Clinical and research markers of oxidative stress in chronic kidney disease

Associations between oxidative balance score and chronic kidney disease events in US adults: a population-based study

Oxidative Balance Scores (OBS) are utilized to assess an individual's antioxidant status, encompassing both dietary and lifestyle factors that contribute to oxidative balance. This study investigates the relationship between OBS and chronic kidney disease (CKD) prevalence among U.S. adults, utilizing data from the National Health and Nutrition Examination Survey (NHANES) 2007-2018. The study involved a cross-sectional analysis of 13,373 individuals from NHANES, focusing on adults aged 20 years or older. OBS was calculated using 20 components, including dietary and lifestyle factors. CKD was identified based on albumin-to-creatinine ratio and estimated glomerular filtration rate, with patients stratified into mild, moderate, and high-risk groups. Statistical analysis included logistic regression models and restricted cubic splines to explore the OBS-CKD relationship. Our findings indicate a statistically significant negative correlation between OBS and CKD prevalence, particularly in mild and moderate-risk groups. Higher OBS quartiles were associated with a decreased likelihood of CKD (OR 0.70; 95% CI 0.53-0.92; P = 0.013). Restricted cubic splines indicated a non-linear, inverse association between OBS and CKD odds for the overall population (P for nonlinearity = 0.017). For mild and moderate CKD risk groups, the relationships were less pronounced (P for nonlinearity = 0.053 and 0.184, respectively), suggesting variability in the OBS-CKD link across different risk levels. The study highlights the potential of elevated OBS as a primary prevention measure for CKD, particularly in individuals with mild to moderate risk. These findings underscore the importance of antioxidant status in CKD risk management and encourage further research into the role of dietary and lifestyle factors in CKD prevention.

Management Challenges of Sleep-Disordered Breathing in a Child With Chronic Kidney Disease: A Case Report of a Child on Peritoneal Dialysis

Chronic kidney disease in children is a challenging condition that requires careful management. When combined with sleep-disordered breathing, it can pose even greater difficulties. This case report highlights the management challenges of a child with chronic kidney disease and sleep-disordered breathing. Through careful analysis and effective intervention, we were able to address the challenges and improve the child's quality of life. Understanding the complex interaction between these two conditions is crucial for healthcare professionals to provide effective care for children with chronic kidney disease and sleep-disordered breathing.

Increasing obstructive sleep apnea risk is associated with albuminuria in Korean adults: cross-sectional analysis

Several studies have shown an association between albuminuria and obstructive sleep apnea (OSA). However, studies on the relationship between the STOP-BANG questionnaire that can screen for OSA and microalbuminuria are still insufficient. Therefore, this study attempted to clarify the relationship between microalbuminuria and OSA risk using the STOP-BANG questionnaire in Korean adults. A total of 7478 participants (3289 men and 4189 women) aged over 40 were enrolled in the Korean National Health and Nutrition Examination Survey from 2019 to 2020. STOP-BANG questionnaire to screen OSA was obtained from subjects. The urinary albumin/creatinine ratio (ACR) and proteinuria were measured via a single dipstick to evaluate renal function. The high OSA risk group had a higher mean ACR value than the low OSA risk group (36.8 ± 172.2 vs 17.7 ± 82.5; P < 0.001). The proportion of subjects with values of 30 ≤ ACR < 300 mg/g (11.9% vs 6.1%; P < 0.001) and ACR > 300 mg/g (2.1% vs 0.7%; P < 0.001) was significantly higher in high OSA risk group. Multivariate logistic regression results confirmed that microalbuminuria (OR 1.279, 95% confidence interval (CI) 1.068-1.532, P = 0.008) was significantly correlated with high OSA risk. In addition, significant correlation with high OSA risk was also found in macroalbuminuria (OR 1.684, 95% CI 1.073-2.530, P = 0.022) and proteinuria (OR 1.355, 95% CI 1.030-1.783, P = 0.030). We confirmed a significant correlation between high OSA risk and albuminuria/proteinuria in Korean adults. Therefore, renal function evaluation is required in high OSA risk patients, and OSA diagnosis through PSG test and treatment is necessary.

Effect of Anemia on Physical Function and Physical Activity in CKD: The National Health and Nutrition Examination Survey, 1999-2016

Key Points

In a large sample representative of the US adult noninstitutionalized population, among participants with CKD stages 3–5, anemia was associated with a significantly lower level of physical activity. The presence of CKD and anemia showed a positive interaction on physical functioning outcomes. Among participants with CKD, physical functioning was worse in patients with anemia compared with those without anemia.

Background

CKD is a major public health problem worldwide. Anemia, a frequent and treatable complication of CKD, is associated with decreased physical functioning and physical activity. The objective of this study was to evaluate the joint association of CKD and anemia with physical functioning and physical activity in a representative sample of the US population.

Methods

Cross-sectional study using the National Health and Nutrition Examination Survey (NHANES) 1999–2016 for physical functioning outcomes (N =33,300) and NHANES 2007–2016 for physical activity (N =22,933). The NHANES physical functioning questionnaire included 19 items. The NHANES physical activity questionnaire captured work-related, leisure-time, and sedentary activities. Higher physical functioning scores represent worse function. CKD was classified using Kidney Disease Outcomes Quality Initiative 2002 criteria, and anemia was defined using the World Health Organization criteria.

Results

The adjusted mean differences (95% confidence interval) in overall physical functioning score comparing participants with anemia with those without anemia among participants with no CKD, CKD stages 1–2, and stages 3–5 were 0.5 (−0.1 to 1.0), 1.5 (0.2 to 2.8), and 3.6 (2.0 to 5.2). Anemia and CKD showed a supra-additive interaction for all physical functioning outcomes among participants in CKD stages 3–5. The prevalence of high physical activity was also lower in participants with anemia compared with those without anemia among participants in CKD stages 3–5 (adjusted prevalence ratio, 0.74; 95% confidence interval, 0.54 to 1.01).

Conclusions

CKD and anemia were associated with impairments in physical functioning and reduced physical activity. For physical functioning outcomes, the combined presence of CKD and of anemia showed a stronger effect than what was expected from their independent effects.

Primary Processes of Free Radical Formation in Pharmaceutical Formulations of Therapeutic Proteins

Oxidation represents a major pathway for the chemical degradation of pharmaceutical formulations. Few specific details are available on the mechanisms that trigger oxidation reactions in these formulations, specifically with respect to the formation of free radicals. Hence, these mechanisms must be formulated based on information on impurities and stress factors resulting from manufacturing, transportation and storage. In more detail, this article focusses on autoxidation, metal-catalyzed oxidation, photo-degradation and radicals generated from cavitation as a result of mechanical stress. Emphasis is placed on probable rather than theoretically possible pathways.

Oxidative stress, inflammation and hormesis: The role of dietary and lifestyle modifications on aging

Oxidative stress (OS) is primarily caused by the formation of free radicals and reactive oxygen species; it is considered as one of the prominent factors in slowing down and degrading cellular machinery of an individual, and it eventually leads to aging and age-related diseases by its continuous higher state. The relation between molecular damage and OS should be particularized to understand the beginning of destruction at the cellular levels, extending outwards to affect tissues, organs, and ultimately to the organism. Several OS biomarkers, which are established at the biomolecular level, are useful in investigating the disease susceptibility during aging. Slowing down the aging process is a matter of reducing the rate of oxidative damage to the cellular machinery over time. The breakdown of homeostasis, the mild overcompensation, the reestablishment of homeostasis, and the adaptive nature of the process are the essential features of hormesis, which incorporates several factors, including calorie restriction, nutrition and lifestyle modifications that play an important role in reducing the OS. In the current review, along with the concept and theories of aging (with emphasis on free radical theory), various manifestations of OS with special attention on mitochondrial dysfunction and age-related diseases have been discussed. To alleviate the OS, hormetic approaches including caloric restriction, exercise, and nutrition have also been discussed.

