Diabetic nephropathy: Linking histology, cell biology, and genetics

Long Non-coding RNA ZFAS1 Regulates Fibrosis and Scortosis in the Cell Model of Diabetic Nephropathy Through miR-525-5p/SGK1 Axis

Diabetic nephropathy (DN) is a common clinical syndrome in diabetic patients. Functional characterization of non-coding (ncRNAs) involved in the progression of DN can provide insights into the diagnosis and therapeutic management of DN. Human kidney proximal tubular epithelial cells (HK-2) were challenged by high glucose (HG, 50 mM) as a cell model of DN. The expression level of long non-coding RNA (lncRNA) ZFAS1 was quantified by qRT-PCR. The proteins and cytokines related to fibrosis and scortosis in DN (NLRP3, GSDMD-N, IL-1β and Caspase 1, fibronectin, collagen I, collagen III, IL-1β, and IL-18) were examined by western blot or ELISA. RNA precipitation and luciferase reporter activity experiments were conducted to assess the molecular associations. ZFAS1 and SGK1 were highly induced in HK-2 cells challenged with HG, while miR-525-5p downregulated upon HG treatment. ZFAS1 knockdown attenuated HG-induced fibrosis and scortosis in HK-2 cells by reducing the levels of NLRP3, GSDMD-N, Caspase 1, fibronectin, collagen I/III, IL-1β, and IL-18. Mechanically, ZFAS1 knockdown protected HK-2 cells from HG-induced injury by upregulating miR-525-5p and repressing SGK1 expression. Overall, our results suggest that knocking down ZFAS1 may be formulated as a protective strategy in ameliorating DN progression through regulating miR-525-5p/SGK1 pathway. Targeting ZFAS1 could be further explored as a potential approach for the management of DN.

Extracellular vesicles as tools and targets in therapy for diseases

Extracellular vesicles (EVs) are nano-sized, membranous structures secreted into the extracellular space. They exhibit diverse sizes, contents, and surface markers and are ubiquitously released from cells under normal and pathological conditions. Human serum is a rich source of these EVs, though their isolation from serum proteins and non-EV lipid particles poses challenges. These vesicles transport various cellular components such as proteins, mRNAs, miRNAs, DNA, and lipids across distances, influencing numerous physiological and pathological events, including those within the tumor microenvironment (TME). Their pivotal roles in cellular communication make EVs promising candidates for therapeutic agents, drug delivery systems, and disease biomarkers. Especially in cancer diagnostics, EV detection can pave the way for early identification and offers potential as diagnostic biomarkers. Moreover, various EV subtypes are emerging as targeted drug delivery tools, highlighting their potential clinical significance. The need for non-invasive biomarkers to monitor biological processes for diagnostic and therapeutic purposes remains unfulfilled. Tapping into the unique composition of EVs could unlock advanced diagnostic and therapeutic avenues in the future. In this review, we discuss in detail the roles of EVs across various conditions, including cancers (encompassing head and neck, lung, gastric, breast, and hepatocellular carcinoma), neurodegenerative disorders, diabetes, viral infections, autoimmune and renal diseases, emphasizing the potential advancements in molecular diagnostics and drug delivery.

Multifaceted relationship between diabetes and kidney diseases: Beyond diabetes

Diabetes mellitus is one of the most common causes of chronic kidney disease. Kidney involvement in patients with diabetes has a wide spectrum of clinical presentations ranging from asymptomatic to overt proteinuria and kidney failure. The development of kidney disease in diabetes is associated with structural changes in multiple kidney compartments, such as the vascular system and glomeruli. Glomerular alterations include thickening of the glomerular basement membrane, loss of podocytes, and segmental mesangiolysis, which may lead to microaneurysms and the development of pathognomonic Kimmelstiel-Wilson nodules. Beyond lesions directly related to diabetes, awareness of the possible coexistence of nondiabetic kidney disease in patients with diabetes is increasing. These nondiabetic lesions include focal segmental glomerulosclerosis, IgA nephropathy, and other primary or secondary renal disorders. Differential diagnosis of these conditions is crucial in guiding clinical management and therapeutic approaches. However, the relationship between diabetes and the kidney is bidirectional; thus, new-onset diabetes may also occur as a complication of the treatment in patients with renal diseases. Here, we review the complex and multifaceted correlation between diabetes and kidney diseases and discuss clinical presentation and course, differential diagnosis, and therapeutic oppor-tunities offered by novel drugs.

Efficacy and safety of eplerenone treatment for patients with diabetic nephropathy: A meta-analysis

Diabetic nephropathy (DN), which is correlated with an increased risk of cardiovascular disease, significantly elevates the morbidity and mortality of patients with diabetes. Recently, the benefits of mineralocorticoid receptor antagonists in chronic kidney disease (CKD), such as their anti-inflammatory and anti-fibrotic properties, have been discovered. Thus, the present meta-analysis aimed to systematically assess the efficacy and safety of eplerenone treatment in patients with DN. Six electronic databases—PubMed, The Cochrane Library, Embase, Web of Science, CNKI (China National Knowledge Infrastructure), and CBM(Chinese BioMedical Literature Database)—were searched to retrieve randomized controlled trials that assessed eplerenone treatment in patients with DN and were published up to July 31, 2021. Eight randomized controlled trials involving 838 patients were included. Between the eplerenone treatment groups and controls, significant differences were identified in 24-h urine protein levels (mean difference [MD], −19.63 [95% CI, −23.73 to −15.53], P < 0.00001), microalbuminuria (MD, -7.75 [95% CI, -9.75 to -5.75], P < 0.00001), urinary albumin-creatinine ratio (MD, -48.29 [95% CI, -64.45 to -32.14], P < 0.00001), systolic blood pressure (SBP) (MD, -2.49 [95% CI, -4.48 to -0.50], P = 0.01), serum potassium levels (MD, 0.19 [95% CI, 0.13 to 0.24], P < 0.00001), and levels of the renal fibrosis indicator laminin (MD, -8.84 [95% CI, -11.93 to -5.75], P < 0.00001). However, for the effect of estimated glomerular filtration rate (MD, 1.74 [95% CI, -0.87 to 4.35], P = 0.19) and diastolic blood pressure (MD, -0.51 [95% CI, -1.58 to 0.57], P = 0.36), the differences between the two groups were not significant. In addition, no noticeable difference was identified in the adverse events of hyperkalemia and cough between them. These findings suggest that eplerenone exerts beneficial effects on DN by significantly reducing urinary albumin or protein excretion, SBP, and laminin levels, without increasing the incidence of hyperkalemia and other adverse events.

Management of hypertension and renin-angiotensin-aldosterone system blockade in adults with diabetic kidney disease: Association of British Clinical Diabetologists and the Renal Association UK guideline update 2021

People with type 1 and type 2 diabetes are at risk of developing progressive chronic kidney disease (CKD) and end-stage kidney failure. Hypertension is a major, reversible risk factor in people with diabetes for development of albuminuria, impaired kidney function, end-stage kidney disease and cardiovascular disease. Blood pressure control has been shown to be beneficial in people with diabetes in slowing progression of kidney disease and reducing cardiovascular events. However, randomised controlled trial evidence differs in type 1 and type 2 diabetes and different stages of CKD in terms of target blood pressure. Activation of the renin-angiotensin-aldosterone system (RAAS) is an important mechanism for the development and progression of CKD and cardiovascular disease. Randomised trials demonstrate that RAAS blockade is effective in preventing/ slowing progression of CKD and reducing cardiovascular events in people with type 1 and type 2 diabetes, albeit differently according to the stage of CKD. Emerging therapy with sodium glucose cotransporter-2 (SGLT-2) inhibitors, non-steroidal selective mineralocorticoid antagonists and endothelin-A receptor antagonists have been shown in randomised trials to lower blood pressure and further reduce the risk of progression of CKD and cardiovascular disease in people with type 2 diabetes. This guideline reviews the current evidence and makes recommendations about blood pressure control and the use of RAAS-blocking agents in different stages of CKD in people with both type 1 and type 2 diabetes.

