Oxidative DNA damage and mortality in hemodialysis and peritoneal dialysis patients

Leukocyte 8-hydroxy-2'-deoxyguanosine as an oxidative stress marker to predict cardiovascular events and death in chronic hemodialysis patients

BACKGROUND

Hemodialysis patients have a markedly increased risk of cardiovascular (CV) morbidity and mortality. Oxidative stress plays a pathogenic role in the progression of atherosclerosis and CV disease among chronic hemodialysis patients. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) content in leukocyte deoxyribonucleic acid (DNA) has been shown as a sensitive and well-known biomarker of oxidant-induced DNA damage in chronic hemodialysis patients.

METHODS

We conducted a retrospective cohort study to investigate the association of leukocyte 8-OHdG and CV events and deaths in patients of chronic hemodialysis. In this study, 217 chronic hemodialysis patients were recruited from 2016 to 2021. The 8-OHdG content of leukocyte DNA was measured by a high-performance liquid chromatography electrochemical detection method. Study outcomes were CV events as well as CV and all-cause deaths. The patients were followed until May 2021.

RESULTS

The median follow-up period was 34.8 months. At the end of May 2021, 57 first CV events and 89 all-CV events occurred. Among the first and all CV events, 17 (29.8%) and 32 (36.0%) were fatal, respectively. Multivariate Cox regression analysis showed per 1/10 5 dG increment in leukocyte 8-OHdG values increased risk of CV events (adjusted hazard ratio [aHR], 1.19; 95% CI, 1.10-1.41; p < 0.001), CV death (aHR, 1.27; 95% CI, 1.03-1.72; p = 0.034), and all-cause death (aHR, 1.11; 95% CI, 1.01-1.30; p = 0.038).

CONCLUSION

This is the first study to demonstrate that oxidative stress assessed by 8-OHdG levels of leukocyte DNA predicted CV events as well as CV and all-cause deaths among chronic hemodialysis patients.

Coronary artery calcification and aortic valve calcification in patients with kidney failure: a sex-disaggregated study

BACKGROUND

Chronic kidney disease (CKD) is linked to an increased cardiovascular disease (CVD) burden. Albeit underappreciated, sex differences are evident in CKD with females being more prone to CKD development, but males progressing more rapidly to kidney failure (KF). Cardiovascular remodelling is a hallmark of CKD with increased arterial and valvular calcification contributing to CKD. However, little is known regarding sex differences in calcific cardiovascular remodelling in KF patients. Thus, we hypothesise that sex differences are present in coronary artery calcification (CAC) and aortic valve calcification (AVC) in patients with KF.

METHODS

KF patients, males (n = 214) and females (n = 107), that had undergone computer tomography (CT) assessment for CAC and AVC were selected from three CKD cohorts. All patients underwent non-contrast multi-detector cardiac CT scanning, with CAC and AVC scoring based on the Agatston method. Baseline biochemical measurements were retrieved from cohort databases, including plasma analyses for inflammation markers (IL-6, TNF, hsCRP) and oxidative stress by skin autofluorescence measuring advanced glycation end-products (AGE), amongst other variables.

RESULTS

Sex-disaggregated analyses revealed that CAC score was associated with age in both males and females (both p < 0.001). Age-adjusted analyses revealed that in males CAC was associated with diabetes mellitus (DM) (p = 0.018) and CVD (p = 0.011). Additionally, for females CAC associated with IL-6 (p = 0.005) and TNF (p = 0.004). In both females and males CAC associated with AGE (p = 0.042 and p = 0.05, respectively). CAC was associated with mortality for females (p = 0.015) independent of age. AVC in females was not reviewed due to low AVC-positive samples (n = 14). In males, in multivariable regression AVC was associated with age (p < 0.001) and inflammation, as measured by IL-6 (p = 0.010).

CONCLUSIONS

In female KF patients inflammatory burden and oxidative stress were associated with CAC. Whereas in male KF patients oxidative stress and inflammation were associated with CAC and AVC, respectively. Our findings suggest a sex-specific biomarker signature for cardiovascular calcification that may affect the development of cardiovascular complications in males and females with KF.

Associations between liver function parameters and poor clinical outcomes in peritoneal dialysis patients

Patients with end-stage renal disease (ESRD) have significantly lower survival rates compared with the general population of the same age. Peritoneal dialysis (PD) is an effective treatment for patients with ESRD, but the clinical outcome of PD patients is still not promising. The survival of PD patients is associated with various clinical factors, and exploring some valid risk predictors may be beneficial for this population. In this review, by integrating the latest research, we summarized the association of some common and novel liver function parameters (ALT, AST, ALP, GGT, serum bilirubin, pre-albumin, albumin, albumin-globulin ratio [AGR], serum ferritin, and hyaluronic acid) with clinical outcomes in PD patients. It may contribute to a better understanding of potential risk factors and help to develop strategies to prevent the disease progression.

Oxidation State in Peritoneal Dialysis in Patients with Type 2 Diabetes Mellitus

End-stage renal disease (ESRD) progression is closely related to oxidative stress (OS). The study objective was to determine the oxidant and antioxidant status in peritoneal dialysis (PD) patients with type 2 diabetes mellitus (DM). An analytical cross-sectional study from the PD program was carried out with 62 patients, 22 with and 40 without DM. Lipoperoxides (LPO) levels in patients with DM, 3.74 ± 1.09 mM/L, and without DM, 3.87 ± 0.84 mM/L were found to increase compared to healthy controls (HC) 3.05 ± 0.58 mM/L (p = 0.006). The levels of the oxidative DNA damage marker (8-OH-dG) were found to be significantly increased in patients with DM, 1.71 ng/mL (0.19-71.92) and without DM, 1.05 ng/mL (0.16-68.80) front to 0.15 ng/mL (0.15-0.1624) of HC (p = 0.001). The antioxidant enzyme superoxide dismutase (SOD) activity was found to be significantly increased in patients with DM, 0.37 ± 0.15 U/mL, and without DM, 0.37 ± 0.17 compared to HC, 0.23 ± 0.05 U/mL (p = 0.038). The activity of the enzyme glutathione peroxidase (GPx) showed a significant increase (p < 0.001) in patients with DM, 3.56 ± 2.18 nmol/min/mL, and without DM, 3.28 ± 1.46 nmol/min/mL, contrary to the activity obtained in HC, 1.55 ± 0.34 nmol/min/mL. In conclusion, we found an imbalance of oxidative status in patients undergoing PD with and without DM through the significant increase in LPO oxidants and the marker of oxidative damage in DNA. The activity of the antioxidant enzymes SOD and GPx were significantly increased in patients with and without DM undergoing PD, possibly in an attempt to compensate for the deregulation of oxidants. Antioxidant enzymes could be promising therapeutic strategies as a complement to the management of chronic kidney diseases.

