Flavonoids and the oxidation of low-density lipoprotein

The Influence of Plants from the Alliaceae Family on Morphological Parameters of the Intestine in Atherogenic Rats

Bulbs from the Alliaceae family have been well-known and valued spices for thousands of years, not only for their unique flavor and aroma features, but also for their high nutritional and health-promoting values. Long-term or excessive consumption of these vegetables, especially raw garlic, can have side effects in the body (including in the digestive tract), causing a number of pathological changes in the intestinal wall; these changes lead, in turn, to its damage, dysfunction, and disorder development. Therefore, the aim of this study was to investigate the effect of the addition of freeze-dried vegetables from the Alliaceae family, i.e., garlic (Allium sativum L.), white onion, and red onion (Allium cepa L.) on the morphometric parameters (intestinal villi length, crypt depth, thickness of tunica mucosa, and the thickness of tunica muscle) of the jejunum of rats fed a semi-synthetic atherogenic diet (1% dietary cholesterol). In freeze-dried vegetables administered to rats, the contents of selected bioactive ingredients and their antioxidant potentials were determined. The effect of the onion vegetable supplements on growth parameters, serum lipid profile, plasma antioxidant potential, and the intestinal morphological parameters of rats loaded with cholesterol was determined. In an animal experiment, 30 male Wistar rats were divided into 5 diet groups, diet consumption and FER were studied. Supplementation of the atherogenic diet with vegetables improved the blood plasma lipid profiles and atherogenic indices, in a manner that was dependent on the type of supplementation used, with the best hypolipidemic and anti-atherosclerotic effects found in garlic use. The atherogenic diet, as well as the supplementation of this diet with the tested vegetables from the Alliaceae family, influenced the histological changes in the epithelium of the jejunum of rats. The damage to the intestinal mucosa was the greatest in animals fed an atherogenic diet supplemented with garlic. Bearing in mind that the desired beneficial therapeutic or prophylactic effects of onion vegetables (in particular garlic) in the course of various metabolic ailments (including atherosclerosis) are achieved during long-term supplementation, it is important to remember their possible cytotoxic effects (e.g., on the digestive tract) in order to achieve real benefits related to the supplementation with vegetables from the Alliaceae family.

Relationship between diet and plasma long-chain n-3 PUFAs in older people: impact of apolipoprotein E genotype

The main risk factors for Alzheimer's disease, age and the ε4 allele of the APOE gene (APOE4), might modify the metabolism of n-3 PUFAs and in turn, their impact on cognition. The aim of this study was to investigate the association between dietary fat and plasma concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in elderly persons, taking the APOE4 genotype into account. The sample was composed of 1,135 participants from the Three-City study aged 65 years and over, of whom 19% were APOE4 carriers. Mean plasma proportions of EPA [1.01%, standard deviation (SD) 0.60] and DHA (2.41%, SD 0.81) did not differ according to APOE4. In multivariate models, plasma EPA increased with frequency of fish consumption (P < 0.0001), alcohol intake (P = 0.0006), and female gender (P = 0.02), and decreased with intensive consumption of n-6 oils (P = 0.02). The positive association between fish consumption and plasma DHA was highly significant whatever the APOE genotype (P < 0.0001) but stronger in APOE4 noncarriers than in carriers (P = 0.06 for interaction). Plasma DHA increased significantly with age (P = 0.009) in APOE4 noncarriers only. These findings suggest that dietary habits, gender, and APOE4 genotype should be considered when designing interventions to increase n-3 PUFA blood levels in older people.

Low-density-lipoprotein (LDL)-bound flavonoids increase the resistance of LDL to oxidation and glycation under pathophysiological concentrations of glucose in vitro

The higher susceptibility of low-density lipoprotein (LDL) to oxidation and glycation in diabetes has been shown to be related to poor glycemic control. The aim of this study was to determine whether LDL-bound flavonoids attenuate high-glucose (HG)-mediated LDL oxidation and glycation. For this purpose, human plasma was preincubated with individual flavonoids for 3 h, followed by sequential ultracentrifugation and extensive dialysis to remove unbound flavonoid samples. Enriched LDL was subsequently isolated and challenged for its resistance to oxidation and glycation. Results showed that glucose (5-30 mM) dose-dependently accelerates copper (Cu(2+))-mediated LDL oxidative modification. The enrichment of flavonoids such as luteolin, naringenin, and kaempferol significantly increased the resistance of LDL to oxidation and prevented endogenous alpha-tocopherol consumption caused by HG/Cu(2+) (p < 0.05). The long-term glycation of LDL, which was measured by advanced glycation endproducts (AGEs)-related fluorescence and boronate affinity chromatography, was found to be inhibited by LDL-bound flavonoids in the following order: rutin > luteolin > quercetin > kaempferol > naringenin > catechin approximately EC > naringin. Moreover, a solid-phase extraction system with HPLC-diode array detection provided evidence that flavonoids were bound to LDL particles to a certain extent concurrently facilitating the lipoprotein antioxidant and antiglycation activities. In conclusion, this study supports the hypothesis that HG promoted oxidative and glycative modifications of LDL. This is the first study to show that the introduction of flavonoids into LDL particles protects the lipoprotein against glycotoxin-mediated adverse effects.

