Urinary excretion of 8-oxo-7, 8-dihydro-2'-deoxyguanosine as a predictor of the development of diabetic nephropathy

Comparative Analysis of Biomarkers in Type 2 Diabetes Patients With and Without Comorbidities: Insights Into the Role of Hypertension and Cardiovascular Disease

Background

Type 2 diabetes mellitus (T2DM) are 90% of diabetes cases, and its prevalence and incidence, including comorbidities, are rising worldwide. Clinically, diabetes and associated comorbidities are identified by biochemical and physical characteristics including glycemia, glycated hemoglobin (HbA1c), and tests for cardiovascular, eye and kidney disease.

Objectives

Diabetes may have a common etiology based on inflammation and oxidative stress that may provide additional information about disease progression and treatment options. Thus, identifying high-risk individuals can delay or prevent diabetes and its complications.

Design

In patients with or without hypertension and cardiovascular disease, as part of progression from no diabetes to T2DM, this research studied the changes in biomarkers between control and prediabetes, prediabetes to T2DM, and control to T2DM, and classified patients based on first-attendance data. Control patients and patients with hypertension, cardiovascular, and with both hypertension and cardiovascular diseases are 156, 148, 61, and 216, respectively.

Methods

Linear discriminant analysis is used for classification method and feature importance, This study examined the relationship between Humanin and mitochondrial protein (MOTSc), mitochondrial peptides associated with oxidative stress, diabetes progression, and associated complications.

Results

MOTSc, reduced glutathione and glutathione disulfide ratio (GSH/GSSG), interleukin-1β (IL-1β), and 8-isoprostane were significant (P < .05) for the transition from prediabetes to t2dm, highlighting importance of mitochondrial involvement. complement component 5a (c5a) is a biomarker associated with disease progression and comorbidities, gsh gssg, monocyte chemoattractant protein-1 (mcp-1), 8-isoprostane being most important biomarkers.

Conclusions

Comorbidities affect the hypothesized biomarkers as diabetes progresses. Mitochondrial oxidative stress indicators, coagulation, and inflammatory markers help assess diabetes disease development and provide appropriate medications. Future studies will examine longitudinal biomarker evolution.

ELF5: A Molecular Clock for Breast Aging and Cancer Susceptibility

Breast cancer is predominantly an age-related disease, with aging serving as the most significant risk factor, compounded by germline mutations in high-risk genes like BRCA1/2. Aging induces architectural changes in breast tissue, particularly affecting luminal epithelial cells by diminishing lineage-specific molecular profiles and adopting myoepithelial-like characteristics. ELF5 is an important transcription factor for both normal breast and breast cancer development. This review focuses on the role of ELF5 in normal breast development, its altered expression throughout aging, and its implications in cancer. It discusses the lineage-specific expression of ELF5, its regulatory mechanisms, and its potential as a biomarker for breast-specific biological age and cancer risk.

Pathomechanisms of Diabetic Kidney Disease

The worldwide occurrence of diabetic kidney disease (DKD) is swiftly rising, primarily attributed to the growing population of individuals affected by type 2 diabetes. This surge has been transformed into a substantial global concern, placing additional strain on healthcare systems already grappling with significant demands. The pathogenesis of DKD is intricate, originating with hyperglycemia, which triggers various mechanisms and pathways: metabolic, hemodynamic, inflammatory, and fibrotic which ultimately lead to renal damage. Within each pathway, several mediators contribute to the development of renal structural and functional changes. Some of these mediators, such as inflammatory cytokines, reactive oxygen species, and transforming growth factor β are shared among the different pathways, leading to significant overlap and interaction between them. While current treatment options for DKD have shown advancement over previous strategies, their effectiveness remains somewhat constrained as patients still experience residual risk of disease progression. Therefore, a comprehensive grasp of the molecular mechanisms underlying the onset and progression of DKD is imperative for the continued creation of novel and groundbreaking therapies for this condition. In this review, we discuss the current achievements in fundamental research, with a particular emphasis on individual factors and recent developments in DKD treatment.

Novel biomarkers for prognosticating diabetic kidney disease progression

The global burden of diabetic kidney disease (DKD) is escalating, and it remains as a predominant cause of the end-stage renal disease (ESRD). DKD is associated with increased cardiovascular disease and morbidity in all types of diabetes. Prediction of progression with albuminuria and eGFR is challenging in DKD, especially in non-proteinuric DKD patients. The pathogenesis of DKD is multifactorial characterized by injury to all components of the nephron, whereas albuminuria is an indicator of only glomerular injury. The limits in the diagnostic and prognostic value of urine albumin demonstrate the need for alternative and clinically significant early biomarkers, allowing more targeted and effective diabetic treatment, to reduce the burden of DKD and ESRD. Identification of biomarkers, based on multifactorial pathogenesis of DKD can be the crucial paradigm in the treatment algorithm of DKD patients. This review focuses on the potential biomarkers linked to DKD pathogenesis, particularly with the hope of broadening the diagnostic window to identify patients with different stages of DKD progression.

Tenovin-1 Ameliorates Renal Fibrosis in High-Fat-Diet-Induced Diabetic Nephropathy via Antioxidant and Anti-Inflammatory Pathways

High-fat diet (HFD)-induced obesity has been involved in the development of diabetic nephropathy (DN). Tenovin-1, a potent selective SIRT1/2 inhibitor, regulates various target proteins. The present study evaluated the protective effect of Tenovin-1 against renal fibrosis in HFD-induced Zucker diabetic fatty (ZDF) rats. Rats were fed a normal chow diet or HFD. Tenovin-1 (45 mg/kg) administered to HFD-fed rats decreased inflammatory cytokine expression in the serum of the rats. The antioxidant status and oxidative damage to lipids or DNA were significantly restored by Tenovin-1. Additionally, Tenovin-1 reduced the levels of blood urea nitrogen (BUN), serum creatinine (sCr), microalbumin, and urinary protein-based biomarkers in the urine of HFD-fed rats. The abnormal architecture of the kidney and pancreas was restored by Tenovin-1 administration. Tenovin-1 also reduced apoptosis in the kidneys of the HFD-fed rats and HG-treated NRK-52E cells. It significantly lowered the levels of ECM proteins in the kidneys of HFD-fed rats and HG-treated NRK-52E cells. Additionally, Tenovin-1 markedly reduced claudin-1, SIRT1, and SIRT2, but increased SIRT3 and SIRT4 in HFD-fed rats and NRK-52E cells treated with HG. Furthermore, Tenovin-1 altered epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor-β (PDGFR-β), and signal transducer and activator of transcription 3 (STAT3) levels in the kidneys of HFD-fed rats. Conclusively, this study shows that Tenovin-1 can be a potential candidate drug for the treatment of HFD-induced renal fibrosis, in vivo and in vitro models.