The clinical relevance of detectable plasma iron species in iron overload states and subsequent to intravenous iron-carbohydrate administration

Many disorders of iron homeostasis (e.g., iron overload) are associated with the dynamic kinetic profiles of multiple non-transferrin bound iron (NTBI) species, chronic exposure to which is associated with deleterious end-organ effects. Here we discuss the chemical nature of NTBI species, challenges with measuring NTBI in plasma, and the clinical relevance of NTBI exposure based on source (iron overload disorder vs. intravenous iron-carbohydrate complex administration). NTBI is not a single entity but consists of multiple, often poorly characterized species, some of which are kinetically non-exchangeable while others are relatively exchangeable. Prolonged presence of plasma NTBI is associated with excessive tissue iron accumulation in susceptible tissues, with consequences, such as endocrinopathy and heart failure. In contrast, intravenous iron-carbohydrate nanomedicines administration leads only to transient NTBI appearance and lacks evidence for association with adverse clinical outcomes. Assays to measure plasma NTBI are typically technically complex and remain chiefly a research tool. There have been two general approaches to estimating NTBI: capture assays and redox-activity assays. Early assays could not avoid capturing some iron from transferrin, thus overestimating NTBI. By contrast, some later assays may have promoted the donation of NTBI species to transferrin during the assay procedure, potentially underestimating NTBI levels. The levels of transferrin saturation at which NTBI species have been detectable have varied between different methodologies and between patient populations studied.

Elevated levels of biomarkers of oxidative stress and renal injury linked to nitrogenous flame retardants exposure in e-waste dismantling site: A case study in China

Nitrogenous flame retardants (NFRs) have aroused worldwide public concern as their nephrotoxic effect. However, knowledge regarding the pathogenesis mechanism of their exposure to induce kidney injury remains largely unknown. In this study, eight NFRs, four oxidative stress biomarkers (OSBs), and one kidney injury biomarker, namely neutrophil gelatinase-associated lipocalin (NGAL), were measured in urine specimens collected from residents living around e-waste disassembly and reference areas, representing two exposure scenarios. Significant higher concentrations of Σ₈NFR (median: 70.6 vs. 33.8 μg/g Cre) and five biomarkers (124 vs. 97.4 μg/g Cre) were found in urines of populations living in e-waste site compared to those in the reference site (p < 0.05). Primary NFRs exhibited significant positive associations with OSBs and NGAL regardless of the population examined, implying that chronic NFRs exposure could induce oxidative stress and kidney damage. By using structure equation model, we found that oxidative stress, particularly DNA and RNA oxidation mediated 16.1% of the total effect of NFRs on NGAL in e-waste related people, but not on the general population. Overall, this study suggests long-term chronic exposure to NFRs can induce oxidative stress and renal injury in humans but the pathogenesis mode may be scenario-specific.

Antioxidant Phytochemicals as Potential Therapy for Diabetic Complications

The global prevalence of diabetes continues to increase partly due to rapid urbanization and an increase in the aging population. Consequently, this is associated with a parallel increase in the prevalence of diabetic vascular complications which significantly worsen the burden of diabetes. For these diabetic vascular complications, there is still an unmet need for safe and effective alternative/adjuvant therapeutic interventions. There is also an increasing urge for therapeutic options to come from natural products such as plants. Hyperglycemia-induced oxidative stress is central to the development of diabetes and diabetic complications. Furthermore, oxidative stress-induced inflammation and insulin resistance are central to endothelial damage and the progression of diabetic complications. Human and animal studies have shown that polyphenols could reduce oxidative stress, hyperglycemia, and prevent diabetic complications including diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy. Part of the therapeutic effects of polyphenols is attributed to their modulatory effect on endogenous antioxidant systems. This review attempts to summarize the established effects of polyphenols on endogenous antioxidant systems from the literature. Moreover, potential therapeutic strategies for harnessing the potential benefits of polyphenols for diabetic vascular complications are also discussed.

Targeted biomarkers of progression in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is an increasingly significant health issue worldwide. Early stages of CKD can be asymptomatic and disease trajectory difficult to predict. Not everyone with CKD progresses to kidney failure, where kidney replacement therapy is the only life-sustaining therapy. Predicting which patients will progress to kidney failure would allow better use of targeted treatments and more effective allocation of health resources. Current diagnostic tests to identify patients with progressive disease perform poorly but there is a suite of new and emerging predictive biomarkers with great clinical promise.

METHODS

This narrative review describes new and emerging biomarkers of pathophysiologic processes of CKD development and progression, accessible in blood or urine liquid biopsies. Biomarkers were selected based on their reported pathobiological functions in kidney injury, inflammation, oxidative stress, repair and fibrosis. Biomarker function and evidence of involvement in CKD development and progression are reported.

CONCLUSION

Many biomarkers reviewed here have received little attention to date, perhaps because of conflicting conclusions of their utility in CKD. The functional roles of the selected biomarkers in the underlying pathobiology of progression of CKD are a powerful rationale for advancing and validating these molecules as prognosticators and predictors of CKD trajectory.

The Interplay Between Nonalcoholic Fatty Liver Disease and Kidney Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, involving approximately 25% of the general population and increasing in prevalence in patient populations afflicted with metabolic syndrome and type 2 diabetes. This article discusses the complex interplay between NAFLD and chronic kidney disease (CKD), as well as the underlying pathogenesis and mechanisms through which NAFLD and CKD are linked. Exploration of these sophisticated relationships and causative factors is essential to accurately assessing kidney function in patients with NAFLD, recommending pharmacologic treatment of disease, and identifying favorable avenues for future investigation.

Indoxyl sulfate, homocysteine, and antioxidant capacities in patients at different stages of chronic kidney disease

BACKGROUND/OBJECTIVES

Increased levels of uremic toxins and decreased antioxidant capacity have a significant impact on the progression of chronic kidney disease (CKD). However, it remains unclear whether they interact with each other to mediate the damage of kidney function. The purpose of this study was to investigate whether uremic toxins (i.e., homocysteine and indoxyl sulfate [IS]), as well as glutathione-dependent antioxidant enzyme activities are dependently or independently associated with kidney function during different stages of CKD patients.

SUBJECTS/METHODS

One hundred thirty-two patients diagnosed with CKD at stages 1 to 5 participated in this cross-sectional study.

RESULTS

Patients who had reached an advanced CKD stage experienced an increase in plasma uremic toxin levels, along with decreased glutathione peroxidase (GSH-Px) activity. Plasma homocysteine, cysteine, and IS concentrations were all positively associated with each other, but negatively correlated to GSH-Px activity levels after adjusting for potential confounders in all CKD patients. Although plasma homocysteine, cysteine, IS, and GSH-Px levels were significantly associated with kidney function, only plasma IS levels still had a significant association with kidney function after these parameters were simultaneously adjusted. In addition, plasma IS could interact with GSH-Px activity to be associated with kidney function.