Enhanced Oxidative DNA-Damage in Peritoneal Dialysis Patients via the TXNIP/TRX Axis

Peritoneal dialysis (PD) is an effective method of renal replacement therapy, providing a high level of patient autonomy. Nevertheless, the long-term use of PD is limited due to deleterious effects of PD fluids to the structure and function of the peritoneal membrane leading to loss of dialysis efficacy. PD patients show excessive oxidative stress compared to controls or chronic kidney disease (CKD) patients not on dialysis. Therefore, defense systems against detrimental events play a pivotal role in the integrity of the peritoneal membrane. The thioredoxin-interacting-protein (TXNIP)/thioredoxin (TRX) system also plays a major role in maintaining the redox homeostasis. We hypothesized that the upregulation of TXNIP negatively influences TRX activity, resulting in enhanced oxidative DNA-damage in PD patients. Therefore, we collected plasma samples and human peritoneal biopsies of healthy controls and PD patients as well. Using ELISA-analysis and immunohistochemistry, we showed that PD patients had elevated TXNIP levels compared to healthy controls. Furthermore, we demonstrated that PD patients had a reduced TRX activity, thereby leading to increased oxidative DNA-damage. Hence, targeting the TXNIP/TRX system as well as the use of oxidative stress scavengers could become promising therapeutic approaches potentially applicable in clinical practice in order to sustain and improve peritoneal membrane function.

The Influence of Sevelamer Hydrochloride and Calcium Carbonate on Markers of Inflammation and Oxidative Stress in Hemodialysis at Six Months of Follow-Up

Patients with end-stage renal disease (ESRD) present alterations in mineral and bone metabolism. Hyperphosphatemia in ESRD is considered an independent risk factor for cardiovascular disease (CVD), increasing morbidity, and mortality. Sevelamer hydrochloride is a calcium-free, non-absorbable phosphate-chelating polymer. Calcium carbonate chelator is helpful in controlling serum phosphate levels. There is insufficient information on the influence of sevelamer hydrochloride and calcium carbonate on the behavior of oxidative stress (OS) markers and inflammation in patients on hemodialysis (HD). A randomized open clinical trial was carried out on patients to evaluate sevelamer hydrochloride and calcium carbonate influence at 6 months of study follow-up. Levels of oxidants (LPO, NO, and 8-isoprostanes), antioxidants (SOD and TAC), oxidative DNA damage (8-OHdG and hOGG1), pro-inflammatory cytokines (IL-6 and TNF-α), and inflammation markers (ferritin and C-reactive protein) were measured with colorimetric and ELISA methods. We found a significant increase in oxidants LPO and NO, and antioxidants SOD and TAC, and downregulation of IL-6 and TNF-α. Ferritin decrease at 6 months follow-up in the sevelamer hydrochloride group. Increase in C-reactive protein was found in the group of patients treated with calcium carbonate. In conclusion, we found an oxidative state imbalance with increase in LPO and NO oxidants. The activity of the antioxidant enzymes (SOD and TAC) was also found to increase, suggesting a compensatory effect in the face of increase in oxidants. The same phenomenon was observed with increase in the oxidative damage marker to DNA and the increase in the DNA repair enzyme, suggesting a compensatory effect. Pro-inflammatory cytokines were predominantly downregulated by TNF-α in the group that ingested sevelamer hydrochloride in the final determination at 6 months of follow-up. Serum ferritin levels decreased significantly at the end of follow-up in patients on HD in the sevelamer hydrochloride group. The management of hyperphosphatemia with sevelamer hydrochloride appears to have obvious anti-inflammatory and antioxidant benefits.

Inflammation and Oxidative Stress in Chronic Kidney Disease and Dialysis Patients

Significance: Chronic kidney disease (CKD) can be regarded as a burden of lifestyle disease that shares common underpinning features and risk factors with the aging process; it is a complex constituted by several adverse components, including chronic inflammation, oxidative stress, early vascular aging, and cellular senescence. Recent Advances: A systemic approach to tackle CKD, based on mitigating the associated inflammatory, cell stress, and damage processes, has the potential to attenuate the effects of CKD, but it also preempts the development and progression of associated morbidities. In effect, this will enhance health span and compress the period of morbidity. Pharmacological, nutritional, and potentially lifestyle-based interventions are promising therapeutic avenues to achieve such a goal. Critical Issues: In the present review, currents concepts of inflammation and oxidative damage as key patho-mechanisms in CKD are addressed. In particular, potential beneficial but also adverse effects of different systemic interventions in patients with CKD are discussed. Future Directions: Senotherapeutics, the nuclear factor erythroid 2-related factor 2-kelch-like ECH-associated protein 1 (NRF2-KEAP1) signaling pathway, the endocrine klotho axis, inhibitors of the sodium-glucose cotransporter 2 (SGLT2), and live bio-therapeutics have the potential to reduce the burden of CKD and improve quality of life, as well as morbidity and mortality, in this fragile high-risk patient group. Antioxid. Redox Signal. 35, 1426-1448.

