疾病动物模型,2型糖尿病模型 z-bio 2021-03-17 283

　　The incidence of type 2 diabetes and its complications, especially cardiovascular disease, is increasing worldwide. Type 2 diabetes is a genetic susceptibility disease caused by multiple genes. Its outstanding feature is the existence of insulin resistance and relatively insufficient insulin secretion. Due to the lack of understanding of the genetic susceptibility mechanism of insulin resistance, especially the pathogenesis of insulin resistance accelerating atherosclerosis and other diabetic complications, the progress of strategies to improve insulin resistance is limited. Chronic hyperglycemia has harmful effects on both insulin secretion and insulin activity (glycotoxic effects). Studies have found that the loss of insulin sensitivity of muscle, the largest blood sugar utilization organ, is related to the abnormal increase in liver glucose production and the decrease in peripheral glucose utilization. Therefore, hyperglycemia may be partly related to insulin-mediated defects in blood glucose utilization.

　　Numerous genetically modified rodent models have been applied to the study of insulin resistance mechanisms. Important advances include insulin receptor (INSR1), downstream signaling molecules insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 ( The effect of IRS2) gene structure changes on insulin resistance. These studies show that genetic mutations can cause changes in insulin-stimulated blood glucose transport in muscles, causing secondary changes in fat cells, similar to the situation in humans with type 2 diabetes. Similarly, the loss of insulin sensitivity in muscle or adipose tissue also leads to stimulation of hepatic glucose release. Recent studies on peroxisome proliferator-activated receptor α, β and γ genes (PPAR-α, β, γ) and their antagonists have found that there is an interaction between metabolism, inflammation and atherosclerosis New regulation mechanism. It can be seen that these genetically modified rodent models provide important information for us to understand the effects of changing the function/signaling of INSR and PPAR, but they cannot reproduce all the phenotypes that lead to glucose intolerance and type 2 diabetes. The main factors (for example, insulin resistance, obesity, hypertriglyceridemia and hypercholesterolemia). Therefore, more suitable animal models are needed to study the mechanism of insulin resistance-mediated complications in patients with type 2 diabetes. Based on the high degree of consistency found in the metabolic mechanism and atherosclerosis research with humans, pigs have become a promising model for the study of insulin resistance mechanisms in type 2 diabetes, which is hopefully used to determine the mechanisms that lead to diabetic complications, as well as to develop and test New treatments.

　　1. Type 2 diabetes induced by simple high-sugar and high-fat foods Spontaneous diabetes rarely occurs in pigs. However, type 2 diabetes can be induced artificially through high-sugar and high-fat diets. Miniature pigs like sweets and can generally tolerate high-sugar and high-fat feed. Chen Hua and others used high-sugar and high-fat feed to simultaneously induce Guangxi Bama mini-pigs, Wuzhishan mini-pigs and large and small-sized pigs. The animals were 3-6 months old and weighed 15-30kg. The induced feed formula: sucrose 35%, tallow 10% , Basic feed 55%. Basic feed formula: corn 48%, wheat flour 20%, soybean cake 15%, rice bran 12%, fish meal 5%. One Guangxi Bama mini-pig showed the earliest symptoms of diabetes, and its fasting blood glucose reached 13.05mmol/L in the 5th month after applying the induction feed. By 8 months after the experiment, 3/18 animals (2 Wuzhishan mini-pigs, 1 Bama mini-pig) were diagnosed as diabetic animals, and 3/18 animals (2 Wuzhishan mini-pigs, 1 Bama mini-pig) were pre-diabetic animals. Equine mini-pigs), 12 animals without diabetes (2 Wuzhishan mini-pigs, 4 Bama mini-pigs and 6 large- and small-sized pigs). Experimental results show that simple high-sugar and high-fat food can induce type 2 diabetes in miniature pigs. It takes more than 1 year for stable type 2 diabetes to occur, and not all animals have the disease. Different breeds of miniature pigs have different susceptibility to diabetes. Wuzhishan Miniature pigs are relatively more susceptible, but large and small pigs are less susceptible; miniature pigs of the same breed are highly susceptible to diabetes induced by high-sugar and high-fat diet; there is no significant change in the morphology of pancreatic islets and the number of beta cells in miniature pigs, and no inflammation Sex cell infiltration; miniature pigs fed with high-sugar and high-fat diets have accelerated body weight gain, with obvious obesity and extensive fat deposits.

　　Larsen et al. fed male Göttingen minipigs with a high-fat and high-energy diet for 3 months and found that the animal's body weight increased significantly, with a significant increase in total fat and trunk fat, but a relative decrease in non-fat body weight. Fasting blood glucose and insulin also increased slightly, but oral glucose tolerance has not changed significantly. Insulin secretion stimulated by intravenous glucose increased, but the rate of blood glucose clearance did not change, suggesting a certain degree of insulin resistance. In short, Göttingen minipigs fed a high-fat and high-energy diet for 3 months can induce slight abnormalities in glucose tolerance and insulin sensitivity, and it will take longer to induce type 2 diabetes. Xi et al. applied high-sugar and high-fat feed to Guizhou miniature pigs for 6 months. Among them, 4/5 of them had elevated fasting blood glucose (7.2～9.8mmol/L), abnormal oral glucose tolerance, and showed diabetic or pre-diabetic changes. There was no abnormality in blood glucose of 1/5 animals. Liu et al. used Bama mini-pigs to observe the effect of simple high-sugar and high-fat diet on the kidneys of mini-pigs. They fed 10-month-old male miniature pigs with high-sugar and high-fat diets (37% sucrose, 10% lard, 2% cholesterol and 51% regular full-price nutrient feed) for 5 months, and found that the oral glucose tolerance of the miniature pigs was abnormal The blood glucose levels at 90 minutes and 120 minutes after sugar administration were significantly higher than those in the control group. Although the mini-pigs’ serum creatinine and urea nitrogen indicators were not abnormal, the urine glucose/creatinine, albumin/creatinine, and N-acetyl-β- Glucosamine/creatinine was elevated, and slight abnormalities in kidney morphology were also seen, suggesting early kidney injury.

