Ezetimibe: its novel effects on the prevention and the treatment of cholesterol gallstones and nonalcoholic Fatty liver disease

Resistance to Cholesterol Gallstone Disease: Hepatic Cholesterol Metabolism

Cholesterol gallstone disease (CGD) is one of the most common digestive diseases, and it is closely associated with hepatic cholesterol metabolism. Cholesterol gallstones may be caused by abnormal hepatic cholesterol metabolism, such as excessive cholesterol biosynthesis within the liver, interfering with the uptake or export of cholesterol in the liver, and abnormal hepatic cholesterol esterification. In this review, we begin with a brief overview of the clinical diagnosis and treatment of gallstone disease (GSD). Then, we briefly describe the major processes of hepatic cholesterol metabolism and summarize the key molecular expression changes of hepatic cholesterol metabolism in patients with gallstones. We review and analyze the recent advances in elucidating the relationships between these key molecules and CGD, and some targets significantly impacting on CGD via hepatic cholesterol metabolism are also listed. We also provide a significant discussion on the relationship between CGD and nonalcoholic fatty liver disease (NAFLD). Finally, the new discoveries of some therapeutic strategies associated with hepatic cholesterol metabolism to prevent and treat CGD are summarized.

Metabolic dysfunction-associated gallstone disease: expecting more from critical care manifestations

About 20% of adults worldwide have gallstones which are solid conglomerates in the biliary tree made of cholesterol monohydrate crystals, mucin, calcium bilirubinate, and protein aggregates. About 20% of gallstone patients will definitively develop gallstone disease, a condition which consists of gallstone-related symptoms and/or complications requiring medical therapy, endoscopic procedures, and/or cholecystectomy. Gallstones represent one of the most prevalent digestive disorders in Western countries and patients with gallstone disease are one of the largest categories admitted to European hospitals. About 80% of gallstones in Western countries are made of cholesterol due to disturbed cholesterol homeostasis which involves the liver, the gallbladder and the intestine on a genetic background. The incidence of cholesterol gallstones is dramatically increasing in parallel with the global epidemic of insulin resistance, type 2 diabetes, expansion of visceral adiposity, obesity, and metabolic syndrome. In this context, gallstones can be largely considered a metabolic dysfunction-associated gallstone disease, a condition prone to specific and systemic preventive measures. In this review we discuss the key pathogenic and clinical aspects of gallstones, as the main clinical consequences of metabolic dysfunction-associated disease.

Peroxisome Proliferator-Activated Receptor-γ Prevents Cholesterol Gallstone Formation in C57bl Mice by Regulating Bile Acid Synthesis and Enterohepatic Circulation

To investigate the role of the peroxisome proliferator-activated receptor-γ (PPARγ) in the progression of cholesterol gallstone disease (CGD), C57bl/6J mice were randomized to the following groups (n=7/group): L (lithogenic diet, LGD), LM (LGD+pioglitazone), CM (chow diet+pioglitazone), and NC (normal control, chow diet). Gallbladder stones were observed by microscopy. Histological gallbladder changes were assessed. Bile acids (BA) and cholesterol were measured in the serum, bile, and feces. Proteins and mRNA expression of genes involved in BA metabolism and enterohepatic circulation were assessed by western blotting and real-time RT-PCR. PPARγ activation was performed in LO2 cell by lentivirus transfection and in Caco2 cell by PPARγ agonist treatment. Downregulation of farnesoid X receptor (FXR) by small interference RNA (siRNA) was performed in L02 cells and Caco2 cells, respectively. Results showed that pharmacological activation of PPARγ by pioglitazone prevents cholesterol gallstone formation by increasing biliary BA synthesis and enterohepatic circulation. Activated PPARγ induced the expression of genes involved in enterohepatic circulation and bile acid synthesis (like PCG1α, BSEP, MRP2, MRP3, MRP4, NTCP, CYP7A1, CYP27A1, ASBT, OSTα, and OSTβ). Downregulation of FXR repressed expression of partial genes involved in BA enterohepatic circulation. These findings suggest a new function of PPARγ in preventing CGD by handling BA synthesis and transport through a FXR dependent or independent pathway.

