Effect of phytosterols and their oxidation products on lipoprotein profiles and vascular function in hamster fed a high cholesterol diet

Human diets contain phytosterols and their oxidation products. We investigated effect of β-sitosterol (Si), stigmasterol (St), β-sitosterol oxidation products (SiOP) and stigmasterol oxidation products (StOP) on plasma total cholesterol and their interaction with the gene expression of enzymes, proteins and transporters involved in cholesterol absorption and metabolism. Sixty male hamsters were fed the control diet or one of four experimental diets containing 0.1% Si, 0.1% SiOP, 0.1% St and 0.1% StOP, respectively, for six weeks. SiOP and StOP groups had the relative liver weights greater than their corresponding non-oxidized forms, indicating they were possibly toxic. Results showed both Si and St groups reduced while SiOP and StOP hamsters lost the capacity of lowering plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL) and triacylglycerols (TG) compared with the control group. Si and St but not SiOP and StOP were anti-atherosclerotic. RT-PCR analysis demonstrated Si and St but not SiOP and StOP down-regulated mRNA levels of intestinal acyl CoA: cholesterol acyltransferase (ACAT2) and microsomal triglyceride protein (MTP). Aortas from Si and St hamsters relaxed better than those from the control and their corresponding SiOP and StOP-treated hamsters. It was concluded that Si and St not SiOP and StOP were beneficial in improving lipoprotein profile and aortic function.     

Cholesterol reduction by different plant stanol mixtures and with variable fat intake.

Our aim was to investigate (1) whether different campestanol/sitostanol mixtures in margarine differ in reducing serum cholesterol, and (2) whether sitostanol ester in butter decreases serum cholesterol and alters cholesterol absorption and metabolism. Twenty-three postmenopausal women replaced 25 g dietary fat with (1) sitostanol ester-rich (campestanol to sitostanol ratio 1:11) and (2) campestanol ester-rich (campestanol to sitostanol ratio 1:2) rapeseed oil margarine, (3) butter, and (4) sitostanol ester-rich (campestanol to sitostanol ratio 1:13) butter. The respective scheduled stanol intake was 3.18, 3.16, and 2.43 g/d. The 6-week margarine periods and, after an 8-week washout, 5-week butter periods were double-blind and in random order. Serum cholesterol precursor sterols (indicators of cholesterol synthesis) and plant sterols (indicators of cholesterol absorption) were quantified with gas-liquid chromatography (GLC). Low-density lipoprotein (LDL) cholesterol was reduced by 8% and 10% with the sitostanol and campestanol ester-rich margarines versus baseline (P < .05 for both) and high-density lipoprotein (HDL) cholesterol was increased by 6% and 5% (P < .05), so the LDL/HDL cholesterol ratio was reduced by 15% (P < .05 for both). Sitostanol ester-rich butter decreased LDL cholesterol 12% and the LDL/HDL cholesterol ratio 11% (P < .05 for both) versus the butter period. The serum proportions of plant sterols and cholestanol were similarly reduced and those of cholesterol precursor sterols were similarly increased during all periods (P < .05 for all). Serum proportions of sitostanol and campestanol were slightly increased, indicating that their absorption related to their dietary intake. During all stanol interventions, serum vitamin D and retinol concentrations and alpha-tocopherol to cholesterol ratios were unchanged, whereas those of alpha- and beta-carotenes were significantly reduced. We conclude that varying the campestanol to sitostanol ratio from 1:13 to 1:2 in margarine and in butter similarly decreased cholesterol absorption, LDL cholesterol, and the LDL/HDL cholesterol ratio such that the serum lipids became less atherogenic.     

Effects of phytosterol ester-enriched margarine on plasma lipoproteins in mild to moderate hypercholesterolemia are related to basal cholesterol and fat intake

Dietary phytosterols have been reported to lower total and low-density lipoprotein (LDL) cholesterol. However, less is known about the influence of cholesterol and fat intake on the cholesterol-lowering effect of esterified phytosterols in mild to moderate hypercholesterolemia. Sixty-three healthy subjects (38 women, 25 men, 42 +/- 11 years, LDL cholesterol > 130 mg/dL) were investigated in a randomized, double-blind, placebo-controlled, cross-over study. A total of 20 g/d of a phytosterol ester-enriched margarine (1.82 g/d of phytosterols) was compared with a control margarine (0.06 g/d of phytosterols). After 3 weeks of intake, participants crossed over to the other margarine. A 3-day dietary recall was performed at the beginning and at the end of the study to assess cholesterol, fat, and energy intake. Phytosterol ester-enriched margarine significantly changed total cholesterol (-3.4%, P <.005), LDL cholesterol (-5.4%, P <.001, 144 +/- 28 v 154 +/- 26 mg/dL), high-density lipoprotein (HDL) cholesterol (+3.4%, P <.05), apolipoprotein B (-4.0%, P <.005), and LDL/HDL cholesterol ratio (-7.8%, P <.001) compared with the control margarine. In the tertiles with the highest dietary intake of cholesterol, energy, total fat, and saturated fatty acids, and with the highest baseline proportion of campesterol to cholesterol, LDL cholesterol reduction was 11.6% (P <.001), 9.5% (P =.001), 9.4% (P =.001), 8.4% (P =.005), and 6.2% (P =.014), respectively. Triglycerides, plasma viscosity, and fibrinogen concentration did not change significantly. The improvements of LDL, HDL, total cholesterol, apolipoprotein B concentrations, and LDL/HDL cholesterol ratio during the daily consumption of a phytosterol ester-enriched margarine were most marked in those subjects with a high dietary intake of cholesterol, energy, total fat, and saturated fatty acids and with high baseline cholesterol absorption.     

