Protective Effects of a Lipid Extract from Hard-Shelled Mussel (Mytilus coruscus) on Intestinal Integrity after Lipopolysaccharide Challenge in Mice

Abstract

This study investigated the protective effects of a lipid extract from hard-shelled mussel (HMLE) on intestinal integrity and the underlying mechanisms after a lipopolysaccharide (LPS) challenge in mice by using a 3 × 2 factorial design. Mice received olive oil, fish oil, and HMLE (n = 12 per group) by using gastric gavage for six weeks, respectively. Then half the mice in each group was injected intraperitoneally with LPS and the other half with phosphate buffered saline. Four hours after injection, mice were sacrificed and samples were collected. n-3 PUFAs were significantly enriched in erythrocytes following fish oil and HMLE supplementation. Both fish oil and HMLE improved intestinal morphology by restoring the ileac villus height and barrier function, which is indicated by decreased colonic myeloperoxidase activity and increased diamine oxidase activity as well as enhanced mRNA expression of intestinal tight junction proteins known as occludin and claudin-1 when compared with olive oil. In addition, both fish oil and HMLE increased colon production and the expression of anti-inflammatory cytokine, IL-10, while they inhibited the abnormal production and expression of pro-inflammatory cytokines including TNF-α, IL-1β, and IL-6 relative to the olive oil. Lastly, in comparison with olive oil, both fish oil and HMLE downregulated the TLR-4 signaling pathway by reducing the expression of two key molecules in this pathway, which are called TLR-4 and MyD88. These results suggest that HMLE had a protective effect on intestinal integrity after the LPS challenge, which was equivalent to that of fish oil. This effect might be associated with the regulation of inflammatory mediators and the inhibition of the TLR-4 signaling pathway.

Keywords: Mytilus coruscus; TLR-4 signaling pathway; hard-shelled mussel; intestinal integrity; lipopolysaccharide.

Figure 1

Schematic of study design.

Figure 2

Changes in the body weight of mice. Data are represented as the mean ± SD.

Figure 3

Histological evaluation for the villus height and crypt depth (100×).

Figure 4

The potential mechanism of a protective effect of HMLE on intestinal morphology and barrier function after an injury induced by LPS using a mouse model (this model could also be applied to fish oils rich in n-3 long chain n-3 PUFA based on the current findings).