Studies on bile acids: The microquantitative separation of cellular bile acids by gas-liquid chromatography

Beneficial Effects of Coconut Water Feeding on Lipid Metabolism in Cholesterol-Fed Rats

The purpose of this study was to determine the effect of coconut water feeding in cholesterol-fed rats. Male albino rats were fed tender coconut water and mature coconut water at a dose level of 4 mL/100 g of body weight. Cholesterol feeding caused a marked increase in total cholesterol, very low-density lipoprotein (VLDL) + low-density lipoprotein (LDL) cholesterol, and triglycerides in serum. Administration of coconut water counteracts the increase in total cholesterol, VLDL + LDL cholesterol, and triglycerides, while high-density lipoprotein cholesterol was higher. Lipid levels in the tissues viz. liver, heart, kidney, and aorta were markedly decreased in cholesterol-fed rats supplemented with coconut water. Feeding coconut water resulted in increased activities of 3-hydroxy-3-methylglutaryl-CoA reductase in liver, lipoprotein lipase in heart and adipose tissue, and plasma lecithin:cholesterol acyl transferase, while lipogenic enzymes showed decreased activities. An increased rate of cholesterol conversion to bile acid and an increased excretion of bile acids and neutral sterols were observed in rats fed coconut water. Histopathological studies of liver and aorta revealed much less fatty accumulation in these tissues in cholesterol-fed rats supplemented with coconut water. Feeding coconut water resulted in increased plasma L-arginine content, urinary nitrite level, and nitric oxide synthase activity. These results indicate that both tender and mature coconut water has beneficial effects on serum and tissue lipid parameters in rats fed cholesterol-containing diet.

Combined effect of selenium and ascorbic acid on alcohol induced hyperlipidemia in male guinea pigs

Alcoholics usually suffer from malnutrition and are especially deficient in micronutrients like vitamin C, selenium and Zn. In the present study, combined effects of selenium and ascorbic acid on alcohol-induced hyperlipidemia were studied in guinea pigs. Four groups of male guinea pigs were maintained for 45 days as follows: control (1 mg ascorbate (AA)/100 g body mass/day), ethanol (900 mg ethanol/100 g body mass + 1 mg AA/100 g body mass/day), selenium+ascorbic acid [(25 mg AA + 0.05 mg Se)/100 g body mass/day], ethanol+selenium+ascorbic acid [(25 mg AA + 0.05 mg Se + 900 mg ethanol)/100 g body mass/day]. Co-administration of selenium and ascorbic acid along with alcohol reduced the concentration of all lipids, as also evidenced from the decreased activities of hydroxymethylglutaryl-CoA reductase and enhanced activities of plasma lecithin cholesterol acyl transferase and lipoprotein lipase. Concentrations of bile acids were increased. We conclude that the supplementation of Se and ascorbic acid reduced alcohol induced hyperlipidemia, by decreased synthesis and increased catabolism.

Flavonoids from Emblica officinalis and Mangifera indica-effectiveness for dyslipidemia

Flavonoids from Emblica officinalis and Mangifera indica effectively reduce lipid levels in serum and tissues of rats induced hyperlipidemia. Hepatic HMG CoA reductase activity was significantly inhibited in rats fed E. officinalis flavonoids. But increase of this enzyme was observed in rats administered M. indica flavonoids. LCAT showed elevated levels in rats fed flavonoids from E. officinalis and M. indica. The degradation and elimination of cholesterol was highly enhanced in both the groups. In E. officinalis, the mechanism of hypolipidemic action is by the concerted action of inhibition of synthesis and enhancement of degradation. In the other group (M. indica) inhibition of cholesterogenesis was not encountered but highly significant degradation of cholesterol was noted, which may be the pivotal factor for hypolipidemic activity in this case. Though the mechanisms differ in the two cases, the net effect is to lower lipid levels.

