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Biomedical subjects

V Burke

Publications and source records attributed to V Burke.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effects of regular ingestion of black tea on haemostasis and cell adhesion molecules in humans.

OBJECTIVE: To assess the effects in humans of regular ingestion of black tea on haemostasis-related variables and cell adhesion molecules. DESIGN: Twenty-two subjects were recruited from the general population to a randomised-controlled crossover study. Subjects stopped drinking tea, apart from that provided, for the duration of the study. During a 4-week baseline period all subjects drank 5 cups/day (250 ml) of hot water. The effects of 5 cups/day of black tea for 4 weeks were then compared with hot water. Platelet aggregation in response to three doses of collagen and ADP, plasma concentrations of coagulation and fibrinolytic factors (fibrinogen, factor VII, tPA, PAI-1) and plasma concentrations of cell adhesion molecules (soluble P-selectin, E-selectin, ICAM-1, VCAM-1) were assessed twice, one week apart, at the end of each period. Twenty-four hour urinary concentration of 4-O-methylgallic acid (4OMGA), assessed once at the end of each period, was used as a marker of black tea polyphenol intake. RESULTS: The 24 h urinary excretion of 4OMGA was increased during regular ingestion of black tea in comparison to hot water (P<0.0001). Black tea resulted in lower soluble P-selectin (P=0.01) in comparison to hot water, but did not influence other adhesion molecules. Soluble P-selectin was significantly correlated with mean collagen-stimulated platelet aggregation at baseline (r=0.61, P=0.003), and during regular ingestion of hot water (r=0.70, P<0.0001) and black tea (r=0.51, P=0.01). However, platelet aggregation was not different between the black tea and hot water periods for collagen- or ADP-stimulated aggregation at any dose. Coagulation and fibrinolytic factors were also not different between periods. CONCLUSIONS: The effect of black tea on soluble P-selectin provides a potential mechanism for cardiovascular benefits of regular ingestion of tea. SPONSORSHIP: This study was supported by grants from the Tea Trade Health Research Association and the National Heart Foundation of Australia.

Adult↗
PubMed2001

Family lifestyle and parental body mass index as predictors of body mass index in Australian children: a longitudinal study.

OBJECTIVE: To investigate associations between body mass index (BMI) and family characteristics, including lifestyle, in parents and offspring from Australian families. DESIGN AND SUBJECTS: Longitudinal survey of 219 families of Australian children who had been surveyed 3-yearly between the ages of 9 and 18 y. MEASUREMENTS: Socio-economic status, weight and height, diet from 3 day records or food frequency questionnaires, alcohol consumption, smoking habits and physical fitness in offspring (bicycle ergometry in 18-y-olds). RESULTS: In 18-y-olds, in models examining offspring's lifestyle variables, BMI was predicted negatively by physical fitness (P=0.012), and positively by alcohol intake (P=0.046) in sons while, in daughters, only a negative association with physical fitness was significant. In models including parental characteristics, BMI in 18-y-old sons and daughters was significantly predicted by mothers' and fathers' BMI, independently of offsprings' alcohol intake, smoking, physical fitness and parents' education, and, in daughters, by fathers' alcohol intake. These models explained 48% of variance in daughters and 33% in sons. In both sons and daughters, BMI over the 9 y of the survey was consistently higher in offspring with overweight or obese fathers (P=0.033 for sons, P=0.024 for daughters) or mothers (P=0.031 for sons, P=0.037 for daughters). Physical fitness at the ages of 12, 15 and 18 y was negatively related to fathers' obesity in daughters and mothers' obesity in sons. Obesity in fathers was associated with a four-fold increase in risk of obesity at the age of 18 y in both sons and daughters with an independent eight-fold increase in risk for daughters if mothers were obese. Birthweight was unrelated to overweight or obesity in the 18-y-olds. Alcohol intake in sons related significantly to alcohol intake in either parent while, for daughters, there was a significant association only with fathers' alcohol consumption. In daughters, fat intake was positively associated with fat intake score in both fathers and mothers. CONCLUSION: Parental overweight or obesity may identify children at risk for a range of unhealthy behaviours. Promotion of a healthy lifestyle targeting overweight families, particularly in lower socio-economic groups, should be a priority.

