Thiobarbituric acid reactive substances are increased in the subcutaneous fat tissue of patients with end-stage renal disease

Hemodialysis raises oxidative stress through carbon-centered radicals despite improved biocompatibility

Leukocyte activation and the resulting oxidative stress induced by bioincompatible materials during hemodialysis impact the prognosis of patients. Despite multiple advances in hemodialysis dialyzers, the prognosis of hemodialysis patients with complications deeply related to oxidative stress, such as diabetes mellitus, remains poor. Thus, we re-evaluated the effects of hemodialysis on multiple reactive oxygen species using electron spin resonance-based methods for further improvement of biocompatibility in hemodialysis. We enrolled 31 patients in a stable condition undergoing hemodialysis using high-flux polysulfone dialyzers. The effects of hemodialysis on reactive oxygen species were evaluated by two methods: MULTIS, which evaluates serum scavenging activities against multiple hydrophilic reactive oxygen species, and i-STrap, which detects lipophilic carbon-center radicals. Similar to previous studies, we found that serum hydroxyl radical scavenging activity significantly improved after hemodialysis. Unlike previous studies, we discovered that scavenging activity against alkoxyl radical was significantly reduced after hemodialysis. Moreover, patients with diabetes mellitus showed a decrease in serum scavenging activity against alkyl peroxyl radicals and an increase in lipophilic carbon-center radicals after hemodialysis. These results suggest that despite extensive improvements in dialyzer membranes, the forms of reactive oxygen species that can be eliminated during dialysis are limited, and multiple reactive oxygen species still remain at increased levels during hemodialysis.

Seasonal variations in nutritional status and oxidative stress in patients on hemodialysis: Are they related?

OBJECTIVE

Seasonal variations in body composition and parameters that reflect nutritional status are well established in patients on hemodialysis (HD). However, to our knowledge, no study has assessed the changes in oxidative stress (OS). The aims of this study were to assess seasonal variations in OS, body composition, and other nutritional parameters.

METHODS

Seasonal variations in fat tissue mass (FTM), fat tissue index (FTI), adipose tissue mass (ATM), lean tissue mass (LTM), lean tissue index (LTI), body cell mass (BCM), overhydration (OH) volume, and OS (blood levels of derivatives of reactive oxygen metabolites [d-ROMs], thiobarbituric reactive substances, plasma protein reduced thiol content [THIOLS], and ferric reducing ability of plasma) were assessed in 45 patients on HD, 70 y of age (60.5-76.5 y).

RESULTS

FTM (P < 0.001), FTI (P < 0.001), and ATM (P < 0.001) significantly increased, whereas LTI (P < 0.001), LTM (P < 0.001), BCM (P < 0.001), and OH volume (P = 0.004) significantly decreased over the season. Additionally, significant seasonal variations in the levels of d-ROMs (P = 0.02) and THIOLS (P = 0.02) were found. Levels of d-ROMs were found to be a significant predictor of LTM and BCM (β = -0.57; 95% confidence interval [CI], -1.08 to -0.06; P = 0.03; β = -0.04; 95% CI, -0.075 to -0.006; P = 0.02). Furthermore, hip circumference was found to be the most significant predictor of the level of d-ROMs (β = 2.66; 95% CI; 0.28-5.04; P = 0.03) and waist-to-height ratio (β = 251; 95% CI, 16.6-477.2; P = 0.03) and serum prealbumin levels of THIOLS (β = 263; 95% CI, 6.8-521.1; P = 0.04).

CONCLUSION

These results suggest seasonal variations in OS in patients on HD and a possible interaction between OS and nutritional status in these patients.

CHANGES IN ANTIOXIDANT CAPACITY OF KOALAS (PHASCOLARCTOS CINEREUS) BASED ON HEALTH STATUS AND MEASUREMENT OF THE ANTIOXIDANT ASCORBATE IN EUCALYPT LEAVES

