Cumulative incidence of type 1 diabetes in 10,168 siblings of Finnish young-onset type 1 diabetic patients

Familial aggregation and heritability of childhood-onset and adult-onset type 1 diabetes: a Swedish register-based cohort study

BACKGROUND

Type 1 diabetes in children is known to be highly heritable, but much less is known about the heritability of adult-onset type 1 diabetes. Thus, our objective was to compare the familial aggregation and heritability of type 1 diabetes in adults and children.

METHODS

This Swedish nationwide register-based cohort study included individuals born from Jan 1, 1982, to Dec 31, 2010, identified through the Medical Birth Register who were linked to their parents, full siblings, half siblings, and cousins through the Multi-Generation Register (MGR). We excluded multiple births, deaths within the first month of life, individuals who could not be linked to MGR, or individuals with contradictory information on sex. Information on diagnoses of type 1 diabetes was retrieved by linkages to the National Diabetes Register and National Patient Register (1982-2020). Individuals with inconsistent records of diabetes type were excluded. We estimated the cumulative incidence and hazard ratios (HRs) of type 1 diabetes in adults (aged 19-30 years) and children (aged 0-18 years) by family history of type 1 diabetes and the heritability of adult-onset and childhood-onset type 1 diabetes based on tetrachoric correlations, using sibling pairs.

FINDINGS

2 943 832 individuals were born in Sweden during the study period, 2 832 755 individuals were included in the analysis of childhood-onset type 1 diabetes and 1 805 826 individuals were included in the analysis of adult-onset type 1 diabetes. 3240 cases of adult-onset type 1 diabetes (median onset age 23·4 years [IQR 21·1-26·2]; 1936 [59·7%] male and 1304 [40·2%] female) and 17 914 cases of childhood-onset type 1 diabetes (median onset age 9·8 years [6·2-13·3]; 9819 [54·8%] male and 8095 [45·2%] female) developed during follow-up. Having a first-degree relative with type 1 diabetes conferred an HR of 7·21 (95% CI 6·28-8·28) for adult-onset type 1 diabetes and 9·92 (9·38-10·50) for childhood-onset type 1 diabetes. The HR of developing type 1 diabetes before the age 30 years was smaller if a first-degree relative developed type 1 diabetes during adulthood (6·68 [6·04-7·39]) rather than during childhood (10·54 [9·92-11·19]). Similar findings were observed for type 1 diabetes in other relatives. Heritability was lower for adult-onset type 1 diabetes (0·56 [0·45-0·66]) than childhood-onset type 1 diabetes (0·81 [0·77-0·85]).

INTERPRETATION

Adult-onset type 1 diabetes seems to have weaker familial aggregation and lower heritability than childhood-onset type 1 diabetes. This finding suggests a larger contribution of environmental factors to the development of type 1 diabetes in adults than in children and highlights the need to identify and intervene on such factors.

FUNDING

Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, Swedish Diabetes Foundation, and the China Scholarship Council.

Maternal autoimmune disease associated with a higher risk of offspring with type 1 diabetes: A nationwide mother-child cohort study in Taiwan

AIM

The incidence of type 1 diabetes continues to increase. However, the strategies to prevent or reduce its occurrence are inadequate. Therefore, we attempted to investigate if mothers with autoimmune disease were more likely to have children with type 1 diabetes.

METHODS

We identified 1,288,347 newborns from the Taiwan Maternal and Child Health Database between January 1, 2009, and December 31, 2016, and followed them up to December 31, 2019. We used a multivariable Cox regression model to compare the childhood-onset type 1 diabetes risk between children whose mother had or did not have an autoimmune disease.

RESULTS

The multivariable model demonstrated significantly higher risks of type 1 diabetes in the children with maternal autoimmune disease (aHR 1.55, 95% CI 1.16-2.08), type 1 diabetes (aHR 11.33, 95% CI 4.62-27.77), Hashimoto's thyroiditis (aHR 3.73, 95% CI 1.70-8.15), and inflammatory bowel diseases (aHR 2.00, 95% CI 1.07-3.76).

CONCLUSION

This nationwide mother and child cohort study showed a higher risk of type 1 diabetes in the children whose mothers had autoimmune disease, including Hashimoto's thyroiditis, and inflammatory bowel diseases.

Clinical traits and systemic risks of familial diabetes mellitus according to age of onset and quantity: an analysis of data from the community-based KoGES cohort study

OBJECTIVES

The aim of this study was to clarify the clinical trait of familial diabetes mellitus (DM) by analyzing participants' risk of DM according to the age of DM onset in parents and siblings, and to evaluate individuals' risk of DM-associated cardiometabolic diseases.

METHODS

Altogether, 211,173 participants aged ≥40 years from the Korean Genome and Epidemiology Study were included in this study. The participants were divided into groups based on the number (1 or 2 relatives) and age of onset (no DM and early, common, or late onset) of familial DM. Participants' risk of DM was assessed using a Cox regression model with hazard ratios and 95% confidence intervals (CIs). A logistic regression model with odds ratios was used to evaluate associations among the participants' likelihood of acquiring cardiometabolic diseases such as hypertension, chronic kidney disease (CKD), and cardiovascular disease.

RESULTS

The risk of developing DM was 2.02-fold (95% CI, 1.88 to 2.18) and 2.88-fold (95% CI, 2.50 to 3.33) higher, respectively, in participants with 1 and 2 family members diagnosed with familial DM. It was 2.72-fold (95% CI, 2.03 to 3.66) higher in those with early-onset familial DM. In the early-onset group, the respective risks of hypertension and CKD were 1.87-fold (95% CI, 1.37 to 2.55) and 4.31-fold (95% CI, 2.55 to 7.27) higher than in the control group.

CONCLUSIONS

The risk of DM and related cardiometabolic diseases was positively associated with the number of family members diagnosed with DM and an early diagnosis in family members with DM.

Functional and Taxonomic Traits of the Gut Microbiota in Type 1 Diabetes Children at the Onset: A Metaproteomic Study

Type 1 diabetes (T1D) is a chronic autoimmune metabolic disorder with onset in pediatric/adolescent age, characterized by insufficient insulin production, due to a progressive destruction of pancreatic β-cells. Evidence on the correlation between the human gut microbiota (GM) composition and T1D insurgence has been recently reported. In particular, 16S rRNA-based metagenomics has been intensively employed in the last decade in a number of investigations focused on GM representation in relation to a pre-disease state or to a response to clinical treatments. On the other hand, few works have been published using alternative functional omics, which is more suitable to provide a different interpretation of such a relationship. In this work, we pursued a comprehensive metaproteomic investigation on T1D children compared with a group of siblings (SIBL) and a reference control group (CTRL) composed of aged matched healthy subjects, with the aim of finding features in the T1D patients' GM to be related with the onset of the disease. Modulated metaproteins were found either by comparing T1D with CTRL and SIBL or by stratifying T1D by insulin need (IN), as a proxy of β-cells damage, showing some functional and taxonomic traits of the GM, possibly related to the disease onset at different stages of severity.

Sib-pair subgroup familial type 1 diabetes mellitus in children in the state of Qatar

Background

Type 1 diabetes is the most common type of diabetes mellitus (DM) in children. It can be sporadic in onset or cluster in families, which comprises parent-offspring and sib-pair subgroups. The risk of developing DM in first-degree relatives of affected individuals is 8–15 fold higher. There is limited data about familial DM from the Gulf region. This study aims to describe the clinical, biochemical and genetic characteristics of sib-pair familial type 1 diabetes in Qatar.

Methods

Every child with DM following up at Sidra Medicine was recruited. Data was collected regarding clinical features, family history, type 1 diabetes autoantibodies and whole genome sequencing was performed. Genetic analysis for MODY genes and HLA association analysis was conducted.

