Effect of chronic ethanol feeding on hepatic mitochondria in the monkey

Megamitochondria plasticity: function transition from adaption to disease

As the cell's energy factory and metabolic hub, mitochondria are critical for ATP synthesis to maintain cellular function. Mitochondria are highly dynamic organelles that continuously undergo fusion and fission to alter their size, shape, and position, with mitochondrial fusion and fission being interdependent to maintain the balance of mitochondrial morphological changes. However, in response to metabolic and functional damage, mitochondria can grow in size, resulting in a form of abnormal mitochondrial morphology known as megamitochondria. Megamitochondria are characterized by their considerably larger size, pale matrix, and marginal cristae structure and have been observed in various human diseases. In energy-intensive cells like hepatocytes or cardiomyocytes, the pathological process can lead to the growth of megamitochondria, which can further cause metabolic disorders, cell damage and aggravates the progression of the disease. Nonetheless, megamitochondria can also form in response to short-term environmental stimulation as a compensatory mechanism to support cell survival. However, extended stimulation can reverse the benefits of megamitochondria leading to adverse effects. In this review, we will focus on the findings of the different roles of megamitochondria, and their link to disease development to identify promising clinical therapeutic targets.

Animal Models of Alcoholic Liver Disease for Hepatoprotective Activity Evaluation

Background: The reported statistics suggest that alcoholic liver disease is on the rise. Furthermore, medications used to treat the disease have unpleasant effects, and this necessitates the need to continuously investigate hepatoprotective agents. This study investigates animal models of alcoholic liver disease used to evaluate hepatoprotective activity. Content: A good number of published articles evaluating hepatoprotective activity were summarized. The studies used three ethanol-induced liver injury models: the acute ethanol-induced liver injury model, the chronic ethanol-induced liver injury model, and Lieber– DeCarli model. Summary: Wistar rats were primarily used in the ethanol-induced liver injury model. High levels of alanine transaminase (ALT) and aspartate transaminase (AST) and histopathological alterations were found in all animal models (acute ethanol-induced liver injury, chronic ethanol-induced liver injury, and Lieber–DeCarli models). Severe steatosis was shown in both chronic ethanol-induced liver injury and Lieber–DeCarli models. However, fibrosis was undetected in all models.

Acetyl-L-carnitine and lipoic acid improve mitochondrial abnormalities and serum levels of liver enzymes in a mouse model of nonalcoholic fatty liver disease

Mitochondrial abnormalities are suggested to be associated with the development of nonalcoholic fatty liver. Liver mitochondrial content and function have been shown to improve in oral feeding of acetyl-L-carnitine (ALC) to rodents. Carnitine is involved in the transport of acyl-coenzyme A across the mitochondrial membrane to be used in mitochondrial β-oxidation. We hypothesized that oral administration ALC with the antioxidant lipoic acid (ALC + LA) would benefit nonalcoholic fatty liver. To test our hypothesis, we fed Balb/C mice a standard diet (SF) or SF with ALC + LA or high-fat diet (HF) or HF with ALC + LA for 6 months. Acetyl-L-carnitine and LA were dissolved at 0.2:0.1% (wt/vol) in drinking water, and mice were allowed free access to food and water. Along with physical parameters, insulin resistance (blood glucose, insulin, glucose tolerance), liver function (alanine transaminase [ALT], aspartate transaminase [AST]), liver histology (hematoxylin and eosin), oxidative stress (malondialdehyde), and mitochondrial abnormalities (carbamoyl phosphate synthase 1 and electron microscopy) were done. Compared with SF, HF had higher body, liver, liver-to-body weight ratio, white adipose tissue, ALT, AST, liver fat, oxidative stress, and insulin resistance. Coadministration of ALC + LA to HF animals significantly improved the mitochondrial marker carbamoyl phosphate synthase 1 and the size of the mitochondria in liver. Alanine transaminase and AST levels were decreased. In a nonalcoholic fatty liver mice model, ALC + LA combination improved liver mitochondrial content, size, serum ALT, and AST without significant changes in oxidative stress, insulin resistance, and liver fat accumulation.

