P3783A higher habitual flavonoid intake is associated with a lower risk of atrial fibrillation

Background

Our understanding of how diet affects future risk of atrial fibrillation (AF) is limited. Evidence suggests that higher habitual intakes of flavonoids, bio-active compounds found in plant-based foods and beverages, lower cardiovascular disease risk, attenuate inflammation, and may have anti-arrhythmic properties.

Purpose

To investigate the association between flavonoid intake and clinically apparent AF in a large cohort of Danish men and women.

Methods

Baseline data from 55 634 participants without AF of the Danish Diet, Cancer and Health Study, recruited from 1993 to 1997, were cross-linked with Danish nationwide registries. Flavonoid intake was calculated from validated food frequency questionnaires using the Phenol-Explorer database. Associations between flavonoid intake and AF hospitalisation were examined using restricted cubic splines based on Cox proportional hazards models with adjustments for age, sex, BMI, smoking status, physical activity, alcohol intake, income, and hyperthyroidism.

Results

After a median [IQR] follow-up of 21 [18–22] years, 6 301 participants were hospitalised with AF. Non-linear associations were observed for total flavonoid intake and for all flavonoid sub-classes. For total flavonoid intake, after adjusting for potential lifestyle confounders and compared to participants in quintile 1 (median intake: 173 mg/day), those in quintile 3 (median intake: 320 mg/day) and quintile 4 (median intake: 494 mg/day) had a significantly lower risk of AF, with hazard ratios (95% CI) of 0.93 (0.87, 0.99) and 0.92 (0.86, 0.98), respectively. Compared to median intake in the lowest quintile, a total flavonoid intake of 1000 mg/day was associated with a lower risk of AF in smokers [0.86 (0.77, 0.96)] but not in non-smokers [0.96 (0.88, 1.05)], a lower risk of AF in high alcohol consumers [>20 g/d: 0.84 (0.75, 0.94)] but not in low-to-moderate alcohol consumers [<20 g/d: 0.97 (0.89, 1.06], a trending lower risk of AF in diabetics [0.76 (0.51, 1.14)] but not in non-diabetics [0.95 (0.89, 1.02)], and a trending lower risk of AF in those with ischaemic heart disease [0.84 (0.65, 1.09)] but not in those without [0.96 (0.89, 1.03), Figure 1].

Figure 1

Conclusion

We observed an inverse association between total flavonoid intake and AF, most notably in sub-populations with known lifestyle and disease risk factors for AF. This finding warrants investigation in randomised controlled trials. If confirmed, ensuring the adequate consumption of flavonoid-rich foods, particularly in individuals “at risk”, may be an important strategy to mitigate AF risk.

Acknowledgement/Funding

The Danish Diet, Cancer, and Health Study was funded by the Danish Cancer Society.

Effect of weight loss on neutrophil resolvins in the metabolic syndrome

BACKGROUND

Non-resolving inflammation associates with obesity and insulin resistance, and may be dependent on the balance of inflammatory substances and specialised pro-resolving mediators of inflammation (SPM) that act to halt the inflammatory response. This controlled trial examined the effect of weight loss on neutrophil synthesis of SPM in volunteers with the metabolic syndrome (MetS).

METHODS

Volunteers with MetS (n = 42) were matched for age and gender and randomly assigned to a 12-wk weight loss program followed by 4-wk weight stabilization or a 16-wk weight maintenance program. At baseline and 16 weeks, isolated neutrophils were stimulated with calcium ionophore and the released SPM were measured by LC-MS/MS.

RESULTS

At baseline the SPM resolvin (Rv) E1, 18R-RvE3, RvD2 and Maresin-1 (MaR-1) were detected from stimulated neutrophils. The concentration of released RvE1 was at least 6-fold that of other detected SPM. Weight loss of 4.7 ± 0.8 kg, led to a 2-fold increase in RvE1, P = 0.013, relative to the weight maintenance group. The increase in RvE1 after weight loss was related to, but independent of leukotriene B_4. CONCLUSION: Following weight loss, human neutrophils from individuals with the metabolic syndrome are capable of releasing larger amounts of RvE1 upon stimulation.