Molineria recurvata Ameliorates Streptozotocin-Induced Diabetic Nephropathy through Antioxidant and Anti-Inflammatory Pathways

Molineria recurvata (MR) has been traditionally used to manage diabetes mellitus in India. However, the molecular mechanism of MR on the diabetic-induced nephropathy has not been clearly investigated. Thus, this study investigates the protective effects of the MR extract on nephropathy in streptozotocin (STZ)-induced diabetic rats. Diabetes was instigated by a single intraperitoneal injection of STZ (45 mg/kg) in male Sprague-Dawley rats. Once the diabetes was successfully induced, the MR extract (200 mg/kg/day) or metformin (200 mg/kg/day) was orally administered for 14 days. Renal function, morphology changes and levels of inflammatory cytokines were measured. Blood glucose concentrations were considerably reduced in STZ-induced diabetic rats following treatment with the MR extract. The administration of the MR extract substantially restored the abnormal quantity of the oxidative DNA damage marker 8-hydroxy-2′-deoxy-guanosine (8-OHdG), malondialdehyde, glutathione, oxidized glutathione, superoxide dismutase, catalase, interleukin (IL)-1β, IL-6, IL-10, and transforming growth factor-β (TGF-β). The urinary excretion of kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), selenium binding protein 1 (SBP1), and pyruvate kinase M2 (PKM2) was significantly reduced in diabetes rats after administration of the MR extracts. In the kidneys of STZ-induced diabetic rats, the MR extracts markedly downregulated the expression of fibronectin, collagen-1, and α-smooth muscle actin (α-SMA). In particular, the MR extracts markedly increased the level of SIRT1 and SIRT3 and reduced claudin-1 in the kidney. These results suggest that the MR extracts exhibits therapeutic activity in contrast to renal injury in STZ-induced diabetic rats through repressing inflammation and oxidative stress.

The Pathophysiological Basis of Diabetic Kidney Protection by Inhibition of SGLT2 and SGLT1

SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes mellitus and slow the progression towards end-stage kidney disease. Blocking tubular SGLT2 and spilling glucose into the urine, which triggers a metabolic counter-regulation similar to fasting, provides unique benefits, not only as an anti-hyperglycemic strategy. These include a low hypoglycemia risk and a shift from carbohydrate to lipid utilization and mild ketogenesis, thereby reducing body weight and providing an additional energy source. SGLT2 inhibitors counteract hyperreabsorption in the early proximal tubule, which acutely lowers glomerular pressure and filtration and thereby reduces the physical stress on the filtration barrier, the filtration of tubule-toxic compounds, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity and improved mitochondrial function and autophagy, can reduce pro-inflammatory, pro-senescence, and pro-fibrotic signaling and preserve tubular function and GFR in the long-term. By shifting transport downstream, SGLT2 inhibitors more equally distribute the transport burden along the nephron and may mimic systemic hypoxia to stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs. SGLT1 inhibition improves glucose homeostasis by delaying intestinal glucose absorption and by increasing the release of gastrointestinal incretins. Combined SGLT1 and SGLT2 inhibition has additive effects on renal glucose excretion and blood glucose control. SGLT1 in the macula densa senses luminal glucose, which affects glomerular hemodynamics and has implications for blood pressure control. More studies are needed to better define the therapeutic potential of SGLT1 inhibition to protect the kidney, alone or in combination with SGLT2 inhibition.

Mechanistic Insight into Oxidative Stress-Triggered Signaling Pathways and Type 2 Diabetes

Oxidative stress (OS) is a metabolic dysfunction mediated by the imbalance between the biochemical processes leading to elevated production of reactive oxygen species (ROS) and the antioxidant defense system of the body. It has a ubiquitous role in the development of numerous noncommunicable maladies including cardiovascular diseases, cancers, neurodegenerative diseases, aging and respiratory diseases. Diseases associated with metabolic dysfunction may be influenced by changes in the redox balance. Lately, there has been increasing awareness and evidence that diabetes mellitus (DM), particularly type 2 diabetes, is significantly modulated by oxidative stress. DM is a state of impaired metabolism characterized by hyperglycemia, resulting from defects in insulin secretion or action, or both. ROS such as hydrogen peroxide and the superoxide anion introduce chemical changes virtually in all cellular components, causing deleterious effects on the islets of β-cells, in turn affecting insulin production. Under hyperglycemic conditions, various signaling pathways such as nuclear factor-κβ (NF-κβ) and protein kinase C (PKC) are also activated by ROS. All of these can be linked to a hindrance in insulin signaling pathways, leading to insulin resistance. Hyperglycemia-induced oxidative stress plays a substantial role in complications including diabetic nephropathy. DM patients are more prone to microvascular as well as atherosclerotic macrovascular diseases. This systemic disease affects most countries around the world, owing to population explosion, aging, urbanization, obesity, lifestyle, etc. However, some modulators, with their free radical scavenging properties, can play a prospective role in overcoming the debilitating effects of OS. This review is a modest approach to summarizing the basics and interlinkages of oxidative stress, its modulators and diabetes mellitus. It may add to the understanding of and insight into the pathophysiology of diabetes and the crucial role of antioxidants to weaken the complications and morbidity resulting from this chronic disease.

Diabetic nephropathy: A twisted thread to unravel

Diabetic nephropathy (DN), a persistent microvascular problem of diabetes mellitus is described as an elevated level of albumin excretion in urine and impaired renal activity. The morbidity and mortality of type-1 diabetics and type-2 diabetics due to end stage renal disease is also a result of the increased prevalence of DN. DN typically occurs as a consequence of an association among metabolic and hemodynamic variables, activating specific pathways leading to renal injury. According to current interventions, intensive glucose regulation decreases the threat of DN incidence and growth, and also suppressing the renin-angiotensin system (RAS) is a significant goal for hemodynamic and metabolism-related deformities in DN. However, the pathogenesis of DN is multifactorial so novel approaches other than glucose and blood pressure control are required for treatment. This review briefly summarizes the reported pathogenesis of DN, current interventions for its treatment, and possible novel interventions to unweave the thread of DN.

Cyclophilin A (CyPA) as a Novel Biomarker for Early Detection of Diabetic Nephropathy in an Animal Model

BACKGROUND AND AIM

Type 2 diabetes mellitus (DM) is the most common single cause of the end-stage renal disease (ESRD). Cyclophilin A (CyPA) is an 18-kD protein. The connection between diabetic nephropathy (DN) and the secreted form of CyPA (sCyPA) has been elucidated in this study that aims to investigate sCyPA correlation with renal dysfunction.

MATERIALS AND METHODS

Thirty-four male adult Wistar rats weighing 180-220 g were used. Animals were divided into a study group and a control group, 17 rats in each. Streptozotocin (STZ) and nicotine amide were used to damage some pancreatic cells for induction of type 2 DM. Comparison was made between the study and the control groups. Moreover, a comparison was made between the members of the study group before and after induction of DN.

RESULTS

The rat model that exhibited a higher concentration of urinary sCyPA was detected early in the eighth week. There was a significantly higher level of 24-h urinary CyPA in the study group compared to the control group (p-value=0.004) and there was a significant elevation in the 24-h urinary Cyp-A in the study group after injection of STZ compared to the values before injection (p-value <0.001). Immunohistochemical analysis of renal tissue revealed that the mean expression of CyPA was higher in the study group than in the control group. For the urinary 24-h CYP-A, using a cutoff of 1.15 ng/mL, the accuracy was 72.4%, sensitivity was (77.8%) and specificity was (67%).

CONCLUSION

According to this animal study, we proved that CyPA is a valuable marker for DN. It is a more sensitive, noninvasive and rapid biomarker for early detection of any renal affection in human diabetic patients.

Oxidative Stress Markers in Chronic Kidney Disease with Emphasis on Diabetic Nephropathy

Diabetes prevalence is increasing worldwide, especially through the increase of type 2 diabetes. Diabetic nephropathy occurs in up to 40% of diabetic patients and is the leading cause of end-stage renal disease. Various factors affect the development and progression of diabetic nephropathy. Hyperglycaemia increases free radical production, resulting in oxidative stress, which plays an important role in the pathogenesis of diabetic nephropathy. Free radicals have a short half-life and are difficult to measure. In contrast, oxidation products, including lipid peroxidation, protein oxidation, and nucleic acid oxidation, have longer lifetimes and are used to evaluate oxidative stress. In recent years, different oxidative stress biomarkers associated with diabetic nephropathy have been found. This review summarises current evidence of oxidative stress biomarkers in patients with diabetic nephropathy. Although some of them are promising, they cannot replace currently used clinical biomarkers (eGFR, proteinuria) in the development and progression of diabetic nephropathy.

