Diabetes Genetic Susceptibility Research Articles

Serum Medium-Chain Fatty Acids and the Risk of Incident Diabetes: Findings from the 4C Study.

Emerging studies have revealed associations between dietary medium-chain fatty acids (MCFAs) and glucose homeostasis. However, the relationship between serum MCFAs and the incidence of diabetes, and potential interactions with genetic predisposition, remains unclear in prospective cohort studies. To investigate associations and genetic susceptibility between serum MCFAs and diabetes risk. We investigated baseline serum MCFAs (n=5) in a nested case-control study comprising incident diabetes cases (n=1,707) and matched normoglycemic control subjects (n=1,707) from the China Cardiometabolic Disease and Cancer Cohort Study. Associations between MCFAs and type 2 diabetes mellitus (T2DM) were examined, both overall and stratified by diabetes genetic susceptibility. Genetic risk scores (GRS) were calculated based on 86 T2DM-associated genetic variants. In the fully adjusted conditional logistic regression model, serum octanoic acid and nonanoic acid exhibited inverse dose-response relationships with diabetes risk, showing odds ratios (95% confidence intervals) of 0.90 (0.82-0.98) and 0.84 (0.74-0.95), respectively. Subgroup analysis demonstrated that inverse associations between MCFAs and incident diabetes were more pronounced among individuals with physical inactivity (Pinteraction = 0.042, 0.034, and 0.037, for octanoic, nonanoic and decanoic acid, respectively). Moreover, inverse associations of octanoic acid with diabetes risk were notably enhanced among individuals with high genetic risk compared to those with low genetic risk. Significant interactions were observed between octanoic acid and GRS on T2DM risk (Pinteraction = 0.003). These findings provide evidence supporting inverse associations between serum MCFAs and T2DM risk, and reveal potential interplay between genetic susceptibility and circulating octanoic acid in modulating diabetes risk.

Autoantibodies to truncated GAD(96-585) antigen stratify risk of early insulin requirement in adult-onset diabetes.

We investigated whether characterisation of full-length (f-)GADA responses could identify early insulin requirement in adult-onset diabetes. In 179 f-GADA positive participants diagnosed with type 2 diabetes, we assessed associations of truncated (t-)GADA positivity, f-GADA IgG subclasses, and f-GADA affinity with early insulin requirement (<5 years), type 1 diabetes genetic risk score (T1D GRS), and C-peptide. t-GADA positivity was lower in f-GADA positive without early insulin in comparison to f-GADA positive type 2 diabetes requiring insulin within 5 years, and type 1 diabetes (75% vs. 91% and 95% respectively, p<0.0001). t-GADA positivity (in those f-GADA positive) identified a group with a higher type 1 diabetes genetic susceptibility (mean T1D GRS 0.248 vs. 0.225, p=0.003), lower C-peptide (1156 pmol/L vs. 4289 pmol/L, p=1x10-7), and increased IA-2A positivity (23% vs. 6%, p=0.03). In survival analysis, t-GADA positivity was associated with early insulin requirement compared with those only positive for f-GADA, independently from age of diagnosis, f-GADA titre and duration of diabetes [adjusted HR 5.7 (95% CI 1.4, 23.5), p=0.017]. The testing of t-GADA in f-GADA positive individuals with type 2 diabetes identifies those who have genetic and clinical characteristics comparable to type 1 diabetes and stratifies those at higher risk of early insulin requirement.

Diabetes status, genetic susceptibility, and incident arrhythmias: A prospective cohort study of 457,151 participants

