Ethanol and the Human Liver

Alterations in mitochondrial function and morphology in chronic liver disease: pathogenesis and potential for therapeutic intervention

Studies assessing mitochondrial function and structure in livers from humans or experimental animals with chronic liver disease, including liver cirrhosis, revealed a variety of alterations in comparison with normal subjects or control animals. Depending on the etiology of chronic liver disease, the function of the electron transport chain and/or ATP synthesis was found to be impaired, leading to decreased oxidative metabolism of various substrates and to impaired recovery of the hepatic energy state after a metabolic insult. Changes in mitochondrial structure include megamitochondria with reduced cristae, dilatation of mitochondrial cristae and crystalloid inclusions in the mitochondrial matrix. The most important strategies to maintain an adequate mitochondrial function per liver are mitochondrial proliferation and increases in the activity of critical enzymes or in the content of cofactors per mitochondrion. Possibilities to assess hepatic mitochondrial function and to treat mitochondrial dysfunction in patients with chronic liver disease are discussed.

Adaptation of mitochondrial metabolism in liver cirrhosis. Different strategies to maintain a vital function

Mitochondrial function and structure in cirrhotic livers from humans or rats show a variety of changes as compared to control livers. Mitochondrial ATP production is reduced in rats with CCl4- or thioacetamide-induced liver cirrhosis and in rats with secondary biliary cirrhosis. Activity of the electron transport chain is decreased in rats with secondary biliary cirrhosis. In rats with CCl4-induced cirrhosis, the mitochondrial content of certain constituents of the respiratory chain (cytochrome a + a3, cytochrome b and ubiquinone) is increased and activities of cytochrome c oxidase and ATPase are elevated. Similarly, in humans with liver cirrhosis, mitochondrial cytochrome a + a3 content is elevated and has been used to assess the risk for hepatectomy. In rats with secondary biliary cirrhosis, compensatory strategies include increased mitochondrial volume per hepatocyte and possibly increased extramitochondrial ATP production (increased glycolysis). Thus, a variety of adaptive mechanisms are used to maintain mitochondrial function in cirrhotic livers.

Quantitative ultrastructural analysis of hepatoprotective effects of (+)-cyanidanol-3 on alcoholic liver damage

Biochemical considerations suggest that bioflavonoids may be effective antihepatotoxic and hepatoprotective agents. We, therefore, designed a morphometric study to examine the effect of (+)-cyanidanol-3 on ethanol-induced hepatocellular alterations. Using a stereologic point and intersection counting method we determined the volume fraction of cytoplasmic components, the surface area of cytoplasmic membranes, some parameters of mitochondria, and numerical densities of some organelles, after chronic ethanol intoxication and hepato-protective treatment of rats. Consistent with previous qualitative and quantitative descriptions, chronic ethanol feeding caused increases in parameters of mitochondria, microsome, and Golgi complex. The hepatoprotective (+)-cyanidanol-3 treatment restored most of the morphologic distortion caused by ethanol ingestion. The (+)-cyanidanol-3 treatment alone caused an elevation of the surface area of smooth endoplasmic reticulum and nonsignificant changes in mitochondrial parameters, possibly due to its inducing effect on microsomes and activating effect on mitochondrial enzymes. These data indicate that bioflavonoids could be of potential benefit in hepatotoxic or alcohol-related liver disease.

Ultrastructural morphogenesis of mitochondria in alcoholic liver

Electron microscopic studies of 53 diagnostic liver biopsies from 23 patients were done. Ultrastructural study revealed most striking alteration to be in the mitochondria such as pleomorphism in shape and size, especially giant mitochondria with disorganization, crystalline inclusions and calcium-like electron dense bodies. These ultrastructural changes might have been induced by specific biochemical abnormality in alcohol bearing condition. Diagnostic use of electron microscopy will be useful in detecting alcoholic injury in alcoholic patient who fails to demonstrate any discernible laboratory and light microscopic abnormalities.

