Heart-Protective Effects of Echinodorus grandiflorus in Rabbits That Are Fed a High-cholesterol Diet.

Excess weight and dyslipidemia are among the most serious health problems in Western societies. These conditions enhance the risk of cardiac disease and have been linked with a higher prevalence of cardiac arrhythmias and sudden death. The present study investigated the cardioprotective effects of Echinodorus grandiflorus on ventricular remodeling in rabbits that were fed a 1% cholesterol-rich diet. We first obtained an ethanol-soluble fraction of E. grandiflorus and performed a detailed phytochemical study by liquid chromatography-DAD/ESI-MS. For 60 days, male rabbits were fed the cholesterol-rich diet or a diet without the addition of cholesterol. After 30 days, different groups of rabbits were treated with the ethanol-soluble fraction of E. grandiflorus (10, 30, and 100 mg/kg, p. o.), simvastatin (2.5 mg/kg), or vehicle once daily for 30 days. At the end of 60 days, the serum lipoprotein ratio, electrocardiographic profile, histopathological alterations, and the cardiac antioxidant defense system were investigated. Echocardiographic analysis showed morphological and functional alterations in cholesterol-rich diet-fed animals, indicating left ventricle hypertrophy. The total cholesterol/high-density lipoprotein ratio and low-density lipoprotein/high-density lipoprotein ratio were significantly higher in cholesterol-rich diet-fed rabbits. Myocardial flaccidity, fatty degeneration, and concentric left ventricular hypertrophy were observed. An increase in lipid peroxidation levels, a decrease in superoxide dismutase activity, and a decrease in reduced glutathione levels were observed in the myocardium of all cholesterol-rich diet-fed rabbits. Treatment with the ethanol-soluble fraction of E. grandiflorus, especially the highest dose, significantly reduced all of these alterations, thus demonstrating the cardioprotective effect of the ethanol-soluble fraction of E. grandiflorus on cardiac changes that are induced by a cholesterol-rich diet.

The effect of plant sterol-enriched turkey meat on cholesterol bio-accessibility during in vitro digestion and Caco-2 cell uptake.

This study evaluated the effect of a plant sterol-enriched turkey product on cholesterol bio-accessibility during in vitro digestion and cholesterol uptake by Caco-2 monolayers. Turkey products, one plant sterol-enriched (PS) and one plant sterol-free (C), were produced in an industrial pilot plant. Before simulated digestion, matrices were spiked with cholesterol (1:5 weight ratio of cholesterol to plant sterol). Plant sterols were included at a concentration equivalent to the minimum daily intake recommended by the European Food Safety Authority (EFSA) for cholesterol lowering. After simulated digestion, the percentage of cholesterol micellarization and uptake by Caco-2 cells in the presence of PS meat were measured. Compared to C meat, PS meat significantly inhibited cholesterol micellarization on average by 24% and Caco-2 cell accumulation by 10%. This study suggests that plant sterols in meat can reduce cholesterol uptake by intestinal epithelia and it encourages efforts to make new PS-based functional foods.

Time of ingestion relative to meal intake determines gastrointestinal responses to a plant sterol-containing yoghurt drink.

PURPOSE: Plant sterol (PS)-enriched food products are known to reduce plasma cholesterol concentrations by inhibiting the absorption of dietary and biliary cholesterol. The physiological responses induced by food intake in the gastrointestinal tract are all important factors in determining the overall effect of PS. The aim of this study was therefore to assess the effect of timing of consumption of a plant sterol (PS)-containing yoghurt drink relative to meal ingestion on gastric emptying (GE) of the drink and gallbladder (GB) volume. METHODS: This is a randomized, single-centre, controlled study with crossover design in 12 healthy male volunteers. Three treatments were tested; a 100 mL PS yoghurt drink (labeled with 1,000 mg acetaminophen) was consumed 45 min prior to, during and 45 min after a solid meal. Plasma samples were taken, and gallbladder volumes were measured at baseline and at regular intervals during a 6-h study period. RESULTS: When consumed before the consumption of a meal, the yoghurt drink exhibited fast GE. The solid meal intake caused a significant contraction of the gallbladder. Consumption of the PS drink before the meal had no significant effect on GB volume as compared to baseline and compared to during and after meal consumption. CONCLUSIONS: The PS-containing drink, which empties fast from the stomach, does not sufficiently trigger gallbladder contraction without co-ingestion of a solid meal and in consequence does not induce the necessary physiological changes needed to allow PS to exhibit their effect on inhibiting cholesterol absorption.

