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U Beuers

Publications and source records attributed to U Beuers.

At least 55 records · Page 3Linked to original sources
PubMed1996

Tauroursodeoxycholic acid activates protein kinase C in isolated rat hepatocytes.

BACKGROUND & AIMS: Ursodeoxycholic acid (UDCA) improves liver function in patients with chronic cholestatic liver diseases by an unknown mechanism. UDCA is conjugated to taurine in vivo, and tauroursodeoxycholic acid (TUDCA) is a potent hepatocellular Ca2+ agonist and stimulates biliary exocytosis and hepatocellular Ca2+ influx, both of which are defective in experimental cholestasis. Protein kinase C (PKC) mediates stimulation of exocytosis in the liver. The aim of this study was to determine the effects of TUDCA on PKC in isolated hepatocytes. METHODS: The effect of TUDCA on the distribution of PKC isoenzymes within the hepatocyte was studied using immunoblotting and immunofluorescence techniques. In addition, the effect of TUDCA on the accummulation of sn-1,2-diacylglycerol (DAG), the intracellular activator of PKC, and hepatocellular PKC activity was studied using radioenzymatic techniques. RESULTS: Immunoblotting studies showed the presence of four isoenzymes (alpha, delta, epsilon, and zeta). The phorbol ester phorbol 12-myristate 13-acetate (1 mumol/L) induced translocation of alpha-PKC, delta-PKC, and epsilon-PKC from cytosol to a particulate membrane fraction, a key step for activation of PKC. TUDCA, but not taurocholic acid, selectively induced translocation of the alpha-PKC isoenzyme from cytosol to the membranes. In addition, TUDCA induced a significant increase in hepatocellular DAG mass and stimulated membrane-associated PKC activity. CONCLUSIONS: TUDCA might stimulate Ca(2+)-dependent hepatocellular exocytosis into bile in part by activation of alpha-PKC.

Animals↗
PubMed1996

Serum concentrations of 7alpha-hydroxy-4-cholesten-3-one reflect bile acid synthesis in humans.

Serum concentrations of 7alpha-hydroxy-4-cholesten-3-one (alpha-HC) have recently been shown to reflect the activity of cholesterol 7 alpha-hydroxylase in humans. To evaluate the relationship between alpha-HC in serum and bile acid synthesis, serum concentrations of alpha-HC, and rates of bile acid synthesis, as measured by the isotope dilution technique using gas chromatography-mass spectrometry, were determined simultaneously. Regression analysis revealed a positive linear correlation of serum alpha-Hc with synthesis of cholic acid (CA) (r = .59, P = .02), chenodeoxycholic acid (CDCA) (r = .75, P = .001), and total synthesis of both primary bile acids (r = .83, P < .001) in patients with gallstones and normal liver function (n = 15). alpha-HC was also correlated to input rates of deoxycholic acid (DCA) (r = .53, P <.05). Addition of patients with chronic cholestatic liver disease (n = 5) improved the correlation between serum alpha-HC and synthesis of CA (r = .75, P < .001), CDCA (r = .77, P < .001), and both primary bile acid combined (r = .87), P < .001). Our data are in agreement with the concept that synthesis of bile acids is regulated by cholesterol 7 alpha-hydroxylase activity and that alpha-HC in serum may serve as a convenient marker for the semiquantitative assessment of bile acid synthesis in humans.

Adult↗
PubMed1995

Effect of dietary fiber on serum bile acids in patients with chronic cholestatic liver disease under ursodeoxycholic acid therapy.

During ursodeoxycholic acid therapy for chronic cholestatic liver disease, the serum levels of lithocholic acid increase about twofold. Lithocholic acid has been shown to be hepatotoxic in some animal species. Administration of psyllium hydrophilic mucilloid (PHM), a dietary fiber, has been reported to increase the bile acid mass excreted by the feces. We, therefore, studied the effect of PHM (3 x 3.25 g/day) on serum bile acids including lithocholic acid in 12 patients with primary sclerosing cholangitis (n = 7) and primary biliary cirrhosis (n = 5) receiving ursodeoxycholic acid therapy. After 2 and 6 weeks of treatment with PHM, the serum levels of ursodeoxycholic acid increased by 52.4 +/- 72.8% (p < 0.05) and 40.5 +/- 69.6% (NS), respectively. The absolute serum levels of lithocholic acid were not significantly changed. This led to a decrease of the relative amount of lithocholic acid as referred to total bile acids and to ursodeoxycholic acid in serum by 27.4 +/- 34.5% (p < 0.05) and 25.5 +/- 32.8% (p < 0.05), respectively, after 6 weeks of PHM treatment.