Biochemical and morphological alterations of baboon hepatic mitochondria after chronic ethanol consumption

Baboons fed ethanol (50% of total calories) chronically develop ultrastructural alterations of hepatic mitochondria. To determine whether mitochondrial functions are also altered, mitochondria were isolated from nine baboons fed ethanol chronically and their pair-fed controls. At the fatty liver stage, ADP-stimulated respiration was depressed in ethanol-fed baboons by 59.4% with glutamate, 43.2% with acetaldehyde, 45.1% with succinate and 51.1% with ascorbate as substrates. A similar decrease was noted in the ADP/O ratio (14 to 28%) and respiratory control ratio (20 to 44%) with all substrates. Similar alterations of mitochondrial functions were observed in baboons with more advanced stages of liver disease, namely fibrosis. These changes after ethanol treatment were associated with decreases in the enzyme activities of mitochondrial respiratory chain: glutamate, NADH and succinate dehydrogenase (42, 24 and 28%, respectively), glutamate-, NADH- or succinate-cytochrome c reductase (42, 27 and 32%, respectively) and cytochrome oxidase (59.6%). The content of all cytochromes was also decreased in ethanol-fed baboons, especially aa3 (57%). Moreover, [14C]leucine incorporation into mitochondrial membranes was depressed by 21% after ethanol treatment. On the other hand, glutamate dehydrogenase activities of serum and cytosol in ethanol-fed baboons were significantly higher than those in pair-fed controls. Morphologically, mitochondria of ethanol-fed baboons were larger than those of pair-fed controls. However, the mitochondrial protein content per mitochondrial DNA was unchanged. From these results, we conclude that, morphologically and functionally, hepatic mitochondria in baboons are altered by chronic ethanol consumption; it is noteworthy that these changes are fully developed already at the fatty liver stage, and that morphological alteration appears to reflect the damage of mitochondrial membranes rather than an adaptive hypertrophy.

Alcohol-induced mitochondrial changes in the liver

The chronic ingestion of ethanol results in liver-cell damage, and characteristic features of this injury are the marked alterations in both the functions and morphology of the mitochondria. Morphologically, the changes observed in human alcoholics and experimental animals appear similar. Bizarrely shaped mitochondria and megamitochondria are detected at the fatty liver stage and persist as the disease progresses. As yet, however, no correlation has been found between the severity of these morphological changes and the development of cirrhosis. Analysis of the mitochondrial membranes indicates that ethanol consumption produces changes in both the protein and lipid composition of the membrane. Profound decreases in the components of the respiratory chain have been detected, and these changes are associated with marked depressions in the activity of NAD+-linked dehydrogenases, cytochrome oxidase, and the ATP synthetase complex. On the other hand, no consistent pattern has emerged as to the effect of chronic ethanol consumption on the composition of the membrane phospholipids. Many of the changes appear to be dependent on the sex of the animal, the dietary status, and the duration of ethanol intake, and are suggestive of changes in fatty acid desaturase activity. Mitochondria isolated from ethanol-fed rats displayed impaired respiration and a lowered steady-state rate of ATP synthesis. Whether or not these functional changes are directly related to alterations in the physical properties of the membranes remains to be resolved. This marked depression of respiratory functions in isolated mitochondria was not reflected by a significant decrease in O2 consumption by the livers of ethanol-fed animals.

Effect of chronic ethanol feeding on hepatic mitochondria in the monkey

The effect of chronic ethanol feeding on hepatic mitochondrial morphology and histochemically measured succinic dehydrogenase activity was assessed. Five monkeys of the species Macaca radiata received a nutritionally adequate diet containing 50% of the calories as ethanol, while five others were pair-fed the same diet except that ethanol was isocalorically substituted by carbohydrate. Liver morphology was assessed at 12 and 24 months and at sacrifice after 40 to 48 months of ethanol feeding. The ethanol-fed animals developed mild to moderate fatty liver as did some of the controls. No necrosis or fibrosis developed. All ethanol-fed animals developed centrilobolar megamitochondria and centrilobular "shift" in histochemically assayed succinic dehydrogenase activity characteristic of animals fed ethanol for prolonged periods. These mitochondrial changes persisted throughout the 48-month test period without progressive increase in severity or accompanying pathology. It is concluded that the morphologic and histochemically assessed mitochondrial changes do not necessarily represent a progressive destructive effect of ethanol.