Antioxidants have a crucial role in protecting the body from oxidative stress, which would otherwise result in cellular damage and possibly predispose animals to disease. The antioxidant capacity of koalas (Phascolarctos cinereus) and its association with health or disease status is currently unknown. Ascorbate, a dietary antioxidant, has previously been identified in a few eucalypt species eaten by koalas. This study aimed to determine 1) differences between the antioxidant capacity of healthy and diseased koalas, and 2) concentration of the antioxidant ascorbate in Eucalyptus spp. leaves eaten by koalas. To determine differences in antioxidant capacity of koalas, plasma samples from clinically healthy koalas in Kangaroo Island, South Australia (SA) (n = 23), euthanized koalas with oxalate nephrosis from Mount Lofty Ranges, SA (n = 11), and euthanized koalas with chlamydiosis from Moggill, Queensland (n = 11) were analyzed for the three antioxidants α-tocopherol, ascorbate, and retinol and for two measures of antioxidant capacity, ferric reducing ability of plasma (FRAP), and trolox equivalent antioxidant capacity (TEAC). The thiobarbituric acid reactive substance (TBARS) measured formation of oxidants, and an oxidative stress index (OSI) was calculated by TBARS/(TEAC + FRAP). Ascorbate concentration was measured in dietary eucalypt leaves from Mount Lofty Ranges and Moggill. Results showed that in diseased Mount Lofty Ranges and Moggill koalas, plasma α-tocopherol concentrations were significantly lower, and ascorbate, TBARS, and OSI was significantly higher compared with clinically healthy koalas from Kangaroo Island. Ascorbate was high in eucalypt leaves, particularly young leaves from the Mount Lofty Ranges. This study showed that disease was associated with some measures of poor antioxidant capacity in koalas and also found that ascorbate is high in the dietary eucalypts of koalas.

A Randomized Controlled Trial of the Effects of Febuxostat Therapy on Adipokines and Markers of Kidney Fibrosis in Asymptomatic Hyperuricemic Patients With Diabetic Nephropathy

BACKGROUND

In observational studies, higher uric acid levels are associated with metabolic syndrome, diabetes, and kidney disease.

OBJECTIVE

The objective of this study is to examine whether reduction of plasma uric acid with febuxostat, a xanthine oxido reductase inhibitor, impacts adipose tissue oxidative stress, adipokines, and markers of systemic inflammation or kidney fibrosis.

DESIGN

This was a double-blinded randomized controlled trial.

SETTING

Academic university setting was used.

PATIENTS

Overweight or obese adults with hyperuricemia and type 2 diabetic nephropathy were included.

MEASUREMENTS

Adipose tissue thiobarbituric acid reducing substances (TBARS) and adiponectin concentrations and urinary transforming growth factor-β (TGF-β) were primary endpoints. Plasma C-reactive protein, high molecular weight-adiponectin, interleukin-6, tumor necrosis factor-α, and TBARS and albuminuria were among predefined secondary endpoints.

METHODS

Participants were randomly assigned to febuxostat (n = 40) or matching placebo (n = 40) and followed for 24 weeks.

RESULTS

Baseline plasma uric acid levels were 426 ± 83 µmol/L; 95% completed the study. Estimated glomerular filtration rate (eGFR) declined from 54 ± 17 mL/min/1.73 m² at baseline to 51 ± 17 mL/min/1.73 m² at 24 weeks (P = .05). In separate mixed-effects models, compared with placebo, febuxostat reduced uric acid by 50% (P < .001) but had no significant effects on subcutaneous adipose tissue TBARS (-7.4%, 95% confidence interval [CI], 57.4%-101.4%) or adiponectin (6.7%, 95% CI, 26.0%-53.8%) levels or urinary TGF-β/creatinine ratio (18.0%, 95% CI, 10.0%-54.8%) or secondary endpoints.

LIMITATIONS

Relatively modest sample size and short duration of follow-up.

CONCLUSIONS

In this population with progressive diabetic nephropathy, febuxostat effectively reduced plasma uric acid. However, no detectable effects were observed for the prespecified primary or secondary endpoints.

TRIAL REGISTRATION

The study was registered in clinicaltrials.gov (NCT01350388).

Protective effect of N-acetylcysteine on early outcomes of deceased renal transplantation

We investigated the effects of the antioxidant N-acetylcysteine (NAC) on early outcomes of deceased donor renal transplantation. Between April 2005 and June 2008, adult primary graft recipients of deceased renal donors were assigned to treatment (n = 38) or control (n = 36) groups and evaluated for 90 days and one year after renal transplantation. The treatment group received NAC orally (600 mg twice daily) from day 0 to 7 postoperatively. Renal function was determined by serum creatinine, MDRD and Cockcroft-Gault estimated GFR (eGFR), delayed graft function (DGF) and dialysis free Kaplan-Meier estimate curve. Serum levels of thiobarbituric acid reactive substances (TBARS), were employed as markers of oxidative stress. The NAC group displayed a lower mean serum creatinine during the first 90 days (P = .026) and at 1 year after transplantation (P = .005). Furthermore, the NAC group showed a higher mean eGFR throughout the first 90 days and at 1 year. DGF was lower among the NAC group (P = .017) and these recipients required fewer days of dialysis (P = .012). Oxidative stress was significantly attenuated with NAC (P < .001). Our results suggested that NAC enhanced early outcomes of deceased donor renal transplantation by attenuating oxidative stress.

