Non-HLA type 1 diabetes genes modulate disease risk together with HLA-DQ and islet autoantibodies

Characterisation of islet antibody-negative type 1 diabetes mellitus in Indian children

AIMS

Islet antibody-negative type 1 diabetes mellitus (T1DM) has not been well characterised. We determined the frequency of antibody-negative T1DM and compared it with antibody-positive T1DM in a cohort of north Indian children.

METHODS

In a multi-centre, prospective, observational study, 176 Indian children (age 1-18 years) were assessed within 2 weeks of diagnosis of T1DM. Antibodies against GAD65 (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A), were estimated using validated ELISA. HLA-DRB1, DQA1 and DQB1 alleles were studied by Luminex-based typing. Monogenic diabetes was determined by targeted next-generation sequencing using the Illumina platform.

RESULTS

After excluding 12 children with monogenic diabetes, GADA, IA-2A and ZnT8A were present in 124 (76%), 60 (37%) and 62 (38%) o children, respectively, while 24 (15%) were negative for all antibodies. A single antibody (most frequently GADA) was present in 68 (41%) of children, while all three antibodies were found in 34 (21%). Islet antibody-negative T1DM (n = 24, 15%) did not differ from antibody-positive children in their clinical features, HbA1c or plasma C-peptide, both at onset or after 1 year follow-up (available in 62 children). The frequency of other organ-specific antibodies or high-risk HLA-DR and DQ alleles were also similar. Children with a single islet antibody did not differ from those with multiple antibodies.

CONCLUSIONS

The frequency of various islet-antibodies, in isolation and combination, differed considerably from studies among children of European descent with T1DM. Children with T1DM who were islet antibody-negative were indistinguishable from those who were antibody-positive.

Primary hyperaldosteronism associated with type 3 autoimmune polyendocrine syndrome: A rare case report

Key Clinical Message

Primary hyperaldosteronism with type 3 autoimmune polyendocrine syndrome was a rare combination of both hyper- and hypoendocrine gland function. Comprehensive treatment including surgery and replacement therapy might be an effective strategy.

Abstract

Primary aldosteronism (PA) is a common cause of secondary hypertension originating from hormones. Type 3 autoimmune polyendocrine syndrome (APS-3) is characterized by the simultaneous or subsequent occurrence of autoimmune-mediated endocrine gland damage, except for Addison disease. Here we reported an extremely rare case of a 63-year-old woman with PA and APS-3 who initially presented with hypertension (HT). The APS-3 of this patient mainly exhibited type 1 diabetes mellitus (T1DM) and Hashimoto's thyroiditis. She underwent the adrenal adenoma resection with a histopathologic diagnosis of adrenal cortical adenoma. After surgery, the HT of this patient was immediately reversed, and the concentration of serum potassium went back to normal. Then, this patient was administered with replacement therapy of insulin and levothyroxine sodium tablets (L-T4).

CTLA4, SH2B3, and CLEC16A diversely affect the progression of early islet autoimmunity in relatives of Type 1 diabetes patients

The HLA region is the major genetic risk determinant of Type 1 diabetes. How non-HLA loci contribute to the genetic risk is incompletely understood, but there are indications that at least some impact progression of asymptomatic autoimmunity. We examined whether SNPs in 7 susceptibility loci (INS, SH2B3, PTPN2, PTPN22, CTLA4, CLEC16A, and IL2RA) could improve prediction of the progression from single to multiple autoantibody positivity, and from there on to diagnosis. SNPs were genotyped in persistently autoantibody positive relatives by allelic discrimination qPCR and disease progression was studied by multivariate Cox regression analysis. In our cohort, only the CTLA4 GA genotype (rs3087243, P = 0.002) and the CLEC16A AA genotype (rs12708716, P = 0.021) were associated with accelerated progression from single to multiple autoantibody positivity, but their effects were restricted to presence of HLA-DQ2/DQ8, and IAA as first autoantibody, respectively. The interaction of CTLA4 and HLA-DQ2/DQ8 overruled the effect of DQ2/DQ8 alone. The HLA-DQ2/DQ8-mediated risk of progression to multiple autoantibodies nearly entirely depended on heterozygosity for CTLA4. The SH2B3 TT genotype (rs3184504) was protective for HLA-DQ8 positive subjects (P = 0.003). At the stage of multiple autoantibodies, only the CTLA4 GA genotype was a minor independent risk factor for progression towards clinical diabetes (P = 0.034). Our study shows that non-HLA polymorphisms impact progression of islet autoimmunity in a subgroup-, stage- and SNP-specific way, suggesting distinct mechanisms. If confirmed, these findings may help refine risk assessment, follow-up, and prevention trials in risk groups.