Results

44 families with sib-pair familial diabetes were identified. Of these, 2 families had 4 affected siblings and 5 families had 3 affected siblings. The majority are of Qatari ethnicity and the most common autoantibody was GAD65. The most common age of onset in the proband was 5–9 years while it was 10–14 years in subsequent siblings. The occurrence of DKA & HbA1c levels were lower in the second affected sibling. No relevant MODY gene variants were found. HLA analysis found 15 variants in at least 50% of the subjects. Most common were HLA-F*01*01*01G, HLA- DPA1*01*03*01G, HLA- DRB3*02*02*01G, HLA- E*01*01*01G & DRB4*03*01N.

Conclusions

The prevalence of sib-pair diabetes is 3.64%. The second affected siblings were older. MODY is unlikely and Class I and II HLA genes was present in sib-pair diabetes.

Incidence of new onset type 1 diabetes in siblings of index cases with type 1 diabetes within the first 11 years in Turkish children

AIM

Although newly diagnosed type 1 diabetes mellitus (T1DM) occurs sporadically in childhood, there is an increased risk of T1DM for first-degree relatives of patients that endure into the advanced years. Determination of T1DM incidence in siblings of children with T1DM helps predict the development of new cases. This study focuses on the incidence of the disease in siblings of children with T1DM.

METHOD

A total of 1497 siblings of 850 children (403 female; 447 male) diagnosed with T1DM between 2007 and 2018 years were retrospectively screened for T1DM. The patients were divided into four onset age groups: 0-4, 5-9, 10-14 and ≥15. The annual incidence was calculated for the region.

RESULTS

A total of 34 siblings diagnosed with T1DM were detected. The incidence relating to the years investigated was between 7.42 and 11.73/100 000 for the newly diagnosed indexes while it ranged between 0 and 5.8% for siblings. The 5-9 year group was the most commonly diagnosed onset age group in index (n = 312) and siblings (n = 20). For siblings, the male sex and 5-9 aged at diagnosis of index were significant risk factors for development of T1DM (OR:2.35 and 2.85).

CONCLUSION

This study shows that in the first years following the diagnosis of an index, incidence of T1DM among the siblings can rise up to 5.8%, and the age group of 5-9 in the index and the male sex in the sibling are the most important risk factors. These findings show that the risk for siblings of children with T1DM remarkably increases in the first years after diagnosis in index cases.

What do parents believe are the causes of their Type 1 diabetic child's condition?

Purpose

This paper aims to investigate parents' beliefs about the causes of their child's Type 1 diabetes to understand if this affects the way diagnosis is processed and if this impacts on sibling parenting.

Design/methodology/approach

Online, semi-structured qualitative interviews with nine parents of children with Type 1 diabetes who have at least one non-diabetic child. The results were analysed using interpretative phenomenological analysis (IPA).

Findings

Two interlinked themes were identified: “What ifs”: parents postulated underlying genetic reasons for their child's diabetes and had working theories about the triggers of diabetes that included stress, infection, vaccination or a virus. Developing a personal aetiology of their child's condition allowed some a feeling of control, while others focused on practical ways to manage diabetes. “Having something to blame”: narratives dwelt on the relationship between beliefs about causes and self-blame. Some believed that acting on an identified trigger reduced personal guilt.

Research limitations/implications

Although internet access is widespread in the UK, a limitation of this research is that it excluded those without internet access.

Practical implications

The findings of this research may provide greater depth and a more holistic perspective to the health promoter to better support parents of Type 1 diabetics.

Social implications

The analysis of illness narratives that this research provides may offer a greater understanding of the social context in which health and illness develop. This research found some examples of parental confidence about the causes and triggers of their child's diabetes being positively associated with a sense of control. This might indicate the value of a more comprehensive larger-scale study to establish whether parents who are supported to develop a personalised conception of the aetiology of their child's diabetes develop a greater sense of coherence and well-being regarding their child's condition.

Originality/value

There is very limited literature focusing on the beliefs of sufferers and their families about Type 1 diabetes causality. Of that which does exist, some research is heterogenous in its sampling of Types 1 and 2 diabetes sufferers. This study offers a rare, focused insight into the beliefs of parents about the background causes and more proximal triggers of their child's Type 1 diabetes.

Type 1 diabetes in a Nigerian family - occurrence in three out of four siblings: A case report

BACKGROUND

Most occurrences of type 1 diabetes cases in any population are sporadic rather than familial. Hence, type 1 diabetes among siblings is a rare occurrence. Even more rare is for three or more siblings to develop type 1 diabetes. In this report, we describe a case of a Nigerian family in which type 1 diabetes occurred in three siblings among four children with neither parent having diabetes. All three siblings are positive for glutamic acid decarboxylase and anti-islet cell antibodies.

CASE SUMMARY

There were four siblings (three males and one female) born to a couple without a diagnosis of diabetes. The eldest child (male) was diagnosed with diabetes at the age of 15, the second child (female) was diagnosed at the age of 11 and the fourth child (male) was diagnosed at the age of 9. All the siblings presented with similar osmotic symptoms and were diagnosed of diabetic ketoacidosis. All of them had markedly reduced serum C-peptide levels with high levels of glutamic acid decarboxylase and insulinoma-associated protein-2 antibodies. We could not perform genetic analysis of HLA-DR, DQ and CTLA4 in the siblings as well as the parents; hence haplotypes could not be characterized. Both parents of the probands have no prior history of diabetes, and their blood glucose and glycated hemoglobin levels were within normal ranges. The third child (male) has no history suggestive of diabetes, and his blood glucose and glycated hemoglobin have remained within normal ranges.

CONCLUSION

Although the occurrence of type 1 diabetes in proband siblings is uncommon, screening for diabetes among siblings especially with islet autoantibodies should be encouraged.

Disease-Modifying Therapies in Type 1 Diabetes: A Look into the Future of Diabetes Practice

The novel understanding that the presence of multiple islet autoantibodies, indicating islet autoimmunity, inevitably leads to type 1 diabetes mellitus (T1DM) has necessitated the development of a new staging classification system for the condition. Coupled with an improved understanding of the disease course, the realization that T1DM appears to be more heterogeneous than previously thought has led to unique opportunities to develop more targeted therapies that may be applied even before the onset of dysglycemia or symptoms. To date, several therapies have been trialed to delay or halt disease progression in both presymptomatic and clinical T1DM, each demonstrating varying degrees of effectiveness, toxicity, and utility. Key research supports the eventual implementation of immunotherapy in autoimmune diabetes, potentially calling for a paradigm shift among care providers. It will likely be necessary to develop new approaches to trial design and to address potential barriers to progress before an effective treatment for the disease may be achieved.

Prenatal Betamethasone interferes with immune system development and alters target cells in autoimmune diabetes

Non-genetic factors are crucial in the pathogenesis of type 1 diabetes (T1D), a disease caused by autoimmunity against insulin-producing β-cells. Exposure to medications in the prenatal period may influence the immune system maturation, thus altering self-tolerance. Prenatal administration of betamethasone –a synthetic glucocorticoid given to women at risk of preterm delivery– may affect the development of T1D. It has been previously demonstrated that prenatal betamethasone administration protects offspring from T1D development in nonobese diabetic (NOD) mice. The direct effect of betamethasone on the immature and mature immune system of NOD mice and on target β-cells is analysed in this paper. In vitro, betamethasone decreased lymphocyte viability and induced maturation-resistant dendritic cells, which in turn impaired γδ T cell proliferation and decreased IL-17 production. Prenatal betamethasone exposure caused thymus hypotrophy in newborn mice as well as alterations in immune cells subsets. Furthermore, betamethasone decreased β-cell growth, reduced C-peptide secretion and altered the expression of genes related to autoimmunity, metabolism and islet mass in T1D target tissue. These results support the protection against T1D in the betamethasone-treated offspring and demonstrate that this drug alters the developing immune system and β-cells. Understanding how betamethasone generates self-tolerance could have potential clinical relevance in T1D.