[The mechanisms of blood LDL-cholesterol lowering by phytosterols--a review]. / Mechanizm dzialania fitosteroli w obnizaniu poziomu cholesterolu LDL we krwi.

Daily cholesterol consumption in western countries reaches as much as 400 mg. According to the health recommendations the daily intake should not exceed 300 mg and in the case of people with cardiovascular disease it should be less than 200 mg. For 50 years it is known that phytosterols can decrease the level of cholesterol in blood. One of the mechanisms is based on the fact that phytosterols stop absorption of cholesterol in digestive tract, which results in the decrease of the concentration of cholesterol in blood. The second mechanism is based on the fact that cholesterol is pumped back out of enterocytes into the lumen of small intestine by ABC transporter and phytosterols increase this process. The above merftioned mechanisms are different than the way statins can lower cholesterol level and they are commonly used as hipocholesterolemic medicine. Because different mechanisms are implemented both statins and fitosterols can be used in therapy of hipercholeserolemia. The people taking statins who still have increased level of total cholesterol and LDL-cholesterol in blood can include phytosterols in their diet what can lead to the decrease of its level.

Combination effects of wild rice and phytosterols on prevention of atherosclerosis in LDL receptor knockout mice.

Dietary modifications including healthy eating constitute one of the first line strategies for prevention and treatment of atherosclerotic cardiovascular diseases (CVD), including atherosclerosis. In this study, we assessed anti-atherogenic effects of a combination of wild rice and phytosterols in low-density lipoprotein receptor knockout (LDL-r-KO) mice. Male LDL-r-KO mice were divided into four groups and fed with: (1) control diet; (2) the control diet containing 60% (w/w) wild rice; (3) the control diet containing 2% (w/w) phytosterols; or (4) the control diet containing both wild rice and phytosterols for 20weeks. All diets were supplemented with 0.06% (w/w) dietary cholesterol. Blood samples, hearts, and feces were collected and used for biochemical and histological examination. Consumption of 60% (w/w) wild rice in combination with 2% (w/w) phytosterols significantly reduced the size and severity of atherosclerotic lesions in the aortic roots as compared to those in the control group. This effect was associated with significant reductions in plasma total, LDL and VLDL cholesterol concentrations as well as an increase in fecal cholesterol excretion. In conclusion, the dietary combination of wild rice and phytosterols prevents atherogenesis in this animal model. Further investigations are needed to understand mechanisms of action and potential clinical outcome of such dietary intervention.

Effect of cholesterol-rich diets with and without added vitamins E and C on the severity of atherosclerosis in rabbits.

Oxysterols as oxidation products of cholesterol are considered an atherogenic factor in the development of atherosclerosis in the arteries of cholesterol-fed rabbits. We compared the atherogenic effects of diets enriched either with 0.5% oxidized cholesterol (OC; characterized by high amounts of oxysterols) or with pure cholesterol (PC). The effects of antioxidant vitamins E and C added to the PC diet were also evaluated in view of their antioxidative properties for lipoproteins and cholesterol and how this could affect the severity of atherosclerosis. Four groups of rabbits were fed the following for 11 wk: 1) a nonpurified stock diet, 2) this stock diet plus 0.5% OC, 3) the stock diet plus 0.5% PC, and 4) the stock diet plus 0.5% PC and 1000 mg vitamin E and 500 mg vitamin C/kg diet (PC + antioxidants). The OC and PC diets were equally hyperlipidemic and hypercholesterolemic. The severity of atherosclerotic lesions was highest with the OC diet and lowest with the PC + antioxidants diet. The plasma oxysterol concentration was proportional to the severity of atherosclerosis in all three groups of cholesterol-fed rabbits. beta-Very-low-density-lipoprotein modification was minimized by vitamins E and C as indicated by its polyacrylamide gel electrophoretic pattern and its increased binding to the rabbit liver membrane in vitro. This study indicated that OC and PC were equally atherogenic but that the addition of antioxidants to the PC diet significantly reduced its severity, even when hypercholesterolemia persisted. This indicated that atherogenesis can result from an excessive accumulation of oxidation products of cholesterol in the plasma.

Cholesterol absorption inhibitors in development as potential therapeutics.