Recent advances in understanding and managing cholesterol gallstones

The high prevalence of cholesterol gallstones, the availability of new information about pathogenesis, and the relevant health costs due to the management of cholelithiasis in both children and adults contribute to a growing interest in this disease. From an epidemiologic point of view, the risk of gallstones has been associated with higher risk of incident ischemic heart disease, total mortality, and disease-specific mortality (including cancer) independently from the presence of traditional risk factors such as body weight, lifestyle, diabetes, and dyslipidemia. This evidence points to the existence of complex pathogenic pathways linking the occurrence of gallstones to altered systemic homeostasis involving multiple organs and dynamics. In fact, the formation of gallstones is secondary to local factors strictly dependent on the gallbladder (that is, impaired smooth muscle function, wall inflammation, and intraluminal mucin accumulation) and bile (that is, supersaturation in cholesterol and precipitation of solid crystals) but also to "extra-gallbladder" features such as gene polymorphism, epigenetic factors, expression and activity of nuclear receptors, hormonal factors (in particular, insulin resistance), multi-level alterations in cholesterol metabolism, altered intestinal motility, and variations in gut microbiota. Of note, the majority of these factors are potentially manageable. Thus, cholelithiasis appears as the expression of systemic unbalances that, besides the classic therapeutic approaches to patients with clinical evidence of symptomatic disease or complications (surgery and, in a small subgroup of subjects, oral litholysis with bile acids), could be managed with tools oriented to primary prevention (changes in diet and lifestyle and pharmacologic prevention in subgroups at high risk), and there could be relevant implications in reducing both prevalence and health costs.

Phyllanthus Niruri Standardized Extract Alleviates the Progression of Non-Alcoholic Fatty Liver Disease and Decreases Atherosclerotic Risk in Sprague-Dawley Rats

Non-alcoholic fatty liver disease (NAFLD) is one of the major global health issues, strongly correlated with insulin resistance, obesity and oxidative stress. The current study aimed to evaluate anti-NAFLD effects of three different extracts of Phyllanthus niruri (P. niruri). NAFLD was induced in male Sprague-Dawley rats using a special high-fat diet (HFD). A 50% methanolic extract (50% ME) exhibited the highest inhibitory effect against NAFLD progression. It significantly reduced hepatomegaly (16%) and visceral fat weight (22%), decreased NAFLD score, prevented fibrosis, and reduced serum total cholesterol (TC) (48%), low-density lipoprotein (LDL) (65%), free fatty acids (FFAs) (25%), alanine aminotransferase (ALT) (45%), alkaline phosphatase (ALP) (38%), insulin concentration (67%), homeostatic model assessment of insulin resistance (HOMA-IR) (73%), serum atherogenic ratios TC/high-density lipoprotein (HDL) (29%), LDL/HDL (66%) and (TC-HDL)/HDL (64%), hepatic content of cholesterol (43%), triglyceride (29%) and malondialdehyde (MDA) (40%) compared to a non-treated HFD group. In vitro, 50% ME of P. niruri inhibited α-glucosidase, pancreatic lipase enzymes and cholesterol micellization. It also had higher total phenolic and total flavonoid contents compared to other extracts. Ellagic acid and phyllanthin were identified as major compounds. These results suggest that P. niruri could be further developed as a novel natural hepatoprotective agent against NAFLD and atherosclerosis.

Quantitation of the rates of hepatic and intestinal cholesterol synthesis in lysosomal acid lipase-deficient mice before and during treatment with ezetimibe

Esterified cholesterol (EC) and triglycerides, contained within lipoproteins taken up by cells, are hydrolysed by lysosomal acid lipase (LAL) in the late endosomal/lysosomal (E/L) compartment. The resulting unesterified cholesterol (UC) is transported via Niemann-Pick type C2 and C1 into the cytosolic compartment where it enters a putative pool of metabolically active cholesterol that is utilized in accordance with cellular needs. Loss-of-function mutations in LIPA, the gene encoding LAL, result in dramatic increases in tissue concentrations of EC, a hallmark feature of Wolman disease and cholesteryl ester storage disease (CESD). The lysosomal sequestration of EC causes cells to respond to a perceived deficit of sterol by increasing their rate of cholesterol synthesis, particularly in the liver. A similar compensatory response occurs with treatments that disrupt the enterohepatic movement of cholesterol or bile acids. Here we measured rates of cholesterol synthesis in vivo in the liver and small intestine of a mouse model for CESD given the cholesterol absorption inhibitor ezetimibe from weaning until early adulthood. Consistent with previous findings, this treatment significantly reduced the amount of EC sequestered in the liver (from 132.43±7.35 to 70.07±6.04mg/organ) and small intestine (from 2.78±0.21 to 1.34±0.09mg/organ) in the LAL-deficient mice even though their rates of hepatic and intestinal cholesterol synthesis were either comparable to, or exceeded those in matching untreated Lal-/- mice. These data reveal the role of intestinal cholesterol absorption in driving the expansion of tissue EC content and disease progression in LAL deficiency.

