Role of transmethylation reactions in alcoholic liver disease

Alcoholic liver disease is a major health care problem worldwide. Findings from many laboratories, induding ours,have demonstrated that ethanol feeding impairs several of the many steps involved in methionine metabolism.Ethanol consumption predominantly results in a decrease in the hepatocyte level of S-adenosylmethionine and the increases in two toxic metabolites, homocysteine and S-adenosylhomocysteine. These changes, in turn,result in serious functional consequences which include decreases in essential methylation reactions via inhibition of various methyltransferases. Of particular interest to our laboratory is the inhibition of three important enzymes, phosphatidylethanolamine methyltransferase,isoprenylcysteine carboxyl methyltransferase and protein L-isoaspartate methyltransferase. Decreased activity of these enzymes results in increased fat deposition, increased apoptosis and increased accumulation of damaged proteinsall of which are hallmark features of alcoholic liver injury.Of all the therapeutic modalities available, betaine has been shown to be the safest, least expensive and most effective in attenuating ethanol-induced liver injury. Betaine, by virtue of aiding in the remethylation of homocysteine,removes both toxic metabolites (homocysteine and S-adenosylhomocysteine), restores S-adenosylmethionine level, and reverses steatosis, apoptosis and damaged proteins accumulation. In conclusion, betaine appears to be a promising therapeutic agent in relieving the methylation and other defects associated with alcoholic abuse.     

Hepatic collagen synthesis in patients with alcoholic and nonalcoholic liver disease

To examine the synthesis of hepatic collagen in patients with alcoholic and nonalcoholic liver disease, liver biopsy specimens were incubated in vitro with 14C-proline, and the radioactivity of the newly synthesized protein-bound 14C-hydroxyproline was measured. Mean hepatic collagen synthesis was 0.82 +/- 0.19 pmole of 14C-hydroxyproline/g liver/2 h in control subjects without histological liver fibrosis. Hepatic collagen synthesis was increased in patients with alcoholic and nonalcoholic liver diseases, especially in those with alcoholic fibrosis, alcoholic cirrhosis and chronic active hepatitis. The raised collagen synthesis in alcoholic liver disease rapidly decreased after withdrawal of alcohol. When alcoholic liver disease were compared with nonalcoholic liver disease, there was no significant difference in hepatic collagen synthesis.     

Hepatic collagen synthesis in patients with alcoholic and nonalcoholic liver disease

To examine the synthesis of hepatic collagen in patients with alcoholic and nonalcoholic liver disease, liver biopsy specimens were incubated in vitro with¹⁴C-proline, and the radioactivity of the newly synthesized protein-bound¹⁴C-hydroxyproline was measured. Mean hepatic collagen synthesis was 0.82±0.19 pmole of¹⁴C-hydroxyproline/g liver/2 h in control subjects without histological liver fibrosis. Hepatic collagen synthesis was increased in patients with alcoholic and nonalcoholic liver diseases, especially in those with alcoholic fibrosis, alcoholic cirrhosis and chronic active hepatitis. The raised collagen synthesis in alcoholic liver disease rapidly decreased after withdrawal of alcohol. When alcoholic liver disease were compared with nonalcoholic liver disease, there was no significant difference in hepatic collagen synthesis. This work was supported in part by a grant-in-aid for EncourageMent of Young Scientists (No.57770489) from the Ministry of Education, Science and Culture of Japan.     

Hepatic venous oxygen content in alcoholic cirrhosis and non-cirrhotic alcoholic liver disease

Blood gas analyses and hepatic blood flow were determined during hepatic vein catheterization in order to establish a possible hypoxic component in alcoholic liver disease. Fifty-six patients (9 non-cirrhotic liver disease, 14 cirrhosis Child-Turcotte class A, 23 class B, 10 class C) and 10 control subjects were studied. Mean hepatic venous oxygen saturation and tension were almost the same in all groups, and hepatic blood flow was inversely correlated to the arteriohepatic venous oxygen difference (r = -0.53, P less than 0.01). Splanchnic oxygen uptake was similar in all groups studied. The arterio-hepatic venous difference of base excess was small and of the same size in all groups, indicating no enhanced production of lactic acid in the liver. Our results do not support the concept that hepatic venous oxygen content is low in alcoholic liver disease and thereby contributes to hypoxic liver damage.     

Hepatic stellate cells and alcoholic liver disease.

