Preproinsulin Gene Research Articles

Gene structure, SNP screening and growth correlation analysis of the preproinsulin gene in grass carp (Ctenopharyngodon idellus)

The preproinsulin gene encodes a precursor protein of insulin, which is the most important hormone for lowering blood glucose levels and promoting the synthesis of glycogen, fat and protein. To explore the correlation between polymorphisms in the preproinsulin gene and growth traits in grass carp, the preproinsulin gene sequence, measuring a total of 5708 bp, was identified in the grass carp genome. The sequence includes a promoter, two introns and three exons, and encodes a 108-aa protein. A total of three SNPs were identified, including SNP1 (g.-2661C>G) in the promoter and SNP2 (g.1305G>C) and SNP3 (g.1682G>A) in intron 2. The correlation between SNPs and growth traits in grass carp was analysed by a general linear model (GLM). The results indicated that no genotype in each single SNP, SNP1 with SNP2, or SNP1 with SNP3 was related to rapid growth and low fatness, respectively. While eight genotypes of SNP1, SNP2 and SNP3 were combined into six types of effective diplotypes, the H5 diplotype was significantly superior to the other diplotypes (P<0.05) concerning body weight, body length, body height and body width, and its fatness was lower than those of the other diplotypes, except for H6 diplotype. This result indicated that the H5 diplotype of the preproinsulin gene in grass carp may be a candidate molecular marker for selecting fast-growing and low-fatness grass carp.

Momordica balsamina Fruit Extracts Enhances Selected Aspects of the Insulin Synthesis/Secretion Pathway

Previous studies have suggested that crude plant extracts of the anti-diabetic medicinal plant, Momordica balsamina (MB) may exert their anti-diabetic effect through either enhancement of insulin sensitivity or inhibition of intestinal glucose absorption. However, the effects of these MB extracts on insulin synthesis and secretion are not well documented in the literature. Therefore, a main purpose of the current research was to examine in vitro effects of MB crude fruit extracts on selected aspects of the insulin synthesis and secretion pathway. The study results indicated that ethanol, ethyl acetate and hexane MB crude extracts had the significantly enhanced the uptake of glucose by RIN-m5F β-cells in a manner depending on concentration. Furthermore, these same MB fruit extracts significantly increased the quantities of synthesized and secreted insulin by RIN-m5F β-cells. In addition, significant upregulation of the pre-proinsulin gene levels by the same MB fruit extracts was detected by the conventional end-point Polymerase Chain Reaction (RT-PCR), whereas a significant upregulation of gene expression levels of the two pancreatic glucose sensors (glucokinase enzyme and Glucose Transporter 2 (GLUT2)) as well as the two insulin gene transcription factors Musculoaponeurotic Fibrosarcoma homolog A (MafA) and Pancreatic Duodenal Homeobox-1 (PDX-1) were detected by means of quantitative reverse transcriptase PCR. In conclusion, the outcomes of this research propose that MB fruit extracts may, in addition to their effects on sensitivity of insulin and inhibition of intestinal glucose absorption, exert their anti-diabetic effects through stimulation of both the insulin synthesis and secretion.

Effects of Sclerocarya birrea Stem-Bark Extracts on Glucose Uptake, Insulin Synthesis and Expression of Selected Genes Involved in the Synthesis and Secretion of Insulin in Rat Insulinoma Pancreatic Beta Cells

The present study reported the effects of Sclerocarya birrea stem-bark (SBSB) extracts on glucose uptake, insulin synthesis and the expression of glucose transporter 2 (GLUT2), glucokinase, pancreatic duodenal homeobox-1 (PDX-1), musculoaponeurotic fibrosarcoma oncogene homolog A (MafA) and pre-proinsulin genes in rat insulinoma (RIN)-m5F pancreatic beta cells. The amount of glucose takenup by RIN-m5F cells was measured using a glucose oxidase-based assay kit. Intracellular and secreted insulin were measured using an enzyme linked immunoassay kit. Pre-proinsulin gene expression was determined using the conventional polymerase chain reaction (PCR) technique, while the expressions of GLUT2, glucokinase, PDX-1 and MafA genes were evaluated using quantitative real-time PCR technique. Of the four SBSB extracts investigated in the study, only the SBSB hexane extract positively affected all the study variables in RIN-m5F cells compared with the DMSO control. Thus, the SBSB hexane extract contains phytochemicals capable of enhancing insulin synthesis partly through up-regulation of the expression of GLUT2, glucokinase, PDX-1, MafA and pre-proinsulin genes.

