Association between serum advanced oxidation protein products and mortality risk in maintenance hemodialysis patients

The Clinical Utility and Plausibility of Oxidative and Antioxidant Variables in Chronic and End-Stage Kidney Disease: A Review of the Literature

Oxidative stress (OS) is caused by an imbalance between the production of reactive oxygen species (ROS) in cells and tissues and the ability of the biological system to detoxify these products. In chronic kidney disease (CKD), OS contributes to deterioration of kidney function and disease progression. In patients with end-stage kidney disease undergoing hemodialysis or peritoneal dialysis, OS is further increased and associated with adverse clinical outcomes, including deterioration and subsequent loss of residual renal function, atherosclerosis, hypertension, cardiovascular disease and death. However, currently, there is no consensus or guidelines for the diagnosis and treatment of OS in these patients. Herein, we aim to present the existing data regarding biomarkers of OS, pro-oxidants (oxidized albumin, advanced oxidation protein products, xanthine oxidase/dehydrogenase, nitrite/nitrate, malondialdehyde) and antioxidants (superoxide dismutase, catalase, vitamin E, total antioxidant capacity, N-acetylcysteine) that are most clinically relevant and have been more extensively studied in patients with chronic kidney disease, aiming to provide a clearer understanding of this complex area.

Post-translational modifications in kidney diseases and associated cardiovascular risk

Patients with chronic kidney disease (CKD) are at an increased cardiovascular risk compared with the general population, which is driven, at least in part, by mechanisms that are uniquely associated with kidney disease. In CKD, increased levels of oxidative stress and uraemic retention solutes, including urea and advanced glycation end products, enhance non-enzymatic post-translational modification events, such as protein oxidation, glycation, carbamylation and guanidinylation. Alterations in enzymatic post-translational modifications such as glycosylation, ubiquitination, acetylation and methylation are also detected in CKD. Post-translational modifications can alter the structure and function of proteins and lipoprotein particles, thereby affecting cellular processes. In CKD, evidence suggests that post-translationally modified proteins can contribute to inflammation, oxidative stress and fibrosis, and induce vascular damage or prothrombotic effects, which might contribute to CKD progression and/or increase cardiovascular risk in patients with CKD. Consequently, post-translational protein modifications prevalent in CKD might be useful as diagnostic biomarkers and indicators of disease activity that could be used to guide and evaluate therapeutic interventions, in addition to providing potential novel therapeutic targets.

A chronic intermittent haemodialysis pig model for functional evaluation of dialysis membranes

Performance evaluation of new dialysis membranes is primarily performed in vitro, which can lead to differences in clinical results. Currently, data on dialysis membrane performance and safety are available only for haemodialysis patients. Herein, we aimed to establish an in vivo animal model of dialysis that could be extrapolated to humans. We created a bilateral nephrectomy pig model of renal failure, which placed a double-lumen catheter with the hub exposed dorsally. Haemodialysis was performed in the same manner as in humans, during which clinically relevant physiologic data were evaluated. Next, to evaluate the utility of this model, the biocompatibility of two kinds of membranes coated with or without vitamin E used in haemodiafiltration therapy were compared. Haemodialysis treatment was successfully performed in nephrectomized pigs under the same dialysis conditions (4 h per session, every other day, for 2 weeks). In accordance with human clinical data, regular dialysis alleviated renal failure in pigs. The vitamin E-coated membrane showed a significant reduction rate of advanced oxidation protein products during dialysis than non-coated membrane. In conclusion, this model mimics the pathophysiology and dialysis condition of patients undergoing haemodialysis. This dialysis treatment model of renal failure will be useful for evaluating the performance and safety of dialysis membranes.

ROS-Induced Endothelial Dysfunction in the Pathogenesis of Atherosclerosis

Various signaling pathways are regulated by reactive oxygen species (ROS), which are radical oxygen intermediates under normal physiological conditions. However, when the buffering capacity of antioxidant enzymes is exceeded by the accumulation of ROS, oxidative stress, and endothelial cell dysfunction occur, which have been recognized as key contributors to the development of atherosclerosis. In this review, an overview is provided on mechanisms underlying ROS generation in endothelial cells and the involved regulatory pathways. Further, we discuss the ROS induced endothelial cell dysfunction and its relationship with atherosclerosis. Current knowledge on ROS-induced endothelial impairment is presented, characterized by decreased NO bioavailability, intracellular dysfunction and ox-LDL accumulation. Furthermore, biomarkers such as oxidative products of lipid, protein, and nucleotide are discussed as measurements for ROS levels. Novel interventions targeting oxidative stress are listed as potential pharmacotherapies in clinical practice. In conclusion, this review presents a systematic analysis of the mechanisms underlying ROS generation and elucidates how manipulation of these mechanisms can safeguard endothelial cell function.

