Reduced Thalamic Gamma Aminobutyric Acid (GABA) in Painless but not Painful Diabetic Peripheral Neuropathy

This is the authors' abstract. We don't add key points for this paper.

Alterations in the structure, function, and microcirculation of the thalamus, a key brain region involved in pain pathways, have previously been demonstrated in patients with Painless- and Painful-diabetic peripheral neuropathy (DPN). However, thalamic neurotransmitter levels including GABA (inhibitory neurotransmitter) and glutamate (excitatory neurotransmitter) in different DPN phenotypes are not known. We performed a Magnetic Resonance Spectroscopy study and quantified GABA and glutamate levels within the thalamus, in a carefully characterised cohort of participants with Painless- and Painful-DPN. Participants with DPN (Painful- and Painless combined) had a significantly lower GABA:H₂O ratio compared to those without DPN (Healthy volunteers [HV] and diabetes without DPN [No-DPN]). Participants with Painless-DPN had the lowest GABA:H₂O ratio, which reached significance compared with HV and No-DPN, but not Painful-DPN. There was no difference in GABA:H₂O in Painful-DPN compared with all other groups. A significant correlation with GABA:H₂O and neuropathy severity was also seen. This study demonstrates that lower levels of thalamic GABA in participants with Painless-DPN may reflect neuroplasticity due to reduced afferent pain impulses. Whereas partially preserved levels of GABA in Painful-DPN may indicate that central GABAergic pathways are involved in the mechanisms of neuropathic pain in diabetes.