[Tryptophan metabolism in liver diseases: a pharmacokinetic and enzymatic study]

Tryptophan is considered to be one of the agents involved in the pathogenesis of hepatic encephalopathy. In our study, we evaluated tryptophan metabolism in liver disease. A bolus of 1.5 g of L-tryptophan was administered intravenously to 14 patients with noncirrhotic liver disease, 40 patients with liver cirrhosis, and 8 healthy volunteers. As pharmacokinetic parameters, the half life, clearance, and volume of distribution of free and total tryptophan were determined using a biexponential formula. In addition, the activity of liver tryptophan pyrrolase, the key enzyme of tryptophan metabolism, was measured in liver biopsy specimens of 15 patients with noncirrhotic liver disease, 8 patients with cirrhosis of the liver, and 4 patients with histologically normal livers. Healthy subjects and patients with noncirrhotic liver disease both showed similar results in measured and calculated data. In contrast, patients with cirrhosis revealed significant alterations of the pharmacokinetic parameters of free and total tryptophan: the half-life was increased by 195% and 176%, the clearance was decreased by 73% and 34%, respectively, and the activity of tryptophan pyrrolase was decreased by 22%. The tryptophan transfer in cirrhosis amounted to only 0.75 +/- 0.03 g per 24 h compared with 2.6 +/- 0.34 g per 24 h in healthy individuals. The findings demonstrate that patients with cirrhosis show a marked reduction in their ability to metabolize tryptophan. This should be taken into account in the oral and parenteral nutrition of those patients.

Mesocaval and distal splenorenal shunts: effect on hepatic function, hepatic hemodynamics, and portal systemic encephalopathy

The effect of the mesocaval interposition shunt (n = 12) and the distal splenorenal shunt (n = 9) on the wedged hepatic venous pressure, the estimated hepatic blood flow, quantitative hepatic function, and the rate of portal systemic encephalopathy was evaluated in 21 patients who had bled from esophageal varices. After mesocaval shunt the wedged hepatic venous pressure was significantly reduced by 42% (from 26 +/- 3 mm Hg to 15 +/- 5 mm Hg, P less than 0.001) compared to 16% only (from 25 +/- 3 mm Hg to 21 +/- 2 mm Hg, P less than 0.005) after distal splenorenal shunt. The estimated hepatic blood flow also decreased significantly after mesocaval shunt by 61% (from 1.45 +/- 0.46 l/min to 0.56 +/- 0.25 l/min, P less than 0.001) compared to 29% (from 1.29 +/- 0.32 l/min to 0.91 +/- 0.39 l/min, P less than 0.05) after distal splenorenal shunt. Despite significantly different influences of both types of shunt operations on wedged hepatic venous pressure and estimated hepatic blood flow (P less than 0.001), postoperative changes of hepatic function were comparable in both groups of patients. The galactose elimination capacity, the initial plasma disappearance rate of Bromsulphalein, and the plasma ratio of valine, leucine, and isoleucine to phenylalanine and tyrosine were reduced by 13%, 26%, and 29%, respectively, after mesocaval shunt, compared to 12%, 25%, and 17% after distal splenorenal shunt. Only two patients of the mesocaval shunt group with the largest decrease in estimated hepatic blood flow developed portal systemic encephalopathy postoperatively, and the distal splenorenal shunt patients with their minor hemodynamic sequelae remained free of portal systemic encephalopathy.

Amino acid, ammonia and neurotransmitter concentrations in hepatic encephalopathy: serial analysis in plasma and cerebrospinal fluid during treatment with an adapted amino acid solution

We evaluated changes of advanced liver disease and hepatic encephalopathy on the concentrations of amino acids (AA) and ammonia in plasma and cerebrospinal fluid (CSF) and of the neurotransmitters norepinephrine, dopamine and 5-hydroxytryptamine (5-HT) as well as the 5-hydroxyindole acetic acid (5-HIAA) in CSF before and at the end of a 3-day period of treatment with infusions enriched with branched chain amino acids (BCAA). The subjects studied were 13 patients with alcoholic cirrhosis and hepatic encephalopathy stages 1-3 (n = 8) and stage 4 (n = 5). The patients in coma stages 1-3 recovered during the treatment (survivors), those in coma stage 4 died before the study period was finished (non-survivors). The data emerging from this study show: Alterations of AA concentrations are much more pronounced in the CSF than in the plasma. In the case of tryptophan the alterations in plasma and CSF were inverse. Before the treatment the CSF-plasma ratios of the concentrations of BCAA and aromatic amino acids (AAA) are increased reflecting an activated transport of both the BCAA and AAA through the blood-brain barrier. High dose BCAA nearly normalized CSF concentrations and CSF-plasma ratios of AAA assuming that the treatment brought about an effective competition of cerebral uptake between BCAA and AAA. The CSF concentrations of ammonia and glutamine decreased significantly during treatment while the plasma concentrations changed only moderately. As to the neurotransmitters, only the concentrations of 5-HT and its metabolite 5-HIAA correlated with the clinical picture and with the concentration of their precursor AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cimetidine on the hepatic extraction of indocyanine green, the portal pressure and the systemic circulation in patients with cirrhosis of the liver

The effect of cimetidine on hepatic and systemic haemodynamic parameters was studied in seven patients with portal hypertension due to alcohol-induced cirrhosis of the liver and in one patient with peliosis hepatis following oral contraceptive steroids. The intravenous administration of cimetidine (350 mg as bolus, followed by 2 mg/min over 60 min) reduced the hepatic extraction of continuously infused indocyanine green (ICG) by 27%; this was statistically significant (P less than 0.01). Since the ICG clearance, calculated independently of hepatic perfusion, was lowered by 19%, this effect seems to be mainly due to a reduced capacity of the liver to remove the dye from the blood, rather than due to changes in perfusion. Cimetidine did not influence the elevated portal pressure in the patients with cirrhosis, or the normal pressure in the patient with peliosis hepatis. No significant effect was observed on heart rate, mean arterial pressure, pulmonary artery pressure, pulmonary capillary pressure and cardiac output. These studies indicate that the reduction of the hepatic ICG extraction following cimetidine is more the result of an inhibited capacity of the liver to remove the dye than of changes in the hepatic perfusion or in the systemic circulation.