A high-cholesterol, n-3 polyunsaturated fatty acid diet causes different responses in rats and hamsters

This study was designed to investigate the response to a high-cholesterol, n-3 polyunsaturated fatty acid (PUFA) or n-6 PUFA diet in rats and hamsters. Animals were fed n-3 or n-6 PUFA with a cholesterol-free diet, or with a diet enriched with cholesterol (0.5%, w/w) for 2 weeks. In rats and hamsters fed a cholesterol-free diet, plasma cholesterol, triglycerides and very-low-density lipoprotein (VLDL)-triglyceride levels in n-3 PUFA group were significantly lower than those in n-6 PUFA group. In contrast, when diets were supplemented with 0.5% cholesterol, the plasma cholesterol- and triglyceride-lowering effect of dietary n-3 PUFA disappeared. In hamsters fed with the atherogenic diet (0.5% dietary cholesterol) for 2 weeks, n-3 PUFA induced hypercholesterolemia more than n-6 PUFA, the increase being in the VLDL and low-density lipoprotein (LDL) fractions. Our data thus indicate that elevation of VLDL- and LDL-cholesterol in hamsters by n-3 PUFA, compared with n-6 PUFA, is dependent on 0.5% dietary cholesterol supplementation. In rats, on the other hand, dietary n-3 PUFA did not induce hypercholesterolemia more than n-6 PUFA when 0.5% cholesterol was supplemented. Although the effects of n-3 PUFA on plasma cholesterol, triglycerides and VLDL-triglycerides were similar in hamsters and rats, the interactive effects of n-3 PUFA and cholesterol on plasma and lipoprotein cholesterol levels differed in the two species. It was also found that plasma triglycerides, cholesterol and lipoprotein cholesterol levels in hamsters are higher than in rats in the presence and absence of dietary cholesterol. In addition, cholesterol feeding induces hypertriglyceridemia and hypercholesterolemia only in hamsters. Moreover, liver triglyceride concentrations increased in rats fed a cholesterol-rich diet and hepatic triglyceride levels of the n-3 PUFA-fed rats were significantly lower than those in the n-6 PUFA-fed rats in the presence and absence of dietary cholesterol. However, triglycerides did not accumulate in the liver in hamsters fed a cholesterol-rich diet and hepatic triglyceride levels of the n-3 PUFA-fed hamsters were not significantly different from those in the n-6 PUFA-fed hamsters in the presence and absence of dietary cholesterol. Therefore, these studies confirm marked species differences in response to the interactive effects of dietary n-3 PUFA and cholesterol.     

Dietary corn oil versus olive oil enhances HDL protein turnover and lowers HDL cholesterol levels in hamsters.

We studied the effect of dietary olive and corn oil on high-density lipoprotein (HDL) metabolism in golden Syrian hamsters. The animals were fed a semipurified diet containing 0.1% cholesterol and 40 energy % in the form of either olive or corn oil for a period of nine weeks. Hamsters fed corn oil had significantly lower very-low density and low-density lipoprotein (VLDL+LDL) cholesterol concentrations than those fed olive oil (0.98+/-0.24 vs. 1.40+/-0.34 mmol/l, means+/-S.D., n = 12), as well as significantly lower HDL cholesterol concentrations (3.31+/-0.50 vs. 3.91+/-0.12 mmol/l). The binding capacity of 125I-labelled HDL to liver membranes was 33% higher in the hamsters fed corn oil instead of olive oil (571+/-29 vs. 429+/-24 ng HDL protein/mg membrane protein, P<0.05, n = 4). HDL protein kinetics were studied with 125I-HDL using a constant infusion technique. Both HDL fractional catabolic rate (0.255+/-0. 058 vs. 0.121+/-0.023 /h, P<0.01, n = 5) and transport rate (2.386+/-0. 753 vs. 1.218+/-0.101 mg/h, P<0.01, n = 5) were about 2-fold higher in the hamsters fed corn oil. The rate of plasma cholesterol esterification by lecithin: cholesterol acyltransferase (LCAT) was essentially the same for the two diets. It is concluded that the low HDL level in the hamsters fed corn oil diets is linked with increased HDL binding and degradation in the liver and possibly other tissues. Due to increased HDL protein turnover, the capacity for reverse cholesterol transport is increased in hamsters fed corn oil despite the relative low HDL concentrations     

