Raw and boiled garlic enhances plasma antioxidant activity and improves plasma lipid metabolism in cholesterol-fed rats

In the present study the effect of garlic, in a form more similar to how most people eat garlic, on lipid and antioxidant metabolism in rats was investigated. The antioxidant activity was determined by the efficacy to scavenge 2, 2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) derived radicals in garlic samples. The highest results were estimated in aqueous fraction in comparison with other extracts divided on the basis of polarity. Wistar male rats were randomly divided into 10 diet groups, each with seven animals. The groups were named: Control, RG (raw garlic), BG (boiled garlic for 20 min), AERG (aqueous extract of raw garlic), AEBG (aqueous extract of boiled garlic), Ch (Cholesterol), Ch/RG, Ch/BG, Ch/AERG and Ch/AEBG. All experimental diets were supplemented with 25 mg of lyophilized garlic/kg body weight obtained from raw, boiled and their aqueous extracts over a period of 30 days.Serum lipid (total cholesterol, LDL-cholesterol and triglycerides) concentrations were higher in all groups fed cholesterol (Ch); however, the increase was significant only in Ch group, without garlic supplementation. In groups of rats fed diets with cholesterol, garlic samples significantly hindered the rise of TC and LDL-C (P < 0.05). A significant increase (P < 0.05) in the plasma antioxidant activity was registered in experimental groups of rats fed cholesterol-free diets supplemented with garlic; oppositely, a significant decrease was only in group of rats given food containing cholesterol without garlic.The protein spectra has shown that during short boiling some proteins change their functional properties such as solubility and mobility, resulting in a number of protein bands in SDS-electrophoresis.

Conclusions

Raw and boiled garlic improved plasma lipid metabolism and plasma antioxidant activity in an experiment on rats. Thus, dietary hypolipidemic garlic was effective in reducing the oxidant stress, which was indicated by an increase of antioxidant activity and a decrease of lipids in the rats' blood. It was found that garlic boiled for 20 min has the same bioactivity as raw garlic in its antioxidant and protein spectra. Therefore it should be added at this time to foods. The selenium and copper content of raw garlic is not altered by boiling. The protein electrophoretic pattern of raw garlic is altered by boiling.     

Oat (Avena sativa L.) and amaranth (Amaranthus hypochondriacus) meals positively affect plasma lipid profile in rats fed cholesterol-containing diets

Cereals are an important part of diets for hypercholesterolemic patients. However, some of these patients are allergic to these natural products. The purpose of the current study was to compare oatmeal with equal in nutritional values two allergy-free amaranth meals to determine whether this pseudocereal can be a substitute for allergic to cereals individuals. The total phenols of the samples were determined with the Folin-Chocalteu reagent, anthocyanins, and flavonoids spectrophotometrically. The antioxidant activities were estimated with nitric oxide scavenging radical (NO) and by beta-carotene bleaching (beta-carotene). It was found that the contents of different protein fractions, antioxidant compounds, and the antioxidant activities of oatmeal were significantly higher than those of the two amaranth samples. The results of kinetic reactions showed that samples differed in their capacities to quench these radicals, and oats have shown more antioxidant activity than amaranth. High correlation was observed between antioxidant activities and phenols (R(2) = 0.99). In the in vivo part of the investigation, 60 male Wistar rats were divided into five diet groups of 12 animals each; these groups were designated as Control, Chol, Chol/Oat, Chol/AmarI, and Chol/AmarII. The rats of the Control group were fed basal diet (BD) only. To the BD of the four other groups were added the following: 1% of cholesterol (Chol), 10% of oat meal and 1% of cholesterol (Chol/Oat), 10% of amaranth I meal, and 1% of cholesterol (Chol/AmarI) and 10% of amaranth II meal and 1% of cholesterol (Chol/AmarII). After 32 days of different feeding, diets supplemented with oat meal and, to lesser degree, with amaranth I and amaranth II hindered the rise in the plasma lipids: a) TC: 3.14 vs. 4.57 mmol/L, - 31.3%; 3.31 vs. 4.57 mmol/L - 27.6%; and 3.40 vs. 4.57, - 25.6%, respectively b) LDL-C: 1.69 vs. 3.31 mmol/L, - 49.9%; 2.05 vs. 3.31 mmol/L, - 38.1%; and 2.16 vs. 3.31 mmol/L, - 34.8%, respectively; c) TG: 0.73 vs. 0.88 mmol/L, - 17.1%; 0.75 vs. 0.88 mmol/L, - 14.8%; and 0.79 vs. 0.88 mmol/L, -10.2%, respectively. The HDL-PH was increased as follows: 0.79 vs. 0.63 mmol/L, -25.3%; 0.75 vs. 0.63 mmol/L, -23.0%; and 0.71 vs. 0.63 mmol/L, -12.7% for the Chol/Oat, Chol/AmarI and Chol/AmarII, respectively. No significant changes in the concentrations of HDL-C and TPH were found; however the HDL-C in the Chol/Oat group was slightly higher than in other groups. No changes in the Control group were registered. In conclusion, oat and amaranth meals positively affect plasma lipid profile in rats fed cholesterol-containing diets. The degree of this positive influence is directly connected to the contents of the bioactive components and the antioxidant activities of the studied samples. It is suggested that amaranth could be a valuable substitute for hypercholesterolemic patients allergic to cereals.     