F2-isoprostanes affect macrophage migration and CSF-1 signalling

F₂-isoprostanes (F₂-IsoP) are formed in vivo via free radical peroxidation of arachidonic acid. Enhanced oxidative stress is implicated in the development of atherosclerosis in humans and F₂-IsoP have been detected in atherosclerotic plaque. Colony stimulating factor-1 (CSF-1) is essential to macrophage survival, proliferation and differentiation and has been detected in human atherosclerotic plaques. Accumulation of macrophages within the vascular wall is an important component of atherosclerosis but little is known about the effect of F₂-IsoP on the migration of these cells. Our aim was to examine the effect of free and lipid-bound 15-F_2t-isoprostane (15-F_2t-IsoP) on macrophage migration and investigate the signalling pathways involved. Mouse macrophages (cell line BAC1.2F5) were pre-incubated with 15-F_2t-IsoP (free, bound to cholesterol or monoacylglycerol or within oxidized phospholipid) and cell migration was assessed using chemotaxis towards CSF-1 in Boyden chambers. Migration was also measured using the wound healing assay with primary mouse bone marrow derived macrophages. We showed that 15-F_2t-IsoP dose-dependently inhibited BAC1.2F5 macrophage spreading and adhesion but stimulated their migration towards CSF-1, with maximum effect at 10 µM. Analysis of CSF-1 stimulated signalling pathways in BAC1.2F5 macrophages showed that phosphorylation of Akt, a key mediator of cell migration, and one of its regulators, the mTORC2 component, Rictor, was significantly decreased. In contrast, phosphorylation of the adhesion kinases, FAK and Pyk2, and the adhesion scaffold protein, paxillin, was enhanced after treatment with 15-F_2t-IsoP. Mouse bone marrow macrophages were transfected with FAK or Pyk2 small interfering RNA (siRNA) to examine the role of FAK and Pyk2 in 15-F_2t-IsoP signalling. Pyk2 silencing inhibited 15-F_2t-IsoP-induced reduction in cell area and phospho-paxillin adhesion numbers. The size distribution of adhesions in the presence of 15-F_2t-IsoP was also affected by Pyk2 silencing and there was a trend for Pyk2 silencing to reduce 15-F_2t-IsoP-stimulated macrophage migration. These results demonstrate that 15-F_2t-IsoP affects macrophage adhesions and migration, which are integral components of macrophage involvement in atherosclerosis.

Long-Term Dietary Nitrate Supplementation Does Not Prevent Development of the Metabolic Syndrome in Mice Fed a High-Fat Diet

BACKGROUND

Nitric oxide (NO) is an important vascular signaling molecule that plays a role in vascular homeostasis. A reduction in NO bioavailability is thought to contribute to endothelial dysfunction, an early risk factor for both cardiovascular disease and type 2 diabetes. Dietary nitrate, through the nitrate-nitrite-NO pathway, may provide an alternate source of NO when the endogenous eNOS system is compromised. In addition to a role in the vascular system, NO may also play a role in the metabolic syndrome including obesity and glucose tolerance.

AIM

To investigate the effect of long-term dietary nitrate supplementation on development of the metabolic syndrome in mice fed a high-fat diet.

METHODS

Following 1 week of acclimatisation, male (6-8 weeks) C57BL6 mice were randomly assigned to the following groups (10/group) for 12 weeks: (i) normal chow + NaCl (1 mmol/kg/day), (ii) normal chow + NaNO₃ (1 mmol/kg/day), (iii) high-fat diet + NaCl (1 mmol/kg/day), and (iv) high-fat diet + NaNO₃ (1 mmol/kg/day). Body weight and food consumption were monitored weekly. A subset of mice (5/group) underwent running wheel assessment. At the end of the treatment period, all mice underwent fasting glucose tolerance testing. Caecum contents, serum, and tissues (liver, skeletal muscle, white and brown adipose, and kidney) were collected, frozen, and stored at -80°C until analysis.

RESULTS

Consumption of the high-fat diet resulted in significantly greater weight gain that was not affected by dietary nitrate. Mice on the high-fat diet also had impaired glucose tolerance that was not affected by dietary nitrate. There was no difference in adipose tissue expression of thermogenic proteins or energy expenditure as assessed by the running wheel activity. Mice on the high-fat diet and those receiving dietary nitrate had reduced caecum concentrations of both butyrate and propionate.

CONCLUSIONS

Dietary nitrate does not prevent development of the metabolic syndrome in mice fed a high-fat diet. This may be due, in part due, to reductions in the concentration of important short-chain fatty acids.

Structural requirements of flavonoids to induce heme oxygenase-1 expression

Population studies suggest cardiovascular health benefits of consuming fruits and vegetables rich in polyphenolic compounds such as flavonoids. We reported previously that the flavonoid quercetin protects arteries from oxidant-induced endothelial dysfunction and attenuates atherosclerosis in apolipoprotein E gene knockout mice, with induction of heme oxygenase-1 (Hmox1) playing a critical role. The present study investigated the structural requirements of flavonoids to induce Hmox1 in human aortic endothelial cells (HAEC). We identified ortho-dihydroxyl groups and an α,β-unsaturated system attached to a catechol as the key structural requirements for Hmox1 induction. Active but not inactive flavonoids had a low oxidation potential and prevented ascorbate autoxidation, suggesting that Hmox1 inducers readily undergo oxidation and that oxidized, rather than reduced, flavonoids may be the biological inducer of Hmox1. To test this hypothesis, we synthesized stable derivatives of caffeic acid (3-(3,4-dihyroxyphenyl)-2-propenoic acid) containing either ortho-dihydroxy or ortho-dioxo groups. Compared with the dihydroxy compound, the quinone analog induced Hmox1 more potently in HAEC and also provided enhanced protection to arteries of wild type animals against oxidant-induced endothelial dysfunction. In contrast, the quinone analog failed to provide protection against oxidant-induced endothelial dysfunction in arteries of Hmox1^-/- mice, establishing a key role for Hmox1 in vascular protection. These results suggest that oxidized forms of dietary polyphenols are the likely inducers of Hmox1 and may explain in part the protective cardiovascular effects of diets rich in these compounds.