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.

Efficacy and safety of mineralocorticoid receptor antagonists with ACEI/ARB treatment for diabetic nephropathy: A meta-analysis

BACKGROUND

To explore the efficacy and safety of adding mineralocorticoid receptor antagonists (MRAs) to the treatment in diabetic nephropathy (DN) with ACEI/ARB.

METHODS

We systematically searched the PubMed, Embase and Cochrane Library databases for randomised controlled trials up to November 1st 2018 that evaluated the effects of MRAs with ACEI/ARB treatment.

RESULTS

The combination treatment of MRAs and ACEI/ARB further reduced urinary protein/albumin excretion compared with ACEI/ARB monotherapy (mean difference [MD], -44.17 [95% CIs, -61.73 to -26.61], P < .00001). Although no statistically significant changes in glomerular filtration rate were observed, the combination group significantly increased serum/plasma creatinine (MD, 7.40 [95% CIs, 4.69-10.11], P < .00001). Subgroup analysis based on generations of MRAs suggested a lower relative risk of hyperkalaemia with finerenone (relative risk, 2.22 [95% CIs, 0.13-38.13], P = .58) than eplerenone (relative risk, 2.81 [95% CIs, 1.03-7.69], P = .04) or spironolactone (relative risk, 4.58 [95% CIs, 2.60-8.08], P < .00001).

CONCLUSION

MRAs can significantly reduce proteinuria and increase blood creatinine in DN patients under blockade of the renin-angiotensin system. The combination treatment of finerenone and ACEI/ARB runs a lower risk of hyperkalaemia than eplerenone or spironolactone.

Detection and Characterization of a Biochemical Signature Associated with Diabetic Nephropathy Using Near-infrared Spectroscopy on Tissue Sections

Histological evaluation of renal biopsies is currently the gold standard for acquiring important diagnostic and prognostic information in diabetic nephropathy (DN) patients. Nevertheless, there is an unmet clinical need for new biomarkers that allow earlier diagnosis and risk stratification. As biochemical changes in tissues must precede any symptomatic or morphological expression of a disease, we explored the potential of near-infrared (NIR) spectroscopy in the detection of a biochemical signature associated with DN. Kidney tissue sections were investigated using NIR spectroscopy, followed by principal component analysis and soft independent modelling of class analogy. A biochemical signature indicative of DN was detected, which enabled perfect discrimination between tissue sections with normal histological findings (n = 27) and sections obtained from DN patients (n = 26). Some spectral changes related to carbamoylation and glycation reactions appeared to be similar to the ones obtained in patients with DN. In addition, treatment with the deglycating enzyme fructosamine-3-kinase resulted in partial to pronounced restorations of the spectral pattern. Significant relationships were found between spectral features and laboratory parameters indicative of glycemic and uremic load, such as hemoglobin A1c, urea, creatinine, estimated glomerular filtration rate, and proteinuria. The presented method could be a useful tool to complement histopathological analysis in order to prevent or delay further disease progression, especially in the setting of post-transplant surveillance kidney biopsies.

Occurrence of Diabetic Nephropathy After Renal Transplantation Despite Intensive Glycemic Control: An Observational Cohort Study

OBJECTIVE

The kinetics and risk factors of diabetic nephropathy after kidney transplantation remain unclear. This study investigated the posttransplant occurrence of diabetic nephropathy and the contribution of posttransplant glycemic control.

RESEARCH DESIGN AND METHODS

We performed a single-center prospective cohort study of 953 renal allograft recipients and 3,458 protocol-specified renal allograft biopsy specimens up to 5 years after transplantation. The effects of pretransplant diabetes and glycemic control (glycated hemoglobin levels) on the posttransplant histology were studied.

RESULTS

Before transplantation, diabetes was present in 164 (17.2%) renal allograft recipients, primarily type 2 (n = 146 [89.0%]). Despite intensive glycemic control (glycated hemoglobin 7.00 ± 1.34% [53 ± 14.6 mmol/mol], 6.90 ± 1.22% [52 ± 13.3 mmol/mol], and 7.10 ± 1.13% [54 ± 12.4 mmol/mol], at 1, 2, and 5 years after transplantation), mesangial matrix expansion reached a cumulative incidence of 47.7% by 5 years in the pretransplant diabetes group versus 27.1% in patients without diabetes, corresponding to a hazard ratio of 1.55 (95% CI 1.07-2.26; P = 0.005). Mesangial matrix expansion was not specific for diabetic nephropathy and associated independently with increasing age. Pretransplant diabetes was associated with posttransplant proteinuria but not with estimated glomerular filtration rate, graft failure, or any other structural changes of the glomerular, vascular, or tubulointerstitial renal compartments. The occurrence of diabetic nephropathy was independent of posttransplant glycated hemoglobin levels.

CONCLUSIONS

Mesangial matrix expansion, an early indicator of diabetic nephropathy, can occur rapidly in patients with diabetes before transplantation, despite intensive glycemic control. Prevention of diabetic nephropathy requires more than pursuing low levels of glycated hemoglobin.

Visceral Leishmaniasis and Glomerulonephritis: A Case Report

Visceral leishmaniasis is an endemic in the southwestern region of Saudi Arabia, with a low incidence rate. Clinical presentations of visceral leishmaniasis include recurrent fever, substantial weight loss, hepatosplenomegaly and anemia. However, the clinical features may not be easily evident owing to the involvement of multiple organs. This, in turn, can cause difficulties in establishing the correct diagnosis, and subsequently, in managing the patient. Here, the authors report a case of a 42-year-old male from Jizan, southwestern Saudi Arabia, who presented with impaired renal function. After kidney biopsy, the patient was diagnosed with glomerulonephritis of unknown etiology and treated with mycophenolate and prednisone. After 3 months, the patient developed high fever with hepatomegaly and pancytopenia. Based on the investigations, a possible diagnosis of visceral leishmaniasis was considered. Accordingly, he was treated with liposomal amphotericin B, following which his condition improved significantly. This case report discusses the relationship between glomerulonephritis and visceral leishmaniasis and focuses on the potential consequences of glomerulonephritis management without investigating the etiology of the underlying diseases, especially in patients from tropical and subtropical areas.

