Gestational diabetes mellitus and HLA class II (-DQ, -DR) association: The Digest Study

The relationships between HLA class II alleles and antigens with gestational diabetes mellitus: A meta-analysis

Gestational diabetes mellitus (GDM) is defined as glucose intolerance with onset or first recognition during pregnancy. It is associated with an increased risk of pregnancy complications. Susceptibility to GDM is partly determined by genetics and linked with type 1 diabetes-associated high risk HLA class II genes. However, the evidence for this relationship is still highly controversial. In this study, we assessed the relationship between HLA class II variants and GDM. We performed meta-analysis on all of literatures available in PubMed, Embase, Web of Science and China National Knowledge Infrastructure databases. The odds ratio and 95% confidence interval of each variant were estimated. All statistical analyses were conducted using the Comprehensive Meta Analysis 2.2.064 software. At the allelic analysis, DQB1*02, DQB1*0203, DQB1*0402, DQB1*0602, DRB1*03, DRB1*0301 and DRB1*1302 reached a nominal level of significance, and only DQB1*02, DQB1*0602 and DRB1*1302 were statistically significant after Bonferroni correction. At the serological analysis, none of DQ2, DQ6, DR13 and DR17 was statistically significant following Bonferroni correction although they reached a nominal level of significance. In sum, our meta-analysis demonstrated that there were the associations between HLA class II variants and GDM but more studies are required to elucidate how these variants contribute to GDM susceptibility.

Gestational diabetes mellitus is associated with TCF7L2 gene polymorphisms independent of HLA-DQB1*0602 genotypes and islet cell autoantibodies

AIMS

To test whether the TCF7L2 gene was associated with gestational diabetes, whether the association between TCF7L2 and gestational diabetes was independent of HLA-DQB1*0602 and islet cell autoantibodies, as well as maternal age, number of pregnancies, family history of diabetes and the HLA-DQB1 genotypes, and to test whether the distribution of HLA-DQB1 alleles was affected by country of birth.

METHODS

We genotyped the rs7903146, rs12255372 and rs7901695 single nucleotide polymorphisms of the TCF7L2 gene in 826 mothers with gestational diabetes and in 1185 healthy control subjects in the Diabetes Prediction in Skåne Study. The mothers were also typed for HLA-DQB1 genotypes and tested for islet cell autoantibodies against GAD65, insulinoma-associated antigen-2 and insulin.

RESULTS

The heterozygous genotypes CT, GT and TC of the rs7903146 (T is risk for Type 2 diabetes), rs12255372 (T is risk for Type 2 diabetes) and rs7901695 (C is risk for Type 2 diabetes), respectively, as well as the homozygous genotypes TT, TT and CC of the rs7903146, rs12255372 and rs7901695, respectively, were strongly associated with gestational diabetes (P < 0.0001). These associations remained statistically significant after adjusting for maternal age, number of pregnancies, family history of diabetes and HLA-DQ genotypes and were independent of the presence of islet cell autoantibodies. No interaction was observed between TCF7L2 and HLA-DQB1*0602, which was shown to be negatively associated with gestational diabetes in mothers born in Sweden (P = 0.010).

CONCLUSIONS

The TCF7L2 was associated with susceptibility for gestational diabetes independently of the presence of HLA-DQB1*0602 and islet cell autoantibodies and other factors such as maternal age, number of pregnancies, family history of diabetes and other HLA-DQ genotypes. The HLA-DQB1*0602 was negatively associated with gestational diabetes in mothers born in Sweden.

Gestational diabetes: risk factors and recent advances in its genetics and treatment

The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study of over 23000 diabetes-free pregnancies has shown that at a population level an unequivocal linear relationship exists between maternal glucose concentrations around the beginning of the third trimester of pregnancy and the risk of their baby being born above the ninetieth centile for weight. With the rising incidence of gestational diabetes (GDM) across the developed world, largely paralleling the increased prevalence of obesity, there has been a sharp increase in the risk of pregnancy complications developing related to the birth of macrosomic babies. The associated additional long-term complications of GDM pregnancies means that in the future there is likely to be a large increase in the incidence of type 2 diabetes and associated conditions in both the mothers and their affected offspring. The present review seeks to highlight recent advances and remaining gaps in knowledge about GDM in terms of its genetics (where some of the recently discovered polymorphic risk factors for type 2 diabetes have also proved to be risk factors for GDM) and its treatment by diet, exercise and drugs.