Low dose dietary nitrate improves endothelial dysfunction and plaque stability in the ApoE-/- mouse fed a high fat diet

BACKGROUND

Nitric oxide (NO) is an important vascular signalling molecule. NO is synthesised endogenously by endothelial nitric oxide synthase (eNOS). An alternate pathway is exogenous dietary nitrate, which can be converted to nitrite and then stored or further converted to NO and used immediately. Atherosclerosis is associated with endothelial dysfunction and subsequent lesion formation. This is thought to arise due to a reduction in the bioavailability and/or bioactivity of endogenous NO.

AIM

To determine if dietary nitrate can protect against endothelial dysfunction and lesion formation in the ApoE^-/- mouse fed a high fat diet (HFD).

METHODS AND RESULTS

ApoE^-/- fed a HFD were randomized to receive (i) high nitrate (10mmol/kg/day, n=12), (ii) moderate nitrate (1mmol/kg/day, n=8), (iii) low nitrate (0.1mmol/kg/day, n=8), or (iv) sodium chloride supplemented drinking water (control, n=10) for 10 weeks. A group of C57BL6 mice (n=6) received regular water and served as a healthy reference group. At 10 weeks, ACh-induced vessel relaxation was significantly impaired in ApoE^-/- mice versus C57BL6. Mice supplemented with low or moderate nitrate showed significant improvements in ACh-induced vessel relaxation compared to ApoE^-/- mice given the high nitrate or sodium chloride. Plaque collagen expression was increased and lipid deposition reduced following supplementation with low or moderate nitrate compared to sodium chloride, reflecting increased plaque stability with nitrate supplementation. Plasma nitrate and nitrite levels were significantly increased in all three groups fed the nitrate-supplemented water.

CONCLUSION

Low and moderate dose nitrate significantly improved endothelial function and atherosclerotic plaque composition in ApoE^-/- mice fed a HFD.

Endothelial cationic amino acid transporter-1 overexpression can prevent oxidative stress and increases in arterial pressure in response to superoxide dismutase inhibition in mice

AIM

Oxidative stress may play an important role in the pathogenesis of hypertension. The aim of our study is to examine whether increased expression of the predominant endothelial l-arginine transporter, cationic amino acid transporter-1 (CAT1), can prevent oxidative stress-induced hypertension.

METHODS

Wild-type mice (WT; n = 9) and endothelial CAT1 overexpressing (CAT+) mice (n = 6) had telemetry probes implanted for the measurement of mean arterial pressure (MAP), heart rate (HR) and locomotor activity. Minipumps were implanted for infusion of the superoxide dismutase inhibitor diethyldithiocarbamic acid (DETCA; 30 mg kg(-1) day(-1) ; 14 days) or its saline vehicle. Baseline levels of MAP, HR and locomotor activity were determined before and during chronic DETCA administration. Mice were then killed, and their plasma and kidneys collected for analysis of F2 -isoprostane levels.

RESULTS

Basal MAP was less in CAT+ (92 ± 2 mmHg; n = 6) than in WT (98 ± 2 mmHg; n = 9; P < 0.001). During DETCA infusion, MAP was increased in WT (by 4.2 ± 0.5%; P < 0.001) but not in CAT+, when compared to appropriate controls (PDETCA*genotype = 0.006). DETCA infusion increased total plasma F2 -isoprostane levels (by 67 ± 11%; P = 0.05) in WT but not in CAT+. Total renal F2 -isoprostane levels were greater during DETCA infusion in WT (by 72%; P < 0.001), but not in CAT+, compared to appropriate controls.

CONCLUSION

Augmented endothelial l-arginine transport attenuated the prohypertensive effects of systemic and renal oxidative stress, suggesting that manipulation of endothelial CAT1 may provide a new therapeutic approach for the treatment of cardiovascular disease associated with oxidative stress.

Green coffee polyphenols do not attenuate features of the metabolic syndrome and improve endothelial function in mice fed a high fat diet

We have investigated the effects of the major polyphenol in coffee, chlorogenic acid (CGA), on obesity, glucose intolerance, insulin resistance, systemic oxidative stress and endothelial dysfunction in a mouse model of the metabolic syndrome. Thirty C57BL6 mice were randomly divided into (n=10/group) (i) normal diet (ND), (ii) high fat diet (HFD), or (iii) high fat diet supplemented with 0.5% w/w green coffee bean extract (GCE) rich in chlorogenic acid (HFD+GCE). The high fat diet consisted of 28% fat and all animals were maintained on their diets for 12 weeks. The mice fed a HFD and HFD+GCE displayed symptoms of the metabolic syndrome compared to their normal fed counterparts, although no endothelial dysfunction was detected in the abdominal aortas after 12 weeks. GCE did not attenuate HFD-induced obesity, glucose intolerance, insulin resistance or systemic oxidative stress. Furthermore, GCE did not protect against ex vivo oxidant (hypochlorous acid)-induced endothelial dysfunction.

