| In recent years, with the improvement of living standards, obesity had become a public health problem in the world. At least 0.26 million people had died from overweight, obese or diseases caused by overweight and obesity. Around the world, whether in developed countries, emerging developing countries or the poorest countries, obesity was a social problem highly needed concern. At present, China’s obesity rate also showed a growth trend. Obesity not only leaded to a bloated body, the slow clumsy, affected the physical beauty, but also caused serious psychological burden, what’s the worst was that obesity is closely related to the occurrence and development of hypertension, coronary heart disease, sleep apnea syndrome, chronic non alcoholic fatty liver disease and diabetes. The prevention and treatment of obesity had become an urgent social health problem.Adipose tissue was highly sensitive to estrogen, and human and mouse adipose tissue expressed ER(estrogen receptor) alpha and ER beta, and estrogen directly affected adipose tissue. Estrogen could directly reduce lipoprotein lipase(LPL) activity, thereby reducing lipid absorption and lipogenesis in fat cells. Study confirmed that for the relative lack of estrogen after menopause and male, the risk of obesity was higher than for young female. Nouredine put that phytoestrogens such as genistein were promising treatments of obesity. Phytoestrogen, a kind of plant derived compounds, were similar to steroid hormone both in structure and function, could bind to ER and exert estrogenic effects. Phytoestrogens prevented or treated obesity by reducing food intake and body weight, as well as by inhibiting differentiation and proliferation of adipocytes and inducing apoptosis. In addition, phytoestrogens improved blood lipid, had a protective effect on the liver and heart. Liver is a key organ of lipid metabolism, expresses ER. However, relationship between liver function and the effects of phytoestrogen on obesity and lipid metabolism was not received enough attention. In addition, studies found that pregnancy and juvenile animals were more sensitive than adult animals to hormone levels, trace changes in hormone levels might cause lifelong effects on animals. However, effects of phytoestrogens on pregnancy and juvenile animals, especially effects of phytoestrogen intake during pregnancy and childhood on the adult animals were reraly reported. To investigate the effect of phytoestrogen intake during pregnancy and infancy on liver lipid metabolism and its mechanism in obese ICR mice, selecting genistein as the representative, intervention with genistein from the start of pregnancy, and establishing the model of obesity induced by high fat diet, our research studied the effects of genistein intake from the start of pregnancy on obesity and liver of obese mice. In addition, this study further discussed the regulation mechanism of genistein on liver lipid metabolism in the molecular level. The main contents of our study were as follows:1. Effect of genistein intervention from pregnancy on obesitySoy phytoestrogens(mainly genistein) is a bioactive phytoestrogen isoflavone content, and it is rich especially in soybean and its products, which is about 0.2-1.5mg/g. According to the Chinese Dietary Pagoda, recommended intake of soybean and bean products and the dose conversion between human and mouse, and the previous research, gavage dose of genistein was 25mg/kg(by body weight) in our research. In this study, obese ICR mice model were induced by high fat diet, genistein intragastric administration were taken in the different periods which from pregnancy and put the early childhood of pre weaning gavage as the cutoff point. To investigate the effects of genistein on the obesity and heart of obese mice, body weight and indexes of adipose tissue, heart were detected, and cell morphology of adipose tissue and heart tissue were observed with HE staining. Experimental results showed genistein reduced lipid accumulation induced by a high fat diet, and reduced the body weight of mice; compared with intake of genistein period of the early childhood after, the effects on lipid accumulation were significantly different with period from pregnancy to the early childhood of pre weaning, which prompted intake of genistein from pregnancy to early weaning before had a more significant role in prevention and treatment of obesity. HE staining results of adipose tissue indicated that lipid, effects of genistein on reducing lipid accumulation and body weight might relate to its influence on adipocytes. In addition, in this experiment, obesity had not yet caused heart disease, the reason might be related to the degree of obesity and obese time, so our experiment was not able to determine whether genistein had a protective effect on the