Ethanol self-administration and alterations in the livers of the cynomolgus monkey, Macaca fascicularis

BACKGROUND

Most of the studies of alcoholic liver disease use models in which animals undergo involuntary administration of high amounts of ethanol and consume diets that are often high in polyunsaturated fatty acids. The objectives of this study were (1) to evaluate whether cynomolgus monkeys (Macaca fascicularis) drinking ethanol voluntarily and consuming a diet with moderate amounts of lipid would demonstrate any indices of alcoholic liver disease past the fatty liver stage and (2) to determine whether these alterations were accompanied by oxidative stress.

METHODS

Six adult male and 6 adult female cynomolgus monkeys were allowed to consume ethanol voluntarily for 18 to 19 months. Additional monkeys were maintained on the same consumption protocol, but were not provided with ethanol. During the course of the study, liver biopsy samples were monitored for lipid deposition and inflammation, serum for levels of liver enzymes, and urine for concentrations of the isoprostane (IsoP) metabolite, 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP, a biomarker for oxidative stress. Liver mitochondria were monitored for respiratory control and liver for concentrations of neutral lipids, adenine nucleotides, esterified F(2) isoprostanes, oxidized proteins, 4-hydroxynonenal (HNE)-protein adducts, and protein levels of cytochrome P-450 2E1 and 3A4.

RESULTS

Ethanol consumption ranged from 0.9 to 4.05 g/kg/d over the period of the study. Serum levels of aspartate amino transferase were elevated in heavy-consuming animals compared with those in ethanol-naïve or moderate drinkers. Many of the ethanol consumers developed fatty liver and most showed loci of inflammation. Both hepatic energy charge and phosphorylation potential were decreased and NADH-linked respiration was slightly, but significantly depressed in coupled mitochondria as a result of heavy ethanol consumption. The urinary concentrations of 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP increased as high as 33-fold over that observed in ethanol-abstinent animals. Liver cytochrome P-450 2E1 concentrations increased in ethanol consumers, but there were no ethanol-elicited increases in hepatic concentrations of the esterified F(2) isoprostanes, oxidized proteins, or HNE-protein adducts.

CONCLUSION

Our studies show that cynomolgus monkeys undergoing voluntary ethanol consumption for 1.5 years exhibit many of the features observed in the early stages of human alcoholic liver disease. Ethanol-elicited fatty liver, inflammation, and elevated serum aspartate amino transferase were evident with a diet that contained modest amounts of polyunsaturated lipids. The dramatic increases in urinary IsoP demonstrated that the animals were being subjected to significant oxidative stress that correlated with their level of ethanol consumption.

Ethanol feeding enhances age-related deterioration of the rat hepatic mitochondrion

Chronic ethanol feeding damages the hepatic mitochondrion by increasing mitochondrial DNA (mtDNA) oxidation, lowering mtDNA yields and impairing mitochondrial respiration. These effects are also seen during aging. By employing a 21-day chronic feeding regimen, we investigated the effects of ethanol consumption on mtDNA content and mitochondrial respiration in 2-, 12-, and 24-mo-old male rats. Aging resulted in decreased mtDNA content, increased mtDNA damage (as indicated by inhibition of Taq polymerase progression), and a decline in state 3 respiration; effects that were further exacerbated by ethanol feeding. Additionally, ethanol consumption caused an increase in the levels of citrate synthase while not impacting mitochondrial protein content. In conclusion, ethanol and aging combine to cause deterioration in the structural and functional integrity of the hepatic mitochondrion. The additive effects of aging and ethanol feeding may have serious consequences for hepatic energy metabolism in aged animals, and their detrimental combination may serve as one of the molecular mechanisms underlying the progression of alcoholic liver disease.

Oxidative stress and oval cell accumulation in mice and humans with alcoholic and nonalcoholic fatty liver disease

In animals, the combination of oxidative liver damage and inhibited hepatocyte proliferation increases the numbers of hepatic progenitors (oval cells). We studied different murine models of fatty liver disease and patients with nonalcoholic fatty liver disease or alcoholic liver disease to determine whether oval cells increase in fatty livers and to clarify the mechanisms for this response. To varying degrees, all mouse models exhibit excessive hepatic mitochondrial production of H(2)O(2), a known inducer of cell-cycle inhibitors. In mice with the greatest H(2)O(2) production, mature hepatocyte proliferation is inhibited most, and the greatest number of oval cells accumulates. These cells differentiate into intermediate hepatocyte-like cells after a regenerative challenge. Hepatic oval cells are also increased significantly in patients with nonalcoholic fatty liver disease and alcoholic liver disease. In humans, fibrosis stage and oval cell numbers, as well as the number of intermediate hepatocyte-like cells, are strongly correlated. However, cirrhosis is not required for oval cell accumulation in either species. Rather, as in mice, progenitor cell activation in human fatty liver diseases is associated with inhibited replication of mature hepatocytes. The activation of progenitor cells during fatty liver disease may increase the risk for hepatocellular cancer, similar to that observed in the Solt-Farber model of hepatocarcinogenesis in rats.

