The effect of cholestyramine on the elimination of cholesterol as bile acids in patients with hyperlipoproteinaemia type II and IV

Abstract. The turnover of ¹⁴ C-cholic acid and ³ H-chenodeoxycholic acid was studied in hyperlipaemic patients before and during treatment with cholestyramine. — In five female patients with hyperlipoproteinaemia type IIa the pool size and turnover of cholic acid as well as the total formation of bile acids were significantly lower than in female normolipaemic controls. During treatment with cholestyramine, cholic acid synthesis rose 4–18 fold and the turnover of chenodeoxycholic acid increased about twice. In three of the patients these changes were associated with a normalization of the serum cholesterol levels. Mainly due to the high turnover of cholic acid, total bile acid synthesis was above the normal range in the five male patients with hyperlipoproteinaemia type IV. During treatment with cholestyramine, the serum lipids and cholic acid formation remained unchanged but the turnover of chenodeoxycholic acid increased by a factor of about two. This resulted in a decrease of the abnormally high initial ratio between the formation of cholic acid and chenodeoxycholic acid. The unequal response to cholestramine treatment is taken to be a further indication that hyperlipoproteinaemia type II and type IV are different entities of disease affecting cholesterol and bile acid metabolism.     

The Effect of Clofibrate on the Elimination of Cholesterol as Bile Acids in Patients with Hyperlipoproteinaemia Type II and IV

Abstract. The turnover of ¹⁴C-cholic acid and ³H-chenode-oxycholic acid was studied in hyperlipaemic patients before and during treatment with clofibrate. - Before therapy the total formation of bile acids recorded for 6 patients with hyperlipoproteinnemia type Il (387± 70 mg/day, mean ± S.E.) was considerably less than that encountered for 6 patients with hyperlipoproteinaemia type IV (1 379 ± 221 mg/day). This difference was mainly due to a high synthesis of cholic acid in the latter patients. - The administration of clofibrate had no consistent effect on the half-life, pool size and turnover of the bile acids in the patients with type II lipoprotein pattern. The combined synthesis of cholic acid and chenodeoxycholic acid decreased in all patients with hyperlipoproteinaemia type IV and amounted on average to 549± 97 mg/day. The effect on the formation of chenodeoxycholic acid was insignificant but the turnover of cholic acid decreased from 1076± 243 to 333 ± 85 mg/day.     

The Formation of Bile Acids in Patients with Three Types of Hyperlipoproteinemia

Abstract. ¹⁴C-cholic and ³H-chenodeoxycholic acid were administered orally to patients who were given a standardized diet of the regular type. The total formation of bile acids and the combined cholic and chenodeoxycholic pool in 8 patients with hyper-β-lipoproteinaemia (hyperlipoproteinaemia type II) were significantly lower than those recorded for 10 patients with hyperpre-β-lipoproteinaemia (hyperlipoproteinaemia type IV) and for 3 patients with combined hyperpre-β-lipoproteineamia and hyperchylemicronaemia (hyperlipoproteinaemia type V). These differences were exclusively related to variations of the pool size and turnover of cholic acid. — When compared to a younger group of healthy subjects with a somewhat higher caloric intake, the formation of cholic acid was subnormal in type II and markedly elevated in type TV and V.     

Plasma cholesterol esterification rate in hyperlipoproteinaemia: relation to cholesterol elimination