Coconut kernel protein modifies the effect of coconut oil on serum lipids

Feeding coconut kernel along with coconut oil in human volunteers has been found to reduce serum total and LDL cholesterol when compared to feeding coconut oil alone. This effect of the kernel was also observed in rats. Since many plant proteins have been reported to exert a cholesterol lowering effect, a study was carried out on the effect of isolated kernel protein in rats. Feeding kernel protein resulted in lower levels of cholesterol, phospholipids and triglycerides in the serum and most tissues when compared to casein fed animals. Rats fed kernel protein had (1) increased hepatic degradation of cholesterol to bile acids, (2) increased hepatic cholesterol biosynthesis, and (3) decreased esterification of free cholesterol. In the intestine, however, cholesterogenesis was decreased. The kernel protein also caused decreased lipogenesis in the liver and intestine. This beneficial effect of the kernel protein is attributed to its very low lysine/arginine ratio 2.13% lysine and 24.5% arginine.

Simultaneous determination of bile acids in rat liver tissue by high-performance liquid chromatography

A method for the simultaneous determination of bile acids in rat liver tissue by high-performance liquid chromatography was developed. Without prior fractionation and alkaline hydrolysis, 30 unconjugated, glycine- and taurine-conjugated bile acids were detected by post-column enzymatic reaction and fluorescence detection. They were separated on a reversed-phase column using a linear gradient solvent system of 10 mM tribasic ammonium phosphate-acetonitrile-methanol (44:12:5, v/v/v) and 20 mM dibasic ammonium phosphate-acetonitrile-methanol (2:1:2, v/v/v). The limits of detection were 1-5 pmol, and calibration curves were linear for concentrations ranging between 10 and 4000 pmol per 10 microl injection. This rapid and reliable method is effective for measuring bile acid levels in liver tissue not only of rats but also of patients with hepatobiliary and other diseases.

Hypolipidemic effect of coriander seeds (Coriandrum sativum): mechanism of action

The effect of the administration of coriander seeds (Coriandrum sativum) on the metabolism of lipids was studied in rats fed a high fat diet with added cholesterol. The spice had a significant hypolipidemic action. The levels of total cholesterol and triglycerides decreased significantly in the tissues of the animals of the experimental group which received coriander seeds. Significant increases in beta-hydroxy, beta-methyl glutaryl CoA reductase and plasma lecithin cholesterol acyl transferase activity were noted in the experimental group. The level of LDL + VLDL cholesterol decreased while that of HDL cholesterol increased in the experimental group compared to the control group. The increased activity of plasma LCAT, enhanced hepatic bile acid synthesis and the increased degradation of cholesterol to fecal bile acids and neutral sterols appeared to account for its hypocholesterolemic effect.

Effect of tincture of Crataegus on the LDL-receptor activity of hepatic plasma membrane of rats fed an atherogenic diet

Tincture of Crataegus, (TCR), is a hypocholesterolemic and antiatherosclerotic drug made from berries of hawthorn, Crataegus oxyacantha. Its main constituents are flavonoids, triterpene saponins and a few cardioactive amines. TCR, when administered simultaneously to rats fed an atherogenic diet, significantly increased the binding of 125I-LDL to the liver plasma membranes, in vitro. Scatchard analysis of the specific binding data revealed that under the influence of TCR treatment the liver membranes bound to a greater number of 125I-LDL molecules indicating an enhancement in the LDL-receptor activity. TCR was also shown to increase bile acid excretion and to depress hepatic cholesterol synthesis in atherogenic diet fed rats. With these observations in view, the hypocholesterolemic action of TCR appears to be due to an upregulation of hepatic LDL-receptors resulting in greater influx of plasma cholesterol into the liver. TCR also prevents the accumulation of cholesterol in the liver by enhancing cholesterol degradation to bile acids and by simultaneously suppressing cholesterol biosynthesis. The various constituents of TCR may act synergistically to bring about the observed effects.