Mitochondrial abnormalities in non-alcoholic steatohepatitis

BACKGROUND/AIMS

We assessed mitochondrial morphology by electron microscopy and the prevalence of a mitochondrial gene deletion in patients with non-alcoholic steatohepatitis (NASH), alcohol-related liver disease and non-fatty liver diseases. Respiratory chain function using a cytoplasmic hybrid (cybrid) assay was further studied in NASH patients and healthy controls.

METHODS

Electron microscopy was performed in 26 specimens. Fifteen patients were studied by polymerase chain reaction to detect a 520-bp deletion product of the mitochondrial genome (dmtDNA). Cybrids were created by fusion of platelets with anaerobic neuroblastoma cells in six NASH patients and 12 controls.

RESULTS

Eight of ten NASH, one of seven alcoholics and two of nine other patients had linear crystalline inclusions in megamitochondria (p<0.05). Three of five patients with alcohol-related liver disease had dmtDNA compared to one of five NASH patients and one of five non-steatohepatitis controls. Cybrid respiratory chain function in platelets was not different from that of controls.

CONCLUSIONS

Respiratory chain dysfunction, if present in NASH, is not expressed in platelet-derived mitochondria. In contrast to alcohol-related liver disease with active drinking, NASH patients do not commonly express the 5-kb mitochondrial DNA gene deletion in liver tissue. As previously described in early alcohol-related liver disease, crystalline inclusions of unknown composition are seen in hepatic mitochondria in NASH. Their presence suggests either an adaptive process or mitochondrial injury.

Mitochondrial abnormalities in non-alcoholic steatohepatitis

BACKGROUND/AIMS

We assessed mitochondrial morphology by electron microscopy and the prevalence of a mitochondrial gene deletion in patients with non-alcoholic steatohepatitis (NASH), alcohol-related liver disease and non-fatty liver diseases. Respiratory chain function using a cytoplasmic hybrid (cybrid) assay was further studied in NASH patients and healthy controls.

METHODS

Electron microscopy was performed in 26 specimens. Fifteen patients were studied by polymerase chain reaction to detect a 520-bp deletion product of the mitochondrial genome (dmtDNA). Cybrids were created by fusion of platelets with anaerobic neuroblastoma cells in six NASH patients and 12 controls.

RESULTS

Eight of ten NASH, one of seven alcoholics and two of nine other patients had linear crystalline inclusions in megamitochondria (p<0.05). Three of five patients with alcohol-related liver disease had dmtDNA compared to one of five NASH patients and one of five non-steatohepatitis controls. Cybrid respiratory chain function in platelets was not different from that of controls.

CONCLUSIONS

Respiratory chain dysfunction, if present in NASH, is not expressed in platelet-derived mitochondria. In contrast to alcohol-related liver disease with active drinking, NASH patients do not commonly express the 5-kb mitochondrial DNA gene deletion in liver tissue. As previously described in early alcohol-related liver disease, crystalline inclusions of unknown composition are seen in hepatic mitochondria in NASH. Their presence suggests either an adaptive process or mitochondrial injury.

Cytotoxicity of short-chain alcohols

Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D-mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.