Possible benefits of exogenous melatonin for individuals on dialysis: a narrative review on potential mechanisms and clinical implications

Prevention of oxidative stress and inflammation in chronic kidney disease patients (CKD) on dialysis may reduce dialysis-associated complications. Administration of powerful antioxidants may improve the consequences of peritoneal dialysis (PD) and hemodialysis (HD). This narrative review aimed to show the potential therapeutic effects of melatonin (MLT) on the consequences of CKD patients receiving HD or PD. The results of preclinical and clinical studies have proven that CKD and dialysis are accompanied by reduced endogenous MLT levels and related complications such as sleep disorders. Enhanced oxidative stress, inflammation, cellular damages, and renal fibrosis, along with dysregulation of the renin-angiotensin system (RAS), have been observed in CKD and patients on dialysis. Results of studies have revealed that the restoration of MLT via the exogenous source may regulate oxidative stress, inflammation, and RAS functions, inhibit fibrosis, and improve complications in patients with long-term dialysis patients. In summary, treatment of patients with CKD and dialysis with exogenous MLT is suggested as a practical approach in reducing the outcomes and improving the quality of life in patients via antioxidant, anti-inflammatory, and anti-fibrotic signaling pathways. Therefore, this hormone can be considered in clinical practice to manage dialysis-related complications.

Could Antioxidant Supplementation Delay Progression of Cardiovascular Disease in End-Stage Renal Disease Patients?

In end-stage renal disease patients, the leading causes of mortality are of cardiovascular (CV) origin. The underlying mechanisms are complex, given that sudden heart failure is more common than acute myocardial infarction. A contributing role of oxidative stress is postulated, which is increased even at early stages of chronic kidney disease, is gradually augmented in parallel to progression to endstage renal disease and is further accelerated by renal replacement therapy. Oxidative stress ensues when there is an imbalance between reactive pro-oxidants and physiologically occurring electron donating antioxidant defence systems. During the last decade, a close association of oxidative stress with accelerated atherosclerosis and increased risk for CV and all-cause mortality has been established. Lipid peroxidation has been identified as a trigger for endothelial dysfunction, the first step towards atherogenesis. In order to counteract the deleterious effects of free radicals and thereby ameliorate, or delay, CV disease, exogenous administration of antioxidants has been proposed. Here, we attempt to summarize existing data from studies that test antioxidants for CV protection, such as vitamins E and C, statins, omega-3 fatty acids and N-acetylcysteine.

Mitochondrial Dysfunction Plays a Relevant Role in Pathophysiology of Peritoneal Membrane Damage Induced by Peritoneal Dialysis

Preservation of the peritoneal membrane is an essential determinant of the long-term outcome of peritoneal dialysis (PD). Epithelial-to-mesenchymal transition (EMT) plays a central role in the pathogenesis of PD-related peritoneal membrane injury. We hypothesized that mitochondria may be implicated in the mechanisms that initiate and sustain peritoneal membrane damage in this setting. Hence, we carried out ex vivo studies of effluent-derived human mesothelial cells, which disclosed a significant increase in mitochondrial reactive oxygen species (mtROS) production and a loss of mitochondrial membrane potential in mesothelial cells with a fibroblast phenotype, compared to those preserving an epithelial morphology. In addition, in vitro studies of omentum-derived mesothelial cells identified mtROS as mediators of the EMT process as mitoTEMPO, a selective mtROS scavenger, reduced fibronectin protein expression induced by TGF-ß1. Moreover, we quantified mitochondrial DNA (mtDNA) levels in the supernatant of effluent PD solutions, disclosing a direct correlation with small solute transport characteristics (as estimated from the ratio dialysate/plasma of creatinine at 240 min), and an inverse correlation with peritoneal ultrafiltration. These results suggest that mitochondria are involved in the EMT that human peritoneal mesothelial cells suffer in the course of PD therapy. The level of mtDNA in the effluent dialysate of PD patients could perform as a biomarker of PD-induced damage to the peritoneal membrane.

Herbal antioxidants in dialysis patients: a review of potential mechanisms and medical implications

The consumption of exogenous antioxidants isolated from herbal extracts has shown beneficial effects on ameliorating dialysis-related complications through debilitating oxidative stress and inflammatory process. Many clinical studies available in public databases have reported the improved consequences of dialysis in patients supplemented with herbal antioxidants. Exploration of such data offers great possibilities for gaining insights into the potential mechanisms and medical implications of herbal antioxidants. In this work, the mechanisms and implications of some famous bioactive substances including silymarin, curcumin, resveratrol, emodin, and quercetin on the consequences of dialysis in chronic kidney disease (CKD) patients were explored. The protective features of silymarin are due to the flavonoid complex silybin. Curcumin is an active element from the root of curcuma longa with extensive beneficial properties, including antioxidant, anti-inflammatory activity, and inhibitory effects on cell apoptosis. Resveratrol can reduce the oxidative stress by neutralization of free radicals. Emodin is known as a natural anthraquinone derivative isolated from Chinese herbs. Finally, quercetin has been reported to exhibit several properties including antioxidant, anti-diabetic, analgesic, antihistaminic, antiviral, cholesterol reducer, and renal hemodynamic modulator. However, potential mechanisms and medical implications of the aforementioned herbal antioxidants seem to be more complicated, that is, more studies are required in this field.

Inverse J-shaped relation between coronary arterial calcium density and mortality in advanced chronic kidney disease

BACKGROUND

The coronary artery calcium (CAC) score from cardiac computed tomography (CT) is a composite of CAC volume and CAC density. In the general population, CAC volume is positively and CAC density inversely associated with cardiovascular disease (CVD) events, implying that decreased CAC density reflects atherosclerotic plaque instability. We analysed associations of CAC indices with mortality risk in patients with end-stage renal disease [chronic kidney disease Stage 5 (CKD5)].

METHODS

In 296 CKD5 patients undergoing cardiac CT (median age 55 years, 67% male, 19% diabetes, 133 dialysed), the Framingham risk score (FRS), presence of CVD and protein-energy wasting (PEW; subjective global assessment) and high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) were determined at baseline. During follow-up for a median of 35 months, 51 patients died and 75 patients underwent renal transplantation. All-cause mortality risk was analysed with competing-risk regression models. Vascular calcification was analysed in biopsies of the arteria epigastrica inferior in 111 patients.

