A simplified micro-method for quantification of fecal excretion of neutral and acidic sterols for outpatient studies in humans

Advances and Challenges in Plant Sterol Research: Fundamentals, Analysis, Applications and Production

Plant sterols (PS) are cholesterol-like terpenoids widely spread in the kingdom Plantae. Being the target of extensive research for more than a century, PS have topped with evidence of having beneficial effects in healthy subjects and applications in food, cosmetic and pharmaceutical industries. However, many gaps in several fields of PS's research still hinder their widespread practical applications. In fact, many of the mechanisms associated with PS supplementation and their health benefits are still not fully elucidated. Furthermore, compared to cholesterol data, many complex PS chemical structures still need to be fully characterized, especially in oxidized PS. On the other hand, PS molecules have also been the focus of structural modifications for applications in diverse areas, including not only the above-mentioned but also in e.g., drug delivery systems or alternative matrixes for functional foods and fats. All the identified drawbacks are also superimposed by the need of new PS sources and technologies for their isolation and purification, taking into account increased environmental and sustainability concerns. Accordingly, current and future trends in PS research warrant discussion.

A Transient Inflammatory Response Induced by Lipopolysaccharide Infusion Lowers Markers of Endogenous Cholesterol and Bile Acid Synthesis in Healthy Normocholesterolemic Young Men

Inflammation is associated with changes in plasma lipids, lipoproteins, and cholesterol efflux capacity (CEC). It is unknown if the changes in lipids and lipoproteins during inflammation are related to changes in cholesterol absorption, synthesis, and bile acid synthesis. We, therefore, examined the effects of acute lipopolysaccharide (LPS)-induced transient systemic inflammation on lipids, lipoproteins, CEC, and markers of cholesterol metabolism. We also evaluated whether markers for cholesterol metabolism at baseline predict the intensity of the inflammatory response. Eight healthy young subjects received LPS infusion, and blood was sampled for the following 24 h. In addition to lipids, lipoproteins, and CEC, we also measured markers for cholesterol absorption and synthesis, bile acid synthesis, and inflammation. Compared with baseline, plasma total cholesterol, low-density lipoprotein cholesterol, and CEC decreased, while triglycerides increased in the 24 h following LPS infusion. TC-standardized levels of cholesterol synthesis markers (lathosterol, lanosterol, and desmosterol) and a bile acid synthesis marker (7α-OH-cholesterol) also decreased, with no changes in cholesterol absorption markers (campesterol, sitosterol, and cholestanol). Baseline TC-standardized levels of desmosterol and 7α-OH-cholesterol were positively correlated with concentrations of various inflammatory markers. Changes in TC-standardized desmosterol and 7α-OH-cholesterol were negatively correlated with concentrations of inflammatory markers. LPS infusion reduced endogenous cholesterol synthesis and bile acid synthesis in healthy young men.

Serum Low Density Lipoprotein Cholesterol Concentration Is Not Dependent on Cholesterol Synthesis and Absorption in Healthy Humans

Introduction. Pharmacological reduction of cholesterol (C) synthesis and C absorption lowers serum low-density lipoprotein C (LDL-C) concentrations. We questioned whether high baseline C synthesis or C absorption translates into high serum LDL-C concentrations or if there was no connection. Therefore, we studied the association between serum LDL-C and C synthesis or C absorption in healthy subjects. Methods. Three published data sets of young subjects on different diets (study 1), mildly hypercholesterolemic subjects without cardiovascular disease (study 2) and healthy controls of the Framingham study (study 3) were used. The three study populations varied in sex, age, and weight. C synthesis and C fractional absorption rate (FAR) were measured with fecal sterol balance and stable isotope techniques (studies 1 and 2). Additionally, serum lathosterol and campesterol concentrations corrected for the serum total C concentration (R_lathosterol and R_campesterol) were used as markers for hepatic C synthesis and C FAR, respectively (studies 1−3). Linear regression analysis was applied to evaluate associations between LDL-C, C synthesis, and C absorption. Results. Seventy-three, 37, and 175 subjects were included in studies 1, 2, and 3, respectively. No statistically significant associations were found between LDL-C and the measured C synthesis and C FAR, nor for R_lathosterol and R_campesterol in any of the study groups. This lack of associations was confirmed by comparing the male subjects of studies 1 and 2. Study 1 subjects had a 50% lower serum LDL-C than the study 2 subjects (p < 0.01), but not a lower C synthesis, C FAR, R-lathosterol, or R_campesterol. Conclusions. Under physiological conditions, C synthesis and C FAR are not major determinants of circulating serum LDL-C concentrations in healthy subjects. The results need to be confirmed in large-scale studies in healthy subjects and patients at risk for cardiovascular disease.

Cholesterol-lowering activity of protocatechuic acid is mediated by increasing the excretion of bile acids and modulating gut microbiota and producing short-chain fatty acids

The present study aimed to investigate the effects of protocatechuic acid (PCA) on plasma lipid profiles and associated mechanisms with a focus on reshaping gut microbiota. Twenty-four male hamsters were randomly divided into three groups receiving a high-cholesterol diet (HCD) and two HCD diets containing 0.5% (PL) and 1% (PH) PCA, respectively. Feeding PL and PH diets for six weeks significantly reduced plasma total cholesterol by 18% and 24%, respectively. PL and PH diets also significantly lowered plasma non-HDL cholesterol by 37% and 44%, respectively. This was accompanied by an increase in fecal short-chain fatty acids (SCFAs) and fecal bile acids with up-regulation on gene of cholesterol 7α-hydroxylase and down-regulation of 3-hydroxy-3-methylglutaryl-CoA reductase in the liver. Dietary PCA supplementation decreased hepatic lipid accumulation, whereas it increased fecal excretion of lipids. The 16S rRNA analysis found that dietary PCA significantly reduced the ratio of Firmicutes to Bacteroidetes and increased the relative abundance of Bacteroidales S24-7, whereas it reduced the abundance of Lactobacillaceae. It was concluded that dietary PCA favorably modulated plasma lipid profiles and prevented the accumulation of hepatic cholesterol and lipid disposition. Such effect was mediated at least partially by increasing gut production of SCFAs and fecal excretion of bile acids via modulating the gut microbiome.

Inhibition of Extracellular Cathepsin D Reduces Hepatic Lipid Accumulation and Leads to Mild Changes in Inflammationin NASH Mice

Background & Aims

The lysosomal enzyme, cathepsin D (CTSD) has been implicated in the pathogenesis of non-alcoholic steatohepatitis (NASH), a disease characterised by hepatic steatosis and inflammation. We have previously demonstrated that specific inhibition of the extracellular CTSD leads to improved metabolic features in Sprague-Dawley rats with steatosis. However, the individual roles of extracellular and intracellular CTSD in NASH are not yet known. In the current study, we evaluated the underlying mechanisms of extracellular and intracellular CTSD fractions in NASH-related metabolic inflammation using specific small-molecule inhibitors.

Methods

Low-density lipoprotein receptor knock out (Ldlr-/-) mice were fed a high-fat, high cholesterol (HFC) diet for ten weeks to induce NASH. Further, to investigate the effects of CTSD inhibition, mice were injected either with an intracellular (GA-12) or extracellular (CTD-002) CTSD inhibitor or vehicle control at doses of 50 mg/kg body weight subcutaneously once in two days for ten weeks.

Results

Ldlr-/- mice treated with extracellular CTSD inhibitor showed reduced hepatic lipid accumulation and an associated increase in faecal bile acid levels as compared to intracellular CTSD inhibitor-treated mice. Furthermore, in contrast to intracellular CTSD inhibition, extracellular CTSD inhibition switched the systemic immune status of the mice to an anti-inflammatory profile. In line, label-free mass spectrometry-based proteomics revealed that extra- and intracellular CTSD fractions modulate proteins belonging to distinct metabolic pathways.