Mitochondrial proteins that regulate apoptosis and necrosis are induced in mouse fatty liver

Fatty liver is common in nonalcoholic, obese individuals and in lean people who consume alcohol chronically. Although fatty liver is typically benign, a subset of individuals with steatosis develop steatohepatitis and eventually cirrhosis. The disparate outcomes of fatty liver suggest that it reflects a generally beneficial, adaptive response to obesity or alcohol-related stress, but may also increase hepatocyte vulnerability to other challenges. Thus, both protective factors (e.g., Bcl-2 and Bcl-xL) and factors that promote hepatocyte death by apoptosis (e.g., Bax) or necrosis (e.g., UCP2) may be increased in fatty livers. To evaluate this possibility, hepatocyte apoptosis, necrosis, and the expression of factors that regulate cellular viability were assessed in two models of fatty liver (i.e., genetically obese [ob/ob] mice and ethanol [EtOH]-fed lean mice). Findings in mice with fatty livers were compared with lean, control mice that did not have hepatic steatosis. Immunohistochemistry showed striking induction of hepatocyte proteins that promote (e.g., Bax) and inhibit (e.g., Bcl-2 and Bcl-xL) apoptosis in both groups with fatty liver. Both models of fatty liver also increased hepatic transcripts for UCP2, a mitochondrial uncoupling protein, and the protein itself was induced in ob/ob hepatocytes. Despite the up-regulation of factors that threaten cell viability, hepatocyte death was not increased in either ob/ob or EtOH-fed mice, confirming that the liver's protective responses were sufficient under the conditions studied. However, if UCP2 induction reduces the efficiency of adenosine triphosphate (ATP) synthesis, this initially harmless response might enhance the vulnerability of hepatocytes to necrosis.

Protective effect of P. fraternus against ethanol-induced mitochondrial dysfunction

Chronic ethanol consumption (10 g per kg body weight) significantly decreased the rate of respiration, P/O ratio, and respiratory control ratio (RCR). The activities of NADH dehydrogenase and cytochrome oxidase were significantly decreased in submitochondrial particles by ethanol administration compared to control. No significant difference was observed in membrane potential of submitochondrial particles. Cytochrome b, c and aa3 content of mitochondria were significantly decreased by ethanol feeding. Ethanol-induced inhibition on rate of respiration, P/O ratio, and RCR was relieved to a great extent by the administration of the aqueous extract of Phyllanthus fraternus (100 mg dry powder of the plant per kg body weight) along with ethanol. The decrease in the content of cytochromes due to ethanol administration was revived partially by aqueous extract of P. fraternus.

Complete suppresion of ethanol-induced formation of megamitochondria by 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-OH-TEMPO)

An attempt has been made to suppress the ethanol-induced formation of megamitochondria (MG) in the rat liver by 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-OH-TEMPO), a free radical scavenger, and by allopurinol (AP), a xanthine oxidase inhibitor. Changes observed in the liver of animals given ethanol (EtOH) for 1 month were remarkable decreases both in the body weight gains during the course of the experiment and in the liver weight at the time of sacrifice compared to those of the control; remarkable increases in the level of thiobarbituric acid reactive substances and lipid soluble fluorophores both in microsomes and mitochondria; decreases in the content of cytochrome a+a3 and b and lowered phosphorylating ability of mitochondria; and formation of MG in the liver. A combined treatment of animals with EtOH plus 4-OH-TEMPO completely suppressed the formation of MG in the liver induced by EtOH and distinctly improved the changes caused by EtOH, as specified above, while AP partly suppressed the MG formation. Results described herein provide additional insight into chronic hepatotoxicity of EtOH besides that previously reported. A novelty of the present work is that we were able for the first time to demonstrate reversibility of EtOH-mediated ultrastructural changes of the liver by a simple administration of aminoxyl-type free radical scavenger, 4-OH-TEMPO. Our results suggest that free radicals may be involved in the mechanism of the formation of MG induced by EtOH.

Giant mitochondria induced in rat pancreatic exocrine cells by ethanol and iron

BACKGROUND

Mitochondria are sensitive indicators of cellular pathology. Under certain circumstances, these organelles respond to cellular insult by a marked increase in size, resulting in the formation of giant mitochondria (megamitochondria). Ethanol has been implicated in the induction of giant mitochondria in rat hepatocytes. Since ethanol is reported to affect pancreatic mitochondria, we examined this organ for evidence of mitochondrial giantism in rats administered ethanol and a relatively small amount of supplementary iron.

METHODS

Diets were administered via a chronically implanted gastrostomy catheter. Rats were segregated in four groups: 1) basic high-fat diet, 2) ethanol and a high fat diet, 3) carbonyl iron and a high-fat diet, and 4) ethanol and carbonyl iron combined with a high-fat diet. After the animals were on their respective diets for 16 weeks, specimens of pancreas were extirpated and processed for and examined by transmission electron microscopy.

