Effects Of Soybean Isoflavones On Growth And Leptin Signaling Pathway Of Ctenopharyngodon Idellus

The purpose of this study was to investigate the effects of different levels of soybean isoflavones(0,10,50,100,500,1000 mg/kg)added to the diet on the growth,immunity,antioxidation and leptin signaling pathway of grass carp(Ctenopharyngodon idellus).The results show that:1.The final weight,average weight gain rate,specific growth rate and feed efficiency of grass carp increased significantly with the increase of soybean isoflavones(P<0.05).The addition level of 100 and 500 mg/kg was significantly higher than that of the control group(P<0.05).The final weight,average weight gain rate and specific growth rate of grass carp reached the highest level when the content of soybean isoflavone was 100 mg/kg.The feed efficiency of grass carp reached the highest level when the content of soybean isoflavone was 500 mg/kg.2.Soybean isoflavone can improve the immune function of grass carp.After the feeding trial,a bacterial challenge was carried out by injecting A.hydrophila intraperitoneally for 7 days.The results showed that with the increase of soybean isoflavone levels,the expression levels of INF-?2 and IL-12p40 m RNA in grass carp kidney before challenge test showed a trend of up-regulation and down-regulation.The 100 and 500 mg/kg groups were significantly higher than the control group(P<0.05).After the challenge test,the expression levels of INF-? and IL-12p40 m RNA first increased and then decreased.INF-? m RNA was significantly higher in the 100 and 500 mg/kg groups than in the control group(P<0.05).IL-12p40 m RNA had the highest expression level in the 500 mg/kg group(P<0.05).The expression levels of M-CSF2,IL-4 and IL-6 m RNA in grass carp kidney before the challenge test were highest in the 500 mg/kg group and were significantly different from the control group(P<0.05).After challenge test,the levels of M-CSF2,IL-4 and IL-6 m RNA showed a trend of up-regulation and then down-regulation.M-CSF2 m RNA was significantly higher in the 500 mg/kg group than in the control group(P<0.05).The IL-6 m RNA expression levels in the 100 and 500 mg/kg groups were significantly higher than those in the control group(P<0.05).The IL-4 m RNA expression levels in all test groups were significantly higher than those in the control group(P<0.05).The highest expression level was found in the 500 mg/kg group(P<0.05).There was no significant difference in the expression levels of TNF-? m RNA between grass carp kidney groups before the challenge test.After challenge test,the expression level of TNF-? m RNA first increased and then decreased,and it was significantly higher in the 100 and 500 mg/kg groups than in the control group(P<0.05).In addition,we also observed the m RNA expression of each immune gene in the spleen of grass carp before and after the challenge test,and obtained similar test results.We also observed the resistance of grass carp to Aeromonas hydrophila,and we found that diets supplemented with Soybean isoflavone could improve the resistance of grass carp to Aeromonas hydrophila.The survival rates of the 100 and 500 mg/kg groups were significantly higher than Control group(P<0.05).At the end of the challenge test,the 7-day cumulative survival rates of the fish in the 0,10,50,100,500,and 1000 mg/kg groups were 47.92±5.51 %?54.17±2.08 %?56.25±3.61 %?60.42±5.51 %?64.58±2.08 % and 58.33±2.08 %.3.Soybean isoflavone can improve the antioxidant capacity of grass carp's serum and liver.Soybean isoflavone have significant effects on the activity of SOD in the liver and serum of grass carp when soybean isoflavones are added to the feed.With the increase of soybean isoflavone,the SOD activity of grass carp increased first and then decreased.When the soybean isoflavone was added at 500 mg/kg,it was significantly higher than the control group(P<0.05).The CAT activity of grass carp showed an increasing trend with the increase of soybean isoflavones.When the soybean isoflavones were added at a level of 100-1000 mg/kg,grass carp serum CAT activity was significantly higher than that of the control group(P<0.05).There was a maximum in the 500 mg/kg group.When soybean isoflavone was added at a level of 10-1000 mg/kg,the activity of CAT in grass carp liver was significantly higher than that in the control group(P<0.05).There was a maximum in the 100 mg/kg group.The activity of grass carp serum GSH-Px showed an increasing trend with the increase of soybean isoflavone levels,which was significantly higher than that of the control group at 50-1000 mg/kg(P<0.05).The activity of GSH-Px in grass carp liver increased first and then decreased with the increase of soybean isoflavones.It had a maximum value in the 500 mg/kg group and was significantly higher than the control group(P<0.05).Grass carp serum AKP activity showed an increasing trend with the increase of soybean isoflavone levels,which was significantly higher than that of the control group at 100-1000 mg/kg(P<0.05).There was a maximum in the 100 mg/kg group.The activity of AKP in grass carp liver had no significant effect.4.Soybean isoflavone can affect the JAK-STAT signaling pathway mediated by leptin,and have significant effects on the expression of upstream and downstream genes.Soybean isoflavone can promote the expression of grass carp brain leptin(Lep)and intestinal leptin receptor(Lep-R),and show an increasing trend with the increase of the added level.When the added level of soybean isoflavone is 100-1000 mg/kg The expression of Lep and Lep-R m RNA in grass carp brain was significantly up-regulated(P<0.05).Soybean isoflavone can promote the expression of grass carp brain Lep-R.The expression levels of each test group were significantly higher than those of the control group(P<0.05).The expression level was the highest when soybean isoflavone was added at 100 mg/kg,and it was significantly higher.In other groups(P<0.05).Soybean isoflavone can promote the expression of JAK2,STAT1,STAT2,STAT3,and Pep T1 m RNA in the intestine of grass carp,and they all show a trend of up-regulation and then down-regulation.The relative expression of JAK2 m RNA was significantly higher in the 100 mg/kg group than in the control group(P<0.05).The expression of STAT1 m RNA in the 100 and 1000 mg/kg groups was significantly higher than that in the control group(P<0.05).STAT2 m RNA expression was significantly higher in the 100 and 500 mg/kg groups than in the control group(P<0.05).The relative expression levels of STAT1 and STAT2 were highest in the 100 mg/kg group.The relative expression levels of STAT3 and Pep T1 m RNA in the 10-1000 mg/kg group were significantly higher than those in the control group(P<0.05).The relative expression levels of STAT3 and Pep T1 m RNA were highest in the 500 and 100 mg/kg groups,respectively.In addition,we injected different levels of soybean isoflavones(0,4,6,8,10 ?g/g)into grass carp in vivo,and found that different injection doses of soybean isoflavones also affected m RNA expression of upstream and downstream genes of the leptin signaling pathway.And its m RNA expression pattern is similar to the results measured after the culture test.