Association of dietary patterns and risk of cardiovascular disease events in the MASHAD cohort study

BACKGROUND

Cardiovascular disease (CVD) is the principal cause of mortality and disability in Iranian adults. We aimed to evaluate the relationship between dietary patterns and CVD incidence in a large sample of adults in northeastern Iran.

METHODS

The present study comprised a prospective study of 5706 CVD-free men and women aged 35-65 years who participated in a cohort study. All of the participants were followed up for a 6-year period. Dietary patterns were derived from a 65-item validated food frequency questionnaire and the factor analysis method was used to determine dietary patterns.

RESULTS

We identified two major dietary patterns: (i) a Balanced dietary pattern (a high intake of green leafy vegetables, other vegetables, fruits, dairy products, red meats, poultry, seafoods, legumes and nuts, as well as a low intake of sugar) and (ii) a Western dietary pattern (a high intake of sugar, tea, egg, snacks, fast foods, potato, carbonated beverages, pickled foods, organs meat and butter) by factor analysis. The hazard ratio (HR) and 95% confidence intervals (CIs) of total CVD in the highest versus lowest tertiles of the Balanced pattern were 1.29 (95% CI = 0.67-2.47; P = 0.44). The HR and 95% CIs of CVD in the highest versus lowest tertiles of Western pattern were 2.21 (95% CI = 1.08-4.45; P = 0.03).

CONCLUSIONS

During the 6-year follow-up, we found that adherence to a Balanced dietary pattern was not significantly associated with CVD events. However, adherence to a Western dietary pattern was associated with a significantly increased risk of CVD events and its associated risk.

Correlation between expression of CatSper1,2 and sperm parameters in the gamma irradiated adult mouse testis

Propose: CatSper protein channels are responsible for the entry of Ca2+ into sperm cells. These proteins play an important role in motility and male fertility. So it is important to find out whether or not environmental factors, such as gamma radiation, have an effect on the expression of Catsper genes. In this study, we investigated the effects of gamma radiation on the expression of CatSper1 and CatSper2 genes. Materials and methods: Twenty-one male NMRI mice were divided into three groups: a control group without gamma radiation, and two experimental groups; Group 1 treated with 1 Gy of gamma radiation, and Group 2 treated with a higher dose of 2 Gy gamma radiation. Testes were removed from all groups of animals 35 days following irradiation and the testicular tissue, processed and embedded in paraffin blocks for sectioning and histological examination. Sperm samples were also taken from the epididymis for microscopic. Sperm parameters such as sperm count, morphology, motility, and viability rates were analyzed. Expression of CatSper genes was evaluated using Real-time PCR. Data were analyzed using the SPSS software and ANOVA test. Results: Our results showed that after treatment with gamma radiation, testes morphology was changed. Epididymal sperm count, motility, and morphology rates were significantly affected in both experimental groups compared to the control group. The relative expressions of CatSper 1 and 2 genes were significantly reduced in the irradiated mice (1 Gy and 2 Gy) than non-irradiated ones. Conclusions: Gamma radiations not only change testes histology and sperm parameters, but also decrease the expression of CatSper 1 and 2 genes in male mice.

The effect of electro-acupuncture on pro-oxidant antioxidant balance values in overweight and obese subjects: a randomized controlled trial study

Objective To undertake a randomized controlled trial in 196 obese subjects to examine the effect of electro-acupuncture on serum pro-oxidant antioxidant balance (PAB) values. Methods Subjects received authentic acupuncture (cases) or sham acupuncture (controls) for 6 weeks in combination with a low-calorie diet. In the following 6 weeks, they received the low-calorie diet alone. Serum PAB was measured at baseline, and 6 and 12 weeks later. Results We found that serum PAB values decreased significantly in the group receiving the authentic acupuncture compared to the sham treatment (p<0.001) at week 6, and whilst serum PAB increased significantly (p<0.05) in the second phase of the study, a significant difference between two groups remained at 12 weeks (p<0.05). Conclusions Electro-acupuncture in combination with a low-calorie diet was more effective at reducing serum PAB values in obese subjects compared to diet alone. Further work is required to determine the mechanism by which electro-acupuncture has this effect.

Cytokine profiles in overweight and obese subjects and normal weight individuals matched for age and gender

Background Obesity is associated with a state of systemic inflammation, mediated by adipose tissue-derived cytokines that may also have metabolic effects, including an effect on insulin resistance. The aim of this study was to compare the serum profile of pro- and anti-inflammatory cytokines in obese and non-obese subjects. Methods A total of 242 subjects who were either overweight or obese (body mass index [BMI] ≥ 25 kg/m²) and non-obese subjects (body mass index <25 kg/m²), were recruited in Mashhad in northeastern Iran. The concentrations of serum interleukin-1α, -1β, -2, -4, -6, -8 and -10 (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8 and IL-10), were measured in all subjects, together with serum vascular endothelial growth factor, interferon-γ, epidermal growth factor, monocyte chemoattractant protein-1 and tumour necrosis factor-α. Results The groups differed significantly with respect to measures of adiposity and fasted lipid profile. Serum pro-inflammatory cytokines interferon-γ and interleukin-1α, and anti-inflammatory cytokines, interleukin-10, and epidermal growth factor were significantly different between obese and non-obese individuals, as was serum high-sensitivity C-reactive protein. Multivariate regression showed that waist circumference was significantly and independently related to serum monocyte chemoattractant protein-1concentrations ( P = 0.001). Conclusion Despite significant differences in several cytokines between the groups, only monocyte chemoattractant protein-1appeared to be independently related to a measure of adiposity in this population sample from Iran.

Review: Insulin-like growth factor-related proteins and diabetic complications

The insulin-like growth factor system and, in particular, insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-1 (IGFBP-1) are dysregulated in type 1 and type 2 diabetes. Serum IGF-I levels are low in both forms of diabetes, and this may be in part genetically determined. It is possible that the reduced serum levels of IGF-I are involved in the development of microvascular and macrovascular complications. Fasting serum IGFBP-1 levels are usually low in early type 2 diabetic patients with insulin resistance and hyperinsulinaemia but may be raised in patients with particularly poor glycaemic control and severe beta-cell failure. Treatment with IGF-I/binding protein complexes has been shown to improve glycaemic control in conjunction with insulin and may in future have a place in the treatment of diabetes, potentially to prevent diabetic complications. Serum IGFBP-1 determination may have utility in the assessment of cardiovascular risk and as an indicator for insulin resistance.

Erythropoietin and a nonerythropoietic peptide analog promote aortic endothelial cell repair under hypoxic conditions: role of nitric oxide

The cytoprotective effects of erythropoietin (EPO) and an EPO-related nonerythropoietic analog, pyroglutamate helix B surface peptide (pHBSP), were investigated in an in vitro model of bovine aortic endothelial cell injury under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The potential molecular mechanisms of these effects were also explored. Using a model of endothelial injury (the scratch assay), we found that, under hypoxic conditions, EPO and pHBSP enhanced scratch closure by promoting cell migration and proliferation, but did not show any effect under normoxic conditions. Furthermore, EPO protected bovine aortic endothelial cells from staurosporine-induced apoptosis under hypoxic conditions. The priming effect of hypoxia was associated with stabilization of hypoxia inducible factor-1α, EPO receptor upregulation, and decreased Ser-1177 phosphorylation of endothelial nitric oxide synthase (NOS); the effect of hypoxia on the latter was rescued by EPO. Hypoxia was associated with a reduction in nitric oxide (NO) production as assessed by its oxidation products, nitrite and nitrate, consistent with the oxygen requirement for endogenous production of NO by endothelial NOS. However, while EPO did not affect NO formation in normoxia, it markedly increased NO production, in a manner sensitive to NOS inhibition, under hypoxic conditions. These data are consistent with the notion that the tissue-protective actions of EPO-related cytokines in pathophysiological settings associated with poor oxygenation are mediated by NO. These findings may be particularly relevant to atherogenesis and postangioplasty restenosis.