The effects of 1-year treatment with a haemodiafiltration with on-line regeneration of ultrafiltrate (HFR) dialysis on biomarkers of oxidative stress in patients with chronic renal failure

In the last few years haemodiafiltration with on-line regeneration of ultrafiltrate (HFR) has been shown to have a positive impact on inflammation and oxidative stress biomarkers, but its effect on antioxidant levels and on oxidative damage to biomolecules in the long-term is still unknown. This is a randomised clinical study over 12 months involving 40 patients on haemodialysis, comparing the effect of HFR (n=25) dialysis with haemodialysis with polysulfone (HD-PS, n=15) on oxidative stress. Total antioxidant capacity, enzymatic antioxidant [superoxide dismutase (SOD), catalase and glutathione peroxidase], non-enzymatic (GSH) and biomarkers of oxidative stress (TBARs, carbonyl groups and 8-OH-dG) were evaluated. The antioxidant activity decreased in the lymphocytes of patients dialysed with HFR, with a significant decrease in the enzyme SOD. In the oxidative stress biomarkers, an increase was seen in the levels of 8-OH-dG in patients on HD-PS dialysis but not in those treated with HFR. Throughout the year the changes in antioxidant levels and biomarkers of oxidative damage in patients dialysed with HFR were generally more modest and fluctuated less than those dialysed with HD-PS. Our study indicates that, in general, long-term dialysis with HFR does not modified antioxidant parameters or increases the oxidative damage to biomolecules. The HFR showed to be a biocompatible technique for long-term dialysis.

Low fat adiponectin expression is associated with oxidative stress in nondiabetic humans with chronic kidney disease--impact on plasma adiponectin concentration

In spite of association between high plasma adiponectin and high metabolic and cardiovascular (CV) risk, highest adiponectin increments retain CV and metabolic protective effects in advanced chronic kidney disease (CKD). Passive accumulation can favor CKD-associated hyperadiponectinemia but potential additional regulation by adipose tissue remains undefined. Oxidative stress (OS) is associated with metabolic and CV disease and with CKD [increasing from conservative treatment (CT) to maintenance hemodialysis (MHD)], and OS can reduce adiponectin expression in experimental models. OS (in the form of plasma thiobarbituric acid-reactive substances: TBARS), subcutaneous adipose adiponectin mRNA, and plasma adiponectin were studied in CKD patients (stages 4 and 5) on CT (n = 7) or MHD (n = 11). Compared with CT and controls (C: n = 6) MHD had highest TBARS and lowest adiponectin mRNA (P < 0.05) with lower adipose adiponectin protein (P < 0.05 vs. CT). MHD also had lower plasma adiponectin than CT, although both had higher adiponectin than C (P < 0.05). In renal transplant recipients (RT: CKD stage 3; n = 5) normal TBARS were, in turn, associated with normal adiponectin mRNA (P < 0.05 vs. MHD). In all CKD (n = 23), adiponectin mRNA was associated positively with adiponectin plasma concentration (P < 0.01). In all subjects (n = 29), adiponectin mRNA was related (P < 0.05) negatively with TBARS after adjusting for plasma C-reactive protein (CRP) or CRP and creatinine. Thus altered OS, adiponectin expression, and plasma concentration represent a novel cluster of metabolic and CV risk factors in MHD that are normalized in RT. The data suggest novel roles of 1) MHD-associated OS in modulating adiponectin expression and 2) adipose tissue in contributing to circulating adiponectin in advanced CKD.

"New" cardiovascular risk factors in patients with chronic kidney disease: role of folic acid treatment

Cardiovascular disease (CVD) is the principal cause of mortality in patients with chronic renal disease undergoing hemodialysis. In addition to the CVD risk factors, a new hypothesis has recently been aroused related to "new" factors involved in the development of atherosclerosis in the uremic patient; worthwhile mentioning are the homocysteine, inflammation, and oxidative stress, among others. The potential utility of the folic acid in the hyperhomocysteinemia control is well known, although its mechanism of action, either as antioxidant or anti-inflammatory, has not been established. Our results confirm that the patients undergoing dialysis demonstrate hyperhomocysteinemia, an increased inflammatory status, and an increase of the lipid peroxidation markers. The administration of IV folinic acid induces a reduction of homocysteine levels subordinate to the inflammatory status of the patient. Additionally, although no inflammatory effects were shown, the results provide evidence for the antioxidant effect of IV folinic acid administration by reducing the lipid peroxidation marker levels. The statistic analysis demonstrates no correlation among the 3 markers, in spite of its higher levels in these particular patients. Homocysteine does not independently predict mortality in patients taking oral folic acid. Nevertheless, the PCR (an inflammation marker) and the antibody antioxidative-LDL (a lipidic peroxidation marker) show a good prediction of mortality at the 24-month follow-up analysis. The knowledge of these "new" CV risk factors, as well as the factors that influence them, could be useful to prevent the development of atherosclerosis in patients with chronic renal disease.

