Blood 8-hydroxy-2'-deoxyguanosine is associated with erythropoietin resistance in haemodialysis patients

Efficacy and safety of recombinant human erythropoietin (Hema-Plus®) for management of anemia in Thai patients on peritoneal dialysis

BACKGROUND

Hema-Plus, a recombinant human erythropoietin (rHuEPO) or epoetin alfa has shown effectiveness in correction of anemia in Thai population in clinical practice. This study was aimed to demonstrate efficacy and safety under the evidence-based approach.

AIM

To evaluate the efficacy and safety of rHuEPO (Hema-Plus) for treatment of anemia over 12 wk in Thai patients with Stage V chronic kidney disease (CKD) on peritoneal dialysis (PD).

METHODS

This study was an open-label, multi-center study to enroll 30 CKD patients identified to start PD with hemoglobin (Hb) less than 9.5 g/dL, serum ferritin more than 100 ng/mL, serum transferrin saturation more than or equal to 20% and who had not previously received epoetin. Patients with conditions that could increase the risk of adverse effects from study participation or interfere with study outcomes, were using concomitant androgens or had secondary hyperparathyroidism were excluded. All eligible patients started Hema-Plus by SC injection at 4000 IU once or twice weekly (week 0) and with follow-up at weeks 2, 4, 8, and 12. Dosage adjustment could be done to achieve Hb level of 11-12 g/dL. Primary end point was mean change in Hb level from baseline to end of treatment (week 12). Safety was assessed throughout the study. Quality of life (QoL) was assessed using KDQOL-36.

RESULTS

All 30 enrolled patients completed the study. Mean (standard deviation) Hb at baseline (week 0) to the end of 12 wk was significantly increased from 7.39 (1.29) g/dL to 11.15 (1.73) g/dL (paired t-test, P value < 0.001). Overall change of Hb means from baseline over the other 4 visits was statistically significantly increased (repeated measure ANOVA, P value < 0.001). Ten out of 39 adverse events (AEs) were serious. Two serious AEs were probably related to study medication by investigators’ assessment. At week 12, the QoL scores in all domains were significantly increased from baseline.

CONCLUSION

Hema-Plus administered for 12 wk for treatment of anemia in patients on PD effectively increased Hb levels with acceptable safety profile.

The Effect of Iron Deficiency Anemia and Different Treatment Methods on DNA Damage: 8-hydroxy-2-deoxyguanosine Level

Ionic iron causes damages at the cellular level by forming free radicals. Reactive oxygen species lead to the formation of oxidative base damages in DNA. Among these forms the most common one and the one which has the best known mutagenity is 8-hydroxy-2′-deoxyguanosine (8-OHdG). We aimed to determine iron deficiency anemia (IDA) and its different forms of treatments; probable oxidative damage on DNA by looking at the level of 8-OHdG. The patients were divided into 4 subgroups: Oral treatment (p.o.) group; Intramuscular treatment (i.m.) group; Intravenous treatment (i.v.) group; Healthy control group. Blood and urine samples were taken from all patients totally 4 times. 8-OHdG levels detected in blood and urine samples were compared with the control group. IDA and the treatment of it affect the level of 8-OHdG. p.o. therapy should be the top priority on children.

Paper-Based Sensing Device for Electrochemical Detection of Oxidative Stress Biomarker 8-Hydroxy-2'-deoxyguanosine (8-OHdG) in Point-of-Care

This work presents a cost-effective, label-free in point-of-care (POC) biosensor for the sensitive detection of 8-hydroxy-2′-deoxyguanosine (8-OHdG), the most abundant oxidative product of DNA, that may allow a premature assessment of cancer disease, thereby improving diagnosis, prognostics and survival rates. The device targets the direct detection of 8-OHdG by using for the first time a carbon-ink 3-electrode on a paper substrate coupled to Differential Pulse Voltammetry readings. This design was optimized by adding nanostructured carbon materials to the ink and the conducting polymer PEDOT, enhancing the electrocatalytic properties of the sensor towards 8-OHdG detection. Meanwhile, the ability of this oxidative stress biomarker to undertake an oxidation reaction enabled the development of the sensing electrochemical device without the need of chemical probes and long incubation periods. This paper-modified sensor presented high electrochemical performance on the oxidation of 8-OHdG with a wide linear range (50–1000 ng/ml) and a low detection limit (14.4 ng/ml). Thus, our results showed the development of a direct and facile sensor with good reproducibility, stability, sensitivity and more importantly, selectivity. The proposed carbon-based electrochemical sensor is a potential candidate to be miniaturized to small portable size, which make it applicable for in-situ 8-OHdG sensing in real biological samples.