Cloning and Expression of Recombinant Human Insulin Gene in Pichia pastoris

The main goal of the current study was cloning and expression of the human insulin gene in Pichia pastoris expression system, using genetic engineering techniques and its treatment application. Total RNA was purified from fresh normal human pancreatic tissue. RNA of good quality was chosen to obtain a first single strand cDNA. Human preproinsulin gene was amplified from cDNA strand, by using two sets of specific primers contain EcoR1 and Notl restriction sites. The amplified preproinsulin gene fragment was double digested with EcoRI and Not 1 restriction enzymes, then inserted into pPIC9K expression vector. The new pPIC9K-hpi constructive expression vector was transformed by the heat-shock method into the E.coli DH5α competent cells. pPic9k –hpi, which was propagated in the positive transformant E. coli cells, was isolated from cells and then linearised by restriction enzyme SalI, then transformed into Pichia pastoris GS115 using electroporation method. Genomic DNA of His+ transformants cell was extracted and used as a template for PCR analysis. The results showed, that the pPic9k – hpi was successfully integrated into the P. pastoris genome, for selected His+ transformants clones on the anticipated band at 330 bp, which is corresponded to the theoretical molecular size of the human insulin gene. To follow the insulin expression in transformans, Tricine–SDS gel electrophoresis and Western blot analysis were conducted. The results showed a successful expression of recombinant protein was detected by the presence of a single major band with about (5.8 KDa) on the gel. These bands correspond well with the size of human insulin with the theoretical molecular weight (5.8 KDa).

The effects of gene therapy with PEI-pDNA complex containing human preproinsulin gene on structural and ultrastructural characteristics of several organs in mice of different ages at experimental diabetes mellitus

The effects of gene therapy with PEI-pDNA complex containing human preproinsulin gene on structural and ultrastructural characteristics of several organs in mice of different ages at experimental diabetes mellitus

Monogenic Diabetes: What It Teaches Us on the Common Forms of Type 1 and Type 2 Diabetes.

To date, more than 30 genes have been linked to monogenic diabetes. Candidate gene and genome-wide association studies have identified > 50 susceptibility loci for common type 1 diabetes (T1D) and approximately 100 susceptibility loci for type 2 diabetes (T2D). About 1-5% of all cases of diabetes result from single-gene mutations and are called monogenic diabetes. Here, we review the pathophysiological basis of the role of monogenic diabetes genes that have also been found to be associated with common T1D and/or T2D. Variants of approximately one-third of monogenic diabetes genes are associated with T2D, but not T1D. Two of the T2D-associated monogenic diabetes genes-potassium inward-rectifying channel, subfamily J, member 11 (KCNJ11), which controls glucose-stimulated insulin secretion in the β-cell; and peroxisome proliferator-activated receptor γ (PPARG), which impacts multiple tissue targets in relation to inflammation and insulin sensitivity-have been developed as major antidiabetic drug targets. Another monogenic diabetes gene, the preproinsulin gene (INS), is unique in that INS mutations can cause hyperinsulinemia, hyperproinsulinemia, neonatal diabetes mellitus, one type of maturity-onset diabetes of the young (MODY10), and autoantibody-negative T1D. Dominant heterozygous INS mutations are the second most common cause of permanent neonatal diabetes. Moreover, INS gene variants are strongly associated with common T1D (type 1a), but inconsistently with T2D. Variants of the monogenic diabetes gene Gli-similar 3 (GLIS3) are associated with both T1D and T2D. GLIS3 is a key transcription factor in insulin production and β-cell differentiation during embryonic development, which perturbation forms the basis of monogenic diabetes as well as its association with T1D. GLIS3 is also required for compensatory β-cell proliferation in adults; impairment of this function predisposes to T2D. Thus, monogenic forms of diabetes are invaluable "human models" that have contributed to our understanding of the pathophysiological basis of common T1D and T2D.

