Cholesterol metabolism and its implications for therapeutic interventions in patients with hypercholesterolaemia

A General Review of Methodologies Used in the Determination of Cholesterol (C27H46O) Levels in Foods

Cholesterol (C27H46O) is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes, and cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly led to the accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, and spectrophotometric methods; enzymatic, nonenzymatic, and electrochemical sensors; and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. This review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

Cholesterol metabolism: Towards a therapeutic approach for multiple sclerosis

Growing evidence points to the importance of cholesterol in preserving brain homeostasis. Cholesterol makes up the main component of myelin in the brain, and myelin integrity is vital in demyelinating diseases such as multiple sclerosis. Because of the connection between myelin and cholesterol, the interest in cholesterol in the central nervous system increased during the last decade. In this review, we provide a detailed overview on brain cholesterol metabolism in multiple sclerosis and its role in promoting oligodendrocyte precursor cell differentiation and remyelination.

α-globulin-rich rice cultivar, low glutelin content-1 (LGC-1), decreases serum cholesterol concentration in exogenously hypercholesterolemic rats

BACKGROUND

Rice α-globulin has been reported to have serum cholesterol-lowering activity in rats. However, it is still unclear whether α-globulin exerts this effect when taken as one of the dietary components. In the present study, we investigated the effect of two cultivars of rice, low glutelin content (LGC)-1 and LGC-Jun, on reducing serum cholesterol in exogenously hypercholesterolemic (ExHC) rats. LGC-1 is enriched in α-globulin (10.6 mg g^-1 rice flour, which is an approximately 1.5 times higher α-globulin content than in Koshihikari a predominant rice cultivar in Japan), whereas LGC-Jun is a globulin-negative cultivar.

METHODS

ExHC rats, the model strain of diet-induced hypercholesterolemia, were fed 50% LGC-1 or LGC-Jun and 0.5% cholesterol-containing diets for 2 weeks, followed by measurement of cholesterol metabolism parameters in serum and tissues.

RESULTS

Serum cholesterol and non-high-density lipoprotein cholesterol levels were significantly lower in the LGC-1 group compared to the LGC-Jun group. Cholesterol intestinal absorption markers, hepatic and serum levels of campesterol and β-sitosterol, and lymphatic cholesterol transport were not different between the two groups. Levels of 7α-hydroxycholesterol, an intermediate of bile acid synthesis, showed a downward trend in the livers of rats that were fed LGC-1 (P = 0.098). There was a significant decrease in the hepatic mRNA expression of Cyp7a1 (a synthetic enzyme for 7α-hydroxycholesterol) in the LGC-1 group compared to the LGC-Jun group.

CONCLUSION

Dietary LGC-1 significantly decreased serum cholesterol levels in ExHC rats. The possible mechanism for the cholesterol-lowering activity of LGC-1 is partial inhibition of bile acid and cholesterol synthesis in the liver. © 2021 Society of Chemical Industry.

Resolving the Egg and Cholesterol Intake Controversy: New Clinical Insights Into Cholesterol Regulation by the Liver and Intestine

OBJECTIVE

Cardiovascular disease is the number one cause of death. Achieving American Heart Association low-density lipoprotein (LDL) cholesterol treatment goals is very difficult for many patients. The importance of a low cholesterol diet is controversial and not emphasized by most physicians. Of critical importance is determining whether each individual is a "hyper- or hypo-absorber" of dietary cholesterol. Furthermore, the quantity of each individual's baseline daily dietary cholesterol and saturated fat intake is important in assessing the effect of added egg yolk cholesterol and saturated fat on blood LDL cholesterol.

METHODS

Gut cholesterol is absorbed via a specific enteric receptor (the Niemann- Pick-like receptor). Dietary cholesterol contributes one fourth of the absorbed cholesterol, while the remaining gut cholesterol is derived from secreted bile cholesterol. This dietary quantity of cholesterol is significant when other determinants are constant. For some individuals, dietary cholesterol has no adverse effects and in others, a significant elevation in blood LDL cholesterol may occur.

RESULTS

There are no readily available blood tests to determine the effect of egg yolk cholesterol and saturated fat on an individual's plasma LDL cholesterol. However, a one month trial of a low cholesterol and saturated fat diet will provide the needed information to make clinical decisions.

CONCLUSION

This article delineates the mechanisms that are altered by genetic and environmental factors that determine the net effects of dietary cholesterol and saturated fat on circulating LDL cholesterol. It then makes a practical clinical recommendation based on these mechanisms.