20-Hydroxyeicosatetraenoic acid synthesis is increased in human neutrophils and platelets by angiotensin II and endothelin-1

The cytochrome P-450 arachidonic acid metabolite 20-HETE is central to the regulation of vascular tone, renal function, and blood pressure and is synthesized in the rat kidney in response to angiotensin II (ANG II) and endothelin-1 (ET-1). There are very few studies examining the cellular synthesis of 20-HETE in humans. We aimed to measure human neutrophil and platelet 20-HETE levels under basal conditions and after ANG II, ET-1, and calcium ionophore (CaI). 20-HETE was measured in human platelets and neutrophils after saline (control), CaI (2.5 μg/ml), and ANG II or ET-1 (10 nmol/l-1 μmol/l) incubations. The effect of cells, which were preincubated with the ω-hydroxylase inhibitor N-hydroxy-N'-(4-butyl-2-methylphenyl) (HET0016, 10 nM), ANG II types 1 or 2 (AT(1) or AT(2)) receptor inhibition with irbesartan (1 μmol/l) or PD-123319 (1 μmol/l), or endothelin receptor subtypes A or B (ET(A) or ET(B)) receptor inhibition with BQ-123 or BQ-778 (100 nmol/l), was studied. Neutrophil and platelet content and release of 20-HETE was significantly increased by CaI and blocked by the ω-hydroxylase inhibitor HET0016. ANG II and ET-1 significantly increased neutrophil and platelet content and release of 20-HETE. ANG II increased 20-HETE via the AT(2) receptor. ET-1 increased 20-HETE through the ET(B) receptor in platelets and both the ET(A) and ET(B) receptors in neutrophils. These studies show that human platelets and neutrophils synthesize 20-HETE in response to ANG II and ET-1. 20-HETE synthesis in both cell types was predominantly mediated via the AT(2) and ET(B) receptors. Stimulation via these receptor pathways has generally been thought to be cardioprotective and requires further studies in clinical situations associated with low-grade inflammation or where ANG II and ET-1 are elevated to clarify the role of 20-HETE.

Sesame supplementation does not improve cardiovascular disease risk markers in overweight men and women

BACKGROUND AND AIMS

Pre-clinical studies suggest that sesame and its lignans induce beneficial changes in risk factors related to cardiovascular disease and increase the bioavailability of mammalian lignans. However, only very few intervention trials have investigated the potential bioactivities of sesame in humans. We aimed to investigate the effects of sesame supplementation in humans on blood lipids, blood pressure, systemic oxidative stress, inflammatory biomarkers and mammalian lignan metabolism.

METHODS AND RESULTS

We conducted a randomized, placebo-controlled cross-over intervention trial at a university research centre. Overweight or obese men and women (n=33) consumed 25g/d of sesame ( approximately 50mg/d of sesame lignan) and an iso-caloric placebo matched for macronutrient composition for 5 wks each. Each intervention period was preceded by a 4-wk washout period. Blood lipid profiles, day time ambulatory blood pressure, oxidative stress and inflammatory biomarkers and urinary mammalian lignans were measured before and after each intervention. Results are presented as the effect of sesame supplementation relative to placebo. Urinary excretion of the mammalian lignans, enterolactone and enterodiol, increased by approximately 8-fold (P<0.001). Blood lipids and blood pressure were not altered. In addition, markers of systemic inflammation (C-reactive protein, interleukin-6, tumor necrosis factor-alpha) and lipid peroxidation (F(2)-isoprostanes) were not affected.

CONCLUSION

Supplementation with 25g/d of sesame can significantly increase the exposure to mammalian lignans. However, this did not cause any improvement in markers of cardiovascular disease risk in overweight or obese men and women.

Impaired ex vivo leukotriene B4 production characterizes the metabolic syndrome and is improved after weight reduction

CONTEXT

Neutrophil (polymorphonuclear neutrophil) production of leukotriene B4 (LTB4) may be associated with alterations in immune and inflammatory function that characterize the metabolic syndrome (MetS).

OBJECTIVE

We investigated whether polymorphonuclear neutrophil production of LTB(4) and its metabolites 20-hydroxy-LTB4 (20-OH-LTB4) and 20-carboxyl-LTB4 were altered in subjects with features of the MetS before and after weight reduction.

DESIGN, SETTING, PATIENTS, AND INTERVENTION

In a case-controlled comparison, men and postmenopausal women with features of the MetS were matched with controls. Subjects with MetS were then matched and randomly assigned to either a 12-wk weight reduction study followed by 4-wk weight stabilization or 16-wk weight maintenance.

MAIN OUTCOME MEASURES

Measurements were performed at baseline and at the end of the 16-wk period. Stimulated neutrophil LTB4 and its metabolites were measured by HPLC.

RESULTS

In the case-controlled study, body mass index, waist circumference, blood pressure, fasting triglycerides, and glucose were all significantly increased in subjects with features of the MetS (P < 0.05). Production of LTB4 and 20-OH-LTB4 was significantly lower compared with controls (P < 0.005). The weight loss intervention resulted in a 4.6-kg reduction in body weight and 6.6-cm decrease in waist circumference relative to controls and a significant increase in LTB4 and 20-OH-LTB4.

CONCLUSIONS

Subjects with features of the MetS have lower stimulated LTB4, which is not due to increased metabolism of LTB4. Weight reduction restored the production of neutrophil LTB4, suggesting that in addition to modifying cardiovascular risk, weight loss may also help with the management of perturbed inflammatory responses in overweight subjects.

