Monogenic diabetes in adults: A multi-ancestry study reveals strong disparities in diagnosis rates and clinical presentation

AIM

Identification of monogenic diabetes (MgD) conveys benefits for patients' care. Algorithms for selecting the patients to be genetically tested have been established in EuroCaucasians, but not in non-EuroCaucasian individuals. We assessed the diagnosis rate, the phenotype of MgD, and the relevance of selection criteria, according to ancestry in patients referred for a suspected MgD.

METHODS

Seven genes (GCK, HNF1A, HNF4A, HNF1B, ABCC8, KCNJ11, INS) were analyzed in 1975 adult probands (42% non-EuroCaucasians), selected on the absence of diabetes autoantibodies and ≥2 of the following criteria: age ≤40 years and body mass index <30 kg/m² at diagnosis, and a family history of diabetes in ≥2 generations.

RESULTS

Pathogenic/likely pathogenic variants were identified in 6.2% of non-EuroCaucasian and 23.6% of EuroCaucasian patients (OR 0.21, [0.16-0.29]). Diagnosis rate was low in all non-EuroCaucasian subgroups (4.1-11.8%). Common causes of MgD (GCK, HNF1A, HNF4A), but not rare causes, were less frequent in non-EuroCaucasians than in EuroCaucasians (4.1%, vs. 21.1%, OR 0.16 [0.11-0.23]). Using ethnicity-specific body mass index cutoffs increased the diagnosis rate in several non-EuroCaucasian subgroups.

CONCLUSION

The diagnosis rate of MgD is low in non-EuroCaucasian patients, but may be improved by tailoring selection criteria according to patients'ancestry.

Anaemia and its risk factors and association with treatments in patients with diabetes: A cross-sectional study

BACKGROUND

Anaemia is frequently seen in patients with diabetes and the main cause is renal failure. At all stages of renal failure, however, the prevalence of anaemia is higher in diabetes patients than expected for their glomerular filtration rate, suggesting that causes of anaemia other than renal failure are at work. The present cross-sectional study was conducted to investigate the possible iatrogenic causes of anaemia in patients with diabetes.

SUBJECTS AND METHODS

This was a hospital-based cross-sectional study of all patients who had biological and clinical data covering a 2-year period. All had been in contact with the diabetes department either as outpatients or as inpatients mostly for educational purposes. Clinical factors, including type of diabetes, known diabetes complications, treatments received and biological data, were reviewed for their possible involvement in anaemia.

RESULTS

A total of 4145 consecutive patients were included. Anaemia was observed in 1065 (25.7%) of them. Patients with anaemia were more frequently women and those with longer durations of diabetes. Haemoglobin concentrations were decreased, and prevalence of anaemia was increased at all stages of renal failure, already at stage 2, KDIGO classification. Anaemia patients were more frequently taking insulin, antiplatelet agents and renin-angiotensin system blockers (RASBs). After exclusion of patients with specific causes of anaemia, logistic regression analysis of all parameters correlated with anaemia on univariate analysis revealed that anaemia was associated with gender, antiplatelet agents and RASBs.

CONCLUSION

This study has confirmed that anaemia is frequently seen in diabetes patients and strongly associated with renal failure (already at stage 2). Our observations highlight the adjuvant role of drugs, particularly RASBs, in the risk of anaemia in patients with diabetes.

Conventional and Neo-antigenic Peptides Presented by β Cells Are Targeted by Circulating Naïve CD8+ T Cells in Type 1 Diabetic and Healthy Donors

Although CD8⁺ T-cell-mediated autoimmune β cell destruction occurs in type 1 diabetes (T1D), the target epitopes processed and presented by β cells are unknown. To identify them, we combined peptidomics and transcriptomics strategies. Inflammatory cytokines increased peptide presentation in vitro, paralleling upregulation of human leukocyte antigen (HLA) class I expression. Peptide sources featured several insulin granule proteins and all known β cell antigens, barring islet-specific glucose-6-phosphatase catalytic subunit-related protein. Preproinsulin yielded HLA-A2-restricted epitopes previously described. Secretogranin V and its mRNA splice isoform SCG5-009, proconvertase-2, urocortin-3, the insulin gene enhancer protein ISL-1, and an islet amyloid polypeptide transpeptidation product emerged as antigens processed into HLA-A2-restricted epitopes, which, as those already described, were recognized by circulating naive CD8⁺ T cells in T1D and healthy donors and by pancreas-infiltrating cells in T1D donors. This peptidome opens new avenues to understand antigen processing by β cells and for the development of T cell biomarkers and tolerogenic vaccination strategies.

Determinants of a good perinatal outcome in 588 pregnancies in women with type 1 diabetes

AIM

This study assessed pregnancy outcomes in women with type 1 diabetes (T1D) over the last 15 years and identified modifiable factors associated with good perinatal outcomes.

METHODS

Pregnancy outcomes were prospectively assessed in this cohort study of 588 singleton pregnancies (441 women) managed by standardized care from 2000 to 2014. A good perinatal outcome was defined as the uncomplicated delivery of a normally formed, non-macrosomic, full-term infant with no neonatal morbidity. Factors associated with good perinatal outcomes were identified by logistic regression.

RESULTS

The rate of severe congenital malformations was 1.5%, and 0.7% for perinatal mortality. The most frequent perinatal complications were macrosomia (41%), preterm delivery (16%) and neonatal hypoglycaemia (11%). Shoulder dystocia occurred in 2.6% of cases, but without sequelae. Perinatal outcomes were good in 254 (44%) pregnancies, and were associated with lower maternal HbA_1c values at delivery [adjusted odds ratio (aOR): 2.78, 95% CI: 2.04-3.70, for each 1% (11mmol/mol) absolute decrease], lower gestational weight gains (aOR: 1.06, 95% CI: 1.02-1.10) and absence of preeclampsia (aOR: 2.63, 95% CI: 1.09-6.25). The relationship between HbA_1c at delivery and a good perinatal outcome was continuous, with no discrimination threshold.

CONCLUSION

In our study, rates of severe congenital malformations and perinatal mortality were similar to those of the general population. Less severe complications, mainly macrosomia and late preterm delivery, persisted. Also, our study identified modifiable risk factors that could be targeted to further improve the prognosis of pregnancy in T1D.