Polyphenols synergistically inhibit oxidative stress in subjects given red and white wine

Aim of this study was to analyse the relationship between the plasma levels of polyphenols and the antioxidant activity of red and white wine. Twenty healthy subjects (HS) were randomly allocated to drink 300 ml of red (n = 10) or white n = 10 wine for 15 days. Ten HS who refrained from any alcohol beverage for 15 days were used as control. Urinary PGF-2alpha-III, a marker of oxidative stress and plasma levels of polyphenols were measured. Urinary PGF-2alpha-III significantly fell in subjects taking wine with a higher percentage decrease in subjects given red wine (-38.5 +/- 6%, p < 0.001) than in those given white wine (-23.1 +/- 6%). Subjects taking red wine had higher plasma polyphenols than those taking white wine (1.9 +/- 0.6 microM versus 1.5 +/- 0.33 microM, p < 0.001). Plasma polyphenols were inversely correlated with urinary PGF2alpha (r = 0.77, p < 0.001). No changes of urinary isoprostanes were observed in subjects who refrained from wine intake. In vitro study demonstrated that only a mixture of polyphenols, all in a range corresponding to that found in human circulation, inhibited LDL oxidation and PKC-mediated NADPH oxidase activation. Such inhibitory effects were more marked using the concentrations of polyphenols detected in human circulation after red wine intake. This study shows that red wine is more antioxidant than white wine in virtue of its higher content of polyphenols, an effect that may be dependent upon a synergism among polyphenols.

Effects of soy or milk protein durign a high-fat feeding challenge on oxidative stress, inflammation, and lipids in healthy men

Soy isoflavones may impede atherogenic processes associated with cardiovascular disease. Research suggests that the postprandial generation of TG-rich remnants contributes to the development of atherosclerosis. The purpose of the current study was to determine if 39 g soy (85 mg aglycone isoflavones, treatment) compared with 40 g milk protein (0 mg aglycone isoflavones, control) in combination with a high-fat meal can modify postprandial, atherogenic-associated events and biomarkers for oxidative stress, inflammation, and thrombosis. Fifteen healthy men (20-47 yr) participated in a double-blind cross-over meal-challenge study occurring on two nonconsecutive days. The study meals consisted of two high-fat apple muffins consumed with either a soy or milk shake (229 mL, 41% fat, 41% carbohydrate, and 18% protein). Blood samples were obtained at baseline (fasted) and hours two, four, and six postprandial. Plasma TG significantly increased in both treatment and control meal challenges compared with baseline. There were no significant differences (P > 0.05) between treatment (soy) and control (milk) for ex vivo copper-induced LDL oxidation, serum C-reactive protein, serum interleukin-6 (IL-6), serum fibrinogen, or plasma lipids (total cholesterol, HDL, LDL, TG). IL-6-concentrations significantly decreased as a function of time during either meal challenge (P = 0.005). These data suggest that consumption of soy or milk protein in conjunction with a high-fat meal does not acutely modify postprandial oxidative stress, inflammation, or plasma lipid concentrations in young, healthy men.

Commercial dietary antioxidant supplements assayed for their antioxidant activity by different methodologies

Seven commercial dietary antioxidant supplements were evaluated for their in vitro antioxidant capacity by different methodologies: antiradical activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH.), inhibition of methyl linoleate (MeLo) autoxidation, and resistance to ion-dependent oxidation of human low-density lipoprotein (LDL). Great variability in antioxidant activity was seen among the supplements, as well as different patterns of antioxidant capacity depending on the method used. The same orders of activity were found for the MeLo autoxidation and LDL-induced oxidation methods, but the differences recorded by the former were wider. "Food/compound intake equivalents" of the doses recommended by the manufacturers were calculated in terms of quercetin, strawberries, and red wine for each of the supplements studied. Food/compound intake equivalents varied between 7.9 and 190 mg of quercetin according to the DPPH. scavenging method, between 0.20 and 98 mg according to the MeLo autoxidation method, and between 3.4 and 83 mg according to LDL-induced oxidation. In equivalent terms of red wine, the food/compound intake equivalents varied between 7 and 159 mL, between 3 and 1354 mL, and between 4 and 89 mL for the same three methods. In terms of equivalents of strawberry, they varied between 14 and 343 mg according to the DPPH. scavenging method and between 57 g and 26 kg according to the MeLo autoxidation method. These results show the need to standardize dietary supplements in terms of their antioxidant capacity to match required doses to the oxidative status of consumers.