Eritadenine-induced alterations of plasma lipoprotein lipid concentrations and phosphatidylcholine molecular species profile in rats fed cholesterol-free and cholesterol-enriched diets

The effects of dietary eritadenine on the concentration of plasma lipoprotein lipids and the molecular species profile of plasma lipoprotein phosphatidylcholine (PC) were investigated in rats fed cholesterol-free and cholesterol-enriched diets to obtain insights into the relationship between the changes in PC molecular species profile and the hypocholesterolemic action of eritadenine. The effect of eritadenine on the secretion rate of very low density lipoprotein (VLDL) from the liver was also estimated. Rats were fed the control or eritadenine-supplemented (50 mg/kg) diets with or without exogenous cholesterol for 14 d. Eritadenine supplementation significantly decreased the cholesterol of major plasma lipoproteins, high density lipoprotein and VLDL, in rats fed cholesterol-free and cholesterol-enriched diets, respectively. The ratio of PC to phosphatidylethanolamine, delta6-desaturase activity, and the ratio of arachidonic acid to linoleic acid in liver microsomes were markedly decreased by eritadenine irrespective of the presence or absence of exogenous cholesterol. Dietary eritadenine increased the proportion of 16:0-18:2 molecular species with a decrease in 18:0-20:4 in plasma lipoprotein PC in both rats fed cholesterol-free and cholesterol-enriched diets. Eritadenine did not depress the secretion rate of VLDL in rats fed a cholesterol-free diet containing a high level of choline. The results indicate that dietary eritadenine elicits its hypocholesterolemic action with modulations of the fatty acid and molecular species profiles of PC irrespective of the presence or absence of exogenous cholesterol. The eritadenine-induced alteration of PC molecular species profile is discussed in relation to the hypocholesterolemic action of eritadenine.     

Red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits and their influence on plasma lipid levels and plasma antioxidant activity in rats fed with cholesterol-containing and cholesterol-free diets

Bioactive compounds of peels and peeled red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits were analyzed and their antioxidant potential was assessed. The dietary fibers were determined according to Prosky et al., the total polyphenol content by Folin-Ciocalteu method and measured at 765 nm, minerals and trace elements by atomic absorption spectrometer, phenolic and ascorbic acids by HPLC and the antioxidant potential by two different antioxidant assays (DPPH and beta-carotene linoleate model system). It was found that the contents of most studied bioactive compounds in both qualities are comparable. Only the contents of total polyphenols and flavonoids were higher in red grapefruits, but not significant. The antioxidant potentials of red peeled grapefruits and their peels were significantly higher than of blond peeled grapefruits and their peels (P<0.05 in both cases). Diets supplemented with peeled red and blond qualities of Jaffa grapefruits and their peels have increased the plasma antioxidant capacity and improved plasma lipid levels, especially in rats fed with cholesterol added diet. In conclusion, both qualities of Jaffa grapefruits contain high quantities of bioactive compounds, but the antioxidant potential of red grapefruits is significantly higher. Diets supplemented with both qualities of Jaffa grapefruits improve the plasma lipid levels and increase the plasma antioxidant activity, especially in rats fed with cholesterol added diets. Jaffa grapefruits, especially their red Star Ruby quality, could be a valuable supplementation for diseases-preventing diets.     