Adult↗
PubMed1993

Effects of tauroursodeoxycholic acid on cytosolic Ca2+ signals in isolated rat hepatocytes.

BACKGROUND: Tauroursodeoxycholic acid (TUDCA) is of potential benefit in cholestatic disorders. However, the effects of TUDCA on cytosolic free calcium [(Ca2+)i], which regulates hepatocyte secretion, are unknown. METHODS: The effect of TUDCA on (Ca2+)i was investigated in groups of isolated rat hepatocytes by microspectrofluorometry and in single cells by confocal line scanning microscopy. RESULTS: Administration of TUDCA (5-50 mumol/L) induced a nearly fourfold increase of basal levels of (Ca2+)i. After a 15 minute treatment period, the TUDCA (10 mumol/L)-induced change in (Ca2+)i was higher than that of other mono-, di-, and trihydroxy bile acids at equimolar concentrations. Pretreatment with TUDCA (10 mumol/L) markedly reduced or abolished increases in (Ca2+)i induced by phenylephrine (1 mumol/L), the microsomal Ca(2+)-translocase inhibitor 2,5-di-(tert-butyl)-1,4-benzohydroquinone (25 mumol/L), or taurolithocholic acid (10-25 mumol/L). In Ca(2+)-free medium, TUDCA caused only a reduced and transient increase in (Ca2+)i. TUDCA (10 mumol/L) induced Ca2+ oscillations in all single cells that responded. However, levels of inositol-1,4,5-trisphosphate (IP3) in hepatocytes were not increased by treatment with TUDCA (10 mumol/L). CONCLUSIONS: TUDCA at physiological concentrations potently modulates (Ca2+)i signals in hepatocytes by (1) mobilizing microsomal IP3-sensitive Ca2+ stores by an IP3-independent mechanism, (2) initiating Ca2+ oscillations, and (3) inducing influx of extracellular Ca2+.

Animals↗
PubMed1993

Tauroursodeoxycholic acid stimulates hepatocellular exocytosis and mobilizes extracellular Ca++ mechanisms defective in cholestasis.

To assess the effects of tauroursodeoxycholic acid (TUDCA) on bile excretory function, we examined whether TUDCA modulates vesicular exocytosis in the isolated perfused liver of normal rats in the presence of high (1.9 mM) or low (0.19 mM) extracellular Ca++ and in cholestatic rats 24 h after bile duct ligation. In addition, the effects of TUDCA on Ca++ homeostasis were compared in normal and in cholestatic hepatocytes. In the isolated perfused rat liver, TUDCA (25 microM) stimulated a sustained increase in the biliary excretion of horseradish peroxidase, a marker of the vesicular pathway, in the presence of high, but not low extracellular Ca++ or in the cholestatic liver. In contrast, TUDCA stimulated bile flow to the same extent regardless of the concentration of extracellular Ca++ or the presence of cholestasis. In indo-1-loaded hepatocytes, basal cytosolic free Ca++ ([Ca++]i) levels were not different between normal and cholestatic cells. However, in cholestatic cells [Ca++]i increases induced by TUDCA (10 microM) and its 7 alpha-OH epimer taurochenodeoxycholic acid (50 microM) were reduced to 22% and 26%, respectively, compared to normal cells. The impairment of TUDCA-induced [Ca++]i increase in cholestatic cells could be mimicked by exposing normal cells to low extracellular Ca++ (21%) or to the Ca++ channel blocker NiCl2 (23%). These data indicate that (a) dihydroxy bile acid-induced Ca++ entry may be of functional importance in the regulation of hepatocellular vesicular exocytosis, and (b) this Ca++ entry mechanism across the plasma membrane is impaired in cholestatic hepatocytes. We speculate that the beneficial effect of ursodeoxycholic acid in cholestatic liver diseases may be related to the Ca+(+)-dependent stimulation of vesicular exocytosis by its conjugate.

