Effects Of Soybean Isoflavone On OB-Rb, JAK2,P-STAT3, SOCS3and NPY Expressions In Brain And Gastrointestinal Tracts Of Rats

Objective:This paper aims to investigate the effects of soybean isoflavone (SIF) on leptin-induced protein signal transduction pathway in the obese rat’s brain and gastrointestinal tract and discuss the intervention mechanism of SIF on obese rats.Method:Male Sprague-Dawley rats were fed a high sugar and fat diet (HSF) or basal diet for eight weeks. The criterion for obese rats is that the body weight of rats in HSF group is higher than average body weights of rats in the basal group plus1.4times of standard deviation.40selected obese rats were randomly divided into four groups with10rats in each group and fed with soy isoflavones (group Ⅰ0mg/kg, group Ⅱ50mg/kg, group Ⅲ150mg/kg and group IV450mg/kg) for four weeks. The control rats (group V) were fed with basal diet for four weeks. Soy isoflavones was gavaged with0.5%sodium carboxymethyl cellulose solutions. Food intake and animal weights were recorded weekly. At the end of the experiment, brain and gastrointestinal tract were obtained and fixed in4%neutral buffered formalin, then processed, trimmed and embedded in paraffin. By using immunohistochemical SABC staining, expressions and distributions of OB-Rb,JAK2,p-STAT3, SOCS3and NPY proteins were studied.Results:Obese rats models were established successfully after experiments last for8weeks. During the following intervention experiment, we found that rats supplied with SIF gained less weight than those in control group. Rats in group V had the largest ingestion. The SIF intervention groups, as compared with the obese control group, had reduced amount of food intake(P<0.05).The immunohistochemical results are as follows:①The OB-Rb,JAK2,p-STAT3, SOCS3and NPY proteins distrubuted in arcuate nuclei(ARC), dorsomedial nucleus of hypothalamus (DMN) and periventricular hypothalamic nucleus(PVN), which showed that OB-Rb,JAK2,p-STAT3, SOCS3and NPY played a wide role in the hypothalamus. The five factors expressed in the ARC, DMN and PVN suggests that these factors are closely related with leptin-signaling pathway in the regulation of obesity.The positive area and optic density(OD) of five factors expressed in the ARC, DMN and PVN are significantly different among each group. DMN had the highest reading. The positive area and OD of OB-Rb protein expression cells in ARC, DMN and PVN of group Ⅰ,Ⅱ,Ⅲ, Ⅳ is successively increased. The positive area and OD of JAK2and p-STAT3proteins in group V had the highest reading, while group I did the reverse, and compared group Ⅱ, Ⅲ and Ⅳ, the difference is significantly (P<0.05). The positive area and OD of SOCS3of all groups are significantly different (P<0.05). The positive area and OD of NPY in group Ⅳ, Ⅴ are also significantly different(P<0.05). The NPY proteins positive area and OD values in ARC of group Ⅴ had the highest reading, while group IV did the reverse. However, in DMN, group Ⅲ had the maximum NPY proteins positive area and OD values, while in group Ⅴ, the values were minimum. And in PVN, NPY proteins positive area and OD values were highest in group Ⅱ and lowest in group IV and group V. These results implied positive correlations among OB-Rb、JAK2and p-STAT3expressions. The level of the NPY in the ARC, DMN and PVN decreased with the increased dose of SIF.②OB-Rb, JAK2, p-STAT3, SOCS3and NPY existed in different regions of rats’ gastrointestinal tract and the distribution range of OB-Rb, SOCS3and NPY were greater than JAK2and p-STAT3..NPY proteins were widely distributed in the gastrointestinal wall and most of them were localized in the myenteric plexus and mucosal plexus. By comparison, no JAK2, p-STAT3and SOCS3positive reactions were observed. Concluded from the above results, we suggest that the expression of NPY in myenteric nerve plexus and mucosal plexus were not regulated by the JAK/STAT signal pathway. The OB-Rb, JAK2, p-STAT3, SOCS3and NPY existed in the same region of gastric glands and intestinal cells which showed that the expression of NPY may be regulated by leptin. From the positive area and OD values analysis, we concluded that the total positive areas and OD of OB-Rb, JAK2, p-STAT3, SOCS3and NPY in the gastrointestinal tracts treated with different dose of SIF were significantly different. It had sharp distinction between group Ⅰ and Ⅳ. The total positive areas in stomach increased significantly compared with intestine (P<0.05). The total positive areas and OD of OB-Rb, JAK2and p-STAT3in the duodenum, jejunum, ileum, colon and rectum were different. In the stomach, duodenum, jejunum, ileum, colon and rectum, total positive areas and OD of OB-Rb were higher in group Ⅳ, Ⅴ than in group Ⅰ. These results showed that SIF has the ability to promote OB-Rb expression in intestinal tracts.Compared with group IV, the total positive areas and OD of OB-Rb, JAK2and p-STAT3values were greater than group Ⅰ(P<0.05). The total positive areas and OD of SOCS3in group Ⅱ, Ⅲ and IV were significantly different (P<0.05). The positive area and OD of SOCS3in gastrointestinal tracts in group Ⅱ, Ⅲ and IV were successively decreased. And likewise, the OD of NPY in group Ⅱ, Ⅲ and IV decreased, while except duodenum, the positive area did the reverse. Conclusion:The positive area and OD of OB-Rb, JAK2, p-STAT3, SOCS3and NPY in the ARC, DMN and PVN in the group I,V are significantly different.The high dose of SIF has effect on five factors’ expressions. Furthermore, the similarity of OB-Rb, JAK2and p-STAT3changing tendency implied that they were correlated and cooperated during the function process of SIF on hypothalamus. Besides, our results showed that OB-Rb, JAK2, p-STAT3, SOCS3and NPY existed in different regions of rats’gastrointestinal tracts, this suggests that leptin is able to influence gastrointestinal tracts function through JAK/STAT signal pathway. The present experiment showed the distribution differences of OB-Rb, JAK2, p-STAT3, SOCS3and NPY and demonstrated that SIF could promote the expression of leptin in a dose-dependent way.