The rs705708 A allele of the ERBB3 gene is associated with lower prevalence of diabetic retinopathy and arterial hypertension and with improved renal function in type 1 diabetic patients

INTRODUCTION

The Erb-b2 receptor tyrosine kinase 3 (ERBB3) is involved in autoimmune processes related to type 1 diabetes mellitus (T1DM) pathogenesis. Accordingly, some studies have suggested that single nucleotide polymorphisms (SNPs) in the ERBB3 gene confer risk for T1DM. Proliferation-associated protein 2G4 (PA2G4) is another candidate gene for this disease because it regulates cell proliferation and adaptive immunity. Moreover, PA2G4 regulates ERBB3. To date, no study has evaluated the association of PA2G4 SNPs and T1DM.

AIM

To evaluate the association of ERBB3 rs705708 (G/A) and PA2G4 rs773120 (C/T) SNPs with T1DM and its clinical and laboratory characteristics.

METHODS

This case-control study included 976 white subjects from Southern Brazil, categorized into 501 cases with T1DM and 475 non-diabetic controls. The ERBB3 and PA2G4 SNPs were genotyped by allelic discrimination-real-time PCR.

RESULTS

ERBB3 rs705708 and PA2G4 rs773120 SNPs were not associated with T1DM considering different inheritance models and also when controlling for covariables. However, T1DM patients carrying the ERBB3 rs705708 A allele developed T1DM at an earlier age vs. G/G patients. Interestingly, in the T1DM group, the rs705708 A allele was associated with lower prevalence of diabetic retinopathy and arterial hypertension as well as with improved renal function (higher estimated glomerular filtration rate and lower urinary albumin excretion levels) compared to G/G patients.

CONCLUSIONS

Although no association was observed between the ERBB3 rs705708 and PA2G4 rs773120 SNPs and T1DM, the rs705708 A allele was associated, for the first time in literature, with lower prevalence of diabetic retinopathy and arterial hypertension. Additionally, this SNP was associated with improved renal function.

Exercise and Type 1 Diabetes

Diabetes mellitus (DM) is the most common endocrine and metabolic disease caused by absolute or insufficient insulin secretion. Under the context of an aging population worldwide, the number of diabetic patients is increasing year by year. Most patients with diabetes have multiple complications that severely threaten their survival and living quality. DM is mainly divided into type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). T1DM is caused by absolute lack of insulin secretion, so the current treatment for T1DM patients is exogenous insulin replacement therapy. At present, exercise therapy has been widely recognized in the prevention and treatment of diabetes, and regular aerobic exercise has become an important part of T1DM treatment. At the same time, exercise therapy is also used in conjunction with other treatments in the prevention and treatment of diabetic complications. However, for patients with T1DM, exercise still has the risk of hypoglycemia or hyperglycemia. T1DM Patients and specialist physician need to fully understand the effects of exercise on metabolism and implement individualized exercise programs. This chapter reviews the related content of exercise and T1DM.

The Association between rs2292239 Polymorphism in ERBB3 Gene and Type 1 Diabetes: A Meta-Analysis

Objectives

The purpose of this study was to explore the association between rs2292239 polymorphism in ERBB3 gene and type 1 diabetes (T1D).

