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.

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.

Plasma protein lipofuscin-like fluorophores in men with coronary artery disease treated with statins.

BACKGROUND: Lipid oxidation products react with protein to produce lipofuscin-like fluorophores (P-LLF) and modified apolipoprotein B that is an important element of the atherogenic properties of oxidized low-density lipoprotein (oxLDL). The aim of this study was to compare plasma concentrations of P-LLF between men with coronary artery disease (CAD) treated with statin drugs and healthy controls and to identify determinants of P-LLF. METHODS: Plasma markers of protein modification including P-LLF and oxidized low-density lipoprotein-4E6 (oxLDL-4E6), low-density lipoprotein-conjugated dienes (LDL-CD), lipid peroxides, apolipoprotein B, and serum albumin were measured in 24 men with CAD who were receiving statin therapy and 20 healthy men in the same age range. RESULTS: Plasma P-LLF (+23%, p = 0.001) was significantly higher and plasma oxLDL-4E6 (-33%, p <0.001) and apolipoprotein B (apoB) (-30%, p <0.001) concentrations were significantly lower in men with CAD compared with controls. Plasma P-LLF concentration was correlated significantly with plasma apoB (r = -0.596, p <0.001), serum albumin (r = 0.518, p <0.001), and age (r = 0.390, p = 0.009) and these variables were independent predictors of P-LLF in the study population. Plasma P-LLF was no longer significantly higher in men with CAD when plasma apoB concentration was taken into account. CONCLUSIONS: Plasma P-LLF concentration is abnormally high and appears to be closely associated with lower levels of apoB in men with CAD receiving statin therapy. ApoB may be a preferential target of reactive aldehydic lipid oxidation products and a decrease in apoB may increase the quantity of these products available for condensation with albumin.

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.

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.

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.

HRT does not improve urinary albumin excretion in postmenopausal diabetic women.

The effect of 6 months combined, continuous hormone replacement therapy (HRT) with conjugated equine oestrogen (0.625 mg) and medroxyprogesterone acetate (2.5 mg) on albumin/creatinine ratio (ACR) was determined in postmenopausal diabetic women in a randomised, controlled study. Mean (interquartile range) change in plasma ACR was not (P=0.96) different in women receiving HRT [2 (-11, 21) mg/g, n=20] compared with those randomised to placebo [2 (-1, 14) mg/g, n=27]. Also, the proportion of women with microalbuminuria did not change (P=0.75) during HRT (baseline, 0.45; end of study, 0.53). Furthermore, several risk factors for microalbuminuria including systolic blood pressure (SBP), fasting blood glucose, glycated haemoglobin (HbA1c) and adiposity did not vary significantly during HRT. These data suggest that 6 months HRT does not reverse microalbuminuria caused by prolonged hyperglycaemia and other risk factors that underlie leakage of albumin into the urine in postmenopausal women with type 2 diabetes.

Release of cholesterol from cell membranes to postprandial plasma from mildly hypercholesterolemic subjects: the effect of meals rich in olive and safflower oils.

Triglyceride-rich lipoproteins increase net transport of cell cholesterol to postprandial plasma from healthy subjects after a meal rich in fat and cholesterol. The aim of the present study was to determine the effect of meals rich in polyunsaturated fats (PUFA) and monounsaturated fats (MUFA) and low in cholesterol on net in vitro transport of cholesterol from red blood cells (RBCs) to postprandial plasma from 21 men with mild to moderate hypercholesterolemia in a randomized, crossover trial. Cholesterol concentration increased by 12% due to accumulation of cell cholesterol in fasted hypercholesterolemic plasma incubated with a 2/1 (vol/vol) excess of RBCs at 37 degrees C for 18 hours. The increase in cell cholesterol in plasma was mainly localized in the low-density lipoprotein (LDL) fraction (64%) and the remainder was approximately equally divided between the very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) fractions. Accumulation of cell cholesterol in the LDL fraction prevented the significant decrease in LDL cholesterol in plasma incubated alone. When RBCs were incubated with postprandial plasma isolated 4 hours and 6 hours after liquid meals rich in safflower and olive oils, the accumulation of cell cholesterol in plasma increased significantly (11%, P <.004) above values for fasted plasma and irrespective of the type of fat in the meal. Also, the content of cell cholesterol increased significantly (70%, P <.001) in triglyceride (TG)-rich lipoproteins and decreased significantly (P =.006) in the LDL fraction, which remained the main ultimate destination of cell cholesterol in postprandial plasma. The increased loss of cell cholesterol to fasted and postprandial plasma was closely correlated (r > 0.823, P <.001) with the concomitant increase in plasma cholesteryl esters (CE) generated by lecithin cholesterol acyltransferase (LCAT) activity. There was a small (5%), significant (P <.001) increase in plasma cholesterol esterification in postprandial plasma. These data suggest that high-fat meals rich in MUFA and PUFA and low in cholesterol may produce a small postprandial increase in the capacity of plasma to accept cell membrane cholesterol that is limited by a concomitant small increase in plasma cholesterol esterification, in hypercholesterolemic subjects. Thus, low-fat, lipid-lowering diets may have a minimal effect on this capacity but will reduce levels of atherogenic LDL cholesterol that appear to be maintained by diffusion of cell cholesterol to plasma.

Effect of meals rich in heated olive and safflower oils on oxidation of postprandial serum in healthy men.

The present randomised, crossover study sought to determine the effect of meals rich in safflower oil and olive oil (60 g) which had been heated for 8 h at 210 degrees C and the corresponding unheated oils on copper ion oxidation of dilute serum from 16 healthy men. Four hours after the meals rich in the heated oils, there were significant decreases of similar magnitude (-12%) in the lag time in conjugated diene formation during diluted serum oxidation. In the 12 subjects who consumed meals containing unheated oils, the lag time also decreased (-11%) significantly after the meal rich in unheated safflower oil (US) and did not change significantly after the unheated olive oil (UO) meal and these changes were different between the meals at a marginal level of significance (P=0.05). Our data suggest that susceptibility to oxidation of lipoproteins in low antioxidant environments similar to dilute serum may be increased in the postprandial period following meals rich in heat-modified vegetable oils and unheated oils rich in polyunsaturated fatty acids but not following meals rich in native olive oil. These findings may be relevant to the choice of fat to replace saturated fats in lipid-lowering diets and to low risk of coronary heart disease in communities which have a high consumption of olive oil.