Anne Barden

Advanced glycation end-products: a review.

Abstract Advanced glycation end-products are a complex and heterogeneous group of compounds that have been implicated in diabetes related complications. At present it is not known if they are the cause or the consequence of the complications observed. We discuss the chemistry of advanced glycated end-product formation and their patho-biochemistry particularly in relation to the diabetic microvascular complications of retinopathy, neuropathy and nephropathy as well as their role in the accelerated vasculopathy observed in diabetes. The concept of carbonyl stress as a cause for advanced glycated end-product toxicity is mentioned. We discuss alterations in the concentrations of advanced glycated end-products in the body, particularly in relation to changes occuring with age, diabetes and its complications such as nephropathy. Problems relating to current methods of advanced glycated end-product detection and measurement are highlighted including the lack of a universally established method of detection or unit of measurement. Agents used for the treatment of advanced glycated end-product accumulation are reviewed, with an emphasis on the results of the recent phase III trials using aminoguanidine and diabetes related complications. [Diabetologia (2001) 44: 129–146]

Effects of purified eicosapentaenoic acid and docosahexaenoic acid on platelet, fibrinolytic and vascular function in hypertensive type 2 diabetic patients

BACKGROUND Type 2 diabetes and hypertension are both associated with an increased risk of atherothrombosis. We assessed whether purified eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil have differential effects on platelet, fibrinolytic and vascular function in patients with both conditions. METHODS In a double-blind placebo-controlled trial of parallel design, 59 treated-hypertensive Type 2 diabetic men and postmenopausal women, were randomised to 4 g/day of EPA, DHA or olive oil (placebo) for 6 weeks. Collagen and PAF-stimulated platelet aggregation, collagen-stimulated thromboxane release (TXB2), plasma tPA and PAI-1 antigens, von Willebrand factor, p-selectin, and flow-mediated and glyceryl-trinitrate-mediated dilatation of the brachial artery, were examined before and at the end of intervention. RESULTS Thirty-nine men and 12 women aged 61.2+/-1.2 year completed the study. Relative to placebo, DHA but not EPA supplementation significantly reduced collagen aggregation (16.9%, P=0.05) and TXB2 (18.8%, P=0.03). There were no significant changes in either PAF-stimulated platelet aggregation, fibrinolytic function or vascular function in either the EPA or DHA group relative to placebo. CONCLUSION Highly purified DHA may be a more effective anti-thrombotic agent than EPA. However, longer-term studies assessing morbidity and mortality are needed in order to establish if DHA contributes to reducing CHD amongst Type 2 diabetic patients with treated hypertension.

Red Wine and Beer Elevate Blood Pressure in Normotensive Men

A positive relationship between alcohol consumption and blood pressure (BP) is well-established but the relative effect of specific alcoholic beverages is controversial. This study aimed to determine whether red wine may improve vascular function and have less of an impact on blood pressure because of its high content of antioxidant vasodilator polyphenolic compounds. Healthy normotensive men entered a 4-period crossover study comparing in random order 4 weeks of control–abstinence with similar periods of daily consumption of red wine (375 mL; 39 grams alcohol), de-alcoholized red wine (375 mL), or beer (1125 mL; 41 grams alcohol). Ambulatory systolic BP and diastolic BP and heart rate (HR) were measured together with vascular function as assessed by flow-mediated dilatation (FMD) and glyceryl trinitrate-mediated (GTNMD) dilatation of the brachial artery. The systolic and diastolic BP and HR were not different between control–abstinence and de-alcoholized red wine. However, compared with control–abstinence, both red wine and beer increased awake systolic BP (2.9 and 1.9 mm Hg, respectively; P<0.05) and asleep HR (5.0 and 4.4 bpm; P<0.05). There were no specific effects of red wine, de-alcoholized red wine, or beer on FMD or GTNMD. Daily consumption of ≈40 grams alcohol as either red wine or beer for 4 weeks results in similar increases in systolic BP and HR. De-alcoholized red wine did not lower BP, and neither red wine nor de-alcoholized red wine influenced vascular function, suggesting that red wine polyphenolics do not have a significant role in mitigating the blood pressure-elevating effects of alcohol in men.