Beneficial Effect of Chloroquine and Amodiaquine on Type 1 Diabetic Tubulopathy by Attenuating Mitochondrial Nox4 and Endoplasmic Reticulum Stress

BACKGROUND

Oxidative stress induced by chronic hyperglycemia is recognized as a significant mechanistic contributor to the development of diabetic kidney disease (DKD). Nonphagocytic nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) is a major source of reactive oxygen species (ROS) in many cell types and in the kidney tissue of diabetic animals. We designed this study to explore the therapeutic potential of chloroquine (CQ) and amodiaquine (AQ) for inhibiting mitochondrial Nox4 and diabetic tubular injury.

METHODS

Human renal proximal tubular epithelial cells (hRPTCs) were cultured in high-glucose media (30 mM D-glucose), and diabetes was induced with streptozotocin (STZ, 50 mg/kg i.p. for 5 days) in male C57BL/6J mice. CQ and AQ were administered to the mice via intraperitoneal injection for 14 weeks.

RESULTS

CQ and AQ inhibited mitochondrial Nox4 and increased mitochondrial mass in hRPTCs under high-glucose conditions. Reduced mitochondrial ROS production after treatment with the drugs resulted in decreased endoplasmic reticulum (ER) stress, suppressed inflammatory protein expression and reduced cell apoptosis in hRPTCs under high-glucose conditions. Notably, CQ and AQ treatment diminished Nox4 activation and ER stress in the kidneys of STZ-induced diabetic mice. In addition, we observed attenuated inflammatory protein expression and albuminuria in STZ-induced diabetic mice after CQ and AQ treatment.

CONCLUSION

We substantiated the protective actions of CQ and AQ in diabetic tubulopathy associated with reduced mitochondrial Nox4 activation and ER stress alleviation. Further studies exploring the roles of mitochondrial Nox4 in the pathogenesis of DKD could suggest new therapeutic targets for patients with DKD.

Diabetic Retinopathy Screening Using a Gold Nanoparticle-Based Paper Strip Assay for the At-Home Detection of the Urinary Biomarker 8-Hydroxy-2'-Deoxyguanosine

PURPOSE

We sought to assess a smartphone-based, gold nanoparticle-based colorimetric lateral flow immunoassay paper sensor for quantifying urine 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a biomarker for diabetic retinopathy (DR) screening.

METHODS

Paper strips incorporate gold nanoparticle-8-OHdG antibody conjugates that produce color changes that are proportional to urine 8-OHdG and that are discernible on a smartphone camera photograph. Paper strip accuracy, precision, and stability studies were performed with 8-OHdG solutions of varying concentrations. Urine was collected from 97 patients with diabetes who were receiving DR screening examinations, including 7-field fundus photographs. DR was graded by standard methods as either low risk (no or mild DR) or high risk (moderate or severe DR). Paper sensor assays were performed on urine samples from patients and 8-OHdG values were correlated with DR grades. The differences in 8-OHdG values between the low- and high-risk groups were analyzed for outliers to identify the threshold 8-OHdG value that would minimize false-negative results.

RESULTS

Lateral flow immunoassay paper strips quantitatively measure 8-OHdG and were found to be accurate, precise, and stable. Average urine 8-OHdG concentrations in study patients were 22 ± 10 ng/mg of creatinine in the low-risk group and 55 ± 11 ng/mg of creatinine in the high-risk group. Screening cutoff values of 8-OHdG >50 ng/mg of creatinine or urine creatinine >1.5 mg minimized screen failures, with 91% sensitivity and 81% specificity.

CONCLUSIONS

Urinary 8-OHdG is a useful biomarker to screen DR. Quantitative 8-OHdG detection with the lateral flow immunoassay paper sensor and smartphone camera demonstrates its potential in DR screening. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Leukocyte Telomere Length, DNA Oxidation, and Risk of Lower-Extremity Amputation in Patients With Long-standing Type 1 Diabetes

OBJECTIVE

Telomere shortening and DNA oxidation are associated with premature vascular aging, which may be involved in lower-extremity amputation (LEA). We sought to investigate whether leukocyte telomere length (LTL) and plasma 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of DNA oxidation, were associated with LEA in subjects with type 1 diabetes at high vascular risk.

RESEARCH DESIGN AND METHODS

LTL (quantitative PCR) and plasma 8-OHdG concentrations (immunoassay method) were assessed at baseline in the GENEDIAB (Génétique de la Néphropathie Diabétique) type 1 diabetes cohort. Logistic and Cox proportional hazards regression models were fitted to estimate odds ratio (OR) (at baseline) and hazard ratio (HR) (during follow-up), with related 95% CI, by increasing biomarker tertiles (T1, T2, T3).

RESULTS

Among 478 participants (56% male, mean ± SD age 45 ± 12 years and diabetes duration 29 ± 10 years), 84 patients had LEA at baseline. Baseline history of LEA was associated with shorter LTL (OR for T2 vs. T1 0.62 [95% CI 0.32-1.22] and for T3 vs. T1 0.41 [0.20-0.84]) but not with plasma 8-OHdG (1.16 [0.56-2.39] and 1.24 [0.61-2.55], respectively). New cases of LEA occurred in 34 (12.3%) participants during the 10-year follow-up. LTL were shorter (HR T2 vs. T1 0.25 [95% CI 0.08-0.67] and T3 vs. T1 0.29 [0.10-0.77]) and plasma 8-OHdG higher (2.20 [0.76-7.35] and 3.11 [1.07-10.32]) in participants who developed LEA during follow-up compared with others. No significant interaction was observed between biomarkers on their association with LEA.

CONCLUSIONS

We report the first independent association between LTL shortening and excess risk of LEA in type 1 diabetes. High plasma 8-OHdG was also associated with incident LEA but partly dependent on cofounding variables.

Development of a solid-phase microextraction LC-MS/MS method for determination of oxidative stress biomarkers in biofluids

Recently the connection between oxidative stress and various diseases, including cancer and Alzheimer's, attracts notice as a pathway suitable for diagnostic purposes. 8-Oxo-deoxyguanosine and 8-oxo-deoxyadenosine produced from the interaction of reactive oxygen species with DNA become prominent as biomarkers. Several methods have been developed for their determination in biofluids, including solid-phase extraction and enzyme-linked immunosorbent assays. However, still, there is a need for reliable and fast analytical methods. In this context, solid-phase microextraction offers many advantages such as flexibility in geometry and applicable sample volume, as well as high adaptability to high-throughput sampling. In this study, a solid-phase microextraction method was developed for the determination of 8-oxo-deoxyguanosine and 8-oxo-deoxyadenosine in biofluids. The extractive phase of solid-phase microextraction consisted of hydrophilic-lipophilic balanced polymeric particles. In order to develop a solid-phase microextraction method suitable for the determination of the analytes in saliva and urine, several parameters, including desorption solvent, desorption time, sample pH, and ionic strength, were scrutinized. Analytical figures of merit indicated that the developed method provides reasonable interday and intraday precisions (<15% in both biofluids) with acceptable accuracy. The method provides a limit of quantification for both biomarkers at 5.0 and 10.0 ng/mL levels in saliva and urine matrices, respectively.