Acetylglucosaminidase↗
PubMed1992

Effect of ursodeoxycholic acid on the kinetics of the major hydrophobic bile acids in health and in chronic cholestatic liver disease.

Beneficial effects of ursodeoxycholic acid in chronic cholestatic liver diseases have been attributed to displacement of hydrophobic bile acids from the endogenous bile acid pool. To test this hypothesis, we determined pool sizes, fractional turnover rates, synthesis/input rates and serum levels of deoxycholic acid and chenodeoxycholic acid before and 1 mo after the start of treatment with ursodeoxycholic acid (13 to 15 mg/kg body wt/day) in four healthy volunteers and five patients with chronic cholestatic liver diseases (three with primary biliary cirrhosis and two with primary sclerosing cholangitis). Bile acid kinetics were determined by combined capillary gas chromatography-isotope ratio mass spectrometry in serum samples after administration of [2H4] deoxycholic acid and [13C]chenodeoxycholic acid. In healthy volunteers, deoxycholic acid pool sizes decreased during administration of ursodeoxycholic acid by 72%. In patients with cholestatic liver diseases, deoxycholic acid pool sizes before ursodeoxycholic acid treatment were only 13% of those in healthy volunteers and were unaffected by ursodeoxycholic acid treatment. Chenodeoxycholic acid pool sizes were not different in healthy volunteers and in patients with cholestatic liver disease, and were not altered by ursodeoxycholic acid treatment. In both healthy volunteers and patients with cholestatic liver disease, synthesis/input rates and serum levels of deoxycholic acid and chenodeoxycholic acid were not altered by ursodeoxycholic acid treatment. Because in our patients improvement of serum liver tests during short-term ursodeoxycholic acid treatment was noted without a decrease of the pool sizes of the major hydrophobic bile acids, we conclude that displacement of hydrophobic endogenous bile acids is not the mechanism of action of ursodeoxycholic acid in chronic cholestatic liver disease.

Adult↗
PubMed1992

Ursodeoxycholic acid for treatment of primary sclerosing cholangitis: a placebo-controlled trial.

The efficacy and safety of ursodeoxycholic acid for the treatment of primary sclerosing cholangitis were evaluated in a prospective, randomized, double-blind, placebo-controlled trial. Fourteen patients with primary sclerosing cholangitis documented by cholestatic serum enzyme pattern, liver histological appearance and endoscopic retrograde cholangiography were included in the trial. Six patients received ursodeoxycholic acid (13 to 15 mg/kg body wt/day), and eight patients received placebo. Two patients had to be withdrawn from the study, one because of UDCA-related diarrhea and the other because of worsening of the disease during placebo treatment. Patients in the ursodeoxycholic acid group improved significantly during 1 yr of treatment with respect to serum levels of bilirubin (median = -50%), alkaline phosphatase (median = -67%), gamma-glutamyltransferase (median = -53%), AST (median = -54%) and ALT (median = -36%) compared with the placebo group, but not with respect to serum levels of hydrophobic bile acids. During ursodeoxycholic acid treatment, histopathological features also improved significantly, as evaluated by multiparametric score. Expression of human leukocyte antigen class I molecules appeared to be markedly reduced on liver cells after ursodeoxycholic acid treatment. We conclude that ursodeoxycholic acid is beneficial in reducing disease activity in patients with primary sclerosing cholangitis.

Adolescent↗
PubMed1992

Deterioration of cholestasis after endoscopic retrograde cholangiography in advanced primary sclerosing cholangitis.

Complications of endoscopic retrograde cholangiography specific to patients with primary sclerosing cholangitis have not yet been reported. We observed transient rises of serum bilirubin after diagnostic endoscopic retrograde cholangiography in five of 15 patients and persistent rises in three of 15 patients with primary sclerosing cholangitis examined consecutively by endoscopic retrograde cholangiography from 1985 to 1990. Deterioration of cholestasis was particularly associated with advanced disease. Seven of eight patients with deterioration after endoscopic retrograde cholangiography had septal fibrosis (stage III) or cirrhosis (stage IV) and a priori elevated serum bilirubin levels. In contrast, all patients with no deterioration of cholestasis following endoscopic retrograde cholangiography had early histological changes (stage I-II), and all but one patient had normal serum bilirubin levels. We conclude that the potentially harmful effects on biliary excretion must be taken into account when the use of endoscopic retrograde cholangiography is being considered in patients with advanced primary sclerosing cholangitis.