CONCLUSIONS

IS plays a more dominant role than homocysteine and GSH-Px activity in relation to kidney function.

Advanced lipoprotein parameters could better explain atheromatosis in non-diabetic chronic kidney disease patients

Background

Chronic kidney disease (CKD) patients have a high burden of atheromatous cardiovascular disease (ASCVD) not fully explained by traditional lipid parameters. Lipoprotein composition and subclass particle number information could improve ASCVD risk assessment. The objective of this study is to investigate the association of advanced lipoprotein parameters with the risk of atheromatosis in a subpopulation of the NEFRONA study.

Methods

This was a cross-sectional study in 395 non-diabetic individuals (209 CKD and 186 non-diabetic and non-CKD) without statin therapy. Vascular ultrasound examination assessing 10 territories was combined with advanced lipoprotein testing performed by nuclear magnetic resonance spectroscopy. Logistic regression was used to estimate adjusted odds ratios (ORs) per 1 standard deviation increment.

Results

Atheromatosis was more prevalent in CKD patients (33.9% versus 64.6%). After adjusting for age, gender, smoking habit and CKD stage, the amount of triglycerides (TGs) within low-density lipoprotein (LDL) lipoproteins was independently and positively associated with atheromatosis [OR 1.33; 95% confidence interval (CI) 1.03–1.74; P = 0.03]. Similarly, total and medium LDL particles (LDL-Ps) showed a positive association (OR 1.29; 95% CI 1.00–1.68; P = 0.05 and OR 1.34; 95% CI 1.04–1.75; P = 0.03, respectively). TG-loaded medium LDL-Ps were higher in CKD patients compared with controls and showed an adjusted OR of 1.40 (95% CI 1.09–1.82; P = 0.01) in non-diabetic patients (CKD and non-CKD individuals). In contrast, non-diabetic CKD patients showed a similar coefficient but the significance was lost (OR 1.2; 95% CI 0.8–1.7; P = 0.359).

Conclusions

Non-diabetic CKD patients showed a higher amount of TG-loaded medium LDL-Ps compared with controls. These particles were independently associated with atheromatosis in non-diabetic patients.

Oxidative Modification of Proteins: From Damage to Catalysis, Signaling, and Beyond

Significance: The systematic investigation of oxidative modification of proteins by reactive oxygen species started in 1980. Later, it was shown that reactive nitrogen species could also modify proteins. Some protein oxidative modifications promote loss of protein function, cleavage or aggregation, and some result in proteo-toxicity and cellular homeostasis disruption. Recent Advances: Previously, protein oxidation was associated exclusively to damage. However, not all oxidative modifications are necessarily associated with damage, as with Met and Cys protein residue oxidation. In these cases, redox state changes can alter protein structure, catalytic function, and signaling processes in response to metabolic and/or environmental alterations. This review aims to integrate the present knowledge on redox modifications of proteins with their fate and role in redox signaling and human pathological conditions. Critical Issues: It is hypothesized that protein oxidation participates in the development and progression of many pathological conditions. However, no quantitative data have been correlated with specific oxidized proteins or the progression or severity of pathological conditions. Hence, the comprehension of the mechanisms underlying these modifications, their importance in human pathologies, and the fate of the modified proteins is of clinical relevance. Future Directions: We discuss new tools to cope with protein oxidation and suggest new approaches for integrating knowledge about protein oxidation and redox processes with human pathophysiological conditions. Antioxid. Redox Signal. 35, 1016-1080.

Molecular mechanisms underlying curcumin-mediated microRNA regulation in carcinogenesis; Focused on gastrointestinal cancers

Curcumin is a bioactive ingredient found in the Rhizomes of Curcuma longa. Curcumin is well known for its chemopreventive and anti-cancer properties. Recent findings have demonstrated several pharmacological and biological impacts of curcumin, related to the control and the management of gastrointestinal cancers. Mechanistically, curcumin exerts its biological impacts via antioxidant and anti-inflammatory effects through the interaction with various transcription factors and signaling molecules. Moreover, epigenetic modulators such as microRNAs (miRNAs) have been revealed as novel targets of curcumin. Curcumin was discovered to regulate the expression of numerous pathogenic miRNAs in gastric, colorectal, esophageal and liver cancers. The present systematic review was performed to identify miRNAs that are modulated by curcumin in gastrointestinal cancers.

Analysis of Global Oxidative Status Using Multimarker Scores Reveals a Specific Association Between Renal Dysfunction and Diuretic Therapy in Older Adults

Aging and chronic kidney disease (CKD) are important interrelated cardiovascular risk (CVR) factors linked to oxidative stress, but this relationship has not been well studied in older adults. We assessed the global oxidative status in an older population with normal to severely impaired renal function. We determined the oxidative status of 93 older adults (mean age 85 years) using multimarker scores. OxyScore was computed as index of systemic oxidative damage by analyzing carbonyl groups, oxidized low-density lipoprotein, 8-hydroxy-2'-deoxyguanosine, and xanthine oxidase activity. AntioxyScore was computed as index of antioxidant defense by analyzing catalase and superoxide dismutase (SOD) activity and total antioxidant capacity. OxyScore and AntioxyScore were higher in subjects with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 than in peers with eGFR >60 mL/min/1.73 m2, with protein carbonyls, catalase, and SOD activity as major drivers. Older adults with a recent cardiovascular event had similar OxyScore and AntioxyScore as peers with eGFR >60 mL/min/1.73 m2. Multivariate linear regression analysis revealed that both indices were associated with decreased eGFR independently of traditional CVR factors. Interestingly, AntioxyScore was also associated with diuretic treatment, and a more pronounced increase was seen in subjects receiving combination therapy. The associations of AntioxyScore with diuretic treatment and eGFR were mutually independent. In conclusion, eGFR is the major contributor to the imbalance in oxidative stress in this older population. Given the association between oxidative stress, CKD, and CVR, the inclusion of renal function parameters in CVR estimators for older populations, such as the SCORE-OP, might improve their modest performance.

Implications of oxidative stress in chronic kidney disease: a review on current concepts and therapies

Moderate levels of endogenous reactive oxygen species (ROS) are important for various cellular activities, but high levels lead to toxicity and are associated with various diseases. Levels of ROS are maintained as a balance between oxidants and antioxidants. Accumulating data suggest that oxidative stress is a major factor in deterioration of renal function. In this review, we highlight the possible mechanism by which oxidative stress can lead to chronic kidney disease (CKD). This review also describes therapies that counter the effect of oxidative stress in CKD patients. Numerous factors such as upregulation of genes involved in oxidative phosphorylation and ROS generation, chronic inflammation, vitamin D deficiency, and a compromised antioxidant defense mechanism system cause progressive detrimental effects on renal function that eventually lead to loss of kidney function. Patients with renal dysfunction are highly susceptible to oxidative stress, as risk factors such as diabetes, renal hypertension, dietary restrictions, hemodialysis, and old age predispose them to increased levels of ROS. Biomolecular adducts (DNA, proteins, and lipids) formed due to reaction with ROS can be used to determine oxidative stress levels. Based on the strong correlation between oxidative stress and CKD, reversal of oxidative stress is being explored as a major therapeutic option. Xanthine oxidase inhibitors, dietary antioxidants, and other agents that scavenge free radicals are gaining interest as treatment modalities in CKD patients.