Clinical and biochemical characteristics of familial type 1 diabetes mellitus (FT1DM) compared to non-familial type 1 DM (NFT1DM)

INTRODUCTION

Familial type 1 diabetes mellitus (FT1DM) comprises parent-offspring and sib-pair subgroups. The clinical and genetic characteristics of FT1DM cases with and without affected family members have been previously studied with varying results. Some investigators found similarity of presenting features whereas others reported significant differences between the two groups.

OBJECTIVE

To describe the clinical and biochemical characteristics of children with FT1DM in comparison with those with non-familial type 1 diabetes mellitus (NFT1DM).

PATIENTS AND METHODS

We performed a cross-sectional retrospective study in a cohort of children and adolescents with T1DM (n=424) aged between 6 months - 16 years attending to Hamad General Hospital Pediatric Diabetes Center, Doha (Qatar) from 2012-2016. They were divided into 2 groups. Group 1 consisted of 62 children and adolescent with FT1DM (parent-offspring or sib-pair). The other group (Group 2) consisted of 431 children and adolescents with NFT1DM. The clinical presentation and prevalence of β-cell autoimmunity (anti-glutamic acid decarboxylase (GAD) antibodies , anti-islet cell and anti-insulin antibodies), thyroid function (Free thyroxine: FT4 and thyroid-stimulating hormone: TSH), anti-thyroid peroxidase antibody (TPO) and anti-tissue transglutaminase (ATT) at their first presentation were recorded, described and analyzed.

RESULTS

FT1 DM was more prevalent in boys versus girls (1.4:1, respectively) whereas the prevalence of NFT1DM did not differ between genders (1:1.1, respectively). F1DM occurred relatively early in childhood (40.7% before the age of 4 years and 72% before 9 years of age) versus NFT1DM which occurred relatively later in life (80% after the age of 4 years and 40% after the age of 9 years). 35.2% of FT1DM presented with diabetic ketoacidosis (DKA) versus 32.5% of T1DM patients. Anti-islet antibodies (Ab) were detected more frequently in FT1DM versus NFT1DM. The prevalence of positive anti-insulin and anti- GAD antibodies did not differ between the two groups. Anti TPO were detected in 27.2% of NFT1DM and 35.5% of FT1DM. A primary hypothyroidism, with positive ATPO, was more prevalent in FT1DM versus NFT1DM. ATT IgA was high in 5% of NFT1DM and 19.8% of FT1DM whereas ATT IgG was high in 4.4 % of NFT1DM and 15.4% of FT1DM.

CONCLUSIONS

FT1DM is more prevalent in boys versus girls and occurs earlier in childhood compared to NFT1DM. Primary hypothyroidism was more prevalent in NFT1DM versus FT1DM. Anti-islet Ab and ATT antibodies were more prevalent in the FT1DM versus NFT1DM. The genetic background may explain some differences between FT1DM and NFT1DM including the age of onset, gender affection, as well as associated autoimmune disorders.

Diabetes in Childhood and Adolescence

BACKGROUND

The incidence of type 1 diabetes mellitus in childhood and adolescence is steadily rising and now stands at 22.9 new cases per year per 100 000 persons up to age 15.

METHODS

This review is based on pertinent publications retrieved by a selective literature search, with special attention to the current German S3 guideline on diabetes in childhood and adolescence.

RESULTS

Polydipsia, polyuria, and weight loss are the characteristic presenting symptoms of diabetes mellitus. The acutely presenting patient needs immediate stabilization because of the danger of rapid metabolic decompensation (risk of keto - acidosis, 21.1%). Long-term insulin therapy can be delivered either by subcutaneous injection or by an insulin pump. The goals of treatment are the near-normalization of glucose metabolism (HbA1c <7.5%), the avoidance of acute complications (hypoglycemia and ketoacidosis), the reduction of diabetes-specific sequelae (retinopathy, nephropathy, neuropathy, hypertension, and hyperlipidemia), unrestricted participation in age-appropriate everyday activities, and normal physical and psychosocial development. Children and adolescents with diabetes need individualized treatment with frequent adjustments and holistic overall care so that these goals can be effectively met.

CONCLUSION

Every physician must be able to diagnose the initial presentation of diabetes and to initiate the first steps in its management. The patient should be referred as soon as possible to a diabetes team that has experience in the treatment of children and adolescents.

The recurrence risk of genetic complex diseases

Complex inherited diseases affected by an interaction between collective effects of the genotype at one or multiple loci either to increase or to lower susceptibility to disease, combined with a variety of environmental exposures that may trigger, accelerate, exacerbate, or protect against the disease process. The new aspects of genetic techniques have been opened for diagnosis and analysis of inherited disorders. While appropriate Mendelian laws is applied to estimate the recurrence risk of single gene diseases, using empirical recurrence risks are the most important and available method to evaluate pedigree of complex (multifactorial), chromosomal, and unknown etiology disorders. Although, generally, empirical recurrent risks are not accurate, either because of the difference of gene frequencies and environmental factors among populations or heterogeneity of disease; using results of plenty family population studies, computerized estimating programs, genotyping technologies, and Genome-wide association studies (GWASs) of single nucleotide polymorphisms (SNPs), can make it possible nowadays to estimate these risks. The specific family situation and importance recurrence risks of some common complex genetic diseases will be presented in this review and some important multifactorial disorders’ recurrence risks will be summarized to help genetic counselors for supporting families and representing better view of genetic disorders.

Type 1 Diabetes at-risk children highly recognize Mycobacterium avium subspecies paratuberculosis epitopes homologous to human Znt8 and Proinsulin

Mycobacterium avium subspecies paratuberculosis (MAP) has been previously associated to T1D as a putative environmental agent triggering or accelerating the disease in Sardinian and Italian populations. Our aim was to investigate the role of MAP in T1D development by evaluating levels of antibodies directed against MAP epitopes and their human homologs corresponding to ZnT8 and proinsulin (PI) in 54 T1D at-risk children from mainland Italy and 42 healthy controls (HCs). A higher prevalence was detected for MAP/ZnT8 pairs (62,96% T1D vs. 7,14% HCs; p < 0.0001) compared to MAP/PI epitopes (22,22% T1D vs. 9,52% HCs) and decreasing trends were observed upon time-point analyses for most peptides. Similarly, classical ZnT8 Abs and GADA decreased in a time-dependent manner, whereas IAA titers increased by 12%. Responses in 0–9 year-old children were stronger than in 10–18 age group (75% vs. 69,1%; p < 0.04). Younger age, female sex and concomitant autoimmune disorders contributed to a stronger seroreactivity suggesting a possible implication of MAP in multiple autoimmune syndrome. Cross-reactivity of the homologous epitopes was reflected by a high correlation coefficient (r² > 0.8) and a pairwise overlap of positivity (>83% for MAP/ZnT8).

