Changes in plasma amino acids during the oral glucose tolerance test in hepatic diseases

We have measured the plasma concentration of neutral amino acids before and after an oral glucose tolerance test (100 g) in patients with liver cirrhosis (LC), chronic active hepatitis (CAH), chronic persistent hepatitis (CPH), acute hepatitis in the acute stage (AHa) and acute hepatitis in the convalescent stage (AHc) and normal controls. The ratio of the concentration of an amino acid to the sum of those of the other neutral amino acids that compete during transport through the blood brain barrier (BBB), which was reported to correlate well with the brain level of the amino acid, was compared in patients with various liver diseases. The ratios of Trp (Trp/Tyr + Phe + Ile + Leu + Val), Tyr, Phe, and Val increased after glucose loading in all subjects, except Tyr in normal controls, which slightly decreased. On the other hand, Ile and Leu ratios decreased (Trp; tryptophan, Tyr; tyrosine, Phe; phenylalanine, Ile; isoleucine, Leu; leucine, Val; valine). LC showed a characteristic pattern; the ratios of Trp and Tyr were highest among all diseases at 3 hours after glucose loading, and those of Ile, Leu and Val were lowest. We assumed that delta an amino acid ratio = the amino acid ratio at 3 hrs after glucose loading minus the amino acid ratio at 0 hr. In LC, delta Trp ratio and delta Tyr ratio were highest, while delta Val ratio was lowest. The delta Phe ratios in AHa and AHc were significantly higher than those in healthy controls. From these results, the uptake of Trp and Tyr might be supposed to be highest and that of Val was lowest in LC, after glucose loading.