Oxidative stress and uremia

Oxidative stress is a pathogenic element of great importance in uremic patients, with a great impact on their survival. The cause of oxidative stress in patients on hemodialysis is traditionally attributed to the recurrent activation of polymorphonucleate neutrophils and monocytes. The effects of oxidative stress are evident on all biochemical components of biological tissues: lipids, proteins, carbohydrates, and nucleic acids. This study briefly reviews the effects of different dialytic techniques and of kidney transplant on several parameters of oxidative stress. Many different modalities of pharmaceutical intervention are then analyzed, and the clinical evidences reported.

Oxidative stress during leukocyte absorption apheresis

Leukocyte absorption apheresis absorbs leukocytes to the apheresis columns involving leukocyte activation. This process is regarded as bioincompatible and avoided in hemodialysis or other extracorporeal circulation processes. Thus, leukocyte apheresis has a potential risk to exacerbate in vivo oxidative stress. We evaluated the changes in plasma oxidative stress during leukocyte apheresis. Patients diagnosed as ulcerative colitis (UC) and treated with leukocyte apheresis were studied. Adacolumn (celluloseacetate beads) or Cellsorba EX (polyethylenephtarate fiber) was used for the leukocyte absorption device. Oxidative stress was measured by thiobarbituric acid reactive substances (TBARS) and hydroxyl radical ((*)OH) scavenging activity. Plasma samples were collected from the pre- and post-column sampling port at the start, and from the pre-column sampling port at the end of the treatment. The (*)OH signal intensities (OHRI) significantly increased during a column passage, indicating a loss of plasma (*)OH scavenging activity. However, OHRI was reduced at the end, suggesting a recovery of radical scavenging activity during leukocyte apheresis. Significant decreases of OHRI and TBARS were only observed in the early phase of the therapeutic course. No differences of OHRI and TBARS levels were observed between the two columns. These results indicate that though the plasma antioxidant activity was diminished by a column passage, plasma antioxidant activity recovers during the procedure. This efficient antioxidative effect is limited to the early phase of the therapeutic course.

Association between plasma oxidized low-density lipoprotein and diabetic nephropathy

To investigate the association of oxidized low-density lipoprotein (ox-LDL) with the development of diabetic nephropathy, plasma levels of ox-LDL were measured in 70 patients with type 2 diabetes mellitus. A sandwich enzyme-linked immunoadsorbent assay (ELISA) using the mouse monoclonal antibody FOH1a/DLH3, which specifically recognizes oxidized phosphatidylcholine, and a horseradish peroxidase (HRP)-labeled goat anti-human apolipoprotein B IgG was used to measure ox-LDL levels. The mean age of the patients was 57.0+/-1 3.4 years, and the mean duration of diabetes was 13.4+/-8.5 years. Plasma ox-LDL levels were similar in patients with normoalbuminuria (13.7+/-3.9 U/ml), patients with microalbuminuria (12.8+/-3.9 U/ml), and normal controls (12.5+/-4.2 U/ml). However, the plasma ox-LDL level in patients with macroalbuminuria (16.8+/-7.5 U/ml) was significantly higher than those in the other groups (P<0.05). Hemoglobin A1c (HbA1c) levels were similar in diabetic patients with normoalbuminuria (8.2+/-2.2%), microalbuminuria (7.8+/-1.3%), or macroalbuminuria (7.2+/-1.4%). There was no significant correlation between the ox-LDL level and the HbA1c level. The significantly elevated plasma ox-LDL levels in patients with macroalbuminuria suggest that ox-LDL may play an important role in the progression of diabetic nephropathy.

Dehydroascorbic acid and oxidative stress in haemodialysis patients

BACKGROUND

The amount of dehydroascorbic acid contained within total ascorbic acid (oxidized as well as non-oxidized forms) in plasma, hereafter referred to as the dehydroascorbic acid fraction, may be a measure of oxidative stress during haemodialysis. In the present study, we determined this fraction in chronic haemodialysis patients.

