya Hospital of Central South University in this case control study. Serum ACE levels and other indexes were tested with commercial kit.

Results

ACE levels in DN were significantly higher than T2DM and controls (F = 9.66, P < 0.001). Serum ACE levels significantly correlated with UmALB (r = 0.3650, P < 0.001), BUN (r = 0.3102, P < 0.001), HbA1c (r = 0.2046, P = 0.0221), ACR (r = 0.4187, P < 0.001), ALB (r = -0.1885, P = 0.0192), and eGFR (r = -0.3955, P < 0.001), and we got an equation that Y = 2.839 + 0.648X1 + 2.001X2 + 0.003X3 - 6.637X4 +0.416X5 - 0.134X6 (Y: ACE; X1: BUN; X2: HbA1C; X3: UmALB; X4: gender; X5: ALB; X6: eGFR, R2 = 0.655). When DN patients were divided into advanced-stage and early-stage with or without DR, ACE levels would increase when early-stage DN develops into advanced-stage or companied with DR.

Conclusion

Elevated serum ACE levels may hint DN progression or retina impaired of DN patients.

L-NAME Administration Enhances Diabetic Kidney Disease Development in an STZ/NAD Rat Model

One of the most important risk factors for developing chronic kidney disease (CKD) is diabetes. To assess the safety and efficacy of potential drug candidates, reliable animal models that mimic human diseases are crucial. However, a suitable model of diabetic kidney disease (DKD) is currently not available. The aim of this study is to develop a rat model of DKD by combining streptozotocin and nicotinamide (STZ/NAD) with oral N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) administration. Diabetes was induced in male Wistar rats by intravenous injection of 65 mg/kg STZ, 15 min after intraperitoneal injection of 230 mg/kg NAD. Rats were assigned to different groups receiving L-NAME (100 mg/kg/day) (STZ/NAD/L-NAME) or vehicle (STZ/NAD) for a period of 9 or 12 weeks by daily oral gavage. All rats developed hyperglycemia. Hyperfiltration was observed at the start of the study, whereas increased serum creatinine, albumin-to-creatinine ratio, and evolving hypofiltration were detected at the end of the study. Daily L-NAME administration caused a rapid rise in blood pressure. Histopathological evaluation revealed heterogeneous renal injury patterns, which were most severe in the STZ/NAD/L-NAME rats. L-NAME-induced NO-deficiency in STZ/NAD-induced diabetic rats leads to multiple characteristic features of human DKD and may represent a novel rat model of DKD.

Trajectories of kidney function in diabetes: a clinicopathological update

Diabetic nephropathy has been traditionally diagnosed based on persistently high albuminuria and a subsequent decline in glomerular filtration rate (GFR), which is widely recognized as the classical phenotype of diabetic kidney disease (DKD). Several studies have emphasized that trajectories of kidney function in patients with diabetes (specifically, changes in GFR and albuminuria over time) can differ from this classical DKD phenotype. Three alternative DKD phenotypes have been reported to date and are characterized by albuminuria regression, a rapid decline in GFR, or non-proteinuric or non-albuminuric DKD. Although kidney biopsies are not typically required for the diagnosis of DKD, a few studies of biopsy samples from patients with DKD have demonstrated that changes in kidney function associate with specific histopathological findings in diabetes. In addition, various clinical and biochemical parameters are related to trajectories of GFR and albuminuria. Collectively, pathological and clinical characteristics can be used to predict trajectories of GFR and albuminuria in diabetes. Furthermore, cohort studies have suggested that the risks of kidney and cardiovascular outcomes might vary among different phenotypes of DKD. A broader understanding of the clinical course of DKD is therefore crucial to improve risk stratification and enable early interventions that prevent adverse outcomes.

Renal sinus fat volume in type 2 diabetes mellitus is associated with glycated hemoglobin and metabolic risk factors

AIMS

We aimed to compare renal sinus fat volume assessed by MRI between patients with type 2 diabetes and healthy volunteers, and investigate the association between renal sinus fat and metabolic traits.

METHODS

In this cross-sectional study, renal sinus fat and parenchyma volumes measured on abdominal MRI were compared between patients and controls using analysis of covariance. Associations of renal parameters with clinical characteristics were analyzed using linear regression analysis.

RESULTS

A total of 146 participants were enrolled, consisting of 95 type 2 diabetes patients (57.2±8.8years, 49.5% male) and 51 controls (54.0±9.2years, 43.1% male). Patients with diabetes demonstrated larger sinus fat volumes (15.4±7.5cm³ vs. 10.3±7.1cm³, p<0.001) and sinus fat-parenchyma ratio than controls. In the total population, renal sinus fat was positively associated with HbA1c, abdominal VAT, cholesterol and triglycerides, after adjustment for age, sex, ethnicity and type 2 diabetes. In type 2 diabetes patients, increased sinus fat volume was significantly associated with urinary albumin-to-creatinine ratio.

CONCLUSION

Renal sinus fat volume is positively associated with several metabolic risk factors including HbA1c level and urinary albumin-to-creatinine ratio in type 2 diabetes patients, indicating a potential role of renal sinus fat in the development of diabetic nephropathy. Future studies are needed to investigate whether sinus fat volume can serve as an early biomarker for diabetic nephropathy.

Inhibition of NLRP3 inflammasome ameliorates podocyte damage by suppressing lipid accumulation in diabetic nephropathy

BACKGROUND

Nucleotide leukin-rich polypeptide 3 (NLRP3) inflammasome is documented as a potent target for treating metabolic diseases and inflammatory disorders. Our recent work demonstrated that inhibition of NLRP3 inflammasome activation inhibits renal inflammation and fibrosis in diabetic nephropathy. This study was to investigate the effect of NLRP3 inflammasome on podocyte injury and the underlying mechanism in diabetic nephropathy.

METHODS

In vivo, db/db mice were treated with MCC950, a NLRP3 inflammasome specific inhibitor. NLRP3 knockout (NKO) mice were induced to diabetes by intraperitoneal injections of streptozotocin (STZ). We assessed renal function, albuminuria, podocyte injury and glomerular lipid accumulation in diabetic mice. In vitro, apoptosis, cytoskeleton change, lipid accumulation, NF-κB p65 activation and reactive oxygen species (ROS) generation were evaluated in podocytes interfered with NLRP3 siRNA or MCC950 under high glucose (HG) conditions. In addition, the effect and mechanism of IL-1β on lipid accumulation was explored in podocytes exposed to normal glucose (NG) or HG.

RESULTS

MCC950 treatment improved renal function, attenuated albuminuria, mesangial expansion, podocyte loss, as well as glomerular lipid accumulation in db/db mice. The diabetes-induced podocyte loss and glomerular lipid accumulation were reversed in NLRP3 knockout mice. The increased expression of sterol regulatory element-binding protein1 (SREBP1) and SREBP2, and decreased expression of ATP-binding cassette A1 (ABCA1) in podocytes were reversed by MCC950 treatment or NLRP3 knockout in diabetic mice. In vitro, NLRP3 siRNA or MCC950 treatment markedly inhibited HG-induced apoptosis, cytoskeleton change, lipid accumulation, NF-κB p65 activation, and mitochondrial ROS production in cultured podocytes. In addition, BAY11-7082 or tempol treatment inhibited HG-induced lipid accumulation in podocytes. Moreover, exposure of IL-1β to podocytes induced lipid accumulation, NF-κB p65 activation and mitochondrial ROS generation.