Luminex and other multiplex high throughput technologies for the identification of, and host response to, environmental triggers of type 1 diabetes

Complex interactions between a series of environmental factors and genes result in progression to clinical type 1 diabetes in genetically susceptible individuals. Despite several decades of research in the area, these interactions remain poorly understood. Several studies have yielded associations of certain foods, infections, and immunizations with the onset and progression of diabetes autoimmunity, but most findings are still inconclusive. Environmental triggers are difficult to identify mainly due to (i) large number and complex nature of environmental exposures, including bacteria, viruses, dietary factors, and environmental pollutants, (ii) reliance on low throughput technology, (iii) less efforts in quantifying host response, (iv) long silent period between the exposure and clinical onset of T1D which may lead to loss of the exposure fingerprints, and (v) limited sample sets. Recent development in multiplex technologies has enabled systematic evaluation of different classes of molecules or macroparticles in a high throughput manner. However, the use of multiplex assays in type 1 diabetes research is limited to cytokine assays. In this review, we will discuss the potential use of multiplex high throughput technologies in identification of environmental triggers and host response in type 1 diabetes.

The emerging global epidemic of type 1 diabetes

Type 1 diabetes mellitus (T1D) can occur at any age, with a peak in incidence around puberty. Classification between T1D and type 2 diabetes becomes more challenging with increasing age of onset of T1D over time develops in genetically predisposed individuals. The main susceptibility is conferred with human leukocyte antigen (HLA) genes. Some of the geographic variation in incidence and familial aggregation is explained by differences in HLA haplotypes. In many populations, the incidence is somewhat higher in males than in females, and a 1.3- to 2.0-fold male excess in incidence after about 15 years of age exists in most populations. The incidence of childhood-onset T1D varies markedly among countries. East Asian and native American populations have low incidences (approximately 0.1-8 per 100 000/year), while the highest rates are found in Finland (>60 per 100 000/year), Sardinia (40 per 100 000/year), and Sweden (47 per 100 000/year). The risk is highest in European-derived populations. About 10 %-20 % of newly diagnosed childhood cases of T1D have an affected first-degree relative. Those with an affected sibling or parent have a cumulative risk of 3 %-7 % up to about 20 years of age, as compared with <1 % in the general population. The cumulative incidence among the monozygotic co-twins of persons with T1D is less than 50 %. Thus, the majority of genetically predisposed people do not develop T1D. Studies assessing temporal trends have shown that the incidence of childhood-onset T1D has increased in all parts of the world. The average relative increase is 3 %-4 % per calendar year. For instance, in Finland, the incidence today is 5 times higher than 60 years ago. At the same time, the age at onset of T1D in children has become younger. It is strongly believed that nongenetic factors are important for the development of T1D and its increase, but the causative evidence is missing. The causes for this increasing trend and current epidemic still remain unknown.

The prenatal environment and type 1 diabetes

There is ample evidence that environmental factors are involved in the aetiology of type 1 diabetes, but the nature and timing of the interactions are poorly understood. The intrauterine environment is known to play a role in the later development of type 2 diabetes, and this review considers a possible role in type 1 diabetes. Autoimmune type 1 diabetes is rare in those diagnosed before 6 months of age, but endogenous autoantibodies predictive of future type 1 diabetes may be detectable by 6-12 months of age, suggesting that environmental factors may operate before this age in some cases. Indirect evidence of a protective effect for the intrauterine environment comes from the observation that mothers with type 1 diabetes are less likely than affected fathers to transmit diabetes to their offspring, although the precise role (if any) is unclear. The risk of childhood-onset type 1 diabetes increases with maternal age at delivery, and with high birthweight, but these associations are weak and heterogeneous, and these factors are unlikely to be directly causally related to type 1 diabetes. No firm conclusion can be drawn from studies of maternal enteroviral infection or from various nutritional exposures. The birth process itself may play a role, as suggested by the slightly increased risk in children born by Caesarean section; lack of contact with maternal bacteria is one suggested mechanism. In sum, there is circumstantial evidence, but no proof of principle, that maternal or intrauterine conditions may modulate genetic risk of type 1 diabetes. The disease process culminating in type 1 diabetes typically begins in early life, but it is not clear whether the trail begins before or after birth.

Decline in titers of anti-idiotypic antibodies specific to autoantibodies to GAD65 (GAD65Ab) precedes development of GAD65Ab and type 1 diabetes

The humoral Idiotypic Network consisting of antibodies and their anti-idiotypic antibodies (anti-Id) can be temporarily upset by antigen exposure. In the healthy immune response the original equilibrium is eventually restored through counter-regulatory mechanisms. In certain autoimmune diseases however, autoantibody levels exceed those of their respective anti-Id, indicating a permanent disturbance in the respective humoral Idiotypic Network. We investigated anti-Id directed to a major Type 1 diabetes (T1D)-associated autoantibody (GAD65Ab) in two independent cohorts during progression to disease. Samples taken from participants of the Natural History Study showed significantly lower anti-Id levels in individuals that later progressed to T1D compared to non-progressors (anti-Id antibody index of 0.06 vs. 0.08, respectively, p = 0.02). We also observed a significant inverse correlation between anti-Id levels and age at sampling, but only in progressors (p = 0.014). Finally, anti-Id levels in progressors showed a significant decline during progression as compared to longitudinal anti-Id levels in non-progressors (median rate of change: -0.0004 vs. +0.0004, respectively, p = 0.003), suggesting a loss of anti-Id during progression. Our analysis of the Diabetes Prediction in Skåne cohort showed that early in life (age 2) individuals at risk have anti-Id levels indistinguishable from those in healthy controls, indicating that low anti-Id levels are not an innate characteristic of the immune response in individuals at risk. Notably, anti-Id levels declined significantly in individuals that later developed GAD65Ab suggesting that the decline in anti-Id levels precedes the emergence of GAD65Ab (median rate of change: -0.005) compared to matched controls (median rate of change: +0.001) (p = 0.0016). We conclude that while anti-Id are present early in life, their levels decrease prior to the appearance of GAD65Ab and to the development of T1D.

Targeting the trimolecular complex: the pathway towards type 1 diabetes prevention

George Eisenbarth devoted his life to understanding the basic immunology of the autoimmune polyglandular syndromes and type 1 diabetes, while providing exceptional clinical care to individuals afflicted with these disorders. Over the last 5 years, I was privileged to know George Eisenbarth as a mentor, colleague, and friend. His enthusiasm for science and specifically understanding the basic immunology of type 1 diabetes was infectious. George was the first to initially hypothesize that type 1 diabetes is a chronic autoimmune disorder. He made diabetes a predictable disease by developing biochemical assays to measure islet autoantibodies and provided this technology worldwide to researchers and the medical community. His work identifying and detecting islet autoantibodies allowed for clinical intervention trials aimed at preventing type 1 diabetes. George worked fervently to prevent the disease. During my time as a fellow in George's laboratory and faculty member at the Barbara Davis Center for Diabetes, we focused our efforts for diabetes prevention at the trimolecular complex (human leukocyte antigen molecule, self-peptide, and T cell receptor), which plays a pivotal role in diabetes pathogenesis. It is our belief that targeting this complex with safe and specific therapies will lead to the prevention of type 1 diabetes and an improved understanding as to why diabetes develops.

