Influence of dietary sucrose and copper content in a rat model of non-alcoholic fatty-liver disease

Nutrigenomics analysis was used to investigate the molecular responses to dietary Cu deficiency independently and in combination with 30% (w/w) sucrose in a mature rat model of NAFLD. Low Cu significantly decreased hepatic and serum Cu, and induced NAFLD-like histopathology, mild steatosis, up-regulated transcripts in inflammation and hepatic stellate cell activation, and significantly increased oxidative stress. Rats fed low Cu together with 30% sucrose also developed insulin resistance, increased ATP citrate lyase and FASN expression, and greater oxidative stress. High sucrose with adequate Cu also promoted inflammation and fibrosis, but not steatosis. This study indicates that low dietary Cu and sucrose consumption are singular and synergistic dietary factors in promotion of NAFLD and NASH that act independently of obesity or severe steatosis, likely by promoting oxidative stress and activation of inflammation and fibrosis. Mature (6 months old) male Wistar Rats that had been allowed ad libitum access to Mazuri rodent pellets were used in the study. Twenty-four rats were divided into four groups and fed for 12 weeks with diets based on the Purified AIN76A formulation, modified for target sucrose and Cu content (Custom Animal Diets, Bangor, NJ). Sucrose and copper content in diets were as follows: ‘A’ CuD/30%- Cu deficient (<0.3 mg Cu/kg)/30% sucrose, ‘B’ CuA/30%- Cu adequate (125 mg/kg)/30% sucrose, ‘C’ CuD/10%- <0.3 mg/kg Cu/10% sucrose, and ‘D’ CuA (125 mg/kg Cu)/10% sucrose (control). Starch and dextrin were used to equalize carbohydrates.

本研究采用营养基因组学（Nutrigenomics）分析方法，在非酒精性脂肪性肝病（Non-Alcoholic Fatty Liver Disease, NAFLD）成熟大鼠模型中，分别探究膳食铜缺乏以及铜缺乏联合30%（w/w）蔗糖对机体分子应答的影响。低铜膳食可显著降低大鼠肝脏与血清铜水平，并诱发类非酒精性脂肪性肝病的组织病理学改变，包括轻度脂肪变性、炎症相关转录本及肝星状细胞（hepatic stellate cell）激活相关转录本的上调，同时显著升高氧化应激水平。同时饲喂低铜膳食与30%蔗糖的大鼠还会出现胰岛素抵抗、ATP柠檬酸裂解酶（ATP citrate lyase）与脂肪酸合成酶（Fatty Acid Synthase, FASN）表达上调，以及更为严重的氧化应激。高蔗糖搭配充足铜膳食同样会促进炎症与纤维化进程，但不会引发脂肪变性。本研究表明，膳食铜摄入不足与蔗糖过量摄入分别是促进非酒精性脂肪性肝病及非酒精性脂肪性肝炎（Non-Alcoholic Steatohepatitis, NASH）发生的独立危险因素，同时二者还具有协同效应，且该效应不依赖于肥胖或重度脂肪变性，其潜在机制可能为促进氧化应激、激活炎症与纤维化通路。本研究选用6月龄雄性Wistar大鼠，实验前可自由采食Mazuri啮齿类动物颗粒饲料。将24只大鼠随机分为4组，采用基于纯化AIN76A配方的饲料进行12周饲喂，根据目标蔗糖与铜含量进行定制调整（定制动物饲料，Custom Animal Diets，班戈，新泽西州）。各组饲料的蔗糖与铜含量如下：A组：CuD/30%——铜缺乏（<0.3 mg Cu/kg）/30%蔗糖；B组：CuA/30%——铜充足（125 mg/kg）/30%蔗糖；C组：CuD/10%——铜缺乏（<0.3 mg/kg）/10%蔗糖；D组：CuA（125 mg/kg Cu）/10%蔗糖（对照组）。以淀粉与糊精平衡各组碳水化合物含量，使其保持一致。