Antioxidant status of oral mucosal tissue and plasma levels in smokers and non-smokers

The antioxidant status of an individual is thought to be important in the development of potentially malignant oral lesions (PMOL) and oral squamous cell carcinoma (OSCC). To date, little detailed information on mucosal antioxidant status is available in a United Kingdom population and neither has the relationship between smoking and mucosal antioxidant status been established. Furthermore, it has been implied that serum levels of antioxidants and tissue levels in the oral mucosa should be equivalent, but that is unproven. To address these deficiencies in our knowledge we studied 60 individuals, all of whom had an oral mucosal biopsy and simultaneous venous blood sampling. Antioxidant levels were measured using high performance liquid chromatography. Smokers (n= 19) were found to have significantly lower levels of plasma beta-carotene (P<0.05) and significantly lower levels of tissue alpha-carotene (P<0.05) than non-smokers (n=41). Tissue alpha-carotene correlated with plasma levels, but this was not the case with alpha-tocopherol, retinol, lycopene or beta-carotene. This is the first data on oral mucosal antioxidant levels and provides baseline data from which to study patients with potentially malignant oral lesions and oral squamous cell carcinoma.

Paraoxonase polymorphisms are not associated with cardiovascular risk in renal transplant recipients

BACKGROUND

Paraoxonase (PON1) gene variants have been identified as risk factors for cardiovascular disease (CVD). There are two common PON1 polymorphisms at position 55 (Leu-Met change) and 192 (Gln-Arg change) of the amino acid chain. Leucine at position 55 and arginine at position 192 have been associated with increased cardiovascular risk. The increased prevalence of CVD in renal transplant recipients can be only partly explained by the increased prevalence of conventional risk factors.

METHODS

We therefore investigated PON1 polymorphisms in renal transplant recipients (N = 491) with (N = 103) and without CVD (N = 388) using polymerase chain reaction-restriction fragment length analysis. PON1 polymorphisms and their associated PON1/arylesterase activities were also assessed in a subgroup of patients (N = 165).

RESULTS

The genotype distribution and allele frequencies for both polymorphisms were similar in both groups. The frequencies for LL, LM, and MM genotypes for the 55 position in patients with CVD were 0.39, 0.51, and 0.10, respectively, compared with 0.43, 0.43, and 0.14 in patients without CVD (P = 0.31). The distribution for the QQ, QR, and RR genotypes at the 192 position were 0.48, 0.43, and 0.09, respectively, in patients with CVD compared with 0.46, 0.46, and 0.08 in patients without CVD (P = 0.8). There were highly significant differences in serum activities of PON1/arylesterase between genotypes defined by 55 and 192 polymorphisms. Leucine at position 55 and arginine at position 192 were associated with higher activities.

CONCLUSION

These data indicate that there is no association between the PON1 gene variants, conferring higher enzyme activity, and the increased cardiovascular risk in renal transplant recipients.

Antioxidants, but not B-group vitamins increase the resistance of low-density lipoprotein to oxidation: a randomized, factorial design, placebo-controlled trial

We have conducted an intervention trial to assess the effects of antioxidants and B-group vitamins on the susceptibility of low-density lipoprotein (LDL) to oxidation. A total of 509 men aged 30-49 from a local workforce were screened for total plasma homocysteine. The 132 selected (homocysteine concentration > or = 8.34 mumol/l) men were randomly assigned, using a factorial design, to one of four groups receiving supplementation with B group vitamins alone (1 mg folic acid, 7.2 mg pyridoxine, 0.02 mg cyanocobalamin), antioxidant vitamins (150 mg ascorbic acid, 67 mg alpha-tocopherol, 9 mg beta-carotene), B vitamins with antioxidant vitamins, or placebo. Intervention was double-blind. A total of 101 men completed the 8-week study. The lag time of LDL isolated ex vivo to oxidation (induced by 2 mumol/l cupric chloride) was increased in the two groups receiving antioxidants whether with (6.88 +/- 1.65 min) or without (8.51 +/- 1.77 min) B-vitamins, compared with placebo (-2.03 +/- 1.50) or B-vitamins alone (-3.34 +/- 1.08) (Mean +/- S.E., P < 0.001). Antibodies to malondialdehyde (MDA) modified LDL were also measured, but there were no significant changes in titers of these antibodies in any group of subjects whether receiving antioxidants or not. Contrast analysis showed that there was no interaction between antioxidants and B-group vitamins. This study indicates that while B-group vitamins lower plasma homocysteine they do not have an antioxidant effect. Thus B-group vitamins and antioxidants appear to have separate, independent effects in reducing cardiovascular risk.