Serum high-sensitivity C-reactive protein as a biomarker in patients with metabolic syndrome: evidence-based study with 7284 subjects

BACKGROUND/OBJECTIVES

Metabolic syndrome (MetS) is characterized by abdominal obesity, dyslipidemia, hypertension and glucose intolerance, and is associated with an increased risk of developing cardiovascular disease (CVD), diabetes mellitus and related diseases. Circulating levels of inflammatory markers such as C-reactive-protein (CRP) have reported to be associated with CVD. Against this background, the prevalence of MetS is increasing globally, and thus predictive biomarkers are required for identification of MetS patients at an increased risk. Here we explored the value of CRP as a biomarker in 7284 subjects and also investigated which features of MetS have the greatest association with the hs-CRP level.

SUBJECTS/METHODS

The subjects were recruited from the Mashhad stroke and heart atherosclerotic disorder study. Anthropometric factors and biochemical parameters (for example, high-sensitivity CRP (hs-CRP), high-density lipoprotein/low-density lipoprotein, triglycerides (TGs) and fasting blood glucose (FBG)) were determined. Univariate and multivariate analyses were conducted to evaluate the association of hs-CRP and MetS.

RESULTS

Our results illustrated that the concentration of serum hs-CRP increased progressively with the number of MetS components, and subjects who fulfilled the criteria of MetS for waist circumference, TGs, blood pressure and FBG were found to have hs-CRP of 0.53, 0.38, 0.34 and 0.71 mg/l, respectively, higher than matched-subjects. Importantly, FBG had the greatest association with hs-CRP concentration.

CONCLUSIONS

Our data demonstrate the significant association between MetS components with hs-CRP, indicating that this association was cumulative by increasing the number of the defining features of MetS, supporting further studies to explore the value of emerging marker as a novel method for detecting individuals at high risk of developing MetS.

Micronutrient intake and the presence of the metabolic syndrome

Background:

Dietary micronutrients have been proposed to protect against oxidative damage and related clinical complications.

Aims:

We aimed to compare the micronutrient intake between individuals with and without metabolic syndrome (MS).

Materials and Methods:

This cross-sectional study included 3800 men and women who were aged between 35 and 65 years. The diagnosis of the MS was based on International Diabetes Federation criteria. Dietary intake of participants was assessed using a questionnaire for 24 h dietary recall. Student's t-test and Mann–Whitney U-tests were used for comparing the micronutrient intake of subjects with or without the MS and the odds ratio for the presence of the MS was calculated for each micronutrient by control for total energy intake adjusted by the residue method.

Results:

The mean age of MS subjects and the control group was 48.8 ± 7.9 years and 47.6 ± 7.6 years, respectively. Energy-adjusted intake of vitamin E (P < 0.05), B2 (P < 0.01), and B12 (P < 0.05) was higher in normal women compared with women with MS. Energy-adjusted intake of vitamin B1 was significantly higher in women with MS. After logistic regression analysis, no significant association between micronutrient intake and MS was shown.

Conclusion:

We found no significant association between micronutrient intake and MS.

The relationship between established coronary risk factors and serum copper and zinc concentrations in a large Persian cohort

INTRODUCTION

The relationship between demographic and biochemical characteristics, including several established coronary risk factors, and serum copper and zinc was assessed in a large Iranian population sample.

MATERIALS AND METHODS

A group of 2233 individuals, 15-65 years of age [1106 (49.5%) males and 1127 (50.5%) females] was recruited from residents of the Greater Khorasan province in northeast of Iran. Demographic data were collected using questionnaires. Coronary risk factors were determined using standard protocols, and trace elements were measured in serum using atomic absorption spectroscopy.

RESULTS

Degree of glucose tolerance and smoking habit were not associated with serum zinc and copper levels. Serum copper levels were significantly higher in obese and hypertensive than in normal subjects (p<0.001). In the whole group and for the female subgroup, serum zinc (p<0.01) and copper (p<0.001) were both significantly lower in individuals with normal versus high levels of low-density lipoprotein cholesterol. A strong positive correlation was found between serum copper and body mass index (BMI) (r=0.85, p<0.001). Weaker positive associations were found between serum copper and calculated 10 years' coronary risk (r=0.11, p<0.001). Serum zinc/copper ratio was strongly inversely associated with calculated 10 years' coronary risk (r=-0.10, p<0.001). The partial Eta squared (PES) values for factors determining serum zinc were hypertension (0.007, p=0.01) and BMI (0.004, p=0.01); and for serum copper, they were gender (0.02, p=0.001), hypertension (0.004, p=0.009), and 10 years' coronary risk for men (0.003, p=0.03) and women (0.002, p=0.07).

CONCLUSION

Significant associations between serum trace element concentrations and several coronary risk factors, including calculated 10 years' coronary risk scores, were found.

Biphasic modulation of atherosclerosis induced by graded dietary copper supplementation in the cholesterol-fed rabbit

There has been considerable debate about how copper status may affect the biochemical and cellular processes associated with atherogenesis. We have investigated the effects of graded dietary copper supplementation on processes likely to contribute to atherogenesis, using the cholesterol-fed New Zealand White rabbit model. Rabbits (n = 40) were fed a 0.25-1% cholesterol diet deficient in copper. Animals received either 0, 1, 3 or 20 mg copper/day and were killed after 13 weeks. Plasma cholesterol levels were similar in each dietary group. Aortic concentrations of copper were higher in the 20 mg copper/day animals compared to those receiving 0 mg copper/day (3.70 +/- 0.78 vs. 1.33 +/- 0.46 microg/g wet tissue; P < 0.05). Aortic superoxide dismutase activity was higher in animals receiving 20 mg copper/day (323 +/- 21 IU/mg tissue) compared to the other groups (187 +/- 21; 239 +/- 53; 201 +/- 33 IU/mg tissue) (P > 0.05). En face staining of aortae with oil red O showed that both high copper supplementation (20 mg/day) (67.1 +/- 5.5%) and a deficient diet (0 mg/day) (63.1 +/- 4.8%) was associated with significantly larger lesions (P < 0.05) compared to moderately supplemented animals (1 mg/day and 3 mg/day) (51.3 +/- 6.3 and 42.8 +/- 7.9%). These data indicate that in the cholesterol-fed rabbit, there is an optimal dietary copper intake and that dietary copper deficiency or excess are associated with an increased susceptibility to aortic atherosclerosis. Many Western diets contain insufficient copper and these findings indicate that a moderate dietary copper content may confer a degree of cardiac protection to the human population.

Changes in serum concentration of antioxidants following treadmill exercise testing in patients with suspected ischaemic heart disease

Twenty-four subjects with suspected ischaemic heart disease underwent a treadmill exercise stress test (TEST). Nine individuals developed ischaemia as defined by standard criteria. Total plasma antioxidant status (TPAS), and serum concentrations of vitamin E were measured pre-TEST, and 0, 1, 2, 4, 8 and 24 h following the treadmill test. Mean serum vitamin E concentrations fell by 33% in the group as a whole (from 9.53 +/- 0.92 mg/L pre-TEST to 6.39 +/- 1.06 mg/L immediately post stress test, P < 0.02) and rose to baseline over the subsequent 24 h. The levels of serum vitamin E fell by 34% in the group of patients who had a positive TEST, and 32% in those who did not develop ischaemia during the TEST. Serum cholesterol concentrations also fell significantly during the TEST. In the total group serum cholesterol fell by 6.5% (P = 0.0052), and in the subgroup who were positive for ischaemia the fall in serum cholesterol was 10.3% (P = 0.004). The reduction in serum cholesterol was 4.1% in the subgroup who did not develop ischaemia (P > 0.05). Mean total plasma antioxidant status showed no significant temporal change for the group as a whole, although there was a nonsignificant decrease immediately post-TEST in the ischaemic group and a slight rise at 8 h in the group negative for ischaemia.

