Objective To investigate the effects of RNA interference (RNAi) targeting angiotensinconverting enzyme (ACE) on blood glucose,insulin resistance,as well as oxidative stress in type 2 diabetic rats.Methods Type 2 diabetic rats were divided into diabetes control group (caudal intravenation with control adenovirus named Ad5),gene treatment group (caudal intravenation with recombinant adenoviral vectors named Ad5-ACE-shRNA,expressing ACE gene-specific shRNA),and enalapril group (intragastric administration with enalapril every day).At the same time,the normal blood glucose control group was set up.All rats were injected two times during the experiment period.Blood glucose was measured before and after the intervention.At the third day of the experiment,expressions of ACE mRNA and protein in pancreas were evaluated by RT-PCR and Western blot,and serum concentrations of ACE and Ang Ⅱ were measured by ELISA.By the end of the experiment,insulin sensitivity index was calculated and expressions of glucose transporter 4 (GLUT4) protein of epididymal adipose tissue and NAD (P) H (p22phox) protein of pancreas were measured.Results Blood glucose levels in the gene treatment group [(17.8 ±1.1) mmol/L] and the enalapril group [(17.9 ± 1.2) mmol/L] were lower than that in the diabetes control group [(24.9 ± 1.3) mmol/L] when the experiment was finished.ACE mRNA and protein expressions in pancreas of the gene treatment group were significantly decreased compared with the diabetes control group (P ＜ 0.05).Serum concentrations of ACE and Ang Ⅱ in the gene treatment group were (16.37 ± 3.01) ng/ml and (18.24 ± 3.69)pg/ml,significantly lower than those of the diabetes control group [(46.67 ± 3.92) ng/ml and (44.93 ± 4.12) pg/ml respectively,both P＜0.05].Insulin sensitivity indexes of the gene treatment group and the enalapril group were (-5.14 ± 0.41) and (-5.17 ± 0.38),being all significantly higher than that of the diabetes control group (-6.18 ±0.46,both P＜0.05).Expressions of GLUT4 protein in epididymal adipose tissue were higher and expressions of p22phox protein in pancreas were lower in the gene treatment group and the enalapril group than those of the diabetes control group (both P＜0.05).Conclusions RNAi targeting ACE gene may delay the progress of hyperglycaemia and improve the situation of insulin resistance and oxidative stress.The RNAi technology may be used as a new strategy of gene therapy for diabetes mellitus.