Oleanolic acid improved intestinal immune function by activating and potentiating bile acids receptor signaling in E. coli-challenged piglets

Chenyu Xue; Hongpeng Jia; Rujing Cao; Wenjie Cai; Weichen Hong; Jianing Tu; Songtao Wang; Qianzhi Jiang; Chongpeng Bi; Anshan Shan; Na Dong

doi:10.1186/s40104-024-01037-0

Oleanolic acid improved intestinal immune function by activating and potentiating bile acids receptor signaling in E. coli-challenged piglets

J Anim Sci Biotechnol. 2024 May 18;15(1):79. doi: 10.1186/s40104-024-01037-0.

Authors

Chenyu Xue^#¹, Hongpeng Jia^#¹, Rujing Cao^#¹, Wenjie Cai¹, Weichen Hong¹, Jianing Tu¹, Songtao Wang¹, Qianzhi Jiang¹, Chongpeng Bi¹, Anshan Shan¹, Na Dong²

Affiliations

¹ The Laboratory of Molecular Nutrition and Immunity, College of Animal Science and Technology, Northeast Agricultural University, Harbin, P. R. China.
² The Laboratory of Molecular Nutrition and Immunity, College of Animal Science and Technology, Northeast Agricultural University, Harbin, P. R. China. ndong@neau.edu.cn.

^# Contributed equally.

Abstract

Background: Infection with pathogenic bacteria during nonantibiotic breeding is one of the main causes of animal intestinal diseases. Oleanolic acid (OA) is a pentacyclic triterpene that is ubiquitous in plants. Our previous work demonstrated the protective effect of OA on intestinal health, but the underlying molecular mechanisms remain unclear. This study investigated whether dietary supplementation with OA can prevent diarrhea and intestinal immune dysregulation caused by enterotoxigenic Escherichia coli (ETEC) in piglets. The key molecular role of bile acid receptor signaling in this process has also been explored.

Results: Our results demonstrated that OA supplementation alleviated the disturbance of bile acid metabolism in ETEC-infected piglets (P < 0.05). OA supplementation stabilized the composition of the bile acid pool in piglets by regulating the enterohepatic circulation of bile acids and significantly increased the contents of UDCA and CDCA in the ileum and cecum (P < 0.05). This may also explain why OA can maintain the stability of the intestinal microbiota structure in ETEC-challenged piglets. In addition, as a natural ligand of bile acid receptors, OA can reduce the severity of intestinal inflammation and enhance the strength of intestinal epithelial cell antimicrobial programs through the bile acid receptors TGR5 and FXR (P < 0.05). Specifically, OA inhibited NF-κB-mediated intestinal inflammation by directly activating TGR5 and its downstream cAMP-PKA-CREB signaling pathway (P < 0.05). Furthermore, OA enhanced CDCA-mediated MEK-ERK signaling in intestinal epithelial cells by upregulating the expression of FXR (P < 0.05), thereby upregulating the expression of endogenous defense molecules in intestinal epithelial cells.

Conclusions: In conclusion, our findings suggest that OA-mediated regulation of bile acid metabolism plays an important role in the innate immune response, which provides a new diet-based intervention for intestinal diseases caused by pathogenic bacterial infections in piglets.

Keywords: Bile acid receptors; Enterotoxigenic Escherichia coli; Intestinal innate immunity; Oleanolic acid.