Endogenous neutralizing antibodies against platelet-derived growth factor-aa inhibit atherogenesis in the cholesterol-fed rabbit

Previous studies have shown that the B chain of platelet-derived growth factor (PDGF) has an important role in atherogenesis. In this study we have investigated the contribution of PDGF-A chain in cholesterol-induced atherogenesis in the New Zealand White rabbit. High titers of antibodies to PDGF-AA or to platelet cytosolic protein (PCP) were induced in these animals by immunization against recombinant human PDGF-AA or human PCP. Rabbits were then fed a 0.25% to 1% cholesterol-containing diet for 10 weeks to induce atherosclerotic lesions; the rabbits were then humanely killed and perfusion-fixed and their aortas were removed. The extent of atherosclerosis in the thoracic aortas was determined by quantitative morphometry after staining with oil red O. The intimal and medial areas in histological sections taken at the level of the first intercostal branch were quantified by image analysis. Immunization against PDGF-AA and PCP, but not against adjuvant alone, resulted in rising titers of antibodies within 2 weeks, the levels of which reached a plateau by 8 weeks. The antibodies to PDGF-AA were isoform-specific, recognized both human and rabbit PDGF-AA, and neutralized the biological activity of PDGF-AA in vitro. Integrated plasma cholesterol levels were similar in both groups. Compared with nonimmune rabbits (n=10), animals immunized against PDGF-AA (n=10) or PCP (n=10) had significantly smaller areas of the aorta covered by atherosclerotic lesions (24.6+/-5.1% and 18.7+/-4.2%, respectively, vs 34.4+/-4.3%; P<0.05). This was associated with a reduced aortic intimal-medial area ratio in PDGF-AA-immunized (0.009+/-0.006) and PCP-immunized (0.025+/-0.017) rabbits than in nonimmune animals (0.159+/-0.066; P<0.05). These data suggest that PDGF-AA is actively involved in cholesterol-induced atherosclerosis in the rabbit.

Minor myocardial injury after elective uncomplicated successful PTCA with or without stenting: detection by cardiac troponins

Cardiac troponins are sensitive and specific markers for the detection of minor myocardial injury. However, they have been rarely used to monitor myocardial injury after coronary stenting. The purpose of the study was to measure cardiac troponin I (cTnI) and cardiac troponin T (cTnT) levels after elective uncomplicated successful percutaneous transluminal coronary angioplasty (PTCA) with or without coronary stenting and to compare their results with serum creatinine kinase MB isoenzyme (CKMB). CTnI and cTnT levels were compared with those of CK or CKMB in 98 consecutive patients with stable angina undergoing elective uncomplicated successful PTCA with stenting (n = 71) or without stenting (n = 27). Markers were measured before and 6, 12, 24, and 48 hr after the procedure. Peak postprocedural levels for each marker were compared and related to angiographic and procedural characteristics as well as to the occurrence of side-branch occlusion. None of the patients had abnormal markers before the procedure. Abnormal postprocedural values of one or more markers were observed in 28 patients (29%), 23 after stenting and 5 after PTCA alone. The frequencies of abnormal cTnI and cTnT levels were significantly higher than that of CKMB after coronary intervention (26% and 18% vs. 7%; P = 0.00016 and 0.015, respectively), with cTnI being the most significant. When compared with troponin-negative patients, abnormal cardiac troponin values were significantly related to total time of inflation (223 +/- 128 vs. 170 +/- 105 sec; P = 0.008) and inflation maximal pressure (12.9 +/- 2.3 vs. 12.0 +/- 2.7 atm; P = 0.04). Small side-branch occlusion was noticed in 36% of the troponin-positive patients and in 6% of the troponin-negative group (P = 0.00047). In conclusion, minor myocardial injury is not uncommon after elective uncomplicated successful PTCA with or without stenting. Cardiac troponins, especially cTnI, are more sensitive than CKMB for the detection of this minor myocardial injury. Total time of inflation and inflation maximal pressure are predictors of postprocedural elevation of cardiac troponins. Side-branch occlusion may account for some, but not all, periprocedural minor myocardial injury.

Changes in serum concentrations of markers of myocardial injury following treadmill exercise testing in patients with suspected ischaemic heart disease

BACKGROUND

The treadmill exercise test (TEST) is frequently used in patients with suspected ischaemic heart disease to establish a diagnosis and estimate future risk. However, its predictive value is poor. We aimed to investigate whether measurement of biochemical markers of myocardial injury could improve the diagnostic value of the procedure.

MATERIAL AND METHODS

Twenty-four subjects with suspected acute coronary syndrome underwent a treadmill exercise stress test. Of these 13 had had a previous myocardial infarction and two had a past history of coronary artery bypass grafting. Nine subjects were found to be positive for coronary ischaemia during the treadmill test. Serum cardiac markers (total creatine kinase [CK], CK-MB, Troponin I and Troponin T) were measured pre-TEST, and 0, 1, 2, 4, 8 and 24 hours following the treadmill test.

RESULTS

Total CK remained within the reference range for all subjects and showed no significant rise. However, mean serum concentrations of CK-MB were significantly higher than pre-test values at 2 hours (p < 0.03) following treadmill exercise testing in subjects who had a positive exercise stress test, but not in those with a negative test. In the subjects with a positive stress test, CK-MB levels returned to pre-Test value by 24 hours. Levels of neither serum troponin I, nor troponin T altered significantly at any point.

CONCLUSION

The measurement of CK-MB, but not cardiac troponins may add to the diagnostic utility of the TEST.

Effect of vitamin E supplementation on circulating cell adhesion molecules pre- and post-coronary angioplasty

The soluble adhesion molecules P-selectin (sP-selectin) and intercellular adhesion molecule-1 (sICAM-1) are derived from platelets and endothelial cells. Circulating concentrations of these soluble adhesion molecules are raised in patients with atherosclerosis and following percutaneous transluminal coronary angioplasty (PTCA). We have investigated the effects of vitamin E supplements (800 IU/day) on circulating plasma ICAM-1 and P-selectin levels pre- and post-PTCA. Patients, randomized to group, were pre-treated with vitamin E or placebo (soybean oil) for 1 month before routine PTCA. Plasma sICAM-1 and sP-selectin were measured by enzyme-linked immunosorbent assay on blood taken immediately pre- and post-PTCA. Total protein and alpha-tocopherol were measured on the same samples. Plasma alpha-tocopherol concentrations increased in patients receiving vitamin E: 19.1 (1.5) [mean (standard error of the mean, SEM)] mg/mL post-PTCA versus 13.9 (0.6) mg/mL pre-PTCA (n=23; P<0.01). Plasma sP-selectin and sICAM-1 levels were not significantly increased following PTCA in the vitamin E group. Pre-angioplasty mean (SEM) plasma sP-selectin concentration in the vitamin E group was 8.83 (0.97) ng/mg protein; the corresponding mean post-angioplasty value was 9.34 (0.89) ng/mg protein (P=0.85). The mean (SEM) pre-angioplasty sICAM-1 concentration in this group was 2.18 (0.24) ng/mg protein, and was 2.20 (0.23) ng/mg protein following angioplasty (P = 0.84). In the placebo group (n = 24) there was a significant increase in mean (SEM) sP-selectin concentration following angioplasty, from 7.48 (0.73) to 9.70 (0.78) ng/mg protein (P<0.05). The change (mean, SEM) in plasma sP-selectin concentration following angioplasty was significantly greater for the placebo group [2.22 (0.50) ng/mg protein] than for the group receiving vitamin E [0.50 (0.50) ng/mg protein] (P<0.02). This difference remained significant (P<0.05) even after adjustment for pre-angioplasty P-selectin concentrations. Mean (SEM) plasma sICAM-1 concentrations remained unchanged following angioplasty [pre-angioplasty: 2.16 (0.20) ng/mg protein; post-angioplasty: 1.97 (0.13) ng/mg protein]. Vitamin E may therefore limit platelet or endothelial activation during PTCA.

