Inhibition of CD36, a fatty acid transporter, has been reported to prevent glucotoxicity and ameliorate high glucose induced beta cell dysfunction. Ezetimibe is a selective cholesterol absorption inhibitor that blocks Niemann Pick C1-like 1 protein, but may exert its effect through suppression of CD36. We attempted to clarify the beneficial effect of ezetimibe on insulin secreting cells and to determine whether this effect is related to change of CD36 expression. mRNA expression of insulin and CD36, intracellular peroxide level and glucose stimulated insulin secretion (GSIS) under normal (5.6 mM) or high glucose (30 mM) condition in INS-1 cells and primary rat islet cells were compared. Changes of the aforementioned factors with treatment with ezetimibe (20 μM) under normal or high glucose condition were also assessed. mRNA expression of insulin was decreased with high glucose, which was reversed by ezetimibe in both INS-1 cells and primary rat islets. CD36 mRNA expression was increased with high glucose, but decreased by ezetimibe in INS-1 cells and primary rat islets. Three-day treatment with high glucose resulted in an increase in intracellular peroxide level; however, it was decreased by treatment with ezetimibe. Decrease in GSIS by three-day treatment with high glucose was reversed by ezetimibe. Palmitate uptake following exposure to high glucose conditions for three days was significantly elevated, which was reversed by ezetimibe in INS-1 cells. Ezetimibe may prevent glucotoxicity in pancreatic β-cells through a decrease in fatty acid influx via inhibition of CD36.
Animals ; Anticholesteremic Agents/*pharmacology ; Antigens, CD36/antagonists & inhibitors/genetics/*metabolism ; Cells, Cultured ; Ezetimibe/*pharmacology ; Flow Cytometry ; Glucose/toxicity ; Insulin/genetics/metabolism/secretion ; Insulin-Secreting Cells/cytology/*drug effects/metabolism ; Male ; Palmitic Acid/metabolism ; RNA, Messenger/metabolism ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species/metabolism ; Real-Time Polymerase Chain Reaction

Mammalian pancreatic β-cells play a pivotal role in development and glucose homeostasis through the production and secretion of insulin. Functional failure or decrease in β-cell number leads to type 2 diabetes (T2D). Despite the physiological importance of β-cells, the viability of β-cells is often challenged mainly due to its poor ability to adapt to their changing microenvironment. One of the factors that negatively affect β-cell viability is high concentration of free fatty acids (FFAs) such as palmitate. In this work, we demonstrated that Yes-associated protein (Yap1) is activated when β-cells are treated with palmitate. Our loss- and gain-of-function analyses using rodent insulinoma cell lines revealed that Yap1 suppresses palmitate-induced apoptosis in β-cells without regulating their proliferation. We also found that upon palmitate treatment, re-arrangement of F-actin mediates Yap1 activation. Palmitate treatment increases expression of one of the Yap1 target genes, connective tissue growth factor (CTGF). Our gain-of-function analysis with CTGF suggests CTGF may be the downstream factor of Yap1 in the protective mechanism against FFA-induced apoptosis.
Actins ; metabolism ; Adaptor Proteins, Signal Transducing ; antagonists & inhibitors ; genetics ; metabolism ; Animals ; Apoptosis ; drug effects ; physiology ; Bridged Bicyclo Compounds, Heterocyclic ; pharmacology ; Cell Line, Tumor ; Connective Tissue Growth Factor ; genetics ; metabolism ; pharmacology ; Cytochalasin D ; pharmacology ; Fatty Acids, Nonesterified ; pharmacology ; HEK293 Cells ; Humans ; Immunohistochemistry ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; Mice ; Microscopy, Fluorescence ; Palmitic Acid ; pharmacology ; Phosphoproteins ; antagonists & inhibitors ; genetics ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Rats ; Recombinant Proteins ; genetics ; metabolism ; pharmacology ; Thiazolidines ; pharmacology