Effects of psyllium on plasma total and lipoprotein cholesterol and hepatic cholesterol in hamsters fed n-3 PUFA or n-6 PUFA with high cholesterol levels

This study was conducted to determine whether psyllium is known to alter cholesterol metabolism modulate the hypercholesterolemic effect of a high cholesterol, n-3 polyunsaturated fatty acids (PUFA) diet in hamsters. Concentrations of plasma, hepatic total cholesterol and lipoprotein cholesterol were measured in male hamsters fed an n-3 PUFA plus psyllium (8%, wt/wt) diet combined with variable levels of cholesterol (0, 0.05, 0.1%, wt/wt) or a cholesterol-enriched (0.2%, wt/wt) n-3 PUFA or n-6 PUFA diet that contained either 8% methyl cellulose or psyllium for 4 weeks. In the n-3 PUFA-fed hamsters, we have found that psyllium was able to reduce plasma total cholesterol and low density lipoprotein (LDL)-cholesterol significantly when 0.1% cholesterol was added to the diet. In contrast, the effects of psyllium were not seen in the n-3 PUFA-fed hamsters without dietary cholesterol or with 0.05% dietary cholesterol. However, no matter in the presence of psyllium or not, the increase of plasma total cholesterol, very-low-density lipoprotein (VLDL)-cholesterol, LDL-cholesterol and high-density lipoprotein (HDL)-cholesterol levels was depend on the content of dietary cholesterol. Although the cholesterol diet increased the liver total cholesterol level, 80 g psyllium/kg diet resulted in a significantly lower concentration of liver total cholesterol in the cholesterol-fed hamsters. In the second experiment, we have also found that psyllium feeding lowered significantly plasma total cholesterol and VLDL-cholesterol concentrations in hamsters fed n-3 PUFA but not in those fed n-6 PUFA. However, the levels of plasma total cholesterol, VLDL-cholesterol and LDL-cholesterol levels of the (n-6) PUFA-fed hamsters were significantly lower than those in the (n-3) PUFA-fed hamsters in the absence or presence of dietary psyllium. Our data also showed that hamsters fed both high-cholesterol n-3 PUFA and n-6 PUFA diets had a significant decrease in hepatic cholesterol with intake of psyllium. Liver total cholesterol concentrations were significantly lower in n-3 PUFA-fed hamsters compared with the n-6 PUFA-fed groups. Therefore, these data may contribute to understanding the interactive effect of psyllium and cholesterol or the type of fat on plasma and liver cholesterol in hamsters.     

Reduction of the plasma LDL-cholesterol level among young healthy men as a result of the change from butter to soft margarine in the unbalanced diet

The aim of the study was to evaluate the level of lipid profile on 83 healthy males consuming soft type margarine instead of butter, in their unbalanced diet. For this purpose double blind, cross-over methodology was applied. After stabilization period of consuming the diet, the whole sample was randomly divided into two subgroups (A n--37; B n--46). First group was consuming 15 g of the butter twice a day (30 g in total) and the second identically packed soft type margarine (also twice a day 15 g; 30 g in total) containing high level (33.3 g/100 g) of polyunsaturated fatty acids. After four weeks, the diet of subgroups was mutually exchanged--group consuming margarine consumed butter and the opposite. The feeding pattern of both groups was monitored with the aid of FOOD 2 computer programme. The group under investigation consisted of healthy males at the age 23.3 +/- 2.5, BMI 24.4 +/- 3.9 kg/m2; WHR 0.82 + -0.06 and normal blood pressure. Exchange of butter into soft margarine caused the increase of P/S ratio from 0.30 to 0.78 in their diet. Both investigated groups shoved average decrease of 10.7% of blood cholesterol content (in group A 13.8%), LDL cholesterol of about 9.8% and triglycerides ca 12.7% (higher decrease in group B--16.7%). Both groups while on margarine diet shoved small decrease of HDL cholesterol (3.9%). It can not be the matter of serious concern due to average HDL content in both groups was ca 52 mg/dl (ca 1.4 mmol/l)--it means considerably excessive the limited risk (35 mg/dl; 0.90 mmol/l). Application of the margarine diet in group A caused the decrease the ratios of total cholesterol to HDL cholesterol from 3.84 into 3.52; whereas in group B from 4.15 into 3.75. It was also concluded, that the low trans isomer margarine show no effect on lipoprotein Lp(a). Back to the diet with butter after 4 weeks carry down the beneficial effects of diet with margarine on lipid profile. The results indicate that for lipid profile the consumption of soft margarine was more beneficial than butter, even for unbalanced diet.     

