The alteration of glutamate involved in the brain of Parkinson's disease patients using glutamate chemical exchange saturation transfer (GluCEST)

Abstract

Increased levels of glutamate, a novel regulator of neuroinflammation, is involved in the pathogenesis of Parkinson's disease (PD). Although glutamate chemical exchange saturation transfer (GluCEST) is widely used in central nervous system (CNS) disorders, it has been less commonly used in clinical practice for PD. Here, to explore the clinical significance of variations in glutamate levels in the striatum and thalamus in PD, we included forty-nine PD patients and forty-four healthy controls (HCs). Glutamate levels were analyzed by performing magnetization transfer ratio asymmetry (MTRasym) using GluCEST data. Four regions of interest (ROIs) were manually outlined on GluCEST images, and MTRasym values were calculated for each. FreeSurfer was used to calculate the volumes. We found that MTRasym values in the striatum and thalamus were elevated in PD. Variations in MTRasym values were correlated with motor scores. It has been found that the volume of the left pallidal nucleus were reduced in PD. The glutamate levels in the striatum and thalamus were significantly different from those in HCs and associated with disease progression. Collectively, glutamate metabolic abnormalities may be present in PD pathophysiology and associated with disease progression. GluCEST imaging may have potential to become an imaging technology for measuring glutamate alterations in the striatum and thalamus in PD.