Conclusion

We have provided clinically translatable evidence that extracellular CTSD inhibition shows some beneficial metabolic and systemic inflammatory effects which are distinct from intracellular CTSD inhibition. Considering that intracellular CTSD inhibition is involved in essential physiological processes, specific inhibitors capable of blocking extracellular CTSD activity, can be promising and safe NASH drugs.

Vinegars but not acetic acid are effective in reducing plasma cholesterol in hamsters fed a high-cholesterol diet

The present study compares the effect of two types of vinegars, Balsamic vinegar of Modena (BV) and Chinese Shanxi vinegar (SV), with acetic acid on plasma cholesterol using hamsters as a model. Hamsters (n = 40) were divided into five groups (n = 8 each) with two control groups being fed a low-cholesterol diet (LCD) or a high-cholesterol diet containing 0.2% cholesterol (HCD). The three experimental groups were given a HCD diet and gavaged with 8 ml of BV, SV, and acetic acid solution (AC) per kg body weight, respectively. Acetic acid in BV, SV, and AC solutions was adjusted with water to be 20 mg ml-1. The whole experiment lasted for 9 weeks. Plasma total cholesterol (TC) in BV and SV groups but not in the AC group was reduced by 17% and 20%, respectively, compared with that in HCD hamsters. BV and SV significantly reduced cholesterol in the liver and increased the fecal excretion of neutral sterols and bile acids. Real-time PCR analysis demonstrated that BV and SV significantly up-regulated the mRNA of cholesterol 7 alpha-hydroxylase (CYP7A1) in the liver. In conclusion, BV and SV but not AC were effective in reducing plasma TC and non-HDL-C concentrations at least in hypercholesterolemic hamsters.

In Vitro and In Vivo Digestibility of Soybean, Fish, and Microalgal Oils, and Their Influences on Fatty Acid Distribution in Tissue Lipid of Mice

The digestion rates of microalgal (docosahexaenoic acid, DHA, 56.8%; palmitic acid, 22.4%), fish (DHA, 10.8%; eicosapentaenoic acid, EPA, 16.2%), and soybean oils (oleic, 21.7%; linoleic acid, 54.6%) were compared by coupling the in vitro multi-step and in vivo apparent digestion models using mice. The in vitro digestion rate estimated based on the released free fatty acids content was remarkably higher in soybean and fish oils than in microalgal oil in 30 min; however, microalgal and fish oils had similar digestion rates at longer digestion. The in vivo digestibility of microalgal oil (91.49%) was lower than those of soybean (96.50%) and fish oils (96.99%). Among the constituent fatty acids of the diet oils, docosapentaenoic acid (DPA) exhibited the highest digestibility, followed by EPA, DHA, palmitoleic, oleic, palmitic, and stearic acid, demonstrating increased digestibility with reduced chain length and increased unsaturation degree of fatty acid. The diet oils affected the deposition of fatty acids in mouse tissues, and DHA concentrations were high in epididymal fat, liver, and brain of mice fed microalgal oil. In the present study, microalgal oil showed lower in vitro and in vivo digestibility, despite adequate DHA incorporation into major mouse organs, such as the brain and liver.

Dietary calcium affects body composition and lipid metabolism in rats

Calcium (Ca) intakes may affect cardiovascular disease risk by altering body composition (body weight and fat) and serum lipid profile, but results have been inconsistent and the underlying mechanisms are not well understood. The effects of dietary Ca on body composition and lipid metabolism were examined in rats. Male Sprague-Dawley rats were fed high-fat, high-energy diets containing (g/kg) low (0.75Ca, 0.86 ± 0.05; 2Ca, 2.26 ± 0.02), normal (5Ca, 5.55 ± 0.08) or high (10Ca, 11.03 ± 0.17; 20Ca, 21.79 ± 0.15) Ca for 10 weeks. Rats fed the lowest Ca diet (0.75Ca) had lower (p < 0.05) body weight and fat mass compared to other groups. Rats fed the high Ca diets had lower serum total and LDL cholesterol compared to rats fed normal or low Ca. Liver total cholesterol was lower in rats fed high compared to low Ca. In general, liver mRNA expression of genes involved in cholesterol uptake from the circulation (Ldlr), cholesterol synthesis (Hmgcr and Hmgcs1), fatty acid oxidation (Cpt2) and cholesterol esterification (Acat2) were higher in rats fed higher Ca. Apparent digestibility of total trans, saturated, monounsaturated and polyunsaturated fatty acids was lower in rats fed the high compared to the low Ca diets, with the largest effects seen on trans and saturated fatty acids. Fecal excretion of cholesterol and total bile acids was highest in rats fed the highest Ca diet (20Ca). The results suggest little effect of dietary Ca on body composition unless Ca intakes are very low. Decreased bile acid reabsorption and reduced absorption of neutral sterols and saturated and trans fatty acids may contribute to the better serum lipid profile in rats fed higher Ca.

Cholesterol Absorption and Synthesis in Vegetarians and Omnivores

SCOPE

Vegetarian diets are considered health-promoting; however, a plasma cholesterol lowering effect is not always observed. We investigate the link between vegetarian-diet-induced alterations in cholesterol metabolism.

METHODS AND RESULTS

We study male and female omnivores, lacto-ovo vegetarians, lacto vegetarians, and vegans. Cholesterol intake, absorption, and fecal sterol excretion are measured as well as plasma concentrations of cholesterol and noncholesterol sterols. These serve as markers for cholesterol absorption, synthesis, and catabolism. The biliary cholesterol secretion rate is estimated. Flux data are related to body weight. Individual vegetarian diet groups are statistically compared to the omnivore group. Lacto vegetarians absorb 44% less dietary cholesterol, synthesized 22% more cholesterol, and show no differences in plasma total and LDL cholesterol. Vegan subjects absorb 90% less dietary cholesterol, synthesized 35% more cholesterol, and have a similar plasma total cholesterol, but a 13% lower plasma LDL cholesterol. No diet-related differences in biliary cholesterol secretion and absorption are observed. Total cholesterol absorption is lower only in vegans. Total cholesterol input is similar under all vegetarian diets.

CONCLUSIONS

Unaltered biliary cholesterol secretion and higher cholesterol synthesis blunt the lowered dietary cholesterol intake in vegetarians. LDL cholesterol is significantly lower only in vegans.

The value of surrogate markers to monitor cholesterol absorption, synthesis and bioconversion to bile acids under lipid lowering therapies

INTRODUCTION

Regulation of cholesterol (Chol) homeostasis is controlled by three main fluxes, i.e. intestinal absorption, de novo synthesis (ChS) and catabolism, predominantly as bile acid synthesis (BAS). High serum total Chol and LDL-Chol concentrations in particular are considered risk factors and markers for the development of atherosclerosis. Pharmaceutical treatments to lower serum Chol have focused on reducing absorption or ChS and increasing BAS. Monitoring of these three parameters is complex involving isotope techniques, cholesterol balance experiments and advanced mass spectrometry based analysis methods. Surrogate markers were explored that require only one single fasting blood sample collection. These markers were validated in specific, mostly physiological conditions and during statin treatment to inhibit ChS. They were also applied under cholesterol absorption restriction, but were not validated in this condition. We retrospectively evaluated the use of serum campesterol (Camp), sitosterol (Sit) and cholestanol (Cholol) as markers for cholesterol absorption, lathosterol (Lath) as marker for ChS and 7α-hydroxycholesterol (7α-OH-Ch) and 27-hydroxycholesterol (27-OH-Ch) as markers for BAS under conditions of Chol absorption restriction. Additionally, their values were corrected for Chol concentration (R_sterol or oxysterols).

