Advances in natural polysaccharides in Alzheimer's disease and Parkinson's disease: Insights from the brain-gut axis

Background: Due to the rapid increase in aging population, there has been a rise in cases of neurodegenerative diseases (NDs), which is a major challenge for human health. Alzheimer's disease (AD) and Parkinson's disease (PD) are common degenerative disorders with complex causes and limited treatment options. The brain-gut axis is an important pathway that facilitates communication between the brain and gut. It involves intricate interactions among various systems such as nervous, immune, and endocrine systems. Recent evidence suggests a strong connection between gut microbiota and central nervous system (CNS) diseases. Scope and approach: The involvement of polysaccharides in AD and PD holds promise as a potential avenue for the development of novel therapeutic strategies. This review aims to comprehensively investigate the impact of polysaccharides derived from food on NDs through the brain-gut axis, and explore the preclinical therapeutic effects of representative polysaccharides on NDs. Key findings and conclusions: Our objective is to investigate the metabolic processes of polysaccharides in the gastrointestinal tract, examine their interactions with intestinal microbes, and comprehend how these processes influence the nervous system through the brain-gut axis. Furthermore, we aim to analyze the degradation process of polysaccharides in the gut, elucidate their regulatory mechanisms on microflora, provide evidence supporting their potential therapeutic applications for NDs, and emphasize clinical research data related to polysaccharides in CNS disorders. This review presents compelling evidence that gut microbiota serve as crucial regulators of naturally occurring polysaccharides while offering novel insights into utilizing various structural types of polysaccharides for addressing NDs.