Effect Of Fish Oil On Inflammatory Response And Liver Injury In Piglets After Lipopolysaccharide Challenge

This study was conducted to investigate the effect of fish oil on inflammatory response and liver injury in piglets subjected to an immunological stress.1. Thirty-two crossbred (Duroc′Large White′Landrace) piglets (11.57±0.74 kg BW) weaned at 28±3 d of age were used to investigate the effects of fish oil supplementation on growth performance, pro-inflammatory parameters and hypothalamus-pituitary-adrenal axis in a 2×2 factorial design. The main factors consisted of diet (5% corn oil or 5% fish oil) and immunological challenge (lipopolysaccharide [LPS] or saline). On d 19, pigs were injected intraperitoneally with either 150μg/kg body weight (BW) of LPS or an equivalent amount of sterile saline. Blood samples were collected at pre-injection (0 h), or 2, 4 hours post-injection for analysis, and then piglets were sacrificed for liver samples collection. The results showed that: (1) Fish oil had no effect on growth performance compared to corn oil; (2) At 2 hrs post-injection, LPS challenge×diet interactions were observed for tumor necrosis factor-α(TNF-α), prostaglandin E2 (PGE2), cortisol such that these measurements responded to the LPS challenge to a lesser extent in pigs receiving the fish oil diet than in pigs fed the corn oil diet (P<0.05). Pigs fed fish oil had lower ACTH level compared with those fed corn oil (P<0.001). At 4 hrs post-injection, among LPS-treated pigs, pigs fed fish oil had lower TNF-αthan those fed corn oil (P<0.05). Pigs fed fish oil had lower PGE2 and ACTH levels (P<0.05) compared with those fed corn oil. These results suggest that fish oil alters hypothalamus-pituitary-adrenal axis, which might be due to the inhibition of pro-inflammatory cytokine during an immunological challenge.2. In order to elucidate the protection mechanism on liver injury, the experiment was conducted to investigate the effect of fish oil on liver morphology, function indices, hepatocyte proliferation, pro-inflammatory parameters and NF-κB expression. The results showed that: (1) LPS challenge caused liver morphological changes. Fish oil, to some extent, alleviated the liver morphological changes induced by LPS; (2) At 2 hrs post-injection, aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose (GLU), albumin (ALB), total protein (TP) were observed. LPS decreased plasma ALB (P<0.05), GLU (P<0.001) content at 2 hrs, and TP (P<0.01), ALB (P<0.01), GLU (P<0.001) content at 4 hrs. LPS increased plasma AST content (P<0.05) at 4 hrs. Meanwhile, piglets fed fish oil had higher ALT (P<0.01) level at 2 hrs and ALT (P<0.001) at 4 hrs, lower ALB (P<0.05) levels at 4 hrs compared with those fed corn oil (P<0.001); (3) LPS challenge increased the hepatocyte proliferation (P<0.01), and fish oil decreased it (P<0.05); (4) LPS challenge increased TNF-αcontent (P<0.05) and heat shock protein 70 (HSP70) (P<0.05) expression in hepatocyte, while fish oil decreased TNF-α(P<0.05) and HSP70 (P<0.05). Among LPS treated pigs, pigs fed with fish oil had lower PGE2 level than those fed corn oil (P<0.05) in liver; (5) LPS challenge increased hepatocyte nuclear factor-κB (NF-κB) expression (P<0.01) and fish oil decreased it (P<0.05). These results suggest that fish oil reduced the pro-inflammatory mediators and the expression of NF-κB in liver cells, which attenuates liver injury induced by LPS challenge.In summary, fish oil could attenuate hepatic functional injury induced by LPS challenge in piglets. The protective effect of fish oil may due to the lowered release of pro-inflammatory mediators through decreasing expression of NF-κB.