CONCLUSION

Inhibition of NLRP3 inflammasome protects against podocyte damage through suppression of lipid accumulation in diabetic nephropathy. IL-1β/ROS/NF-κB p65 mediates diabetes-associated lipid accumulation in podocytes. The suppression of NLRP3 inflammasome activation may be an effective therapeutic approach to diabetic nephropathy.

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.

Pathological Hyperinsulinemia and Hyperglycemia in the Impaired Glucose Tolerance Stage Mediate Endothelial Dysfunction Through miR-21, PTEN/AKT/eNOS, and MARK/ET-1 Pathways

BACKGROUND

Impaired glucose tolerance (IGT) is an important prediabetic stage characterized by elevated concentrations of glucose and insulin in the blood. The pathological hyperglycemia and hyperinsulinemia in IGT may regulate the expression of microRNA-21 (miR-21) and affect the downstream insulin signaling pathways, leading to endothelial cell dysfunction and early renal damage.

METHODS

The individual and combined effects of insulin and glucose were investigated using human glomerular endothelial cells (HGECs). The expression levels of miR-21, and PTEN/AKT/eNOS and MAPK/ET-1 pathway proteins in the treated cells were measured. The levels of nitric oxide (NO) and endothelin-1 (ET-1) secreted by the cells were also measured. The role of miR-21 in mediating the regulatory effects of insulin and glucose was assessed by overexpression/inhibition of this miRNA using mimics/inhibitor.

RESULTS

High (>16.7 mmol/L) concentration of glucose upregulated the expression of miR-21, leading to the activation and inhibition of the PTEN/AKT/eNOS and MAPK/ET-1 pathways, and upregulation of NO and downregulation of ET-1 secretion, respectively. High (>25 ng/mL) concentration of insulin downregulated the expression of miR-21, and lead to the activation of the MAPK/ET-1 and inhibition of the PTEN/AKT/eNOS pathway, thereby upregulating the expression of ET-1 and downregulating the secretion of NO. MiR-21 was observed to play a key role by directly controlling the activation of the insulin signaling pathways when the cells were cotreated with different concentrations of insulin and glucose. The expression of miR-21 was found to be dependent on the relative concentration of insulin and glucose. Under simulated conditions of the IGT stage (8.3 mmol/L glucose + 50 ng/mL insulin), the inhibitory effect of high insulin concentration on miR-21 expression in the cells attenuated the activation by high glucose concentration, resulting in the downregulation of miR-21, upregulation of ET-1 and downregulation of NO secretion.

CONCLUSION

Taken together, these results indicate that high insulin and glucose concentrations regulate the secretory function of glomerular endothelial cells in opposite ways by regulating the expression of miRNA-21. Pathological concentrations of insulin and glucose in the IGT stage may lead to a decrease in miR-21 expression, thereby disordering the secretion of vasoactive factors, resulting in renal tubule ischemia.

Multiplex Bead Array Assay of a Panel of Circulating Cytokines and Growth Factors in Patients with Albuminuric and Non-AlbuminuricDiabetic Kidney Disease

A panel of cytokines and growth factors, mediating low-grade inflammation and fibrosis, was assessed in patients with type 2 diabetes (T2D) and different patterns of chronic kidney disease (CKD). Patients with long-term T2D (N = 130) were classified into four groups: no signs of CKD; estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² without albuminuria; albuminuria and eGFR ≥60 mL/min/1.73 m²; albuminuria and eGFR <60 mL/min/1.73 m². Thirty healthy subjects were acted as control. Twenty-seven cytokines and growth factors were assessed in serum by multiplex bead array assay. Serum hs-CRP, urinary nephrin, podocine, and WFDC2 were measured by ELISA. Patients with T2D showed elevated IL-1Ra, IL-6, IL-17A, G-CSF, IP-10, MIP-1α, and bFGF levels; concentrations of IL-4, IL-12, IL-15, INF-γ, and VEGF were decreased. IL-6, IL-17A, G-CSF, MIP-1α, and bFGF correlated negatively with eGFR; IL-10 and VEGF demonstrated negative associations with WFDC2; no relationships with podocyte markers were found. Adjusted IL-17A and MIP-1α were predictors of non-albuminuric CKD, IL-13 predicted albuminuria with preserved renal function, meanwhile, IL-6 and hsCRP were predictors of albuminuria with eGFR decline. Therefore, albuminuric and non-albuminuric CKD in T2D patients are associated with different pro-inflammatory shifts in the panel of circulating cytokines.

Insights into the Role of Renal Biopsy in Patients with T2DM: A Literature Review of Global Renal Biopsy Results

INTRODUCTION

Renal biopsy performed in patients with type 2 diabetes mellitus (T2DM) for atypical or suspected diabetic kidney disease (DKD) reveals one of three possibilities: diabetic nephropathy (DN, pathological diagnosis of DKD), nondiabetic kidney disease (NDKD) and DN plus NDKD (mixed form). NDKD (including the mixed form) is increasingly being recognized worldwide. With the emerging concept of DKD and the complexity of routine application of renal biopsy, the identification of "clinical indicators" to differentiate DKD from NDKD has been an area of active research.

METHODS

The PubMed database was searched for relevant articles mainly according to the keyword search method. We reviewed prevalence of the three types of DKD and different pathological lesions of NDKD. We also reviewed the clinical indicators used to identify DKD and NDKD.

RESULTS

The literature search identified 40 studies (5304 data) worldwide between 1977 and 2019 that looked at global renal biopsy and pathological NDKD lesions. The overall prevalence rate of DN, NDKD and DN plus NDKD is reported to be 41.3, 40.6 and 18.1%, respectively. In Asia, Africa (specifically Morocco and Tunisia) and Europe, the most common isolated NDKD pathological type is membranous nephropathy, representing 24.1, 15.1 and 22.6% of cases, respectively. In contrast, focal segmental glomerulosclerosis is reported to be the primary pathological type in North America (specifically the USA) and Oceania (specifically New Zealand), representing 22% and 63.9% of cases, respectively. Tubulointerstitial disease accounts for a high rate in the mixed group (21.7%), with acute interstitial nephritis being the most prevalent (9.3%), followed by acute tubular necrosis (9.0%). Regarding clinical indicators to differentiate DKD from NDKD, a total of 14 indicators were identified included in 42 studies. Among these, the most commonly studied indicators included diabetic retinopathy, duration of diabetes, proteinuria and hematuria. Regrettably, indicators with high sensitivity and specificity have not yet been identified.

