Human leukocyte antigen identity and DQ risk alleles in autoantibody-positive siblings of children with IDDM are associated with reduced early insulin response. Childhood Diabetes in Finland (DiMe) Study Group

Cause or effect? A review of clinical data demonstrating beta cell dysfunction prior to the clinical onset of type 1 diabetes

Background

Limited successes of conventional approaches to type 1 diabetes (T1D) prevention and treatment have highlighted the need for improved understanding of risk factors contributing to or hastening progression to clinical diagnosis.

Scope of review

This review summarizes beta cell function metabolic phenotyping data from clinical studies conducted in at-risk individuals before T1D onset and healthy controls. Data are drawn from studies comparing at-risk individuals who progress to T1D to at-risk individuals who do not progress to T1D, as well as from studies comparing at-risk individuals to controls without a T1D family history.

Major conclusions

Rapid loss of beta cell insulin secretion occurs in the months immediately preceding clinical onset. However, evidence of beta cell dysfunction is present even years earlier. Comparisons to controls without a family history suggest that many individuals in families impacted by T1D have evidence of beta cell dysfunction, even individuals who are unlikely to develop clinical disease. These findings may mean that underlying metabolic beta cell dysfunction contributes to T1D development and may explain some of the heterogeneity observed in the disease.

Class II HLA Genotype Association With First-Phase Insulin Response Is Explained by Islet Autoantibodies

CONTEXT

A declining first-phase insulin response (FPIR) is characteristic of the disease process leading to clinical type 1 diabetes. It is not known whether reduced FPIR depends on class II human leukocyte antigen (HLA) genotype, islet autoimmunity, or both.

OBJECTIVE

To dissect the role of class II HLA DR-DQ genotypes and biochemical islet autoantibodies in the compromised FPIR.

DESIGN, SETTING, PARTICIPANTS

A total of 438 children with defined HLA DR-DQ genotype in the prospective Finnish Type 1 Diabetes Prediction and Prevention Study were analyzed for FPIR in a total of 1149 intravenous glucose tolerance tests and were categorized by their HLA DR-DQ genotype and the number of biochemical islet autoantibodies at the time of the first FPIR. Age-adjusted hierarchical linear mixed models were used to analyze repeated measurements of FPIR.

MAIN OUTCOME MEASURE

The associations between class II HLA DR-DQ genotype, islet autoantibody status, and FPIR.

RESULTS

A strong association between the degree of risk conferred by HLA DR-DQ genotype and positivity for islet autoantibodies existed (P < 0.0001). FPIR was inversely associated with the number of biochemical autoantibodies (P < 0.0001) irrespective of HLA DR-DQ risk group. FPIR decreased over time in children with multiple autoantibodies and increased in children with no biochemical autoantibodies (P < 0.0001 and P = 0.0013, respectively).

CONCLUSIONS

The class II HLA DR-DQ genotype association with FPIR was secondary to the association between HLA and islet autoimmunity. Declining FPIR was associated with positivity for multiple islet autoantibodies irrespective of class II HLA DR-DQ genotype.

Insulin resistance and fasting plasma glucose in first degree relatives of patients with type 1 diabetes

BACKGROUND

We analyzed the relationship between fasting plasma glucose (FPG), the presence of autoantibodies, first phase of insulin secretion and insulin resistance in the first degree relatives of patients with type 1 diabetes.

MATERIALS AND METHODS

The group studied consisted of 90 healthy relatives, divided into two groups: "high-normal" FPG group (≥88mg/dl) and "low-normal" FPG group (<88/mg/dl). All subjects underwent an intravenous glucose tolerance test, and the 1st phase insulin response (FPIR) and FPIR-to-HOMA-IR-ratio were calculated. Additionally, islet autoantibodies (GADA, IAA and IA-2A) were determined by radioimmunoassays.

RESULTS

The subjects with "high-normal" FPG were older (p=0.0009), had higher BMI (p<0.0001) and lower HOMA%B (p=0.0004), FPIR (p=0.006) and FPIR-to-HOMA-IR-ratio (p=0.004) in comparison with the "low-normal" FPG group. Autoantibodies were present in 40.9% and in 21.7% of the subjects with "high-normal" and "low-normal" FPG, respectively. In the "high-normal" FPG group, FPG correlated positively with GADA (r=0.31, p=0.04), and HOMA-IR (r=0.19, p=0.02), and negatively with HOMA%B (r=-0.36, p=0.001), whereas FPIR correlated positively with HOMA%B (r=0.55, p=0.0001) and BMI (r=0.30, p=0.04). After an adjustment for BMI, the difference in FPIR between the "high-normal" and "low-normal" FPG groups remained significant (p=0.025), whereas the difference in FPIR-to-HOMA-IR-ratio became insignificant.