Effect of exposure of rats to cigarette smoke on the metabolism of lipids

Prolonged exposure of rats to cigarette smoke resulted in significant alterations in the metabolism of lipids. There was a significant increase in the concentration of cholesterol, triglycerides and phospholipids in most of the tissues, particularly the heart, aorta and lungs. Cholesterol, triglycerides and phospholipids decreased in the serum HDL and increased in LDL + VLDL. There was increased cholesterogenesis in the heart, lungs and liver, as evidenced by increased activity of HMG-CoA reductase and increased incorporation of labelled acetate into cholesterol. Incorporation of label into the triglycerides also increased in these tissues. Activity of lipoprotein lipase in the extrahepatic tissues was decreased. Activity of glucose-6-phosphate dehydrogenase and malic enzyme increased in the heart and lungs. There was decreased concentration of bile acids in the liver.

Effects of cholesterol feeding to maternal rats on metabolism of cholesterol and bile acids in the dams and their offspring

The influence of feeding cholesterol to rats during pregnancy and postpartum (from the 11th day of gestation to the third day after delivery) on the serum and hepatic cholesterol levels and on the bile acid composition in the pool and in the liver in relationship to the dams and their pups was examined. The hepatic content of cholesterol in both dam and offspring increased during cholesterol feeding without any changes in serum cholesterol level. In the dams, mainly the esterified cholesterol was increased; in the pups, mainly the free cholesterol was increased. Cholesterol feeding led to a pronounced increase in the pool of beta-muricholic acid and a relative decrease in the lithocholic acid concentration in pregnant rats. In fetal rats, the chenodeoxycholic acid pool was increased by cholesterol intake. The lithocholic acid pool was larger in the postpartum rats fed cholesterol than in the controls, while the concentration of alpha- and beta-muricholic acids was decreased. The neonates of cholesterol-fed dams had a larger pool of chenodeoxycholic acid but a smaller pool of beta-muricholic acid. These results suggest that the metabolism of cholesterol and of bile acids in dams and their offspring respond differently to cholesterol intake.

Improved enzymatic hydrolysis of conjugated bile acids

The hydrolysis of conjugated bile acids by cholylglycine hydrolase (EC 3.5.1.24) using the standard procedure for a commercial enzyme preparation was found to be incomplete, as judged by the use of 24-14C-taurocholic acid as a tracer. A method is proposed that incorporates the nonionic detergent Triton X-100 into the reaction mixture to achieve almost complete hydrolysis. It is proposed that the observed enhancement of enzyme activity is due to the formation of micelles by the detergent.

Analysis and structure determination of unsaturated 5 beta - cholanoic acids

Unsaturated cholanoic acids are known to arise as artifacts of chemical transformation processes and during storage and high-temperature gas liquid chromatography (GLC) of various derivatives of saturated bile acids. Nevertheless, there is evidence for their natural occurrence and isolation under conditions where artifactual formation of unsaturated bile acids would be unlikely. Since structural identification of such compounds is often complicated by a lack of knowledge of their analytical properties, a representative series of monounsaturated cholanoic acids with double bonds in rings A, B and C were prepared by POCl3 and ZnCL2 dehydration of saturated bile acids with selectively blocked hydroxyl functions. The cholenoic acids were indistinguishable from their saturated analogs by thin layer chromatography (TLC) on plain silica gel, but those compounds with sterically exposed double bonds were resolved by AgNO3-TLC, using chloroform/methanol solvent systems. The synthetic 5 beta-cholenoic acids obeyed the general rules of GLC mobility based on the overall shape of the molecule and the number and configuration of the functional groups. Constant retention factors attributable to the double bond were observed for all of the double bond types on several GLC phases, and theoretical retention times could be calculated for combinations of double bonds and functional groups not specifically represented among the synthetic standards. With gas chromatography-mass spectrometry (GC-MS), the unsaturated bile acids gave several characteristic fragments, which, in conjunction with the chromatographic properties of the parent compounds, permitted an unambiguous distinction among different unsaturated acids, and between unsaturated and saturated bile acids of the same number and configuration of functional groups. For complete structural identification of saturated and unsaturated bile acids, capillary GC-MS represents the ideal state of the art, but the less expensive combination of AgNO3-TLC and GLC also can yield much useful information concerning the structure of natural and synthetic 5 beta-cholenoic acids. This study emphasizes the need for special precautions in the isolation and derivatization of bile acids intended for studies of unsaturated components.