Interval increase in the prevalence of symptomatic cholelithiasis-associated non-alcoholic fatty liver disease over a ten-year period in an Asian population

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) is frequently associated with cholelithiasis. The prevalence of NAFLD in Asia has been on the rise, but the magnitude of this increase had not been studied previously.

METHODS

A retrospective cohort study was conducted on consecutive patients who underwent laparoscopic or open cholecystectomy from November 2001 to November 2004 (Cohort 1) and from November 2011 to November 2014 (Cohort 2) at Singapore General Hospital. Preoperative diagnostic scans (e.g. ultrasonography, computed tomography and magnetic resonance imaging) and clinical data were reviewed for the presence of fatty liver. Statistical analysis was performed.

RESULTS

In Cohorts 1 and 2, 127 patients and 99 patients were operated on, respectively. Cohort 2 had significantly higher proportions of patients with NAFLD (56.6% vs. 40.2%; p < 0.015) and hyperlipidaemia (45.5% vs. 18.9%; p < 0.001) as compared to Cohort 1. Binary logistic regression analysis showed that hypertension (odds ratio [OR] 2.558; p < 0.004) and Indian ethnicity (OR 5.448; p < 0.043) were significantly associated with NAFLD.

CONCLUSION

Similar to other international studies, we found a significant increase in the prevalence of patients with NAFLD presenting symptomatically for cholecystectomy over an interval of ten years in Singapore. Hypertension and Indian ethnicity were significantly associated with NAFLD in both time periods. This trend supports the need for concerted public health intervention to stem the increasing incidence of NAFLD and prevent its progression to more advanced liver disease.

Oxidized LDL at the crossroads of immunity in non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is viewed as the hepatic manifestation of the metabolic syndrome and is a condition hallmarked by lipid accumulation in the liver (steatosis) along with inflammation (hepatitis). Currently, the etiology and mechanisms leading to obesity-induced hepatic inflammation are not clear and, as a consequence, strategies to diagnose or treat NASH in an accurate manner do not exist. In the current review, we put forward the concept of oxidized lipids as a significant risk factor for NASH. We will focus on the contribution of the different types of oxidized lipids as part of the oxidized low-density lipoprotein (oxLDL) to the hepatic inflammatory response. Furthermore, we will elaborate on the underlying mechanisms linking oxLDL to inflammatory responses in the liver and on how these cascades can be used as therapeutic targets to combat NASH. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.

Potential Therapeutic Agents for the Treatment of Fatty Degeneration of Liver and Atheromatous Plaques: An Experimental Study in Rats

Background:

Since long high fat diet (HFD) is being blamed for causing fatty degeneration of liver and formation of atheromatous plaques. At present, no proper pharmacotherapy is available for both the conditions. In this study, different substances containing monounsaturated fatty acids were used to observe their protective effects in the HFD induced damage to liver and coronary vessels.

Objectives:

To discover effective therapeutic agents for HFD induced fatty degeneration of liver and atheromatous plaques.

Materials and Methods:

The study was conducted from September 2015 to April 2016. In this study, rats were divided into nine groups according to dietary regimen. Each group comprised six rats. Saturated fat was given in the form of butter, and unsaturated fat was given in the form of corn oil, olive oil, Nigella sativa oil, and crushed garlic. Serum samples were taken to estimate lipid profile, liver functions, cardiac functions, and kidney functions. Visceras were removed after animal sacrifice, and histopathological examination was done.

Results and Conclusion:

During the study period, the weight of animals changed significantly in some groups. Those animals which were given crushed garlic along with high saturated fat diet, showed protection against accumulation of lipids in the hepatocytes. Olive oil and Nigella sativa oil were comparatively less effective.