A Preliminary Evaluation of Advanced Oxidation Protein Products (AOPPs) as a Potential Approach to Evaluating Prognosis in Early-Stage Breast Cancer Patients and Its Implication in Tumour Angiogenesis: A 7-Year Single-Centre Study

Breast cancer (BrC) is a highly prevalent tumour among women. The high incidence and mortality rate of BrC prompts researchers to search for new markers that will provide information on the possible impact of the therapy on the risk of cancer-related events. This study aimed to investigate whether the level of advanced oxidation protein products (AOPPs) may have a potential impact on disease-free (DFS) and overall survival (OS) in BrC patients with early-stage cancer. Additionally, we tried to assess the relationship between AOPPs and angiogenic parameters. In this study, the pre- and post-treatment AOPP levels were examined in the serum of 70 newly diagnosed BrC women. The receiver operating characteristic curve identified pre- and post-treatment AOPPs to be above 9.37 μM and 10.39 μM, respectively, as the best cut-off values to predict the risk of cancer relapse. Additionally, Kaplan-Meier survival analysis indicated that pre- and post-treatment AOPPs above 9.37 μM and 10.39 μM were associated with significantly poorer OS. The uni- and multivariate Cox regression analysis highlighted that lower levels of pre- and post-treatment AOPPs were associated with a longer duration without relapse or cancer-related death. A positive correlation between concentrations of pre-treatment AOPPs and vascular endothelial growth factor A, and negative correlations with levels of soluble forms of vascular endothelial growth factor receptor type 1 and 2, were found. In conclusion, AOPPs appear to have an important role in predicting cancer-related events and may potentially serve as a simple prognostic marker in clinical practice.

Increased cardiovascular risk in patients with chronic kidney disease

Cardiovascular disease (CVD) is highly prevalent in patients suffering from chronic kidney disease (CKD). The risk of patients with CKD developing CVD is manifested already in the early stages of CKD development. The impact of declined kidney function on increased cardiovascular risk and the underlying mechanisms are complex and multifactorial. This review discusses the impact of (a) traditional cardiovascular risk factors such as smoking, dyslipidemia, diabetes, and hypertension as well as (b) CKD-specific pathophysiological and molecular mechanisms associated with an increased cardiovascular risk. The latter include uremic toxins, post-translational modifications and uremic lipids, innate immune cell activation and inflammation, oxidative stress, endothelial cell dysfunction, increased coagulation and altered platelet responses, vascular calcification, renin-angiotensin-aldosterone-system (RAAS) and sympathetic activation, as well as anemia. Unraveling the complex interplay of different risk factors, especially in the context of patient subcohorts, will help to find new therapeutic approaches in order to reduce the increased cardiovascular risk in this vulnerable patient cohort.

A cross-sectional study to correlate antioxidant enzymes, oxidative stress and inflammation with prevalence of hypertension

AIMS

Hypertension a multifactorial consequence of environmental factors, life style and genetics is the well-recognized risk factor contributing to coronary heart diseases. The antioxidant imbalance, excessive reactive oxygen species (ROS) leads to oxidative stress which is pivotal in progression of hypertension. The present study aims to understand the complex interaction between oxidative stress, inflammation and antioxidant system which is crucial to maintain cellular homeostasis which further can exaggerate hypertension pathophysiology.

MATERIALS AND METHODS

The metabolic profile of hypertensive and normotensive subjects from Malwa region, Punjab was compared by estimating lipid profile, cardiac, hepatic and renal markers. The oxidative stress markers (protein carbonyls and lipid peroxidation), inflammatory markers (Nitric oxide, Myeloperoxidase and advanced oxygen protein products), and antioxidant enzymes (Superoxide Dismutase, Catalase, and Total Antioxidant Capacity) were analyzed.