Exploring the Bacterial Impact on Cholesterol Cycle: A Numerical Study

High blood cholesterol levels are often associated with cardiovascular diseases. Therapeutic strategies, targeting different functions involved in cholesterol transport or synthesis, were developed to control cholesterolemia in human. However, the gut microbiota is also involved in cholesterol regulation by direct biotransformation of luminal cholesterol or conversion of bile salts, opening the way to the design of new strategies to manage cholesterol level. In this report, we developed for the first time a whole-body human model of cholesterol metabolism including the gut microbiota in order to investigate the relative impact of host and microbial pathways. We first used an animal model to investigate the ingested cholesterol distribution in vivo. Then, using in vitro bacterial growth experiments and metabolite measurements, we modeled the population dynamics of bacterial strains in the presence of cholesterol or bile salts, together with their bioconversion function. Next, after correct rescaling to mimic the activity of a complex microbiota, we developed a whole body model of cholesterol metabolism integrating host and microbiota mechanisms. This global model was validated with the animal experiments. Finally, the model was numerically explored to give a further insight into the different flux involved in cholesterol turn-over. According to this model, bacterial pathways appear as an important driver of cholesterol regulation, reinforcing the need for development of novel "bacteria-based" strategies for cholesterol management.

Duodenal Niemann-Pick C1-like 1 expression was negatively correlated with liver X receptor expression in nonalcoholic fatty liver disease

BACKGROUND/AIMS

Intestinal cholesterol absorption includes intestinal Niemann-Pick C1-like 1 (NPC1L1) and is an important target pathway in nonalcoholic fatty liver disease (NAFLD). We investigated the expression of NPC1L1 and its correlation with liver X receptor (LXR) expression in peripheral mononuclear (PMN) cells in patients with NAFLD.

METHODS

We evaluated intestinal expression of NPC1L1 in 25 NAFLD patients and 28 healthy controls. We calculated the mRNA expression levels of LXR and farnesoid X receptor (FXR), which are master players of cholesterol metabolism in PMN cells. The protein expression of ABCA1, ABCG5/8, NPC1L1, SREBP, LXR, FXR, and CD36 was measured on tissue samples from the duodenum and ileum.

RESULTS

The expression of LXR (p = 0.01) and FXR (p = 0.03) in PMN cells was increased in the NAFLD group compared to the control group. Duodenal NPC1L1 decreased in the NAFLD group compared to the healthy controls (3.38 ± 1.4 vs. 2.42 ± 1.2, p = 0.05). NPC1L1 expression in the duodenum was negatively correlated with LXR expression in PMN cells. Expression of LXR and FXR in the ileum was also negatively correlated with the expression of LXR in PMN cells.

CONCLUSION

Duodenal NPC1L1 expression was decreased in NAFLD and was negatively correlated with LXR expression in PMN cells.

Hepatitis C virus-apolipoprotein interactions: molecular mechanisms and clinical impact

INTRODUCTION

Chronic hepatitis C virus (HCV) infection is a leading cause of cirrhosis, hepatocellular carcinoma and liver failure. Moreover, chronic HCV infection is associated with liver steatosis and metabolic disorders. With 130-150 million people chronically infected in the world, HCV infection represents a major public health problem. One hallmark on the virus is its close link with hepatic lipid and lipoprotein metabolism. Areas covered: HCV is associated with lipoprotein components such as apolipoproteins. These interactions play a key role in the viral life cycle, viral persistence and pathogenesis of liver disease. This review introduces first the role of apolipoproteins in lipoprotein metabolism, then highlights the molecular mechanisms of HCV-lipoprotein interactions and finally discusses their clinical impact. Expert commentary: While the study of virus-host interactions has resulted in a improvement of the understanding of the viral life cycle and the development of highly efficient therapies, major challenges remain: access to therapy is limited and an urgently needed HCV vaccine remains still elusive. Furthermore, the pathogenesis of disease biology is still only partially understood. The investigation of HCV-lipoproteins interactions offers new perspectives for novel therapeutic approaches, contribute to HCV vaccine design and understand virus-induced liver disease and cancer.

Cholesterol metabolism: A review of how ageing disrupts the biological mechanisms responsible for its regulation

Cholesterol plays a vital role in the human body as a precursor of steroid hormones and bile acids, in addition to providing structure to cell membranes. Whole body cholesterol metabolism is maintained by a highly coordinated balancing act between cholesterol ingestion, synthesis, absorption, and excretion. The aim of this review is to discuss how ageing interacts with these processes. Firstly, we will present an overview of cholesterol metabolism. Following this, we discuss how the biological mechanisms which underpin cholesterol metabolism are effected by ageing. Included in this discussion are lipoprotein dynamics, cholesterol absorption/synthesis and the enterohepatic circulation/synthesis of bile acids. Moreover, we discuss the role of oxidative stress in the pathological progression of atherosclerosis and also discuss how cholesterol biosynthesis is effected by both the mammalian target of rapamycin and sirtuin pathways. Next, we examine how diet and alterations to the gut microbiome can be used to mitigate the impact ageing has on cholesterol metabolism. We conclude by discussing how mathematical models of cholesterol metabolism can be used to identify therapeutic interventions.