SUMMARY

Consumption of Garlic, Nigella Sativa and Olive oil significantly improved/revised the Fatty Degeneration of liver induced by intake of High Fat Diet.

No fat deposition was found in the liver when Garlic, Nigella Sativa and Olive oil, were given concomitantly with HFD.

Hepatocytes functioned better even in comparison to control and a decrease in liver enzymes was found with use of Garlic.

Use of Garlic, Nigella Sativa and Olive oil, prevented the plaque formation in the vessels and decreased serum lipids.

Beneficial effects of Garlic were significant in comparison to Nigella Sativa and Olive oil.

Abbreviations used: HFD: High Fat Diet; NS: Nigella Sativa; TQ: Thymoquinone; KFMRC: King Fahad Medical Research Center; BUN: Blood Urea Nitrogen; BNF: Buffered Neutral Formalin; G: Group

Lipid-lowering agents inhibit hepatic steatosis in a non-alcoholic steatohepatitis-derived hepatocellular carcinoma mouse model

Non-alcoholic fatty liver disease (NAFLD) is associated with various metabolic disorders, and the therapeutic strategies for treating NAFLD and non-alcoholic steatohepatitis (NASH) have not been fully established. In the present study, we examined whether lipid-lowering agents inhibited the progression of NAFLD and tumorigenesis in a non-alcoholic steatohepatitis-derived hepatocellular carcinoma model mouse (STAM mice) generated by streptozotocin injection and a high-fat diet. Seven-week-old STAM mice were divided into groups fed a high-fat diet (Ctl) or a high-fat diet supplemented with ezetimibe (Ez), fenofibrate (Ff), rosuvastatin (Rs), ezetimibe plus fenofibrate (EF), or ezetimibe plus rosuvastatin (ER) for 4 weeks. At the end of the experiments, an oral glucose tolerance test, an insulin tolerance test, biochemical analyses using serum and liver, and a histological analysis of liver were performed in 11-week-old STAM mice. The lipid-lowering agents did not affect the body weight or the casual blood glucose levels in any of the groups. The serum triglyceride level was significantly decreased by Ff, Rs, and EF. Glucose tolerance was improved by Ez and Ff, but none of these agents improved insulin sensitivity. A histochemical analysis revealed that the lipid-lowering agents, with the exception of Rs, significantly inhibited the progression of hepatic steatosis. Nonetheless, no significant changes in the incidence of hepatic tumors were observed in any of the groups. Lipid-lowering agents inhibited the progression of hepatic steatosis without suppressing tumorigenesis in STAM mice. Our data has implications for the mechanism underlying steatosis-independent hepatic tumorigenesis in mice.

Epidemiology, management, and economic evaluation of screening of gallstone disease among type 2 diabetics: A systematic review

The knowledge of gallstone disease (GSD) is crucial to manage this condition when organizing screening and preventive strategies and identifying the appropriated clinical therapies. Although cholecystectomy still be the gold standard treatment for patients with symptomatic GSD, expectant management could be viewed as a valid therapeutic method for this disorder. If early treatment of GSD decreases the morbidity or avoids further cholecystectomy, it may save clinical care costs in later disease periods sufficiently to offset the screening and early treatment costs. In addition, whether routine screening for GSD is worthwhile depends on whether patients are willing to pay the ultrasonography screening cost that would reduce the risk of cholecystectomy. In this review we discuss the epidemiology, management, and economic evaluation of screening of GSD among type 2 diabetics.

Ezetimibe for the treatment of nonalcoholic steatohepatitis: assessment by novel magnetic resonance imaging and magnetic resonance elastography in a randomized trial (MOZART trial)

