PhD candidate The University of Queensland Brisbane, Queensland, Australia
Background: Pituitary pars intermedia dysfunction (PPID) is a prevalent dopaminergic degeneration in aging horses, mirroring the pathogenesis of Parkinson’s disease (PD). Despite the known association between intestinal inflammation and PD via the gut-brain axis, this association remains unexplored in PPID. Objective/hypothesis: Horses with PPID have more severe inflammatory histopathological changes in the large intestine. Samples: Archived tissue (cecum, large colon, and small colon) from horses with PPID (pituitary grades 4 or 5/5, n = 6–10) and age-matched controls (pituitary grade 1 or 2/5, n = 6–10) were reviewed.
Methods: Epithelium injury, crypt morphology, mucosal fibrosis, goblet cell counts, prevalence of ciliated protozoa and Lewy bodies were evalueted. Lymphocytes and plasma cells, eosinophils, neutrophils, and macrophages in the mucosa and submucosa were quantified across 8 randomly selected fields. Differences between the two groups within an intestinal segment or layer were compared by unpaired t-test or Mann-Whitney test depending on distribution.
Results: Horses with PPID had significantly higher number of lymphocytes and plasma cells (control vs. PPID: 54 [49–72] vs. 79 [64–88], P = .01) and macrophages (5 [4–7] vs. 8 [6–11], P = .004), more frequent Lewy bodies (10% vs. 66.7%, P = .04), and higher grade of fibrosis (0 [0–0] vs. 1 [0–1], P = .01) in cecum. Conclusions and clinical importance: Chronic intestinal inflammation is associated with PPID mirroring findings in PD and highlighting the importance of gastrointestinal health in the management for PPID horses.
