Differences in metabolic and liver pathobiology induced by two dietary mouse models of nonalcoholic fatty liver disease

Abstract

Non-alcoholic fatty liver disease (NAFLD) is a growing epidemic associated with key aspects of metabolic disease such as obesity and diabetes. The first stage of NAFLD is characterized by lipid accumulation in hepatocytes, but this can further progress into non-alcoholic steatohepatitis (NASH), fibrosis or cirrhosis, and hepatocellular carcinoma (HCC). A western diet, high in fats, sugars and cholesterol is linked to NAFLD development. Murine models are often used to experimentally study NAFLD, as they can display similar histopathological features as humans;however, there remains debate on which diet-induced model most appropriately and consistently mimics both human disease progression and pathogenesis. In this study, we performed a side-byside comparison of two popular diet models of murine NAFLD/NASH and associated HCC: a high fat diet supplemented with 30% fructose water (HFHF) and a western diet high in cholesterol (WDHC), comparing them to a common grain-based chow diet (GBD). Mice on both experimental diets developed liver steatosis, while WDHC-fed mice had greater levels of hepatic inflammation and fibrosis than HFHF-fed mice. In contrast, HFHF-fed mice were more obese and developed more severe metabolic syndrome, with less pronounced liver disease. Despite these differences, WDHC-fed and HFHF-fed mice had similar tumour burdens in a model of diet-potentiated liver cancer. Response to diet and resulting phenotypes were generally similar between sexes, albeit delayed in females. Notably, although metabolic and liver disease phenotypes are often thought to progress in parallel, this study shows that modest differences in diet can significantly uncouple glucose homeostasis and liver damage. In conclusion, long-term feeding of either HFHF or WDHC are reliable methods to induce NASH and diet-potentiated liver cancer in mice of both sexes; however, the choice of diet involves a trade-off between severity of metabolic syndrome and liver damage. HCC Mouse CohortWild-type inbred C57BL/6N genetic background mice were housed in the same fashion as the NASH cohort mice described above. Mice were injected with 25 mg of diethylnitrosamine (DEN) per kg body mass at 2 weeks of age. Mice were fed ad libitum either the HFHF diet or the WDHC diet as described above. 14 males (n=6 on HFHF, n=8 on WDHC) and 14 females (n=7 on HFHF and n=7 on WDHC). Body mass was taken weekly, and mice were sacrificed after 24 weeks of feeding following a 3-hour fast. Samples were processed in a similar manner as the NASH cohort. Blood CollectionA minimum concentration of 3.2 µL per 600 µL blood of Aprotinin from bovine lung (Sigma, MA, USA) was added to all blood samples (except those taken during the glucose tolerance test) to prevent protein degradation. Blood collected during the oral glucose tolerance test (OGTT) was collected in Microvette Ò 100µL K3 EDTA (Sarstedt, Germany). Blood was incubated at 4°C for 90 minutes, followed by an 8-minute centrifugation at 4000 rpm at 4°C. The top layer of serum was collected and stored at -80°C unti...

Hepatocyte PPARγ contributes to the progression of non-alcoholic steatohepatitis in male and female obese mice

“…The progression of HFCF-induced NASH in female mice is not extensively explored. Nonetheless, it was recently reported that long-term feeding (>30 weeks) with NASH- inducing diets promotes NASH with fibrosis in female mice, but at a lesser level than males [53, 54]. We also show that NASH is more accentuated in males than females with pre-established diet-induced obesity, with a significant staining of collagen fibers in male mice just after 16 weeks of HFCF diet.…”

“…Although the Amylin liver NASH (AMLN) diet or the Gubra AMLN (GAN) diet required more than 30 weeks to induced NASH in male mice [26, 44], these diets induce NASH after 16 weeks of feeding in leptin-deficient hyperphagic mouse model (ob/ob) [26, 56]. It should be noted that long term feeding of AMLN and GAN diets does not promote adiposity as 16 weeks of HFD-feeding [24, 53], despite the GAN diet increasing fat mass tissue [44]. This evidence suggests that inducing obesity and human-like NASH together in mice is a challenge.…”

“…However, when the fat source of this HFCF diet (partially hydrogenated corn oil) is replaced with lard or palm oil, the mice show an increased amount of fat mass [24, 44], so, it is possible that the trans-fat reduces adiposity in mice. Also, glucose intolerance and insulin resistance are commonly associated with NAFLD and obesity, but long term-HFCF feeding did not promote glucose intolerance nor insulin resistance [13, 24, 53]. When mice fed AMLN or GAN diets are compared to chow-fed mice, these diets show significant negative effects on glucose homeostasis [24, 44, 56].…”

FXR activation protects against NAFLD via bile-acid-dependent reductions in lipid absorption

“…The standard rodent diet contains relatively little dietary fat, and mice fed this diet typically do not develop fatty liver disease. In (legend continued on next page) ll Article contrast, when rodents are fed a diet rich in fat (Western-type diet; WD), they accumulate significantly more TAGs in the liver, reminiscent of NAFLD (Zhang et al, 2020). To better understand the role of FXR in controlling elevated hepatic lipid levels, we fed wild-type and Fxr À/À mice WD for 8 weeks to promote hepatic lipid accumulation.…”

Non-alcoholic Steatohepatitis Pathogenesis, Diagnosis, and Treatment

“…Consumption of a high-calorie diet with high fat and high sugar (western diet) results in weight gain and is the initial event for the development of fatty liver ( 125 – 127 ). Particular types of lipids and carbohydrates play important roles in the progression of NASH.…”