Methods

A systematic search of studies on the association of rs2292239 polymorphism in ERBB3 gene with T1D susceptibility was conducted in PubMed, Web of science, Elsevier Science Direct, and Cochrane Library. Eventually, 9 published studies were included. The strength of association between rs2292239 polymorphism and T1D susceptibility was assessed by odds ratios (ORs) with its 95% confidence intervals (CIs).

Results

A total of 9 case-control studies, consisting of 5369 T1D patients and 6920 controls, were included in the meta-analysis. This meta-analysis showed significant association between ERBB3 rs2292239 polymorphism and T1D susceptibility in overall population (A vs. C, OR: 1.292, 95% CI= 1.224-1.364, P _H=0.450, P _H is P value for the heterogeneity test). Similar results were found in subgroup analysis by ethnicity.

Conclusions

ERBB3 rs2292239 polymorphism is associated with T1D susceptibility and rs2292239-A allele is a risk factor for T1D. However, more large-scale studies are warranted to replicate our findings.

CD226 gene polymorphism (rs763361 C>T) is associated with susceptibility to type 1 diabetes mellitus among Egyptian children

OBJECTIVE

Genetic factors contribute significantly to type 1 diabetes (T1D) etiology. A single nucleotide polymorphism in the CD226 gene (rs763361 C>T) has been associated with T1D susceptibility in European patients, but data from other populations is limited. Our aim was to study the contribution of this polymorphism to T1D susceptibility among Egyptian children.

METHODS

A case-control study including 74 children with T1D and 82 healthy children as a control group. Genotyping of CD226 gene polymorphism was performed for all participants by DNA extraction followed by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The frequency of T allele was 78.4% in patients and 68.3% in controls (OR, 1.68; 95% CI, 1.01-2.8; P=0.046). TT, TC, and CC genotypes were found in 62.2%, 32.4%, and 5.4% of the patients, respectively, and in 41.5%, 53.7%, and 4.9% of controls, respectively. Under the recessive model, TT genotype was significantly associated with T1D risk (OR, 2.32; 95% CI, 1.21-4.41; P=0.010). The mean age at diabetes onset was significantly lower in patients carrying T allele compared with C allele (8.03±3.8 year vs. 10.5±2.54 year; P<0.001) and among those with TT genotype compared with the pooled TC+CC genotypes (7.5±2.6 year vs. 10.6±2.6 year; P<0.001). No significant difference was found between genotypes or alleles regarding the HbA1c level.

CONCLUSION

T allele and TT genotype of the CD226 rs763361 polymorphism is associated with susceptibility to T1D and with a lower age of disease onset among Egyptian children.

Association of protein tyrosine phosphatase non-receptor type 22 gene functional variant C1858T, HLA-DQ/DR genotypes and autoantibodies with susceptibility to type-1 diabetes mellitus in Kuwaiti Arabs

