S. L. Nuttall

Oxidative stress and normal pregnancy

objective To determine whether, in normal pregnancies, there is evidence of oxidative stress that is related to the lipid changes observed in pregnancy.

Changes in plasma lipids and markers of oxidative stress in normal pregnancy and pregnancies complicated by diabetes

The purpose of the present study was to determine changes in plasma lipids and markers of oxidative stress longitudinally in pregnancy complicated by diabetes compared with non-diabetic pregnancy. This was carried out by following a group of normal pregnant women (n=17) and groups of pregnant women with Type I diabetes (n=19), Type II diabetes (n=12) and gestational diabetes mellitus (n=12) throughout pregnancy, with sampling carried out at the end of each trimester. Serum total cholesterol and triacylglycerols (triglycerides) were determined using standard colorimetric techniques and low-density lipoprotein (LDL) subfraction profile by disc PAGE. Total antioxidant capacity (TAC) was determined by enhanced chemiluminescence and lipid hydroperoxides by the ferrous oxidation of Xylenol Orange method. Total cholesterol and triacylglycerols increased significantly throughout pregnancy in all groups, but there were no significant differences between normal and diabetic women with respect to either. The LDL score was significantly higher (P<0.001) in diabetic women compared with normal women at each point throughout pregnancy, although there were no significant differences between the diabetic groups. There was evidence of greater oxidative stress in diabetic compared with normal women throughout. Corrected TAC was significantly lower (P<0.001) in all diabetic women throughout pregnancy. In addition, lipid hydroperoxides were higher in all diabetic compared with normal women, particularly so in those with Type II diabetes (P<0.05). These changes may have important implications for diabetic women during pregnancy, as an elevated risk of pre-eclampsia is thought to reflect an oxidative stress-related mechanism. In addition, these changes may have important implications for the development of atherosclerosis and the long-term cardiovascular health of women with diabetes.

An evaluation of the antioxidant activity of a standardized grape seed extract, Leucoselect®

Coronary Artery Disease (CAD) remains the major cause of mortality and morbidity in the Western World. The oxidation of low‐density lipoproteins (LDLs) by free radicals is associated with initiation of atherosclerosis and therefore, development of CAD. LDLs are protected from oxidation by antioxidants and in times of antioxidant deficiency are more likely to be oxidized. Hypercholesterolaemic patients are at a higher cardiovascular risk and may, therefore, require more antioxidant protection. Increased consumption of red wine containing antioxidants is thought to account for the lower incidence of CAD in Mediterranean countries. Red wine, although rich in antioxidants, is not suitable as routine therapy for prevention of CAD. Objective: To evaluate the effects of a capsule formulation of an antioxidant polyphenolic extract of grapes on serum total antioxidant activity and vitamin C and E levels. Method: A single‐blinded randomised, placebo‐controlled cross‐over study was undertaken in 20 young volunteers. Subjects were given two capsules containing 300 mg of grape procyanidin extracts (Leucoselect™‐phytosome®) or placebo daily for 5 days. Blood samples were taken at the start of the study and end of the study and assayed for antioxidant activity and vitamins C and E levels. After a washout period of at least 2 weeks, the study was repeated with the second treatment. Results: The extract had no effect on serum vitamins C and E levels but increased serum total antioxidant activity (TAC). On day 5, TAC increased from 408·1±22·9 to 453·3±453·3 μmol/l trolox equivalents 1 hour postdose. Conclusion: The capsules increased serum antioxidant activity but the longer‐term clinical implications need to be assessed in further randomised clinical trials

