Astragalus Polysaccharide Alleviates Cognitive Decline in D-Galactose-Induced Aging

Astragalus polysaccharide (APS) is a biologically active water-soluble polysaccharide extracted from stems or roots, which has been proven to have antiaging effects. The aim of this study was to investigate the effects of APS on cognitive function in d-galactose (d-gal)-induced aging rats and explore the potential underlying molecular mechanisms. The rats were induced to age by intraperitoneal injection with 400 mg/kg/d d-gal for 8 weeks. Aging of rats was assessed through the Morris water maze test, step-down test, open field test, and grip strength test. Pathological changes in the hippocampal CA3 and CA1 regions were determined by Hematoxylin and eosin and Nissl staining. The superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), and total antioxidant capacity (T-AOC) in the serum were measured. Telomere length, dual oxidase 1 (Duox1), dual oxidase 2 (Duox2), peroxiredoxin 1 (Prdx1), p21, p16, p53, telomerase reverse transcriptase (TERT), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), nicotinamide phosphoribosyl transferase (NAMPT), and sirtuin 1 (SIRT1) were detected via real-time PCR, Western blotting, and immunohistochemical staining. The results indicated that APS ameliorated the general status in d-gal-induced aging rats, mitigated neuronal degeneration in the CA3 and CA1 regions, reduced the oxidative stress levels, modulated senescence-related β-GAL and protein expression, and maintained telomere length. Furthermore, APS significantly reduced p53 expression and increased p-PI3K, p-AKT, NAMPT, SIRT1, and TERT expression. Therefore, d-gal-induced aging and cognitive impairment in rats can be prevented by APS, likely through regulation of the TERT/p53 signaling axis via the PI3K/Akt and NAMPT/SIRT1 signaling pathways.