Fish‐Oils Protect Against Hepatic Inflammation Following LPS Stimulation
Authors: Schaller Megan L. , Kamm Dakota R. , Harris Matthew P. , Witt Ken A. , Sandoval Karin E. , Wooten Joshua S. 
Published: June 2021

Non‐alcoholic steatohepatitis (NASH) is an advanced form of NAFLD characterized by steatosis and chronic inflammation. Obesity and diet induced imbalances in the gut microbiome resulting in the increased concentration of the circulating endotoxin lipopolysaccharide (LPS) is a model used to characterize the pathogenesis of NASH. Circulating LPS stimulates the expression of hepatic pro‐inflammatory cytokines that characterize chronic inflammation during NASH. Omega‐3 polyunsaturated fatty acids (ω‐3 FA) have shown to possess anti‐inflammatory properties; however, it remains unclear if ω‐3 FA can provide protection against LPS induced inflammation. Therefore, the purpose of this investigation was to determine the effects of dietary fat on hepatic cytokine gene expression and secretion following LPS stimulation. 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 (control) LPS (25 μg/mL media) for 20 hours. The cytokines interferon‐γ (IFN‐γ), interleukin‐1β (IL‐1β), IL‐6, IL‐10, monocyte chemoattractant protein‐1 (MCP‐1), and tumor necrosis factor‐α (TNF‐α) were evaluated. A 2‐way factorial ANOVA was performed to identify significant (p<0.05) differences between fat amount (low‐fat vs. high‐fat) and fat type (lard vs. fish‐oils) on gene expression and cytokine release. Following 32 weeks, body mass of HFL was significantly greater (p<0.05) than the other diet groups while body mass of HFFO was not different than LFL or LFFO. In control samples, only IL‐1β 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‐1β media concentration. When comparing fat type, control IL‐10 and TNF‐α expression was 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. Following LPS stimulation, MCP‐1 and TNF‐α 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 control samples, LPS stimulation increased the mRNA expression of IL‐1β 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‐γ and TNF‐α were 2.3‐fold (p=0.033) and 2‐fold (p=0.007) lower, respectively, in fish‐oil 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‐γ, TNF‐α, and IL‐6 were observed between diet types. The higher basal (control) expression and secretion of IL‐1β in high‐fat diets show that IL‐1β response is independent to fat type. In contrast, IFN‐γ and TNF‐α expression were more sensitive to fat type versus amount of fat, exemplified by lower activities post‐LPS stimulation. In conclusion, these results display the protective role of fish‐oils against chronic hepatic inflammation associated with obesity.

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Funded by: R21 NS090282‐01

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.