CONCLUSIONS

Our results suggest that taking into account the impact of age and BMI on insulin sensitivity, it would be expected that the relatives of patients with type 1 diabetes with "high-normal" glucose levels would become gradually unable to compensate for increasing insulin resistance.

Insulin secretion and sensitivity in the prediction of type 1 diabetes in children with advanced β-cell autoimmunity

OBJECTIVE

Reduced early insulin response has been shown to predict type 1 diabetes (T1D) in first-degree relatives of diabetic patients, while its role, as well as that of insulin resistance, has remained poorly defined in young children representing the general population. The predictive values of these markers and their relation to other risk factors of T1D were assessed in children with advanced β-cell autoimmunity, i.e. persistent positivity for two or more autoantibodies.

DESIGN AND METHODS

Intravenous glucose tolerance tests (IVGTTs) were carried out in 218 children with HLA-DQB1-conferred disease susceptibility and advanced β-cell autoimmunity. Baseline, metabolic and growth data were compared between children progressing to diabetes and those remaining unaffected. Hazard ratios for the disease predictors and the progression rate of T1D were assessed.

RESULTS

Children developing T1D were younger at seroconversion, progressed more rapidly to advanced β-cell autoimmunity and had lower first-phase insulin response (FPIR) and homeostasis model assessment index for insulin resistance (HOMA-IR) than those remaining non-diabetic. The levels of HOMA-IR/FPIR, islet cell antibodies, insulin autoantibodies (IAA) and islet antigen 2 antibodies (IA-2A) were higher in progressors. BMI SDS, FPIR, age at IVGTT and levels of IAA and IA-2A were predictive markers for T1D.

CONCLUSIONS

Young age, higher BMI SDS, reduced FPIR and higher levels of IAA and IA-2A predicted T1D in young children with HLA-DQB1-conferred disease susceptibility and advanced β-cell autoimmunity. Disease risk estimates were successfully stratified by the assessment of metabolic status and BMI. The role of insulin resistance as an accelerator of the disease process was minor.

Prediction of type 1 diabetes in the general population

OBJECTIVE

To evaluate the utility of GAD antibodies (GADAs) and islet antigen-2 antibodies (IA-2As) in prediction of type 1 diabetes over 27 years in the general population and to assess the 6-year rates of seroconversion.

RESEARCH DESIGN AND METHODS

A total of 3,475 nondiabetic subjects aged 3-18 years were sampled in 1980, and 2,375 subjects (68.3%) were resampled in 1986. All subjects were observed for development of diabetes to the end of 2007. GADAs and IA-2As were analyzed in all samples obtained in 1980 and 1986.

RESULTS

A total of 34 individuals (1.0%; 9 developed diabetes) initially had GADAs and 22 (0.6%; 9 developed diabetes) IA-2As. Seven subjects (0.2%) tested positive for both autoantibodies. The positive seroconversion rate over 6 years was 0.4% for GADAs and 0.2% for IA-2As, while the inverse seroconversion rates were 33 and 57%, respectively. Eighteen subjects (0.5%) developed type 1 diabetes after a median pre-diabetic period of 8.6 years (range 0.9-20.3). Initial positivity for GADAs and/or IA-2As had a sensitivity of 61% (95% CI 36-83) for type 1 diabetes. Combined positivity for GADAs and IA-2As had both a specificity and a positive predictive value of 100% (95% CI 59-100).

CONCLUSIONS

One-time screening for GADAs and IA-2As in the general childhood population in Finland would identify approximately 60% of those individuals who will develop type 1 diabetes over the next 27 years, and those subjects who have both autoantibodies carry an extremely high risk for diabetes. Both positive and inverse seroconversions do occur over time reflecting a dynamic process of beta-cell autoimmunity.

[Susceptibility markers in Tunisian first-degree relatives of patients with type 1 diabetes]

To identify the profile of anti-pancreas autoantibodies and elucidate the HLA DRB1, DQB1 polymorphism in Tunisian first-degree relatives of patients with type 1 diabetes, we recruited 96 relatives from 21 families with at least one diabetic child. Islet cell antibodies (ICA) were detected by immunofluorescence on monkey pancreas; glutamate decarboxylase (GADA), IA2 (IA2-A) and insulin (IAA) antibodies were measured by RIA. HLA class II DRB1 and DQB1 alleles were typed by PCR-SSP. ICA, GADA, IA2-A and IAA were found in respectively 11.5, 4.2, 5.2 and 8.3% of relatives. Twenty-two out of 96 had at least one antibody and 20 out of these 22 had a susceptibility allele (DRB1*03, DRB1*04, DQB1*02 or DQB1*0302) with or without protective allele (DRB1*11, DRB1*13, DRB1*15 or DQB1*06). All of the 5 relatives having 2 autoantibodies or more carried the DRB1*04-DQB1*0302 susceptible haplotype. In conclusion, this observational study confirms in a Tunisian population known epidemiological data and demonstrates the usefulness of follow-up to determine the predictive value of studied markers.