METHODS

Thirty-seven healthy male omnivore subjects were studied under treatments with placebo (PLAC), ezetimibe (EZE) to inhibit cholesterol absorption, simvastatin (SIMVA) to reduce cholesterol synthesis and a combination of both (EZE+SIMVA). Results were compared to those obtained in 18 pure vegetarian subjects (vegans) whose dietary Chol intake is extremely low. Relative or fractional Chol absorption (FrChA) was measured with the continuous feeding stable isotope procedure, ChS and BAS with the cholesterol balance method. The daily Chol intake (DICh) was inventoried and the daily Chol absorption (DACh) calculated.

RESULTS

Monitoring cholesterol absorption, R_Camp, R_Sit and R_Cholol responded sensitively to changes in FrChA. R_Camp correlated well with FrChA in all omnivore treatment groups and in the vegan group. R_Camp confirmed reduced FrChA under EZE treatment and reduced DACh in the vegan subjects. R_Sit and R_Cholol did not accurately reflect FrChA or DACh in all situations. Monitoring endogenous cholesterol synthesis, R_Lath correlated with ChS in the vegan group, but in none of the omnivore treatment groups. R_Lath confirmed increased ChS under EZE treatment and was reduced under SIMVA treatment, while ChS was not. An increased ChS under EZE+SIMVA treatment could not be confirmed with R_Lath. R_Lath responded very insensitively to a change in ChS. Monitoring BAS, R_7α-OH-Ch but not R_27-OH-Ch correlated with BAS during PLAC, EZE and SIMVA treatments. In line with BAS, R_7α-OH-Ch did not differ in any of the omnivore treatment groups. R_7α-OH-Ch responded insensitively to a change in BAS.

CONCLUSIONS

Under Chol absorption restriction, serum R_Camp is a sensitive and valid marker to monitor FrChA in a population with a normal DICh. Also, major changes in DACh can be detected in vegans. Serum R_Lath does not reflect ChS measured with the cholesterol balance method during EZE treatment. This result initiates the question whether the measured ChS reflects pure de novo synthesis. Serum R_7α-OH-Ch appears to be a valid but insensitive marker for BAS.

Chemically induced mouse liver tumors are resistant to treatment with atorvastatin

Background

Atorvastatin is a potent inhibitor of the mevalonate pathway and widely used as a hypolipidemic drug. Some epidemiological studies and animal experiments indicate that the long-term use of atorvastatin and structurally related drugs might be associated with a reduced risk of developing hepatocellular carcinoma (HCC), the most common hepatocellular malignancy in humans. However, the potential of atorvastatin to inhibit HCC formation is controversially discussed.

Methods

Hepatocellular tumors were chemically induced by treatment of C3H/He mice with 10 μg/g body weight N-nitrosodiethylamine and the ability of atorvastatin to interfere with tumor formation was investigated by treatment of mice with 0.1% atorvastatin in the diet for 6 months. Tumor size and tumor multiplicity were analyzed, as were tissue levels of cholesterol and atorvastatin.

Results

Atorvastatin treatment efficiently reduced serum cholesterol levels. However, the growth of tumors driven by activated MAPK (mitogen-activated protein kinase) signaling was not attenuated by the presence of the drug, as evidenced by a lack of reduction of tumor volume or tumor multiplicity by atorvastatin. Levels of the atorvastatin uptake transporters Oatp1a4 and Oatp1b2 were down-regulated at the mRNA and protein levels in chemically induced mouse liver tumors, but without striking effects on atorvastatin concentrations in the tumor tissue.

Conclusion

In summary, the present data provide substantial evidence that atorvastatin does not beneficially influence tumor growth in mouse liver and thereby challenge the hypothesis that statin use might protect against hepatocellular cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-766) contains supplementary material, which is available to authorized users.

Probiotics L. plantarum and L. curvatus in combination alter hepatic lipid metabolism and suppress diet-induced obesity

OBJECTIVE

To determine the effects of naturally derived probiotic strains individually or combination on a short-term diet-induced obesity model.

DESIGN AND METHODS

C57BL/6J mice (n = 50) were randomly divided into five groups, then fed a high-fat high-cholesterol diet (HFCD), HFCD and Lactobacillus plantarum KY1032 (PL, 10(10) cfu/day), HFCD and Lactobacillus curvatus HY7601 (CU, 10(10) cfu/day), HFCD and in combination with PL+CU (10(10) cfu/day), or a normal diet (ND) for 9 weeks.

RESULTS

PL and CU showed distinct and shared metabolic activity against a panel of 50 carbohydrates. Fat accumulation in adipose tissue and liver was significantly reduced by probiotic strains CU or PL+CU. Probiotic strains CU or PL+CU reduced cholesterol in plasma and liver, while PL+CL had a synergistic effect on hepatic triglycerides. Probiotic strains PL+CU combination was more effective for inhibiting gene expressions of various fatty acid synthesis enzymes in the liver, concomitant with decreases in fatty acid oxidation-related enzyme activities and their gene expressions.

CONCLUSIONS

Multi-strain probiotics may prove more beneficial than single-strain probiotics to combat fat accumulation and metabolic alterations in diet-induced obesity.

Measurement of reverse cholesterol transport pathways in humans: in vivo rates of free cholesterol efflux, esterification, and excretion

BACKGROUND

Reverse cholesterol transport from peripheral tissues is considered the principal atheroprotective mechanism of high-density lipoprotein, but quantifying reverse cholesterol transport in humans in vivo remains a challenge. We describe here a method for measuring flux of cholesterol though 3 primary components of the reverse cholesterol transport pathway in vivo in humans: tissue free cholesterol (FC) efflux, esterification of FC in plasma, and fecal sterol excretion of plasma-derived FC.

METHODS AND RESULTS

A constant infusion of [2,3-(13)C(2)]-cholesterol was administered to healthy volunteers. Three-compartment SAAM II (Simulation, Analysis, and Modeling software; SAAM Institute, University of Washington, WA) fits were applied to plasma FC, red blood cell FC, and plasma cholesterol ester (13)C-enrichment profiles. Fecal sterol excretion of plasma-derived FC was quantified from fractional recovery of intravenous [2,3-(13)C(2)]-cholesterol in feces over 7 days. We examined the key assumptions of the method and evaluated the optimal clinical protocol and approach to data analysis and modeling. A total of 17 subjects from 2 study sites (n=12 from first site, age 21 to 75 years, 2 women; n=5 from second site, age 18 to 70 years, 2 women) were studied. Tissue FC efflux was 3.79±0.88 mg/kg per hour (mean ± standard deviation), or ≍8 g/d. Red blood cell-derived flux into plasma FC was 3.38±1.10 mg/kg per hour. Esterification of plasma FC was ≍28% of tissue FC efflux (1.10±0.38 mg/kg per hour). Recoveries were 7% and 12% of administered [2,3-(13)C(2)]-cholesterol in fecal bile acids and neutral sterols, respectively.

CONCLUSIONS

Three components of systemic reverse cholesterol transport can be quantified, allowing dissection of this important function of high-density lipoprotein in vivo. Effects of lipoproteins, genetic mutations, lifestyle changes, and drugs on these components can be assessed in humans. (J Am Heart Assoc. 2012;1:e001826 doi: 10.1161/JAHA.112.001826.).

Experimental models for the investigation of high-density lipoprotein-mediated cholesterol efflux

Reduction of low-density lipoprotein cholesterol by statin therapy has only modestly decreased coronary heart disease (CHD)-associated mortality in developed countries, which has prompted the search for alternative therapeutic strategies for CHD. Epidemiologic and interventional studies have clearly established an inverse association between plasma levels of high-density lipoprotein (HDL) cholesterol and incidence of atherosclerosis. The atheroprotective benefits of HDL are not only dependent on HDL concentrations (quantity), but also on HDL function (quality). Therefore, several techniques have been recently developed to assess the different properties of HDL. Because reverse cholesterol transport (RCT) is considered a key player in the beneficial action of HDL, this review focuses on the different methods used to evaluate cholesterol efflux. Measuring the in vivo function of HDL could be of significant importance for both the clinical evaluation of an individual patient and to evaluate the effectiveness of different RCT-enhancing therapeutic approaches.

