Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This contribution presents data from the literature as well as our own results concerning the mechanisms of hepatic encephalopathy (HE). 1. Blood chemistry: In patients with liver cirrhosis, the plasma levels of ammonia, phenylalanine, tyrosine, phenolic acids, and octopamine correlated with the stages of HE. Methionine and free tryptophan concentrations were increased only in stages 2-4. Further, branched chain amino acids were below the normal range. Experimental findings in animals elucidated some mechanisms of these changes. 2. Effects of administered substances: With ammonia, methionine, methanethiol, tryptophan, phenolic substances, and fatty acids central nervous disturbances were observed. 3. Interactions: Anemia, methanethiol, and fatty acids favored ammonia toxicity. Alkalosis diminished cerebral symptoms. 4. Neurotransmitters: HE was accompanied by an enhanced turnover of serotonin and by increased amounts of false neurotransmitters (like octopamine) in the brain. 5. Oxydative brain metabolism: Disorders of cerebral oxygen and glucose utilization were mainly documented in cases of long term HE with EEG alterations. 6. Structural changes of the brain: Most of them are irreversible.
 ...
PMID:[Pathogenesis of hepatic encephalopathy (author's transl)]. 1 66

The liver is actively involved in the metabolism of the sulphur-containing essential amino acid, methionine. Methionine is transformed into S-adenosyl-L-methionine (SAMe) and then into sulphur-containing metabolites (cysteine, taurine and glutathione) via the trans-sulphuration pathway. Liver disease may affect the trans-sulphuration pathway and decrease the clearance of methionine, which leads to increased fasting methionine concentrations in blood and reduced formation of cysteine and glutathione. There is evidence that this defect, located at the level of SAMe-synthetase, may cause nutritional defects and contribute to negative nitrogen balance whenever non-essential sulphur-containing amino acids are not supplied in adequate amounts. In addition, cirrhotic patients may be at increased risk of hepatotoxicity after treatment with substances which are detoxified via glutathione. The SAMe-synthetase block may be overcome by administration of oral or intravenous SAMe, which improves the fasting amino acid profile and increases the hepatic glutathione concentration. Controlled studies on long term SAMe treatment in patients with cirrhosis are needed to confirm this possible beneficial effect.
 ...
PMID:Mechanisms and consequences of the impaired trans-sulphuration pathway in liver disease: Part II. Clinical consequences and potential for pharmacological intervention in cirrhosis. 208 82

We measured fasting plasma amino acids in 26 children aged 6 months to 5 years with extrahepatic biliary atresia and cirrhosis and compared them with fasting values in 95 normal control children aged 4 months to 12 years. We found that the cirrhotic children had elevations of total free plasma amino acids implying reduced hepatic metabolism of amino acids and that the molar ratio of the branched chain amino acids (isoleucine, leucine, and valine) to the aromatic amino acids (phenylalanine and tyrosine) was significantly depressed. Methionine was also markedly elevated, and taurine concentrations were significantly decreased. Manipulation of the amino acid distribution in dietary protein to normalize plasma amino acids prior to orthotopic hepatic transplantation may be helpful in improving amino acid utilization.
 ...
PMID:Amino acid abnormalities in infants with extrahepatic biliary atresia and cirrhosis. 368 71

Administration of total parenteral nutrition (TPN) solutions high in branched chain amino acids (BCAA) is thought to improve metabolic support during stress. This prospective, randomized, double blind study compared 45 per cent BCAA with 25 per cent BCAA in 12 patients. Seven patients had multiple trauma; two, gastrointestinal surgery; one, pancreatitis; and two, cirrhosis. The TPN regimen was 1.0-1.5 gm/kg/day amino acids and 30-45 glucose kcal/kg/day. The BCAA formula used was high in isoleucine and valine, but not leucine. Amino acid plasma levels, blood chemistries, 3-methylhistidine excretion, and nitrogen balance were studied. Control studies showed negative nitrogen balance (-7.1 +/- 2.9 gm) (mean +/- SEM), elevated insulin (61 +/- 21 microunit/ml), and elevated 3-methylhistidine (3MH) excretion (688 +/- 309 micromol); plasma leucine (93 +/- 11 nmol/ml) and isoleucine (37 +/- 23) were low, and valine (155 +/- 20) was elevated. Plasma methionine (40 +/- 9) and tyrosine (70 +/- 12) were high normal. Phenylalanine (85 +/- 5) was elevated. Both groups showed increased nitrogen excretion and positive nitrogen balance during the study (25 per cent, 2.0 +/- 1.4 gm/day; 45 per cent, 1.2 +/- 2.6 gm/day). Three-methylhistidine excretion changed little in either group (557 +/- 149, 414 +/- 91), insulin rose (135 +/- 27, 65 +/- 19), and plasma leucine (82 +/- 4, 71 +/- 9) changed little. Plasma isoleucine (51 +/- 3, 155 +/- 16) and valine (173 +/- 11, 691 +/- 23) both rose, more in the 45 per cent group. Methionine (67 +/- 12, 37 +/- 4) and tyrosine (51 +/- 6, 50 +/- 10) changed little.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Comparison of total parenteral nutrition with 25 per cent and 45 per cent branched chain amino acids in stressed patients. 393 93