Naturally Occurring Compounds: New Potential Weapons against Oxidative Stress in Chronic Kidney Disease

Oxidative stress is a well-described imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense system of cells and tissues. The overproduction of free radicals damages all components of the cell (proteins, lipids, nucleic acids) and modifies their physiological functions. As widely described, this condition is a biochemical hallmark of chronic kidney disease (CKD) and may dramatically influence the progression of renal impairment and the onset/development of major systemic comorbidities including cardiovascular diseases. This state is exacerbated by exposure of the body to uremic toxins and dialysis, a treatment that, although necessary to ensure patients' survival, exposes cells to non-physiological contact with extracorporeal circuits and membranes with consequent mitochondrial and anti-redox cellular system alterations. Therefore, it is undeniable that counteracting oxidative stress machinery is a major pharmacological target in medicine/nephrology. As a consequence, in recent years several new naturally occurring compounds, administered alone or integrated with classical therapies and an appropriate lifestyle, have been proposed as therapeutic tools for CKD patients. In this paper, we reviewed the recent literature regarding the "pioneering" in vivo testing of these agents and their inclusion in small clinical trials performed in patients affected by CKD.

Evaluation of the Impact of a New Synthetic Vitamin E-Bonded Membrane on the Hypo-Responsiveness to the Erythropoietin Therapy in Hemodialysis Patients: A Multicenter Study

BACKGROUND

Oxidative stress has been related to hypo-response to erythropoiesis-stimulating agents (ESAs) in hemodialysis (HD) patients. The aim of this study was to verify whether vitamin E (ViE) on a synthetic polysulfone dialyzer can improve ESA responsiveness.

METHODS

This controlled, multicenter study involved 93 HD patients on stable ESA therapy, who were randomized to either ViE-coated polysulfone dialyzer or to a low-flux synthetic dialyzer. The primary outcome measure was the change in ESA resistance index (ERI) from baseline.

RESULTS

Mean ERI decreased in the ViE group by 1.45 IU/kg*g/dl and increased in the control group by 0.53 IU/kg*g/dl, with a mean difference of 1.98 IU/kg*g/dl (p = 0.001 after adjusting for baseline ERI, as foreseen by the study protocol). Baseline ERI was inversely related to its changes during follow-up only in the control group (R2 = 0.29).

CONCLUSIONS

The ViE dialyzer can improve ESA response in HD patients. Changes in ERI during follow-up are independent from baseline ERI only in the ViE group. Video Journal Club 'Cappuccino with Claudio Ronco' at http://www.karger.com/?doi=453442.

The Beneficial Effects of Renal Transplantation on Altered Oxidative Status of ESRD Patients

Renal transplantation (RT), has been considered the best therapeutic option for end stage renal disease (ESRD). Objective. To determine the effect of RT on the evolution of oxidative DNA status. Methods. Prospective cohort (N = 50 receptors of RT); genotoxic damage, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and DNA repair enzyme, human 8-oxoguanine-DNA-N- glycosylase-1 (hOGG1); and antioxidants, superoxide dismutase (SOD) and glutathione peroxidase (GPx), were evaluated. Results. Before RT, 8-OHdG were significantly elevated (11.04 ± 0.90 versus 4.73 ± 0.34 ng/mL) compared to healthy controls (p = 0.001), with normalization after 6 months of 4.78 ± 0.34 ng/mL (p < 0.001). The same phenomenon was observed with hOGG1 enzyme before RT with 2.14 ± 0.36 ng/mL (p = 0.01) and decreased significantly at the end of the study to 1.20 ng/mL (p < 0.001) but was higher than controls, 0.51 ± 0.07 ng/mL (p < 0.03). Antioxidant SOD was elevated at 24.09 ± 1.6 IU/mL versus healthy controls (p = 0.001) before RT; however, 6 months after RT it decreased significantly to 16.9 ± 1.6 IU/mL (p = 0.002), without achieving the levels of healthy controls (p = 0.01). The GPx, before RT, was significantly diminished with 24.09 ± 1.6 IU/mL versus healthy controls (39.0 ± 1.58) (p = 0.01), while, in the final results, levels increased significantly to 30.38 ± 3.16 IU/mL (p = 0.001). Discussion. Patients with ESRD have important oxidative damage before RT. The RT significantly reduces oxidative damage and partially regulates the antioxidant enzymes (SOD and GPx).

