Enhanced efficacy of sitostanol-containing versus sitostanol-free phytosterol mixtures in altering lipoprotein cholesterol levels and synthesis in rats

Effects of microcrystalline plant sterol suspension and a powdered plant sterol supplement on hypercholesterolemia in genetically obese Zucker rats

Because dietary fat appears to be an effective vehicle for dispensing plant sterols into the diet, a special plant-sterol-containing ingredient has recently been developed. This ingredient is a plant sterol suspension in oil in which the sterols are in microcrystalline form. The objective of the present study was to analyse the cholesterol-lowering effects and safety of two different plant sterol preparations, an orally administered microcrystalline plant sterol suspension (MPS) in rapeseed oil and a powdered plant sterol supplement, in obese Zucker rats. Dietary plant sterol supplements (0.5%, w/w) were given concurrently with a high cholesterol diet (HCD, 1% cholesterol and 18% fat, w/w). No significant changes in serum triglyceride, blood glucose, serum glutamate oxaloacetic transaminase and glutamic pyruvic transaminase values or body and liver weights were observed. The powdered plant sterol supplement lowered the serum cholesterol by 25% (P< 0.05) and the MPS diet by 35% (P< 0.001) compared with HCD by the end of the 12-week experiment. Interestingly, the plant sterol supplements also produced a marked reduction in serum ubiquinone levels, suggesting a possible effect on isoprene synthesis. Unlike the powdered plant sterol, both MPS and plain rape-seed oil decreased the serum baseline diene conjugation values, suggesting that they protect against oxidative stress-induced lipid peroxidation in rats. This lipid peroxidation diminishing effect is probably due to some antioxidative components in rapeseed oil. These findings indicate that an unesterified plant sterol, such as the microcrystalline suspension in oil, effectively prevents cholesterol absorption in obese Zucker rats.

New insights into the molecular actions of plant sterols and stanols in cholesterol metabolism

Plant sterols and stanols (phytosterols/phytostanols) are known to reduce serum low-density lipoprotein (LDL)-cholesterol level, and food products containing these plant compounds are widely used as a therapeutic dietary option to reduce plasma cholesterol and atherosclerotic risk. The cholesterol-lowering action of phytosterols/phytostanols is thought to occur, at least in part, through competition with dietary and biliary cholesterol for intestinal absorption in mixed micelles. However, recent evidence suggests that phytosterols/phytostanols may regulate proteins implicated in cholesterol metabolism both in enterocytes and hepatocytes. Important advances in the understanding of intestinal sterol absorption have provided potential molecular targets of phytosterols. An increased activity of ATP-binding cassette transporter A1 (ABCA1) and ABCG5/G8 heterodimer has been proposed as a mechanism underlying the hypocholesterolaemic effect of phytosterols. Conclusive studies using ABCA1 and ABCG5/G8-deficient mice have demonstrated that the phytosterol-mediated inhibition of intestinal cholesterol absorption is independent of these ATP-binding cassette (ABC) transporters. Other reports have proposed a phytosterol/phytostanol action on cholesterol esterification and lipoprotein assembly, cholesterol synthesis and apolipoprotein (apo) B100-containing lipoprotein removal. The accumulation of phytosterols in ABCG5/G8-deficient mice, which develop features of human sitosterolaemia, disrupts cholesterol homeostasis by affecting sterol regulatory element-binding protein (SREBP)-2 processing and liver X receptor (LXR) regulatory pathways. This article reviews the progress to date in studying these effects of phytosterols/phytostanols and the molecular mechanisms involved.

Corn fiber oil and sitostanol decrease cholesterol absorption independently of intestinal sterol transporters in hamsters

OBJECTIVE

The aim of this study was to investigate the cholesterol-lowering mechanisms of corn fiber oil (CFO), ferulate phytostanyl esters (FPEs) and parent compounds of FPE, including sitostanol and ferulic acid, in hamsters.

METHOD

Seventy male Golden Syrian hamsters were randomly assigned to six experimental diets for 4 weeks: (1) cornstarch-casein-sucrose-based control diet (control); and (2) control diet plus 0.1% (wt/wt) cholesterol (cholesterol-control). The remaining four groups were given cholesterol-control diet with: (3) 10% (wt/wt) CFO; (4) 0.5% (wt/wt) sitostanol; (5) 0.23% (wt/wt) ferulic acid; and (6) 0.73% (wt/wt) FPE. At the end of dietary intervention, total plasma cholesterol, high-density lipoprotein cholesterol and triglyceride concentrations were determined. Parameters of cholesterol kinetics, including cholesterol absorption and synthesis, as well as mRNA expression of sterol transporters such as Niemann-Pick C1 like 1 (NPC1L1), ATP-binding cassette G5 (ABCG5) and ABCG8, were assessed.

RESULTS

Supplementation with CFO decreased (P<.0001) plasma total cholesterol levels by 29% as compared with the cholesterol-control group, while FPE and sitostanol reduced (P<.02) cholesterolemia by 15% and 14%, respectively. CFO and sitostanol decreased (P<.05) cholesterol absorption by 24% compared to the cholesterol-control group. Dietary intervention did not alter the intestinal gene expression of ABCG5, ABCG8 and NPC1L1.

CONCLUSION

The present results show that the CFO-induced and sitostanol-induced decrease in cholesterol absorption is independent of intestinal enterocyte sterol transporters such as ABCG5, ABCG8 and NPC1L1 in hamsters.