Molecular Studies on Preproinsulin Gene

Insulin plays an important role in maintaining the blood glucose level of the body. The β-cells of pancreas produce insulin in the form of precursor that is preproinsulin. The gene of preproinsulin provides an interesting system for addressing question related to molecular evolution. Recombinant DNA technology has made it possible to isolate and sequence the chromosomal genes coding for unique protein products. Although preproinsulin of various organism has been isolated and cloned, but there is no report from buffalo (Bubalus bubalis) that is our major livestock. The genomic DNA of buffalo was isolated using Laura-Lee-Boodram method. The part of preproinsulin gene (596bp and 520bp) using BPPI-UPS and bpiful_F as forward and BC1-C as reverse primer was amplified. Cloning of amplified fragments of gene were performed in pCR 2.1 vector. Positive clones were screened on the basis of blue white selection. The band obtained on 596bp and 520bp after colony PCR confirmed the successful cloning of preproinsulin gene in pCR 2.1 vector.

Plasma insulin levels are regulated by release, rather than transcription or translation, in barfin flounder, Verasper moseri

We evaluated whether transcription or translation of the preproinsulin gene or insulin release into plasma is the primary regulator of plasma insulin level in barfin flounder. Three experimental groups were used: one tested 2h after feeding (Fed), one tested after fasting for 5days (Fasted), and one tested 2h after feeding following 5days of fasting (Refed). No significant differences in insulin transcription, insulin concentrations in the principal islets (PI), or plasma total insulin-like growth factor-I (IGF-I) levels were observed between the three groups. In contrast, plasma insulin level in the Fasted group was significantly lower (P<0.002) than that in the other groups. These results suggest that insulin release is the primary regulator of plasma insulin level and is more sensitive to short-term changes in nutritional conditions than IGF-I level. Furthermore, we estimated the capacity for insulin release. Based on various individual measures, the average insulin stored in the PI was 82.8μg/kg body weight (BW), and the maximum plasma content of insulin was estimated to be <1.7μg/kg BW. The half-life of plasma insulin in diabetogenic chemically (alloxan) treated flounder injected with insulin was estimated to be 2.79h, which is much longer than that in mammals, assuming a two-compartment model for the β phase. These results suggest that the capacity for insulin release in fish is ensured by at least two systems, such as the ability to store excess insulin in Brockman bodies, and enhanced efficiency of insulin storage by elongating its half-life.

Preparation of Preproinsulin Gene Construct Containing the Metallothionein2A (pBINDMTChIns) and Its Expression in NIH3T3 Cell Line and Muscle Tissue of Alloxan Diabetic Rabbits

Background: Diabetes mellitus type 1, formerly called insulin-dependent diabetes, is one of the autoimmune diseases where insulinproducing cells are destroyed by autoimmune response via T cells. The new approaches in treatment of diabetes are using the stem cells, cell transplantation of islet β cell, gene transfer by virus based plasmids, and non-viral gene constructs. Objectives: The purpose of this study was to construct glucose inducible insulin gene plasmid and use it in the muscle tissue of the rabbit. Materials and Methods: To achieve this goal, the preproinsulin, metallothionein2A promoter and the response element to carbohydrate genes were cloned into pBIND plasmid by standard cloning methods, to construct pBINDMTChIns. The gene cloning products were confirmed by the polymerase chain reaction (PCR) and restriction enzyme digestion template. The recombinant plasmid, containing the preproinsulin gene, was transferred into NIH3T3 cells and insulin gene expression was evaluated by reverse transcriptase PCR and western blotting techniques. Plasmid naked DNA containing the preproinsulin gene was injected into the rabbits’ thigh muscles, and its expression was confirmed by western blotting method. Results: This study shows the prepared gene construct is inducible by glucose. Gene expression of preproinsulin was observed in muscle tissue of rabbits. Conclusions: These finding indicated that research in diabetes mellitus gene therapy could be performed on larger animals.

