GFAP and Parkinson disease: Multiple studies have documented a reactive glial state in PD, marked by increased glial fibrillary acidic protein (GFAP) expression and changes in glial morphology and localization, which are linked to dysmotility, tissue damage, heightened epithelial barrier permeability, and dysbiosis (Emmi et al. 2023; Thomasi et al. 2023; Thomasi et al. 2024; Thomasi et al. 2022).