Basal plasma concentrations of plant sterols can predict LDL-C response to sitosterol in patients with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is associated with a high risk of coronary heart disease. Pharmacological treatment and diet are both essential for the management of FH. Foods rich in plant sterols (PS) may play an important role in the treatment of patients with these disorders.

OBJECTIVE

To test the effect of the intake of PS on low-density lipoprotein (LDL) concentration, endothelial function (EF) and LDL particle size in 30 patients with FH.

DESIGN

Randomized and crossover dietary intervention study.

SETTING

Tertiary outpatient care.

SUBJECTS

Thirty-eight were recruited, but only 30 were subjected to four low-fat dietary intervention periods, each of 4 weeks.

METHODS

Each intervention had a different content of cholesterol (<150 or 300 mg/day) and sitosterol (<1 or 2 g/day). Lipid response, EF and LDL particle size were analysed after the intervention.

RESULTS

Plasma sitosterol/cholesterol ratio was higher during both plant sterol-rich periods than during the low plant sterols periods. Basal sitosterol concentrations predicted the LDL-cholesterol response during the intake of plant sterol-enriched diets. The change in LDL-cholesterol was significantly greater in subjects in the upper and intermediate tertiles of basal plasma sitosterol concentrations (-21+/-8 mg/dl, P=0.03; -19+/-7 mg/dl, P=0.04, respectively) than in subjects in the lower tertile (8+/-5 mg/dl) when they changed from a low cholesterol diet to a low cholesterol plus plant sterol diet.

CONCLUSION

Our study demonstrates that basal sitosterol values can predict hypolipidemic response in patients with FH.

Effect of esterified 4-desmethylsterols and -stanols or 4,4′-dimethylsterols on cholesterol and bile acid metabolism in hamsters

4-Desmethylsterols and -stanols reduce plasma total cholesterol (TC) and LDL cholesterol by inhibition of intestinal cholesterol absorption, while the cholesterol-lowering potential of 4,4′-dimethylsterols is less well defined. The present study aimed to compare the effects of 4-desmethylsterols, -stanols, and 4,4′-dimethylsterols on plasma and hepatic cholesterol, sterol excretion and bile acid metabolism. Male golden Syrian hamsters were fed diets containing 13 g/100 g fat, 0·08 g/100 g cholesterol and 0 (control), 0·24 or 0·48 % (w/w) esterified 4-desmethylsterols (sterols) and esterified hydrogenated 4-desmethylsterols (stanols) from common vegetable oils or esterified 4,4′-dimethylsterols from rice bran oil for 5 weeks. Sterol and stanol esters at the dose of 0·24 % were equally effective and significantly (P<0·05) lowered TC by 15 %, while 0·24 % 4,4-dimethylsterols reduced TC by 10 %. Liver total and esterified cholesterol concentrations were significantly (P<0·05) lowered by 40, 22, 43 and 31 % in hamsters fed 0·48 % sterols, 0·24 % stanols, 0·48 % stanols or 0·48 % dimethylsterols, respectively. Daily faecal bile acid excretion and hepatic cholesterol 7α-hydroxylase activity were not altered, indicating that sterols, stanols and dimethylsterols had no effect on the intestinal re-absorption of bile acids or on hepatic bile acid synthesis. Daily excretion of cholesterol was significantly higher in hamsters fed esterified sterols and stanols, but was only slightly increased in those fed dimethylsterols. The results indicate that esterified sterols and stanols were equally effective in lowering plasma TC and LDL cholesterol, while dimethylsterol esters caused a weaker cholesterol-lowering effect. Sterols and stanols achieve their cholesterol-lowering effect by stimulating faecal cholesterol excretion through inhibiting intestinal cholesterol absorption, but do not affect bile acid excretion. Other mechanisms need to be considered to explain the effect on plasma and hepatic cholesterol of dimethylsterols.

Plant stanol ascorbate esters reduce body weight gain through decreased energy absorption in hamsters

OBJECTIVE

The objective of this study was to determine the effects of disodium ascorbyl phytostanyl phosphate (DAPP), a novel hydrophilic phytostanol analogue, on energy homeostasis, including body weight and intestinal energy absorption, and plasma triglyceride concentrations, in hamsters.

METHODS

Male Golden Syrian hamsters (n = 50) were fed for 5 weeks with experimental diets varying in cholesterol and phytostanol content. Diets included (i) non-cholesterol (semipurified diet without added cholesterol), (ii) cholesterol-control (semipurified diet with 0.25% cholesterol), (iii) stanol (cholesterol-control with 1% free phytostanols), (iv) DAPP 0.7% (cholesterol-control with 0.71% DAPP) or (v) DAPP 1.4% (cholesterol-control with 1.43% DAPP). Fecal samples were collected continuously for 3 days on week 3, and fecal energy output was measured by bomb calorimetry.