Podocyte-derived microparticles promote proximal tubule fibrotic signaling via p38 MAPK and CD36

Tubulointerstitial fibrosis is a hallmark of advanced diabetic kidney disease that is linked to a decline in renal function, however the pathogenic mechanisms are poorly understood. Microparticles (MPs) are 100–1000 nm vesicles shed from injured cells that are implicated in intercellular signalling. Our lab recently observed the formation of MPs from podocytes and their release into urine of animal models of type 1 and 2 diabetes and in humans with type 1 diabetes. The purpose of the present study was to examine the role of podocyte MPs in tubular epithelial cell fibrotic responses. MPs were isolated from the media of differentiated, untreated human podocytes (hPODs) and administered to cultured human proximal tubule epithelial cells (PTECs). Treatment with podocyte MPs increased p38 and Smad3 phosphorylation and expression of the extracellular matrix (ECM) proteins fibronectin and collagen type IV. MP-induced responses were attenuated by co-treatment with the p38 inhibitor SB202190. A transforming growth factor beta (TGF-β) receptor inhibitor (LY2109761) blocked MP-induced Smad3 phosphorylation and ECM protein expression but not p38 phosphorylation suggesting that these responses occurred downstream of p38. Finally, blockade of the class B scavenger receptor CD36 completely abrogated MP-mediated p38 phosphorylation, downstream Smad3 activation and fibronectin/collagen type IV induction. Taken together our results suggest that podocyte MPs interact with proximal tubule cells and induce pro-fibrotic responses. Such interactions may contribute to the development of tubular fibrosis in glomerular disease.

Involvement of MicroRNAs in Diabetes and Its Complications

Diabetes is a severe condition worldwide. It is characterized by chronic hyperglycemia and is caused by defects in insulin production, secretion, and action. Both genetic and environmental factors contribute to the development of type 1 and type 2 diabetes. The pathogenesis of diabetes is complex and the underlying molecular mechanisms are only partially understood. MicroRNAs (miRNAs) play a fundamental role in diabetes and its complications. This chapter focuses on the dysregulation of miRNAs involved in the regulation of pancreatic islet insulin production and secretion as well as action and signaling in peripheral tissues. The roles of miRNAs in the development of diabetic complications are also discussed. Modulating miRNA expression, by either upregulation or inhibition, holds a promise as a strategy for treating this metabolic disease.

Effect of Saxagliptin on Renal Outcomes in the SAVOR-TIMI 53 Trial

OBJECTIVE

Dipeptidyl peptidase 4 inhibitors may have a protective effect in diabetic nephropathy.

RESEARCH DESIGN AND METHODS

We studied renal outcomes of 16,492 patients with type 2 diabetes, randomized to saxagliptin versus placebo and followed for a median of 2.1 years in the Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus-Thrombolysis in Myocardial Infarction 53 (SAVOR-TIMI 53) trial.

RESULTS

At baseline, 9,696 (58.8%) subjects had normoalbuminuria (albumin/creatinine ratio [ACR] <30 mg/g), 4,426 (26.8%) had microalbuminuria (ACR 30-300 mg/g), and 1,638 (9.9%) had macroalbuminuria (ACR >300 mg/g). Treatment with saxagliptin was associated with improvement in and/or less deterioration in ACR categories from baseline to end of trial (EOT) (P = 0.021, P < 0.001, and P = 0.049 for individuals with baseline normoalbuminuria, microalbuminuria, and macroalbuminuria, respectively). At 2 years, the difference in mean ACR change between saxagliptin and placebo arms was -19.3 mg/g (P = 0.033) for estimated glomerular filtration rate (eGFR) >50 mL/min/body surface area per 1.73 m² (BSA), -105 mg/g (P = 0.011) for 50 ≥ eGFR ≥ 30 mL/min/BSA, and -245.2 mg/g (P = 0.086) for eGFR <30 mL/min/BSA. Analyzing ACR as a continuous variable showed reduction in ACR with saxagliptin (1 year, P < 0.0001; 2 years, P = 0.0143; and EOT, P = 0.0158). The change in ACR did not correlate with that in HbA_1c (r = 0.041, 0.052, and 0.036; 1 year, 2 years, and EOT, respectively). The change in eGFR was similar in the saxagliptin and placebo groups. Safety renal outcomes, including doubling of serum creatinine, initiation of chronic dialysis, renal transplantation, or serum creatinine >6.0 mg/dL, were similar as well.

CONCLUSIONS

Treatment with saxagliptin improved ACR, even in the normoalbuminuric range, without affecting eGFR. The beneficial effect of saxagliptin on albuminuria could not be explained by its effect on glycemic control.

Effect of losartan and spironolactone on triglyceride-rich lipoproteins in diabetic nephropathy

Angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARBs) can improve dyslipidemia in patients with diabetes and albuminuria. Whether combined ACEi+ARB or ACEi+mineralocorticoid receptor blockade improves dyslipidemia is not known. We hypothesized long-term administration of either losartan 100 mg or spironolactone 25 mg once daily added onto lisinopril 80 mg once daily would improve dyslipidemia in diabetic nephropathy (DN). We measured lipid levels, very-low-density (V), intermediate-density (I), low-density (LDL), high-density (HDL) lipoprotein, LDL particle size with their respective cholesterol (C) and apolipoprotein B levels (ApoB), and urine albumin/creatinine ratio (UACR) at 12-week interval during a 48-week randomized, double-blind placebo-controlled trial in 81 patients with DN. Plasma lipids and lipoprotein C were analyzed enzymatically and Apo B was determined chemically. Data were analyzed by mixed model repeated measures. ΔUACR differed among treatment arms (placebo −24.6%, los −38.2%, spiro −51.6%, p=0.02). No correlation existed between ΔUACR and ΔTG or any of the lipid or lipoprotein measurements. Compared with placebo losartan, but not spironolactone, decreased TG (−20.9% vs +34.3%, p<0.01), V+I C(−18.8% vs +21.3%, p<0.01), and V+I-ApoB (−13.2% vs +21%, p<0.01). There were no significant changes in body weight, HbA1c or other lipoprotein variables. We conclude losartan improves dyslipidemia in patients with DN. We speculate the mechanism improved clearance of VLDL and remnant lipoproteins.

Nodular glomerulosclerosis and renin angiotensin system in Chinese patients with type 2 diabetes

BACKGROUND

Diabetic nephropathy (DN) is a multifactorial and polygenic disease with nodular glomerulosclerosis (NGS) pathognomonic for diabetes and hypertension. Patients with type 2 diabetes and hypertension have characteristic renin-angiotensin system (RAS) gene polymorphisms.

METHODS AND RESULTS

In this retrospective cohort study, we correlated the presence of NGS with renal function, angiotensin-converting enzyme (ACE) genotypes (DD, DI, and II), angiotensinogen (AGT) genotypes (MM, MT, and TT) and immunohistochemical staining characteristics of RAS components in 847 patients and 172 consecutive autopsy cases with type 2 diabetes. T allele of AGT was associated with macroalbuminuria (P = 0.040). Multitude regression analysis revealed ACE insertion (I)/deletion (D) polymorphism as an independent determinant for estimated glomerular filtration rate (eGFR) less than 60 mL min(-1)·1.73 m(-2) (DD carriers: odds ratio [OR] = 3.46, 95% confidence interval [CI] = 1.08-11.07; DI carriers: OR = 3.51, 95% CI = 1.63-7.56). A significant association between NGS and eGFR less than 60 mL min(-1)·1.73 m(-2) also persisted after adjusting for nonlinear relationship (P < 0.001). In NGS patients, immunoreactivity of angiotensin I converting enzyme 2 (ACE2) significantly decreased in glomeruli with mesangial nodules compared with glomeruli without the mesangial nodules.

CONCLUSIONS

These data suggest associations of ACE D allele with glomerular filtration impairment, and NGS with glomerular ACE2 down-regulation and reduced glomerular filtration in Chinese patients with type 2 diabetes.

