Bile acid binding in plasma: the importance of lipoproteins.

Bile acid (BA) hydrophobicity, evaluated by the octanol-water partition coefficient, decreases along the series deoxycholic acid-chenodeoxy cholic acid-hyodeoxycholic acid-ursodeoxycholic acid-cholic acid (CA)-ursocholic acid (UCA). In vitro experiments carried out using dialysis techniques (to determine the maximum BA binding) and ultrafiltration of plasma pre-incubated with 0.1 mM BA (to assess the distribution of BA between the different lipoprotein fractions) showed that the maximum binding of BA to plasma and lipoproteins follows the same order of hydrophobicity. The fraction not bound to proteins, greater with the hydrophilic BA (UCA and CA), is distributed in the lipoprotein fractions and in particular in high density lipoproteins.

Relationships between squalene and cholesterol in bile: effect of ursodeoxycholic acid administration in patients with radiolucent gallstones.

Squalene is an obligate intermediate of cholesterol synthesis and plasma squalene to cholesterol ratio correlates significantly with cholesterol synthesis rate in the liver. Sixteen nonobese patients with radiolucent gallstones were randomly allocated into two treatment groups receiving 15 mg/kg/day ursodeoxycholic acid (group A) or 15 mg/kg/day lactose (group B) administered three times daily for 30 days. In group A, biliary squalene to cholesterol ratio was significantly lowered (from 1.19 to 0.86, P less than 0.02), as was cholesterol saturation (from 1.39 to 0.95, P less than 0.001); levels of plasma very-low-density lipoprotein cholesterol (VLDL-C) (from 30 to 26 mg/dL) and plasma VLDL-triglyceride (VLDL-TG) (from 81 to 68 mg/dL) decreased significantly only in the group taking ursodeoxycholic acid. No variations of squalene concentrations and squalene to cholesterol ratio were observed in the plasma of both groups. Biliary cholesterol saturation during ursodeoxycholic acid administration correlated directly with squalene to cholesterol ratio in bile; reduction of these two parameters is accompanied by decreased VLDL-C levels.

Different resistance of mammalian red blood cells to hemolysis by bile salts.

To evaluate why hemolysis of red blood cells (RBC) by bile acids varies in different mammalian species, we determined the mean corpuscular volume (MCV), lipid content and the concentrations of the conjugates of deoxycholate and of NaCl inducing 50% hemolysis of RBC from healthy humans, pigs, horses, cows, sheep and jaundiced humans. A volume of 0.05 mL of washed RBC at 1% hematocrit, which has the same lipid content but different phospholipid composition and number of erythrocytes (owing to the variable MCV), was incubated in taurodeoxycholate (TDC) solution (0-5 mM) to determine the TDC concentration inducing 50% hemolysis (TDC50). The TDC50 was highest in RBC of sheep and decreased within the series sheep > pig > cow > horse > healthy human > jaundiced human, which have generally increasing MCV. The osmotic resistance followed an inverse order, with jaundiced human > healthy human > horse > cow > pig > sheep. Although we found no correlation between the TDC50 and phospholipid composition of the erythrocytes tested, the extent of bile salt-induced hemolysis seemed to depend on both the MCV and the number of erythrocytes in the incubation medium.

Steatorrhoea in cirrhosis: effect of ursodeoxycholic acid administration.

In a double-blind, crossover study, 10 cirrhotic patients (Child B rating) with steatorrhoea (daily output of faecal fat greater than 8 g) and dyspepsia were placed on a controlled diet for 14 days. Patients then received 150 mg ursodeoxycholic acid (UDCA) or placebo twice daily for 14 days. Faecal fat excretion was reduced from 14.7 to 10.6 g/day by UDCA and dyspepsia symptom scores were also reduced. Serum aspartate aminotransferase concentrations declined significantly (P less than 0.02) following UDCA treatment, whereas serum bile acid levels increased from 35 to 40.5 microM and the percentage of UDCA increased to 22%. It is concluded that UDCA may be useful for many of the symptoms present in patients with liver cirrhosis.

