目的 了解蛋氨酸和胆碱缺乏（MCD）饮食对非酒精性脂肪肝炎（NASH）的诱导作用及性别差异。方法 于KM品系孕鼠分娩后第3日，将每只母鼠喂养子鼠数量调整至10只。子代于离乳后分为雌性组（F组）和雄性组（M组），喂养标准饮食至第10周。从第11个星期开始，根据饲料种类将子代随机分为雌性对照组（F-CTR组）、雌性MCD组（F-MCD组）、雄性对照组（M-CTR组）和雄性MCD组（M-MCD组），其中对照组继续喂养标准饲料，MCD组喂养MCD饲料，每周记录体质量。持续喂养4个星期后处死，取动物肝脏和血清。HE染色光学显微镜下观察肝脏的组织形态学特点；透射电子显微镜观察肝细胞的超微结构；全自动生化仪检测血清丙氨酸氨基转移酶（ALT）和天门冬氨酸氨基转移酶（AST）水平；Real-Time PCR方法检测肝脏组织的肿瘤坏死因子-α （TNF-α） 和白介素-6 （IL-6）mRNA的表达水平。结果 喂养至第10个星期时，M组小鼠的体质量明显高于F组（P<0.05）；第11个星期起MCD小鼠的体质量出现下降。HE染色结果显示：与CTR组相比，MCD组小鼠的肝脏出现脂质沉积、肝细胞气球样变和炎症细胞聚集等改变，M-MCD组的改变程度较F-MCD组更严重。M-MCD组小鼠血清中ALT与AST水平升高较F-MCD组更为明显，肝脏组织TNF-α mRNA表达水平也显著高于F-MCD组（P<0.05）；但各组间IL-6 mRNA表达水平比较差异无统计学意义（P>0.05）。结论 MCD可诱导肝脏发生NASH的病理改变，为非酒精性脂肪肝病(NAFLD)研究提供了可选的动物模型；而雄性动物对MCD饮食诱导的NASH较雌性更严重，尤其体现在炎症反应程度上。TNF-α表达上调可能参与雄性小鼠的炎症损伤。

Objective To explore effects of methionine and choline deficient diets (MCD diets) on non-alcoholic steatohepatitis (NASH) development in KM mice, and to study the possible differences between the genders. Methods Three days after delivery, the litter size was adjusted to 10 pups per dam to allow comparable calorie intakes during lactation. After weaning, the pups were fed with standard diets until 10 weeks. Then the offspring were randomly divided into four groups: female control group (F-CTR), female MCD diets group (F-MCD), male control group (M-CTR), and male MCD diets group (M-MCD). Mice in control or MCD groups were fed with standard or MCD diets respectively for 4 weeks. The body weights were recorded once a week. The samples of serum and liver tissue were obtained after sacrificing. Liver morphologic analysis was performed by HE staining; The ultra-structure of hepatocyte was observed using transmission electron microscope. Serum alanine aminotransferase (ALT) and aspartate transaminase (AST) were determined by automatic biochemical analyzing system. The mRNA levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were determined by qualitative Real-time PCR. Results The body weights of male mice were higher than those of female mice before 11 weeks of age (P<0.05). After MCD diets were induced, the body weights declined significantly compared with those fed with standard diets. In MCD groups, HE staining showed typical characteristics of NASH, including steatosis, hepatocyte ballooning, and inflammatory cells infiltration. Moreover, in MMCD group, the changes of NASH were more severe. Serum AST and AST levels were higher in M-MCD group than those in F-MCD group. The mRNA levels of TNF-α, but not IL-6, were also higher in M-MCD group than those in F-MCD group (P<0.05). Conclusion Deficiency in methionine and choline induced typical pathological changes of NASH in KM mice. This could serve as an ideal animal model for non-alcoholic fatty liver disease (NAFLD) research work. Male mice were more susceptible to MCD diets-induced NASH compared with female mice, with more severe inflammation. Up-regulation of TNF-α expression may participate in the inflammatory injury in mice.