Temporal trends of HLA, CTLA-4 and PTPN22 genotype frequencies among type 1 diabetes in Continental Italy

The incidence of type 1 diabetes has, progressively, increased worldwide over the last decades and also in Continental Italian population. Previous studies performed in northern European countries, showed, alongside a general increase in the disease incidence, a decreasing frequency of the highest risk HLA genotype in type 1 diabetes populations, thus emphasizing the role of environmental factors. The aim of the study was to evaluate whether a decreasing trend of high risk HLA, CTLA-4 and PTPN22 genotypes would be present in type 1 diabetes subjects of Continental Italy, a country considered at low incidence of the disease compared to northern European populations. N = 765 type 1 diabetes patients diagnosed from 1980 to 2012 in Lazio region were included. For HLA, CTLA4 and PTPN22 temporal trend evaluation, subjects were subdivided into groups of years according to age at diagnosis. All subjects were typed for HLA-DRB1 and DQB1 by a reverse line blot. The CT60 polymorphism of the CTLA4 and C1858T of the PTPN22 gene were genotyped using ABI PRISM 7900HT (n = 419 and n = 364 respectively). HLA genotypes were divided in high, moderate and low risk categories. The proportion of the HLA risk categories was not statistically different over the three decades in subjects with age of onset <15 years and ≥ 15 years. The genotype distribution of CT60 polymorphism of CTLA4 gene did not show any change in the frequencies during time. The analysis of the PTPN22 C1858T variant revealed, instead, that the frequency of CT+TT susceptibility genotypes decreased during time (23.9% vs 13.6%, p = 0.017). We can hypothesize that the pressure of the diabetogenic environment could be milder and therefore not sufficient to reduce the need of a strong genetic background (HLA) "to precipitate" diabetes; the increased pressure of the environment could have, instead, some effects on minor susceptibility genes in our population.

Type 1 diabetes: translating mechanistic observations into effective clinical outcomes

Type 1 diabetes (T1D) remains an important health problem, particularly in western countries, where the incidence has been increasing in younger children. In 1986, Eisenbarth described T1D as a chronic autoimmune disease. Work over the past three-and-a-half decades has identified many of the genetic, immunological and environmental factors that are involved in the disease and have led to hypotheses concerning its pathogenesis. Clinical trials have been conducted to test these hypotheses but have had mixed results. Here, we discuss the findings that have led to our current concepts of the disease mechanisms involved in T1D and the clinical studies promoted by these studies. The findings from preclinical and clinical studies support the original proposed model for how T1D develops but have also suggested that this disease is more complex than was originally thought and will require broader treatment approaches.

How do autoimmune diseases cluster in families? A systematic review and meta-analysis

BACKGROUND

A primary characteristic of complex genetic diseases is that affected individuals tend to cluster in families (that is, familial aggregation). Aggregation of the same autoimmune condition, also referred to as familial autoimmune disease, has been extensively evaluated. However, aggregation of diverse autoimmune diseases, also known as familial autoimmunity, has been overlooked. Therefore, a systematic review and meta-analysis were performed aimed at gathering evidence about this topic.

METHODS

Familial autoimmunity was investigated in five major autoimmune diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid disease, multiple sclerosis and type 1 diabetes mellitus. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed. Articles were searched in Pubmed and Embase databases.

RESULTS

Out of a total of 61 articles, 44 were selected for final analysis. Familial autoimmunity was found in all the autoimmune diseases investigated. Aggregation of autoimmune thyroid disease, followed by systemic lupus erythematosus and rheumatoid arthritis, was the most encountered.

CONCLUSIONS

Familial autoimmunity is a frequently seen condition. Further study of familial autoimmunity will help to decipher the common mechanisms of autoimmunity.

Targeting the trimolecular complex

Class II major histocompatibility molecules (MHC) confer disease risk for multiple autoimmune disorders including type 1 diabetes. The interaction between the components of the trimolecular complex (CD4(+) T cell receptors, self-peptide, and MHC class II molecules) plays a pivotal role in autoimmune disease pathogenesis. The development of therapies targeting various components of the trimolecular complex for the prevention of type 1 diabetes is actively being pursued. This review focuses on the components of the anti-insulin trimolecular complex, registers of insulin peptide binding to 'diabetogenic' MHC class II molecules, and therapies targeting each component of the trimolecular complex.

The risk of proliferative retinopathy in siblings with Type 1 diabetes

AIMS

The siblings first affected by Type 1 diabetes (probands) within a sibship have been shown to have a lower age at onset of Type 1 diabetes compared with their later-affected siblings. The aim of the present study was to investigate whether this difference affects the long-term risk of proliferative diabetic retinopathy.

METHODS

A cohort of 396 siblings with Type 1 diabetes in 188 sibships was drawn from a larger Finnish Diabetic Nephropathy Study population (4800 patients). Ophthalmic records were obtained for 369/396 (93%) patients. Retinopathy was graded based on fundus photographs and/or repeated ophthalmoscopies.

RESULTS

The median age at onset of Type 1 diabetes was 8.4 (interquartile range 4.2-13.3) years in probands and 16.9 (interquartile range 10.2-27.8) years in later-affected siblings (P < 0.001). Proliferative retinopathy was diagnosed in 115/369 (31%) patients. The cumulative incidence estimates for proliferative retinopathy, accounting for the competing risk of death, were 21% (95% CI 15-27) in probands and 26% (95% CI 19-35) in later-affected siblings at 20 years of diabetes duration, and the respective 30 years' incidences were 37% (95% CI 29-45) and 53% (95% CI 40-64), (P = 0.05, Gray's test). The risk of proliferative retinopathy, adjusted for conventional risk factors, age at onset and sibship size, was higher in later-affected siblings [hazard ratio 1.75 (95% CI 1.13-2.75), P = 0.01] compared with their probands.

CONCLUSION

The siblings first affected by Type 1 diabetes had a better long-term prognosis with regards to development of proliferative retinopathy compared with their later-affected siblings.

Diabetes and asthma case identification, validation, and representativeness when using electronic health data to construct registries for comparative effectiveness and epidemiologic research

BACKGROUND

Advances in health information technology and widespread use of electronic health data offer new opportunities for development of large scale multisite disease-specific patient registries. Such registries use existing data, can be constructed at relatively low cost, include large numbers of patients, and once created can be used to address many issues with a short time between posing a question and obtaining an answer. Potential applications include comparative effectiveness research, public health surveillance, mapping and improving quality of clinical care, and others.

OBJECTIVE AND DISCUSSION

This paper describes selected conceptual and practical challenges related to development of multisite diabetes and asthma registries, including development of case definitions, validation of case identification methods, variation in electronic health data sources; representativeness of registry populations, including the impact of attrition. Specific challenges are illustrated with data from actual registries.

Challenges in diagnosing type 1 diabetes in different populations

Diabetes affects today an estimated 366 million people world-wide, including 20 million to 40 million of patients with type 1 diabetes (T1D). While T1D accounts for 5% to 20% of those with diabetes, it is associated with higher morbidity, mortality and health care cost than the more prevalent type 2 diabetes. Patients with T1D require exogenous insulin for survival and should be identified as soon as possible after diagnosis to avoid high morbidity due to a delay in insulin treatment. It is also important to present to the patient correct prognosis that differs by the type of diabetes. From the research point of view, correct classification should help to identify the etiologies and to develop specific prevention for T1D. This review summarizes evidence that may be helpful in diagnosing T1D in various ethnic groups. Challenges in interpretation of results commonly used to determine the type of diabetes are highlighted.

Interbirth interval is associated with childhood type 1 diabetes risk

Short interbirth interval has been associated with maternal complications and childhood autism and leukemia, possibly due to deficiencies in maternal micronutrients at conception or increased exposure to sibling infections. A possible association between interbirth interval and subsequent risk of childhood type 1 diabetes has not been investigated. A secondary analysis of 14 published observational studies of perinatal risk factors for type 1 diabetes was conducted. Risk estimates of diabetes by category of interbirth interval were calculated for each study. Random effects models were used to calculate pooled odds ratios (ORs) and investigate heterogeneity between studies. Overall, 2,787 children with type 1 diabetes were included. There was a reduction in the risk of childhood type 1 diabetes in children born to mothers after interbirth intervals <3 years compared with longer interbirth intervals (OR 0.82 [95% CI 0.72-0.93]). Adjustments for various potential confounders little altered this estimate. In conclusion, there was evidence of a 20% reduction in the risk of childhood diabetes in children born to mothers after interbirth intervals <3 years.

