Caroline Mercer

Plasma Glutathione Peroxidase Activity Is Reduced in Haemodialysis Patients

Cardiovascular disease is the major cause of morbidity and mortality in patients with end-stage renal failure. Increased free radical production and antioxidant depletion may contribute to the greatly increased risk of atherosclerosis in these patients. Glutathione peroxidase (GPX) is an important antioxidant, the plasma form of which is synthesized mainly in the kidney (eGPX). The aim of this study was to assess the activity of eGPX in patients with end-stage renal failure on haemodialysis. Venous blood was collected from 87 haemodialysis patients immediately prior to and after dialysis and from 70 healthy controls. Serum eGPX activity was measured using hydrogen peroxide as substrate and immunoreactivity determined by ELISA. eGPX activity was significantly reduced in dialysis patients when compared to controls (106 ± 2.7 and 281 ± 3.6 U/l respectively, p < 0.001). Following haemodialysis, eGPX activity rose significantly to 146 ± 3.8 U/l, p < 0.001, although remaining below control values (p < 0.005). Immunoreactive eGPX, however, was similar in all groups (pre-dialysis 14.10 ± 1.26 µg/ml, post-dialysis 14.58 ± 1.35 µg/ml, controls 15.20 ± 1.62 µg/ml, p = NS). A decrease was observed in the specific activity of eGPX in patients when compared to controls (8.81 ± 1.14, 10.71 ± 1.54 and 21.97 ± 1.68 U/mg respectively, p < 0.0001). eGPX activity is impaired in patients undergoing haemodialysis and so may contribute to atherogenesis in renal failure.

Very low density lipoprotein subfractions in Type II diabetes mellitus: alterations in composition and susceptibility to oxidation

Aims/hypothesis. Type II (non-insulin-dependent) diabetes mellitus is associated with raised triglycerides and increased very low density lipoprotein cholesterol. The aim of this study was to assess if very low density lipoprotein subfraction composition and potential to oxidise were altered in this condition.¶Methods. Very low density lipoprotein was separated into four subfractions (A→D) by a novel, rapid ultracentrifugation procedure. Analysis of each subfraction included lipid and fatty acid composition. Preformed peroxides were measured spectrophotometrically and conjugated dienes were used as an indicator of in vitro lipid oxidation.¶Results. In all results we compared patient and control subfractions. Mean fasting plasma glucose was 8.9 ± 2.0 mmol/l in patients vs 5.1 ± 0.4 mmol/l in control subjects (p < 0.001); patient HbA1 c was 7.6 ± 1.4 %. Patient total lipid standardised for apo B was higher than controls in subfractions A, B and C; A, 201 vs 60; B, 191 vs 40; C, 63 vs 21; D, 29 vs 34 μmol lipid per mg apo B (p < 0.05). Preformed peroxides were higher in all patient subfractions compared with controls: A, 340 vs 48; B, 346 vs 42; C, 262 vs 28; D, 54 vs 16 nmol per mg apo B (p < 0.001). Patient subfractions A and D were more susceptible to in vitro oxidation. Monounsaturated fatty acids were lower in patients subfractions, 35.2 vs 36.7; B, 35.1 vs 38.7; C, 34.4 vs 36.5; D, 33.0 vs 35.5 as per cent total (p < 0.05).¶Conclusions/interpretation. These results indicate abnormalities in very low density lipoprotein subfraction composition and oxidation profile in Type II diabetic subjects, which are characteristic of more atherogenic particles and that may contribute to the development of cardiovascular disease in these patients. [Diabetologia (2000) 43: 485–493]

Alcohol increases homocysteine and reduces B vitamin concentration in healthy male volunteers—a randomized, crossover intervention study

BACKGROUND Few studies have examined the effect of alcohol consumption on total homocysteine (tHcy) concentrations. AIM To assess the effect of an 8-week intervention with vodka or red wine on plasma tHcy and B vitamin concentrations in healthy male volunteers. To assess the effect on tHcy according to methylenetetrahydrofolate reductase (MTHFR) 677C>T genotype. DESIGN AND METHODS A randomized controlled crossover intervention study measuring tHcy and serum folate and vitamin B(12) concentrations was conducted in 78 male subjects (21-70 years). Following a 2-week washout period during which no alcohol was consumed, all subjects consumed 24 g alcohol (either 240 ml red wine or 80 ml vodka)/day for a 2-week period. Following a further 2-week washout, participants consumed the alternate intervention for 2 weeks. RESULTS A significant increase in plasma tHcy was observed after the 2-week red wine intervention (5%, P = 0.03), and a non-significant increase in tHcy with vodka intervention (3%, P = 0.09). When the two interventions were compared, the change in tHcy did not differ between the vodka and red wine interventions (P = 0.57). There were significant decreases in serum vitamin B(12) and folate concentrations, and this decrease did not differ between interventions. The increase in tHcy observed in both interventions did not vary by MTHFR 677C>T genotype. CONCLUSION A 2-week alcohol intervention resulted in a decrease in folate and vitamin B(12) status and an increase in plasma tHcy. The effect of alcohol intervention on tHcy, folate and vitamin B(12) concentrations did not differ between the red wine and vodka intervention groups.