Urinary Cyclophilin A as a New Marker for Diabetic Nephropathy: A Cross-Sectional Analysis of Diabetes Mellitus

Type 2 diabetes mellitus (DM) is the most common single cause of end-stage renal disease. Albuminuria is the most commonly used marker to predict onset of diabetic nephropathy (DN) without enough sensitivity and specificity to detect early DN. This is the first study to identify urinary cyclophilin A (CypA) as a new biomarker for early DN.We recruited DM outpatients and healthy control subjects from January 2014 to December 2014. In this cross-sectional study, patients' urine samples were collected to determine the expression of urinary CypA. We also treated mesangial (MES-13) and tubular (HK-2) cells with glucose or free radicals to observe the expression of secreted CypA in Western blot analysis.A total of 100 DN patients and 20 healthy control subjects were enrolled. All variables were matched. In univariate analysis, the concentration of urinary CypA correlated well with the progression of renal function. A significant increase in urinary CypA was noted in stage 2 DN and persisted in later stages. We could diagnose stage 2 DN using urinary CypA with a sensitivity of 90.0% and specificity of 72.7%. The area under curve was up to 0.85, indicating a good discriminatory power. In cellular models, MES-13 and HK-2 cells can both release CypA.Urinary CypA is a good biomarker for early DN detection in humans and it can be released from either mesangial or tubular cells. The underlying molecular mechanisms still need further clarification in cellular and animal studies.

Update on blood pressure control and renal outcomes in diabetes mellitus

Diabetic nephropathy (DN) is associated with a high incidence of cardiovascular (CV) morbidity and mortality. Although relationships between hypertension and diabetic nephropathy are complex, blood pressure (BP) control is an important management strategy in the prevention of onset and progression of DN in patients with diabetes mellitus (DM). Recent guidelines recommend less stringent BP targets among patients with type 2 DM and chronic kidney disease. These recommendations are based mostly on lack of benefit in CV outcomes with a low BP target. We review the current information on efficacy of BP control in improving renal outcomes in patients with type 2 DM. Presently, although intensive BP control has been was beneficial in decreasing albuminuria, it has not translated into reductions in risks of hard renal endpoints, such as progression to end-stage renal disease, the need for renal replacement therapy, and mortality from renal causes.

Finerenone : third-generation mineralocorticoid receptor antagonist for the treatment of heart failure and diabetic kidney disease

INTRODUCTION

The mineralocorticoid receptor antagonists (MRAs) spironolactone and eplerenone reduce the risk of hospitalizations and mortality in patients with heart failure (HF) with reduced ejection fraction (HFrEF), and attenuate progression of diabetic kidney disease. However, their use is limited by the fear of inducing hyperkalemia, especially in patients with renal dysfunction. Finerenone is a novel nonsteroidal MRA, with higher selectivity toward the mineralocorticoid receptor (MR) compared to spironolactone and stronger MR-binding affinity than eplerenone.

AREAS COVERED

This paper discusses the chemistry, pharmacokinetics, clinical efficacy and safety of finerenone.

EXPERT OPINION

The selectivity and greater binding affinity of finerenone to the MR may reduce the risk of hyperkalemia and renal dysfunction and thereby overcome the reluctance to start and uptitrate MRAs in patients with HF and diabetic kidney disease. Studies conducted in patients with HFrEF and moderate chronic kidney disease and diabetic kidney disease, showed promising results. Phase III trials will have to show whether finerenone might become the third-generation MRA for the treatment of HF and diabetic kidney disease.

Differential expression and therapeutic efficacy of microRNA-346 in diabetic nephropathy mice

Diabetic nephropathy (DN) is a major cause of end-stage renal disease, in which the SMAD signaling pathway plays an important role. The aim of the present study was to identify differentially expressed microRNAs (miRNAs) during the progression of DN and to investigate a selected miRNA in relation to SMAD3/4 and its therapeutic efficacy. The miRNA microarray was used to identify differentially expressed miRNAs in db/db DN mice. Reverse transcription-quantitative polymerase chain reaction and immunoblot analyses were used to detect SMAD3/4 expression. The development of DN in the db/db mice was demonstrated by glucose dysregulation and typical morphological changes in the kidney. miRNA-346 (miR-346) was identified as one of the differentially expressed miRNAs. The expression of SMAD3/4 was significantly attenuated by miR-346 administration and the therapeutic effects of miR-346 were observed in the DN mouse models. miR-346 was identified as a negative regulator of SMAD3/4. SMAD3/4 was upregulated in the renal tissue of db/db mice. The administration of miR-346 attenuated the SMAD3/4 expression in renal tissue and ameliorated the renal function and glomerular histology in DN mice. This study paves the way for clinical studies of miR-346 in DN.

Combination of Angiotensin Converting Enzyme Insertion/Deletion (I/D) (rs4646994) and VEGF Polymorphism (+405G/C; rs2010963) Synergistically Associated With the Development, of Albuminuria in Iranian Patients With Type 2 Diabetes

BACKGROUND

Angiotensin-converting enzyme (ACE) insertion/deletion (I/D) and vascular endothelial growth factor (VEGF) polymorphisms have been shown to associate with diabetic nephropathy (DN).

OBJECTIVES

We examined the hypothesis that ACE-D and VEGF-G alleles act synergistically in association with DN, in patients with type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

The VEGF (rs2010963) and ACE (rs4646994) genotypes were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 490 T2DM patients. Diabetic patients were classified as T2DM patients with and without albuminuria (control). The PCR and RFLP were used to detect the VEGF and ACE alleles.

RESULTS

A total of 255 consecutive patients with T2DM and microalbuminuria (Group A) and 235 patients with T2DM and normoalbuminuria (Group B) were included in the study. In univariate analysis, the groups were statistically similar for all variables, except for glycated hemoglobin (HbA1c) (P = 0.034), and the frequency of ACE (P = 0.015) and VEGF (P = 0.006) genotypes. Our study showed that the VEGF-G and ACE-D alleles are independently associated with the development of nephropathy. According to our data, the combination of these two risk factors had a significant synergistic effect on the risk of microalbuminuria development.

CONCLUSIONS

Our study indicated that ACE-D and VEGF-G alleles can be an independent risk factor for microalbominuria in T2DM patients.

Rosuvastatin ameliorates inflammation, renal fat accumulation, and kidney injury in transgenic spontaneously hypertensive rats expressing human C-reactive protein

Recently, we derived "humanized" spontaneously hypertensive rats (SHR-CRP) in which transgenic expression of human CRP induces inflammation, oxidative stress, several features of metabolic syndrome and target organ injury. In addition, we found that rosuvastatin treatment of SHR-CRP transgenic rats can protect against pro-inflammatory effects of human CRP and also reduce cardiac inflammation and oxidative damage. In the current study, we tested the effects of rosuvastatin (5 mg/kg) on kidney injury in SHR-CRP males versus untreated SHR-CRP and SHR controls. All rats were fed a high sucrose diet. In SHR-CRP transgenic rats, treatment with rosuvastatin for 10 weeks, compared to untreated transgenic rats and SHR controls, was associated with significantly reduced systemic inflammation which was accompanied with activation of antioxidative enzymes in the kidney, lower renal fat accumulation, and with amelioration of histopathological changes in the kidney. These findings provide evidence that, in the presence of high CRP levels, rosuvastatin exhibits significant anti-inflammatory, anti-oxidative, and renoprotective effects.