Homocysteine and B-group vitamins in renal transplant patients

Increased plasma homocysteine is an independent risk factor for cardiovascular disease. We have investigated homocysteine and B-group vitamin levels in renal transplant patients. Fasting blood was collected from 55 renal transplant recipients with good renal function and 32 age/sex matched control subjects. Total homocysteine was increased in transplant recipients in comparison to controls (10.9+/-1.5 vs. 6.7+/-1.3 micromol/l, P < 0.001). There was no difference in homocysteine between patients receiving cyclosporin (n = 39, homocysteine 11.0+/-1.5 micromol/l) and patients receiving prednisolone + azathioprine (n = 16, 10.8+/-1.6 micromol/l, mean+/-S.D.), although there was a significant correlation between homocysteine and serum cyclosporin concentration in the sub-group of patients receiving that immunosuppressive regimen (r = 0.42, P < 0.05). Levels of B-group vitamins were similar in patients and controls. Plasma homocysteine is increased in renal transplant recipients even in the presence of minor degrees of renal impairment and normal levels of B-group vitamins.

HDL composition and HDL antioxidant capacity in patients on regular haemodialysis

Recent evidence suggests that HDL can directly inhibit LDL oxidation, a key early stage in atherogenesis. Patients with chronic renal failure are at increased cardiovascular risk, have reduced HDL levels and altered HDL composition. We have therefore investigated whether compositional changes in HDL lead to decreased HDL antioxidant capacity in these patients. In comparison to control subject HDL, patient HDL contained less total cholesterol, cholesterol esters, phospholipids and alpha-tocopherol. LDL, HDL and LDL + HDL were standardised for protein and oxidised in the presence of Cu2+. The rate of propagation during HDL oxidation was reduced in the patient group (3.28+/-0.65 x 10(-5) vs. 4.60+/-0.97 x 10(-5) abs. U/min, P < 0.01). Lipid peroxide generation in patient HDL was decreased: 6.56+4.4 versus 13.42+/-7.0 nmol malondialdehyde (MDA)/mg HDL protein after 90 min and 14.45+/-3.8 versus 20.11+/-7.8 nmol MDA/mg HDL protein after 180 min. This is attributable to reduced HDL polyunsaturated fatty acid content in patients (0.53+/-0.12 vs. 0.72+/-0.16 mmol/g HDL, P < 0.01). The inhibitory effect of HDL on LDL oxidation was similar: 71 and 33% for patient HDL compared to 68 and 31% for control HDL, after 90 and 180 min, respectively. Compositional changes of HDL in patients on haemodialysis did not affect the antioxidant capacity of HDL after standardisation for HDL protein. However, reduced HDL levels in vivo may result in reduced HDL antioxidant capacity in these patients.

Absorption and antioxidant effects of quercetin from onions, in man

OBJECTIVE

To investigate the in vivo effects of quercetin following the ingestion of fried onions.

DESIGN

Five healthy volunteers, three males and two females aged between 25 and 39 y, ingested 225 g of fried onions after an overnight fast and peripheral venous blood was collected 0, 2, 4, 24 and 48 h after consumption. Quercetin in the plasma, total antioxidant capacity and susceptibility of low density lipoproteins (LDL) to oxidation were measured.

RESULTS

Following the onion meal, quercetin levels increased from baseline values (28.4 +/- 1.9 ng/ml) to peak after 2 h (248.4 +/- 103.9 ng/ml), decreasing to baseline again after 24 h (P > 0.05). This was accompanied by an increase in the total antioxidant activity of the plasma from baseline (1.70 +/- 0.04 mmol/l trolox equivalents) to 1.75 +/- 0.10 mmol/l trolox equivalents after 2 h and 1.76 +/- 0.08 mmol/l trolox equivalents after 4 h. There was no significant change in the susceptibility of the plasma or the isolated LDL to oxidation over the 48 h period after consumption of the fried onions. In view of these negative findings, we isolated LDL and other lipoproteins from plasma at each time point. Quercetin was not detected in either LDL or VLDL, but was present in the HDL fraction, although this fraction also contains other proteins including albumin.

CONCLUSIONS

Quercetin can be absorbed in humans from dietary sources to high enough concentrations to increase the overall antioxidant activity of the plasma. Quercetin, however, has a strong affinity for protein and provides no direct protective effect during LDL oxidation.

