Reduction of Polyunsaturated Fatty Acids with Tumor Progression in a Lean Non-Alcoholic Steatohepatitis-Associated Hepatocellular Carcinoma Mouse Model

Abstract

Background and Aim: Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in Western countries. While obesity and diabetes are the hallmarks of NAFLD, it also develops in lean individuals in the absence of metabolic syndrome, with a prevalence of 7 percent in the U.S. and 25-30 percent in some Asian countries. NAFLD represents the spectrum of liver disease, starting with excess liver fat accumulation (NAFL) that can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and ultimately hepatocellular carcinoma (HCC). To date, the pathogenesis of lean NASH-HCC is poorly understood and a mouse model is lacking. We aimed to develop a mouse model of lean NASH-HCC using a choline deficient and high trans-fat/sucrose/cholesterol diet to enable better understanding of its molecular pathogenesis. Methods: C57BL/6N mice were fed this diet starting at 4 weeks of age for 52 weeks and were compared to mice fed an isocaloric low fat control diet for the same duration. C57BL/6N mice were chosen instead of the C57BL/6J mice due to the high susceptibility of C57BL/6J mice to diet-induced obesity. The plasma and tumor fatty acid profile of these mice was also investigated. Results: Nearly 61% of the mice developed lean NASH-HCC. These mice showed reduction of plasma polyunsaturated fatty acids (PUFAs) (linolenic acids (α and γ, ω-3 and ω-6, respectively), eicosapentanoic acid (ω-3), docosahexanoic acid (ω-3), and linoleic acid (ω-6)) and increasing levels over time in mice with pre-malignant lesions. Conclusions: We developed a novel high penetrance diet-induced lean NASH-HCC mouse model. Plasma PUFA levels were reduced with tumor progression in parallel with reduced expression of genes controlling desaturase expression suggesting their potential use as biomarkers for lean NASH-HCC progression as well as chemopreventive molecules.

The Role of Fatty Acids in Non-Alcoholic Fatty Liver Disease Progression: An Update

“…For instance, an increase in FFA 16:1 [90] and a decrease in the FA composition (18:2 n-6, 20:4 n-6, 16:0 and 18:1 n-9) in the plasma phospholipids of HCC patients have been reported [91]. In turn, in a NASH-associated HCC mouse model, reduced levels of FFAs 18:3 n-3, 20:5 n-3, 22:6 n-3, and 18:2 n-6 were found [92]. An untargeted lipidomic analysis revealed that the blood levels of almost all lipid groups were decreased in HCC patients when compared to CLD subjects and that many specific lipid classes were upor dowregulated in HCC patients with respect to healthy controls [45].…”

Lipid alterations in chronic liver disease and liver cancer

“…90 Conversely, serum levels of PUFAs are decreased in the blood of patients with HCC. 90 , 118 , 122 …”

“…Several studies have demonstrated that a high-fat, high-cholesterol diet can trigger HCC in mice, 122 , 134 , 140 , 141 via a neoplastic transformation of hepatocytes caused by broad transcriptional deregulation of genes involved in metabolic pathways (`metabolism in cancer´ hallmark) and calcium signalling. 140 It has been shown that statins, which block hepatic cholesterol synthesis, protect against HCC 142 and CCA 143 development, as well as resulting in decreased risk of mortality.…”

Differential progression of unhealthy diet-induced hepatocellular carcinoma in obese and non-obese mice

“…The Institutional Animal Care and Use Committee at the University of Nebraska Medical Center approved this study (Protocol #: 17–018) and it was also conducted in compliance with the ARRIVE guidelines. Male (n = 103) and female (n = 25) C57BL/6N mice (Charles River Laboratories) were allowed to acclimate and housed as previously described starting at 3 weeks of age [ 15 ]. They were housed in a temperature-, humidity-, and ventilation-controlled vivarium on a 12-h light/dark cycle in specific pathogen-free conditions.…”

“…Furthermore, a genetic murine model of NASH revealed distinct patterns of serum and tissue fatty acid levels that correlate with early-stage HCC [ 13 ]. Higher levels of free fatty acids were observed in the livers of mice with diet-induced NAFLD [ 14 ] and polyunsaturated fatty acids were reduced in the plasma of mice with lean NASH-HCC [ 15 ].…”