Effects of Fish‐Oils on Markers of Hepatic Steatosis and Cholesterol Homeostasis in C57BL/6 Mice

Abstract

Non‐alcoholic fatty liver disease (NAFLD), characterized by hepatic lipid accumulation exceeding 7% of total liver mass, is the most prevalent liver disease in America. Recent evidence proposes that altered cholesterol metabolism during NAFLD may drive the liver disease progression to non‐alcoholic steatohepatitis (NASH). In this cholesterol‐focal model of NASH, imbalances in cholesterol homeostasis promotes genes that stimulate de novo lipogenesis and chronic inflammation. Emerging evidence; however, has shown diets rich in fish‐oils have strong inhibitory effects on hepatic triglyceride accumulation and this may be due in part to restoring cholesterol homeostasis as determined by the total cholesterol to free cholesterol ratio. Therefore, the purpose of this study was to determine the effects of fish‐oils on markers of hepatic steatosis and cholesterol homeostasis in C57BL/6 mice. In our study, male C57BL/6 mice were randomly assigned to four dietary groups based on percentage and type of dietary fat for 32 weeks: 10% lard (LFL), 10% fish‐oil (LFFO), 41% lard (HFL), and 41% fish‐oil (HFFO). A two‐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 markers of hepatic steatosis, cholesterol homeostasis, and dyslipidemia. At the end of 32 weeks (Table 1), the HFL group was significantly heavier (p<0.001) than the other diet groups, despite for no significant difference between groups for average calories consumed per week. When compared to HFFO, mice in the HFL group showed higher hepatic total lipid percentage and triglyceride concentration by 89% (p<0.001) and 1.4‐fold (p<0.001), respectively. No significant difference was observed between LFL and LFFO for body mass, hepatic lipid percentage, hepatic cholesterol, net glucose AUC, plasma insulin, plasma glucose, or HOMA‐IR. HFFO mice showed a 3‐fold (p<0.001) lower hepatic total cholesterol and 5‐fold (p<0.001) lower hepatic free cholesterol, as well as a 43% (p<0.001) lower free cholesterol:total cholesterol ratio when compared to HFL mice. This may be due to improved insulin sensitivity bolstered by fish‐oils, as HFFO mice showed 2.2‐fold (p<0.001) lower HOMA‐IR, 30% (p<0.001) lower net glucose AUC, 1.3‐fold (p<0.001) lower plasma insulin, and 43% (p<0.001) lower plasma glucose when compared to HFL mice. Based on previous studies and our data taken together, we believe that the improvements in hepatic steatosis in mice consuming a diet high in fish‐oils was due to collective improvements in insulin sensitivity and a lower free cholesterol:total cholesterol ratio. In summary, fish‐oils improved hepatic lipid profiles that were associated with cholesterol homeostasis and insulin sensitivity.Support or Funding InformationR21 NS090282‐01This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.