Effect of dietary fat source on lipoprotein composition and plasma lipid concentrations in pigs

Most studies of the effects of dietary fat sources on plasma lipid components have used diets with extreme fat compositions; the current study was designed to more nearly mimic human dietary fat intake. Young growing pigs were fed diets containing either 20 or 40% of energy as soy oil, beef tallow or a 50/50 blend of soy oil and tallow. Different dietary fats did not affect concentrations of cholesterol, triacylglycerol or protein in plasma or major lipoprotein fractions. The concentration of phospholipid was less in plasma and in very low density lipoproteins with soy oil feeding than with tallow feeding. The weight percentage of cholesteryl ester in the low density lipoprotein fraction tended to be greater with 40% than with 20% tallow and tended to be less with 40% than with 20% soy oil. Phospholipid as a weight percentage of low density lipoprotein was least in pigs fed soy oil. Tallow feeding increased the percentage of myristic, palmitic, palmitoleic and oleic acids in plasma, relative to both other groups. Soy oil feeding increased the percentage of linoleic and linolenic acids. These moderate diets were not hypercholesterolemic, but they did alter plasma fatty acid composition and phospholipid concentrations in plasma and very low density lipoprotein.     

Supplementation of vitamins C and E increases the vitamin E status but does not prevent the formation of oxysterols in the liver of guinea pigs fed an oxidised fat

Summary Background Dietary oxidised fats are a source of oxidative stress. They cause deleterious effects in animal organism by lowering the antioxidant status of tissues and enhancement of the formation of lipid oxidation products. The vitamins E and C might be useful to prevent the formation of oxidation products by dietary oxidised fats. Aim of the study The purpose of this study was to investigate whether or not supplementation of diets with vitamins E and C is able to prevent oxidative stress and the formation of lipid oxidation products caused by dietary oxidised fats. Among lipid oxidation products, oxysterols should be particularly considered because of their high pathophysiological effects. Methods Male guinea pigs were divided into five groups. Four groups were fed diets with an oxidised fat supplemented with 35 or 175 mg -tocopherol equivalents/kg and 300 or 1000 mg of vitamin C/kg for 29 days. One group, used as a control, was fed the same basal diet with fresh fat with 35 mg -tocopherol equivalents/kg and 300 mg of vitamin C/kg. Results The guinea pigs fed the oxidised fat diet with 35 mg -tocopherol equivalents/kg and 300 mg vitamin C/kg had significantly lower concentrations of tocopherols in various tissues, higher concentrations of various oxysterols and thiobarbituric acid-reactive substances in the liver, higher concentrations of glutathione in the liver and lower concentrations of glutathione in erythrocytes than the control animals fed the fresh fat. Increasing the dietary vitamin E concentration from 35 to 175 mg -tocopherol equivalents/kg and/or the dietary vitamin C concentration from 300 to 1000 mg/kg increased tissue tocopherol concentrations in guinea pigs fed the oxidised fat but did not influence concentrations of oxidation products in the liver and glutathione concentrations in liver and erythrocytes. Conclusion The results demonstrated that supplementation of vitamins E and C improves the vitamin E status but does not prevent the formation of lipid oxidation products in the liver of guinea pigs fed oxidised fats.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phospholipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phosphlipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Postprandial lipoprotein composition in pigs fed diets differing in type and amount of dietary fat.

To determine the effects of diet on postprandial lipoprotein composition, growing pigs were fed diets containing 20 or 40% of energy as soybean oil, tallow or a 50:50 blend of soybean oil and tallow. At the end of wk 6, a blood sample was drawn from pigs fasted for 12 h. Pigs were then fed, and blood samples were drawn 1 and 4 h later. In LDL, concentrations of free and total cholesterol were greater in pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.02). Pigs fasted for 12 h had lesser concentrations of triacylglycerol and greater concentrations of phospholipid in LDL and HDL than did pigs fasted for 1 and 4 h (P less than 0.05). In HDL, total cholesterol and phospholipid concentrations were greater in pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.01). A greater concentration of triacylglycerol was found in VLDL of pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.01). Amount of dietary fat had a greater effect than did type of dietary fat on composition of lipoproteins from postprandial pigs.     

