Ingestion of thermally oxidized sunflower oil decreases postprandial lipemia mainly in younger individuals.

Animal studies have shown that diets rich in thermally oxidized fat increase glucose and decrease insulin and triglyceride (TG) concentrations in the blood. We hypothesized that ingestion of a potato meal rich in thermally oxidized sunflower oil (TOSO) would decrease postprandial concentrations of insulin, incretins, and TG and increase plasma glucose concentrations. Twenty healthy subjects aged 22 to 70 years consumed meals rich in TOSO or unheated sunflower oil and containing paracetamol (1.5 g) in a randomized, crossover trial. Blood samples were taken at baseline and 10, 20, 30, 60, 90, and 120 minutes after the meals and glucose, insulin, TG, nonesterified fatty acids, glucagon-like polypeptide-1, glucose-independent polypeptide, and paracetamol (as a marker of gastric emptying) were measured in plasma or serum. The incremental areas under the curve of glucose, insulin, nonesterified fatty acid, incretins, and paracetamol levels were not significantly different between the meals. Plasma TG incremental area under the curve was 44% lower after the TOSO meal at a marginal level of significance (P = .06) in the total study population and was significantly (P = .04) and 61% lower in those of median age and younger (n = 11). These data suggest that ingestion of TOSO may acutely decrease plasma TG mainly in younger individuals and does not acutely affect glucose and insulin metabolism or gastric emptying in healthy subjects.

Oral but not intravenous glucose acutely decreases circulating interleukin-6 concentrations in overweight individuals.

BACKGROUND: Plasma interleukin-6 (IL-6) concentrations decrease acutely 1 h after ingestion of a glucose load or mixed meals and this may be mediated by an anti-inflammatory effect of insulin. The aim of the present study was to compare the effect of higher versus lower insulin levels on plasma IL-6 concentrations following oral compared with intravenous glucose administration in overweight/obese subjects. METHODS AND FINDINGS: Fifteen subjects (12 women and 3 men) with BMI >28 kg/m(2) were given an oral glucose load (75 g) followed a week later by an intravenous infusion of glucose aimed at matching plasma glucose concentrations during the oral glucose load. A week later, they drank a volume of water equivalent to the volume consumed with the oral glucose load. Plasma glucose, insulin, nonesterified fatty acids, and IL-6 concentrations and blood hematocrit were measured at 30 minute intervals for 2 h following each intervention. Plasma IL-6 decreased (13-20%) significantly (P = 0.009) at 30 min to 90 min following the oral glucose load and did not change significantly following the other two interventions. The incremental area under the curve for plasma IL-6 concentrations following oral intake of glucose was significantly lower compared with concentrations following intravenous glucose (P = 0.005) and water control (P = 0.02). Circulating insulin concentrations were significantly (P<0.001) and 2.8 fold higher following oral compared with intravenous glucose administration. CONCLUSIONS: These data show that plasma IL-6 concentrations did not decrease during isoglycemic, intravenous glucose administration suggesting that the markedly higher circulating insulin levels and/or gut-related factors may mediate the acute decrease in plasma IL-6 after oral glucose intake in overweight/obese subjects. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12612000491864.

Postprandial response of plasma IL-6 to isoenergetic meals rich in casein or potato singly and combined in obese women.

Milk consumption decreases inflammatory stress in overweight and obese subjects. Casein is the major protein in milk and enhances the secretion of insulin that has anti-inflammatory activity. The aim of the present study was to compare the acute effect of meals rich in casein and carbohydrate and a combination of both nutrients on postprandial plasma concentrations of IL-6, a marker of inflammation, in obese women. A total of twenty-five obese women aged 38-68 years consumed isoenergetic meals rich in potato (POT) or casein (CA) or a combination of both these meals (POT + CA), in random order in a cross-over trial. After an overnight fast, blood samples were collected before and at 1 and 4 h after the meals and circulating concentrations of IL-6, glucose, insulin and NEFA were measured. Plasma IL-6 concentrations increased significantly (P < 0·001) during 4 h after the meals. The AUC of postprandial IL-6 concentrations was not significantly (P = 0·77) different among the meals. Postprandial serum insulin concentration AUC was significantly higher during the POT + CA meal compared with the POT meal (P = 0·001) and the CA meal (P < 0·05), which in turn was significantly higher than the POT meal (P < 0·05). These data show that while ingestion of CA alone or combined with POT acutely increases circulating insulin concentrations, it does not appreciably alter the postprandial increase in plasma IL-6 concentrations in obese women.

