Overall, we believe that the reported decrease in glutamate concentration does not have to be inconsistent with what is known about the role of glutamate in signaling glioma; it might rather reflect imbalanced glutamate turnover in gliomas, favoring routing large quantities of glutamate to proline through PYCR1 in an attempt to maintain redox balance. This evidence concerns the gene PYCR1 and glioma.