Combined deficiency of vitamins E and C causes paralysis and death in guinea pigs

BACKGROUND: On the basis of in vitro studies, the antioxidant nutrients vitamins E and C are postulated to interact in vivo. OBJECTIVE: We developed a guinea pig model to evaluate the combined deficiency of vitamins E and C in vivo. DESIGN: Weanling guinea pigs were fed a control diet or a vitamin E-deficient diet for 14 d, after which one-half of each group had vitamin C removed from their diet, thus creating 4 diet groups. Some animals were observed for clinical signs. Others were killed for evaluation. RESULTS: Of 21 guinea pigs that were observed after being fed the diet deficient in both vitamins, 8 died 9 +/- 2 d (x +/- SD) after starting the diet. Eight additional guinea pigs developed a characteristic syndrome at 11 +/- 3 d. First, they became paralyzed in the hind limbs. Within a few hours, the paralysis progressed to include all 4 limbs and caused difficulty in breathing, which would have caused death had the animals not been euthanized. Histopathologic evaluation did not identify a lesion in the muscles or nervous system that could account for the paralysis. Biochemical measurements confirmed the deficiencies and indicated that the double deficiency caused lipid peroxidation in the central nervous system. CONCLUSIONS: A distinct clinical syndrome of combined vitamin E and vitamin C deficiency occurs in guinea pigs. This syndrome indicates that these antioxidant vitamins are related in vivo. We speculate that acute oxidative injury in the central nervous system underlies the clinical syndrome.     

Plasma and liver cholesterol concentrations in mice fed semipurified diets differing in the amount of cholesterol and type of fat

Male and female mice of two inbred strains were fed semipurified diets with or without added cholesterol (1%, w/w) containing 18% by weight of either coconut fat or corn oil. After 28 days coconut fat had produced higher concentrations of plasma cholesterol than corn oil in almost all groups, irrespective of whether the diets contained cholesterol or were cholesterol-free. On the cholesterol-free diets, the type of fat did not influence the concentration of liver cholesterol. Dietary cholesterol caused a marked increase in liver cholesterol, the magnitude of the effect being dependent on the strain of mice and being greater in females than males. In all groups fed cholesterol corn oil caused significantly higher concentrations of liver cholesterol than coconut fat.     

Plasma thyroxine and cholesterol concentrations of miniature pigs are influenced by thermally oxidized dietary lipids

To investigate the effect of a dietary oxidized oil on thyroid hormone status and circulating cholesterol, we conducted a study with 16 male miniature pigs fed a nutritionally adequate diet with 15% of either fresh or thermoxidized oil for 35 d (n = 8/group). The thermoxidized oil was prepared by heating sunflower oil at 110 degrees C for 48 h. The fresh oil consisted of a mixture of sunflower oil and lard (94:6, v/v) which had a fatty acid composition similar to the thermoxidized oil. At the end of the study, there were no differences in body weight gains and plasma clinicochemical variables between groups, suggesting that the thermoxidized oil did not induce general toxic symptoms. However, pigs fed the thermoxidized oil had significantly higher plasma concentrations of total and free thyroxine (P < 0.05) and a tendency for a higher plasma concentration of thyroid hormone-stimulating hormone (P < 0.1) than pigs fed the fresh oil. Additionally, pigs fed the thermoxidized oil had lower concentrations of cholesterol in plasma, LDL and HDL (P < 0.05). There were significant negative correlations between the plasma concentrations of total (r = -0.29) and free thyroxine (r = -0.40) and that of cholesterol (P < 0.05), suggesting that there is a causal relationship between the changes in thyroxine concentration and the reduction of plasma cholesterol. Our results indicate that there is a close relationship between alterations of thyroid hormone status and cholesterol metabolism in pigs fed a thermoxidized oil, and dietary oxidized fats should be considered in thyroid hormone disorders.     

谷物膳食纤维对脂代谢紊乱小鼠肝脏脂毒性影响

目的 观察不同类型谷物膳食纤维(DF)对脂代谢紊乱小鼠血脂和肝脏脂毒性影响。方法 48只雄性C57BL/6J小鼠(6周龄)按体重随机分为4组:对照组、模型组、燕麦DF组、小麦DF组, 连续干预24周,实验期间每周称体重并记录摄食量, 每8周内眦静脉采血, 进行血脂和血糖连续动态观察;干预结束后测定空腹血糖、血清总胆固醇(TC)、甘油三酯(TG)和游离脂肪酸(FFAs)及肝组织TG含量。结果 与对照组比较, 模型组小鼠体重[(37.69±2.66)g]、空腹血糖[(8.21±2.06)mmol/L]、血清TC、TG、FFAs水平 [分别为(2.69±0.45)、(1.77±0.64) mmol/L、(2.12±0.38) mEq/L]明显升高(P<0.05);与模型组比较, 燕麦DF与小麦DF组小鼠体重[分别为(34.41±2.93)、(34.43±1.72)g]、血清TC、TG水平[分别为(2.03±0.44)、(2.22±0.50)与(1.64±0.43)、(1.39±0.41) mmol/L]均明显下降(P<0.05);燕麦DF组小鼠血清FFAs水平[(1.75±0.49) mEq/L]明显降低(P<0.05)。结论 谷物DF可以改善脂代谢紊乱小鼠血脂和肝脏脂毒性, 燕麦DF改善血脂和肝脏脂毒性的作用优于小麦DF。     