The amount of dietary cholesterol changes the mode of effects of (n-3) polyunsaturated fatty acid on lipoprotein cholesterol in hamsters

This study was designed to investigate the effects of the interaction between dietary (n-3) polyunsaturated fatty acids (PUFA) and different dietary cholesterol content on plasma and liver cholesterol in hamsters. Male Syrian hamsters consumed diets containing an incremental increase in dietary cholesterol content (0, 0.025, 0.05, 0.1 and 0.2%, w/w) with either (n-3) PUFA (21 g/100 g fatty acids) or (n-6) PUFA (37.4 g/100 g fatty acids) fat for 6 weeks. In hamsters fed the nonatherogenic diet (0 or 0.025% dietary cholesterol), very low density lipoprotein (VLDL)-cholesterol levels in the (n-3) PUFA group were not significantly different from those in the (n-6) PUFA group, and low density lipoprotein (LDL)-cholesterol levels in the (n-3) PUFA group were significantly lower than those in the (n-6) PUFA group. In contrast, in hamsters fed the atherogenic diet (0.1 or 0.2% dietary cholesterol), VLDL- and LDL-cholesterol levels in the (n-3) PUFA group were significantly higher than those in the (n-6) PUFA group, in a dose-dependent manner. When the hamsters were fed with 0, 0.025, 0.05, 0.1 or 0.2% (w/w) dietary cholesterol, high density lipoprotein (HDL) cholesterol concentration was significantly lower in the (n-3) PUFA group than those in the (n-6) PUFA group. Hepatic cholesteryl esters were significantly lower, while hepatic microsomal acyl-coenzyme A:cholesterol acyltransferase activity and VLDL-cholesteryl esters were significantly higher in hamsters fed (n-3) PUFA with the atherogenic diet (0.1 or 0.2% dietary cholesterol) than in those fed (n-6) PUFA with the atherogenic diet. Our results demonstrate that the amount of dietary cholesterol is an important factor in determining the mode and extent of effects of dietary (n-3) PUFA, especially on VLDL- and LDL-cholesterol levels. When dietary cholesterol intake was above 0.1% (w/w), the plasma cholesterol-lowering effect of (n-3) PUFA disappeared, and instead, it showed a cholesterol-increasing effect. However, the effects of dietary (n-3) PUFA on HDL-cholesterol are independent of dietary cholesterol content.     

Gender differences in response to a hypercholesterolemic diet in hamsters: effects on plasma lipoprotein cholesterol concentrations and early aortic atherosclerosis.

Gender is a strong predictor of coronary heart disease (CHD) susceptibility and reports indicate that males are more likely to develop CHD compared to age-matched premenopausal females. To test whether similar gender differences exist in hamsters, 16 male and 16 female F1B Golden Syrian hamsters, aged 10 weeks, were fed a hypercholesterolemic nonpurified diet (HCD) containing 10% coconut oil and 0.05% cholesterol for 12 weeks. Plasma lipid and lipoprotein cholesterol concentrations, LDL oxidative susceptibility, LDL tocopherol concentrations, LDL fatty acid composition, LDL particle size, plasma estradiol and testosterone concentrations, and early aortic atherosclerosis were analyzed. Female hamsters had significantly lower plasma total cholesterol and nonhigh-density lipoprotein cholesterol (nonHDL-C) and greater high-density lipoprotein cholesterol (HDL-C) concentrations compared to male hamsters (-15, -33, and 33%; respectively). Female hamsters had significantly greater LDL particle size (4%), LDL 22:6 (21%) fatty acid, and rate of LDL oxidation (34%) compared to male hamsters. Female hamsters had a significantly higher concentration of plasma estradiol (49%) compared to male hamsters. Female hamsters also had significantly less early aortic atherosclerosis compared to male hamsters (-77%). In female hamsters, aortic fatty streak formation was significantly associated with plasma nonHDL-C (r = 0.76, P<0.0007), LDL particle size (r = -0.66, P<0.005), plasma TC (r = 0.68. P<0.004), and lag phase of LDL oxidation (r = 0.84. P<0.02). In male hamsters, aortic fatty streak formation was significantly associated with plasma nonHDL-C (r = 0.52, P<0.04), plasma TC (r = 0.55, P<0.03), plasma TG (r = 0.79, P<0.0003), and LDL 22:6 (r = -0.78, P<0.03) with no association with any measures of LDL oxidation susceptibility. This study demonstrates that female hamsters have an improved plasma lipoprotein cholesterol profile, larger LDL particle size, and less early aortic atherosclerosis compared to male hamsters fed the same HCD.     