The present study was undertaken to determine the relationship between plasma lecithin: cholesterol acyl transfer (LCAT) rate and cholesterol and bile acid turnover in hyperlipidaemia. Nineteen healthy controls, 19 patients with hyperlipoproteinaemia (HLP) type IIa and 12 patients with HLP type IV were studied under standardized dietary conditions. Bile acid kinetics was determined with the aid of [14C]labelled cholic acid and chenodeoxycholic acid. In the hyperlipidaemic patients, cholesterol balance was calculated as the sum of bile acid synthesis plus daily faecal excretion of neutral C27 steroids minus dietary intake of cholesterol. The plasma LCAT rate was determined simultaneously. The mean values of bile acid formation, cholesterol balance, and LCAT rate in HLP type IV patients exceeded those in HLP type IIa patients or in the controls. An increased plasma LCAT rate was found among HLP type IV patients with and without evidence of cardiovascular disease. Plasma LCAT rate correlated positively with bile acid formation (Rs = +0.78, p less than 0.01) and cholesterol balance (Rs = +0.88, p less than 0.002) in HLP type IV. No such relationships were obtained in the controls or in HLP type IIa. It is suggested that an increased production and/or flux of VLDL in HLP type IV is linked to an enhanced plasma LCAT rate and to an increased formation and metabolism of cholesterol in the liver.     

Plasma cholesterol esterification rate in hyperlipoproteinaemia: Relation to cholesterol elimination

The present study was undertaken to determine the relationship between plasma lecithin: cholesterol acyl transfer (LCAT) rate and cholesterol and bile acid turnover in hyperlipidaemia. Nineteen healthy controls, 19 patients with hyperlipoproteinaemia (HLP) type IIa and 12 patients with HLP type IV were studied under standardized dietary conditions. Bile acid kinetics was determined with the aid of [¹⁴C]labelled cholic acid and chenodeoxycholic acid. In the hyperlipidaemic patients, cholesterol balance was calculated as the sum of bile acid synthesis plus daily faecal excretion of neutral C₂₇ steroids minus dietary intake of cholesterol. The plasma LCAT rate was determined simultaneously. The mean values of bile acid formation, cholesterol balance, and LCAT rate in HLP type IV patients exceeded those in HLP type IIa patients or in the controls. An increased plasma LCAT rate was found among HLP type IV patients with and without evidence of cardiovascular disease. Plasma LCAT rate correlated positively with bile acid formation (R_s = +0.78, p<0.01) and cholesterol balance (R_s = +0.88, p<0.002) in HLP type IV. No such relationships were obtained in the controls or in HLP type IIa. It is suggested that an increased production and/or flux of VLDL in HLP type IV is linked to an enhanced plasma LCAT rate and to an increased formation and metabolism of cholesterol in the liver.     

Biliary lipid composition during treatment with different hypolipidaemic drugs.

In an attempt to clarify the possible lithogenic effects of commonly used hypolipidaemic drugs, gallbladder bile was obtained from patients with primary hyperlipoproteinaemia before and during treatment with nicotinic acid (n = 13), cholestyramine (n = 19), clofibrate (n = 11), and a combination of cholestyramine and clofibrate (n = 11). Each treatment period was minimum 6 weeks, and standardized dietary conditions were obtained. Both nicotinic acid and clofibrate treatment caused an increase in biliary cholesterol concentration relative to biliary total lipids (bile acids, phospholipids, and cholesterol). During cholestyramine medication the relative cholesterol concentration fell. A combination of cholestyramine with clofibrate medication led to a decrease of bile saturation to pretreatment levels in nine of the eleven subjects. In the other two a further increase in the cholesterol saturation of the bile occurred. Treatment with nicotinic acid and clofibrate but not with cholestyramine is thus probably associated with an increased risk for development of cholesterol gallstones. It is suggested that addition of cholestyramine may be a possible way to prevent the lithogenic effect of clofibrate in patients with hyperlipoproteinaemia when not only hypocholesterolaemic but also hypotriglyceridaemic effects are wanted.     