RESULTS

Patients in the middle tertile of CAC density had the highest CAC score, CAC volume, age, CVD, PEW, FRS, hsCRP and IL-6. In competing risk analysis, the middle {subhazard ratio [sHR] 10.7 [95% confidence interval (CI) 2.0-57.3]} and high [sHR 8.9 (95% CI 1.5-51.8)] tertiles of CAC density associated with increased mortality, independent of CAC volume. The high tertile of CAC volume, independent of CAC density, associated with increased mortality [sHR 8.9 (95% CI 1.5-51.8)]. Arterial media calcification was prominent and associated with CAC volume and CAC density.

CONCLUSIONS

In CKD5, mortality increased linearly with higher CAC score and CAC volume whereas for CAC density an inverse J-shaped pattern was observed, with the crude mortality rate being highest for the middle tertile of CAC density. CAC volume and CAC density were associated with the extent of arterial media calcification.

Oxidative Stress and Inflammation as Predictors of Mortality and Cardiovascular Events in Hemodialysis Patients: The DREAM Cohort

Aim: Both oxidative stress and inflammation are involved in the pathogenesis of cardiovascular disease (CVD). The serum level of derivatives of reactive oxygen metabolites (d-ROMs) is a measure of the total amount of hydroperoxides serving as a marker of oxidative stress. We investigated whether d-ROMs could predict the clinical outcomes in hemodialysis patients and whether the associations of d-ROMs with the outcomes are independent of a marker of inflammation, C-reactive protein (CRP).

Methods: This was a prospective cohort study in hemodialysis patients. The key exposures were the serum levels of d-ROMs and CRP. The outcome measures were all-cause mortality and new CVD events.

Results: A total of 517 patients were analyzed. d-ROMs correlated positively with CRP. During follow-up for 5 years, 107 patients died, and 190 patients experienced new CVD events. In the Kaplan–Meier analyses, both higher d-ROMs and higher CRP levels predicted higher risks for mortality and CVD events. By Cox proportional-hazard regression analysis adjusted for potential confounders excluding CRP, d-ROMs exhibited a significant association with all-cause mortality, but this association was no longer significant after further adjustment for CRP. Using the same model, CRP exhibited a significant association with all-cause mortality, but this association was no longer significant after further adjustment for d-ROMs. When we analyzed new CVD events as the outcome, CRP was a significant predictor, whereas the level of d-ROMs was not.

Conclusions: Although d-ROMs predicted mortality and CVD events in unadjusted models, the associations of d-ROMs with these outcomes were not independent of CRP. Oxidative stress and inflammation appear to share common causal pathways.

Alteration and association between serum ACE2/ angiotensin(1-7)/Mas axis and oxidative stress in chronic kidney disease: A pilot study

Activation of the renin angiotensin system and renal oxidative stress (OS) are critical contributors in the progression of chronic kidney disease(CKD). Recent studies have confirmed that the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas(ACE2/Ang(1-7)/Mas) axis, the important components of renin angiotensin system, protected kidneys against damage by antagonizing angiotensin II and attenuating OS in rats with several nephropathy models, but its effect needs to be further evaluated in clinic. In this study, we aimed to detected serum ACE2/Ang (1-7)/Mas axis, OS conditions and described its clinical associations in patients with CKD at different stages.A total of 48 patients with CKD and 6 healthy controls (CT) were enrolled, and serum angiotensin converting enzyme (ACE), ACE2, Ang (1-7), 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined by ELISA. Serum extracellular glutathione peroxidase(eGSH-Px) activity and renal functions were determined by the biochemical method.Serum ACE and ACE2 levels in CKD stages 3 to 5 and serum Ang(1-7) levels in CKD stages 4 to 5 without Ang II receptor blockers treatment significantly increased compared to those in the CT group. However, ACE2 was decreased and Ang(1-7) level increased in early CKD stage with Ang II receptor blockers treatment. Higher serum 8-OHdG levels and lower eGSH-Px activity were noted in CKD stages 4 to 5. Serum 8-OHdG level was correlated with serum ACE2, Ang(1-7) expression. Estimated glomerular filtration rate (eGFR) was correlated with serum ACE, ACE2, Ang(1-7), 8-OHdG, Hcy levels and serum eGSH-Px activity. Multiple-regression analysis eGFR was predicted by ACE, Hcy, eGSH-Px, and also can be predicted by ACE2, Ang(1-7), Hcy in CT subgroup.The ACE2/Ang(1-7)/Mas axis is associated with OS, and both them were associated with eGFR in the progression of CKD. Activation of ACE2/Ang(1-7)/Mas axis may have renoprotective effect and can be a potential therapeutic target in patients with early CKD stages.

Aortic Valve Calcium Associates with All-Cause Mortality Independent of Coronary Artery Calcium and Inflammation in Patients with End-Stage Renal Disease

BACKGROUND

Aortic valve calcium (AVC) and coronary artery calcium (CAC) are common complications in end-stage renal disease (ESRD). We investigated the prognostic significance of overlapping presence of AVC and CAC, and whether AVC was associated with all-cause mortality independent of the presence of CAC in ESRD.

METHODS

259 ESRD patients (median age 55 years, 67% males) undergoing cardiac computed tomography were included. Framingham risk score (FRS), presence of cardiovascular disease (CVD), statin use, nutritional status and other relevant laboratory data were determined at baseline. During follow-up for median 36 months, 44 patients died, and 68 patients underwent renal transplantation.

RESULTS

The baseline overlap presence of AVC and CAC was 37%. Multivariate regression analysis showed that FRS (odds ratio (OR) 2.25; 95% confidence interval (95% CI), 1.43-3.55) and CAC score (OR (95% CI), 2.18 (1.34-3.59)) were independent determinants of AVC. In competing-risk regression models adjusted for presence of CAC, inflammation, nutritional status, CVD, FRS and statin use, AVC remained independently associated with all-cause mortality (sub-hazard ratio (95% CI), 2.57 (1.20-5.51)).

CONCLUSIONS

The overlap of AVC and CAC was 37% in this ESRD cohort. AVC was associated with increased all-cause mortality independent of presence of CAC, traditional risk factors and inflammation.