Increased serum pigment epithelium-derived factor is associated with microvascular complications, vascular stiffness and inflammation in Type 1 diabetes

AIMS

To determine in Type 1 diabetes patients if levels of pigment epithelium-derived factor (PEDF), an anti-angiogenic, anti-inflammatory and antioxidant factor, are increased in individuals with complications and positively related to vascular and renal dysfunction, body mass index, glycated haemoglobin, lipids, inflammation and oxidative stress.

METHODS

Serum PEDF levels were measured by ELISA in a cross-sectional study of 123 Type 1 diabetic patients (71 without and 52 with microvascular complications) and 31 non-diabetic control subjects. PEDF associations with complication status, pulse-wave analysis and biochemical results were explored.

RESULTS

PEDF levels [geometric mean (95% CI)] were increased in patients with complications 8.2 (7.0-9.6) microg/ml, vs. complication-free patients [5.3 (4.7-6.0) microg/ml, P < 0.001] and control subjects [5.3 (4.6-6.1) microg/ml, P < 0.001; anova between three groups, P < 0.001], but did not differ significantly between control subjects and complication-free patients (P > 0.05). In diabetes, PEDF levels correlated (all P < 0.001) with systolic blood pressure (r = 0.317), pulse pressure (r = 0.337), small artery elasticity (r = -0.269), glycated haemoglobin (r = 0.245), body mass index (r = 0.362), renal dysfunction [including serum creatinine (r = 0.491), cystatin C (r = 0.500)], triglycerides (r = 0.367), and inflammation [including log(e)C-reactive protein (CRP; r = 0.329), and soluble vascular cell adhesion molecule-1 (r = 0.363)]. Age, blood urea nitrogen, systolic blood pressure, pulse pressure and log(e)CRP correlated with PEDF levels in control subjects (all P < 0.04). PEDF levels were not significantly correlated with measures of oxidative stress: isoprostanes, oxidized low-density lipoprotein or paraoxonase-1 activity. On stepwise linear regression analysis (all subjects), independent determinants of PEDF levels were renal function, triglycerides, inflammation, small artery elasticity and age (r(2) = 0.427).

CONCLUSIONS

In Type 1 diabetes, serum PEDF levels are associated with microvascular complications, poor vascular health, hyperglycaemia, adiposity and inflammation.

Retinol supplementation in murine Plasmodium berghei malaria: Effects on tissue levels, parasitaemia and lipid peroxidation

Reduced plasma retinol concentrations occur in human malaria but the benefits of supplementation remain uncertain. We assessed the in vivo efficacy of retinol administration, and its effect on lipid peroxidation, in a Plasmodium berghei murine model. Animals received vehicle (n=17) or retinol (i) before P. berghei inoculation (four doses), (ii) at parasitaemia 10-15% (three to four doses) or (iii) before and after inoculation (six to seven doses; n=15 in each group), with euthanasia on day 8 post-inoculation or when the parasitaemia exceeded 50%. Multiple-dose pre-inoculation retinol reduced endpoint parasitaemia by 24% (P=0.001 versus controls). A reduction of 18% (P=0.042) was observed when retinol was given to parasitaemic animals. Retinol was ineffective when given both before and after infection (11% reduction; P=0.47). Although retinol supplementation did not change plasma retinol concentrations, liver retinol content increased and correlated inversely with endpoint parasitaemia (r=-0.45, P=0.001). Malaria infection augmented concentrations of the free radical lipid peroxidation end-product F(2)-isoprostanes in plasma, erythrocytes and liver by 1.8-, 2.8- and 4.9-fold, respectively, but retinol supplementation had no effect on these increases. Consistent with some human malaria studies, prophylactic retinol reduces P. berghei parasitaemia. This effect relates to augmentation of tissue retinol stores rather than to retinol-associated changes in oxidant status.

Vitamin E metabolism

The aim of this paper is to provide an overview of vitamin E metabolism. The topics covered include: major classes of vitamin E metabolites; their production pathways and route of excretion; possible biological activities of vitamin E metabolites; and use of vitamin E metabolites as markers of oxidant generation. Recent investigations into vitamin E metabolism have also highlighted important new areas of research, such as the potential for high dose vitamin E supplementation to interfere with drug metabolism, as well as alternative methods to alter vitamin E bioavailability in vivo. These issues will also be discussed in the review.

Antioxidant activity of prenylated flavonoids from the West African medicinal plant Dorstenia mannii

The antioxidant activities of three prenylated flavonoids from Dorstenia mannii (6,8-diprenyleriodictyol, dorsmanin C and dorsmanin F) were compared to the common, non-prenylated flavonoid, quercetin. The prenylated flavonoids were found to be potent scavengers of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), and are more potent than butylated hydroxy toluene (BHT), a common antioxidant used as a food additive. The prenylated flavonoids also inhibited Cu(2+)-mediated oxidation of human low density lipoprotein (LDL). Dose-response studies indicated that the prenylated flavonoids were effective inhibitors of lipoprotein oxidation with IC50 values <1 microM and had similar inhibitory potency compared to quercetin, but was not directly related to Cu binding. Unlike quercetin, they did not show any pro-oxidant activity at high doses in the Cu(2+)-mediated lipoprotein oxidation system. The medicinal action of Dorstenia mannii may be related to the high concentration of potent antioxidant prenylated flavonoids in this species.

