OBJECTIVETo assess the effect of RNA interference-mediated gene silencing of plasma membrane-related Ca(2+)-ATPase-1 (PMR1) gene on the insulin secretion in islet beta cells NIT-1 in vitro.

METHODSA small interfering RNA duplex (siPMR1) corresponding to the nucleotides 337-357 of mouse PMR1 cDNA was introduced into NIT-1 cells via liposomes. The gene silencing effect was assessed by RT-PCR, and the total insulin level in the transfected cells was measured by radioimmunoassay.

RESULTSTransfection with siPMR1 resulted in obviously reduced PMR1 expression and increased insulin secretion in NIT-1 cells.

CONCLUSIONThe synthesized siPMR1 can significantly silence the expression of PMR1 and promote the secretion of insulin in the islet cells in vitro, which shed light on further studies of RNAi-based therapy of diabetes.

Animals ; Calcium-Transporting ATPases ; deficiency ; genetics ; Cell Line ; Gene Expression Regulation ; Insulin ; secretion ; Insulin-Secreting Cells ; metabolism ; secretion ; Mice ; RNA Interference ; RNA, Messenger ; genetics ; metabolism

OBJECTIVETo study the effect of a new obesity-related gene NYGGF4 on the insulin sensitivity and secretory function of adipocytes.

METHODS3T3-L1 preadipocytes transfected with either an empty expression vector (pcDNA3.1; control group) or an NYGGF4 expression vector (NYGGF4-pcDNA3.1) were cultured in vitro and differentiated into the matured adipocytes with the standard insulin plus dexamethasone plus 3-isobutyl-methylxanthine (MDI) induction cocktail. 2-deoxy-D-[3H] glucose uptake was determined by liquid scintillation counting. Western blot was performed to detect the protein content and translocation of glucose transporter 4 (GLUT4). The supernatant concentrations of TNF-alpha, IL-6, adiponectin and resistin were measured using ELISA.

RESULTSNYGGF4 over-expression in 3T3-L1 adipocytes reduced insulin-stimulated glucose uptake. NYGGF4 over-expression impaired insulin-stimulated GLUT4 translocation without affecting the total protein content of GLUT4. The concentrations of TNF-alpha, IL-6, adiponectin and resistin in the culture medium of 3T3-L1 transfected with NYGGF4 were not significantly different from those in the control group.

CONCLUSIONSNYGGF4 over-expression impairs the insulin sensitivity of 3T3-L1 adipocytes through decreasing GLUT4 translocation and had no effects on the secretory function of adipocytes.

3T3-L1 Cells ; Adipocytes ; drug effects ; secretion ; Adiponectin ; secretion ; Animals ; Carrier Proteins ; genetics ; physiology ; Glucose ; metabolism ; Glucose Transporter Type 4 ; analysis ; metabolism ; Insulin ; pharmacology ; Interleukin-6 ; secretion ; Mice ; Resistin ; analysis ; Transfection ; Tumor Necrosis Factor-alpha ; secretion

Animals ; Animals, Newborn ; Cells, Cultured ; Cyclic AMP ; metabolism ; Glucagon-Like Peptide 1 ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; secretion ; Peptide Fragments ; pharmacology ; RNA, Messenger ; genetics ; Rats

This cohort study was designed to evaluate the association of transcription factor 7-like 2 (TCF7L2) and proglucagon gene (GCG) variants with disordered glucose metabolism and the incidence of type 2 diabetes mellitus (T2DM) in a rural adult Chinese population. A total of 7,751 non-T2DM participants ⋝18 years old genotyped at baseline were recruited. The same questionnaire interview and physical and blood biochemical examinations were performed at both baseline and follow-up. During a median 6 years of follow-up, T2DM developed in 227 participants. After adjustment for potential contributory factors, nominally significant associations were seen between TT genotype and the recessive model of TCF7L2 rs7903146 and increased risk of T2DM [hazard ratio (HR)=4.068, 95% confidence interval (CI): 1.270-13.026; HR=4.051, 95% CI: 1.268-12.946, respectively]. The TT genotype of rs7903146 was also significantly associated with higher fasting plasma insulin level and the homeostasis model assessment of insulin resistance in case of new-onset diabetes. In addition, the TCF7L2 rs290487 TT genotype was associated with abdominal obesity and the GCG rs12104705 CC genotype was associated with both general obesity and abdominal obesity in case of new-onset diabetes.
Adult ; Cohort Studies ; Diabetes Mellitus, Type 2 ; complications ; genetics ; Female ; Humans ; Insulin ; secretion ; Insulin Resistance ; genetics ; Male ; Middle Aged ; Obesity ; complications ; genetics ; Polymorphism, Single Nucleotide ; Proglucagon ; genetics ; Transcription Factor 7-Like 2 Protein ; genetics

