The insulin gene in diabetes

Single-cell transcriptomic profiling of human pancreatic islets reveals genes responsive to glucose exposure over 24 h

AIMS/HYPOTHESIS

Disruption of pancreatic islet function and glucose homeostasis can lead to the development of sustained hyperglycaemia, beta cell glucotoxicity and subsequently type 2 diabetes. In this study, we explored the effects of in vitro hyperglycaemic conditions on human pancreatic islet gene expression across 24 h in six pancreatic cell types: alpha; beta; gamma; delta; ductal; and acinar. We hypothesised that genes associated with hyperglycaemic conditions may be relevant to the onset and progression of diabetes.

METHODS

We exposed human pancreatic islets from two donors to low (2.8 mmol/l) and high (15.0 mmol/l) glucose concentrations over 24 h in vitro. To assess the transcriptome, we performed single-cell RNA-seq (scRNA-seq) at seven time points. We modelled time as both a discrete and continuous variable to determine momentary and longitudinal changes in transcription associated with islet time in culture or glucose exposure. Additionally, we integrated genomic features and genetic summary statistics to nominate candidate effector genes. For three of these genes, we functionally characterised the effect on insulin production and secretion using CRISPR interference to knock down gene expression in EndoC-βH1 cells, followed by a glucose-stimulated insulin secretion assay.

RESULTS

In the discrete time models, we identified 1344 genes associated with time and 668 genes associated with glucose exposure across all cell types and time points. In the continuous time models, we identified 1311 genes associated with time, 345 genes associated with glucose exposure and 418 genes associated with interaction effects between time and glucose across all cell types. By integrating these expression profiles with summary statistics from genetic association studies, we identified 2449 candidate effector genes for type 2 diabetes, HbA1c, random blood glucose and fasting blood glucose. Of these candidate effector genes, we showed that three (ERO1B, HNRNPA2B1 and RHOBTB3) exhibited an effect on glucose-stimulated insulin production and secretion in EndoC-βH1 cells.

CONCLUSIONS/INTERPRETATION

The findings of our study provide an in-depth characterisation of the 24 h transcriptomic response of human pancreatic islets to glucose exposure at a single-cell resolution. By integrating differentially expressed genes with genetic signals for type 2 diabetes and glucose-related traits, we provide insights into the molecular mechanisms underlying glucose homeostasis. Finally, we provide functional evidence to support the role of three candidate effector genes in insulin secretion and production.

DATA AVAILABILITY

The scRNA-seq data from the 24 h glucose exposure experiment performed in this study are available in the database of Genotypes and Phenotypes (dbGap; https://www.ncbi.nlm.nih.gov/gap/ ) with accession no. phs001188.v3.p1. Study metadata and summary statistics for the differential expression, gene set enrichment and candidate effector gene prediction analyses are available in the Zenodo data repository ( https://zenodo.org/ ) under accession number 11123248. The code used in this study is publicly available at https://github.com/CollinsLabBioComp/publication-islet_glucose_timecourse .

The structure of the TH/INS locus and the parental allele expressed are not conserved between mammals

Parent-of-origin-specific expression of imprinted genes is critical for successful mammalian growth and development. Insulin, coded by the INS gene, is an important growth factor expressed from the paternal allele in the yolk sac placenta of therian mammals. The tyrosine hydroxylase gene TH encodes an enzyme involved in dopamine synthesis. TH and INS are closely associated in most vertebrates, but the mouse orthologues, Th and Ins2, are separated by repeated DNA. In mice, Th is expressed from the maternal allele, but the parental origin of expression is not known for any other mammal so it is unclear whether the maternal expression observed in the mouse represents an evolutionary divergence or an ancestral condition. We compared the length of the DNA segment between TH and INS across species and show that separation of these genes occurred in the rodent lineage with an accumulation of repeated DNA. We found that the region containing TH and INS in the tammar wallaby produces at least five distinct RNA transcripts: TH, TH-INS1, TH-INS2, lncINS and INS. Using allele-specific expression analysis, we show that the TH/INS locus is expressed from the paternal allele in pre- and postnatal tammar wallaby tissues. Determining the imprinting pattern of TH/INS in other mammals might clarify if paternal expression is the ancestral condition which has been flipped to maternal expression in rodents by the accumulation of repeat sequences.

Molecular Mechanisms in the Etiology of Polycystic Ovary Syndrome (PCOS): A Multifaceted Hypothesis Towards the Disease with Potential Therapeutics

Among the premenopausal women, Polycystic Ovary Syndrome (PCOS) is the most prevalent endocrinopathy affecting the reproductive system and metabolic rhythms leading to disrupted menstrual cycle. Being heterogeneous in nature it is characterized by complex symptomology of oligomennorhoea, excess of androgens triggering masculine phenotypic appearance and/or multiple follicular ovaries. The etiology of this complex disorder remains somewhat doubtful and the researchers hypothesize multisystem links in the pathogenesis of this disease. In this review, we attempt to present several hypotheses that tend to contribute to the etiology of PCOS. Metabolic inflexibility, aberrant pattern of gonadotropin signaling along with the evolutionary, genetic and environmental factors have been discussed. Considered a lifelong endocrinological implication, no universal treatment is available for PCOS so far however; multiple drug therapy is often advised along with simple life style intervention is mainly advised to manage its cardinal symptoms. Here we aimed to present a summarized view of pathophysiological links of PCOS with potential therapeutic strategies.

Root extracts of Anacardium occidentale reduce hyperglycemia and oxidative stress in vitro

Background

Hyperglycemia is the hallmark of diabetes, and the associated oxidative stress is a major concern that invites an array of diabetic complications. The traditional practices of medicare are of great, current interest due to the high cost and side effects of conventional diabetic medications. The present in vitro study focuses on evaluating the potential of various A. occidentale root extracts for their antihyperglycemic and antioxidant potentials.

Materials and methods

The four different solvent extracts petroleum ether (PEAO), chloroform (CHAO), ethyl acetate (EAAO), and 80 % methanol (80 % MAO) of A. occidentale roots were evaluated for their total phenolic, flavonoid, and antioxidant capacity. Using MIN6 pancreatic β-cells, the cytotoxicity of the extracts was evaluated by MTT assay and the antidiabetic potential by quantifying the insulin levels by ELISA at a higher concentration of glucose. The effect of 80 % MAO on INS gene expression was determined by qRT PCR analysis.

Results

Among the four different solvent extracts of A. occidentale roots, 80 % MAO showed the highest concentration of phenolics (437.33 ± 0.03 µg GAE/mg), CHAO to be a rich source of flavonoids (46.04 ± 0.1 µg QE/mg) and with the highest total antioxidant capacity (1865.33 ± 0.09 µg AAE/ mg). Evaluation of the free radical scavenging and reducing properties of the extracts indicated 80 % MAO to exhibit the highest activity. The MTT assay revealed the least cytotoxicity of all four extracts. 80 % MAO enhanced INS up-regulation as well as insulin secretion even under high glucose concentration (27mM).

Conclusions

The present study demonstrated that the A. occidentale root extracts have effective antihyperglycemic and antioxidative properties, together with the potential of normalizing the insulin secretory system of β-cells. Above mentioned properties have to be studied further by identifying the active principles of A. occidentale root extracts and in vivo effects. The prospect of the present study is identifying drug leads for better management of diabetes from the A. occidentale root extracts.

