Expression of retinol-binding protein 4 and phosphatidylinositol 3 kinase in insulin resistant rats and the role of pioglitazone intervention / 中华老年医学杂志

ABSTRACT

Objective To observe the expression of retinol-binding protein 4 (RBP4) and phosphatidylinositol 3 kinase (PI3K) in insulin resistant (IR) rats and the role of pioglitazone intervention. MethodsThirty-five male Wistar rats in SPF level were randomly divided into control fed with normal diet (n= 11 ) and IR model fed with high fat sucrose diet (HFSD) (n= 24). The IR rats were then randomly divided into two subgroups, namely IR fed with HFSD(n = 12) and pioglitazone intervention (n= 12) given a daily dose of 20 mg · kg 1 · d-1 pioglitazone and HFSD (IR +Pio group )for 8 weeks.All rats were killed after 16 weeks and the levels of serum TG, high density lipoprotein (HDL-C), low density lipoprotein (LDL-C), fasting blood-glucose (FBG), fasting serum insulin (FIns) and insulin resistance index (HOME-1R) were measured.Enzyme-linked immunosorbent assay (ELISA) and RT-PCR were employed to detect the level of serum RBP4 and the mRNA expression of RBP4 in the epididymis adipose tissues, respectively. Immunohistochemistry was used to detect the protein expression of PI3K in skeletal muscles while UV spectrophotometer was employed to measure level of serum AOPP. The ratio of visceral fat weight of mesentery, epididymis and peritoneum in abdominal cavity to body weight (BW) was calculated. Results(1) the level of BW, TG, LDL-C, FINS and the ratio of visceral fat weight to BW were higher in IR group than in control group, but HDL-C decreased significantly. After the intervention of pioglitazone, the level of BW,TG, LDL-C, FINS, and the ratio of visceral fat weight to BW in IR+Pio group were lower and HDL-C increased significantly than those in IR group.(2) The level of RBP4 from serum and epididymis adipose and serum AOPP were higher in IR group than in control and lower significantly in IR+Pio group than in IR group (all P＜0.05). (3) The expression of PI3K in skeletal muscles were lower in IR group than in NC group, and increased after the invention of pioglitazone. (4) FIns, the ratio of visceral fat weight to BW and LDL-C were positively correlated with RBP4 while HDL-C and PI3K negatively correlated with RBP4. Conclusions(1) The increased RBP4 can lead to metabolic disturbances and oxidative stress in IR rats.(2) RBP4 may decrease the insulin sensibility by weakening insulin signal transduction. (3) Pioglitazone can ameliorate insulin resistance by decreasing the level of RBP4 and serum AOPP and increasing the level of PI3K in skeletal muscles of IR rats.