Glutathione: in sickness and in health

There is increasing evidence that free radical damage may be an important cause of some of the adverse effects of disease and advancing age. Much of the clinical evidence to support this hypothesis is based on the protective effect sometimes observed in those on diets high in antioxidants and those given antioxidants therapeutically. Further support would be obtained if plasma markers for oxidative damage such as lipid peroxidation products (lipid hydroperoxide [LHP]) were raised and antioxidants such as glutathione were low in the old and the sick, particularly in those who are acutely and severely ill. We have therefore measured plasma glutathione and LHP in healthy young individuals, healthy older individuals, and two groups of elderly patients, one with chronic ill-health attending outpatients and one acutely ill and in hospital. We studied 66 young healthy volunteers (mean 24· 5 [SD 4· 7] years) and 58 community-based healthy elderly individuals (70· 7 [4· 8] years). Health was defined as an absence of major medical or surgical illness in the previous 5 years, no hospital admissions, no current medication, and a subjective perception of good health. We also studied 49 patients attending general medical clinics (75· 7 [8· 3] years) with a variety of chronic illnesses including ischaemic heart disease, arthritis, diabetes, and hypertension. Finally, 47 hospitalised elderly patients (77· 2 [8· 6] years) were studied during the course of an acute illness within the first week of admission. Non-fasting venous blood was sampled into standard edetic acid (glutathione) and lithium heparin (LHP) tubes. Samples were all taken by one person (SN) and care was taken to minimise haemolysis. They were centrifuged immediately at 3500 rpm, 4oC for 15 min, and plasma stored at -80oC until analysis. Plasma for glutathione was pre-treated with 30% perchloric acid to stabilise thiol groups. Total plasma glutathione was determined by enzyme-rate assay and plasma LHP by ferrous oxidation of xylenol orange. A sample size of at least 47 in each group was needed to detect a 20% change in plasma glutathione with 80% power at the 95% confidence limit. Statistical difference between groups was determined by ANOVA and the level of significance taken as p<0· 05. The results are presented in the figure. The plasma glutathione in young healthy adults was 0· 54 (SE 0· 02) μmol/L. In the healthy elderly glutathione was significantly lower (0· 29 [0· 01] μmol/L, p<0· 0001). The age-adjusted values for elderly outpatients were significantly lower than in the healthy elderly (0· 24 [0· 01] μmol/L, p<0· 0001) and values for elderly inpatients were lower than for elderly outpatients (0· 17 [0· 01] μmol/L, p<0· 01). The marker for oxidative damage, LHP, was low in the healthy young adults (2· 14 [0· 17] μmol/L) and higher in the healthy elderly (3· 14 [0· 20] μmol/L, p<0· 01). It was higher in the sick elderly (8· 51 [0· 66] and 8· 84 [0· 63] μmol/L in outpatients and inpatients, respectively [p<0· 0001 compared with healthy elderly]).

Oxidative stress in malignant and non-malignant phase hypertension

Malignant hypertension (MHT) is a rare and severe form of hypertension characterised by arteriolar necrosis and severe vascular damage, leading to stroke, myocardial infarction and death. We hypothesised that in addition to endothelial damage, MHT may be associated with increased oxidative stress. Lipid hydroperoxides (LHP, an index of oxidative damage) and plasma von Willebrand factor (vWf, an index of endothelial damage/dysfunction) were measured in 16 patients with MHT and compared with 16 non-malignant essential hypertensives and 32 normotensive controls. vWf was greater in MHT (mean 117 iU/dL) than in non-malignant hypertensives (97 iU/dL) or normotensive controls (100 iU/dL) (ANOVA P = 0.017). However, although LHP were greater in MHT (mean 10.6 μmol/L) than in normotensives (4.5 μmol/L, P < 0.001), the levels in MHT were similar to those in non-malignant hypertension (12.3 μmol/L). In conclusion endothelial damage (raised vWf) was more evident in MHT compared with both normotensive controls and with non-malignant hypertension, whilst oxidative stress (raised LHP) was increased to a similar extent in both hypertension groups when compared with normotensive controls. These observations raise the possibility abnormal oxidative stress is probably not the mechanism responsible for the endothelial damage seen in malignant phase hypertension.

The impact of therapeutic doses of paracetamol on serum total antioxidant capacity

Introduction:  A link between regular paracetamol intake and asthma in adults has recently been postulated. Detoxification of paracetamol may deplete stores of glutathione, which is one of the major antioxidants present in the lung. A reduced source of glutathione in the lung may lead to increased oxidative damage to the epithelium and hence increased frequency and severity of asthma attacks in susceptible individuals.