Kinetics of primary bile acids in patients after orthotopic liver transplantation

Administration of cyclosporin A (CsA) may induce cholestasis, and this effect has been attributed to impaired hepatocellular uptake, transport, secretion and intestinal absorption of bile acids. Disturbances of the enterohepatic circulation may affect metabolism of bile acids. To test whether liver transplantation and treatment with CsA alters pool sizes or synthesis and turnover rates, we determined kinetics of primary bile acids in patients after orthotopic liver transplantation on CsA. Two male and four female patients were studied 6–20 months after transplantation. They had no overt signs of cholestasis, graft dysfunction or rejection. Kinetics of cholic acid (CA) and chenodeoxycholic acid (CDCA) were simultaneously determined after oral administration of [24-¹³C]-CA and [24-¹³C]-CDCA on the basis of isotope dilution in a single pool of bile acids. Ten healthy volunteers served as controls. After orthotopic liver transplantation, pool sizes, fractional turnover rates and synthesis rates of both primary bile acids, CA and CDCA were not significantly different from control subjects. In spite of the known interference of CsA with the enterohepatic circulation of bile acids, in the majority of patients after orthotopic liver transplantation without cholestasis, graft dysfunction or rejection, treatment with CsA does not disturb kinetics of primary bile acids.     

Kinetics of primary bile acids in patients with non-operated Crohn's disease

Abstract. The metabolism of cholic acid and cheno-deoxycholic acid was studied in seventeen patients with non-operated Crohn's disease, eleven ileitis and six ileocolitis patients. The turnover of cholic acid was significantly increased in patients with ileitis ( k = 2.0±1.13 days^-1; P <0.001) and ileocolitis ( k = 0.91±0.47 days^-1; P <0.005) as compared to normals ( k = 0.35±0.19 day^-1). Although chenodeoxycholic acid was better preserved in the enterohepatic circulation than cholic acid its turnover was also significantly faster in ileitis ( k = 0.81±0.56 days^-1; P <0.005) and ileocolitis patients ( k = 0.62±0.18 days^-1; P <0.01) than in normals ( k = 0.20±0.09 days^-1). The fractional turnover of cholic acid was related to the length of ileal involvement ( r = 0.761; P <0.001; n = 17). Patients with Crohn's ileitis tended to preserve normal fasting total bile acid pools by increased synthesis of primary bile acids and efficient absorption of deoxycholic acid and ursodeoxycholic acid by the normal colon. Patients with active ileocolitis had decreased total fasting pool sizes (2.62±1.83 mmol; P <0.001) as compared to normals (7.69±1.61 mmol). In these patients there was no increase in bile acid synthesis as compared to normals and secondary bile acids were absent from bile. It is concluded that the colon has an important role in maintaining the fasting pool size to a normal level in the presence of an interrupted enterohepatic circulation of bile acids due to ileal disease.     

Bile acid metabolism in hypothyroid subjects: response to substitution therapy

Bile acid kinetics and biliary lipid composition were determined in ten hypothyroid patients before and after treatment with L-thyroxine. Hypothyroid patients had normal synthesis rates of cholic acid and chenodeoxycholic acid. Hormone treatment, which lowered plasma cholesterol by about 35%, stimulated the formation of chenodeoxycholic acid by about 40% but did not significantly change the synthesis of cholic acid or total primary bile acids. The mean relative biliary concentration of deoxycholic acid was decreased from 30% to 19% and that of chenodeoxycholic acid was concomitantly increased. Cholesterol saturation of bile was decreased by treatment in six of the patients, but the mean value before treatment (135 +/- 13%) was not significantly different from that obtained after treatment (108 +/- 9%). It is suggested that the hypocholesterolaemic effect of thyroid hormones is not primarily due to an increased degradation of cholesterol to bile acids. Similar to what is observed in heterozygous familial hypercholesterolaemia, the defective receptor mediated degradation of plasma low density lipoproteins in hypothyroidism is thus apparently associated with a quantitatively normal catabolic rate of cholesterol to bile acids.     