RESULTS

Hamsters fed 1.4% DAPP gained less (P<0.05) weight than hamsters fed non-cholesterol and stanol diets. Diets had no effect on total food consumption or gross energy intake after 5 weeks, but lower (P<0.05) weekly food consumptions in hamsters fed 1.4% DAPP were observed at weeks 1 and 2 of the experiment in comparison to animals fed the non-cholesterol diet. In comparison to non-cholesterol and cholesterol-control diets, DAPP 1.4% increased (P<0.01) fecal energy output by 47 and 46%, respectively. In hamsters supplemented with 1.4% DAPP, plasma triglyceride concentrations were 45% lower (P<0.05) than in cholesterol-control fed hamsters. Furthermore, plasma triglyceride levels in the DAPP 1.4% group was 49% lower (P<0.01) than in the stanol group, despite the fact that both diets contained equivalent amounts of phytostanols. The lower concentration of DAPP (0.7%) also reduced plasma triglycerides (P<0.05) compared with the stanol diet.

CONCLUSION

Stanol-ascorbate decreases body weight gain in hamsters, likely due to lower energy absorption at the intestinal level. In addition to its previously observed powerful cholesterol-lowering effect, DAPP has a hypotriglyceridemic function in hamsters.

Fish oil fatty acid esters of phytosterols alter plasma lipids but not red blood cell fragility in hamsters

In an attempt to combine the hypocholesterolemic properties of plant sterols with the hypotriglyceridemic action of fish oil FA, plant sterols have recently been esterified to fish oil n-3 PUFA. The objective of this study was to determine the effects of plant sterols esterified to n-3 PUFA on plasma lipid levels and erythrocyte fragility. For 5 wk, male Golden Syrian hamsters were fed diets varying in cholesterol and plant sterol content: (i) Non-cholesterol (semipurified diet with no added cholesterol or plant sterols) (ii), Cholesterol (0.25% cholesterol) (iii), Sterols (0.25% cholesterol plus 1% nonesterified plant sterols), or (iv) Fish oil esters of plant sterols (0.25% cholesterol plus 1.76% EPA and DHA sterol esters, providing 1% plant sterols). The addition of fish oil esters of plant sterols to the cholesterol diet decreased (P = 0.001) plasma total cholesterol levels by 20%, but nonesterified plant sterols did not have such a beneficial impact. In addition, non-HDL cholesterol concentrations were 29% lower in hamsters fed fish oil esters of plant sterols than in hamsters fed nonesterified plant sterols (P < 0.0001). Despite higher (P < 0.0001) plant sterol levels in whole erythrocytes of hamsters fed nonesterified plant sterols and fish oil esters of plant sterols compared with hamsters fed no plant sterols, no difference was observed in erythrocyte fragility. The present results show that EPA and DHA esters of plant sterols have a hypocholesterolemic effect in hamsters, and that these new esters of plant sterols exert no detrimental effect on erythrocyte fragility.

A comparison of the effect of medium- vs. long-chain triglycerides on the in vitro solubilization of cholesterol and/or phytosterol into mixed micelles

Despite clinical evidence of the cholesterol-lowering effects of phytosterols, the exact mechanisms involved are still unclear. Displacement of cholesterol by phytosterols from mixed micelles, which is due to their greater hydrophobicity, is one of the hypotheses for the lumenal effects contributing to the reduction of intestinal cholesterol absorption. In this study a dynamic in vitro lipolysis method was used to examine the solubilization behavior of cholesterol and/or phytosterols during lipolysis to probe the efficacy of cholesterol displacement from mixed micelles by phytosterols. The effects of lipid chain length on sterol solubilization were studied by using microcrystalline suspensions containing 17% phytosterol or cholesterol, formulated in long-chain TG (LCT) and medium-chain TG (MCT). When digesting cholesterol-suspended in LCT, the entire cholesterol dose was incorporated into the micellar phase. For the cholesterol formulation suspended in MCT, 50.3% of the initial dose was recovered in the micelles. Under the respective conditions, we observed lower solubilization of phytosterols than of cholesterol (roughly fourfold). Only 25% of the initial phytosterol dose was solubilized from suspensions formulated with LCT, and 13% was solubilized from MCT formulations. Co-administration of phytosterol and cholesterol suspensions showed a significant reduction of cholesterol solubilization, particularly when dosed in MCT, with approximately 25% of the cholesterol dose solubilized. Insignificant amounts of cholesterol were displaced by phytosterols when cholesterol was presolubilized in the mixed micelles. The results show that, compared with LCT, mixed micelles containing MCT lipolysis products have a reduced solubilizing capacity for cholesterol, which adds to the effectiveness of the phytosterols in displacing cholesterol. This suggests potential benefits of using medium chain length lipids in cholesterol-lowering phytosterol products.

Effects of a water-soluble phytostanol ester on plasma cholesterol levels and red blood cell fragility in hamsters

The aim of this study was to assess the efficacy of a novel water-soluble phytostanol analog, disodium ascorbyl phytostanyl phosphates (DAPP), on plasma lipid levels and red blood cell fragility in hamsters fed atherogenic diets. For 5 wk, 50 male Golden Syrian hamsters were fed a semipurified diet without added cholesterol (noncholesterol, group 1), or a semipurified diet with 0.25% cholesterol (cholesterol-control, group 2). Groups 3-5 were fed the cholesterol-control diet with an addition of 1% phytostanols (diet 3), 0.71% DAPP (DAPP 0.7%, diet 4), or 1.43% DAPP (DAPP 1.4%, diet 5). Diets 4 and 5 provided 0.5 and 1% phytostanols, respectively. Supplementation of 0.71 and 1.43% DAPP decreased plasma total cholesterol concentrations by 34 (P < 0.001) and 46% (P< 0.001), respectively, in comparison with the cholesterol-control group, whereas free stanols reduced (P = 0.007) plasma cholesterol concentrations by 14%. Similarly, non-HDL-cholesterol concentrations were reduced by 39 (P < 0.001) and 54% (P < 0.001) in hamsters supplemented with DAPP 0.7% and DAPP 1.4%, respectively, relative to the cholesterol-control group. The hypocholesterolemic effect of DAPP 1.4% was threefold stronger than that of free stanols. In hamsters supplemented with DAPP 1.4%, plasma TG concentrations were 45% lower (P= 0.018) than in cholesterol-control-fed hamsters, whereas no such beneficial effect was observed in the free stanol group. Erythrocyte fragility was unaffected by DAPP or free phytostanols. Results of the current study demonstrate that DAPP lowers cholesterol more efficiently than free stanols, without an adverse effect on erythrocyte fragility in hamsters.