Dietary sodium loading in normotensive healthy volunteers does not increase arterial vascular reactivity or blood pressure.

BACKGROUND: Studies of dietary sodium on vascular function and blood pressure in normotensive volunteers have shown conflicting results. There are very limited data available on the effect of chronic sodium loading from a low-sodium diet to a high-sodium diet on vascular function and blood pressure in normotensive volunteers. OBJECTIVE: To assess the effect of modifying dietary sodium intake on arterial function and surrogate markers of arterial remodelling in normal healthy volunteers. DESIGN: Twenty-three normotensive volunteers met the inclusion criteria. After a 2 week run-in with a low-sodium diet (60 mmol/day), the participants maintained their low-sodium diets and were randomly assigned to receive sequentially one of three interventions for 4 weeks, with a 2 week washout between interventions: sodium-free tomato juice (A), tomato juice containing 90 mmol Na (B) and tomato juice containing 140 mmol Na (C). The outcomes measured were changes in pulse wave velocity (PWV), systolic blood pressure and diastolic blood pressure. RESULTS: There was no difference in PWV between interventions (B-A 0.00 m/s, 95% CI: -0.30, 0.31 m/s; C-A 0.01 m/s, 95% CI: -0.38, 0.40 m/s). There was also no change in pulse wave analysis, systolic or diastolic blood pressure between interventions. There was an appropriate increase in urinary sodium excretion in the added sodium interventions. CONCLUSION: Dietary salt loading did not produce significant increases in PWV and blood pressure in normotensive subjects with systolic blood pressure <130 mmHg. The lack of an observed effect supports Guyton's pressure-natriuresis hypothesis with appropriate renal excretion of the excess sodium load.

Paraoxonase 1 activity in chylomicrons and VLDL: the effect of type 2 diabetes and meals rich in saturated fat and oleic acid.

Paraoxonase 1 (PON 1) has antioxidant and cardioprotective properties and is abnormally low in type 2 diabetic serum. This study aimed to determine the effect of type 2 diabetes and meals rich in saturated fat and oleic acid on PON1 activity in chylomicrons and very low density lipoproteins (VLDL). PON1 arylesterase activity was measured in chylomicrons and VLDL that were isolated in serum from 20 patients with type 2 diabetes and 20 age- and gender-matched, overweight controls 3 h after meals rich in cream or olive oil in a randomized, cross-over study. Chylomicron-PON1 activity (45%, P = 0.02), ratio chylomicron-PON1/chylomicron-triacylglycerides (TAG) (42%, P = 0.03) and chylomicron-protein content (46%, P < 0.001) were significantly lower in patients with type 2 diabetes compared with controls after the olive oil meal with comparable findings after the meal rich in cream. After ingestion of olive oil, chylomicron-PON1 activity was significantly higher in controls (P = 0.01) and marginally higher (P = 0.06) in diabetic patients and chylomicron-TAG were significantly (P < 0. 05) higher in both groups of subjects, compared with values after ingestion of cream. VLDL-PON1 increased (two-fold) significantly (P < 0.003) during both meals. Chylomicron-PON1 activity was correlated significantly with chylomicron-protein (P < 0.001, n = 40) and with postprandial serum PON1 activity (P ≤ 0.001, n = 40). Our data suggest that type 2 diabetes is associated with abnormally low chylomicron-PON1 activity after fatty meals and this may be linked to lower chylomicron-protein content and serum PON1 activity. Switching from saturated fat to olive oil in the meal increases PON1 activity in the chylomicron fraction largely due to increased numbers of chylomicron particles.

Anti-inflammatory effect of an insulin infusion in patients on maintenance haemodialysis: a randomized controlled pilot study.