A Single Nucleotide Polymorphism in the CYP4F2 but not CYP4A11 Gene Is Associated With Increased 20-HETE Excretion and Blood Pressure

Arachidonic acid is a major fatty acid that can be metabolized by the cytochrome P450 enzyme to a number of bioactive eicosanoids. A major metabolite of this oxidation is 20-hydroxyeicosatetraenoic acid, which acts as a potent vasoconstrictor. However, in the kidney, its vasoconstrictor actions can be offset by its natriuretic properties. A guanine-to-adenine polymorphism in the CYP4F2 gene was associated with a reduction in 20-hydroxyeicosatetraenoic acid production in vitro. A thymidine-to-cytosine polymorphism in the CYP4A11 gene reduced catalytic activity by >50% in vitro and was associated with hypertension. The aim was to determine whether these 2 mutations are associated with urinary 20-hydroxyeicosatetraenoic acid excretion and blood pressure in humans. For the CYP4F2, 51% were homozygous for the G allele, 40% were carriers, and 9% were homozygous for the A allele. For CYP4A11, 72% were homozygous for the T allele, 25% were carriers, and 3% were homozygous for the C allele. The CYP4F2 GA/AA genotype was significantly associated with an increase in both 20-hydroxyeicosatetraenoic acid excretion and systolic blood pressure. The CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-hydroxyeicosatetraenoic acid excretion but was not associated with blood pressure. We have demonstrated for the first time in humans that polymorphisms of the CYP4F2 and CYP4A11 genes have opposite effects on 20-hydroxyeicosatetraenoic acid excretion. The positive association between the CYP4F2 GA/AA genotype and both systolic blood pressure and 20-hydroxyeicosatetraenoic acid excretion strengthens a role for 20-hydroxyeicosatetraenoic acid in the modulation of blood pressure.

Effects of n-3 polyunsaturated fatty acid supplementation in pregnancy on maternal and fetal erythrocyte fatty acid composition

Objective: The aim of this study was to assess the effects of fish oil supplementation in pregnancy on maternal erythrocyte fatty acid composition at different stages of pregnancy and in the post-partum period, and on neonatal erythrocyte fatty acid composition.Design: A double-blind, randomised, placebo-controlled study.Setting: Subiaco, Western Australia.Subjects: In all, 98 women booked for delivery at St John of God Hospital, Subiaco, were recruited from private rooms of obstetricians. In total, 83 women and their healthy full-term babies completed the study.Interventions: Women received either 4 g of fish oil (n=52) (56% docosahexaenoic acid (DHA) and 28% eicosapentaenoic acid (EPA) or placebo (olive oil) (n=46) per day from 20 weeks gestation until delivery.Main outcome measures: Erythrocyte phospholipid fatty acids were measured in maternal peripheral blood at 20, 30 and 37 weeks of pregnancy and at 6 weeks post partum, and from cord blood collected at birth.Results: Compared to the control group, maternal EPA and DHA were significantly higher in the fish oil group at 30 and 37 weeks gestation, and remained elevated at 6 weeks post partum (P<0.001). The proportions of n-6 polyunsaturated (arachidonic acid, 22:3n-6 and 22:4n-6) were significantly lower in the fish oil supplemented group at the same time periods (P<0.001). Similarly, the proportions of EPA and DHA were significantly higher (P<0.001), and those of n-6 polyunsaturated fatty acids arachidonic acid, 20:3n-6, 22:3n-6 and 22:4n-6 were significantly lower (P<0.001), in erythrocytes from neonates in the fish oil group, compared to those in the control group.Conclusions: Fish oil supplementation from 20 weeks of pregnancy until birth is an effective means of enhancing n-3 fatty acid status of both mothers and neonates. Furthermore, the changes in maternal erythrocyte fatty acid composition are retained until at least 6 weeks post partum. It is essential to assess the effects of concomitant decreases in arachidonic acid status before any dietary recommendations can be made.Sponsorship: The study was supported by grants from the NH & MRC and Raine Medical Research Foundation, Australia.