Mechanism of hypercholesterolemia produced by biotin deficiency

The effect of biotin deficiency on the metabolism of cholesterol was studied in rats fed cholesterol-free and cholesterol-containing diet. Biotin deficiency induced by feeding raw egg-white resulted in higher cholesterol in the serum and aorta, and higher high density lipoprotein cholesterol and low density lipoprotein + very low density lipoprotein cholesterol. In the liver, cholesterol increased only in the cholesterol diet group but not in the cholesterol-free diet group. Levels of triglycerides were lower in the biotindeficient, cholesterol-free diet group, but triglycerides were elevated in the cholesterol diet group. Concentration of bile acids in the liver and activity of lipoprotein lipase in the heart and adipose tissue were significantly decreased in the biotin-deficient rats. Release of lipoproteins into the circulation, incorporation of [1,2-¹⁴C] acetate into cholesterol, and activity of plasma lecithin: cholesterol acyl transferase were higher.     

Effect of coix on plasma, liver, and fecal lipid components in the rat fed on lard- or soybean oil-cholesterol diet

To determine the influence of dietary coix on lipid metabolism, the effect of coix on plasma, liver, and fecal lipid components was studied using Sprague-Dawley male rats. All rats were divided into four groups, and the rats of each group were fed the coix-lard diet, coix-soybean oil diet, or the respective control diets (containing 1% cholesterol each) for 27 days. Plasma and liver cholesterol levels in the coix-lard diet group significantly decreased as compared with those in the control group, whereas there was no effect on the fecal excretion of cholesterol. The decreases in the concentrated liver triglyceride and the increases in the fecal excretion of triglyceride were found in coix-soybean oil diet group. Moreover, liver and fecal phospholipid levels in both coix diet groups significantly increased. But there were no significant changes in plasma and fecal bile acids in either coix diet group. These results suggest the possibilities that coix may have an inhibitory action on cholesterol synthesis in liver, a facilitating effect on biliary excretion of triglyceride, and an acceleratory action on phospholipid synthesis in liver.     

Serum Cholesterol-Decreasing Effect of Heat-Moisture-Treated High-Amylose Cornstarch in Cholesterol-Loaded Rats

Rats were fed on a diet containing cholesterol (Chol) at a level corresponding to the standard Chol intake in humans, and the influence of heat-moisture-treated high-amylose cornstarch (HHA) on their serum Chol level was investigated. HHA decreased the serum level of Chol in rats fed on the diet containing 0.1% Chol, which corresponds to a Chol intake in humans of 800 mg/d, although the liver levels of Chol increased in these rats. HHA did not influence the fecal excretion of Chol/bile acids. It is possible that the decrease in serum Chol level in the rats fed on the high-Chol diet can be attributed to the promotion of Chol uptake in the liver.     

Serum cholesterol-decreasing effect of heat-moisture-treated high-amylose cornstarch in cholesterol-loaded rats

Rats were fed on a diet containing cholesterol (Chol) at a level corresponding to the standard Chol intake in humans, and the influence of heat-moisture-treated high-amylose cornstarch (HHA) on their serum Chol level was investigated. HHA decreased the serum level of Chol in rats fed on the diet containing 0.1% Chol, which corresponds to a Chol intake in humans of 800 mg/d, although the liver levels of Chol increased in these rats. HHA did not influence the fecal excretion of Chol/bile acids. It is possible that the decrease in serum Chol level in the rats fed on the high-Chol diet can be attributed to the promotion of Chol uptake in the liver.     