Adolescent↗
PubMed2001

Recent developments concerning diet and hypertension.

1. Recent data from randomized controlled dietary trials have shown blood pressure-lowering effects of foodstuffs and dietary patterns to be of practical importance for both individual and population blood pressure control. 2. The salient studies include Dietary Approaches to Stop Hypertension (DASH) trials, on complex dietary patterns and of additive effects of salt restriction, Trial of Nonpharmacologic Interventions in the Elderly (TONE), on weight control and sodium restriction as substitutes for drug therapy, and two Australian trials showing additive effects of dietary fish and weight control and of dietary protein and fibre in treated hypertensives. 3. Regular coffee drinking raised blood pressure in older hypertensives, whereas potential antihypertensive effects of dietary anti-oxidants require further scrutiny.

Animals↗
PubMed2001

Coffee and coronary heart disease.

BACKGROUND: The role of coffee consumption in the onset of myocardial infarction remains uncertain. A review of published reports showed that although cohort data suggest very little excess risk of coronary heart disease among habitual coffee drinkers, case-control data suggest an excess risk of the order of 60% for people drinking five or more cups per day. METHODS: We obtained as much information as possible on the lifestyle and habits, including coffee consumption, of people admitted with chest pain to the Coronary Care Unit at the Royal Perth Hospital, Australia. A questionnaire was given to them by the attending nursing staff. Details were recorded by the patient, often with help from the nursing staff. A similar questionnaire was completed by patients attending the Cardiology Outpatient Clinic. RESULTS: One of the outstanding differences between the 182 patients with myocardial infarction or unstable angina and 185 patients with chronic stable coronary heart disease who filled in forms while waiting in the Cardiology Outpatient Clinic was that more people with acute coronary syndromes were drinking in excess of five cups of coffee per day (18 vs 7.5%; P = 0.003). In logistic regression analysis adjusted for age, smoking status (past and current), hypertension, dyslipidaemia and diabetes, the odds ratio was 2.51 (95% CI 1.43,4.43; P = 0.021). CONCLUSION: The present case-control study provides evidence for an increased risk of myocardial infarction or unstable angina among individuals drinking more than five cups of coffee per day.

Journal Article↗
PubMed2001

Non pharmacologic therapy and lifestyle factors in hypertension.

Lifestyle factors are now recognised to be key determinants of both the rise in blood pressure with ageing and the cardiovascular disease associated with essential hypertension. This paper summarises recent evidence for independent or additive effects of different aspects of diet and behavioural factors on blood pressure levels and some related cardiovascular risk factors. The influence of single nutrients, fats, fibre, protein, antioxidants, caffeine, complex dietary patterns, physical activity, alcohol and smoking will be considered against a background of obesity and psychological factors contributing to blood pressure elevation.

Blood Pressure↗
PubMed2001

Angiotensin-converting enzyme activity and the ACE Alu polymorphism in autosomal dominant polycystic kidney disease.

BACKGROUND: Previous studies concerning Alu I/D polymorphism in the ACE gene and ADPKD severity have used the Alu genotypes as a representative of the true biological variable, namely ACE activity. However, wide individual and ethnic differences in the proportion of variance in ACE activity explained by the I/D genotype may have confounded these studies. This investigation examines the association between ADPKD severity and ACE in terms of plasma enzyme activity and I/D genotypes in individuals from three different countries. METHODS: Blood samples were collected from 307 ADPKD patients (116 Australian, 124 Bulgarian and 67 Polish) for determination of ACE activity levels and I/D genotypes. Chronic renal failure (CRF) was present in 117 patients and end-stage renal failure (ESRF) in 68 patients. RESULTS: ACE activity was related to the I/D genotype, showing a dosage effect of the D allele (P=0.006). The proportion of variance due to the Alu polymorphism was 14%. No difference in ACE activity and I/D genotype distribution was found between patients with CRF versus normal renal function (P=0.494; P=0.576) or between those with ESRF versus those without ESRF (P=0.872; P=0.825). No effect of the I/D genotype on age at development and progression to renal failure (CRF; ESRF) was detected in the overall group, and in subgroups based on ethnic origin, linkage status and sex. CONCLUSION: ACE is not likely to play a role as a determinant of ADPKD phenotype severity.

