Krankheitsbilder bei Leberschädigung durch Alkohol

Influence of ethanol, nicotinamide, orotic acid and caffeine upon the induction of tyrosine aminotransferase, the NAD content and the ADPR transferase activity in rat liver

Chronic uptake of ethanol leads to irreversible damage of liver cells. Until now the cause of this alteration is unknown. To get more information experiments presented in this paper were performed. Contrary to normal fed animals the enzyme tyrosine aminotransferase (TAT) can be induced by ethanol in starved rats. Orotic acid induces the TAT at a dose of 500 mg/kg. This effect is enhanced to some extent by ethanol. Ethanol increases the minor effect of 50 mg/kg caffeine on TAT induction markedly. Only 500 mg/kg nicotinamide (NA) enhances TAT activity. Here ethanol has a minor stimulatory effect. A combination of nicotinamide with orotic acid or with caffeine leads to substances with a higher effect on TAT induction. Besides nicotinamide and its derivatives only caffeine changes the NAD+ + NADH content of the liver. Ethanol and caffeine reduce the activity of the ADPR transferase. The results indicate that the effect of ethanol might be due to interference with NAD-adenoribosylation metabolism.

Red cell metabolic and membrane features in haemolytic anaemia of alcoholic liver disease (Zieve's syndrome)

Zieve's syndrome (ZS), which consists of transient haemolytic anaemia, jaundice, hyperlipoproteinaemia, and alcohol-induced liver disease, was studied in male patients during the acute (n = 20) and the remittent (n = 10) phase. Chronic alcoholics (n = 10) without haemolysis and healthy male persons (n = 10) served as controls. Erythrocytes were separated into old and young cells by means of density-layer centrifugation. Those fractions which contained older red cells disclosed a pyruvate-kinase instability which resulted in impaired metabolism. Changes in membrane lipid composition as indicated by increased cholesterol and polyunsaturated fatty acids (PUFA) were also detected in patients during the acute phase of ZS. Alcohol-induced red-cell vitamin-E deficiency with a decrease in PUFA levels may provoke an oxidation of reduced red-cell glutathione which in turn results in the enzyme instability. This study lends further support to the hypothesis that the putative role of the red-cell metabolic injury in the origin of haemolysis in ZS cannot be envisaged without introducing membrane-linked and extracellular cofactors.

[Human ethanol-induced hyperlipoproteinemia (author's transl)]

Reversible hyperlipoproteinemia may be observed after ethanol loads in healthy man before any ethanol-induced disease is being established. Different pathogenetic ways to this acute ethanol-induced hyperlipoproteinemia have been investigated or postulated in recent years. Two main sites have appeared: changes in the metabolism of lipids and their precursors which depend from acutal oxidation of ethanol in the liver, and ethanol-induced activation of lipolysis in adipose tissue, transmitted by the sympathico-adrenal system. The changes in liver metabolism during ethanol oxidation have been well confirmed in many experiments, they nevertheless do not seem to lead to hyperlipoproteinemia in many experimental designs in animals and after drinkable amounts of ethanol in healthy man when lipolysis of adipose tissue is blocked and no food is ingested. After the intake of a fatty meal these triglycerides are becoming importance as a source of fatty acids. A possible increased de novo synthesis of palmitic acid may to a minor degree contribute to hypertriglyceridemia.