BACKGROUNDIslet transplantation represents an ideal therapeutic approach for treatment of type 1 diabetes but islet function and regeneration may be influenced by necrosis or apoptosis induced by oxidative stress and other insults. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in the catabolism of heme into biliverdin, releasing free iron and carbon monoxide. It has also been reported to be an antioxidant enzyme which can improve the function of grafted islets by cytoprotection via free radical scavenging and apoptosis prevention. In the present study, we investigated whether transduction of HO-1 genes into human islets with an adenovirus vector has cytoprotective action on islets cultured in vitro and discuss this method of gene therapy for clinical islet transplantation.

METHODSCadaveric pancreatic islets were isolated and purified in vitro. Transduction efficiency of islets was determined by infecting islets with adenovirus vector containing the enhanced green fluorescent protein gene (Ad-EGFP) at multiplicities of infection (MOI) of 2, 5, 10, or 20. Newly isolated islets were divided into three groups: EGFP group, islets transduced with Ad-EGFP using MOI = 20; HO-1 group, transduced with adenovirus vectors containing the human HO-1 gene using MOI = 20; and control group, mock transduced islets. Insulin release after glucose stimulation of the cell lines was determined by a radioimmunoassay kit and the stimulation index was calculated. Flow cytometry was used to detect apoptotic cells in the HO-1 group and in the control group after induction by recombinant human tumor necrosis factor-alpha (rTNFalpha) and cycloheximide (CHX) for 48 hours.

RESULTSAdenovirus vectors have a high efficiency of gene transduction into adult islet cells. Transduction of islets with the Ad-EGFP was most successful at MOI 20, at which MOI fluorescence was very intense on day 7 after transduction and EGFP was expressed in cultured islet cells for more than four weeks in vitro. The insulin release in the control group was (182.36 +/- 58.96) mIU/L after stimulation by high glucose media (16.7 mmol/L), while insulin release from the HO-1 group and the EGFP group were (270.09 +/- 89.37) mIU/L and (175.95 +/- 75.05) mIU/L respectively. Compared to the control group and the EGFP group, insulin release in the HO-1 group increased significantly (P < 0.05). After treatment with rTNFalpha and CHX the apoptotic ratio of islet cells was (63.09 +/- 10.86)% in the HO-1 group, significantly lower than (90.86 +/- 11.25)% in the control group (P < 0.05).

CONCLUSIONSTransduction of human islets with Ad-HO-1 can protect against TNF-alpha and CHX mediated cytotoxicity. The HO-1 gene also appears to facilitate insulin release from human islets. Transduction of donor islets with the adenovirus vector containing an HO-1 gene might have potential value in clinical islet transplantation.

Adenoviridae ; genetics ; Apoptosis ; drug effects ; Cycloheximide ; pharmacology ; Cytoprotection ; Genetic Therapy ; Heme Oxygenase-1 ; genetics ; physiology ; Humans ; Insulin ; secretion ; Islets of Langerhans ; physiology ; Transduction, Genetic ; Tumor Necrosis Factor-alpha ; pharmacology

Animals ; Glucose ; pharmacology ; Homeodomain Proteins ; analysis ; genetics ; physiology ; Immunohistochemistry ; Insulin ; secretion ; Male ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Trans-Activators ; analysis ; genetics ; physiology

BACKGROUNDMu opioid receptor plays an important role in many physiological functions. Fentanyl is a widely used opioid receptor agonist for analgesia. This study was conducted to test the role of mu-opioid receptor on insulin release by determining whether fentanyl affected insulin release from freshly isolated rat pancreatic islets and if small interfering RNAs (siRNA) targeting mu-opioid receptor in the islets could knock down mu-opioid receptor expression.

METHODSIslets were isolated from ripe SD rats' pancreas by common bile duct intraductal collagenase V digestion and purified by discontinuous Ficoll density gradient centrifugation. The siRNA knock-down of mu-opioid receptor mRNA and protein in islet cells was analyzed by semi-quantitative real time-PCR and Western blotting. After siRNA-transfection for 48 hours, the islets were co-cultured with fentanyl as follows: 0 ng/ml, 3 ng/ml and 30 ng/ml for 48 hours. Then glucose-evoked insulin release was performed. As a control, the insulin release was also analyzed in islets without siRNA-trasfection after being co-cultured with fentanyl for 48 hours.