Skin autofluorescence, arterial stiffness and Framingham risk score as predictors of clinical outcome in chronic kidney disease patients: a cohort study

BACKGROUND

The risk of cardiovascular disease (CVD) is predicted by Framingham's CVD risk scores (FRS) but the high CVD-related mortality in patients with chronic kidney disease (CKD) is only partially explained by traditional CVD risk markers. Therefore, there is a need to explore whether other CVD risk markers may improve risk prediction. Although arterial stiffness measured by augmentation index (AIx) and tissue content of advanced glycation end-products (AGEs) measured by skin autofluorescence (SAF) are two biomarkers that associate with CVD and mortality in CKD, it is not known how they compare with FRS. We evaluated associations between SAF, AIx and FRS, and their associations with CVD and mortality in CKD patients.

METHODS

SAF (AGE Reader) and AIx (SphygmoCor; adjusted for 75 heart beats per minute) were measured in 261 clinically stable and extensively phenotyped patients with CKD Stage 5 (median age 56 years, 66% male, 20% diabetes; 130 non-dialysed, 93 patients on peritoneal dialysis and 38 patients on haemodialysis). Multivariate receiver operator characteristics (ROC) curve analysis and multivariate Cox models followed by C-statistics were used to evaluate CVD-related and all-cause mortality risk associated with SAF, AIx and FRS during follow-up for median 25 months with 46 deaths.

RESULTS

In multivariate regression analysis, SAF associated with FRS, haemoglobin, fat body mass index and CVD, and inversely with per cent handgrip strength (HGS). AIx associated with FRS, and inversely with per cent HGS. Associations of SAF and AIx with high-sensitivity C-reactive protein (hsCRP), serum albumin, statin therapy and renal replacement therapy were not statistically significant. In ROC analysis, area under the curve (AUC) for CVD mortality ranged from AUC = 0.72 (AIx and FRS, respectively) to AUC = 0.78 (FRS + AIx), and for all-cause mortality from AUC = 0.70 (AIx) to AUC = 0.79 (FRS + AIx). In multivariate Cox analysis, after adjusting for 1-standard deviation (1-SD) of FRS, 1-SD increase of SAF associated with all-cause mortality and 1-SD increase of AIx associated with CVD mortality and all-cause mortality. After further adjustments for hsCRP, albumin and presence of CVD, AIx (but not SAF) remained independently associated with CVD mortality, hazard ratio (HR) 2.14 [95% confidence interval (95% CI) 1.18-3.89] and all-cause mortality, HR 1.74 (95% CI 1.16-2.60).

CONCLUSIONS

In patients with CKD Stage 5, SAF and aortic stiffness associated with mortality, independently of FRS. After adjusting for additional confounders including inflammation, aortic stiffness remained as an independent predictor of outcome. Since the contribution of SAF and aortic stiffness compared with FRS in ROC curve analysis was relatively modest, this underlines the importance of traditional CVD risk factors in CKD.

Serum 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage, is associated with mortality independent of inflammation in chronic kidney disease

BACKGROUND

Oxidative stress and low-grade systemic inflammation are common interrelated sequelae of chronic kidney disease (CKD) that associate with mortality. We investigated the association of serum 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, with mortality in CKD individuals and analyzed whether inflammation modifies the association.

METHODS

In 376 individuals with a wide range of estimated glomerular filtration rate (eGFR); >60 ml/min (n = 53), 15-60 ml/min (n = 60) and <15 ml/min (n = 263), cut-off values of serum 8-OHdG, high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), and tumor necrosis factor (TNF) as predictors of mortality were determined by ROC curves. We analyzed associations of 8-OHdG with inflammation markers and the overlapping effect of hsCRP, IL-6 and TNF on the association between 8-OHdG and all-cause mortality by multivariate generalized linear models.

RESULTS

In separate individual exposure analyses, higher 8-OHdG, hsCRP, and IL-6 (but not TNF) were each independently associated with increased risk of death in multivariate models adjusted for age, sex, diabetes mellitus, cardiovascular disease, protein-energy wasting, cohort calendar year, blood sample storage time and eGFR. For 8-OHdG, the multivariate relative risk ratio, RR_8-OHdG (95% confidence interval) 1.17 (1.08-1.26), remained essentially unchanged when adjusting also for inflammation in three separate models including: hsCRP, RR_8-OHdG = 1.15 (1.06-1.25); IL-6, RR_8-OHdG = 1.15 (1.07-1.25); and TNF, RR_8-OHdG = 1.16 (1.07-1.26).

CONCLUSIONS

Serum 8-OHdG, a biomarker of oxidative DNA damage, is associated with increased all-cause mortality risk in individuals with a wide range of eGFR and this association is independent of inflammation.

The Behavior of the Type of Peritoneal Transport in the Inflammatory and Oxidative Status in Adults Under Peritoneal Dialysis

Peritoneal dialysis (PD) is an alternative for managing the end-stage renal disease (ESRD). The peritoneal membrane (PM) is not just a membrane that passively responds to diffusion and convection. The characteristics of PM result in the peritoneal equilibrium test (PET) and with this test is possible to obtain the type of peritoneal transport (PT). The patient on PD can be classified in different types of PT as; Low, Low Average, High Average, and High. The aim of the study was to compare the inflammatory cytokines, oxidants, antioxidants, and oxidative DNA damage markers in the different types of PT. A cross-sectional analytical study of 77 adult PD patients was performed. Levels of lipoperoxides (LPO) were higher in all types of PT vs. healthy volunteer controls (HC) (p < 0.0001). Nitric oxide (NO) levels were found significantly down-regulated in all types of PT (p < 0.0001). The activity of the superoxide dismutase enzyme (SOD) was found to be significantly increased in all types of PT vs. the HC (p < 0.0001). The levels of the DNA repair enzyme were found to be decreased in all types of PT. The levels of the pro-inflammatory cytokines TNF-α, IL-6, the marker of oxidative DNA damage, 8-IP and the total antioxidant capacity (TAC) were all significantly decreased, contrary to the levels in HC, possibly by the clearance in the dialysis fluid in all types of PT or due to down-regulation of their expression. In conclusion, we found significant changes in markers of inflammation, oxidative stress, and oxidative damage to DNA in all types of PT; Low, low average, high average, and high PT in the values of D/P creatinine at 4 h compared to HC.