Adolescent↗
PubMed2001

Long-term predictors of coronary artery disease and mortality in type 1 diabetes.

We assessed clinical and biochemical predictors of death and/or cardiovascular disease in 147 type 1 diabetes mellitus (DM) patients followed-up for 14 years. At follow-up, 28 of patients (19%) had died, and 25 patients (18%) had developed or died of coronary artery disease (CAD). At baseline, those who died had significantly higher serum creatinine (p=0.001) and urine albumin/creatinine ratio (p=0.016), greater prevalence of retinopathy (p=0.006), lower serum apolipoprotein A1 (p=0.046), and lower daily insulin dose (p=0.024) than those who survived. CAD patients had a longer duration of diabetes (p<0.001), were older at the onset of diabetes and at presentation (p=0.001), and had higher prevalences of retinopathy (p=0.005) and neuropathy (p=0.016). The CAD group also had higher baseline serum creatinine (p=0.02), lower HDL cholesterol (p=0.004) and apolipoprotein A1 (p=0.007) and higher LDL cholesterol (p=0.028) and apolipoprotein B concentrations (p=0.027). Under logistic regression analysis (adjusted for age and sex), baseline urine albumin/creatinine ratio (p=0.003), presence of retinopathy (p=0.004), serum creatinine (p=0.028), and serum urea (p=0.034) were the most powerful predictors of mortality, while duration of diabetes (p<0.0001), baseline HDL cholesterol (p=0.012), serum creatinine (p=0.02), apolipoprotein B (p=0.038), LDL cholesterol (p=0.039), and systolic blood pressure (p=0.055) were the strongest predictors of CAD. These findings emphasize the role of abnormal lipoprotein metabolism in the development of CAD in type 1 DM. Indicators of renal impairment and the presence of retinopathy seem to be of greater importance in predicting overall mortality.

Adult↗
PubMed2001

Tracking of blood pressure in Australian children.

OBJECTIVE: Tracking of blood pressure (BP) from childhood occurs in populations but, for individuals, prediction of adult BP from childhood levels is poor. We examined factors that may influence tracking of BP to identify better predictors of higher BP in early adult life. DESIGN: A prospective study of children recruited at the age of 9 years by random sampling of Perth metropolitan schools stratified by socio-economic status. SETTING: Community based with re-surveys 3-yearly for 9 years. PARTICIPANTS: A total of 516 boys and 520 girls at 9 years; 680 boys and 630 girls at 12 years; 318 boys and 300 girls at 15 years; 330 men and 326 women at 18 years. MAIN OUTCOME MEASURES: Systolic (SBP) and diastolic (DBP) BP. RESULTS: Persistence in the highest quartile for SBP between surveys was seen in 34-48% of subjects and in 37% between the ages of 9 and 18 years. The proportion increased to around 60% in those in the highest quartile for body mass index (BMI), to 70% in those in the highest quartile for change in BMI and to 60% if there was a family history of hypertension. In log-linear models, persistence in a quartile for SBP was significantly related to a family history of hypertension, previous SBP, BMI and change in BMI. Relationships were similar for DBP. CONCLUSIONS: Excessive weight gain in adolescence and a family history of hypertension substantially increase the risk of higher BP persisting into early adult life. Recognition of children at risk would allow early intervention emphasizing weight control with potential long-term benefits.

Adolescent↗
PubMed2001

Long-term effects of exercise on blood pressure and lipids in healthy women aged 40-65 years: The Sedentary Women Exercise Adherence Trial (SWEAT).