AIM: A pilot study to investigate the anti-inflammatory effect of insulin in patients on maintenance haemodialysis. BACKGROUND: Elevated concentrations of pro-inflammatory and oxidative mediators are thought to contribute to the increased cardiovascular risk in haemodialysis. Insulin has been demonstrated to have anti-inflammatory properties and a continuous low-dose insulin infusion in critically ill patients is associated with improved outcomes. The anti-inflammatory effects of insulin in haemodialysis have not been investigated. METHODS: In a single-blind cross-over study, 11 stable, non-diabetic, haemodialysis patients received a continuous insulin infusion (Actrapid 2 IU/h) during a dialysis of 4 h or a conventional dialysis in random order. Normoglycaemia was maintained by a modified glucose dialysate and glucose infusion. Blood samples were collected at baseline, 1, 4, 6 and 24 h. C-reactive protein (CRP), tumour necrosis factor-α, interleukin-6, neopterin, vascular cell adhesion molecule 1, protein thiols, dityrosine and peroxides were measured. RESULTS: Insulin produced a significant reduction in median CRP over the immediate dialysis phase (confidence interval) by 6% (2-9% (95% CI), P=0.006) and an even greater decline at 24 h (19% (8-28%, 95% CI), P=0.001) compared with values of the conventional dialysis. No significant changes were observed in the other markers. Median glucose levels were comparable during both dialysis sessions. CONCLUSIONS: During haemodialysis, insulin may have a modest anti-inflammatory effect as evident by a reduction in CRP that appears to have a persistent effect over the next 24 h post dialysis. More studies are required to examine longer-term benefits as well as the potential role in more high-risk individuals.

Ingestion of native and thermally oxidized polyunsaturated fats acutely increases circulating numbers of endothelial microparticles.

Circulating numbers of endothelial microparticles (EMP) are an index of endothelial injury and dysfunction; and microparticles positive to CD31 antibody increase acutely after cooked, fatty fast-food meals that are rich in saturated fatty acids (SAFA) and lipid oxidation products. The aim of this study was to determine the acute effect of meals rich in SAFA and native and thermally oxidized polyunsaturated vegetable oil on circulating numbers of EMP positive to CD144 antibody, a more specific marker of EMP. Twenty-two apparently healthy subjects received isocaloric meals rich in cream (CR), unheated sunflower oil, or heated sunflower oil in a randomized crossover study design. Circulating numbers of CD144-EMP and plasma lipids and Svedberg unit of flotation (S(f)) greater than 400 triglyceride content were measured before and 1 and 3 hours after the meals. Triglycerides in the plasma S(f) greater than 400 fraction increased significantly (P < .001) after the meals, with a significantly (P < .05) larger increase after the CR meal. Plasma CD144-EMP increased significantly (20%, P < .05) after the unheated sunflower oil and heated sunflower oil meals and did not increase significantly (P = .55) after the CR meal. This response was significantly different among the meals (P = .002) when first-visit fasting plasma glucose was a covariate. In conclusion, these data suggest that ingestion of meals rich in n-6 polyunsaturated vegetable oil irrespective of whether it has been mildly thermally oxidized may acutely alter the state of the vascular endothelium, resulting in increased shedding of CD144-EMP. The physiologic implications of these findings remain to be determined.

The effect of glucose ingestion on inflammation and oxidative stress in obese individuals.

Ingestion of 75 g glucose during an oral glucose tolerance test (OGTT) increases systemic inflammation and oxidative stress in healthy subjects and patients with type 2 diabetes mellitus, but the effect in overweight/obese nondiabetic individuals is uncertain. The aim of the present study was to determine the effect of an OGTT on plasma concentrations of inflammatory cytokines and peroxides in 33 subjects with body mass index >27 kg/m(2). After an overnight fast, blood samples were taken from participants immediately before and at 30, 60, 90, and 120 minutes after ingestion of 75 g glucose. Plasma glucose, insulin, free fatty acid, interleukin (IL)-6, tumor necrosis factor alpha, and peroxides were measured during the tests. Plasma IL-6 concentrations decreased (13%) significantly (P < .001) at 30 and 60 minutes, whereas plasma peroxide concentrations decreased slightly (3%, P = .003) at 30 minutes during the tests. The 30-minute decrease in plasma IL-6 was correlated significantly and inversely with the concomitant increase in plasma insulin (r = -0.410, P = .02) and with the ratio of insulin to glucose at 30 minutes during the OGTT (r = -0.366, P = .04). These data suggest that plasma concentrations of IL-6 are acutely decreased possibly because of the predominance of the anti-inflammatory effect of hyperinsulinemia over the proinflammatory effect of hyperglycemia after ingestion of a large quantity of glucose in obese individuals.