Ezetimibe inhibits intestinal cholesterol absorption and lowers low-density lipoprotein cholesterol. Uncontrolled studies have suggested that it reduces liver fat as estimated by ultrasound in nonalcoholic steatohepatitis (NASH). Therefore, we aimed to examine the efficacy of ezetimibe versus placebo in reducing liver fat by the magnetic resonance imaging-derived proton density-fat fraction (MRI-PDFF) and liver histology in patients with biopsy-proven NASH. In this randomized, double-blind, placebo-controlled trial, 50 patients with biopsy-proven NASH were randomized to either ezetimibe 10 mg orally daily or placebo for 24 weeks. The primary outcome was a change in liver fat as measured by MRI-PDFF in colocalized regions of interest within each of the nine liver segments. Novel assessment by two-dimensional and three-dimensional magnetic resonance elastography was also performed. Ezetimibe was not significantly better than placebo at reducing liver fat as measured by MRI-PDFF (mean difference between the ezetimibe and placebo arms -1.3%, P = 0.4). Compared to baseline, however, end-of-treatment MRI-PDFF was significantly lower in the ezetimibe arm (15%-11.6%, P < 0.016) but not in the placebo arm (18.5%-16.4%, P = 0.15). There were no significant differences in histologic response rates, serum alanine aminotransferase and aspartate aminotransferase levels, or longitudinal changes in two-dimensional and three-dimensional magnetic resonance elastography-derived liver stiffness between the ezetimibe and placebo arms. Compared to histologic nonresponders (25/35), histologic responders (10/35) had a significantly greater reduction in MRI-PDFF (-4.35 ± 4.9% versus -0.30 ± 4.1%, P < 0.019).

CONCLUSIONS

Ezetimibe did not significantly reduce liver fat in NASH. This trial demonstrates the application of colocalization of MRI-PDFF-derived fat maps and magnetic resonance elastography-derived stiffness maps of the liver before and after treatment to noninvasively assess treatment response in NASH.

Cholesterol cholelithiasis in pregnant women: pathogenesis, prevention and treatment

Epidemiological and clinical studies have found that gallstone prevalence is twice as high in women as in men at all ages in every population studied. Hormonal changes occurring during pregnancy put women at higher risk. The incidence rates of biliary sludge (a precursor to gallstones) and gallstones are up to 30 and 12%, respectively, during pregnancy and postpartum, and 1-3% of pregnant women undergo cholecystectomy due to clinical symptoms or complications within the first year postpartum. Increased estrogen levels during pregnancy induce significant metabolic changes in the hepatobiliary system, including the formation of cholesterol-supersaturated bile and sluggish gallbladder motility, two factors enhancing cholelithogenesis. The therapeutic approaches are conservative during pregnancy because of the controversial frequency of biliary disorders. In the majority of pregnant women, biliary sludge and gallstones tend to dissolve spontaneously after parturition. In some situations, however, the conditions persist and require costly therapeutic interventions. When necessary, invasive procedures such as laparoscopic cholecystectomy are relatively well tolerated, preferably during the second trimester of pregnancy or postpartum. Although laparoscopic operation is recommended for its safety, the use of drugs such as ursodeoxycholic acid (UDCA) and the novel lipid-lowering compound, ezetimibe would also be considered. In this paper, we systematically review the incidence and natural history of pregnancy-related biliary sludge and gallstone formation and carefully discuss the molecular mechanisms underlying the lithogenic effect of estrogen on gallstone formation during pregnancy. We also summarize recent progress in the necessary strategies recommended for the prevention and the treatment of gallstones in pregnant women.

The effects of ezetimibe on non-alcoholic fatty liver disease and glucose metabolism: a randomised controlled trial

AIMS/HYPOTHESIS

The cholesterol absorption inhibitor ezetimibe has been shown to ameliorate non-alcoholic fatty liver disease (NAFLD) pathology in a single-armed clinical study and in experimental animal models. In this study, we investigated the efficacy of ezetimibe on NAFLD pathology in an open-label randomised controlled clinical trial.

METHODS

We had planned to enrol 80 patients in the trial, as we had estimated that, with this sample size, the study would have 90% power. The study intervention and enrolment were discontinued because of the higher proportion of adverse events (significant elevation in HbA(1c)) in the ezetimibe group than in the control group. Thirty-two patients with NAFLD were enrolled and randomised (allocation by computer program). Ezetimibe (10 mg/day) was given to 17 patients with NAFLD for 6 months. The primary endpoint was change in serum aminotransferase level. Secondary outcomes were change in liver histology (12 control and 16 ezetimibe patients), insulin sensitivity including a hyperinsulinaemic-euglycaemic clamp study (ten control and 13 ezetimibe patients) and hepatic fatty acid composition (six control and nine ezetimibe patients). Hepatic gene expression profiling was completed in 15 patients using an Affymetrix gene chip. Patients and the physician in charge knew to which group the patient had been allocated, but people carrying out measurements or examinations were blinded to group.