PCSK9 inhibition fails to alter hepatic LDLR, circulating cholesterol, and atherosclerosis in the absence of ApoE

LDL cholesterol (LDL-C) contributes to coronary heart disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) increases LDL-C by inhibiting LDL-C clearance. The therapeutic potential for PCSK9 inhibitors is highlighted by the fact that PCSK9 loss-of-function carriers exhibit 15-30% lower circulating LDL-C and a disproportionately lower risk (47-88%) of experiencing a cardiovascular event. Here, we utilized pcsk9(-/-) mice and an anti-PCSK9 antibody to study the role of the LDL receptor (LDLR) and ApoE in PCSK9-mediated regulation of plasma cholesterol and atherosclerotic lesion development. We found that circulating cholesterol and atherosclerotic lesions were minimally modified in pcsk9(-/-) mice on either an LDLR- or ApoE-deficient background. Acute administration of an anti-PCSK9 antibody did not reduce circulating cholesterol in an ApoE-deficient background, but did reduce circulating cholesterol (-45%) and TGs (-36%) in APOE*3Leiden.cholesteryl ester transfer protein (CETP) mice, which contain mouse ApoE, human mutant APOE3*Leiden, and a functional LDLR. Chronic anti-PCSK9 antibody treatment in APOE*3Leiden.CETP mice resulted in a significant reduction in atherosclerotic lesion area (-91%) and reduced lesion complexity. Taken together, these results indicate that both LDLR and ApoE are required for PCSK9 inhibitor-mediated reductions in atherosclerosis, as both are needed to increase hepatic LDLR expression.

R. L. Narasimhacharya A. Physiological Role of a Multigrain Diet in Metabolic Regulations of Lipid and Antioxidant Profiles in Hypercholesteremic Rats: Multigrain diet in hyperlipemia

OBJECTIVES

The objective of the present study was to investigate the lipid and the antioxidant regulatory potential of a multigrain diet in laboratory animals with reference to lipid profiles, tissue lipid peroxidation and antioxidant status.

METHODS

Two types of diets, with or without addition of cholesterol, were used in the study - a commercial diet and a formulated multigrain diet (with Sorghum vulgare, Avena sativa, Pennisetum typhoideum, Oryza sativa, Eleusine coracana and Zea mays grains). After a 10-week period of feeding the diets to albino rats the plasma, liver and fecal lipid profiles and the hepatic and renal antioxidant status of the animals that were fed the commercial and the formulated diets (with and without cholesterol addition) were assessed.

RESULTS

The commercial diet supplemented with cholesterol elevated the levels of plasma total lipids, total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein cholesterol (VLDL-C), as well as the atherogenic index (AI). The high-density lipoprotein cholesterol (HDL-C) content and the antioxidant profiles (total ascorbic acid, superoxide dismutase, catalase, glutathione peroxidase reduced glutathione) declined along with increases in lipid peroxidation. The formulated diet (with and without addition of cholesterol) was found to be more efficient than the commercial diet in controlling plasma, hepatic and fecal lipid profiles, as well as hepatic and renal lipid peroxidation and antioxidant status, than of the hypercholesteremic animals.

CONCLUSION

The multigrain diet used in the present study is effective in countering the hyperlipidemia and oxidative stress caused by high cholesterol intake.

Antiobesity and vasoprotective effects of resveratrol in apoE-deficient mice

This study was performed to investigate the hypolipidemic, antiobese, and antiatherogenic effects of resveratrol in apoE-deficient mice fed an atherogenic diet (20% fat and 1% cholesterol). These animals were fed an atherogenic diet containing 0.02% lovastatin (w/w) or 0.02% resveratrol (w/w) for 12 weeks. Resveratrol and lovastatin supplementation significantly reduced either the body weight or epididymal fat weight without altering the food intake and food efficiency ratio. Resveratrol significantly decreased the plasma total cholesterol (total-C), low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C) concentrations, apoB/apoA-I ratio, hepatic cholesterol, and triglyceride (TG) contents, whereas significantly it increased the plasma HDL-C concentration compared with the control and lovastatin groups. Plasma and hepatic TG and plasma apoB levels were significantly lower in both the lovastatin and resveratrol groups than in the control group without altering the plasma apoA-I concentration. Both resveratrol and lovastatin significantly decreased hepatic fatty acid and TG synthesis, whereas they increased fatty acid oxidation (β-oxidation) except for the carnitine palmitoyltransferase activity compared with the control group. However, there was no difference in hepatic 3-hydroxyl-3-methylglutaryl-CoA reductase activity among the groups, although hepatic acyl-CoA: cholesterol acyltransferase activity was significantly lower in the lovastatin groups than in the control group. In epididymal adipose tissue, resveratrol supplementation led to an increase in β-oxidation and decrease in TG synthesis, compared with the control group. Tissue morphology revealed that there were dramatic decreases in hepatic lipid droplets and aortic fatty streaks by resveratrol and lovastatin supplementation. This study demonstrates that resveratrol exerts not only antiobesity and hypolipidemic effects, but also protective effects for the liver and aorta through the modulation of lipid metabolism in both the liver and white adipose tissues.