Molecular basis of predisposition to develop type 1 diabetes mellitus in North Indians

Type 1 diabetes (T1D) mellitus is a multifactorial autoimmune disease where more than 90% of insulin-producing pancreatic beta cells are destroyed before the clinical manifestations, warranting a need to identify the children predisposed to get the disease. Of the 20 genomic intervals implicated for the risk to develop T1D, the major histocompatibility complex (MHC) region on chromosome 6p21.31 (IDDM1) has been the major contributor, followed by 5' regulatory region of the insulin (INS) gene on chromosome 11p15.5 (IDDM2). MHC has a role in antigen presentation and IDDM2 has been shown to have a role in transcription of insulin in the thymus. Hence, alleles of human leukocyte antigen (HLA)-DRB1, DQB1, and insulin-linked variable number of tandem repeats (INS-VNTR) were studied in 110 T1D patients and 112 healthy controls using polymerase chain reaction and hybridization with sequence-specific oligonucleotide probes (PCR-SSOP) and PCR restriction fragment length polymorphism (PCR-RFLP), respectively. HLA-DRB1*0301 was significantly increased in the T1D patients along with associated DQB1*0201 followed by DRB1*0401 and DRB1*0405. DRB1*0701 was observed to be the most protective allele followed by DRB1*0403 and DRB1*0404. Although DQB1*0302 which is associated with both the protective and susceptible DR4 alleles was not significantly increased, heterozygous DQB1*0201, *0302 was significantly increased in the TID patients. Because INS-VNTR class I homozygosity was also significantly increased in the patients, simultaneous presence of DRB1*0301 along with homozygous INS-VNTR class I, gave a relative risk (RR) of 70.81. However, a similar analysis of DQB1*0201 and *0302 along with INS-VNTR alleles did not give such high RRs. Thus, the two independently assorting alleles at two loci i.e., DRB1*0301 and INS-VNTR class I, on two different chromosomes may have the potential to predict a prediabetic in North India.

Pathophysiology of immune-mediated (type 1) diabetes mellitus: potential for immunotherapy

Type 1 diabetes mellitus is a chronic T cell-mediated disease resulting from autoimmune destruction of pancreatic beta-cells. This process leads to progressive and irreversible failure of insulin secretion. Development of the disease involves both genetic and environmental factors. Genetic predisposition is mainly connected with the human leucocyte antigen (HLA) region, which encodes structures responsible for antigen presentation. A comprehensive molecular understanding of the pathogenesis of the disease is essential for the design of rational and well tolerated means of prevention. This paper describes recent experimental and clinical findings and elucidates the current possibilities for immunotherapy of type 1 diabetes. The nature of breakdown of self-tolerance and the mechanisms involved in its recovery are discussed.

Prognostic factors for the course of beta cell function in autoimmune diabetes

This study presents a 2-yr follow-up of 281 patients, aged 15-34 yr, diagnosed with diabetes between 1992 and 1993. At diagnosis, 224 (80%) patients were positive for at least one of the following autoantibodies: islet cell antibodies (ICAs), glutamic acid decarboxylase antibodies (GADAs), or tyrosine phosphatase antibodies (IA-2As); the remaining 57 (20%) patients were negative for all three autoantibodies. At diagnosis, C-peptide levels were lower (0. 27; 0.16-0.40 nmol/L) in autoantibody-positive patients compared with autoantibody-negative patients (0.51; 0.28-0.78 nmol/L; P: < 0. 001). After 2 yr, C-peptide levels had decreased significantly in patients with autoimmune diabetes (0.20; 0.10-0.37 nmol/L; P: = 0. 0018), but not in autoantibody-negative patients. In patients with autoimmune diabetes, a low initial level of C-peptide (odds ratio, 2. 6; 95% confidence interval, 1.7-4.0) and a high level of GADAs (odds ratio, 2.5; 95% confidence interval, 1.1-5.7) were risk factors for a C-peptide level below the reference level of 0.25 nmol/L 2 yr after diagnosis. Body mass index had a significant effect in the multivariate analysis only when initial C-peptide was not considered. Factors such as age, gender, levels of ICA or IA-2A or insulin autoantibodies (analyzed in a subset of 180 patients) had no effect on the decrease in beta-cell function. It is concluded that the absence of pancreatic islet autoantibodies at diagnosis were highly predictive for a maintained beta-cell function during the 2 yr after diagnosis, whereas high levels of GADA indicated a course of decreased beta-cell function with low levels of C-peptide. In autoimmune diabetes, an initial low level of C-peptide was a strong risk factor for a decrease in beta-cell function and conversely high C-peptide levels were protective. Other factors such as age, gender, body mass index, levels of ICA, IA-2A or IAA had no prognostic importance.