Novel Therapies of Diabetic Nephropathy

Diabetic nephropathy is currently the most common cause of end stage renal disease not only in the Western hemisphere but also in the developing nations. While the available therapeutic options remain not very effective, there is a strong ongoing effort to understand the pathogenesis better and develop more useful biomarkers. As the pathogenic mediators and signaling pathways get better defined, the scope of novel pharmaceutical agents to address such mediating factors as therapeutic targets is advancing. This review provides, in addition to a brief synopsis of currently used strategies, a comprehensive review of potential therapies that have been evolving in the past decade with a specific focus on the promising agents.

Role of endoplasmic reticulum stress in apoptosis of differentiated mouse podocytes induced by high glucose

Podocytes are terminally differentiated epithelial cells lacking the ability to proliferate. The loss of podocytes is a hallmark of progressive kidney diseases, including diabetic nephropathy (DN). Endoplasmic reticulum stress (ERS)-induced apoptosis is involved in a number of pathological conditions, including DN. The aim of the present study was to investigate whether a high glucose environment induces the apoptosis of podocytes through ERS. Differentiated mouse podocytes were divided into three groups: the normal glucose group (NG, 1 g/l D-glucose), the high glucose group (HG, 4.5 g/l D-glucose) and the mannitol group (M, 1 g/l D-glucose plus 24.4 mM mannitol). The cells were harvested following stimulation with the indicated treatments for 12, 24, 48 and 72 h. Podocyte apoptosis was determined using TUNEL assay and flow cytometry (propidium iodide staining). Glucose-regulated protein 78 (GRP78), CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP/GADD153) and caspase-12 expression was analyzed by RT-PCR, western blot analysis and immunocytochemistry. The apoptotic rate increased significantly in the HG group compared with the NG and M groups at 48 and 72 h (all P<0.01). GRP78 expression, an indicator of ERS, was increased from 12 h, indicating that ERS was activated. Subsequently, two ER-associated death (ERAD) pathways, the CHOP/GADD153- and caspase‑12-dependent pathways, were detected. CHOP/GADD153 expression reached its peak at 48 h, and caspase-12 expression gradually increased with time. Spearman's correlation analysis revealed that caspase-12 and CHOP/GADD153 positively correlated with the apoptotic rate (r=0.915, P<0.01 and r=0.639, P<0.01). Our results demonstrated that hyperglycemia (high glucose) induced apoptosis partly through ERS in the differentiated mouse podocytes, which possibly contributes to the pathogenesis of DN.

A potentially functional polymorphism in the regulatory region of let-7a-2 is associated with an increased risk for diabetic nephropathy

Diabetic nephropathy (DN) is a major diabetic complication. However, the initiating molecular events triggering DN are unknown. MicroRNAs (miRNAs) have recently been identified as regulators that modulate the target gene expression and are involved in DN. However, the evidence of the mechanism is still insufficient in human samples. In this study, microRNA microarray assay was used to study gene differential expression profiles in DN and diabetes mellitus (DM) patients. One of the specific differentially expressed microRNAs, let-7a, was down-expressed in DN. Additionally, the expression of let-7a was also decreased in DN by real-time RT PCR in the patients' samples. Moreover, single nucleotide polymorphism (SNP) analysis was used to evaluate the relationship between three SNPs in the regulatory region of let-7a-2 gene and the risk of DN in the Chinese Han population by means of PCR-restriction fragment length polymorphism (RFLP-PCR). Also, the genotype and allele frequencies of let-7a-2 polymorphism were tested in 274 individuals, including 108 DN, 104 DM patients and 62 health control individuals (CON). It was found that a variant rs1143770 and the distributions of CT/TT genotypes were significantly different in three groups, and the CT+TT genotypes frequencies were significantly higher in DN and DM groups than that in CON group. In conclusion, let-7a-2 might participate in the regulation of the occurrence of DN, and a potential variant rs1143770 was significantly associated with the increased risk for DN.

Predictors of diabetic nephropathy

Diabetic nephropathy (DN) is a leading cause of morbidity and mortality in diabetic patients representing a huge health and economic burden. Alarming recent data described diabetes as an unprecedented worldwide epidemic, with a prevalence of ∼6.4% of the world population in 2010, while the prevalence of CKD among diabetics was approximately 40%. With a clinical field hungry for novel markers predicting DN, several clinical and laboratory markers were identified lately with the promise of reliable DN prediction. Among those are age, gender, hypertension, smoking, sex hormones and anemia. In addition, eccentric left ventricular geometric patterns, detected by echocardiography, and renal hypertrophy, revealed by ultrasonography, are promising new markers predicting DN development. Serum and urinary markers are still invaluable elements, including serum uric acid, microalbuminuria, macroalbuminuria, urinary liver-type fatty acid-binding protein (u-LFABP), and urinary nephrin. Moreover, studies have illustrated a tight relationship between obstructive sleep apnea and the development of DN. The purpose of this review is to present the latest advances in identifying promising predictors to DN, which will help guide the future research questions in this field. Aiming at limiting this paramount threat, further efforts are necessary to identify and control independent modifiable risk factors, while developing an integrative algorithm for utilization in DN future screening programs.

Clinical value of NGAL, L-FABP and albuminuria in predicting GFR decline in type 2 diabetes mellitus patients

OBJECTIVES

Neutrophil gelatinase-associated lipocalin (NGAL) and liver-type fatty acid binding protein (L-FABP) are emerging as excellent biomarkers in the urine and plasma for the early prediction of acute and chronic kidney injury. The aims of this prospective study were to determine the role of albuminuria, and that of serum and urine levels of NGAL and L-FABP as predictors of a decline in the glomerular filtration rate (GFR) in patients with type 2 diabetes.

METHODS

A longitudinal cohort study with one hundred forty type 2 diabetic patients was conducted. Serum and urine levels of NGAL and L-FABP, and the urine albumin excretion rate were determined. The correlation between the kidney injury biomarkers and rate of GFR decline was analyzed.

RESULTS

The eGFR of study subjects decreased significantly as the study progressed (86.4±31.1 vs. 74.4±27.3 ml/min/1.73 m(2), P<0.001), and the urine albumin excretion rate increased significantly (264.9±1060.3 vs. 557.7±2092.5 mg/day, P = 0.009). The baseline urine albumin excretion rate and serum L-FABP level were significantly correlated with baseline eGFR (P<0.05). The results of regression analysis for the correlations between the rate of eGFR change and the baseline levels of NGAL and L-FABP, and the urine albumin excretion rate showed that only the urine albumin excretion rate was significantly correlated with the rate of eGFR change (standardized coefficients: -0.378; t: -4.298; P<0.001).

CONCLUSIONS

Tubular markers, such as NGAL and L-FABP, may not be predictive factors associated with GFR decline in type 2 diabetic patients.

Prevalence and risk factors of diabetic nephropathy in omani type 2 diabetics in Al-dakhiliyah region

OBJECTIVE

To assess the prevalence and risk factors of diabetic nephropathy among Omani type 2 diabetics in Al-Dakhiliyah region of the Sultanate of Oman.

METHODS

A cross-sectional and a case control study designs were used to assess the prevalence and risk factors respectively. For the prevalence study a sample of 699 diabetic subjects were selected randomly from two polyclinics in Al-Dakhiliyah region; Sumail and Nizwa polyclinics. For the case control study, a sample consisting of 215 cases and 358 controls were randomly selected from those who were included in the cross-sectional study. A well designed questionnaire has been used to collect data regarding the disease and risk factors. Data was analyzed using SPSS19 statistical program.