DNA Damage in Chronic Kidney Disease: Evaluation of Clinical Biomarkers

Patients with chronic kidney disease (CKD) exhibit an increased cancer risk compared to a healthy control population. To be able to estimate the cancer risk of the patients and to assess the impact of interventional therapies thereon, it is of particular interest to measure the patients' burden of genomic damage. Chromosomal abnormalities, reduced DNA repair, and DNA lesions were found indeed in cells of patients with CKD. Biomarkers for DNA damage measurable in easily accessible cells like peripheral blood lymphocytes are chromosomal aberrations, structural DNA lesions, and oxidatively modified DNA bases. In this review the most common methods quantifying the three parameters mentioned above, the cytokinesis-block micronucleus assay, the comet assay, and the quantification of 8-oxo-7,8-dihydro-2′-deoxyguanosine, are evaluated concerning the feasibility of the analysis and regarding the marker's potential to predict clinical outcomes.

Does chronic raise of metal ion levels induce oxidative DNA damage and hypoxia-like response in patients with metal-on-metal hip resurfacing?

Metal-on-metal hip resurfacing (MOM-HR) represents a viable alternative to traditional arthroplasty. Nevertheless, in MOM coupling both metal nanoparticles and ions are released, whose toxicity remains a matter of concern. We investigated whether 'endogenous' chronic exposure to cobalt and chromium induced a state of oxidative stress, DNA damage and a hypoxia-like response in patients with well-functioning MOM-HR. Twenty-two patients with unilateral MOM-HR were recruited at long-term. Twenty-one osteoarthritic subjects were enrolled for comparison. Serum ion levels were measured and correlated with 8-hydroxydeoxyguanosine and circulating-free-DNA, as markers of oxidative DNA damage. Moreover, the hypoxia-inducible factor-1α, marker of hypoxic state, was evaluated. Ion concentrations were found to be 5-to-15 times higher in MOM-HR patients than in presurgery subjects (p < 0.001); circulating-free-DNA, 8-hydroxydeoxyguanosine, and hypoxia-inducible factor-1α levels were not significantly different between groups and did not correlate with ion levels. Analyzing the results according to gender, MOM-HR males had higher 8-hydroxydeoxyguanosine levels (p = 0.01) compared with MOM-HR females. Similarly, circulating-free-DNA values were higher in males than females, even if this difference did not reach statistical significance. This research is the first that attempted to investigate the long-term effects of ion dissemination in subjects with well-fixed MOM implants. A significant correlation between biomarkers increase and ion levels was not demonstrated. Nevertheless, both circulating-free-DNA and 8-hydroxydeoxyguanosine showed a tendency to increase in MOM-HR males. Further studies with a larger sample size should be performed to detect the clinical relevance of biomarkers increase especially in younger subjects, where a chronic moderately elevated exposure has to be faced. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 460-466, 2017.

Association of plasma F2-isoprostanes and isofurans concentrations with erythropoiesis-stimulating agent resistance in maintenance hemodialysis patients

Background

In patients undergoing maintenance hemodialysis (HD), hyporesponsiveness to erythropoiesis stimulating agents (ESAs) is associated with adverse clinical outcomes. Systemic inflammation is highly prevalent in HD patients and is associated with ESA hyporesponsiveness. Oxidative stress is also highly prevalent in HD patients, but no previous study has determined its association with ESA response. This study assessed the association of plasma markers of oxidative stress and inflammation with ESA resistance in patients undergoing maintenance HD.