CONCLUSION

To date, renal biopsy is still the gold standard to diagnose diabetes complicated with renal disease, especially when T2DM patients present atypical DKD symptoms (e.g. absence of diabetic retinopathy, shorter duration of diabetes, microscopic hematuria, sub-nephrotic range proteinuria, lower glycated hemoglobin, lower fasting blood glucose). We conclude that renal biopsy as early as possible is of great significance to enable personalized treatment to T2DM patients.

Renal structure in type 2 diabetes: facts and misconceptions

The clinical manifestations of diabetic nephropathy are similar in type 1 and type 2 diabetes, while the renal lesions may differ. Indeed, diabetic glomerulopathy is the predominant renal lesion in type 1 diabetes, although also tubular, interstitial and arteriolar lesions are present in the advanced stages of renal disease. In contrast, in type 2 diabetes renal lesions are heterogeneous, and a substantial number of type 2 diabetic patients with diabetic kidney disease have mild or absent glomerulopathy with tubulointerstitial and/or arteriolar abnormalities. In addition, a high prevalence of non-diabetic renal diseases, isolated or superimposed on classic diabetic nephropathy lesions have been reported in patients with type 2 diabetes, often reflecting the bias of selecting patients for unusual clinical presentations for renal biopsy. This review focuses on renal structural changes in type 2 diabetes, emphasizing the contribution of research kidney biopsy studies to the understanding of the pathogenesis of DKD and of the structural lesions responsible for the different clinical phenotypes. Also, kidney biopsies could provide relevant information in terms of renal prognosis, and help to understand the different responses to different therapies, especially SGLT2 inhibitors, thus allowing personalized medicine.

Hyperinsulinemia contributes to impaired-glucose-tolerance-induced renal injury via mir-7977/SIRT3 signaling

Background:

Increasing evidence indicates that impaired glucose tolerance (IGT) is independently associated with chronic kidney disease, but the characteristics and underlying mechanisms remain largely unknown.

Methods:

Here, the cross-sectional study was performed to study the characteristics of IGT-induced renal injury (IGT-RI). Furthermore, urine microRNA profile was evaluated and microRNAs involved in tubular injury were determined by in-vitro experiments.

Results:

It was found that 12.1% of IGT patients had microalbuminuria, which we termed “IGT-RI.” Overall, 100% of patients with IGT-RI exhibited reabsorption dysfunction and 58.3% had structural damage in the renal tubules. Two-hour postprandial insulin, retinol-binding protein, and N-acetyl-β-glucosaminidase were significantly associated with microalbuminuria and they were independent risk factors for IGT-RI. The expression of mir-7977 was altered in IGT-RI patients and may be involved in cellular response to oxidative stress. In proximal tubule epithelial cells in vitro, a high level of insulin increased the expression of mir-7977 and decreased that of sirtuin 3 (SIRT3), leading to oxidative stress. Overexpression of mir-7977 further decreased SIRT3 expression, whereas inhibition of mir-7977 had the opposite effect. Furthermore, mir-7977 can bind to the 3′-untranslated region of SIRT3 mRNA and inhibit its expression. Moreover, inhibition of SIRT3 reduced the expression of cubilin and the endocytosis of albumin.

Conclusions:

In conclusion, IGT-RI mainly manifests as tubular injury, especially reabsorption dysfunction. Compensatory hyperinsulinemia may be involved. A high level of insulin can activate mir-7977/SIRT3 signaling, resulting in tubular injury by inducing oxidative stress as well as reabsorption dysfunction by inhibiting the expression of cubilin, ultimately contributing to IGT-RI.

Peripheral perfusion, measured by perfusion index, is a novel indicator for renal events in patients with type 2 diabetes mellitus

Diabetic kidney disease (DKD) is one of the leading causes of end stage renal disease. Despite recent therapies, mortality due to DKD and resources spent on healthcare are important problems. Thus, appropriate markers are needed to predict renal outcomes. Therefore, we investigated the role of peripheral perfusion as an indicator for renal events in patients with type 2 diabetes mellitus. This retrospective cohort study included 566 patients who were admitted to Matsushita Memorial Hospital in Osaka, Japan for type 2 diabetes mellitus. Peripheral perfusion was assessed using perfusion index (PI), which represents the level of circulation through peripheral tissues and was measured on each toe using a Masimo SET Radical-7 (Masimo Corporation, Irvine, CA, USA) instrument. The duration of follow up was 3.0 years. The median age of patients was 70 years (IQR range: 61–77 years) and median PI value was 2.9% (IQR range: 1.8–4.8%). Multiple logistic regression analyses showed that PI (per 1% increase) was associated with an odds ratio of composite of end-stage renal disease (ESRD) and/or doubling of serum creatinine level; n = 40 (odds ratio 0.823 [95% CI: 0.680–0.970]), and composite of ESRD, doubling of serum creatinine level, and renal death and/or cardiovascular death; n = 44 (odds ratio 0.803 [95% CI: 0.665–0.944]). The factors which were statistically significant in univariate analysis and those known to be related factors for renal event were considered simultaneously as independent variables for multiple logistic regression analysis. PI can be a novel indicator for renal events in patients with type 2 diabetes mellitus.

Establishment and Validation of a Risk Prediction Model for Early Diabetic Kidney Disease Based on a Systematic Review and Meta-Analysis of 20 Cohorts

BACKGROUND

Identifying patients at high risk of diabetic kidney disease (DKD) helps improve clinical outcome.

PURPOSE

To establish a model for predicting DKD.

DATA SOURCES

The derivation cohort was from a meta-analysis. The validation cohort was from a Chinese cohort.

STUDY SELECTION

Cohort studies that reported risk factors of DKD with their corresponding risk ratios (RRs) in patients with type 2 diabetes were selected. All patients had estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m² and urinary albumin-to-creatinine ratio (UACR) <30 mg/g at baseline.

DATA EXTRACTION

Risk factors and their corresponding RRs were extracted. Only risk factors with statistical significance were included in our DKD risk prediction model.

DATA SYNTHESIS

Twenty cohorts including 41,271 patients with type 2 diabetes were included in our meta-analysis. Age, BMI, smoking, diabetic retinopathy, hemoglobin A_1c, systolic blood pressure, HDL cholesterol, triglycerides, UACR, and eGFR were statistically significant. All these risk factors were included in the model except eGFR because of the significant heterogeneity among studies. All risk factors were scored according to their weightings, and the highest score was 37.0. The model was validated in an external cohort with a median follow-up of 2.9 years. A cutoff value of 16 was selected with a sensitivity of 0.847 and a specificity of 0.677.

LIMITATIONS

There was huge heterogeneity among studies involving eGFR. More evidence is needed to power it as a risk factor of DKD.

CONCLUSIONS

The DKD risk prediction model consisting of nine risk factors established in this study is a simple tool for detecting patients at high risk of DKD.