High-sensitivity C-reactive protein does not improve the differential diagnosis of HNF1A-MODY and familial young-onset type 2 diabetes: A grey zone analysis

AIM

Low plasma levels of high-sensitivity C-reactive protein (hs-CRP) have been suggested to differentiate hepatocyte nuclear factor 1 alpha-maturity-onset diabetes of the young (HNF1A-MODY) from type 2 diabetes (T2D). Yet, differential diagnosis of HNF1A-MODY and familial young-onset type 2 diabetes (F-YT2D) remains a difficult challenge. Thus, this study assessed the added value of hs-CRP to distinguish between the two conditions.

METHODS

This prospective multicentre study included 143 HNF1A-MODY patients, 310 patients with a clinical history suggestive of HNF1A-MODY, but not confirmed genetically (F-YT2D), and 215 patients with T2D. The ability of models, including clinical characteristics and hs-CRP to predict HNF1A-MODY was analyzed, using the area of the receiver operating characteristic (AUROC) curve, and a grey zone approach was used to evaluate these models in clinical practice.

RESULTS

Median hs-CRP values were lower in HNF1A-MODY (0.25mg/L) than in F-YT2D (1.14mg/L) and T2D (1.70mg/L) patients. Clinical parameters were sufficient to differentiate HNF1A-MODY from classical T2D (AUROC: 0.99). AUROC analyses to distinguish HNF1A-MODY from F-YT2D were 0.82 for clinical features and 0.87 after including hs-CRP. For the grey zone analysis, the lower boundary was set to miss<1.5% of true positives in non-tested subjects, while the upper boundary was set to perform 50% of genetic tests in individuals with no HNF1A mutation. On comparing HNF1A-MODY with F-YT2D, 65% of patients were classified in between these categories - in the zone of diagnostic uncertainty - even after adding hs-CRP to clinical parameters.

CONCLUSION

hs-CRP does not improve the differential diagnosis of HNF1A-MODY and F-YT2D.

Potential role of IL-17-producing iNKT cells in type 1 diabetes

We explored in this study the status and potential role of IL-17-producing iNKT cells (iNKT17) in type 1 diabetes (T1D) by analyzing these cells in patients with T1D, and in NOD mice, a mouse model for T1D. Our analysis in mice showed an increase of iNKT17 cells in NOD vs control C57BL/6 mice, partly due to a better survival of these cells in the periphery. We also found a higher frequency of these cells in autoimmune-targeted organs with the occurrence of diabetes, suggesting their implication in the disease development. In humans, though absent in fresh PMBCs, iNKT17 cells are detected in vitro with a higher frequency in T1D patients compared to control subjects in the presence of the proinflammatory cytokine IL-1β, known to contribute to diabetes occurrence. These IL-1β-stimulated iNKT cells from T1D patients keep their potential to produce IFN-γ, a cytokine that drives islet β-cell destruction, but not IL-4, with a reverse picture observed in healthy volunteers. On the whole, our results argue in favour of a potential role of IL-17-producing iNKT cells in T1D and suggest that inflammation in T1D patients could induce a Th1/Th17 cytokine secretion profile in iNKT cells promoting disease development.

Severe acute renal failure in patients treated with glucagon-like peptide-1 receptor agonists

We report two patients with diabetes in whom acute renal failure requiring hemodialysis occurred while on treatment with glucagon-like peptide-1 receptor agonists. We discuss the mechanisms of this complication and the potential for its prevention.

Factors associated with the presence of glutamic acid decarboxylase and islet antigen-2 autoantibodies in patients with long-standing type 1 diabetes

AIM

Glutamic acid decarboxylase (GAD) and/or islet antigen-2 (IA-2) autoantibodies (ab) are present in 90% of patients at the onset of type 1 diabetes (T1D). Few studies have shown that they may persist in the long-term. We analysed the frequency of GADab and IA-2ab and the factors associated with their persistency in patients with long-lasting T1D.

METHODS

This cross-sectional study included 430 adult patients with T1D of at least 10-year duration, consecutively seen over one year. GADab and IA-2ab were determined by radio-binding assays. Autoantibodies to thyroperoxydase, gastric parietal cells and transglutaminase were assessed in 418 patients, and HLA DRB1 genotyping in 359. Parameters associated with the persistency of antibodies were studied by multivariate analysis.

RESULTS

Median age at diagnosis of T1D was 12 years, and median diabetes duration was 19 years. Extrapancreatic autoimmunity was present in 38% of the patients, and associated autoimmune diseases in 21%. GADab and/or IA-2ab were found in 56% of the patients, and in 32% in those with more than 25-year diabetes duration. GADab were more frequent than IA-2ab. Female sex, an older age at diagnosis, and a shorter duration of diabetes were independently associated with the presence of ab. The same factors and the DR3 allele were associated with GADab, while only diabetes duration and the DR4 allele were associated with IA-2ab.

CONCLUSION

In a large proportion of the patients with T1D, the long-term persistency of diabetes-associated antibodies allows aetiological diagnosis, even far from the onset of hyperglycaemia.

Allelic variations of the vitamin D receptor (VDR) gene are associated with increased risk of coronary artery disease in type 2 diabetics: the DIABHYCAR prospective study

AIM

Vitamin D deficiency is associated with coronary artery disease (CAD), and the actions of vitamin D are mediated by binding to a specific nuclear vitamin D receptor (VDR). This study investigated the associations of VDR gene variants with CAD in two cohorts of type 2 diabetes patients.

METHODS

A cohort of 3137 subjects from the prospective DIABHYCAR study (CAD incidence: 14.8%; follow-up: 4.4 ± 1.3 years) and an independent, hospital-based population of 713 subjects, 32.3% of whom had CAD, were assessed. Three SNPs in the VDR gene were genotyped: rs1544410 (BsmI); rs7975232 (ApaI); and rs731236 (TaqI).

RESULTS

In the DIABHYCAR cohort, an association was observed between the A allele of BsmI and incident cases of CAD (HR: 1.16, 95% CI: 1.05-1.29; P = 0.002). Associations were also observed between BsmI (P = 0.01) and TaqI (P = 0.04) alleles and baseline cases of CAD. The AAC haplotype (BsmI/ApaI/TaqI) was significantly associated with an increased CAD prevalence at the end of the study compared with the GCT haplotype (OR: 1.12, 95% CI: 1.02-1.28; P = 0.04). In a cross-sectional study of the independent hospital-based cohort, associations of ApaI (P = 0.009) and TaqI (P = 0.03) alleles with CAD were observed, with similar haplotype results (OR: 1.33, 95% CI: 1.03-1.73; P = 0.03).