Impact of foods enriched with n-3 long-chain polyunsaturated fatty acids on erythrocyte n-3 levels and cardiovascular risk factors

Consumption of fish or fish oils rich in the n-3 long chain PUFA EPA and DHA may improve multiple risk factors for CVD. The objective of this study was to determine whether regular consumption of foods enriched with n-3 long-chain PUFA can improve n-3 long-chain PUFA status (erythrocytes) and cardiovascular health. Overweight volunteers with high levels of triacylglycerols (TG; >1.6 mmol/l) were enrolled in a 6-month dietary intervention trial conducted in Adelaide (n 47) and Perth (n 39), and randomised to consume control foods or n-3-enriched foods to achieve an EPA + DHA intake of 1 g/d. Test foods were substituted for equivalent foods in their regular diet. Erythrocyte fatty acids, plasma TG and other CVD risk factors were monitored at 0, 3 and 6 months. There were no significant differences between groups for blood pressure, arterial compliance, glucose, insulin, lipids, C-reactive protein (CRP) or urinary 11-dehydro-thromboxane B2 (TXB2) over 6 months, even though regular consumption of n-3-enriched foods increased EPA + DHA intake from 0.2 to 1.0 g/d. However, the n-3 long-chain PUFA content of erythrocytes increased by 35 and 53 % at 3 and 6 months, respectively, in subjects consuming the n-3-enriched foods. These increases were positively associated with measures of arterial compliance and negatively associated with serum CRP and urinary 11-dehydro-TXB2 excretion. Sustainable increases in dietary intakes and erythrocyte levels of n-3 long-chain PUFA can be achieved through regular consumption of suitably enriched processed foods. Such increases may be associated with reduced CV risk.

Targeted alteration of dietary n-3 and n-6 fatty acids for the treatment of chronic headaches: a randomized trial.

Summary A dietary intervention increasing n‐3 and reducing n‐6 fatty acids reduced headache pain, altered antinociceptive lipid mediators, and improved quality of life in a chronic headache population. Abstract Omega‐3 and n‐6 fatty acids are biosynthetic precursors to lipid mediators with antinociceptive and pronociceptive properties. We conducted a randomized, single‐blinded, parallel‐group clinical trial to assess clinical and biochemical effects of targeted alteration in dietary n‐3 and n‐6 fatty acids for treatment of chronic headaches. After a 4‐week preintervention phase, ambulatory patients with chronic daily headache undergoing usual care were randomized to 1 of 2 intensive, food‐based 12‐week dietary interventions: a high n‐3 plus low n‐6 (H3‐L6) intervention, or a low n‐6 (L6) intervention. Clinical outcomes included the Headache Impact Test (HIT‐6, primary clinical outcome), Headache Days per month, and Headache Hours per day. Biochemical outcomes included the erythrocyte n‐6 in highly unsaturated fatty acids (HUFA) score (primary biochemical outcome) and bioactive n‐3 and n‐6 derivatives. Fifty‐six of 67 patients completed the intervention. Both groups achieved targeted intakes of n‐3 and n‐6 fatty acids. In intention‐to‐treat analysis, the H3‐L6 intervention produced significantly greater improvement in the HIT‐6 score (−7.5 vs −2.1; P < 0.001) and the number of Headache Days per month (−8.8 vs −4.0; P = 0.02), compared to the L6 group. The H3‐L6 intervention also produced significantly greater reductions in Headache Hours per day (−4.6 vs −1.2; P = 0.01) and the n‐6 in HUFA score (−21.0 vs −4.0%; P < 0.001), and greater increases in antinociceptive n‐3 pathway markers 18‐hydroxy‐eicosapentaenoic acid (+118.4 vs +61.1%; P < 0.001) and 17‐hydroxy‐docosahexaenoic acid (+170.2 vs +27.2; P < 0.001). A dietary intervention increasing n‐3 and reducing n‐6 fatty acids reduced headache pain, altered antinociceptive lipid mediators, and improved quality‐of‐life in this population.

Fish oil supplementation in pregnancy lowers F2-isoprostanes in neonates at high risk of atopy