Methionine is a sulfur-containing essential amino acid and there are optic isomers of L- and D-type. It has been known that there are two metabolic pathways in methionine metabolism-the transsulfuration and the transamination. The purposes of the present investigation are to clarify the existence of transaminative pathway in human by the quantitative analysis of 3-methylthiopropionate (3-MTP), one of the metabolites of methionine, and to study its clinical significance in patients with liver cirrhosis. 3-MTP in urine was analysed by gas chromatograph equipped with the flame photometric detector (FPD) which has a highly specific sensitivity to the sulfur compounds. Fasting levels of 3-MTP concentration in urine in healthy subjects (n = 20) and patients with liver cirrhosis (n = 21) were 39.1 +/- 9.7 ng/mg. Cr. (Mean +/- SE) and 103.6 +/- 24.2 ng/mg. Cr., respectively. 3-MTP concentration in urine in cirrhotic patients was significantly higher than that in healthy subjects (p less than 0.05). In some cases, 3-MTP concentration in urine was measured every hour for 3 to 6 hours after the oral loading of 2 g of D- or L-methionine. In healthy subjects, 3-MTP concentration in urine increased remarkably at 1 hour period after oral loading of 2 g of D-methionine, and subsequently its concentration showed a tendency to decrease gradually. However, there were no such changes after oral loading of 2 g of L-methionine. When 2 g of D-methionine was loaded orally, decreasing curves of 3-MTP concentration in urine were different between healthy subjects and patients with liver cirrhosis, and half-disappearance time of 3-MTP concentration in urine was remarkably prolonged in cirrhotic patients. These findings seem to indicate that 3-MTP is one of the metabolites of methionine (especially of D-methionine) and the transaminative pathway exists in human. It was also suggested that there was the impairment of the transaminative pathway of methionine metabolism in patients with liver cirrhosis. Pharmacokinetics of 3-MTP in urine seems to contribute to the clinicopathological investigation of the liver cirrhosis.
 ...
PMID:[Analysis of methionine metabolism studied by the gas chromatographic determination of 3-methylthiopropionate in urine and its clinical application]. 399 54

Methionine metabolism impairment in human liver disease has been related with an alteration in SAM-synthetase. This deficiency is produced by a post-translational event since human liver cirrhosis presents normal levels of SAM-synthetase mRNA in spite of a more than 50% diminution in its activity. A series of different experiments on the structure and activity of this enzyme have provided strong evidence that SAM-synthetase is regulated by reduced/oxidized glutathione ratio. Restoration of glutathione levels by the addition of S-adenosyl-methionine or glutathione esters in various experimental conditions (buthionine sulfoximine and carbon tetrachloride intoxication) resulted in a normalization of the SAM-synthetase diminution caused by the toxics and an attenuation of the morfological alteration produced in the liver, including fiber production. This findings might have pharmacological implications in the treatment of liver diseases, since the possible beneficial effect of long term administration of SAM could include a reduction of fiber production.
 ...
PMID:S-adenosyl-L-methionine synthetase and methionine metabolism deficiencies in cirrhosis. 774 Oct 2