Insulin resistance and insulin secretion deficiency are main machanisms in inducing type 2 diabetes mellitus (T2DM), and mitochondria damage plays an important role in them. Research shows that autophagy is a self-protective mechanism of cells, which plays an important role in maintaining the normal structure and function of pancreatic β cells and improving insulin resistance. Previous studies show that traditional Chinese medicine can regulate cell autophagy to influence β cells and insulin resistance, type 2 diabetes mellitus and its complications. Thus this review will talk about the process of the relationship between autophagy and T2DM and the intervention effect of traditional Chinese medicine.
Animals ; Autophagy ; drug effects ; Diabetes Mellitus, Type 2 ; drug therapy ; metabolism ; physiopathology ; Drugs, Chinese Herbal ; therapeutic use ; Humans ; Insulin ; metabolism ; Insulin Resistance ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism

OBJECTIVE: To explore the eff ect of silibinin on β cells in C57BL/6J mice fed a high-fat diet and the possible mechanisms. METHODS: A total of 18 male C57BL/6J mice at 3 weeks old were divided into a normal chow group (n=6), a high-fat diet group (n=6) and a high-fat diet plus silibinin group (n=6). Aft er intervention for 10 weeks, fasting blood glucose (FBG), fasting insulin (FINS), triglycerides (TG), alanine aminotransferase (ALT), creatinine (Cr) and blood urea nitrogen (BUN), lipid metabolism, antioxidant enzyme activities and apoptosis were evaluated. Pancreatic tissues were isolated to examine insulin-induced gene-1 (Insig-1), sterol regulatory element binding protein-1c (SREBP-1c) and fatty acid synthetase (FAS) mRNA and protein expression. RESULTS: Compared with the high-fat diet group, the function of insulin secretion was improved, and the level of blood glucose was decreased in the high-fat diet plus silibinin group (P<0.05). The levels of lipid content and oxidative stress and the rates of β cell apoptosis were lower in high-fat diet plus silibinin group than those in the high-fat diet group (both P<0.05). Simultaneously, the silibinin could promote the expression of Insig-1 and depress the expression of SREBP-1c and FAS (all P<0.05). Moreover, there was no significant difference in the levels of serum ALT, Cr and BUN among the 3 groups (all P>0.05). CONCLUSION Silibinin can protect β cells of mice fed a high-fat diet, and this effect might be related to, at least partially, increase in its antioxidative ability through regulation of insig-1/SREBP-1c pathway. Moreover, silibinin is safe for long-term treatment.
Alanine Transaminase ; blood ; Animals ; Apoptosis ; Blood Glucose ; analysis ; Blood Urea Nitrogen ; Creatinine ; blood ; Diet, High-Fat ; Fatty Acid Synthases ; metabolism ; Insulin ; blood ; Insulin-Secreting Cells ; cytology ; drug effects ; Lipid Metabolism ; Lipids ; Male ; Membrane Proteins ; metabolism ; Mice ; Mice, Inbred C57BL ; Oxidative Stress ; Silybin ; Silymarin ; pharmacology ; Sterol Regulatory Element Binding Protein 1 ; metabolism ; Triglycerides ; blood

OBJECTIVETo study the effect of Mudan Granule (MD) on the glucose metabolism and beta cell function in monosodium glutamate (MSG) induced obese mice with insulin resistance (IR).

METHODSMSG obese mice were induced by subcutaneous injecting MSG (4 g/kg for 7 successive days in neonatal ICR mice). Forty MSG mice with IR features were recruited and divided into four groups according to body weight, fasting blood glucose, triglyceride (TG), total cholesterol (TC), and the percentage of blood glucose decreased within 40 min in the IR test, i.e., the model group (Con), the low dose MD group, the high dose MD group, and the Metformin group (Met). Besides, another 10 ICR mice were recruited as the normal control group (Nor). The water solvent of 2.5 g/kg MD or 5 g/kg MD was respectively administered to mice in the low dose MD group and the high dose MD group. Metformin hydrochloride was given to mice in the Met group at 0.2 g/kg body weight. Equal dose solvent distilled water was administered to mice in the Nor group and the Con group by gastrogavage, once per day. All medication was lasted for 15 weeks. Insulin tolerance test (ITT) and oral glucose tolerance test (OGTT) were performed after 6 weeks of treatment. Beta cell function was assessed by hyperglycemic clamp technique. The morphological changes in the pancreas were evaluated by hematoxylin-eosin (HE) staining. Changes of iNOS, NF-kappaB p65, and p-NF-kappaB p65 in the pancreas were tested.