Influence of cholic and chenodeoxycholic acid on biliary cholesterol secretion in man

The interrelationships between biliary bile acid, lecithin and cholesterol secretion rates were studied druing depletion of the bile acid pool and during duodenal administration of cholic or chenodeoxycholic acid in thirteen patients 7-12 days after operation for uncomplicated gallstone disease. The mean lecithin secretion rate was signigicantly higher during cholic acid than during chenodeoxycholic acid infusion. The relationship between bile acid and cholesterol secretion rates was curvilinear, y = x/(a + bx) during bile acid pool depletion and during duodenal cholic acid infusion. At low bile acid secretion rates, during bile acid pool depletion and during cholic acid infusion, the lecithin secretion rate was significantly correlated to the cholesterol secreation rate. The bile acid and cholesterol secretion rates were not significantly correlated during chenodeoxycholic acid infusion. However, under this experimental condition a significant curvilinear relationship between lecithin and cholesterol secretion rates was found. The hepatic bile became unsaturated in cholesterol at significantly lower bile acid secretion rate during chenodeoxycholic acid infusion (10.7 +/- 0.3 mumol min-1) than during cholic acid infusion (15.6 +/- 0.5 mumol min-1).     

Intestinal solubilization, absorption, pharmacokinetics and bioavailability of chenodeoxycholic acid*

Abstract. Little is known about the physical state, intestinal solubilization, absorption and bioavailability of chenodeoxycholic acid used in the medical treatment of gallstones. Therefore the concentrations of unconjugated chenodeoxycholic acid were measured in the supernatant and precipitate phases of intestinal contents aspirated from stomach, duodenum and jejunum of nine control subjects who took 500 mg chenodeoxycholic acid (4 times 125 mg gelatin-coated capsules) either fasting or together with a standard liquid meal. Chenodeoxycholic acid solubility was markedly influenced by luminal pH but was little affected by endogenous conjugated bile acids when their concentrations were > 1–2 mmol/1.
Systemic bioavailability of 250, 500 and 750 doses of chenodeoxycholic acid was measured in five subjects by comparing areas under 4 h serum concentration-time curves after giving the bile acid first as a bolus intraduodenal aqueous infusion of ³H-labelled chenodeoxycholic acid containing either ¹⁴C-polyethylene glycol or bromsulphthalein as non-absorbable markers, and then as gelatin-coated capsules by mouth.
Absorption was assessed by measuring the ratio of marker: bile acid in intestinal contents aspirated for 2 h from sites 60 and 120 cm distal to the duodenal infusion port and in three subjects quantitative recovery of marker was measured proximal to an occluding intestinal balloon. Absorption of duodenally-infused chenodeoxycholic acid was 96–99% complete and bioavailability was complete with the 250 and 500 mg doses but fell to 81% with the 750 mg dose.     

Determination of cholic acid and chenodeoxycholic acid pool sizes and fractional turnover rates by means of stable isotope dilution technique, making use of deuterated cholic acid and chenodeoxycholic acid

A procedure is described for the simultaneous determination of cholic acid and chenodeoxycholic acid pool sizes and fractional turnover rates. After oral administration of known amounts of 11,12-dideuterated chenodeoxycholic acid and 2,2,4,4-tetradeuterated cholic acid, the ratios of chenodeoxycholic acid-D2/chenodeoxycholic acid and cholic acid-D4/cholic acid are measured in consecutive serum samples, after which fractional turnover rates and pool sizes of chenodeoxycholic acid and cholic acid are determined arithmetically. In 7 healthy volunteers pool sizes for chenodeoxycholic acid and cholic acid were 22.9 +/- 7.8 and 24.1 +/- 11.7 mumol/kg, respectively. The corresponding values for the fractional turnover rates were 0.23 +/- 0.10 and 0.29 +/- 0.12/day. After oral administration of the labelled bile acids in capsule, the obtained pool sizes were significantly higher than after administration in a bicarbonate solution. Bile acid kinetics were also performed in a patient suffering from a cholesterol synthesis deficiency and in a patient very likely suffering from a bile acid synthesis deficiency. Furthermore, the kinetics of the intestinal absorption and hepatic clearance of unconjugated bile acids have been investigated in 2 healthy subjects.     