Mononuclear cell adhesion to collagen ex vivo is related to pulse pressure in elderly subjects

Mononuclear cells and platelets are intimately involved in the pathogenesis and complications of cardiovascular disease. Platelet activation has been reported in hypertension, though the activation-state of monocytes has received less attention. In this study the adhesiveness of monocytes and platelets was assessed and any relationship between the adhesive properties of these cellular elements and plasma levels of soluble adhesion molecules and blood pressure parameters determined. Fifty six elderly volunteers, of whom 32 were classified hypertensive (daytime SBP > or = 135 mmHg), underwent 24 h blood pressure monitoring, assessment of monocyte and platelet adhesion and measurement of the plasma soluble adhesion molecules ICAM-1, L-selectin, E-selectin and vWF. In the elderly hypertensive subjects, monocyte adhesion to collagen coated (P < 0.05) and tissue culture plastic microwells (P < 0.05) was significantly elevated and circulating levels of soluble ICAM-1 (P < 0.01) and soluble E-selectin (P < 0.05) were significantly raised compared to their normotensive counterparts. A significant correlation was found to exist between monocyte adhesion to collagen and daytime pulse pressure (r = 0.39, P < 0.01) and also between plasma levels of soluble E-selectin and clinic DBP (r = 0.40, P < 0.001). The increased monocyte adhesion witnessed in hypertensive subjects and with increasing pulse pressure may contribute to the increased risk of cardiovascular disease in hypertension. Whether this increased adhesiveness is a property of the monocytes. or reflects endothelial cell activation, remains to be determined.

Detection of minor myocardial injury after successful percutaneous transluminal coronary angioplasty with or without stenting

Cardiac troponins are sensitive and specific markers for the detection of minor myocardial injury. However, they have been rarely used to monitor myocardial injury after coronary stenting. The purpose of the study was to measure cardiac troponin I (cTnI) and cardiac troponin T (cTnT) levels after apparently successful percutaneous transluminal coronary angioplasty (PTCA) with or without coronary stenting and to compare their results with serum creatine kinase (CK) and its isoform, creatine kinase-MB (CKMB). CTnI and cTnT levels were compared with those of CK or CKMB in 50 consecutive patients with stable angina undergoing visually successful PTCA with stenting (n = 35) or without stenting (n = 15). Cardiac TnI, cTnT, CK and CKMB levels were measured before and 6, 24, and 48 hours after the procedures was performed. None of the patients had abnormal cTnI or cTnT levels, CK activity, or CKMB levels before the procedures. Moreover, no patient showed electrocardiographic evidence of myocardial infarction. 13 patients (26%) had abnormal peak values of one or more markers at 24 hours after coronary intervention. Troponin I was elevated in 10/35 patients after coronary stenting (29%) and in 2/15 patients after PTCA (13%) (P = 0.327). Troponin T was elevated in 6 patients (17%) and CKMB activity was elevated in 3 patients (9%) of the coronary stenting group. CTnI was more significant than CKMB (P = 0.023) in detecting minor myocardial injury. When compared with cTnI and CKMB, cTnT did not reach significance (P = 0.129 and 0.489, respectively). 5 out of the 13 patients with abnormal markers (38%) developed side branch occlusion after stenting. In conclusion, cTnI was a very sensitive marker in detecting minor myocardial injury after coronary angioplasty with or without stenting. The frequency of increased serum levels of cardiac troponins was higher in patients undergoing stent implantation than in those treated with angioplasty alone but did not reach significance. Side branch occlusion may have accounted for some, but not all, periprocedural minor myocardial injury in the stent group.

Antioxidant vitamin concentrations and LDL oxidation in nephrotic syndrome

The increased risk of atherosclerosis in nephrotic syndrome is attributable in part to the associated hyperlipidaemia. The importance of oxidation of LDL in the atherogenic process has been recognized over the last 15 years. However, there are few data on the balance of antioxidant defences and lipoprotein oxidation in nephrotic syndrome. Plasma antioxidant vitamin concentrations and indices of LDL oxidation (LDL lipid hydroperoxide content and the susceptibility of LDL to oxidation) were measured in two groups of patients; group I comprised 29 nephrotic patients and group II comprised 25 patients with haematuria. Plasma ascorbate concentration was significantly lower in group I (the nephrotic group) compared with group II (median 13.3 versus 22.2 micromol/L; P<0.001). Vitamin E concentrations were higher in group I but were not significantly different if corrected for total plasma cholesterol (6.12 versus 5.88 micromol/mmol; P=0.33). However, these changes resulted in a low ascorbate:vitamin E ratio in group I (0.19 versus 0.87; P<0.0001). Despite these changes in important antioxidant vitamin concentrations, we were unable to demonstrate any increased susceptibility to LDL oxidation in vitro or any difference in LDL lipid hydroperoxide content. These data suggest that there may be a relative defect of oxidant/antioxidant balance in nephrotic syndrome which could predispose to increased oxidative stress. However, measures of LDL oxidation were not significantly different between the two groups. LDL was protected from oxidation despite the severe hyperlipidaemia and the low circulating vitamin C concentrations.

Effect of vitamin C on ambulatory blood pressure and plasma lipids in older persons

OBJECTIVES

To determine the effect of oral vitamin C supplements on ambulatory blood pressure and plasma lipids.

DESIGN

A 6-month double-blind randomized placebo-controlled cross-over study with a 1 -week washout between cross-over periods.

METHODS

Vitamin C 500 mg daily or matching placebo was given to 40 men and women aged between 60 and 80 years for 3 months each in a cross-over fashion. Clinic and 24-h ambulatory blood pressure, plasma ascorbate and lipids were measured at baseline and at the end of each cross-over phase.

RESULTS

Clinic blood pressure did not change between placebo and vitamin C phases. Daytime ambulatory blood pressure showed a small but significant fall in systolic blood pressure (2.0 +/- 5.2 mmHg; 95% confidence interval 0-3.9 mmHg) but not in diastolic blood pressure. Regression analysis showed that with increasing baseline daytime blood pressure the fall in blood pressure with vitamin C supplementation increased. Regression analysis of the change in high-density lipoprotein (HDL) cholesterol showed a significant effect of sex on the change in HDL cholesterol. In women, but not men, HDL cholesterol increased significantly by 0.08 +/- 0.11 mmol/l, P=0.007. There was no change in low-density lipoprotein cholesterol between treatment periods.

