title: Impact of plasma transaminase levels on the peripheral blood glutamate levels and memory functions in healthy subjects.
abstract: OBJECTIVE
  Blood aspartate aminotransferase (AST) and alanine transaminase (ALT) levels are the most frequently reliable biomarkers of liver injury. Although AST and ALT play central roles in glutamate production as transaminases, peripheral blood levels of AST and ALT have been regarded only as liver injury biomarkers. Glutamate is a principal excitatory neurotransmitter, which affects memory functions in the brain. In this study, we investigated the impact of blood transaminase levels on blood glutamate concentration and memory.
  
  
  METHODS
  Psychiatrically, medically, and neurologically healthy subjects (n = 514, female/male: 268/246) were enrolled in this study through local advertisements. Plasma amino acids (glutamate, glutamine, glycine, d-serine, and l-serine) were measured using a high performance liquid chromatography system. The five indices, verbal memory, visual memory, general memory, attention/concentration, and delayed recall of the Wechsler Memory Scale-Revised were used to measure memory functions.
  
  
  RESULTS
  Both plasma AST and ALT had a significant positive correlation with plasma glutamate levels. Plasma AST and ALT levels were significantly negatively correlated with four of five memory functions, and plasma glutamate was significantly negatively correlated with three of five memory functions. Multivariate analyses demonstrated that plasma AST, ALT, and glutamate levels were significantly correlated with memory functions even after adjustment for gender and education.
  
  
  CONCLUSIONS
  As far as we know, this is the first report which could demonstrate the impact of blood transaminase levels on blood glutamate concentration and memory functions in human. These findings are important for the interpretation of obesity-induced metabolic syndrome with elevated transaminases and cognitive dysfunction.
authors.affiliation: Department of Molecular Biochemistry & Clinical Investigation, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan; Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kamada
authors.affiliation: Molecular Research Center for Children's Mental Development, United Graduate School of Child Development, Osaka University, Suita, Osaka 565-0871, Japan; Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Hashimoto
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Hidenaga
authors.initials: H
authors.lastname: Yamamori
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yasuda
authors.affiliation: Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takehara
authors.affiliation: Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba, Chiba 260-8670, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba, Chiba 260-8670, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: Department of Molecular Biochemistry & Clinical Investigation, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Miyoshi
keywords: ALT, alanine aminotransferase; AST, aspartate aminotransferase; Alanine aminotransferase; Aspartate aminotransferase; BBB, blood brain barrier; GOT, glutamate-oxalacetate transaminase; GPT, glutamate-pyruvate transaminase; Gln, glutamine; Glu, glutamate; Glutamate; Gly, glycine; MSG, monosodium glutamate; Memory function; Mets, metabolic syndrome; NAFL, nonalcoholic fatty liver; NAFLD, nonalcoholic fatty liver disease; NASH, nonalcoholic steatohepatitis; WMS-R, Wechsler Memory Scale-Revised