The effect of rosiglitazone on oxidative stress and insulin resistance in overweight individuals.

OBJECTIVE: The purpose of this study was to examine the chronic effect of rosiglitazone on oxidative stress, inflammatory markers and hepatic risk factors for type 2 diabetes in overweight individuals. In addition we examined the effect of rosiglitazone on post-glucose challenge levels of glucose and insulin. RESEARCH DESIGN AND METHODS: Forty overweight individuals (BMI>27kg/m(2)) were randomized in a double blind fashion to receive 6 months treatment with either rosiglitazone 4mg/day or placebo. Primary endpoints were markers of oxidative stress (plasma peroxides), inflammatory markers (IL-6, TNF-alpha and CRP) and postprandial glucose metabolism (glucose and insulin). Secondary endpoints were changes in insulin resistance as measured by HOMA, first and second phase insulin secretion, adiponectin and effects on lipid and hepatic parameters. RESULTS: Plasma peroxides (-15%) decreased significantly during 6 months in the group that received rosiglitazone compared with placebo. Fasting plasma insulin concentrations decreased by 24% and HOMA increased by 35% in those receiving rosiglitazone. Plasma IL-6 (-25%), CRP (-55%) and GGT (-25%) concentrations declined significantly in the rosiglitazone group. Rosiglitazone increased plasma adiponectin by 81%. Treatment with rosiglitazone also resulted in significantly reduced first phase (-33%) and second phase (-20%) insulin release. CONCLUSIONS: In overweight non-diabetic people rosiglitazone reduces oxidative stress and improves insulin sensitivity. Rosiglitazone also improves first and second phase insulin secretion and reduces markers of inflammation and GGT.

Postprandial cytokine concentrations and meal composition in obese and lean women.

The aim of this study was to compare the acute effect of (i) meals rich in saturated fat, oleic acid, and alpha-linolenic acid and (ii) meals rich in starch and fiber on markers of inflammation and oxidative stress in obese and lean women. In a crossover study, 15 abdominally obese women (age, 54 +/- 9 years; BMI, 37.3 +/- 5.5 kg/m2) and 14 lean women (age, 53 +/- 10 years; BMI, 22.9 +/- 1.9 kg/m2) consumed meals rich in cream (CR), olive oil (OL), canola oil (CAN), potato (POT), and All-Bran (BRAN) in random order. Blood samples were collected before and up to 6 h after the meals and plasma interleukin-6 (IL-6), IL-8, tumor necrosis factor-alpha (TNF-alpha), lipid peroxides (LPOs), free-fatty acids (FFAs), insulin, glucose, and cortisol were measured. Plasma IL-6 decreased significantly 1 h after the meals then increased significantly above baseline at 4h and 6h in obese women and at 6h in lean women. The incremental area under the curve (iAUC) for IL-6 was significantly (P = 0.02) higher in obese compared with lean women and was significantly lower following the high fiber BRAN meal compared with a POT meal (P = 0.003). Waist circumference (R = 0.491, P = 0.007) and cortisol AUC (R = -0.415, P = 0.03) were significant determinants of the magnitude of 6h changes in plasma IL-6 after the meals. These findings suggest that the postprandial response of plasma IL-6 concentrations may be influenced by the type of carbohydrate in the meal, central adiposity, and circulating cortisol concentrations in women.

Effect of dietary cholesterol and fat on cell cholesterol transfer to postprandial plasma in hyperlipidemic men.

