非酒非精性脂肪肝,动物模型 z-bo 2020-07-23 866

　　Non-alcoholic fatty liver disease (NAFLD) is a liver syndrome without alcohol abuse, including simple fatty liver, steatohepatitis, fatty liver fibrosis and cirrhosis. It can range from simple fatty liver to non-alcoholic steatohepatitis (NASH) to liver fibrosis, and can lead to end-stage liver diseases, such as cirrhosis, hepatocellular carcinoma (HCC) and liver failure.

　　A study by Younossi et al. showed: "AFLD is one of the most important causes of liver disease in the world, and may be the main cause of liver disease at the end of the next few decades. It will affect adults and children."

　　ASH diagnostic gold standard is liver biopsy, but this method is very invasive. Liver enzymes in patients with AFLD are sometimes normal. Ultrasound can detect fatty liver, but not fibrosis or inflammation. Since there is currently no approved treatment for NAFLD, research is not only aimed at the development of NASH treatments, but also for new diagnostic methods, and pharmaceutical companies and biotech companies are investing heavily in NAFLD/NASH research. I will. Animal models play an important role in elucidating the pathophysiological mechanism of non-alcoholic fatty liver and developing new drugs. Preclinical research should use different animal models according to the specific NAFLD phenotype being studied. The preclinical animal models of AFLD and NASH can be divided into four categories. Diet induction model, chemical induction model, gene editing model and compound model. 1. Diet-induced model

　　Animal is a fatty liver model established by feeding animals with a high-fat and high-sugar diet. The main cause is overnutrition. The fat, cholesterol and/or carbohydrates in food are too much to be fully absorbed and utilized. , Lipids accumulate in the liver to cause fatty liver, and hepatitis and fibrosis occur. This model is similar to human NAFLD and is the most common animal model of NAFLD. Different diet induction models have different characteristics. One challenge of diet-induced models is that it takes a long time to build the model before starting research.

　　2, chemically induced model

　　Small dose of streptozotocin combined with a high-fat diet can produce NAFLD in mice, which can cause steatosis, inflammation, fibrosis and even hepatocellular carcinoma. Carbon tetrachloride (CCl4) can cause liver damage, and its use alone or in combination with a high-fat diet can cause fatty liver or liver fibrosis. The main mechanism is that CCl4 induces oxidative stress in the liver, leading to the continuous production and accumulation of harmful lipid and protein peroxidation products and severe necrosis, leading to the destruction of liver cell structure and function. This method took some time to establish a model, but its etiology, changes in disease progression and histomorphology are very different from human fatty liver. The drug is highly toxic and easily causes death.

　　3. Gene editing model

　　The production and removal of fat in liver cells are regulated by a variety of genes. Mutations, deletions, overexpression or modifications can affect fat metabolism, cause fatty liver and artificially manipulate animal gene interventions may change the NAFLD animal model. Regarding the cause of NAFLD, the "second blow" theory is a widely accepted theory. The "first blow" refers to fatty liver caused by insulin resistance, and the "second blow" refers to factors such as oxidative stress, inflammatory factors, endotoxin and other factors.

　　Ob/ob mice have ob (Lepo) homozygous mutations, obesity and steatosis. db/db mice or Zucker rats become slender due to mutations in the db gene or the fa gene (the gene encoding the leptin receptor). When the leptin receptor function is lost, the leptin resistance becomes ob/ob mice with similar genetic phenotypes. However, these models cannot spontaneously change from fatty liver to steatohepatitis, and when combined with diet or chemicals, they must cause a "second attack" and develop a NASH phenotype. PTEN is a lipid phosphatase involved in fatty acid β-oxidation and triglyceride synthesis in liver cells, and is a negative regulator of signaling pathways such as apoptosis, cell proliferation and differentiation, and tumorigenesis. SatoW et al. found that liver-specific PTEN knockout mice can cause liver damage similar to human NASH. These mice may develop steatohepatitis, liver fibrosis, and liver adenoma after 10 weeks of birth. The last 66% of HCC is complex in mice. PPAR-α is a transcription factor involved in the transcriptional regulation of liver mitochondria and peroxisome β-oxidation genes, and can regulate ATP production. MTP is a key enzyme for β-oxidation of mitochondrial fatty acids. AOX is the rate-limiting enzyme of the β-oxidation reaction of long-chain fatty acids in peroxisomes, which can produce hydrogen peroxide. Modifications of these genes can affect the β-oxidation of fatty acids and can prepare NAFLD models. Methionine adenyltransferase 1A (MAT-1A) is a liver-specific rate-limiting enzyme for methionine metabolism, which can catalyze the production of S-adenosylmethionine, the main liver methyl donor. form. Antioxidants (such as glutathione) in MAT-1A knockout mice are reduced, and the expression of genes related to lipid oxidation in the liver is suppressed. Generally, Apoe knockout mice used to study atherosclerosis will develop NASH phenotypes such as steatosis, inflammation and fibrosis when they eat a high-fat, high-cholesterol diet. Although gene editing and chemical induction methods can make the model faster, the model may have nothing to do with the induction mechanism of the disease.

　　4. Composite model

　　None of the previous three models completely simulate the etiology of human NAFLD, and its phenotype is different from that of human NAFLD. Many scholars combine gene editing models with diet or drug transfer to make the phenotype and etiology of the combined model closer to human NAFLD. The disease has evolved from simple fatty liver to NASH, and from NASH to liver fibrosis. Can reflect the ongoing process.

　　The most commonly used combination model:

　　ob/ob mice + methionine choline deficiency (MCD), db/db mice + methionine choline deficiency (MCD) diet, Zucker rat + methionine choline deficiency (MCD) diet treatment/high-fat diet. These models may form typical NAFLD histological changes.

　　The db/db mouse + MCD diet model is more serious than the ob/ob mouse + MCD diet model. There is inflammation and fibrosis around the cells, and the modeling cycle is significantly shortened. Therefore, the diet model of the db/db mouse + MCD diet model is more serious. Commonly used. The compound model can maximize the simulation of human NAFLD and have more pathological changes, but the modeling process is more complicated. Fatty liver animal models created by different methods have different phenotypes and formation mechanisms. Use the best animal model according to your research goals, and consider the complexity of the NAFLD model to ensure that your animal model is not affected. Choosing an experimental model similar to human NAFLD has simple method, high success rate, low animal mortality, short modeling time, and good repeatability. The NAFLD/NASH model described in this article is not perfect, so if you need a gene-edited mouse, please consult.