Amino acids and transaminases activity in ventricular CSF and in brain of normal and Alzheimer patients

The present study was conducted to determine the concentration of amino acids in the cerebrospinal spinal fluid (CSF) and the activities of two tramsaminases: glutamic oxaloacetate transaminase (GOT) and glutamic pyruvate transaminase (GPT) in human Alzheimer disease (AD) and normal brain. l-Glutamic acid, l-glutamine and l-alanine are the most abundant amino acids in the CSF (50-55% of total amino acids). l-Glutamine occurs at much higher levels in Alzheimer CSF compared to the normal CSF (229 ± 91.8 nmol/ml in AD versus 107 ± 47.2 nmol/ml in normal; P = 0.0041). In contrast, l-aspartate occurs at significantly lower concentrations in Alzheimer CSF than normal CSF (46.1 ± 25.7 nmol/ml in Alzheimer versus 95.2 ± 52.6 nmol/ml in normal; P = 0.020). In Alzheimer brain (frontal, parietal and occipital cortices) GOT is present at significantly higher activities than in normal brain cortices (about 1.5 times higher; P < 0.01). No significant differences for GPT activity occurred between normal and AD brain. Since CSF receives amino acids from brain tissues, and since GOT catalyzes the conversion of l-aspartate to l-glutamate, the higher concentrations of l-glutamine (which is derived from l-glutamate), and the lower concentrations of l-aspartate found in Alzheimer CSF could be considered as a consequence of the higher activity of GOT that occurs in Alzheimer brain.