Modeling plasma lipoprotein-bile lipid relationships: Differential impact of psyllium and cholestyramine in hamsters fed a lithogenic diet

Hamsters fed a lithogenic diet become hyperlipemic with elevated very-low-density lipoprotein (VLDL) and high-density lipoprotein 2 (HDL₂) cholesterol pools and develop lithogenic bile in which chenodeoxycholate (cheno) typically predominates. The relationship between these distorted lipoprotein and bile lipid profiles and gallstone induction was investigated in male Syrian hamsters fed for 5 weeks a gallstone-inducing purified diet (5% butter, 0.4% cholesterol) or the same diet supplemented with 5% psyllium or 1% cholestyramine, agents known to alter bile acid metabolism. The gallstone diet essentially doubled plasma cholesterol level, whereas psyllium decreased it to near normal, and cholestyramine to a subnormal level, while correcting the distorted distribution of cholesterol among lipoproteins. Both the gallstone diet and psyllium produced cholesterol-laden livers, in contrast to subnormal values produced by cholestyramine. Fecal bile acid excretion was increased eightfold with cholestyramine and fourfold with psyllium relative to the value produced by the gallstone diet and a literature control value. Supersaturated bile developed with the gallstone diet (lithogenic index [LI], 2.3 ± 0.6), whereas the LI was decreased by psyllium (1.2 ± 0.4) and cholestyramine (0.7 ± 0.3). The gallstone diet decreased the concentration of bile acids in gallbladder bile, but greatly increased the percentage of taurochenodeoxycholic acid, whereas psyllium preferentially decreased all taurine-conjugated bile acid levels and expanded glycocholate output. Cholestyramine greatly decreased the secretion of biliary cholesterol and cheno independent of its conjugation. Accordingly, psyllium increased the glycine to taurine ratio of gallbladder bile fivefold, whereas cholestyramine did not affect this ratio, but increased the cholate to cheno ratio dramatically (25-fold) as compared with a threefold increase with psyllium. This combination of biliary lipid and bile acid alterations induced coordinated responses in the LI and the hydrophobicity index (HI) such that cholesterol gallstones developed in 11 of 12 hamsters fed the gallstone diet, whereas only one of 11 of the psyllium-fed and none of 12 cholestyramine-fed hamsters had cholesterol stones. Thus, psyllium and cholestyramine differentially increased bile acid excretion, which improved the lipoprotein profile and inhibited cholesterol gallstone formation. Both agents operated by different means to decrease biliary cholesterol secretion and the percentage of cheno, which decreased the LI and HI, respectively.     

Lipids, lipoproteins, and endocrine profiles during pregnancy in the African green monkey (Cercopithecus aethiops)

In an attempt to establish relationships between the endocrine and lipid metabolism during pregnancy, the changes in total plasma cholesterol (TPC) and lipoprotein cholesterol that occur during pregnancy in the African green monkey were investigated longitudinally in ten females in relation to the changes in progesterone, estradiol, and fasting insulin concentrations. Respective means for TPC, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) plus very low-density lipoprotein (VLDL) cholesterol were 343 +/- 35, 108 +/- 9, and 235 +/- 36 mg/dL prior to the estimated date of conception in ten females fed a high-fat, high-cholesterol diet. The concentration of these lipids fell to 225 +/- 31, 54 +/- 4, and 168 +/- 29 mg/dL for TPC (P less than 0.001), HDL cholesterol (P less than 0.001), and LDL + VLDL cholesterol (P less than 0.001), respectively, by midpregnancy (84 days). Progesterone concentrations increased during the first 60 days of pregnancy and were negatively correlated with HDL cholesterol concentrations (r = -0.57, P less than 0.02). After reaching their highest mean value, progesterone concentrations then plateaued at lower concentrations until parturition. The decrease in progesterone concentrations was associated with an initial rise in estradiol concentrations, which reached their highest concentrations in late pregnancy and were inversely correlated with HDL-cholesterol concentrations (r = -.32, P less than 0.01). Although glucose concentrations remained steady during gestation, insulin concentrations were elevated compared to postpartum concentrations (P less than 0.05) suggesting that insulin resistance occurred during the pregnancy in this nonhuman primate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of hydrogenated fat and butter on CVD risk factors: remnant-like particles, glucose and insulin, blood pressure and C-reactive protein

