Fish-Oils Protect Against Hepatic Inflammation Following LPS Stimulation

ABSTRACT Omega-3 polyunsaturated fatty acids (w-3 FA) have shown to possess anti-inflammatory properties; however, it remains unclear if w-3 FA can provide protection against LPS induced inflammation in hepatic tissue. PURPOSE: To determine the effects of dietary fat on hepatic cytokine gene expression and secretion following LPS stimulation. METHODS: Male C57Bl/6J mice were randomly assigned to one of four diet groups for 32 weeks: low-fat lard (LFL, 10% fat), low-fat fish-oil (LFFO, 10% fat), high-fat lard (HFL, 41% fat), or high-fat fish-oil (HFFO, 41% fat). Hepatic gene expression and release of cytokines were induced by incubating liver tissue (100 mg) with or without LPS (25 mg/mL media) for 20 hours. The cytokines interferon-g (IFN-g), interleukin-1b (IL-1b), IL-6, IL-10, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-a (TNF-a) were evaluated. A 2-way factorial ANOVA was performed to identify significant (pRESULTS: In samples without LPS, only IL-1b expression was significantly (p=0.044) greater (2-fold) in high-fat compared to low-fat diets, matching a 2.7-fold higher (p=0.004) IL-1b media concentration. When comparing fat type in samples without LPS, IL-10 and TNF-a expression were 5-fold (p=0.006) and 2-fold higher (p=0.014), respectively, in lard-based diets leading to 1.5-fold (p=0.007) and 2-fold (p=0.014) higher media concentrations compared to fish-oil diets. Following LPS stimulation, MCP-1 and TNF-a mRNA expression were 3-fold (p=0.045) and 71% (p=0.023) higher, respectively, in high-fat when compared to low-fat groups. In contrast to samples without LPS, LPS stimulation increased the mRNA expression of IL-1b such that it was 47% higher (p=0.008) in the low-fat groups when compared to the high-fat groups. When comparing fat type following LPS, expression of IFN-g and TNF-a were 2.3-fold (p=0.033) and 2-fold (p=0.007) lower, respectively, in the fish-oil diets when compared to lard diets. In contrast, IL-6 mRNA expression was 5-fold (p=0.044) higher in fish-oil diets following LPS stimulation. No difference in media concentrations of IFN-g, TNF-a, and IL-6 were observed between diet types. CONCLUSION: The higher basal (untreated LPS samples) cytokine gene expression and secretion of IL-1b in high-fat diets showed that IL-1b response is independent to fat type. In contrast, IFN-g and TNF-a expression were more sensitive to fat type versus amount of fat consumed, exemplified by lower cytokine activities post-LPS stimulation. These results display the protective role of fish-oils against chronic hepatic inflammation associated with obesity