Combined effects of ezetimibe and phytosterols on cholesterol metabolism: a randomized, controlled feeding study in humans

BACKGROUND

Both ezetimibe and phytosterols inhibit cholesterol absorption. We tested the hypothesis that the combination of ezetimibe and phytosterols is more effective than ezetimibe alone in altering cholesterol metabolism.

METHODS AND RESULTS

Twenty-one mildly hypercholesterolemic subjects completed a randomized, double-blind, placebo-controlled, triple-crossover study. Each subject received a phytosterol-controlled diet plus (1) ezetimibe placebo+phytosterol placebo, (2) 10 mg/d ezetimibe+phytosterol placebo, and (3) 10 mg/d ezetimibe+2.5 g phytosterols for 3 weeks each. All meals were prepared in a metabolic kitchen. Primary outcomes were intestinal cholesterol absorption, fecal cholesterol excretion, and low-density lipoprotein cholesterol levels. The combined treatment resulted in significantly lower intestinal cholesterol absorption (598 mg/d; 95% confidence interval [CI], 368 to 828) relative to control (2161 mg/d; 95% CI, 1112 to 3209) and ezetimibe alone (1054 mg/d; 95% CI, 546 to 1561; both P<0.0001). Fecal cholesterol excretion was significantly greater (P<0.0001) with combined treatment (962 mg/d; 95% CI, 757 to 1168) relative to control (505 mg/d; 95% CI, 386 to 625) and ezetimibe alone (794 mg/d; 95% CI, 615 to 973). Plasma low-density lipoprotein cholesterol values during treatment with control, ezetimibe alone, and ezetimibe+phytosterols averaged 129 mg/dL (95% CI, 116 to 142), 108 mg/dL (95% CI, 97 to 119), and 101 mg/dL (95% CI, 90 to 112; (P<0.0001 relative to control).

CONCLUSION

The addition of phytosterols to ezetimibe significantly enhanced the effects of ezetimibe on whole-body cholesterol metabolism and plasma low-density lipoprotein cholesterol. The large cumulative action of combined dietary and pharmacological treatment on cholesterol metabolism emphasizes the potential importance of dietary phytosterols as adjunctive therapy for the treatment of hypercholesterolemia.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00863265.

Effects of konjac glucomannan on putative risk factors for colon carcinogenesis in rats fed a high-fat diet

The aim of this study was to determine effects of konjac glucomannan (KGM) in a high fat corn oil diet on risk factors of colon carcinogenesis, that is, fecal β-glucuronidase, mucinase, and bile acids, and on preventive factors, that is, fecal microflora and cecal short-chain fatty acids (SCFAs). Sprague-Dawley rats (n = 8 animals per group) were fed a normal-fat fiber-free (5% corn oil, w/w) or high-fat (25% corn oil, w/w) diet containing no fiber, KGM (5%, w/w), or inulin (5%, w/w, as a prebiotic control) for 4 weeks. Results indicated that the high-fat fiber-free diet significantly elevated the fecal β-glucuronidase and mucinase activities and total bile acid concentration and decreased cecal SCFA contents, as compared with its normal-fat counterpart. The incorporation of KGM, as well as inulin, into the high-fat fiber-free diet beneficially reduced the fecal β-glucuronidase and mucinase activities and lithocholic acid (secondary bile acid) concentration. Although KGM elevated the daily fecal total bile acid excretion, the change was due to the primary, instead of the secondary, bile acids. In addition, KGM beneficially promoted the daily fecal excretion of bifidobacteria and lactobacilli and cecal SCFA contents, as compared with the high-fat fiber-free diet. Therefore, the present study suggests that KGM potentially attenuated the high fat-induced risk in colon carcinogenesis.

Ameliorative effects of konjac glucomannan on human faecal β-glucuronidase activity, secondary bile acid levels and faecal water toxicity towards Caco-2 cells

Konjac glucomannan (KGM) has been shown to increase human colon microbial ecology and reduce faecal toxicity in mice. The main goal of the present study was to assess the effects of a KGM supplement into a low-fibre diet on precancerous markers of colon cancer in a double-blind, placebo- and diet-controlled study. Adult volunteers consumed defined diets supplemented with konjac (4·5 g/d) or placebo (maize starch) for 4 weeks. Stools collected before and at the end of the supplementation were analysed for β-glucosidase, β-galactosidase and β-glucuronidase activities, microflora and bile acids. Faecal water was co-incubated with Caco-2 cells, a model of human colonocytes, to determine the cytotoxicity and DNA-damaging effect as assessed by the comet assay. The results indicated that the KGM supplement significantly decreased faecal β-glucuronidase activity by 25·6 (se 7·8) % and faecal secondary bile acid level by 42·4 (se 11·8) %. In contrast, consuming the defined diet supplemented with placebo for 4 weeks did not improve these determinants. The KGM-supplemented diet, but not the placebo diet, significantly increased the survival rate (%) of Caco-2 cells co-incubated with faecal water for 1 and 3 h, respectively. In addition, KGM significantly reduced the DNA damage induced by the faecal water alone or in combination with H2O2. The faecal bifidobacteria and lactobacilli levels increased only with the KGM-supplemented diet. Therefore, we conclude that supplementation of KGM into a low-fibre diet improved the faecal microbial ecology and metabolites, which may contribute to the reduced toxicity of faecal water and precancerous risk factors of human colon cancer.

Future therapeutic directions in reverse cholesterol transport

Despite a robust inverse association between high-density lipoprotein (HDL) cholesterol levels and atherosclerotic cardiovascular disease, the development of new therapies based on pharmacologic enhancement of HDL metabolism has proven challenging. Emerging evidence suggests that static measurement of HDL levels has inherent limitations as a surrogate for overall HDL functionality, particularly with regard to the rate of flux through the macrophage reverse cholesterol transport (RCT) pathway. Recent research has provided important insight into the molecular underpinnings of RCT, the process by which excess cellular cholesterol is effluxed from peripheral tissues and returned to the liver for ultimate intestinal excretion. This review discusses the critical importance and current strategies for quantifying RCT flux. It also highlights therapeutic strategies for augmenting macrophage RCT via three conceptual approaches: 1) improved efflux of cellular cholesterol via targeting the macrophage; 2) enhanced cholesterol efflux acceptor functionality of circulating HDL; and 3) increased hepatic uptake and biliary/intestinal excretion.

Comparative effects of cellulose and soluble fibers (pectin, konjac glucomannan, inulin) on fecal water toxicity toward Caco-2 cells, fecal bacteria enzymes, bile acid, and short-chain fatty acids

The aim of this study was to compare the effects of cellulose and three soluble dietary fibers, pectin, konjac glucomannan (KGM), and inulin, on the cytotoxicity and DNA damage of fecal water-treated Caco-2 cells, a human colon adenocarcinoma cell line, and to investigate the fecal components that potentially modulate the fecal toxicity, that is, bacterial enzymes, bile acids, and short-chain fatty acids. Six-week-old BALB/cJ mice were randomly allocated to consume an AIN-93 diet that contained no dietary fiber (fiber-free) or 5% (w/w) cellulose, pectin, KGM, and inulin for 3 weeks. Feces were collected during days 18-21. Fecal waters were co-incubated with Caco-2 cells to determine the cytotoxicity and DNA damage. In addition, the fecal bacterial enzymes, bile acids, and short-chain fatty acids were determined. Results indicated that all fiber diets similarly increased the survival rate (%) of fecal water-treated Caco-2 cells as compared with the fiber-free diet. The inhibition of fecal water-induced DNA damage in Caco-2 cells was greater for the pectin and inulin diets than for the cellulose and KGM diets. In contrast, cellulose exerted the greatest inhibitory effect on the fecal β-glucuronidase activity. Cellulose and all soluble dietary fibers reduced the secondary bile acid concentrations in the fecal water, but only soluble fibers increased the fecal concentrations of short-chain fatty acids, as compared with no fiber. Therefore, this study suggests that all dietary fibers substantially reduced the fecal water toxicity, which is associated with decreased secondary bile acid levels by all fibers, reduced fecal β-glucuronidase activity by cellulose, and increased short-chain fatty acid levels by soluble dietary fibers.