Protective effect of EX-527 against high-fat diet-induced diabetic nephropathy in Zucker rats

High-fat diet (HFD)-induced obesity is implicated in diabetic nephropathy (DN). EX-527, a selective Sirtuin 1 (SIRT1) inhibitor, has multiple biological functions; however, its protective effect against DN is yet to be properly understood. This study was aimed to explore the protective effect of EX-527 against DN in HFD-induced diabetic Zucker (ZDF) rats. After 21 weeks of continually feeding HFD to the rats, the apparent characteristics of progressive DN were observed, which included an increase in kidney weight (~160%), hyperglycemia, oxidative stress, and inflammatory cytokines, and subsequent renal cell damage. However, the administration of EX-527 for 10 weeks significantly reduced the blood glucose concentration and kidney weight (~59%). Furthermore, EX-527 significantly reduced the serum concentration of transforming growth factor-β1 (49%), interleukin (IL)-1β (52%), and IL-6 in the HFD-fed rats. Overall, the antioxidant activities significantly increased, and oxidative damage to lipids or DNA was suppressed. Particularly, EX-527 significantly reduced blood urea nitrogen (81%), serum creatinine (71%), microalbumin (43%), and urinary excretion of protein-based biomarkers. Histopathological examination revealed expansion of the extracellular mesangial matrix and suppression of glomerulosclerosis following EX-527 administration. EX-527 downregulated the expression of α-SMA (~64%), TGF-β (25%), vimentin, α-tubulin, fibronectin, and collagen-1 in the kidneys of the HFD-fed rats. Additionally, EX-527 substantially reduced claudin-1 and SIRT1 expression, but increased the expression of SIRT3 in the kidneys of the HFD-fed rats. EX-527 also inhibited the growth factor receptors, including EGFR, PDGFR-β, and STAT3, which are responsible for the anti-fibrotic effect of SIRT-1. Therefore, the administration of EX-527 protects against HFD-induced DN.

Protective effects of Croton hookeri on streptozotocin-induced diabetic nephropathy

In this study, the protective effects of Croton hookeri (CH) extract on renal injury were investigated in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by a single injection of STZ (45 mg/kg) to Sprague-Dawley rats. After 5 days, CH extract (200 mg/kg) was administered daily by oral gavage for 2 weeks. Administration of CH extracts significantly reduced blood glucose levels in STZ-induced diabetic rats. STZ-induced changes in total cholesterol, LDL, HDL, ALT, AST, BUN, and serum creatinine levels were significantly restored by treatment with CH extract. Abnormal levels of SOD, catalase, glutathione, and oxidized GSH (GSSG) in STZ-treated rats were also significantly recovered by CH extract treatment. CH extract markedly reduced the expression of collagen-1, fibronectin, and α-SMA in the kidney of STZ-induced diabetic rats. In particular, oxidative DNA damages, MDA, TGF-β, IL-1β, and IL-6 levels were significantly reduced in STZ-treated rats following treatment with CH extract, whereas IL-10 showed opposite trend. STZ-induced SIRT1, SIRT3 downregulation and cloudin-1 upregulation in the kidney were dramatically recovered by CH extract treatment. Our data suggest that CH extract protects against diabetic-induced nephropathy by inhibiting oxidative stress and inflammation. Therefore, it has potential as a food supplement to alleviate renal dysfunction caused by diabetes-induced nephropathy.

Oxidative Stress in the Pathogenesis and Evolution of Chronic Kidney Disease: Untangling Ariadne's Thread

Amplification of oxidative stress is present since the early stages of chronic kidney disease (CKD), holding a key position in the pathogenesis of renal failure. Induction of renal pro-oxidant enzymes with excess generation of reactive oxygen species (ROS) and accumulation of dityrosine-containing protein products produced during oxidative stress (advanced oxidation protein products—AOPPs) have been directly linked to podocyte damage, proteinuria, and the development of focal segmental glomerulosclerosis (FSGS) as well as tubulointerstitial fibrosis. Vascular oxidative stress is considered to play a critical role in CKD progression, and ROS are potential mediators of the impaired myogenic responses of afferent renal arterioles in CKD and impaired renal autoregulation. Both oxidative stress and inflammation are CKD hallmarks. Oxidative stress promotes inflammation via formation of proinflammatory oxidized lipids or AOPPs, whereas activation of nuclear factor κB transcription factor in the pro-oxidant milieu promotes the expression of proinflammatory cytokines and recruitment of proinflammatory cells. Accumulating evidence implicates oxidative stress in various clinical models of CKD, including diabetic nephropathy, IgA nephropathy, polycystic kidney disease as well as the cardiorenal syndrome. The scope of this review is to tackle the issue of oxidative stress in CKD in a holistic manner so as to provide a future framework for potential interventions.

The role of serum and urinary biomarkers in the diagnosis of early diabetic nephropathy in patients with type 2 diabetes

Background

Previous studies have shown that a variety of biomarkers are closely related to the occurrence and development of early-stage diabetic nephropathy (DN) in patients. The aim of this study was to evaluate the role of multiple sera and urinary biomarkers in the diagnosis of early-stage DN in patients with type 2 diabetes.

Methods

We enrolled 287 patients with type 2 diabetes, who were classified into normoalbuminuria (n = 144), microalbuminuria (n = 94), or macroalbuminuria (n = 49) groups based on their urine albumin to creatinine ratios (UACR), along with 42 healthy controls. We assessed 13 biomarkers, including transferrin (Tf), immunoglobulin G (IgG), podocalyxin, neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-beta-glucosaminidase, α-1-microglobulin, 8-hydroxy-deoxyguanosine, tumor necrosis factor-alpha (TNF-α), and interleukin-18 in urine samples, along with cystatin C, total bilirubin, and uric acid in sera samples, to evaluate their diagnostic roles. From the measurements, the blood neutrophil to lymphocyte ratio was also calculated.

Results

Urinary Tf, IgG, NGAL, and TNF-α were significantly related to the UACR. We calculated the area under the receiver operating characteristic curves (area under the curve) and found that urinary IgG (0.894), NGAL (0.875), Tf (0.861), TNF-α (0.763), and the combination of urinary Tf + IgG + TNF-α + NGAL (0.922) showed good diagnostic value for early-stage DN.

Conclusions

Urinary Tf, IgG, NGAL, TNF-α, and the combination of all four biomarkers demonstrated excellent diagnostic value for early-stage DN in patients with type 2 diabetes.

Blood urea nitrogen is independently associated with renal outcomes in Japanese patients with stage 3-5 chronic kidney disease: a prospective observational study

Background

Blood urea nitrogen (BUN) is one of the substances that affects the calculated serum osmolality (cSosm). A previous study demonstrated that BUN and cSosm were independently associated with the development of chronic kidney disease (CKD) in patients with preserved kidney function. In advanced CKD stages, there is a concomitant increase in cSosm and BUN levels. However, it remains unclear whether BUN or cSosm levels are related to renal outcomes in patients with moderate to severe kidney dysfunction. The aim of this study was to clarify whether the BUN or cSosm level is associated with kidney disease progression in patients with advanced CKD.

Methods

In this prospective study, we enrolled 459 patients with CKD (stages 3–5). The composite renal endpoint was end-stage renal disease (ESRD) or death, and ESRD alone was added as an alternative outcome. A Cox proportional hazards model was utilized to determine the risk factors for a poor renal outcome. We adjusted for covariates including estimated glomerular filtration rate (eGFR). The cSosm (mOsm/kg) was calculated using the following formula: (2 × sodium) + (BUN/2.8) + (glucose/18).

