Molecular Changes and Gut-Related Biomarkers in Parkinson’s Disease for Early Detection

Parkinson’s disease (PD) is the second most common neurodegenerative disorder after Alzheimer’s disease. It is characterized by both motor and nonmotor symptoms. However, mounting evidence suggests that nonmotor symptoms start to manifest in the enteric nervous system (ENS) long before reaching the central nervous system (CNS). These nonmotor signs include constipation and other gastrointestinal dysfunctions. Therefore, much attention has been given to those early prodromal symptoms and ENS-associated pathologies in particular, as they may serve as early biomarkers that help in detecting preclinical PD. This chapter discusses the molecular changes that are linked with the ENS involving alpha-synuclein, miRNAs, and genetic markers. The gut-brain axis and neuroinflammatory markers, as well as the role of metabolic products on mitochondrial functions, are also touched upon. Finally, the chapter addresses the sampling process and biobanking of gut bacteria to better study how the gut interacts in disease conditions.