The anti-inflammatory properties of n-3 polyunsaturated fatty acids (n-3 PUFA) have suggested a potential role of these nutrients in dietary modification for prevention of allergic disease in early life. As oxidative stress is known to modify antigen presenting cell (APC) signalling and resulting immune responses, we examined the effects of maternal n-3 PUFA supplementation in pregnancy on markers of oxidative stress and APC function in neonates at high risk of allergy. Eighty-three pregnant atopic women were randomised to receive 4 g daily of either fish oil (n=40) or olive oil (n=43) capsules in a controlled trial from 20 weeks gestation until delivery. Plasma (cord blood) and urinary F2-isoprostanes were measured as markers of lipid peroxidation. Cord erythrocyte fatty acids and markers of APC function (HLA-DR expression and cytokine responses) were measured and related to levels of plasma F2-isoprostanes. Maternal fish oil supplementation lowered plasma (p<0.0001) and urinary (p=0.06) F2-isoprostanes. HLA-DR expression on APC was not different between the groups. In multiple regression analysis, 28.8% of the variance in plasma F2-isoprostanes was explained by positive relationships with erythrocyte arachidonic acid (AA) and monocyte HLA-DR expression and a negative relationship with erythrocyte eicosapentaenoic acid (EPA). This study shows that maternal supplementation with fish oil can attenuate neonatal lipid peroxidation. Clinical follow-up of these infants will help to determine if there are sustained effects on postnatal oxidative stress and expression of allergic disease.

Does a predisposition to the metabolic syndrome sensitize women to develop pre-eclampsia?

OBJECTIVE This study aimed to identify those factors in the non-pregnant state that distinguished women who developed pre-eclampsia from those who had normotensive pregnancies. DESIGN AND SETTING This was a retrospective analysis of anthropometry, blood pressure, biochemical and haematological variables in 62 women with pre-eclampsia and 84 normotensive pregnant women who took part in studies of the pathophysiology of pre-eclampsia. Pregnant volunteers were seen, after admission to hospital or in the outpatient clinic, and followed-up at 6 weeks and 6 months post-partum in the outpatient clinic or their home. Participants Proteinuric pre-eclampsia was defined as blood pressure > or = 140/90 mmHg with proteinuria of at least 300 mg/24 h after 20 weeks gestation, in women with no history of hypertension and whose blood pressure returned to normal levels by 6 months post-partum. Normotensive pregnancy was defined as blood pressure < 130/90 mmHg without proteinuria. MAIN OUTCOME MEASURES The primary outcome measures were blood pressure, body mass index (BMI), triglycerides, total cholesterol, low density lipoprotein (LDL) and high density lipoprotein cholesterol and markers of severity of pre-eclampsia. RESULTS Regardless of parity, women with pre-eclampsia had elevated BMI before, during and after pregnancy compared with women who had normotensive pregnancies. Triglycerides were significantly elevated in women who had pre-eclampsia both before and after delivery, while total and LDL cholesterol were elevated significantly at both visits after delivery. Systolic and diastolic blood pressure, which by definition were elevated antepartum in women with pre-eclampsia, remained higher at post-partum visits compared with women who had normotensive pregnancies. Women with pre-eclampsia reported a greatly increased frequency of both maternal hypertension and pre-eclampsia. Markers of severity of pre-eclampsia, which normalized by 6 months postpartum, included plasma creatinine, uric acid, albumin, endothelin 1 and urinary protein, 2,3, dinor-6-keto-PGF1alpha, blood platelet and neutrophil counts. CONCLUSION The relative elevation of blood pressure, BMI and lipids in the non-pregnant state are features of the metabolic syndrome and may be important sensitizing factors contributing to the pathogenesis of pre-eclampsia. A familial predisposition to pre-eclampsia may operate partly through these mechanisms.

HDL is the major lipoprotein carrier of plasma F2-isoprostanes

Enhanced oxidative stress is implicated in the development of atherosclerosis in humans and animal models. F2-isoprostanes are formed in vivo via free radical peroxidation of arachidonic acid, and their quantification has allowed assessment of oxidative stress in vivo. F2-isoprostanes associate with lipids, although their distribution in human plasma lipoproteins is unknown. Our aim was to determine the distribution and levels of F2-isoprostanes in lipoproteins isolated from human plasma by ultracentrifugation and fast protein liquid chromatography (FPLC). F2-isoprostanes were significantly higher in HDL compared with LDL or VLDL after isolation by ultracentrifugation or FPLC. Furthermore, HDL3 particles contained elevated levels of F2-isoprostanes compared with HDL2. Platelet activating factor acetylhydrolase (PAF-AH), which hydrolyses esterified F2-isoprostanes from phospholipids, was predominantly associated with LDL. Reduced F2-isoprostanes in LDL may be related to higher PAF-AH activity in LDL. Paraoxonase 1 (PON-1) activity was associated with HDL2 and may be a contributing factor to the lower F2-isoprostanes in HDL2 compared with HDL3. Further studies are required to establish the implications of these findings on HDL function.