Effect of a new beta-sitosterol analogue on plasma lipid concentrations in rats

N-Substituted succinamic acid beta-sitosteryl ester derivatives were prepared and evaluated. Compounds 1 and 2 were prepared in 76-92% yields by the reaction of beta-sitosterol and succinic anhydride, followed by the activation of the resulting acid compound 1 by thionyl chloride or methyl chloroformate, and finally by amination with appropriate amines. Compound 2a (DANA87) was also easily obtained in one step by the direct addition of beta-sitosterol to dicyclohexylcarbodiimide (DCC) in 80% yield. Administration of the dietary compound DANA87 resulted in significant decreases in total plasma cholesterol (TC) and low-density lipoprotein (LDL) cholesterol concentrations compared with controls in a rat model. High-density lipoprotein cholesterol and plasma triglyceride levels were not affected. These findings indicate that DANA87 functions as TC and LDL cholesterol-reducing agent.

The effects of bitter melon (Momordica charantia) on serum and liver triglyceride levels in rats

Effects of three different varieties (Koimidori, Powerful-Reishi, and Hyakunari) of bitter melon (Momordica charantia) and those of methanol fraction extract of Koimidori variety on serum and liver triglycerides were studied in rats. Feeding of diets containing either bitter melon or various fractions isolated by organic solvents caused no adverse effects on food intake or growth of rats. When the effect of three different varieties of bitter melon was compared, the Koimidori variety was found to be the most effective in lowering hepatic triglyceride levels as compared to the other two varieties, suggesting a variety-dependent difference in their activity. Furthermore, the active component(s) responsible for the liver triglyceride lowering activity of Koimidori variety was assumed to be concentrated in the methanol fraction, but not in other fractions such as the n-hexane, the acetone, or the residual fraction. The triglyceride lowering activity was furthermore confirmed by the dose-dependent reduction of hepatic triglyceride, resulting the lowest level in rats fed 3.0% supplementation. In these experiments, the effects on serum lipids were marginal. The results of the present and previous studies clearly show that bitter melon, especially Koimidori variety, exhibits a potent liver triglyceride-lowering activity.

Metabolic effects of plant sterols and stanols (Review)

High serum LDL cholesterol concentration is a major risk factor for cardiovascular complications. This risk can be lowered by diet. In this respect foods containing plant sterol or stanol esters can be useful for mildly- and hypercholesteraemic subjects. Plant sterols and stanols, which are structurally related to cholesterol, decrease the incorporation of dietary and biliary cholesterol into micelles. This lowers cholesterol absorption. Furthermore, these components increase ABC-transporter expression, which may also contribute to the decreased cholesterol absorption. Consequently, cholesterol synthesis and LDL receptor activity increase, which ultimately leads to decreased serum LDL cholesterol concentrations. Animal studies have further shown that these dietary components may also lower atherosclerotic lesion development. Plant sterols and stanols also lower plasma lipid-standardized concentrations of the hydrocarbon carotenoids, but not those of the oxygenated cartenoids and tocopherols. Also, vitamin A and D concentrations are not affected. Although absorption of plant sterols and stanols (0.02-3.5%) is low compared to cholesterol (35-70%), small amounts are found in the circulation and may influence other physiological functions. However, there is no consistent evidence that plant sterols or stanols can change the risk of colon or prostate cancer, or immune status. In conclusion, plant sterols and stanols effectively reduce serum LDL cholesterol and atherosclerotic risk. In addition potential effects of plant sterols and stanols on other metabolic processes remain to be elucidated.

Subchronic toxicity of plant sterol esters administered by gavage to Sprague-Dawley rats

The purpose of this study was to investigate the potential subchronic toxicity of plant sterol esters by a 13-week repeated oral dose in Sprague-Dawley rats. The test article was administered once daily by gavage to male and female rats at dose levels of 0, 1000, 3000 and 9000 mg/kg/day for 13 weeks. At the end of treatment period, 10 rats/sex/group were sacrificed, while six rats/sex in the negative control and highest dose groups were sacrificed after a 4-week recovery period. During the test period, clinical signs, mortality, body weights, food and water consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights and histopathology were examined. Slight decreases in body weight gain were noted at lower doses but were only statistically different from the control animals in the highest dose group. In histopathological examinations, an increase in the incidence of cardiomyopathy with mononuclear cell infiltration was observed in males of the 9000 mg/kg group. Decreased body weight gain and increased incidence of cardiomyopathy observed in the highest dose group were not recovered until the end of the recovery period. There were no adverse effects on mortality, clinical signs, food and water consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, necropsy findings and organ weights in any treatment group. Based on these results, it was concluded that the 13-week repeated oral dose of plant sterol esters resulted in the suppression of body weight gains in both sexes and cardiomyopathy in males at a dose level of 9000 mg/kg/day. The target organ was determined to be heart in males, but not in females. The no-observed-adverse-effect level (NOAEL) was considered to be 3000 mg/kg/day for both sexes.