RESULTS

Total prevalence of diabetic nephropathy was calculated as 42.5% (95% C.I: 38.83% - 46.15%). The difference in the prevalence in the two polyclinic catchment area was not significant. The prevalence was significantly higher among males (51.6%) compared to females (36.5%). Crude analysis of the risk factors showed significant association between diabetic nephropathy and the following factors; male gender, decreased literacy, long duration of diabetes mellitus, hypertension, retinopathy, neuropathy, family history of diabetic nephropathy, poor glycemic control (high HbA1c), and hypertriglyceridemia. Multivariate analysis showed the following factors to be independent risk factors; male gender, decreased literacy, long duration of diabetes, family history of diabetic nephropathy and poor glycaemic control (high HbA1c).

CONCLUSION

The prevalence of diabetic nephropathy in this study was 42.5% and the significant risk factors associated with it included male gender, decreased literacy, long duration of diabetes, family history of diabetic nephropathy and poor glycemic control (high HbA1c).

Kidneys in chronic liver diseases

Acute kidney injury (AKI), defined as an abrupt increase in the serum creatinine level by at least 0.3 mg/dL, occurs in about 20% of patients hospitalized for decompensating liver cirrhosis. Patients with cirrhosis are susceptible to developing AKI because of the progressive vasodilatory state, reduced effective blood volume and stimulation of vasoconstrictor hormones. The most common causes of AKI in cirrhosis are pre-renal azotemia, hepatorenal syndrome and acute tubular necrosis. Differential diagnosis is based on analysis of circumstances of AKI development, natriuresis, urine osmolality, response to withdrawal of diuretics and volume repletion, and rarely on renal biopsy. Chronic glomerulonephritis and obstructive uropathy are rare causes of azotemia in cirrhotic patients. AKI is one of the last events in the natural history of chronic liver disease, therefore, such patients should have an expedited referral for liver transplantation. Hepatorenal syndrome (HRS) is initiated by progressive portal hypertension, and may be prematurely triggered by bacterial infections, nonbacterial systemic inflammatory reactions, excessive diuresis, gastrointestinal hemorrhage, diarrhea or nephrotoxic agents. Each type of renal disease has a specific treatment approach ranging from repletion of the vascular system to renal replacement therapy. The treatment of choice in type 1 hepatorenal syndrome is a combination of vasoconstrictor with albumin infusion, which is effective in about 50% of patients. The second-line treatment of HRS involves a transjugular intrahepatic portosystemic shunt, renal vasoprotection or systems of artificial liver support.

Therapeutic modalities in diabetic nephropathy: standard and emerging approaches

Diabetes mellitus is the leading cause of end stage renal disease and is responsible for more than 40% of all cases in the United States. Current therapy directed at delaying the progression of diabetic nephropathy includes intensive glycemic and optimal blood pressure control, proteinuria/albuminuria reduction, interruption of the renin-angiotensin-aldosterone system through the use of angiotensin converting enzyme inhibitors and angiotensin type-1 receptor blockers, along with dietary modification and cholesterol lowering agents. However, the renal protection provided by these therapeutic modalities is incomplete. More effective approaches are urgently needed. This review highlights the available standard therapeutic approaches to manage progressive diabetic nephropathy, including markers for early diagnosis of diabetic nephropathy. Furthermore, we will discuss emerging strategies such as PPAR-gamma agonists, Endothelin blockers, vitamin D activation and inflammation modulation. Finally, we will summarize the recommendations of these interventions for the primary care practitioner.

The role of vascular endothelial growth factor +405 G/C polymorphism and albuminuria in patients with type 2 diabetes mellitus

Observations on the association between the vascular endothelial growth factor (VEGF) gene polymorphism and nephropathy have been inconsistent, which might be due to ethnic and geographical variations. Furthermore, the relationship between +405 G/C polymorphism and albuminuria in the diabetic population has not been sufficiently studied. The aim of this study was to evaluate for the first time the possible association between +405 G/C polymorphism and albuminuria in an population from Tehran of Iran. A total of 255 consecutive patients with type 2 diabetes and microalbuminuria (Group A) and 235 patients with type 2 diabetes and normoalbuminuria (Group B) were included. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to detect the VEGF alleles. In univariate analysis, the groups were statistically similar in all variables except for HbA1c (8.53 ± 1.7 in Group A vs. 8.2 ± 1.73 in Group B; P = 0.034), 24-h urinary albumin (201.33 ± 84.8 in Group A vs. 22.88 ± 3.5 in Group B; P < 0.001), and the frequency of GG genotype (31% in Group A vs. 18.7% in Group B; P = 0.006). The GG genotype was the independent predictor of albuminuria [P = 0.014, OR = 1.771, 95% confidence interval (CI) = 1.124-2.790]. Our study showed that the G allele was not associated with albuminuria, but the GG genotype in the VEGF gene is independently associated with development of nephropathy in the our diabetic population.

MicroRNAs as mediators and therapeutic targets in chronic kidney disease

Chronic kidney disease (CKD) is characterized by tubulointerstitial deposition of extracellular matrix, tubular atrophy and dilatation; the replacement of organ architecture by connective tissue results in progressive loss of organ function. Micro (mi)RNAs are important mediators of tissue fibrosis under various pathological conditions and are of potential therapeutic relevance. These short, noncoding nucleotides (∼22 bases) regulate target messenger RNAs at the post-transcriptional level. Several hundred miRNAs regulate a considerable amount of the human genome and are involved in virtually all biological processes, including cellular proliferation, apoptosis and differentiation. Thus, miRNA deregulation often results in impaired cellular function and development of disease. Here, we summarize the current knowledge on the role of miRNAs in CKD, with particular emphasis on hypertensive kidney disease, diabetic nephropathy, glomerular biology, and IgA nephropathy. Identification of miRNA regulation and function in renal pathology may pinpoint miRNAs as new therapeutic targets in kidney fibrosis and related diseases. A new class of RNA therapeutics, that is, miRNA modulators (such as antagomirs) have been developed, which enable specific targeting of miRNAs and respective downstream gene networks in vivo, thus influencing the mechanisms that underlie disease initiation or progression. The therapeutic potential of miRNA-based treatment strategies in CKD are discussed.

The emerging role of biomarkers in diabetic and hypertensive chronic kidney disease

Currently used measures to assess kidney function and injury are largely inadequate. Markers such as serum creatinine, formulas to estimate glomerular filtration rate, cystatin C, and proteinuria largely identify an underlying disease process that is well established. Thus, there has been a recent effort to identify new biomarkers that reflect kidney function, early injury, and/or repair that ultimately can relate to progression or regression of damage. Several biomarkers emerged recently that are able to detect kidney damage earlier than is currently possible with traditional biomarkers such as serum creatinine and proteinuria. Identification of urine biomarkers has proven to be beneficial in recent years because of ease of handling, stability, and the ability to standardize the various markers to creatinine or other peptides generally already present in the urine. Recent markers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and podocin have garnered a lot of attention. The emergence of these and other biomarkers is largely because of the evolution of novel genomic and proteomic applications in investigations of acute kidney injury and chronic kidney disease. In this article, we focus on the applications of these biomarkers in disease.