RESULTSCompared with the Nor group, the blood glucose level, AUC, and fasting blood insulin, ONOO-contents, iNOS activities, and the expression of iNOS, NF-kappaB p65 subunit, pNF-kappaB p65 subunit obviously increased; decreased percentage of blood glucose within 40 min in ITT, glucose infusion rate (GIR), Clamp 1 min insulin, and Max-Insulin obviously decreased in the Con group (P < 0.05, P < 0.01). Compared with the Con group, the aforesaid indices could be improved in the Met group (P < 0.05, P < 0.01). In the low dose MD group, AUC, iNOS activities, and the expression of iNOS and p-NF-kappaB p65 subunit obviously decreased; percentage of blood glucose within 40 min in ITT and GIR obviously increased (P < 0.05, P < 0.01). In the high dose MD group, AUC, ONOO-contents, iNOS activities, and the expression of iNOS, NF-kappaB p65 subunit, and p-NF-KB p65 subunit obviously decreased; percentage of blood glucose within 40 min in ITT, Max-Insulin, and GIR obviously increased (P < 0.05, P < 0.01).

CONCLUSIONMD could significantly improve IR and functional disorder of 3 cells in MSG obese mice, which might be associated with lowering inflammatory reaction in the pancreas.

Animals ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; Female ; Insulin Resistance ; Insulin-Secreting Cells ; drug effects ; metabolism ; Male ; Metformin ; pharmacology ; Mice ; Mice, Inbred ICR ; Mice, Obese ; Obesity ; chemically induced ; metabolism ; Pancreas ; cytology ; drug effects ; Sodium Glutamate

AIM: To observe the effect of modified Si-Miao-San (mSMS) on advanced glycation end products (AGEs)-induced pancreatic B cell dysfunction, as well as examining the underlying mechanisms. METHOD: Pancreatic B cells (INS-1) were stimulated with advanced glycation end products (AGEs, 200 μg·mL(-1)) for 24 h to produce dysfunction in pancreatic B cells and the effects of mSMS observed on insulin secretion, NF-κB (p65) phosphorylation, reactive oxygen species (ROS) production, mitochondria membrane potential (Δψm), cell apoptosis, phosphorylation of AMP-kinase (AMPK), and caspase 3 activity. RESULTS: The AGEs challenge resulted in increased basal insulin secretion, but decreased insulin secretion in response to high glucose, whereas this situation was reversed by mSMS treatment. AGEs stimulation induced NF-κB (p65) phosphorylation and reactive oxygen species (ROS) production, as well as Δψm collapse and cell apoptosis. mSMS inhibited ROS production and inhibited NF-κB activation by attenuating p65 phosphorylation. Meanwhile, AGEs-induced Δψm collapse and cell apoptosis were also reversed by mSMS treatment. Compound C, an inhibitor of AMP-Kinase (AMPK), abolished the beneficial effects of mSMS on the regulation of B cell function, indicating the involvement of AMPK. CONCLUSION mSMS ameliorated AGEs-induced B cell dysfunction by suppressing ROS-associated inflammation, and this action was related to its beneficial regulation of AMPK activity.
AMP-Activated Protein Kinases ; genetics ; metabolism ; Animals ; Apoptosis ; drug effects ; Cell Line, Tumor ; Drugs, Chinese Herbal ; pharmacology ; Glucose ; metabolism ; Glycation End Products, Advanced ; metabolism ; Humans ; Inflammation ; drug therapy ; enzymology ; genetics ; metabolism ; Insulin-Secreting Cells ; cytology ; drug effects ; enzymology ; metabolism ; Phosphorylation ; Rats ; Reactive Oxygen Species ; metabolism

Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca(2+)-dependent manner. In diabetic animal models, different aspects of the calcium signaling pathway in beta-cells are altered, but there is no consensus regarding their relative contributions to the development of beta-cell dysfunction. In this study, we compared the increase in cytosolic Ca(2+) ([Ca(2+)]i) via Ca(2+) influx, Ca(2+) mobilization from endoplasmic reticulum (ER) calcium stores, and the removal of Ca(2+) via multiple mechanisms in beta-cells from both diabetic db/db mice and non-diabetic C57BL/6J mice. We refined our previous quantitative model to describe the slow [Ca(2+)]i recovery after depolarization in beta-cells from db/db mice. According to the model, the activity levels of the two subtypes of the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA) pump, SERCA2 and SERCA3, were severely down-regulated in diabetic cells to 65% and 0% of the levels in normal cells. This down-regulation may lead to a reduction in the Ca(2+) concentration in the ER, a compensatory up-regulation of the plasma membrane Na(+)/Ca(2+) exchanger (NCX) and a reduction in depolarization-evoked Ca(2+) influx. As a result, the patterns of glucose-stimulated calcium oscillations were significantly different in db/db diabetic beta-cells compared with normal cells. Overall, quantifying the changes in the calcium signaling pathway in db/db diabetic beta-cells will aid in the development of a disease model that could provide insight into the adaptive transformations of beta-cell function during diabetes development.
Animals ; Calcium ; metabolism ; Calcium Signaling ; drug effects ; Cell Membrane Permeability ; drug effects ; Cells, Cultured ; Down-Regulation ; drug effects ; Endoplasmic Reticulum ; metabolism ; Glucose ; pharmacology ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; Mice ; Mice, Inbred C57BL ; Mice, Obese ; Potassium Chloride ; pharmacology ; Sarcoplasmic Reticulum Calcium-Transporting ATPases ; metabolism ; Sodium-Calcium Exchanger ; metabolism ; Thapsigargin ; pharmacology ; Up-Regulation ; drug effects

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

Recent evidence has suggested that human skin fibroblasts may represent a novel source of therapeutic stem cells. In this study, we report a 3-stage method to induce the differentiation of skin fibroblasts into insulin-producing cells (IPCs). In stage 1, we establish the isolation, expansion and characterization of mesenchymal stem cells from human labia minora dermis-derived fibroblasts (hLMDFs) (stage 1: MSC expansion). hLMDFs express the typical mesenchymal stem cell marker proteins and can differentiate into adipocytes, osteoblasts, chondrocytes or muscle cells. In stage 2, DMEM/F12 serum-free medium with ITS mix (insulin, transferrin, and selenite) is used to induce differentiation of hLMDFs into endoderm-like cells, as determined by the expression of the endoderm markers Sox17, Foxa2, and PDX1 (stage 2: mesenchymal-endoderm transition). In stage 3, cells in the mesenchymal-endoderm transition stage are treated with nicotinamide in order to further differentiate into self-assembled, 3-dimensional islet cell-like clusters that express multiple genes related to pancreatic beta-cell development and function (stage 3: IPC). We also found that the transplantation of IPCs can normalize blood glucose levels and rescue glucose homeostasis in streptozotocin-induced diabetic mice. These results indicate that hLMDFs have the capacity to differentiate into functionally competent IPCs and represent a potential cell-based treatment for diabetes mellitus.
Animals ; Biological Markers/metabolism ; *Cell Culture Techniques ; *Cell Differentiation ; Cell Proliferation/drug effects ; Cell Separation ; Cells, Cultured ; Dermis/*cytology/drug effects ; Diabetes Mellitus, Experimental/*surgery ; Female ; Fibroblasts/*cytology/drug effects ; Genitalia, Female/*cytology ; Glucose/metabolism ; Hepatocyte Nuclear Factor 3-beta/metabolism ; Homeodomain Proteins/metabolism ; Humans ; Insulin/pharmacology/secretion ; Insulin-Secreting Cells/*cytology/metabolism ; *Islets of Langerhans Transplantation ; Mesenchymal Stem Cells/*cytology/drug effects/metabolism ; Mice ; Mice, Nude ; Niacinamide/pharmacology ; Recovery of Function ; SOXF Transcription Factors/metabolism ; Sodium Selenite/pharmacology ; Trans-Activators/metabolism ; Transferrin/pharmacology

Animals ; Exocytosis ; drug effects ; physiology ; Glucose ; pharmacology ; Insulin ; secretion ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; Mice ; Microscopy, Fluorescence ; methods ; Potassium ; pharmacology ; Recombinant Fusion Proteins ; genetics ; metabolism ; Vesicle-Associated Membrane Protein 2 ; genetics ; metabolism