Metabolic alterations produced in the liver by chronic ethanol administration. Comparison between the effects produced by ethanol and by thyroid hormones

Interaction of glycolysis and respiration in perfused rat liver. Changes in oxygen uptake following the addition of ethanol

The effect of ethanol on hepatic respiration and glycolysis was studied in perfused rat livers. 1. Ethanol increased the rate of oxygen uptake in livers from fed rats, but decreased the rate in livers from fasted animals perfused in the absence of added substrates. 2. Addition of ethanol decreased the rate of lactate + pyruvate production reflecting an inhibition of glycolysis irrespective of whether glycogen or added glucose was the substrate. 3. Half-maximal stimulation of respiration and inhibition of glycolysis were observed at ethanol concentrations between 0.2 and 0.4 mM. 4. A stoichiometric relationship of one mole of stimulated oxygen uptake to 3.6 mol of decreased lactate + pyruvate production was observed under a variety of experimental conditions. 5. The effects of ethanol on oxygen uptake and lactate + pyruvate production were abolished by the addition of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, but were unaffected by aminooxyacetate, an inhibitor of hydrogen transport across the mitochondrial membrane. 6. Carboxyatractyloside, an inhibitor of adenine nucleotide translocase, largely abolished the increase in oxygen uptake due to ethnol, but had little effect on the inhibitory action of ethanol on glycolysis. These data indicate that the ethanol-stimulated oxygen uptake is due to an increased flux through the mitochondrial respiratory chain and that it involves the NAD+-dependent oxidation of ethanol by alcohol dehydrogenase. The data are consistent with the hypothesis that the ethanol-stimulated respiration results from an increased demand for mitochondrial oxidative phosphorylation as a consequence of the decreased extramitochondrial ATP generation following inhibition of glycolysis by ethanol.

Possible relationship between the rate of ethanol metabolism and the severity of hepatic damage in chronic alcoholics

The rate of ethanol metabolism (EMR) was determined in alcoholic patients with or without hepatic necrosis, steatosis, and/or cirrhosis. Fifty six cases were studied after 9-25 days of abstinence (mean 15 days). A significant increase in EMR (P less than 0.01) was found in alcoholics with hepatic necrosis (265 +/- 20.5 mg/kg/hr) compared with alcoholics with normal liver histology (154 +/- 17) and nonalcoholic controls (159 +/- 15). In alcoholics with liver steatosis but without necrosis a lesser increase in EMR (207 +/- 20, P less than 0.05 was also observed. Patients with slight fibrosis but without other abnormalities in their liver biopsies and cirrhotics with overt liver failure (jaundice, ascites) showed EMR similar to controls.

Ethanol-host interactions determined by radiorespirometry of 14C glucoses

1. Theoretical considerations in continuous flow analysis by Walker, Shepherdson and McGowan have been applied to continuous flow radiorespirometry of 14C-glucoses to demonstrate ethanol response differences between water- and ethanol preferring mice. 2. Ethanol dosages in the n mols/kg range stimulated glucose utilization rates more in ethanol-than in water-preferring mice, while intermediate dosages (micron and low mmol/kg) produced equal stimulation but at different dosages. Pharmacological dosages (20-88 mmols/kg) inhibited glucose rates in water-preferring mice. The inhibition was released at 44 mmols/kg in ethanol-preferring mice. 3. Inhibition release was shown to be associated more with glucose carbons other than one, and considered consistent with a sodium-plus potassium-activated ATPase mechanism. 4. Intermediate ethanol dosage changes could be assigned to differences induced in glucose carbon one metabolism with H2O2-catalase and/or microsomal-ethanol-oxidizing systems (MEOS) mechanisms. 5. Our studies suggest that measurements of adenylate deaminase activities might clarify shifts in transaminations (human) and shifts in mononucleotides seen following chronic ethanol ingestion.

Lack of thyroid hormone effect on activation energy of NaK-ATPase

In order to differentiate whether activation of NaK-ATPase in thyroid thermogenesis is due to increased numbers of active 'sodium pump' units or due to a change in the kinetics of the enzyme, the effect of T3 on activation energy (Ea) of NaK-ATPase was determined in rat liver, kidney and brain. Injection of T3 produced significant increases in the specific activity of NaK-ATPase in liver and kidney but not in brain homogenates. T3 injections produced no significant change in the Ea of NaK-ATPase in any of the three tissues. The data are compatible with the hypothesis that thyroid stimulation of the sodium pump is brought about by an increase in the number of active pump units.

[Biochemical and clinical aspects of alcoholic liver damage]

Alcoholism is the most common form of drug abuse and alcoholic liver disease is a major health problem which in terms of increasing incidence is only rivaled by viral hepatitis. Cirrhosis of the liver, most of which is probably alcoholic, is among the leading causes of morbidity and mortality between the ages of 25 to 65 in Western countries. Alcoholic liver disease includes adaptive and toxic ultrastructural alterations, alcoholic fatty liver, alcoholic hepatitis and alcoholic cirrhosis, later accompanied by hepatoma.