Use of ultrasound to enhance PEI-mediated gene delivery in vivo on diabetic model

Background and aims Gene therapy has strong therapeutic potential for the personalized treatment of type 1 diabetes. Local gene delivery methods for gene therapy are a promising strategy to increase the therapeutic genes concentration at the target location. Transient ultrasound can cause the local increase of cell membrane permeability thus promoting the penetration of transfection particles into the cell. The objective of this work is to evaluate transfection efficiency and safety for intrahepatic polyplex-mediated gene delivery by sonoporation. Methods Polyplexes of expression vector DNAs complexed to galactose-bearing polyethylenimine (L-PEI) have been used. Expression vectors are two plasmids containing expression cassette for full-size human preproinsulin gene controlled with CMV promoter and flanked by inverted terminal repeats of AAV (pTRhins) and the same cassette for marker gfp gene (pTRegfp). Animals were injected under US guidance with polyplexes in a dose of 40 µg pTRegfp /0.7 ml (rat) and of 15 µg pTRhins /0.15 ml (diabetic mouse) into the liver parenchyma of subdiaphragmal segments using 31 G needles. Afterwards injection locus in depth of 1 cm during 180 sec was insonated by 130 Db ultrasound using multifrequency 3-5 MHz probe. Results Sonoporation is able to increase polyplex gene transfer to liver cells in vivo. Flow cytometry analysis of primary hepatocytes isolated from the liver of experimental rats showed that ultrasound -enhanced polyplex gene transfer was highly localized, and was superior to all controls. At least 42% of the liver cells in vivo can be transfected in this way with ultrasound exposure versus 1.2% without it. Hypoglycemic effect of the insulin gene delivery followed by 3m in US exposure was observed on the third day: glucose level of diabetic mice (hyperglycemic 6- week) decreased in average by 30%. Nevertheless sonoporation does not increase naked plasmid DNA (without L-PEI ) transfection efficiency. A week and a month after the procedure serial sections from rat liver injected with polyplexes containing 40 µg marker plasmid or saline solution alone exposed to US and without it was analyzed for the presence of inflammation. Pathomorphological and histological analysis of experimental livers revealed no inflammatory processes in tissues, and any detectable side effects of US-enhanced gene delivery were seen. Experimental mice and rat liver DNAs were positive in transgene PCR for 3 months after gene delivery. Conclusions

Full-length cDNA cloning and structural characterization of preproinsulin in Alligator sinensis.

Insulin is an important endocrine hormone that plays a critical physiological role in regulating metabolism and glucostasis in vertebrates. In this study, the complete cDNA of Alligator sinensis preproinsulin gene was cloned for the first time by reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends methods; the amino acid sequence encoded and protein structure were analyzed. The full-length of preproinsulin cDNA sequence consists of 528 base pairs (bp), comprising a 34-bp 5'-untranslated region, a 170-bp 3'-untranslated region and an open reading frame that is 324 bp in length. The open reading frame encodes a 107-amino acid preproinsulin with a molecular weight of approximately 12,153.8 Da, theoretical isoelectric point of 5.68, aliphatic index of 92.06, and grand average of hydropathicity of -0.157, from which a signal peptide, a B-chain, a C-peptide, and an A-chain are derived. Online analysis suggested that the deduced preproinsulin amino acid sequence contains a transmembrane region, and that it has a signal peptide whose cleavage site occurs between alanine 24 and alanine 25. Comparative analysis of preproinsulin amino acid sequences indicated that the A-chain and B-chain sequences of preproinsulins are highly conserved between reptiles and birds, and that the preproinsulin amino acid sequence of Alligator sinensis shares 89% similarity to that of Chelonia mydas, but low similarity of 48-63% to those of mammals and fishes. The phylogenetic tree constructed using the neighbor-joining method revealed that preproinsulin of Alligator sinensis had high homology with reptiles and birds, such as Chelonia mydas, Gallus gallus, and Columba livia.