Dietary trans fatty acids/partially-hydrogenated fat has been associated with increased risk of developing cardiovascular disease (CVD), possibly greater than predicted from changes in lipoprotein levels. To explore this issue further potential risk factors were assessed in subjects provided with each of six diets in randomized order containing as the major source of fat: soybean oil, semi-liquid margarine, soft margarine, shortening, traditional stick margarine or butter. Plasma fatty acid profiles reflected diet, with triglyceride and phospholipid subfractions affected to a greater extent than cholesteryl ester. Non-fasting LDL-cholesterol levels were 144+/-27, 141+/-27, 146+/-26, 148+/-30, 151+/-29 and 165+/-31 mg/dl (P<0.001) and total cholesterol/HDL-cholesterol ratios were 5.50+/-1.25, 5.54+/-1.50, 5.69+/-1.29, 5.82+/-1.40, 6.11+/-1.30 and 5.94+/-1.43 (P=0.011), respectively, whereas other lipoprotein levels were not significantly different. Remnant-like particles levels were unaffected by dietary fat, either in the fasting or non-fasting state. Differences in fasting insulin and glucose levels were small and would not be predicted to have a large impact on glucose homeostasis. There was no significant effect of dietary fat type on C-reactive protein levels or blood pressure. These data suggest that, as previously demonstrated, the major CVD risk factor adversely affected by dietary trans fatty acids/partially-hydrogenated fat is LDL-cholesterol levels and total cholesterol/HDL-cholesterol ratios.     

Impact of dietary fat type within the context of altered cholesterol homeostasis on cholesterol and lipoprotein metabolism in the F1B hamster

Cholesterol status and dietary fat alter several metabolic pathways reflected in lipoprotein profiles. To assess plasma lipoprotein response and mechanisms by which cholesterol and dietary fat type regulate expression of genes involved in lipoprotein metabolism, we developed an experimental model system using F1B hamsters fed diets (12 weeks) enriched in 10% (wt/wt) coconut, olive, or safflower oil with either high cholesterol (0.1%; cholesterol supplemented) or low cholesterol coupled with cholesterol-lowering drugs 10 days before killing (0.01% cholesterol, 0.15% lovastatin, 2% cholestyramine; cholesterol depleted). Irrespective of dietary fat, cholesterol depletion, relative to supplementation, resulted in lower plasma non-high-density lipoprotein (non-HDL) and HDL cholesterol, and triglyceride concentrations (all Ps < .05). In the liver, these differences were associated with higher sterol regulatory element binding protein-2, low-density lipoprotein receptor, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and 7α-hydroxylase messenger RNA (mRNA) levels; higher scavenger receptor B1 and apolipoprotein A-I mRNA and protein levels; lower apolipoprotein E protein levels; and in intestine, modestly lower sterol transporters adenosine triphosphate-binding cassette (ABC) A1, ABCG5, and ABCG8 mRNA levels. Irrespective of cholesterol status, coconut oil, relative to olive and safflower oils, resulted in higher non-HDL cholesterol and triglyceride concentrations (both Ps < .05) and modestly higher sterol regulatory element binding protein-2 mRNA levels. These data suggest that, in F1B hamsters, differences in plasma lipoprotein profiles in response to cholesterol depletion are associated with changes in the expression of genes involved in cholesterol metabolism, whereas the effect of dietary fat type on gene expression was modest, which limits the usefulness of the experimental animal model.     

Intestinal rather than hepatic microsomal triglyceride transfer protein as a cause of postprandial dyslipidemia in diabetes

Postprandial dyslipidemia may be a major cause of atherosclerosis in diabetes. Microsomal triglyceride transfer protein (MTP) is essential for the synthesis of the chylomicron particle in the intestine and very low-density lipoprotein (VLDL) in the liver. The purpose of the present study was to examine the effect of diabetes on MTP mRNA expression in a rabbit model of diabetes, which develops atherosclerosis. Male New Zealand white rabbits were fed a 0.5% cholesterol diet. Diabetes was induced with alloxan monohydrate. The lymphatic duct was cannulated and lymph collected for isolation of chylomicrons by ultracentrifugation. Apolipoprotein B48 (apo B48) and apo B100 were separated by polyacrylamide gradient gel electrophoresis and quantified by densitometry. MTP mRNA was determined in liver and intestine by RNase protection analysis, and MTP activity was measured. Diabetic animals had significantly increased plasma triglyceride and decreased high-density lipoprotein (HDL) cholesterol (P <.05). They also secreted more lymph chylomicron apo B48 and apo B100 (P <.05) and more lymph chylomicron total and esterified cholesterol/h (P <.05). Lymph chylomicron particles in the diabetic animals contained significantly less lipid/apo B (P <.05). Intestinal MTP activity and mRNA were significantly higher in diabetic compared with control rabbits (0.07 +/- 0.01 v 0.04 +/- 0.015 fluorescent units/microg microsomal protein and 66 +/- 21 v 37 +/- 11 amol MTP mRNA/microg total RNA (P <.005). There was no difference in MTP activity or mRNA expression in the liver. This study suggests that MTP may play an important role in the postprandial dyslipidemia of diabetes.     

