Monitoring Amino Acid Neurotransmitters in Plasma Profiles and Predicting Early Progression of Ischemic Stroke

Abstract

Progressing stroke is a devastating condition, but neither a good nor a safe predictor has been determined in previous studies. Elevated levels of excitatory amino acid (glutamate) and inhibitory amino acid (glycine) have been detected in cerebrospinal fluid (CSF) or brain tissue after acute ischemic stroke by microdialysis studies in humans. However which amino acid is increased in plasma and the duration of elevation after acute ischemic stroke is still unclear in spite of the fact that there is a positive correlation of glutamate concentrations between CSF and plasma in progressing strokes. The purpose of this study was to evaluate these amino acids in plasma could predict acute ischemic stroke or progression of ischemic strokes. The study included 22 ischemic stroke patients admitted within 24 hours of acute ischemic stroke onset. The plasma concentrations of glutamate and glycine were determined by HPLC (high-performance liquid chromatography), Progression was defined as when the NIHSS (National Institute of Health Stroke Scale) rose by three or more points within 48 hours after acute ischemic stroke. The infarction area was calculated from brain CT (brain computerized tomography) or brain MRI (magnetic resonance image) when the infarct was not visible on brain CT. Our study found a rapid elevation of glycine but not glutamate in plasma during stroke progression. Significantly lower Aue (area under plasma concentration –time curve) levels of glutamate and glycine during progression was also found in large vessel infarction including middle cerebral artery occlusion or internal carotid artery occlusion. This indicates that plasma glycine may be a good and non-invasive predictor for progressing stroke. Low Ave of plasma glutamate and glycine in progressing stroke may indicate a large vessel infarct and act as a poor prognostic factor in acute ischemic stroke.