1,25(OH)2D3 provides protection against diabetic kidney disease by downregulating the TLR4-MyD88-NF-κB pathway

The over-activation of Toll-like receptors (TLRs) is a typical immune response to injury. Previous work has suggested that controlling the over-activation of TLR4-MyD88-NF-κB may represent a new therapeutic option for diabetic kidney disease (DKD). 1,25(OH)₂D₃ has also been shown to exert a protective effect on DKD, although the mechanism involved has yet to be elucidated. The aim of this study was to investigate whether 1,25(OH)₂D₃ protects against DKD by down-regulating the innate immune TLR-NF-κB pathway. NRK-52E cells were cultured under normal or high-glucose conditions. We then used siRNA to knock down TLR4 expression under high-glucose conditions. NRK-52E cells cultured under high-glucose conditions, and streptozotocin (STZ)-induced diabetic rats, were treated with different doses of 1,25(OH)₂D₃ and used as in vitro and in vivo models, respectively. Renal biochemical indicators were then measured to evaluate the influence of 1,25(OH)₂D₃ treatment on DKD in diabetic rats. Histological analysis was also performed to determine the extent of infiltration by inflammatory cells and tubulointerstitial fibrosis. Using RT-qPCR, western blotting, immunohistochemistry and immunofluorescence, we determined the expression levels of TLR4, MyD88, NF-κB p65, MCP-1 and α-SMA to investigate whether 1,25(OH)₂D₃ could reduce the development of tubulointerstitial fibrosis. Knocking down TLR4 abolished the tubulointerstitial fibrosis caused by high-glucose conditions. High doses of 1,25(OH)₂D₃ consistently reduced the expression of TLR4-MyD88-NF-κB in NRK-52E cells. Moreover, high doses of 1,25(OH)₂D₃ had an obvious protective effect on kidney injury and inhibited the infiltration of inflammatory cells and tubulointerstitial fibrosis in diabetic rats. In conclusion, high doses of 1,25(OH)₂D₃ protected against tubulointerstitial fibrosis both in vitro and in vivo by downregulating the expression of TLR4-MyD88-NF-κB.

Analysis of serum inflammatory mediators in type 2 diabetic patients and their influence on renal function

Aim

To evaluate the serum concentrations of inflammatory mediators in patients with type 2 diabetes mellitus (T2DM) with or without renal alteration (RA) function.

Methods

Serum samples from 76 patients with T2DM and 24 healthy individuals were selected. Patients with T2DM were divided into two groups according to eGFR (> or < 60mL/min/1.73m²). Cytokines, chemokines and adipokines levels were evaluated using the Multiplex immunoassay and ELISA.

Results

TNFR1 and leptin were higher in the T2DM group with RA than in the T2DM group without RA and control group. All patients with T2DM showed increased resistin, IL-8, and MIP-1α compared to the control group. Adiponectin were higher and IL-4 decreased in the T2DM group with RA compared to the control group. eGFR positively correlated with IL-4 and negatively with TNFR1, TNFR2, and leptin in patients with T2DM. In the T2DM group with RA, eGFR was negatively correlated with TNFR1 and resistin. TNFR1 was positively correlated with resistin and leptin, as well as resistin with IL-8 and leptin.

Conclusion

Increased levels of TNFR1, adipokines, chemokines and decrease of IL-4 play important role in the inflammatory process developed in T2DM and decreased renal function. We also suggest that TNFR1 is a strong predictor of renal dysfunction in patients with T2DM.

Renal Benefits of SGLT 2 Inhibitors and GLP-1 Receptor Agonists: Evidence Supporting a Paradigm Shift in the Medical Management of Type 2 Diabetes

Diabetic nephropathy (DN) is one of the most perilous side effects of diabetes mellitus type 1 and type 2 (T1DM and T2DM).). It is known that sodium/glucose cotransporter 2 inhibitors (SGLT 2i) and glucagone like peptide-1 receptor agonists (GLP-1 RAs) have renoprotective effects, but the molecular mechanisms are still unknown. In clinical trials GLP-1 analogs exerted important impact on renal composite outcomes, primarily on macroalbuminuria, possibly through suppression of inflammation-related pathways, however enhancement of natriuresis and diuresis is also one of possible mechanisms of nephroprotection. Dapagliflozin, canagliflozin, and empagliflozin are SGLT2i drugs, useful in reducing hyperglycemia and in their potential renoprotective mechanisms, which include blood pressure control, body weight loss, intraglomerular pressure reduction, and a decrease in urinary proximal tubular injury biomarkers. In this review we have discussed the potential synergistic and/or additive effects of GLP 1 RA and SGLT2 inhibitors on the primary onset and progression of kidney disease, and the potential implications on current guidelines of diabetes type 2 management.

Histological Examination of the Diabetic Kidney

The increasing prevalence of diabetes worldwide has led to a concomitant rise in diabetic kidney disease (DKD) as a major cause of end-stage renal disease. Glomerular lesions constitute the most striking and consistent features identified in biopsies from patients with DKD, although tubulointerstitial injury has an important and often under-recognized role in the progression to overt nephropathy. In advanced stages of the disease, podocyte detachment is a pivotal event in the loss of glomerular filtration barrier integrity and may explain, at least in part, the inability of current therapies to halt renal function decline. This chapter details the systematic method that can be used to study renal tissue samples from diabetic patients, and the specific role of different imaging techniques, such as light microscopy, immunofluorescence microscopy, and transmission and scanning electron microscopy in detecting histologic lesions specific to DKD.

Albuminuric and non-albuminuric patterns of chronic kidney disease in type 2 diabetes

A growing body of evidence supports a shift in the natural history of chronic kidney disease (CKD) in subjects with diabetes. Specifically, normoalbuminuric chronic kidney disease (NA-CKD), which is characterized by a decline in the glomerular filtration rate in the absence of a preceding or accompanying elevation of albuminuria, has become a widely prevalent variant of renal impairment in diabetes. Diabetic women and nonsmoking individuals with better glycemic control have a better chance of preserving normoalbuminuria, even in the case of declining renal function. The wide use of renin-angiotensin system blockers, advances in antihyperglycemic, antihypertensive, and hypolipidemic therapy, and smoking cessation are suspected to be responsible for an increasing proportion of NA-CKD among diabetic subjects with renal impairment. Significant differences in the sets of risk factors, renal morphology, comorbidity, and outcomes were found between the albuminuric and normoalbuminuric CKD patterns. NA-CKD, even if a more favorable option in terms of the risk of end-stage renal disease, is clearly associated with cardiovascular disease and its risk factors. The presence of NA-CKD in patients with diabetes increases the risk of myocardial infarction, stroke, and cardiovascular death. The study of the molecular pathways, clinical course, and outcomes of NA-CKD in diabetic subjects and the search for more specific diagnostic and treatment options are challenges for future research.

Hyperinsulinemia Can Cause Kidney Disease in the IGT Stage of OLETF Rats via the INS/IRS-1/PI3-K/Akt Signaling Pathway

AIMS

We investigated the changes of renal structure and its function in normal glucose tolerance (NGT), impaired glucose tolerance (IGT), diabetes mellitus (DM), and diabetic kidney disease (DKD) stages in OLETF rats and explored the role of the INS/IRS-1/PI3-K/Akt signaling pathway.