Efficacy of combination of Ezetimibe 10 mg and rosuvastatin 2.5 mg versus rosuvastatin 5 mg monotherapy for hypercholesterolemia in patients with type 2 diabetes

BACKGROUND

Statins are used to treat hypercholesterolemia in patients with type 2 diabetes mellitus, but many of these patients fail to achieve the target LDL-C level. Recent reports have suggested that a synergistic effect can be obtained by concomitant administration of the cholesterol absorption inhibitor ezetimibe and a statin. However, in patients with type 2 diabetes who are already being treated with satins, it remains unclear whether it is more effective to add ezetimibe or to increase the statin dose. Therefore, this study was performed to examine the effects of these two regimens on LDL-C and lipoproteins.

METHODS

The subjects were type 2 diabetic patients under treatment with rosuvastatin (2.5 mg daily), who had LDL-C levels ≥80 mg/dL. They were randomly allocated to a group that received add-on therapy with ezetimibe at 10 mg/day (combination group, n = 40) or an increase of the rosuvastatin dose to 5 mg/day (dose escalation group, n = 39). These two groups were compared at baseline and after 12 weeks of treatment.

RESULTS

The percent change of LDL-C was -31% in the combination group and -12% in the dose escalation group. Both groups showed a significant decrease, but the decrease was greater in the combination group. In both groups, there was a significant decrease in the levels of small dense LDL-C, oxidized LDL and remnant-like lipoprotein cholesterol. For all of these parameters, the percent changes were greater in the combination group. Only the combination group showed a significant decrease of triglycerides. Multivariate analysis was performed to identify factors associated with reaching an LDL-C level <80 mg/dL. As a result, add-on therapy with ezetimibe was extracted as a factor related to improvement of LDL-C.

CONCLUSIONS

Compared with increasing the dose of rosuvastatin, the combination of rosuvastatin and ezetimibe not only achieves quantitative but also qualitative improvement of serum lipid levels in type 2 diabetic patients, suggesting that this combination could suppress the progression of atherosclerosis.

TRIAL REGISTRATION

UMIN000011005.

Cyanidin-3-O-β-glucoside upregulates hepatic cholesterol 7α-hydroxylase expression and reduces hypercholesterolemia in mice

SCOPE

Although previous studies have shown that consumption of anthocyanin extract from plant foods reduces hypercholesterolemia and the severity of atherosclerosis in different animal models, the mechanisms of these actions remained unclear. This study investigated whether pure anthocyanin inhibit atherosclerosis development and reduce hypercholesterolemia in the apolipoprotein E (ApoE)-deficient mice through enhancement of fecal bile acid excretion, a critical pathway for eliminating circulation cholesterol from the body.

METHODS AND RESULTS

Five-week-old male ApoE-deficient mice were fed the AIN-93G diet supplemented with or without cyanidin-3-O-β-glucoside (0.06% w/w) for 12 weeks. Results showed that cyanidin-3-O-β-glucoside consumption inhibited the formation of aortic sinus plaque and reduced hypercholesterolemia, along with promoted fecal bile acid excretion and upregulated hepatic cholesterol 7a-hydroxylase expression (CYP7A1). In mouse primary hepatocytes, cyanidin-3-O-β-glucoside treatment increased bile acid synthesis and CYP7A1 expression in a liver X receptor alpha (LXRα)-)-dependent manner. Scintillation proximity and time-resolved fluorescence resonance energy transfer assays revealed that cyanidin-3-O-β-glucoside functions as an agonist of LXRα.

CONCLUSION

Our results indicate that the hypocholesterolemic activity of cyanidin-3-O-β-glucoside was, at least in part, mediated by activating the potential LXRα-CYP7A1-bile acid excretion pathway, thus contributing to the antiatherogenic effect of cyanidin-3-O-β-glucoside. Importantly, cyanidin-3-O-β-glucoside could activate LXRα in an agonist-dependent manner.

Potential beneficial effects of butyrate in intestinal and extraintestinal diseases

The multiple beneficial effects on human health of the short-chain fatty acid butyrate, synthesized from non-absorbed carbohydrate by colonic microbiota, are well documented. At the intestinal level, butyrate plays a regulatory role on the transepithelial fluid transport, ameliorates mucosal inflammation and oxidative status, reinforces the epithelial defense barrier, and modulates visceral sensitivity and intestinal motility. In addition, a growing number of studies have stressed the role of butyrate in the prevention and inhibition of colorectal cancer. At the extraintestinal level, butyrate exerts potentially useful effects on many conditions, including hemoglobinopathies, genetic metabolic diseases, hypercholesterolemia, insulin resistance, and ischemic stroke. The mechanisms of action of butyrate are different; many of these are related to its potent regulatory effects on gene expression. These data suggest a wide spectrum of positive effects exerted by butyrate, with a high potential for a therapeutic use in human medicine.

