Parkinson’s disease (PD) is a multifactorial movement disorder which is the second most common neurodegenerative disorder. The primary cause of this disease is the loss of dopaminergic neurons in the substantia nigra and the abnormal accumulation of intracellular alpha-synuclein. The condition is prevalent in those aged 65 or older and accounts for 1% of cases in adults over the age of 60. Contrary to this, inflammatory bowel disease (IBD) is a chronic systemic inflammation disorder which includes ulcerative colitis (UC) and Crohn’s disease (CD). It has been reported in 1.8 million adults in the United States (US) and emerging studies have suggested an epidemiological link between the IBD and PD since both these conditions involves the gut-brain axis. A research highlight by Heather Wood published in March 2024 suggested that alpha-synuclein aggregation which is a key pathological hallmark of PD, was found in the gut and brain of individuals and animal modes with IBD. These findings further supported the notion that alpha-synuclein pathology originates in the periphery and spreads to the brain through the vagus nerve according to the author.  However, a United Kingdom (UK) biobank prospective cohort study with 468,556 participants with IBD did not support the relationship between IBD and PD. In fact, the study concluded that there were no significant association between IBD and PD even after 13.39 years of follow-up period. However, some argued that the leucine-rich repeat kinase 2 (LRRK2) has been identified in both of these conditions, and this gene is responsible for transporting biomolecular between cells; therefore, this gene is increased in neuroinflammation, confers the risk of both PD and CD. Nevertheless, more work needs to be done in this area to develop a deeper understanding on how IBD and PD works and ways to optimise treatment in these patients.

References

7. Li H-x, et al. Front Med (Lausanne). 2023 Apr 20;10:1137366.  8. Wood H. Nat Rev Neurol. 2024 Apr;20(4):203.  9. Wang HL, et al. Front Aging Neurosci 2023; 15: 1294879.  10. Lee HS, Let al. Gut 2021; 70(2): 408-17.