Methods

We analyzed data from 165 patients enrolled in the Provision of Antioxidant Therapy in Hemodialysis study, a randomized controlled trial evaluating antioxidant therapy in prevalent HD patients. Linear and mixed-effects regression were used to assess the association of baseline and time-averaged high sensitivity F2-isoprostanes, isofurans, C-reactive protein (hsCRP), and interleukin-6 (IL-6) with ESA resistance index (ERI), defined as the weekly weight-adjusted ESA dose divided by blood hemoglobin level. Unadjusted models as well as models adjusted for potential confounders were examined. Predicted changes in ERI per month over study follow-up among baseline biomarker quartiles were also assessed.

Results

Patients with time-averaged isofurans in the highest quartile had higher adjusted mean ERI compared with patients in the lowest quartile (β = 14.9 ng/ml; 95 % CI 7.70, 22.2; reference group <0.26 ng/ml). The highest quartiles of hsCRP and IL-6 were also associated with higher adjusted mean ERI (β = 10.8 mg/l; 95 % CI 3.52, 18.1 for hsCRP; β = 10.2 pg/ml; 95 % CI 2.98, 17.5 for IL-6). No significant association of F2-isoprostanes concentrations with ERI was observed. Analyses restricted to baseline exposures and ERI showed similar results. Baseline hsCRP, IL-6, and isofurans concentrations in the highest quartiles were associated with greater predicted change in ERI over study follow-up compared to the lowest quartiles (P = 0.008, P = 0.004, and P = 0.04, respectively). There was no association between baseline F2-isoprostanes quartile and change in ERI.

Conclusions

In conclusion, higher concentrations of isofurans, hsCRP and IL-6, but not F2-isoprostanes, were associated with greater resistance to ESAs in prevalent HD patients. Further research is needed to test whether interventions that successfully decrease oxidative stress and inflammation in patients undergoing maintenance HD improve ESA responsiveness.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0074-9) contains supplementary material, which is available to authorized users.

Association of plasma ortho-tyrosine/para-tyrosine ratio with responsiveness of erythropoiesis-stimulating agent in dialyzed patients

Objectives Patients with end-stage renal failure (ESRF) treated with erythropoiesis-stimulating agents (ESAs) are often ESA-hyporesponsive associated with free radical production. Hydroxyl free radical converts phenylalanine into ortho-tyrosine, while physiological isomer para-tyrosine is formed enzymatically, mainly in the kidney. Production of 'para-tyrosine' is decreased in ESRF and it can be replaced by ortho-tyrosine in proteins. Our aim was to study the role of tyrosines in ESA-responsiveness. Methods Four groups of volunteers were involved in our cross-sectional study: healthy volunteers (CONTR; n = 16), patients on hemodialysis without ESA-treatment (non-ESA-HD; n = 8), hemodialyzed patients with ESA-treatment (ESA-HD; n = 40), and patients on continuous peritoneal dialysis (CAPD; n = 21). Plasma ortho-, para-tyrosine, and phenylalanine levels were detected using a high performance liquid chromatography (HPLC)-method. ESA-demand was expressed by ESA-dose, ESA-dose/body weight, and erythropoietin resistance index1 (ERI1, weekly ESA-dose/body weight/hemoglobin). Results We found significantly lower para-tyrosine levels in all groups of dialyzed patients when compared with control subjects, while in contrast ortho-tyrosine levels and ortho-tyrosine/para-tyrosine ratio were comparatively significantly higher in dialyzed patients. Among groups of dialyzed patients the ortho-tyrosine level and ortho-tyrosine/para-tyrosine ratio were significantly higher in ESA-HD than in the non-ESA-HD and CAPD groups. There was a correlation between weekly ESA-dose/body weight, ERI1, and ortho-tyrosine/para-tyrosine ratio (r = 0.441, P = 0.001; r = 0.434, P = 0.001, respectively). Our most important finding was that the ortho-tyrosine/para-tyrosine ratio proved to be an independent predictor of ERI1 (β = 0.330, P = 0.016). In these multivariate regression models most of the known predictors of ESA-hyporesponsiveness were included. Discussion Our findings may suggest that elevation of the ratio of ortho-tyrosine/para-tyrosine could be responsible for decreased ESA-responsiveness in dialyzed patients.