Plasma chain-breaking antioxidants in Alzheimer's disease, vascular dementia and Parkinson's disease

We studied the plasma chain-breaking antioxidants alpha carotene, beta carotene, lycopene, Vitamin A, Vitamin C, Vitamin E and a measure of total antioxidant capacity, TAC, in 79 patients with Alzheimer's disease (AD), 37 patients with vascular dementia (VaD), 18 patients with Parkinson's disease and dementia (PDem), and 58 matching controls, together with 41 patients with Parkinson's disease (PD) and 41 matching controls. Significant reductions in individual antioxidants were observed in all dementia groups. When compared to controls, the following were reduced: Vitamin A in AD (p < 0.01) and VaD (p < 0.001); Vitamin C in AD (p < 0.001), VaD (p < 0.001) and PDem (p < 0.01); Vitamin E in AD (p < 0.01) and VaD (p < 0.001); beta carotene in VaD (p = 0.01); lycopene in PDem (p < 0.001). Lycopene was also reduced in PDem compared to AD (p < 0.001) and VaD (p < 0.001). Antioxidant levels in PD were not depleted. No significant change in TAC was seen in any group. The reduction in plasma chain-breaking antioxidants in patients with dementia may reflect an increased free-radical activity, and a common role in cognitive impairment in these conditions. Increased free-radical activity in VaD and PDem could be associated with concomitant AD pathology. Individual antioxidant changes are not reflected in TAC.

Influence of cycle frequency, muscle strain and muscle length on work and power production of rainbow trout (Oncorhynchus mykiss) ventricular muscle

This study investigates the effects of cycle frequency, strain and length on work and power output of isolated rainbow trout (Oncorhynchus mykiss) ventricular preparations using the work loop technique. These effects are discussed in the context of the whole heart using analogies with heart rate, stroke volume and end-diastolic volume. Power output was dependent on cycle frequency, increasing threefold beween 0.3 and 1.1 Hz. The frequency for maximum power output was approximately 1.1 Hz, corresponding to the frequency for maximum power in perfused heart experiments. The length for maximum work production (Lopt) was found to be the same as the length for maximum isometric force production (Lmax). The decline in net work at lengths greater than Lopt/Lmax was attributed to an increase in passive work (the work done on an unstimulated muscle) or to hysteresis and to a large increase in lengthening work. The strain yielding maximum work decreased with increasing frequency. This is discussed in the context of the decline in stroke volume observed at increased heart rates in vivo. Muscle strain in intact hearts paced at 0.3 Hz was +/-11.9 % (23.8 % peak to peak), a value similar to the optimum strain at 0.3 Hz in vitro (+/-12 %).

Genotype/phenotype correlations in familial hypercholesterolaemia

It is now possible to identify the specific gene defect in the majority of patients with familial hypercholesterolaemia. A potential benefit of this knowledge, in addition to helping with family screens, is to be able to predict the future clinical course. In order to do this, detailed genotype/phenotype correlation studies are required.

A simple method for assessing copper-mediated oxidation of very-low-density lipoprotein isolated by rapid ultracentrifugation

The association of very-low-density lipoprotein (VLDL) with atherosclerosis remains controversial. However, studies have shown that oxidative modification of VLDL can promote foam cell formation, leading to the development of atherosclerosis. A rapid method is described which will allow the significance of VLDL oxidation to be assessed in clinical studies. VLDL was isolated from heparinized plasma by a 1-h, single spin ultracentrifugation. Total protein was standardized to 25 mg/L. Oxidation was promoted by the addition of copper ions (17.5 mumol/L, final concentration) incubated at 37 degrees C. Conjugated diene production was followed at 234 nm. Total assay preparation time was 2 h. Urate greatly inhibited the oxidation of VLDL and was successfully removed by size exclusion chromatography. VLDL isolated from frozen plasma (-70 degrees C) was stable for 15 weeks. This simple, rapid method for the isolation of VLDL may be applied to assess the significance of VLDL oxidation in disease.

Oxidative stress in chronic renal failure

Cardiovascular disease is the major cause of morbidity and mortality in chronic renal failure. The aim of this review is to summarise current evidence suggesting that there is increased free radical production, antioxidant depletion and changes in lipoprotein composition in renal failure which will lead to oxidation of LDL and hence to accelerated development of atherosclerosis.