Hydrophobic surfactant inhibits hypercholesterolemia in pair-fed rabbits on a cholesterol-free, low-fat diet

Poloxalene, a hydrophobic surfactant, is known to prevent hypercholesterolemia in animals fed a high-fat, high-cholesterol diet. It has not been demonstrated, however, whether this agent is of benefit when hypercholesterolemia is induced in animals by means other than the feeding of a high-fat diet. In this study, hypercholesterolemia was produced in rabbits by feeding a low-fat, cholesterol-free diet with dietary protein supplied by casein for a period of 8 weeks. Controls were given this diet without poloxalene and experimentals were given the diet with poloxalene. Total serum cholesterol levels increased in both groups, but the rise was greater for the control group. Lipoprotein analysis performed at the conclusion of the study showed significantly greater low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels in the control group as compared to the experimental group. Total protein and apolipoprotein B (apo B) were also greater in control LDL. It was concluded that poloxalene favorably affects this model of hypercholesterolemia as total serum cholesterol, LDL cholesterol, and LDL apo B were all less and the HDL cholesterol to LDL cholesterol ratio was higher in surfactant-treated rabbits.     

Additive effect of plant sterol-ester margarine and cerivastatin in lowering low-density lipoprotein cholesterol in primary hypercholesterolemia

The objective of this study was to evaluate whether plant sterol-ester margarine has an additive or interactive effect on low-density lipoprotein (LDL) cholesterol reduction when ingested in combination with a statin drug. This was a multicenter, randomized, double-blind study with 4 parallel treatment arms in a balanced 2 x 2 factorial design. The 4 daily treatment options were: (1) placebo plus regular margarine 25 g (n = 38); (2) placebo plus sterol-ester margarine 25 g (2 g of plant sterol) (n = 39); (3) cerivastatin 400 microg plus regular margarine 25 g (n = 38); and (4) cerivastatin 400 microg plus sterol-ester margarine 25 g (n = 37). The study was conducted in men and women with primary hypercholesterolemia with baseline LDL cholesterol >/=97 mg/dl (mean 206). The primary efficacy parameter was the percent change in LDL cholesterol between baseline and at the end of 4 weeks' treatment. Cerivastatin (vs placebo) reduced LDL cholesterol by 32% (95% confidence intervals 28% to 36%, p <0.0001) and sterol-ester margarine (vs regular margarine) by 8% (95% confidence interval 4% to 12%, p <0.0001). The effect of sterol-ester margarine and cerivastatin together was additive (39% reduction in LDL cholesterol), but there was no significant interactive effect between sterol-ester margarine and cerivastatin (p = 0.29). The treatments were generally well tolerated with no major differences in adverse events between groups. In subjects with primary hypercholesterolemia, statin and sterol-ester margarine used together produce a purely additive effect on LDL cholesterol reduction. The addition of sterol-ester margarine to statin therapy offers LDL cholesterol reduction equivalent to doubling the dose of statin.     

Combined effect of exogenous insulin and sucrose on alterations in plasma lipoproteins induced by cholesterol feeding in the rat

We have recently reported increased cholesterol concentrations in high-density and very-low-density lipoproteins (HDL and VLDL) in sucrose-fed rats with exogenous hyperinsulinemia. In order to see if exogenous hyperinsulinemia has any effect on the alterations in plasma lipoproteins induced by cholesterol feeding, we fed a cholesterol-rich diet supplemented with lard, cholic acid and propylthiouracil to hyperinsulinemic, sucrose-supplemented rats and examined plasma lipoprotein profiles. Three control groups were investigated: one receiving chow only, the other receiving a cholesterol-rich diet, the third receiving exogenous insulin, sucrose, and no cholesterol-rich diet but chow. Hyperinsulinemia was induced by a constant s.c. infusion of porcine insulin (6 U/day) from an osmotic minipump. Insulin infusion plus sucrose produced an increase in HDL cholesterol concentrations similar to that seen in the previously reported injection model in the face of no change in total and low-density lipoprotein (LDL) cholesterol. Rats receiving a cholesterol-rich diet but no insulin developed marked hypercholesterolemia characterized by an elevation of cholesterol not only in LDL but also in intermediate-density lipoprotein (IDL) and VLDL. Infusing insulin into cholesterol-fed rats produced a further increase in IDL and VLDL cholesterol but was not accompanied by any further increase in LDL cholesterol. HDL cholesterol was decreased below normal.     

Genes that affect cholesterol synthesis, cholesterol absorption, and chylomicron assembly: the relationship between the liver and intestine in control and streptozotosin diabetic rats