Results

During a median follow-up of 25.8 months, the renal endpoint was observed in 210 patients. Multivariable Cox analysis determined the hazard ratio (HR) [95% confidence interval (CI)] for the composite renal outcome in the second, third, and fourth BUN quartiles were 1.36 (0.72–2.58), 1.87 (0.95–3.66), and 2.66 (1.23–5.76) (P for trend < 0.01), respectively compared with the first BUN quartile. Conversely, by multivariable Cox analysis, the HRs (95% CIs) for poor outcomes in the second, third, and fourth cSosm quartiles, compared with the first cSosm quartile, were 1.13 (0.69–1.87), 0.95 (0.58–1.55), and 1.26 (0.78–2.03), respectively (P for trend = 0.39). In addition, with regard to the renal outcome of ESRD alone, higher BUN quartiles had a significantly increased risk for the outcome, but cSosm levels were not associated with the outcome.

Conclusions

Higher BUN levels, but not cSosm levels, were associated with adverse renal outcomes independent of the eGFR, suggesting that BUN may be a useful marker for predicting kidney disease progression.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1306-1) contains supplementary material, which is available to authorized users.

Combinedin silicoandin vitrostudy of an aptasensor based on citrate-capped AuNPs for naked-eye detection of a critical biomarker of oxidative stress

An elevated level of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) in biosamples has been found to correlate to oxidative stress, and it has been assigned as a critical biomarker of various diseases. Herein, insights into the mechanisms of an aptasensor, based on citrate-capped gold nanoparticles (AuNPs), for 8-oxo-dG detection were elucidated using molecular dynamics (MD) simulations and validated experimentally. We found that the binding mechanism for binding between the anti-8-oxo-dG aptamer and 8-oxo-dG has the following characteristic stages: (i) adsorption stage, (ii) binding stage, and (iii) complex stabilization stage. Our simulations also reveal the binding sites between the anti-8-oxo-dG aptamer and 8-oxo-dG formed through hydrogen bonding during complex formation. A shortened anti-8-oxo-dG-aptamer was also engineered using in silico design, which was expected to improve the analytical performance of the colorimetric aptasensor. The mechanisms of the colorimetric aptasensor in the presence and absence of 8-oxo-dG were also investigated, and found to be in good agreement with the experiments. Complete understanding of the mechanism of the colorimetric aptasensor would open the door for development of novel naked-eye aptasensors.

A visual strategy for 8-oxo-dG monitoring based upon the dispersion of citrate-capped gold nanoparticles has been developed.

Serum proteins C and S levels as early biomarkers for kidney dysfunction in hemophilic patients

BACKGROUND

Hemophilia is an inherited genetic disease characterized by the inability to coagulate blood after injury. The rationale of the current study was to evaluate serum proteins S and C and correlate to kidney function test in hemophilic patients for early diagnosis of abnormality in renal function.

SUBJECTS AND METHODS

This study was conducted on 80 males subjects divided into four groups. Group I: Control: Healthy subjects. Group II: Renal dysfunction (serum Creatinine >2mg/dl): Group III: Hemophilic patients. Group IV: Hemophilic patients with renal disorder. Serum urea, creatinine, sodium, potassium, protein C and protein S level were determined.

RESUTS

Protein C and S levels showed a significant decrease in hemophilic/and with renal dysfunction (P < 0.001, p<0.001). The level of plasma protein C and S levels were positively correlated with increased urinary albumin (P < 0.01). Urinary albumin was increased about 15 folds in hemophilic patients with renal dysfunction and nephrotic patients as compared with the control group. The cut-off value in 90% patients at the hemophilic patients with renal dysfunction 70%. Positive correlations were observed between urinary albumin (r=0.66), and creatinine (r=0.73).

CONCLUSION

These biomarkers showed good predictive values with regard to ROC-AUC (0.41 and 0.75 for Proteins C and S, respectively).

Plasma concentrations of 8-hydroxy-2'-deoxyguanosine and risk of kidney disease and death in individuals with type 1 diabetes

AIMS/HYPOTHESIS

Oxidative stress is involved in the pathogenesis of diabetic kidney disease. We evaluated the association between 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of DNA oxidative damage, and end-stage renal disease (ESRD) or death in individuals with type 1 diabetes.

METHODS

Plasma 8-OHdG concentrations were measured at baseline in participants with type 1 diabetes from GENEDIAB (n = 348) and GENESIS (n = 571) cohorts. A follow-up was conducted in 205 and 499 participants for a mean ± SD duration of 8.9 ± 2.3 years and 5.2 ± 1.9 years, respectively. We tested associations between 8-OHdG concentrations and urinary albumin concentration (UAC) or eGFR at baseline, and the risk of ESRD or all-cause mortality during follow-up. Analyses were performed in pooled cohorts.

RESULTS

The highest UAC (geometric mean [95% CI]) was observed in the third 8-OHdG tertile (tertile 1, 9 [6, 13] mg/l; tertile 2, 10 [7, 16] mg/l; tertile 3, 16 [10, 25] mg/l; p = 0.36 for tertile 1 vs tertile 2 and p = 0.003 for tertile 3 vs tertile 1) after adjustment for potential confounding covariates. The lowest eGFR (mean [95% CI]) was observed in the third tertile (tertile 1, 87 [82, 93] ml min^-1 1.73 m^-2; tertile 2, 88 [82, 94] ml min^-1 1.73 m^-2; tertile 3, 74 [68, 80] ml min^-1 1.73 m^-2; p = 0.61 for tertile 1 vs tertile 2; p < 0.001 for tertile 3 vs tertile 1). ESRD and death occurred in 48 and 64 individuals, respectively. The HR for ESRD, but not death, was higher in the third tertile than in the first (tertile 2 vs tertile 1, 1.45 [0.45, 5.04], p = 0.54; tertile 3 vs tertile 1, 3.05 [1.16, 9.60], p = 0.02) after multiple adjustments.

CONCLUSIONS/INTERPRETATION

Higher plasma concentrations of 8-OHdG were independently associated with increased risk of kidney disease in individuals with type 1 diabetes, suggesting that this marker can be used to evaluate the progression of diabetic kidney disease.

Oxidative DNA Damage and Carotid Intima Media Thickness as Predictors of Cardiovascular Disease in Prediabetic Subjects

Prediabetes is considered as a risk factor for the development of diabetes mellitus and cardiovascular disease. The present study was conducted with the aim of finding out the relationship between oxidative DNA damage and carotid intima media thickness for the prediction of cardiovascular disease in prediabetic subjects. The study included 100 prediabetic subjects and 100 normal individuals as controls. In both cases and controls, 8-OHdG was measured by ELISA, and CIMT was measured by B mode ultrasonography. Both 8-OHdG and CIMT were significantly higher in subjects with prediabetes as compared to controls (185.80 ± 10.72 pg/mL vs. 126.13 ± 16.01 pg/mL, p < 0.001 and 0.70 ± 0.04 mm vs. 0.57 ± 0.03 mm, p < 0.001, respectively). There was significant and positive correlation of IGT with 8-OHdG (r = 0.783; p < 0.001) and CIMT (r = 0.787; p < 0.001) in prediabetic subjects. Moreover, 8-OHdG showed significant positive correlation with CIMT (r = 0.704; p < 0.001) in prediabetic subjects. In conclusion, increased 8-OHdG and CIMT in prediabetic subjects indicate that biochemical changes of atherosclerosis start even before the onset of diabetes mellitus. Hence, 8-OHdG and CIMT could be used as indicators of cardiovascular disease risk in these subjects.