Twenty-four-hour urinary free cortisol in patients with acquired immunodeficiency syndrome

Many patients with acquired immune deficiency syndrome (AIDS) have symptoms consistent with adrenal insufficiency, but only a small subset of these patients meet criteria for adrenal insufficiency during a short corticotropin (ACTH) stimulation test. We hypothesized that patients with AIDS and symptoms of adrenal insufficiency who produce normal amounts of cortisol in response to administration of 0.25 mg cosyntropin may nevertheless produce lower amounts of cortisol in a course of 24 hours than comparably sick AIDS patients without symptoms of adrenal insufficiency or comparably sick patients without AIDS. We studied four groups of male patients: AIDS patients with symptoms suggestive of adrenal insufficiency but with a normal response to cosyntropin (group I), AIDS patients without symptoms suggestive of adrenal insufficiency (group II), human immunodeficiency virus (HIV)-negative patients with serious acute or chronic illness (group III), and healthy subjects (group IV). The following variables were examined: age, CD4 cell count, Acute Physiologic and Chronic Health Evaluation (APACHE) score, serum cortisol and plasma ACTH at baseline; serum cortisol at 30 and 60 minutes after intravenous administration of 0.25 mg cosyntropin; and 24-hour urinary free cortisol. The four groups had a similar mean age and baseline plasma ACTH and serum cortisol levels. However, a change in cortisol from baseline to 30 and 60 minutes after administration of cosyntropin was significantly smaller in both groups of AIDS patients than in the sick patients without AIDS and normal subjects. There were also differences noted between the two groups of AIDS patients: both baseline and stimulated levels of cortisol tended to correlate directly with ACTH levels in patients without symptoms of adrenal insufficiency, while this relationship appeared to be inverse in patients with symptoms suggestive of adrenal insufficiency (r = -.57 to -.7, P < .05 to .14). The 24-hour urinary free cortisol levels were similar among all groups, but correlated strongly with baseline and stimulated serum cortisol levels only in patients with AIDS and symptoms of adrenal insufficiency (r = .8 to .9, P < .002 to .015). We conclude that (1) AIDS patients with and without symptoms of adrenal insufficiency may have either normal adrenal function or somewhat suboptimal adrenal reserve as demonstrated by a blunted cortisol response during the short ACTH stimulation test in comparison to HIV-negative comparably sick patients or healthy subjects; and (2) 24-hour urinary free cortisol is not a useful test for detection of subtle abnormalities of adrenal function in patients with AIDS.

Misleading serum free thyroxine results during low molecular weight heparin treatment

Measured free thyroxine concentrations in serum increase markedly after intravenous heparin administration, but the effect of heparin administered subcutaneously has not been adequately documented. We found in vitro increases of up to 63% in measured FT4 after a single dose of subcutaneous heparin (enoxaparin, 2000 units) in nine healthy volunteers, and the magnitude of these increases was correlated with initial serum triglyceride concentrations (r = 0.93, P <0.005) and in vitro free fatty acid release (r = 0.88, P <0.005). In 10 cardiac inpatients receiving repeated doses of enoxaparin (2000 units twice daily), measured FT4 increased by up to 171% in specimens taken 2-6 h after injection. When specimens were obtained 10 h after injection, the effect appeared to be minimized, with in vitro increases of <40%, but such increases may still be sufficient to cause interpretative errors. If FT4 estimation is absolutely necessary in patients receiving enoxaparin, specimens should be taken > or =10 h postdose and analyzed within 24 h.

Electron spin resonance spectroscopic detection of oxygen-centred radicals in human serum following exhaustive exercise

Free radicals or oxidants are continuously produced in the body as a consequence of normal energy metabolism. The concentration of free radicals, together with lipid peroxidation, increases in some tissues as a physiological response to exercise - they have also been implicated in a variety of pathologies. The biochemical measurement of free radicals has relied in the main on the indirect assay of oxidative stress by-products. This study presents the first use of electron spin resonance (ESR) spectroscopy in conjunction with the spin-trapping technique, to measure directly the production of radical species in the venous blood of healthy human volunteers pre- and post-exhaustive aerobic exercise. Evidence is also presented of increased lipid peroxidation and total antioxidant capacity post-exercise.