The Relationship between Advanced Oxidation Protein Products, Vascular Calcifications and Arterial Stiffness in Predialysis Chronic Kidney Disease Patients

Background and Objectives: Cardiovascular morbidity and mortality are increased in patients with chronic kidney disease (CKD). It is likely that the accumulation of uremic toxins resulting in increased oxidative stress (OS) is a major contributing factor, but no clear link has been identified. The purpose of this research is to establish if advanced oxidation protein product (AOPP) levels in the serum of predialysis patients are a contributing factor to vascular calcification and increased arterial stiffness. Materials and Methods: After obtaining the informed consent, 46 predialysis patients (CKD stages G3-G5) were included in the study. In order to identify vascular calcifications, hand and pelvic radiographs were performed. Valvular calcifications were identified using cardiac ultrasound. AOPP were measured using a commercially available ELISA kit. The relationships between serum AOPP values and biochemical parameters relevant in the evaluation of CKD patients were analyzed. In addition to identifying the differences in AOPP levels between patients with/without vascular or valvular calcifications, the research focused on describing the relationship between OS and arterial stiffness assessed by oscillometric pulse-wave velocity (PWV) measurement. Results: No significant relationship between serum AOPP and vascular or valvular calcifications was highlighted, but significant correlations of AOPP with C-reactive protein (p = 0.025), HDL-cholesterol levels (p = 0.04), HbA1c (p = 0.05) and PWV values (p = 0.02) were identified. Conclusions: The usefulness of (OS) measurement in clinical practice remains debatable; however, the relationship between AOPP and arterial stiffness could be valuable in improving cardiovascular risk assessment of patients with CKD.

Fibroblast growth factor 21 is associated with increased serum total antioxidant capacity and oxidized lipoproteins in humans with different stages of chronic kidney disease

Background and aims

Oxidative stress (OS) induces the production of fibroblast growth factor 21 (FGF21). Previous data have revealed that FGF21 protects cells from OS injury and death, making it a potential therapeutic option for many diseases with increased OS. However, the association of this growth factor with OS markers in humans with chronic kidney disease (CKD) remains unknown. This study aims to evaluate the association of serum FGF21 with serum total antioxidant capacity (TAC) and oxidized low-density lipoproteins (OxLDL) in subjects in different stages of kidney disease.

Methods

This is a cross-sectional study that included 382 subjects with different stages of CKD, irrespective of type 2 diabetes (T2D) diagnosis. Associations of serum FGF21 with OxLDL, TAC, sex, age, body mass index (BMI), fasting plasma glucose, estimated glomerular filtration rate (eGFR), T2D, and smoking, were evaluated through bivariate and partial correlation analyses. Independent associations of these variables with serum FGF21 were evaluated using multiple linear regression analysis.

Results

Serum FGF21 was significantly and positively correlated with age (r = 0.236), TAC (lnTAC) (r = 0.217), and negatively correlated with eGFR (r = -0.429) and male sex (r = -0.102). After controlling by age, sex, BMI, T2D, smoking, and eGFR; both TAC and OxLDL were positively correlated with FGF21 (r = 0.117 and 0.158 respectively, p < 0.05). Using multiple linear regression analysis, eGFR, male sex, T2D, OxLDL, and TAC were independently associated with serum FGF21 (STDβ = -0.475, 0.162, -0.153, 0.142 and 0.136 respectively; p < 0.05 for all) adjusted for age, BMI, smoking, and fasting plasma glucose.

Conclusion

A positive association between serum FGF21 and OS has been found independently of renal function in humans. Results from the present study provide novel information for deeper understanding of the role of FGF21 in OS in humans with CKD and T2D; mechanistic studies to explain the association of serum FGF21 with oxidative stress in CKD are needed.

Uremic Toxins, Oxidative Stress, Atherosclerosis in Chronic Kidney Disease, and Kidney Transplantation

Patients with chronic kidney disease (CKD) are at a high risk for cardiovascular disease (CVD), and approximately half of all deaths among patients with CKD are a direct result of CVD. The premature cardiovascular disease extends from mild to moderate CKD stages, and the severity of CVD and the risk of death increase with a decline in kidney function. Successful kidney transplantation significantly decreases the risk of death relative to long-term dialysis treatment; nevertheless, the prevalence of CVD remains high and is responsible for approximately 20-35% of mortality in renal transplant recipients. The prevalence of traditional and nontraditional risk factors for CVD is higher in patients with CKD and transplant recipients compared with the general population; however, it can only partly explain the highly increased cardiovascular burden in CKD patients. Nontraditional risk factors, unique to CKD patients, include proteinuria, disturbed calcium, and phosphate metabolism, anemia, fluid overload, and accumulation of uremic toxins. This accumulation of uremic toxins is associated with systemic alterations including inflammation and oxidative stress which are considered crucial in CKD progression and CKD-related CVD. Kidney transplantation can mitigate the impact of some of these nontraditional factors, but they typically persist to some degree following transplantation. Taking into consideration the scarcity of data on uremic waste products, oxidative stress, and their relation to atherosclerosis in renal transplantation, in the review, we discussed the impact of uremic toxins on vascular dysfunction in CKD patients and kidney transplant recipients. Special attention was paid to the role of native and transplanted kidney function.

The importance of polymorphisms of regulatory and catalytic antioxidant proteins in chronic kidney disease

Both excessive production of reactive oxygen species (ROS) and impaired antioxidant function are found in patients with chronic kidney disease (CKD). Therefore, individual susceptibility towards CKD can be induced by functional variations of genes encoding antioxidant regulatory (nuclear factor erythroid 2 - related factor 2 (Nrf2)) and catalytic (superoxide dismutase (SOD2) and glutathione peroxidase (GPX1)) proteins. Several types of single nucleotide polymorphisms (SNPs) have been found within the genes encoding these proteins, with Nrf2 (-617C/A), SOD2 (Ala16Val) and GPX1 (Pro198Leu) conferring impaired catalytic activity. The most unexplored gene polymorphism in CKD susceptibility, progression and survival, with only two original studies published, is the Nrf2 (-617C/A) polymorphism. The results of these studies showed that there was no individual impact of this polymorphism on the susceptibility towards end stage renal disease (ESRD) development, oxidative phenotype and mortality. However, Nrf2 had a significant role in ESRD risk and survival, when combined with other antioxidant genes. The results regarding the impact of SOD2 (Ala16Val) and GPX1 (Pro198Leu) polymorphisms on either CKD or ESRD are still inconclusive. Namely, some studies showed that patients having variant SOD2 (Val) or GPX1 (Leu) allele were at increased risk of CKD development and progression, while other studies reported only weak or no association between these polymorphisms and CKD. Surprisingly, the only study that reported an association of GPX1 polymorphism with overall/cardiovascular survival in ESRD patients showed a significant impact of low activity GPX1 (Leu/Leu) genotype on better survival. In this review, we comprehensively and critically appraise the literature on these polymorphisms related to oxidative stress in CKD patients, in order to identify gaps and provide recommendations for further clinical research and translation. New developments in the field of antioxidant polymorphisms in CKD patients could lead to better stratification of CKD patients, based on a prognostic antioxidant gene panel, and provide a more personalised medicine approach for the need of antioxidant therapy in these patients.