Inflammation and oxidative stress markers in diabetes and hypertension

Background

Inflammation and oxidative stress are important factors associated with chronic disease such as essential hypertension (HTN) and type 2 diabetes mellitus (T2DM). However, the association of inflammation and oxidative stress in HTN with T2DM as a comorbidity is inconclusive due to the multifactorial nature of these cardiometabolic diseases.

Methodology

The influence of pathophysiological factors include genetics, age of patient, and disease progression change throughout the lifespan and require further investigation. The study population included 256 participants attending a rural health screening program who were tested for markers of inflammation, oxidative stress, and coagulation/fibrinolysis. Demographic and clinical variables included, age, gender, systolic and diastolic blood pressures, blood glucose, hemoglobin A1c, estimated glomerular filtration rate, and cholesterol profile. Data were tested for normality, and nonparametric statistics were applied to analyze the sample with significance set at p<0.05.

Results

Of the inflammatory markers, interleukin-1β (IL-1β) and IL-10 were significantly different between the control and hypertensive group (p<0.03) and between the HTN+T2DM compared to the HTN group (p<0.05). Significant results for oxidative stress were observed for urinary 8-iso-PGF₂α and insulin-like growth factor 1 (IGF-1) between the control and the HTN+T2DM group (p<0.01). Glutathione (GSH) was also significant between the HTN and HTN+T2DM group (p<0.05). Investigation of the progression of HTN also found significant changes in the inflammatory markers IGF-1, monocyte chemoattractant protein 1 (MCP-1), and (MCP-1/IGF-1)*IL-6 (p<0.05).

Conclusion

This study demonstrated that 8-iso-PGF₂α and erythrocyte GSH may be clinically useful for assessing HTN and HTN with T2DM as a comorbidity, while significant changes in the inflammatory profile were also observed with HTN progression.

Oxidative Stress, Apoptosis, and Mitochondrial Function in Diabetic Nephropathy

Diabetic nephropathy (DN) is the second most frequent and prevalent complication of diabetes mellitus (DM). The increase in the production of oxidative stress (OS) is induced by the persistent hyperglycemic state capable of producing oxidative damage to the macromolecules (lipids, carbohydrates, proteins, and nucleic acids). OS favors the production of oxidative damage to the histones of the double-chain DNA and affects expression of the DNA repairer enzyme which leads to cell death from apoptosis. The chronic hyperglycemic state unchains an increase in advanced glycation end-products (AGE) that interact through the cellular receptors to favor activation of the transcription factor NF-κB and the protein kinase C (PKC) system, leading to the appearance of inflammation, growth, and augmentation of synthesis of the extracellular matrix (ECM) in DN. The reactive oxygen species (ROS) play an important role in the pathogenesis of diabetic complications because the production of ROS increases during the persistent hyperglycemia. The primary source of the excessive production of ROS is the mitochondria with the capacity to exceed production of endogenous antioxidants. Due to the fact that the mechanisms involved in the development of DN have not been fully clarified, there are different approaches to specific therapeutic targets or adjuvant management alternatives in the control of glycemia in DN.

Urinary Markers of Oxidative Stress Are Associated With Albuminuria But Not GFR Decline

Introduction

Markers of oxidative stress increase with age and are prevalent with chronic kidney disease. However, the role of oxidative stress markers as predictors for kidney function decline in the general population is unclear.

Methods

We investigated whether a baseline urinary excretion of oxidative DNA damage (8-oxo-7,8-dihydro-2′-deoxyguanosine [8-oxodG]) and oxidative RNA damage (8-oxo-7,8-dihydroguanosine [8-oxoGuo]) was associated with the age-related glomerular filtration rate (GFR) decline or incident low-grade albuminuria during a median of 5.6 years of follow-up. In the Renal Iohexol Clearance Survey in the Sixth Tromsø Study, we measured GFR using iohexol clearance in 1591 participants without renal disease, diabetes, or cardiovascular disease. Low-grade albuminuria was defined as an albumin-creatinine ratio >1.13 mg/mmol.

Results

The mean (SD) annual GFR change was −0.84 (2.00) ml/min per 1.73 m² per year. In linear mixed models, urinary 8-oxodG and 8-oxoGuo levels were not associated with the GFR change rate. In a multivariable adjusted logistic regression model, a baseline urinary 8-oxoGuo in the highest quartile was associated with an increased risk of low-grade albuminuria at follow-up (odds ratio: 2.64; 95% confidence interval: 1.50–4.65). When the highest quartile of urinary 8-oxoGuo was added to the baseline model, the area under the receiver operating characteristics curve for predicting low-grade albuminuria at follow-up improved from 0.67 to 0.71 (P = 0.002).

Conclusion

Oxidative stress measured as urinary 8-oxoGuo excretion was independently associated with incident low-grade albuminuria, but neither 8-oxoGuo nor 8-oxodG predicted an accelerated age-related GFR decline in a cohort representative of the middle-aged general population during almost 6 years of follow-up.

Increased Oxidative Damage of RNA in Early-Stage Nephropathy in db/db Mice

To evaluate RNA oxidation in the early stage of diabetic nephropathy, we applied an accurate method based on isotope dilution high-performance liquid chromatography-triple quadruple mass spectrometry to analyze the oxidatively generated guanine nucleosides in renal tissue and urine from db/db mice of different ages. We further investigated the relationship between these oxidative stress markers, microalbumin excretion, and histological changes. We found that the levels of 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) were increased in the urine and renal tissue of db/db mice and db/db mice with early symptoms of diabetic nephropathy suffered from more extensive oxidative damage than lean littermate control db/m mice. Importantly, in contrast to the findings in db/m mice, the 8-oxoGuo levels in the urine and renal tissue of db/db mice were higher than those of 8-oxodGuo at four weeks. These results indicate that RNA oxidation is more apparent than DNA oxidation in the early stage of diabetic nephropathy. RNA oxidation may provide new insight into the pathogenesis of diabetic nephropathy, and urinary 8-oxoGuo may represent a novel, noninvasive, and easily detected biomarker of diabetic kidney diseases if further study could clarify its source and confirm these results in a large population study.

The role of novel biomarkers in predicting diabetic nephropathy: a review

Diabetic nephropathy (DN) is one of the microvascular complications of the kidney arising commonly from type 1 diabetes mellitus (T1DM), and occasionally from type 2 diabetes mellitus (T2DM). Microalbuminuria serves as an early indicator of DN risk and a predictor of its progression as well as cardiovascular disease risk in both T1DM and T2DM. Although microalbuminuria remains the gold standard for early detection of DN, it is not a sufficiently accurate predictor of DN risk due to some limitations. Thus, there is a paradigm shift to novel biomarkers which would help to predict DN risk early enough and possibly prevent the occurrence of end-stage kidney disease. These new biomarkers have been broadly classified into glomerular biomarkers, tubular biomarkers, biomarkers of inflammation, biomarkers of oxidative stress, and miscellaneous biomarkers which also include podocyte biomarkers, some of which are also considered as tubular and glomerular biomarkers. Although they are potentially useful for the evaluation of DN, current data still preclude the routine clinical use of majority of them. However, their validation using high-quality and large longitudinal studies is of paramount importance, as well as the subsequent development of a biomarker panel which can reliably predict and evaluate this renal microvascular disease. This paper aims to review the predictive role of these biomarkers in the evaluation of DN.

