We all learnt it growing up: the appendix is a useless relic from our evolutionary past, only used to help digest the bark we consumed as cave men and women. But research has now identified this (often dismissed) organ’s role in monitoring pathogens in the immune system. What’s more, it may even play a part in the development of Parkinson’s disease.
Emerging research, published October 2018, saw Labrie and colleagues at the Van Andel Research Institute analyse data from nearly 1.7 million Swedes over the course of half a century. During this longitudinal study, removal of the appendix in early adulthood resulted in a 19 percent decrease in the risk of developing Parkinson’s disease in later life.
Parkinson’s disease (PD) is a neurodegenerative condition which results in a wide variety of physical and psychological symptoms, including involuntary shaking, stiff muscles, memory problems, and sometimes even the loss of senses. Parkinson’s affects over 10 million people globally, and yet the causes are still unknown — making it a critical research topic. While a causal factor is yet to be firmly identified, the disease is often associated with an abnormal ‘clumping’ of alpha-synuclein protein, and subsequent neuronal cell death, within the substantia nigra (a brain structure implicated in movement). Interestingly, pre-clinical symptoms of Parkinson’s disease may be evident long before diagnosis — symptoms found in the gut.
Research now reveals that these ‘protein clumps’ are found in abundance within the human appendix, potentially providing evidence for the involvement of this organ in the development of Parkinson’s disease. But how do these abnormal protein aggregations travel from the gut to the brain?
The gut-brain axis, a bidirectional system involved in communication between the central nervous system and gastrointestinal tract, is now believed to be involved in the transmission of PD symptoms from the gut to the brain. Evidence in the literature suggests pro-inflammatory bacteria may increase gut permeability, enabling the ‘leakage’ of abnormal alpha-synuclein protein, which then propagates via the gut-brain axis, to the central nervous system.
So, what are the implications of these findings? Clearly the appendix is not the whole story (or appendectomy patients would never suffer from Parkinson’s), but research does provide evidence of a possible ‘breeding ground’ of PD in the gut, and highlights the importance of gut health for neurological and behavioural maintenance. Labrie and colleagues stated, “preventing excessive alpha-synuclein clump formation in the appendix, and its departure from the gastrointestinal tract, could be a useful new form of therapy.” Some researchers even speculate that diet is key, and that food-based remedies may be the future of neurodegenerative disease management.
B. Killinger et al. The vermiform appendix impacts the risk of developing Parkinson’s disease. Science Translational Medicine. Published online October 31, 2018. doi:10.1126/scitranslmed.aar5280.
Perez-Pardo, P., Hartog, M., Garssen, J. and Kraneveld, A.D., 2017. Microbes tickling your tummy: the importance of the gut-brain axis in Parkinson’s disease. Current behavioral neuroscience reports, 4(4), pp.361–368.
Perez-Pardo, P., Kliest, T., Dodiya, H.B., Broersen, L.M., Garssen, J., Keshavarzian, A. and Kraneveld, A.D., 2017. The gut-brain axis in Parkinson’s disease: Possibilities for food-based therapies. European journal of pharmacology, 817, pp.86–95.