CONCLUSION

The haplotype comprising the minor allele of BsmI, major allele of ApaI and minor allele of TaqI of VDR (AAC) was associated with an increased risk of CAD in type 2 diabetes patients. This effect was independent of the effects of other known cardiovascular risk factors.

Zinc transporter (ZnT)8(186-194) is an immunodominant CD8+ T cell epitope in HLA-A2+ type 1 diabetic patients

AIMS/HYPOTHESIS

Anti-zinc transporter (ZnT)8 autoantibodies are commonly detected in type 1 diabetic patients. We hypothesised that ZnT8 is also recognised by CD8(+) T cells and aimed to identify HLA-A2 (A*02:01)-restricted epitope targets.

METHODS

Candidate epitopes were selected by ZnT8 plasmid DNA immunisation of HLA-A2/DQ8 transgenic mice and tested for T cell recognition in peripheral blood mononuclear cells of type 1 diabetic, type 2 diabetic and healthy participants by IFN-γ enzyme-linked immunospot.

RESULTS

White HLA-A2(+) adults (83%) and children (60%) with type 1 diabetes displayed ZnT8-reactive CD8(+) T cells that recognised a single ZnT8(186-194) (VAANIVLTV) epitope. This ZnT8(186-194)-reactive fraction accounted for 50% to 53% of total ZnT8-specific CD8(+) T cells. Another sequence, ZnT8(153-161) (VVTGVLVYL), was recognised in 20% and 25% of type 1 diabetic adults and children, respectively. Both epitopes were type 1 diabetes-specific, being marginally recognised by type 2 diabetic and healthy participants (7-12% for ZnT8(186-194), 0% for ZnT8(153-161)).

CONCLUSIONS/INTERPRETATION

ZnT8-reactive CD8(+) T cells are predominantly directed against the ZnT8(186-194) epitope and are detected in a majority of type 1 diabetic patients. The exceptional immunodominance of ZnT8(186-194) may point to common environmental triggers precipitating beta cell autoimmunity.

Decreased insulin secretion and increased risk of type 2 diabetes associated with allelic variations of the WFS1 gene: the Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) prospective study

AIMS/HYPOTHESIS

We investigated associations of allelic variations in the WFS1 gene with insulin secretion and risk of type 2 diabetes in a general population prospective study.

METHODS

We studied 5,110 unrelated French men and women who participated in the prospective Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study. Additional cross-sectional analyses were performed on 4,472 French individuals with type 2 diabetes and 3,065 controls. Three single nucleotide polymorphisms (SNPs) were genotyped: rs10010131, rs1801213/rs7672995 and rs734312.

RESULTS

We observed statistically significant associations between the major alleles of the three variants and prevalent type 2 diabetes in the DESIR cohort at baseline. Cox analyses showed an association between the G-allele of rs10010131 and incident type 2 diabetes (HR 1.34, 95% CI 1.08-1.70, p = 0.007). Similar results were observed for the G-allele of rs1801213 and the A-allele of rs734312. The GGA haplotype was associated with an increased risk of diabetes as compared with the ACG haplotype (HR 1.26, 95% CI 1.04-1.42, p = 0.02). We also observed statistically significant associations of the three SNPs with plasma glucose, HbA(1c) levels and insulin secretion at baseline and throughout the study in individuals with type 2 diabetes or at risk of developing diabetes. However, no association was observed in those who remained normoglycaemic at the end of the follow-up. Associations between the three variants and type 2 diabetes were replicated in cross-sectional studies of type 2 diabetic patients in comparison with a non-diabetic control group.

CONCLUSIONS/INTERPRETATION

The most frequent haplotype at the haplotype block containing the WFS1 gene modulated insulin secretion and was associated with an increased risk of type 2 diabetes.

Familial young-onset forms of diabetes related to HNF4A and rare HNF1A molecular aetiologies

OBJECTIVE

We have dissected the rare molecular anomalies that may affect hepatocyte nuclear factor-1a (HNF1A) and hepatocyte nuclear factor-4a (HNF4A) in patients with familial young-onset diabetes for whom HNF1A mutations have been excluded by sequence analysis.

METHODS

Eighty-four unrelatedHNF1A-negative patients with diabetes diagnosed before the age of 40 years, a family history of diabetes and the absence of features suggestive of Type 2 diabetes were included. We analysed by sequencing the HNF4A promoter and coding regions, the HNF1A promoter region and specific regions of HNF1A(B) and HNF1A(C) isoforms and searched for large deletions of HNF1A and HNF4A by multiplex ligation-dependent probe amplification (MLPA).

RESULTS

We identified five novel HNF4A mutations (5 ⁄ 84, 6%), including four missense and one in-frame deletion, and one mutation of the HNF1A promoter (1 ⁄ 84). Sequence analysis of isoform-specific coding regions of HNF1A did not reveal any mutation. We next identified two whole gene deletions of HNF1A and HNF4A, respectively (2 ⁄ 84, 2.4%).

CONCLUSIONS

Altogether, the search for rare molecular events in HNF1A and HNF4A led us to elucidate 8 ⁄ 84 (9.5%) of our HNF1A-negative cases.This study shows that genetic aetiologies remain to be elucidated in familial young-onset diabetes. It also highlights the difficulty of the differential diagnosis with Type 2 diabetes because of the wide clinical expression of monogenic young-onset diabetes and the absence of specific biomarkers.

The clinical variability of maternally inherited diabetes and deafness is associated with the degree of heteroplasmy in blood leukocytes

CONTEXT

Maternally inherited diabetes and deafness (MIDD) is a rare form of diabetes with a matrilineal transmission, sensorineural hearing loss, and macular pattern dystrophy due to an A to G transition at position 3243 of mitochondrial DNA (mtDNA) (m.3243A>G). The phenotypic heterogeneity of MIDD may be the consequence of different levels of mutated mtDNA among mitochondria in a given tissue.

OBJECTIVE

The aim of the present study was thus to ascertain the correlation between the severity of the phenotype in patients with MIDD and the level of heteroplasmy in the blood leukocytes.

PARTICIPANTS

The GEDIAM prospective multicenter register was initiated in 1995. Eighty-nine Europid patients from this register, with MIDD and the mtDNA 3243A>G mutation, were included. Patients with MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) or with mitochondrial diabetes related to other mutations or to deletions of mtDNA were excluded.