Drugs that lower low-density lipoprotein cholesterol through their actions in the gastrointestinal tract have been used for > 30 years. Bile acid sequestrants have very excellent safety profiles but their poor tolerability means they have limited clinical use. Recently developed new compounds are better tolerated in clinical trials and show greater benefit in reducing low-density lipoprotein cholesterol level, as compared to "older" sequestrants. Cholesterol absorption inhibitors and bile acid transporter inhibitors have recently been reported to show clinical efficacy and safety as novel gut-acting drugs for lowering cholesterol. Further advances in our understanding of the cholesterol absorption mechanism will provide novel therapeutic targets, such as the ATP-binding cassette transporter. This approach in the treatment of lowering cholesterol appears to play a more significant role in the clinical field of atherosclerotic vascular disease.

Ezetimibe and cholesterol absorption.

Cholesterol, an important biological lipid and excessive dietary intake, is associated with hypercholesterolemia, a prevalent cardiovascular risk factor. Because cholesterol is essentially a water insoluble molecule, its transport within and absorption from the aqueous medium of the intestine is rather complex. This takes place in a series of orderly and interrelated steps, including emulsification, hydrolysis by specific pancreatic esterases, micellar transport, mucosal absorption, resynthesis in enterocytes and assembly with apolipoproteins to form chylomicrons. Many of these processes are not well characterized at the molecular level. Besides being generally inefficient, cholesterol absorption is highly variable with a between-subject variability that depends in part on genetic factors and an intraindividual variability, which may be modulated by physiological and dietary conditions. All of the sequential steps in intestinal cholesterol absorption can be interfered with by dietary components or drugs and therefore are potential therapeutic targets for rendering cholesterol absorption even more inefficient in an attempt to lower cholesterol levels.

Berberine decreases cholesterol levels in rats through multiple mechanisms, including inhibition of cholesterol absorption.

OBJECTIVE: The objective was to determine the mechanisms of action of berberine (BBR) on cholesterol homeostasis using in vivo and in vitro models. METHODS: Male Sprague-Dawley rats were fed the AIN-93G diet (normal control) or modified AIN-93G diet containing 28% fat, 2% cholesterol and 0.5% cholic acid with treatment of 0 (atherogenic control), 50, 100, and 150 mg/kg·d of BBR, respectively by gavaging in water for 8 weeks. Cholesterol absorption rate was measured with the dual stable isotope ratio method, and plasma lipids were determined using the enzymatic methods. Gene and protein expressions of Acyl-coenzyme A:cholesterol acyltransferase-2 were analyzed in vivo and in vitro. Cholesterol micellarization, uptake and permeability were determined in vitro. RESULTS: Rats on the atherogenic diet showed significantly hypercholesterolemic characteristics compared to normal control rats. Treatment with BBR in rats on the atherogenic diet reduced plasma total cholesterol and nonHDL cholesterol levels by 29%-33% and 31%-41%, respectively, with no significant differences being observed among the three doses. The fractional dietary cholesterol absorption rate was decreased by 40%-51%. Rats fed the atherogenic diet showed lower plasma triacylglycerol levels, and no changes were observed after the BBR treatment. BBR interfered with cholesterol micellarization, decreased cholesterol uptake by Caco-2 cells and permeability through Caco-2 monolayer. BBR also inhibited the gene and protein expressions of acyl-coenzyme A cholesterol acyltransferease-2 in the small intestine and Caco-2 cells. CONCLUSION: BBR lowered blood cholesterol levels at least in part through inhibiting the intestinal absorption and further by interfering with intraluminal cholesterol micellarization and decreasing enterocyte cholesterol uptake and secretion.

Effect of high-dose statin versus low-dose statin plus ezetimibe on endothelial function: a meta-analysis of randomized trials.

BACKGROUND: Combining low-dose statin and ezetimibe reduces the low-density lipoprotein cholesterol (LDL-C) similar to high-dose statin. However, whether there is a difference in the effect of these 2 lipid-lowering regimes on endothelial function is still controversial. METHODS: We performed a systematic search of databases (MEDLINE [1950 to September 2011], EMBASE [1966 to September 2011]) and references of identified studies. Completely published randomized controlled trials comparing the effect of high-dose statin with low-dose stain plus ezetimibe on endothelial function (flow-mediated dilation [FMD] method) were included in this study. RESULTS: Six trials with a total of 213 participants were included in the meta-analysis. The pooled weighted mean difference of FMD did not differ between the 2 lipid-lowering regimes (0.22%; 95% confidence interval [CI]: -0.85%-1.29%, P = .68). Furthermore, no significant reduction in LDL-C and C-reactive protein (CRP) occurred with high-dose statin versus low-dose statin plus ezetimibe (pooled weighted mean differences of LDL-C and CRP were -4.12 mg/dL, 95% CI: -9.54-1.12 mg/dL, P = .12, and -0.02 mg/L, 95% CI: -0.31-0.27 mg/L, P = .89, respectively). CONCLUSIONS: Based on the currently available evidence, combining a low-dose statin with ezetimibe may provide similar beneficial effects on endothelial function as high-dose statin.

