OBJECTIVETo investigate the protective effect of losartan against angiotensin II (AngII)-induced beta cell (RIN-m) impairment and explore its mechanism.

METHODSIn vitro cultured RIN-m cells were divided into control group, 100 nmol/L AngII group and losartan pretreatment group. After cell incubation with the corresponding agents for 24 h, the amount of basal (3.3 mmol/L) and glucose-stimulated (16.7 mmol/L) insulin secretion (GSIS) was detected by radioimmunoassay, and the cellular reactive oxygen species (ROS) was assayed by flow cytometry with DCFH-DA staining; the mRNA and protein expressions of uncoupling protein 2 (UCP2) were determined by RT-PCR and Western blotting, respectively.

RESULTSThe basal insulin secretion showed no significant differences between the 3 groups (P>0.05). The GSIS in 100 nmol/L AngII group was significantly lower than that of the control group (P<0.001), but losartan pretreatment markedly restored the insulin secretion function to a level comparable to that of the control group (P<0.05). Compared with the control group, 100 nmol/L AngII significantly increased the cellular ROS level and the mRNA and protein expressions of UCP2 (P<0.05), and these changes were eliminated by losartan pretreatment.

CONCLUSIONSLosartan pretreatment offers protective effect against AngII-induced impairment of the GSIS of beta cells possibly by antagonizing the effects of AngII that causes increased ROS level and UCP2 expressions in beta-cells.