RESULTS

Serum total cholesterol was significantly decreased in the ezetimibe group. The fibrosis stage and ballooning score were also significantly improved with ezetimibe treatment. However, ezetimibe treatment significantly increased HbA1c and was associated with a significant increase in hepatic long-chain fatty acids. Hepatic gene expression analysis showed coordinate downregulation of genes involved in skeletal muscle development and cell adhesion molecules in the ezetimibe treatment group, suggesting a suppression of stellate cell development into myofibroblasts. Genes involved in the L-carnitine pathway were coordinately downregulated by ezetimibe treatment and those in the steroid metabolism pathway upregulated, suggestive of impaired oxidation of long-chain fatty acids.

CONCLUSIONS/INTERPRETATION

Ezetimibe improved hepatic fibrosis but increased hepatic long-chain fatty acids and HbA1c in patients with NAFLD. These findings shed light on previously unrecognised actions of ezetimibe that should be examined further in future studies.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN) Clinical Trials Registry UMIN000005250.

FUNDING

The study was funded by grants-in-aid from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and research grants from MSD.

Ezetimibe markedly attenuates hepatic cholesterol accumulation and improves liver function in the lysosomal acid lipase-deficient mouse, a model for cholesteryl ester storage disease

Lysosomal acid lipase (LAL) plays a critical role in the intracellular handling of lipids by hydrolyzing cholesteryl esters (CE) and triacylglycerols (TAG) contained in newly internalized lipoproteins. In humans, mutations in the LAL gene result in cholesteryl ester storage disease (CESD), or in Wolman disease (WD) when the mutations cause complete loss of LAL activity. A rat model for WD and a mouse model for CESD have been described. In these studies we used LAL-deficient mice to investigate how modulating the amount of intestinally-derived cholesterol reaching the liver might impact its mass, cholesterol content, and function in this model. The main experiment tested if ezetimibe, a potent cholesterol absorption inhibitor, had any effect on CE accumulation in mice lacking LAL. In male Lal(-/-) mice given ezetimibe in their diet (20 mg/day/kg bw) for 4 weeks starting at 21 days of age, both liver mass and hepatic cholesterol concentration (mg/g) were reduced to the extent that whole-liver cholesterol content (mg/organ) in the treated mice (74.3±3.4) was only 56% of that in those not given ezetimibe (133.5±6.7). There was also a marked improvement in plasma alanine aminotransferase (ALT) activity. Thus, minimizing cholesterol absorption has a favorable impact on the liver in CESD.

New insights into the molecular mechanism of intestinal fatty acid absorption

BACKGROUND

Dietary fat is one of the most important energy sources of all the nutrients. Fatty acids, stored as triacylglycerols (also called triglycerides) in the body, are an important reservoir of stored energy and derived primarily from animal fats and vegetable oils.

DESIGN

Although the molecular mechanisms for the transport of water-insoluble amphipathic fatty acids across cell membranes have been debated for many years, it is now believed that the dominant means for intestinal fatty acid uptake is via membrane-associated fatty acid-binding proteins, that is, fatty acid transporters on the apical membrane of enterocytes.

RESULTS

These findings indicate that intestinal fatty acid absorption is a multistep process that is regulated by multiple genes at the enterocyte level, and intestinal fatty acid absorption efficiency could be determined by factors influencing intraluminal fatty acid molecules across the brush border membrane of enterocytes. To facilitate research on intestinal, hepatic and plasma triacylglycerol metabolism, it is imperative to establish standard protocols for precisely and accurately measuring the efficiency of intestinal fatty acid absorption in humans and animal models. In this review, we will discuss the chemical structure and nomenclature of fatty acids and summarize recent progress in investigating the molecular mechanisms underlying the intestinal absorption of fatty acids, with a particular emphasis on the physical chemistry of intestinal lipids and the molecular physiology of intestinal fatty acid transporters.

CONCLUSIONS

A better understanding of the molecular mechanism of intestinal fatty acid absorption should lead to novel approaches to the treatment and the prevention of fatty acid-related metabolic diseases that are prevalent worldwide.

