Ethanol is mainly absorbed by the small intestine and,
to a lesser degree, through the stomach. Gastric alcohol
dehydrogenase (ADH) initiates alcohol metabolism.Three
enzyme systems account for metabolism of
alcohol
in the liver. These include cytosolic ADH, the
microsomal ethanol oxidizing system (MEOS), and
peroxisomal catalase. The majority of ethanol oxidation
occurs via ADH to form acetaldehyde, which is a
highly reactive molecule that may have multiple effects.
Ultimately, acetaldehyde is metabolized to acetate by
aldehyde dehydrogenase (ALDH). Intake of ethanol
increases intracellular accumulation of triglycerides by
increasing fatty acid uptake and by reducing fatty acid
oxidation and lipoprotein secretion. Protein synthesis,
glycosylation, and secretion are impaired. Oxidative
damage to hepatocyte membranes occurs due to the
formation of reactive oxygen species; acetaldehyde is a
highly reactive molecule that combines with proteins
to form protein-acetaldehyde adducts. These adducts
may interfere with specific enzyme activities, including
microtubular formation and hepatic protein trafficking.
With acetaldehyde-mediated hepatocyte damage, certain
reactive oxygen species can result in Kupffer cell
activation.