Obese diet-induced mouse models of nonalcoholic steatohepatitis-tracking disease by liver biopsy

AIM:To characterize development of diet-induced nonalcoholic steatohepatitis(NASH)by performing live biopsy in wild-type and genetically obese mice.METHODS:Male wild-type C57BL/6J(C57)mice(DIO NASH)and male Lep ob/Lep ob(ob/ob)mice(ob/ob-NASH were maintained on a diet high in trans-fat(40%)fructose(22%)and cholesterol(2%)for 26 and 12 wk respectively.A normal chow diet served as control in C57 mice(lean chow)and ob/ob mice(ob/ob chow)After the diet-induction period,mice were liver biopsied and a blinded histological assessment of steatosis and fibrosis was conducted.Mice were then stratified into groups counterbalanced for steatosis score and fibrosi stage and continued on diet and to receive daily PO dosing of vehicle for 8 wk.Global gene expression in liver tissue was assessed by RNA sequencing and bioin formatics.Metabolic parameters,plasma liver enzyme and lipids(total cholesterol,triglycerides)as well a hepatic lipids and collagen content were measured b biochemical analysis.Non-alcoholic fatty liver disease activity score(NAS)(steatosis/inflammation/ballooningdegeneration)and fibrosis were scored.Steatosis and fibrosis were also quantified using percent fractional area.RESULTS:Diet-induction for 26 and 12 wk in DIONASH and ob/ob-NASH mice,respectively,elicited progressive metabolic perturbations characterized by increased adiposity,total cholesterol and elevated plasma liver enzymes.The diet also induced clear histological features of NASH including hepatosteatosis and fibrosis.Overall,the metabolic NASH phenotype was more pronounced in ob/ob-NASH vs DIO-NASH mice.During the eight week repeated vehicle dosing period,the metabolic phenotype was sustained in DIO-NASH and ob/ob-NASH mice in conjunction with hepatomegaly and increased hepatic lipids and collagen accumulation.Histopathological scoring demonstrated significantly increased NAS of DIO-NASH mice(0 vs4.7±0.4,P<0.001 compared to lean chow)and ob/ob-NASH mice(2.4±0.3 vs 6.3±0.2,P<0.001compared to ob/ob chow),respectively.Furthermore,fibrosis stage was significantly elevated for DIO-NASH mice(0 vs 1.2±0.2,P<0.05 compared to lean chow)and ob/ob NASH(0.1±0.1 vs 3.0±0.2,P<0.001compared to ob/ob chow).Notably,fibrosis stage was significantly(P<0.001)increased in ob/ob-NASH mice,when compared to DIO-NASH mice.CONCLUSION:These data introduce the obese dietinduced DIO-NASH and ob/ob-NASH mouse models with biopsy-confirmed individual disease staging as a preclinical platform for evaluation