Treatment of chronic constipation by a bulk-forming laxative (Fibrolax).

Seventy-five patients affected by chronic constipation were treated for 4 weeks with an Ispaghula Husk preparation (Fibrolax), a bulk-forming laxative. Frequency, stool consistency, abdominal pain and signs of venous stasis improved after treatment. No important side-effect was recorded. Cholesterol, HDL-cholesterol and triglycerides did not show significant changes.

[Polyunsaturated phosphatidylcholine and bile lipid composition]. / Fosfatidilcolina polinsatura e composizione lipidica della bile.

The lipid composition of bile and the molar percentages of its components (cholesterol, lecithin [Lec], and bile salts) are influenced by diet composition (for example the content of cholesterol) and during fasting. Molecular species of Lec can be affected by the species of dietary fatty acids (a high n-3 fatty acid content in the diet increases their proportion in biliary Lec). The administration of polyunsaturated Lec (EPL), rich in 18:2-18:2-PC, increases the percentage of linoleic acid at position 2 of biliary lecithin, which is often reduced in subjects with cholesterol gallstones.

[Effects of insulin on the deformability of normal erythrocytes suspended on artificial tampons, in normal plasma and plasma of diabetic patients]. / Effetti dell'insulina sulla deformabilità dei globuli rossi normali sospesi in tampone artificiale, in plasma normale ed in plasma di pazienti diabetici.

The effect of different insulin concentrations on the deformability of normal red blood cells resuspended in different media was studied in vitro. Insulin enhances red blood cell deformability measured by the filtration method and the observed increases are directly correlated with insulin concentrations. When red blood cells are resuspended in plasma of diabetic patients, the red blood cell filterability through Nucleopore filters is slower than that observed by resuspending the erythrocytes in normal plasma. This suggests that the plasma of diabetic patients contains an unknown factor able to reduce red blood cell deformability.

[Chemico-physical property and bile acid binding capacity of several antacids]. / Proprietà chimico-fisiche e capacità legante gli acidi biliari di alcuni antiacidi.

Liquid alginate (Gaviscon) binds small amount of bile acids. At pH 7 its viscosity (at low shear rate) is higher than that of other antiacids. High viscosity reduces the diffusion rate of bile salts and glucose and this property can play a role in the treatment of gastro-esophageal and duodeno-gastric refluxes.

Medical treatment of biliary duct stones: effect of ursodeoxycholic acid administration.

Twenty-eight patients with radiolucent biliary duct stones without cholangitis and jaundice were randomly allocated into two treatment groups receiving ursodeoxycholic acid 12 mg/kg (group A) or placebo (group B) in three daily doses for 24 months. In group A stones disappeared completely in seven patients and partially in one; placebo administration had no effect on stone size and three patients of group B (only one of group A) went to surgery for complications. Ursodeoxycholic acid treatment did not adversely affect liver function tests, and alkaline phosphatase decreased. Abdominal and biliary colics also became less frequent in the first six months of therapy in group A, but not in the placebo group. The bile was supersaturated with cholesterol in both groups, but decreased significantly only in patients receiving ursodeoxycholic acid even though the lithogenic index remained high. Cholesterol saturation of bile does not seem to be the only factor determining the dissolution of biliary duct stones which sometimes contain cholesterol as the main component.

Membrane lipid composition of red blood cells in liver disease: regression of spur cell anaemia after infusion of polyunsaturated phosphatidylcholine.

