Lactobacillus plantarum QL01 Alleviates D-Galactose-Induced Oxidative Stress and Restores Gut Microbiota in Ageing Mice

Background/Objectives: This study aimed to evaluate the in vivo antioxidant effects of Lactobacillus plantarum QL01 and to provide a theoretical basis for the use of probiotics in alleviating conditions associated with oxidative stress. Methods: A D-galactose-induced aging model was established in fifty 8-week-old SPF male Kunming mice, which were randomly allocated into five groups: normal control (NC), model control (MC), positive control (VC, ascorbic acid 200 mg kg−1 day−1), low-dose bacterial (LP, 1 × 109 CFU kg−1 day−1), and high-dose bacterial (HP, 1 × 1010 CFU kg−1 day−1) groups. Except for the NC group, all mice received the daily intraperitoneal injection of D-galactose (125 mg kg−1 day−1) for 8 weeks to induce oxidative stress. Corresponding treatments or equal volumes of saline were administered daily by gavage. Results: After 8 weeks, serum, liver, colon, and fecal samples were collected and analyzed to evaluate the efficacy of QL01 in counteracting oxidative stress and restoring gut microbiota homeostasis. The results demonstrated that tissue atrophy and the levels of various inflammatory factors, including interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-10, were inhibited (p < 0.05). It was further demonstrated that the levels of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and malondialdehyde (MDA) were significantly reversed in hepatic tissues by QL01 intervention (p < 0.05), thereby leading to the alleviation of inflammatory responses and oxidative stress in ageing mice. Pathological observations revealed that QL01 mitigated the damage to liver and colon tissues in mice. In addition, the intervention of QL01 led to an improvement in the expression of tight junction proteins in the colonic tissues of mice, as determined by qPCR. Additionally, the host’s intestinal microbiota and metabolites were restored. Conclusions: Overall, this study revealed that Lactobacillus plantarum QL01 is a promising candidate for modulating oxidative stress and the homeostasis of the host’s gut flora.