Advancing maternal age is associated with lower bone mineral density in young adult male offspring

SUMMARY

Advancing maternal age has been related to increased risk of fetal death and morbidity, as well as higher fracture risk during childhood, in the offspring. In the present study, we demonstrate that advancing maternal age is independently associated with reduced bone mass in the young adult male offspring.

INTRODUCTION

In Sweden the maternal age in both primi- and multipara mothers has steadily increased during the last three decades. It has been previously reported that advancing maternal age increases the risk of fetal death, but also of morbidity in the offspring, such as chromosome abnormalities, leukemia, diabetes mellitus type 1, and schizophrenia. Whether or not maternal age influences peak bone mass has not been reported. The aim of the present study was to investigate whether a high maternal age was associated with lower peak bone mass, as measured using DXA in a large cohort of male offspring [the Gothenburg Osteoporosis and Obesity Determinants study (GOOD)].

METHODS

Through the Swedish multi-generation register, we identified the mothers of 1,009 GOOD study subjects. From the Swedish medical birth register detailed information about the medical circumstances at the time of child birth were obtained, including maternal and offspring anthropometrics (birth height and weight), maternal age, and smoking habits, parity and length of pregnancy.

RESULTS

Maternal age was inversely correlated to areal BMD (aBMD) at the total body (r =-0.07, p = 0.03) and the lumbar spine (r =-0.09, p < 0.01). Using a linear regression model (with covariates including current physical activity, smoking, calcium intake, weight, present height and birth height, total body lean and fat mass in the offspring, and length of pregnancy), we found that maternal age negatively independently predicted lumbar spine aBMD (β =-0.08, p < 0.01) in the male offspring.

CONCLUSIONS

In conclusion, our results suggest that advancing maternal age could negatively affect bone mass in young adult men.

Family history of diabetes and distribution of class II HLA genotypes in children with newly diagnosed type 1 diabetes: effect on diabetic ketoacidosis

OBJECTIVE

Our purpose was to assess whether family history of diabetes or the HLA-DR-DQ genotype of the index case was associated with the frequency of diabetic ketoacidosis (DKA) at diagnosis of childhood type 1 diabetes.

PATIENTS AND METHODS

The study cohort comprised 1518 children aged <15 years and diagnosed with type 1 diabetes in Finland in 2002-2005. Family history of type 1 and type 2 diabetes among first-degree relatives (FDRs) and grandparents was assessed at diagnosis. HLA-DR-DQ genotypes were analysed using time-resolved fluorometry.

RESULTS

In total, 12.6 and 1.7% of children had at least one FDR affected with type 1 or type 2 diabetes, respectively, and 6.6 and 34.8% had at least one grandparent with type 1 or type 2 diabetes. DKA (pH <7.30) occurred less frequently in children having a type 1 diabetes affected FDR (7.4 vs 20.5%, P<0.001). Type 2 diabetes among the parents or grandparents had no such effect. Lower risk HLA genotypes were observed to predispose to DKA (P<0.024). In a logistic regression analysis, the risk of DKA was independently associated with the absence of a family member affected by type 1 diabetes, the presence of a low-risk HLA genotype and older age at diagnosis (odds ratio 3.23, 1.45 and 1.07 respectively).

CONCLUSION

The presence of type 1 diabetes in an FDR is associated with an decreased risk of DKA at diagnosis. The rate of DKA seems to be higher in children with lower HLA-conferred risk for type 1 diabetes.

Discovery of low-affinity preproinsulin epitopes and detection of autoreactive CD8 T-cells using combinatorial MHC multimers

Autoreactive cytotoxic CD8 T-cells (CTLs) play a key pathogenic role in the destruction of insulin-producing beta-cells resulting in type 1 diabetes. However, knowledge regarding their targets is limited, restricting the ability to monitor the course of the disease and immune interventions. In a multi-step discovery process to identify novel CTL epitopes in human preproinsulin (PPI), PPI was digested with purified human proteasomes, and resulting COOH-fragments aligned with algorithm-predicted HLA-binding peptides to yield nine potential HLA-A1, -A2, -A3 or -B7-restricted candidates. An UV-exchange method allowed the generation of a repertoire of multimers including low-affinity HLA-binding peptides. These were labeled with quantum dot-fluorochromes and encoded in a combinatorial fashion, allowing parallel and sensitive detection of specific, low-avidity T-cells. Significantly increased frequencies of T-cells against four novel PPI epitopes (PPI(4-13)/B7, PPI(29-38)/A2, PPI(76-84)/A3 and PPI(79-88)/A3) were detected in stored blood of patients with recent onset diabetes but not in controls. Changes in frequencies of circulating CD8 T-cells against these novel epitopes were detected in blood of islet graft recipients at different time points after transplantation, which correlated with clinical outcome. In conclusion, our novel strategy involving a sensitive multiplex detection technology and requiring minimal volumes of stored blood represents a major improvement in the direct ex-vivo characterization and enumeration of immune cells in the pathogenesis of type 1 diabetes.

The three ZNT8 autoantibody variants together improve the diagnostic sensitivity of childhood and adolescent type 1 diabetes

AIMS

We tested whether autoantibodies to all three ZnT8RWQ variants, GAD65, insulinoma-associated protein 2 (IA-2), insulin and autoantibodies to islet cell cytoplasm (ICA) in combination with human leukocyte antigen (HLA) would improve the diagnostic sensitivity of childhood type 1 diabetes by detecting the children who otherwise would have been autoantibody-negative.

METHODS

A total of 686 patients diagnosed in 1996-2005 in Skåne were analyzed for all the seven autoantibodies [arginin 325 zinc transporter 8 autoantibody (ZnT8RA), tryptophan 325 zinc transporter 8 autoantibody (ZnT8WA), glutamine 325 Zinc transporter 8 autoantibody (ZnT8QA), autoantibodies to glutamic acid decarboxylase (GADA), Autoantibodies to islet-antigen-2 (IA-2A), insulin autoantibodies (IAA) and ICA] in addition to HLA-DQ genotypes.

RESULTS

Zinc transporter 8 autoantibody to either one or all three amino acid variants at position 325 (ZnT8RWQA) was found in 65% (449/686) of the patients. The frequency was independent of age at diagnosis. The ZnT8RWQA reduced the frequency of autoantibody-negative patients from 7.5 to 5.4%-a reduction by 28%. Only 2 of 108 (2%) patients who are below 5 years of age had no autoantibody at diagnosis. Diagnosis without any islet autoantibody increased with increasing age at onset. DQA1-B1(*)X-0604 was associated with both ZnT8RA (p = 0.002) and ZnT8WA (p = 0.01) but not with ZnT8QA (p = 0.07). Kappa agreement analysis showed moderate (>0.40) to fair (>0.20) agreement between pairs of autoantibodies for all combinations of GADA, IA-2A, ZnT8RWQA and ICA but only slight ( < 0.19) agreement for any combination with IAA.

CONCLUSIONS

This study revealed that (1) the ZnT8RWQA was common, independent of age; (2) multiple autoantibodies were common among the young; (3) DQA1-B1(*)X-0604 increased the risk for ZnT8RA and ZnT8WA; (4) agreement between autoantibody pairs was common for all combinations except IAA. These results suggest that ZnT8RWQA is a necessary complement to the classification and prediction of childhood type 1 diabetes as well as to randomize the subjects in the prevention and intervention of clinical trials.

Extended family history of diabetes and autoimmune diseases in children with and without type 1 diabetes

OBJECTIVE

To determine the extended family history of diabetes or autoimmune diseases in families with and without children having type 1 diabetes.