Impaired endothelial function in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) patients suffer from excess cardiac deaths due to accelerated atherosclerosis. Endothelial dysfunction is a marker of early atherosclerosis. We tested the hypothesis that SLE patients have impaired endothelial function and assessed the relationship between endothelial function and clinical outcome over the subsequent five years. Thirty-six female SLE patients were compared with 22 healthy age and sex matched controls. Endothelial dependent vasodilatation (EDD) was assessed at the brachial artery in response to shear stress. Endotheliumindependent dilatation induced by glyceryl trinitrate was also measured. Patients were followed for up to five years and the development of damage in the cardiovascular and other systems recorded. SLE patients showed significantly impaired endothelial function (median EDD 5.6%, IQR 3.1–7.2%) compared with healthy controls (median EDD 8.0%, IQR 6.3–9.3%; P = 0.001). Endothelium independent dilatation did not differ between the two groups. Endothelial function was significantly worse in postmenopausal compared with premenopausal women (median EDD 6.6%, IQR 3.9–7.8% versus 3.1%, IQR 2.6–5.1%; P = 0.016). Total cholesterol was inversely correlated with endothelial function in SLE patients (Spearman correlation r = -0.422, P = 0.025). There was no relationship between endothelial function and the development of damage in any organ system, including the cardiovascular system during patient follow-up. Patients with SLE have impaired endothelial function. In the small number of patients studied impaired endothelial function was not associated with a worse cardiovascular outcome over five years.

Cross-sectional analysis of abnormalities of mineral homeostasis, vitamin D and parathyroid hormone in a cohort of pre-dialysis patients. The chronic renal impairment in Birmingham (CRIB) study.

Background: Disturbances in mineral and vitamin D metabolism, which affect parathyroid hormone (PTH) synthesis, are well recognized in patients receiving dialysis. However, it is unclear at what stage of chronic kidney disease (CKD) these abnormalities develop. Methods: The associations between CKD stages 3 and 5, and alterations of calcium, phosphate, vitamin D and PTH concentrations were assessed in 249 patients (mean age 61 years, 66% male) and 79 age- and sex-matched healthy controls. Results: As compared to controls, serum phosphate concentrations were elevated among CKD patients (1.40 vs. 1.11 mmol/l; p < 0.0001). And levels of both 25-hydroxyvitamin D (42.1 vs. 60.4 nmol/l; p < 0.0001) and 1,25-dihydroxyvitamin D (58.2 vs. 119.5 pmol/l; p < 0.0001) were lower among patients with CKD, even among those with only stage 3 CKD and despite 73% of patients receiving vitamin D supplements. The ratio of 1,25-dihydroxy- to 25-hydroxyvitamin D was lower than controls, even among patients with stage 3 CKD (p = 0.0001), and this ratio diminished with advancing renal impairment. Concomitant elevations were observed in intact PTH (13.8 vs. 4.2 pmol/l; p < 0.0001) and whole PTH (7.9 vs. 2.7 pmol/l; p < 0.0001). Conclusion: Impaired conversion of 25-hydroxy- to 1,25-dihydroxyvitamin D is an early feature of renal disease, and progresses as renal function deteriorates.

A comparison of the β1-selectivity of three β1-selective β-blockers

Objective: To determine the relative β1‐selectivity of three β‐blockers (nebivolol, bisoprolol and atenolol), administered orally at normal therapeutic doses, by assessing their impact on the β2‐mediated, haemodynamic and biochemical responses to a terbutaline infusion, which decreases serum potassium and increases serum glucose and insulin.

Anti-oxidative properties of beta-blockers and angiotensin-converting enzyme inhibitors in congestive heart failure.

Chronic elevation of plasma catecholamines and sympathetic stimulation in chronic heart failure (CHF) leads to increased production of free radicals, and so possibly to endothelial damage/dysfunction and atheroma formation. Abnormal oxidative stress may therefore be related to some of the high mortality and morbidity in CHF. The objective of the present prospective open study was to compare the effects of β‐blockers and ACE inhibitors in relation to oxidative stress and endothelial damage in CHF.