Graphical abstract

Autocrine IGF2 programmes β-cell plasticity under conditions of increased metabolic demand

When exposed to nutrient excess and insulin resistance, pancreatic β-cells undergo adaptive changes in order to maintain glucose homeostasis. The role that growth control genes, highly expressed in early pancreas development, might exert in programming β-cell plasticity in later life is a poorly studied area. The imprinted Igf2 (insulin-like growth factor 2) gene is highly transcribed during early life and has been identified in recent genome-wide association studies as a type 2 diabetes susceptibility gene in humans. Hence, here we investigate the long-term phenotypic metabolic consequences of conditional Igf2 deletion in pancreatic β-cells (Igf2βKO) in mice. We show that autocrine actions of IGF2 are not critical for β-cell development, or for the early post-natal wave of β-cell remodelling. Additionally, adult Igf2βKO mice maintain glucose homeostasis when fed a chow diet. However, pregnant Igf2βKO females become hyperglycemic and hyperinsulinemic, and their conceptuses exhibit hyperinsulinemia and placentomegalia. Insulin resistance induced by congenital leptin deficiency also renders Igf2βKO females more hyperglycaemic compared to leptin-deficient controls. Upon high-fat diet feeding, Igf2βKO females are less susceptible to develop insulin resistance. Based on these findings, we conclude that in female mice, autocrine actions of β-cell IGF2 during early development determine their adaptive capacity in adult life.

Study on the Mechanism of Prunella Vulgaris L on Diabetes Mellitus Complicated with Hypertension Based on Network Pharmacology and Molecular Docking Analyses

The role of traditional Chinese medicine Prunella vulagaris L in the treatment of tumors and inflammation has been widely confirmed. We found that some signaling pathways of Prunella vulgaris L action can also regulate diabetes and hypertension, so we decided to study the active ingredients, potential targets and signaling pathway of Prunrlla vulgaris L, and explore the "multi-target, multi-pathway" molecular mechanism of Prunella vulgaris L on diabetes mellitus complicated with hypertension(DH). Methods. Based on TCMSP(Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform) and CNKI(China National Knowledge Infrastructure), the components and action targets related to Prunella vulgaris L were screened. The OMIM(Online Mendelian Inheritance in Man) and GeneCards (The human gene database) were used to search for targets related to DH. The "gene - drug - disease" relationship map was drawn by Cytoscape_v3.7.2 plug-in. The target was amplified by the STRING platform, and the "protein - protein" interaction relationship (PPI) network of the interacting target was obtained by the STRING online analysis platform and the Cytoscape_v3.7.2 plug-in. Finally, GO enrichment analysis and KEGG pathway enrichment analysis were conducted on David and Metascape platform to study the co-acting targets. Results. 11 active components, 41 key targets and 16 significant signaling pathways were identified from Prunella vulgaris L. The main active components of Prunella vulgaris L against DH were quercetin and kaumferol, etc, and potential action targets were IL-6 and INS, etc and signaling pathways were AGE-RAGE signaling pathway, TNF signaling pathway, MAPK signaling pathway, PI3K-AKT signaling pathway, etc. It involves in biological processes such as cell proliferation, apoptosis and inflammatory response. Conclusions. The main molecular mechanism of Prunella vulgaris L against DH is that sterols and flavonoids play an active role by affecting TNF signaling pathway, AGE-RAGE signaling pathway, MAPK pathway, PI3K-Akt pathway related targets such as IL-6 and INS.

Association of insulin gene VNTR INS -23/Hph1 A>T (rs689) polymorphism with type 1 diabetes mellitus in Egyptian children

Background

Type1 diabetes mellitus (T1DM) has a multi-factorial pathogenesis; the interplay between genetic susceptibility and environmental factors is thought to provide the fundamental element for the disease. Apart from HLA, more than 50 genetic variants are associated with T1DM. INS -23/Hph1 A>T (rs689) is one of the effective loci with inconsistent reports in the literature. Accordingly, this study was designed to define the frequencies of INS -23/Hph1 A>T polymorphism and its association with T1DM in Egyptian diabetic children and their non-diabetic family members as compared to healthy controls.

Methods

Using polymerase chain reaction-restriction fragment length polymorphism methodology, analysis of insulin gene VNTR polymorphism was performed for 496 samples (91 patients, 179 parents, 130 siblings, and 96 controls); parents and siblings were apparently healthy.

Results

INS genotypes and allele frequencies were comparable between patients, non-diabetic siblings, and parents (p = 0.97 and 0.77, respectively). However, the TT/AT genotype and T allele were over-presented in the three family groups compared to controls (p = 0.0015 and 0.0029, respectively).

Comparing patients to controls, the T allele is considered a risk factor for the development of TIDM (OR 2.56, 95% CI 1.42–4.62, p = 0.0017).

INS -23/Hph1 A>T polymorphism showed concordance between patients and their mothers (Kappa = 0.446, p = 0.000) but not with their fathers (Kappa = 0.031, p = 0.765).

Conclusions

INS -23/Hph1 A>T gene polymorphism was shown to be a risk factor for the development of TIDM. This is in agreement with some and in disagreement with other reports. Studies of risk susceptibility factors have to be carried out locally in each community; results cannot be extrapolated from one ethnic group to another.

Identification of insulin gene variants in neonatal diabetes

OBJECTIVES

Permanent neonatal diabetes (PNDM) is caused by mutations in the genes responsible for the synthesis of different proteins that are important for the normal behavior of beta cells in the pancreas. Mutations in the insulin gene (INS) are considered as one of the causes of diabetes in neonates. This study aimed to investigate the genetic variations in the INS gene in a group of Egyptian infants diagnosed with PNDM.

METHODS

We screened exons 2 and 3 with intronic boundaries of the INS gene by direct gene sequencing in 30 PNDM patients and 20 healthy controls. A detailed clinical phenotyping of the patients was carried out to specify the diabetes features in those found to carry an INS variant.

RESULTS

We identified five variants (four SNPs and one synonymous variant), c(0).187 + 11T > C, c.-17-6T > A, c.*22A > C, c.*9C > T, and c.36G > A (p.A12A), with allelic frequencies of 96.7%, 80%, 75%, 5%, and 1.7%, respectively. All showed no statistically significance difference compared with the controls, with the exception of c.*22A > C.

CONCLUSION

Genetic screening for the INS gene did not reveal an evident role in the diagnosis of PNDM.

Insulin-like Growth Factor 2 Overexpression Induces β-Cell Dysfunction and Increases Beta-cell Susceptibility to Damage

The human insulin-like growth factor 2 (IGF2) and insulin genes are located within the same genomic region. Although human genomic studies have demonstrated associations between diabetes and the insulin/IGF2 locus or the IGF2 mRNA-binding protein 2 (IGF2BP2), the role of IGF2 in diabetes pathogenesis is not fully understood. We previously described that transgenic mice overexpressing IGF2 specifically in β-cells (Tg-IGF2) develop a pre-diabetic state. Here, we characterized the effects of IGF2 on β-cell functionality. Overexpression of IGF2 led to β-cell dedifferentiation and endoplasmic reticulum stress causing islet dysfunction in vivo. Both adenovirus-mediated overexpression of IGF2 and treatment of adult wild-type islets with recombinant IGF2 in vitro further confirmed the direct implication of IGF2 on β-cell dysfunction. Treatment of Tg-IGF2 mice with subdiabetogenic doses of streptozotocin or crossing these mice with a transgenic model of islet lymphocytic infiltration promoted the development of overt diabetes, suggesting that IGF2 makes islets more susceptible to β-cell damage and immune attack. These results indicate that increased local levels of IGF2 in pancreatic islets may predispose to the onset of diabetes. This study unravels an unprecedented role of IGF2 on β-cells function.