AimsThe association of diabetes onset age and duration with incident arrhythmias remains unclear. This study evaluates the association of diabetes onset age and duration with incident arrhythmias and assesses modifications by the genetic predisposition to atrial fibrillation (AF). MethodsWe included 457,151 participants from the UK Biobank study. Multivariable Cox regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) were used for the association between diabetes status, genetic predisposition, and risk of incident arrhythmias. The polygenic risk score (PRS) for AF comprised 142 single-nucleotide variants. ResultsOver 12 years of follow-up, we documented 23,518 AF, 9079 bradyarrhythmia, 9280 conduction system diseases, 3358 supraventricular arrhythmias, and 3095 ventricular arrhythmias. Compared with non-diabetes, the risks of AF increased by 19%, 25%, and 36% for those with diabetes durations <5, 5–9, and ≥10 years, respectively. After multivariate adjustment, with the increase in diabetes onset age, the HRs of outcomes were gradually attenuated. The multivariable-adjusted HRs (95% CI) of diabetes for AF were 1.46 (1.24–1.71) in early middle age (<55 years), 1.21 (1.12–1.30) in late middle age (55–64 years), and 1.15 (1.06–1.24) in the elderly population (≥65 years). A significant interaction between diabetes status and AF-PRS for incident AF was observed (P for interaction <0.001). The same trends were observed for the other arrhythmias. ConclusionsDiabetes was associated with higher risks of incident arrhythmias, and younger age at onset of diabetes was significantly associated with higher risk of subsequent arrhythmias.

Sex differences in type 2 diabetes genetic susceptibility

Introduction. In the last few years gender and sex differences in type 2 diabetes (T2D) predisposition are paid much attention. This gap can be caused by the hormonal and genetic background and require further traits.Aim. The aim of this study was to identify genetic markers of T2D predisposition depending on sex using 17 polymorphic markers of genes involved in various links of T2D pathogenesis.Material and Methods. 536 patients with T2D and 1,476 healthy individuals were examined. Amplification of 17 polymorphic gene loci was performed by polymerase chain reaction. Associations of DNA polymorphisms with T2D were evaluated by logistic regression using the SNPStats program. The degree of association was assessed in the odds ratio (OR) scores. Correction for multiplicity of comparisons and multivariate analysis was used.Results. The genotypes of increased T2D risk for men are CC of CCL20 rs6749704 marker (OR = 3.85, P = 0.0002) in recessive model, D/I of CCR5 rs333 marker (OR = 4.42, P = 0.0208); by GRIA1 marker rs2195450 - CT and TT in the dominant model (OR = 2.42, P = 0.0002), TT - in the recessive model (OR = 2.89, P = 0.0070). The genotypes of increased risk of T2D in women according to the marker TCF7L2 rs7903146 - CT and TT in the dominant model (OR = 1.69, P = 0.0003), TT - in recessive (OR = 1.61, P = 0.0124), according to the marker ADIPOQ rs17366743 - TC (OR = 2.55, P = 0.0168).Conclusion. The established genotypes of increased T2D risk depending on gender make it possible to personalize approaches to primary T2D prevention.

The phenotype of type 1 diabetes in sub-Saharan Africa.

The phenotype of type 1 diabetes in Africa, especially sub-Saharan Africa, is poorly understood. Most previously conducted studies have suggested that type 1 diabetes may have a different phenotype from the classical form of the disease described in western literature. Making an accurate diagnosis of type 1 diabetes in Africa is challenging, given the predominance of atypical diabetes forms and limited resources. The peak age of onset of type 1 diabetes in sub-Saharan Africa seems to occur after 18-20 years. Multiple studies have reported lower rates of islet autoantibodies ranging from 20 to 60% amongst people with type 1 diabetes in African populations, lower than that reported in other populations. Some studies have reported much higher levels of retained endogenous insulin secretion than in type 1 diabetes elsewhere, with lower rates of type 1 diabetes genetic susceptibility and HLA haplotypes. The HLA DR3 appears to be the most predominant HLA haplotype amongst people with type 1 diabetes in sub-Saharan Africa than the HLA DR4 haplotype. Some type 1 diabetes studies in sub-Saharan Africa have been limited by small sample sizes and diverse methods employed. Robust studies close to diabetes onset are sparse. Large prospective studies with well-standardized methodologies in people at or close to diabetes diagnosis in different population groups will be paramount to provide further insight into the phenotype of type 1 diabetes in sub-Saharan Africa.