METHODS

OLETF rats were assigned into four groups on the basis of OGTT results and 24 h urinary microalbumin: NGT, IGT, DM, and DKD groups. The changes of renal structure and function and the corresponding pathological changes were observed. The absorption of albumin and the expression of megalin, cubilin, IRS-1, PI3-K, and Akt in NRK-52E cells were measured after being stimulated by different concentrations of insulin.

RESULTS

In the IGT group, the index which reflects the function of renal tubule-like N-acetyl-β-glucosaminidase, neutrophil gelatinase-associated lipocalin, retinol-binding protein, and cystatin C was higher than those in the control group and the NGT group (P < 0.05). Significant renal structure damages, especially in renal tubules, were observed in the IGT group. In the presence of insulin at a high concentration, the IRS-1/PI3-K/Akt signaling pathway in renal tubular epithelial cells was inhibited, and the expression of megalin and cubilin was significantly downregulated which was accompanied by a minimum uptake of albumin.

CONCLUSIONS

In contrast to DKD, the renal structural damage and functional changes in the IGT stage, in which we propose the term "IGT kidney disease," mainly manifest as renal tubular injury. Insulin resistance and compensatory hyperinsulinemia may be involved in its pathogenesis.

Normoalbuminuric chronic kidney disease in diabetes

Urinary albumin excretion (UAE) is widely used in clinical practice as indicator of diabetic kidney disease. According to the classical concept of the natural course of diabetic nephropathy, an increase in UAE usually precedes a decline in renal function. Meanwhile, a growing body of evidences indicates a high prevalence of normoalbuminuric chronic kidney disease (NA-CKD) in diabetic subjects, especially among patients with type 2 diabetes. An increase in NA-CKD prevalence can be results of improved glucose, blood pressure, and lipid control, widespread use of renin-angiotensin system blockers, and smoking cessation. It was shown that NA-CKD is more prevalent among women and is associated with arterial hypertension and coronary artery disease. The renal structure in subjects with NA-CKD is more heterogeneous when compared to patients with increased albuminuria, wherein interstitial changes and arteriolosclerosis could be the principal morphological findings, while signs of glomerulopathy may be absent. The prognostic value of NA-CKD needs to be clarified. It was shown that NA-CKD increases the risk of myocardial infarction, stroke and cardiovascular death in patients with diabetes. The search for alternative diagnostic markers for detecting of diabetic kidney disease in the absence of albuminuria, is of practical importance. The evaluations of the markers of tubular damage and interstitial fibrosis, as well as proteomic approaches, are considered as perspective diagnostic and prognostic options in NA-CKD. The study of pathogenesis, pathology, clinical course of NA-CKD in diabetic patients, as well as the development of more specific diagnostic and treatment options is a challenge for future research.

Urinary epidermal growth factor, monocyte chemoattractant protein-1 or their ratio as predictors for rapid loss of renal function in type 2 diabetic patients with diabetic kidney disease

BACKGROUND

Increased monocyte chemoattractant protein-1 (MCP-1) and decreased epidermal growth factor (EGF) are promising biomarkers to predict progressive decline in kidney function in non-diabetic kidney diseases. We aimed to evaluate the performance of urinary EGF, MCP-1 or their ratio in predicting rapid decline of GFR in a cohort of Type 2 diabetic patients (T2DM) with diabetic kidney disease (DKD).

METHODS

T2DM patients (n = 83) with DKD at high risk for renal progression were followed up prospectively. The baseline urine values of MCP-1 to creatinine ratio (UMCP-1), EGF to creatinine ratio (UEGF), EGF to MCP-1 ratio (UEGF/MCP-1) and albumin to creatinine ratio (UACR) were measured. The primary outcome was a decline in estimated glomerular filtration rate (GFR) of ≥25% yearly from baseline.

RESULTS

During follow-up time of 23 months, patients with rapid decline in estimated GFR of ≥25% yearly from baseline had significantly higher baseline levels of UMCP-1, and UACR and lower UEGF and UEGF/MCP-1 ratio. All renal biomarkers predicted primary outcomes with ROC (95%CI) for UMCP-1=0.73 (0.62-0.84), UEGF=0.68 (0.57-0.80), UEGF/MCP-1=0.74 (0.63-0.85), and UACR =0.84 (0.75-0.93). By univariate analysis, blood pressure, GFR, UACR, UMCP-1, UEGF, and UEGF/MCP-1 were associated with rapid decline GFR. By multivariate analysis, UACR, systolic blood pressure, and UMCP-1 or UEGF/MCP-1 were independently associated with rapid GFR decline.

CONCLUSIONS

UMCP-1 or UEGF/MCP-1 ratio were associated with rapid renal progression independent from conventional risk factors in DKD.

Assessment of Glomerular and Tubular Function in the Evaluation of Diabetic Nephropathy: A Cross-sectional Study

BACKGROUND

Diabetic nephropathy (DN) occurs in 20%-40% of patients with diabetes, and it is characterized by proteinuria and progressive loss of renal functions ultimately leading to end-stage renal disease. Classically, albuminuria is regarded as a consequence of diabetes-induced glomerular damage. It is now being appreciated that the renal tubulointerstitium also plays a role in the development of DN.[1] Urinary cystatin C (UCC) is an emerging marker of DN. It is totally catabolized by proximal tubular cells and is not normally present in the urine. However, in the presence of tubulopathy, it is excreted in urine, and serum levels also are elevated due to lack of catabolism.

MATERIALS AND METHODS

The present study was conducted to evaluate the presence of glomerulopathy and tubulopathy in patients with type 2 diabetes mellitus (T2DM) and to correlate them with established risk factors for nephropathy. We aimed at evaluating the level of UCC as a marker of tubulointerstitial damage in patients with T2DM in relation to the level of albuminuria and other parameters. Seventy-two patients with T2DM (mean age, 47.44 ± 10.40 years) and 45 healthy age- and sex-matched subjects were evaluated for UCC, serum creatinine, and urinary albumin-creatinine ratio (UACR) along with other parameters.

RESULTS

Of the 72 patients included in the study, microalbuminuria was found in 26% and macroalbuminuria in 10% of cases. UCC was significantly higher in micro- and macro-albuminuric groups in comparison with normoalbuminuric patients and correlated positively with UACR. Among the 46 patients with normoalbuminuria, 11 had elevated UCC levels indicating early tubular dysfunction.

CONCLUSIONS

This finding may support the hypothesis of a "tubular phase" of diabetic kidney disease preceding overt DN, and hence, the use of UCC measurement for early evaluation of renal involvement.