Association of insulin gene variable number of tandem repeats regulatory polymorphism with polycystic ovary syndrome

The present meta-analysis aimed to investigate the association between insulin gene variable number of tandem repeats (INS VNTR) and polycystic ovary syndrome (PCOS). Systematic searches of electronic databases, reference lists of included articles, and the abstracts presented at related scientific societies meetings were performed. Statistical analyses were conducted using software Stata 11.0. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were applied. Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 9 studies including 1075 PCOS patients and 2878 controls were included in the meta-analysis. There were evidence of statistical significant association between INS VNTR and PCOS in allelic model (OR=1.25, 95% CI=1.08-1.43, P=0.002) and dominant model (OR=1.34, 95% CI=1.11-1.63, P=0.003) but not in additive model (OR=1.38, 95% CI=0.93-2.04, P=0.11) and recessive model (OR=1.26, 95% CI=0.96-1.65, P=0.09). No significant publication bias was shown by funnel plots and Egger's regression tests. In conclusion, our meta-analysis suggests that the III allele of INS VNTR is associated with increased risk of PCOS.

The relationship between type 2 diabetes family history, body composition and blood basal glycemia in sedentary people

The aim of this study was to verify whether there is a positive correlation between family history to type 2 diabetes mellitus and body mass and composition, and alterations in blood basal glycaemia levels in sedentary male and female. Anthropometric variables, blood parameters, body composition and body surface area were evaluated on 183 male and 237 female sedentary individuals. Participants were classified into two groups: FH(+) (family history positive) and FH(-) (familiar history negative) according to their medical history. The FH(+) group showed higher values of body mass and body surface area than FH(-) group. These differences were statistically significant (p < 0.05) for the female subgroup. When compared to the FH(-) group, FH(+) female individuals showed a significantly greater fat mass (p < 0.01) and a significantly lower free fat mass-to-fat mass ratio (FFM/FM ratio) (p < 0.05). FH(+) female individuals showed significant lower levels of basal glucose values for Kg of FFM (p < 0.05), FM (p < 0.01) and BSA (p < 0.01) than FH(-) group. The results of this study indicate that body mass and composition correlate positively to family history to type 2 diabetes. The relationship between family history and body composition is particularly evident in young FH(+) female. Thus, as family history might represent a risk factor for the development of type 2 diabetes, this could be considered as an important parameter able to predict the onset of the disease itself. This knowledge could be used to improve preventive interventions (i.e. increasing levels of physical activity) promoting healthy lifestyle.

Genetics of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a highly complex endocrine disorder, characterized by hyperandrogenemia, menstrual irregularities and polycystic ovaries. A strong genetic component to the etiology of PCOS is evident. However, due to the genetic and phenotypic heterogeneity of PCOS and the lack of insufficiently large cohorts, studies to identify specific contributing genes to date have yielded only few conclusive results. In this review we discuss the current status of the genetic analysis of PCOS including the results of numerous association studies with candidate genes involved in TGF-β and insulin signaling, type 2 diabetes mellitus and obesity susceptibility. Furthermore, we address current challenges in genetic studies of PCOS, and the promise of new approaches, including genome-wide association studies and next-generation sequencing.

Chromatin structure, epigenetic mechanisms and long-range interactions in the human insulin locus

Regulation of gene expression in eukaryotes is largely dependent on variations in chromatin structure. More recently, it has become clear that this may involve not only local chromatin organization but also distant regulatory elements that participate in large-scale chromatin architecture within the nucleus. We describe recent methods that make possible the detection of such structures and apply them to analysis of the human insulin (INS) locus in pancreatic islets. We show that the INS gene is part of an extended 'open' chromatin domain that includes adjacent genes as well. We also find that in islets, the INS promoter is in physical contact with distant sites on the same human chromosome and notably, with the SYT8 gene, located nearly 300 kb away. The strength of the contact between INS and SYT8 is increased by glucose, and this results in stimulation of SYT8 expression. Inhibition of INS transcription decreases SYT8 expression. Furthermore, downregulation of SYT8 results in decreased secretion of insulin. Our results thus establish the existence of a regulatory network between the INS gene and other distant genes through long-range physical interactions, and suggest that such networks may have general importance for insulin biology and diabetes.

Association between INS-VNTR polymorphism and polycystic ovary syndrome in a Korean population

Polycystic ovary syndrome (PCOS) is a common disorder in women of reproductive ages. But its etiology is not fully understood yet. Variability in the number of tandem repeats of the insulin gene (INS-VNTR) is known to associate with PCOS, and it is associated with an increased risk of diabetes mellitus and other cardiovascular diseases. The aim of our study was to analyze an association between the INS-VNTR polymorphism and PCOS in a Korean population. The -23/Hph I polymorphism was used as a surrogate marker for INS-VNTR polymorphism and a total of 218 PCOS patient and 141 control DNAs were analyzed by restriction fragment length polymorphism method. Statistical analysis of genotyping results were performed using HapAnalyzer. χ² test and logistic regression were used to analyze the association between two groups. A p value <0.05 was considered statistically significant. The frequencies of A/A and A/T genotypes indicated a similar change between PCOS patients and controls. In conclusion, there was no association between PCOS and INS-VNTR polymorphism (p = 0.0544, odds ratio = 1.69). Our present data demonstrate that INS-VNTR polymorphism is not related with PCOS in Korean women. Thus, it is suggested that INS-VNTR polymorphism is not a key factor in the etiology and the pathogenesis of PCOS in a Korean population.

The influence of the microbiota on type-1 diabetes: on the threshold of a leap forward in our understanding

The last several years have seen breakthroughs in techniques to track the symbiont communities that normally colonize mammals (the microbiota) and in cataloguing the universe of the genes they carry (the microbiome). Applying these methods to human patients and corresponding murine models should allow us to decipher just how the microbiota impacts type-1 diabetes, i.e. which particular microbes are responsible and the cellular and molecular processes that are involved. Here, at its threshold, we set the stage for what promises to be an exciting rejuvenated area of investigation.

Tests for genetic interactions in type 1 diabetes: linkage and stratification analyses of 4,422 affected sib-pairs

OBJECTIVE

Interactions between genetic and environmental factors lead to immune dysregulation causing type 1 diabetes and other autoimmune disorders. Recently, many common genetic variants have been associated with type 1 diabetes risk, but each has modest individual effects. Familial clustering of type 1 diabetes has not been explained fully and could arise from many factors, including undetected genetic variation and gene interactions.

RESEARCH DESIGN AND METHODS

To address this issue, the Type 1 Diabetes Genetics Consortium recruited 3,892 families, including 4,422 affected sib-pairs. After genotyping 6,090 markers, linkage analyses of these families were performed, using a novel method and taking into account factors such as genotype at known susceptibility loci.

RESULTS

Evidence for linkage was robust at the HLA and INS loci, with logarithm of odds (LOD) scores of 398.6 and 5.5, respectively. There was suggestive support for five other loci. Stratification by other risk factors (including HLA and age at diagnosis) identified one convincing region on chromosome 6q14 showing linkage in male subjects (corrected LOD = 4.49; replication P = 0.0002), a locus on chromosome 19q in HLA identical siblings (replication P = 0.006), and four other suggestive loci.