OBJECTIVES: To evaluate the long-term effects of regular moderate or vigorous intensity exercise on blood pressure and blood lipids in previously sedentary older women. DESIGN: Subjects were randomly assigned to either a supervised centre-based (CB) or a minimally supervised home-based (HB) exercise program, initially for 6 months. Within each program, subjects were further randomized to exercise either at moderate (40-55% heart rate reserve, HRres) or vigorous intensity (65-80% HRres). After 6 months, all groups continued a HB moderate or vigorous exercise program for another 12 months. METHODS: Healthy, sedentary women (aged 40-65 years) (n = 126) were recruited from the community. Subjects exercised three times per week for 30 min. They were evaluated at baseline, 6, 12 and 18 months. RESULTS: There was a significant fall of 2.81 mmHg in systolic blood pressure (P = 0.049) and 2.70 mmHg in diastolic blood pressure (P = 0.004) after correction for age and baseline values with moderate exercise, but not with vigorous-intensity exercise. When this analysis was repeated with the change in body mass included, the results were unchanged. After correction for potential confounding factors, there was a significant fall in total cholesterol and low density lipoprotein cholesterol with vigorous but not moderate exercise at 6 months (P < 0.05) but not at 18 months. CONCLUSIONS: In this largely normotensive population of older women, a moderate, but not vigorous exercise program, achieved sustained falls in resting systolic and diastolic blood pressure over 18 months. The study demonstrates that, in older women, moderate intensity exercise is well accepted, sustainable long-term and has the health benefit of reduced blood pressure.

Adult↗
PubMed2001

Improved analysis of brachial artery ultrasound using a novel edge-detection software system.

Brachial artery ultrasound is commonly employed for noninvasive assessment of endothelial function. However, analysis is observer dependent and susceptible to errors. We describe studies on a computerized edge-detection and wall-tracking software program to allow more accurate and reproducible measurement. In study 1, three purpose-built Perspex phantom arteries, 3.00, 4.00, and 6.00 mm in diameter, were measured with the software. There was a mean bias of 11 microm (P < 0.001 at each level) between known and measured values; the mean resolving power of the software was estimated as 8.3 microm. In study 2, the mean intraobserver coefficient of variation of repeated measures of flow-mediated dilation (FMD) using the software (6.7%) was significantly lower than that for traditional manual measurements using the intima-lumen interfaces (24.8%, P < 0.05) and intima-media interfaces (32.5%, P < 0.05). In study 3, 24 healthy volunteers underwent repeat testing twice within 1 wk; the coefficients of variation for between-visit reproducibility of FMD and response to glyceryl trinitrate using the software were 14.7 and 17.6%, respectively. Assuming 80% power and an alpha of 0.05, eight subjects with matched controls would be required, in a parallel designed study, to detect an absolute 2.5% change in FMD. In summary, we have developed a semiautomated computerized vascular ultrasound analysis system that will improve the power of clinical intervention studies to detect small changes in arterial diameter.

Analysis of Variance↗
PubMed2001

Dietary protein and soluble fiber reduce ambulatory blood pressure in treated hypertensives.

In population studies, higher blood pressure has been associated with lower intake of protein and, possibly, lower fiber consumption. In the present randomized controlled trial, we sought to determine whether dietary protein and fiber had additive effects on blood pressure reduction in hypertensives. Treated hypertensive patients changed for 4 weeks (familiarization) to a diet low in protein (12.5% energy) and fiber (15 g/d). Patients (n=41) were then randomized to 1 of 4 groups in an 8-week factorial study of parallel design in which they continued the low-protein, low-fiber diet alone or had supplements of soy protein to increase protein intake to 25% energy, of psyllium to provide an additional 12 g soluble fiber/d, or of both protein and fiber. The 24-hour ambulatory blood pressure was compared from the end of familiarization to the end of intervention. In the 36 subjects who provided complete data, protein and fiber had significant additive effects to lower 24-hour and awake systolic blood pressure. Relative to control subjects, the net reduction in 24-hour systolic blood pressure was 5.9 mm Hg with fiber and with protein. Findings were independent of age, gender, and change in weight, alcohol intake, or urinary sodium and potassium. Relative to reduced fiber and protein intake, dietary protein and soluble fiber supplements lower blood pressure additively in hypertensives. These findings have important implications for the prevention and management of hypertension, particularly in populations in which high blood pressure is prevalent in association with diets low in protein, fiber, or both.