The nutritional and metabolic indices in rats fed cholesterol-containing diets supplemented with durian at different stages of ripening

The aim of this investigation was to assess the nutritional and health properties of Mon Thong durian cultivar at different stages of ripening. The assessment was carried out in vitro and in vivo. The contents of dietary fibers, minerals and trace metals at different stages of ripening were comparable. Total polyphenols (mgGAE/100 g FW) and flavonoids (mg CE/100 gFW) in ripe durian (358.8 +/- 31.4 and 95.4 +/- 9.3) were significantly higher (p < 0.05) than in mature (216.1 +/- 1 and 39.9 +/- 3.8) and overripe (283.3 +/- 26.2 and 53.5 +/- 4.9). Antioxidant capacity (muMTE/100 g FW) in total polyphenol extracts of ripe durian measured by 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and [2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) assays (259.4 +/- 23.6 and 2341.8 +/- 93.2) were significantly higher (p < 0.05) than that of mature (151.6 +/- 15.2 and 1394.6 +/- 41.5) and overripe (201.7 +/- 19.4 and 1812.2 +/- 61.4) samples. The correlation coefficients between the bioactive compounds in different stages of ripening and their antioxidant capacities were high (R;{2} = 0.99). Then 35 male Wistar rats were divided into 5 dietary groups each of 7 and named Control, Chol, Chol/Mature, Chol/Ripe and Chol/Overripe. During 30 days of the experiment the rats of all 5 groups were fed basal diet (BD), which included wheat starch, casein, soybean oil, vitamin and mineral mixtures. The rats of the Control group were fed a BD only. To the BD of the Chol group was added 1% of cholesterol. The BD of the Chol/Mature, Chol/Ripe and Chol/Overripe groups was supplemented with 1% of cholesterol and 5% of the mature, ripe and overripe durian as freeze-dried powder, respectively. Diets containing ripe and to a lesser degree mature and overripe durian significantly hindered the rise in plasma lipids and also hindered a decrease in plasma antioxidant activity. The nitrogen retention in rats of the Chol/Ripe group was significantly higher (63.6%, P < 0.05) than in other diet groups and the level of the plasma glucose remained normal. A decrease in fibrinogen fraction with ripe durian included in rat's diets was shown by electrophoretic separation. These changes were detected mostly in the low molecular weight proteins of rat's serum. Histological examination of aorta showed only slight differences in the tissue. In conclusion, ripe durian contains higher quantity of bioactive compounds, has higher antioxidant capacity and nutritional value. It positively affects the plasma lipid profile, the plasma glucose and the antioxidant activity in rats fed cholesterol enriched diets. Therefore, the ripe durian supplemented diet could be beneficial for patient suffering from hypercholesterolemia and diabetes mellitus. <     

Cholelithiasis in a male rhesus monkey (Macaca mulatta) fed a cholesterol-containing diet.

In this report we describe the development of cholelithiasis in a male rhesus monkey fed a cholesterol-containing diet for 24 months. This represents the only case of cholelithiasis in this species of nonhuman primate that we have observed out of a population of over 500 rhesus monkeys fed similar cholesterol-containing diets. Associated with the appearance of gallstones was the production of bile saturated with cholesterol, and the excretion of bile with an abnormal bile acid composition.     

Stronger suppression of plasma cholesterol and enhancement of the fecal excretion of steroids by a buckwheat protein product than by a soy protein isolate in rats fed on a cholesterol-free diet

We investigated the effects of a buckwheat protein product (BWP), soy protein isolate (SPI) and casein on the plasma cholesterol level and fecal steroid excretion in rats fed on a cholesterol-free diet. The consumption of BWP suppressed plasma cholesterol by enhancing the fecal excretion of both neutral and acidic steroids. These effects of BWP were stronger than those of SPI.     