Adult↗
PubMed1991

Formation of iso-ursodeoxycholic acid during administration of ursodeoxycholic acid in man.

The appearance of iso-ursodeoxycholic acid (isoUDCA; 3 beta,7 beta-dihydroxy-5 beta-cholan-24-oic acid) in serum of patients with chronic cholestatic liver disease and of healthy subjects during administration of ursodeoxycholic acid (UDCA) is reported. Comparison of the mass spectrum of the newly appearing bile acid with that of authentic 3 beta,7 beta-dihydroxy-5 beta-cholan-24-oic acid revealed its identity as the 3 beta-epimer of UDCA. The appearance of 13C-isoUDCA in serum after ingestion of 13C-UDCA proved its product precursor relationship with UDCA. The putative intermediate in the epimerization of UDCA to isoUDCA, 3-oxo-7 beta-hydroxy-5 beta-cholan-24-oic acid, was identified in serum of patients with cholestatic liver disease during treatment with UDCA. Serum concentrations of isoUDCA after 4 weeks of UDCA treatment were 1.37 +/- 0.79 mumol/l (mean +/- S.D.) in eight patients with primary biliary cirrhosis (PBC), 1.25 +/- 0.91 mumol/l in six patients with primary sclerosing cholangitis (PSC) and 3.87 +/- 0.44 mumol/l in four healthy controls. The intestinal bacterial flora as well as microsomal enzymes of the liver may be involved in the epimerization of UDCA to isoUDCA as indicated by decreased serum levels of isoUDCA under antibiotic treatment with doxycycline (100 mg/day) in healthy subjects and a correlation (r = 0.873, p less than 0.001) between the hepatic microsomal function measured by the 14C-aminopyrine breath test and the fractional conversion of applied UDCA to isoUDCA (isoUDCA/UDCA + isoUDCA) in patients with PBC or PSC. Future studies of bile acid metabolism under UDCA treatment should include measurement of isoUDCA to further elucidate its biological role.

Adult↗
PubMed1991

Klinefelter's syndrome and liver adenoma.

We describe the occurrence of a liver adenoma in a young patient with Klinefelter's syndrome, diagnosed by classic 47,XXY karyotype in all investigated cells and a sex hormone imbalance. To our knowledge, this is the first report of such an association, which might suggest a simple coincidence. However, a pathogenetic link between Klinefelter's syndrome and liver adenoma can be suggested in view of the following facts: Liver adenoma mostly affects women of child-bearing age using oral contraceptives. It is very rare in men, and affected men frequently have been treated with androgens. Both groups are characterized by a sex hormone imbalance. Also, the risk of breast cancer, another hormone-sensitive tumor, is greatly elevated in men with Klinefelter's syndrome, possibly due to sex hormone imbalance.

Adult↗
PubMed1991

Prognostic value of the intravenous 14C-aminopyrine breath test compared to the Child-Pugh score and serum bile acids in 84 cirrhotic patients.

The prognostic value of the intravenous 14C-aminopyrine breath test (ABT) in liver cirrhosis was compared to that of the well-established multiparametric Child-Pugh classification and that of serum bile acids, an endogenous parameter of liver function for which a prognostic value in patients with liver cirrhosis has been demonstrated previously. 84 patients with liver cirrhosis were studied. 32 of the patients died during the observation period. Survival was analyzed for periods of 3, 6 and 12 months after examination. For all chosen observation periods, the Child-Pugh score was of prognostic value. ABT gave prognostic information for periods of 6 and 12 months of survival, but was by far inferior to the Child-Pugh score. Serum bile acids in our population did not yield prognostic information at any time interval studied. We conclude that in our group of cirrhotic patients, the prognostic value of the Child-Pugh classification was by far superior to quantitative liver function tests in predicting survival.

Aminopyrine↗