RESULTS

Mitochondria in rats on the basic high fat diet resemble those in untreated controls. With ethanol and a high-fat diet, some mitochondria in virtually every exocrine cell are profoundly altered. Such organelles, which are of normal size, have undergone rearrangement of their internal membranes, with three of four parallel cristae residing at one or both poles of spherical to ovate mitochondria. In rats receiving both ethanol and carbonyl iron, giant mitochondria are present in pancreatic exocrine cells. Except for their size, megamitochondria in many cases are virtual likenesses of the altered mitochondria in the alcohol-high-fat rats, having several stacked cristae at either pole and an enhanced matrix compartment. Many of the giant mitochondria have at least one expanded crista, which contains packets of helically coiled filaments. When control rats are fed carbonyl iron without ethanol, the pancreatic mitochondria display a marked propensity for forming clusters of tightly interlocked organelles, formations that may be a prelude to mitochondrial fusion.

CONCLUSIONS

It appears that iron supplementation sets the stage for organelle fusion, hence enlargement, with the ethanol providing the stimulus for fusion to actually take place, and controlling the final morphology of the resultant megamitochondria.

Effects of adenosine administration on the function and membrane composition of liver mitochondria in carbon tetrachloride-induced cirrhosis

The effect of chronic carbon tetrachloride (CCl4) administration on liver mitochondria function and the protective action of adenosine on CCl4-induced damage were assessed in rats made cirrhotic by long-term exposure to the hepatotoxin (8 weeks). The CCl4 treatment decreased the ADP-stimulated oxygen consumption, respiratory control, and ADP/O values, mainly for substrates oxidation of site I, in isolated mitochondria. This impaired mitochondrial capacity for substrate oxidation and ATP synthesis was accompanied by an important diminution (approximately 30 mV) of membrane electrical potential. Disturbances of the mitochondrial membrane, induced by CCl4 treatment, were also evidenced as increased mitochondria swelling and altered oscillatory states of mitochondrial volume, both energy-linked processes. The deleterious effects of CCl4 on mitochondrial function were also reflected as a deficient activity of the malate-aspartate shuttle that correlated with abnormal distribution of cholesterol and phospholipids in membranes obtained from submitochondrial particles. Adenosine treatment of CCl4-poisoned rats partially prevented the alterations in mitochondria membrane composition and prevented, almost completely, the impairment of mitochondria function induced by CCl4. Although the nature of the protective action of adenosine on CCl4-induced mitochondria injury remains to be elucidated, such action at this level might play an important role in the partial prevention of liver damage induced by the CCl4.

Biochemistry of alcoholic liver disease

The biochemistry of alcohol liver disease as it relates to clinical medicine and experimental alcohol liver disease is presented. Clinical features are emphasized in the diagnosis of alcohol liver disease, particularly as it relates to staging the disease and predictors of prognosis. Currently, it is true that the biochemical diagnosis of alcohol liver disease is at best very limited in terms of the sensitivity tests and specificity of the test. It is particularly difficult to detect alcohol liver disease biochemically in the early stages when steatohepatitis is not severe. Consequently, 50% of the patients have already developed cirrhosis at the time they are diagnosed clinically. In this review indicators of malnutrition are emphasized because they have the strongest implications regarding survival during the acute hospitalization stage of the disease. They are also the best indicators of response to therapy during the recovery phase. With respect to experimental work on the pathogenesis of alcohol liver disease, it appears that necrosis is due to the inability to increase blood flow to compensate for increased oxygen utilization. The hypothesis that mitochondrial damage is the cause of liver cell damage is regarded as less important in the pathogenesis of necrosis. The shift in the redox state during alcohol metabolism accounts for the fatty change noted in the central lobular area of the liver in animals fed alcohol. Apparently, there is strong experimental evidence that highly reactive intermediates are important in the pathogenesis of liver damage due to the induction of the isozyme cytochrome P450 IIE1 by alcohol ingestion. This mechanism is enhanced by a diet high in polyunsaturated fatty acids.