Aldo-Keto Reductases: Multifunctional Proteins as Therapeutic Targets in Diabetes and Inflammatory Disease

Aldose reductase (AR) is an NADPH-dependent aldo-keto reductase that has been shown to be involved in the pathogenesis of several blinding diseases such as uveitis, diabetic retinopathy (DR) and cataract. However, possible mechanisms linking the action of AR to these diseases are not well understood. As DR and cataract are among the leading causes of blindness in the world, there is an urgent need to explore therapeutic strategies to prevent or delay their onset. Studies with AR inhibitors and gene-targeted mice have demonstrated that the action of AR is also linked to cancer onset and progression. In this review we examine possible mechanisms that relate AR to molecular signaling cascades and thus explain why AR inhibition is an effective strategy against colon cancer as well as diseases of the eye such as uveitis, cataract, and retinopathy.

Diabetic Kidney Disease: Challenges, Progress, and Possibilities

Diabetic kidney disease develops in approximately 40% of patients who are diabetic and is the leading cause of CKD worldwide. Although ESRD may be the most recognizable consequence of diabetic kidney disease, the majority of patients actually die from cardiovascular diseases and infections before needing kidney replacement therapy. The natural history of diabetic kidney disease includes glomerular hyperfiltration, progressive albuminuria, declining GFR, and ultimately, ESRD. Metabolic changes associated with diabetes lead to glomerular hypertrophy, glomerulosclerosis, and tubulointerstitial inflammation and fibrosis. Despite current therapies, there is large residual risk of diabetic kidney disease onset and progression. Therefore, widespread innovation is urgently needed to improve health outcomes for patients with diabetic kidney disease. Achieving this goal will require characterization of new biomarkers, designing clinical trials that evaluate clinically pertinent end points, and development of therapeutic agents targeting kidney-specific disease mechanisms (e.g., glomerular hyperfiltration, inflammation, and fibrosis). Additionally, greater attention to dissemination and implementation of best practices is needed in both clinical and community settings.

INTRODUCTION

High glucose instigates tubulointerstitial injury by stimulating hetero-dimerization of adiponectin and angiotensin II receptors

Abnormal expression and dysfunction of adiponectin and the cognate receptors are involved in diabetes and diabetic kidney disease (DKD), whereas angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) alleviate diabetic albuminuria and prevent development of DKD through upregulation of adiponectin expression. Here we report that high glucose stimulates expression of angiotensin II (AngII) receptors (AT1 and AT2) in renal proximal tubular epithelial cells (NRK-52E). These receptors underwent hetero-dimerization with adiponectin receptor AdipoR1 and AdipoR2, respectively. High glucose inhibited the dimerization between AT1 and AT2. Interestingly, these hetero-dimers instigated tubulointerstitial injury by inhibiting the cytoprotective action of the adiponectin receptors. These modes of receptor-receptor hetero-dimerization may contribute to high glucose-induced renal tubulointerstitial injury and could be potential therapeutic targets.

Inhibition of high glucose-induced inflammation and fibrosis by a novel curcumin derivative prevents renal and heart injury in diabetic mice

Hyperglycemia-induced inflammation and fibrosis have important roles in the pathogenesis of diabetic nephropathy and cardiomyopathy. With inflammatory cytokines and signaling pathways as important mediators, targeting inflammation may be an effective approach to new avenue for treating diabetic complications. J17, a molecule with structural similarities to curcumin, exhibited good anti-inflammatory activities by inhibiting LPS-induced inflammatory response in macrophages. However, its ability to alleviate hyperglycemia-induced injury via its anti-inflammatory actions remained unclear. Thus, we reported that J17 exerts significant inhibitory effects on hyperglycemia-induced inflammation and fibrosis in NRK-52E cells, H9C2 cells and a streptozotocin-induced diabetic mouse model. We also found that the anti-inflammatory and anti-fibrosis activities of J17 are associated with the inhibition of the P38 and AKT signal pathway, respectively. In vivo oral administration of J17 suppressed hyperglycemia-induced inflammation, hypertrophy and fibrosis, thereby reducing key markers for renal and cardiac dysfunction and improving in fibrosis and pathological changes in both renal and cardiac tissues of diabetic mice. The results of this study indicated that J17 can be potentially used as a cardio- and reno-protective agent and that targeting the P38 and AKT pathways may be an effective therapeutic strategy for diabetic complications.

Mesenchymal Stem Cell-Based Therapies against Podocyte Damage in Diabetic Nephropathy

Injury to podocytes is an early event in diabetic nephropathy leading to proteinuria with possible progression to end-stage renal failure. The podocytes are unique and highly specialized cells that cover the outer layer of kidney ultra-filtration barrier and play an important role in glomerular function. In the past few decades, adult stem cells, such as mesenchymal stem cells (MSCs) with a regenerative and differentiative capacity have been extensively used in cell-based therapies. In addition to their capability for regeneration and differentiation, MSCs contributes to their milieu by paracrine action of a series of growth factors via antiapoptotic, mitogenic and other cytokine actions that actively participate in treatment of podocyte damage through prevention of podocyte effacement, detachment and apoptosis. It is hoped that novel stem cell-based therapies will be developed in the future to prevent podocyte injury, thereby reducing the burden of kidney disease.

Comparison of Urine Albumin-to-Creatinine Ratio (ACR) Between ACR Strip Test and Quantitative Test in Prediabetes and Diabetes

BACKGROUND

Albuminuria is generally known as a sensitive marker of renal and cardiovascular dysfunction. It can be used to help predict the occurrence of nephropathy and cardiovascular disorders in diabetes. Individuals with prediabetes have a tendency to develop macrovascular and microvascular pathology, resulting in an increased risk of retinopathy, cardiovascular diseases, and chronic renal diseases. We evaluated the clinical value of a strip test for measuring the urinary albumin-to-creatinine ratio (ACR) in prediabetes and diabetes.

METHODS

Spot urine samples were obtained from 226 prediabetic and 275 diabetic subjects during regular health checkups. Urinary ACR was measured by using strip and laboratory quantitative tests.

RESULTS

The positive rates of albuminuria measured by using the ACR strip test were 15.5% (microalbuminuria, 14.6%; macroalbuminuria, 0.9%) and 30.5% (microalbuminuria, 25.1%; macroalbuminuria, 5.5%) in prediabetes and diabetes, respectively. In the prediabetic population, the sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of the ACR strip method were 92.0%, 94.0%, 65.7%, 99.0%, and 93.8%, respectively; the corresponding values in the diabetic population were 80.0%, 91.6%, 81.0%, 91.1%, and 88.0%, respectively. The median [interquartile range] ACR values in the strip tests for measurement ranges of <30, 30-300, and >300 mg/g were 9.4 [6.3-15.4], 46.9 [26.5-87.7], and 368.8 [296.2-575.2] mg/g, respectively, using the laboratory method.

CONCLUSIONS

The ACR strip test showed high sensitivity, specificity, and negative predictive value, suggesting that the test can be used to screen for albuminuria in cases of prediabetes and diabetes.