Oxidative Storm Induced by Tryptophan Metabolites: Missing Link between Atherosclerosis and Chronic Kidney Disease

Chronic kidney disease (CKD) occurrence is rising all over the world. Its presence is associated with an increased risk of premature death from cardiovascular disease (CVD). Several explanations of this link have been put forward. It is known that in renal failure, an array of metabolites cannot be excreted, and they accumulate in the organism. Among them, some are metabolites of tryptophan (TRP), such as indoxyl sulfate and kynurenine. Scientists have become interested in them in the context of inducing vascular damage in the course of chronic kidney impairment. Experimental evidence suggests the involvement of TRP metabolites in the progression of chronic kidney disease and atherosclerosis separately and point to oxidative stress generation as one of the main mechanisms that is responsible for worsening those states. Since it is known that blood levels of those metabolites increase significantly in renal failure and that they generate reactive oxygen species (ROS), which lead to endothelial injury, it is reasonable to suspect that products of TRP metabolism are the missing link in frequently occurring atherosclerosis in CKD patients. This review focuses on reports that shed a light on TRP metabolites as contributing factors to vascular damage in the progression of impaired kidney function.

The Role of Eryptosis in the Pathogenesis of Renal Anemia: Insights From Basic Research and Mathematical Modeling

Red blood cells (RBC) are the most abundant cells in the blood. Despite powerful defense systems against chemical and mechanical stressors, their life span is limited to about 120 days in healthy humans and further shortened in patients with kidney failure. Changes in the cell membrane potential and cation permeability trigger a cascade of events that lead to exposure of phosphatidylserine on the outer leaflet of the RBC membrane. The translocation of phosphatidylserine is an important step in a process that eventually results in eryptosis, the programmed death of an RBC. The regulation of eryptosis is complex and involves several cellular pathways, such as the regulation of non-selective cation channels. Increased cytosolic calcium concentration results in scramblase and floppase activation, exposing phosphatidylserine on the cell surface, leading to early clearance of RBCs from the circulation by phagocytic cells. While eryptosis is physiologically meaningful to recycle iron and other RBC constituents in healthy subjects, it is augmented under pathological conditions, such as kidney failure. In chronic kidney disease (CKD) patients, the number of eryptotic RBC is significantly increased, resulting in a shortened RBC life span that further compounds renal anemia. In CKD patients, uremic toxins, oxidative stress, hypoxemia, and inflammation contribute to the increased eryptosis rate. Eryptosis may have an impact on renal anemia, and depending on the degree of shortened RBC life span, the administration of erythropoiesis-stimulating agents is often insufficient to attain desired hemoglobin target levels. The goal of this review is to indicate the importance of eryptosis as a process closely related to life span reduction, aggravating renal anemia.

Plasma Protein Carbonyls as Biomarkers of Oxidative Stress in Chronic Kidney Disease, Dialysis, and Transplantation

Accumulating evidence indicates that oxidative stress plays a role in the pathophysiology of chronic kidney disease (CKD) and its progression; during renal replacement therapy, oxidative stress-derived oxidative damage also contributes to the development of CKD systemic complications, such as cardiovascular disease, hypertension, atherosclerosis, inflammation, anaemia, and impaired host defence. The main mechanism underlying these events is the retention of uremic toxins, which act as a substrate for oxidative processes and elicit the activation of inflammatory pathways targeting endothelial and immune cells. Due to the growing worldwide spread of CKD, there is an overwhelming need to find oxidative damage biomarkers that are easy to measure in biological fluids of subjects with CKD and patients undergoing renal replacement therapy (haemodialysis, peritoneal dialysis, and kidney transplantation), in order to overcome limitations of invasive monitoring of CKD progression. Several studies investigated biomarkers of protein oxidative damage in CKD, including plasma protein carbonyls (PCO), the most frequently used biomarker of protein damage. This review provides an up-to-date overview on advances concerning the correlation between plasma protein carbonylation in CKD progression (from stage 1 to stage 5) and the possibility that haemodialysis, peritoneal dialysis, and kidney transplantation improve plasma PCO levels. Despite the fact that the role of plasma PCO in CKD is often underestimated in clinical practice, emerging evidence highlights that plasma PCO can serve as good biomarkers of oxidative stress in CKD and substitutive therapies. Whether plasma PCO levels merely serve as biomarkers of CKD-related oxidative stress or whether they are associated with the pathogenesis of CKD complications deserves further evaluation.

Role of Oxidative Stress in Hepatic and Extrahepatic Dysfunctions during Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is a pathology that contains a broad liver dysfunctions spectrum. These alterations span from noninflammatory isolated steatosis until nonalcoholic steatohepatitis (NASH), a more aggressive form of the disease characterized by steatosis, inflammatory status, and varying liver degrees fibrosis. NAFLD is the most prevalent chronic liver disease worldwide. The causes of NAFLD are diverse and include genetic and environmental factors. The presence of NASH is strongly associated with cirrhosis development and hepatocellular carcinoma, two conditions that require liver transplantation. The liver alterations during NAFLD are well described. Interestingly, this pathological condition also affects other critical tissues and organs, such as skeletal muscle and even the cardiovascular, renal, and nervous systems. Oxidative stress (OS) is a harmful state present in several chronic diseases, such as NAFLD. The purpose of this review is to describe hepatic and extrahepatic dysfunctions in NAFLD. We will also review the influence of OS on the physiopathological events that affect the critical function of the liver and peripheral tissues.

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.

Oxidative stress accelerates the carotid atherosclerosis process in patients with chronic kidney disease

INTRODUCTION

The atherosclerosis process is highly accelerated in patients with chronic kidney disease (CKD). Oxidative stress is considered as one of the pro-atherogenic factors involved in accelerating the atherosclerosis process of the carotid artery. The aim of the present study was to determine the relationship between oxidative stress markers and the progression of carotid atherosclerosis in CKD patients.

MATERIAL AND METHODS

The study was conducted on 162 patients with CKD and 40 controls, and the disease stage was scored between 2 and 5D. Blood samples were taken and advanced oxidative protein product, myeloperoxidases, malondialdehyde, nitric oxide, glutathione, and oxidised low-density lipoprotein were measured. Furthermore, we studied the correlations between these biomarkers and clinical and para-clinical cardiovascular complications.

RESULTS

The average age of patients was 56.5 years. The oxidative stress markers average ± SD levels in CKD groups compared to the control were as follows: advanced oxidation protein product (61.89 ±1.4 vs. 26.65 ±1.05 µmol/l), myeloperoxidase (59.89 ±1.98 vs. 38.45 ±1.98 UI/ml), malondialdehyde (6.1 ±0.12 vs. 3.26 ±0.03 µmol/l), nitric oxide (65.82 ±1.06 vs. 52.19 ±2.1 µmol/l), glutathione (52.21 ±1.3 vs. 89.4 ±2.6 IU/ml), and oxLDL (15.57 ±1.07 vs. 1.72 ±0.82 µmol/l). While the glutathione level decreased significantly in advanced CKD stage (p < 0.05), the concentrations of all the other biomarkers increased significantly in accordance with CKD score (p < 0.05).

CONCLUSIONS

Cardiovascular diseases, mainly atherosclerosis, can be diagnosed indirectly by measuring oxidative stress markers. Furthermore, theses markers can be used to predict the progression of CKD, for better management of the disease.