Neuropsychological dysfunction and developmental defects associated with genetic changes in infants with neonatal diabetes mellitus: a prospective cohort study

Neonatal diabetes mellitus is a rare genetic form of pancreatic β-cell dysfunction. We compared phenotypic features and clinical outcomes according to genetic subtypes in a cohort of patients diagnosed with neonatal diabetes mellitus before age 1 year, without β-cell autoimmunity and with normal pancreas morphology. We prospectively investigated patients from 20 countries referred to the French Neonatal Diabetes Mellitus Study Group from 1995 to 2010. Patients with hyperglycaemia requiring treatment with insulin before age 1 year were eligible, provided that they had normal pancreatic morphology as assessed by ultrasonography and negative tests for β-cell autoimmunity. We assessed changes in the 6q24 locus, KATP-channel subunit genes (ABCC8 and KCNJ11), and preproinsulin gene (INS) and investigated associations between genotype and phenotype, with special attention to extra-pancreatic abnormalities. We tested 174 index patients, of whom 47 (27%) had no detectable genetic defect. Of the remaining 127 index patients, 40 (31%) had 6q24 abnormalities, 43 (34%) had mutations in KCNJ11, 31 (24%) had mutations in ABCC8, and 13 (10%) had mutations in INS. We reported developmental delay with or without epilepsy in 13 index patients (18% of participants with mutations in genes encoding KATP channel subunits). In-depth neuropsychomotor investigations were done at median age 7 years (IQR 1-15) in 27 index patients with mutations in KATP channel subunit genes who did not have developmental delay or epilepsy. Developmental coordination disorder (particularly visual-spatial dyspraxia) or attention deficits were recorded in all index patients who had this testing. Compared with index patients who had mutations in KATP channel subunit genes, those with 6q24 abnormalities had specific features: developmental defects involving the heart, kidneys, or urinary tract (8/36 [22%] vs 2/71 [3%]; p=0·002), intrauterine growth restriction (34/37 [92%] vs 34/70 [48%]; p<0·0001), and early diagnosis (median age 5·0 days, IQR 1·0-14·5 vs 45·5 days, IQR 27·2-95·0; p<0·0001). Remission of neonatal diabetes mellitus occurred in 89 (51%) index patients at a median age of 17 weeks (IQR 9·5-39·0; median follow-up 4·7 years, IQR 1·5-12·8). Recurrence was common, with no difference between the groups who had 6q24 abnormalities versus mutations in KATP channel subunit genes (82% vs 86%; p=0·36). Neonatal diabetes mellitus is often associated with neuropsychological dysfunction and developmental defects that are specific to the underlying genetic abnormality. A multidisciplinary assessment is therefore essential when patients are diagnosed. Features of neuropsychological dysfunction and developmental defects should be tested for in adults with a history of neonatal diabetes mellitus. Agence Nationale de la Recherche-Maladies Rares Research Program Grant, the Transnational European Research Grant on Rare Diseases, the Société Francophone du Diabète-Association Française du Diabète, the Association Française du Diabète, Aide aux Jeunes Diabétiques, a CIFRE grant from the French Government, HRA-Pharma, the French Ministry of Education and Research, and the Société Française de Pédiatrie.

The Krüppel-Like Protein Gli-Similar 3 (Glis3) Functions as a Key Regulator of Insulin Transcription

