Antioxidant status and gut microbiota change in an aging mouse model as influenced by exopolysaccharide produced by Lactobacillus plantarum YW11 isolated from Tibetan kefir

This study investigated the effect of exopolysaccharide (EPS) produced by Lactobacillus plantarum YW11 on the oxidative status and gut microbiota in an aging mouse model induced with d-galactose. The in vitro assay of the antioxidant activity of the EPS showed concentration-dependent (0.25-3.0 mg/mL) activities. At 3.0 mg/mL, the EPS reached the highest scavenging activities with half maximal inhibitory concentration values against hydroxyl radicals at 75.10% and 1.22 mg/mL, superoxide anion at 62.71% and 1.54 mg/mL, 2, 2-diphenyl-1-picrylhydrazyl at 35.11% and 0.63 mg/mL, and the maximal chelating rate on ferrous ion and the half-maximal chelating concentration of the EPS at 41.09% and 1.07 mg/mL, respectively. High doses of EPS (50 mg/kg per day) effectively relieved the oxidative stress in the aging mice with increased levels of glutathione peroxidase, superoxide dismutase, catalase, and total antioxidant capacity in mice serum by 21.55, 33.14, 61.09, and 38.18%, respectively, and decreased malondialdehyde level from 11.69 to 5.89 mmol/mL compared with those in the untreated aging mice model. The analysis of pyrosequencing sequence data from the gut microbiota revealed that the EPS could recover the microbiota diversity and phylotypes decreased or eliminated by the d-galactose treatment. The EPS could selectively decrease the abundance of Flexispira (37.5 fold), and increase the abundance of Blautia (36.5 fold) and Butyricicoccus (9.5 fold), which correspondingly decreased the content of nitrogen oxides to 9.87% and increased the content of short-chain fatty acids by 2.23 fold, thereby improving the oxidative and health conditions of the host intestinal tract. Further correlation analysis of core-microbiota variation induced by different treatments showed a strong correlation with oxidative phenotypes [catalase, goodness of prediction (Q2) = 0.49; total antioxidant capacity, Q2 = 0.45; nitrogen oxides, Q2 = 0.67; short-chain fatty acids, Q2 = 0.55]. The fermented milk with L. plantarum YW11 containing EPS also showed favorable antioxidant and gut microbiota regulating activities. The present finding provided new insights into the functional mechanism of probiotics bioactivity.