Effects of Ganoderma lucidum polysaccharide on learning and memory impairment and intestinal flora in mice with D-galactose-induced aging.

Learning and memory impairment is one of the main manifestations of cognitive impairment. Gut flora can affect cognitive function and behavior through the gut-brain axis. Ganoderma lucidum polysaccharide (GLP) is one of the main effective components of G. lucidum, with antioxidant and anti-aging effects. In this study, the learning and memory impairment model of aging mice was established by injecting D-galactose (D-gal). The learning and memory ability of mice was tested by a water maze experiment. Also, the biochemical indexes of mouse serum and brain tissue were determined. In addition, 16S rRNA sequencing was performed on mouse feces. The results showed that GLP significantly shortened the latency of mice to find a safe platform. Also, they enhanced superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, increased glutamate (Glu) and acetylcholine (ACh) contents, and decreased malondialdehyde (MDA) and gamma-aminobutyric acid (GABA) contents in mice to improve antioxidant capacity, remove free radicals, and reduce lipid peroxidation and oxidative stress, thereby improving learning and memory disorders in mice. The analysis of the microflora after the intervention of GLP to improve learning and memory disorders in mice revealed changes in Lactobacillus abundance. In conclusion, D-gal causes learning memory impairment and reduced intestinal microbial diversity in aging mice, whereas GLP may ameliorate learning memory impairment by altering the distribution of Lactobacillus in the intestinal tract of mice and regulating the biosynthesis of peptidoglycan and secondary bile acids.