Background: Parkinson's disease (PD) is a neurodegenerative aging disease, with idiopathic PD being most common. Gastrointestinal tract disorders (GITD) and microbiota changes may trigger idiopathic PD. Neurotoxins from microbiota can travel from the gut to the brain via the brain-gut axis (BGA), leading to α-syn protein misfolding and dopaminergic neuron death. Methods: The aim of the current study was to investigate the link between PD and GITD by measuring several biochemical and immunological markers in 142 patients. The biochemical markers measured were vitamins B6, B12, and D, calcium, serotonin, ghrelin, dopamine, and α-syn protein. The immunological markers included transforming growth factor-beta (TGF-β), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interferon-gamma (IFN-γ). All markers were measured using the Enzyme-Linked Immunosorbent Assay (ELISA) technique. Results: PD patients were significantly older (63.76±12.29 years) compared to GITD and control groups (41.00±15.54 and 41.25±18.30 years, respectively). Males predominated in the PD group (74.5%), while females were more common in the GITD and control groups. PD and GITD patients showed significantly lower levels of vitamins and neurotransmitters but higher calcium and α synuclein compared to controls. Immunological markers were elevated in PD and GITD groups, with significant differences between them (P-value < 0.001). Conclusion: The study concluded that certain biochemical and immunological markers provide strong evidence of the brain-gut axis's involvement in the initiation of idiopathic Parkinson's disease.