Morphologic alterations of rat Leydig cells induced by ethanol

Ultrastructural morphometric studies were employed to compare the morphology of Leydig cells found in the testes of rats fed ethanol, accounting for 36% of total calories for 6 weeks, and those found in the testes of rats isocalorically fed a diet in which ethanol was isocalorically replaced with dextrimaltose. The testes of alcohol-fed rats weighed significantly less (p less than 0.01) than those of the isocaloric controls. Moreover, plasma testosterone in the alcohol-fed animals was reduced (p less than 0.01), as compared to the controls. Morphologically, two main differences were encountered between the Leydig cells of alcohol-fed animals and those of the isocalorically-fed controls. These were: (1) an increase in the number of elongated and cup-shaped mitochondria; and (2) an increase in cytoplasmic protrusions in the form of pseudopods. Using morphometric techniques, the Leydig cells of alcohol-fed animals were smaller (p less than 0.05), had less cytoplasm (p less than 0.05), larger mitochondria (p less than 0.01), and less smooth endoplasmic reticulum (p less than 0.05) than did those of the isocaloric controls. These morphologic characteristics of Leydig cells of alcohol-fed animals are similar to those reported to occur in the liver and suggest that the biochemical mechanisms responsible for alcohol-induced cellular injury are similar in the testes and the liver.

Ultrastructural and biochemical studies of the brain and other organs in rats after chronic ethanol administration. IV. Stereological analysis of mitochondria from rat liver cells after intoxication with various ethanol doses

Ultrastructural and stereological analysis of mitochondria of liver cells from rats was performed after intoxication with various doses of ethanol administered for various time periods in increasing concentrations. The following changes were observed in the cells of the experimental animals as compared with the control ones: -- a decrease of the surface area of mitochondria per unit volume of the hepatocyte, -- a decrease of the mean number of mitochondrial profiles per 100 micrometers 2 surface area of hepatocyte cross section, -- a decrease in the value of the axial ratio of mitochondrial profiles. A diminished volume fraction of the mitochondria was not observed. The above presented results show that, after ethanol poisoning, the mitochondria in hepatic cells become enlarged and rounded and their number seems to diminish. Qualitative studies demonstrated that the structure of mitochondria is frequently damaged, this consisting in injury to their membranes, formation of lamellar structures, and destruction of the system of cristae and matrix. This leads to the presence of degenerated, sometimes monstrously large mitochondria in the cells. The above described changes occurred as early as after 4 weeks of ethanol administration in increasing doses from 2.5 to 10 per cent. An increase of ethanol concentration to 42 per cent and prolongation of the period of treatment with ethanol to 12 weeks did not markedly enhance the changes.

Effect of ethanol on rat liver. 4. The influence of vitamins, electrolytes and amino acids on the structure and function of mitochondria from rats receiving ethanol

1. Feeding rats with a 15% ethanol solution for several weeks caused structural and functional changes in their liver mitochondria, although their intake of solid food was about the same as that of the controls.

2. Attempts were made to counteract these effects of ethanol by increasing the intake of amino acids, vitamins, lipotropic compounds and electrolytes beyond that which is adequate when water is the drinking fluid.

3. An increased intake of nicotinic acid, together with aqueous ethanol, caused a further enlargement of the mitochondria above that obtained with ethanol solution alone. the diluted matrix observed with the ethanol and nicotinic acid treatment suggested that water imbibition by the mitochondria caused this further enlargement.

4. In rats receiving ethanol fortified with magnesium sulphate and lipotropic compounds (choline, methionine) there was a further increase in mitochondrial size, as compared with those receiving ethanol alone. The matrix was, however, of the same density as in the mitochondria from the rats receiving ethanol alone. the oxidation rate of pyruvate and succinate was unchanged, but α-glycerophosphate and β-hydroxybutyrate were oxidized at a higher rate than in mitochondria from rats drinking ethanol or water.

5. When the ethanol solution was supplemented with amino acids (casein hydrolysate), vitamins and electrolytes, the mitochondrial enlargement after 120 days of treatment was less than with ethanol alone and was completely absent after 300 days. the oxidation rate of pyruvate and succinate was, however, not fully restored to normal.