Effects of dehulled adlay on plasma glucose and lipid concentrations in streptozotocin-induced diabetic rats fed a diet enriched in cholesterol

Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) is a cereal food for humans and has been also used as a superior medical herb substance and functional food for traditional treatment of diabetes in China. However, its scientific basis as a functional food is still unclear. The purpose of this study was to investigate the effect of dietary dehulled adlay on plasma lipid and glucose concentrations in diabetic rats. The diabetic male Sprague-Dawley (SD) rats, induced by injection of streptozotocin (60 mg/kg subcutaneously), were fed a cholesterol-rich diet (0.5% cholesterol) containing corn starch or dehulled adlay for four weeks. After completion of the experimental period, the abdominal adipose tissue and liver of rats were excised and weighed, and the plasma glucose, triglyceride, and lipoprotein cholesterol concentrations were assayed. The results showed that diabetic rats fed a dehulled adlay diet exhibited a greater adipose tissue weight (9.36 +/- 3.43 vs. 5.39 +/- 3.04 g, p < 0.05) and a reduced food intake (39.3 +/- 5.9 vs. 61.0 +/- 11.7 g/day, p < 0.05) when compared with animals fed a cornstarch diet. Significantly decreased plasma glucose (261.6 +/- 96.6 vs. 422.1 +/- 125.4 mg/dL, p < 0.05), total cholesterol (289.4 +/- 140.6 vs. 627.3 +/- 230.5 mg/dL, p < 0.05), and triglyceride (52.3 +/- 14.4 vs. 96.5 +/- 36.6 mg/dL, p < 0.05) levels were observed in rats fed the dehulled adlay diet. In addition, the ingestion of dehulled adlay appears to significantly decrease plasma low-density lipoprotein (LDL) plus very low-density lipoprotein (VLDL) cholesterol concentrations. Rats fed a dehulled adlay diet showed an increase in fecal weight and cholesterol contents of stools. Although a significantly decreased plasma thiobarbituric reactive substances (TBARS) value was observed in diabetic rats fed the dehulled adlay diet (6.2 +/- 3.4 vs. 11.0 +/- 3.8 nmol malondialdehyde (MDA)/mL, p < 0.05), no significant difference in the hepatic TBARS value was observed between the two dietary groups. Results from the present study suggest that dehulled adlay exhibited not only a hypolipidemic effect but also displayed a hypoglycemic ability in diabetic rats, indicating that dehulled adlay may play an important role in the regulation of plasma lipid and glucose metabolisms in diabetic rats induced by streptozotocin.     

Effects of dietary fat and conjugated linoleic acid on plasma metabolite concentrations and metabolic responses to homeostatic signals in pigs

Sixteen female cross-bred (Large White x Landrace) pigs (initial weight 65 kg) with venous catheters were randomly allocated to four treatment groups in a factorial design. The respective factors were dietary fat (25 or 100 g/kg) and dietary conjugated linoleic acid (CLA; 0 or 10 g CLA-55/kg). Pigs were fed every 3 h (close to ad libitum digestible energy intake) for 8 d and were bled frequently. Plasma glucose and non-esterified fatty acid (NEFA) responses to insulin and adrenaline challenges were determined on day 8. Plasma concentrations of NEFA were significantly increased (10.5 and 5.4 % for low- and high-fat diets respectively, P=0.015) throughout the experiment, suggesting that there was a possible increase in fat mobilisation. The increase in lipolysis, an indicator of ss-adrenergic stimulated lipolysis, was also evident in the NEFA response to adrenaline. However, the increase in plasma triacylglycerol (11.0 and 7.1 % for low- and high-fat diets respectively, P=0.008) indicated that CLA could have reduced fat accretion via decreased adipose tissue triacylglycerol synthesis from preformed fatty acids, possibly through reduced lipoprotein lipase activity. Plasma glucose, the primary substrate for de novo lipid synthesis, and plasma insulin levels were unaffected by dietary CLA suggesting that de novo lipid synthesis was largely unaffected (P=0.24 and P=0.30 respectively). In addition, the dietary CLA had no effect upon the ability of insulin to stimulate glucose removal.     