CONCLUSIONS

This is the largest linkage study reported for any disease. Our data indicate there are no major type 1 diabetes subtypes definable by linkage analyses; susceptibility is caused by actions of HLA and an apparently random selection from a large number of modest-effect loci; and apart from HLA and INS, there is no important susceptibility factor discoverable by linkage methods.

Induction of mixed chimerism with MHC-mismatched but not matched bone marrow transplants results in thymic deletion of host-type autoreactive T-cells in NOD mice

OBJECTIVE

Induction of mixed or complete chimerism via hematopoietic cell transplantation (HCT) from nonautoimmune donors could prevent or reverse type 1 diabetes (T1D). In clinical settings, HLA-matched HCT is preferred to facilitate engraftment and reduce the risk for graft versus host disease (GVHD). Yet autoimmune T1D susceptibility is associated with certain HLA types. Therefore, we tested whether induction of mixed chimerism with major histocompatibility complex (MHC)-matched donors could reverse autoimmunity in the NOD mouse model of T1D.

RESEARCH DESIGN AND METHODS

Prediabetic wild-type or transgenic BDC2.5 NOD mice were conditioned with a radiation-free GVHD preventative anti-CD3/CD8 conditioning regimen and transplanted with bone marrow (BM) from MHC-matched or mismatched donors to induce mixed or complete chimerism. T1D development and thymic deletion of host-type autoreactive T-cells in the chimeric recipients were evaluated.

RESULTS

Induction of mixed chimerism with MHC-matched nonautoimmune donor BM transplants did not prevent T1D in wild-type NOD mice, although induction of complete chimerism did prevent the disease. However, induction of either mixed or complete chimerism with MHC-mismatched BM transplants prevented T1D in such mice. Furthermore, induction of mixed chimerism in transgenic BDC2.5-NOD mice with MHC-matched or -mismatched MHC II(-/-) BM transplants failed to induce thymic deletion of de novo developed host-type autoreactive T-cells, whereas induction of mixed chimerism with mismatched BM transplants did.

CONCLUSIONS

Induction of mixed chimerism with MHC-mismatched, but not matched, donor BM transplants re-establishes thymic deletion of host-type autoreactive T-cells and prevents T1D, with donor antigen-presenting cell expression of mismatched MHC II molecules being required.

Quantitative phosphoproteomic analysis of T cell receptor signaling in diabetes prone and resistant mice

Type 1 diabetes, in human patients and NOD mice, results from an immune attack on insulin-producing beta-cells of the pancreas by autoreactive T lymphocytes. In NOD mice, genetically controlled perturbations in the signaling pathways downstream of the antigen-specific T cell receptor (TCR) may be instrumental in the altered responses of T cells, manifest as inefficient induction of apoptosis after recognition of self-antigens in the thymus or as perturbed reactivity of mature T cells in peripheral organs. To map this signaling difference(s), we have used mass spectrometry-based quantitative phosphoproteomics to compare the activation of primary CD4(+) T cells of diabetes-prone NOD and -resistant B6.H2g7 mice. Immunoprecipitation and IMAC purification of tyrosine-phosphorylated peptides, combined with a stable-isotope iTRAQ labeling, enabled us to identify and quantify over 77 phosphorylation events in 54 different proteins downstream of TCR stimulation of primary CD4(+) T cells. This analysis showed a generally higher level of phosphotyrosine in activated NOD cells, as well as several phosphorylation sites that appeared to be differentially regulated in these two strains (involving TXK, CD5, PAG1, and ZAP-70). These data highlight the differences in signaling between CD4(+) T cell compartments of NOD and B6g7 mice and may underlie the dysregulation of T cells in NOD mice.

Association of single nucleotide polymorphisms in cytotoxic T-lymphocyte antigen 4 and susceptibility to autoimmune type 1 diabetes in Tunisians

In addition to HLA and insulin genes, the costimulatory molecule CTLA-4 gene is a confirmed type 1 diabetes (T1D) susceptibility gene. Previous studies investigated the association of CTLA-4 genetic variants with the risk of T1D, but with inconclusive findings. Here, we tested the contributions of common CTLA-4 gene variants to T1D susceptibility in Tunisian patients and control subjects. The study subjects comprised 228 T1D patients (47.8% females) and 193 unrelated healthy controls (45.6% females). Genotyping for CTLA-4 CT60A/G (rs3087243), +49A/G (rs231775), and -318C/T (rs5742909) was performed by PCR-restriction fragment length polymorphism (RFLP) analysis. The minor-allele frequencies (MAF) for the three CTLA-4 variants were significantly higher in T1D patients, and significantly higher frequencies of homozygous +49G/G and homozygous CT60G/G genotypes were seen in patients, which was confirmed by univariate regression analysis (taking the homozygous wild type as a reference). Of the eight possible three-locus CTLA-4 haplotypes (+49A/G, -318C/T, and CT60A/G) identified, multivariate regression analysis confirmed the positive association of ACG (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.26 to 2.94), GCG (OR, 2.40; 95% CI, 1.11 to 5.21), and GTA (OR, 4.67; 95% CI, 1.52 to 14.39) haplotypes with T1D, after confounding variables were adjusted for. Our results indicate that CTLA-4 gene variants are associated with increased T1D susceptibility in Tunisian patients, further supporting a central role for altered T-cell costimulation in T1D pathogenesis.

Genetic basis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with obesity and manifests with reproductive, hyperandrogenic and metabolic features. Although the etiology of PCOS is complex and incompletely understood, genetics plays an important role (heritability: ∼70%). Potential problems with studying the genetics of PCOS include the heterogeneity of the condition and associated sub-fertility. A candidate gene approach has been used in over 70 published studies on PCOS, most of which have been inadequately powered to detect a statistically meaningful association. Furthermore, these studies often fail to replicate prior published studies on the same candidate gene in different populations. The first genome-sequence variant (identified from a genome-wide association study in subjects with Type 2 diabetes mellitus) to be studied in PCOS (FTO gene) has been shown by our group to associate with susceptibility for the development of PCOS. This is the first genetic corroboration of a link between PCOS and obesity. Future directions include a genome-wide association study in PCOS.

No association of the insulin gene VNTR polymorphism with polycystic ovary syndrome in a Han Chinese population

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with an increased risk of type II diabetes mellitus. The results of previous research about the association of the VNTR polymorphism in 5-prime flanking region of the insulin (INS) gene with PCOS have been inconsistent. The present study was to investigate the association of the INS-VNTR polymorphism with PCOS in a Han Chinese population.

METHODS

The -23/HphI polymorphism as a surrogate marker of the INS-VNTR length polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) in 216 PCOS patients and 192 non-PCOS women as a control group. Allelic and genotypic frequencies were compared between patients and controls, and these results were analyzed in respect to clinical test data.

RESULTS

No significant differences were observed between the cases and controls groups either in allele (P = 0.996) or genotype (P = 0.802) frequencies of INS-VNTR polymorphism; Regarding anthropometric data and hormone levels, there were no significant differences between INS-VNTR genotypes in the PCOS group, as well as in the non-PCOS group.

CONCLUSION

The present study demonstrated for the first time that the INS-VNTR polymorphism is not a key risk factor for sporadic PCOS in the Han Chinese women. Further studies are needed to give a global view of this polymorphism in pathogenesis of PCOS in a large-scale sample, family-based association design or well-defined subgroups of PCOS.