CONCLUSION

In older adults high intakes of ascorbic acid have modest effects on lowering high systolic blood pressure, which could contribute to the reported association between higher vitamin C intake and lower risk of cardiovascular disease and stroke.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Cardiac markers for assessing the acute coronary syndromes. A focus on cardiac troponins

Markers of myocardial injury will continue to play an essential role in the assessment and management of patients presenting within the spectrum of acute coronary syndromes, a term representing the continuum of acute myocardial ischemia ranging from angina through Q-wave myocardial infarction. Coronary artery lesion instability can be detected by markers of plaque inflammation and disruption, platelets reactivity, and thrombosis. When myocardial injury occurs with severe impairment of coronary blood flow, several markers are released from the damaged myocyte. For many years, creatine kinase-MB isoenzyme has been the conventional marker for myocardial infarction. Despite its inadequate sensitivity and specificity for myocardial injury, creatine kinase-MB remains an essential component in assessing re-infarction or infarct extension, as well as in monitoring reperfusion after thrombolytic therapy when combined with myoglobin. Among the many cardiac markers for myocardial necrosis, cardiac troponins possess superior sensitivity and specificity for the detection of myocardial injury. In addition to their superior performance in detecting minor myocardial damage, cardiac troponins can be useful in detecting perioperative myocardial infarction, infarct size, improving risk stratification, and facilitating therapeutic decision making in patients with acute coronary syndromes.

Dietary copper supplementation reduces atherosclerosis in the cholesterol-fed rabbit

There has been considerable debate about how copper status may affect the biochemical and cellular processes associated with atherogenesis. In the present study we have attempted to address this issue directly by investigating the effects of dietary copper supplementation on processes likely to contribute to atherogenesis, using the cholesterol-fed New Zealand White rabbit model. Age matched rabbits (n = 16) were fed a 0.25-1% cholesterol diet to maintain plasma cholesterol concentrations at approximately 30 mmol/l. Eight of these animals also received 0.2% copper acetate. Control animals (n = 8) received rabbit chow without supplements. After 13 weeks on the experimental diets the animals were killed. Integrated cholesterol levels were similar for the cholesterol-fed animals (31.1+/-2.5 vs. 29.9+/-1.9 mmol/l weeks; P>0.05). Although integrated plasma copper levels were higher in the animals receiving the copper supplements, these did not differ significantly (19.0+/-4.8 vs. 15.1+/-2.9 micromol/l weeks; P>0.05). Tissue concentrations of copper were higher in the copper fed animals compared to those on cholesterol alone in aortic 14.0+/-0.75 vs. 1.8+/-0.2 microg/g wet tissue; P<0.05), carotid artery (11.4+/-3.5 vs. 4.9+/-0.9 microg/g wet tissue; P<0.05), and hepatic (332.5+/-28.6 vs. 3.3+/-1.1 microg/g wet tissue; P<0.0001) samples. The concentration of copper within the carotid artery was also significantly higher than that within the aorta (7.5+/-1.8 vs. 2.4+/-0.4 microg/g wet tissue; P<0.05). In animals fed a normal rabbit chow aortic, carotid and hepatic copper concentrations were 3.7+/-0.8, 9.4+/-3.4, and 5.0+/-1.6 microg/g, respectively. These values did not differ significantly from the cholesterol-fed animals (P>0.05). Plasma concentrations of caeruloplasmin, the major copper carrying protein, were estimated as plasma ferroxidase activity and were similar for the groups (P>0.05), as were aortic superoxide dismutase activity levels (P>0.05). Copper supplementation was associated with increased mononuclear cell adhesion to the endothelium of the carotid endothelium, with 2.6+/-0.3 adherent monocytes/1000 endothelial cells in the cholesterol plus copper-fed animals compared to 1.3+/-0.3 in the cholesterol-fed group (P = 0.0006), and 0.1+/-0.1 in the control animals (P<0.002). This may reflect the higher concentrations of copper found within the carotid artery. Histology of the thoracic aorta at the level of the third and sixth intercostal arteries, showed that copper supplementation was associated with significantly smaller intimal lesions (P<0.05 and P<0.01, respectively). These data suggest that copper supplements possibly inhibit the progression of atherogenesis.

Effects of vitamin E on human platelet and mononuclear cell responses in vitro

Recent epidemiological studies have provided evidence supporting the potential benefits of antioxidants in coronary prevention. We have investigated the effects of vitamin E on platelets, monocytes and endothelial cells in vitro. Pre-incubation of platelets with vitamin E inhibited subsequent thrombin- (P < 0.05, n = 5), collagen- (P < 0. 0001, n = 5) and ADP-(P < 0.05, n = 4) induced platelet aggregation measured using a microtitre plate method, or conventional aggregometry. The adhesion of thrombin-activated platelets to collagen was also inhibited by vitamin E (P < 0.05, n = 8), but not by vitamin C (P > 0.05, n = 8); nor was the adhesion of unstimulated platelets significantly affected (P > 0.05, n = 8). Pre-incubation of monocytes with vitamin E inhibited their subsequent adhesion to plastic (P < 0.05, n = 9), and was also associated with an 18% reduction in adhesion to EA.hy 926 endothelial cells (n = 8), although this failed to reach statistical significance. Pre-incubation of the endothelial cells with vitamin E also significantly reduced subsequent mononuclear cell adhesion by 56% (P < 0.05, n = 3).

Genetic markers to predict polygenic disease: a new problem for social genetics

Many genetic markers that relate to common multifactorial disease in adults have been identified during the past 15 years. Their use as adjuncts for the diagnosis, prognosis, prediction of disease or targeting therapy for these disorders has begun, good examples being the Factor V Leiden mutation for venous-thromboembolism, lipoprotein lipase mutations for hypertriglyceridaemia and the apolipoprotein E4 variant for Alzheimer's dementia. However, extensive gene-gene and gene-environment interactions make their use more complex than markers for the simpler monogenic disorders (such as cystic fibrosis, or Duchenne's muscular dystrophy). Possible misapplication of the genetic markers for multifactorial disease in the fields of risk prediction, direct sales to the public, life assurance, employment rights, and legislation for regulation of their use are discussed.

Immunization with bacillus Calmette-Guerin vaccine increases aortic atherosclerosis in the cholesterol-fed rabbit

New Zealand White rabbits were injected subcutaneously with either a human dose of bacillus Calmette Guerin (BCG) vaccine (n = 7) or saline (n = 7). A further half dose of BCG or saline was injected after a further 4 weeks. The animals were subsequently fed a 0.25-1% cholesterol diet for 10 weeks, 8 weeks after the first injection. The rabbits were killed and perfusion fixed with 4% paraformaldehyde. The integrated plasma cholesterol levels did not differ significantly between the groups (P > 0.05). Plasma levels of anti-mycobacterial antibodies rose following BCG immunization, reaching a peak after 8 weeks (P < 0.05) compared to basal titers and the control group. BCG immunization was also associated with increased peripheral lymphocyte and monocyte activation, as evidenced by increased surface expression of IL-2 receptor (CD25) (P < 0.02) and MAC-I (CD11b) (P < 0.05), respectively. Significantly more mononuclear cells bound to the aortic endothelium of BCG immunized, cholesterol-fed rabbits (1.93+/-0.77 mononuclear cells/1000 endothelial cells) than to that of saline immunized rabbits (0.08+/-0.08 mononuclear cells/1000 endothelial cells; P < 0.01). The aortic intimal:medial ratio was greater in the BCG immunized rabbits (0.19+/-0.08) than those treated with saline (0.04+/-0.03; P < 0.05). This suggests that BCG immunization enhances peripheral leucocyte activation, aortic monocyte recruitment and atherogenesis in the cholesterol-fed rabbit.

Infection, immunisation and atherosclerosis: is there a link?

