The FATZO mouse, a next generation model of type 2 diabetes, develops NAFLD and NASH when fed a Western diet supplemented with fructose

Abstract

Background: Metabolic disorders such as insulin resistance, obesity, and hyperglycemia are prominent risk factors for the development of non-alcoholic fatty liver disease (NAFLD)/steatohepatitis (NASH). Dietary rodent models employ high fat, high cholesterol, high fructose, methionine/choline deficient diets or combinations of these to induce NAFLD/NASH. The FATZO mice spontaneously develop the above metabolic disorders and type 2 diabetes (T2D) when fed with a normal chow diet. The aim of the present study was to determine if FATZO mice fed a high fat and fructose diet would exacerbate the progression of NAFLD/NASH.

Methods: Male FATZO mice at the age of 8 weeks were fed with high fat Western diet (D12079B) supplemented with 5% fructose in the drinking water (WDF) for the duration of 20 weeks. The body weight, whole body fat content, serum lipid profiles and liver function markers were examined monthly along with the assessment of liver histology for the development of NASH. In addition, the effects of obeticholic acid (OCA, 30 mg/kg, QD) on improvement of NASH progression in the model were evaluated.

Results: Compared to normal control diet (CD), FATZO mice fed with WDF were heavier with higher body fat measured by qNMR, hypercholesterolemia and had progressive elevations in AST (~ 6 fold), ALT (~ 6 fold), liver over body weight (~ 2 fold) and liver triglyceride (TG) content (1.4-2.9 fold). Histological examination displayed evidence of NAFLD/NASH, including hepatic steatosis, lobular inflammation, ballooning and fibrosis in FATZO mice fed WDF. Treatment with OCA for 15 weeks in FATZO mice on WDF significantly alleviated hypercholesterolemia and elevation of AST/ALT, reduced liver weight and liver TG contents, attenuated hepatic ballooning, but did not affect body weight and blood TG levels.

Conclusion: WDF fed FATZO mice represent a new model for the study of progressive NAFLD/NASH with concurrent metabolic dysregulation.

Keywords: FATZO mouse; Liver disease; Metabolic disease; NAFLD; NASH.

Fig. 1

Development of NAFLD/NASH in FATZO mice fed with CD or WDF diet. (a) Body weight, (b) body fat, (c) total cholesterol, (d) triglyceride, (e) ALT, (f) AST, (g) liver weight, and (h) hepatic triglyceride content in FATZO mice fed with CD or WDF for 20 weeks. Data were presented as mean ± SEM. ^ap < 0.05, ^aaap < 0.005 vs vehicle controls using two-way ANOVA with Dunnett’s post-hoc comparison

Fig. 2

Histological evidence of NAFLD/NASH in FATZO mice fed WDF. Representative images of H&E and Picro Sirius Red (PSR) staining of livers removed from FATZO mice fed WDF or CD for 4, 16 and 20 weeks. Denotes steatosis, denotes ballooning, denotes lobular inflammation and denotes fibrosis

Fig. 3

NASH scoring of the liver from WDF or CD fed FATZO mice for 16 and 20 weeks. (a) Steatosis, (b) hepatic ballooning, (c) lobular inflammation, (d) Fibrosis and (e) NAS scores. Data were presented as mean ± SEM. ^ap < 0.05vs vehicle controls using two-way ANOVA with Dunnett’s post-hoc comparison

Fig. 4

OCA treatment improves liver function and lipid metabolism in FATZO mice fed WDF. (a) Body weight, (b) blood triglyceride, (c) total cholesterol, (d) LDL, (e) ALT, (f) AST, (g) liver weight, and (h) hepatic triglyceride content in WDF fed FATZO mice treated with vehicle or OCA (30 mg/kg, QD). Data were presented as mean ± SEM. ^ap < 0.05, ^aap < 0.01, ^aaap < 0.005vs vehicle controls using two-way ANOVA with Dunnett’s post hoc comparison (a-f) or unpaired student t-test (g, h)

Fig. 5

OCA treatment improves hepatic ballooning in NASH FATZO mice. Representative images of H&E and Picro Sirius Red (PSR) staining of the livers removed from NAFLD/NASH FATZO mice treated with OCA or vehicle for 15 weeks

Fig. 6

Histological improvement of WDF fed FATZO mice treated with OCA. (a) Hepatic ballooning, (b) Steatosis, (c) Lobular inflammation, (d) Fibrosis and (e) NAS score. Data were presented as mean ± SEM. ^aaap < 0.005 vs vehicle controls, using unpaired student t-test