Association of insulin-like growth factor 2 with the insulin-linked polymorphic region in cultured fetal thymus cells

The insulin-linked polymorphic region (ILPR) is a regulatory sequence in the promoter region upstream of the human insulin gene and is widely recognized as a locus of type 1 diabetes susceptibility. Polymorphism of the ILPR sequence can affect expression of both insulin and the adjacent insulin-like growth factor 2 (IGF-2) gene. Several ILPR variants form G-quadruplex DNA structures in vitro that exhibit affinity binding to insulin and IGF-2. It has been suggested that the ILPR may form G-quadruplexes in vivo as well, raising the possibility that insulin and IGF-2 may bind to these structures in the ILPR in chromatin of live cells. This work establishes the presence of IGF-2 in the nucleus of cells cultured from human fetal thymus and its association with the ILPR in the chromatin of these cells. In vitro experiments support the involvement of G-quadruplex DNA in the binding interaction.

A genome-inspired DNA ligand for the affinity capture of insulin and insulin-like growth factor-2

The insulin-linked polymorphic region (ILPR) of the human insulin gene contains tandem repeats of similar G-rich sequences, some of which form intramolecular G-quadruplex structures in vitro. Previous work showed affinity binding of insulin to an intramolecular G-quadruplex formed by ILPR variant a. Here, we report on interactions of insulin and the highly homologous insulin-like growth factor-2 (IGF-2) with ILPR variants a, h, and i. Circular dichroism indicated intramolecular G-quadruplex formation for variants a and h. Affinity MALDI MS and surface plasmon resonance were used to compare protein capture and binding strengths. Insulin and IGF-2 exhibited high binding affinity for variants a and h but not i, indicating the involvement of intramolecular G-quadruplexes. Interaction between insulin and variant a was unique in the appearance of two binding interactions with K(D) approximately 10(-13) M and K(D) approximately 10(-7) M, which was not observed for insulin with variant h (K(D) approximately 10(-8) M) or IGF-2 with either variant (K(D)s approximately 10(-9) M). The results provide a basis for the design of DNA binding ligands for insulin and IGF-2 and support a new approach to discovery of DNA affinity binding ligands based on genome-inspired sequences rather than the traditional combinatorial selection route to aptamer discovery.

Aire

Mutations in the transcriptional regulator, Aire, cause APECED, a polyglandular autoimmune disease with monogenic transmission. Animal models of APECED have revealed that Aire plays an important role in T cell tolerance induction in the thymus, mainly by promoting ectopic expression of a large repertoire of transcripts encoding proteins normally restricted to differentiated organs residing in the periphery. The absence of Aire results in impaired clonal deletion of self-reactive thymocytes, which escape into the periphery and attack a variety of organs. In addition, Aire is a proapoptotic factor, expressed at the final maturation stage of thymic medullary epithelial cells, a function that may promote cross-presentation of the antigens encoded by Aire-induced transcripts in these cells. Transcriptional regulation by Aire is unusual in being very broad, context-dependent, probabilistic, and noisy. Structure/function analyses and identification of its interaction partners suggest that Aire may impact transcription at several levels, including nucleosome displacement during elongation and transcript splicing or other aspects of maturation.

Update in endocrine autoimmunity

CONTEXT

The endocrine system is a common target in pathogenic autoimmune responses, and there has been recent progress in our understanding, diagnosis, and treatment of autoimmune endocrine diseases.

SYNTHESIS

Rapid progress has recently been made in our understanding of the genetic factors involved in endocrine autoimmune diseases. Studies on monogenic autoimmune diseases that include endocrine phenotypes like autoimmune polyglandular syndrome type 1 and immune dysregulation, polyendocrinopathy, enteropathy, X-linked have helped reveal the role of key regulators in the maintenance of immune tolerance. Highly powered genetic studies have found and confirmed many new genes outside of the established role of the human leukocyte antigen locus with these diseases, and indicate an essential role of immune response pathways in these diseases. Progress has also been made in identifying new autoantigens and the development of new animal models for the study of endocrine autoimmunity. Finally, although hormone replacement therapy is still likely to be a mainstay of treatment in these disorders, there are new agents being tested for potentially treating and reversing the underlying autoimmune process.

CONCLUSION

Although autoimmune endocrine disorders are complex in etiology, these recent advances should help contribute to improved outcomes for patients with, or at risk for, these disorders.

Insulin gene polymorphisms in type 1 diabetes, Addison's disease and the polyglandular autoimmune syndrome type II

Background

Polymorphisms within the insulin gene can influence insulin expression in the pancreas and especially in the thymus, where self-antigens are processed, shaping the T cell repertoire into selftolerance, a process that protects from β-cell autoimmunity.

Methods

We investigated the role of the -2221Msp(C/T) and -23HphI(A/T) polymorphisms within the insulin gene in patients with a monoglandular autoimmune endocrine disease [patients with isolated type 1 diabetes (T1D, n = 317), Addison's disease (AD, n = 107) or Hashimoto's thyroiditis (HT, n = 61)], those with a polyglandular autoimmune syndrome type II (combination of T1D and/or AD with HT or GD, n = 62) as well as in healthy controls (HC, n = 275).

Results

T1D patients carried significantly more often the homozygous genotype "CC" -2221Msp(C/T) and "AA" -23HphI(A/T) polymorphisms than the HC (78.5% vs. 66.2%, p = 0.0027 and 75.4% vs. 52.4%, p = 3.7 × 10^-8, respectively).

The distribution of insulin gene polymorphisms did not show significant differences between patients with AD, HT, or APS-II and HC.

Conclusion

We demonstrate that the allele "C" of the -2221Msp(C/T) and "A" -23HphI(A/T) insulin gene polymorphisms confer susceptibility to T1D but not to isolated AD, HT or as a part of the APS-II.

Joint effects of HLA, INS, PTPN22 and CTLA4 genes on the risk of type 1 diabetes

BACKGROUND/HYPOTHESIS

HLA, INS, PTPN22 and CTLA4 are considered to be confirmed type 1 diabetes susceptibility genes. HLA, PTPN22 and CTLA4 are known to be involved in immune regulation. Few studies have systematically investigated the joint effect of multiple genetic variants. We evaluated joint effects of the four established genes on the risk of childhood-onset type 1 diabetes.

METHODS

We genotyped 421 nuclear families, 1,331 patients and 1,625 controls for polymorphisms of HLA-DRB1, -DQA1 and -DQB1, the insulin gene (INS, -23 HphI), CTLA4 (JO27_1) and PTPN22 (Arg620Trp).

RESULTS

The joint effect of HLA and PTPN22 on type 1 diabetes risk was significantly less than multiplicative in the case-control data, but a multiplicative model could not be rejected in the trio data. All other two-way gene-gene interactions fitted multiplicative models. The high-risk HLA genotype conferred a very high risk of type 1 diabetes (OR 20.6, using the neutral-risk HLA genotype as reference). When including also intermediate-risk HLA genotypes together with risk genotypes at the three non-HLA loci, the joint odds ratio was 61 (using non-risk genotypes at all loci as reference).

CONCLUSION

Most established susceptibility genes seem to act approximately multiplicatively with other loci on the risk of disease except for the joint effect of HLA and PTPN22. The joint effect of multiple susceptibility loci conferred a very high risk of type 1 diabetes, but applies to a very small proportion of the general population. Using multiple susceptibility genotypes compared with HLA genotype alone seemed to influence the prediction of disease only marginally.