Transcriptional regulation of insulin in pancreatic β-cells is mediated primarily through enhancer elements located within the 5' upstream regulatory region of the preproinsulin gene. Recently, the Krüppel-like transcription factor, Gli-similar 3 (Glis3), was shown to bind the insulin (INS) promoter and positively influence insulin transcription. In this report, we examined in detail the synergistic activation of insulin transcription by Glis3 with coregulators, CREB-binding protein (CBP)/p300, pancreatic and duodenal homeobox 1 (Pdx1), neuronal differentiation 1 (NeuroD1), and v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA). Our data show that Glis3 expression, the binding of Glis3 to GlisBS, and its recruitment of CBP are required for optimal activation of the insulin promoter in pancreatic β-cells not only by Glis3, but also by Pdx1, MafA, and NeuroD1. Mutations in the GlisBS or small interfering RNA-directed knockdown of GLIS3 diminished insulin promoter activation by Pdx1, NeuroD1, and MafA, and neither Pdx1 nor MafA was able to stably associate with the insulin promoter when the GlisBS were mutated. In addition, a GlisBS mutation in the INS promoter implicated in the development of neonatal diabetes similarly abated activation by Pdx1, NeuroD1, and MafA that could be reversed by increased expression of exogenous Glis3. We therefore propose that recruitment of CBP/p300 by Glis3 provides a scaffold for the formation of a larger transcriptional regulatory complex that stabilizes the binding of Pdx1, NeuroD1, and MafA complexes to their respective binding sites within the insulin promoter. Taken together, these results indicate that Glis3 plays a pivotal role in the transcriptional regulation of insulin and may serve as an important therapeutic target for the treatment of diabetes.

Novel diabetes mellitus treatment: mature canine insulin production by canine striated muscle through gene therapy

Muscle-targeted gene therapy using insulin genes has the potential to provide an inexpensive, low maintenance alternative or adjunctive treatment method for canine diabetes mellitus. A canine skeletal muscle cell line was established through primary culture, as well as through transdifferentiation of canine fibroblasts after infection with a myo-differentiation gene containing adenovirus vector. A novel mutant furin-cleavable canine preproinsulin gene insert (cppI4) was designed and created through de novo gene synthesis. Various cell lines, including the generated canine muscle cell line, were transfected with nonviral plasmids containing cppI4. Insulin and desmin immunostaining were used to prove insulin production by muscle cells and specific canine insulin ELISA to prove mature insulin secretion into the medium. The canine myoblast cultures proved positive on desmin immunostaining. All cells tolerated transfection with cppI4-containing plasmid, and double immunostaining for insulin and desmin proved present in the canine cells. Canine insulin ELISA assessment of medium of cppI4-transfected murine myoblasts and canine myoblast and fibroblast mixture proved presence of mature fully processed canine insulin, 24 and 48 h after transfection. The present study provides proof of principle that canine muscle cells can be induced to produce and secrete canine insulin on transfection with nonviral plasmid DNA containing a novel mutant canine preproinsulin gene that produces furin-cleavable canine preproinsulin. This technology could be developed to provide an alternative canine diabetes mellitus treatment option or to provide a constant source for background insulin, as well as C-peptide, alongside current treatment options.

Construction of Plasmid Insulin Gene Vector Containing Metallothionein IIA (pcDNAMTChIns) and Carbohydrate Response Element (ChoRE), and Its Expression in NIH3T3 Cell Line

BackgroundType 1 diabetes mellitus is one of the metabolic diseases that cause insulin-producing pancreatic ß cells be destroyed by immune system self-reactive T cells. Recent­ly, new treatment methods have been developed including use of the stem cells, ß islet cells transplantation and gene therapy by viral and non-viral gene constructs.ObjectivesThe aim of this project was preparing the non-viral vector containing the glucose inducible insulin gene and using it in the NIH3T3 cell line.Materials and MethodsCloning was carried out by standard methods. Total RNA was extracted from pancreatic tissue, RNA was converted to cDNA using RT-PCR reaction and preproinsulin gene was amplified using specific primers. PNMTCH plasmid was extract­ed and digested by NotI, HindIII, and MTIIA and ChoRE genes were purified and cloned into pcDNA3.1 (-) plasmid and named pcDNAMTCh. Finally, the preproinsulin genes were cloned into pcDNA3.1 (-) plasmid and pcDNAMTChIns was built.ResultsThe cloned gene constructs were evaluated by restriction enzyme digestion and RT-PCR. The NIH3T3 cells were transfected by plasmid naked DNA containing preproinsu­lin gene and expression was confirmed by Reverse Transcriptase PCR and Western Blot­ting Techniques.ConclusionsGel electrophoresis of PCR products confirmed that cloning was per­formed correctly. The expression of preproinsulin gene in recombinant plasmid in NI­H3T3 cell line was observed for the first time. The findings in this study can be the basis of further research on diabetes mellitus type 1 gene therapy on animals.