Blood Pressure↗
PubMed2000

Differential effects of eicosapentaenoic acid and docosahexaenoic acid on vascular reactivity of the forearm microcirculation in hyperlipidemic, overweight men.

BACKGROUND: Recent evidence supports differential effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the 2 major omega3 fatty acids of marine origin, on blood pressure in humans and vascular reactivity in adult spontaneously hypertensive rats. We investigated possible differences in the effects of purified EPA or DHA on forearm vascular reactivity in overweight hyperlipidemic men that might contribute to the blood pressure-lowering effects of fish oils. METHODS AND RESULTS: With a double-blind, placebo-controlled trial of parallel design, 59 overweight, mildly hyperlipidemic men were randomized to receive 4 g/d purified EPA, DHA, or olive oil (placebo) capsules while continuing their usual diets for 6 weeks. Forearm blood flow (FBF) was measured with venous occlusion, strain-gauge plethysmography during the sequential intra-arterial administration of acetylcholine (7.5, 15, and 30 microg/min), sodium nitroprusside (1.5, 3, and 10 microg/min), norepinephrine (10, 20, and 40 ng/min), a single-dose infusion of N:(G)-monomethyl-L-arginine (L-NMMA) (1 mg/min), and coinfusion of acetylcholine (7.5, 15, and 30 microg/min) and L-NMMA. Forty of the 56 subjects who completed the study underwent FBF measurements. Plasma phospholipid EPA levels increased significantly (P:<0.0001) after supplementation with EPA, and DHA composition increased with DHA supplementation (P:<0.0001). Relative to placebo, DHA, but not EPA, supplementation significantly improved FBF in response to acetylcholine infusion (P:=0.040) and coinfusion of acetylcholine with L-NMMA (P:=0.040). Infusion of L-NMMA alone showed no group differences. DHA significantly enhanced dilatory responses to sodium nitroprusside (P:<0.0001) and attenuated constrictor responses to norepinephrine (P:=0.017). CONCLUSIONS: Relative to placebo, DHA, but not EPA, enhances vasodilator mechanisms and attenuates constrictor responses in the forearm microcirculation. Improvements in endothelium-independent mechanisms appear to be predominant and may contribute to the selective blood pressure-lowering effect observed with DHA compared with EPA in humans.

Acetylcholine↗
PubMed2000

Angiotensin-converting enzyme gene polymorphism and premature coronary heart disease.

Since the initial report of the association of the deletion/insertion (D/I) polymorphism in the gene for angiotensin-converting enzyme (ACE) with myocardial infarction (MI), there has been considerable controversy. Some have found the D allele to be associated with MI, coronary heart disease (CHD) or other cardiac pathology, while others have not. In the present study 713 consecutive patients, < 50 years of age, documented prospectively with angiographic CHD (> 50% diameter stenosis of at least one coronary artery), with or without MI, were studied, along with 688 community control subjects, also < 50 years of age, selected randomly from the electoral rolls and without a history of CHD or MI. Genotyping was done by standard methods. Most of the subjects in both groups were Anglo-Celtic Caucasians (547 in the CHD group and 642 in the community group), and the report concerns primarily these subjects. ACE genotype distributions were not different between the Caucasian community control group and the CHD or the MI subgroups; the odds ratios and 95% confidence limits for the CHD group were 0.96 (0.73-1.27) for the D allele and 1.02 (0.80-1.31) for D homozygotes; for the MI group these values were 1.00 (0.83-1.20) and 0.99 (0.74-1.32) respectively. This negative result was supported in multivariate analysis accounting for conventional risk factors. There was a significant racial difference in ACE genotypes between Caucasians, Asians and Australian Aborigines in the CHD group (P < 0.001); for example, in this group, 158 of 540 (29%) Caucasians had the DD genotype compared with eight of 84 (10%) Aboriginals (P < 0.001) and six of 59 (10%) Asians (P = 0.002). Failure to account for such racial differences would have led to erroneous conclusions. In conclusion, we found no evidence that the D/I ACE gene polymorphism plays a role in the development of CHD or MI at an early age in a Western Australian Caucasian population. While this result refers uniquely to premature CHD and MI, and could be population specific, it is in general agreement with recent meta-analysis of the larger previous studies.