Regular consumption of soft drinks is associated with type 2 diabetes incidence in Mexican adults: findings from a prospective cohort study

BackgroundAlthough high consumption of soft drinks has been associated with excess of type 2 diabetes risk, the strength of this association in the Mexican population, where a type 2 diabetes genetic susceptibility has been well established, has been scarcely studied. This study aimed to estimate the risk of type 2 diabetes due to soft drinks consumption in a cohort of Mexicans.MethodsWe used data on 1445 participants from the Health Workers Cohort Study, a prospective cohort conducted in Cuernavaca, Mexico. Soft drinks consumption was assessed with a semi-quantitative 116-item food frequency questionnaire. Incident type 2 diabetes was defined as self-report of physician-diagnosed type 2 diabetes, fasting glucose > 126 mg/dl, or hypoglycemic medication at any examination. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazard models.ResultsWith a total of 9526.2 person-years of follow-up, 109 incident cases of type 2 diabetes were observed. Type 2 diabetes incidence rate was 7.6, 11.0, and 17.1 per 1000 person-years across levels of soft drinks consumption of < 1, 1–4, and ≥ 5 servings/week, respectively (p < 0.001 for trend). The intake of ≥5 soft drinks/week was significantly associated with an increased risk of type 2 diabetes (HR 1.9 95% CI:1.0–3.5) compared with consumption of < 1/week (p-trend = 0.040). The HR was attenuated by further adjustment for body mass index (HR 1.5 95%CI:0.8–2.8) and abdominal obesity (HR 1.6 95%CI:0.8–3.0).ConclusionsThe consumption of soft drinks was associated with a higher risk of type 2 diabetes in a cohort of Mexican adults. Our results further support recommendations to limit soft drinks intake to address the growing diabetes epidemic in Mexico.

Discovery of 318 new risk loci for type 2 diabetes and related vascular outcomes among 1.4 million participants in a multi-ancestry meta-analysis.

We investigated type 2 diabetes (T2D) genetic susceptibility via multi-ethnic meta-analysis of 228,499 cases and 1,178,783 controls in the Million Veteran Program, DIAMANTE, Biobank Japan, and other studies. We report 568 associations, including 286 autosomal, 7 X chromosomal, and 25 identified in ancestry-specific analyses that were previously unreported. Transcriptome-wide association analysis detected 3,568 T2D-associations with genetically predicted gene expression in 687 novel genes; of these, 54 are known to interact with FDA-approved drugs. A polygenic risk score was strongly associated with increased risk of T2D-related retinopathy and modestly associated with chronic kidney disease (CKD), peripheral artery disease (PAD), and neuropathy. We investigated the genetic etiology of T2D-related vascular outcomes in MVP and observed statistical SNP-T2D interactions at 13 variants, including coronary heart disease, CKD, PAD, and neuropathy. These findings may help to identify potential therapeutic targets for T2D and genomic pathways that link T2D to vascular outcomes.

Superagonist diabetogenic peptides

Autoimmunity Type 1 diabetes is an autoimmune disease triggered in part by activation of CD4+ T cells specific for insulin-derived autoantigens. Wang et al. prepared ternary complexes of a diabetogenic T cell receptor with insulin B-peptides and major histocompatibility complex class II proteins known to be associated with genetic susceptibility to diabetes. Fusion peptides with a covalent linkage of the carboxyl terminus of an insulin B-chain peptide to specific fragments of insulin C-peptide were highly potent ligands, enabling avid binding of both mouse and human T cell receptors. Transpeptidation reactions in lysosomes may therefore be a potential source of superagonist chimeric insulin peptides and play an important driver role in autoimmune diabetes. Sci. Immunol. 4 , eaav7517 (2019).

The Influence of Type 1 Diabetes Genetic Susceptibility Regions, Age, Sex, and Family History on the Progression From Multiple Autoantibodies to Type 1 Diabetes: A TEDDY Study Report.