Is oxidative stress an issue in peritoneal dialysis?

During the last two decades, oxidative stress (OS) has emerged as a novel risk factor for a variety of adverse events, including atherosclerosis and mortality in chronic kidney disease (CKD) patients. Increased OS occurs even in early stages of the disease, progresses with deterioration of renal function and is further aggravated by hemodialysis (HD), due to the bioincompatibility of the method. Compared to HD, peritoneal dialysis (PD) is a more biocompatible dialysis modality, characterized by a significantly reduced, but still high, OS status. The culprit for OS in PD is mainly the composition of PD solutions (low pH, lactate buffer, increased osmolarity and high glucose concentration). After heat sterilization of PD solutions, formation of glucose degradation products (GDPs) and advanced glycation end-products (AGEs) trigger inflammation and enhance OS. Chronic exposure of the peritoneum to this toxic, hyperglycemic environment leads to OS-derived morphologic damage of peritoneal cells, loss of ultrafiltration capacity and decreased technique survival. Moreover, OS is linked with peritonitis, loss of residual renal function, inflammation, atherosclerosis, cardiovascular (CV) disease, and increased mortality. To ameliorate OS status in PD, a multitargeted approach is necessary that includes use of neutral pH, low GDP, low lactate and iso-ismolar PD solutions, strict glycemic control, optimal volume management and, probably supplementation with antioxidants, N-acetylcysteine being the most promising among them.

Beyond a Measure of Liver Function-Bilirubin Acts as a Potential Cardiovascular Protector in Chronic Kidney Disease Patients

Bilirubin is a well-known neurotoxin in newborn infants; however, current evidence has shown that a higher serum bilirubin concentration in physiological ranges is associated with a lower risk for the development and progression of both chronic kidney disease (CKD) and cardiovascular disease (CVD) in adults. The protective mechanisms of bilirubin in CVD, CKD, and associated mortality may be ascribed to its antioxidant and anti-inflammatory properties. Bilirubin further improves insulin sensitivity, reduces low-density lipoprotein cholesterol levels and inhibits platelet activation in at-risk individuals. These effects are expected to maintain normal vascular homeostasis and thus reduce the incidence of CKD and the risks of cardiovascular complications and death. In this review, we highlight the recent advances in the biological actions of bilirubin in the pathogenesis of CVD and CKD progression, and further propose that targeting bilirubin metabolism could be a potential approach to ameliorate morbidity and mortality in CKD patients.

Oxidative stress in hemodialysis: Causative mechanisms, clinical implications, and possible therapeutic interventions

Oxidative stress (OS) is the result of prooxidant molecules overwhelming the antioxidant defense mechanisms. Hemodialysis (HD) constitutes a state of elevated inflammation and OS, due to loss of antioxidants during dialysis and activation of white blood cells triggering production of reactive oxygen species. Dialysis vintage, dialysis methods, and type and condition of vascular access, biocompatibility of dialyzer membrane and dialysate, iron administration, and anemia all can play a role in aggravating OS, which in turn has been associated with increased morbidity and mortality. Oral or intravenous administration of antioxidants may detoxify the oxidative molecules and at least in part repair OS-mediated tissue damage. Lifestyle interventions and optimization of a highly biocompatible HD procedure might ameliorate OS development in dialysis.

Relationship Between Plasma 8-OH-Deoxyguanosine and Cardiovascular Disease and Survival in Type 2 Diabetes Mellitus: Results From the ADVANCE Trial

Background

8‐Oxo‐2′‐deoxyguanosine (8‐oxo‐2′‐dG) is a biomarker of oxidative DNA damage that is associated with cardiovascular disease and premature mortality in the general population. Although oxidative stress has a proven role in cardiovascular complications in diabetes mellitus, evidence for a relationship between plasma 8‐oxo‐2′‐dG and major cardiovascular outcomes in diabetes mellitus is weak.

Methods and Results

A case‐cohort study was performed in 3766 participants with prevalent diabetes mellitus in the ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation) trial (http://ClinicalTrials.gov number NCT00145925). The hazard ratios for mortality and major acute cardiovascular events were derived using Cox regression models. During a median of 5 years of follow‐up, 695 (18.4%) participants in this enriched cohort died (including 354 deaths from cardiovascular disease). Individuals with higher levels of 8‐oxo‐2′‐dG were more likely to die. After adjusting for cardiovascular disease risk factors, the hazard ratio for a 1‐SD increase in plasma 8‐oxo‐2′‐dG was 1.10 (95% confidence interval, 1.01–1.20; P=0.03). This was driven by an independent association between plasma 8‐oxo‐2′‐dG and cardiovascular death (hazard ratio, 1.23; 95% confidence interval, 1.10–1.37 [P<0.001]). By contrast, no association was seen between 8‐oxo‐2′‐dG and noncardiovascular disease death (of which cancer was the major single cause). 8‐Oxo‐2′‐dG was also not significantly associated with either nonfatal myocardial infarction or nonfatal stroke.

Conclusions

In adults with type 2 diabetes mellitus, increased levels of 8‐oxo‐2′‐dG are independently associated with all‐cause mortality and cardiovascular mortality in adults with longstanding type 2 diabetes mellitus who participated in the ADVANCE trial, consistent with the role of oxidative damage in the development and progression of cardiovascular decompensation in diabetes mellitus.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00145925.

The higher mortality associated with low serum albumin is dependent on systemic inflammation in end-stage kidney disease

BACKGROUND

The correlation of low serum albumin with mortality in patients with chronic kidney disease (CKD) is partly linked to its association with systemic inflammation. However, it is not clear to what extent albumin's correlation with mortality depends on concomitant systemic inflammation. Here we addressed this question in patients with CKD stage 5.