RESULTS

A significant negative correlation was found between levels of heteroplasmy and age of the patients at the time of sampling for molecular analysis, age at the diagnosis of diabetes, and body mass index. After adjustment for age at sampling for molecular study and gender, the correlation between heteroplasmy levels and age at the diagnosis of diabetes was no more significant. The two other correlations remained significant. A significant positive correlation between levels of heteroplasmy and HbA(1c) was also found and remained significant after adjustment for age at molecular sampling and gender.

CONCLUSIONS

These results support the hypothesis that heteroplasmy levels are at least one of the determinants of the severity of the phenotype in MIDD.

Retinal and renal complications in patients with a mutation of mitochondrial DNA at position 3,243 (maternally inherited diabetes and deafness). A case-control study

AIMS/HYPOTHESIS

We assessed the prevalence and determinants of retinal and renal complications in patients with maternally inherited diabetes and deafness (MIDD).

METHODS

This was a multicentre prospective study comparing the prevalence of retinopathy and renal disease in 74 patients with MIDD and 134 control patients matched for sex, age and clinical presentation at onset of diabetes, duration of diabetes and current treatment. Comparisons were adjusted for HbA(1c) and hypertension.

RESULTS

In MIDD patients, HbA(1c) (7.6 +/- 1.6 vs 8.5 +/- 2.0%, p < 0.002), systolic blood pressure (126.6 +/- 16.2 vs 133.1 +/- 17.3 mmHg, p < 0.007) and prevalence of hypertension (33.8 vs 64.2%, p < 0.0001) were lower than in control patients. Prevalence of diabetic retinopathy was 3.7-fold lower in MIDD patients (6/74, 8 vs 40/134, 29.6%, p < 0.0001). Differences between groups remained significant after adjustment for hypertension, systolic blood pressure and HbA(1c). In MIDD, urinary albumin excretion (314.8 vs 80.1 mg/24 h, p = 0.035) and creatinine plasma levels (103.5 vs 82.2 micromol/l, p = 0.0178) were higher and GFR was lower. Impaired renal function (GFR <60 ml/min) was four- to sixfold more frequent in MIDD. Differences between MIDD and control diabetic patients further increased when adjusted for HbA(1c) and systolic blood pressure (p < 0.0001). Adjustment for treatment with an ACE inhibitor or angiotensin II receptor antagonist did not modify the results.

CONCLUSIONS/INTERPRETATION

This study indicates that diabetic retinopathy is less prevalent in MIDD than in control diabetes. This suggests that retinal alterations due to mitochondrial disease may have a protective role. By contrast, nephropathy is far more frequent in MIDD, suggesting the presence of a specific renal disease independent of diabetic nephropathy.

A standardized protocol to achieve normoglycaemia during labour and delivery in women with type 1 diabetes

AIM

To evaluate a standardized protocol for maintaining near-normoglycaemia during labour and delivery in women with type 1 diabetes.

METHODS

Over a nine-year period (1997-2005), 229 pregnancies in 174 women with type 1 diabetes were delivered at one centre. The same regimen was used for the induction of labour (group 1) and in women admitted in spontaneous labour (group 2): 10% dextrose (80ml/h) intravenous was given along with short-acting insulin, starting at 1IU/h intravenous via an infusion pump. Capillary blood glucose (CBG) was determined hourly, and the insulin infusion rate was modified accordingly.

RESULTS

Labour was induced in 85 cases (37%) and spontaneous in 23 cases (10%), and an elective C-section was performed in 121 cases (53%). Maternal glycaemia during labour was 6.1+/-1.6 (range: 3.9-9.2)mmol/l in group 1, and 6.9+/-2.0 (range: 4.7-12.0)mmol/l in group 2. Maternal glycaemia at delivery was 5.8+/-1.5 (range: 3.4-9.4) and 6.3+/-1.9 (range: 4.1-11.4)mmol/l in groups 1 and 2, respectively. Women who underwent an elective C-section were not included in the standardized protocol and had higher glycaemia at delivery 7.1+/-2.0 (range: 2.7-13.5)mmol/l. Neonatal hypoglycaemia occurred in 30 infants (13%), and was only associated with preterm delivery.

CONCLUSION

Using a standardized simple protocol during labour, maternal glycaemia was maintained within a near-normal range in 80-85% of cases.

Stress myocardial scintigraphy and dobutamine echocardiography in the detection of coronary disease in asymptomatic patients with type 2 diabetes

OBJECTIVE

The aims of this prospective study were: (1) to compare stress thallium-201 single photon emission computed tomography (SPECT) and dobutamine echocardiography (DE) in the detection of silent myocardial ischemia (SMI) in asymptomatic high risk diabetic patients; (2) to analyse long-term outcome after intensive care of SMI in these patients.

METHODS

SPECT was performed in 100 high risk diabetic patients and DE in the first 75 patients. Coronary angiography was realized in patients with SMI, with revascularization for suitable lesions. Intensive treatment of atherosclerosis risk factors was performed in all patients. Patients were followed 2 +/- 0.5 years for the subsequent occurrence of cardiac death, myocardial infarction and revascularization.

RESULTS

SMI was detected by SPECT in 62% and by DE in 10% of the patients (p < 0.0001), whereas significant coronary stenosis at angiography was detected by SPECT in 26% and by DE in 5% of the patients (p < 0.02). Independent predictive factors of significant coronary stenosis were male gender (p < 0.03) and peripheral arterial disease (p < 0.007). Nonfatal acute coronary syndrome occurred during follow-up in 2 patients (2%). Subsequent revascularization procedure was needed in 9 patients. Baseline patients' characteristics, as well as SMI, were not predictive of cardiac event during follow up.

CONCLUSION

SPECT seems more accurate than DE to detect significant coronary stenosis in high risk asymptomatic diabetic patients. In this population, aggressive treatment of SMI with systematic revascularization combined with intensive care of risk factors is associated with a favorable long-term prognosis, similar in diabetic patients with and without initial SMI.

Factors associated with preterm delivery in women with type 1 diabetes: a cohort study

OBJECTIVE

The reported rate of preterm delivery in women with type 1 diabetes ranges from 22 to 45%, but the reasons are unclear. The purpose of this study was to identify factors associated with preterm delivery in these women.