Intestinal solubilization, absorption, pharmacokinetics and bioavailability of chenodeoxycholic acid*

Abstract Little is known about the physical state, intestinal solubilization, absorption and bioavailability of chenodeoxycholic acid used in the medical treatment of gallstones. Therefore the concentrations of unconjugated chenodeoxycholic acid were measured in the supernatant and precipitate phases of intestinal contents aspirated from stomach, duodenum and jejunum of nine control subjects who took 500 mg chenodeoxycholic acid (4 times 125 mg gelatin-coated capsules) either fasting or together with a standard liquid meal. Chenodeoxycholic acid solubility was markedly influenced by luminal pH but was little affected by endogenous conjugated bile acids when their concentrations were > 1–2 mmol/1.
Systemic bioavailability of 250, 500 and 750 doses of chenodeoxycholic acid was measured in five subjects by comparing areas under 4 h serum concentration-time curves after giving the bile acid first as a bolus intraduodenal aqueous infusion of ³H-labelled chenodeoxycholic acid containing either ¹⁴C-polyethylene glycol or bromsulphthalein as non-absorbable markers, and then as gelatin-coated capsules by mouth.
Absorption was assessed by measuring the ratio of marker: bile acid in intestinal contents aspirated for 2 h from sites 60 and 120 cm distal to the duodenal infusion port and in three subjects quantitative recovery of marker was measured proximal to an occluding intestinal balloon. Absorption of duodenally-infused chenodeoxycholic acid was 96–99% complete and bioavailability was complete with the 250 and 500 mg doses but fell to 81% with the 750 mg dose.     

Bile acid synthesis and excretion following release of total extrahepatic cholestasis by percutaneous transhepatic drainage

Abstract. Urinary, biliary and serum bile acids were studied in three patients before and after percutaneous transhepatic drainage for total bile duct obstruction.
Before drainage high urinary excretion often different bile acids occurred. The percentage distribution was: cholic and chenodeoxycholic acid (66–86%), hyo-cholic (3–16%), 3β 12α-dihydroxy-5-cholenoic (3–6%) and 3β-hydroxy-5-cholenoic acid (2–8%). These acids were regularly found in serum. In addition small amounts (less than 2%) of norcholic, allocholic, 3β, 7α-dihydroxy-5β-cholanoic, 3α, 7α-dihydroxy-5α-cholanoic and lithocholic acid were excreted in urine. Trace amounts of these bile acids were found in serum.
After start of drainage biliary bile acid excretion increased rapidly during the first day, dropped to a minimum during the second or third day and then slowly increased again. In spite of normal volumes of bile produced, the total serum bile acids and the urinary excretion of bile acids remained increased during a drainage period of 19 days. The bile acids were of the same type as observed during cholestasis. In serum the increase was mainly due to high concentrations of chenodeoxycholic and 3β-hydroxy-5-cholenoic acid, as sulphate esters.
Glycine and taurine conjugates of cholic, chenodeoxycholic and hyocholic acid were mainly excreted in bile. Bile acid sulphate esters were only present in trace amounts in bile and were mainly excreted in urine. This, combined with low renal clearance, explains the elevated serum levels of sulphate esters of chenodeoxycholic and 3β-hydroxy-5-cholenoic acid conjugates.     

Bile Acid Kinetics in Relation to Sex, Serum Lipids, Body Weights, and Gallbladder Disease in Patients with Various Types of Hyperlipoproteinemia