heart. Conclusion: Genistein intervention reduced lipid accumulation caused by high-fat diet, reduced body weight, might be used for the prevention and treatment of obesity, and from pregnancy to early weaning before intragastric administration of genistein had a more significantly effect.2. Protective effect of genistein intervention from pregnancy on liver in obese mice beganThe accumulation of fat might induce a series of changes of physiological functions, and obesity is closely associated with liver dysfunction. In this study, obese ICR mice model were induced by high fat diet, genistein intervention were taken in the different periods which from pregnancy and put the early childhood of pre weaning gavage as the cutoff point. Liver index were determined, and the morphology of liver were observed with HE staining, and we further detected the content of lipid in liver tissue. Results showed that, compared with the obese model group, liver index of groups of genistein intervention were increased, and effects of on liver index of female mice treated with genistein intervention from the beginning of pregnancy to early childhood pre weaning were significantly increased. HE staining results of liver showed that genistein intervention decreased lipid droplet vacuoles in liver tissue, reduced the high-fat diet induced hepatic steatosis. The results of liver lipid content showed that genistein intervention reduced TG, TC content of liver.The results of HE and liver lipid content showed genistein intake during different periods showed no significant differences in liver morphology and lipid content, which suggested that genistein had liver protective effect but different periods treatment showed no significant differences. Conclusion: genistein treatment from the beginning of pregnancy to pre weaning early childhood and juvenile period after, reduced the high-fat diet induced liver steatosis, protected liver, and different periods treatment showed no significant differences.3. Preliminary study of mechanism on liver lipid metabolism of genistein intervention from pregnancy in obese miceObesity was often accompanied by the disorder of lipid metabolism, and genistein can improve lipid metabolism disorder. Therefore, further study of the mechanism of action of genistein regulating lipid metabolism is important. In this study, obese ICR mice model were induced by high fat diet, genistein intervention were taken in the different periods which from pregnancy and put the early childhood of pre weaning gavage as the cutoff point. Serum TG, TC, HDL, LDL levels were detected to evaluate the effects of genistein on lipid metabolism in obese mice. The content of the key enzyme in fatty acid synthesis—FASN of liver were determined with the method of Elisa, and the expression of PPAR alpha in the liver were determined by RT-PCR and IHC(immunohistochemistry).Our results showed that genistein intervention reduced TG, LDL level in serum, increased the level of HDL, thereby regulating lipid metabolism in obese mice. Results of Elisa, RT-PCR and IHC showed that genistein significantly reduced the content of FASN in liver, increased the expression of m RNA and protein PPAR alpha, which suggested that genistein might regulate lipid metabolism by regulating the level of FASN and expression of PPAR alpha in the liver in molecular level. Conclusion: genistein regulated lipid metabolism, and its mechanism might be related to the regulation of PPAR alpha expression and FASN level.In summary, our research established ICR mice obesity model induced by high-fat diet, and intervened with genistein in the different periods which from pregnancy and put the early childhood of pre weaning gavage as the cutoff point. The bodyweight, viscera index of adipose tissue, liver tissue and heart tissue were detected and their morphologies were observed with HE staining. Serum lipid, liver lipid content, lipid metabolism related enzymes and protein content and expression were further determined with Elisa, RT-PCR, IHC etc. Our results showed that genistein inhibited the increase of body weight induced by high fat diet, reduced lipid accumulation, alleviated hepatic steatosis. Genistein reduced TG and LDL level in serum, and increased the level of HDL, reduced the content of FASN in liver, improved the m RNA expression and expression of PPAR alpha. The experimental results suggested that genistein had effects of liver protection, prevention and treatment of obesity, and genistein regulated liver lipid metabolism by regulating the expression of PPAR alpha and the level of FASN. The experimental results can provide some reference for the creation of foodborne phytoestrogens risk assessment platform during pregnancy and infancy, and the guide of people’s daily diet. |
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