RESEARCH DESIGN AND METHODS

We studied the influence of maternal and diabetes-related factors on the occurrence of preterm delivery in 168 single pregnancies occurring in 127 women with type 1 diabetes. Women with spontaneous or indicated preterm delivery were compared with those who delivered after 37 weeks of gestation using polytomous logistic regression.

RESULTS

The overall rate of preterm delivery was 24%, fivefold higher than the French prematurity rate in single pregnancy. Preterm delivery was spontaneous in 9% and indicated in 15%. HbA1c > or =7% at delivery was associated with spontaneous preterm delivery (odds ratio [OR] 5.3 [95% CI 1.1-26.8]). Nulliparity (12.0 [2.3-64.1]), progression of nephropathy (7.7 [1.3-46.9]), preeclampsia (12.0 [3.1-47.1]), and HbA1c > or =7% (7.5 [1.5-37.9]) at delivery were all associated with indicated preterm delivery. Preterm delivery was associated with significant neonatal morbidity as the risks for neonatal hypoglycemia and respiratory distress syndrome were increased by three- to sixfold compared with the reference group.

CONCLUSIONS

The rate of preterm delivery remains high in women with type 1 diabetes. Different factors were associated with spontaneous and indicated preterm delivery, respectively. Because poor glycemic control was a risk factor for both outcomes, part of preterm delivery might be preventable.

The Gly482Ser polymorphism in the peroxisome proliferator-activated receptor-gamma coactivator-1 gene is associated with hypertension in type 2 diabetic men

AIMS/HYPOTHESIS

Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) acts as a cofactor for several nuclear hormone receptors in many tissues and organs implicated in blood pressure regulation. Here, we assessed the association between the Gly482Ser variant of PPARGC1 and the arterial hypertension frequently found in subjects with type 2 diabetes.

METHODS

We studied a group of 479 men and 253 women with type 2 diabetes. Arterial hypertension was present in 70% of the men and in 73% of the women. Genotypes were examined by PCR restriction fragment length polymorphism. A logistic regression analysis was performed to assess the covariables associated with arterial hypertension.

RESULTS

There was an association between Ser allele homozygosis and arterial hypertension in type 2 diabetic men (odds ratio of 2.52 vs Gly allele homozygosis; 95% CI: 1.32-5.00; p=0.0064), but not in women. The prevalence of arterial hypertension in type 2 diabetic men was 77% vs 73% vs 67% for Ser-Ser, Gly-Ser and Gly-Gly carriers respectively (p=0.021). Age, BMI, the use of insulin, and triglyceride and creatinine levels were also independently associated with arterial hypertension in this cohort.

CONCLUSIONS/INTERPRETATION

We have observed a sex-specific association between the PPARGC-1 gene Gly482Ser polymorphism and arterial hypertension in type 2 diabetic men. Further studies are needed to investigate the genetic, biochemical and pathophysiological basis of this allelic association.

Cumulative adverse effects of diabetes mellitus and hypertension on coronary flow velocity reserve

BACKGROUND

this study aimed to assess the hypothesis that essential hypertension (EH) may increase coronary microcirculation dysfunction in patients with type 2 diabetes mellitus (DM). Microvascular dysfunction has been reported in patients with DM or EH. Discordant results have been reported on cumulative adverse effects of the simultaneous presence of DM and EH on coronary flow velocity reserve (CFR).

METHODS

CFR were compared in 13 hypertensive diabetics (group 1), 12 normotensive diabetics (group 2), 11 hypertensive non diabetics (group 3) and 29 normotensive non diabetic patients (group 4). CFR was calculated using an intracoronary Doppler-tipped flow wire.

RESULTS

CFR was significantly lower in patients with both DM and EH (2.2 +/- 0.4 in group 1 vs 2.8 +/- 0.5, 2.8 +/- 0.6 and 2.9 +/- 0.7 in groups 2, 3 and 4 respectively, p<0.01). The presence of hypertension reduced CFR in diabetic patients with angiographically abnormal but unobstructed coronary arteries (2.1 +/- 0.3 in hypertensive vs 3.1 +/- 0.2 in normotensive diabetic patients, p<0.02). No cumulative adverse effect was observed in diabetics with angiographically normal coronary arteries (2.3 +/- 0.6 in hypertensive vs 2.6 +/- 0.5 in normotensive diabetic patients, NS). Multivariate analysis revealed that combination of DM and EH (p<0.007) was independently related to CFR.

CONCLUSIONS

the presence of hypertension appears to worsen coronary microangiopathy in diabetic patients with unobstructed coronary artery disease. The cumulative effect of EH and DM on CFR impairment has consequences for decision-making during coronary angioplasty and could identify patients at risk for cardiomyopathy.

Heterogeneity of diabetes phenotype in patients with 3243 bp mutation of mitochondrial DNA (Maternally Inherited Diabetes and Deafness or MIDD)

OBJECTIVE

In patients with maternally inherited diabetes and deafness (MIDD), due to 3 243 A > G mutation of mitochondrial DNA (mtDNA), diabetes may present with variable phenotypes.

OBJECTIVE

To ascertain the existence of two distinct phenotypes, MIDD1 and MIDD2, in a series of patients with MIDD.

DESIGN

Multicenter prospective study.

PATIENTS

77 patients with diabetes and the mtDNA 3243 mutation and 139 control patients with type 1 (T1D) or type 2 (T2D) diabetes, matched according to initial presentation of diabetes, age at onset, sex, and duration of diabetes (24 T1D and 115 T2D, including 55 treated with insulin).

MEASUREMENTS

Anthropometric characteristics (height, body weight, body mass index [BMI], sex), family history of diabetes, and characteristics of diabetes (age at onset, treatment, hemoglobin A1c [HbA1c]), extrapancreatic manifestations.

