Study On The Prevention Of T2DM Insulin Resistance Of Okara And Its Dietary Fiber Andprotein

Okara is the main by-product generated in the process of soybean products production. Soybean production is widespread in China, and a large number of okara was produced in soybean processing industry every year. However, the resourceful okara haven’t been made the best of, a small amount of okara was utilized and most were regarded as feed or discarded as garbage, which results in the resources waste and environmental pollution. Type 2 diabetes(T2DM) is one of the main threats of public health in the 21 st century and has become a worldwide public health problem. The increasing number of T2 DM patients is associated with high sugar and fat diet and lack of exercise. Insulin resistance(IR),an early symptom and key part in the development of T2 DM, exists throughout the occurrence and development of T2 DM. Besides, IR is the main cause of many related complications, such as cardiovascular and so on. Dietary change, especially increase the intake of dietary fiber, can prevent T2 DM and IR effectively. Dietary fiber is the main component of okara, followed by protein. Dietary fiber and protein accounted for about 60% and 20% of the dry weight of okara respectively, which can meet people’s pursuit of healthy and high dietary fiber diet. Therefore, the research about okara and its functional ingredients has important implications for increasing the utilization of okara. The article studied the prevention of insulin resistance induced by high-fat diet of defatted okara and its composition(ditary fiber and protein) only, investigated the component playing the main role and the mechanism of prevention of IR. The results were as follows:1. The physical and chemical properties of defatted okara(DO), total dietary fiber(TDF), soluble dietary fiber(SDF), insoluble dietary fiber(IDF) and protein were studied. Okara SDF, IDF and protein were extracted respectively from okara, TDF were mixture of SDF and IDF according to their content in the defatted okara. The results showed that, okara SDF had higher water-holding capacity and swelling than DO, IDF and okara protein; the adsorption of oil was in the sequence of DO>okara SDF>okara protein>okara IDF; okara TDF and SDF had far higher adsorption ability of cholesterol and bile acid sodium than DO, okara IDF and okara protein; okara SDF had higher ability of adsorption of sodium nitrite and cation exchange than DO, okara TDF and IDF; the reduction ability and clear ability of ·OH and DPPH· of okara protein increased with the increase of protein concentration, but were far lower than ascorbic acid.2. The preventive effects of defatted okara and its dietary fiber and protein on high sugar and high fat diet induced insulin resistance in mice were studied. Mice were feed with high-fat diet containing 10% DO, 6.7% okara TDF and 2.3% okara protein respectively for 16 weeks, comparing with the mice feed with high-fat diet only. The results indicated that high-fat feeding mice for 16 weeks induced insulin resistance model characterized by hyperglycemia and hyperlipidemia successfully; the addition of 10% DO and 6.7% okara TDF could reduce mice weight gain, food intake, liver weight and visceral fat accumulation, fasting blood glucose, serum insulin levels, and serum TG, CHO and LDL-C concentration(p<0.05), increase insulin sensitivity and the content of HDL-C(p<0.05), as well as improve glucose tolerance and alleviate liver steatosis, significantly. The addition of 2.3% okara protein could enhance insulin sensitivity, improve glucose tolerance and decrease serum CHO concentration significantly(p<0.05). All of DO, its dietary fiber and protein could prevent or improve insulin resistance in mice, but dietary fiber played a main role, which may be related to the weaker physiological function and lower dosage of okara protein.3. The mechanisms about the preventive effects of okara, okara fiber and okara protein on IR in mice were studied. Results showed that the addition of 10% DO and 6.7% oakra TDF increased the content of hepatic glycogen, decreased liver FFA levels, increase T-AOC level and SOD activity in the liver, improved serum Apo A1 concentration and reduced serum Apo B concentration, increased the excretion of fecal lipids and bile acid, reduced serum TNF-α level, and enhanced the expression of insulin Rβ and IRS-1, significantly(p<0.05); the addition of 2.3% okara protein could reduce liver FFA levels, increase SOD activity, improve serum Apo A1 concentration and reduce serum Apo B concentration, and increase fecal bile acid excretion, significantly(p<0.05). These results indicated that DO, okara TDF and okara protein could prevent and improve insulin resistance by improving glucose metabolism and lipid metabolism, enhancing liver antioxidant, reducing inflammation and liver lipotoxicity, and improve the insulin signaling by enhancing the expression of insulin Rβ and IRS-1. The effect of okara deitary fiber on insulin resistance was superior to okara protein, which may be related to the predominant role of dietary fiber and the lower addition of protein.