Urinary markers of oxidative stress respond to infection and late-life in wild chimpanzees

Oxidative stress (OS) plays a marked role in aging and results from a variety of stressors, making it a powerful measure of health and a way to examine costs associated with life history investments within and across species. However, few urinary OS markers have been examined under field conditions, particularly in primates, and their utility to non-invasively monitor the costs of acute stressors versus the long-term damage associated with aging is poorly understood. In this study, we examined variation in 5 urinary markers of oxidative damage and protection under 5 validation paradigms for 37 wild, chimpanzees living in the Kibale National Park, Uganda. We used 924 urine samples to examine responses to acute immune challenge (respiratory illness or severe wounding), as well as mixed-longitudinal and intra-individual variation with age. DNA damage (8-OHdG) correlated positively with all other markers of damage (F-isoprostanes, MDA-TBARS, and neopterin) but did not correlate with protection (total antioxidant capacity). Within individuals, all markers of damage responded to at least one if not both types of acute infection. While OS is expected to increase with age, this was not generally true in chimpanzees. However, significant changes in oxidative damage were detected within past-prime individuals and those close to death. Our results indicate that OS can be measured using field-collected urine and integrates short- and long-term aspects of health. They further suggest that more data are needed from long-lived, wild animals to illuminate if common age-related increases in inflammation and OS damage are typical or recently aberrant in humans.

Interrelationship of environmental melamine exposure, biomarkers of oxidative stress and early kidney injury

Melamine contamination has remained pervasive in the environment even after the 2008 toxic milk scandal. Exposure to chronic low dosages of melamine is known to induce renal tubular damage, increasing the risk of stone formation and early kidney injury. This damage may come about via increased oxidative stress, but no studies of this possibility have been performed in humans. We conducted two human studies in 80 workers from melamine tableware factories (melamine workers) and 309 adult patients with calcium urolithiasis (stone patients) to evaluate the relationships between urinary melamine levels and two urinary biomarkers of oxidative stress, 8-oxo-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA). Both human studies showed urinary melamine levels to be significantly and positively correlated with urinary 8-OHdG and MDA, indicating melamine exposure can increase oxidative stress. Additionally, we used structure equation modeling to evaluate relative contribution of type of melamine-induced oxidative stress on renal tubular injury and found that MDA mediated 36 %-53 % of the total effect of melamine on a biomarker of renal tubular injury, N-Acetyl-β-d Glucosaminidase (NAG). In conclusion, our findings suggest exposure to low-dose melamine can increase oxidative stress and increase the risk of early damage to kidneys in humans.

Circulating inflammation-related factors are correlated with systemic redox status in IgA nephropathy; a case-control study

BACKGROUND

IgA nephropathy (IGAN) is characterized by oxidative stress and inflammation. In the present study, we explored the relationship of redox status vs. that of circulating inflammation-related factors with other biomarkers in patients with IGAN.

METHODS

This is a case-control study comparing patients with IGAN (Stage 1-4) to healthy controls. Forty patients and 40 controls were matched for age and sex. Two circulating dynamic redox parameters were analysed: oxidized free cysteine (Cys) and nitrate. Thirty-seven inflammation-related factors were measured in serum.

RESULTS

The patients had elevated levels of oxidized free Cys and nitrate, indicating the presence of oxidative stress. Nine circulating inflammation-related factors were higher in the serum of patients than in that of controls. The most important factors were APRIL, MMP-3, osteopontin, TNFR1 and TWEAK. Inflammation-related factors were positively correlated with oxidized free Cys, nitrate, creatinine and parathyroid hormone (PTH) in the patients. The correlation coefficients of Latent Inflammatory Factor vs. oxidized free Cys and nitrate were r = 0.43 (p = 0.007) and r = 0.51 (p = 0.001), respectively. This finding persisted after adjusting for the glomerular filtration rate.

CONCLUSIONS

Patients with IGAN had disturbed redox status. Several circulating inflammation-related factors were elevated, suggesting activation of the non-canonical NF-kB pathway. There was a positive relationship between systemic redox status and the level of inflammation-related factors, partially independent of GFR. The present findings raise the question of whether circulating oxidized free Cys and/or nitrate may be employed as prognostic biomarkers for IGAN in the future.

The Disposal of Reactive Carbonyl Species through Carnosine Conjugation: What We Know Now

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Reactive Carbonyl Species are electrophiles generated by the oxidative cleavage of lipids and sugars. Such compounds have been described as important molecules for cellular signaling, whilst their accumulation has been found to be cytotoxic as they may trigger aberrant modifications of proteins (a process often referred to as carbonylation).

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A correlation between carbonylation of proteins and human disease progression has been shown in ageing, diabetes, obesity, chronic renal failure, neurodegeneration and cardiovascular disease. However, the fate of reactive carbonyl species is still far from being understood, especially concerning the mechanisms responsible for their disposal as well as the importance of this in disease progression.

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In this context, some data have been published on phase I and phase II deactivation of reactive carbonyl species. In the case of phase II mechanisms, the route involving glutathione conjugation and subsequent disposal of the adducts has been extensively studied both in vitro and in vivo for some of the more representative compounds, e.g. 4-hydroxynonenal.

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There is also emerging evidence of an involvement of carnosine as an endogenous alternative to glutathione for phase II conjugation. However, the fate of carnosine conjugates is still poorly investigated and, unlike glutathione, there is little evidence of the formation of carnosine adducts in vivo. The acquisition of such data could be of importance for the development of new drugs, since carnosine and its derivatives have been proposed as potential therapeutic agents for the mitigation of carbonylation associated with disease progression.

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Herein, we wish to review our current knowledge of the binding of reactive carbonyl species with carnosine together with the disposal of carnosine conjugates, emphasizing those aspects still requiring investigation such as conjugation reversibility and enzyme assisted catalysis of the reactions.

NAFLD as a driver of chronic kidney disease

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are worldwide public health problems, affecting up to 25-30% (NAFLD), and up to 10-15% (CKD) of the general population. Recently, it has also been established that there is a strong association between NAFLD and CKD, regardless of the presence of potential confounding diseases such as obesity, hypertension and type 2 diabetes. Since NAFLD and CKD are both common diseases that often occur alongside other metabolic conditions, such as type 2 diabetes or metabolic syndrome, elucidating the relative impact of NAFLD on the risk of incident CKD presents a substantial challenge for investigators working in this research field. A growing body of epidemiological evidence suggests that NAFLD is an independent risk factor for CKD and recent evidence also suggests that associated factors such as metabolic syndrome, dysbiosis, unhealthy diets, platelet activation and processes associated with ageing could also contribute mechanisms linking NAFLD and CKD. This narrative review provides an overview of the literature on: a) the evidence for an association and causal link between NAFLD and CKD and b) the underlying mechanisms by which NAFLD (and factors strongly linked with NAFLD) may increase the risk of developing CKD.

