The Alteration Of Expression Of The MRNAs Of Specific Insulin Signaling Molecules In Peripheral Leukocytes From Insulin-Resistant Rats And The Protecting Role Of Aminoguanidine

Objectives: To study the alteration of the expression of the mRNAs of specific insulin signaling molecules and inducible nitric oxide synthase (iNOS) in peripheral leukocytes from insulin-resistant rats fed with sucrose and supplemented with aminoguanidine(AG). And by evaluating the alteration of the plasma biochemistry in the rats, to explore the pathogenesis of insulin resistance and the protection mechanism of AG at transcription level.Methods: Wistar rats were randomly divided into the control group, the sucrose fed group and the AG -supplemented group. The expression of the mRNAs of iNOS, insulin receptor (IR), phosphatidylinositol-3-kinase (PI-3K) P85a subunit, protein kinase Ba (PKBa), protein kinase Bβ (PKBP) and glucose transporter 2 (GLUT2) in peripheral leukocytes from the rats was determined by an optimized in situ hybridization method designed by our laboratory with the blood obtained by the tail cut method every month for 6 months. The fasting plasma glucose, plasma insulin, plasma glycosylated serum protein (GSP) and nitric oxide (NO) were detected every month. At last, analysis of the difference of plasma biochemistry and the expression of mRNAs of iNOS and insulin signaling molecules among the three groups was performed. Results: The plasma levels of glucose, insulin, NO and GSP were higher and insulin sensitivity was lower in sucrose fed group than in control group. The expression of iNOS mRNA and PKBa mRNA in peripheral leukocytes was higher and theexpression of IR mRNA, PI-3K P85ct subunit mRNA, PKBp mRNA was lower in sucrose fed group, and there was no statistic difference of the expression of GLUT2 mRNA between the two groups.The results obtained as to plasma biochemistry and the expression of mRNAs of the signal molecules in peripheral leukocytes in AG-supplemented group were similar to which in sucrose fed group compared with control group. While the plasma NO was lower and the expression of IR mRNA in peripheral leukocytes was higher in AG-supplemented group than in sucrose fed group after 2 months. The plasma glucose and GSP were lower in AG-supplemented group after 5 months. The expression of iNOS mRNA and PKBa mRNA in peripheral leukocytes was lower in AG-supplemented group, and the latter declined to normal after 5 months. The expression of PI-3K P85a subunit mRNA and PKBp mRNA was higher, and the former increased to normal on the 6th month. And the insulin sensitivity was higher in AG-supplemented group on the 6th month. There was no difference between the two groups as for plasma insulin and the expression of GLUT2 mRNA in peripheral leukocytes.Conclusions: 1. High sucrose feeding can lead to insulin resistance, overexpression of iNOS mRNA in peripheral leukocytes, and high plasma levels of GSP and NO in Wistar rats.2. High sucrose feeding can cause a change in the expression profile of the mRNAs of key insulin signaling molecules in peripheral leukocytes: the expression of the mRNAs of IR, PI-3K P85a subunit and PKBP decreases, contributing to the onset of insulin resistance; the expression of PKBa mRNA increases, playing a certain compensating role; while the expression of GLUT2 mRNA remains unchanged.3. AG can cause a decrease of the plasma NO by inhibiting iNOS activity and iNOS mRNA expression in peripheral leukocytes, promote the expression of the mRNAs of IR, PI-3K P85ot subunit and PKBp and prevent the overexpression of PKBa mRNA, which enhance the insulin sensitivity in peripheral tissues and attenuate hyperglycemia and high plasma GSP. In this way, AG prevents and treats insulin resistance effectively.