Lower plasma triglyceride level in Syrian hamsters fed on skim milk fermented with Lactobacillus casei strain Shirota

The effect of fermented skim milk (FSM) by Lactobacillus casei strain Shirota on plasma lipids in hamsters was examined. Hamsters fed on cholesterol-free and -enriched diets containing 30% FSM had lower levels of plasma triglyceride than those fed on the control diet. In the experiment with the cholesterol-enriched diet-fed hamsters, the plasma triglyceride level was suppressed by FSM at concentrations of 10% to 30%. Unfermented milk tended to lower the level of triglyceride, but not significantly. The plasma cholesterol concentration was not affected by an FSM and unfermented skim milk supplement to the diet. L. casei strain Shirota grew well in the presence of mixed lipid micelles containing bile acid, but did not have the ability to remove cholesterol from the culture broth. These results indicate that FSM lowered the plasma triglyceride level in hamsters.     

Effect of dietary inclusion of Lactobacillus acidophilus ATCC 43121 on cholesterol metabolism in rats

This study examined the effects of Lactobacillus acidophilus ATCC 43121 (LAB) on cholesterol metabolism in hypercholesterolemia-induced rats. Four treatment groups of rats (n = 9) were fed experimental diets: normal diet, normal diet+LAB (2 x 10(6) CFU/day), hypercholesterol diet (0.5% cholesterol, w/w), and hypercholesterol diet + LAB. Body weight, feed intake, and feed efficiency did not differ among the four groups. Supplementation with LAB reduced total serum cholesterol (25%) and VLDL + IDL + LDL cholesterol (42%) in hypercholesterol diet groups, although hepatic tissue cholesterol and lipid contents were not changed. In the normal diet group, cholesterol synthesis (HMG-CoA reductase expression), absorption (LDL receptor expression), and excretion via bile acids (cholesterol 7 alpha-hydroxylase expression) were increased by supplementation with LAB, and increased cholesterol absorption and decreased excretion were found in the hypercholesterol diet group. Total fecal acid sterols excretion was increased by supplementation with LAB. With proportional changes in both normal and hypercholesterol diet groups, primary bile acids (cholic and chenodeoxycholic acids) were reduced, and secondary bile acids (deoxycholic and lithocholic acids) were increased. Fecal neutral sterol excretion was not changed by LAB. In this experiment, the increase in insoluble bile acid (lithocholic acid) reduced blood cholesterol level in rats fed hypercholesterol diets supplemented with LAB. Thus, in the rat, L. acidophilus ATCC 43121 is more likely to affect deconjugation and dehydroxylation during cholesterol metabolism than the assimilation of cholesterol into cell membranes.     

Hypolipidemic effect of diet supplementation with bacterial levan in cholesterol-fed rats

Levan polysaccharide, a type of fructan, has been shown to have industrial applications as a new industrial gum in the fields of cosmetics, foods like dietary fiber and pharmaceutical goods. The objective of this current study was to investigate the possible hypolipidemic and antioxidative effects of levan in rats fed with a high-cholesterol diet. Animals were allocated into four groups of six rats each: a normal diet group (Control), normal rats received levan (L), a high-cholesterol diet group (Chol) and a high-cholesterol diet with a daily dose of levan equivalent to 5%. Treated hypercholesterolemic rats were administrated with levan in drinking water through oral gavage for 60 days. After the treatment period, the plasma antioxidant enzymes and lipid profiles were determined. Our results show that treatment with levan polysaccharide positively changed plasma antioxidant enzyme activities and lipid profiles (total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides) in cholesterol-rats, and thus may have potential hypolipidemic and antioxidant effects. Levan could protect against oxidative stress linked atherosclerosis and decrease the atherogenic index.     

Stronger Suppression of Plasma Cholesterol and Enhancement of the Fecal Excretion of Steroids by a Buckwheat Protein Product than by a Soy Protein Isolate in Rats Fed on a Cholesterol-free Diet

We investigated the effects of a buckwheat protein product (BWP), soy protein isolate (SPI) and casein on the plasma cholesterol level and fecal steroid excretion in rats fed on a cholesterol-free diet. The consumption of BWP suppressed plasma cholesterol by enhancing the fecal excretion of both neutral and acidic steroids. These effects of BWP were stronger than those of SPI.     

