| Type 2 diabetes mellitus(T2DM), non-insulin-dependent diabetes mellitus, is mainly caused by insulin resistance or insufficient insulin secretion, which makes people can’t use insulin effectively and it is a kind of polygenic diseases which make the patients lake insulin relatively. More and more people have the T2 DM disease and intervention and prevention of T2 DM is urgent. Okara is a byproduct of soy milk, tofu and other soy products which has rich protein and dietary fiber. Since okara is easily corrupted for the high moisture, it has a low utilization ratio. Diet therapy is very important for treatment of diabetes and it is useful for controling the occurrence and development of diabetes to regulate metabolism and diet correctly. Recently, many researchers found that diet with high dietary fiber or high plant protein can play a good role in the adjuvant treatment of diabetes. Okara, as a compound of dietary fiber and protein, has not been largely studied about the intervention effect of okara on T2 DM and the mechanism. In this study, defated okara, okara protein and dietary fiber was treated as the breakthrough point to improve T2 DM, and combined extraction process of okara protein and dietary fiber was optimized and the components of okara and its extrat were analyzed. T2 DM mouse model was established by injected with low dosage of streptozotocin(STZ) and fed with high fat diet. It was studied that hypoglycemic activity-guided fractionation in okara such as protein and dietary fiber and the alleviation effects of them on T2 DM to disscuss whether okara has beter intervention effect on T2 DM than single okara protein or dietary fiber as the compound of dietary fiber and protein. The main contents were as follows:Firstly, combined extraction process of okara protein and dietary fiber was optimized and the components of okara and its extrat were analyzed. All that solid-to-liquid ratio, extraction p H, extraction temperature and extraction time had strong associations with the extraction ratio of okara protein, insoluble dietary fiber and soluble dietary fiber. The influence order was: p H>extraction temperature>extraction time>solid-to-liquid ratio. The optimum extraction conditions of okara protein, insoluble dietary fiber and soluble dietary fiber were: solid-to-liquid ratio=1:20, p H=10, extraction temperature=65°C, extraction time=120min, and the okara protein and dietary fiber obtained in this condition had certain antioxidant capacity and swelling capacity.Secondly, the established method of T2 DM mouse model was studied by comparing the difference of achievement ratio of single high dose of intraperitoneal injection of STZ and several times and small dose of STZ intraperitoneal injection to determine the specific method to establish mouse model of T2 DM. The result showed that both these two methods had significant effect on body weight, diet intake and fasting blood glucose of type 2 diabetic mice but their effect on water intake was not significant.The method of several times and small dose of STZ intraperitoneal injection showed a higher achievement ratio which was more appropriate to simulate the initiation and progression of T2 DM compared with the method of single high dose of intraperitoneal injection of STZ and could lay a good foundation for subsequent studies about diabetes pathogenesis and the prevention and intervention effect on T2 DM of drug or functional food. Hence, T2 DM mouse model was established with four times and small dose(45mg/kg b.w.) of STZ intraperitoneal injection.Thirdly, T2 DM mouse model was established and defatted okara, okara protein and okara dietary fiber were administrated to type 2 diabetic mice. Diet intake, water intake, fasting blood glucose, glucose tolerance, insulin tolerance and organ index were measured to study the intervention effect of defatted okara, okara protein and dietary fiber on T2 DM. The result showed that glucose torlerance and insulin torlerance of type 2 diabetic mice were improved after the treatment of okara, okara protein and dietary fiber. Okara protein could significantly enhance the insulin sensitivity and alleviate the change of organ such as liver, kidney and pancreas of type 2 diabetic mice.Fourthly, the mechanism of the intervation effect on T2 DM of defatted okara, okara protein and dietary fiber was studied by measuring the index about glycometabolism, lipid metabolism, antioxidation ability and anti-inflammatory ability. The result showed that defatted okara, okara protein and dietary fiber can alleviate T2 DM by regulating glycometabolism, lipid metabolism, antioxidation ability and anti-inflammatory ability. In glycometabolism, serum insulin level decreased which enhanced insulin sensitivity and decreased insulin resistance. Hepatic glycogen content increased and improved insulin receptor and insulin receptor substrate expression were found after the treatment of okara, okara protein and dietary fiber. As to lipid metabolism, total cholesterol and low density lipoprotein cholesterol was reduced and high density lipoprotein cholesterol was enhanced by okara, okara protein and dietary fiber, but the effect on triglyceride level of them was not significant. Furthermore, enhanced serum apolipoprotein A1 and decreased serum apolipoprotein B were also found after the treatment of okara, protein and dietary fiber compared with the untreated type 2 diabetic mice. As to antioxidation ability of the liver, the activities of SOD and GSH-PX, and the total antioxidation activity(T-AOC) were enhanced and the level of MDA which was the lipoxidation was decreased after the treatment of okara, okara protein and dietary fiber. In the anti-inflammatory ability, defatted okara, okara protein and dietary fiber coule alleviate the levels of serum TNF-α and IL-6 which was the evidence of improved anti-inflammatory ability.This study explored the intervention effect on T2 DM of defatted okara, okara protein and dietary fiber and the mechanism which could provide theory foundation for diet therapy of T2 DM and multiple utilize of soybean by-product. |
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