Abstract: Objective: To investigate the protective effect of Lactobacillus casei on acrylamide-induced intestinal injury in rats. Methods: Male Wistar rats were randomly divided into following seven groups: control group (normal saline), low-, medium-, and high-dose acrylamide (5, 15, and 30 mg/(kg·d mb)) groups, and Lactobacillus casei [2.1 × 109 CFU/(kg·d mb)] plus low-, medium-, and high-dose acrylamide (5, 15, and 30 mg/(kg·d mb )) groups. The experimental period was 4 weeks. Feces were collected after the last treatment. Twelve hours after fasting, the rats were anesthetized to collect blood samples. The small intestine was obtained for the observation of ultrastructural changes by transmission electron microscope (TEM). Plasma D-lactic acid (D-LA) and diamine oxidase (DAO) concentration were measured by enzymelinked immunosorbent assay. The intestinal microbiota was detected by real-time PCR. Results: The ultrastructural changes observed by TEM showed that the tight junction was swelled; the microvilli, with significantly shortened length (P < 0.05), were loosely arranged in the medium-, and high-dose acrylamide groups. However, the control group did not show abnormal ultrastructure. Abnormal ultrastructural changes were rescued by Lactobacillus casei treatment. The plasma concentration of D-LA and DAO in the medium-, and high-dose acrylamide (15 and 30 mg/kg) groups were significantly elevated (P < 0.05) when compared with the control group. But in the Lactobacillus casei treatment groups, the plasma concentrations of D-LA and DAO were significantly reduced (P < 0.05) when compared with the medium-, and high-dose acrylamide (15 and 30 mg/kg) groups. Compared with the control group, Escherichia coli and Enterococcus faecalis were significantly increased (P < 0.05), and Bifidobacterium and Lactobacillus were significantly decreased (P < 0.05) in the medium-, and high-dose acrylamide (15 and 30 mg/kg) groups. But in the Lactobacillus casei treatment groups, Escherichia coli and Enterococcus faecalis were decreased, and Bifidobacterium and Lactobacillus were increased when compared with the medium-, and highdose acrylamide groups. Conclusion: Lactobacillus casei showed some protective effect on acrylamide-induced intestinal injury in rats. The underlying mechanism may be associated with the protection of intestinal mucosal barrier function and the regulation of the intestinal microbiota.

Key words: Lactobacillus casei, acrylamide, D-lactic acid, diamine oxidase, intestinal microbiota