The effect of high-amylose cornstarch on lipid metabolism in OVX rats is affected by fructose feeding

We examined whether the effects of high-amylose cornstarch (HACS) on lipid metabolism in ovariectomized (OVX) rats were affected by high-fructose feeding. Sucrose (482 g/kg diet) was used as fructose source. OVX rats were fed one of the following four diets for 21 days: a sucrose-based or cornstarch-based cholesterol-free diet with or without HACS (150 g/kg diet). Body weight and food intake were increased by sucrose. Plasma total cholesterol and low-density lipoprotein cholesterol concentrations were increased by sucrose and decreased by HACS in cornstarch-fed rats, but not in sucrose-fed rats. Liver total lipids and concentrations of plasma and liver triacylglycerol (TAG) were increased by sucrose, whereas plasma TAG concentration was decreased by HACS, in sucrose-fed rats. However, liver cholesterol concentration was not affected by diet. The amount of cholesterol in small-intestinal contents was increased in sucrose-fed rats, but not in cornstarch-fed rats, but that of bile acids was not affected by diet. Fecal excretions of bile acids and neutral sterols were increased by HACS. The level of sterol-regulatory element-binding protein-1c mRNA was increased by sucrose and decreased by HACS in sucrose-fed rats, but not in cornstarch-fed rats. The level of farnesoid X receptor mRNA was decreased by sucrose and increased by HACS in cornstarch-fed rats, but not in sucrose-fed rats, as was the level of cholesterol 7α-hydroxylase mRNA. These results show that the effect of HACS on hyperlipidemia induced by ovarian hormone deficiency would be affected by the consumption of fructose-rich sweeteners such as sucrose and high-fructose syrup.     

Cholesterol-rich diets have different effects on lipid peroxidation, cholesterol oxides, and antioxidant enzymes in rats and rabbits

The objective of this study was to compare the effect of cholesterol feeding of rats and rabbits. The levels of lipid peroxidation products and oxysterols in the plasma of the two species plus the antioxidant enzyme activities in the liver and erythrocytes were measured to explain their different susceptibilities to atherosclerosis. Our study showed that rats are less susceptible than are rabbits to the atherogenic effect of a cholesterol-rich diet because of differences in lipid peroxidation products as well as antioxidant enzymes activities in their livers. In rabbits, cholesterol feeding produced severe hypercholesterolemia (43-fold increase) and increased plasma and liver lipid peroxidation. Total as well as the individual oxysterol contents of 7alpha-, 7beta-hydroxycholesterol, alpha-epoxy, beta-epoxycholesterol, cholestanetriol, 7-keto, and 27-hydroxycholesterol significantly increased in the plasma of hypercholesterolemic (HC) rabbits. Erythrocyte glutathione peroxidase (GSH-Px) activity significantly decreased whereas catalase activity significantly increased in HC rabbits. In rats cholesterol feeding increased the plasma cholesterol only twofold and had no effect on plasma or liver lipid peroxidation. Only 7alpha- and 7beta-hydroxycholesterol increased and no change was observed in any of the antioxidant enzymes activity in the erythrocytes. Although cholesterol feeding caused a 10-fold increase of liver cholesterol as ester in both rats and rabbits, the antioxidant enzyme GSH-Px and catalase activities in the liver significantly increased in rats but significantly decreased in rabbits. The increase of GSH-Px and catalase activities in the liver of cholesterol fed rats could have a protective role against oxidation, thus preventing the formation of lipid peroxidation and oxysterols.     

Nigella sativa thymoquinone-rich fraction greatly improves plasma antioxidant capacity and expression of antioxidant genes in hypercholesterolemic rats