Novel protective mechanism of reducing renal cell damage in diabetes: Activation AMPK by AICAR increased NRF2/OGG1 proteins and reduced oxidative DNA damage

Exposure of renal cells to high glucose (HG) during diabetes has been recently proposed to be involved in renal injury. In the present study, we investigated a potential mechanism by which AICAR treatment regulates the DNA repair enzyme, 8-oxoG-DNA glycosylase (OGG1) in renal proximal tubular mouse cells exposed to HG and in kidney of db/db mice. Cells treated with HG for 2 days show inhibition in OGG1 promoter activity as well as OGG1 and Nrf2 protein expression. In addition, activation of AMPK by AICAR resulted in an increase raptor phosphorylation at Ser⁷⁹² and leads to increase the promoter activity of OGG1 through upregulation of Nrf2. Downregulation of AMPK by DN-AMPK and raptor and Nrf2 by siRNA resulted in significant decease in promoter activity and protein expression of OGG1. On the other hand, downregulation of Akt by DN-Akt and rictor by siRNA resulted in significant increase in promoter activity and protein expression of Nrf2 and OGG1. Moreover, gel shift analysis shows reduction of Nrf2 binding to OGG1 promoter in cells treated with HG while cells treated with AICAR reversed the effect of HG. Furthermore, db/db mice treated with AICAR show significant increased in AMPK and raptor phosphroylation as well as OGG1 and Nrf2 protein expression that associated with significant decrease in oxidative DNA damage (8-oxodG) compared to non-treated mice. In summary, our data provide a novel protective mechanism by which AICAR prevents renal cell damage in diabetes and the consequence complications of hyperglycemia with a specific focus on nephropathy.

Early detection of diabetic kidney disease: Present limitations and future perspectives

Diabetic kidney disease (DKD) is one of the most common diabetic complications, as well as the leading cause of chronic kidney disease and end-stage renal disease around the world. To prevent the dreadful consequence, development of new assays for diagnostic of DKD has always been the priority in the research field of diabetic complications. At present, urinary albumin-to-creatinine ratio and estimated glomerular filtration rate (eGFR) are the standard methods for assessing glomerular damage and renal function changes in clinical practice. However, due to diverse tissue involvement in different individuals, the so-called “non-albuminuric renal impairment” is not uncommon, especially in patients with type 2 diabetes. On the other hand, the precision of creatinine-based GFR estimates is limited in hyperfiltration status. These facts make albuminuria and eGFR less reliable indicators for early-stage DKD. In recent years, considerable progress has been made in the understanding of the pathogenesis of DKD, along with the elucidation of its genetic profiles and phenotypic expression of different molecules. With the help of ever-evolving technologies, it has gradually become plausible to apply the thriving information in clinical practice. The strength and weakness of several novel biomarkers, genomic, proteomic and metabolomic signatures in assisting the early diagnosis of DKD will be discussed in this article.

Markers of Inflammation and Oxidative Stress in the Development and Progression of Renal Disease in Diabetic Patients

The prevalence of diabetes is increasing and has already reached pandemic proportions. Diabetes is a well-known risk factor for chronic kidney disease. Diabetic kidney disease (DKD) occurs in up to 40% of people with type 1 or 2 diabetes and is nowadays the leading cause of end-stage renal disease (ESRD). Among several factors involved in the development and progression of DKD are also inflammation and oxidative stress. Unfortunately, there is a paucity of sensitive and specific biomarkers for the early prediction of patients who will develop DKD or will progress to ESRD. This review summarizes the evidence regarding the prognostic value and benefits of targeting markers of inflammation (pro-inflammatory cytokines, tumour necrosis factor-α (TNF-α) and TNF-α receptors, adhesion molecules, chemokines) and markers of oxidative stress. Some of these biomarkers are promising, but further studies are needed before they can be used in clinical practice.

Analysis of the oxidative damage of DNA, RNA, and their metabolites induced by hyperglycemia and related nephropathy in Sprague Dawley rats

We used a sensitive and accurate method based on isotope dilution high-performance liquid chromatography-triple quadrupole mass spectrometry (ID-LC-MS/MS) to determine the levels of 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxo-dGsn) and 8-oxo-7,8-dihydroguanosin (8-oxo-Gsn) in various tissue specimens, plasma, and urine of hyperglycemic Sprague Dawley rats induced by streptozotocin (STZ). The oxidative DNA and RNA damages were observed in various organs and the amounts of 8-oxo-dGsn and 8-oxo-Gsn derived from DNA and RNA were increased with hyperglycemic status. In contrast to the results of the nucleic acid samples derived from tissues, the levels of 8-oxo-Gsn in urine and plasma were significantly higher compared with that of 8-oxo-dGsn, which most likely reflected the RNA damage that occurs more frequently compared with DNA damage. For the oxidative stress induced by hyperglycemia, 8-oxo-Gsn in urine may be a sensitive biomarker on the basis of the results in urine, plasma, and tissues. In addition, high levels of urinary 8-oxo-Gsn were observed before diabetic microvascular complications. Based on that the 8-oxo-dGsn was associated with diabetic nephropathy and RNA was more vulnerable to oxidative stress compared with DNA. We also propose that 8-oxo-Gsn is correlated with diabetic nephropathy and that 8-oxo-Gsn in urine could be a useful and sensitive marker of diabetic nephropathy.

Body fluid peptide and protein signatures in diabetic kidney diseases

Body fluid protein-based biomarkers carry the hope of improving patient management in diabetes by enabling more accurate and earlier detection of diabetic kidney disease (DKD), but also of defining the most suitable therapeutic targets. We present the data on some of the best studied individual protein markers in body fluids and conclude that their potential in clinical application for assessing DKD is moderate. Proteome-based approaches aiming at the identification of panels of body fluid biomarkers might be a valid alternative. We discuss the past (first) clinical proteomics studies in DKD, stressing their drawbacks but also the lessons that could be learned from them, as well as the more recent studies that have a potential for actual clinical implementation. We also highlight relevant issues and current problems associated with clinical proteomics from discovery towards application, and give suggestions for solutions that may help guiding proteomic studies, thereby removing some of the current hurdles for implementation of potentially beneficial results.

Urinary Biomarkers in the Assessment of Early Diabetic Nephropathy

Diabetic nephropathy (DN) is a frequent and severe complication of diabetes mellitus (DM). Its diagnosis in incipient stages may allow prompt interventions and an improved prognosis. Towards this aim, biomarkers for detecting early DN can be used. Microalbuminuria has been proven a remarkably useful biomarker, being used for diagnosis of DN, for assessing its associated condition-mainly cardiovascular ones-and for monitoring its progression. New researches are pointing that some of these biomarkers (i.e., glomerular, tubular, inflammation markers, and biomarkers of oxidative stress) precede albuminuria in some patients. However, their usefulness is widely debated in the literature and has not yet led to the validation of a new "gold standard" biomarker for the early diagnosis of DN. Currently, microalbuminuria is an important biomarker for both glomerular and tubular injury. Other glomerular biomarkers (transferrin and ceruloplasmin) are under evaluation. Tubular biomarkers in DN seem to be of a paramount importance in the early diagnosis of DN since tubular lesions occur early. Additionally, biomarkers of inflammation, oxidative stress, podocyte biomarkers, and vascular biomarkers have been employed for assessing early DN. The purpose of this review is to provide an overview of the current biomarkers used for the diagnosis of early DN.