Addition of angiotensin receptor blockade or mineralocorticoid antagonism to maximal angiotensin-converting enzyme inhibition in diabetic nephropathy

Aldosterone promotes glomerular and tubular sclerosis independent of angiotensin II in animal models of diabetic nephropathy. Most human studies testing the renoprotective benefit of adding an angiotensin receptor blocker or a mineralocorticoid receptor antagonist to a regimen based on inhibition of angiotensin-converting enzyme (ACE) used relatively low doses of ACE inhibitors. Furthermore, these studies did not determine whether antiproteinuric effects were independent of BP lowering. We conducted a double-blind, placebo-controlled trial in 81 patients with diabetes, hypertension, and albuminuria (urine albumin-to-creatinine ratio > or =300 mg/g) who all received lisinopril (80 mg once daily). We randomly assigned the patients to placebo, losartan (100 mg daily), or spironolactone (25 mg daily) for 48 wk. We obtained blood and urine albumin, urea, creatinine, electrolytes, A1c, and ambulatory BP at baseline, 24, and 48 wk. Compared with placebo, the urine albumin-to-creatinine ratio decreased by 34.0% (95% CI, -51.0%, -11.2%, P = 0.007) in the group assigned to spironolactone and by 16.8% (95% CI, -37.3%, +10.5%, P = 0.20) in the group assigned to losartan. Clinic and ambulatory BP, creatinine clearance, sodium and protein intake, and glycemic control did not differ between groups. Serum potassium level was significantly higher with the addition of either spironolactone or losartan. In conclusion, the addition of spironolactone, but not losartan, to a regimen including maximal ACE inhibition affords greater renoprotection in diabetic nephropathy despite a similar effect on BP. These results support the need to conduct a long-term, large-scale, renal failure outcomes trial.

Genome-wide association scan for diabetic nephropathy susceptibility genes in type 1 diabetes

OBJECTIVE

Despite extensive evidence for genetic susceptibility to diabetic nephropathy, the identification of susceptibility genes and their variants has had limited success. To search for genes that contribute to diabetic nephropathy, a genome-wide association scan was implemented on the Genetics of Kidneys in Diabetes collection.

RESEARCH DESIGN AND METHODS

We genotyped approximately 360,000 single nucleotide polymorphisms (SNPs) in 820 case subjects (284 with proteinuria and 536 with end-stage renal disease) and 885 control subjects with type 1 diabetes. Confirmation of implicated SNPs was sought in 1,304 participants of the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) study, a long-term, prospective investigation of the development of diabetes-associated complications.

RESULTS

A total of 13 SNPs located in four genomic loci were associated with diabetic nephropathy with P < 1 x 10(-5). The strongest association was at the FRMD3 (4.1 protein ezrin, radixin, moesin [FERM] domain containing 3) locus (odds ratio [OR] = 1.45, P = 5.0 x 10(-7)). A strong association was also identified at the CARS (cysteinyl-tRNA synthetase) locus (OR = 1.36, P = 3.1 x 10(-6)). Associations between both loci and time to onset of diabetic nephropathy were supported in the DCCT/EDIC study (hazard ratio [HR] = 1.33, P = 0.02, and HR = 1.32, P = 0.01, respectively). We demonstratedexpression of both FRMD3 and CARS in human kidney.

CONCLUSIONS

We identified genetic associations for susceptibility to diabetic nephropathy at two novel candidate loci near the FRMD3 and CARS genes. Their identification implicates previously unsuspected pathways in the pathogenesis of this important late complication of type 1 diabetes.

The pathogenesis of diabetic nephropathy

Between 20% and 40% of patients with diabetes ultimately develop diabetic nephropathy, which in the US is the most common cause of end-stage renal disease requiring dialysis. Diabetic nephropathy has several distinct phases of development and multiple mechanisms contribute to the development of the disease and its outcomes. This Review provides a summary of the latest published data dealing with these mechanisms; it focuses not only on candidate genes associated with susceptibility to diabetic nephropathy but also on alterations in various cytokines and their interaction with products of advanced glycation and oxidant stress. Additionally, the interactions between fibrotic and hemodynamic cytokines, such as transforming growth factor beta1 and angiotensin II, respectively, are discussed in the context of new information concerning nephropathy development. We touch on the expanding clinical data regarding markers of nephropathy, such as microalbuminuria, and put them into context; microalbuminuria reflects cardiovascular and not renal risk. If albuminuria levels continue to increase over time then nephropathy is present. Lastly, we look at advances being made to enable identification of genetically predisposed individuals.

Effects of cholesterol-tagged small interfering RNAs targeting 12/15-lipoxygenase on parameters of diabetic nephropathy in a mouse model of type 1 diabetes

We previously showed that the 12/15-lipoxygenase (12/15-LO) pathway of arachidonate acid metabolism is involved in multiple events related to diabetic nephropathy (DN), including glomerular hypertrophy and extracellular matrix deposition (Kang SW, Adler SG, Nast CC, LaPage J, Gu JL, Nadler JL, Natarajan R. Kidney Int 59: 1354-1362, 2001; Kang SW, Natarajan R, Shahed A, Nast CC, LaPage J, Mundel P, Kashtan C, Adler SG. J Am Soc Nephrol 14: 3178-3187, 2003; Kim YS, Lanting L, Adler SG, Natarajan R. Kindney Int 64: 1702-1714, 2003; Reddy MA, Adler SG, Kim YS, Lanting L, Rossi JJ, Kang SW, Nadler JL, Shahed A, Natarajan R. Am J Physiol Renal Physiol 283: F985-F994, 2002). In this study, we investigated whether in vivo delivery of small interfering RNAs (siRNAs) targeting 12/15-LO can ameliorate renal injury and DN in a streptozotocin-injected mouse model of type 1 diabetes. To achieve greater in vivo access and siRNA expression in the kidney, we used double-stranded 12/15-LO siRNA oligonucleotides conjugated with cholesterol. Diabetic DBA/2J mice were injected subcutaneously with either cholesterol-tagged 12/15-LO siRNA, mismatched control siRNA, or vehicle alone, twice weekly for 7 wk. Relative to controls, mice that received 12/15-LO siRNA showed significant reduction in albuminuria, kidney-to-body weight ratios, glomerular mesangial matrix expansion, renal structural damage, and monocyte/macrophage infiltration. These effects were associated with lower renal cortical or glomerular levels of profibrotic markers transforming growth factor-beta, connective tissue growth factor, type I and type IV collagens, plasminogen activator inhibitor 1, and fibronectin. The diabetes-induced increase in glomerular cyclin-dependent kinase inhibitors that are associated with hypertrophy was also prevented by siRNA administration. Our results show for the first time that systemic delivery of cholesterol-tagged siRNAs targeting 12/15-LO has renoprotective effects under diabetic conditions and therefore could be a novel therapeutic approach for DN.