Postprandial chylomicrons are potent ultimate acceptors of cell membrane cholesterol and are believed to accelerate reverse cholesterol transport (RCT). We compared the effects of meals rich in polyunsaturated fat (PUFA) and either high (605 mg) or low (151 mg) in cholesterol and a meal rich in dairy fat (DF) in the form of cream on net in vitro transport of red blood cell (RBC) membrane cholesterol to 4 and 6 h postprandial plasma in eight normotriglyceridemic (NTG-H) and eight hypertriglyceridemic (HTG-H) men with mild to moderate hypercholesterolemia. In HTG-H men, cell cholesterol accumulation in 6-h postprandial plasma was significantly (P = 0.02) less after the PUFA-HC meal compared with the other meals. The significant (P < 0.001) increase in cell plus endogenous cholesterol accumulation in the triglyceride-rich lipoprotein (TRL) fraction of 4 h postprandial plasma incubated with RBC was significantly (P = 0.007) higher after the PUFA-HC meal compared with DF meal in HTG-H men. In NTG-H men, cholesterol accumulation in plasma and plasma lipoproteins in the presence and absence of RBC was not significantly affected by the type of meal ingested. These data suggest that addition of large amounts of cholesterol to a PUFA meal may impair diffusion-mediated transport of cell membrane cholesterol to postprandial plasma and that replacing DF with PUFA in a meal increases postprandial lipemia and may potentially increase cholesterol accumulation in atherogenic postprandial TRL in HTG-H men.

The impact of standard high-flux polysulfone versus novel high-flux polysulfone dialysis membranes on inflammatory markers: a randomized, single-blinded, controlled clinical trial.

BACKGROUND: This study is a prospective, randomized, single-blind, clinical trial over 12 months involving 60 stable hemodialysis patients comparing standard high-flux polysulfone dialyzer membranes with a novel high-flux polysulfone dialyzer membrane (Helixone; Fresenius Medical Care, St Wendel, Germany) modified in the fiber-spinning process to enhance middle-molecule clearance through changing the distribution of pore size and increased filtration. METHODS: Markers of protein and lipid oxidation and inflammatory markers, including proinflammatory cytokines and cell adhesion molecules, were compared. The hypothesis tested was that improved clearances of middle molecules with the FX80 membrane would lead to less oxidative stress and inflammation compared with the high-flux polysulfone (HF80) membrane. RESULTS: Type of dialysis membrane used did not significantly affect lipid and protein peroxidation, C-reactive protein level, interleukin 6 level, or sgp130 level during 12 months. beta(2)-Microglobulin concentrations decreased significantly in the Helixone membrane group compared with those dialyzed using conventional polysulfone membranes during the study (-15%; 95% confidence interval, -20 to -10). CONCLUSION: Long-term dialysis with a Helixone membrane did not modify any parameters of oxidative stress or inflammation in this stable hemodialysis population compared with a high-flux polysulfone dialysis membrane.

Vitamin E supplementation and plasma 8-isoprostane and adiponectin in overweight subjects.

OBJECTIVE: Isoprostanes are a marker of oxidant stress and atherosclerotic risk, and plasma concentrations are elevated in obesity. Adiponectin is a regulator of insulin sensitivity, and low circulating levels are associated with oxidant stress and obesity. The aim of this study was to determine the effect of vitamin E supplementation on plasma concentrations of 8-isoprostane and adiponectin in overweight/obese subjects. RESEARCH METHODS AND PROCEDURES: The study was a 6-month, randomized, double-blind, placebo-controlled trial in 80 overweight subjects (60 women and 20 men, BMI >27 kg/m(2)). Exclusion criteria were serious illness, smoking, or taking antioxidant supplements. Participants were randomized to receive 800 IU/d natural vitamin E (n = 39) or placebo (n = 41) for 3 months with an increase in the dose to 1200 IU/d for a further 3 months. Plasma 8-isoprostane and adiponectin concentrations were measured at baseline and 3 and 6 months. RESULTS: During 6 months of supplementation with vitamin E, plasma vitamin E concentration increased significantly (p < 0.001) by 76%, and plasma 8-isoprostane concentrations decreased significantly (-11%, p = 0.03), whereas plasma adiponectin concentrations did not change significantly. DISCUSSION: These findings suggest that supplementation with high-dose vitamin E decreases systemic oxidative stress and 8-isoprostane concentrations in overweight/obese individuals. A decrease in plasma 8-isoprostane has the potential to reduce risk of cardiovascular disease in obesity.

Variation in the cholesteryl ester transfer protein (CETP) gene does not influence individual plasma cholesterol response to changes in the nature of dietary fat.

