Aromatic and branched-chain amino acids in autopsied brain tissue from cirrhotic patients with hepatic encephalopathy

Concentrations of the branched-chain amino acids (BCAAs) valine, leucine, and isoleucine and the aromatic amino acids (AAAs) phenylalanine and tyrosine were measured in three areas of dissected brain tissue obtained at autopsy from nine cirrhotic patients who died in hepatic encephalopathy. The controls were an equal number of subjects free from neurological, psychiatric or hepatic diseases, matched for age and time interval from death to freezing of autopsied brain samples. Amino acids were measured using high-performance liquid chromatography with fluorimetric detection. In brain tissue of cirrhotic patients, no changes in BCAA concentrations were observed compared with controls. On the other hand, phenylalanine levels were found to be increased 141% in prefrontal cortex, 86% in frontal cortex and 26% in caudate nucleus, and tyrosine content was increased by 71% in prefrontal cortex and 28% in frontal cortex with no significant increase in caudate nucleus. Alterations in the concentration of AAAs may lead to disturbances of monoamine neurotransmitters in brain. Such changes could play a role in the pathogenesis of hepatic encephalopathy resulting from chronic liver disease in man.