This article seeks to determine whether factors related to autoimmunity risk remain significant after the initiation of two or more diabetes-related autoantibodies and continue to contribute to type 1 diabetes (T1D) risk among autoantibody-positive children in The Environmental Determinants of Diabetes in the Young (TEDDY) study. Characteristics included are age at multiple autoantibody positivity, sex, selected high-risk HLA-DR-DQ genotypes, relationship to a family member with T1D, autoantibody at seroconversion, INS gene (rs1004446_A), and non-HLA gene polymorphisms identified by the Type 1 Diabetes Genetics Consortium (T1DGC). The risk of progression to T1D was not different among those with or without a family history of T1D (P = 0.39) or HLA-DR-DQ genotypes (P = 0.74). Age at developing multiple autoantibodies (hazard ratio = 0.96 per 1-month increase in age; 95% CI 0.95, 0.97; P < 0.001) and the type of first autoantibody (when more than a single autoantibody was the first-appearing indication of seroconversion [P = 0.006]) were statistically significant. Female sex was also a significant risk factor (P = 0.03). Three single nucleotide polymorphisms were associated with increased diabetes risk (rs10517086_A [P = 0.03], rs1534422_G [P = 0.006], and rs2327832_G [P = 0.03] in TNFAIP3) and one with decreased risk (rs1004446_A in INS [P = 0.006]). The TEDDY data suggest that non-HLA gene polymorphisms may play a different role in the initiation of autoimmunity than they do in progression to T1D once autoimmunity has appeared. The strength of these associations may be related to the age of the population and the high-risk HLA-DR-DQ subtypes studied.

Type 1 diabetes genetic susceptibility and dendritic cell function: potential targets for treatment.

Type 1 diabetes is an autoimmune disease that results from the defective induction or maintenance of T cell tolerance against islet β cell self-antigens. Under steady-state conditions, dendritic cells with tolerogenic properties are critical for peripheral immune tolerance. Tolerogenic dendritic cells can induce T cell anergy and deletion and, in some contexts, induce or expand regulatory T cells. Dendritic cells contribute to both immunomodulatory effects and triggering of pathogenesis in type 1 diabetes. This immune equilibrium is affected by both genetic and environmental factors that contribute to the development of type 1 diabetes. Genome-wide association studies and disease association studies have identified >50 polymorphic loci that lend susceptibility or resistance to insulin-dependent diabetes mellitus. In parallel, diabetes susceptibility regions known as insulin-dependent diabetes loci have been identified in the nonobese diabetic mouse, a model for human type 1 diabetes, providing a better understanding of potential immunomodulatory factors in type 1 diabetes risk. Most genetic candidates have annotated immune cell functions, but the focus has been on changes to T and B cells. However, it is likely that some of the genomic susceptibility in type 1 diabetes directly interrupts the tolerogenic potential of dendritic cells in the pathogenic context of ongoing autoimmunity. Here, we will review how gene polymorphisms associated with autoimmune diabetes may influence dendritic cell development and maturation processes that could lead to alterations in the tolerogenic function of dendritic cells. These insights into potential tolerogenic and pathogenic roles for dendritic cells have practical implications for the clinical manipulation of dendritic cells toward tolerance to prevent and treat type 1 diabetes.

Type 1 Diabetes Prone NOD Mice Have Diminished Cxcr1 mRNA Expression in Polymorphonuclear Neutrophils and CD4+ T Lymphocytes.

In humans, CXCR1 and CXCR2 are two homologous proteins that bind ELR+ chemokines. Both receptors play fundamental roles in neutrophil functions such as migration and reactive oxygen species production. Mouse Cxcr1 and Cxcr2 genes are located in an insulin-dependent diabetes genetic susceptibility locus. The non obese diabetic (NOD) mouse is a spontaneous well-described animal model for insulin-dependent type 1 diabetes. In this disease, insulin deficiency results from the destruction of insulin-producing beta cells by autoreactive T lymphocytes. This slow-progressing disease is dependent on both environmental and genetic factors. Here, we report descriptive data about the Cxcr1 gene in NOD mice. We demonstrate decreased expression of mRNA for Cxcr1 in neutrophils and CD4+ lymphocytes isolated from NOD mice compared to other strains, related to reduced NOD Cxcr1 gene promoter activity. Looking for Cxcr1 protein, we next analyze the membrane proteome of murine neutrophils by mass spectrometry. Although Cxcr2 protein is clearly found in murine neutrophils, we did not find evidence of Cxcr1 peptides using this method. Nevertheless, in view of recently-published experimental data obtained in NOD mice, we argue for possible Cxcr1 involvement in type 1 diabetes pathogenesis.

