>L-glu along with glutamine is the most abundant free amino acid in the central nervous system
this would suggest that L-glu is highly regulated in the body. Abundance usually means there should be storage of it if level swings can bring "inbalance" to it's usage.
on top of that, from this study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3698427/
>In the brain, Glu, which is locally produced completely de novo from glucose, acts as a major excitatory neurotransmitter, and its activity regulates synaptic plasticity, learning, memory, motor activity, and neural development. But dietary Glu is almost impermeable into the circulating blood. Also there is the blood–brain barrier against Glu in between blood and brain so as to not to incorporate into it the brain.
if high MSG(or just G from other sources) consumption did cause neurodegenerative diseases, shouldn't we see that data clearly in places that consume more in culture?