Lycopene is an antioxidant which has potential anti-diabetic activity, but the cellular mechanisms have not been clarified. In this study, different concentrations of lycopene were used to treat pancreatic alpha and beta cell lines, and the changes of cell growth, cell apoptosis, cell cycle, reactive oxygen species (ROS), ATP levels and expression of related cytokines were determined. The results exhibited that lycopene did not affect cell growth, cell apoptosis, cell cycle, ROS and ATP levels of alpha cells, while it promoted the growth of beta cells, increased the ratio of S phase, reduced the ROS levels and increased the ATP levels of beta cells. At the same time, lycopene treatment elevated the mRNA expression levels of tnfα, tgfβ and hif1α in beta cells. These findings suggest that lycopene plays cell-specific role and activates pancreatic beta cells, supporting its application in diabetes therapy.
Adenosine Triphosphate ; metabolism ; Apoptosis ; Carotenoids ; pharmacology ; Cell Cycle ; Cells, Cultured ; Cytokines ; metabolism ; Glucagon-Secreting Cells ; drug effects ; Humans ; Insulin-Secreting Cells ; drug effects ; Lycopene ; pharmacology ; Reactive Oxygen Species ; metabolism

Nesidioblastosis is a term used to describe pathologic overgrowth of pancreatic islet cells. It also means maldistribution of islet cells within the ductules of exocrine pancreas. Generally, nesidioblastosis occurs in beta-cell and causes neonatal hyperinsulinemic hypoglycemia or adult noninsulinoma pancreatogenous hypoglycemia syndrome. Alpha-cell nesidioblastosis and hyperplasia is an extremely rare disorder. It often accompanies glucagon-producing marco- and mircoadenoma without typical glucagonoma syndrome. A 35-year-old female was referred to our hospital with recurrent acute pancreatitis. On radiologic studies, 1.5 cm sized mass was noted in pancreas tail. Cytological evaluation with EUS-fine-needle aspiration suggested serous cystadenoma. She received distal pancreatectomy. The histologic examination revealed a 1.7 cm sized neuroendocrine tumor positive for immunohistochemical staining with glucagon antibody. Multiple glucagon-producing micro endocrine cell tumors were scattered next to the main tumor. Additionally, diffuse hyperplasia of pancreatic islets and ectopic proliferation of islet cells in centroacinar area, findings compatible to nesidioblastosis, were seen. These hyperplasia and almost all nesidioblastic cells were positive for glucagon immunochemistry. Even though serum glucagon level still remained higher than the reference value, she has been followed-up without any evidence of recurrence or hormone related symptoms. Herein, we report a case of alpha-cell nesidioblastosis and hyperplasia combined with glucagon-producing neuroendocrine tumor with literature review.
Adult ; Chromogranin A/blood ; Female ; Glucagon/*metabolism ; Glucagon-Secreting Cells/metabolism ; Humans ; Hyperplasia/complications/*diagnosis ; Islets of Langerhans/metabolism/ultrasonography ; Nesidioblastosis/complications/*diagnosis ; Neuroendocrine Tumors/complications/*diagnosis/pathology ; Pancreas/*pathology ; Tomography, X-Ray Computed

Oxidative stress induced by chronic hyperglycemia in type 2 diabetes plays a crucial role in progressive loss of beta-cell mass through beta-cell apoptosis. Glucagon like peptide-1 (GLP-1) has effects on preservation of beta-cell mass and its insulin secretory function. GLP-1 possibly increases islet cell mass through stimulated proliferation from beta-cell and differentiation to beta-cell from progenitor cells. Also, it probably has an antiapoptotic effect on beta-cell, but detailed mechanisms are not proven. Therefore, we examined the protective mechanism of GLP-1 in beta-cell after induction of oxidative stress. The cell apoptosis decreased to ~50% when cells were treated with 100 microM H2O2 for up to 2 hr. After pretreatment of Ex-4, GLP-1 receptor agonist, flow cytometric analysis shows 41.7% reduction of beta-cell apoptosis. This data suggested that pretreatment of Ex-4 protect from oxidative stress-induced apoptosis. Also, Ex-4 treatment decreased GSK3beta activation, JNK phosphorylation and caspase-9, -3 activation and recovered the expression of insulin2 mRNA in beta-cell lines and secretion of insulin in human islet. These results suggest that Ex-4 may protect beta-cell apoptosis by blocking the JNK and GSK3beta mediated apoptotic pathway.
Animals ; *Apoptosis ; Caspase 3/metabolism ; Caspase 9/metabolism ; Cells, Cultured ; Cricetinae ; Flow Cytometry ; Glucagon-Like Peptide 1/pharmacology ; Glycogen Synthase Kinase 3/*metabolism ; Humans ; Hydrogen Peroxide/toxicity ; Insulin/genetics/metabolism ; Insulin-Secreting Cells/drug effects/*enzymology/metabolism ; JNK Mitogen-Activated Protein Kinases/*metabolism ; *Oxidative Stress ; Peptides/*pharmacology ; Phosphorylation ; Receptors, Glucagon/agonists/metabolism ; Signal Transduction ; Venoms/*pharmacology