The effect of thyroid hormone on bile salt-independent bile flow and Na+, K+ -ATPase activity in liver plasma membranes enriched in bile canaliculi

The relationship between bile salt-independent canalicular flow and ATPase activity in liver plasma membranes (LPM) enriched in bile canaliculi, was studied in control, hyperthyroid, and hypothyroid rats. Canalicular bile production was significantly increased in hyperthyroid rats (3.19 +/- 0.23 mul/min per g liver) compared to controls (2.27 +/- 0.24 mul/min per g liver), while it diminished in hypothyroid animals (1.58 +/- 0.17 mul/min per g liver). Although bile salt excretion was also increased in hyperthyroid animals (62.4 +/- 13.3 vs. 41.2 +/- 8.4 nmol/min per g liver), the stimulation in canalicular secretion was primarily related to enhancement of the bile salt-independent fraction of flow (2.47 mul/min per g liver in hyperthyroid rats vs. 1.67 mul/min per g liver in controls). LPM Na+, K+-ATPase activity doubled in hyperthyroid animals (21.5 +/- 5.8 vs. 10.7 +/- 3.1 mumol Pi/mg protein per h) while Mg++-ATPase activity remained unchanged and 5'-nucleotidase activity increased to a small but significant extent. In hypothyroid rats, bile salt excretion remained unchanged from control values so that the reduced secretion was entirely secondary to an inhibition of bile salt-independent secretion (1.19 mul/min per g liver). Na+, K+-ATPase activity in the LPMs from hypothyroid animals decreased by nearly 50% (5.4 +/- 1.6 mumol Pi/mg protein per h), although comparable reductions in the specific activity of Mg++-ATPase and 5'-nucleotidase were also observed. Administration of L-thyroxine to hypothyroid animals restored both bile salt-independent canalicular secretion and membrane enzymes to control values within 2 and 4 days, respectively. Sodium dodecyl sulfate gel electrophoresis demonstrated no significant changes in LPM protein fractions from any of the treatment groups. These studies indicate that thyroid hormone has a parallel effect on bile salt-independent canalicular secretion and LPM Na+, K+-ATPase activity, supporting the hypothesis that Na+ transport and Na+, K+-ATPase may be determinants of bile salt-independent canalicular flow.

Studies on the serum lipid and lipoproteins in steatosis of the liver

In a medical department, specialized in liver diseases, 45 patients (33 men and 12 women) suffering from steatosis of the liver have been examined with reference to serum lipid abnormalities. Twenty-eight of the patients were chronic alcoholics. Annual check-ups, including biopsy of the liver, were made to evaluate the development of the steatosis. The patients did not receive treatment with drugs or diet. Thirteen patients showed hypercholesterolemia, 16 increased serum triglyceride and 8 increased serum phosphorus lipid. Two showed a type I lipoprotein anomaly and 33 a type II-like pattern, defined as increased beta-lipoprotein associated with increase of serum cholesterol, was found in four cases. Three had a type III and three a type IV abnormal pattern, with increased pre-beta-lipoprotein and serum triglyceride levels. Correlation analysis revealed correlations between pre-beta-lipoprotein and serum triglyceride as well as between serum triglyceride and serum free fatty acid levels.

Experimental alcohol-induced hepatic necrosis: suppression by propylthiouracil

We have previously reported that a hypermetabolic state, resembling that produced by thryoid hormones, exists in the livers of animals treated chronically with ethanol. We propose that this alteration produces a relative hypoxia in the centrilobular zone of the liver which, if severe enough, leads to cellular death and to the production of hepatitis. Rats consuming ethanol for 30 days, given with a nutritionally adequate diet, and exposed to reduced oxygen tensions for only 6 hr, developed histological and biochemical evidence of hepatocellular necrosis and inflammatory lesions confined to the centrilobular zone. The severity was proportional to the degree of hypoxia. Pair-fed (nonalcohol) controls showed no such lesions. Treatment of the animals with propylthiouracil for 3-10 days abolished the hypermetabolic state of the liver in ethanol-consuming animals, and drastically reduced the histological and biochemical effects of hypoxia in them. These findings may have implications for pathogenesis and treatment of alcoholic hepatitis in man.

Some endocrine aspects of alcoholism

This review has focused on the more recent studies of ethanol-endocrine relationships. The data were evaluated from a fairly unbiased point of view and an attempt was made to point out some of the deficiencies in knowledge of the effects of ethanol on the endocrine system and the underlying mechanisms. The adrenal, for example, has been given the greatest attention in alcohol research, and yet the occurrence of atrophy or hypoplasia, despite alcohol's role as a stressor which can increase cortisol secretion, remains unexplained. In addition, our studies of the alcoholic subject have been conducted exclusively on the "skid-row" individual and may not be descriptive of the middle-class alcoholic subject who has not undergone similar nutritional and environmental stresses. While it is far from obvious that alcoholism is primarily an endocrine disease, the effects of ethanol on hormone metabolism are numerous and deserve further attention.

Rate-limiting steps in ethanol metabolism and approaches to changing these rates biochemically

Ethanol is oxidized to acetate primarily by a system involving liver alcohol and aldehyde dehydrogenases coupled with reoxidation of NADH by the mitochondria. All of these steps are at least partially rate-limiting in ethanol metabolism, with alcohol dehydrogenase and oxidative phosphorylation probably slower than the others. More research is required to assess the quantitative roles of various steps. Many agents are ineffective in changing the rate of metabolism of ethanol, but fructose and dinitrophenol may increase the rate by up to 1.5-fold in vivo. The failure of single agents to increase the rate substantially may indicate that when one step is accelerated, another step becomes rate-limited. Therefore, combinations of agents that affect several steps simultaneously may be required for acceleration. Effective experimental methods for inhibiting alcohol dehydrogenase in vivo are available.