Comparative study on the correlation of plasma γ-aminobutyric acid and pipecolic acid with liver function in patients with liver cirrhosis

Abstract

γ-Aminobutyric acid (GABA) is an inhibitory neurotransmitter, elevated in plasma of patients with liver cirrhosis. Pipecolic acid (PA), a metabolite of lysine, and known to be a GABA receptor agonist, is also seen high levels in the plasma. To clarify the relationship of GABA, PA and liver function, plasma GABA and PA in three groups of chronic liver diseases (compensated cirrhosis, decompensated cirrhosis and decompensated cirrhosis with hepatic encephalopathy, HE) were analyzed and their liver functions were compared. This analysis demonstrated that both plasma GABA and PA were higher in these patients than in normal subjects. Plasma PA, but not plasma GABA, was closely correlated with plasma ammonia concentration in each group. No correlation was noted between plasma GABA and PA in each group. Plasma pipecolic acid was significantly higher in patients with esophageal varices than in patients with no varices. These findings suggest that increased PA may reflect the degree of portal hypertension. Although both GABA and PA are increased in chronic liver disease, they may have a different origin and disappearance rate including metabolic mechanism.