KEY FINDINGS

It is observed that the metabolic markers are altered in hypertensive subjects which further these subjects showed increased oxidative, inflammatory profile and compromised antioxidant status when compared with normotensive subjects. Co-relation analysis validated the involvement of inflammation and oxidative stress in impaired endothelial function and vital organ damage.

SIGNIFICANCE OF STUDY

These markers may act as early indicators of hypertension which usually do not show any physical symptoms, thus can be diagnosed and treated at the earliest. The current study suggests that disturbed homeostasis, a consequence of altered interaction between antioxidant system and inflammatory events raises the oxidative stress levels which eventually leads to hypertension and associated complications. These indicators can serve as early indicators of future chronic complications of hypertension.

Head-to-Head Comparison of Oxidative Stress Biomarkers for All-Cause Mortality in Hemodialysis Patients

Oxidative stress (OS) presents even in the early chronic kidney disease (CKD) stage and is exacerbated in patients with end-stage renal disease (ESRD) undergoing maintenance hemodialysis (MHD). There is still a debate over the association between oxidative stress and mortality. Our study aims to compare head-to-head the prognostic value of different oxidative markers for all-cause mortality in hemodialysis (HD) patients. We thus enrolled 347 patients on HD in this prospective study. Four OS biomarkers were measured (carbonyl proteins, myeloperoxidase (MPO), advanced oxidation protein products (AOPPs), and oxidized low-density lipoprotein (ox-LDL)). During the 60-month follow-up period, 9 patients have been lost to follow-up and 168 (48.4%) patients died. Concerning the oxidative stress (ox-stress) byproducts, carbonyl proteins were lower in survivors (105.40 ng/mL (IQR 81.30−147.85) versus 129.65 ng/mL (IQR 93.20−180.33); p < 0.001), with similar results for male patients (103.70 ng/mL (IQR 76.90−153.33) versus 134.55 ng/mL (IQR 93.95−178.68); p = 0.0014). However, there are no significant differences in MPO, AOPP, and ox-LDL between the two groups. Kaplan−Meier survival analysis indicated that patients in the higher carbonyl proteins concentration (>117.85 ng/mL group) had a significantly lower survival rate (log-rank test, p < 0.001). Univariate Cox regression analysis showed a positive correlation between carbonyl proteins and all-cause mortality in the higher and lower halves. Even after adjustment for conventional risk factors, it remained a statistically significant predictor of an increased risk of death in MHD. Univariate Cox regression analysis of MPO showed that continuous MPO and Log MPO were significantly associated with all-cause mortality, except for binary MPO (divided according to the median of MPO). Multivariate Cox analysis for MPO showed that the mortality prediction remains significant after adjusting for multiple factors. In conclusion, not all ox-stress biomarkers predict all-cause mortality in HD patients to a similar extent. In the present study, carbonyl proteins and MPO are independent predictors of all-cause mortality in HD patients, whereas AOPPs and oxLDL are clearly not associated with all-cause mortality in HD patients.

The Mutual Contribution of 3-NT, IL-18, Albumin, and Phosphate Foreshadows Death of Hemodialyzed Patients in a 2-Year Follow-Up

Patients with chronic kidney disease (CKD), especially those who are hemodialyzed (HD), are at significantly high risk of contracting cardiovascular disease and having increased mortality. This study aimed to find potential death predictors, the measurement of which may reflect increased mortality in HD patients, and then combine the most promising ones in frames of a simple death risk assessment model. For this purpose, HD patients (n=71) with acute myocardial infarction in the last year (HD group) and healthy people (control group) as a comparative group (n=32) were included in the study. Various laboratory determinations and non-invasive cardiovascular tests were performed. Next, patients were followed for two years, and data on cardiovascular (CV) deaths were collected. On this basis, two HD groups were formed: patients who survived (HD-A, n=51) and patients who died (HD-D, n=20). To model HD mortality, 21 out of 90 potential variables collected or calculated from the raw data were selected. The best explanatory power (95.5%) was reached by a general linear model with four variables: interleukin 18, 3-nitrotyrosine, albumin, and phosphate. The interplay between immuno-inflammatory processes, nitrosative and oxidative stress, malnutrition, and calcium-phosphate disorders has been indicated to be essential in predicting CV-related mortality in studied HD patients. ClinicalTrials.gov Identifier: NCT05214872.