| The sweet potato (Ipomoea batatas) is a dicotyledonous plant which is cultivated widely in the tropical and subtropical regions and can be used for the human food, animal feed and industrial raw materials. The contents of essential amino acids of soluble proteins in sweet potato are higher than most of other vegetable proteins,and amino acid compositions are in line with the WHO / FAO recommended standards. With a high biological value,its nutritional value is asgood as milk and meat. Sporamin is the major soluble protein in the root tuber of the sweet potato and it accounted for more than 60%-80% of the total proteins. Sporamin, together with patatin from potato and dioscorin from Dioscorea, belongs to specific storage proteins in metamorphosed rhizomes organ. In addition, sporamin is a trypsin inhibitor with a kunitz-type trypsin inhibitory activity which has potential applications in the transgenic insect-resistant plants. At the same time, sporamin displays both dehydroascorbate reductase and monodehydroascorbate reductase activities, due to the intermolecular disulfide linkages which result in the reduction of free radicals. At present, the studies about sporamin as one type of tuber-specific storage protein focus on a variety of breeding for the disease resistance of transgenic crops, while the reports about its biological activity are quite few. And there is no research on the effect of sporamin from sweet potato to the prevention and treatment of obesity. Firstly in this study, ammonium sulfate precipitation, ion-exchange chromatography andgel filtration were performed in the separation and purification of sporamin from sweet potato species 55-2,and two sporamin proteins which were separated into sporamin A and sporamin B. Secondly,the differentiation and proliferation effects of sporamin in 3T3-L1 preadipocytes were investigated. With berberine as a positive control , different concentrations of sporamin (0.000,0.125, 0.025, 0.250, 0.500 and 1.000mg/mL)were used to treat 3T3-L1 preadipocytes. Intracellular fat accumulation and the degree of adipogenesis were quantified using oil red O staining and colorimetry. Preadipocytes differentiation was measured by3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide(MTT) spectrophotometric assay. The result showed that after being treated by different concentrations of sporamin, the differentiation of 3T3-L1 preadipocytes was significantly inhibited, compared with the positive control.When the sporamin solution concentration was 0.500mg/mL, the accumulation of lipid droplets within the cells was significantly decreased and the optical density (OD) value of the solution from destained Oil Red O reached to 0.35, which was the lowest value ( p<0.05). The proliferation of 3T3-L1 preadipocytes was significantly inhibited by treating at higher Sporamin concentrations. In addition, the inhibitory effect was more obvious with the prolonged treatment time (p<0.05). The differentiation and proliferation of 3T3-L1 preadipocytes could be inhibited significantly by the addition of higher concentration sporamin. Lastly,KunMing mice was used to study the effects of sporamin on obesity prevention and weight loss by determining the bodyweight, fat / body weight ratio,and blood lipids profiles. The results showed sporamin can obviously improve the obese symptom of mice caused by high-fat feed :â… .Sporamin does not have toxic effects on mice at agiven dose.â…¡. Sporamin can prevent and treat obestiy of mice in experiment by suppressing appetite and increase of weight . â…¢.Sporamin has the effects to inhibit the increasing of TC, TG and the reducing of the HDL-C, and it can also reduce the possibility of suffering from atherosclerosis in mice.The present study showed that,sporamin hasgood weight-losing and lipid-lowering effects, and is an ideal source for development and utilization. |