Association of Hypertension and Obesity with Risk Factors of Cardiovascular Diseases in Children Aged 6-9 Years Old in the Eastern Cape Province of South Africa

Cardiovascular disease (CVD) risk factors are known to begin early in life, but limited data on the relationship of obesity and hypertension with other known CVD risk factors, such as endothelial dysfunction, oxidative stress, and chronic low-grade inflammation is available on children. In this cross-sectional study involving 6–9 years old school children aged from the Eastern Cape Province of South Africa the relationship between obesity/hypertension and other risk factors for CVDs was investigated. General anthropometric parameters were measured, followed by blood pressure (BP) measurements and pulse wave velocity (PWV). Urine samples were collected for the determination of albumin, creatinine, asymmetric dimethylarginine (ADMA), 8-hydroxy-2deoxyguanosine (8-OHdG), and thiobarbituric acid-reactive substance (TBARS). Overweight/obesity (19.28%) and pre-hypertension/hypertension (42.16%) were prevalent in children. Mid-upper arm circumference (MUAC), a marker of obesity, was positively correlated with ADMA, while ADMA and PWV were significantly different (p < 0.05) between hypertensive and normotensive children. Also, TBARS and 8-OHdG were significantly (p < 0.05) increased in hypertensive subjects. Creatinine was significantly (p < 0.05) increased in obese, as well as in hypertensive children, and positively associated with waist circumference (WC) and neck circumference (NC). In conclusion, obesity and hypertension were associated with renal-cardiovascular disease risk, while oxidative stress showed a possible association with obesity in 6 to 9 year old South African children of African descent. This suggests that South African children of African descent may be becoming more prone to developing CVDs, and therefore may require early intervention for the prevention of CVDs in the near future.

Oxidative Stress in Hemodialysis Pediatric Patients

BACKGROUND:

Oxidative stress may play a role in complications of hemodialysis patients as atherosclerosis, thrombosis, and inflammation.

AIM:

The aim of the study was to evaluate the oxidative stress in hemodialysis pediatric patients through measurement of oxidative stress enzymes as paraoxanase activity (PON), arylesterase activity (ASA), superoxide dismutase (SOD) and also non-enzymatic antioxidant vitamins as vitamins A, C and E levels.

METHODS:

The study included 50 hemodialysis pediatric patients with mean age 11.4 ± 5.4 years and 30 normal children of matched sex and age as a control group. Assessment of oxidative stresses was done using ELIZA technique.

RESULTS:

SOD, ASA, and vitamin C were significantly lower among hemodialysis patients in comparison to control group (p = 0.004, 0.004, > 0.001 respectively).

CONCLUSION:

The study concluded that oxidative stress was common finding in hemodialysis pediatric patients which may play a role in complications encountered among these patients.

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

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

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

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

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.

Preclinical study of the long-range safety and anti-inflammatory effects of high-dose oral meglumine

Meglumine is a methylamino derivative of sorbitol that is an approved drug excipient. Recent preclinical studies suggest that administration of high-dose oral meglumine can exert beneficial medicinal effects to treat diabetes, obesity, and fatty liver disease (NAFLD/nonalcoholic steatohepatitis [NASH]). Here we address gaps in knowledge about the pharmacology and toxicology of this substance administered at high concentrations to explore its medicinal potential. We observed that high-dose meglumine limited secretion of proinflammatory cytokines and cell adhesion molecules from activated human THP-1 or murine RAW264.7 monocytes. Preclinical pharmacokinetic analysis in Swiss mice confirmed that meglumine was orally available. Informed by this data, oral doses of 18 to 75 mM meglumine were administered ad libitum in the drinking water of Sprague-Dawley rats and two cohorts of C57BL/6 mice housed in different vivariums. In a 32-week study, urinary isoprostane levels trended lower in subjects consistent with the possibility of anti-inflammatory effects. In full lifespan studies, there was no detrimental effect on longevity. Heart function evaluated in C57BL/6 mice using an established noninvasive cardiac imaging system showed no detrimental effects on ejection fraction, fractional shortening, left ventricle function or volume, and cardiac output in mice up to 15-month old, with a potential positive trend in heart function noted in elderly mice consistent with earlier reported benefits on muscle stamina. Finally, in a transgenic model of inflammation-associated skin carcinogenesis, the incidence, number, and growth of skin tumors trended lower in subjects receiving meglumine. Overall, the evidence obtained illustrating the long-range safety of high-dose oral meglumine support the rationale for its evaluation as a low-cost modality to limit diabetes, hypertriglyceridemia, and NAFLD/NASH.

Factors affecting arteriovenous fistula dysfunction: A narrative review

Vascular access dysfunction is one of the most important causes of morbidity and mortality in haemodialysis patients, contributing to up to one third of hospitalisations and accounting for a significant amount of the health care costs of these patients. In the past decades, significant scientific advances in understanding mechanisms of arteriovenous fistula maturation and failure have contributed to an increase in the amount of research into techniques for creation and strategies for arteriovenous fistula dysfunction prevention and treatment, in order to improve patient care and outcomes. The aim of this review is to describe the pathogenesis of vascular access failure and provide a comprehensive analysis of the associated risk factors and causes of vascular access failure, in order to interpret possible future therapeutic approaches. Arteriovenous fistula failure is a multifactorial process resulting from the combination of upstream and downstream events with consequent venous neo-intimal hyperplasia and/or inadequate outward remodelling. Inflammation appears to be central in the biology of arteriovenous fistula dysfunction but important triggers still need to be revealed. Given the significant association of arteriovenous fistula failure and patient's prognosis, it is therefore imperative to further research in this area in order to improve prevention, surveillance and treatment, and ultimately patient care and outcomes.

Oxidative Stress in Animal Models of Acute and Chronic Renal Failure

Introduction

Kidney disease is a worldwide health and economic burden, with rising prevalence. The search for biomarkers for earlier and more effective disease screening and monitoring is needed. Oxidative stress has been linked to both, acute kidney injury (AKI) and chronic kidney disease (CKD). The aim of our study was to investigate whether the concentrations of systemic markers of oxidative stress and antioxidant status are affected by AKI and CKD, and to identify potential biomarkers.

Methods

In adult male Wistar rats, AKI was induced by bilateral nephrectomy, and CKD was induced by 5/6 nephrectomy. Blood was collected 48 hours after surgery in AKI and 6 months after surgery in CKD. Advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), advanced glycation end products (AGEs), fructosamine, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) were measured.

Results

Impaired renal function was confirmed by high concentrations of plasma creatinine and urea in AKI and CKD animals. AOPP and fructosamine were higher by 100% and 54% in AKI, respectively, and by 100% and 199% in CKD, respectively, when compared to corresponding control groups. Similarly, there was approximately a twofold increase in AGEs (by 92%) and TAC (by 102%) during AKI. In CKD, concentrations of FRAP, as an antioxidative status marker, were doubled (by 107%) when compared to the control group, but concentration of TAC, another marker of antioxidative status, did not differ between the groups.

Conclusions

AKI and CKD led to increased systemic oxidative stress. AOPP and fructosamine could be considered potential biomarkers for both, acute and chronic kidney damage. On the other hand, AGEs, TAC, and FRAP seem to be disease specific, which could help to differentiate between acute and chronic kidney injuries. However, this needs further validation in clinical studies.

