Effect Of Diet Glucose And NaCl Levels On Sglt1/Glut2 Expression And Transport Activity In The Intestine Of Common Carp (Cyprinus Carpio L.)

Na~+/glucose co-transporter 1(Na~+/glucose co-transporter,Sglt1)is an important carrier for glucose transport proteins,their expression level and factors determining transport activity is the body's glucose metabolism;glucose transporter 2(glucose co-transporter,Glut2)is located on the epithelial basement membrane by facilitated diffusion carrier Glut2 and Sglt1,constitutes the main way of glucose metabolism.Using common carp(Cyprinus Carpio L.)as the experimental animal,we study the gene expression of Sglt1,transport activity and expression of Sglt1-Glut2 association,clarify the CARP intestinal Sglt1 and its circadian rhythm of transport activity,explore dietary Na~+concentration,the concentration of glucose on expression of Sglt1 and regulation of transport activity.With a view to partially reveal the molecular mechanism of glucose metabolism in fish,rich in aquatic animal nutrition theory and promote the science of glucose in aquatic animal feed use.The effect of diet glucose levels on Sglt1/Glut2 expression and activity in the intestinal of common carp(Cyprinus carpio L.)To explore the effect of diet glucose levels on Sglt1/Glut2 expression and activity in the intestinal of common carp,we designed five kinds of isonitrogenous and isoenergetic diets,which were formulated with glucose at 10%,20%,30%,40%,and 50%(Glu10%,Glu20%,Glu30%,Glu40%,and Glu50%),The feeding experiment lasted for 70 d.After the feeding experiments,we detected the growth indicators,Serum biochemical indicators,the expression and transport activity of Sglt1/Glut2 in the intestinal of common carp.The results showed that,the optimal dietary glucose contents for common carp were 40%.With the increasing diet glucose level,the blood glucose and CHO(cholesterol)levels were gradually rising,while TG(triglyceride)showed the opposite trend.Between the five test groups,there were no significant difference about the contents of the ALT(alanine aminotransferase),AST(aspartate aminotransferase),HDL(high density lipoprotein)and LDL(low density lipoprotein)(P>0.05).Meanwhile,by measuring the length of the intestine villi for common carp,we found that the proximal intestine was significantly higher than mid intestine and distal intestine(P<0.05),and the mid intestine was significantly higher than the distal intestine(P<0.05).In the intestine of the common carp,the expression of Sglt1 mRNA and protein is gradually expanding as the diet glucose level increases.The Glut2 mRNA and protein of 30% and 50% groups were significantly higher than the other groups(P<0.05).At the same time,in 40%group,the expression of the proximal intestine was significantly higher than the mid intestine,and significantly higher than the distal intestine(P<0.05).Combined with the observation and measurement of the length of the villus,the proximal intestine was the main absorptive site of nutrients.In addition,the Sglt1 and Glut2 mRNA expression of correlation analysis showed that the Sglt1 and Glut2 mRNA expression was significantly positively correlated(P<0.05).The transport activity of glucose in the intestine of common carp increased with the increase in the diet glucose level.The effect of diet NaCl on Sglt1/Glut2 expression and activity in the intestinal of common carp(Cyprinus carpio L.)Respectively in the base purification diet adding different concentration of NaCl(0%,1%,3%,5%)production which was isonitrogenous and isoenergetic diets,and for a 70 days feeding experiment.After the experiment,the growth index,serum biochemical index,intestinal Sglt1 and Glut2 expression and transshipment activity were detected.The results showed that the optimum NaCl was 1%.Adding a moderate amount of salt to the diets is beneficial to the growth of the carp,but the high salt level reduces the survival rate of the carp.The increase in blood glucose content with salt increases(P<0.05),indicating that the high sodium content increases the blood glucose level.With the increase of diet NaCl level,the intestinal villus length significantly increased(P<0.05),which is beneficial to the absorption of nutrients of common carp,but too high NaCl content to the diets will cause intestinal damage.In each bowel segment,the expression of sglt1 and glut2 mRNA significantly increased with the increase of diet NaCl levels(P<0.05).At the same time,in the 1% group,the expression of sglt1 and glut2 mRNA in the proximal intestine of the common carp were significantly higher than in the mid and distal intestine.Sglt1 and glut2 mRNA expressions are positively correlated(P<0.05).Sglt1 gene expression and protein expression was increased with the increase of diet NaCl level increased(P<0.05),but the amount of Glut2 protein expression in the levels of NaCl,there was no significant difference between 3% and 5%(P<0.05).The transport activity of glucose in the intestine of the common carp increased(P<0.05)as the level of diet NaCl increased.The expression and transport activity of Sglt1/Glut2 in the intestine of common carp(Cyprinus carpio L.)during circadian rhythmFeeding affects the changes in blood glucose and stimulates changes in the expression of Sglt1 and Glut2 in the intestine,which in turn affects the absorption of intestinal glucose.The gene and protein expression of Sglt1 and Glut2 in the intestine of the carp were significantly circadian and rhythmic.In addition,a certain feeding rhythm was shown,and the expression of Sglt1 and Glut2 genes and protein decreased gradually after feeding.The transport activity of Sglt1 to glucose in the intestine of the carp is also the same as its expression,and there is also obvious circadian rhythm.