Ezetimibe increases hepatic iron levels in mice fed a high-fat diet

Accumulating evidence suggests that ezetimibe may be a promising agent for treatment of nonalcoholic fatty liver disease and steatohepatitis (NAFLD/NASH). Phlebotomy and dietary iron restriction reduce serum transaminase in NAFLD/NASH patients. Recent studies have shown that a mutual effect exists between lipid metabolism and iron metabolism. Accordingly, we examined the effect of ezetimibe on iron metabolism in mice fed a high-fat diet with or without iron. We fed C57BL/6 mice the following diets for 12 weeks. Experiment 1 comprised [1] a control diet (C), [2] C plus ezetimibe (0.3 mg/day; 4 weeks) (CE), [3] a high-fat diet (H), and [4] H plus ezetimibe (HE). Experiment 2 comprised [1] C containing carbonyl iron (average; 22.4 mg/day; 6 weeks) (CI), [2] CI plus ezetimibe (CIE), [3] H containing carbonyl iron (HI), and [4] HI plus ezetimibe (HIE). Blood, livers, and duodenum were removed after 12 weeks. In experiment 1, the hepatic iron levels were higher in HE than H, whereas there was no difference between C and CE. Hepatic mRNA expression of transferrin receptor 1 and 2, ferritins, and hepcidin were increased more in CE than C, and more in HE than H. In the duodenum, divalent metal transporter 1, ferritin H, and hephaestin mRNA levels were increased in CE compared with C. In experiment 2, hepatic iron concentrations were higher in HIE than HI. Hepatic mRNA expression of ferritin L and hepcidin were increased in HIE compared with HI. In duodenum, ferritin L mRNA was increased in HIE compared with CIE. Ezetimibe induced hepatic iron uptake transporter expression in mice fed a high-fat diet, causing increased hepatic iron concentrations.

Current views on genetics and epigenetics of cholesterol gallstone disease

Cholesterol gallstone disease, one of the commonest digestive diseases in western countries, is induced by an imbalance in cholesterol metabolism, which involves intestinal absorption, hepatic biosynthesis, and biliary output of cholesterol, and its conversion to bile acids. Several components of the metabolic syndrome (e.g., obesity, type 2 diabetes, dyslipidemia, and hyperinsulinemia) are also well-known risk factors for gallstones, suggesting the existence of interplay between common pathophysiological pathways influenced by insulin resistance, genetic, epigenetic, and environmental factors. Cholesterol gallstones may be enhanced, at least in part, by the abnormal expression of a set of the genes that affect cholesterol homeostasis and lead to insulin resistance. Additionally, epigenetic mechanisms (mainly DNA methylation, histone acetylation/deacetylation, and noncoding microRNAs) may modify gene expression in the absence of an altered DNA sequence, in response to different lithogenic environmental stimuli, such as diet, lifestyle, pollutants, also occurring in utero before birth. In this review, we will comment on various steps of the pathogenesis of cholesterol gallstones and interaction between environmental and genetic factors. The epigenomic approach may offer new options for therapy of gallstones and better possibilities for primary prevention in subjects at risk.

Antilithiasic and hypolipidaemic effects of Raphanus sativus L. var. niger on mice fed with a lithogenic diet

In Mexico, Raphanus sativus L. var. niger (black radish) has uses for the treatment of gallstones and for decreasing lipids serum levels. We evaluate the effect of juice squeezed from black radish root in cholesterol gallstones and serum lipids of mice. The toxicity of juice was analyzed according to the OECD guidelines. We used female C57BL/6 mice fed with a lithogenic diet. We performed histopathological studies of gallbladder and liver, and measured concentrations of cholesterol, HDL cholesterol and triglycerides. The juice can be considered bioactive and non-toxic; the lithogenic diet significantly induced cholesterol gallstones; increased cholesterol and triglycerides levels, and decreased HDL levels; gallbladder wall thickness increased markedly, showing epithelial hyperplasia and increased liver weight. After treatment with juice for 6 days, cholesterol gallstones were eradicated significantly in the gallbladder of mice; cholesterol and triglycerides levels decreased too, and there was also an increase in levels of HDL (P < 0.05). Gallbladder tissue continued to show epithelial hyperplasia and granulocyte infiltration; liver tissue showed vacuolar degeneration. The juice of black radish root has properties for treatment of cholesterol gallstones and for decreasing serum lipids levels; therefore, we confirm in a preclinical study the utility that people give it in traditional medicine.