Type 1 diabetes mellitus is caused by the autoimmune destruction of beta cells within the islets. In recent years, innate immunity has been proposed to play a key role in this process. High-mobility group box 1 (HMGB1), an inflammatory trigger in a number of autoimmune diseases, activates proinflammatory responses following its release from necrotic cells. Our aim was to determine the significance of HMGB1 in the natural history of diabetes in non-obese diabetic (NOD) mice. We observed that the rate of HMGB1 expression in the cytoplasm of islets was much greater in diabetic mice compared with non-diabetic mice. The majority of cells positively stained for toll-like receptor 4 (TLR4) were beta cells; few alpha cells were stained for TLR4. Thus, we examined the effects of anti-TLR4 antibodies on HMGB1 cell surface binding, which confirmed that HMGB1 interacts with TLR4 in isolated islets. Expression changes in HMGB1 and TLR4 were detected throughout the course of diabetes. Our findings indicate that TLR4 is the main receptor on beta cells and that HMGB1 may signal via TLR4 to selectively damage beta cells rather than alpha cells during the development of type 1 diabetes mellitus.
Animals ; Diabetes Mellitus, Type 1/immunology/*metabolism/pathology ; Female ; Gene Expression Regulation ; Glucagon-Secreting Cells/immunology/metabolism/pathology ; HMGB1 Protein/*genetics/metabolism ; Humans ; Immunity, Innate ; Insulin-Secreting Cells/immunology/metabolism/*pathology ; Macrophages/immunology/pathology ; Mice ; Mice, Inbred C57BL ; Mice, Inbred NOD ; Necrosis ; Protein Binding ; Signal Transduction ; Toll-Like Receptor 4/*antagonists & inhibitors/genetics/immunology

BACKGROUNDGlucagon-like peptide-1 (GLP-1) reduces fatty acid-induced beta-cell lipotoxicity in diabetes; however, the explicit mechanisms underlying this process are not fully understood. This study was designed to investigate the involvement of microRNA, which regulates gene expression by the sequence-specific inhibition of mRNA transcription in the GLP-1 mediation of beta-cell function.

METHODSThe cell viability and apoptosis were determined using an methyl thiazoleterazolium (MTT) assay and flow cytometry. The expression of genes involved in beta-cell function, including microRNA-34a and sirtuin 1, were investigated using real-time PCR. The underlying mechanisms of microRNA-34a were further explored using cell-transfection assays.

RESULTSA 24-hours incubation of INS-1 cells with palmitate significantly decreased cell viability, increased cell apoptosis and led to the activation of microRNA-34a and the suppression of sirtuin 1. A co-incubation with GLP-1 protected the cells against palmitate-induced toxicity in association with a reduction in palmitate-induced activation of microRNA-34a. Furthermore, palmitate-induced apoptosis was significantly increased in cells that were infected with microRNA-34a mimics and decreased in cells that were infected with microRNA-34a inhibitors.

CONCLUSIONMicroRNA-34a is involved in the mechanism of GLP-1 on the modulation of beta-cell growth and survival.

Animals ; Apoptosis ; drug effects ; Cell Line ; Cell Survival ; drug effects ; Fatty Acids, Nonesterified ; toxicity ; Glucagon-Like Peptide 1 ; pharmacology ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; MicroRNAs ; genetics ; metabolism ; Palmitic Acid ; pharmacology ; Rats ; Real-Time Polymerase Chain Reaction