Atherosclerosis is the predominant underlying pathology responsible for coronary heart disease (CHD). It bears all the hallmarks of a chronic inflammatory disease and typical atherosclerotic lesions contain activated macrophages and T-cells. There have been several reports of possible associations between prior exposure to a number of specific micro-organisms and subsequent CHD, and prospective epidemiological studies have reported that elevated plasma levels of particular acute phase reactants (APRs) are predictors of future cardiac events. Investigators have also shown that immunisations exacerbate atherosclerosis in experimental animal models. These data raise the possibility that immunostimulation associated with natural infection by certain organisms, or vaccination, may promote atherosclerosis. A hypothesis which may explain all these findings, is that the cellular--and perhaps humoral--responses associated with immune stimulation may enhance atherogenesis.

The possible role of copper ions in atherogenesis: the Blue Janus

It has been proposed that the oxidative modification of low density lipoprotein (LDL) is a key event in human atherogenesis. Copper ions can catalyse the oxidative modification of LDL in vitro and there is some evidence that they may also participate in the oxidation of LDL within the arterial wall. However, copper ions also form an intrinsic constituent of superoxide dismutase and caeruloplasmin, enzymes that may be involved in preventing oxidative injury. Atherosclerotic lesions frequently contain considerable quantities of extracellular matrix molecules. These may contribute to the expansion of the arterial neointima, causing luminal narrowing. They may also play a beneficial role by stabilising the plaque. Copper is an essential component of lysyl oxidase, an enzyme involved in the biosynthesis of collagen, which is a major constituent of the extracellular matrix. The impact of alterations in body copper status on atherogenesis is therefore difficult to predict. Experimental and epidemiological data are conflicting and therefore do not provide a clear resolution of this issue. We have reviewed the biochemical and cellular effects of copper ions that may play a role in atherogenesis.

Dietary vitamin E supplementation inhibits thrombin-induced platelet aggregation, but not monocyte adhesiveness, in patients with hypercholesterolaemia

Several recent studies have indicated the possible beneficial effects of antioxidants, specifically vitamin E, in primary and secondary coronary prevention. These studies suggest that a diet enriched in vitamin E is insufficient to have a significant protective effect, whereas supplements, in excess of 200 international units (IU) per day, are efficacious in preventing coronary disease in both men and women. The mechanisms by which vitamin E may exert its protection are uncertain, but, vitamin E is lipophilic and has been shown to inhibit the oxidative modification of low density lipoprotein (LDL), a process thought to be of crucial importance in atherogenesis. We have also previously shown that alpha-tocopherol (the biologically most potent isomer of vitamin E) has important direct effects on vascular endothelial and smooth muscle cells. In the present study we have investigated the effects of oral supplements of vitamin E (400 IU per day) on platelet and mononuclear cell function in patients with hypercholesterolaemia. We found that although vitamin E supplementation had no significant effect on mononuclear cell adhesion ex vivo, it had a significant effect on the thrombin-induced platelet aggregation (P < 0.01; ANOVA): 6 weeks after starting the vitamin E supplements, the mean EC50 for thrombin-induced aggregation increased 132% (P < 0.05; paired t-test) compared to treatment with placebo. The effects of vitamin E on platelet function may, in part, explain its anti-atherogenic properties.

Endogenously elicited antibodies to platelet derived growth factor-BB and platelet cytosolic protein inhibit aortic lesion development in the cholesterol-fed rabbit

Several studies have indicated that growth factors, such as platelet derived growth factor (PDGF), may be important in atherogenesis. These factors are released from platelets, or expressed by cells of the arterial wall. In order to study their role in atherogenesis more directly, rabbits were immunized with PDGF-BB, platelet cytosolic protein, or human serum albumin (HSA), until high titres of antibody were attained. Atherosclerotic lesions were subsequently induced by feeding the animals with a 2% cholesterol enriched diet. At the end of approximately 3 months, the extent of aortic lesion development was assessed by image analysis of en face preparations of aortae stained with Oil Red-O, and histological segments of aortae taken at the level of the first intercostal artery branch point. The endogenous antibodies were characterized with respect to their cross-reactivity, and ability to neutralize PDGF and platelet cytosol-induced cell proliferation and migration in vitro. The endogenous, anti-PDGF-BB antibody was isoform specific, and neutralized the mitogenic and chemotactic properties of PDGF-BB and rabbit platelet cytosolic protein in vitro. The anti-platelet cytosol antibody partially inhibited the chemotactic and mitogenic properties of rabbit platelet cytosolic protein. Compared to non-immune rabbits (n = 5), animals immunized with HSA (n = 4) had a significantly larger area of aortic lesion involvement (P < 0.01), whereas aortic lesions in rabbits immunized with PDGF-BB (n = 5), or platelet cytosolic protein (n = 7) were significantly smaller than either non-immune animals, or animals immunized with HSA (P < 0.05). The same pattern was observed for other measures of aortic lesion involvement including aortic intima:media ratio at the level of the first intercostal artery. These data suggest that PDGF-BB, and possibly other platelet-associated growth factors, are involved in cholesterol-induced atherosclerosis.

RT-PCR study on the effects of minimally modified low-density lipoproteins and probucol treatment on gene expressions of interleukin-1 and platelet-derived growth factor B-chain in human peripheral blood mononuclear cells

Oxidatively modified low-density lipoprotein has been identified in early atherosclerotic lesions and may play an important role in atherogenesis. Minimally modified low-density lipoprotein (MM-LDL) derived by prolonged storage under sterile conditions results in mild oxidation and is recognised by the LDL receptor rather than the scavenger receptor. Therefore, it may be closer to the real pathophysiological circumstances in the initial state of atherosclerosis. Using a reverse transcription-polymerase chain reaction (RT-PCR) technique, the present study demonstrates that MM-LDL is capable of inducing gene expression of both interleukin-1 alpha (IL-1 alpha) and interleuking-1 beta (IL-1 beta) in human peripheral blood mononuclear cells in a dose-dependent manner. Concomitant treatment of the cells with the anti-oxidant probucol results in an inhibitory effect in steady-state levels of both IL-1 alpha and IL-1 beta mRNA and the effects were also shown in a dose-dependent fashion. We also found an inhibitory effect of MM-LDL on gene expression of platelet-derived growth factor B chain (PDGF-B) mRNA levels by mononuclear cells. Hence MM-LDL is biologically active and may contribute to the early stages of atherogenesis by stimulating the inflammatory cytokine IL-1 and the efficacy of probucol in inhibiting the progression of atherosclerosis may be due, both to its inhibition of IL-1 expression by intimal macrophages, and its prevention of LDL oxidation.

Recombinant insulin-like growth factor-1 modulates aggregation in human platelets via extracellular calcium

Insulin like growth factor-1 (IGF-1) potentiated aggregation of human platelets induced by thrombin-, collagen- and ADP in a dose-dependent manner over the range 30-300 nM. IGF-1 (100 nM) reduced EC50 values for thrombin, collagen and ADP-induced aggregation by 19.6%, 53.6% and 22.8% respectively. Potentiation by IGF-1 was dependent on the presence of extracellular Ca2+ and was inhibited by verapamil or nifedipine. Further, IGF-1 enhanced the elevation in free intraplatelet Ca2+ induced by the platelet agonists collagen and thrombin.

Insulin-like growth factor-I modulates monocyte adhesion to EAhy 926 endothelial cells

IGF-I is a ubiquitous growth factor, found in platelets and elaborated by many other cell types. It is thought to be involved in several pathophysiological processes including embryonic development, angiogenesis and wound healing. We report that the adherence of human peripheral blood monocytes to an endothelial cell line (EAhy 926) is inhibited in a dose and time-dependent manner by pre-incubating the endothelial cells with IGF-I (P < 0.001). Monocyte adhesion was inhibited 17.9 +/- 1.9% by IGF-I at a dose of 1000 ng/ml (P < 0.01). In contrast, IGF-I had no significant effect on monocyte adherence to plastic. The inhibitory effects of IGF-I were reversed by co-incubating the endothelial cells with the nitric oxide synthase inhibitor, L-NAME. These data suggest that the effects of IGF-I are mediated by the release of nitric oxide from the endothelial cells.

