Abstract: The aim of this study was to evaluate the protective effect of yogurt fermented by a mixed culture of Lactobacillus plantarum NDC75017 and Streptococcus thermophilus on D-galactose (D-Gal)-induced brain damage in rats. Wistar rats were divided into six groups, including normal control, negative control, low-, medium- and high-dose yogurt, and D-Gal + VE (positive control) groups. The activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and inducible nitric oxide synthase (iNOS), and malondialdehyde (MDA) and nitric oxide (NO) concentrations in rat serum and brain tissue, body weight, and the expression of caspase-3 and caspase-9 in rat brain were tested. Histopathological examination with hematoxylin and eosin (HE) staining was used to analyze the extent of brain damage. The results showed that compared with the negative control group, all doses of the yogurt enhanced SOD, GSH-Px and CAT activities, and decreased MDA and NO concentrations as well as iNOS activity in rat brain. The yogurt at high dose was the most effective in enhancing SOD and GSH-Px activities, resulting in an increase of 67.8% and 22.8% compared with the negative control group, respectively (P < 0.05). Moreover, brain CAT activity in the high-dose yoghurt group was comparable to that in the positive control group (P > 0.05). In rat brain, MDA level declined with increasing dose (P > 0.05), closest to that of the normal control group at high dose. At the same time, all doses of the yogurt also reduced NO level and iNOS activity. Conclusion: Yogurt co-fermented by Lactobacillus plantarum and Streptococcus thermophilus can protect the rat brain against D-Gal-induced oxidative damage by improving antioxidant enzymes activities in serum and brain tissue, reducing MDA and NO concentrations and iNOS activity, and decreasing the expression of caspase-9 and caspase-3, which was also confirmed by HE staining results.

Key words: Lactobacillus plantarum, yogurt, D-galactose, antioxidant, brain protection