Effect of B-group vitamins and antioxidant vitamins on hyperhomocysteinemia: a double-blind, randomized, factorial-design, controlled trial

Mild hyperhomocysteinemia is accepted as a risk factor for premature cardiovascular disease. In a population with a high prevalence of cardiovascular disease, we screened a group of clinically healthy working men aged 30-49 y (n = 509) for plasma homocysteine and 5,10-methylene tetrahydrofolate reductase (MTHFR) genotype status. Those with mildly elevated homocysteine concentrations (> or = 8.34 micromol/L) were selected for intervention. In a randomized, factorial-design, controlled trial we assessed the effects of B-group vitamins and antioxidant vitamin supplementation on homocysteine concentrations. The 132 men were randomly assigned to one of four groups: supplementation with B-group vitamins alone (1 mg folic acid, 7.2 mg pyridoxine, and 0.02 mg cyanocobalamin), antioxidant vitamins alone (150 mg ascorbic acid, 67 mg RRR-alpha-tocopherol, and 9 mg beta-carotene), B-group vitamins with antioxidant vitamins, or placebo. Intervention was double-blind. A total of 101 men completed the 8-wk intervention. When homocysteine concentrations were analyzed by group, significant (P < 0.001) decreases (32.0% and 30.0%, respectively) were observed in both groups receiving B-group vitamins either with or without antioxidants. The effect of B-group vitamins alone over 8 wk was a reduction in homocysteine concentrations of 27.9% (95% CI: 22.0%, 33.3%; P < 0.001) whereas antioxidants alone produced a nonsignificant increase of 5.1% (95% CI: -2.8%, 13.6%; P = 0.21). There was no evidence of any interaction between the two groups of vitamins. The effect of B-group vitamin supplementation seemed to depend on MTHFR genotype. Supplementation with the B-group vitamins with or without antioxidants reduced homocysteine in the men with mildly elevated concentrations, and hence may be effective in reducing cardiovascular risk.

Black tea consumption does not protect low density lipoprotein from oxidative modification

OBJECTIVE

To investigate the in vivo and in vitro effects of black tea on the oxidative modification of low density lipoprotein (LDL).

DESIGN

The antioxidant activity of the tea was studied in vitro by measuring the resistance of the LDL to oxidative modification in the presence of copper. The effects of tea consumption in vivo were investigated in two settings. Firstly, to assess the acute effects of tea consumption, five fasting healthy subjects ingested 600 mls (50.7+/-5.4 mg flavonoids) of black tea and peripheral venous blood was collected at 0, 30, 60, 90, 120 and 180 min after consumption. Secondly, to assess the effects of chronic tea consumption, a randomised crossover trial of tea (126.8+/-13.5 mg flavonoids) and coffee consumption was carried out in ten healthy subjects.

RESULTS

Black tea extract increased the resistance of LDL in vitro in a concentration dependent manner. There was no significant change in total plasma antioxidant capacity or susceptibility of the LDL to oxidation over the 3 h period after consumption of black tea. The four-week crossover study in which coffee was used as a control against the black tea showed no significant difference in the total plasma antioxidant capacity or susceptibility of LDL to oxidation between the tea and coffee groups. Serum lipids, including total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol did not change significantly throughout the study.

CONCLUSIONS

The consumption of moderate quantities of black tea acutely or for one week does not increase plasma total antioxidant capacity or alter the susceptibility of LDL to oxidation.

Body composition and energy expenditure of patients with chronic cardiac failure

BACKGROUND

Patients with acute cardiac failure have excess body water, and it is commonly assumed that this is also so in patients with stable chronic cardiac failure (CCF).

METHODS

To investigate this, we measured total body water (TBW) using stable isotope dilution and single-frequency bioelectrical impedance (BIA), and also extracellular volume (ECV) using bromide dilution in 12 patients with CCF and eight matched control subjects.

RESULTS

TBW [kg(-1) bodyweight] was similar in the two groups [median 18O dilution 53.2% (range 46.5-57.1%) in patients vs. 54.8% (47.9-62.7) in control subjects; BIA 56.6% (42.7-73.1) vs. 58.0% (52.0-68.6)]. ECV was also similar in the two groups [0.25 Lkg(-1) (0.20-0.29) vs. 0.25 (0.19-0.35)]. There was a strong correlation between stable isotope and BIA measurements of TBW for all subjects (r = 0.76), but BIA overestimated TBW by a mean difference of 2.4 kg (limits of agreement of -4.1 kg to +8.9 kg). Body fat content was similar in the two groups, whether measured by skinfold anthropometry, whole-body densitometry or by 18O dilution. Resting energy expenditure (REE), calculated from indirect calorimetry, and total energy expenditure (TEE), calculated from the ratio of 2H to 18O elimination rate after drinking doubly labelled water, were also similar in the two groups.

CONCLUSION

It is concluded that the patients with stable CCF in this study had normal ECV and TBW, and so excess body water did not account for their persistent symptoms.