Effects of a novel hydrophilic phytostanol analog on plasma lipid concentrations in gerbils

This study was designed to determine the effects of a novel hydrophilic phytostanol analog, FM-VP4, on total plasma cholesterol, total plasma triglyceride, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol concentrations after acute oral administration to gerbils. Gerbils were administered a standard gerbil diet for 4 continuous weeks, and daily water and food intake was monitored and replaced. The diet contained either no FM-VP4 (control) or FM-VP4 at the following concentrations: 0.25, 0.50, 1.0, or 2.0% w/w; six gerbils were fed each diet formulation. After 4 weeks of receiving a single diet formulation, blood was obtained from each gerbil by cardiac puncture and the animals were sacrificed humanely. Plasma obtained from this blood was analyzed for total cholesterol, total triglyceride, and HDL cholesterol levels by standard enzymatic and precipitation techniques. LDL cholesterol levels were calculated using the Friedewald equation. Administration of dietary FM-VP4 resulted in significant decreases in total plasma cholesterol and LDL cholesterol concentrations compared with controls. Dietary FM-VP4 at concentrations of 1% and 2% (w/w) decreased total plasma cholesterol by 3.4 mmol/L compared with controls. This decrease was entirely due to the loss of cholesterol from the LDL pool because LDL cholesterol was decreased by 3.3 and 3.2 mmol/L after 1% and 2% (w/w) FM-VP4, respectively. There were no significant changes in plasma triglyceride or HDL cholesterol concentrations after the administration of FM-VP4. Animals administered 1% or 2% (w/w) FM-VP4 also had significantly lower body weight after 4 weeks of treatment compared with the other groups. However, no unusual behavior was observed in these animals. No major differences in daily water or food intake were observed throughout the study. These findings indicate that FM-VP4 decreases total and LDL cholesterol concentrations.

Injected phytosterols/stanols suppress plasma cholesterol levels in hamsters

Although plant sterols are known to suppress intestinal cholesterol absorption, whether plasma and hepatic lipid levels are influenced through non-gut related internal mechanisms has not been established. To examine this question 50 male hamsters were divided into 5 groups and fed semi-purified diets containing 20% energy as fat and 0.25% (w/w) cholesterol ad libitum for 60 days. The control group (i) received diet alone, while four additional groups consumed the diet plus one of four equivalent phytosterol mixtures (5 mg/kg/day) given either as (ii) tall oil phytosterols/stanols mixed with diet (oralSA), (iii) tall oil phytosterols/stanols subcutaneously injected (subSA), (iv) soybean oil phytosterols alone mixed with diet (oralSE), or (v) soybean oil subcutaneous injected phytosterols alone (subSE). The control group and both orally supplemented groups also received placebo subcutaneous sham injections. Neither food consumption, body weight, nor liver weight differed across treatment groups. Subcutaneous administration of SA and SE decreased plasma total cholesterol levels by 21% and 23% (p < 0.0001) and non-apolipoprotein-A cholesterol concentrations by 22% and 15% (p < 0.0002), respectively, compared to control. HDL cholesterol and TG concentrations remained unchanged across all groups, except for a decline of 25% (p < 0.0001) in HDL concentration in the subSE group versus control. Plasma campesterol levels were lower (p < 0.05) in the subSA group relative to all other groups. Plasma campesterol:cholesterol and campesterol:sitosterol ratios were, however, higher (p < 0.0001) for both the oral and subSE groups. Hepatic cholesterol levels were higher (p < 0.0001) in the oral and subSE phytosterol groups by 30% and 31%, respectively, relative to control. We conclude that low doses of subcutaneously administered plant sterols reduce circulating cholesterol levels through mechanisms other than inhibiting intestinal cholesterol absorption.

Dietary vegetable oil and wood derived plant stanol esters reduce atherosclerotic lesion size and severity in apoE*3-Leiden transgenic mice

The hypolipidemic and anti-atherosclerotic effects of vegetable oil- and wood-based dietary plant stanol esters were compared in female apoE*3-Leiden transgenic mice at relevant plasma cholesterol levels. The plant stanol esters derived from vegetable oil (sitostanol 65.7%, campestanol 30.1%) had different contents of sitostanol and campestanol than the plant stanol esters derived from wood (sitostanol 87.6%, campestanol 9.5%) or from a mixture of vegetable oil and wood (sitostanol 73.0%, campestanol 24.7%). The mice (10 per group) received for 38 weeks a control diet or diets containing 1.0% (w/w) plant stanol esters derived from either vegetable oil, wood or a mixture of both. Vegetable oil (-46%), wood (-42%) and vegetable oil/wood (-51%) plant stanol esters decreased the plasma cholesterol levels (P<0.0001) by reducing the cholesterol content in plasma very low density-, intermediate density- and to a lesser extent in low density-lipoprotein. Plant stanol ester feeding did not change plasma triglyceride levels. Dietary plant stanol esters reduced the atherosclerotic lesion area by 91+/-13% (vegetable oil), 97+/-4% (wood) and 78+/-34% (vegetable oil/wood) (P<0.0001) and the severity from regular intimal fatty streaks/mild plaques (on average type 2--3 lesions) in controls to individual intimal foam cells (<type 1 lesions) in the treatment groups (P<0.0001). Plant stanol esters had no effect on adherence of monocytes to the vessel wall. Feeding of plant stanol esters dramatically reduced, independent of its sources, the extent and severity of atherosclerotic lesions, by decreasing VLDL-, IDL- and to a lesser extent LDL-cholesterol in apoE*3-Leiden transgenic mice.

