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MicroRNAs (miRs) are small non-coding RNAs that regulate the target gene expression. A change in miR profile in the pancreatic islets during diabetes is known, and multiple studies have demonstrated that miRs influence the pancreatic β-cell function. The miR-204 is highly expressed in the β-cells and reported to regulate insulin synthesis. Here we investigated whether the absence of miR-204 rescues the impaired glycemic control and obesity in the genetically diabetic (db/db) mice. We found that the db/db mice overexpressed miR-204 in the islets. The db/db mice lacking miR-204 (db/db-204 -/- ) initially develops hyperglycemia and obesity like the control (db/db) mice but later displayed a gradual improvement in glycemic control despite remaining obese. The db/db-204 -/- mice had a lower fasting blood glucose and higher serum insulin level compared to the db/db mice. A homeostatic model assessment (HOMA) suggests the improvement of β-cell function contributes to the improvement in glycemic control in db/db-204 -/- mice. Next, we examined the cellular proliferation and endoplasmic reticulum (ER) stress and found an increased frequency of proliferating cells (PCNA + ve) and a decreased CHOP expression in the islets of db/db-204 -/- mice. Next, we determined the effect of systemic miR-204 inhibition in improving glycemic control in the high-fat diet (HFD)-fed insulin-resistant mice. MiR-204 inhibition for 6 weeks improved the HFD-triggered impairment in glucose disposal. In conclusion, the absence of miR-204 improves β-cell proliferation, decreases islet ER stress, and improves glycemic control with limited change in body weight in obese mice., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The present study investigated the cytoprotective effects of cyanidin‑3‑glucoside (C3G), isolated from mulberry fruits, on the glucotoxicity‑induced apoptosis of pancreatic β‑cells to evaluate the antidiabetic effects of this compound. MIN6N pancreatic β‑cells were used to investigate the cytoprotective effects of C3G. In addition, the effects of C3G on the glucotoxicity‑induced apoptosis of pancreatic β‑cells was evaluated using MTT assay, immunofluorescent staining, flow cytometric and western blot analyses. The pancreatic β‑cells cultured under high glucose conditions exhibited distinct apoptotic features. C3G decreased the generation of intracellular reactive oxygen species, DNA fragmentation and the rate of apoptosis. C3G also prevented pancreatic β‑cell apoptosis induced by high glucose conditions by interfering with the intrinsic apoptotic pathways. In addition, C3G treatment resulted in increased insulin secretion compared with treatment with high glucose only. In conclusion, the results of the present study suggested that C3G obtained from mulberry fruits may be a potential phytotherapeutic agent for the prevention of diabetes.

The extract obtained from berries contains high amounts of anthocyanins, and this extract is used as a phytotherapeutic agent for different types of diseases. In this study, we examined the cytoprotective effects of cyanidin-3-glucoside (C3G) isolated from mulberry fruit against pancreatic β-cell apoptosis caused by hydrogen peroxide (H2O2)-induced oxidative stress. The MIN6 pancreatic β-cells were used to investigate the cytoprotective effects of C3G on the oxidative stress-induced apoptosis of cells. Cell viability was examined by MTT assay and lipid peroxidation was assayed by thiobarbituric acid (TBA) reaction. Immunofluorescence staining, flow cytometry and western blot analysis were also used to determine apoptosis and the expression of proteins associated with apoptosis. Our results revealed that H2O2 increased the rate of apoptosis by stimulating various pro-apoptotic processes, such as the generation of intracellular reactive oxygen species (ROS), lipid peroxidation, DNA fragmentation and caspase-3 activation. However, C3G reduced the H2O2-induced cell death in the MIN6N pancreatic β-cells. In addition, we confirmed that H2O2 activated mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK) and p38 MAPK. C3G inhibited the phosphorylation of ERK and p38 without inducing the phosphorylation of JNK. Furthermore, C3G regulated the intrinsic apoptotic pathway-associated proteins, such as proteins belonging to the Bcl-2 family, cytochrome c and caspase-3. Taken together, our results suggest that C3G isolated from mulberry fruit has potential for use as a phytotherapeutic agent for the prevention of diabetes by preventing oxidative stress-induced β-cell apoptosis.

Among the many environmental stresses, excessive production of reactive oxygen species (ROS) and the ensuring oxidative stress are known to cause significant cellular damage. This has clinical implications in the onset of type 1 diabetes, which is triggered by the destruction of pancreatic β-cells and is associated with oxidative stress. In this study, we investigated the protective and antioxidative effects of mulberry extract (ME) in insulin-producing pancreatic β-cells. We found that ME protects pancreatic β-cells against hydrogen peroxide (H2O2)-induced oxidative stress and the associated apoptotic cell death. ME treatment significantly reduced the levels of H2O2-induced 2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and lipid peroxidation and intracellular ROS accumulation. In addition, ME inhibited DNA condensation and/or fragmentation induced by H2O2. These results suggest that ME protects pancreatic β-cells against hydrogen peroxide-induced oxidative stress.

Reactive oxygen species (ROS) are key mediators of mammalian cellular damage and are associated with diseases such as aging, arteriosclerosis, inflammation, rheumatoid arthritis and diabetes. Type 1 diabetes develops upon the destruction of pancreatic β-cells, which is partly due to ROS activity. In this study, we investigated the cytoprotective and anti-oxidative effects of fractionated mulberry extracts in mouse insulin-producing pancreatic β-cells (MIN6N cells). Treatment with hydrogen peroxide (H2O2) induced significant cell death and increased intracellular ROS levels, lipid peroxidation and DNA fragmentation in the MIN6N cells. Fractionated mulberry extracts significantly reduced the H2O2-dependent production of intracellular ROS, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and lipid peroxidation. In addition, mulberry extracts inhibited DNA fragmentation induced by H2O2. Thus, the antioxidant properties of mulberry extracts in pancreatic β-cells may be exploited for the prevention or treatment of type 1 diabetes.

Reactive oxygen species (ROS) have been shown to cause DNA damage, protein denaturation, loss of antioxidative enzyme activity, and lipid peroxidation. Thus, ROS are associated with tissue damage and are considered to be prime contributing factors in inflammation, diabetes, aging, and cancer. In this study, we investigated whether or not hispidin protects pancreatic MIN6N β-cells from oxidative stress caused by hydrogen peroxide. Treatment of MIN6N β-cells with 0.5 mM hydrogen peroxide for 4 hours caused significant loss of cell viability and an increase in the number of apoptotic cells. However, pretreatment of MIN6N β-cells with hispidin for 24 hours reduced loss of cell viability and decreased the number of apoptotic cells. In addition, 70 μM hispidin significantly scavenged intracellular ROS and inhibited apoptosis and caspase-3 induced by hydrogen peroxide. Furthermore, the generation of thiobarbituric acid-reactive substances was inhibited in the presence of hispidin in a dose-dependent manner. Also, 70 μM hispidin significantly increased insulin secretion in hydrogen peroxide-treated MIN6N β-cells. These results suggest that hispidin may be effective for protecting MIN6N β-cells from ROS toxicity in diabetes.