Integrated serum, urine metabolomics and 16S rRNA sequencing to investigate the modulatory effect of Ziziphi Spinosae Folium flavonoid on D-galactose-induced aging of rats

Ziziphi Spinosae Folium, the leaf of Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chou (LZJS), was widely distributed in northern China. Our previous study showed that LZJS flavonoid (LZJSF) exerted antioxidant activity at chemical and PC12 cell levels, respectively. Here, we further studied the function of LZJSF on aging-related oxidative stress in D-galactose (D-gal)-induced rats and the potential mechanisms were explored. The aging model was established by intraperitoneal injection of D-gal (300 mg·kg-1·day-1) for 36 days, the low-dose of LZJSF (LLZJSF 100 mg·kg-1·day-1) and the high-dose of LZJSF (HLZJSF, 200 mg·kg-1·day-1) were administered daily by oral gavage at the same time, respectively. Their spatial and learning memory abilities were evaluated by the Morris water maze test. HLZJSF was observed to significantly ameliorate cognitive ability and oxidative indexes, such as reduction of MDA and augmentation of SOD, GSH-Px, T-AOC and CAT, and the effect of HLZJSF on these indexes was stronger than that of LLZJSF. A precise and well-defined research strategy was successfully applied to screen serum differential metabolites. Furthermore, integrated serum and urine metabolomics showed that the derivations of nine significant differential metabolites could be regulated by administration of HLZJSF, which suggested that the intervention effect of HLZJSF against aging may involve in the amino acid metabolism including D-Glutamine and D-glutamate, alanine, aspartate and glutamate, arginine and proline metabolism and arginine biosynthesis. 16S rRNA sequencing analysis showed that HLZJSF could descend the relative abundance of Firmicutes and Actinobacteria, as well as the ratio of Firmicutes/Bacteroidetes, and increase the relative abundance of Bacteroidetes and Proteobacteria. Finally, correlation analysis further showed that the beneficial effects of HLZJSF resulted from the regulation of the disturbance of gut microbiota through the “microbiota-gut-brain” axis to affect amino acid metabolism and regulate oxidative stress. This study will provide a foundation for the development and utilization of LZJSF as functional foods and healthy beneficial food products.