BACKGROUND AND AIMS: Some individuals respond to a greater extent than others to changes in dietary fat and cholesterol even when dietary intake is consistent. A prospective study has been undertaken in which two groups of individuals according to cholesteryl ester transfer protein (CETP) genotype were compared in terms of plasma lipid response to altering the nature of dietary fat in a free-living situation. METHODS AND RESULTS: Following genotyping, 35 individuals with the CETP Taq1 B1B1 genotype were paired with age and sex-matched individuals with one or two CETP B2 alleles, to undertake a single crossover trial with a diet high in saturated fat and a diet high in polyunsaturated fat. There was no washout period between the two 4-week phases. Plasma lipoproteins were measured at the beginning and end of each phase. The difference (95% CI) in plasma LDL-cholesterol concentration at the end of the PUFA and SAFA diets was 0.95 (0.71, 1.19) mmol/l in the CETP B1B1 group and 0.80 (0.57, 1.04) mmol/l in the group with at least one CETP B2 allele. The dietary induced changes in the two genotype groups were not significantly different (p=0.38) from each other. Comparable results were observed for plasma total cholesterol. The high PUFA and SAFA diets did not significantly alter plasma HDL concentration in either of the CETP genotype groups. Response was also similar according to apolipoprotein E genotype (E3E3 vs E4+) and lipoprotein lipase genotype (S447X). CONCLUSIONS: The results of this study do not support previous studies in which CETP genotype predicted plasma LDL-cholesterol response to diet. CETP genotype does not significantly affect the change in plasma total and LDL-cholesterol concentrations that occur when altering the nature of dietary fat. These data suggest that the influence of genetic factors on total and LDL-cholesterol may be relatively small in comparison with the effect of dietary manipulation.

Aged garlic extract improves endothelial function in men with coronary artery disease.

Endothelium-dependent vasodilation is impaired and predicts the risk of a coronary event in patients with coronary artery disease (CAD). Oxidant stress and increased systemic inflammation may contribute to this endothelial dysfunction. Aged garlic extract (AGE) contains antioxidant compounds and increases nitric oxide production and decreases the output of inflammatory cytokines from cultured cells. The aim of this study was to test the effect of treatment with AGE on brachial artery flow mediated endothelium-dependent dilation (FMD) and circulating markers of oxidative stress and systemic inflammation. The trial included 15 men with angiographically proven CAD in a randomized, placebo-controlled, cross-over design with 2-week treatment and washout periods. During AGE supplementation, FMD increased (44%) significantly (p = 0.04) from the baseline and mainly in men with lower baseline FMD. Levels of FMD at the end of AGE treatment were significantly (p = 0.03) higher compared with the corresponding levels at the end of placebo treatment when the variation in baseline body weight was taken into account. Markers of oxidant stress (plasma oxidized low density lipoprotein and peroxides), systemic inflammation (plasma C-reactive protein ad interleukin-6) and endothelial activation (VCAM-1) did not change significantly during the study. These data suggest that short-term treatment with AGE may improve impaired endothelial function in men with CAD treated with aspirin and a statin. Whether improvement in endothelial function decreases the risk of future cardiovascular events remains to be determined.

Hypochlorous acid and 3,4-dihydroxyphenylalanine increase the formation of serum protein lipofuscin-like fluorophores in vitro.

INTRODUCTION: Serum protein lipofuscin-like fluorophores (LLFs) that include fluorescent advanced glycation end products (AGEs), are an index of protein modification and levels are abnormally high in hemodialysis patients. To investigate the possibility that hypochlorous acid (HOCl) and 3,4-dihydroxyphenylalanine (DOPA) may contribute to high LLFs concentrations, we have examined the effect of these factors on serum protein LLF formation in vitro. METHODS: Protein LLF concentration was measured at excitation 350 nm and emission 460 nm and was expressed in arbitrary units relative to quinine sulphate fluorescence. Oxidation of serum or other solutions with HOCl was carried out at room temperature for 30 minutes and serum was delipidated before measurement of protein LLFs. RESULTS: Serum protein LLF concentration increased non-linearly by a maximum 247% with increasing HOCl concentration in the range 6.5-32.9 mmol/L and this was mirrored by a decrease in protein tryptophan fluorescence. HOCl (32.9 mmol/L) increased LLFs in human gamma-globulin solutions (15-fold in 12 mg/mL and 5-fold in 60 mg/mL solutions) and did not alter LLFs appreciably in human serum albumin solution (60 mg/mL). Addition of DOPA (265 micromol/L) significantly (P<0.001) increased LLF formation in serum by nearly 2-fold during 3 days incubation under air. CONCLUSIONS: These data suggest that HOCl and DOPA are capable of generating serum protein LLFs and that gamma-globulins appear to be an important substrate for protein LLF formation in human serum. These findings may be relevant to the abnormally high concentrations of serum protein LLFs and impaired immune response in hemodialysis patients.