RESULTSAfter 48 hours of transfections, specific siRNA targeting of mu-opioid receptors produced significant reduction of mu-opioid receptor mRNA and protein (P < 0.01). Fentanyl significantly inhibited glucose-evoked insulin release in islets in a concentration dependent manner (P < 0.01). But after siRNA-transfection for 48 hours, the inhibition on glucose-evoked insulin release was reversed (P < 0.01).

CONCLUSIONSRNA interference specifically reduces mu-opioid receptor mRNA and protein expression, leading to reversal of the fentanyl-induced inhibition on glucose-evoked insulin release of rat islets. The activation of opioid receptor induced by fentanyl functions to inhibit insulin release. The use of RNAi presents a promising tool for future research in diabetic mechanisms and a novel therapy for diabetes.

Analgesics, Opioid ; pharmacology ; Animals ; Cell Survival ; drug effects ; Cells, Cultured ; Fentanyl ; pharmacology ; Glucose ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; secretion ; Male ; RNA Interference ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; antagonists & inhibitors ; genetics ; physiology

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

Hypoxic damage is one of the major causes of islet graft failure and VEGF is known to play a crucial role in revascularization. To address the effectiveness of a cationic lipid reagent as a VEGF gene carrier, and the beneficial effect of VEGF-transfected islets on glycemic control, we used effectene lipid reagent in a transfection experiment using mouse islets. Transfection efficiencies were highest for 4 microgram/microliter cDNA and 25 microliter effectene and cell viabilities were also satisfactory under this condition, and the overproduction of VEGF mRNA and protein were confirmed from conditioned cells. A minimal number of VEGF-transfected islets (100 IEQ/animal) were transplanted into streptozotocin (STZ)-induced diabetic mice. Hyperglycemia was not controlled in the islet transplantation (IT)-alone group (0/8) (non- diabetic glucose mice number/total recipient mice number) or in the IT-pJDK control vector group (0/8). However, hyperglycemia was completely abrogated in the IT-pJDK-VEGF transduced group (8/8), and viable islets and increased VEGF-transfected grafts vascularization were observed in renal capsules.
Animals ; Body Weight ; Cell Survival ; Diabetes Mellitus, Experimental/*complications/metabolism ; Disease Models, Animal ; Glucose/pharmacology ; Glucose Tolerance Test ; Hyperglycemia/complications/*metabolism/*therapy ; Insulin/secretion ; Islets of Langerhans/blood supply/cytology/secretion ; *Islets of Langerhans Transplantation ; Liposomes/*administration & dosage/chemistry ; Male ; Mice ; Mice, Inbred BALB C ; Neovascularization, Physiologic ; RNA, Messenger/genetics/metabolism ; Research Support, Non-U.S. Gov't ; Streptozocin ; Transfection ; Vascular Endothelial Growth Factors/biosynthesis/*genetics/*metabolism/secretion

OBJECTIVETo investigate the relationship of insulin resistance and the polymorphisms of insulin receptor-related genes in essential hypertension patients of two different kinds of TCM constitution.

METHODSOral glucose tolerance test (OGTT) and insulin release test (InRT) were conducted in 217 essential hypertensive patients of either sluggish meticulous (SM) constitution (139 cases) or prosperous impetuous (PI) constitution (78 cases), and the polymorphism of three genes, including insulin-like growth factor-1 receptor (IGF-1R), insulin receptor substrate-1 (IRS-1) and 2 (IRS-2) genes were detected.

RESULTS(1) OGTT, InRT and insulin resistance index (Homa-IR) were higher and insulin sensitive index (ISI) was lower in the patients of SM constitution than those in patients of PI constitution. (2) Significant difference of ISI and Homa-IR was shown in patients of both constitutions with genotype G of the 3 genes.

CONCLUSIONDecrease of insulin sensitivity and increase of insulin resistance are more obvious in hypertensive patients with genotype G of the 3 genes of SM constitution than in those of PI constitution. Therefore, the difference in constitution might be one of the genetic characteristics for insulin resistance in hypertensive patients.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Blood Glucose ; Body Constitution ; physiology ; Female ; Glucose Tolerance Test ; Humans ; Hypertension ; genetics ; Insulin ; secretion ; Insulin Resistance ; physiology ; Male ; Middle Aged ; Phenotype ; Polymorphism, Genetic