ABSTRACT
BACKGROUND AND AIMS: Suppression of stearoyl-coenzyme A desaturase (SCD) activity leads to reduction of obesity, fatty liver as well as of insulin resistance. It was, however, recently reported to enhance atherogenesis. The aim of the present study was to investigate whether inhibition of SCD by Aramchol, a fatty acid bile conjugate with known hypocholesterolemic effects, will affect atherogenesis and how. METHODS: Aramchol was tested in vitro in cultured cells and in vivo in rodents. RESULTS: Aramchol, at very low concentrations, reduced SCD activity in liver microsomes of mice. Aramchol enhanced cholesterol efflux from macrophages more than twofold. In vivo it increased fecal sterol output and decreased markedly plasma cholesterol levels in mice. In ApoE(-/-), LDRL(-/-) and C57Bl6 mice, the effects of Aramchol on atherogenesis were non-atherogenic. CONCLUSIONS: Aramchol reduces SCD activity and is non-atherogenic. It may offer a means to obtain the desirable hepatic metabolic effects of SCD inhibition without the deleterious atherogenic effect.
Subject(s)
Atherosclerosis/etiology , Cholic Acids/pharmacology , Liver/drug effects , Liver/enzymology , Stearoyl-CoA Desaturase/antagonists & inhibitors , Animals , Apolipoproteins E/deficiency , Apolipoproteins E/genetics , Cholesterol/metabolism , Cricetinae , Diet, Atherogenic , Enzyme Inhibitors/pharmacology , Female , Macrophages, Peritoneal/drug effects , Macrophages, Peritoneal/metabolism , Male , Mesocricetus , Mice , Mice, Inbred C57BL , Mice, Knockout , Receptors, LDL/deficiency , Receptors, LDL/geneticsABSTRACT
BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in industrialized countries. It has no accepted medical therapy. Fatty acid-bile acid conjugates (FABACs) were proven to prevent diet-induced NAFLD in rodents. AIM: This study was undertaken to test whether oral FABACs are also effective in reducing liver fat in preestablished diet-induced NAFLD. METHODS: NAFLD was induced in mice and rats by a high-fat diet and maintained by various proportions thereof. The FABACs used were conjugates of cholic acid with either arachidic or stearic acids. RESULTS: FABAC therapy reduced liver fat in all four series of experiments. The rapidity of the effect was inversely proportional to the concentration of fat in the maintenance diet. In mice on a 25% maintenance diet FABACs decreased total liver lipids by about 30% in 4 weeks (P<0.03). Diglycerides (P<0.003) and triglycerides (P<0.01) were the main neutral liver lipids that decreased during FABAC therapy. Both FABACs tested reduced liver fat in NAFLD at doses of 25 and 150 mg/kg/day. High-fat diet increased, whereas FABAC therapy decreased plasma 16 : 1/(16 : 0+16 : 1) fatty acid ratio - a marker of stearoyl CoA desaturase activity. In HepG2 cells FABACs decreased de-novo fatty acid synthesis dose dependently. CONCLUSION: Oral FABAC therapy decreased liver fat in preestablished NAFLD in mice and rats. Inhibition of stearoyl CoA desaturase activity and fatty acid synthesis are mechanisms that may contribute to this decrease. FABACs may be potential therapeutic agents for human NAFLD.
Subject(s)
Bile Acids and Salts/therapeutic use , Dietary Fats/adverse effects , Fatty Acids/therapeutic use , Fatty Liver/drug therapy , Animals , Blood Glucose/metabolism , Cholic Acids/therapeutic use , Dietary Fats/administration & dosage , Disease Models, Animal , Drug Evaluation, Preclinical , Fatty Acids/biosynthesis , Fatty Liver/etiology , Fatty Liver/metabolism , Fatty Liver/pathology , Lipid Metabolism , Liver/metabolism , Male , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Rats , Rats, Inbred F344 , Stearoyl-CoA Desaturase/blood , Weight GainABSTRACT
Fatty acid bile acid conjugates (FABACs) prevent and dissolve cholesterol gallstones and prevent diet induced fatty liver, in mice. The present studies aimed to test their hypocholesterolemic effects in mice. Gallstone susceptible (C57L/J) mice, on high fat (HFD) or regular diet (RD), were treated with the conjugate of cholic acid with arachidic acid (FABAC; Aramchol). FABAC reduced the elevated plasma cholesterol levels induced by the HFD. In C57L/J mice, FABAC reduced plasma cholesterol by 50% (p<0.001). In mice fed HFD, hepatic cholesterol synthesis was reduced, whereas CYP7A1 activity and expression were increased by FABAC. The ratio of fecal bile acids/neutral sterols was increased, as was the total fecal sterol excretion. In conclusion, FABACs markedly reduce elevated plasma cholesterol in mice by reducing the hepatic synthesis of cholesterol, in conjunction with an increase of its catabolism and excretion from the body.
