The Effectcs Of Berberine On The Expression Of RBP4and The Level Of Phospho-IRS-1in Rats Fed On High Fat

Objective:The discovery of the new function of RBP4provided the treatment target oninsulin resistance and diabetes.Berberine had effects of increasing insulinsensitivity.Animal experiments showed improvement of insulin sensitivity couldlower the serum level of RBP4, so we hypothesized that Berberine also could havethis effect via animal experiments, this study discussed:1. The change of RBP4in serum, liver of IGT rats fed on high fat.2.The influence of berberines on the expression of RBP4in serum, liver and the levelof Phospho-IRS-1in muscular tissue of IGT rats fed on high fat.Materials and methods:Thirty male SD rats in SPF level were randomly divided into controlfed with normal diet(NC,n=10) and model group fed with high fat diet （F,n=20）.Themodel group rats were then randomly divided into two subgroups, namely model ratfed with high fat die（tFC,n=10) and berberine intervention (BBR,n=10) given a dailydose of150mg·kg1d-1berberine for8weeks. All rats were killed after16weeksand the levels of serum TC,TG, high density lipoprotein (HDL-C), low densitylipoprotein (LDL-C), fasting blood-glucose (FBG), fasting serum insulin (FIns) andinsulin resistance index (HOMA-IR) were measured.Serum RBP4and INS wereanalyzed by Enzyme-linked immunosorbent assay (ELISA);RT-PCR and western blotwere employed to detect the level of the mRNA expression of RBP4and RBP4protein in the liver tissues, respectively. Enzyme-linked immunosorbent assay(ELISA) was used to detect the level of Phospho-IRS-1in muscles tissues.Results(1) The level of BW,TC,TG,LDL-C,FBG,FINS and HOMA-IR were higher in FCgroup than in control group, but HDL-C decreased significantly. After the intervention of berberines, the level of BW,TC,TG, LDL-C, FBG,FINS andHOMA-IR in BBR group were lower and HDL-C increased significantly than thosein FC group.(2)The level of RBP4from serum and liver were higher in FC group than in controland lower significantly in berberine group than in FC group (all P value <0.05).(3)The level of Phospho-IRS-1in muscles tissues were lower in FC group than in NCgroup, and increased after the invention of berberine.(4) FINS、HOMA-IR and LDL-C were positively correlated with RBP4while HDL-Cand the level of Phospho-IRS-1negatively correlated withRBP4.Conclusions(1) The increased RBP4can lead to metabolic disturbances in IGT rats.(2) RBP4may decrease the insulin sensibility by weakening insulin signaltransduction.(3)Berberine can ameliorate insulin resistance by decreasing the level of RBP4andincreasing the level of Phospho-IRS-1in muscles tissues of IGT rats.(4) In IGT state, the liver might be a main source for serumRBP4.However, because we did not assay the RBP4expressions in other tissues,such as adipocytes,muscules and kidney,we could not exclude the contribution ofother tissues to serum RBP4in the state of IGT, and the influence of berberineagonist on RBP4expression in those tissues.