Other therapies for reducing low-density lipoprotein cholesterol: medications in development.

Although the past 30 years have been fruitful and productive in lipid research, from basic science to drug development to demonstration of clinical benefit, cardiovascular disease remains the major cause of mortality and morbidity in industrialized societies. With the rapid industrialization of countries, such as India and China, cardiovascular disease rapidly is becoming the leading cause of global death and disability. Although most of the effective lipid-lowering drugs, the statins, have become generic and inexpensive, there remains a need for effective and safe agents. Hopefully, some of those discussed in this article will fill that need.

Ezetimibe analogs with a reorganized azetidinone ring: Design, synthesis, and evaluation of cholesterol absorption inhibitions.

The underlying principle of drug design in this paper is that the maximum retention of the functional groups that exist in the marketed drug would provide a higher probability for comparable safety while the conformational changes in the newly created analogs should not constitute a significant structural variation to adversely affect biological activity. Four individual isomers of backbone re-organized ezetimibe analogs were designed and synthesized. Their effects on the cholesterol levels in rat serum were evaluated by a high-cholesterol and high-fat diet feeding experiment. All the new analogs showed significant effect in lowering the levels of total cholesterol in serum.

Class B scavenger receptor-mediated intestinal absorption of dietary beta-carotene and cholesterol.

There is now a general consensus that the intestinal absorption of water-insoluble, dietary lipids is protein-mediated, but the assignment of protein(s) to this function is still a matter of debate. To address this issue, we measured beta-carotene and cholesterol absorption in wild-type and SR-BI knockout mice and the uptake of these lipids in vitro using brush border membrane (BBM) vesicles. From the comparison of the in vivo and in vitro results we conclude that both BBM-resident class B scavenger receptors, SR-BI and CD36, can facilitate the absorption of beta-carotene and cholesterol. SR-BI is essential for beta-carotene absorption, at least in mice on a high fat diet. This is due to the fact that the absorption of beta-carotene is restricted to the duodenum and SR-BI is the predominant receptor in the mouse duodenum. In contrast, SR-BI may be involved but is not essential for cholesterol absorption in the small intestine. The question of whether SR-BI contributes to cholesterol absorption in vivo is still unresolved. Transfection of COS-7 cells with SR-BI or CD36 confers on these cells lipid uptake properties closely resembling those of enterocytes and BBM vesicles. Both scavenger receptors facilitate the uptake of dietary lipids such as beta-carotene, free and esterified cholesterol, phospholipids, and fatty acids into COS-7 cells. This lipid uptake is effected from three different lipid donor particles: mixed bile salt micelles, phospholipid small unilamellar vesicles, and trioleoylglycerol emulsions which are all likely to be present in the small intestine. Ezetimibe, a representative of a new class of drugs that inhibit intestinal cholesterol absorption, blocks SR-BI- and CD36-facilitated uptake of cholesterol into COS-7 cells.

Ezetimibe: a novel cholesterol-lowering agent that highlights novel physiologic pathways.

Ezetimibe is a US Food and Drug Administration-approved novel drug that targets the absorption of cholesterol in the intestine. The identification of this drug has also led to the elucidation of the dietary cholesterol receptor. Ezetimibe is efficacious as a plasma cholesterol-lowering agent as monotherapy, but its greatest utility seems to be as a combination with a low-dose statin, where it results in cholesterol lowering that is equivalent to using maximum-dose statins. It has a very favorable side-effect profile, as well as a lack of drug-drug interactions. In addition, it prevents the absorption of noncholesterol sterols, such as plant sterols. In clinical studies, it has been shown to be highly efficacious in lowering plant sterols in a rare genetic disorder, sitosterolemia. Both the disease, as well as this therapeutic agent, have led to the concept that ezetimibe may be also useful in dissecting the role of these noncholesterol sterols in the pathogenesis of atherosclerosis.

Long-term low-dose treatment with reserpine of cholesterol-fed rabbits reduces cholesterol in plasma, non-high density lipoproteins and arterial walls.