Fecal bile acid excretion and messenger RNA expression levels of ileal transporters in high risk gallstone patients

BACKGROUND

Cholesterol gallstone disease (GS) is highly prevalent among Hispanics and American Indians. In GS, the pool of bile acids (BA) is decreased, suggesting that BA absorption is impaired. In Caucasian GS patients, mRNA levels for ileal BA transporters are decreased. We aimed to determine fecal BA excretion rates, mRNA levels for ileal BA transporter genes and of regulatory genes of BA synthesis in Hispanic GS patients.

RESULTS

Excretion of fecal BA was measured in seven GS females and in ten GS-free individuals, all with a body mass index < 29. Participants ingested the stool marker Cr2O3 (300 mg/day) for 10 days, and fecal specimens were collected on the last 3 days. Chromium was measured by a colorimetric method, and BA was quantitated by gas chromatography/mass spectroscopy. Intake of calories, nutrients, fiber and cholesterol were similar in the GS and GS-free subjects. Mean BA excretion levels were 520 +/- 80 mg/day for the GS-free group, and 461 +/- 105 mg/day for the GS group. Messenger RNA expression levels were determined by RT-PCR on biopsy samples obtained from ileum during diagnostic colonoscopy (14 GS-free controls and 16 GS patients) and from liver during surgery performed at 8 and 10 AM (12 GS and 10 GS-free patients operated on for gastrointestinal malignancies), all with a body mass index < 29. Messenger RNA level of the BA transporter genes for ileal lipid binding protein, multidrug resistance-associated protein 3, organic solute transporter alpha, and organic solute transporter beta were similar in GS and GS-free subjects. Messenger RNA level of Cyp27A1, encoding the enzyme 27alpha-hydroxylase, the short heterodimer partner and farnesoid X receptor remained unchanged, whereas the mRNA level of Cyp7A1, the rate limiting step of BA synthesis, was increased more than 400% (p < 0.01) in the liver of GS compared to GS-free subjects.

CONCLUSION

Hispanics with GS have fecal BA excretion rates and mRNA levels of genes for ileal BA transporters that are similar to GS-free subjects. However, mRNA expression levels of Cyp7A1 are increased in GS, indicating that regulation of BA synthesis is abnormal in Hispanics with GS.

Changes in cholesterol absorption and cholesterol synthesis caused by ezetimibe and/or simvastatin in men

This study evaluates changes in cholesterol balance in hypercholesterolemic subjects following treatment with an inhibitor of cholesterol absorption or cholesterol synthesis or coadministration of both agents. This was a randomized, double blind, placebo-controlled, four-period crossover study to evaluate the effects of coadministering 10 mg ezetimibe with 20 mg simvastatin (ezetimibe/simvastatin) on cholesterol absorption and synthesis relative to either drug alone or placebo in 41 subjects. Each treatment period lasted 7 weeks. Ezetimibe and ezetimibe/simvastatin decreased fractional cholesterol absorption by 65% and 59%, respectively (P < 0.001 for both relative to placebo). Simvastatin did not significantly affect cholesterol absorption. Ezetimibe and ezetimibe/simvastatin increased fecal sterol excretion (corrected for dietary cholesterol), which also represents net steady state cholesterol synthesis, by 109% and 79%, respectively (P < 0.001). Ezetimibe, simvastatin, and ezetimibe/simvastatin decreased plasma LDL-cholesterol by 20, 38, and 55%, respectively. The coadministered therapy was well tolerated. The decreases in net cholesterol synthesis and increased fecal sterol excretion yielded nearly additive reductions in LDL-cholesterol for the coadministration of ezetimibe and simvastatin.

Beyond high-density lipoprotein cholesterol levels evaluating high-density lipoprotein function as influenced by novel therapeutic approaches

A number of therapeutic strategies targeting high-density lipoprotein (HDL) cholesterol and reverse cholesterol transport are being developed to halt the progression of atherosclerosis or even induce regression. However, circulating HDL cholesterol levels alone represent an inadequate measure of therapeutic efficacy. Evaluation of the potential effects of HDL-targeted interventions on atherosclerosis requires reliable assays of HDL function and surrogate markers of efficacy. Promotion of macrophage cholesterol efflux and reverse cholesterol transport is thought to be one of the most important mechanisms by which HDL protects against atherosclerosis, and methods to assess this pathway in vivo are being developed. Indexes of monocyte chemotaxis, endothelial inflammation, oxidation, nitric oxide production, and thrombosis reveal other dimensions of HDL functionality. Robust, reproducible assays that can be performed widely are needed to move this field forward and permit effective assessment of the therapeutic potential of HDL-targeted therapies.

Effect of orlistat on fecal fat, fecal biliary acids, and colonic cell proliferation in obese subjects

BACKGROUND & AIMS

Orlistat is a weight management agent that selectively inhibits gastrointestinal lipase activity. Because of orlistat's mode of action, increased fecal fat is presented to the colonic mucosa, and fecal bile acid and free fatty acid composition may be altered during treatment. Our aim was to assess the effect of treatment of obese subjects with orlistat 120 mg 3 times a day for 6 weeks on fecal lipid and bile acid parameters and colonic mucosal cell proliferation.

METHODS

Twenty-four obese (body mass index, 30-40 kg/m2) but otherwise healthy male and female subjects were enrolled in a single-center, randomized, double-blind, placebo-controlled, parallel-group study. Participants were hospitalized during days 1-3 and 33-42 of treatment and were treated as outpatients for the remaining days.

RESULTS

Treatment with orlistat for 6 weeks resulted in significantly greater increases in fecal weight, total fecal fat, and fecal free fatty acids than placebo. Total fecal bile acid amounts decreased slightly with orlistat, and increased significantly with placebo treatment (P < .05 between-group difference). Orlistat did not alter colonic cell proliferation as assessed by the 3 proliferative indices (5-bromo-2-deoxyuridine, whole crypt mitotic count, and proliferating cell nuclear antigen).

CONCLUSIONS

Biochemical changes in fecal composition related to the pharmacodynamic mode of action of orlistat are not accompanied by altered colonic cell proliferation, a putative biomarker of colon cancer risk.