Similarity in the distribution of F(2)-isoprostanes in the lipid subfractions of atherosclerotic plaque and in vitro oxidised low density lipoprotein

Oxidation of low density lipoprotein (LDL) in vivo is thought to play a critical role in the initiation of atherosclerosis. F(2)-isoprostanes are compounds resulting from non-enzymatic oxidation of arachidonic acid and elevated levels are present in human atherosclerotic plaque. However, little is known about the formation of F(2)-isoprostanes in plaque lesions or their distribution in lipid subclasses. Given that LDL and tissue lipid subfractions (such as phospholipids, cholesterol esters and triglycerides) all contain significant levels of arachidonic acid, the aim of this study was to examine the relative distribution of F(2)-isoprostanes in the different lipid fractions of LDL oxidised in vitro, and compare this to the distribution in atherosclerotic plaque. The results reveal that while the majority of F(2)-isoprostanes are present in the phospholipid or surface lipid fractions, the core lipids (cholesterol esters/triglycerides) contribute at least 10% of the total F(2)-isoprostanes in both LDL oxidised in vitro and human atherosclerotic plaque. The remarkably similar profiles between the oxidised LDL and advanced atherosclerotic plaque suggests oxidation in vivo, is predominantly via non-enzymatic processes directed towards the surface lipids.

Coenzyme Q10 improves blood pressure and glycaemic control: a controlled trial in subjects with type 2 diabetes

OBJECTIVE

Our objective was to assess effects of dietary supplementation with coenzyme Q10 (CoQ) on blood pressure and glycaemic control in subjects with type 2 diabetes, and to consider oxidative stress as a potential mechanism for any effects.

SUBJECTS AND DESIGN

Seventy-four subjects with uncomplicated type 2 diabetes and dyslipidaemia were involved in a randomised double blind placebo-controlled 2x2 factorial intervention.

SETTING

The study was performed at the University of Western Australia, Department of Medicine at Royal Perth Hospital, Australia.

INTERVENTIONS

Subjects were randomly assigned to receive an oral dose of 100 mg CoQ twice daily (200 mg/day), 200 mg fenofibrate each morning, both or neither for 12 weeks.

MAIN OUTCOME MEASURES

We report an analysis and discussion of the effects of CoQ on blood pressure, on long-term glycaemic control measured by glycated haemoglobin (HbA(1c)), and on oxidative stress assessed by measurement of plasma F2-isoprostanes.

RESULTS

Fenofibrate did not alter blood pressure, HbA(1c), or plasma F2-isoprostanes. There was a 3-fold increase in plasma CoQ concentration (3.4+/-0.3 micro mol/l, P<0.001) as a result of CoQ supplementation. The main effect of CoQ was to significantly decrease systolic (-6.1+/-2.6 mmHg, P=0.021) and diastolic (-2.9+/-1.4 mmHg, P=0.048) blood pressure and HbA(1c) (-0.37+/-0.17%, P=0.032). Plasma F2-isoprostane concentrations were not altered by CoQ (0.14+/-0.15 nmol/l, P=0.345).

CONCLUSIONS

These results show that CoQ supplementation may improve blood pressure and long-term glycaemic control in subjects with type 2 diabetes, but these improvements were not associated with reduced oxidative stress, as assessed by F2-isoprostanes.

SPONSORSHIP

This study was supported by a grant from the NH&MRC, Australia.

Effect of dietary cholesterol oxidation products on the plasma clearance of chylomicrons in the rat

Oxidized cholesterols in the diet have been shown to exacerbate arterial cholesterol deposition and the development of atherosclerosis in animal models. Dietary oxidized cholesterols are absorbed through the intestine and incorporated into lymph chylomicrons. The aim of this study was to investigate the effect of oxidized cholesterols on the metabolism of nascent chylomicrons in vivo. It was shown that oxidized cholesterols markedly delay the clearance of chylomicrons from plasma compared to rats given TG alone. However, there was no difference in the clearance of chylomicrons containing oxidized cholesterols vs. purified cholesterol, although the presence of oxysterols did appear to exacerbate the removal of these particles from circulation. The impaired clearance of chylomicrons containing oxidized cholesterols was not due to impaired lipolysis and slower conversion to the remnant form. Moreover, the incorporation of oxidized cholesterols did not alter the hepatic or splenic uptake of chylomicrons compared to chylomicrons isolated from rats given purified cholesterol or TG alone. Collectively, the results of this study suggest that the exacerbated delay in clearance of chylomicron remnants enriched with oxysterols may be due to impaired uptake by tissues other than the liver and spleen. Apolipoprotein (apo) analysis showed that oxysterol incorporation reduced the apoE content and altered the apoC phenotype of chylomicrons, which may have an impact on the removal of chylomicron remnants from plasma. In conclusion, dietary oxysterols appear to have the potential to adversely affect chylomicron metabolism. Therefore, further investigations in humans are required to determine whether dietary oxidized cholesterols found in cholesterol-rich processed foods delay the clearance of postprandial remnants, which may contribute to and exacerbate the development of atherosclerosis.