Liver fibrosis represents a significant health problem worldwide for which no effective therapy exists. A great deal of research has been carried out to understand the molecular mechanisms responsible for the development of liver fibrosis. Activated stellate cells are the primary cell type responsible for the production of collagen I, the key protein involved in the development of liver fibrosis. Excessive deposition of collagen I occurs along with impaired extracellular matrix remodeling. Following a fibrogenic stimulus stellate cells transform into an activated collagen type I-producing cell. Numerous changes in gene expression are associated with stellate cell activation, including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Activation of stellate cells is mediated by factors released from hepatocytes and Kupffer cells as they produce reactive oxygen species, nitric oxide, cytokines, growth factors, and cyclooxygenase and lipoxygenase metabolites, which provide pivotal paracrine effects in the liver milieu. Inhibition of stellate cell activation, proliferation, and the increased production of extracellular matrix (i.e. collagen type I) are therefore crucial steps for intervention in hepatic fibrogenesis.     

Hepatic expression of gamma-glutamyltranspeptidase in the human liver of patients with alcoholic liver disease

Background: Gamma-glutamyltranspeptidase (GGT) has been recognized as an enzyme that converts glutathione into cysteine, and it is localized predominantly within the liver. Serum GGT is clinically recognized as the most useful marker for diagnosis of alcoholic liver disease (ALD). Methods: GGT localization within the liver was examined immunohistochemically using an anti-GGT antibody and was visualized by confocal laser scanning microscopy in ALD and normal livers. Double immunostaining for GGT and dipeptidylpeptidase-IV (DPP-IV) was carried out to evaluate GGT localization in greater detail. Results: Expression of GGT protein and mRNA was studied with immunoblot analysis and in situ hybridization, respectively. Immunohistochemically, the expression of GGT in the normal liver was faintly demonstrated in the bile canaliculi of hepatocytes and in biliary epithelial cells. In ALD livers, GGT was clearly demonstrated at the same sites. Double immunostaining demonstrated that GGT and DPP-IV were colocalized in hepatocytes in the ALD liver. In situ hybridization clearly demonstrated GGT-mRNA within the cytoplasm of hepatocytes and biliary epithelial cells. Immunoblot analysis revealed that GGT protein expression was increased in the ALD livers compared with that seen in the normal livers. Conclusion: These findings indicate that GGT in control and alcoholic livers is synthesized in hepatocytes and biliary epithelial cells, and is localized within the bile canalicular membrane and the luminal membrane in those cells, respectively. In conclusion, GGT synthesis and protein expression are increased in ALD livers, leading to the elevation of serum levels of GGT that are commonly noted in patients with the disease.     

Hepatic prolyl hydroxylase and collagen synthesis in patients with alcoholic liver disease

Hepatic prolyl hydroxylase activity and collagen synthesis were measured in patients with alcoholic liver disease to determine the feasibility of using the enzyme prolyl hydroxylase as a marker of hepatic fibrogenesis. Alcoholic patients with liver histopathology consistent with normal, steatosis, alcoholic hepatitis, early cirrhosis, or advanced cirrhosis were analysed for liver prolyl hydroxylase activity and in vitro collagen synthesis. Prolyl hydroxylase activity and the rate of in vitro collagen synthesis were correlated when these parameters were measured in samples of the same liver biopsy. Mean prolyl hydroxylase activity was significantly raised in all groups of alcoholic patients with alcoholic liver disease, except those with steatosis, when compared with alcoholic patients with normal morphology. Alcoholic patients with early cirrhosis had enzyme activity (mean ± SE: 1·367 ±0·162 mU/mg protein) significantly raised over all other groups. Mean enzyme activity was less raised (0·985 ± 0·097 mU/mg protein) in patients with advanced cirrhosis. The percentage of collagen synthesis in patients with early or advanced cirrhosis was also raised compared with alcoholic patients with normal morphology. Prolyl hydroxylase activity and the rate of collagen synthesis are significantly correlated (r=0·62). These findings suggest that hepatic prolyl hydroxylase activity is a useful indicator of hepatic fibrogenesis and its measurement on available liver biopsy tissue should be a potent diagnostic tool reflecting active fibrogenesis and predicting progression of alcoholic liverdisease.     

Hepatic alcohol dehydrogenase activity in alcoholic subjects with and without liver disease

Alcohol dehydrogenase activity was measured in samples of liver tissue from a group of alcoholic and non-alcoholic subjects to determine whether decreased liver alcohol dehydrogenase activity is a consequence of ethanol consumption or liver damage. The alcoholic patients were classified further into the following groups: control subjects with no liver disease (group 1), subjects with non-cirrhotic liver disease (group 2), and subjects with cirrhotic liver disease (group 3). The non-alcoholic subjects were also divided, using the same criteria, into groups 4, 5, and 6, respectively. The analysis of the results showed no significant differences when mean alcohol dehydrogenase activities of alcoholic and non-alcoholic patients with similar degrees of liver pathology were compared (groups 1 v 4, 2 v 5, and 3 v 6. Alcohol dehydrogenase activity was, however, severely reduced in patients with liver disease compared with control subjects. Our findings suggest that alcohol consumption does not modify hepatic alcohol dehydrogenase activity. The reduction in specific alcohol dehydrogenase activity in alcoholic liver disease is a consequence of liver damage.     