Effect of high-dose vitamin E on insulin resistance and associated parameters in overweight subjects.

OBJECTIVE: Markers of oxidative stress and plasma alanine transferase (ALT) levels are increased and circulating antioxidant concentrations are reduced in individuals with insulin resistance. Vitamin E improves glycemic control in people with diabetes. We tested the hypothesis that vitamin E would decrease markers of oxidative stress and plasma ALT levels and improve insulin sensitivity in overweight individuals. RESEARCH DESIGN AND METHODS: Eighty overweight individuals (BMI >27 kg/m(2)) were randomly allocated to receive either 800 IU vitamin E per day or a matching placebo for 3 months. The dose of vitamin E was increased to 1,200 IU per day for a further 3 months. RESULTS: Plasma peroxides decreased by 27% at 3 months and by 29% at 6 months in the group that received vitamin E and were positively correlated with plasma vitamin E concentrations at the 6-month time point. At 3 months, fasting plasma glucose and insulin concentrations were significantly reduced and homeostasis model assessment increased. These changes were not apparent at 6 months. Plasma ALT concentrations declined significantly throughout the study period. CONCLUSIONS: In conclusion, these findings indicate that vitamin E improves oxidative stress and hepatocellular function. Although insulin resistance also improves, this effect appears transient.

Acute effect of drinking red and white wines on circulating levels of inflammation-sensitive molecules in men with coronary artery disease.

There is evidence that moderate consumption of red wine with its high content of polyphenolic antioxidants may be more protective than white wine against development of coronary artery disease (CAD). The aim of this study was to compare the acute effects of ingestion of red wine and white wine on markers of inflammation in men with CAD. Thirteen men with angiographically-proven CAD were studied in a cross-over trial. The men consumed 4 mL/kg (2 to 3 glasses) red wine and white wine in random order during a light meal and with at least a week between interventions. Later, the men also consumed an isoenergetic nonalcoholic beverage (control) in the same study protocol. Venous blood was taken at baseline, 1 hour, and 6 hours after the drinks. Plasma interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), blood alcohol, plasma lipids, and plasma polyphenols were measured. Mean +/- SD blood alcohol was 6.5 +/- 2.2 mmol/L and 6.9 +/- 1.1 mmol/L at 1 hour and returned to baseline at 6 hours after intake of red wine and white wine, respectively. Plasma IL-6 concentration increased significantly (P =.01) during 6 hours after ingestion of red wine (56%) and white wine (63%). The increase in plasma IL-6 concentration after ingestion of wine was significantly higher (P =.045) compared with the corresponding increase (11%) following intake of the nonalcoholic beverage. Plasma IL-6 levels at 6 hours (r =.631, P =.02) were correlated significantly with plasma alcohol levels at 1 hour after ingestion of red wine. These data suggest that moderate wine intake may acutely increase plasma levels of IL-6 in men with CAD. It is possible that this increase in plasma IL-6 is a response to alcohol-induced oxidative stress in the liver.

Hypochlorous acid and low serum paraoxonase activity in haemodialysis patients: an in vitro study.