Insulin is secreted upon glucose stimulation by both gastrointestinal enteroendocrine K-cells and L-cells engineered with the preproinsulin gene.

Transgenic mice carrying the human insulin gene driven by the K-cell glucose-dependent insulinotropic peptide (GIP) promoter secrete insulin and display normal glucose tolerance tests after their pancreatic p-cells have been destroyed. Establishing the existence of other types of cells that can process and secrete transgenic insulin would help the development of new gene therapy strategies to treat patients with diabetes mellitus. It is noted that in addition to GIP secreting K-cells, the glucagon-like peptide 1 (GLP-1) generating L-cells share/ many similarities to pancreatic p-cells, including the peptidases required for proinsulin processing, hormone storage and a glucose-stimulated hormone secretion mechanism. In the present study, we demonstrate that not only K-cells, but also L-cells engineered with the human preproinsulin gene are able to synthesize, store and, upon glucose stimulation, release mature insulin. When the mouse enteroendocrine STC-1 cell line was transfected with the human preproinsulin gene, driven either by the K-cell specific GIP promoter or by the constitutive cytomegalovirus (CMV) promoter, human insulin co-localizes in vesicles that contain GIP (GIP or CMV promoter) or GLP-1 (CMV promoter). Exposure to glucose of engineered STC-1 cells led to a marked insulin secretion, which was 7-fold greater when the insulin gene was driven by the CMV promoter (expressed both in K-cells and L-cells) than when it was driven by the GIP promoter (expressed only in K-cells). Thus, besides pancreatic p-cells, both gastrointestinal enteroendocrine K-cells and L-cells can be selected as the target cell in a gene therapy strategy to treat patients with type 1 diabetes mellitus.

Diabetes caused by insulin gene (INS) deletion: clinical characteristics of homozygous and heterozygous individuals

Mutations of the preproinsulin gene (INS) account for both permanent neonatal diabetes (PND) and adult-onset diabetes. The molecular mechanism of complete INS deletion has recently been published and we now add clinical data of homozygous and heterozygous subjects as well as the detailed mapping of the 646 bp deletion of the INS gene. Location and size of the INS deletion was mapped in one case with PND and INS genotype of the whole family was further characterized by breakpoint-spanning PCR. The phenotype of monoallelic loss of INS was studied in 33 adult family members of a large consanguineous kindred with INS deletion. The 646 bp deletion was found in two individuals with PND that included exons 1 and 2 of the INS gene (chr11: g.2138434_2139080del646) and results in loss of approximately half of the preproinsulin protein. The two boys with homozygous INS deletion (D/D) presented with reduced birth weight, PND within the first 24 h of life and complete absence of C-peptide. Adult family members with the N/D had diabetes onset with earliest 25 years, while the oldest subject without diabetes was 45 years. INS-deletion-diabetes was initially treated with oral antidiabetic drugs but then transferred to insulin within 5-16 years. Overall, N/D-subjects (n=11) had a higher risk to develop insulin-dependent diabetes up to the fifth decade, if compared with normal subjects (n=22). Complete loss of the human INS gene results in neonatal diabetes, while heterozygous INS deletion is a strong risk factor for developing insulin-dependent diabetes at adult age.

Nucleo-cytosolic Shuttling of FoxO1 Directly Regulates Mouse Ins2 but Not Ins1 Gene Expression in Pancreatic Beta Cells (MIN6)