Further observations in lincomycin-induced cholelithiasis in guinea-pigs

Further experiments are reported on Lincomycin-induced cholelithiasis in guinea-pigs. The biochemical events in the bile and blood, and the chemical composition of gallstones, have been studied. The gallstones resemble human pigment stones in chemical composition. The clear hepatic bile and the normality of the bile salt--phospholipid--cholesterol equilibrium, the rise in beta-glucuronidase and hexosamine levels with the gallbladder, have reaffirmed that epithelial injury is most probably the primary lithogenic factor. Ligation of the cystic duct and the construction of a common hepatic duct-duodenum bypass did not prevent the development of acute cholecystitis, suggesting the lithogenic factor was mediated through the blood circulation and not through the enterohepatic circulation of bile.

The application of high pressure liquid chromatography to the analysis of bile salts in human bile

Two high pressure liquid chromatography (HPLC) systems have been evaluated for the separation of conjugated bile salts from human bile. Partisil-10 ODS with mobile phase of methanol/water pH 2 (55 : 45) at 200 nm, 0.1 AUF UV detection gave only partial separation of bile salts. However, a mu Bondapak fatty acid analysis column using isopropanol/8.8 mmol/l potassium phosphate pH 2.5 (32 : 68) as the mobile phase and 193 nm, 0.1 AUF UV detection separated all the six conjugated bile salts in bile. The limit of detection ranged from 0.1 microgram for sodium taurocholate to 0.2 microgram for sodium glycodeoxycholate. The reproducibility and the application of the method to the analysis of conjugated bile salts was demonstrated using bile from five patients. Its application to the studies of hepato-biliary disease is discussed.

Bile acids in tissues: binding of lithocholic acid to protein

Human liver contains two forms of lithocholic acid. One form is readily extractable by 95% ethanol/0.1% ammonia (soluble lithocholate, SL), while the other remains firmly bound to the residue (tissue-bound lithocholate, TBL). TBL could be hydrolytically released using clostridial cholanoylamino acid hydrolase, suggesting a peptide link between lithocholate and protein. With bovine serum albumin (BSA), lithocholic acid showed spontaneous amino group-modifying activity. When small molecular weight lysine (alpha-t-BOC-1-lysyl-beta-naphthylamide) and arginine peptides (alpha-CBZ-di-arginyl-beta-naphthylamide) were used in place of BSA, lithocholate bound specifically to the lysine peptide. The unusual affinity for lysine suggested that this amino acid might be involved as a residue in TBL. Synthesis of lithocholyl lysines and comparison with products of acid hydrolysis of TBL established epsilon-lithocholyl lysine as the predominant form in which lithocholic acid is found in tissue bound form.

A radioimmunoassay for lithocholic acid conjugates in human serum and liver tissue

A sensitive and specific radioimmunoassay for glycine and taurine conjugates of lithocholic acid (CLCA) has been developed. 3H-glycolithocholic acid (S.A. = 17Ci/mmol) was used as tracer. Separation of free from antibody-bound bile acid was carried out using ammonium sulphate (saturated solution). The antiserum showed high specificity for both glyco and tauro conjugated lithocholate (100% cross reaction) and lithocholic acid (25% cross reaction). The sensitivity of the assay (1 pmole/tube), was adequate for measuring CLCA in peripheral blood and hepatic tissue in man.