To explore the effect of glucagon-like peptide-1 receptor agonist--Exendin-4 (Ex-4) on murine MIN6 pancreatic beta-cells apoptosis induced by oxidative stress, the morphological changes of cell damage were evaluated by epifluorescence microscopy after staining with AO-EB. The percentage of cell apoptosis was determined by flow cytometric assay after Annexin-V-FITC-PI staining. Nitric oxide level was measured by Griess reagent assay. Inducible nitric oxide synthase (iNOS) protein and NF-kappaBp65 fragment were detected by Western blotting. Ex-4 inhibited the increase of nitrite level and percentage of apoptosis induced by t-BHP in MIN6 cells. Furthermore, Ex-4 partly reduced the expression of iNOS protein and the ratio of NF-kappaBp65 protein in nucleus:cytosol induced by t-BHP. These results suggest that Ex4 protects MIN6 pancreatic kappa-cells from oxidative stress-induced apoptosis via down-regulation of NF-kappaB-iNOS-nitric oxide pathway.
Animals ; Apoptosis ; drug effects ; Down-Regulation ; Glucagon-Like Peptide-1 Receptor ; Hypoglycemic Agents ; pharmacology ; Incretins ; agonists ; Insulin-Secreting Cells ; cytology ; metabolism ; Lizards ; Mice ; Nitric Oxide ; metabolism ; Nitric Oxide Synthase Type II ; metabolism ; Oxidative Stress ; drug effects ; Peptides ; pharmacology ; Receptors, Glucagon ; agonists ; Signal Transduction ; Transcription Factor RelA ; metabolism ; Venoms ; pharmacology ; tert-Butylhydroperoxide ; pharmacology

BACKGROUNDUncoupling protein (UCP) 2 is related to the dysfunction of beta cells induced by fatty acids. However, whether UCP2 has similar effects on alpha cell is still not clear. This study aimed to investigate the effects of UCP2 and its possible mechanisms in lipotoxicity-induced dysfunction of pancreatic alpha cells.

METHODSThe alpha TC1-6 cells were used in this study to evaluate the effects of palmitate and/or UCP2 inhibit factors on the glucagon secretory function, glucagon content, the glucagon mRNA level and the nitrotyrosine level in the supernatant. Meantime, the expression levels of UCP2 and peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1 alpha) were measured by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. Furthermore, the possible relationship between UCP2 and insulin signal transduction pathway was analyzed.

RESULTSPalmitate stimulated alpha cell glucagon secretion and the expression of UCP2 and PGC-1 alpha, which could be partially decreased by the inhibition of UCP2. Palmitate increased nitrotyrosine level and suppressed insulin signal transduction pathway in alpha cells. Inhibition of UCP2 influenced the effects of free fatty acid on alpha cells and may relate to glucagon secretion.

CONCLUSIONUCP2 played an important role on alpha cell dysfunction induced by free fatty acid in vitro, which may be related to its effects on oxidative stress and insulin signal transduction pathway.

Animals ; Cells, Cultured ; Glucagon ; secretion ; Glucagon-Secreting Cells ; drug effects ; physiology ; Insulin ; pharmacology ; Insulin Receptor Substrate Proteins ; metabolism ; Ion Channels ; genetics ; physiology ; Iridoid Glycosides ; pharmacology ; Iridoids ; Mice ; Mitochondrial Proteins ; genetics ; physiology ; Oxidative Stress ; Palmitic Acid ; toxicity ; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha ; Phosphorylation ; RNA, Messenger ; analysis ; Signal Transduction ; Trans-Activators ; genetics ; physiology ; Transcription Factors ; Tyrosine ; analogs & derivatives ; metabolism ; Uncoupling Protein 2

Metformin has been reported to increase the expression of the glucagon-like peptide-1 (GLP-1) receptor in pancreatic beta cells in a peroxisome proliferator-activated receptor (PPAR)-alpha-dependent manner. We investigated whether a PPARalpha agonist, fenofibrate, exhibits an additive or synergistic effect on glucose metabolism, independent of its lipid-lowering effect, when added to metformin. Non-obese diabetic Goto-Kakizaki (GK) rats were divided into four groups and treated for 28 days with metformin, fenofibrate, metformin plus fenofibrate or vehicle. The random blood glucose levels, body weights, food intake and serum lipid profiles were not significantly different among the groups. After 4 weeks, metformin, but not fenofibrate, markedly reduced the blood glucose levels during oral glucose tolerance tests, and this effect was attenuated by adding fenofibrate. Metformin increased the expression of the GLP-1 receptor in pancreatic islets, whereas fenofibrate did not. During the intraperitoneal glucose tolerance tests with the injection of a GLP-1 analog, metformin and/or fenofibrate did not alter the insulin secretory responses. In conclusion, fenofibrate did not confer any beneficial effect on glucose homeostasis but reduced metformin's glucose-lowering activity in GK rats, thus discouraging the addition of fenofibrate to metformin to improve glycemic control.
Animals ; Blood Glucose/metabolism ; Body Weight/drug effects ; Diabetes Mellitus, Experimental/*drug therapy/*metabolism ; Drug Therapy, Combination ; Feeding Behavior/drug effects ; Fenofibrate/*pharmacology/therapeutic use ; Glucagon-Like Peptide 1/agonists/metabolism ; Glucose/*metabolism ; Glucose Tolerance Test ; Homeostasis/*drug effects ; Immunohistochemistry ; Injections, Intraperitoneal ; Insulin-Secreting Cells/drug effects/metabolism/pathology ; Lipid Metabolism/drug effects ; Male ; Metformin/*pharmacology/therapeutic use ; Peptides/administration & dosage/pharmacology ; Rats ; Receptors, Glucagon/metabolism ; Venoms/administration & dosage/pharmacology

