That is not true because glucagon-like peptide is a powerful neuropeptide that's directly synthesized in the brain
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For the researchers, parenteral high-dose thiamine was effective in reversing Parkinsons disease symptoms, that a dysfunction of thiamine-dependent metabolic processes could cause selective neural damage in the centers typically affected by this disease and that Thiamine could have both restorative and [nerve-protecting] action in Parkinsons disease. Source: Costantini, Antonio, Maria Immacolata Pala, Enzo Grossi, Stella Mondonico, Luisa Ercoli Cardelli, Carina Jenner, Sabrina Proietti, Marco Colangeli, and Roberto Fancellu
[2] [5] These mechanisms collectively improve blood glucose control in patients with type 2 diabetes
Glycogen synthase kinase 3 (GSK3) has been shown to regulate synaptic homeostasis in the brain (Collingridge et al., 2010)