The incidence of type-1 Diabetes Mellitus (T1DM) has increased steadily in Kuwait during recent years and it is now considered amongst the high-incidence countries. An interaction between susceptibility genes, immune system mediators and environmental factors predispose susceptible individuals to T1DM. We have determined the prevalence of protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene functional variant (C1858T; R620W, rs2476601), HLA-DQ and DR alleles and three autoantibodies in Kuwaiti children with T1DM to evaluate their impact on genetic predisposition of the disease. This study included 253 Kuwaiti children with T1DM and 214 ethnically matched controls. The genotypes of PTPN22 gene functional variant C1858T (R620W; rs2476601) were detected by PCR-RFLP method and confirmed by DNA sequencing. HLA-DQ and DR alleles were determined by sequence-specific PCR. Three autoantibodies were detected in the T1DM patients using radio-immunoassays. A significant association was detected between the variant genotype of the PTPN22 gene (C1858T, rs2476601) and T1DM in Kuwaiti Arabs. HLA-DQ2 and DQ8 alleles showed a strong association with T1DM. In T1DM patients which carried the variant TT-genotype of the PTPN22 gene, 93% had at least one DQ2 allele and 60% carried either a DQ2 or a DQ8 allele. Amongst the DR alleles, the DR3-DRB5, DR3-3, DR3-4 and DR4-4 showed a strong association with T1DM. Majority of T1DM patients who carried homozygous variant (TT) genotype of the PTPN22 gene had either DR3-DRB5 or DRB3-DRB4 genotypes. In T1DM patients who co-inherited the high risk HLA DQ, DR alleles with the variant genotype of PTPN22 gene, the majority were positive for three autoantibodies. Our data demonstrate that the variant T-allele of the PTPN22 gene along with HLA-DQ2 and DQ8 alleles constitute significant determinants of genetic predisposition of T1DM in Kuwaiti children.

Identification of non-HLA genes associated with development of islet autoimmunity and type 1 diabetes in the prospective TEDDY cohort

Traditional linkage analysis and genome-wide association studies have identified HLA and a number of non-HLA genes as genetic factors for islet autoimmunity (IA) and type 1 diabetes (T1D). However, the relative risk associated with previously identified non-HLA genes is usually very small as measured in cases/controls from mixed populations. Genetic associations for IA and T1D may be more accurately assessed in prospective cohorts. In this study, 5806 subjects from the TEDDY (The Environmental Determinants of Diabetes in the Young) study, an international prospective cohort study, were genotyped for 176,586 SNPs on the ImmunoChip. Cox proportional hazards analyses were performed to discover the SNPs associated with the risk for IA, T1D, or both. Three regions were associated with the risk of developing any persistent confirmed islet autoantibody: one known region near SH2B3 (HR = 1.35, p = 3.58 × 10-7) with Bonferroni-corrected significance and another known region near PTPN22 (HR = 1.46, p = 2.17 × 10-6) and one novel region near PPIL2 (HR = 2.47, p = 9.64 × 10-7) with suggestive evidence (p < 10-5). Two known regions (PTPN22: p = 2.25 × 10-6, INS; p = 1.32 × 10-7) and one novel region (PXK/PDHB: p = 8.99 × 10-6) were associated with the risk for multiple islet autoantibodies. First appearing islet autoantibodies differ with respect to association. Two regions (INS: p = 5.67 × 10-6 and TTC34/PRDM16: 6.45 × 10-6) were associated if the fist appearing autoantibody was IAA and one region (RBFOX1: p = 8.02 × 10-6) was associated if the first appearing autoantibody was GADA. The analysis of T1D identified one region already known to be associated with T1D (INS: p = 3.13 × 10-7) and three novel regions (RNASET2, PLEKHA1, and PPIL2; 5.42 × 10-6 > p > 2.31 × 10-6). These results suggest that a number of low frequency variants influence the risk of developing IA and/or T1D and these variants can be identified by large prospective cohort studies using a survival analysis approach.

The rs2292239 polymorphism in ERBB3 gene is associated with risk for type 1 diabetes mellitus in a Brazilian population