Improved efficacy for ezetimibe and rosuvastatin by attenuating the induction of PCSK9

Reducing circulating LDL-cholesterol (LDL-c) reduces the risk of cardiovascular disease in people with hypercholesterolemia. Current approaches to reduce circulating LDL-c include statins, which inhibit cholesterol synthesis, and ezetimibe, which blocks cholesterol absorption. Both elevate serum PCSK9 protein levels in patients, which could attenuate their efficacy by reducing the amount of cholesterol cleared from circulation. To determine whether PCSK9 inhibition could enhance LDL-c lowering of both statins and ezetimibe, we utilized small interfering RNAs (siRNAs) to knock down Pcsk9, together with ezetimibe, rosuvastatin, and an ezetimibe/rosuvastatin combination in a mouse model with a human-like lipid profile. We found that ezetimibe, rosuvastatin, and ezetimibe/rosuvastatin combined lower serum cholesterol but induce the expression of Pcsk9 as well as the Srebp-2 hepatic cholesterol biosynthesis pathway. Pcsk9 knockdown in combination with either treatment led to greater reductions in serum non-HDL with a near-uniform reduction of all LDL-c subfractions. In addition to reducing serum cholesterol, the combined rosuvastatin/ezetimibe/Pcsk9 siRNA treatment exhibited a significant reduction in serum APOB protein and triglyceride levels. Taken together, these data provide evidence that PCSK9 inhibitors, in combination with current therapies, have the potential to achieve greater reductions in both serum cholesterol and triglycerides.

Gene expression analysis of a human enterocyte cell line reveals downregulation of cholesterol biosynthesis in response to short-chain fatty acids

It has been suggested that the short-chain fatty acids (SCFAs) produced by anaerobic bacterial intestinal fermentation of soluble fiber may regulate lipid metabolism in intestine, thus reducing plasma cholesterol levels. However, the exact mechanism of action of SCFAs in lowering cholesterol levels is not fully understood. The aims of this study were to test the effects of SCFAs on gene expression in a human enterocyte cell line Caco-2/TC-7 and to validate microarray data by real-time PCR. Human Caco-2/TC-7 enterocytes were cultured on transwell filter inserts and incubated with the SCFAs acetate (Ac), propionate (Pr), and butyrate (Bu). Total RNA was then isolated for microarrays and quantitative real-time PCR analysis. Treatment of human enterocytes with Pr and Bu affects a wide variety of genes. These genes were classified according to the PANTHER classification system, and the results showed that different biological processes and metabolic pathways were modified by Pr and Bu treatment, including the intestinal cholesterol biosynthesis pathway. Differential array expression analysis showed that nine genes were downregulated in this pathway, and these results were validated by real-time PCR. This in vitro study allowed us to identify a wide variety of biological processes and metabolic pathways affected by the SCFAs tested. Importantly, our results show that the global effect of Pr and Bu is to downregulate the expression of nine key genes involved in intestinal cholesterol biosynthesis, thus possibly inhibiting this pathway.

Cholesterol and non-cholesterol sterol transporters: ABCG5, ABCG8 and NPC1L1: a review

1. Whole-body sterol (cholesterol and xenosterol) balance is delicately regulated by the gastrointestinal tract and liver, which control sterol absorption and excretion, respectively, in addition to the contribution to the cholesterol pool by whole-body cholesterol synthesis. In the past ten years enormous strides have been made not only in establishing that specific transporters mediate the entry and exit of sterols and how these may regulate selective sterol access to the body pools, but also in how these pathways operate to integrate these physiological pathways. 2. The entry of sterols from the gastrointestinal and biliary canalicular lumen into the body is mediated by NPC1L1, which was discovered by a novel method, via a genomics-bioinformatics approach. 3. Identification of the genetic basis responsible for causing sitosterolaemia, characterized by plant sterol accumulation, led to the identification of two half-transporters (ABCG5 and ABCG8) that normally efflux plant sterols (and cholesterol) into the intestinal and biliary lumen for faecal excretion. 4. The objective of this review is to provide up-to-date knowledge on genomics, proteomics and function of these two transporter systems.

Hypocholesterolemic effect of stilbenes containing extract-fraction from Cajanus cajan L. on diet-induced hypercholesterolemia in mice

Cajanus cajan (L) is a natural plant which contains a lot of potential active components. In the present study, we identified the effects of the stilbenes containing extract-fraction from Cajanus cajan L (sECC) on diet-induced (for 4 weeks) hypercholesterolemia in Kunming mice. All experimental mice were divided into 5 groups: control group, model group, sECC-treated with 200 or 100 mg/kg/day, and simvastatin group. The effects of sECC were investigated by monitoring serum and liver lipid profile (cholesterol homeostasis and triglyceride) as well as serum superoxide dismutase activity in those mice. To further explore the mechanism of sECC, hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase), cholesterol 7α-hydroxylase (CYP7A1), and low density lipoprotein receptor (LDL receptor) expressions in cholesterol homeostasis were analyzed by reverse transcription PCR. After 4 weeks pretreatment, compared with model group, the increased serum and hepatic total cholesterol were markedly attenuated by sECC (200 mg/kg) by 31.4% and 22.7% (p<0.01), respectively, the triglyceride levels of serum and liver were also lowered by 22.98% and 14.39%, respectively. At the same time, serum LDL cholesterol decreased by 52.8% (p<0.01) accompanied with the activities of serum superoxide dismutase increased by 20.98%. Atherogenic index and body weight were also reduced markedly. The mRNA expressions of HMG-CoA reductase, CYP7A1, and LDL-receptor were significantly enhanced in the mice administered with sECC (200 mg/kg/day), whereas those expressions were suppressed by the hypercholesterolemic diet. These data indicate that sECC reduces the atherogenic properties of dietary cholesterol in mice. Its hypocholesterolemic effect may involve enhancement of the hepatic LDL-receptor and cholesterol 7alpha-hydroxylase expression levels and bile acid synthesis.

