S. Keiding

Ethanol metabolism in heavy drinkers after massive and moderate alcohol intake

Some alcoholics have a regular daily alcohol consumption of more than 100 g. In preliminary observations we had the impression that the claimed alcohol intake in such heavy drinkers was higher than could be accounted for by the ethanol elimination rate as measured routinely at 10 mmol/l (0.5 g/l). We therefore measured the ethanol elimination rate at very high blood ethanol concentrations of 40-80 mmol/l (2-4 g/l) found in eight alcoholics following heavy alcohol intake by measuring the falling blood ethanol concentrations until being less than 1 mmol/l. The elimination rate, on average 83 mumol/min per 1 blood, was about 49% higher than the elimination rate measured at 10 mmol/l in the same subject, being on average 58 mumol/min per 1/blood (paired t-test, P less than 0.05). The elimination rate following the high initial ethanol concentrations remained high until the concentration was below 5 mmol/l. Calculations of elimination rates are based on a number of assumptions concerning the physiologic and metabolic conditions. We examined specifically if the concentration-time curves could be adequately described by assuming metabolism according to a Michaelis-Menten pathway with a low Km value (simulating alcoholdehydrogenase with Km 0.2 mmol/l) or by assuming metabolism by two pathways with an alternative high-Km pathway with Km about 10 mmol/l. It was not necessary, in the statistical analysis, to include an alternative high-Km pathway. On the other hand, the data does give room for up to 50% elimination via such alternative pathways. The elimination rate at the high concentrations corresponded roughly to the claimed daily alcohol intake; furthermore the measured elimination rate at the lower concentrations were similar to values in non-alcoholics.

CCl4 cirrhosis in rats: irreversible histological changes and differentiated functional impairment

Cirrhosis of the rat liver was induced by a 12 week individualized CCl4/phenobarbital treatment. After treatment, all surviving animals (81%) showed cirrhosis of the liver. The cirrhosis induced was irreversible when evaluated 24 weeks after cessation of treatment. Quantitative liver function measurements were reduced in a differentiated manner. Ranked according to the most pronounced changes they are: capacity of urea-N synthesis (CUNS), galactose elimination capacity (GEC) and antipyrine clearance (APC). Hepatic glutathione concentrations were only slightly decreased after the CCl4 treatment. It is possible to produce a high incidence of irreversible cirrhosis with differentiated functional impairment in the rat.

Hepatic galactose elimination kinetics in the intact pig

The hepatic galactose elimination kinetics was studied in eight anaesthetized pigs by hepatic vein catheterization. Galactose was given as successive constant intravenous infusions so that steady-state concentrations, ranging from 50 mumol/l to 8 mmol/l, were obtained. Concentrations were measured in a peripheral artery and in the hepatic veins. Hepatic blood flow was determined by constant infusion of indocyanine green. The elimination kinetics is described by a mathematical model which assumes that the liver sinusoids are perfused with unidirectional blood flow and that the elimination in the hepatocytes takes place according to Michaelis-Menten kinetics. This creates a decreasing sinusoidal blood concentration from the inlet to the outlet of the liver. The estimated maximal elimination rate, Vmax, was on average 0.67 mmol min-1 kg-1 liver (range 0.55-0.95) and the half saturation concentration Km 0.25 mmol/l (0.12-0.58). The estimate of Km is similar to the value found in the isolated perfused pig liver (0.23 mmol/l), whereas the estimate of Vmax is about 50% higher (0.43 mmol min-1 kg-1 liver), probably due to both extrahepatic elimination in the splanchnic area and a better function of the liver in situ than in the isolated preparation.

Kinetics of ethanol inhibition of galactose elimination in perfused pig liver.

The effect of ethanol (5--25 mM) on the galactose elimination kinetics in the intact liver was studied in the isolated perfused pig liver, using the steady-state infusion technique. Ethanol reduced galactose-Vmax on average to 0.07 mmol/min kg liver in six experiments from 0.43 mmol/min kg obtained in control experiments without ethanol. Also Km was significantly reduced from 0.23 mmol/l plasma water to 0.03 mmol/l. Ethanol increased UDP-galactose ten-fold simultaneous with a rise in hepatic outflow ratio of lactate to pyruvate to about 300 from 10; this indicates that ethanol inhibits epimerase. In experiments with increasing galactose elimination rates, the concentration of galactose-1-P increased much less than the concentration of galactose, and the phosphorylation of galactose therefore seems to be rate-limiting. In vitro galactokinase is inhibited by galactose-1-P. In the present study ethanol increased galactose-1-P five to ten times, and the reduction of Vmax and Km by ethanol could be explained by uncompetitive inhibition by galactose-1-P with Ki about 0.1 mmol/l. Ethanol decreased UDP-glucose to about 40% and UTP to less than 5%, probably due to trapping as UDP-galactose. This may depress the forward transferase reaction, and therefore the other co-substrate galactose-1-P rises--and inhibits galactokinase.