The relationship between red cell distribution width with erythropoietin resistance in iron replete hemodialysis patients

BACKGROUND

Recently, erythropoietin resistance (ER) has been shown to be related with cardiovascular and overall mortality in hemodialysis (HD) patients. Red blood cell distribution width (RDW) has also shown to be associated with cardiovascular and all cause mortality in general population. Thus in the current study we tested the hypothesis that RDW and erythropoietin resistance as determined by erythropoiesis stimulating agents (ESA) hyporesponsiveness index (EHRI) may be related with each other in iron replete HD patients.

METHODS

Study participants underwent medical history taking, physical examination, calculation of dialysis adequacy and biochemical analysis. EHRI was calculated as the weekly dose of EPO divided by per kilogram of body weight divided by the hemoglobin level.

RESULTS

Two separate analyses were performed. In the first analysis performed in 94 HD patients; the stepwise linear regression analysis revealed that being female (P=0.031), HD duration (P=0.021), presence of diabetes mellitus (P=0.008), RDW (P=0.023), and predialysis sodium (P=0.05) were independently related with logarithmically converted EHRI. We made second analysis after 4 months. The second analysis revealed that when compared to first EHRI, the EHRI was increased in 40, unchanged in one and decreased in 40 patients The second stepwise regression analysis also showed that the independent relationship with RDW and EHRI was persisted (β=0.050, CI: 0.022-0.078, P=0.001).

CONCLUSION

Red blood cell distribution width was independently related with EHRI in iron replete HD patients.

The effect of oral alpha-lipoic acid on oxidative stress in adolescents with type 1 diabetes mellitus

BACKGROUND

Oxidative stress has been implicated in the pathophysiology of diabetic complications. Alpha-lipoic acid (LA), a potent antioxidant, has been shown to be an effective treatment for diabetic neuropathy when given intravenously. Recently, an oral controlled-release formulation of alpha-lipoic acid (CRLA) was developed, and a pharmacokinetic study demonstrated that CRLA maintained significant plasma levels for 67% longer than a common quick-release formulation.

OBJECTIVE

To determine if CRLA is an effective antioxidant in type 1 diabetes mellitus (T1D) by measuring its effects on markers of oxidative damage and total antioxidant status.

METHODS

Forty pubertal and postpubertal adolescents with T1D underwent a double-blind, randomized, placebo-controlled study of CRLA for 3 months. 8-hydroxy-2'-deoxyguanosine, 2-thiobarbituric acid-reactive substances, protein carbonyl, total reactive antioxidant potential, hemoglobin A1c (HbA1c), and spot random urine collected for albumin to creatinine ratio were measured before and after treatment.

RESULTS

There was no significant change in any measurement of oxidative damage, total antioxidant status, HbA1c, or microalbuminuria prevalence after treatment with either placebo or CRLA.

CONCLUSION

In this pilot study, CRLA was not an effective treatment for decreasing oxidative damage in T1D, although efficacy may have been limited by issues with compliance.

Total antioxidant status and 8-hydroxy-2'-deoxyguanosine levels in gingival and peripheral blood of periodontitis patients

INTRODUCTION

The aim of this study was to determine 8-OHdG concentration as a biomarker of oxidant-induced DNA damage and to assess total antioxidant status (TAS) in gingival and peripheral blood during periodontal lesion.

MATERIALS AND METHODS

The study included 56 untreated periodontitis patients (26 with aggressive periodontitis, and 30 with chronic periodontitis (CP). The control group consisted of 25 healthy volunteers without pathological changes in the periodontium. Competitive ELISA was used to measure 8-OHdG. A colorimetric method based on the reduction of ABTSo+ radical cation generation was used to measure TAS.