METHODS

Using high performance liquid chromatography, dehydroascorbic acid and total ascorbic acid levels were measured in 80 maintenance haemodialysis patients for a period of > 2 years as well as in 49 controls, to examine a possible association of these compounds with clinical parameters and/or drugs taken by the patients.

RESULTS

Dialysis patients who had an increased plasma urate level (P < 0.05) and had been taking allopurinol (P < 0.05) or NSAID (non-steroid anti-inflammatory drugs) (P < 0.01), and dialysis patients who were younger (< or = 55 years), as compared with older dialysis patients (P < 0.01), were found to have a lower dehydroascorbic acid fraction by multivariate analysis. Mean plasma dehydroascorbic acid levels and dehydroascorbic acid fractions were significantly lower in the younger haemodialysis patients (4.8 +/- 0.7 micromol/l and 28.4 +/- 3.9%) than in healthy younger controls (13.3 +/- 1.1 micromol/l and 41.1 +/- 1.8%) (P < 0.0001 and P < 0.01, respectively). Moreover, a correlation was found between plasma dehydroascorbic acid fraction and plasma lipid peroxide (r = 0.66, P < 0.01) in patients who had not been taking allopurinol and/or NSAID.

CONCLUSION

We found that dehydroascorbic acid fraction was related to patients' age, plasma urate level and to taking allopurinol or NSAID. Dehydroascorbic acid fraction may be another indirect index of oxidative stress.

Non-traditional cardiovascular disease risk factors in end-stage renal disease: oxidate stress and hyperhomocysteinemia

Studies in experimental animals have shown that oxidative stress and hyperhomocyst(e)inemia culminate in abnormal vascular and endothelial regulation, functional nitric oxide deficiency, vascular hypertrophy, and atherosclerosis. Oxidative stress is accompanied by increased advanced glycation endproducts and oxidized low density lipoproteins. Studies of patients with end-stage renal disease provide extensive indirect, evidence of increased oxidative stress and more than ninety percent are hyperhomocyt(e)inemic. Presently, only uncontrolled or observational studies are available to assess the effects of anti-oxidant therapy for oxidative stress or folate therapy for hyperhomocyst(e)inemia in these patients. Promising developments include the reports of beneficial effects of a vitamin E coated dialyzer, and the reduction in homocyst(e)ine levels in patients with end-stage renal disease given an intravenous folate metabolite. However, there is presently no therapy available to reverse fully oxidative stress or hyperhomocyst(e)inemia. Therefore, the causative role of these nontraditional risk factors of cardiovascular disease remains untested.

Hemolipodialysis attenuates oxidative stress and removes hydrophobic toxins

Uremic patients undergoing hemodialysis often have increased oxidant stress and accumulation of uremic toxins. Hemodialysis, per se, often can exacerbate oxidant stress and may be inefficient at removing hydrophobic or protein bound toxins. We describe a new hemodialytic method that incorporates liposomes and antioxidants to remove hydrophobic/uremic toxins and minimize free radical mediated damage. In vitro experiments measured advanced oxidation protein products (AOPP), malonaldehyde, reactive carbonyls, and the removal of platelet activating factor (PAF) and bilirubin during extracorporeal circulation with or without liposomes. We observed a significant reduction of oxidation products as well as a significant removal of PAF and bilirubin compared to normal hemodialysis.

Antioxidant status and dialysis: plasma and saliva antioxidant activity in patients with fluctuating urate levels

The present study is concerned with the influence of processes occurring during dialysis on the antioxidant capacity of plasma and saliva. The biological fluids were also tested for uric acid and total protein content. Before hemodialysis, plasma antioxidant status of hemodialyzed patients appears slightly higher than the corresponding status in normal subjects; after hemodialysis it is found unchanged. The result can be explained by a balance between a reduction in uric acid plasma content, due to the dialytic procedure, and an increase in protein content, possibly due to a dialysis-related hemoconcentration. Moreover, pre-dialysis total antioxidant capacity of whole saliva samples is higher than in healthy individuals and drastically decreases towards normal values following dialytic procedure. Our data indicate a certain concentration of the uric acid in the saliva of hemodialyzed patients and evidence that both total protein concentration and uric acid level show a good correlation with saliva total antioxidant capacity, suggesting that proteins are major antioxidants of this fluid. Further observations are needed to assess whether this improved saliva antioxidant ability has any consequence on the periodontal conditions of hemodialyzed subjects.