Low-density lipoprotein receptor-related protein-5 C/T polymorphism in exon 18 is associated with C peptide and proinsulin levels in control women and patients with polycystic ovary syndrome

OBJECTIVE

To assess the previously unstudied potential role of C/T (A1330V) polymorphism of the low-density lipoprotein receptor-related protein-5 gene in insulin sensitivity and secretion in polycystic ovary syndrome. The low-density lipoprotein receptor-related protein-5 gene has been found to play a role in determining insulin secretion in animal models.

DESIGN

Case-control study.

SETTING

Tertiary outpatient clinic.

PATIENT(S)

Women with polycystic ovary syndrome (n = 299; age, 27.5 +/- 7.1 y [mean +/- SD]), according to the European Society of Human Reproduction and Embryology criteria, as well as healthy control women (n = 187, age, 28.9 +/- 9.8 y).

INTERVENTION(S)

Oral glucose tolerance test, blood sampling.

MAIN OUTCOME MEASURE(S)

Glucose, insulin, C peptide, proinsulin during oral glucose tolerance tests, and lipids. Genotyping of C/T (A1330V) polymorphism by polymerase chain reaction-restriction fragment length polymorphism.

RESULT(S)

There was no difference in the frequency of genotypes between women with polycystic ovary syndrome (CC/CT/TT: 80.3%, 18.4%, 1.3%) and the control women (79.1%, 19.8%, and 1.1%). Carriers of the T allele had statistically significantly higher basal and stimulated C peptide and proinsulin levels than CC homozygotes, both basally and at the 180th minute. Regarding insulin sensitivity, there was no difference between T carriers and CC homozygotes.

CONCLUSION(S)

Polymorphism of C/T in the low-density lipoprotein receptor-related protein-5 gene is associated with C-peptide and proinsulin secretion but does not influence insulin sensitivity in either healthy women or women with polycystic ovary syndrome.

Islet autoantibody development during follow-up of high-risk children from the general Norwegian population from three months of age: design and early results from the MIDIA study

We describe the design of the MIDIA study and present serial islet autoantibody data from 3 months of age in the 526 first enrolled children from the general population carrying the type 1 diabetes high-risk HLA-DRB1*0401-DQA1*03-DQB1*0302/DRB1*0301-DQA1*05-DQB1*02 genotype. Blood samples were obtained from children at ages 3, 6, 9 and 12 months and annually thereafter to a median age of 12 months. Autoantibodies to insulin, glutamic acid decarboxylase and insulinoma-associated antigen-2 were measured with radiobinding assays. About 25,000 general population newborns were genotyped, and among 526 children with the high-risk HLA genotype, 2104 samples were assayed. Fourteen children were positive in at least two consecutive samples, including 12 who were positive for > or =2 autoantibodies at least once, of which five developed type 1 diabetes at median age 15.3 months. Seven of 14 persistently positive children seroconverted before 9 months, including two before 6 months of age. The estimated cumulative probability of multiple autoantibody positivity at 5 years was 7.3% (95% confidence interval: 3.5-12.4%). Thus, persistent islet autoimmunity is not uncommon in the first year of life in children from the general population carrying the high-risk HLA genotype, and may develop as early as at 6 months of age.

The genetics of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a very common endocrine disorder that has a strong genetic component and is characterized by polycystic ovaries, hyperandrogenemia, and menstrual irregularity. During the past decade, the roles of more than 70 candidate genes have been evaluated for a causal role in PCOS; however, because of genetic and phenotypic heterogeneity and underpowered studies, the results of many of these studies remain inconclusive. Here, the results of the genetic analysis of several candidate genes and gene regions-CYP11A (encoding cytochrome P450, family 11, subfamily A polypeptides), CAPN10 (encoding calpain 10), the insulin gene VNTR (variable number of tandem repeats), and D19S884 (a dinucleotide repeat marker mapping to chromosome 19p13.2)-are discussed in detail. Although past genetic studies of PCOS have yielded only modest results, resources and techniques have been assembled to remedy the major deficits of these early studies, promising that the next few years will be a very exciting and rewarding era for the genetic analysis of PCOS.

Elimination of insulitis and augmentation of islet beta cell regeneration via induction of chimerism in overtly diabetic NOD mice

Type 1 diabetes in both humans and nonobese diabetic (NOD) mice results from autoreactive T cell destruction of insulin-producing beta cells. Cure of type 1 diabetes may require both reversal of autoimmunity and regeneration of beta cells. Induction of chimerism via allogeneic hematopoietic cell transplantation has been shown to reestablish tolerance in both prediabetic and diabetic NOD mice. However, it is unclear whether this therapy augments beta cell regeneration. Furthermore, this procedure usually requires total body irradiation conditioning of recipients. The toxicity of total body irradiation conditioning and potential for graft-versus-host disease (GVHD) limit the application of allogeneic hematopoietic cell transplantation for treating type 1 diabetes. Here we report that injection of donor bone marrow and CD4+ T cell-depleted spleen cells induced chimerism without causing GVHD in overtly diabetic NOD mice conditioned with anti-CD3/CD8 and that induction of chimerism in new-onset diabetic NOD mice led to elimination of insulitis, regeneration of host beta cells, and reversal of hyperglycemia. Therefore, this radiation-free GVHD preventive approach for induction of chimerism may represent a viable means for reversing type 1 diabetes.

Extreme genetic risk for type 1A diabetes

Type 1A diabetes (T1D) is an autoimmune disorder the risk of which is increased by specific HLA DR/DQ alleles [e.g., DRB1*03-DQB1*0201 (DR3) or DRB1*04-DQB1*0302 (DR4)]. The genotype associated with the highest risk for T1D is the DR3/4-DQ8 (DQ8 is DQA1*0301, DQB1*0302) heterozygous genotype. We determined HLA-DR and -DQ genotypes at birth and analyzed DR3/4-DQ8 siblings of patients with T1D for identical-by-descent HLA haplotype sharing (the number of haplotypes inherited in common between siblings). The children were clinically followed with prospective measurement of anti-islet autoimmunity and for progression to T1D. Risk for islet autoimmunity dramatically increased in DR3/4-DQ8 siblings who shared both HLA haplotypes with their diabetic proband sibling (63% by age 7, and 85% by age 15) compared with siblings who did not share both HLA haplotypes with their diabetic proband sibling (20% by age 15, P < 0.01). 55% sharing both HLA haplotypes developed diabetes by age 12 versus 5% sharing zero or one haplotype (P = 0.03). Despite sharing both HLA haplotypes with their proband, siblings without the HLA DR3/4-DQ8 genotype had only a 25% risk for T1D by age 12. The risk for T1D in the DR3/4-DQ8 siblings sharing both HLA haplotypes with their proband is remarkable for a complex genetic disorder and provides evidence that T1D is inherited with HLA-DR/DQ alleles and additional MHC-linked genes both determining major risk. A subset of siblings at extremely high risk for T1D can now be identified at birth for trials to prevent islet autoimmunity.

The relation between size at birth and risk of type 1 diabetes is not influenced by adjustment for the insulin gene (-23HphI) polymorphism or HLA-DQ genotype

AIMS/HYPOTHESIS

Associations have been described between higher birthweight and increased risk of type 1 diabetes, and of insulin (INS) and human leucocyte antigen (HLA) genotypes that protect against diabetes with larger size at birth. We studied simultaneously the effects of size at birth, INS and HLA genotypes on the risk of type 1 diabetes to test whether the relation between size at birth and risk of type 1 diabetes would be strengthened after adjustment for INS and HLA genotypes.