RESULTS

In 13 cases (17%, MIDD1), diabetes presented as insulin-dependent from the onset, with ketoacidosis in 6 cases. In 64 cases (83%, MIDD2), diabetes resembled T2D, and was treated with diet in 12 cases, oral hypoglycemic agents in 21 cases, or insulin in 31 cases. Compared with patients with MIDD2, patients with MIDD1 were characterized by lower age at onset of first manifestation of MIDD (25.4 +/- 9.6 vs 33.7 +/- 13.2 Years, P<0.0005), lower body weight (49.1 +/- 7.4 vs 56.3 +/- 10.9 kg, P<0.0025), lower BMI (18.2 +/- 2.3 vs 20.9 +/- 3.6 kg/m2, P<0.0005), and higher HbA1c levels (9.5 +/- 2.0 vs 7.5 +/- 1.6%, P<0.0005). Frequency of family history of diabetes and of extrapancreatic manifestations was the same in both MIDD subtypes. No difference was found within the MIDD2 subtype when comparing patients treated with or without insulin. Compared with matched controls, patients with MIDD had a lower BMI (MIDD1/T1D 18.2 +/- 2.3 vs 24.0 +/- 3.6 kg/m2 and MIDD2/T2D 20.9 +/- 3.6 vs 30.2 +/- 5.9 kg/m2, P<0.0025). Lastly, male patients with MIDD had a shorter height than controls (MIDD1/T1D: 166.1 +/- 3.2 vs 177.3 +/- 6.6 cm and MIDD2/T2D: 168.4 +/- 7.2 vs 173.6 +/- 6.6 cm P<0.025).

CONCLUSIONS

These results confirm the existence of two different phenotypes in MIDD, MIDD1 and MIDD2, which may be related to the severity of the mitochondrial disease. The role of other genetic and/or environmental factors in the variable phenotype of MIDD remains to be elucidated.

[Insulin and weight gain: myth or reality?]

Most patients with type 2 diabetes gain weight when treated with insulin. Weight gain is observed when insulin is introduced after oral agents have failed, but also when insulin is introduced shortly after the diagnosis of diabetes. The mechanisms of this weight gain are incompletely understood, but reduction of energy lost by glucosuria and reduction of energy needed for glucose production are main determinants. The same reasons apply to the weight gain observed at the beginning of treatment with sulfonylureas, even though patients usually gain less weight with sulfonyulreas than with insulin. In the UKPDS, at 10 years of the study, patients treated with insulin gained 2 kg more, i.e. 2.5% of the average weight of patients included in the trial, than patients treated with sulfonylureas. The reasons of the excess of weight gain with insulin as compared with sulfonylureas remain unclear. Patients with type 2 diabetes treated with insulin gain weight only during the first 2-3 years after insulin introduction. The weight stabilizes thereafter. Type 2 diabetes usually remains unknown for years before diagnosis and patients may lose weight during this long period of time preceding diagnosis. It is hypothesized that the weight gain observed after the introduction of insulin may simply correspond to the reexpression of the physiologically controlled body weight.

A dinucleotide repeat polymorphism at the poly(ADP-ribose) polymerase gene is not associated with predisposition to type 1 diabetes in French Caucasians

The poly (ADP-ribose) polymerase (PARP) is a nuclear enzyme that detects and binds DNA strand breaks. Excessive PARP activation leads to the death of mice islet beta-cells by depleting cellular energy reserves. On the other hand, PARP-mutant mice are resistant to streptozotocine-induced diabetes, and in the non-obese diabetic (NOD) mouse model, treatment with nicotinamide, a PARP inhibitor, protects islet cells against cytotoxic actions in vitro and results in a decreased incidence of type 1 diabetes. PARP gene in human is located within a recently identified type 1 diabetes-susceptibility region on chromosome 1q41-42, and contains a polymorphic CA dinucleotide repeat in the promoter region. To consider the putative involvement of PARP polymorphism in predisposition to type 1 diabetes, we performed genotyping for the various alleles of the CA dinucleotide repeat in 158 unrelated French Caucasian patients with type 1 diabetes and 193 ethnically-matched healthy controls. We found no significant difference of PARP alleles distribution between patients and controls, even after stratification of the patients according to HLA class II genotype or to age at disease onset. Our results suggest that this PARP polymorphism does not influence susceptibility to type 1 diabetes in French Caucasians.

Vitamin D receptor gene polymorphisms are associated with obesity in type 2 diabetic subjects with early age of onset

OBJECTIVE

Allelic variations in the vitamin D receptor (VDR) gene were reported to modulate insulin secretion in response to glucose. VDR was investigated as a candidate gene for type 2 diabetes mellitus (T2DM).

METHOD

Four single nucleotide polymorphisms (SNPs) in intron 8 (BsmI, Tru9I, ApaI) and exon 9 (TaqI) of the VDR gene were examined in 309 unrelated French subjects with T2DM and 143 controls.

RESULTS

The distribution of alleles and genotypes of the four SNPs was similar in patients and controls. However, in patients whose age at diagnosis of diabetes was < or =45 years, homozygous subjects for the T-allele of the TaqI SNP had a higher body mass index (BMI) (31.7+/-6.7 kg/m2, P=0.0058) and an increased prevalence of obesity (81%, P=0.005) with respect to heterozygous subjects (27.9+/-5.0 kg/m2; 46%) or homozygous subjects for the t-allele (27.7+/-5.0 kg/m2; 52%). Similar results were observed for homozygous subjects for the b-allele of the BsmI SNP. Logistic regression analysis demonstrated that TT homozygosity was independently associated with obesity in these subjects (odds ratio, 4.64; 95% confidence interval (CI), 1.64-14.76; P=0.0056).

CONCLUSION

VDR is not a major gene for T2DM in French Caucasians. However, polymorphisms in the VDR gene are associated with the susceptibility to obesity in subjects with early-onset T2DM. The pathophysiological mechanisms of these associations remain unexplained, but they could be related to a direct effect of vitamin D in adypocyte differentiation and metabolism, or to an indirect effect by modulation of insulin secretion.

Heterogeneity of fetal growth in type 1 diabetic pregnancy

OBJECTIVE

To investigate the frequency of macrosomia in an homogeneous cohort of type 1 diabetic mothers and to analyze the influence of maternal factors and glycemic control on the incidence of fetal macrosomia.

MATERIAL AND METHODS

Fifty-five consecutive type 1 diabetic first-pregnancies were prospectively studied. Macrosomia was defined by a ponderal index above the 90(th) percentile. Venous cord blood levels of insulin, C peptide and leptin were measured at delivery. The influence of HbA1c levels and other maternal variables on the occurrence of macrosomia and on the ponderal index was assessed using a stepwise regression logistic model.