Hypocholesterolemic and antioxidant properties of 3-(4-hydroxyl)propanoic acid derivatives in high-cholesterol fed rats

The purpose of the present study was to evaluate the in vivo efficacy of two cinnamic acid synthetic derivatives (allyl 3-[4-hydroxyphenyl]propanoate; HPP304, 1-naphthyl-methyl 3-[4-hydroxyphenyl]propanoate; HPP305) in high-cholesterol fed rats and compare their actions to that of cinnamic acid. Cinnamic acid and its synthetic derivatives were supplemented with a high-cholesterol diet for 42 days at a dose of 0.135 mmol/100g of diet. The supplementation of HPP304 and HPP305 significantly lowered cholesterol and triglyceride levels in the plasma and liver with a simultaneous increase in the HDL-cholesterol concentration, whereas cinnamic acid only lowered the plasma cholesterol concentration. Cinnamic acid lowered hepatic HMG-CoA reductase activity in high-cholesterol fed rats, however, its synthetic derivatives (HPP304 and HPP305) did not affect HMG-CoA reductase activity compared to the control group. Instead, the HPP304 and HPP305 supplements significantly lowered hepatic acyl coenzyme A:cholesterol acyltransferase activity and increased the fecal bile acid. The SOD activity of the erythrocytes and liver was not different between the groups, however, the activities of CAT and GSH-Px, and the level of GSH in the erythrocytes were significantly higher in the HPP304 and HPP305 groups than in the control group. On the other hand, the activities of CAT and GSH-Px, and the level of malondialdehyde in the liver were significantly lower in the HPP304 and HPP305 groups. The antioxidant activities of these cinnamic acid synthetic derivatives were similar to the cinnamic acid in the high-cholesterol fed rats. In addition, HPP304 and HPP305 lowered amniotransferase activity in the plasma. These results suggest that two cinnamic acid synthetic derivatives (HPP304 and HPP305) exert lipid-lowering action and antioxidant properties without hepatotoxicity in high-cholesterol fed rats.

Phase transitions, solubility, and crystallization kinetics of phytosterols and phytosterol-oil blends

The thermal properties, solubility characteristics, and crystallization kinetics of four commercial phytosterol preparations (soy and wood sterols and stanols) and their blends with corn oil were examined. Differential scanning calorimetry (DSC) revealed narrow melting peaks between 138 and 145 degrees C for all phytosterol samples, reversible on rescan. Broader and less symmetrical melting transitions at lower temperatures with increasing oil content were observed for two samples of phytosterol-oil admixtures. The estimated, from the solubility law, deltaH values (34.7 and 70.7 mJ/mg for wood sterols and stanols, respectively), were similar to the DSC experimental data. Fatty acid esters of soy stanols differing in the chain length of the acyl groups (C2-C12) exhibited suppression of the melting point and increase of the fusion enthalpy with increasing chain length of the acyl group; the propionate ester exhibited the highest melting point (Tm: 151 degrees C) among all stanol-fatty acid esters. Solubility of phytosterols in corn oil was low (2-3% w/w at 25 degrees C) and increased slightly with a temperature rise. Plant sterols appeared more soluble than stanols with higher critical concentrations at saturation. The induction time for recrystallization of sterol-oil liquid blends, as determined by spectrophotometry, depended on the supersaturation ratio. The calculated interfacial free energies between crystalline sediments and oil were smaller for sterol samples (3.80 and 3.85 mJ/m2) than stanol mixtures (5.95 and 6.07 mJ/m2), in accord with the higher solubility of the sterol crystals in corn oil. The XRD patterns and light microscopy revealed some differences in the characteristics among the native and recrystallized in oil phytosterol preparations.

Hypocholesterolemic and antioxidative effects of naringenin and its two metabolites in high-cholesterol fed rats

This study was conducted to compare the hypocholesterolemic and antioxidant effects of naringenin (0.02%), and its metabolites, rho-hyproxyphenylpropionic acid (PHPP, 0.012%) and rho-hydroxybenzoic acid (PHB, 0.012%), in 1% cholesterol diet-fed rats. All supplements significantly lowered the plasma total-cholesterol (total-C), triglyceride (TG) and atherogenic index, and hepatic cholesterol levels compared with the control group. The plasma high-density lipoprotein-cholesterol (HDL-C) concentration was significantly higher in these supplemented groups. However, PHB group only affected the reduction of hepatic TG content. The hydroxyl-3-methylglutaryl-coenzyme A reductase (HMGR) activity was significantly lower in all supplemented groups, whereas only the naringenin group reduced the acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity compared with the control group. The fecal acidic sterol excretion and hepatic superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were significantly higher in all supplemented groups. All supplements also significantly decreased the contents of plasma and hepatic thiobarbituric acid reactive substances (TBARS). Accordingly, it was considered that naringenin and its metabolites were effective on improving the cholesterol and antioxidant metabolism.

The lipid-lowering effect of ezetimibe in pure vegetarians

Results of previous studies have shown that ezetimibe (10 mg/day) reduces LDL cholesterol in patients with mild hypercholesterolemia on a normal-cholesterol diet (dietary intake of 200-500 mg/day) by 16-22%. However, the LDL cholesterol-lowering effect of ezetimibe in subjects with an extremely low dietary cholesterol intake (vegetarians) has not been studied. We conducted a randomized, double-blind, placebo-controlled, two-phase crossover study in 18 healthy pure vegetarians to assess the effect of ezetimibe (10 mg/day) on plasma lipids, cholesterol absorption, and its synthesis. Treatment periods lasted 2 weeks each, with an intervening 2 week washout period. Fractional cholesterol absorption was determined using the continuous dual stable isotope feeding method. Mean dietary cholesterol intake in the pure vegetarians was extremely low and averaged 29.4 +/- 16.8 and 31.4 +/- 14.4 mg/day during the placebo and ezetimibe administration phases, respectively. Fractional cholesterol absorption during the placebo phase was 48.2 +/- 8.2% and was decreased by 58% during ezetimibe treatment to 20.2 +/- 6.2% (P < 0.001). This change in intestinal cholesterol absorption was followed by a significant reduction in LDL cholesterol of 17.3%. In individuals with extremely low dietary cholesterol intake, treatment with ezetimibe (10 mg/day) leads to a significant reduction of cholesterol absorption and a clinically relevant decrease of plasma LDL cholesterol, comparable to that of subjects with a normal dietary cholesterol intake. Thus, the lipid-lowering effect of ezetimibe is mediated mainly through a reduction of the absorption of endogenous (biliary) cholesterol.

Mechanism of hypolipidemic effect of crocin in rats: Crocin inhibits pancreatic lipase

The hypolipidemic mechanism of crocin, an active ingredient in Gardenia jasminoides Ellis and Crocus sativus L, was examined in rats. In diet-induced hyperlipidemic rats, a 10-day treatment with crocin significantly reduced serum triglyceride, total cholesterol, low density lipoprotein (LDL) cholesterol and very low density lipoprotein (VLDL) cholesterol level in the daily dose range of 25 to 100 mg/kg. Results of the modified fat-loading method indicated that crocin inhibited the absorption of fat and cholesterol and this inhibition is closely related to the hydrolysis of fat. In addition, the modified fat-balance method demonstrated that crocin increased the fecal excretion of fat and cholesterol in rats, but had no influence on the elimination of bile acids. The results of the in situ loop method and enzyme assay indicated that crocin could not directly block the absorption of cholesterol from rat jejunum but could selectively inhibit the activity of pancreatic lipase as a competitive inhibitor. These findings suggest that crocin yielded its hypolipidemic effect by inhibiting pancreatic lipase, leading to the malabsorption of fat and cholesterol.

Vitamin E supplementation alters HDL-cholesterol concentration and paraoxonase activity in rabbits fed high-cholesterol diet: comparison with probucol

Vitamin E and probucol are well-known antioxidants that prevent cells from the oxidative stress, which is a risk factor of atherosclerosis. Male rabbits were fed either 0.03% vitamin E or 0.05% probucol in a 0.5% high-cholesterol (HC) diet for 8 weeks. Vitamin E and probucol significantly suppressed an increase in plasma total-cholesterol (total-C) and low-density lipoprotein cholesterol compared to HC-control group. However, plasma high-density lipoprotein-cholesterol (HDL-C) and HDL-C/total-C ratio levels and plasma paraoxonase activity were only significantly higher in vitamin E group after 8 weeks. Hepatic ACAT activity was significantly lower in both vitamin E and probucol groups than in HC-control group, while HMG-CoA reductase activity was the highest only in the probucol group. Total fecal sterol content was significantly higher in probucol and vitamin E groups than in the two control groups. Some atherogenic signs were discovered in the aortic fatty streak of HC-control group, yet not in other groups. Hepatic mRNA expressions of apo B-100 and apo C-III were significantly lower in probucol group than in other groups. Vitamin E supplementation was found to alter the plasma HDL-C-related factors; meanwhile, probucol supplementation was very effective in enhancing cholesterol metabolism, except for a negative effect that reduced plasma HDL-C concentration.