The absolute and relative concentrations of 16 plasma amino acids in 48 mostly dystrophic infants and children (median of age 1 1/2 years) with extrahepatic biliary atresia and mainly stable preterminal cirrhosis were compared with those of controls. Patient plasma amino acid data were analysed statistically for diagnostic usefulness and correlated with standard biochemical quantities of liver function and of liver perfusion. In the patients the total amounts of non-essential and essential amino acids were reduced by 19% and with the same significance (p < 0.0005). Plasma tyrosine was increased (+40%), while taurine (-44%) and branched chain amino acids (+28.8% to -34.7%) were decreased. Methionine values varied widely. In the molar fractional plasma amino acid profile, only alanine, valine, and leucine were decreased, while threonine, methionine, tyrosine, phenylalanine, ornithine, and serine were increased. Discriminate function analysis showed that the plasma amino acid data discriminated 93.8% of the patients from controls. The concentrations of some amino acids in plasma seemed to have been influenced by protein-calorie deficiency in the patients. The valine/tyrosine ratio and the Fischer index (ratio branched chain/aromatic amino acids) were significantly reduced in the patients versus controls (1.54 +/- 0.55 vs 3.08 +/- 0.55 and 1.66 +/- 0.39 vs 3.00 +/- 0.48). A number of significant correlations (range of r: 0.37-0.59, p < 0.05, 30-48 data pairs) were calculated between plasma amino acid data and several standard biochemical quantities of liver function. The statistical analyses also showed that the Fischer index began to decrease gradually and linearly early in the progression of liver failure.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The plasma amino acid profile and its relationships to standard quantities of liver function in infants and children with extrahepatic biliary atresia and preterminal liver cirrhosis. 831 65

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.
 ...
PMID:Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases. 889 26

The fasting plasma level of reduced glutathione (GSH), a methionine-derived tripeptide, is reduced in cirrhosis. There is evidence that a reduced activity of S-adenosyl-L-methionine synthetase limiting the flux of methionine along the transmethylation/transsulfuration pathway may contribute to decrease GSH levels. No studies have analyzed plasma GSH in response to a methionine load. In 6 control subjects and in 10 patients with cirrhosis, plasma sulfur amino acid and plasma and erythrocyte GSH levels were measured in response to a L-methionine load (0.1 g/kg). Blood samples were obtained throughout the day after the oral load. Urine was collected for measurement of sulfur excretion. During the study period, all subjects consumed a standard diet of 1,683 kcal containing 2% protein and virtually no methionine. Plasma methionine increased in both groups to a peak level exceeding 20 times the basal value 90 minutes after the load, and declined thereafter. Methionine clearance, calculated on the descending part of the methionine-time curve, was reduced by 50% in cirrhosis (P = .0001). Fasting GSH was higher in controls (mean +/- SD, 3.9 +/- 1.3 v 1.6 +/- 0.7 micromol/L, P = .0004). In response to a methionine load, it peaked at 10.2 +/- 7.2 and 3.2 +/- 1.3 micromol/L, respectively (P = .009). Thereafter, plasma GSH progressively declined, and after 24 hours, it returned to the fasting preinfusion values in both groups. Plasma cysteine and taurine concentrations, as well as the erythrocyte GSH time course, paralleled plasma GSH levels, with less significant differences between groups. Sulfate excretion was delayed. GSH synthesis is stimulated by a methionine load. The reduced flux of methionine along the transmethylation/transsulfuration pathway reduces GSH synthesis in cirrhosis. Defective methionine metabolism also may be responsible for reduced fasting GSH.
 ...
PMID:Synthesis of glutathione in response to methionine load in control subjects and in patients with cirrhosis. 1109 7

Much progress has been made in the understanding of the pathogenesis of alcoholic liver disease, resulting in improvement of treatment. Therapy must include correction of nutritional deficiencies, while taking into account changes of nutritional requirements. Methionine is normally activated to S-adenosylmethionine (SAMe). However, in liver disease, the corresponding enzyme is depressed. The resulting deficiencies can be attenuated by the administration of SAMe but not by methionine. Similarly, phosphatidylethanolamine methyltransferase activity is depressed, but the lacking phosphatidylcholine (PC) can be administrated as polyenylphosphatidylcholine (PPC). Chronic ethanol consumption increases CYP2E1, resulting in increased generation of toxic acetaldehyde and free radicals, tolerance to ethanol and other drugs, and multiple ethanol-drug interactions. Experimentally, PPC opposes CYP2E1 induction and fibrosis. Alcoholism and hepatitis C infection commonly co-exist, with acceleration of fibrosis, cirrhosis, and hepatocellular carcinoma. PPC is being tested clinically as a corresponding antifibrotic agent. Available antiviral agents are contraindicated in the alcoholic. Anti-inflammatory agents, such as steroids, may be selectively useful. Finally, anticraving agents, such as naltrexone or acamprosate, should be part of therapy.
 ...
PMID:Liver diseases by alcohol and hepatitis C: early detection and new insights in pathogenesis lead to improved treatment. 1126 19


1 2 Next >>