Dietary plant stanol esters reduce VLDL cholesterol secretion and bile saturation in apolipoprotein E*3-Leiden transgenic mice

Dietary plant stanols lower serum cholesterol levels in humans and in hyperlipidemic rodents, mainly by inhibition of the intestinal cholesterol absorption. We used female apolipoprotein E*3-Leiden transgenic mice to investigate the consequences of this effect on serum lipid levels and hepatic lipid metabolism. Five groups of 6 or 7 mice received for 9 weeks a diet containing 0.25% cholesterol and 0.0%, 0.25%, 0.5%, 0.75%, or 1.0% (wt/wt) plant stanols (sitostanol 88% [wt/wt], campestanol 10% [wt/wt]) esterified to fatty acids. Compared with the control diet, plant stanol ester treatment dose-dependently reduced serum cholesterol levels by 10% to 33% (P<0.05), mainly in very low density lipoproteins (VLDLs), intermediate density lipoproteins, and low density lipoproteins. Furthermore, 1.0% of the dietary plant stanols significantly decreased the liver contents of cholesteryl esters (-62%), free cholesterol (-31%), and triglycerides (-38%) but did not change the hepatic VLDL-triglyceride and VLDL-apolipoprotein B production rates. However, plant stanol ester feeding significantly decreased the amounts of cholesteryl esters and free cholesterol incorporated in nascent VLDLs by 72% and 30%, respectively, resulting in a net 2-fold decreased VLDL cholesterol output. Liver mRNA levels of low density lipoprotein receptors, 3-hydroxy-3-methylglutaryl coenzyme A synthase, cholesterol 7alpha-hydroxylase, and sterol 27-hydroxylase were not changed by plant stanol ester feeding. Nevertheless, the serum lathosterol-to-cholesterol ratio was significantly increased by 23%, indicating that dietary plant stanol esters increased whole-body cholesterol synthesis. Plant stanol esters also significantly decreased the cholesterol saturation index in bile by 55%. In conclusion, in apolipoprotein E*3-Leiden transgenic mice, plant stanol ester feeding dose-dependently lowered serum cholesterol levels as a result of a reduced secretion of VLDL cholesterol. This was caused by a decreased hepatic cholesterol content that also resulted in a lowered biliary cholesterol output, indicative of a reduced lithogenicity of bile in these mice.

Plant stanol ester margarine lowers serum total and low-density lipoprotein cholesterol concentrations of healthy children: the STRIP project. Special Turku Coronary Risk Factors Intervention Project

OBJECTIVE

To investigate cholesterol-lowering efficacy and safety of plant stanol ester margarine in healthy 6-year-old children already consuming a low-saturated-fat, low-cholesterol diet.

STUDY DESIGN

Eighty-one intervention children from the STRIP project, a randomized prospective trial aimed at reducing exposure of young children to the known environmental atherosclerosis risk factors, were recruited to this double-blind crossover study at 6 years of age. In randomized order the families were advised to replace daily 20 g of the child's dietary fat intake with plant stanol ester margarine or control margarine for 3 months. The washout period lasted 6 weeks. Statistical analysis was performed according to intention-to-treat principle with analysis of variance for crossover design.

RESULTS

The mean daily plant stanol ester margarine consumption was 18.2 g (1.5 g plant stanol). The well-tolerated plant stanol ester margarine reduced serum total and low-density lipoprotein cholesterol concentrations by 5.4% and 7.5%, respectively (P =.0001 for both). The serum high-density lipoprotein cholesterol and triglyceride concentrations and alpha-tocopherol to low-density lipoprotein cholesterol ratio remained unchanged. The serum beta-carotene to low-density lipoprotein cholesterol ratio decreased by 19% (P =.003).

CONCLUSION

Plant stanol ester margarine significantly diminishes serum total and low-density lipoprotein cholesterol concentration without adverse clinical effects in healthy children who already consume a low-saturated-fat, low-cholesterol diet but decreases the serum beta-carotene to low-density lipoprotein cholesterol ratio.