The relationships of cholesterol metabolism and plasma plant sterols with the severity of coronary artery disease

Changes in the balance of cholesterol absorption and synthesis and moderately elevated plasma plant sterols have been suggested to be atherogenic. Measuring cholestanol, lathosterol, campesterol, and sitosterol, we investigated the relationships of cholesterol metabolism and plasma plant sterols with the severity of coronary artery disease (CAD) in 2,440 participants of the Ludwigshafen Risk and Cardiovascular health (LURIC) study. The coronary status was determined by angiography, and the severity of CAD was assessed by the Friesinger Score (FS). An increase in the ratio of cholestanol to cholesterol was associated with high FS (P = 0.006). In contrast, a high ratio of lathosterol to cholesterol went in parallel with low FS (P < 0.001). Whereas the campesterol to cholesterol ratio significantly correlated with the FS (P = 0.026), the relationship of the sitosterol to cholesterol ratio with the FS did not reach statistical significance in the whole group. Increased campesterol, sitosterol, and cholestanol to lathosterol ratios were associated high FS (P < 0.001). To conclude, there is a modest association of high cholesterol absorption and low cholesterol synthesis with an increased severity of CAD. An atherogenic role of plasma plant sterols themselves, however, seems unlikely in subjects without sitosterolaemia.

Ezetimibe: cholesterol lowering and beyond

Ezetimibe is a cholesterol absorption inhibitor that blocks the intestinal absorption of both biliary and dietary cholesterol. It appears to exert its effect by blocking intestinal sterol transporters, specifically Niemann-Pick C1-like 1 proteins, thereby inhibiting the intestinal absorption of cholesterol, phytosterols and certain oxysterols. Ezetimibe monotherapy and in combination with statin therapy is primarily indicated for lowering LDL-cholesterol levels. In addition, it may favorably affect other parameters that could potentially further reduce atherosclerotic coronary heart disease risk, such as raising HDL-cholesterol and lowering levels of triglycerides, non-HDL-cholesterol, apolipoprotein B and remnant-like particle cholesterol. Further effects of ezetimibe include a reduction in circulating phytosterols and oxysterols and, when used in combination with statins, a reduction in high-sensitivity C-reactive protein. The clinical significance of the LDL-cholesterol lowering and other effects of ezetimibe is being evaluated in clinical outcome studies.

The efficacy of statin monotherapy uptitration versus switching to ezetimibe/simvastatin: results of the EASEGO study

OBJECTIVE

To assess the incremental low-density lipoprotein-cholesterol (LDL-C) lowering efficacy of doubling the statin dose or switching to the ezetimibe/simvastatin 10/20 mg combination tablet (EZE/SIMVA) in patients on simvastatin 20 mg or atorvastatin 10 mg not at LDL-C target < 2.5 mmol/L.

STUDY DESIGN AND METHODS

Patients with documented coronary heart disease (CHD) and/or type 2 diabetes (DM2) with LDL-C > or = 2.5 and < 5.0 mmol/L despite treatment with atorvastatin 10 mg or simvastatin 20 mg were randomized to (1) double statin dose or (2) switch to ezetimibe/simvastatin 10/20, according to a PROBE study design. LDL-C, lipoprotein subfractions and safety data were assessed during the study.

RESULTS

119 of 178 (67%) patients in the EZE/SIMVA group and 49 of 189 (26%) in the doubling statin group reached target LDL-C < 2.5 mmol/L. The odds ratio of success for EZE/SIMVA versus doubling statin treatment in reaching the LDL-C target of < 2.5 mmol/L was 5.7 (95% CI: 3.7-9.0, p < 0.0001). A reduction in total cholesterol (TC), total/high density lipoprotein (HDL) cholesterol ratio and apolipoprotein B was observed in both groups, but this reduction was significantly more pronounced in the EZE/SIMVA group as compared with the doubling statin dose group. Treatment was well tolerated and no difference was observed between the two groups with regard to adverse effects.

CONCLUSIONS

In CHD/DM2 patients treated with simvastatin or atorvastatin with LDL-C persistently > or = 2.5 mmol/L, switching to the EZE/SIMVA was more effective in attaining the LDL-C target of < 2.5 mmol/L than doubling the statin dose.

Serum adipokines are associated with cholesterol metabolism in the metabolic syndrome

BACKGROUND

The purpose of this study was to investigate whether cholesterol metabolism is associated with serum adipokines and inflammatory markers.