The effects of long-term low-dose treatment with reserpine on plasma lipoproteins and arterial cholesterol were determined in cholesterol-fed rabbits. Hepatic low-density lipoprotein (LDL) receptors; uptake of LDL by liver, heart, and kidneys; plasma fibrinogen; blood pressure; and heart rate were also determined. Reserpine at 43 microg/kg. d was continuously infused subcutaneously via implanted minipumps for 6 weeks into conscious unrestrained male New Zealand White rabbits (n = 5) fed a 0.2% cholesterol-enriched diet. Compared with controls, reserpine (n = 4) significantly reduced the elevated levels of plasma total cholesterol and esterified and unesterified cholesterol throughout the study, and at 6 weeks of treatment these reductions were 42, 41, and 49%, respectively. The increased cholesterol in the aortic walls (n = 5) produced by the atherogenic diet was reduced by 73% (p < 0.004) and 125I-tyramine cellobiose-labeled LDL by 67 to 86% (0.05 < p <0.004), respectively. The aortic intimal-medial thickness ratio was reduced by 70%. The decrease in elevated plasma total cholesterol was mainly due to cholesterol reductions in both LDL (41%) and non-high density lipoprotein (HDL) of density < 1.019 g/ml (51%). HDL cholesterol and triglyceride levels were unchanged. Reserpine had no significant effects on the clearance of 125I-tyramine cellobiose-LDL from plasma and there was a trend towards an increase in hepatic LDL receptor expression. Heart rate was decreased by 28%. There were no significant effects on blood pressure, liver and heart lipids, hematocrit, or plasma fibrinogen. The results suggest that treatment of cholesterol-fed rabbits with reserpine at a low dose over a long period prevents increases in plasma atherogenic lipoproteins. Reserpine decreases the cholesterol in aortic walls and the intima-media thickness ratio. This anti-atherosclerotic effect of reserpine may have therapeutic implication.

Identification of a receptor mediating absorption of dietary cholesterol in the intestine.

Here we show that scavenger receptor class B type I is present in the small-intestine brush border membrane where it facilitates the uptake of dietary cholesterol from either bile salt micelles or phospholipid vesicles. This receptor can also function as a port for several additional classes of lipids, including cholesteryl esters, triacylglycerols, and phospholipids. It is the first receptor demonstrated to be involved in the absorption of dietary lipids in the intestine. In liver and steroidogenic tissues, the physiological ligand of this receptor is high-density lipoprotein. We show that binding of high-density lipoprotein and apolipoprotein A-I to the brush border membrane-resident receptor inhibits uptake of cholesterol (sterol) into the brush border membrane from lipid donor particles. This finding lends further support to the conclusion that scavenger receptor BI catalyzes intestinal cholesterol uptake. Our findings suggest new therapeutic approaches for limiting the absorption of dietary cholesterol and reducing hypercholesterolemia and the risk of atherosclerosis.

Upregulation of LOX-1 expression in aorta of hypercholesterolemic rabbits: modulation by losartan.

Angiotensin-II (Ang-II) enhances the modification of LDL and the expression of its lectin-like receptor (LOX-1) by activating type 1 (AT(1)) receptors. This study was designed to determine the effect of hypercholesterolemia on LOX-1 expression in aorta and its modulation by the AT(1) receptor blocker losartan. Male New Zealand White rabbits were fed regular chow (Control group), chow with 1% cholesterol and 4% peanut oil (HC-diet group), or 1% cholesterol and 4% peanut oil diet plus losartan (25 mg/kg/day) (Losartan + HC-diet group) for 10 weeks. Animal body weight, serum cholesterol levels, and arterial blood pressure were measured. Aortic intimal thickening was quantitated in H&E-stained segments. LOX-1 expression in aortas was examined by immunohistochemistry and semi-quantitative RT-PCR. High-cholesterol diet did not affect body weight, but induced hypercholesterolemia and extensive intimal thickening. Aortas of rabbits in the control group showed a modest LOX-1 expression in the endothelium. Aortic intimal proliferation in HC-diet group was associated with a marked increase in LOX-1 expression (protein and mRNA) in the endothelium and neointima. Treatment with losartan attenuated aortic intimal proliferation and markedly decreased the enhanced LOX-1 expression. Thus high-cholesterol diet induces the upregulation of LOX-1 expression in neointima of aortas of rabbits. Treatment with losartan, an AT(1) blocker, markedly decreases this enhanced LOX-1 expression.