Coenzyme Q(10) improves endothelial dysfunction of the brachial artery in Type II diabetes mellitus

AIM/HYPOTHESIS

We assessed whether dietary supplementation with coenzyme Q(10) improves endothelial function of the brachial artery in patients with Type II (non-insulin-dependent) diabetes mellitus and dyslipidaemia.

METHODS

A total of 40 patients with Type II diabetes and dyslipidaemia were randomized to receive 200 mg of coenzyme Q(10) or placebo orally for 12 weeks. Endothelium-dependent and independent function of the brachial artery was measured as flow-mediated dilatation and glyceryl-trinitrate-mediated dilatation, respectively. A computerized system was used to quantitate vessel diameter changes before and after intervention. Arterial function was compared with 18 non-diabetic subjects. Oxidative stress was assessed by measuring plasma F(2)-isoprostane concentrations, and plasma antioxidant status by oxygen radical absorbance capacity.

RESULTS

The diabetic patients had impaired flow-mediated dilation [3.8 % (SEM 0.5) vs 6.4 % (SEM 1.0), p = 0.016], but preserved glyceryl-trinitrate-mediated dilation, of the brachial artery compared with non-diabetic subjects. Flow-mediated dilation of the brachial artery increased by 1.6 % (SEM 0.3) with coenzyme Q(10) and decreased by -0.4 % (SEM 0.5) with placebo (p = 0.005); there were no group differences in the changes in pre-stimulatory arterial diameter, post-ischaemic hyperaemia or glyceryl-trinitrate-mediated dilation response. Coenzyme Q(10) treatment resulted in a threefold increase in plasma coenzyme Q(10) (p < 0.001) but did not alter plasma F(2)-isoprostanes, oxygen radical absorbance capacity, lipid concentrations, glycaemic control or blood pressure.

CONCLUSION/INTERPRETATION

Coenzyme Q(10) supplementation improves endothelial function of conduit arteries of the peripheral circulation in dyslipidaemic patients with Type II diabetes. The mechanism could involve increased endothelial release and/or activity of nitric oxide due to improvement in vascular oxidative stress, an effect that might not be reflected by changes in plasma F(2)-isoprostane concentrations.

Alcohol and endothelial function: a brief review

1. In spite of the dose-related effects of alcohol consumption to increase blood pressure, regular light to moderate alcohol intake appears to confer protection against both coronary artery disease and ischaemic stroke. In contrast, heavy alcohol consumption increases the risk of coronary artery disease and the risk of both haemorrhagic and ischaemic stroke. 2. Effects of alcohol consumption on endothelial cell function may be relevant to these disparate effects on cardiovascular outcomes. In in vitro animal studies, low doses of alcohol have been demonstrated to increase release of nitric oxide and augment endothelium-mediated vasodilatation, whereas higher doses impair endothelium-dependent relaxation responses. In contrast, chronic administration of alcohol to rats has generally been associated with tolerance to the acute inhibitory effects of alcohol on endothelium-mediated vasodilatation and may even result in augmentation of such responses. 3. The few human studies to date that have examined the effects of alcohol on endothelial function have focused on postischaemic flow-mediated dilation of the brachial artery (FMD). Although blunted FMD responses have been reported in alcoholic subjects, acute administration of alcohol or short-term interventions to reduce alcohol intake have had no effect to either improve or impair FMD. 4. Further studies in humans assessing acute and longer term dose-related effects of alcohol on endothelial function in both conduit and resistance vessels will be necessary if the relevance of the findings from in vitro and in vivo animal studies are to be understood in the context of the complex interrelationships of alcohol with cardiovascular disease.

Differential regulation of endobiotic-oxidizing cytochromes P450 in vitamin A-deficient male rat liver

1. The hepatic CYP4A-dependent omega-hydroxylation of arachidonic acid and CYP2C11-dependent 2alpha-/16alpha-hydroxylations of testosterone were decreased to 74 and 60% of respective control in microsomal fractions from vitamin A-deficient rats. Decreases in the rates of arachidonic acid omega-1-hydroxylation and testosterone 6beta-, 7alpha- and 17alpha-hydroxylations were less pronounced. 2. Corresponding decreases in microsomal CYP4A and CYP2C11 immunoreactive protein expression to 64 and 68% of respective control were observed in vitamin A-deficient rat liver. Expression of CYP3A proteins was unchanged from vitamin A-adequate control. 3. Northern analysis revealed a selective decrease in CYP4A2 mRNA expression in vitamin A-deficient rat liver to approximately 5% of control; expression of the related CYP4A1/4A3 mRNAs was not decreased. CYP2C11 mRNA expression was also decreased in vitamin A-deficient male rat liver to 39% of control levels. 4. Intake of the deficient diet containing all-trans-retinoic acid (ATRA) during the final week of the experiment restored CYP4A2 mRNA and CYP4A protein. Administration of exogenous androgen or episodic growth hormone was ineffective. In contrast, CYP2C11 expression was restored by ATRA and androgen, but not by growth hormone. 5. From these studies it emerges that CYP4A2, a fatty acid omega-hydroxylase in rat liver, is highly dependent on vitamin A for optimal expression, whereas CYP2C11 is indirectly down regulated by androgen deficiency resulting from vitamin A-deficiency. Altered CYP expression in vitamin A-deficiency provides insights into the relationship between dietary constituents and the intracellular formation of vasoactive eicosanoids as well as the clearance of androgenic steroids.