C-reactive protein (CRP) elevation in patients with abdominal aortic aneurysm is independent of the most important CRP genetic polymorphism

OBJECTIVE C-reactive protein (CRP) is a marker of cardiovascular disease. The objective was to determine if abdominal aortic aneurysm (AAA) and CRP serum concentration and its CRP gene are associated. METHODS AND RESULTS AAA patients and AAA negative controls were recruited. CRP concentration was measured and the single nucleotide polymorphism (SNP), rs3091244, assessed. AAA cases were divided into those measuring 30-55 mm and >55 mm in diameter, to assess correlation of CRP with AAA size. A total of 248 (227 male) cases and 400 (388 male) controls were included. CRP concentration was higher in cases (385.0 microl/dL [310.4-442.8] vs 180.3 microl/dL [168.1-196.9]; P < .0001). It was higher in large aneurysms (685.7 microl/dL [511.8-1083.0] vs 291.0 microl/dL [223.6-349.6]; P < .0001), with significant correlation observed to size (r = 0.37, P < .0001). CC was the most common SNP genotype with no difference in distribution (P = .43) between cases and controls. No difference existed in CRP for each genotype in the overall cohort (P = .17), cases (P = .18) and controls (P = .19). CONCLUSION The results demonstrate that CRP production may be related to the presence of AAA, especially in advanced disease. The serum concentration of CRP does not appear to be influenced by the functional SNP of the CRP gene, which also appears to have no association with AAA formation.

The ferroxidase activity of caeruloplasmin is reduced in haemodialysis patients.

Increased free-radical production leading to oxidative stress may contribute to the development of cardiovascular complications in haemodialysis patients. The ferroxidase activity of caeruloplasmin forms an important component of antioxidant defences in body fluids. The aim of this study was to assess ferroxidase activity in haemodialysis patients. Venous blood was collected from 83 haemodialysis patients immediately prior to and after dialysis and from 52 healthy controls. Immunoreactive caeruloplasmin was measured by rate nephelometry, and ferroxidase activity determined by measuring loading of ferrous iron onto iron-free transferrin. A significant reduction in ferroxidase activity was observed in dialysis patients when compared with controls (37 ± 1.20 and 46 ± 1.14 mU/l, respectively; p < 0.001). Following dialysis, ferroxidase activity rose significantly to 41 ± 1.16 mU/l, with a significant difference still remaining between control and patient ferroxidase activity (p < 0.005). Immunoreactive caeruloplasmin was found to be similar in all groups (before dialysis 0.40 ± 0.07 g/l, after dialysis 0.39 ± 0.07 g/l, control 0.42 ± 0.09 g/l: p = NS). A significant difference in caeruloplasmin-specific activity was therefore observed between predialysis, postdialysis and control samples (97 ± 2.31, 105 ± 1.74 and 112 ± 1.51 mU/g; p < 0.001, p < 0.01, respectively). Ferroxidase activity of caeruloplasmin is impaired in renal failure. Inhibition of caeruloplasmin ferroxidase activity in dialysis patients may contribute to increased oxidative stress in these patients.

Plasma free fatty acid patterns and their relationship with CVD risk in a male middle-aged population

Background/Objectives:The role of individual fatty acids in the development of cardiovascular disease (CVD) is well established, but the effects of an overall pattern of fatty acids in CVD risk has yet to be elucidated. Circulating fatty acid levels are related to metabolic disturbances associated with the metabolic syndrome and CVD, due to disturbances in the activity of enzymes that catalyse fatty acid desaturation (Δ-desaturases). Therefore, we determined patterns of fatty acids and estimated desaturase activity in plasma and analysed how these patterns were related to a 10-year CVD risk estimates in a middle-aged male population in Northern Ireland.Subjects/Methods:Principal components analysis (PCA) was performed for defining fatty acid patterns in 379 men aged 30–49 years. Logistic regression analyses were then carried out for analysing the relationship between these fatty acid patterns and the 10-year CVD risk estimates.Results:The PCA generated three high fatty acid patterns: high saturated fatty acid (SFA), high omega 3 fatty acid (omega 3) and high monosaturated fatty acid (MNFA). Results from logistic regression analyses show that a 1 s.d. increase in the SFA pattern score was significantly and positively associated with an increase in the 10-year CVD risk category (odds ratio 1.71, 95% confidence interval 1.33–2.21, P<0.0001) even after adjustment for lifestyle factors. There were no significant relationships between the other two pattern scores and the 10-year CVD risk.Conclusions:An unhealthy fatty acid pattern representing both dietary intake and in vivo fatty acid metabolism is related to the 10-year CVD risk estimates and provide evidence that, as with dietary patterns, the synergistic effect of multiple fatty acids may be more important in relation to the development of CVD risk.

The Influence of COX-2 Single Nucleotide Polymorphisms on Abdominal Aortic Aneurysm Development and the Associated Inflammation

Introduction: Cyclooxygenase (COX)-2 influences cardiovascular disease and serum concentration of high-sensitivity C-reactive protein (hsCRP). The study purpose was to determine the influence of single nucleotide polymorphisms (SNPs) of the COX-2 gene on abdominal aortic aneurysm (AAA) development and serum hsCRP concentrations. Patients and Methods: Patients with AAA and disease-free controls were recruited. High-sensitivity C-reactive protein was measured by an enzyme-linked immunosorbent assay (ELISA) test. The distributions of COX-2 SNPs were investigated (rs20417 and rs4648307). The influence of the COX-2 SNPs on the hsCRP serum concentration was assessed.Results: A total of 230 patients with AAA and 279 controls were included. No difference was found in the genotype distribution of the COX-2 SNPs rs20417 (P = .26) and rs4648307 (P = .90). They did not influence the hsCRP concentration (P = .24 and P = .61, respectively). Haplotype analysis of COX-2 SNPs revealed no difference. Conclusion: These COX-2 SNPs do not play any role in AAA development and do not influence serum hsCRP. These results differentiate AAA development from atherosclerotic diseases.