Liver cholesterol concentrations in mice fed diets containing various sources of fat, carbohydrates or fiber

Liver cholesterol concentrations were measured in mice after feeding for 30 days cholesterol-free, semipurified diets containing various sources of fat, carbohydrates or fiber. Olive oil produced significantly higher liver cholesterol concentrations than tallow, sunflowerseed oil and cocoa fat. In mice fed either fructose or sucrose liver cholesterol was significantly increased when compared with mice fed galactose or lactose. Dietary cellulose, when compared with pectin, did not influence liver cholesterol. The amount of fat in the diet, in the form of either corn oil or coconut fat, had no significant effect on liver cholesterol. It is concluded that the type of carbohydrate and fat in the diet are major determinants of liver cholesterol in mice.     

Hamsters and guinea pigs differ in their plasma lipoprotein cholesterol distribution when fed diets varying in animal protein, soluble fiber, or cholesterol content.

There were two objectives to these studies: 1) to compare the lipoprotein cholesterol distribution in two animal models in response to different dietary treatments and 2) to assess whether the hypercholesterolemia induced by high cholesterol intake could be reversed by consumption of vegetable-protein and/or dietary fiber. Guinea pigs, which carry the majority of plasma cholesterol in LDL, and hamsters, with a higher distribution of cholesterol in HDL, were evaluated in three different studies. In Study 1, animals were fed semi-purified diets for 4 wk with proportions of 60:40, 20:80 or 0:100 (w/w) of casein/ soybean protein. Hamsters and guinea pigs that consumed 100% soybean protein had lower plasma total cholesterol (TC) than those fed diets containing casein (P < 0.01). In Study 2, three doses of dietary pectin (2.7, 5.4, or 10.7 g/100g) added in place of cellulose were tested. Intake of 10.7 g/100 g pectin resulted in the lowest plasma TC concentrations for both species (P < 0.01). Although the TC lowering was similar in studies 1 and 2, the lipoprotein cholesterol distribution differed. Whereas the differences in plasma cholesterol were in LDL in guinea pigs, hamsters exhibited differences in both non-HDL and HDL cholesterol. In study 3, animals were fed 100% soybean protein, 10.7 g/100 g pectin, and three doses of dietary cholesterol: 0.04, 0.08, or 0.16 g/100 g, which is equivalent to 300, 600, or 1,200 mg/d in humans. Guinea pigs and hamsters had the highest plasma LDL and hepatic cholesterol concentrations when they consumed 0.16 g/100 g of cholesterol (P < 0.01). However, intake of 0.08 g/100 g of cholesterol resulted in lower plasma LDL cholesterol concentrations than did consuming high animal protein (60:40 casein/ soy) or low soluble fiber (2.7 g/100 g). Relatively high levels of dietary cholesterol combined with vegetable protein and soluble fiber resulted in desirable lipoprotein profiles in animal models that significantly differ in their lipoprotein cholesterol distribution.     

Effects of the unsaturation of dietary fat and of arachidonate supplementation on cholesterol pool expansion in the guinea pigs.

We have studied the effects of methyl arachidonate supplementation on the lipid metabolism of guinea pigs fed cholesterol. Four groups of guinea pigs were fed a purified diet containing 9.5% hydrogenated coconut oil (HCNO), a highly saturated fat with or without the addition of 1% cholesterol, for 15 weeks. One half of the animals fed the control and the cholesterol-containing diets were supplemented with 15 mg methyl arachidonate three times per week. Supplementation with methyl arachidonate did not alter the concentration of plasma total (TC) or unesterified (FC) cholesterol, erythrocyte cholesterol and plasma phospholipid or the ratio of plasma FC/TC. Accumulation of cholesterol in the major organs of the cholesterol-fed groups was also unchanged. In both control and cholesterol-fed groups, methyl arachidonate decreased the proportion of oleic (18:1) and linoleic acids (18:2) and increased arachidonic acid (20:4) content of plasma and liver phospholipid. A comparison between the results of this study and studies using cottonseed oil showed that the type of dietary fat modifies the effects of cholesterol: plasma cholesterol levels were higher and liver cholesterol storage was lower in animals fed the saturated fat than in those fed the fat rich in polyunsaturated fatty acids (PUFA). Furthermore, in spite of similar changes in erythrocyte cholesterol content and shape abnormalities, no overt hemolytic anemia was observed in the groups fed cholesterol and saturated fat, in contrast to those fed cholesterol + PUFA-containing fat. We conclude that in guinea pigs supplementary methyl arachidonate had no hypocholesterolemic effect at the levels we fed, that circulating cholesterol levels are not a measure of cholesterol accumulation by organs and that the decrease of serum cholesterol in response of PUFA is due in part to an increase of cholesterol storage in the liver.     