Anticholesterolemic effect of 3,4-di(OH)-phenylpropionic amides in high-cholesterol fed rats

Two amide synthetic derivatives of 3,4-di(OH)-hydrocinnamate (HC), 3,4-dihydroxyphenylpropionic (l-serine methyl ester) amide (E030) and 3,4-dihydroxyphenylpropionic (l-aspartic acid) amide (E076), were investigated to compare their lipid-lowering efficacy with HC. Male rats were fed a 1 g/100 g high-cholesterol diet for 6 weeks with supplements of either clofibrate (0.02%, w/w), HC (0.025%, w/w), E030 (0.039%, w/w) or E076 (0.041%, w/w). The clofibrate supplement was used as a positive control for the lipid-lowering efficacy. The food intakes and body weight gains were not significantly different among the groups. The plasma and hepatic cholesterol and triglyceride levels were lower in clofibrate, HC, E030, and E076-supplemented groups compared to the control group. The supplementation of HC and its amide derivatives was as effective as clofibrate in increasing the ratio of HDL-cholesterol to total plasma cholesterol and reducing the atherogenic index (AI). The hepatic cholesterol level in the HC and E076 groups was significantly lower than that in the clofibrate group. The hepatic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA reductase) and acyl-CoA:cholesterol acyltransferase (ACAT) activities were significantly lower in the all test groups than in the control group. The excretion of neutral sterol was significantly higher in the HC, E030, and E076-supplemented groups compared to the control group. The plasma AST and ALT activities, indirect indexes of hepatic toxicity, were significantly lower in the HC, E030, and E076-supplemented groups than in the control group. Accordingly, the current results suggest that E030 and E076, two amide synthetic derivatives of HC, are effective in lowering lipid activity.

Effects of colesevelam HC1 on sterol and bile acid excretion in patients with type IIa hypercholesterolemia

Colesevelam HC1 is a potent bile acid-binding polymer. This study's aim was to determine effects of colesevelam HCl on sterol and bile acid excretion in patients with type IIa hypercholesterolemia. Twenty-four patients (low-density lipoprotein cholesterol, 130 to 220 mg/dL) enrolled in an open-label, parallel-design study, entered an American Heart Association/National Cholesterol Education Program diet for 6 weeks and were randomized to colesevelam HCl, 2.3 or 3.8 g/day for 4 weeks. In an apparent dose-related manner, respective mean serum concentrations HCl of low-density lipoprotein cholesterol decreased by 10% (P < 0.01) and 13% (P = 0.05), mean total cholesterol levels decreased by 4.9% (P = 0.05) and 6.1% (P = 0.09), and total fecal bile acid excretion showed median changes of +324% (P < 0.05) and +316% (P < 0.05). Colesevelam HCl did not affect fecal neutral sterol or fecal fatty acid excretion; however, 24-hr urinary mevalonic acid levels significantly increased in both treatment groups (P < 0.05). The cholesterol-lowering action of colesevelam HCl appears to be mediated through increased bile acid excretion.

Effect of 3,4-di(OH)-cinnamate synthetic derivative on plasma and hepatic cholesterol level and antioxidant enzyme activities in high cholesterol-fed rats

The effect of 3,4-di(OH)-phenylpropionic acid (L-phenylalanine methyl ester) amide (SL-1063), a synthetic derivative of 3,4-di(OH)-cinnamate, on the cholesterol metabolism and antioxidant enzyme system was examined in rats. Diets that included either SL-1063 (0.046%, w/w) or lovastatin (0.02%, w/w) as a supplement, plus 1 g cholesterol/100 g diet were fed to rats ad libitum for 5 weeks. The total plasma cholesterol and triglyceride levels were significantly lowered by the SL-1063 supplement compared to the control group. Meanwhile, the levels of plasma HDL-cholesterol and ratio of HDL-cholesterol/total cholesterol (%) were significantly higher in the SL-1063 group than in the control group. However, the lovastatin supplement did not affect the plasma lipid level. The hepatic cholesterol level and 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity were significantly lowered in the lovastatin group compared to the SL-1063 group; however, the hepatic triglyceride level did not differ among the groups. The activity of hepatic acyl CoA: cholesterol acyltransferase (ACAT), the enzyme that catalyzes hepatic cholesterol esterification, was significantly lower in the lovastatin and SL-1063 groups than in the control group. Furthermore, the SL-1063 supplement elevated the excretion of fecal sterols. As regards the hepatic antioxidant enzyme system, the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GR) activities were all significantly higher in the SL-1063 group compared to the control group, whereas only the GR activity was significantly increased by the lovastatin supplement. No marked difference in the GSH levels and glucose-6-phosphate dehydrogenase (G6PD) activities was observed among the groups. The levels of plasma and hepatic thiobarbituric acid reactive substances (TBARS) were lowered by the SL-1063 supplement compared to the control group. Accordingly, the current results suggest that SL-1063, a synthetic derivative of 3,4-di(OH)-cinnamate, is effective in lowering the plasma lipids and improving the antioxidant enzyme system.

Plant sterols and stanols

The expanding market of 'functional foods' containing plant sterols and stanols has focused interest on their cholesterol-lowering effects as well on possible adverse effects. Trials of cholesterol lowering demonstrate that intake of 2 g/day of plant sterols and stanols reduces serum low-density lipoprotein (LDL) cholesterol concentrations by approximately 10%. Safety concerns regarding elevations in serum plant sterol levels, or effects on fat-soluble vitamin absorption or hypothetical effects on serum sex hormone balance have received attention and been addressed in studies. Plant sterol (but not stanol) supplementation increased serum plant sterol concentrations but these levels remained much lower than those observed in homozygous sitosterolemia making an adverse health effect unlikely. Prolonged statin therapy also causes elevations in all cholesterol-adjusted plant sterol levels as well as small but significant elevations in serum unadjusted campesterol levels from baseline. This is probably caused by a statin-induced reduction in biliary cholesterol efflux resulting in a diminished intestinal cholesterol pool. The diminished competition with cholesterol molecules allows more plant sterol molecules to become incorporated in mixed micelles facilitating their uptake in enterocytes. With the exception of beta-carotene, reductions in serum concentrations of fat-soluble (pro)vitamins are usually abolished by adjustment for cholesterol suggesting that they reflect reductions in carrier lipoproteins, mainly LDL. The small reductions in serum beta-carotene are not regarded as a major concern, nor have any adverse effects on sex hormone metabolism been demonstrated apart from parenteral administration of large doses in experimental animals. However, as increasing consumer populations become exposed to a large variety of food products enriched with plant sterols and stanols the likelihood of rare adverse effects increases and surveillance is necessary.