SUBJECTS AND METHODS

We designed a population-based case-control study in Norway with 471 cases of childhood-onset type 1 diabetes and 1,369 control subjects who were genotyped for the INS -23HphI polymorphism (surrogate for INS variable number of tandem repeats) and HLA-DQ alleles associated with type 1 diabetes. Data on birthweight and other perinatal factors were obtained from the Medical Birth Registry of Norway by record linkage.

RESULTS

The data fitted a multiplicative model for the protective INS class III allele both within the INS locus and for the model with INS- and HLA-DQ-conferred risk of type 1 diabetes. We found no overall significant association between weight or head circumference at birth and the risk of type 1 diabetes, and adjustment for INS and HLA genotype did not influence this result. There was also no evidence for association of INS or HLA with size at birth among control subjects.

CONCLUSIONS/INTERPRETATION

In contrast to suggestions from previous indirect studies, direct adjustment for INS and HLA genotypes did not lead to a stronger relation between birthweight and the risk of type 1 diabetes.

Glutathione-s-transferase M1 and T1 polymorphisms and associations with type 1 diabetes age-at-onset

Type 1 diabetes (T1D) is an autoimmune disease characterized by pancreatic beta cell destruction involving auto-reactive T-cells, pro-inflammatory cytokines, reactive oxygen species (ROS) and loss of insulin. Monozygotic twin studies show a 20-60% concordance with T1D indicating there may be an environmental component to the disease. Glutathione (GSH) is the major endogenous antioxidant produced by the cell. GSH participates directly in the neutralization of free radicals and plays a role in the immune response. Glutathione-s-transferases (GSTs) conjugate GSH to free-radicals or xenobiotics. GST activity depletes GSH levels and may either detoxify or enhance the toxicity of a compound. Glutathione-s-transferase mu 1 (GSTM1) and glutathione-s-transferase theta 1 (GSTT1) have polymorphic homozygous deletion (null) genotypes resulting in complete absence of enzyme activity. GSTM1 and GSTT1 null genotypes in Caucasian populations have frequencies of approximately 40-60% and 15-20%, respectively. GST null genotypes have been associated with susceptibility to cancer and protection against chronic pancreatitis. The aim of this study was to investigate associations with GSTM1 and GSTT1 polymorphisms in a group T1D patients and control subjects 0-35 years old who participated in the Combined Swedish Childhood Diabetes Registry and Diabetes Incidence Study (1986-1988). Results show that the presence of the GSTM1 and not the null genotype (OR, 2.13 95% CI, 1.23-3.70, p-value, 0.007, Bonferroni corrected p-value, 0.035) may be a susceptibility factor in T1D 14-20 years old. These results suggest that the GSTM1 null genotype is associated with T1D protection and T1D age-at-onset and that susceptibility to T1D may involve GST conjugation.

Mouse models and the genetics of diabetes: is there evidence for genetic overlap between type 1 and type 2 diabetes?

In humans, both type 1 and type 2 diabetes exemplify genetically heterogeneous complex diseases in which epigenetic factors contribute to underlying genetic susceptibility. Extended human pedigrees often show inheritance of both diabetes types. A common pathophysiological denominator in both disease forms is pancreatic beta-cell exposure to proinflammatory cytokines. Hence, it is intuitive that systemically expressed genes regulating beta-cell ability to withstand chronic diabetogenic stress may represent a component of shared susceptibility to both major disease forms. In this review, the authors assemble evidence from genetic experiments using animal models developing clearly distinct diabetes syndromes to inquire whether some degree of overlap in genes contributing susceptibility can be demonstrated. The conclusion is that although overlap exists in the pathophysiological insults leading to beta-cell destruction in the currently studied rodent models, the genetic bases seem quite distinct.

Conditional expression demonstrates the role of the homeodomain transcription factor Pdx1 in maintenance and regeneration of beta-cells in the adult pancreas

The homeodomain transcription factor Pdx1 is essential for pancreas development. To investigate the role of Pdx1 in the adult pancreas, we employed a mouse model in which transcription of Pdx1 could be reversibly repressed by administration of doxycycline. Repression of Pdx1 in adult mice impaired expression of insulin and glucagon, leading to diabetes within 14 days. Pdx1 repression was associated with increased cell proliferation predominantly in the exocrine pancreas and upregulation of genes implicated in pancreas regeneration. Following withdrawal of doxycycline and derepression of Pdx1, normoglycemia was restored within 28 days; during this period, Pdx1(+)/Ins(+) and Pdx(+)/Ins(-) cells were observed in association with the duct epithelia. These findings confirm that Pdx1 is required for beta-cell function in the adult pancreas and indicate that in the absence of Pdx1 expression, a regenerative program is initiated with the potential for Pdx1-dependent beta-cell neogenesis.

Dendritic Cells in Human Thymus and Periphery Display a Proinsulin Epitope in a Transcription-Dependent, Capture-Independent Fashion

The natural expression of tissue-specific genes in the thymus, e.g., insulin, is critical for self-tolerance. The transcription of tissue-specific genes is ascribed to peripheral Ag-expressing (PAE) cells, which discordant studies identified as thymic epithelial cells (TEC) or CD11c+ dendritic cells (DC). We hypothesized that, consistent with APC function, PAE-DC should constitutively display multiple self-epitopes on their surface. If recognized by Abs, such epitopes could help identify PAE cells to further define their distribution, nature, and function. We report that selected Abs reacted with self-epitopes, including a proinsulin epitope, on the surface of CD11c+ cells. We find that Proins+ CD11c+ PAE cells exist in human thymus, spleen, and also circulate in blood. Human thymic Proins+ cells appear as mature DC but express CD8alpha, CD20, CD123, and CD14; peripheral Proins+ cells appear as immature DC. However, DC derived in vitro from human peripheral blood monocytes include Proins+ cells that uniquely differentiate and mature into thymic-like PAE-DC. Critically, we demonstrate that human Proins+ CD11c+ cells transcribe the insulin gene in thymus, spleen, and blood. Likewise, we show that mouse thymic and peripheral CD11c+ cells transcribe the insulin gene and display the proinsulin epitope; moreover, by using knockout mice, we show that the display of this epitope depends upon insulin gene transcription and is independent of Ag capturing. Thus, we propose that PAE cells include functionally distinct DC displaying self-epitopes through a novel, transcription-dependent mechanism. These cells might play a role in promoting self-tolerance, not only in the thymus but also in the periphery.