The antioxidant activities of the thymoquinone-rich fraction (TQRF) extracted from Nigella sativa and its bioactive compound, thymoquinone (TQ), in rats with induced hypercholesterolemia were investigated. Rats were fed a semipurified diet supplemented with 1% (w/w) cholesterol and were treated with TQRF and TQ at dosages ranging from 0.5 to 1.5 g/kg and 20 to 100 mg/kg body wt, respectively, for 8 weeks. The hydroxyl radical (OH^·)-scavenging activity of plasma samples collected from experimental rats was measured by electron spin resonance. The GenomeLab Genetic Analysis System was used to study the molecular mechanism that mediates the antioxidative properties of TQRF and TQ. Plasma total cholesterol and low-density-lipoprotein cholesterol levels were significantly decreased in the TQRF- and TQ-treated rats compared to untreated rats. Feeding rats a 1% cholesterol diet for 8 weeks resulted in a significant decrease in plasma antioxidant capacity, as measured by the capacity to scavenge hydroxyl radicals. However, rats treated with TQRF and TQ at various doses showed significant inhibitory activity toward the formation of OH^· compared to untreated rats. Upon examination of liver RNA expression levels, treatment with TQRF and TQ caused the up-regulation of the superoxide dismutase 1 (SOD1), catalase, and glutathione peroxidase 2 (GPX) genes compared to untreated rats (P < 0.05). In support of this, liver antioxidant enzyme levels, including SOD1 and GPX, were also apparently increased in the TQRF- and TQ-treated rats compared to untreated rats (P < 0.05). In conclusion, TQRF and TQ effectively improved the plasma and liver antioxidant capacity and enhanced the expression of liver antioxidant genes of hypercholesterolemic rats.     

Studies on the regulation of plasma cholesterol levels in squirrel monkeys of two genotypes

Certain individual squirrel monkeys ("hypo-responders") are able to remain normocholesterolemic when fed diets containing cholesterol (0.5 mg/kcal). Other squirrel monkeys ("hyperresponders") when fed the same diet become hypercholesterolemic. The purpose of these studies was to identify the mechanisms which allow hyporesponders to compensate for dietary cholesterol. Using formula diets and sterol balance techniques, we have compared cholesterol absorption, synthesis, excretion, and turnover in hypo- and hyperresponding monkeys. Cholesterol absorption was essentially identical in the two groups (about 55 mg/day). Cholesterol synthesis was likewise similar in the two groups (about 35 mg/day) and there was no evidence of feedback inhibition at the level of cholesterol fed. Hyporesponders had faster turnover rates and smaller body cholesterol pools than did hyperresponders. Excretion of neutral steroids was similar for hypo- and hyperresponders and did not change with cholesterol feeding. In contrast, hyporesponders increased bile acid excretion shortly after cholesterol feeding was begun. Hyperresponders responded more slowly and to a lesser degree. It is concluded that, in this species, the mechanism of control of plasma cholesterol levels is related to the rate of conversion of cholesterol to bile acids.     

Efficacy of piperine, an alkaloidal constituent from Piper nigrum on erythrocyte antioxidant status in high fat diet and antithyroid drug induced hyperlipidemic rats

The main aim of this study was to investigate the effect of piperine on erythrocyte antioxidant status in high fat diet (HFD) and antithyroid drug induced hyperlipidemic rats. Male Wistar rats were divided into eight groups. The first four groups were fed a control diet and in addition were given respectively 1% carboxymethyl cellulose (CMC); 10 mg/kg body weight carbimazole (CM); 10 mg CM + 40 mg/kg body weight piperine and 10 mg CM + 2 mg/kg body weight atorvastatin (ATV). A similar pattern was followed for the next four groups except that they were all fed HFD instead of the control diet. Erythrocyte osmotic fragility, total cholesterol, phospholipids, lipid peroxidation products, enzymic and non-enzymic antioxidant status were studied in all experimental groups. Significantly increased osmotic fragility, total cholesterol/phospholipid ratio, thiobarbituric acid reactive substances and lipid hydroperoxides were observed in the plasma and erythrocytes of HFD fed and CM treated rats compared to the control. Superoxide dismutase, catalase, glutathione peroxidase, vitamin E and reduced glutathione in erythrocytes and vitamin C in the plasma were also significantly lowered in HFD fed, antithyroid drug treated rats compared to control animals. Concurrent piperine supplementation along with HFD and antithyroid drug administration normalized erythrocyte osmotic fragility, reduced lipid peroxidation, and improved the enzymic and non-enzymic antioxidant status compared to those rats that did not receive piperine. Thus, our results indicate that piperine supplementation markedly protects erythrocytes from oxidative stress by improving the antioxidant status in HFD fed antithyroid drug treated rats.