RESULTS

The mean (+/- SD) birth weight was 3482 (+/- 497) g at 37.4 +/- 1.0 weeks gestation. Macrosomia occurred in 29 cases (53.7%). Fetal insulin, C peptide and leptin levels were significantly higher in macrosomic than in non macrosomic infants. Maternal age, duration of diabetes, pregravid body mass index, parity, weight gain during pregnancy, presence of a microangiopathy, nephropathy, smoking habits, gestational hypertension or preeclampsia, and HbA1c levels throughout pregnancy did not differed between mothers of macrosomic and non macrosomic infants. In the stepwise analysis none of these covariates was explanatory of the ponderal index.

CONCLUSIONS

The frequency of macrosomia remains very high in infants of type 1 diabetic mothers despite a reasonable degree of glycemic control. The variability of the fetal growth response to mild hyperglycemia prompts for the identification of other factors involved in the modulation of fetal growth.

A common stromal cell-derived factor-1 chemokine gene variant is associated with the early onset of type 1 diabetes

Type 1 diabetes results from the autoimmune destruction of pancreatic beta-cells. Although the disease shows a strong association with HLA class II alleles, other genes may influence the initiation or the rate of progression of the autoimmune process. The recruitment of mononuclear cells within the islets of Langerhans is a critical step in the pathogenesis of the disease. Because chemokines are cytokines that promote migration of mononuclear cells, we hypothesized that polymorphisms in chemokine receptor or chemokine genes, CCR5 and SDF1, may be involved in susceptibility to or clinical expression of type 1 diabetes. The frequencies of the CCR5-delta32 and SDF1-3'A (801G-->A in the 3' untranslated region) variants were similar in 208 unrelated Caucasian patients with type 1 diabetes and in 120 Caucasian control subjects. They were not modified after stratification for the predisposing HLA-DR3 and -DR4 haplotypes. However, the SDF1-3'A variant was strongly associated with early onset (< 15 years) of the disease (odds ratio 2.6, P = 0.0019). On average, the presence of the SDF1-3'A allele was associated with a 5-year reduction in the age at onset of diabetes (P = 0.0067). Our results suggest that stromal cell-derived factor-1 may be implicated in the aggressiveness of the autoimmune process leading to type 1 diabetes. These preliminary data require replication in other populations.

Variations in the vitamin D-binding protein (Gc locus) and risk of type 2 diabetes mellitus in French Caucasians

Electrophoretic variants of the vitamin D-binding protein (DBP) have been reported to be associated with type 2 diabetes mellitus (DM) or with prediabetic phenotypes in several non-Caucasian populations. Two frequent missense polymorphisms at codons 416 (Asp --> Glu) and 420 (Thr --> Lys) are the genetic basis for the 3 common electrophoretic variants of DBP (Gc1F, Gc1S, and Gc2) and the resulting circulating phenotypes (Gc1F/Gc1F, Gc1F/Gc1S, Gc1S/Gc1S, Gc1F/Gc2, Gc1S/Gc2, and Gc2/Gc2). In this study, we investigated the association of these polymorphisms with type 2 DM in French Caucasian subjects. Variations at codons 416 and 420 were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Allele frequencies at both codons did not differ in type 2 DM patients and in control subjects (Asp416: 42.4% v 46.2%, respectively, P =.33; Lys420: 25.5% v 29.0%, respectively, P =.31). Distribution of genotypes at both codons, of the haplotypes defined by the 2 codons, and of the DBP phenotypes defined by the haplotypes were also similar in diabetic and control subjects. In conclusion, our study suggests that genetic variants of the DBP gene are not associated with the susceptibility to type 2 DM in French Caucasians.

[Should the occurrence of a first coronary event change the management of diabetes?]

The coronary morbi-mortality is particularly high in type 2 diabetes, which represents the vast majority of all diabetes. Hyperglycemia is an independent vascular risk factor in the short and long-term. The relationship between the degree of hyperglycemia and vascular risk is linear with no threshold effect. The occurrence of a first coronary event is an occasion, though late, to review the management of all risk factors in diabetic patients. In these patients, intensive insulin therapy administered in the acute phase of infarction reduces cardiovascular mortality by 30% at 1 and 3 years. There are no specific studies of secondary prevention by optimal therapy of diabetes, but, in the UKPDS, the treatment of hyperglycemia with sulfonylurea or insulin only marginally reduced the number of cardiovascular events. On the other hand, treatment of obese patients with metformin significantly reduced the incidence of myocardial infarction and of mortality diabetes related. These results, though observed with the same level of glycemic control as in the other treatment groups, suggest a cardio-protective effect of metformin itself. These beneficial effects should be weighed up against the potential risk of lactic acidosis which still limits the widespread use of metformin in with coronary heart disease patients. Follow-up studies show that diabetic with coronary heart disease patients do not receive all effective therapeutic inventions in secondary prevention and that the treatment of hyperglycemia is often neglected. Close collaboration between cardiologists and diabetologists is necessary to improve the management of type 2 diabetes.

Mutations in the insulin promoter factor-1 gene in late-onset type 2 diabetes mellitus

OBJECTIVE

Insulin promoter factor-1 (IPF-1) is a transcription factor expressed in pancreatic beta cells. Following the identification of missense variants in the coding regions of the IPF-1 gene, in subjects selected for a strong family history of type 2 diabetes, the aim of our study was to evaluate the prevalence of these variants in the common form of type 2 diabetes.

METHODS

Three variants (C18R, Q59L and D76N) were screened by PCR-RFLP in a group of 296 unrelated French late-onset type 2 diabetic subjects consecutively recruited in a diabetes department of a university hospital, regardless of family history of diabetes.

RESULTS

The C18R and Q59L variants were each found in 0.37% of the diabetic patients, and in none of 147 controls. We did not detect the D76N variant, which was the most frequent variant in subjects with a strong family history of diabetes, in patients or controls.

CONCLUSIONS

We have observed a combined prevalence of missense variants in the coding region of the IPF-1 gene of around 1%, in unselected patients with the common form of late-onset type 2 diabetes. The prevalence of these variants in subjects with a strong family history of type 2 diabetes had been found to be as high as approximately 6%. These differences in prevalence might be related to differences in the clinical profile of patients, such as age of onset of diabetes and associated obesity, as well as a family history of diabetes.

[Is diabetes mellitus a sufficient condition to suspect hemochromatosis?]