Subject(s)
Anticholesteremic Agents/administration & dosage , Anticholesteremic Agents/chemistry , Bile Acids and Salts/administration & dosage , Cholic Acids/administration & dosage , Animals , Anticholesteremic Agents/therapeutic use , Bile Acids and Salts/therapeutic use , Body Weight/drug effects , Body Weight/genetics , Cholesterol/analysis , Cholesterol/blood , Cholic Acids/therapeutic use , Dietary Fats/administration & dosage , Eicosanoic Acids/administration & dosage , Feces/chemistry , Gallstones/enzymology , Gallstones/genetics , Gallstones/physiopathology , Gallstones/prevention & control , Genetic Predisposition to Disease , Lipoproteins/blood , Mice , Mice, Inbred C57BL , Microsomes, Liver/chemistry , Microsomes, Liver/drug effects , Microsomes, Liver/enzymology , Organ Size/drug effects , Organ Size/genetics , Triglycerides/bloodABSTRACT
Cholesterol gallstones usually develop in the gallbladder and rarely form in bile ducts even in patients with highly lithogenic bile. Bile concentration and proteins (e.g. mucin) may affect crystallization, but the exact nature of this effect, especially in relation to crystallization pathways and microstructural evolution remains unclear. We examined lipid microstructures in paired hepatic and gallbladder biles to reveal ones that are essential for crystallization. Combining digital light microscopy with cryogenic-temperature transmission electron microscopy we are able to directly visualize and compare the time evolution of lipid microstructures in paired hepatic, gallbladder and diluted gallbladder biles of gallstone patients and controls, without drying or separating. Gallbladder bile exhibited several multilamellar vesicles and spheroidal micelles preceding and throughout crystallization. Vesicle morphology changed before crystallization was observed. In contrast, hepatic bile revealed almost no crystallization and while a variety of unilamellar vesicles and spheroidal micelles existed throughout the examination, multilamellar vesicles were rare. Diluted gallbladder bile was different from native gallbladder bile, as well as the paired hepatic bile, yielding occasional crystallization. Our findings suggest that maturing multilamellar vesicles precede (and at least partially initiate) crystallization in gallbladder bile. Although microstructural development seems to be concentration dependent, dilution of gallbladder bile to hepatic bile concentrations neither makes it identical to hepatic bile, nor prevents crystallization.
Subject(s)
Bile/chemistry , Gallbladder/metabolism , Liver/metabolism , Bile/metabolism , Bile Acids and Salts/chemistry , Cholesterol/chemistry , Cholesterol/metabolism , Crystallization , Humans , Lipids/chemistry , Micelles , Microscopy/methods , Microscopy, Electron, Transmission , TemperatureABSTRACT
Unnatural bile salts have been synthesized with a cationic group at the side chain of natural bile acids. These cationic bile salts aggregate in water and aqueous salt solutions in a manner similar to their natural counterparts. The critical micellar concentrations of the cationic bile salts were measured using a fluorescence method. Cationic bile salts aggregated at a concentration lower than natural deoxycholic acid. Since dihydroxy bile salt micelles are well known for cholesterol dissolution/removal, the dissolution in the cationic micelles has been evaluated. The cationic analogs dissolve approximately 70 mg/dL of cholesterol, which is comparable to taurochenodeoxycholate micelle under identical bile salt concentrations. Cholesterol dissolution in cationic bile salt micelle enhanced upon adding various amounts of PC. Cholesterol crystallization was studied in model bile at various cationic bile salt concentrations. The addition of 5, 15 and 30 mM of the cationic bile salts attenuated the crystallization process, without influencing the crystal observation time or decreasing the final amount of crystals formed. All these effects were comparable to those observed with cholic acid. These findings suggest that cationic bile salts have physico-chemical properties analogous to those of natural anionic bile salts, and thus may have therapeutic potential.