Combined effect of vegetable protein (soy) and soluble fiber added to a standard cholesterol-lowering diet

Dietary treatment of hyperlipidemia focuses on reducing saturated fat and dietary cholesterol. Other aspects of diet are not emphasized at present, despite growing evidence that a number of plant components decrease serum cholesterol. We therefore determined whether a combination of two plant components, vegetable protein and soluble fiber, further reduce serum lipids when incorporated into the currently advocated low-saturated-fat diet. Thirty-one hyperlipidemic men and women ate two 1-month low-fat (<7% of total energy from saturated fat), low-cholesterol (<80 mg cholesterol/d) metabolic diets in a randomized crossover study. The major differences between test and control diets were an increased amount of vegetable protein (93% v 23% of total protein), of which 33 g/d was soy, and a doubling of soluble fiber. Fasting blood samples were obtained at the start and end of each phase. On the last 3 days of each phase, fecal collections were obtained. Compared with the low-fat control diet, the test diet decreased total cholesterol (6.2% +/- 1.2%, P < .001), low-density lipoprotein (LDL) cholesterol (6.7% +/- 1.7%, P < .001), apolipoprotein B (8.2% +/- 1.2%, P < .001), and the ratios of LDL to high-density lipoprotein (HDL) cholesterol (6.3% +/- 2.0%, P = .004) and apolipoprotein B to A-I (5.4% +/- 1.5%, P = .001). A combination of vegetable protein and soluble fiber significantly improved the lipid-lowering effect of a low-saturated-fat diet. The results support expanding the current dietary advice to include increased vegetable protein and soluble fiber intake so that the gap in effectiveness between a good diet and drug therapy is reduced.

Dietary sitostanol reciprocally influences cholesterol absorption and biosynthesis in hamsters and rabbits

The aim of this study was to examine the efficacy of variable dietary sitostanol (SI) concentrations on cholesterol absorption, synthesis and excretion rates in two animal models. Hamsters and rabbits were fed semi-purified diets supplemented with cholesterol and 1% (w/w) phytosterols containing either 0.007, 0.17, 0.8 or 1% (w/w) SI. The control (0% (w/w) SI) groups consumed the same diets but no phytosterols were added. The dual-isotope plasma ratio of [13C]- and [18O]cholesterol and deuterium incorporation methods were applied to measure simultaneously cholesterol absorption and fractional synthesis, respectively. Plasma total cholesterol levels were lower in rabbits and hamsters fed 0.8 and 1% (w/w) SI, respectively, as compared to their controls. Percent cholesterol absorption was lower (P = 0.03) in hamsters fed 1% (w/w) SI (42.5 +/- 13.3%) than control (65.1 +/- 13.4%). Moreover, cholesterol excretion in the feces was 77 and 57% higher (P = 0.017) in the 1% (w/w) SI- relative to control- and 0.17% (w/w) SI-fed groups, respectively. In rabbits, cholesterol excretion was 64% higher (P = 0.018) in 0.8% (w/w) SI- compared with control-fed groups. Fractional synthesis rate was higher (P = 0.033) in hamsters fed 1% (w/w) SI (0.116 +/- 0.054 pool day(-1)) as compared to control (0.053 +/- 0.034 pool day(-1)). However, cholesterol synthesis rates did not vary among groups fed variable concentrations of SI. In rabbits, percent cholesterol absorption and its fractional synthesis rate varied but did not reach significance. Fractional synthesis rate in hamsters was correlated (r = -0.32, P = 0.03) with percent cholesterol absorption. In conclusion, dietary SI exhibited a dose-dependent action in inhibiting cholesterol absorption while increasing cholesterol excretion and upregulating cholesterogenesis in hamsters resulting in lower circulating lipid levels.

Short-term administration of tall oil phytosterols improves plasma lipid profiles in subjects with different cholesterol levels

To assess the short-term cholesterol-lowering potential of sitostanol-containing tall oil plant sterols, 22 subjects consumed fixed-food diets over two 10-day periods with or without 21.2 mg/kg body weight/d tall oil phytosterols (sitosterol 62%, sitostanol 21%, campesterol 16%, and campestanol 1%) in a randomized crossover study design. On day 10 of each diet, plasma lipoprotein cholesterol levels, plasma phytosterol concentrations, and cholesterol biosynthesis rates were determined. Total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels were lower (P < .01) after administration of tall oil phytosterol (4.7 +/- 0.3 and 3.0 +/- 0.3 mmol/L, respectively) versus placebo (5.0 +/- 0.3 and 3.2 +/- 0.3 mmol/L, respectively). Tall oil treatment had no effect on the plasma high-density lipoprotein (HDL) cholesterol level (1.1 +/- 0.1 mmol/L) versus placebo (1.1 +/- 0.1 mmol/L). Similarly, plasma triglyceride (TG) levels did not differ between tall oil (1.3 +/- 0.2 mmol/L) and placebo (1.4 +/- 0.2 mmol/L) treatments. Plasma campesterol (15.8 +/- 3.7 mmol/mol cholesterol) and sitosterol (6.0 +/- 2.1 mmol/mol cholesterol) levels were not different after tall oil treatment versus placebo treatment (15.4 +/- 2.3 and 6.4 +/- 2.0 mmol/mol cholesterol, respectively). Plasma sitostanol levels were essentially undetectable. No difference was observed in cholesterol biosynthesis between tall oil (0.045 +/- 0.004 pools/d) and placebo (0.034 +/- 0.004 pools/d) treatments; however, the effect of treatments in subjects with different cholesterol levels varied. In subjects with lower cholesterol values, the red blood cell cholesterol fractional synthesis rate (FSR) increased from 0.0291 +/- 0.0054 pools/d after placebo to 0.0509 +/- 0.0049 pools/d (P < .05) after phytosterol treatment. In subjects with higher cholesterol values, the red blood cell cholesterol FSR did not change significantly after treatment. These results demonstrate the short-term efficacy of tall oil plant sterols as cholesterol-lowering agents.

