Bletilla striata polysaccharide alleviates Alzheimer's disease in Caenorhabditis elegans by modulating autophagy via the insulin/AMPK pathway.

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the abnormal aggregation of amyloid-β (Aβ). Bletilla striata polysaccharide (BSP), the primary active component of the traditional Chinese medicine Bletilla striata, exhibits various pharmacological effects including hemostatic, antioxidant, anti-inflammatory, and immunomodulatory activities. This study aimed to systematically investigate the protective effects and molecular mechanisms of BSP in Caenorhabditis elegans AD model. We found that BSP effectively alleviated the paralysis phenotype in AD worms, with optimal efficacy observed at a concentration of 100 μg/mL. Furthermore, BSP significantly extended the lifespan of both wild type and AD worms, reduced lipofuscin deposition and egg-laying capacity, improved neuromuscular function, learning ability, and stress resistance, and lowered the level of oxidative stress in vivo. Additionally, BSP treatment markedly suppressed Aβ aggregation in AD worms. Transcriptomic analysis revealed that BSP significantly regulates the autophagy pathway. In combination with genetic experiments, we further elucidated that BSP coordinates the insulin and AMPK signaling pathways to modulate autophagy, thereby reducing abnormal autophagosome accumulation and restoring autophagic homeostasis. Notably, the neuroprotective effects of BSP were completely abolished in mutants of key insulin signaling pathway genes (daf-2, age-1, akt-1, akt-2, daf-16) and the AMPK homologous gene aak-2, indicating that its efficacy is associated with the insulin/AMPK-autophagy regulatory axis. This study reveals the mechanism by which BSP ameliorates AD pathology through multi-target and multi-pathway regulation of autophagy, providing a new theoretical basis for its development as a candidate therapeutic agent for AD and further highlighting the potential medical value of Bletilla striata in combating AD.