Rosa Roxburghii Tratt Polysaccharides Prevent Alzheimer’s Disease-Like Cognitive Dysfunctions and Pathology in Rats by Regulating the Microbiota-Gut-Brain Axis and Oxidative Stress

The microbial-gut-brain axis and oxidative stress may be important to the pathogenesis of Alzheimer's disease (AD). Rosa roxburghii Tratt polysaccharides (RRTP) have a strong antioxidant effect and can affect the gut microbiota, and whether it can affect AD is unknown. So, AlCl₃ and d-galactose were used to establish AD model rats, and RRTP was used as an intervention treatment. Morris water maze test was used to detect cognitive functions. The hippocampus was used to observe the pathological changes, and the cortex was used to measure antioxidant markers. The stool was collected for 16S rDNA sequencing. Morris water maze test showed that the learning ability and memory level of AD group rats were decreased, and RRTP intervention could mitigate the injury to a certain extent. In the AD group, hematoxylin-eosin staining revealed changes in the morphology of neurons, silver glycine staining revealed neurofibrillary tangles and Congo red staining revealed β-amyloid. RRTP could ameliorate the above changes to some extent. The results of superoxide dismutase, malondialdehyde, and glutathione peroxidase showed that the antioxidant capacity in the RRTP intervention group was significantly higher than that in the AD group. 16S rDNA sequencing results showed that there were differences in the species composition of gut microbiota, and the ratio of Firmicutes to Bacteroidetes in the AD group was decreased. After RRTP intervention, the proportion of Lactobacillus increased. In conclusion, RRTP may prevent AD pathology and cognitive functions in rats to a certain extent through the microbiota-gut-brain axis and oxidative stress.