Chylomicrons and very low-density lipoproteins (VLDLs) are abnormal in diabetes. The aim of this study was to compare the expression of Niemann-Pick C1-like1 (NPC1L1), adenosine triphosphate-binding cassette (ABC) proteins G5 and G8, microsomal triglyceride transfer protein (MTP), and 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase in the fasting and fed states in nondiabetic Sprague-Dawley rats fed a high-fat/cholesterol diet and to examine the messenger RNA (mRNA) expression of these proteins in the liver and intestine of diabetic and control animals using streptozotosin diabetic cholesterol-fed rats. Chylomicron and VLDL concentrations were significantly lower after a 12-hour fast in fasted compared with fed rats (P < .02). There was no change with fasting in mRNA expression of any of the genes in the intestine, but MTP level was significantly lower in the liver after the 12-hour fast (P < .01). There was a positive correlation between intestinal NPC1L1 mRNA and chylomicron cholesterol (P < .01) and between hepatic NPC1L1 mRNA and VLDL cholesterol (P < .01). The diabetic rats had significantly higher chylomicron and VLDL cholesterol, triglyceride, and apolipoprotein B-48 and B-100 levels compared with control rats (P < .0001). They had significantly increased NPC1L1 and MTP mRNA in both liver and intestine (P < .05 and P < .0005, respectively), and ABCG5 and ABCG8 mRNA were significantly reduced (P < .05). HMGCoA reductase mRNA was increased in diabetic animals (P < .01). In conclusion, fasting intestinal gene expression reflects the fed state. In diabetes, intestinal and hepatic gene expression correlates with abnormalities in chylomicron and VLDL cholesterol.     

Changes in plasma lipoprotein concentrations and compositions upon feeding cholesterol in high- and low-responding rhesus monkeys

When fed cholesterol, the high-responding rhesus monkeys develop severe hypercholesterolemia, whereas low-responding rhesus monkeys show only slight increases in plasma cholesterol levels. We report changes in plasma lipoprotein concentrations and compositions along with changes in plasma lipid concentrations in high- and low-responding rhesus monkeys fed a high-cholesterol diet. On low-cholesterol diet, the concentrations and compositions of plasma lipoprotein fractions were similar in the two groups. Upon feeding cholesterol, plasma very-low-density (VLDL), intermediate-density (IDL) and low-density (LDL)-lipoprotein concentrations increased in both groups, but the increases were significantly (p less than 0.01) higher in high-responders than in low-responders. Plasma HDL concentration decreased significantly (p less than 0.01) in high responders but not in low responders. In high responders, percent cholesterol increased in both VLDL and IDL fractions but in low responders, it decreased in VLDL and increased in IDL. Percent triglycerides decreased in VLDL, IDL and LDL fractions in high responders, while in low responders it tended to increase in VLDL, remained unchanged in IDL and decreased in LDL. The composition of HDL did not change in the two groups upon feeding cholesterol. Thus, when fed cholesterol, the high- and the low-responding monkeys respond distinctly differently in plasma lipoprotein concentrations and compositions. The responses occurred simultaneously, suggesting metabolic interrelationships between various lipoproteins.     

The effect of vitamin E, probucol, and lovastatin on oxidative status and aortic fatty lesions in hyperlipidemic-diabetic hamsters

Diabetes mellitus is associated with an increased risk of premature atherosclerosis, which may be due in part to an increased rate of low density lipoprotein (LDL) oxidation. Previous studies have shown that vitamin E, probucol, and lovastatin can reduce the oxidative susceptibility of LDL in normoglycemic animal models; however, few studies have investigated this in conjunction with aortic fatty streak lesion formation in diabetic hyperlipidemic models. Forty-eight Syrian hamsters were made diabetic by intraperitoneal injection of low dose streptozotocin. Diabetic animals (12 animals/groups) received a high saturated fat and cholesterol diet for 12.5 weeks. At 2.5 week of dietary treatments, the diet was supplemented with either: (1) 500 IU/day vitamin E (D+E); (2) 1% probucol w/w of the diet (D+P); (3) 25 mg/kg lovastatin (D+L); or (4) diabetic control (D). An age-matched group of hamsters (n=6) receiving the same diet but not made diabetic (ND) was used as control. At the end of the study, aortic arch foam cell-rich fatty streak lesion, plasma glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), phospholipids, alpha-tocopherol, plasma lipid peroxide and the susceptibility of LDL to copper-catalyzed oxidation were determined. Diabetes increased plasma glucose, and when combined with an atherogenic diet resulted in a further increase of plasma lipids. Vitamin E, probucol, and lovastatin significantly reduced plasma TG in the diabetic hamsters fed the atherogenic diet. Vitamin E treatment increased TC, probucol reduced HDL-C without affecting TC; whereas lovastatin reduced TC and selectively decreased non-HDL-C, and significantly reduced fatty streak lesion formation in the aortic arch. While vitamin E and probucol were effective in reducing several indices of oxidative stress including plasma lipid peroxides, cholesterol oxidation products and in vitro LDL oxidation, they had no effect on fatty streak lesion formation. Our results indicate that the LDL in diabetic animals is more susceptible to oxidation than in non-diabetic hamsters and that not only vitamin E and probucol but also lovastatin provide antioxidant protection. It appears that in this combined model of diabetes and hypercholesterolemia, progression of fatty streak lesion formation is mainly associated with changes in TC and non-HDL-C as affected by lovastatin, and is less dependent on the extent of LDL oxidation, changes in plasma TG level and oxidative stress status.