Genetics of type 2 diabetes mellitus

The clinical picture of type 2 diabetes mellitus (T2DM) is formed by impairment in insulin secretion and resistance to insulin action. As a result of intensive efforts of the scientists around the world mutations and polymorphisms in a number of genes were linked with monogenic and polygenic forms of T2DM. Two major strategies were used in this research: genome scanning and the candidate gene approach. Monogenic forms, despite their rarity, constitute a field where substantial progress has been made in the dissection of the molecular background of T2DM. Monogenic forms of T2DM with profound defect in insulin secretion include subtypes of maturity onset diabetes of the young (MODY), maternally inherited diabetes with deafness (MIDD) caused by mitochondrial mutations, and rare cases resulting from insulin gene mutations. The majority of proteins associated with MODY are transcription factors, such as hepatocyte nuclear factor 4alpha (HNF-4alpha), HNF-1alpha, insulin promoter factor-1 (IPF-1), HNF-1beta, and NEUROD1. They influence expression of the other genes through regulation of mRNA synthesis. Only MODY2 form is associated with glucokinase, a key regulatory enzyme of the beta cell. There are striking differences in the clinical picture of MODY associated with glucokinase and MODY associated with transcription factors. Three monogenic forms of T2DM characterized by severe insulin resistance are the consequence of mutations in the PPARgamma, ATK2, and insulin receptor genes. Patients with monogenic T2DM, particularly with MODY, sometimes, develop discrete extra-pancreatic phenotypes; for example, lipid abnormalities or a variety of cystic renal diseases. Efforts aiming to identify genes responsible for more common, polygenic forms of T2DM were less effective. These forms of T2DM have a middle/late age of onset and occur with both impaired insulin secretion and insulin resistance. Their clinical picture is created by the interaction of environmental and genetic factors, such as frequent polymorphisms of many genes, not just of one. These polymorphisms may be localized in the coding or regulatory parts of the genes and are present, although with different frequencies, in T2DM patients as well as in healthy populations. Sequence differences in a few genes have been associated, so far, with complex, polygenic forms of T2DM, for example, calpain 10, PPARgamma, KCJN11, and insulin. In addition, some evidence exists that genes, such as adiponectin, IRS-1, and some others may also influence the susceptibility to T2DM. It is expected that in the nearest future more T2DM susceptibility genes will be identified.

Defective central tolerance induction in NOD mice: genomics and genetics

The genetic determinism of type-1 diabetes in NOD mice likely involves complementary defects in central T cell tolerance induction and peripheral immunoregulation. To study the contribution of the NOD genetic background to central tolerance, we followed the behavior of BDC2.5 clonotype thymocytes in fetal thymic organ cultures (FTOC). The NOD genetic background encodes a quantitative deficiency in the ability to delete these self-reactive thymocytes and to divert them to the CD8alphaalpha lineage. In genetic analyses, comparing NOD and B6.H2g7 FTOCs, the NOD defect incorporated the influence of several loci (notably ones on chr1 and 3). Microarray analyses assessing FTOCs from the same two strains argued that the NOD abnormality reflects the combined effects of turning down the gene expression program that provokes apoptosis and turning on a new program promoting cell survival. Intersection of the data from the two approaches points to a small set of attractive candidate genes.

The insulin gene variable number tandem repeat and risk of type 2 diabetes in a population-based sample of families and unrelated men and women

Abnormalities in insulin regulation are central to the pathogenesis of type 2 diabetes. We assessed variation in the insulin gene variable number tandem repeat (INS VNTR) minisatellite (using the -23Hph1 A/T single nucleotide polymorphism) as a risk factor for 92 cases of incident type 2 diabetes in 883 unrelated Framingham Heart Study (FHS) subjects and in a separate sample of 698 members of 282 FHS nuclear families with 62 diabetes cases. In the unrelated sample, the -23Hph1 TT genotype frequency was 8.0% and was associated with a diabetes hazard ratio of 1.89 [95% confidence interval (CI), 1.01-3.52; P = 0.045] compared with the AA genotype using diabetes age of onset as the time failure variable in a proportional hazards model adjusted for age, offspring sex, body mass index, parental diabetes, and sex by parental diabetes interactions. In sex-stratified analyses, TT increased risk for diabetes in women (hazard ratio, 4.25; 95% CI, 1.76-10.3), but not men (hazard ratio, 1.01; 95% CI, 0.39-2.60). Using a family-based association test to assess transmission disequilibrium in the sample of related subjects, the age- and sex-adjusted z-score for diabetes associated with the T allele was 2.07 (P = 0.04), and a family-based association test using age of onset in a proportional hazards model was also statistically significant (P = 0.03), indicating that increased risk of diabetes was not attributable to population admixture. These data support the hypothesis that the INS VNTR is a genetic risk factor for type 2 diabetes, with the TT genotype accounting for about 6.6% of cases in the FHS population.

Type 1 diabetes is insulin -2221 MspI and CTLA-4 +49 A/G polymorphism dependent

BACKGROUND

Several studies have demonstrated an association of type 1 diabetes with specific alleles of HLA class II molecules, as with polymorphisms of insulin gene region. The aim of our study was to evaluate the interaction of insulin -2221 MspI polymorphism to type 1 diabetes susceptibility in connection with autoimmunity associated gene--CTLA-4 polymorphism.

MATERIALS AND METHODS

Insulin -2221 MspI C/T and CTLA-4 +49 A/G polymorphisms were detected by restriction fragment-length polymorphism analysis or oligonucleotide hybridization in type 1 (n = 69), type 2 diabetes (n = 301) patients and 158 healthy controls. Regression model adjusted for age, gender and gene polymorphisms was studied.

RESULTS

C-allele of insulin -2221 MspI and G-allele of +49 CTLA-4 were significant risk factors for type 1 diabetes (crude OR 3.53 and 1.59, respectively) and this impact increased in the homozygous form of both alleles. The regression model supported the idea of insulin CC and CTLA-4 GG genotypes for an independent and clearly significant risk for developing type 1 diabetes. We could not detect any significant correlation between investigated polymorphisms and type 2 diabetes.

CONCLUSIONS

There exists a significant association between the C-allele of -2221 MspI in the insulin gene and type 1 diabetes. The CTLA-4 G-allele is also positively correlated with type 1 diabetes. According to the regression model the investigated gene polymorphisms are independent risk factors for development of type 1 diabetes in the Estonian population. We propose that -2221 MspI is a good marker for evaluation of risk of insulin gene haplotype in type 1 diabetes patients.

Back to central tolerance

The establishment and maintenance of immunological tolerance entails both central and peripheral mechanisms. The latter have been highlighted in the past several years, mostly because of great interest in the activities of regulatory T cells. However, an important role for central tolerance mechanisms has been reemphasized by recent results on human autoimmune diseases, including APECED and type 1 diabetes.

Extrapancreatic insulin-producing cells in multiple organs in diabetes

Insulin-producing cells normally occur only in the pancreas and thymus. Surprisingly, we found widespread insulin mRNA and protein expression in different diabetic mouse and rat models, including streptozotocin-treated mice and rats, ob/ob mice, and mice fed high-fat diets. We detected in diabetic mice proinsulin- and insulin-positive cells in the liver, adipose tissue, spleen, bone marrow, and thymus; many cells also produced glucagon, somatostatin, and pancreatic polypeptide. By in situ nucleic acid hybridization, diabetic, but not nondiabetic, mouse liver exhibited insulin transcript-positive cells, indicating that insulin was synthesized by these cells. In transgenic mice that express GFP driven by the mouse insulin promoter, streptozotocin-induced diabetes led to the appearance of GFP-positive cells in liver, adipose tissue, and bone marrow; the fluorescent signals showed complete concordance with the presence of immunoreactive proinsulin. Hyperglycemia produced by glucose injections in nondiabetic mice led to the appearance of proinsulin- and insulin-positive cells within 3 days. Bone marrow transplantation experiments showed that most of the extrapancreatic proinsulin-producing cells originated from the bone marrow. Immunoreactive proinsulin- and insulin-positive cells were also detected in the liver, adipose tissue, and bone marrow of diabetic rats, indicating that extrapancreatic, extrathymic insulin production occurs in more than one species. These observations have implications for the regulation of insulin gene expression, modulation of self-tolerance by insulin gene expression, and strategies for the generation of insulin-producing cells for the treatment of diabetes.