Amino acid composition of ventricular CSF and transaminase activity in Alzheimer's disease brain

In the present study we report the amino acid composition in the third ventricular cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and normal subjects and the concentrations of two aminotransferases: glutamic oxaloacetate transaminase (GOT) and glutamic pyruvate transaminase (GPT). The results obtained indicate that among the various amino acids present in this fluid, glutamic acid, alanine and glutamine are the most abundant amino acids and their sum constitutes 57% of total amino acids in patients with AD and the 49% in normal subjects. L-glutamine occurs at very significantly higher levels in AD patients compared to normal CSF (220 ± 92 nmol/ml in AD vs 107 ± 47 nmol/ml in normal; p = 0.0041). In contrast, L-aspartate is lower in AD than normal CSF (46 ± 26 nmol/ml in AD vs 95 ± 53 nmol/ml in normal; p = 0.020). In the frontal, parietal and occipital cortices of Alzheimer's brain the transaminase GOT is present at significantly higher levels than controls (about 1.5 times higher; p < 0.01). No differences were observed for the GPT activity. Since the CSF receives amino acids and other metabolites from brain tissues, and since GOT catalyzes the conversion of L-aspartate to L-glutamate, the lowest concentration of L-aspartate and the highest levels of L-glutamine (which is derived from L-Glu by amination reaction) found in Alzheimer CSF could be considered as a consequence of the highest activity of GOT that occurs in Alzheimer brain.