Adult↗
PubMed2000

Purified eicosapentaenoic and docosahexaenoic acids have differential effects on serum lipids and lipoproteins, LDL particle size, glucose, and insulin in mildly hyperlipidemic men.

BACKGROUND: Regular consumption of n-3 fatty acids of marine origin can improve serum lipids and reduce cardiovascular risk. OBJECTIVE: This study aimed to determine whether eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids have differential effects on serum lipids and lipoproteins, glucose, and insulin in humans. DESIGN: In a double-blind, placebo-controlled trial of parallel design, 59 overweight, nonsmoking, mildly hyperlipidemic men were randomly assigned to receive 4 g purified EPA, DHA, or olive oil (placebo) daily while continuing their usual diets for 6 wk. RESULTS: Fifty-six men aged 48.8 +/- 1.1 y completed the study. Relative to those in the olive oil group, triacylglycerols fell by 0.45 +/- 0.15 mmol/L ( approximately 20%; P = 0.003) in the DHA group and by 0.37 +/- 0.14 mmol/L ( approximately 18%; P = 0.012) in the EPA group. Neither EPA nor DHA had any effect on total cholesterol. LDL, HDL, and HDL(2) cholesterol were not affected significantly by EPA, but HDL(3) cholesterol decreased significantly (6.7%; P = 0.032). Although HDL cholesterol was not significantly increased by DHA (3. 1%), HDL(2) cholesterol increased by approximately 29% (P = 0.004). DHA increased LDL cholesterol by 8% (P = 0.019). Adjusted LDL particle size increased by 0.25 +/- 0.08 nm (P = 0.002) with DHA but not with EPA. EPA supplementation increased plasma and platelet phospholipid EPA but reduced DHA. DHA supplementation increased DHA and EPA in plasma and platelet phospholipids. Both EPA and DHA increased fasting insulin significantly. EPA, but not DHA, tended to increase fasting glucose, but not significantly so. CONCLUSIONS: EPA and DHA had differential effects on lipids, fatty acids, and glucose metabolism in overweight men with mild hyperlipidemia.

Adult↗
PubMed2000

Acute effects of ingestion of black and green tea on lipoprotein oxidation.

BACKGROUND: Tea has been associated with a reduced risk of cardiovascular disease. One proposed mechanism of this risk reduction involves inhibition of lipoprotein oxidation in vivo by antioxidant polyphenolic compounds derived from tea. However, controlled interventions uniformly failed to show that ingestion of tea can inhibit LDL oxidation ex vivo. The absence of effects in previous studies may be due to the isolation of LDL particles from polyphenolic compounds that are present in the aqueous phase of serum. OBJECTIVE: The objective of this study was to examine the acute effects of ingestion of black and green tea on ex vivo Cu(2+)-induced lipoprotein oxidation without prior isolation of lipoproteins from serum. DESIGN: The acute effects of 4 hot drinks-green tea and black tea (each at a dose equivalent to 4 standard cups), water matched to the teas for caffeine content, and water-were assessed in 20 healthy men by using a Latin-square design. The lag time to lipoprotein diene formation, slope of the propagation phase of the oxidation curve, and area under the oxidation curve were calculated. Urinary concentrations of 4-O-methylgallic acid were used as a marker of uptake and metabolism of polyphenolic compounds from tea. RESULTS: Significant increases in urinary 4-O-methylgallic acid for black and green tea (P < 0. 0001) were observed. Caffeine did not significantly influence lipoprotein oxidation. Compared with the water control, there was a greater lag time for black tea (5.4 +/- 2.9 min; P = 0.05) that was of borderline significance and a similar trend for green tea (4.4 +/- 2.8 min; P = 0.17). Slope and area under the oxidation curve were not altered. CONCLUSION: Black tea has a mild acute effect on ex vivo lipoprotein oxidation in human serum. 2000;71:-7.