Protonated nanostructured aluminosilicate (NSAS) reduces plasma cholesterol concentrations and atherosclerotic lesions in Apolipoprotein E deficient mice fed a high cholesterol and high fat diet

The aim of this work was to assess the effect of chronic administration of protonated nanostructured aluminosilicate (NSAS) on the plasma cholesterol levels and development of atherosclerotic lesions in Apolipoprotein (ApoE) deficient mice fed a high cholesterol and high fat diet. Apolipoprotein E (ApoE) deficient mice were divided into the following treatment groups: protonated NSAS 1.4% (w/w), untreated control and 2% (w/w) stigmastanol mixed with high-cholesterol/high-fat diet. Animals were treated for 12 weeks, blood samples were withdrawn every 4 weeks for determination of plasma cholesterol and triglyceride levels. At the end of the study the aortic roots were harvested for assessment of atherosclerotic lesions. NSAS at 1.4% (w/w) and stigmastanol at 2% (w/w) treatment groups showed significant decreases in plasma cholesterol concentrations at all time points relative to the control animals. The lesion sum area in 1.4% (w/w) NSAS and 2% (w/w) stigmastanol groups were significantly less from the control animals. In conclusion, in this study, the effectiveness of chronic administration of protonated NSAS material in the reduction of plasma cholesterol levels and decrease in development of atherosclerotic lesions was demonstrated in Apo-E deficient mice model.     

Dietary fat type and cholesterol quantity interact to affect cholesterol metabolism in guinea pigs.

Interactions of dietary fat saturation with dietary cholesterol on cholesterol homeostasis in guinea pigs were studied by feeding 15% (wt/wt) fat diets containing lard, olive oil or corn oil, with 0.00, 0.08, 0.17 or 0.33% added cholesterol. Plasma total and LDL cholesterol concentrations significantly increased with increasing dietary cholesterol, with pronounced increments occurring at the pharmacologic (0.33%) level. An interaction between fat type and dietary cholesterol was seen for HDL cholesterol concentrations. Saturated fat and the pharmacologic level of dietary cholesterol increased plasma HDL concentrations, whereas polyunsaturated fat minimized the dietary cholesterol-mediated increase. Interactions were also observed for hepatic cholesterol: dietary cholesterol increased both free and esterified hepatic cholesterol concentrations in all groups fed all the dietary fats, and fat type influenced the extent of hepatic cholesterol accumulation. Lard-fed animals accumulated the least hepatic cholesterol over the range of dietary cholesterol intakes. Dietary cholesterol suppressed hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity, with maximal suppression at all levels of cholesterol intake. Dietary cholesterol had a greater effect on plasma and hepatic cholesterol concentrations and hepatic HMG-CoA reductase activity than did fat type. The data indicated limited interactions of fat type and cholesterol quantity in altering mechanisms regulating plasma cholesterol homeostasis.     

Regulation of cholesterol and lipoprotein metabolism in guinea pigs mediated by dietary fat quality and quantity.

The effects of dietary fat quality and quantity on regulation of cholesterol and lipoprotein metabolism were measured in guinea pigs. The animals were fed 7.5 or 15% (wt/wt) fat diets containing either polyunsaturated corn oil (CO), monounsaturated olive oil (OL) or saturated lard as the fat source. Dietary fat quality had a number of significant effects: animals fed the CO-based diet had lower plasma LDL levels and LDL particles of higher density with decreased ratios of core-to-surface components. Apoprotein B/E receptor-mediated binding of LDL to hepatic membranes was twofold higher for animals fed the CO-based diet. Animals fed the OL-based diet had lower hepatic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity and increased levels of hepatic cholesterol. Hepatic cholesteryl ester levels were lowest for animals fed the lard-based diet. Increasing dietary fat quantity resulted in increased plasma LDL levels and hepatic cholesterol, HMG-CoA reductase activity and receptor affinity for LDL. No changes were observed in LDL binding. These data demonstrate that, independent of dietary fat quantity, CO-based diets lower plasma LDL levels, modify LDL composition and increase hepatic apoprotein B/E receptor number.     