Relative concentrations of individual nonsulfated bile acids in the serum and bile of patients with cirrhosis

The relative concentrations of individual nonsulfated bile acids were determined in samples of serum and bile obtained simultaneously from 16 patients with biopsy-proven alcoholic cirrhosis. A highly significant (P less than 0.001) correlation was found between the fasting relative concentrations of each of the three major bile acids (cholic, chenodeoxycholic, and deoxycholic) in serum and bile. This relationship persisted after manipulation of bile acid pools produced by feeding of individual bile acids. We conclude that the relative concentrations of individual nonsulfated bile acids in serum accurately reflect those in bile and that measurement of individual serum bile acids may be used for screening and serial determination purposes. In particular, low levels of biliary deoxycholate can be reliably predicted by serum measurements.

Formation of bile acids in man. Metabolism of 7alpha-hydroxy-4-cholesten-3-one in normal subjects with an intact enterohepatic circulation

The formation of bile acids in man is thought to involve a series of reactions in which the initial steps are the same for both cholic acid and chenodeoxycholic acid. The point of bifurcation of the pathway is postulated to occur after the formation of 7alpha-hydroxy-4-cholesten-3-one. To test the hypothesis that the entire synthesis of both bile acids proceeds through this intermediate we studied the metabolism of labeled 7alpha-hydroxy-4-cholesten-3-one in eight normal subjects with an intact enterohepatic circulation. If all the production of cholic acid and chenodeoxycholic acid takes place via 7alpha-hydroxy-4-cholesten-3-one, the areas under the specific decay curves of cholic acid and chenodeoxycholic acid should be identical following a single injection of this labeled intermediate. However, in 6 of the 8 subjects studied the area under the cholic acid specific activity decay curve was significantly less than the area under the chenodeoxycholic acid specific activity decay curve. These results that the production of cholic acid in man may not always involve the intermediate 7alpha-hydroxy-4-cholesten-3-one.

Identification and quantitation of cholanoic acids in hepatic and extra-hepatic tissues of rat

Tissues of rats were examined for the presence of cholanoic acids. Quantitation of extraction, deconjugation, and isolation were verified by use of radioactive standards. Identification was made by thin layer and gas liquid chromatographic comparison to standards and mass spectrometry. All tissues examined were found to contain several conjugated cholanoic acids. Liver contained primarily cholic acid and peripheral tissues primarily dihydroxy compounds, mainly hyodeoxycholic acid.

Effect of cholestyramine on bile acid metabolism in normal man

The effect of cholestyramine administration on the enterohepatic circulation of bile acids was studied in eight normal volunteers. In six subjects the metabolism of sodium taurocholate-(14)C was determined after its intravenous injection before and during the 6th wk of cholestyramine administration, 16 g/day. In two subjects, the metabolism of cholic acid-(14)C was observed before and during the 2nd wk of cholestyramine, 16 g/day. Bile acid sequestration resulted in a more rapid disappearance of the injected primary bile acid and its metabolic products. The composition of fasting bile acids was promptly altered by cholestyramine to predominantly glycine-conjugated trihydroxy bile acid. In four subjects, unconjugated bile acid-(14)C was administered during cholestyramine administration; the relative proportion of glycine-conjugated bile acid-(14)C before enterohepatic circulation was similar to the relative proportion of unlabeled glycine-conjugated bile acid present in duodenal contents after an overnight fast, indicating that a hepatic mechanism was responsible for the elevated ratios of glycine- to taurine-conjugated bile acid (G: T ratios) observed. The relative proportions of both dihydroxy bile acids, chenodeoxycholic and deoxycholic, were significantly reduced. Steatorrhea did not occur, and the total bile acid pool size determined after an overnight fast was unaltered by cholestyramine. These findings suggest that in normal man bile acid sequestered from the enterohepatic circulation by cholestyramine is replaced by an increase in hepatic synthesis primarily via the pathway leading to production of glycocholic acid.