The Forkhead box transcription factor FoxO1 regulates metabolic gene expression in mammals. FoxO1 activity is tightly controlled by phosphatidylinositol 3-kinase (PI3K) signaling, resulting in its phosphorylation and nuclear exclusion. We sought here to determine the mechanisms involved in glucose and insulin-stimulated nuclear shuttling of FoxO1 in pancreatic β cells and its consequences for preproinsulin (Ins1, Ins2) gene expression. Nuclear-localized endogenous FoxO1 translocated to the cytosol in response to elevated glucose (3 versus 16.7 mm) in human islet β cells. Real-time confocal imaging of nucleo-cytosolic shuttling of a FoxO1-EGFP chimera in primary mouse and clonal MIN6 β cells revealed a time-dependent glucose-responsive nuclear export, also mimicked by exogenous insulin, and blocked by suppressing insulin secretion. Constitutively active PI3K or protein kinase B/Akt exerted similar effects, while inhibitors of PI3K, but not of glycogen synthase kinase-3 or p70 S6 kinase, blocked nuclear export. FoxO1 overexpression reversed the activation by glucose of pancreatic duodenum homeobox-1 (Pdx1) transcription. Silencing of FoxO1 significantly elevated the expression of mouse Ins2, but not Ins1, mRNA at 3 mm glucose. Putative FoxO1 binding sites were identified in the distal promoter of rodent Ins2 genes and direct binding of FoxO1 to the Ins2 promoter was demonstrated by chromatin immunoprecipitation. A 915-bp glucose-responsive Ins2 promoter was inhibited by constitutively active FoxO1, an effect unaltered by simultaneous overexpression of PDX1. We conclude that nuclear import of FoxO1 contributes to the suppression of Pdx1 and Ins2 gene expression at low glucose, the latter via a previously unsuspected and direct physical interaction with the Ins2 promoter.

Insulin is secreted upon glucose stimulation by both gastrointestinal enteroendocrine K-cells and L-cells engineered with the preproinsulin gene

Transgenic mice carrying the human insulin gene driven by the K-cell glucose-dependent insulinotropic peptide (GIP) promoter secrete insulin and display normal glucose tolerance tests after their pancreatic p-cells have been destroyed. Establishing the existence of other types of cells that can process and secrete transgenic insulin would help the development of new gene therapy strategies to treat patients with diabetes mellitus. It is noted that in addition to GIP secreting K-cells, the glucagon-like peptide 1 (GLP-1) generating L-cells share/ many similarities to pancreatic p-cells, including the peptidases required for proinsulin processing, hormone storage and a glucose-stimulated hormone secretion mechanism. In the present study, we demonstrate that not only K-cells, but also L-cells engineered with the human preproinsulin gene are able to synthesize, store and, upon glucose stimulation, release mature insulin. When the mouse enteroendocrine STC-1 cell line was transfected with the human preproinsulin gene, driven either by the K-cell specific GIP promoter or by the constitutive cytomegalovirus (CMV) promoter, human insulin co-localizes in vesicles that contain GIP (GIP or CMV promoter) or GLP-1 (CMV promoter). Exposure to glucose of engineered STC-1 cells led to a marked insulin secretion, which was 7-fold greater when the insulin gene was driven by the CMV promoter (expressed both in K-cells and L-cells) than when it was driven by the GIP promoter (expressed only in K-cells). Thus, besides pancreatic p-cells, both gastrointestinal enteroendocrine K-cells and L-cells can be selected as the target cell in a gene therapy strategy to treat patients with type 1 diabetes mellitus.

Potential of nucleofected human MSCs for insulin secretion

The goal of this experiment was to generate insulin-producing human mesenchymal stem cells (hMSCs) as a therapeutic source for type I diabetes mellitus, which is caused by insulin deficiency due to the destruction of islet β cells. In various trials for the treatment of type I diabetes, cell-based therapy using adult stem cells is considered to be one of the most useful candidates for the treatment. In this experiment, a non-viral method called nucleofection was used to transfect hMSCs with pEGFP-C2 and furin-cleavable human preproinsulin gene (hPPI) to produce insulin-secreting cells as surrogate β cells. Transfection efficiency was determined using flow cytometry analysis. Expression and production of insulin were tested using RT-PCR and ELISA. The expression, production and maturation of insulin from the genetically engineered hMSCs showed an increase when compared with a non-transfected control group. Insulin expression from hMSCs using nucleofection in this study has shown the potential for type I diabetes therapy. For further study, an evaluation for in vivo experiments and clinical applications must be supplemented.