METHODS

In fifty-eight subjects with impaired fasting glucose or impaired glucose tolerance and features of the metabolic syndrome cholesterol metabolism was assayed with serum non-cholesterol sterol ratios to cholesterol, surrogate markers of synthesis (cholesterol precursors) and dietary absorption % of cholesterol (cholestanol and plant sterols) and related them to serum adiponectin, leptin, high-sensitive C-reactive protein (hs-CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha).

RESULTS

Adiponectin was negatively related to synthesis markers (e.g. desmosterol r=-0.371, P<0.01), and positively to absorption markers (e.g. cholestanol r=0.269, P<0.05). Leptin was associated with synthesis markers (e.g. desmosterol r=0.271, P<0.05) and negatively with absorption markers (e.g. sitosterol r=-0.278, P<0.05). Hs-CRP was negatively associated with absorption markers (e.g. sitosterol r=-0.407, P<0.001). IL-6 and TNF-alpha were not related to cholesterol metabolism. When dividing the subjects into tertiles by the serum desmosterol/cholestanol ratio, the I tertile (high synthesis/low absorption) was associated with low adiponectin concentrations, high BMI and serum leptin concentrations (P<0.05 for all).

CONCLUSIONS

Adiponectin, leptin and hs-CRP were associated with variables of cholesterol metabolism. A high ratio of cholesterol synthesis to absorption is characterized by high serum leptin and low adiponectin concentrations.

Change in the cholesterol metabolism associated with the combined inhibition of synthesis and absorption

A cardiovascularis prevencióban, a lipid célértékek elérésére törekedve megelégszünk a szérum-koleszterinszint mérésével, és keveset törődünk azzal, hogy ez milyen hatások eredményeként alakul ki. A koleszterin vérszintje a diétával elfogyasztott mennyiségen túl nagymértékben függ a bélbe történő felszívódás/kiválasztás és a szintézis egyensúlyától. A felszívódás és a szintézis arányának vizsgálata csak az utóbbi időben került az érdeklődés előterébe. Számos megfigyelés igazolja, hogy a ma legerősebbnek ismert koleszterincsökkentő gyógyszerek hatására, amellett, hogy a májban csökken a szintézis, akár 50%-ot meghaladó mértékben is nőhet a koleszterin felszívódása. Amikor egy statinkezelés hatékonyságát vizsgáljuk, a mindennapi gyakorlatban csak a végeredményt, a szérum-koleszterinszint csökkenését mérjük, és nem vizsgáljuk a szintézis és a felszívódás mértékének változását sem. Az, hogy a szervezetben mennyi koleszterinszintetizálódik,illetve szívódik fel – indirekt módon – a nem-koleszterin szterinek (fitoszterinek) mennyiségének mérésével állapítható meg. Azabszorpciómarkerei a kampeszterin, a szitoszterin, az avenaszterin, valamint a kolesztanol. A koleszterinbioszintézisea latoszterin, a kolesztenol, a dezmoszterin szintjével korrelál. A gyakorlatban a latoszterin vagy latoszterin/koleszterin-koncentráció a szintézis, a kampeszterin vagy kampeszterin/koleszterin-arány a felszívódás markereként értékelhető. Az újabb vizsgálati eredmények tehát azt igazolják, hogy a koleszterin szintézisét gátló statin adása mellett fokozódik a koleszterin felszívódása, és a felszívódást gátló ezetimib hatása pedig a szintézis erősödését eredményezi. A statinok okozta felszívódás emelkedését ezetimibbel kombinálva tudjuk csökkenteni, illetve kivédeni. Ezen adatok azt támasztják alá, hogy a statin és ezetimib kombinációja, a szintézis és felszívódás együttes gátlása biztosítja a leghatékonyabb és legkevesebb mellékhatással járó koleszterinszint-csökkenést.

Statin and resveratrol in combination induces cardioprotection against myocardial infarction in hypercholesterolemic rat

Hypercholesterolemia (HC) is a common health problem that significantly increases risk of cardiovascular disease. Both statin (S) and resveratrol (R) demonstrated cardioprotection through nitric oxide-dependent mechanism. Therefore, the present study was undertaken to determine whether combination therapy with statin and resveratrol is more cardioprotective than individual treatment groups in ischemic rat heart model. The rats were fed with 2% high cholesterol diet and after 8 weeks of high cholesterol diet the animals were treated with statin (1 mg/kg bw/day) and resveratrol (20 mg/kg bw/day) for 2 weeks. The rats were assigned to: (1) Control (C), (2) HC, (3) HCR, (4) HCS and (5) HCRS. The hearts, subjected to 30-min global ischemia followed by 120-min reperfusion were used as experimental model. The left ventricular functional recovery (+dp/dt(max)) was found to be significantly better in the HCRS (1926+/-43), HCR (1556+/-65) and HCS (1635+/-40) compared to HC group (1127+/-16). The infarct sizes in the HCRS, HCS and HCR groups were 37+/-3.6, 43+/-3.3 and 44+/-4.2 respectively compared to 53+/-4.6 in HC. The lipid level was found to be decreased in all the treatment groups when compared to HC more significantly in HCS and HCRS groups when compared to HCR. Increased phosphorylation of Akt and eNOS was also observed in all the treatment groups resulting in decreased extent of cardiomyocyte apoptosis but the extent of reduction in apoptosis was more significant in HCRS group compared to all other groups. In vivo rat myocardial infarction (MI) model subjected to 1 week of permanent left descending coronary artery (LAD) occlusion documented increased capillary density in HCR and HCRS treated group when compared to HCS treatment group. We also documented increased beta-catenin translocation and increased VEGF mRNA expression in all treatment groups. Thus, we conclude that the acute as well as chronic protection afforded by combination treatment with statin and resveratrol may be due to pro-angiogenic, anti-hyperlipidemic and anti-apoptotic effects and long-term effects may be caused by increased neo-vascularization of the MI zone leading to less ventricular remodeling.