Brain metabolism in patients with hepatic encephalopathy studied by PET and MR

We review PET- and MR studies on hepatic encephalopathy (HE) metabolism in human subjects from the point of views of methods, methodological assumptions and use in studies of cirrhotic patients with clinically overt HE, cirrhotic patients with minimal HE, cirrhotic patients with no history of HE and healthy subjects. Key results are: (1) Cerebral oxygen uptake and blood flow are reduced to 2/3 in cirrhotic patients with clinically overt HE but not in cirrhotic patients with minimal HE or no HE compared to healthy subjects. (2) Cerebral ammonia metabolism is enhanced due to increased blood ammonia in cirrhotic patients but the kinetics of cerebral ammonia uptake and metabolism is not affected by hyperammonemia. (3) Recent advantages in MR demonstrate low-grade cerebral oedema not only in astrocytes but also in the white matter in cirrhotic patients with HE.

Oxidative metabolism of astrocytes is not reduced in hepatic encephalopathy: a PET study with [11C]acetate in humans

In patients with impaired liver function and hepatic encephalopathy (HE), consistent elevations of blood ammonia concentration suggest a crucial role in the pathogenesis of HE. Ammonia and acetate are metabolized in brain both primarily in astrocytes. Here, we used dynamic [11C]acetate PET of the brain to measure the contribution of astrocytes to the previously observed reduction of brain oxidative metabolism in patients with liver cirrhosis and HE, compared to patients with cirrhosis without HE, and to healthy subjects. We used a new kinetic model to estimate uptake from blood to astrocytes and astrocyte metabolism of [11C]acetate. No significant differences of the rate constant of oxidation of [11C]acetate (k3) were found among the three groups of subjects. The net metabolic clearance of [11C]acetate from blood was lower in the group of patients with cirrhosis and HE than in the group of healthy subjects (P < 0.05), which we interpret to be an effect of reduced cerebral blood flow rather than a reflection of low [11C]acetate metabolism. We conclude that the characteristic decline of whole-brain oxidative metabolism in patients with cirrhosis with HE is not due to malfunction of oxidative metabolism in astrocytes. Thus, the observed decline of brain oxidative metabolism implicates changes of neurons and their energy turnover in patients with HE.

Age dependence of rat liver function measurements

Changes in the galactose elimination capacity, the capacity of urea-N synthesis and antipyrine clearance were studied in male Wistar rats at the age of 8, 20 and 44 weeks. Further, liver tissue concentrations of microsomal cytochrome P-450, microsomal protein and glutathione were measured. All liver function measurements increased from the age of 8 to 44 weeks when expressed in absolute values. In relation to body weight, these function measurements were unchanged or reduced from week 8 to week 20. At week 44, galactose elimination capacity and capacity of urea-N synthesis related to body weight were increased by 10% and 36%, respectively, and antipyrine plasma clearance was reduced to 50%. Liver tissue concentrations of microsomal cytochrome P-450 and microsomal protein increased with age when expressed in absolute values, but were unchanged per g liver, i.e., closely related to liver weight in the age range studied. Glutathione showed an increase of 35% from 8 to 44 weeks of age expressed per g liver. Careful age matching of control animals is important for experimental rat studies.

Delirium tremens and physical alcohol withdrawal: A double-blind comparison of phenobarbital and barbital treatment

Thirty-seven patients with delirium tremens or other signs of alcohol withdrawal were included in a double-blind randomized study of the effect of phenobarbital (19 patients) versus barbital (18 patients). Since 1909 barbital has been considered the preferred drug for treatment of alcohol withdrawal in Denmark. The patients were treated with tablets of phenobarbital, 100 mg, or barbital, 250 mg, to terminate symptoms of the withdrawal reaction and induce sleep. The groups were comparable as to age, sex distribution, severity of disease, and anamnestic information about drinking habits. The course of treatment was monitored by the Delirum Tremens Rating Scale and by the following outcome measures: medication to sleep, hours to sleep, total medication doses, and hours to last dose. There were no statistically significant differences between phenobarbital- and barbital-treated patients in any of the measures applied. Sleep was induced within a few hours in both groups, and there were no adverse effects of th...

697 HEPATOBILIARY EXCRETION MEASURED BY PET/CT USING THE CONJUGATED BILE ACID TRACER 11C-CSAR: FIRST EXPERIENCES IN PATIENTS WITH INTRAHEPATIC CHOLESTASIS

Results: Treatment of hepatocytes with CA induced SHP upregulation and inhibited Cyp7a1 expression. When L-NAME was present in the incubation medium, CA increased SHP mRNA but was not able to inhibit Cyp7a1 expression. ChIP analysis showed that L-NAME significantly blocked the binding of SHP to the Cyp7a1 promoter upon CA administration. Interestingly, CA induced GAPDH nitrosylation and its nuclear translocation. Likewise, CA promoted nitrosylation of both Sirt1 and HDAC2, proteins which assemble with SHP to form the Cyp7a1 repressor complex. Nitrosylation of GAPDH, Sirt1 and HDAC2 were prevented by treatment of hepatocytes with L-NAME. Conclusions: BS induce NO production in hepatocytes leading to nitrosylation and nuclear translocation of GAPDH and nitrosylation of proteins that integrate the Cyp7a1 repressor complex. Blockade of NO synthesis prevented the binding of SHP to Cyp7a1 promoter impairing the ability of BS to control their own synthesis.