Influence of copper status on the response to acute ethanol exposure in rats

An acute dose of ethanol was used to investigate the biochemical response of tissues with a compromised antioxidant defense system to a surge of oxygen radical production. The copper (Cu)-deficient rat served as the animal model for this study based on its compromised antioxidant defense system. Rats were fed control (10 micrograms Cu/g) or Cu-deficient (0.2 microgram Cu/g) diet for 14 days. In order to minimize secondary effects associated with chronic Cu deficiency, the chelator triethylenetetramine was added to the Cu-deficient diet to shorten the time required for the induction of Cu deficiency. On day 14, rats were gavaged with ethanol (4.5 g/kg b.wt.) or saline and killed 9 hours postgavage. Rats fed the Cu-deficient diets had lower liver superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities than controls. Ethanol treatment had no effect on liver CuZnSOD or Gpx activity, while MnSOD activity was higher than saline control levels following EtOH treatment. Despite low GPx and SOD activity, Cu-deficient rats did not exhibit higher hepatic thiobarbituric acid reacting substances (TBARS) than controls; in fact, hepatic microsomal TBARS were lower in saline-treated Cu-deficient rats relative to Cu-sufficient rats. Ethanol treatment resulted in higher whole homogenate and mitochondrial TBARS than in saline-gavaged rats. Copper status did not influence hepatic TBARS production in response to an acute EtOH load. These data suggest that compensatory mechanisms contribute to the protection of the liver from excessive free radical production in this model of Cu deficiency.

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.

Subcellular changes and apoptosis induced by ethanol in rat liver

The livers of rats given ethanol for 5 weeks showed marked structural alterations of hepatocytes of acinar zone 3 including mitochondrial pleomorphism, increased smooth endoplasmic reticulum and deposition of small (less than 0.5 micron) lipid droplets. In addition, apoptotic bodies involving altered parenchymal cells were frequently observed, together with prominent mononuclear infiltrates adjacent to the terminal hepatic veins. It is suggested that 'age' of liver cells may play a role in the preferential perivenular localization of early ethanol-induced liver damage.

Metabolic state of the rat liver with ethanol: comparison of in vivo 31phosphorus nuclear magnetic resonance spectroscopy with freeze clamp assessment

In vivo 31phosphorus nuclear magnetic resonance spectroscopy was used to measure the hepatic metabolic state in various groups of rats given ethanol, a control liquid diet or a solid chow diet. The use of selective presaturation pulses applied to the broad phosphorus resonances of immobile phospholipids permitted reliable determination of ATP/ADP ratios by quantitation of the ATP-beta and ATP-gamma peak areas. ATP/ADP ratios were depressed by both techniques in rats chronically ingesting ethanol compared to pair-fed animals consuming the control liquid diet. These differences were observed regardless of whether ethanol feeding was continued up to the time of investigation or whether it was discontinued for 24 hr prior to study. Acute alcohol administration in chow-fed rats, not previously ingesting ethanol, did not lower hepatic ATP/ADP ratios by either methodology. In all cases, liver ATP/ADP ratios assessed by 31phosphorus nuclear magnetic resonance spectroscopy were higher than those measured by high-performance liquid chromatography. However, parallel decreases in hepatic ATP/ADP ratios were observed with chronic ethanol consumption by both 31phosphorus nuclear magnetic resonance spectroscopy and the biochemical method, confirming the utility of in vivo 31phosphorus nuclear magnetic resonance spectroscopy for assessment of the hepatic bioenergetic status. The difference in absolute ATP/ADP ratios by the two methods may to some degree be explained by binding effects of ADP with proteins or mitochondrial membranes, rendering it partially invisible to nuclear magnetic resonance or alternatively, by breakdown of high energy phosphate bonds with freeze clamp extraction.

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-nutrition interaction: 1984 update

Alcohol remains a prevailing cause of malnutrition resulting in a variety of deficiency states secondary to decreased intake of nutrients. In addition to various well described primary malnutrition syndromes, secondary malnutrition may result from the interaction of ethanol with nutrient digestion, absorption or utilization. Some of the latter alcohol-nutrient interactions have been recently defined and their pathogenesis is discussed in this review. Included are interactions with thiamine, folic acid, vitamin A and disorders secondary to amino acid imbalances. The rationale for various forms of therapy is reviewed, including the treatment aimed at correcting the "hypermetabolic state" in alcoholics ad the pitfalls of excess nutrient administration (particularly as it pertains to pyridoxine, vitamin A and amino acids). The desirability of recognizing early precirrhotic stages of alcoholic fibrosis is emphasized, in order to start therapy prior to the medical and/or social disintegration of the alcoholic.

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.