Adult↗
PubMed2000

Effect of omega 3 fatty acids on oxidative stress in humans: GC-MS measurement of urinary F2-isoprostane excretion.

Despite the reported benefits associated with omega3 fatty acids for cardiovascular disease, there remains concern that increased intake may lead to increased lipid peroxidation. To date, however, the data, particularly in vivo, are inconclusive. This report describes two interventions, one providing daily fish meals and the other eicosapentaenoic acid (EPA, 20:5 omega3) or docosahexaenoic acid (DHA, 22:6 omega3), the two principal omega3 fatty acids in marine oils, in which in vivo lipid peroxidation was assessed by measurement of urinary excretion of F2-isoprostanes. In both trials, urinary F2-isoprostanes were significantly reduced by 20-27%. Therefore, in contrast with previous reports in the literature, these results demonstrate that omega3 fatty acids reduce in vivo oxidant stress in humans.

Diabetes Mellitus, Type 2↗
PubMed1999

Measurement of urinary F(2)-isoprostanes as markers of in vivo lipid peroxidation-A comparison of enzyme immunoassay with gas chromatography/mass spectrometry.

This study aimed at comparing the two most commonly utilized methods for measuring urinary F(2)-isoprostanes, currently considered one of the best available markers of in vivo lipid peroxidation. The F(2)-isoprostanes were measured in 24-h urine samples from 14 male subjects using electron capture negative ionization gas chromatography-mass spectrometry (ECNI-GCMS) with 8-iso-PGF(2alpha)-d(4) as an internal standard and compared with levels obtained using an enzyme immunoassay (EIA, 8-iso-PGF(2alpha) kit, Cayman Chemical Co.). The methods were compared using Pearson correlation coefficients, and Bland-Altman plots were constructed for the difference in F(2)-isoprostane against the average F(2)-isoprostane measured by either method. Weighted least-products regression was used to determine fixed bias (where there is a consistent difference between the methods) and proportional bias (where one method gives values higher or lower than the other method by an amount proportional to the size of the measurement). The correlation between F(2)-isoprostane levels obtained using EIA and GCMS methods, although significant, was poor (r = 0.628, P < 0.02). Comparison of the methods using the Bland-Altman analysis showed that there were wide limits of agreement between the two methods with only 28% of the values falling within the 95% confidence limits for the difference. The GCMS gave higher values with a mean difference of 298.1 pM (636.6, -40.2; P = 0.079), and a near significant linear association between the differences and the mean F(2)-isoprostane level (r = -0.559, P = 0.05). Weighted least-product regression analysis confirmed the presence of both significant fixed and proportional bias with the EIA giving lower levels of F(2)-isoprostanes at low concentrations and higher levels at higher concentrations. The cross-reactivity in the EIA of 8-iso-15(R)-PGF(2alpha) and 9beta-PGF(2alpha) which coelute with the F(2)-isoprostane peak measured by GCMS was very low, 0.2 and 0.1%, respectively. The proportional bias observed between the methods may in part be due to differences in the relative amounts of 8-iso-15(R)-PGF(2alpha), 9beta-PGF(2alpha), and 8-iso-PGF(2alpha) with increasing lipid peroxidation. This study shows that the measurements of F(2)-isoprostanes by EIA and GCMS are not equivalent. Therefore, comparison of levels derived using a GCMS method which estimates concentration from a peak encompassing a number of F(2)-isoprostane isomers, and levels derived from enzyme immunoassay measuring a specific isoprostane, may be inappropriate.

Adult↗