Effect of vitamin E supplementation on antibody levels against malondialdehyde modified LDL in hyperlipidemic hamsters

Grape polyphenols increase the activity of HDL enzymes in old and obese rats

HDL particles are protein-rich particles that act as a vehicle for reverse cholesterol transport from tissues to the liver. The purpose of this study was to investigate age-dependent changes in the functional activity of HDL and the effect of high-energy diet on this index, as well as to correct it under the influence of grape polyphenols from “Enoant” obtained from Vitis vinifera grapes. We observed the age-dependent composition changes in HDL particle. It was shown that total lipids and triacylglycerol (TG) levels were higher in 24-month-old animals. In obese rats, HDL total lipids and TG levels were higher in 24-month-old than in the 3-month-old and 12-month-old groups but did not differ from 24-month-old group. The plasma HDL paraoxonase (PON) and lecithin:cholesterol acyltransferase (LCAT) activity levels were decreased in old-aged rats, and cholesteryl ester transfer protein (CETP) activity was higher in old rats. Keeping 12-month-old animals on high-fructose diet completely leveled the age differences in the data that have been measured between 12-month-old and 24-month-old rats. After “Enoant” administration, an increase of HDL PON and LCAT activity levels and a reduction of CETP activity were found in 24-month-old and obese rats.

Oral administration of S-nitroso-N-acetylcysteine prevents the onset of non alcoholic fatty liver disease in rats

AIM: To evaluate the potential of S-nitroso-N-acetylcysteine (SNAC) in inhibition of lipid peroxidation and the effect of oral SNAC administration in the prevention of nonalcoholic fatty liver disease (NAFLD) in an animal model.

METHODS: NAFLD was induced in Wistar male rats by choline-deficient diet for 4 wk. SNAC-treated animals (n=6) (1.4 mg/kg/day of SNAC, orally) were compared to 2 control groups: one (n=6) received PBS solution and the other (n=6) received NAC solution (7 mg/kg/d). Histological variables were semiquantitated with respect to macro and microvacuolar fat changes, its zonal distribution, foci of necrosis, portal and perivenular fibrosis, and inflammatory infiltrate with zonal distribution. LOOHs from samples of liver homogenates were quantified by HPLC. Nitrate levels in plasma of portal vein were assessed by chemiluminescence. Aqueous low-density lipoprotein (LDL) suspensions (200 µg protein/mL) were incubated with CuCl₂ (300 µmol/L) in the absence and presence of SNAC (300 µmol/L) for 15 h at 37 °C. Extent of LDL oxidation was assessed by fluorimetry. Linoleic acid (LA) (18.8 µmol/L) oxidation was induced by soybean lipoxygenase (SLO) (0.056 µmol/L) at 37 °C in the presence and absence of N-acetylcysteine (NAC) and SNAC (56 and 560 µmol/L) and monitored at 234 nm.

RESULTS: Animals in the control group developed moderate macro and microvesicular fatty changes in periportal area. SNAC-treated animals displayed only discrete histological alterations with absence of fatty changes and did not develop liver steatosis. The absence of NAFLD in the SNAC-treated group was positively correlated with a decrease in the concentration of LOOH in liver homogenate, compared to the control group (0.7±0.2 nmol/mg vs 3.2±0.4 nmol/mg protein, respectively, P<0.05), while serum levels of aminotransferases were unaltered. The ability of SNAC in preventing lipid peroxidation was confirmed in in vitro experiments using LA and LDL as model substrates.

CONCLUSION: Oral administration of SNAC prevents the onset of NAFLD in Wistar rats fed with choline-deficient diet. This effect is correlated with the ability of SNAC to block the propagation of lipid peroxidation in vitro and in vitro.

Antioxidant Effects of Aqueous Extracts from Dried Calyx of Hibiscus sabdariffa LINN. (Roselle) in Vitro Using Rat Low-Density Lipoprotein (LDL)

The present study quantitatively investigated the antioxidant effects of the aqueous extracts from dried calyx of Hibiscus sabdariffa LINN. (roselle) in vitro using rat low-density lipoprotein (LDL). Formations of the conjugated dienes and thiobarbituric acid reactive substances (TBARs) were monitored as markers of the early and later stages of the oxidation of LDL, respectively. Thus, we demonstrated that the dried calyx extracts of roselle exhibits strong antioxidant activity in Cu(2+)-mediated oxidation of LDL (p<0.05) in vitro. The inhibitory effect of the extracts on LDL oxidation was dose-dependent at concentrations ranging from 0.1 to 5 mg/ml. Moreover, 5 mg/ml of roselle inhibited TBARs-formation with greater potency than 100 microM of vitamin E. In conclusion, this study provides a quantitative insight into the potent antioxidant effect of roselle in vitro.

Alpha-tocopherol and probucol reduce autoantibody titer to MDA-LDL in hypercholesterolemic rabbits

We considered the hypothesis that antioxidant supplementation that increases aortic antioxidant concentrations would reduce autoantibody titer to MDA-LDL, a measure that may indicate in vivo oxidation. We assessed autoantibody titer to MDA-LDL in rabbits before and after 5 months of treatment with a nutritionally adequate hypercholesterolemic diet alone (control) or supplemented with synthetic alpha-tocopherol or probucol. Aortic cholesterol and antioxidants were assessed at the end of treatment. alpha-Tocopherol supplementation increased the ratio of aortic alpha-tocopherol to cholesterol by 20-30-fold, while probucol supplementation increased the ratio of aortic probucol to cholesterol to 4-13 micromol/mol. Before treatment, MDA-LDL autoantibody titer averaged 5.09 +/- 0.24 with no difference among groups (p =.53 by ANOVA). However, after treatment, autoantibody titers differed among groups (p <.03 by ANOVA). Autoantibody titers were similar in rabbits supplemented with alpha-tocopherol and probucol (3.69 +/- 0.21 and 3.73 +/- 0.48, respectively, p = 0.81), and 26% (p <.009) lower in antioxidant supplemented rabbits than unsupplemented hypercholesterolemic rabbits (5.03 +/- 0.47). There was an inverse J relationship between autoantibody titer after treatment and aortic alpha-tocopherol/cholesterol and probucol/cholesterol, with minimum values for autoantibody titers above 8-10 micromol antioxidant/mmol cholesterol. The results of this study are consistent with inhibition of in vivo intra-aortic oxidation when aortic alpha-tocopherol or probucol exceed 8-10 micro;mol/mmol cholesterol.