Blocking lysophosphatidic acid receptor 1 signaling inhibits diabetic nephropathy in db/db mice

Lysophosphatidic acid (LPA) is known to regulate various biological responses by binding to LPA receptors. The serum level of LPA is elevated in diabetes, but the involvement of LPA in the development of diabetes and its complications remains unknown. Therefore, we studied LPA signaling in diabetic nephropathy and the molecular mechanisms involved. The expression of autotaxin, an LPA synthesis enzyme, and LPA receptor 1 was significantly increased in both mesangial cells (SV40 MES13) maintained in high-glucose media and the kidney cortex of diabetic db/db mice. Increased urinary albumin excretion, increased glomerular tuft area and volume, and mesangial matrix expansion were observed in db/db mice and reduced by treatment with ki16425, a LPA receptor 1/3 antagonist. Transforming growth factor (TGF)β expression and Smad-2/3 phosphorylation were upregulated in SV40 MES13 cells by LPA stimulation or in the kidney cortex of db/db mice, and this was blocked by ki16425 treatment. LPA receptor 1 siRNA treatment inhibited LPA-induced TGFβ expression, whereas cells overexpressing LPA receptor 1 showed enhanced LPA-induced TGFβ expression. LPA treatment of SV40 MES13 cells increased phosphorylated glycogen synthase kinase (GSK)3β at Ser9 and induced translocation of sterol regulatory element-binding protein (SREBP)1 into the nucleus. Blocking GSK3β phosphorylation inhibited SREBP1 activation and consequently blocked LPA-induced TGFβ expression in SV40 MES13 cells. Phosphorylated GSK3β and nuclear SREBP1 accumulation were increased in the kidney cortex of db/db mice and ki16425 treatment blocked these pathways. Thus, LPA receptor 1 signaling increased TGFβ expression via GSK3β phosphorylation and SREBP1 activation, contributing to the development of diabetic nephropathy.

Classification and Differential Diagnosis of Diabetic Nephropathy

Diabetic nephropathy (DN) is a major cause of end-stage renal disease throughout the world in both developed and developing countries. This review briefly introduces the characteristic pathological changes of DN and Tervaert pathological classification, which divides DN into four classifications according to glomerular lesions, along with a separate scoring system for tubular, interstitial, and vascular lesions. Given the heterogeneity of the renal lesions and the complex mechanism underlying diabetic nephropathy, Tervaert classification has both significance and controversies in the guidance of diagnosis and prognosis. Applications and evaluations using Tervaert classification and indications for renal biopsy are summarized in this review according to recent studies. Meanwhile, differential diagnosis with another nodular glomerulopathy and the situation that a typical DN superimposed with a nondiabetic renal disease (NDRD) are discussed and concluded in this review.

Genetic Targeting of Arginase-II in Mouse Prevents Renal Oxidative Stress and Inflammation in Diet-Induced Obesity

Obesity is associated with development and progression of chronic kidney disease (CKD). Recent evidence demonstrates that enhanced levels of the L-arginine:ureahydrolase, including the two isoenzymes arginase-I (Arg-I) and arginase-II (Arg-II) in vascular endothelial cells promote uncoupling of endothelial nitric oxide synthase (eNOS), leading to increased superoxide radical anion and decreased NO production thereby endothelial dysfunction. Arg-II but not Arg-I is abundantly expressed in kidney and the role of Arg-II in CKD is uncertain and controversial. We aimed to investigate the role of Arg-II in renal damage associated with diet-induced obesity mouse model. Wild type (WT) C57BL/6 mice and mice deficient in Arg-II gene (Arg-II^−/−) were fed with either a normal chow (NC) or a high-fat-diet (HFD) for 14 weeks (starting at the age of 7 weeks) to induce obesity. In WT mice, HFD feeding caused frequent renal lipid accumulation, enhancement of renal reactive oxygen species (ROS) levels which could be attenuated by a NOS inhibitor, suggesting uncoupling of NOS in kidney. HFD feeding also significantly augmented renal Arg-II expression and activity. All the alterations in the kidney under HFD feeding were reduced in Arg-II^−/− mice. Moreover, mesangial expansion as analyzed by Periodic Acid Schiff (PAS) staining and renal expression of vascular adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) in HFD-fed WT mouse assessed by immunoblotting were reduced in the HFD-fed Arg-II^−/− mice, although there was no significant difference in body weight and renal weight/body weight ratio between the WT and Arg-II^−/− mice. Thus, Arg-II expression/activity is enhanced in kidney of diet-induced obesity mice. Genetic targeting of Arg-II prevents renal damage associated with obesity, suggesting an important role of Arg-II in obesity-associated renal disease development.

Retraction statement: ‘Urotensin II inhibits autophagy in renal tubular epithelial cells and induces extracellular matrix production in early diabetic mice’ by Guan‐Jong Chen, Fei Wu, Xin‐Xin Pang, Ai‐Hua Zhang, Jun‐Bao Shi, Min Lu and Chao‐Shu Tang

AIMS/INTRODUCTION

Urotensin II (UII) and autophagy have been considered as important components in the pathogenesis of diabetic nephropathy. The present study explores whether UII can regulate autophagy in the kidney, and its effect in diabetes.

MATERIALS AND METHODS

Immunohistochemistry and western blot were carried out on the kidney tissues of diabetic UII receptor (UT) gene knockout mice, wild-type diabetic mice and normal control mice. For the in vitro experiment, HK-2 cells were treated with UII (10^-7 mol/L) in the presence or absence of UT antagonist, SB-657510, (10^-6 mol/L) or autophagy inducer, rapamycin (10^-3 mol/L), for 12 h. Markers for autophagy (LC3-II, p62/SQSTM1) and extracellular matrix (fibronectin, collagen IV) were analyzed.

RESULTS

In diabetic UT knockout mice, expression of LC3-II is increased and p62 was reduced in comparison with that of the normal diabetic mice. Fibronectin and collagen IV were downregulated in diabetic UT knockout mice when compared with that of the normal diabetic mice. For the in vitro cell experiment, UII was shown to inhibit expression LC3-II and increase expression of p62 in comparison with that of the normal control. Treatment with SB-657510 can block UII-induced downregulation of LC3-II and upregulation of p62 while inhibiting UII-induced upregulation of fibronectin and collagen IV. Adding autophagy inducer, rapamycin, also inhibited UII-induced upregulation of fibronectin and collagen IV.

CONCLUSIONS

The present study is the first to show that UII can downregulate autophagy in the kidney while accompanying the increased production of extracellular matrix in early diabetes. Our in vitro study also showed that upregulation of autophagy can decrease UII-induced production of extracellular matrix in HK-2 cells.

microRNAs in Diabetic Kidney Disease

Diabetes and diabetic kidney diseases have continually exerted a great burden on our society. Although the recent advances in medical research have led to a much better understanding of diabetic kidney diseases, there is still no successful strategy for effective treatments for diabetic kidney diseases. Recently, treatment of diabetic kidney diseases relies either on drugs that reduce the progression of renal injury or on renal replacement therapies, such as dialysis and kidney transplantation. On the other hand, searching for biomarkers for early diagnosis and effective therapy is also urgent. Discovery of microRNAs has opened to a novel field for posttranscriptional regulation of gene expression. Results from cell culture experiments, experimental animal models, and patients under diabetic conditions reveal the critical role of microRNAs during the progression of diabetic kidney diseases. Functional studies demonstrate not only the capability of microRNAs to regulate expression of target genes, but also their therapeutic potential to diabetic kidney diseases. The existence of microRNAs in plasma, serum, and urine suggests their possibility to be biomarkers in diabetic kidney diseases. Thus, identification of the functional role of microRNAs provides an essentially clinical impact in terms of prevention and treatment of progression in diabetic kidney diseases as it enables us to develop novel, specific therapies and diagnostic tools for diabetic kidney diseases.