Bile acid kinetics were determined in 15 normolipidemic and 61 hyperlipidemic subjects with the aid of [(14)C]cholic acid and [(3)H]chenodeoxycholic acid. The diet was standardized and of natural type. The total bile acid formation was within normal limits in patients with hyperlipoproteinemia types IIa and IIb. On the average the production of cholic acid (C) represented less than 50% of the total bile acid synthesis in both groups. The corresponding value recorded for the controls was 64+/-2% (mean+/-SEM). The synthesis of C in hyperlipoproteinemia type IIa was significantly below normal. Of the 27 patients with the type IV pattern, 18 had a synthesis of C and C + chenodeoxycholic acid (CD) that exceeded the upper range recorded for the controls. In these subjects the C formation represented 73+/-3% of the total bile acid synthesis. Similar findings were also encountered in the five patients with the type V lipoprotein pattern studied. The bile acid pool size of the 11 patients with hyperlipoproteinemia type IV, who had been cholecystectomized or suffered from cholelithiasis, was 900 mg smaller on the average than that of the other subjects with the same type of hyperlipoproteinemia. However, the pool size in the former subjects still tended to be higher than that of the control subjects without evidence of gallbladder "disease". In all groups of subjects the formation of bile acids tended to be higher in the male than in the female subjects. Bile acid synthesis showed no linear correlation to actual body weight, relative body weight, or body surface area. A moderate weight reduction in five patients (one with type IIb and four with type IV pattern) was followed by a 50% reduction of the C and CD synthesis.     

The effect of chenodeoxycholic acid feeding on bile acid kinetics and fecal neutral steroid excretion in patients with hyperlipoproteinemia types II and IV.

The kinetics of 24-14C-cholic acid and 3H-chenodeoxycholic acid and the elimination of cholesterol as fecal neutral steroids were studied in 6 patients with Type II and 7 patients with Type IV lipoprotein pattern before and during the ingestion of 0.8 to 1.0 Gm. of chenodeoxycholic acid per day. During treatment, the pool size of chenodeoxycholic acid increased in all subjects (not studied in one Type IV patient). In Type II patients, this effect was associated with a decrease of the cholic acid pool size from 868 +/- 141 to 213 +/- 51 mg. and of the cholic acid synthesis from 204 +/- 36 to 54 +/- 20 mg. per day. In the patients with hyperlopoproteinemia Type IV, the cholic acid pool size diminished in 6 of the 7 subjects all of whom showed a decrease in the cholic acid synthesis on the average from 607 +/- 155 to 202 +/- 44 mg. per day. It is suggested that the feedback control of cholic acid synthesis is less sensitive in the Type IV than in the Type II patients. Chenodeoxycholic acid feeding did not influence the fecal excretion of cholesterol, coprostanol, and coprostanone in a consistent way.     

Cholestyramine treatment of type IIa hypercholesterolaemia normalizes platelet reactivity against prostacyclin

Abstract. The effect of lowering total plasma and low density lipoprotein (LDL) cholesterol in heterozygous familial hypercholesterolaemia type IIa (FH) on platelet function, thromboxane (TX) formation and platelet sensitivity against iloprost, a stable prostacyclin mimetic, was studied in platelet-rich plasma ex vivo . Seven FH patients were treated with cholestyramine (12 g day^-1) for 8–11 months and were compared with eight untreated FH patients and 11 healthy control subjects. In comparison with platelets from healthy controls, platelets from untreated FH patients exhibited a significantly increased aggregation response and TX formation, and a reduced reactivity against inhibition of platelet aggregation by prostacyclin. Treatment with cholestyramine for 8–11 months resulted in a 21% reduction in total serum and LDL-cholesterol. This was not accompanied by any change in platelet hyperreactivity or TX formation. However, cholestyramine treatment normalized the platelet reactivity of FH patients against iloprost, being no more different from healthy controls. It is concluded that reduction in plasma cholesterol by cholestyramine results in normalization of the reduced platelet sensitivity against prostacyclin. This might contribute to beneficial effects of cholestyramine treatment in preventing thrombembolic complications of atherosclerosis.     

Biliary lipids, bile acids, and gallbladder function in the human female. Effects of pregnancy and the ovulatory cycle.