Elevated Levels of Urinary Markers of Oxidative DNA and RNA Damage in Type 2 Diabetes with Complications

The mechanisms underlying progression of type 2 diabetes are complex and varied. Recent studies indicated that oxidative stress provided a new sight. To further assess the relationship between nucleic acid oxidation and complications in patients with type 2 diabetes and explore its possible molecular mechanisms, we studied 1316 subjects, including 633 type 2 diabetes patients and 683 age- and sex-matched healthy controls. Urinary levels of DNA oxidation marker 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) and RNA oxidation marker 8-oxo-7,8-dihydroguanosine (8-oxoGuo) were measured by ultraperformance liquid chromatography and mass spectrometry (UPLC-MS/MS). Serum glucose, HbA1c, total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides (TG) were also determined. The results showed significantly elevated levels of both the urinary 8-oxodGuo and 8-oxoGuo in diabetes patients with/without complications compared with age-matched healthy control subjects (p = 0.02 and p < 0.001, resp.). Patients with complications, especially macrovascular complications, exhibited higher levels of 8-oxoGuo than those without complications, while there was no difference in the concentrations of serum glucose and lipids. The finding indicates the role for oxidative damage to DNA and RNA, as a molecular mechanism contributing to the progression of type 2 diabetes. Elevated levels of 8-oxoGuo may be a risk factor for type 2 diabetes complications, especially in diabetic macrovascular complications.

Diabetic Cardiovascular Disease Induced by Oxidative Stress

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease.

Recent advances in understanding the role of oxidative stress in diabetic neuropathy

Diabetic neuropathy (DN) is one of the most common and severe manifestations of diabetes mellitus. The mechanisms underlying the structural, functional and metabolic changes in diabetic neuropathy have been under study for a long time. In this review the biochemistry and implications of the four pathways responsible for the development of DN, polyol pathway; increased AGEs (advanced glycation end-products) formation; activation of PKC (protein kinase C) and hexosamine pathway have been discussed. Experimental and clinical evidences suggest a close link between neurodegeneration and oxidative stress which serves as a unifying mechanism, thus linking the four pathways. Recent studies indicate that oxidative stress mediated DNA damage causes poly(ADP-ribose) polymerase (PARP) overactivation and reduced activity of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a factor common to all the four pathways. The exact mechanism of PARP mediated cell death in DN needs further investigation. Based on current studies neuroprotective and antioxidant therapy have been suggested as potential treatment and preventive solutions for DN.

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.

Association of serum total bilirubin with renal outcome in Japanese patients with stages 3-5 chronic kidney disease

OBJECTIVE

Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology.

MATERIALS AND METHODS

This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome.

RESULTS

The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group.

CONCLUSIONS

Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.

Diabetic Nephropathy: New Risk Factors and Improvements in Diagnosis

Diabetic nephropathy is the leading cause of end-stage renal disease. Patients with diabetic nephropathy have a high cardiovascular risk, comparable to patients with coronary heart disease. Accordingly, identification and management of risk factors for diabetic nephropathy as well as timely diagnosis and prompt management of the condition are of paramount importance for effective treatment. A variety of risk factors promotes the development and progression of diabetic nephropathy, including elevated glucose levels, long duration of diabetes, high blood pressure, obesity, and dyslipidemia. Most of these risk factors are modifiable by antidiabetic, antihypertensive, or lipid-lowering treatment and lifestyle changes. Others such as genetic factors or advanced age cannot be modified. Therefore, the rigorous management of the modifiable risk factors is essential for preventing and delaying the decline in renal function. Early diagnosis of diabetic nephropathy is another essential component in the management of diabetes and its complications such as nephropathy. New markers may allow earlier diagnosis of this common and serious complication, but further studies are needed to clarify their additive predictive value, and to define their cost-benefit ratio. This article reviews the most important risk factors in the development and progression of diabetic nephropathy and summarizes recent developments in the diagnosis of this disease.

Targeting Mitochondria and Reactive Oxygen Species-Driven Pathogenesis in Diabetic Nephropathy

Diabetic kidney disease is one of the major microvascular complications of both type 1 and type 2 diabetes mellitus. Approximately 30% of patients with diabetes experience renal complications. Current clinical therapies can only mitigate the symptoms and delay the progression to end-stage renal disease, but not prevent or reverse it. Oxidative stress is an important player in the pathogenesis of diabetic nephropathy. The activity of reactive oxygen and nitrogen species (ROS/NS), which are by-products of the diabetic milieu, has been found to correlate with pathological changes observed in the diabetic kidney. However, many clinical studies have failed to establish that antioxidant therapy is renoprotective. The discovery that increased ROS/NS activity is linked to mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, cellular senescence, and cell death calls for a refined approach to antioxidant therapy. It is becoming clear that mitochondria play a key role in the generation of ROS/NS and their consequences on the cellular pathways involved in apoptotic cell death in the diabetic kidney. Oxidative stress has also been associated with necrosis via induction of mitochondrial permeability transition. This review highlights the importance of mitochondria in regulating redox balance, modulating cellular responses to oxidative stress, and influencing cell death pathways in diabetic kidney disease. ROS/NS-mediated cellular dysfunction corresponds with progressive disease in the diabetic kidney, and consequently represents an important clinical target. Based on this consideration, this review also examines current therapeutic interventions to prevent ROS/NS-derived injury in the diabetic kidney. These interventions, mainly aimed at reducing or preventing mitochondrial-generated oxidative stress, improving mitochondrial antioxidant defense, and maintaining mitochondrial integrity, may deliver alternative approaches to halt or prevent diabetic kidney disease.

Urinary biomarkers for early diabetic nephropathy: beyond albuminuria

Diabetic nephropathy (DN) is the most common cause of end-stage kidney disease in the USA and accounts for a significant increase in morbidity and mortality in patients with diabetes. Early detection is critical in improving clinical management. Although microalbuminuria is regarded as the gold standard for diagnosing the onset of DN, its predictive powers are limited. Consequently, great efforts have been made in recent years to identify better strategies for the detection of early stages of DN and progressive kidney function decline in diabetic patients. Here, we review the various urinary biomarkers that have emerged from these studies which hold promise as more sensitive diagnostic tools for the earlier detection of diabetic kidney disease and the prediction of progression to end-stage kidney disease. A number of key biomarkers present in the urine have been identified that reflect kidney injury at specific sites along the nephron, including glomerular/podocyte damage and tubular damage, oxidative stress, inflammation and activation of the intrarenal renin-angiotensin system. We also describe newer approaches, including urinary microRNAs, which are short noncoding mRNAs that regulate gene expression, and urine proteomics, that can be used to identify potential novel biomarkers in the development and progression of diabetic kidney disease.

Biomarkers of Renal Disease and Progression in Patients with Diabetes

Diabetes prevalence is increasing worldwide, mainly due to the increase in type 2 diabetes. Diabetic nephropathy occurs in up to 40% of people with type 1 or type 2 diabetes. It is important to identify patients at risk of diabetic nephropathy and those who will progress to end stage renal disease. In clinical practice, most commonly used markers of renal disease and progression are serum creatinine, estimated glomerular filtration rate and proteinuria or albuminuria. Unfortunately, they are all insensitive. This review summarizes the evidence regarding the prognostic value and benefits of targeting some novel risk markers for development of diabetic nephropathy and its progression. It is focused mainly on tubular biomarkers (neutrophil-gelatinase associated lipocalin, kidney injury molecule 1, liver-fatty acid-binding protein, N-acetyl-beta-d-glucosaminidase), markers of inflammation (pro-inflammatory cytokines, tumour necrosis factor-α and tumour necrosis factor-α receptors, adhesion molecules, chemokines) and markers of oxidative stress. Despite the promise of some of these new biomarkers, further large, multicenter prospective studies are still needed before they can be used in everyday clinical practice.