METHODS

Serum albumin (S-Alb), systemic inflammation (high-sensitive C-reactive protein, hsCRP), cardiovascular disease (CVD) and nutritional status (subjective global assessment, SGA) were assessed at baseline in 822 patients: 523 incident dialysis patients, 212 prevalent hemodialysis (HD) and 87 prevalent peritoneal dialysis (PD) patients. Patients were divided into four groups according to hsCRP and S-Alb in each cohort: Group 1 -normal S-Alb and normal hsCRP (reference); Group 2 -low S-Alb and normal hsCRP; Group 3-normal S-Alb and high hsCRP; Group 4-low S-Alb and high hsCRP. Survival over 60 months was analyzed.

RESULTS

In Cox analysis, Group 4 had an increased mortality risk (adjusted Hazard ratio (95% confidence interval): 1.62 (1.06-2.47); p = 0.02) whereas the augmented mortality risks for Groups 2 and 3 in univariate analyses were not significant after adjustments for age, gender, blood pressure, diabetes mellitus, smoking, SGA, renal function and renal replacement technique.

CONCLUSIONS

Whereas mortality risk was increased in CKD stage 5 patients with low S-Alb and high CRP, it was not increased in patients with low S-Alb and normal CRP. Our observation suggests that inflammatory status should be taken into account when using S-albumin for risk assessment in CKD stage 5 patients.

Oxidative Stress in Patients Undergoing Peritoneal Dialysis: A Current Review of the Literature

Peritoneal dialysis (PD) patients manifest excessive oxidative stress (OS) compared to the general population and predialysis chronic kidney disease patients, mainly due to the composition of the PD solution (high-glucose content, low pH, elevated osmolality, increased lactate concentration and glucose degradation products). However, PD could be considered a more biocompatible form of dialysis compared to hemodialysis (HD), since several studies showed that the latter results in an excess accumulation of oxidative products and loss of antioxidants. OS in PD is tightly linked with chronic inflammation, atherogenesis, peritoneal fibrosis, and loss of residual renal function. Although exogenous supplementation of antioxidants, such as vitamins E and C, N-acetylcysteine, and carotenoids, in some cases showed potential beneficial effects in PD patients, relevant recommendations have not been yet adopted in everyday clinical practice.

Clinical global assessment of nutritional status as predictor of mortality in chronic kidney disease patients

Background

The value of subjective global assessment (SGA) as nutritional assessor of protein-energy wasting (PEW_SGA) in chronic kidney disease (CKD) patients depends on its mortality predictive capacity. We investigated associations of PEW_SGA with markers of nutritional status and all-cause mortality in CKD patients.

Methods

In 1031 (732 CKD1-5 non-dialysis and 299 dialysis) patients, SGA and body (BMI), lean (LBMI) and fat (FBMI) body mass indices, % handgrip strength (% HGS), serum albumin, and high sensitivity C-reactive protein (hsCRP) were examined at baseline. The five-year all-cause mortality predictive strength of baseline PEW_SGA and during follow-up were investigated.

Results

PEW_SGA was present in 2% of CKD1-2, 16% of CKD3-4, 31% of CKD5 non-dialysis and 44% of dialysis patients. Patients with PEW_SGA (n = 320; 31%) had higher hsCRP and lower BMI, LBMI, FBMI, %HGS and serum albumin. But, using receiver operating characteristics-derived cutoffs, these markers could not classify (by kappa statistic) or explain variations of (by multinomial logistic regression analysis) presence of PEW_SGA. In generalized linear models, SGA independently predicted mortality after adjustments of multiple confounders (RR: 1.17; 95% CI: 1.11–1.23). Among 323 CKD5 patients who were re-assessed after median 12.6 months, 222 (69%) remained well-nourished, 37 (11%) developed PEW_SGA de novo, 40 (12%) improved while 24 (8%) remained with PEW_SGA. The latter independently predicted mortality (RR: 1.29; 95% CI: 1.13–1.46).

Conclusions

SGA, a valid assessor of nutritional status, is an independent predictor of all-cause mortality both in CKD non-dialysis and dialysis patients that outperforms non-composite nutritional markers as prognosticator.

S100A12 in renal and cardiovascular diseases

Expression of S100A12, a small calcium-binding protein, by neutrophils and monocytes/macrophages induces proinflammatory responses via ligation with the receptor for advanced glycation end-products (RAGE) and subsequent activation of intracellular signal transduction pathways such as the nuclear factor (NF)-κB pathway. Although S100A12 has been demonstrated to be a useful biomarker during inflammatory conditions, its precise role in the pathogenesis of renal and cardiovascular diseases has not been fully understood. Recently, several studies have employed S100A12 transgenic mice to investigate its pathological effects. Further studies using these models are required before we can translate these findings to human diseases such as renal and cardiovascular diseases.

Chronic Kidney Disease and Disproportionally Increased Cardiovascular Damage: Does Oxidative Stress Explain the Burden?

Chronic kidney disease (CKD) patients are among the groups at the highest risk for cardiovascular disease and significantly shortened remaining lifespan. CKD enhances oxidative stress in the organism with ensuing cardiovascular damage. Oxidative stress in uremia is the consequence of higher reactive oxygen species (ROS) production, whereas attenuated clearance of pro-oxidant substances and impaired antioxidant defenses play a complementary role. The pathophysiological mechanism underlying the increased ROS production in CKD is at least partly mediated by upregulation of the intrarenal angiotensin system. Enhanced oxidative stress in the setting of the uremic milieu promotes enzymatic modification of circulating lipids and lipoproteins, protein carbamylation, endothelial dysfunction via disruption of nitric oxide (NO) pathways, and activation of inflammation, thus accelerating atherosclerosis. Left ventricular hypertrophy (LVH) and heart failure are hallmarks of CKD. NADPH oxidase activation, xanthine oxidase, mitochondrial dysfunction, and NO-ROS are the main oxidative pathways leading to LVH and the cardiorenal syndrome. Finally, a subset of antioxidant enzymes, the paraoxonases (PON), deserves special attention due to abundant clinical evidence accumulated regarding reduced serum PON1 activity in CKD as a contributor to the increased burden of cardiovascular disease. Future, meticulously designed studies are needed to assess the effects of antioxidant therapy on patients with CKD.