Alda-1, an aldehyde dehydrogenase-2 agonist, causes deterioration in renal functions following ischemia-reperfusion injury due to crystalline nephropathy

Renal ischemia-reperfusion injury (IRI) induces the production of aldehydes which are detoxified by aldehyde dehydrogenases (ALDHs). Alda-1 is a selective ALDH2 agonist and its protective effect was demonstrated in several conditions. The effect of Alda-1 on the kidney or on renal IRI was not investigated. We investigated the effect of Alda-1 on the renal dysfunction following IRI. Wistar rats underwent left IRI for 40 min. Group-Alda (n = 11) received Alda-1 starting 24 h before IRI and continued for 7 days thereafter when renal functions were measured. Group-Vx (n = 11) underwent similar protocol but received the dissolvent. Alda-1 did not affect renal blood flow or glomerular filtration rate in the left ischemic kidney in Group-Alda compared to Group-Vx (3.05 ± 0.50 vs. 3.53 ± 0.70, and 0.40 ± 0.06 vs. 0.51 ± 0.08, respectively, p > .05 for both). However, left renal fractional sodium excretion was higher in Group-Alda (2.80 ± 0.43 vs. 1.37 ± 0.36, p = .02). Alda-1 also adversely affected the gene expressions of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin (217 ± 38 vs. 99 ± 13 and 49 ± 13 vs. 20 ± 5, respectively, p < .05 for both) and the alterations in tumor necrosis factor-α, transforming growth factor-β1, plasminogen activator inhibitor-1, fibronectin 1 and p53 (4.4 ± 0.9 vs. 2.1 ± 0.3, 1.5 ± 0.1 vs. 1.1 ± 0.1, 30.0 ± 2.7 vs. 11.7 ± 2.3, 3.6 ± 0.4 vs. 2.1 ± 0.2 and 1.3 ± 0.1 vs. 0.9 ± 0.07, respectively, p ≤ .05 for all). This was associated with intratubular crystal deposition suggestive of crystalline nephropathy. Alda-1 exacerbated the IRI-induced renal tubular dysfunction and alterations in markers of acute kidney injury, biomarkers of inflammation, fibrosis and apoptosis and this was associated with intratubular crystal deposition suggestive of crystalline nephropathy.

Gamma Oryzanol Treats Obesity-Induced Kidney Injuries by Modulating the Adiponectin Receptor 2/PPAR-α Axis

The kidney is an important organ in the maintenance of body homeostasis. Dietary compounds, reactive metabolites, obesity, and metabolic syndrome (MetS) can affect renal filtration and whole body homeostasis, increasing the risk of chronic kidney disease (CKD) development. Gamma oryzanol (γOz) is a compound with antioxidant and anti-inflammatory activity that has shown a positive action in the treatment of obesity and metabolic diseases. Aim. To evaluate the effect of γOz to recover renal function in obese animals by high sugar-fat diet by modulation of adiponectin receptor 2/PPAR-α axis Methods. Male Wistar rats were initially randomly divided into 2 experimental groups: control and high sugar-fat diet (HSF) for 20 weeks. When proteinuria was detected, HSF animals were allocated to receive γOz or maintain HSF for more than 10 weeks. The following were analyzed: nutritional and biochemical parameters, systolic blood pressure, and renal function. In the kidney, the following were evaluated: inflammation, oxidative stress, and protein expression by Western blot. Results. After 10 weeks of γOz treatment, γOz was effective to improve inflammation, increase antioxidant enzyme activities, increase the protein expression of adiponectin receptor 2 and PPAR-α, and recover renal function. Conclusion. These results permit us to confirm that γOz is able to modulate PPAR-α expression, inflammation, and oxidative stress pathways improving obesity-induced renal disease.

Urinary Liver Type Fatty Acid Binding Protein Is Negatively Associated With Estimated Glomerular Filtration Rate in Renal Transplant Recipients With Graft Loss

BACKGROUND

Liver type fatty acid binding protein (L-FABP) is abundant not only in the liver but also in the kidney and is excreted in urine. Its primary function is to facilitate intracellular long chain fatty acid transport and it might also act as an endogenous antioxidant molecular. The purpose of this study was to investigate whether plasma or urinary L-FABP levels were associated with graft function in renal transplant recipients.

PATIENTS AND METHODS

Sixty-seven renal transplant recipients with a mean age of 48.8 years were recruited. The mean duration of renal transplantation was 4131 days. Recipients were divided into 2 groups based on their estimated glomerular filtration rate (eGFR) values: moderate graft function (eGFR ≥60 mL/min/1.73 m²) and low graft function (eGFR <60 mL/min/1.73 m²). Fasting plasma and urinary L-FABP levels were measured.

RESULTS

There was no significant difference in plasma L-FABP level between the 2 groups, although recipients in the low graft function group had significantly lower urinary L-FABP level when compared with recipients in the moderate graft function group. Plasma and urinary L-FABP levels were not associated with eGFR in the 67 recipients; however, urinary L-FABP level (β = -1.24, P = .037) and level adjusted by urinary creatinine (β = -0.75, P = .046) were significantly negatively associated with eGFR in recipients with low graft function after adjusting for potential confounders.

CONCLUSION

Increased urinary L-FABP level seems to be a significant indicator of decreased graft function in renal transplant recipients with loss of graft function.

Cardiovascular risk in chronic kidney disease: what is new in the pathogenesis and treatment?

The prevalence of chronic kidney disease (CKD) has increased markedly over past decades due to the aging of the worldwide population. Despite the progress in the prevention and treatment, the cardiovascular (CV) morbidity and mortality remain high among patients with CKD. Although CKD is a progressive and irreversible condition, it is possible to slow decreasing kidney function, as well as the development and progression of associated with kidney disease comorbidities. Diabetes mellitus has become major cause of CKD worldwide. It is estimated that the prevalence of diabetes will increase from 425 million worldwide in 2017 to 629 million by 2045, substantially the percentage of diabetic nephropathy among CKD patients is set to rise markedly. The results of multicenter trials concerning novel antidiabetic drugs suggest that efficacy in reducing CV risk is independent of the improvement in glycemic control. This review discusses underlying causes of high CV risk and strategies reducing individual burden among CKD patients.

Dietary Oxidative Balance Scores and Biomarkers of Inflammation among Individuals with and without Chronic Kidney Disease

BACKGROUND

Oxidative stress and inflammation are proposed mechanisms of nonspecific kidney injury and progressive kidney failure. Higher dietary oxidative balance scores (OBS) are associated with lower prevalence of chronic kidney disease (CKD).

METHODS

We investigated the association between OBS and biomarkers of inflammation using data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. Nutrient estimates from the Block Food Frequency Questionnaires were used to define tertiles of 11 pro- and antioxidant factors. Points for each OBS component were summed, with a higher score indicating predominance of antioxidant exposures. Multivariable linear regression models were used to estimate the association between OBS and biomarkers of inflammation (interleukin-6 [IL-6], interleukin-8 [IL-8], interleukin-10 [IL-10], fibrinogen, C-reactive protein [CRP], white blood cell count, and cystatin C). An interaction term was included to determine if associations between OBS and inflammatory markers differed between individuals with and without CKD.

RESULTS

Of 682 participants, 22.4% had CKD. In adjusted models, OBS was associated with CRP and IL-6. For every 5-unit increase in OBS, the CRP concentration was -15.3% lower (95% CI: -25.6, -3.6). The association of OBS with IL-6 differed by CKD status; for every 5-unit increase in OBS, IL-6 was -10.7% lower (95% CI: -16.3, -4.7) among those without CKD, but there was no association among those with CKD (p = 0.03).

CONCLUSION

This study suggests that a higher OBS is associated with more favorable levels of IL-6 and CRP, and that the association of OBS and IL-6 may be modified by CKD status.