Glucagon-like peptide-1 (GLP-1) is a potent glucoincretin hormone and an important agent for the treatment of type 2 diabetes. Here we demonstrate that B-cell translocation gene 2 (BTG2) is a crucial regulator in GLP-1-induced insulin gene expression and insulin secretion via upregulation of pancreatic duodenal homeobox-1 (PDX-1) in pancreatic beta-cells. GLP-1 treatment significantly increased BTG2, PDX-1 and insulin gene expression in pancreatic beta-cells. Notably, adenovirus-mediated overexpression of BTG2 significantly elevated insulin secretion, as well as insulin and PDX-1 gene expression. Physical interaction studies showed that BTG2 is associated with increased PDX-1 occupancy on the insulin gene promoter via a direct interaction with PDX-1. Exendin-4 (Ex-4), a GLP-1 agonist, and GLP-1 in pancreatic beta-cells increased insulin secretion through the BTG2-PDX-1-insulin pathway, which was blocked by endogenous BTG2 knockdown using a BTG2 small interfering RNA knockdown system. Finally, we revealed that Ex-4 and GLP-1 significantly elevated insulin secretion via upregulation of the BTG2-PDX-1 axis in pancreatic islets, and this phenomenon was abolished by endogenous BTG2 knockdown. Collectively, our current study provides a novel molecular mechanism by which GLP-1 positively regulates insulin gene expression via BTG2, suggesting that BTG2 has a key function in insulin secretion in pancreatic beta-cells.
Animals ; Gene Expression Regulation/drug effects ; Glucagon-Like Peptide 1/*pharmacology ; Homeodomain Proteins/*genetics/metabolism ; Humans ; Immediate-Early Proteins/genetics/*metabolism ; Insulin/genetics/*secretion ; Insulin-Secreting Cells/drug effects/*metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Peptides/pharmacology ; Promoter Regions, Genetic/genetics ; Protein Binding/drug effects/genetics ; Rats ; Trans-Activators/*genetics/metabolism ; Tumor Suppressor Proteins/genetics/*metabolism ; Venoms/pharmacology

OBJECTIVETo observe the effect of glucagon-like peptide-1 (GLP-1) on interleukin-1β (IL-1β)-induced damage in INS-1 cells and explore its possible mechanisms.

METHODSINS-1 cells were divided into normal control group, IL-1β group, and GLP-1+IL-1β group with corresponding treatments. The cell viability was determined by MTT assay, the expression of IKKβ mRNA was detected by real-time PCR, and that of the protein p65 was detected by Western blotting.

RESULTSIn comparison with the normal control group, the cells in the IL-1β group showed a significantly decreased viability by 29% (P < 0.01); compared with those in IL-1β group, the cells in GLP-1+IL-1β group exhibited an significant increase in the cell viability by 30% (P < 0.01). In comparison with the normal control group, the cells in IL-1β group showed an significantly increased expression of IKKβ mRNA (1.967 ± 0.091 vs 1 ± 0, P < 0.05); GLP-1 significantly reduced IL-1β-induced increment of IKKβ mRNA expression to 1.287 ± 0.084 (P < 0.05). IL-1β treatment significantly increased NF-κB protein expression as compared to the control level (0.814 ± 0.111 vs 0.396 ± 0.026, P < 0.01), and GLP-1 significantly inhibited such effect (0.622 ± 0.059, P < 0.05).

CONCLUSIONSGLP-1 inhibits IL-1β-induced β-cell damage probably by inhibiting the NF-κB pathway.

Cell Line ; Cell Survival ; Glucagon-Like Peptide 1 ; pharmacology ; Humans ; I-kappa B Kinase ; genetics ; metabolism ; Insulin-Secreting Cells ; cytology ; pathology ; Interleukin-1beta ; antagonists & inhibitors ; pharmacology ; NF-kappa B ; antagonists & inhibitors ; Protective Agents ; pharmacology ; RNA, Messenger ; genetics ; metabolism ; Signal Transduction ; drug effects