RESEARCH DESIGN AND METHODS

Three hundred case families and 381 control families were interviewed using structured questionnaires.

RESULTS

The proportion of case children having at least one relative with type 1 diabetes outside the nuclear family was higher than that of control children (50.3 vs. 31.8%, P < 0.001). The proportions of case and control children having relatives with type 2 diabetes or gestational diabetes were similar. Other autoimmune diseases occurred more frequently among the case children (9.7 vs. 1.1%, P < 0.001), in the case nuclear families (22.0 vs. 12.9%, P = 0.002) and in relatives outside the case nuclear family (72.0 vs. 62.2%, P = 0.007).

CONCLUSIONS

Type 1 diabetes and autoimmune diseases not only cluster in the nuclear families of children with type 1 diabetes but are also overrepresented in their extended families.

Advanced paternal age, mortality, and suicide in the general population

Advanced paternal age is a risk factor for adverse health outcomes in the offspring. In a population-based birth cohort from Finland, 10,965 singleton offspring born in 1966 and alive at age 1 were followed to age 39. Hazard ratios were calculated, adjusting for maternal age, gender, paternal social class, and maternal parity. In females but not in males, increasing paternal age was associated with a linear increased risk of suicide (hazard ratio [HR] = 1.13, 95% confidence interval [CI] = 1.04-1.24, p < 0.01) and all-causes mortality (HR = 1.06, 95% CI = 1.01-1.10, p = 0.02). Increasing maternal age was associated with a significantly decreased risk of suicide (HR = 0.93, 95% CI = 0.86-1.00, p = 0.04) and all-causes mortality (HR = 0.96, 95% CI = 0.93-1, p = 0.02) in the entire cohort. For paternal age >/=30, the population attributable risk percentage was 13.7% for all deaths and 7.5% for suicides. Parental age at birth may affect suicide and all-causes mortality risk in the offspring in the general population. The causal pathways and specific disorders associated with this increased mortality are largely unknown.

Age at onset of type 1 diabetes in parents and recurrence risk in offspring

OBJECTIVE

Our aim was to study the recurrence risk of type 1 diabetes in the offspring of parents with adult-onset (15-39 years) type 1 diabetes and to evaluate the transmission of diabetes within a continuum of parental age at onset of diabetes from childhood to adulthood.

RESEARCH DESIGN AND METHODS

Diabetes status of all offspring (n = 9,636) in two Finnish cohorts of parents with type 1 diabetes was defined until the end of year 2007. Cumulative incidences of type 1 diabetes among the offspring were estimated, and several factors contributing to the risk were assessed.

RESULTS

During 137,455 person-years, a total of 413 offspring were diagnosed with type 1 diabetes. The cumulative incidence by 20 years was 4.0% (95% CI 3.1-4.8) for the offspring of parents with adult-onset diabetes. The risk was equal according to the sex of the parents. The cumulative incidence decreased in parallel with the increase in age at onset of diabetes in the fathers. In the offspring of diabetic mothers, the risk was equal regardless of the age at onset of diabetes. However, the reduced risk in the maternal offspring was most pronounced in the daughters of the mothers with a diagnosis age <10 years.

CONCLUSIONS

Type 1 diabetes transmission ratio distortion is strongly related to the sex and age at onset of diabetes in the diabetic parents.

Familial association between type 1 diabetes and other autoimmune and related diseases

AIMS/HYPOTHESIS

In the era of genome-wide association studies, familial risks are used to estimate disease heritability and success in gene identification. We wanted to estimate associations between type 1 diabetes mellitus and 33 autoimmune and related diseases in parents, offspring, singleton siblings and twins.

METHODS

The availability of a Multigeneration Register in Sweden provides reliable access to families throughout the last century. The diseases in individual family members were obtained through linkage to the Hospital Discharge Register. Standardised incidence ratios (SIRs) were calculated as relative risks of contracting type 1 diabetes in family members of affected patients compared with those lacking affected family members.

RESULTS

Among a total of 450,899 patients, 21,168 were diagnosed with type 1 diabetes. Familial cases amounted to 10.3% of all type 1 diabetes patients. SIR for type 1 diabetes was 8.23 in offspring of affected parents, 11.92 in singleton siblings, 39.22 in multiplex families and 21.88 in twins; the calculated risk for monozygotic twins was 32.33. Type 1 diabetes in offspring was associated with 13 diseases in parents, including Addison's disease (SIR 2.41), asthma (1.38), coeliac disease (2.73), Graves' disease/hyperthyroidism (1.86), Hashimoto disease/hypothyroidism (2.35), pernicious anaemia (3.09), primary biliary cirrhosis (3.63), rheumatoid arthritis (2.12), sarcoidosis (1.62), systemic lupus erythematosus (2.04), ulcerative colitis (1.23) and Wegener's granulomatosis (2.12).

CONCLUSIONS/INTERPRETATION

The concordant familial risks for type 1 diabetes were high and the calculated risk for multiplex families and monozygotic twins may be explained by epistatic gene x gene or gene x environment interactions. Familial associations with several autoimmune and related diseases suggest genetic sharing and challenge to gene identification.

Type 1 diabetes in the BB rat: a polygenic disease

OBJECTIVE

Two type 1 diabetes susceptibility genes have been identified in the spontaneously diabetic biobreeding diabetes-prone (BBDP) rat, the major histocompatibility complex (MHC) (RT1) class II u haplotype (Iddm1) and Gimap5 (Iddm2). The strong effects of these have impeded previous efforts to map additional loci. We tested the hypothesis that type 1 diabetes is a polygenic disease in the BBDP rat.

RESEARCH DESIGN AND METHODS

We performed the most comprehensive genome-wide linkage analysis for type 1 diabetes, age of disease onset (AOO), and insulitis subphenotypes in 574 F2 animals from a cross-intercross between BBDP and type 1 diabetes-resistant, double congenic ACI.BBDP-RT1u,Gimap5 (ACI.BB(1u.lyp)) rats, where both Iddm1 and Iddm2 were fixed as BBDP.

RESULTS

A total of 19% of these F2 animals developed type 1 diabetes, and eight type 1 diabetes susceptibility loci were mapped, six showing significant linkage (chromosomes 1, 3, 6 [two loci], 12, and 14) and two (chromosomes 2 and 17) suggestive linkage. The chromosomes 6, 12, and 14 intervals were also linked to the severity of islet infiltration by immunocytes, while those on chromosomes 1, 6 (two loci), 14, 17, and a type 1 diabetes-unlinked chromosome 8 interval showed significant linkage to the degree of islet atrophy. Four loci exhibited suggestive linkage to AOO on chromosomes 2 (two loci), 7, and 18 but were unlinked to type 1 diabetes. INS, PTPN22, IL2/IL21, C1QTNF6, and C12orf30, associated with human type 1 diabetes, are contained within the chromosomes 1, 2, 7, and 12 loci.

CONCLUSIONS

This study demonstrates that the BBDP diabetic syndrome is a complex, polygenic disease that may share additional susceptibility genes besides MHC class II with human type 1 diabetes.

Type 1 diabetes mellitus: primary, secondary, and tertiary prevention

We have entered the era of clinical trials to prevent type 1 diabetes mellitus (T1DM). Before 1922, when insulin was first given to a patient with diabetes, a diagnosis of T1DM was considered a death sentence. Advances in treatment for subjects with diabetes are not yet sufficient to prevent the deleterious impact of diabetes on both day-to-day activities and the early morbidity and mortality still associated with the disease. We now understand a great deal about blood glucose regulation and potential health complications associated with long-term T1DM, but the mystery of why, or the pathogenesis of this devastating disease, remains elusive. Great strides toward unraveling this mystery have been made over the past several decades. Even without definitive answers, we are moving from the period of discovery and animal research to the era of clinical trials. In this review, we wish to convey the palpable excitement in the field. It is time to determine if we can safely change the course of T1DM.

