Pioglitazone/metformin adduct regulates insulin secretion and inhibits high glucose‐induced apoptosis via p21‐p53‐MDM2 signaling in INS‐1 cells

microRNA-206 Regulates Pancreatic-β-Cell Function via Targeting Insulin-Like Growth Factor 1

Background: Diabetes mellitus (DM), a common metabolic disease, is featured with chronic hyperglycemia and dysfunction of pancreatic β-cells. Various evidences suggested that microRNAs (miR-NAs) were tightly related to the occurrence of DM and can be regulated in pancreatic-β-cells. However, whether or not microRNA-206 (miR-206) affects the development of DM and the specific mechanisms remains elusive. We designed this study to clarify the function and associated potential mechanism of miR-206 in pancreatic β-cells via the insulin-like growth factor 1 reporter (IGF1R)/phosphatidylinositide 3-kinase (PI3 K)/protein kinase B (AKT) signaling pathway, which may provide novel diagnostic or therapies for DM. Methods: In this research, the levels of miR-206 and insulin-like growth factor 1 (IGF1) were assessed using quantitative reverse transcription PCR (qRT-PCR) and/or Western bolt assay. Bioinformatics and dual luciferase reporter assays were adopted to illustrate the relationship between miR-206 and IGF1. INS-1 cells were stimulated with stimulatory glucose (16.7 mM) or basal glucose (3.3 mM) for 1 h, and the insulin content was examined by enzyme linked immunosorbent assay (ELISA). Besides, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry (FCM) analysis were conducted to determine the INS1 cell viability and apoptosis. Furthermore, the related proteins in IGF1R/PI3 K/AKT pathway (IGF1R, p-AKT and AKT) were tested using Western blot assay, respectively. Results: Our data suggested that miR-206 level in the blood samples of DM patients was higher than that in healthy donors. IGF1 was identified as a direct target of miR-206. Moreover, we found that miR-206 negatively regulated IGF1 expression in INS-1 cells. It was also confirmed that miR-206 inhibitor led to an increase of total insulin content, an increase of INS-1 cell viability and a decrease of cell apoptosis. Accordingly, miR-206 inhibitor significantly enhanced IGF1R and p-AKT protein expression in INS-1 cells. All these findings were reversed by IGF1-siRNA co-transfection. Conclusion: Our observations clearly demonstrated that miR-206 could regulate the IGF1R/PI3K/AKT pathway by targeting IGF1, thereby regulating the cell viability of pancreatic β cells and the ability of pancreatic β cells to secrete insulin.

MicroRNA‑532‑5p regulates oxidative stress and insulin secretion damage in high glucose‑induced pancreatic β cells by downregulating the expression levels of CCND1

Diabetes mellitus is a metabolic disorder caused by insufficient insulin secretion. The expression of microRNA (miR)-532-5P is downregulated in diabetes, but its specific role in diabetes has not yet been elucidated. The present study aimed to investigate the specific mechanism underlying the effects of miR-532-5p on diabetes. Cell viability was determined using an MTT assay. The expression levels of miR-532-5P, cyclin D1 (CCND1), Insulin1 and Insulin2 were detected using reverse transcription-quantitative PCR. The expression of miR-532-5p and CCND1 were overexpressed in cells by cell transfection. ELISA was used to detect insulin secretion. 2′,7′-dichlorodihydrofluorescein diacetate was used to quantify reactive oxygen species levels in cells. Apoptosis was detected using a TUNEL assay. Western blotting was performed to detect the expression of apoptosis-related proteins, CCND1 and p53. A dual-luciferase reporter assay was conducted, and verified the targeted binding of miR-532-5p and CCND1. The expression of miR-532-5p was downregulated in high glucose (HG)-induced MIN6 cells. Overexpression of miR-532-5p could improve the HG-induced decline in insulin secretion and inhibit HG-induced oxidative stress and apoptosis in cells. miR-532-5p can target and regulate the expression of CCND1. Overexpression of miR-532-5p downregulated HG-induced cell insulin secretion, oxidative stress and apoptosis by downregulating CCND1, which is involved in regulating the expression of p53. To conclude, miR-532-5p regulated oxidative stress and insulin secretion damage in HG-induced pancreatic β cells by downregulating the expression of CCND1, which is involved in the upregulation of the expression of p53.

Enhanced proliferation inhibition and apoptosis in glioma cells elicited by combination of irinotecan and imatinib

Glioma is a kind of lethal malignant tumor, and lacks efficient therapies. Combination therapy has been claimed to be a promising approach to combat cancer, due to its increased anti-cancer effects and reduced side effects. This study aimed to investigate the anti-cancer effect and mechanism of combining imatinib with irinotecan or its active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38). First, we found that this drug combination exerted synergistic antitumor effects against glioma in vitro and in vivo. In addition, flow cytometry results proved that the SN-38-induced apoptosis was further enhanced by imatinib, and similar results were observed by determining the protein expression levels of apoptosis biomarkers. Interestingly, p53 expression was elevated by the SN-38 mono-treatment, and was not further increased after the co-treatment; besides, knockdown of p53 could only reduce the expression of cleaved-PARP partially, and weaken the enhanced proliferation inhibition induced by SN-38 plus imatinib, indicating that there might be other factors involved in the synergistic effects besides p53. Meanwhile, the markedly elevated p21 expression was observed only in the combination group, instead of the mono-treated groups. According to the results of p21 knockdown, we found that p21 was also required for the synergistic inhibitory effects. Moreover, we explored and ruled out the possibility of imatinib enhancing the sensitivity of irinotecan by inhibiting drug efflux pumps. Thus, our findings collectively suggest that combining irinotecan with imatinib could be a promising new strategy to fight against glioma.