Dietary sitostanol reduces plaque formation but not lecithin cholesterol acyl transferase activity in rabbits

The effects of graded amounts of dietary sitostanol (0.01, 0.2 and 0.8% (w/w)) were examined on plasma lipid-profile, coronary artery plaque development and lecithin:cholesterol acyl transferase activity in male New Zealand White rabbits given semi-purified diets for 10 weeks. All diets provided < 10% energy in the form of fat and contained 0.5% (w/w) cholesterol (C). Rabbits fed the semi-purified diet with 0.8% (w/w) (0.64 g/day) sitostanol had lower plasma total cholesterol (TC) (p = 0.006) (15.2 +/- 4.80 mmol/l) and very low-density lipoprotein-cholesterol (VLDL-C) (p = 0.007) (6.31 +/- 3.11 mmol/l) levels compared to the atherogenic control group (n = 6) (29.6 +/- 5.52 and 17.16 +/- 7.43 mmol/l, respectively). Dietary sitostanol at 0.8% (w/w) depressed plaque accretion in coronary arteries (p = 0.0014) and ascending aorta (p = 0.0004) compared with the atherogenic control, 0.01 and 0.2% (w/w) sitostanol-fed groups. No differences (p = 0.24) in the activity of lecithin:cholesterol acyl transferase (LCAT) were observed across groups, although plasma cholesterol fractional esterification rate was higher (p = 0.004) in the 0.8% (w/w) sitostanol fed animals compared with the atherogenic control. Significant negative correlations were demonstrated between sitostanol intake and plasma TC, LDL-C and VLDL-C levels. Hepatic campesterol levels were correlated (r = 0.3, p = 0.03) with plasma but not hepatic TC concentrations. These results demonstrate that dietary sitostanol at a concentration of 0.8% (w/w) or 0.64 g/day lowered plasma cholesterol levels and depressed atherosclerosis development in rabbits, but did not alter LCAT activity.

Effects of variable dietary sitostanol concentrations on plasma lipid profile and phytosterol metabolism in hamsters

To examine how variable sitostanol (SI) levels in phytosterol-supplemented diets influence plasma and hepatic lipid concentrations, fifty hamsters were divided into five groups and fed semipurified diets containing 0.25% (w/w) cholesterol for 45 days ad libitum. Four groups were fed this diet with 1% (w/w) phytosterol mixtures which contained 0.01% (w/w) SI derived from soybean, 0.2% (w/w) SI derived from tall oil, 0.2% (w/w) synthetic SI mixture (SIM) and 1% (w/w) pure SI, respectively. A control group did not receive phytosterols. Dietary SI supplementation at 1% (w/w) decreased total and non-apolipoprotein-A cholesterol levels in plasma by 34% (P=0.001) and 55% (P=0.04), respectively, whereas mean plasma total cholesterol level in the 0.2% (w/w) SI group was 23% (P=0.001) lower than that of the control group. Conversely, plasma lipid profile in hamsters fed 1 or 0.2% (w/w) SI did not differ from the 0.01% (w/w) SI group. Liver weights were 15 and 20% (P=0.012) higher in the control group compared with those fed 0.01% and 1% (w/w) SI, respectively, while the hepatic cholesterol content in the control group was greater (P<0.0001) than that of all other groups. Plasma campesterol levels were higher (P=0.04) in the 0.01% and 0.2% (w/w) SI fed groups than in the control, 0.2% (w/w) SIM and 1% (w/w) SI groups. Hepatic sitosterol content was elevated (P=0.002) in the SIM fed group compared to other groups. We conclude that dietary SI effect is proportional to its concentration in phytosterol mixtures and in the diet. Dietary SI lowered plasma cholesterol levels at concentrations higher than 0.2% (w/w) in hamsters. (c) 1998 Elsevier Science B.V.

"Tall oil"-derived phytosterols reduce atherosclerosis in ApoE-deficient mice

We investigated the effects of a "tall oil"-derived phytosterol mixture (TODPM) on the formation of atherosclerotic lesions in apoE-deficient mice. TODPM was added at 2% (wt/wt) to the chow of nine mice; the control group had six animals. The diet of all animals contained 9% (wt/wt) fat and 0.15% (wt/wt) cholesterol. After 4 weeks, plasma total cholesterol levels were significantly reduced in the TODPM-treated mice (26.6 versus 42.0 mmol/L, P < .0001). The mean body weight of the TODPM-supplemented group was significantly higher at week 5 and throughout the study (29.4 versus 27.7 g, P < .05). The experiment was terminated at 18 weeks. Histological examination showed mature atherosclerotic lesions composed of foam cells underlying the endothelium, a mosaic of extracellular glycosaminoglycans, numerous apparently proliferative smooth muscle cells, and foci of cholesterol clefts in the control animals. By contrast, the TODPM-treated mice showed only early lesions containing mainly superficial foam cells. As assessed by morphometry, the lesion area in the aortic sinuses of TODPM-treated animals was less than half that of control animals (P < .0001). This reduced lesion area was accompanied by a substantial reduction in all lesional components, reflecting a delay in progression of atheromatous changes. A strong positive correlation (r = .69, P < .01) was found between plasma total cholesterol levels and lesion area in the aortic sinuses. TODPM also prevented the occurrence of xanthomatosis. We conclude that supplementation of a cholesterol-enriched diet with TODPM significantly lowers plasma cholesterol and retards development of atherosclerosis in apoE-deficient mice, suggesting a therapeutic potential for the mixture of phytosterols studied.