To study the events that might lead to an increased risk of cholesterol gallstones, we examined biliary lipid composition and secretion and bile acid composition and kinetics at different stages of pregnancy or ovulation in young, nonobese, healthy women. Lipid composition and bile acid distribution were determined in duodenal fluid obtained in the fasting state and after stimulation of the gallbladder. Biliary lipid secretion was measured by the marker-perfusion technique. Bile acid kinetics were determined with cholic and chenodeoxycholic acids labeled with carbon13, by measuring the relative abundance of 13C in duodenal bile acids for 4--5 d. In a subset of patients we measured gallbladder storage and emptying during the kinetic study. The phase of the ovulatory cycle had no effects, but there were significant changes during pregnancy. The lithogenic or cholesterol saturation index of fasting hepatic and gallbladder bile increased during the second and third trimesters. The mean secretion rate of biliary lipids was not altered, but in the last two-thirds of pregnancy, cholesterol secretion increased in relation to bile acid and phospholipid secretion. There was a progressive decrease in the percentage of chenodeoxycholic acid and a similar increase in the percentage of cholic acid. The pool size of each major bile acid increased in the first trimester. Chenodeoxycholic acid and deoxycholic acid pools, but not cholic acid pools, subsequently decreased. The fractional turnover rate of both primary bile acids was slower during pregnancy. The synthesis rate of chenodeoxycholic but not cholic acid decreased in a linear manner during the first 20 wk of pregnancy. The rate of enterohepatic cycling of the bile acid pool was reduced throughout pregnancy. The volume of the fasting gallbladder and the residual volume after a physiologically stimulated contraction were directly correlated with bile acid pool size. The residual volume was also directly related to total bile acid synthesis.     

Effects of rifampin on biliary lipids in humans.

Because the action of rifampin induces hepatic microsomal enzymes, a study was carried out in four patients to determine whether this drug alters the composition of biliary lipids. Several different measurements were made while patients were both on and off rifampin therapy for various infective processes. These measurements included multiple determinations of lipid composition of gallbladder bile, the relative proportions f individual bile acids, and kinetics of cholic acid and chenodeoxycholic acid. In all four patients, the saturation of gallbladder bile increased during rifampin treatment, and the bile consistently became supersaturated. The relative portions of chenodeoxycholic acid and cholic acid were essentially unchanged by treatment, but total synthesis of bile acids increased in three tested patients with rifampin therapy. These results indicate that rifampin increases saturation of bile with cholesterol, but this increase is not due to a reduction in bile acid production.     

Increased formation of ursodeoxycholic acid in patients treated with chenodeoxycholic acid

The formation of ursodeoxycholic acid, the 7 beta-hydroxy epimer of chenodeoxycholic acid, was investigated in three subjects with cerebrotendinous xanthomatosis and in four subjects with gallstones. Total biliary bile acid composition was analyzed by gas-liquid chromatography before and after 4 months of treatment with 0.75 g/day of chenodeoxycholic acid. Individual bile acids were identified by mass spectrometry. Before treatment, bile from cerebrotendinous xanthomatosis (CTX) subjects contained cholic acid, 85%; chenodeoxycholic acid, 7%; deoxycholic acid, 3%; allocholic acid, 3%; and unidentified steroids, 2%; while bile from gallstone subjects contained cholic acid, 45%; chenodeoxycholic acid, 43%; deoxycholic acid, 11%, and lithocholic acid, 1%. In all subjects, 4 months of chenodeoxycholic acid therapy increased the proportion of this bile acid to approximately 80% and decreased cholic acid to 3% of the total biliary bile acids, the remaining 17% of bile acids were identified as ursodeoxycholic acid. After the intravenous injection of [3H]chenodeoxycholic acid, the specific activity of biliary ursodeoxycholic acid exceeded the specific activity of chenodeoxycholic acid, and the resulting specific activity decay curves suggested precursor-product relationships. When [3H]7-ketolithocholic acid was administrated to another patient treated with chenodeoxycholic acid, radioactivity was detected in both the ursodeoxycholic acid and chenodeoxycholic acid fractions. These results indicate that substantial amounts of ursodeoxycholic acid are formed in patients treated with chenodeoxycholic acid. The ursodeoxycholic acid was synthesized from chenodeoxycholic acid presumably via 7-ketolithocholic acid.