Type 1 diabetes genetic susceptibility markers and their functional implications

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by selective destruction of pancreatic β-cells resulting in insulin deficiency....

Association between type 2 diabetes genetic susceptibility loci and visceral and subcutaneous fat area as determined by computed tomography

Visceral fat accumulation has an important role in the development of several metabolic disorders, such as type 2 diabetes, dyslipidemia and hypertension. New genetic loci that contribute to the development of type 2 diabetes have been identified by genome-wide association studies. To examine the association of type 2 diabetes susceptibility loci and visceral fat accumulation, we genotyped 1279 Japanese subjects (556 men and 723 women), who underwent computed tomography for measurements of visceral fat area (VFA) and subcutaneous fat area (SFA) for the following single-nucleotide polymorphisms (SNPs): NOTCH2 rs10923931, THADA rs7578597, PPARG rs1801282, ADAMTS9 rs4607103, IGF2BP2 rs1470579, VEGFA rs9472138, JAZF1 rs864745, CDKN2A/CDKN2B rs564398 and rs10811661, HHEX rs1111875 and rs5015480, TCF7L2 rs7901695, KCNQ1 rs2237892, KCNJ11 rs5215 and rs5219, EXT2 rs1113132, rs11037909, and rs3740878, MTNR1B rs10830963, DCD rs1153188, TSPAN8/LGR5 rs7961581, and FTO rs8050136 and rs9939609. None of the above SNPs were significantly associated with VFA. The FTO rs8050136 and rs9939609 risk alleles exhibited significant associations with body mass index (BMI; P=0.00088 and P=0.0010, respectively) and SFA (P=0.00013 and P=0.00017, respectively). No other SNPs were significantly associated with BMI or SFA. Our results suggest that two SNPs in the FTO gene are associated with subcutaneous fat accumulation. The contributions of other SNPs are inconclusive because of a limitation of the sample power.

Individual and cumulative effect of type 2 diabetes genetic susceptibility variants on risk of coronary heart disease

Type 2 diabetes is a major risk factor for CHD. We hypothesised that diabetes genetic susceptibility variants might be associated with increased CHD risk. We examined the individual and cumulative effect of 38 common genetic variants previously reported to be associated with type 2 diabetes on risk of incident CHD in 20,467 participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) Norfolk Study who had been free of CHD at baseline. During a mean follow-up of 10.7 years, 2,190 participants had a CHD event. Two individual variants next to the TSPAN8 (HR 1.07, 95% CI 1.00-1.14) and the CDKN2A/B region (1.11, 1.04-1.17) were significantly associated with increased CHD risk. A genetic score based on the 38 diabetes variants was significantly associated with an increased risk of CHD (1.08, 1.01-1.14 per score tertile). Adjustment for prevalent and incident diabetes attenuated the association of the TSPAN8 variant (1.06, 0.99-1.13) and the genetic score (1.05, 0.99-1.12 per score tertile) with CHD risk, but not that of the CDKN2A/B variant (1.11, 1.05-1.18). Addition of the genetic score did not improve risk discrimination based on clinical risk factors. The increased risk of CHD observed with genetic susceptibility to type 2 diabetes was at least partly mediated by its diabetes-predisposing effect and was not useful for clinical risk discrimination. The potential role of pathways associated with the variant CDKN2A/B in linking diabetes and CHD needs further exploration.

Association study of type 2 diabetes genetic susceptibility variants and risk of pancreatic cancer: an analysis of PanScan-I data