The Erb-b2 receptor tyrosine kinase 3 (ERBB3) belongs to a family of epidermal growth factor receptors of protein tyrosine kinases, and regulates cell survival, differentiation and proliferation in several cell types. Previous studies have suggested that ERBB3 contributes to T1DM pathogenesis by modulating antigen presenting cell function, autoimmunity and cytokine-induced beta-cell apoptosis. Accordingly, some genome-wide association studies identified ERBB3 gene as a susceptibility locus for T1DM, with the strongest association signal being observed for the rs2292239 single nucleotide polymorphism (SNP) in intron 7 of the gene. Therefore, the aim of the present study was to replicate the association of the ERBB3 rs2292239 SNP with T1DM in a Brazilian population. We analyzed 421 T1DM patients (cases) and 510 nondiabetic subjects (controls). All subjects were self-declared as white. The ERBB3 rs2292239 (A/C) SNP was genotyped by real-time PCR using TaqMan MGB probes. Genotype (P=0.001) and allele (P=0.002) frequencies of the ERBB3 rs2292239 SNP were differently distributed between T1DM patients and nondiabetic controls. Moreover, the A allele was significantly associated with risk for T1DM when considering recessive (OR=1.58, 95% CI 1.11-2.27; P=0.015), additive (OR=1.78, 95% CI 1.21-2.62; P=0.004), and dominant (OR=1.39, 95% CI 1.07-1.81; P=0.016) models of inheritance. However, after adjustment for presence of high-risk HLA DR/DQ genotypes, the rs2292239 SNP remained independently associated with T1DM only for the additive model (OR=1.62, 95% CI 1.02-2.59; P=0.043). Our results suggest that the A/A genotype of the ERBB3 rs2292239 SNP is associated with risk for T1DM in a white Brazilian population.

Early prediction of autoimmune (type 1) diabetes

Underlying type 1 diabetes is a genetic aetiology dominated by the influence of specific HLA haplotypes involving primarily the class II DR-DQ region. In genetically predisposed children with the DR4-DQ8 haplotype, exogenous factors, yet to be identified, are thought to trigger an autoimmune reaction against insulin, signalled by insulin autoantibodies as the first autoantibody to appear. In children with the DR3-DQ2 haplotype, the triggering reaction is primarily against GAD signalled by GAD autoantibodies (GADA) as the first-appearing autoantibody. The incidence rate of insulin autoantibodies as the first-appearing autoantibody peaks during the first years of life and declines thereafter. The incidence rate of GADA as the first-appearing autoantibody peaks later but does not decline. The first autoantibody may variably be followed, in an apparently non-HLA-associated pathogenesis, by a second, third or fourth autoantibody. Although not all persons with a single type of autoantibody progress to diabetes, the presence of multiple autoantibodies seems invariably to be followed by loss of functional beta cell mass and eventually by dysglycaemia and symptoms. Infiltration of mononuclear cells in and around the islets appears to be a late phenomenon appearing in the multiple-autoantibody-positive with dysglycaemia. As our understanding of the aetiology and pathogenesis of type 1 diabetes advances, the improved capability for early prediction should guide new strategies for the prevention of type 1 diabetes.

Beta-cell Specific Autoantibodies: Are they Just an Indicator of Type 1 Diabetes?

BACKGROUND

Autoantibodies (AAbs) against islet autoantigens (AAgs) are used for type 1 diabetes (T1D) diagnosis and prediction. Islet-specific AAbs usually appear early in life and may fluctuate in terms of number and titer sometimes for over 20 years before T1D develops. Whereas their predictive power is high for pediatric subjects with high genetic risk who rapidly progress to multiple AAb positivity, they are less reliable for children with low genetic risk, single AAb positivity and slow disease progression.

OBJECTIVE

It is unknown how AAbs develop and whether they are involved in T1D pathogenesis. So far an increase in AAb number seems to only indicate AAg spreading and progression towards clinical T1D. The goal of this review is to shed light on the possible involvement of AAbs in T1D development.

METHOD

We thoroughly review the current literature and discuss possible mechanisms of AAb development and the roles they may play in disease pathogenesis.

RESULTS

Genetic and environmental factors instigate changes at the molecular and cellular levels that promote AAb development. Although direct involvement of AAbs in T1D is less clear, autoreactive B cells are clearly involved in various immune and autoimmune responses via antigen presentation, immunoregulation and cytokine production.

CONCLUSION

Our analysis suggests that understanding the mechanisms that lead to islet-specific AAb development and the diabetogenic processes that autoreactive B cells promote may uncover additional biomarkers and therapeutic targets.