An autopsy study suggests that diabetic nephropathy is underdiagnosed

The reported prevalence of diabetic nephropathy (DN) among patients with diabetes varies widely. Most studies use the presence of microalbuminuria for clinical onset of DN in the absence of a histopathologic evaluation. In this autopsy study, we collected and analyzed data from a cohort of patients with type 1 or 2 diabetes and determined the prevalence of histologically proven DN in patients with or without clinical manifestations of renal disease. We also examined the distribution among histopathologic classes with respect to clinical parameters. Renal tissue specimens from autopsies and clinical data were collected retrospectively from 168 patients with diabetes. The histopathologic classification for DN was scored as were interstitial and vascular parameters. In this cohort, 106 of 168 patients had histopathologic changes in the kidney characteristic of DN. Twenty of the 106 histologically proven DN cases did not present with DN-associated clinical manifestations within their lifetime. Glomerular and interstitial lesions were associated with renal function but not with proteinuria. We also found that underdiagnosed DN may encompass all histopathologic classes except the sclerotic class. Thus, the prevalence of histologically proven DN was higher than previously appreciated, and we found a relatively high proportion of DN that was clinically underdiagnosed yet histologically proven, suggesting that DN lesions may develop before the onset of clinical findings.

Diabetic nephropathy: What does the future hold?

The consensus management of diabetic nephropathy (DN) in 2015 involves good control of glycaemia, dyslipidaemia and blood pressure (BP). Blockade of the renin-angiotensin-aldosterone system using angiotensin-converting enzyme inhibitors, angiotensin-2 receptor blockers or mineralocorticoid inhibitors are key therapeutic approaches, shown to be beneficial once overt nephropathy is manifest, as either, or both, of albuminuria and loss of glomerular filtration rate. Some significant additional clinical benefits in slowing the progression of DN was reported from the Remission clinic experience, where simultaneous intensive control of BP, tight glycaemic control, weight loss, exercise and smoking cessation were prioritised in the management of DN. This has not proved possible to translate to more conventional clinical settings. This review briefly looks over the history and limitations of current therapy from landmark papers and expert reviews, and following an extensive PubMed search identifies the most promising clinical biomarkers (both established and proposed). Many challenges need to be addressed urgently as in order to obtain novel therapies in the clinic; we also need to examine what we mean by remission, stability and progression of DN in the modern era.

Spironolactone Add-on for Preventing or Slowing the Progression of Diabetic Nephropathy: A Meta-analysis

PURPOSE

The aim of this meta-analysis was to evaluate the benefits and potential adverse effects of adding spironolactone to standard antidiabetic/renoprotective/antihypertensive (AD/RP/AHT) treatment in patients with diabetic nephropathy (DN).

METHODS

PubMed/MEDLINE and Web of Knowledge were searched for relevant randomized, controlled studies (RCTs) or quasi-RCTs of the effects of adding spironolactone to standard AD/RP/AHT treatment in patients with DN. Results were summarized with a random-effects model or a fixed-effects model.

FINDINGS

According to the outcomes measured (benefits and risks of adding spironolactone to standard AD/RP/AHT treatment), compared with controls, the addition of spironolactone significantly decreased end-of-treatment (EOT) 24-hour urinary albumin/protein excretion and significantly increased percentage reduction from baseline in urinary albumin/creatinine ratio (UACR), although it did not significantly affect EOT UACR. The addition of spironolactone further led to a significantly greater reduction from baseline in glomerular filtration rate (GFR)/estimated (e) GFR, although it did not significantly affect EOT GFR/eGFR. Further, the addition of spironolactone significantly reduced EOT in-office, 24-hour, and daytime systolic and diastolic blood pressure (SBP and DBP, respectively) and led to significantly greater reductions from baseline in in-office SBP and DBP, although it did not significantly affect nighttime SBP or DBP. Finally, the addition of spironolactone significantly increased mean serum/plasma potassium levels and the risk for hyperkalemia.

IMPLICATIONS

Spironolactone could be added to preexisting AD/RP/AHT therapy in patients with DN to prevent or slow DN progression by reducing proteinuria. The addition of spironolactone would likely provide even more beneficial effect in patients with DN and hypertension due to the BP reduction associated with spironolactone use. However, the beneficial effects of spironolactone add-on should be weighed against its potential risks, especially hyperkalemia. The long-term effects of spironolactone add-on on renal outcomes and mortality need to be studied.

Non-proteinuric pathways in loss of renal function in patients with type 2 diabetes

Largely on the basis of data from patients with type 1 diabetes, the natural history of diabetic renal disease has been classified as a sequence of three stages: normoalbuminuria, microalbuminuria, and macroalbuminuria. Progressive decline of glomerular filtration rate (GFR) was thought to parallel the onset of macroalbuminuria (overt nephropathy), whereas glomerular hyperfiltration was deemed a hallmark of early disease. However, researchers have since shown that albuminuria is a continuum and that GFR can start to decline before progression to overt nephropathy. In addition to proteinuria, other risk factors might contribute to GFR deterioration including female sex, obesity, dyslipidaemia (in particular hypertriglyceridaemia), hypertension, and glomerular hyperfiltration, at least in a subgroup of patients. This phenomenon could explain why patients with type 2 diabetes can have renal insufficiency even before the onset of overt nephropathy, and might also suggest why the heterogeneous phenotype of type 2 diabetic renal disease does not necessarily associate with typical histological lesions of diabetic renal disease, unlike in type 1 diabetic renal disease. Patients with renal insufficiency but without albuminuria are usually excluded from randomised clinical trials in overt nephropathy, thus optimum treatment for this group of patients is unknown. The wide inter-patient variability of the disease probably needs individually tailored intervention.

Diabetic Kidney Disease: Pathophysiology and Therapeutic Targets

Diabetes is a worldwide epidemic that has led to a rise in diabetic kidney disease (DKD). Over the past two decades, there has been significant clarification of the various pathways implicated in the pathogenesis of DKD. Nonetheless, very little has changed in the way clinicians manage patients with this disorder. Indeed, treatment is primarily centered on controlling hyperglycemia and hypertension and inhibiting the renin-angiotensin system. The purpose of this review is to describe the current understanding of how the hemodynamic, metabolic, inflammatory, and alternative pathways are all entangled in pathogenesis of DKD and detail the various therapeutic targets that may one day play a role in quelling this epidemic.