Hepatic stellate cells and innate immunity in alcoholic liver disease

Constant alcohol consumption is a major cause of chronic liver disease, and there has been a growing concern regarding the increased mortality rates worldwide. Alcoholic liver diseases (ALDs) range from mild to more severe conditions, such as steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The liver is enriched with innate immune cells (e.g. natural killer cells and Kupffer cells) and hepatic stellate cells (HSCs), and interestingly, emerging evidence suggests that innate immu...     

Hepatic aldehyde dehydrogenase activity in liver diseases, with particular emphasis on alcoholic liver disease

Hepatic aldehyde dehydrogenase isozyme activity was measured in 51 patients with various types of liver diseases, including 24 patients with alcoholic liver disease, to elucidate the relationship between hepatic aldehyde dehydrogenase activity and liver disease, especially alcoholic liver disease. The levels of low-Km and total aldehyde dehydrogenase activity in the liver decreased both in alcoholic and nonalcoholic liver disease patients, who showed an isoelectric focusing pattern of the usual type. There was no significant difference in the aldehyde dehydrogenase activity between alcoholic and nonalcoholic liver disease. In alcoholic liver disease, the decrease in the activity was significantly correlated with the progression of liver histology. The activity in liver cirrhosis was significantly lower than that in the other types of alcoholic liver disease. In nonalcoholic liver disease patients, the unusual type of hepatic aldehyde dehydrogenase activity observed was not different from the unusual type observed in nonhepatobiliary disease patients. These results indicate that the reduction of hepatic low-Km aldehyde dehydrogenase activity is a change that occurs subsequent to liver damage. Genetic abnormality in aldehyde dehydrogenase may not be important in the pathogenesis of alcoholic liver injury.     

Hepatic blood flow in alcoholic liver disease measured by an indicator dilution technic

Indicator dilution curves recorded from hepatic venous blood after selective injection of I¹³¹ albumin into the hepatic artery were used to calculate hepatic blood flow in four normal subjects and forty-five patients with alcoholic liver disease.     

Pancreatitis associated with alcoholic liver disease

The prevalence with which alcoholic pancreatitis is associated with alcoholic liver disease is unclear. To investigate this association further, we have reviewed the autopsy findings of 1022 patients who died from alcoholic liver disease and compared these findings with those from 352 patients who died from cardiac or pulmonary disease. All patients who died from liver disease had a history of chronic alcoholism with clinical and biochemical evidence of severe liver damage. Death resulted from hepatic coma, gastrointestinal bleeding, or infection. Liver disease patients were classified into two groups: (1) those with cirrhosis (77%) and (2) those without cirrhosis but with acute and/or chronic sclerosing hyaline necrosis (23%). Anatomic and histopathologic changes characteristic of chronic pancreatitis were found in 203 patients in approximately the same frequency (20% and 18%, respectively) in both groups. Acute pancreatitis without chronic lesions was observed in 8% and 10% of both groups, respectively. In the control group of 352 autopsies (122 cardiac and 230 pulmonary patients), the overall prevalence of pancreatitis, at 2.6%, was significantly (P<0.001) lower than that observed in the alcoholic liver disease groups. A total of 22 cases (50%) dying from acute or chronic sclerosing hyaline necrosis had severe chronic calcifying pancreatitis compared to 29 patients (18%) (P<0.001) dying from cirrhosis. By contrast, dense fibrosis was significantly (P<0.001) more commonly observed in patients with cirrhosis. We conclude that pancreatitis occurs frequently in patients dying from alcoholic liver disease but is an uncommon finding in patients dying from other causes. Biliary tract pathology was more prevalent (P<0.05) in patients dying from cirrhosis without pancreatitis than those patients dying from liver disease with pancreatitis. In the control group of patients dying from pulmonary or cardiac disease, biliary pathology was far less frequently (P<0.01) observed.     