[Tryptophan loading test as a function parameter in liver diseases]

Because of its specific hepatic degradation tryptophan was orally administered (50 mg/kg) to patients with various chronic liver diseases (n = 30) and to healthy volunteers (n = 8) as a test for hepatic function. The plasma half life of tryptophan was determined between 4 and 8 h after the amino acid load. It was found that in patients with cirrhosis (n = 25) the half life of tryptophan was prolonged to 4.7 +/- 0.4 h (means +/- SD), compared to 2.0 +/- 0.1 h in the controls. The tryptophan half life also correlated with the plasma concentration of albumin, bilirubin, cholinesterase and prothrombin time in these patients. In addition a significant correlation was observed with the galactose elimination capacity and the 45 min retention of BSP. Thus, the oral tryptophan loading test may be suitable for a more specific determination of functional impairment of the liver in chronic liver disease. In decompensated cirrhotic patients alterations of the tryptophan metabolism seen to be related to indicators of hepatic encephalopathy. The test may therefore be used to assess the degree and risk of hepatic encephalopathy in such patients.

[Therapy of hepatic encephalopathy. Changes in the cerebrospinal fluid concentration of catecholamine neurotransmitters, ammonia and amino acids in the course of an infusion treatment with branched-chain amino acids]

Infusions containing branched-chain amino acids have recently been used for the therapy of hepatic coma. Their mode of action was attributed to a reduction in the intracerebral concentrations of the aromatic amino acids with resultant normalization of the neurotransmitters noradrenaline, dopamine and serotonin, synthesized from these amino acids. In order to further clarify this therapeutic mechanism an infusion solution consisting of branched-chain amino acids and ammonia-reducing amino acids was administered to patients with porto-systemic encephalopathy. The amino acid pattern, the ammonia in plasma and liquor, and the neurotransmitters noradrenaline, adrenaline and dopamine, in the liquor were determined before and after the course of treatment. Our studies show that the therapeutic effect of branched-chain amino acids in the therapy of hepatic encephalopathy is based on an effective intracerebral reduction of the ammonia concentration by 61%. The actual concentrations of the neurotransmitters were not significantly modified by the therapy. This opens to question the hypothesis that the neurotransmitters are responsible for the development of hepatic encephalopathy.

Therapie der hepatischen Enzephalopathie

Seit kurzem werden Infusionen mit verzweigtkettigen Aminosäuren zur Therapie des Coma hepaticum verabreicht. Der Wirkungsmechanismus wurde auf eine Senkung der intrazerebralen Konzentrationen der aromatischen Aminosäuren und einer daraus resultierenden Normalisierung der aus diesen Aminosäuren synthetisierten Neurotransmitter Noradrenalin, Dopamin und Serotonin zurückgeführt. Es wurde zur weiteren Abklärung des Wirkungsmechanismus bei Patienten mit portosystemischer Enzephalopathie eine Infusionslösung, bestehend aus verzweigtkettigen und ammoniaksenkenden Aminosäuren, verabreicht; vor und nach der Behandlung wurden das Aminosäurenspektrum und der Ammoniak im Plasma und Liquor sowie die Neurotransmitter Noradrenalin, Adrenalin und Dopamin im Liquor bestimmt. Unsere Untersuchungen zeigen, daβ der Wirkungsmechanismus verzweigtkettiger Aminosäuren zur Therapie der hepatischen Enzephalopathie auf einer effektiven intrazerebralen Senkung der Ammoniakkonzentration um 61 % beruht. Die Neurotransmitter-Konzentrationen selbst werden durch die Behandlung nicht signifikant verändert. Dies stellt die Neurotransmitter-Hypothese zur Entstehung der hepatischen Enzephalopathie in Frage.

Acetyl coenzyme A and coenzyme a contents of growing clostridium kluyveri as determined by isotope assays

CoASH and some of its acyl derivatives, especially acetyl-SCoA, occupy a central position in the energy metabolism of the anaerobic Clostridium kluyveri, both as intermediates and as regulatory effectors. The steady state concentrations of these compounds were determined in growing cultures of this organism using an anaerobic and fast deproteinization technique and radio isotope assays. Acetyl-SCoA was determined as [1-14C]citrate formed in the presence of [4-14C]oxaloacetate and citrate synthase; 0.49 mumol/g cell wet wt. were found. CoASH, CoAS-SCoA after borohydride reduction, and total acyl derivatives of coenzyme A after hydrolysis of the thiol esters were converted to thioethers with [2,3-14C]N-ethylmaleimide and brought to radiochemical purity by chromatographic methods. While disulfides of coenzyme A were undetectable, 0.13 mumol CoASH and 1.17 mumol of total acyl-SCoA per g wet wt. were found. These data are consistent with the regulatory scheme of the energy metabolism of C. kluyveri previously proposed.