BACKGROUND: Serum paraoxonase 1 (PON1) is an oxidant-sensitive enzyme associated with high-density lipoprotein (HDL) that inhibits the atherogenic oxidation of low-density lipoprotein (LDL). In haemodialysis patients, production of reactive oxygen species, such as hypochlorous acid (HOCl) and hydrogen peroxide, is increased and serum PON1 arylesterase is abnormally low. We have examined the effect of HOCl and the uraemic milieu on serum PON1 arylesterase activity and the ability of HDL to inhibit LDL oxidation in vitro. METHODS: Serum was incubated with HOCl, hydrogen peroxide and products of HOCl reaction with excess cysteine, lysine and taurine and then serum PON1 arylesterase and serum protein tryptophan fluorescence were measured. The ability of plasma HDL fractions isolated by a dextran-sulphate method, to protect LDL from mild oxidation in air, was determined by a fluorimetric method using oxidation of 2,7-dichlorofluorescein (DCFH). RESULTS: Incubation of healthy serum with HOCl in the range 6.5-32.9 mmol/l resulted in a linear decrease in serum PON1 arylesterase activity to 40% of that without HOCl and a parallel decrease in protein tryptophan fluorescence. The HOCl-induced decrease in serum PON1 activity was completely removed by reaction of HOCl with a 2.7-fold excess of alpha-amino acids but not taurine. In serum incubated for 1 week, the decrease in serum PON1 activity was significantly (P = 0.04) less while the increase in protein fluorescent advanced glycation end-products was significantly larger (P = 0.01) in haemodialysis patients compared with healthy subjects. The mean decrease in mild oxidation of LDL was not significantly different on addition of HDL-rich fractions from haemodialysis patients (100 +/- 6%, n = 7) and healthy subjects (95 +/- 6%, n = 7) or on addition of the HDL-rich fraction from plasma treated with 0.95 mmol/l HOCl (95%) and control HDL (96%). The fraction rich in HDL and other high molecular weight compounds from plasma that had been incubated with increasing HOCl concentrations up to 1.9 mmol/l significantly (P = 0.001) increased (471%) the oxidation of DCFH. CONCLUSIONS: These results suggest that high concentrations of HOCl that severely oxidize serum proteins and tryptophan residues in the active site of PON1 are required to decrease PON1 arylesterase activity in serum. In haemodialysis patients, overproduction of HOCl that leads to high concentrations of severely oxidized proteins and increased oxidants in plasma might also contribute to low serum PON1 arylesterase activity, but does not appear to impair the ability of an HDL molecule to protect LDL from mild oxidation.

Serum protein-bound 3,4-dihydroxyphenylalanine and related products of protein oxidation and chronic hemodialysis.

INTRODUCTION: Protein-bound dihydroxyphenylalanine (PB-DOPA) and its oxidation products are formed by free radical and oxidative attack on proteins. Hemodialysis and uremic toxins can activate leukocytes leading to overproduction of reactive oxygen species such as hydrogen peroxide and hypochlorous acid (HOCl) that increases protein oxidation. METHODS: We have used a sensitive fluorometric method to measure PB-DOPA and its oxidation products in proteins after gamma-irradiation and incubation with HOCl and in serum from hemodialysis patients and healthy controls. These PB-DOPA concentrations were compared with those measured by HPLC (PB-DOPAHPLC). RESULTS: Fluorescent PB-DOPA increased linearly with increasing amounts of human serum and with increasing amounts of gamma-irradiated bovine serum albumin. Concentrations of fluorescent PB-DOPA paralleled PB-DOPAHPLC levels but were approximately 60-70 times higher. Incubation of BSA and human serum albumin (HSA) with HOCl (39.4 mM) significantly (P < 0.0001) increased fluorescent PB-DOPA by 5 fold and 10 fold respectively and PB-DOPAHPLC by 6-fold for both proteins Fluorescent PB-DOPA concentration increased significantly (P < 0.0001) by 16-fold in human serum incubated with HOCl (39.4 mM). Mean serum fluorescent PB-DOPA was significantly (P < 0.0001) higher in 19 hemodialysis patients (57.7 +/- 16.1 microM) compared with 21 healthy controls (33.5 +/- 3.7 microM). Mean PB-DOPAHPLC was 4.45 +/- 1.63 microM in the healthy controls and 12 hemodialysis patients had values within the range of values in these controls while five patients had values that were outside eight SDs of the mean for healthy subjects. Serum fluorescent PB-DOPA was not correlated significantly with PB-DOPAHPLC in these subjects. CONCLUSIONS: The results of this study suggest that fluorophores of the type, which are derived from DOPA can be reproducibly measured in delipidated serum protein and that HOCl can increase levels of these fluorophores-generating proteins and may potentially contribute to the high levels in serum from hemodialysis patients. This high level of fluorescent PB-DOPA compounds is only partially due to authentic PB-DOPA and might also be derived from other related protein oxidation products including those from DOPA oxidation.