The morphology of red blood cells was studied in 30 patients with severe liver cirrhosis, in 10 patients with extrahepatic jaundice, and in 10 control subjects. In all the patients with extrahepatic jaundice more than 30% of red blood cells were target cells with increased resistance to osmotic lysis. In 12 patients with liver cirrhosis more than 30% of red blood cells were spur cells. The cholesterol: phospholipids (C/PL) molar ratio was 0.89 in target cells, 1.33 in spur cells, and 0.74 in normal red blood cells. The red blood cell membrane cholesterol and phospholipids exchanged with plasma lipoproteins, the lipid composition of which was studied in eight patients with spur cells; the free cholesterol: phospholipid (FC/PL) molar ratio was 0.33 (0.16 in the controls) in high density lipoproteins (HDL) and 1.40 (0.82 in the controls) in low density lipoproteins (LDL); in these patients the polyunsaturated fatty acid content was low in both phospholipids and cholesterol esters of lipoproteins. The irregular folds of the spur cells regressed when polyunsaturated lecithin was infused (2 g daily for five days) in eight patients with spur cell anaemia; the infusions decreased both C/PL ratio in RC to 0.88 and the concentration of unconjugated bilirubin (104.3 to 82.0 mumol/l (6.1 to 4.8 mg%)), whereas the activity of the plasma lecithin:cholesterol acyltransferase (LCAT) increased from 31.2 to 54.4 mumol/l/h. Polyunsaturated fatty acid content of RC lecithin increased after the infusion as it did in HDL, the FC/PL ratio of which decreased to 0.23.

Cholesterol absorption and sterol balance in normal subjects receiving dietary fiber or ursodeoxycholic acid.

Twelve normal subjects were placed on a constant diet and evaluated during three treatment periods, each lasting four weeks. Patients received regular diet alone during period A, regular diet plus 60 g/day wheat bran during period B, and regular diet plus 15 mg/kg/day ursodeoxycholic acid during period C. Cholesterol absorption, plasma lipid concentration, daily fecal excretion of neutral and acidic sterols, and sterol balance were determined following each treatment. No changes in serum lipid levels are observed in the three study periods. Bran administration increases fecal neutral sterol excretion and decreases cholesterol absorption (from 50.1 to 42.0%) with respect to period C. Ursodeoxycholic acid administration has no effect on fecal neutral sterol excretion, whereas bile acid excretion is markedly increased. Sterol balance (evaluated as neutral and acidic fecal sterols excreted per day minus dietary cholesterol plus ursodeoxycholic acid given per day) is lower during ursodeoxycholic acid feeding (360 +/- 145 mg/day) than during bran feeding (593 +/- 174 mg/day). In conclusion, ursodeoxycholic acid decreases sterol balance values; bran-rich diet increases sterol balance and reduces cholesterol absorption.

Composition of ascitic fluid in liver cirrhosis: bile acid and lipid content.

The concentrations of lipids, bile acids and proteins were evaluated in the ascitic fluid and plasma of 23 cirrhotics. Ascitic fluid density was highly correlated with its protein content, represented mostly by low molecular weight proteins. The ratio of plasma to ascitic fluid concentrations of nine examined proteins increased with molecular weight, indicating a selective ultrafiltration of the peritoneal transudate. Low density lipoproteins in ascitic fluid had modified electrophoretic mobility. Total cholesterol had a higher plasma to ascitic fluid ratio than high density lipoprotein cholesterol, whereas bile acids and proteins had similar plasma to ascitic fluid ratios. Indeed, bile acids strongly bind to circulating albumin: consequently ascitic fluid contains more cholic acid (less hydrophobic) than other bile acids. Analysis of both plasma and ascitic fluid composition in cirrhotics provides useful information on processes regulating passage of blood components into the peritoneal cavity.

Urinary excretion of bile acids during acute administration in man.

Six healthy subjects, 45-72 years old, received a 10-day feeding of 750 mg of two of the following bile acids: deoxycholate (DCA), chenodeoxycholate (CDCA), cholate (CA), hyodeoxycholate (HDCA), ursodeoxycholate (UDCA), and ursocholate (UCA). The urinary excretion of total bile acids was low during administration of lipophilic bile acids (DCA and CDCA), when serum levels show low postabsorption peaks. Instead, hydrophilic bile acids (UDCA and above all HDCA) were heavily excreted in the urine as sulphates and glucuronides, and serum levels reach high values. Only UCA, strongly hydrophilic, was predominantly excreted as unconjugated fractions. Thus, the physicochemical properties of bile acids (as measured by both the partition between octanol and water, and the water solubility) were factors that influenced the route of bile acid elimination from the body, whereas their conjugation was not always requested for urinary excretion.