Autoantibodies in alcoholic liver disease

PURPOSE: To test the hypothesis that since only a proportion of heavy drinkers develop significant alcoholic liver disease (ALD), an autoimmune pathogenesis is likely. PATIENTS AND METHODS: Autoimmune markers were measured in 47 patients with biopsy-proven ALD and compared to measurements in 20 alcoholics without clinical and hematologic evidence of ALD and 28 patients with autoimmune chronic active hepatitis (CAH). RESULTS: Twenty-two percent of patients with ALD were antinuclear antibody-positive, compared to 71% of patients with CAH. Approximately 60% of patients with ALD had either anti-single-stranded or anti-double-stranded DNA antibodies, slightly more than the patients with CAH. Another marker of autoimmunity, as in systemic lupus erythematosus, is the presence of IgM antibodies to autologous and heterologous lymphocytes, which are cytotoxic at 4 degrees C. Seventy-two percent of patients with CAH had positive antilymphocyte antibodies, compared to 59.6% of patients with ALD. Furthermore, more than 90% of the sera from ALD and CAH patients displayed lymphocytotoxicity. Thirty-two percent and 25.5% of CAH and ALD patients, respectively, had all three autoantibodies present. CONCLUSION: These results suggest that autoimmune mechanisms may indeed play a role in the pathogenesis of ALD in at least some patients.     

Advances in alcoholic liver disease

Cytokines are mediators of cellular communication produced by multiple liver cell types. Cytokines can directly induce either necrosis or apoptosis. They can also recruit such cells as neutrophils and lymphocytes, which can mediate liver damage. Increased levels of hepatotoxic cytokines such as tumor necrosis factor-’are documented in alcoholic liver disease (ALD) and nonalcoholic steatohepatitis (NASH) and have been shown to play a mechanistic role in both of these disease processes. Transforming growth factor-βs a profibrotic cytokine that is critical in hepatic fibrosis. Beneficial cytokines, such as interleukin (IL)-10 and-6, also exist. Such beneficial cytokines as adiponectin are made outside the liver and appear to protect against ALD and NASH. This article reviews the relevance of cytokines in human and experimental forms of liver injury, focusing on modulation of cytokines and the use of beneficial cytokines in treatment and prevention of liver injury in ALD, NASH, and hepatitis C.     

Hepatic fibrosis in fetal alcohol syndrome. Pathologic similarities to adult alcoholic liver disease

The light- and electron-microscopic changes in a biopsy of the liver obtained at age 17 mo from a child with fetal alcohol syndrome were studied. At the time of biopsy, hepatomegaly and raised serum transaminases were present as well as neurologic and growth defects and the typical facial anomalies seen in this syndrome. Light microscopy of the liver biopsy specimen revealed parenchymal fat with portal and perisinusoidal fibrosis. Ultrastructurally, perisinusoidal spaces contained deposits of intermediate-size and large collagen fibers, myofibroblasts and occasional Ito cells, and subendothelial basement membrane-like material. These changes resemble those seen in adult human and baboon alcoholic liver disease and suggest that hepatic fibrosis in fetal alcohol syndrome has a similar pathogenesis.     

Fibrogenesis in alcoholic liver disease

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. In developed countries, ALD is a major cause of end-stage liver disease that requires transplantation. The spectrum of ALD includes simple steatosis, alcoholic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Alcohol abstinence is the most effective therapy for ALD. However, targeted therapies are urgently needed for patients with severe ALD (i.e., alcoholic hepatitis) or those who do not abstain from alcohol. The lack of studies and the availability of animal models that do not reflect all the features of this disease in humans inhibit the development of new drugs for ALD. In ALD-associated fibrosis, hepatic stellate cells are the principal cell type responsible for extracellular matrix production. Although the mechanisms underlying fibrosis in ALD are largely similar to those observed in other chronic liver diseases, oxidative stress, methionine metabolism abnormalities, hepatocyte apoptosis, and endotoxin lipopolysaccharides that activate Kupffer cells may play unique roles in disease-related fibrogenesis. Lipogenesis during the early stages of ALD has recently been implicated as a risk factor for the progression of cirrhosis. Other topics include osteopontin, interleukin-1 signaling, and genetic polymorphism. In this review, we discuss the basic pathogenesis of ALD and focus on liver fibrogenesis.     

Advances in alcoholic liver disease

Alcoholic liver disease (ALD) remains a major cause of morbidity and mortality worldwide. For example, the Veterans Administration Cooperative Studies reported that patients with cirrhosis and superimposed alcoholic hepatitis had a 4-year mortality of >60%. Interactions between acetaldehyde, reactive oxygen and nitrogen species, inflammatory mediators and genetic factors appear to play prominent roles in the development of ALD. The cornerstone of therapy for ALD is lifestyle modification, including drinking and smoking cessation and losing weight, if appropriate. Nutrition intervention has been shown to play a positive role on both an inpatient and outpatient basis. Corticosteroids are effective in selected patients with alcoholic hepatitis and pentoxifylline appears to be a promising anti-inflammatory therapy. Some complementary and alternative medicine agents, such as milk thistle and S-adenosylmethionine, may be effective in alcoholic cirrhosis. Treatment of the complications of ALD can improve quality of life and, in some cases, decrease short-term mortality.