RESULTS

Significantly higher 8-OHdG concentrations were detected in the gingival blood in both groups of patients with periodontitis than in the control group. Subjects with CP had significantly decreased TAS levels in the gingival blood compared with the control group. A significantly decreased TAS level in the peripheral blood in both patient groups compared with the control group was found. Significant positive correlation between TAS levels in venous and gingival blood in all the periodontitis patients and in the CP group was observed.

CONCLUSIONS

The oxidative burst in periodontitis may lead to significant local damage to nucleic acids. The significantly decreased TAS level in the gingival blood of CP patients compared with the healthy subjects suggests the possibility of a significant decrease in local antioxidant system capacity during the course of periodontitis. The decreased TAS level in the peripheral blood in the group of all patients with periodontitis may be one of the pathogenic mechanisms underlying the links between periodontal disease and several systemic diseases for which periodontitis is regarded as a independent risk factor.

Managing erythropoietin hyporesponsiveness

The anemia of chronic kidney disease is associated with cardiovascular disease, decreased quality of life, and mortality. The introduction of recombinant human erythropoietin (rHuEPO) has transformed the management of this condition. However, a significant proportion of patients fail to respond to even high doses of rHuEPO. Several factors have been implicated in the hyporesponsiveness to rHuEPO. Iron deficiency, whether absolute or functional, is considered the most important, and maintenance of adequate iron stores reduces rHuEPO requirements among patients on hemodialysis. However, traditional indices of iron that are currently utilized may not reflect iron stores accurately, and there is also increasing concern regarding the potential long-term toxicity of parenteral iron therapy. Infection and inflammation also influence the response to rHuEPO, both by disruption of iron metabolism and by eliciting the release of cytokines that inhibit erythropoiesis. Oxidative stress may contribute to rHuEPO hyporesponsiveness directly by promoting lipid peroxidation in cell membranes, leading to increased erythrocyte fragility and reduced life span and also through its strong association with inflammation. Severe hyperparathyroidism can lead to a reduced number of erythroid progenitor cells. Inadequate dialysis dose, aluminum overload, nutritional factors such as deficiencies of carnitine, vitamin B12, folic acid, and vitamin C can also reduce the efficacy of rHuEPO therapy. Hyporesponsiveness to rHuEPO presents a challenge to both diagnosis and management in an era where optimizing response to rHuEPO is critical both in limiting the burgeoning costs of anemia management and improving clinical outcomes in the dialysis population.

High iron storage levels are associated with increased DNA oxidative injury in patients on regular hemodialysis

BACKGROUND

Accumulating evidence suggests that oxidative stress is enhanced in patients on regular hemodialysis (HD). Iron supplementation is essential for the treatment of renal anemia, but there is a possibility that it could enhance oxidative stress by inducing the Fenton reaction. Here, we report our investigation of the relation between iron storage and DNA oxidative injury in HD patients.

METHODS

The study subjects were 48 patients on regular HD (age, 62.7 +/- 12.1 years; HD duration, 67.2 +/- 62.5 months; non-diabetic/diabetic; 22:26). Patients who were positive for hepatitis C virus antibody (HCV Ab), or hepatitis B surface antigen (HBsAg), and those with inflammatory or malignant diseases were excluded. The serum 8-hydroxy-2'-deoxyguanosine (8-OHdG) level, a marker of DNA oxidative injury, was measured before the first HD session of the week in all patients, and factors associated with high serum 8-OHdG were investigated. In 9 patients with a serum ferritin level of more than 1000 ng/ml at study entry, serum 8-OHdG levels were followed up for 6 months in the absence of iron supplementation.

RESULTS

Multivariate analysis showed that the serum ferritin level was a significant and independent determinant of serum 8-OHdG, and serum ferritin correlated significantly with the total dose of iron supplementation during the 6-month period of the study. In the nine patients, without iron supplementation, serum 8-OHdG levels, as well as serum ferritin, decreased significantly during follow-up.

CONCLUSIONS

Our results suggest that increased iron storage may induce DNA oxidative injury in patients on regular HD, and that the serum ferritin level is a surrogate marker for this pathological condition.