Overexpression of calmodulin in pancreatic beta cells induces diabetic nephropathy

Recently, endothelial dysfunction induced by an uncoupling of vascular endothelial growth factor (VEGF) and nitric oxide has been implicated in the pathogenesis of diabetic nephropathy (DN). Investigating the pathogenesis of DN has been limited, however, because of the lack of animal models that mimic the human disease. In this report, pancreatic beta cell-specific calmodulin-overexpressing transgenic (CaMTg) mice, a potential new model of DN, are characterized with particular emphasis on VEGF and related molecules. CaMTg mice developed hyperglycemia at 3 wk and persistent proteinuria by 3 mo. Morphometric analysis showed considerable increases in the glomerular and mesangial areas with deposition of type IV collagen. Moreover, the pathologic hallmarks of human DN (mesangiolysis, Kimmelstiel-Wilson-like nodular lesions, exudative lesions, and hyalinosis of afferent and efferent arteries with neovascularization) were observed. In addition, increased VEGF expression was associated with an increased number of peritubular capillaries. Expression of endothelial nitric oxidase synthase was reduced and that of VEGF was markedly elevated in CaMTg mice kidney compared with nontransgenic mice. No differences in VEGF receptor-1 or VEGF receptor-2 expression were observed between CaMTg mice and nontransgenic kidneys. In summary, CaMTg mice develop most of the distinguishing lesions of human DN, and the elevated VEGF expression in the setting of diminished endothelial nitric oxide synthase expression may lead to endothelial proliferation and dysfunction. This model may prove useful in the study of the pathogenesis and treatment of DN.

Pathogenesis of nonimmune glomerulopathies

Nonimmune glomerulopathies are an area of significant research. This review discusses the development of focal segmental glomerulosclerosis, with particular attention to the role of the podocyte in the initiation of glomerulosclerosis and the contribution to glomerulosclerosis from capillary hypertension and soluble factors such as transforming growth factor beta, platelet-derived growth factor, vascular endothelial growth factor, and angiotensin. The effects of these factors on endothelial and mesangial cells are also discussed. In addition, we review our current understanding of the slit diaphragm (a specialized cell junction found in the kidney), slit diaphragm-associated proteins (including nephrin, podocin, alpha-actinin-4, CD2-associated protein, and transient receptor potential channel 6), and the role of these proteins in glomerular disease. We also discuss the most recent research on the pathogenesis of collapsing glomerulosclerosis, human immunodeficiency virus associated nephropathy, Denys-Drash, diabetic nephropathy, Alport syndrome, and other diseases related to the interaction between the podocyte and the glomerular basement membrane.

Reduction of podocytes number in late diabetic alloxan nephropathy: prevention by glycemic control

PURPOSE: To determine podocyte number and GBM thickness in diabetic rats either under glycemic control or without glycemic control at 6 and 12 months after diabetes induction. METHODS: 100 wistar rats weighing 200-300g were divided into 6 groups: Normal group (N6 and N12- 25 rats); Diabetic group (D6 and D12- 25 rats), diabetic treated group ( DT 6 and DT 12- 25 rats) on insulin 1,8- 3,0 IU/Kg associated with acarbose (50mg to 100g of food) daily mixed in chow. Alloxan was injected intravenously in a dose of 42 mg/Kg of weight. Body weight, waterintake, 24-h diuresis, glycemia and glucosuria were determined before induction, 7 and 14 days after induction and monthly thereafter. Treatment started at day 14. Three groups were sacrificed at 6 months (N6,D6, DT6) and 3 groups at 12 months (N12, D12, DT12) with the renal tissue being prepared for electron microscopy. RESULTS: Glycemia in DT6¨and in DT12 was significantly different from that in D6 and D12 rats and similar to that in N6 and N12 animals. The number of podocytes in DT6 was not different from that in N6 and D6 (median = 11); the number of podocytes in DT12 (median = 11) differed from that in D12 (median = 8), but not from that in N12 (median = 11). GBM thickness in D6 (0.18 micrometers) was lower than in D12 (0.29 micrometers); while in DT6 (0.16 micrometers) it was lower than in D6 (0.18 micrometers). In DT12 (0.26 micrometers), it was lower than in D12 (0.29 micrometers). CONCLUSION: The control of hyperglycemia prevented GBM thickening in early and late (12 mo) alloxan diabetic nephropathy and podocyte number reduction.

Dietary protein restriction benefits patients with chronic kidney disease (Review Article)

The prevalence of chronic kidney disease (CKD) is rapidly increasing so every strategy should be used to avoid the complications of CKD. Most CKD symptoms or uraemia are caused by protein intolerance; symptoms arise because the patient is unable to excrete metabolic products of dietary protein and the ions contained in protein-rich foods. Consequently, CKD patients accumulate salt, phosphates, uric acid and many nitrogen-containing metabolic products, and secondary problems of metabolic acidosis, bone disease and insulin resistance become prominent. These problems can be avoided with dietary planning. Protein-restricted diets do not produce malnutrition and with these diets even patients with advanced CKD maintain body weight, serum albumin and normal electrolyte values. Non-compliance is a problem, but this can be detected using standard techniques to provide the patient with appropriate responses. The role of dietary protein restriction in the progression of CKD has not been proven, but it can reduce albuminuria and will prevent uraemic symptoms. Until a means of preventing kidney disease or progression is found, safe methods of management such as dietary manipulation should be available for CKD patients.

Carnosine as a protective factor in diabetic nephropathy: association with a leucine repeat of the carnosinase gene CNDP1

The risk of diabetic nephropathy is partially genetically determined. Diabetic nephropathy is linked to a gene locus on chromosome 18q22.3-q23. We aimed to identify the causative gene on chromosome 18 and to study the mechanism by which the product of this gene could be involved in the development of diabetic nephropathy. DNA polymorphisms were determined in 135 case (diabetic nephropathy) and 107 control (diabetes without nephropathy) subjects. The effect of carnosine on the production of extracellular matrix components and transforming growth factor-beta (TGF-beta) after exposure to 5 and 25 mmol/l d-glucose was studied in cultured human podocytes and mesangial cells, respectively. A trinucleotide repeat in exon 2 of the CNDP1 gene, coding for a leucine repeat in the leader peptide of the carnosinase-1 precursor, was associated with nephropathy. The shortest allelic form (CNDP1 Mannheim) was more common in the absence of nephropathy (P = 0.0028, odds ratio 2.56 [95% CI 1.36-4.84]) and was associated with lower serum carnosinase levels. Carnosine inhibited the increased production of fibronectin and collagen type VI in podocytes and the increased production of TGF-beta in mesangial cells induced by 25 mmol/l glucose. Diabetic patients with the CNDP1 Mannheim variant are less susceptible for nephropathy. Carnosine protects against the adverse effects of high glucose levels on renal cells.

Diabetic nephropathy: the proteinuria hypothesis

BACKGROUND/AIMS

Proteinuria, nearly a universal finding in progressive kidney disease, has been the subject of frequent recent analyses in the renal literature. Proteinuria is a hallmark of diabetic nephropathy: microalbuminuria is the principal early predictor for progression of diabetic glomerulopathy, and proteinuria may be viewed as a measure of the severity and promoter of progression of nephropathy.

METHODS

This article critically reviews for the first time the full scope of diabetic proteinuria--complex molecular mechanisms, natural history, and analysis of treatment trials--in order to address the validity of 'the proteinuria hypothesis', i.e., that diabetic proteinuria is a modifiable determinant of renal progression. This hypothesis is analyzed in detail, including recent studies on the primary therapy of diabetic nephropathy, renin-angiotensin blockade.

RESULTS

As fully developed, this hypothesis consists of three postulates: that higher amounts of proteinuria predict progressive loss of function, that proteinuria reduction correlates with slowing progression, and that proteinuria is a surrogate endpoint for clinical trials. The latter postulate has not before been adequately linked to growing information about the first two postulates as they apply to diabetic kidney disease.

CONCLUSION

While diabetic nephropathy is a disease model for the potential use of proteinuria as a surrogate marker for renal progression, this shift in perspective will require prospective data from additional clinical trials, particularly of non-renin-angiotensin blocking drugs, to be complete.