Enterotoxigenic Escherichia coli (ETEC) infection is one of the most common bacterial causes of diarrhea in children and young farm animals. Medium-chain fatty acids (MCFAs) have been widely used for their antibacterial and immune functions. However, there is limited information regarding the role of MCFAs chelated with Zn in diarrhea induced by ETEC infection. Here, zinc laurate (ZnLa) was used to evaluate its protective effect in a mice diarrhea model induced by ETEC. A total of 45 ICR-weaned female mice were randomly assigned to marginal zinc deficiency (dZn), dZn, and ETEC infection groups (dZn+ETEC); ETEC infection was co-treated with a low, middle, or high dose of ZnLa (ZnLa LOW+ETEC, ZnLa MID+ETEC, and ZnLa HIGH+ETEC), respectively, to explore the effect and its mechanism of ZnLa on diarrhea and intestinal health of mice challenged with ETEC. To further compare the antibacterial efficiency of ZnLa and ZnSO4 in mice with ETEC infection, a total of 36 ICR-weaned female mice were randomly divided into ZnLa, ZnLa+ETEC, ZnSO4, and ZnSO4 and ETEC infection groups (ZnSO4+ETEC); moreover, the growth curve of ETEC also compared ZnLa and ZnSO4 in vitro. Mice pretreated with ZnLa were effectively guarded against body weight losses and increases in diarrhea scores induced by ETEC. ZnLa pretreatment also prevented intestinal barrier damage and ion transport in mice challenged with ETEC, as evidenced by the fact that the intestinal villus height and the ratio of villus height and crypt depth, tight junction protein, and Na+ absorption were higher, whereas intestinal permeability and anion secretion were lower in mice pretreated with ZnLa. In addition, ZnLa conferred effective protection against ETEC-induced intestinal inflammatory responses, as the increases in protein and mRNAs of proinflammatory cytokines were prevented in serum and jejunum, which was likely associated with the TLR4/MYD88/NF-κB signaling pathway. The increase in ETEC shedding and virulence-related gene expression was prevented in mice with ZnLa pretreatment. Finally, the growth of ETEC and virulence-related gene expression were lower in the ZnLa group than in ZnSO4 with an equal concentration of zinc. These findings suggest that ZnLa is a promising prevention strategy to remedy ETEC infection.
Keywords: enterotoxigenic Escherichia coli; intestinal barrier; intestinal inflammation; virulence factors; zinc laurate.