Effect of chronic ethanol administration on cholesterol and bile acid synthesis in vivo

Molecular mechanisms of alcoholic fatty liver

Alcoholic fatty liver is a potentially pathologic condition which can progress to steatohepatitis, fibrosis, and cirrhosis if alcohol consumption is continued. Alcohol exposure may induce fatty liver by increasing NADH/NAD(+) ratio, increasing sterol regulatory element-binding protein-1 (SREBP-1) activity, decreasing peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activity, and increasing complement C3 hepatic levels. Alcohol may increase SREBP-1 activity by decreasing the activities of AMP-activated protein kinase and sirtuin-1. Tumor necrosis factor-alpha (TNF-alpha) produced in response to alcohol exposure may cause fatty liver by up-regulating SREBP-1 activity, whereas betaine and pioglitazone may attenuate fatty liver by down-regulating SREBP-1 activity. PPAR-alpha agonists have potentials to attenuate alcoholic fatty liver. Adiponectin and interleukin-6 may attenuate alcoholic fatty liver by up-regulating PPAR-alpha and insulin signaling pathways while down-regulating SREBP-1 activity and suppressing TNF-alpha production. Recent studies show that paracrine activation of hepatic cannabinoid receptor 1 by hepatic stellate cell-derived endocannabinoids also contributes to the development of alcoholic fatty liver. Furthermore, oxidative modifications and inactivation of the enzymes involved in the mitochondrial and/or peroxisomal beta-oxidation of fatty acids could contribute to fat accumulation in the liver.

Hepatic triacylglycerol accumulation induced by ethanol and carbon tetrachloride: interactions with essential fatty acids and prostaglandins

Triacylglycerol accumulation in the liver (fatty liver) caused by ethanol or carbon tetrachloride involves interactions with essential fatty acids and prostaglandins. The degree to which the fatty liver develops is dependent on total dietary fat intake. Both ethanol and carbon tetrachloride impair desaturation of linoleic acid and dihomo-gamma-linolenic acid and this appears to be relevant to the pathogenesis of fatty liver from two points of view. First, low arachidonic acid in liver phospholipids is associated with increased liver triacylglycerol content whether caused by ethanol, carbon tetrachloride, or essential fatty acid deficiency. Second, essential fatty acids including gamma-linolenic acid and arachidonic acid, as well as the prostaglandins, prevent ethanol- and carbon tetrachloride-induced fatty liver. Arachidonic acid and possibly the prostaglandins are therefore likely to be directly involved in lipoprotein and triacylglycerol secretion by the liver.

Excretion of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol and corticosterone metabolites in rat bile. Studies on the role of alcohol dehydrogenase in steroid metabolism

The monosulphate of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol was identified in bile of female and male rats. The excretion in the female rats decreased from 10-20 nmol/h directly after insertion of the bile cannula to very low values after 6 h. It then increased to reach a constant rate after 24 h that was slightly lower than during the first hour. Administration of 4-methylpyrazole or ethanol failed to change the rate of excretion. Thus there was no increase in the rate of excretion that might have resulted from an inhibited oxidation catalyzed by alcohol dehydrogenase (EC 1.1.1.1). Male rats were fed liquid ethanol-containing and control diets for 24 days prior to insertion of the bile cannula. The excretion during the first 3 h was 10-30 nmol/h in both groups, and chronic ethanol treatment did not change this rate. The effect of 4-methylpyrazole on the ratio between the excretion rates of the 3 beta- and 3 alpha-isomers of 3,11 beta, 21-trihydroxy-5 alpha-pregnan-20-one disulphate was measured by a gas chromatographic-mass spectrometric method. The absence of any significant change indicated that the 3 beta-hydroxysteroid dehydrogenase activity of alcohol dehydrogenase was of no significance in the metabolism of corticosterone.