Limits and perspective of oral therapy with statins and aspirin for the prevention of symptomatic cholesterol gallstone disease

The prevalence of gallstones disease in Western countries is 10 - 15%. Gallstones can be one of two types - cholesterol or pigment - with cholesterol gallstones representing nearly the 80% of the total. Cholesterol and pigment gallstones have different predisposing factors: cholesterol gallstones are related to supersaturated bile in cholesterol, whereas black pigment gallstones are related to hyperbilirubinbilia factors (hemolysis, etc.); these are necessary, but not sufficient, factors to produce gallstones in vivo. Gall bladder mucosa factors (gall bladder secretion of mucin, local bile stasis and production of endogenous biliary β-glucuronidase) may coexist with the aforementioned factors and facilitate gallstone nucleation and growth. The gold-standard treatment for symptomatic gallstones is laparoscopic cholecystectomy. Several studies have reported a significant reduction in the onset of symptomatic gallstones disease in patients undergoing chronic therapy with statins, which can reduce bile cholesterol saturation. Aspirin, which has been shown to reduce the local production of gall bladder mucins (mucosal or parietal factors of gallstone formation) in animal experimental models, does not appear to reduce the risk of symptomatic gallstones disease when tested alone. The new horizon of oral therapy for the prevention of symptomatic gallstone disease needs to evaluate the long-term effect of statins and chronic aspirin administration in patients with dyslipidemia and/or atherosclerosis.

The ABCG5 ABCG8 sterol transporter opposes the development of fatty liver disease and loss of glycemic control independently of phytosterol accumulation

ABCG5 and ABCG8 form a complex (G5G8) that opposes the absorption of plant sterols but is also expressed in liver where it promotes the excretion of cholesterol into bile. Hepatic G5G8 is transcriptionally regulated by a number of factors implicated in the development of insulin resistance and nonalcoholic fatty liver disease. Therefore, we hypothesized that G5G8 may influence the development of diet-induced obesity phenotypes independently of its role in opposing phytosterol absorption. G5G8 knock-out (KO) mice and their wild type (WT) littermates were challenged with a plant sterol-free low fat or high fat (HF) diet. Weight gain and the rise in fasting glucose were accelerated in G5G8 KO mice following HF feeding. HF-fed G5G8 KO mice had increased liver weight, hepatic lipids, and plasma alanine aminotransferase compared with WT controls. Consistent with the development of nonalcoholic fatty liver disease, macrophage infiltration, the number of TUNEL-positive cells, and the expression of proinflammatory cytokines were also increased in G5G8 KO mice. Hepatic lipid accumulation was associated with increased peroxisome proliferator activated receptor γ, CD36, and fatty acid uptake. Phosphorylation of eukaryotic translation initiation factor 2α (eiF2α) and expression of activating transcription factor 4 and tribbles 3 were elevated in HF-fed G5G8 KO mice, a pathway that links the unfolded protein response to the development of insulin resistance through inhibition of protein kinase B (Akt) phosphorylation. Phosphorylation of Akt and insulin receptor was reduced, whereas serine phosphorylation of insulin receptor substrate 1 was elevated.

Water channel proteins in bile formation and flow in health and disease: when immiscible becomes miscible

An essential function of the liver is the formation and secretion of bile, a complex aqueous solution of organic and inorganic compounds essential as route for the elimination of body cholesterol as unesterified cholesterol or as bile acids. In bile, a considerable amount of otherwise insoluble cholesterol is solubilized by carriers including two other classes of lipids, namely phospholipid and bile acids. Formation of bile and generation of bile flow are driven by the active secretion of bile acids, lipids and electrolytes into the canalicular and bile duct lumens followed by the parallel movement of water. Thus, water has to cross rapidly into and out of the cell interior driven by osmotic forces. Bile as a fluid, results from complicated interplay of hepatocyte and cholangiocyte uptake and secretion, concentration, by involving a number of transporters of lipids, anions, cations, and water. The discovery of the aquaporin water channels, has clarified the mechanisms by which water, the major component of bile (more than 95%), moves across the hepatobiliary epithelia. This review is focusing on novel acquisitions in liver membrane lipidic and water transport and functional participation of aquaporin water channels in multiple aspects of hepatobiliary fluid balance. Involvement of aquaporins in a series of clinically relevant hepatobiliary disorders are also discussed.