Effects of oral vitamin C supplementation on oxidative stress and inflammation status in haemodialysis patients

BACKGROUND

There is increasing evidence for the presence of oxidative stress and vitamin C deficiency in dialysis patients. Limited data, however, are available regarding the effects of vitamin C supplementation on oxidative stress and inflammation markers in such patients.

METHODS

We ran a prospective, randomized, open-label trial to assess the effects of oral vitamin C supplementation (250 mg three times per week) for 2 months on well-defined oxidative and inflammatory markers in 33 chronic haemodialysis (HD) patients.

RESULTS

Normalization of plasma total vitamin C and ascorbate levels by oral vitamin C supplementation did not modify plasma levels of carbonyls, C-reactive protein and albumin, or erythrocyte concentrations of reduced and oxidized glutathione.

CONCLUSION

Short-term oral vitamin C supplementation did not modify well-defined oxidative/antioxidative stress and inflammation markers in HD patients. Whether a higher oral dose or the intravenous route can modify these markers remains to be determined.

[Significance of serum oxidative stress related markers and genotype of GST gene in the pathogeneses of primary biliary cirrhosis]

The studies using an immunohistological technique revealed that overexpression of oxidative stress-related substance such as HNE was observed in the liver of primary biliary cirrhosis patients. These data suggested that oxidative stress participated in the pathogenesis of primary biliary cirrhosis. Therefore we analyzed serum oxdative stress marker (8-OHdG) and anti oxidative substances (Mn-SOD and TRX) to evaluate their clinical significance. In addition we analyzed the genotype of anti oxidative substance GST that has been reported to relate susceptibility of autoimmune disease. Serum levels of 8-OHdG, Mn-SOD and TRX in PBC patients were significantly higher than those of healthy subjects (P<0.001). Though there was no relation between serum level of 8-OHdG and clinical data, positive correlation between serum level of Mn-SOD, TRX and serum level of ALP, IgM was observed. Positive correlation was also observed between serum level of Mn-SOD and TRX. Serum levels of Mn-SOD of patients who responded to UDCA therapy were significantly higher than those of patients who did not response to therapy (P<0.01). Although genotypic difference of GSTM1 and GSTT1 by peripheral blood mononuclear cells did not relate to susceptibility of PBC, serum titer of AMA of GSTM1 null and GSTT1 null patients were significantly higher than those of GSTM1 positive and/or GSTT1 positive patients (P< 0.05). These findings suggest that serum oxidative stress-related markers may reflect the extent of liver damage of PBC, and may relate to the efficacy of UDCA therapy on PBC. It also made clear that genotype of GST related to the titer of AMA.

Vitamin C plasma level and response to erythropoietin in patients on maintenance haemodialysis

BACKGROUND

Intravenous vitamin C supplementation to haemodialysis patients might ameliorate responsiveness to recombinant human erythropoietin (rHuEpo). This study was performed to analyse the relation between vitamin C plasma concentration and response to rHuEpo.

METHODS

In a cross-sectional, single-centre observational study including all haemodialysis patients, pre-dialysis plasma vitamin C concentrations were measured by high-performance liquid chromatography and response to rHuEpo (haemoglobin concentration/international units rHuEpo/kg/week) was recorded together with baseline laboratory data.

RESULTS

Univariate analysis yielded a significant correlation between vitamin C plasma levels and response to rHuEpo (n = 130, r = 0.25, P = 0.004), which still persisted after adjustment for transferrin saturation, C-reactive protein, malondialdehyde, parathyroid hormone, route of rHuEpo administration, residual renal function and diabetes mellitus (adjusted r = 0.23, P = 0.014). Analysis per quartiles of vitamin C plasma level revealed a significantly lower response to rHuEpo with decreasing vitamin C values (P = 0.026).

CONCLUSIONS

In unselected haemodialysis patients, vitamin C plasma levels account, at least partially, for the response to rHuEpo. Larger-sized interventional studies are needed to find out whether vitamin C plasma levels may or may not appropriately reflect the potential beneficial effect of vitamin C supplements on rHuEpo responsiveness.