Lipid-lowering efficacy of 3,4-di(OH)-phenylpropionicL-leucine in high-cholesterol fed rats

A preliminary study revealed that 3,4-di(OH)-hydrocinnamate (HC), a polyphenolic compound, lowered the plasma lipids in high-cholesterol fed rats. Accordingly, this study was designed to test the lipid-lowering efficacy of a synthetic derivative, 3,4-di(OH)-phenylpropionic (L-leucine) amide (PPLA), in rats fed a high-cholesterol (1%, wt/wt) diet. As such, HC or PPLA was given as supplement to a high-cholesterol diet for 6 weeks at a dose of 0.137 mmol/100 g diet. The supplementation of HC and PPLA significantly lowered the plasma and hepatic cholesterol and triglyceride levels compared to the control group. The activities of hepatic HMG-CoA reductase (164 +/- 9.12 and 124.74 +/- 17.09 pmol/min/mg protein vs. 245.41 +/- 13.01 pmol/min/mg protein, p < 0.05) and ACAT (411.49 +/- 11.48 and 334.35 +/- 17.68 pmol/min/mg protein vs. 490.41 +/- 16.69 pmol/min/mg protein, p < 0.05) were significantly lower in the HC- and PPLA-supplemented groups than in the control group. However, PPLA was more effective in inhibiting the enzyme activities than HC. The excretion of neutral sterol was significantly higher in HC- and PPLA-supplemented groups than in the control group. Therefore, these results indicate that PPLA, a leucine-attached version of HC, exhibited a similar significant hypocholesterolemic effect to HC in rats fed a high-cholesterol diet.

Sterol transporters: targets of natural sterols and new lipid lowering drugs

Recent insights in the role of ATP-binding cassette (ABC) transporters ABCG5 and ABCG8, the discovery of ezetimibe, the first approved direct cholesterol absorption inhibitor, as well as the identification of Niemann-Pick C1 Like 1 (NPC1L1) protein as sterol transporter in the gut, focused attention on sterol transport processes in the small intestine and the liver. The identification of defective structures in the ABCG5 or ABCG8 transporters in patients with the rare disease of sitosterolemia elucidated their role as sterol efflux pumps regulating at least in parts the intestinal sterol absorption and the hepatic sterol output. ABCG5 and ABCG8 themselves are regulated by cholesterol via liver X receptors (LXRs), which are also activated by oxysterols and some derivatives of plant sterols. NPC1L1 could recently be identified as a major sterol transporter for the intestinal uptake of cholesterol as well as plant sterols. Studies in NPC1L1 knockout mice indicate that this transporter is essential for the intestinal uptake of sterols and that NPC1L1 might also be involved in the mechanism of action of ezetimibe. However, studies with photoreactive cholesterol as well as with photoreactive ezetimibe analogues suggest that other processes might also be involved in the mechanism of action of ezetimibe.

Sitosterolemia—a rare disease

Elevated plasma plant sterol concentrations, xanthomatosis, and accelerated-often fatal-atherosclerosis at young age are the major findings in patients with homozygous sitosterolemia. A defect in the ABCG5 or ABCG8 co-transporter gene locus (STSL) causes an increased intestinal absorption and a decreased biliary elimination of all sterols, plant sterols as well as cholesterol, leading to a 50 to 200-fold increase in plasma plant sterol concentrations. A few recent publications indicate that even moderately elevated plasma plant sterol levels might be associated with an increased risk of atherosclerosis. This raises the question whether plant sterols themselves might be atherogenic or whether elevated plasma levels are a marker for a decreased ABCG5/G8 transporter activity which itself causes an increased risk for atherosclerosis. However, current data are too few to conclude that elevated plant sterol concentrations in plasma are an additional risk factor for coronary heart disease. But especially young patients suffering from xanthomatosis and/or atherosclerotic diseases with only mildly or moderately elevated plasma cholesterol should be screened for sitosterolemia by measurement of plasma plant sterol levels.

Familial hypercholesterolemia in children

PURPOSE OF THIS REVIEW

This review provides an update on recent advances in the diagnosis and management of children with familial hypercholesterolemia.

RECENT FINDINGS

A large cross-sectional cohort study of paediatric familial hypercholesterolemia demonstrated that affected children had a 5-fold more rapid increase of carotid arterial wall intima-media thickness during childhood years than their affected siblings. This faster progression led to a significant deviation in terms of intima-media thickness from the age of 12 years and onwards. Low-density lipoprotein cholesterol was a strong and independent predictor of carotid artery intima-media thickness in these children, which confirms the pivotal role of low-density lipoprotein cholesterol for the development of atherosclerosis. In this condition lipid lowering by statin therapy is accompanied by carotid intima-media thickness regression in familial-hypercholesterolemic children, which suggests that initiation of low-density lipoprotein cholesterol-reducing medication in childhood already can inhibit or possibly reduce the faster progression of atherosclerosis. Furthermore, these trials demonstrated that statins are safe and do not impair growth or sexual development in these children. Conversely, products containing plant sterols reduced low-density lipoprotein cholesterol levels by 14%, but did not improve endothelial dysfunction as assessed by flow-mediated dilatation.

SUMMARY

Children with familial hypercholesterolemia clearly benefit from lipid-lowering strategies. Statins are safe agents and have been proven to reduce elevated low-density lipoprotein cholesterol levels significantly. In addition, statins improve surrogate markers for atherosclerosis. Therefore these agents should become the pivotal therapy in children with familial hypercholesterolemia.

Evaluation of hesperetin 7-O-lauryl ether as lipid-lowering agent in high-cholesterol-fed rats

The lipid-lowering efficacy of hesperetin was revealed in preliminary studies on experimental animals. As such, the current study compared the effect of hesperetin 7-O-lauryl ether, with that of hesperetin and lovastatin on the lipid profile and cholesterol-regulating mechanism in high-cholesterol-fed rats. Male rats were fed a high-cholesterol diet (1%, wt/wt) or high-cholesterol diet supplemented with lovastatin (1, 0.02%, wt/wt), hesperetin (2, 0.02%, wt/wt), or hesperetin 7-O-lauryl ether (3, 0.031%, wt/wt) for six weeks. The supplemental amount of 3 was 0.066mmol/100g diet as an equivalent to the supplemental amount of 2. The plasma total cholesterol and triglyceride levels were significantly lowered by the 2 and 3 supplements compared with the control or 1-supplemented group. The hepatic HMG-CoA reductase activities were also significantly lower in all the supplemented groups compared with the control group, and the hepatic ACAT activity was significantly lower in the 2- and 3-supplemented groups. The supplementation of 3 resulted in a higher excretion of total neutral sterol and total fecal sterol compared with the control or 1-supplemented group. Accordingly, overall, compound 3, exhibited a more potent plasma lipid-lowering effect than compound 1 based on inhibiting cholesterol biosynthesis and esterification, while also increasing the fecal sterol excretion.

Naringin alters the cholesterol biosynthesis and antioxidant enzyme activities in LDL receptor-knockout mice under cholesterol fed condition

The purpose of the current study was to evaluate the lipid lowering and antioxidant capacity of naringin in LDL receptor knockout (LDLR-KO) mice fed a cholesterol (0.1 g/100 g) diet. As such, naringin or lovastatin (0.02 g/100 g) was supplemented in a cholesterol diet for 6 weeks. The naringin and lovastatin supplementation significantly lowered the plasma total cholesterol level compared to the control group. The plasma and hepatic triglyceride level was only lowered by the lovastatin supplement, while the hepatic cholesterol content was lowered by both the naringin and lovastatin supplements compared to the control group. The hepatic HMG-CoA reductase activity was significantly lower in the naringin and lovastatin supplemented groups than in the control group, whereas the ACAT activity was unaffected. The excretion of total sterol was significantly higher in the naringin and lovastatin groups compared to the control group due to significant changes in the acidic and neutral sterol, respectively. When comparing the hepatic antioxidant enzyme activities, the superoxide dismutase, catalase, and glutathione reductase activities were all significantly higher in the naringin-supplemented group than in the control group, while only the lovastatin supplement increased the glutathione reductase activity. Accordingly, the current results confirmed that naringin lowers the plasma cholesterol level via the inhibition of hepatic HMG-CoA reductase activity and increases the excretion of fecal sterol. Naringin was also found to improve the activities of hepatic antioxidant enzymes against oxidative stress in a hypercholesterolemic animal model, i.e. cholesterol-fed LDLR-KO mice.