A study of diabetes mellitus within a large sample of Australian twins

Twin studies of diabetes mellitus can help elucidate genetic and environmental factors in etiology and can provide valuable biological samples for testing functional hypotheses, for example using expression and methylation studies of discordant pairs. We searched the volunteer Australian Twin Registry (19,387 pairs) for twins with diabetes using disease checklists from nine different surveys conducted from 1980-2000. After follow-up questionnaires to the twins and their doctors to confirm diagnoses, we eventually identified 46 pairs where one or both had type 1 diabetes (T1D), 113 pairs with type 2 diabetes (T2D), 41 female pairs with gestational diabetes (GD), 5 pairs with impaired glucose tolerance (IGT) and one pair with MODY. Heritabilities of T1D, T2D and GD were all high, but our samples did not have the power to detect effects of shared environment unless they were very large. Weight differences between affected and unaffected cotwins from monozygotic (MZ) discordant pairs were large for T2D and GD, but much larger again for discordant dizygotic (DZ) pairs. The bivariate genetic analysis (under the multifactorial threshold model) estimated the genetic correlation between body mass index (BMI) and T2D to be 0.46, and the environmental correlation at only 0.06.

Time trends in the incidence of type 1 diabetes in Finnish children: a cohort study

BACKGROUND

Finland has the highest incidence of type 1 diabetes worldwide, reaching 40 per 100,000 people per year in the 1990s. Our aim was to assess the temporal trend in type 1 diabetes incidence since 2000 in Finnish children aged younger than 15 years and to predict the number of cases of type 1 diabetes in the future.

METHODS

Children with newly diagnosed type 1 diabetes in Finland who were listed on the National Public Health Institute diabetes register, Central Drug Register, and Hospital Discharge Register in 1980-2005 were included in a cohort study. We excluded patients with type 2 diabetes and diabetes occurring secondary to other conditions, such as steroid use, Down's syndrome, and congenital malformations of pancreas.

FINDINGS

10,737 children-5816 boys and 4921 girls-were diagnosed with type 1 diabetes before 15 years of age during 1980-2005. The average age-standardised incidence was 42.9 per 100,000 per year (95% CI 42.6-44.3) during this period, increasing from 31.4 per 100,000 per year in 1980 to 64.2 per 100,000 per year in 2005. The age-specific rates per 100,000 per year were 31.0, 50.5, and 50.6 at ages 0-4 years, 5-9 years, and 10-14-years, respectively. We noted a significant non-linear component to the time trend (p<0.0003). In children aged 0-4 years, the increase was largest, at 4.7% more affected every year. The overall boy-to-girl ratio of incidence was 1.1; at the age of 13 years, it was 1.7 (1.4-2.0). The predicted cumulative number of new cases with type 1 diabetes before 15 years of age between 2006 and 2020 was about 10 800.

INTERPRETATION

The incidence of type 1 diabetes in Finnish children is increasing even faster than before. The number of new cases diagnosed at or before 14 years of age will double in the next 15 years and the age of onset will be younger (0-4 years).

Incidence and trends of childhood Type 1 diabetes in Croatia from 1995 to 2003

AIMS/HYPOTHESIS

The aim of this study was to examine incidence and trends of Type 1 diabetes in children aged 0-14 years in Croatia from 1995 to 2003.

METHODS

The incidence data were obtained from two sources. The incidence was calculated as the number of newly diagnosed Type 1 diabetes patients per 100,000 person-years for the age group 0-14 years, and subgroups 0-4, 5-9, and 10-14 years. Standardized incidence was calculated using the method of direct standardization to the world standard population for the age group 0-14 years. The ascertainment was estimated with capture-recapture method. Trends in the incidence of Type 1 diabetes for period from 1995 to 2003 in Croatia were analyzed using Poisson regression model.

RESULTS

The standardized incidence of Type 1 diabetes for the whole age group was 8.87 per 100,000 person-years (95% CI: 5.07-12.68), for girls 8.47 (95% CI: 7.54-9.41) and for boys 9.26 (95% CI: 8.30-10.21). During the studied period, the trend in incidence raised significantly for the whole age group (chi(2)=32.6, p<0.001). The average annual increase in incidence was 9% (95% CI: 5.8-12.2).

CONCLUSIONS/INTERPRETATION

This rate of incidence places Croatia in a group of countries with moderate risk for development of Type 1 diabetes. The average annual increase in incidence of 9% is markedly higher than in most European countries, and probably reflects lifestyle changes upon economic recovery of the country.

Further evidence of a primary, causal association of the PTPN22 620W variant with type 1 diabetes

OBJECTIVE

The minor allele of the nonsynonymous single nucleotide polymorphism (SNP) +1858C>T within the PTPN22 gene is positively associated with type 1 diabetes and other autoimmune diseases. Genetic and functional data underline its causal effect, but some studies suggest that this polymorphism does not entirely explain disease association of the PTPN22 region. The aim of this study was to evaluate type 1 diabetes association within this gene in the Sardinian population.

RESEARCH DESIGN AND METHODS

We resequenced the exons and potentially relevant portions of PTPN22 and detected 24 polymorphisms (23 SNPs and 1 deletion insertion polymorphism [DIP]), 8 of which were novel. A representative set of 14 SNPs and the DIP were sequentially genotyped and assessed for disease association in 794 families, 490 sporadic patients, and 721 matched control subjects.

RESULTS

The +1858C>T variant, albeit rare in the general Sardinian population (allele frequency 0.014), was positively associated with type 1 diabetes (P(one tail) = 3.7 x 10(-3)). In contrast, the background haplotype in which this mutation occurred was common (haplotype frequency 0.117) and neutrally associated with disease. We did not confirm disease associations reported in other populations for non +1858C>T variants (rs2488457, rs1310182, and rs3811021), although they were present in appreciable frequencies in Sardinia. Additional weak disease associations with rare variants were detected in the Sardinian families but not confirmed in independent case-control sample sets and are most likely spurious.

CONCLUSIONS

We provide further evidence that the +1858C>T polymorphism is primarily associated with type 1 diabetes and exclude major contributions from other purportedly relevant variants within this gene.

A genome-wide scan for type 1 diabetes susceptibility genes in nuclear families with multiple affected siblings in Finland

Background

A genome-wide search for genes that predispose to type 1 diabetes using linkage analysis was performed using 900 microsatellite markers in 70 nuclear families with affected siblings from Finland, a population expected to be more genetically homogeneous than others, and having the highest incidence of type 1 diabetes in the world and, yet, the highest proportion in Europe of cases (10%) carrying neither of the highest risk HLA haplotypes that include DR3 or DR4 alleles.

Results

In addition to the evidence of linkage to the HLA region on 6p21 (nominal p = 4.0 × 10^-6), significant evidence of linkage in other chromosome regions was not detected with a single-locus analysis. The two-locus analysis conditional on the HLA gave a maximum lod score (MLS) of 3.1 (nominal p = 2 × 10^-4) on chromosome 9p13 under an additive model; MLS of 2.1 (nominal p = 6.1 × 10^-3) on chromosome 17p12 and MLS of 2.5 (nominal p = 2.9 × 10^-3) on chromosome 18p11 under a general model.

Conclusion

Our genome scan data confirmed the primary contribution of the HLA genes also in the high-risk Finnish population, and suggest that non-HLA genes also contribute to the familial clustering of type 1 diabetes in Finland.