Genetic Hemochromatosis (GH) is a highly prevalent autosomal recessive disorder, which outcome has been dramatically improved by early phlebotomy. Attempts to screen for the disease, using biological and genetic approaches, are currently under evaluation. Diabetes mellitus often complicates GH. However, as it occurs late in the course of the disease, in most cases when cirrhosis is already present, its usefulness for the screening of GH seems reduced. Diabetes mellitus, when isolated, appears also as a poor predictor of hemochromatosis. Indeed, the risk of being carrier of the disease is not increased in diabetic patients compared with non diabetic sujects. This risk is however highly enhanced by the co-existence of cirrhosis. Thus, in the face of a newly diagnosed diabetes mellitus, the search for hemochromatosis must be performed only when it associates with cirrhosis or with other evocative clinical conditions.

Association of a variant in exon 31 of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus in French Caucasians

The sulfonylurea receptor (SUR1) of the pancreatic beta-cell ATP-sensitive potassium channel plays a key role in glucose-induced insulin secretion. The A-allele of a single nucleotide polymorphism (SNP) in exon 31 of the SUR1 gene (AGG-->AGA; Arg1273Arg) has previously been shown to be associated with hyperinsulinemia in nondiabetic Mexican-American subjects. Here, we have investigated the association of this SNP with type 2 diabetes mellitus (T2DM) in French Caucasian subjects. We have observed an increased frequency of the A allele (37.1% vs 27.6%, P=0.0048; odds ratio 1.54), of the AA genotype (15.7% vs 9.8%; P=0.025), and of the combined AA/AG genotypes (58.5% vs 45.5%, P=0.0098; odds ratio 1.69) in patients compared with controls. This association is stronger in the subgroup of patients with age of diagnosis of diabetes equal to or less than 45 years: A allele 43.2% (P=0.0003 compared with controls; odds ratio 1.99), AA genotype 21.4% (P=0.0032), and combined AA/AG genotypes 65.1% (P=0.0022; odds ratio 2.23). Unexpectedly, the G allele is strongly associated with arterial hypertension in obese diabetic subjects (GG vs AA odds ratio 19.97). In conclusion, we have observed an association of an SNP in exon 31 of the SUR1 gene with T2DM. These data reinforce the hypothesis that insulin secretion defects in T2DM might be at least partially related to allelic variations in the SUR1 gene.

Clinical characteristics of type 2 diabetes in patients with mutations of HFE

Genetic hemochromatosis (GH) is associated with two mutations of the HFE gene (Cys282Tyr and His63Asp). Heterozygosity for GH is associated with a mild increase in iron metabolism parameters, and increased iron stores are associated with abnormal glucose tolerance and decreased insulin sensitivity in the general population. We have previously shown that the frequency of the two HFE mutations is not increased in patients with type 2 diabetes. However, to assess whether the presence of HFE mutations modulates the clinical presentation of type 2 diabetes, we studied the clinical characteristics and iron metabolism indexes according to the presence of the two mutations in 266 patients with type 2 diabetes. The Cys282Tyr mutation and the His63Asp mutation were present in 9. 8% and 26% of the patients, respectively. Serum iron, transferrin saturation and ferritin concentrations were significantly increased in patients expressing either HFE mutations, compared to those without any mutation. There was no difference in the clinical characteristics in the two groups except that obesity was significantly less frequent in the patients with at least one mutation than in those without any mutation (27.6% vs 42.8%, p=0.02). This finding suggests that, in the absence of obesity, HFE mutations, through the insulin resistance associated with the increase in iron stores, may contribute to the onset of type 2 diabetes.

[Type 1 diabetes mellitus]

POSITIVE DIAGNOSIS

Among the various diseases leading to chronic hyperglycemia, type 1 diabetes mellitus is distinctive by the presence of specific autoantibodies. The common from of type 1 diabetes mellitus is insulin-dependant diabetes, but type 1 diabetes may also present as non-insulin-dependent. In order to predict insulin-dependence and screen for associated autoimmune diseases, search for autoantibodies is required in all patients with diabetes, whatever the clinical presentation. COMPLEX PATHOPHYSIOLOGY: Diabetes mellitus is a multifactorial disease implicating of environmental and genetic factors leading to breakdown immune tolerance. LONG PRECLINICAL PHASE: Chronic hyperglycemia is preceded by a long preclinical phase during which the only observable anomalies result from activation of the immune system. With the development of simplified techniques for detecting autoantibodies, it would be reasonable to foresee large-scale screening. ONGOING SECONDARY PREVENTION TRIALS: The goal is to prevent the development of chronic hyperglycemia by intervening early, during the infraclinical phase, in patients with signs of immune activation. AT THE TIME OF DIAGNOSIS: When diabetes is discovered, intensive insulin therapy helps preserve residual insulin secretion and guarantees better long-term metabolic control.

Insulin-dependent diabetes mellitus in non-DR3/non-DR4 subjects

Five to 20% insulin-dependent diabetes mellitus (IDDM) patients do not bear the classical HLA class II DR3 or DR4 susceptibility haplotypes. We have studied the clinical characteristics, anti-islet cell antibodies (Ab) and HLA class II genotypes in 72 non-DR3/non-DR4 Caucasian patients, mainly adults, presenting with clinically typical IDDM. The DRB1*08-DQB1*0402-DQA1*0401 haplotype frequency was increased in the patients compared to 272 non-DR3/non-DR4 controls (OR = 5.9, Pc < 0.005). This association was even stronger in the Ab-positive patients (DRB1*08: OR = 7.2, Pc < 0.005; DQB1*0402: OR = 9.2, Pc < 0.005; DQA1*0401: OR = 9, Pc < 0.02). In those subjects the DRB1*15 allele was less frequent than in controls (OR = 0.1, Pc = 0.05). By contrast, IDDM patients with no Ab showed no particular association with HLA class II allele although they had clinical and metabolic characteristics similar to that of Ab-positive subjects. The genetic basis for IDDM predisposition in the Ab-positive subgroup remains elusive since the DRB1*08-DQB1*0402 haplotype encodes an Asp57-positive DQ beta chain. However, all DR8 patients had a non-Asp57 encoding DQB1 allele on the second haplotype. Thus, trans-complementation leading to peculiar predisposing DQ alpha beta heterodimers may occur. Alternatively, a direct role of the DRB1*08 allele cannot be excluded. These results show that autoimmune type 1 diabetes occurs in non-DR3/non-DR4 subjects, mainly adults. They further support that IDDM, when defined on a clinical basis, encompass different pathogenetic entities.