　　2. Efforts to improve the susceptibility of miniature pigs to diabetes. Genetic selection research: In 1979, Phillips of Colorado State University in the United States published the genetic selection of diabetes-susceptible Yucatan miniature pigs. They used IVGTT to screen out two Yucatan minipig strains, one is a strain with high blood glucose clearance (High-K) and the other is a strain with low blood glucose clearance (Low-K). 4 and 5 generations were selected and bred respectively. And using these animals to carry out a series of studies on the establishment of diabetes models, the influence of genetic factors on the formation of diabetes, and the influence of food factors on the formation of diabetes. In 1987, Hand et al. used this group of miniature pigs to conduct a diabetes induction experiment. As a result, they were fed continuously with high-sugar and high-fat feed for 4 months, but they failed to induce diabetes. They believed that they were reproduced to the 7th generation. The breeding characteristics of this group of miniature pigs No longer exists.

　　(1) Osab pig: Osab pig is the only pig that is currently considered to be genetically susceptible to type 2 diabetes. The prevalence of type 2 diabetes in the Osab pig herd is very high. It is speculated that this small pig has been isolated on Osab Island for a long time, living in the natural conditions of abundant food in autumn and relatively scarce in winter, after centuries of evolution. A "thrifty genotype" was formed. The metabolic syndrome of Osab pigs has been fully studied. Although there have not been reports of type 2 diabetes models, these findings in the metabolic syndrome study make Osab pigs a type 2 diabetes pathogenesis study, especially It is an exciting model for studying the complications of type 2 diabetes.

　　(2) Pigs with familial hypercholesterolemia: In the fifth section of this chapter, a spontaneous hypercholesterolemia strain developed by the School of Agriculture and Life Sciences at the University of Wisconsin in the United States is introduced. These pigs are fed with cholesterol-free low-fat foods. Under the circumstances, it manifests spontaneous hypercholesterolemia and can develop into severe coronary and abdominal aortic atherosclerotic lesions. This strain was named the hereditary low-density lipoprotein cholesterol-elevated strain (IHLC). The study found that the pathogenic mutation in IHLC pigs originated from a missense mutation (C253→T253), resulting in Arg94→ Cys94 is replaced, and this mutation is inherited in an autosomal manner, similar to human familial hypercholesterolemia. This spontaneous dyslipidemia is also a characteristic of insulin resistant people and has the potential to establish a type 2 diabetes model.

　　(3) Iberian pig: The LEPR allele of Iberian pig increases uncontrolled appetite, has the potential to accumulate fat under the skin and between muscle fibers, and causes obesity. Torres-Rovira et al. used adult Iberian sows with leptin resistance and fed high-sugar and high-fat diets for 90 days, which can develop into the pre-stage of metabolic syndrome and type 2 diabetes.

　　3. Diagnosis of pig diabetes Diabetes includes a series of different symptoms and a common feature of high blood sugar. Therefore, the diagnosis of diabetes is based on blood glucose as the main basis. The diagnostic criteria for human diabetes comes from the study of large-scale populations and has been widely agreed. Since the blood glucose range of normal mini-pigs is very similar to that of humans, Bellinger et al. believe that the diagnosis of diabetes in mini-pigs can refer to the diagnostic criteria of human diabetes. That is, the fasting blood glucose level between 5.6 and 7.0 mmol/L is pre-diabetes, and the two-hour postprandial blood glucose level is between 7.8 and 11.1 mmol/L as pre-diabetes; the fasting blood glucose level> 7.0 mmol/L is diabetes, and the two-hour postprandial blood glucose level is> 11.1mmol/L is diabetes.

　　Our laboratory tested the fasting blood glucose of 79 Shichuang Bama miniature pigs aged 10 to 14 months, and performed the IVGTT test. The results showed that the fasting blood glucose of the miniature pigs ranged from 3.65 to 6.77 mmol/L ; 95% confidence interval: 3.60～6.30mmol/L; 99% confidence interval: 3.17～6.73mmol/L. IVGTT (2 hours) blood glucose range: 3.89～7.65mmol/L: 95% confidence interval: 4.18～7.52mmol/L; 99% confidence interval: 3.66～8.04mmol/L. Since spontaneous diabetes rarely occurs in minipig populations, our laboratory has screened the fasting blood glucose of 245 adult Bama minipigs. Only one individual with high blood sugar during pregnancy (13.3mmol/L) was found. Therefore, it is believed that Pakistan The diagnostic criteria for diabetes in equine mini-pigs should be higher than the upper limit of the 99% confidence interval, that is, the fasting blood glucose is 6.73 mmol/L, and the 2-hour blood glucose of the IVGTT test is 8.04 mmol/L.

　　The blood glucose level of the animal will be affected by the stress response, so care should be taken during the test.