Tissue distribution of alpha-tocopherol following dietary supplementation in the rat: effects of concomitant cholesterol feeding

Vitamin E is a potent, naturally occurring, lipid-soluble antioxidant, which is reported to be protective against several disease processes, including coronary atherosclerosis. We have measured the alpha-tocopherol content of the aorta, liver, skeletal muscle, and kidney of rats fed one of the following diets for 10 weeks: a normal control chow diet (i); or the same diet containing 1% cholesterol (ii); 0.5% vitamin E (iii); or 1% cholesterol plus 0.5% vitamin E (iv). The alpha-tocopherol content of serum and tissue extracts was measured by HPLC using gamma-tocopherol as an internal standard. Tissue and serum cholesterol content was measured using a cholesterol oxidase enzyme reagent kit. In all animals receiving the 1% cholesterol diet, serum cholesterol levels increased significantly (P < 0.005). By the 10th week, mean serum alpha-tocopherol levels rose significantly in both groups of animals receiving dietary vitamin E supplements (P < 0.0001) compared with their respective control group. This was accompanied by a significant increase in the absolute alpha-tocopherol content of liver (8- to 9-fold) and aorta (3- to 4-fold). The alpha-tocopherol content of renal and skeletal muscle tissue was raised 1- to 2-fold in both groups of rats on vitamin E supplements, however the increased attained significance only for the renal tissue. The aortic tissue alpha-tocopherol/cholesterol ratio was 4-fold higher in the rats receiving concomitant 1% cholesterol plus 0.5% vitamin E compared with animals receiving 1% cholesterol alone (P < 0.02), and was 5-fold higher in the rats receiving 0.5% vitamin E compared with those receiving control chow (P < 0.01). These data suggest that dietary vitamin E supplementation results in a differential uptake of alpha-tocopherol, which may be dependent, in part, on selective lipoprotein particle accumulation.

Insulin-like growth factor binding protein-1 inhibits arterial smooth muscle cell proliferation in vitro but does not reduce the neointimal response to balloon catheter injury

The biological effects of the insulin-like growth factors (IGFs) are modulated by circulating binding proteins (BPs), including IGFBP-1. We have investigated the effects of recombinant IGFBP-1 on smooth muscle cell (SMC) proliferation in vitro using cultured rat aortic SMCs and in vivo using the ballooned rat carotid artery model. IGFBP-1 inhibited IGF-1 induced and spontaneous SMC proliferation dose-dependently. In vivo, the effective half-life of IGFBP-1 was approximately 5 h when administered by intraperitoneal injection. High peri-operative plasma levels of IGFBP-1 (mean 1780 ng/ml) were attained by giving and intravenous dose immediately prior to balloon injury in 9 rats. Animals injected with human serum albumin or saline were used as controls. In vivo cell proliferation was assessed by BrdU pulse labeling each animal prior to the termination of the experiment, 6 days after balloon injury. Absolute intimal thickness, intima-media ratio and cell proliferation indices were measured for each animal. Although IGFBP-1 inhibited SMC proliferation in vitro, high plasma concentrations of IGFBP-1 did not reduce neointimal size or cell proliferation. IGFBP-1 administration was, however, associated with a significantly greater loss of body weight (P < 0.05), indicating that the peptide had a profound metabolic effect. Our data suggest that IGF-1 does not have a major role in inducing SMC proliferation in the early phases following angioplasty.

Differences in onset of impaired endothelial responses and in effects of vitamin E in the hypercholesterolemic rabbit carotid and renal arteries

Hypercholesterolemia (HC) is known to be associated with impaired endothelium-mediated responses in the vasculature. Evidence suggests that increased levels of reactive oxygen species (ROS) in the vessel wall may contribute to the impairment by decreasing the biological activity of endothelium-derived relaxing factor (EDRF). We compared the relative onset of HC-induced impairment of endothelial responses in the carotid and renal arteries and investigated the potentially beneficial effect of the antioxidant vitamin E. Rabbits were fed a 1% cholesterol-enriched diet for 4 and 8 weeks, and vascular responses were compared using isolated ring segments of the carotid and renal arteries. In the carotid artery, relaxant responses to acetylcholine (ACh) were significantly and progressively impaired after 4 and 8 weeks; in the renal artery, however, responses were only slightly impaired after 8 weeks. There were no changes in responsiveness to A23187 or sodium nitroprusside (SNP) in either artery. We tested the effect of 0.2% vitamin E by adding it to the diet for 4 weeks, after an initial 4-week of feeding of 1% cholesterol alone. Vitamin E reversed impaired responses to ACh in the carotid but not the renal artery and also enhanced relaxant responses to A23187. We conclude that the carotid artery is more susceptible than the renal artery to HC-induced endothelial impairment and that ROS may play a role in this impairment in the carotid artery but not in the renal artery.

Hyaluronan (HYAL-BV 5200) inhibits neo-intimal macrophage influx after balloon-catheter induced injury in the cholesterol-fed rabbit

Hyaluronan is a glycosaminoglycan, elaborated by several cell types, and is a major constituent of the extracellular matrix. Recent studies suggest that hyaluronan influences cell migration and proliferation. At high concentrations, it has been shown to inhibit macrophage migration in vitro. We have investigated the effects of hyaluronan administration on neo-intimal lesion development following balloon catheter injury of the common carotid artery in the cholesterol-fed New Zealand White rabbit. Hyaluronan, administered as sodium hyaluronate at the time of surgery and daily until sacrifice, 2 weeks later, reduced the absolute neo-intimal response to injury by 42% (117 +/- 16 microns to 68 +/- 11 microns; P < 0.05), and the intima-media ratio by 35% (0.91 +/- 0.10 to 0.59 +/- 0.11; P < 0.05). This was associated with a 62% reduction in intimal macrophage content (8.63 +/- 1.85% to 3.25 +/- 1.05%; P < 0.02). At the time of killing, serum cholesterol levels and weight gain were comparable between the groups of animals receiving a cholesterol diet (P > 0.05). In both groups mean serum cholesterol levels at the time of the balloon injury and killing were significantly greater than at entry (P < 0.001), and significantly higher than in a group receiving control chow (P < 0.001). These data suggest that the effect of hyaluronic acid on neo-intimal size may be mediated, in part, by an inhibition of monocyte/macrophage influx, and support the view that hyaluronan impairs monocyte migration.

Vitamin E inhibits the intimal response to balloon catheter injury in the carotid artery of the cholesterol-fed rat

We have investigated the effect of the naturally occurring, lipid-soluble antioxidant, vitamin E, on the intimal response to balloon injury in the cholesterol-fed rat. We found that in animals receiving a 0.5% vitamin E plus 1% cholesterol diet, neo-intimal thickening was reduced by 30% (P < 0.025) compared to animals receiving either cholesterol alone, or a control chow diet. In all three dietary groups, the intimal lesion consisted predominantly of smooth muscle cells, and few monocytes/macrophages (< 0.5%) could be identified by staining with the monoclonal antibody ED-1. In vitro, vitamin E inhibited platelet-derived growth factor- (PDGF) (20 ng/ml) and serum (2%)-induced mitogenesis of both adult rat thoracic aortic smooth muscle cells and an embryonic rat aortic smooth muscle cell line (A7r5), dose-dependently. These data suggest that reactive oxygen species may be involved in the intimal response to balloon catheter injury, and that antioxidants, such as vitamin E, may offer some protection against restenosis. Although the way by which it does so is unclear, one possible mechanism is by a direct inhibitory effect on the accumulation of smooth muscle cells within the developing neo-intima.