Oxidant stress in nephrotic syndrome: comparison of F(2)-isoprostanes and plasma antioxidant potential

BACKGROUND

The nephrotic syndrome (NS) is associated with an increased risk of coronary heart disease. Increased oxidant stress may contribute to this by means of hyperlipidaemia and/or hypoalbuminaemia. In this study we assessed the contributory role of oxidant stress, as measured by F(2)-isoprostanes and plasma oxygen radical absorbance capacity (ORAC), in subjects with NS.

METHODS

We studied 14 subjects with NS and 17 age- and sex-matched healthy non-proteinuric controls. Measurement of plasma and urinary F(2)-isoprostanes was carried out using a combination of silica and reverse-phase cartridges, high-performance liquid chromatography, and gas chromatography mass spectrometry using electron-capture negative ionization. The plasma ORAC assay measured the decrease in fluorescence of phycoerythrin added to plasma in the presence of a free-radical generator. The ORAC value (microM) was calculated as the ratio of the area under the fluorescence decay curve for plasma to the area under the fluorescence decay curve for a Trolox standard.

RESULTS

Plasma ORAC was significantly lower in NS patients compared with controls: mean (standard error) NS patients 3306 microM (286); controls 4882 microM (496), P=0.011. In univariate linear regression analysis, plasma albumin was significantly positively correlated with plasma ORAC (r=0.40, P=0.03). Plasma and urinary F(2)-isoprostanes did not differ significantly between NS and control groups.

CONCLUSIONS

This study demonstrates that in the NS there is decreased free-radical trapping capacity of plasma that is inversely correlated with hypoalbuminaemia, but no increase in plasma and urinary F(2)-isoprostanes. Decreased total plasma antioxidant potential in combination with hyperlipidaemia may contribute to the increased risk of cardiovascular disease seen in NS.

Dietary cosupplementation with vitamin E and coenzyme Q(10) inhibits atherosclerosis in apolipoprotein E gene knockout mice

Intimal oxidation of LDL is considered an important early event in atherogenesis, and certain antioxidants are antiatherogenic. Dietary coenrichment with vitamin E (VitE) plus ubiquinone-10 (CoQ(10), which is reduced during intestinal uptake to the antioxidant ubiquinol-10, CoQ(10)H(2)) protects, whereas enrichment with VitE alone can increase oxidizability of LDL lipid against ex vivo oxidation. In the present study, we tested whether VitE plus CoQ(10) cosupplementation is more antiatherogenic than either antioxidant alone, by use of apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet without (control) or with 0.2% (wt/wt) VitE, 0.5% CoQ(10), or 0.2% VitE plus 0.5% CoQ(10) (VitE+CoQ(10)) for 24 weeks. None of the supplements affected plasma cholesterol concentrations, whereas in the VitE and CoQ(10) groups, plasma level of the respective supplement increased. Compared with control, plasma from CoQ(10) or VitE+CoQ(10) but not VitE-supplemented animals was more resistant to ex vivo lipid peroxidation induced by peroxyl radicals. VitE supplementation increased VitE levels in aorta, heart, brain, and skeletal muscle, whereas CoQ(10) supplementation increased CoQ(10) only in plasma and aorta and lowered tissue VITE: All treatments significantly lowered aortic cholesterol compared with control, but only VitE+CoQ(10) supplementation significantly decreased tissue lipid hydroperoxides when expressed per parent lipid. In contrast, none of the treatments affected aortic ratios of 7-ketocholesterol to cholesterol. Compared with controls, VitE+CoQ(10) supplementation decreased atherosclerosis at the aortic root and arch and descending thoracic aorta to an extent that increased with increasing distance from the aortic root. CoQ(10) significantly inhibited atherosclerosis at aortic root and arch, whereas VitE decreased disease at aortic root only. Thus, in apoE-/- mice, VitE+CoQ(10) supplements are more antiatherogenic than CoQ(10) or VitE supplements alone and disease inhibition is associated with a decrease in aortic lipid hydroperoxides but not 7-ketocholesterol.

Clinical and biochemical features, molecular diagnosis and long-term management of a case of cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive sterol storage disease characterised clinically by juvenile bilateral cataracts, progressive neurological dysfunction, and formation of tendon xanthomata. We describe the clinical and biochemical features, molecular diagnosis and long-term management of the first reported Australasian case of CTX. Molecular analysis confirmed the diagnosis of CTX and demonstrated that the patient was homozygous for a G-->A transition in the splice donor site of intron 4 of the sterol 27-hydroxylase gene. Serum cholestanol concentrations were decreased with the HMG-CoA reductase inhibitor simvastatin alone and greater reductions were achieved after the addition of the bile acid chenodeoxycholic acid; suggesting a synergistic effect of this combination. Despite serum cholestanol concentrations remaining within the low-normal range, there has been no significant improvement in mental and physical abilities or in EEG abnormalities with 5 years of treatment. Metabolism of radiolabeled 7-ketocholesterol to aqueous soluble products was absent in CTX-derived macrophages. Consistent with this finding, plasma 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, and 7-ketocholesterol concentrations were increased in the CTX subject compared with controls.