To examine associations between recently identified common type 2 diabetes (T2D) susceptibility genetic variants and pancreatic cancer risk. Using data on individuals of European ancestry from the Cancer Genetic Markers of Susceptibility PanScan-I study (1,763 pancreatic cancer cases and 1,802 controls), we tested associations for 37 T2D susceptibility variants with pancreatic cancer risk. Associations with pancreatic cancer were also tested for three composite T2D susceptibility measures, incorporating data on all 37 variants, and for ten additional variants related to T2D-related phenotypes, including fasting glucose and beta-cell function. Of the 37 T2D risk alleles, two showed nominally significant positive associations with pancreatic cancer risk (FTO rs8050136 per-allele OR = 1.12; CI: 1.02-1.23; MTNR1B rs1387153 OR = 1.11; CI: 1.00-1.23) and one showed an inverse association (BCL11A rs243021 OR = 0.88; CI: 0.80-0.97). The composite T2D susceptibility measures were not associated with pancreatic cancer. The glucose-raising allele of MADD rs11039149 was associated with increased risk of pancreatic cancer (OR = 1.14; CI: 1.03-1.27). Overall, these results do not provide strong evidence that common variants underling T2D or related phenotypes also affect pancreatic cancer risk; however, associations for FTO, MTNR1B, BCL11A, and MADD variants warrant further investigation in larger studies. Hypothesis-driven analyses of existing genome-wide genetic data can be cost-efficient and promising approaches for investigating genetic susceptibility to complex diseases.

Impact of a Booklet about Diabetes Genetic Susceptibility and Its Prevention on Attitudes towards Prevention and Perceived Behavioral Change in Patients with Type 2 Diabetes and Their Offspring

Background. Offspring of type 2 diabetic patients are at a high risk of type 2 diabetes. Information on diabetes genetic susceptibility and prevention should be supplied to the offspring. Methods. A six-page booklet on diabetes genetic susceptibility and prevention was distributed to 173 patients who ere ordered to hand it to their offspring. The patients answered a self-administered questionnaire on booklet delivery and attitudinal and behavioral changes toward diabetes and its prevention in themselves and their offspring. Results. Valid responses were obtained from 130 patients. Forty-nine patients had actually handed the booklet. Booklet induces more relief than anxiety. From the patient's view, favorable attitudinal and/or behavioral changes occurred in more than half of the offspring who were delivered the booklet. Conclusion. The booklet worked effectively on attitudes and behaviors toward diabetes and its prevention both in patients and their offspring. However, the effectiveness of patients as information deliverers was limited.

Enhancing the Understanding of Pre-Type 1 Diabetes in the General Population

Type 1 diabetes occurs in ∼90% of patients with no family history of the disease. The majority of studies seeking to identify at-risk subjects have been conducted in first-degree relatives who comprise just 10% of all cases of type 1 diabetes but may have a 20-fold increased risk for type 1 diabetes (1). Although the peak incidence occurs at adolescence, there are data to suggest that 5–10% of all adults diagnosed with type 2 diabetes may actually have type 1 diabetes (latent autoimmune diabetes in adults [LADA]). If type 1 diabetes is to be prevented, significantly enhanced understanding of both the mechanisms leading to type 1 diabetes and the natural history of the pre-diabetic period is essential. Current evidence suggests that type 1 diabetes results from a complex interaction between type 1 diabetes genetic susceptibility (predominantly HLA Class II associations) and environmental exposure(s) leading to a breakdown of tolerance culminating in β-cell autoimmunity and destruction (2). In the process leading to overt type 1 diabetes, both T and B lymphocytes are activated. B-lymphocyte activation is characterized by the emergence of cytoplasmic islet cell autoantibodies (ICAs) and one or more autoantibodies against the β-cell–specific autoantigen insulin, glutamate decarboxylase, the IA-2 protein tyrosine phosphatase, or the zinc transporter ZnT8 (IAA, GADA, IA-2A, and ZnT8A, respectively). For the most part, IAA, GADA, IA-2A, and ZnT8A have replaced ICA, which is measured using indirect immunofluorescence that requires a subjective evaluation of the fluorescence intensity. The IAA, GADA, IA-2A, and ZnT8A analyses require only small amounts of serum (5–20 μl in most assays) and are thus well suited for large-scale studies comprising both infants and small children. Serum samples can be safely stored at −20°C for years before the measurement of the autoantibodies is undertaken, and the samples usually also tolerate repeated freeze-thaw cycles without …

Genetic variation within the HLA class III influences T1D susceptibility conferred by high-risk HLA haplotypes