Protonated nanostructured aluminosilicate (NSAS) reduces plasma cholesterol concentrations and atherosclerotic lesions in Apolipoprotein E deficient mice fed a high cholesterol and high fat diet

There is a predominance of small and dense LDL cholesterol particles in familial combined hyperlipidemia (FCH). The lipoprotein lipase gene could exert an influence in these circumstances. To study the relationship of pattern B LDL and lipids with N291S polymorphism of lipoprotein lipase (LPL) in FCH patients. Lipid profile, apolipoproteins, diameter of LDL and N291S polymorphism were determined in 93 patients with FCH and 286 individuals from the general population. FCH patients with N291S polymorphism showed a lower mean diameter of LDL. FCH patients with pattern B LDL showed higher concentrations of triglycerides, VLDLc, non-HDLc and apo B100 and lower levels of HDLc than those with pattern A. Of FCH patients with polymorphism 87.5% presented pattern B and 12.5% pattern A, while patients without polymorphism presented pattern A in 69.2% cases and pattern B in 30.8% cases, with differences being statistically significant (p < 0.004). The prevalence of this mutation in our FCH patients was 9.7%. The prevalence of N291S mutation in our FCH patients was similar to the 9.3% described in Dutch FCHL patients but clearly higher than the 2–5% described for other Caucasian populations. No polymorphism was found in our general population sample. FCH patients with phenotype B of LDL possessed an atherogenic lipid profile. The relationship between small and dense LDL and the presence of the N291S mutation may identify patients with high cardiovascular risk.     

Effect of dietary cholesterol and fat levels on lipid peroxidation and the activities of antioxidant enzymes in rats

The aim of this study was to investigate the effect of dietary fat levels, with or without cholesterol, on lipid peroxidation and the activities of antioxidant enzymes in rats. Thirty-two Wistar rats aged 4 weeks were divided into 4 groups and fed high (20%; HF) or low (5%; LF) fat, with or without 1% cholesterol, for 6 weeks. Cholesterol feeding resulted in significantly higher concentrations of serum cholesterol, but lowered serum triacylglycerol levels. Cholesterol feeding also led to markedly decreased levels of hepatic thiobarbituric acid reactive substances (TBARS) and lower activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase, and glucose-6-phosphate dehydrogenase (G6PDH) when compared with cholesterol-free counterparts in both HF and LF diets. On the other hand, rats fed high-fat diets showed increased serum and liver TBARS, but decreased hepatic GSH-Px, SOD, and G6PDH activities. Hepatic catalase activity was lower in rats fed cholesterol-containing diets, but higher in rats fed high-fat diets, and interaction existed between cholesterol and fat feeding. These results suggested that dietary cholesterol might delay lipid peroxidation and decrease the activities of the hepatic antioxidant enzymes. The degree of lipid peroxidation was also influenced by dietary fat levels.     

Thermally oxidized dietary fats increase the susceptibility of rat LDL to lipid peroxidation but not their uptake by macrophages

The aim of this study was to investigate the effect of dietary oxidized fats on the lipoprotein profile and the atherogenicity of LDL. Two experiments with male Sprague-Dawley rats were conducted. In Experiment 1, diets with either fresh fat or oxidized fat, prepared by heating at temperatures of 50, 105 or 190 degrees C, containing either 25 or 250 mg alpha-tocopherol equivalents/kg were used. In Experiment 2, diets with fresh or oxidized fat, heated at a temperature of 55 degrees C, containing 25 mg alpha-tocopherol equivalents/kg, were used. In Experiment 1, rats fed all types of oxidized fats had higher concentrations of HDL cholesterol and lower ratios between plasma and HDL cholesterol than rats fed the diet containing the fresh fat. As determined from the lag time, the susceptibility of LDL to copper-induced lipid peroxidation was higher in rats fed oxidized fats heated at 105 or 190 degrees C than in rats fed the diets containing the fresh fat or the oxidized fat treated at 50 degrees C, irrespective of the dietary vitamin E concentration. However, in Experiment 2, the composition of LDL apolipoproteins and uptake of LDL by macrophages were not different between rats fed the fresh fat diet and those fed the oxidized fat diet. We conclude that ingestion of oxidized fats does not adversely affect the lipoprotein profile in the rat model used, and does not cause modifications of apolipoproteins that would lead to enhanced uptake of LDL via macrophage scavenger receptors.