Vitamin E reverses cholesterol-induced endothelial dysfunction in the rabbit coronary circulation

Hypercholesterolaemia and atherosclerosis are associated with impaired endothelium-dependent vasodilation. In this study we have examined the effects of vitamin E on cholesterol-induced endothelial dysfunction in the rabbit coronary circulation. Rabbits were maintained for 4 or 8 weeks on one of three experimental diets: (a) control chow, (b) 1% cholesterol or (c) 1% cholesterol for the first half of the treatment period followed by 1% cholesterol + 0.2% vitamin E during the last half of the treatment. After sacrifice, vasodilator responses to acetylcholine and sodium nitroprusside in the isolated perfused heart were studied. Responses to sodium nitroprusside were similar between the groups whereas responses to acetylcholine were significantly impaired in cholesterol-fed rabbits after both 4 and 8 weeks when compared to controls. In the cholesterol + vitamin E group, responses to acetylcholine were similar to controls and significantly greater than in the group receiving cholesterol alone. These results show that both 4 and 8 weeks of cholesterol-feeding induces an endothelial dysfunction in the coronary circulation of the rabbit, and that vitamin E protects against this dysfunction. By comparing responses to acetylcholine in the 4 week cholesterol group with the 8 week cholesterol + vitamin E group it was shown that vitamin E may not only prevent further deterioration of the endothelial function in the rabbit heart, but may also reverse the adverse effects of hypercholesterolaemia.

Dietary vitamin E increases the resistance to lipoprotein oxidation and attenuates endothelial dysfunction in the cholesterol-fed rabbit

This study was conducted to determine if vitamin E could reverse or attenuate endothelial dysfunction following an atherogenic diet. Rabbits were initially fed 1% cholesterol for 4 weeks to induce endothelial dysfunction. During the next 4 weeks the rabbits were fed either 1% cholesterol +0.2% vitamin E or 1% cholesterol alone, and were then killed. Endothelium-dependent responses to acetylcholine, calcium ionophore A23187 and sodium nitroprusside (SNP) were studied in the preconstricted perfused rabbit ear. Dietary vitamin E partially reversed the impaired endothelium-dependent responses to acetylcholine associated with cholesterol feeding. The maximum decrease in perfusion pressure in response to acetylcholine was 77.8% +/- 3.6% in control animals, 35.3% +/- 2.6% in cholesterol-fed animals, and 49.1% +/- 4.7% in cholesterol+vitamin E treated animals. The response to A23187 or sodium nitroprusside did not differ between the groups. The susceptibility of rabbit beta-VLDL to oxidation was markedly decreased in the vitamin E treated animals as assessed by the formation of conjugated dienes. The formation of lipid peroxidation products were also significantly inhibited by vitamin E. These data suggest that dietary vitamin E is beneficial in reducing the oxidative injury that may lead to the impairment of nitric oxide (NO)-mediated responses in early hypercholesterolaemia.

Vitamin E restores endothelium dependent vasodilatation in cholesterol fed rabbits: in vivo measurements by photoplethysmography

OBJECTIVE

Pulse curve plethysmography was used to examine the effect of vitamin E on endothelium dependent and independent vasodilatation in unanaesthetised cholesterol fed rabbits in vivo. The height of the dicrotic notch was used as an index of general arterial vasodilatation.

METHODS

Twenty eight rabbits were divided into three study groups; a control group (group 1, n = 8), a group fed 1% cholesterol (group 2, n = 10), and a group fed 1% cholesterol with the addition of 0.2% vitamin E after four weeks (group 3, n = 10). After six weeks on diet the vasodilator responses to acetylcholine and glyceryl trinitrate were measured by photoplethysmography of the rabbit ear. Recordings were made during light sedation at baseline and during infusion of acetylcholine (1.5, 3.0, 6.0, and 12 micrograms.min-1) and glyceryl trinitrate (3.75, 7.5, and 15.0 micrograms.min-1). In a second set of experiments with control fed rabbits (n = 5), acetylcholine infusions were given before and after infusion of L-nitro-arginine (15 mg).

RESULTS

The relative height of the dicrotic notch (which predominantly indicates arterial tone in the larger vessels) was reduced by acetylcholine in a dose dependent manner, but in cholesterol fed rabbits (group 2) this response was significantly decreased. Rabbits receiving concomitant dietary vitamin E responded in a similar manner to controls. The difference was most prominent using acetylcholine at a dose of 3.0 micrograms.min-1, where the mean change from baseline was 11(SEM 4)% in group 2, compared to 31(6)% in group 1 (p = 0.01), and to 26(5)% in group 3 (p = 0.02). Similar differences between the groups were observed for the increase in heart rate during acetylcholine infusions. In contrast, the responses to glyceryl trinitrate were similar in all groups. After infusions of L-nitro-arginine, the responses to acetylcholine were blunted.

CONCLUSIONS

Supplementation with vitamin E restored the otherwise reduced vascular response to acetylcholine in cholesterol fed rabbits. Analysis of photoplethysmographic pulse curves is a simple non-invasive method of evaluating arterial vasodilator effects. However, the nature of the measured dilator response needs to be characterised further.

Oxidative modification of low-density lipoprotein by human polymorphonuclear leucocytes to a form recognised by the lipoprotein scavenger pathway

The oxidative modification of low-density lipoprotein (LDL) results in the formation of cytotoxic and chemotactic lipids which are thought to be of importance in the development of atherosclerotic lesions. In the present study we show that polymorphonuclear leucocytes (PMNs) can modify LDL to a form which is rapidly incorporated by macrophages via a scavenger receptor pathway. Incubation of 125I-labelled LDL with PMNs in Ham's F-10 medium resulted in oxidation as shown by the appearance of thiobarbituric acid-reactive substances, increased electrophoretic mobility of the LDL and increased degradation of the LDL by mouse peritoneal macrophages. The presence of the anti-oxidant butylated hydroxytoluene or the metal ion chelator, EDTA inhibited the PMN-mediated modification. The degradation of 125I-labelled PMN modified LDL by macrophages was competitively inhibited by unlabelled copper-oxidised LDL but not by native LDL, indicating that the degradation was mediated by the scavenger receptor. The oxidative modification of LDL by PMNs could be of pathophysiological importance in inflammation and in the accelerated atherosclerosis seen following cardiac reperfusion injury.

Measurement of plasma probucol levels by high-performance liquid chromatography

An improved assay for measuring plasma levels of probucol using reversed-phase high-performance liquid chromatography has been developed and used to measure probucol in cholesterol-fed rabbits. The sample was extracted with iso-octane, reconstituted in acetonitrile and was analysed using a Hypersil ODS column with a mobile phase consisting of acetonitrile-water (96:4, v/v). Detection was carried out using ultraviolet absorption at 241 nm. The lower detection limit for plasma probucol was 0.5 micrograms/ml. Inter-assay and intra-assay coefficients of variation were 1.8-4.8% and 1.6-3.3%, respectively. The method was applied to measurements of probucol in plasma from rabbits receiving a diet containing 1% probucol and 2% cholesterol for five weeks. Probucol levels at five weeks were significantly higher in the animals receiving concomitant cholesterol, and were close to the steady-state values predicted from the one week measurements. Also, the plasma probucol levels were positively correlated with total plasma cholesterol (r = 0.87, p < 0.001). The results indicate that bioavailability of probucol is dependent on the lipid content of the diet.