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Elevated Circulating S100A12 Associates with Vascular Disease and Worse Clinical Outcome in Peritoneal Dialysis Patients

♦

BACKGROUND

The pro-inflammatory receptor of advanced glycation end-products (RAGE)-ligand S100A12 is thought to promote, whereas anti-inflammatory soluble RAGE (sRAGE) may protect against, vascular disease. We evaluated circulating S100A12 and sRAGE in relation to vascular disease, inflammation, nutritional status, and mortality risk in peritoneal dialysis (PD) patients. ♦

METHODS

Plasma S100A12 and sRAGE, biomarkers of inflammation, nutritional status, and comorbidities were analyzed in 82 prevalent PD patients (median age 65 years; 70% men; median vintage 12 months) and, for comparative analysis, also in 190 hemodialysis (HD) patients and 50 control subjects. Associations between mortality risk and concentrations of S100A12 and sRAGE were assessed in PD and HD patients after a mean follow-up period of 31 and 29 months respectively using a competing risk Cox regression model. ♦

RESULTS

In PD patients, median S100A12, sRAGE and S100A12/sRAGE were markedly higher than in controls, and S100A12 was 1.9 times higher and median sRAGE 14% lower compared with HD patients. In PD patients, S100A12 associated with C-reactive protein (ρ = 0.46; p < 0.001) and interleukin-6 (ρ = 0.38; p < 0.001), and, negatively, with s-albumin (ρ = -0.27; p < 0.05) whereas sRAGE associated negatively with body mass index (ρ = -0.37; p < 0.001), fat body mass index (ρ = -0.34; p < 0.001), and lean body mass index (ρ = -0.36; p < 0.001). Peripheral vascular disease or cerebrovascular disease (PCVD) was present in 28% of PD patients and, in multivariate analysis, associated mainly with high S100A12 (odds ratio [OR] 3.52, p = 0.04). In both PD and HD patients, the highest versus other tertiles of S100A12 associated with increased mortality. In contrast, sRAGE did not associate with PCVD or mortality in PD and HD patients. ♦

CONCLUSIONS

Plasma S100A12 and sRAGE are markedly elevated in PD patients. Soluble RAGE was inversely related to body mass indices while S100A12 associated with increased inflammation, PCVD, and mortality, suggesting that S100A12 may identify PD patients at high risk for vascular disease and increased mortality.

C-reactive Protein: Repeated Measurements will Improve Dialysis Patient Care

Systemic inflammation is a common feature in the uremic phenotype and associates with poor outcomes. The awareness regarding the importance of inflammation assessment in chronic kidney disease (CKD) patients has risen in recent years, and despite the development of novel biomarkers, C-reactive protein (CRP) is still the most measured inflammatory parameter. Notwithstanding, the possible weak points of CRP determination, this biomarker has demonstrated being useful both for guidance in clinical practice and for risk estimation. In addition, regular determination of CRP among dialysis patients has been associated with better outcomes in different dialysis facilities. Because persistent inflammation may be a silent reflection of various pathophysiologic alterations in CKD, it is crucial that inflammatory markers are regularly monitored and therapeutic attempts be made to target this inflammation.

Serum Gamma-Glutamyltransferase Levels Predict Mortality in Patients With Peritoneal Dialysis

Serum gamma-glutamyltransferase (GGT) level has been considered marker of oxidative stress as well as liver function. Serum GGT level has been reported to be associated with the mortality in hemodialysis patients. However, it is not well established whether serum GGT level is associated with all-cause mortality in peritoneal dialysis (PD) patients. The aim of this study was to determine the association between serum GGT levels and all-cause mortality in PD patients.PD patients were included from the Clinical Research Center registry for end-stage renal disease cohort, a multicenter prospective observational cohort study in Korea. Patients were categorized into 3 groups by tertile of serum GGT levels as follows: tertile 1, GGT < 16 IU/L; tertile 2, GGT = 16 to 27 IU/L; and tertile 3, GGT > 27 IU/L. Primary outcome was all-cause mortality.A total of 820 PD patients were included. The median follow-up period was 34 months. Kaplan-Meier analysis showed that the all-cause mortality rate was significantly different according to tertiles of GGT (P = 0.001, log-rank). The multivariate Cox regression analysis showed that higher tertiles significantly associated with higher risk for all-cause mortality (tertile 2: hazard ratio [HR] 2.08, 95% confidence interval [CI], 1.17-3.72, P = 0.013; tertile 3: HR 1.83, 95% CI, 1.04-3.22, P = 0.035) in using tertile 1 as the reference group after adjusting for clinical variables.Our study demonstrated that high serum GGT levels were an independent risk factor for all-cause mortality in PD patients. Our findings suggest that serum GGT levels might be a useful biomarker to predict all-cause mortality in PD patients.

A follow-up study of the chronic kidney disease patients treated with Brazil nut: focus on inflammation and oxidative stress

Brazil nut is the richest known food source of selenium. The supplementation with Brazil nut during 3 months was effective in reducing oxidative stress and inflammation in hemodialysis (HD) patients. However, there are no available data on the antioxidant effect after that supplementation. The objective of this work was to determine if the beneficial effects of one Brazil nut supplementation per day during 3 months for the HD patients could be sustained after 12 months. Twenty-nine HD patients (58.6 % men, 51.0 ± 3.3 years) from RenalCor Clinic, Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study had finished. The plasma levels of antioxidant substances as selenium, glutathione peroxidase (GPx), 8-isoprostane, 8-hydroxy-2-deoxyguanosine (8-OHdG) and cytokines (tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6)) were determined before, after 3 months of supplementation and after 12 months. After 3-months supplementation, cytokines, 8-OHdG and 8-isoprostane plasma levels have decreased and the activity of GPx and selenium plasma levels have increased significantly. Additionally, after 12 months, the values of 8-isoprostane, 8-OHdG and cytokines increased and the activity of GPx and selenium plasma levels decreased significantly. The levels of oxidative stress and inflammation biomarkers after 12 months increased compared to the basal levels. Consequently, it is necessary to motivate patients to adopt different dietary intake patterns.