HLA class II DRB1 and DQB1 represent the major type 1 diabetes (T1D) genetic susceptibility loci; however, other genes in the HLA region are also involved in T1D risk. We analyzed 1411 pedigrees (2865 affected individuals) from the type 1 diabetes genetics consortium (T1DGC) genotyped for HLA classical loci and for 12 SNPs in the class III region previously shown to be associated with T1D in a subset of 886 pedigrees. Using the transmission disequilibrium test, we compared the proportion of SNP alleles transmitted from within the high risk DR3 and DR4 haplotypes to affected offspring. Markers rs4151659 (mapping to CFB) and rs7762619 (mapping 5′ of LTA) were the most strongly associated with T1D on DR3 (p=1.2 × 10−9 and p=2 × 10−12 respectively) and DR4 (p=4 × 10−15 and p= 8 × 10−8 respectively) haplotypes. They remained significantly associated after stratifying individuals in analyses for B*1801, A*0101-B*0801, DPB1*0301, DPB1*0202, DPB1*0401 or DPB1*0402. Rs7762619 and rs4151659 are in strong linkage disequilibrium (LD) (r2=0.82) with each other, but a joint analysis showed that the association for each SNP was not solely due to LD. Our data support a role for more than one locus in the class III region contributing to risk of T1D.

Association analysis of type 2 diabetes Loci in type 1 diabetes.

OBJECTIVE—To search for a possible association of type 1 diabetes with 10 validated type 2 diabetes loci, i.e., PPARG, KCNJ11, WFS1, HNF1B, IDE/HHEX, SLC30A8, CDKAL1, CDKN2A/B, IGF2BP2, and FTO/RPGRIP1L.RESEARCH DESIGN AND METHODS—Two European population samples were studied: 1) one case-control cohort of 514 type 1 diabetic subjects and 2,027 control subjects and 2) one family cohort of 483 complete type 1 diabetic case-parent trios (total 997 affected). A total of 13 tag single nucleotide polymorphisms (SNPs) from the 10 type 2 diabetes loci were analyzed for type 1 diabetes association.RESULTS—No association of type 1 diabetes was found with any of the 10 type 2 diabetes loci, and no age-at-onset effect was detected. By combined analysis using the Wellcome Trust Case-Control Consortium type 1 diabetes data, SNP rs1412829 in the CDKN2A/B locus bordered on significance (P = 0.039) (odds ratio 0.929 [95% CI 0.867–0.995]), which did not reach the statistical significance threshold adjusted for 13 tests (α = 0.00385).CONCLUSIONS—This study suggests that the type 2 diabetes loci do not play any obvious role in type 1 diabetes genetic susceptibility. The distinct molecular mechanisms of the two diseases highlighted the importance of differentiation diagnosis and different treatment principles.

GAD antibodies in probands and their relatives in a cohort clinically selected for Type 2 diabetes

A subset of patients who present as if they have Type 2 diabetes have positive pancreatic autoantibodies, and have been referred to as having latent autoimmune diabetes in adults (LADA). We assessed the prevalence and clinical characteristics of patients with glutamic acid decarboxylase antibodies (GADA) in a cohort clinically selected for Type 2 diabetes and determined the presence of diabetes and GADA in their first-degree relatives. GADA were measured in 2059 subjects, not known to be related, and clinically selected as having Type 2 diabetes for genetic studies. Clinical characteristics were compared in GADA positive and GADA negative subjects. Diabetes and GAD antibody status were compared in 208 first-degree relatives of GADA positive and GADA negative probands. Of the subjects, 136 (7%) were GADA positive. Compared with the GADA negative subjects, they were slimmer (P < 0.001), diagnosed at a younger age (P = 0.011) and progressed to insulin faster (P < 0.001). Thirty-three per cent of GADA positive subjects had a first-degree relative with diabetes compared with 42% of GADA negative subjects (P = 0.034). The overall prevalence of GADA was similar in the first-degree relatives of GADA positive and GADA negative probands (4 v 5%), and 19 of 22 (86%) diabetic relatives of GADA positive probands were GADA negative. Despite clinically selecting a Type 2 diabetes cohort, 7% were GADA positive with an altered phenotype. These GADA positive patients had a strong family history of non-autoimmune diabetes. This suggests that, in this subgroup of patients, autoimmune pancreatic beta-cell destruction occurs on a background of Type 2 diabetes genetic susceptibility.