Liraglutide treatment promotes beta cells proliferation via regulation of microRNA expression

Abstract

Objective To investigate the effect of glucagon-like peptide 1 analogue liraglutide on microRNA expression of db/db mice and rat insulinoma cell line(INS-1). Methods Twenty 4-week old male db/db mice were randomly assigned to receive a subcutaneous injection of liraglutide(300 ng/g bid)or normal saline (0.1 ml bid)(control group) according to random numbers table. Glycated hemoglobin (HbA1c) was determined before and after 8 weeks of intervention. At the end of the intervention, intraperitoneal glucose tolerance test (IPGTT) was performed. Beta cells proliferation rate was determined by using immunohistochemistry methods. INS-1 cells were cultured with 0.5 mmol/L palmitic acid for 0, 48, 72 h or treated by 100 nmol/L liraglutide for 12 h before 72 h of palmitic acid(0.5 mmol/L) culture. microRNA miR-375 and miR-34a expression were examined by real-time polymerase chain reaction(RT-PCR). The t test or ANOVA analysis was used for data analysis. Results Compared with the control group, HbA1c in the liraglutide group was significantly lower (7.3%±0.3% vs 4.7%±0.6%, t=16.47, P<0.01); the glucose aera under curve in the liraglutide group was decreased significantly((4568±197) vs (1927±127) mmol·L-1·min-1,t=26.53, P<0.05), while insulin aera under curve was increased significantly ((1080±247) vs(2818±378)μg·L-1·min-1,t=7.73, P<0.05). Immunohistochemistry showed more insulin staining in single pancreas of db/db mice after liraglutide treatment than in the control group (1.40±0.30 vs 0.37±0.09, t=19.14, P<0.01). More Brdu-positive cells were observed in islets of liraglutide-treated mice than in control mice after intervention(2.40%±0.22% vs 0.73%±0.10%, t=4.97, P<0.01). Compared with control mice, the miR-375 expression of pancreas in liraglutide-treated db/db mice was reduced by 50%(1.1±0.3 vs 2.2±0.5, t=3.08, P<0.05) and miR-34a was reduced by 71%(1.1±0.3 vs 3.8±1.2, t=2.80, P<0.05). In addition, the miR-375 expression of INS-1 cells was up-regulated dose- and time-dependently in response to palmitic acid; and palmitic acid-induced miR-375 expression was suppressed by liraglutide in vitro(F=7.20, P<0.01). Conclusion Liraglutide may preserve beta-cell proliferation in response to lipotoxicity through a regulation of miRNA. Key words: Liratglutide; Islet beta-cells; MicroRNAs