The protective role of Chinese prescription Kangen-karyu extract on diet-induced hypercholesterolemia in rats

This study was carried out to investigate the protective potential of Chinese prescription Kangen-karyu, comprising six crude drugs, on coronary heart disease which is the principal cause of morbidity and mortality worldwide. The diet-induced hypercholesterolemic rat model, which shows an elevation in low density lipoprotein (LDL) cholesterol and atherosclerosis, was employed. The control rats fed a diet of 1% cholesterol and 0.5% cholic acid showed the highest cholesterol levels in serum and feces relative to those fed a normal diet, however, the rats administered Kangen-karyu extract showed reductions in these levels without changes in liver cholesterol, indicating that the reduction of serum total cholesterol by Kangen-karyu extract probably arises from an increase in cholesterol excretion. Furthermore, the administration of Kangen-karyu extract significantly prevented the elevation of serum aspartate aminotransferase and alanine aminotransferase, known as marker enzymes of liver damage. The elevated serum levels of LDL cholesterol were lowered, however, the high density lipoprotein cholesterol level was significantly elevated by Kangen-karyu extract and these were dose-dependent decreases in the atherogenic index to 15.2, 8.8 and 7.5 at oral doses of 50, 100 and 200 mg from the 19.4 control value, respectively. In addition, Kangen-karyu extract inhibited LDL oxidation in a dose-dependent manner, and the elevated level of thiobarbituric acid-reactive substances in control rats showed a decline by the administration of Kangen-karyu extract. The present study suggests that Kangen-karyu could play a protective role against hypercholesterolemia through the regulation of cholesterol levels and inhibition of lipid peroxidation.

Isoprenoids and Alzheimer's disease: a complex relationship

Cholesterol metabolism has been linked to Alzheimer's disease (AD) neuropathology, which is characterized by amyloid plaques, neurofibrillary tangles and neuroinflammation. Indeed, the use of statins, which inhibit cholesterol and isoprenoid biosynthesis, as potential AD therapeutics is under investigation. Whether statins offer benefit for AD will be determined by the outcome of large, placebo-controlled, randomized clinical trials. However, their use as pharmacological tools has delineated novel roles for isoprenoids in AD. Protein isoprenylation regulates multiple cellular and molecular events and here we review the complex roles of isoprenoids in AD-relevant processes and carefully evaluate isoprenoid pathways as potential AD therapeutic targets.

Niemann-Pick C1 like 1 gene expression is down-regulated by LXR activators in the intestine

Niemann-Pick C1 like 1 (NPC1L1) is a protein critical for intestinal cholesterol absorption. The nuclear receptors peroxisome proliferator-activated receptor alpha (PPARalpha) and liver X receptors (LXRalpha and LXRbeta) are major regulators of cholesterol homeostasis and their activation results in a reduced absorption of intestinal cholesterol. The goal of this study was to define the role of PPARalpha and LXR nuclear receptors in the regulation of NPC1L1 gene expression. We show that LXR activators down-regulate NPC1L1 mRNA levels in the human enterocyte cell line Caco-2/TC7, whereas PPARalpha ligands have no effect. Furthermore, NPC1L1 mRNA levels are decreased in vivo, in duodenum of mice treated with the LXR agonist T0901317. In conclusion, the present study identifies NPC1L1 as a novel LXR target gene further supporting a crucial role of LXR in intestinal cholesterol homeostasis.

High-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry determination of cholesterol uptake by Caco-2 cells

A simple, sensitive and selective liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometric method (LC/APCI-MS/MS) was developed and applied to quantitative determination of uptake of cholesterol by Caco-2 human intestine cells. Caco-2 cells were cultured in medium containing cholesterol-3,4-13C2 and phytosterols from nutritional supplements after in vitro digestion. Cellular cholesterol (cholesterol-3,4-13C2) and endogenous cholesterol were extracted using methanol/chloroform (1:2, v/v) and directly analyzed using LC/APCI-MS/MS with selected reaction monitoring (SRM), using cholesterol-2,2,3,4,4,6-d6 as an internal standard. Detection and quantification limits were 2.2 and 7.2 pmol, respectively. This method provides an effective tool for rapid determination of cholesterol uptake by cells with increased selectivity and sensitivity in comparison to previously reported LC/APCI-MS analysis using selected ion monitoring (SIM).