Effects Of High Starch Diet On Growth,Insulin Receptor And Tyrosine Kinase Activity Of Gift Tilapia

An important topic in fish nutrition is how to increase the utilization of feed sugar,exert the energy supply function of sugar and reduce protein consumption as energy.Gift tilapia has become an important species in freshwater aquaculture in China,because of the characteristics of fast growth,high meat yield and high capture rate.The purpose of this experiment is to study the effects of different levels of starch on growth,blood biochemical and immune indexes,tissue insulin receptor level,tyrosine kinase activity,explore the nutritive physiological mechanism of high starch diet and related molecular regulation mechanism of fish carbohydrate metabolism.360 Gift tilapia fish with an average body weight of approximately 31.73±0.68 g were selected and randomly assigned to 12 water circulation tanks.The trial was divided into 3 treatments with 4 replicates per treatment and 30 fish per replicate.Equienerative diets with different levels of carbohydrates were set up.One group of diets added 0% of ?-starch to low-starch group(LS),and the other two groups added 18% and 36% of ?-starch to middle-starch group(MS)and high-starch group(HS).The experiment was carried out for 70 days in a controlled circulating water culture system.Determined using general analysis,biochemical analysis,and molecular biology methods.1.The weight gain rate(WGR)and specific growth rate(SGR)of the high-starch group(HS)are significantly lower than that of the low-starch group(LS)(P<0.05),but there was no significant difference between the middle-starch(MS)group and the the low-starch group(LS)(P>0.05).The weight gain rate(WGR)and the specific growth rate(SGR)showed a downward trend with the increase of the level of dietary starch.Both the high-starch group(HS)and the middle-starch group(MS)significantly(P<0.05)increased the viscerosomatic index(VSI)and conditionfactor(CF)of Gift tilapia.The viscerosomatic index(VSI)and conditionfactor(CF)all showed a trend of increasing with increasing starch levels in the diet.2.Different levels of dietary starch had no significant effect on the crude water(CW),crude protein(CP),ash of the whole fish of Gift tilapia,but the ether extract(EE)content in the high-starch group(HS)was significantly higher than that in the other two groups(P<0.05).3.The concentrations of alanine aminotransferase(ALT),aspartate aminotransferase(ASP),and uric acid(UA)in the high-starch group were significantly higher than those in the low-starch group(LS)(P<0.05).The superoxide dismutase(SOD)and lysozyme(LSZ)in the high-starch group(HS)was significantly lower than that of the low-starch group(LS)(P<0.05).But there was no significant difference between the middle-starch(MS)group and the the low-starch group(LS).4.The liver glycogen content and muscle glycogen content in the medium-starch group(MS)and high-starch group(HS)were significantly higher than that of the low-starch group(LS)(P<0.05).Regardless of the level of starch in the diet,liver glycogen content is always higher than muscle glycogen content.The serum glucose concentration in the high-starch group(HS)and the medium-starch group(MS)was significantly higher than that of the low-starch group(LS)(P<0.05).But different starch levels did not significantly affect insulin concentration.5.The tyrosine kinase concentration in the muscle of high-starch group(HS)and the medium-starch group(MS)were significantly higher than that of the low-starch group(LS)(P<0.05),while the liver tyrosine kinase concentration has no significantly difference in different starch groups.The medium starch diet increased the expression of insulin receptor(IR-1)m RNA in muscle and liver.While the high starch diets reduced the expression of insulin receptor(IR-1)m RNA in the liver and muscle,but the difference was not significant.The results showed that the addition of a certain level of starch to the diet did not affect the growth of Gift tilapia.Instead,it can increase m RNA expression of the insulin receptor(IR-1)gene in muscle and liver and aslo increase tyrosine kinase concentration in muscle tissue,so it can be concluded that this increases the utilization of dietary carbohydrates in Gift tilapia.But high starch diets inhibited growth and immune function of Gift tilapia,reduced gene expression of insulin receptor(IR-1)in liver and muscle tissue,and increased tyrosine kinase concentrations in muscle tissue.The high starch diets affected the expression of key enzymes and associated genes in glucose metabolism of Gift tilapia.