Diabetes related autoimmunity in gestational diabetes mellitus: is it important?

Some GDM women show autoantibody positivity during and after pregnancy and pancreatic autoantibodies can appear for the first time in some patients after delivery. Autoantibody positivity is often accompanied by a high frequency of DR3 and DR4 alleles, which are classically related to the development of type 1 diabetes and, although not all studies agree on this point, by an immunological imbalance expressed by the behaviour of the lymphocyte subpopulation, which can be seen as diabetic anomalies overlapping with the immunological changes that occur during pregnancy. It is worth emphasizing that such patients may develop classical type 1 diabetes during and/or after their pregnancy or they may evolve, often some years after their pregnancy, into cases of latent autoimmune diabetes of adulthood (LADA). Autoimmune GDM accounts for a relatively small number of cases (about 10% of all GDM) but the risk of these women developing type 1 diabetes or LADA is very high, so these patients must be identified in order to prevent the severe maternal and fetal complications of type 1 diabetes developing in pregnancy, or its acute onset afterwards. Since women with autoimmune GDM must be considered at high risk of developing type 1 diabetes in any of its clinical forms, these women should be regarded as future candidates for the immunomodulatory strategies used in type 1 diabetes.

The type 1 diabetes protective HLA DQB1*0602 allele is less frequent in gestational diabetes mellitus

AIMS/HYPOTHESIS

We tested whether gestational diabetes mellitus (GDM) is associated with HLA-DQ genotypes.

METHODS

A total of 764 mothers with non-autoimmune (GAD65, insulinoma-associated protein 2 [IA-2] and insulin autoantibody-negative) GDM were ascertained between September 2000 and August 2004 in the population-based Diabetes Prediction in Skåne (DiPiS) study. HLA-DQB1 genotypes were determined in these mothers and in 1191 randomly selected non-diabetic control mothers also negative for islet autoantibodies. The data were analysed in relation to maternal age, country of birth, number of pregnancies/siblings and pregnancy weight gain.

RESULTS

The frequency of type 1 diabetes high-risk HLA-DQ alleles (DQB1*0201, DQB1*0302) did not differ between GDM mothers and controls. In contrast, the low-risk DQB1*0602 allele was less prevalent (OR 0.64, 95% CI = 0.51-0.80, p = 0.0006) in GDM than in control mothers. The difference in DQB1*0602 frequency between GDM mothers and controls remained after multiple logistic regression analysis correcting for maternal age, country of birth, number of pregnancies/siblings and weight gain during pregnancy (OR 0.67, 95% CI 0.51-0.88, p = 0.009).

CONCLUSIONS/INTERPRETATION

The negative association between mothers who have non-autoimmune GDM and HLA-DQ*0602 suggest that this allele may protect not only from type 1 diabetes but also from GDM.

Balancing selection and heterogeneity across the classical human leukocyte antigen loci: a meta-analytic review of 497 population studies

This paper presents a meta-analysis of high-resolution human leukocyte antigen (HLA) allele frequency data describing 497 population samples. Most of the datasets were compiled from studies published in eight journals from 1990 to 2007; additional datasets came from the International Histocompatibility Workshops and from the AlleleFrequencies.net database. In all, these data represent approximately 66,800 individuals from throughout the world, providing an opportunity to observe trends that may not have been evident at the time the data were originally analyzed, especially with regard to the relative importance of balancing selection among the HLA loci. Population genetic measures of allele frequency distributions were summarized across populations by locus and geographic region. A role for balancing selection maintaining much of HLA variation was confirmed. Further, the breadth of this meta-analysis allowed the ranking of the HLA loci, with DQA1 and HLA-C showing the strongest balancing selection and DPB1 being compatible with neutrality. Comparisons of the allelic spectra reported by studies since 1990 indicate that most of the HLA alleles identified since 2000 are very-low-frequency alleles. The literature-based allele-count data, as well as maps summarizing the geographic distributions for each allele, are available online.

O papel do complexo principal de histocompatibilidade na fisiologia da gravidez e na patogênese de complicações obstétricas

Este trabalho tem por objetivo discutir a estrutura e função dos Antígenos Leucocitários Humanos (HLA), seus métodos de detecção, nomenclatura e os mecanismos imunopatológicos que o associam com a fisiologia da gestação e morbidades obstétricas. Sabe-se que o equilíbrio imunológico entre mãe e concepto é imprescindível na manutenção da gravidez. Moléculas do HLA - notadamente o HLA-G expresso na interface materno-fetal - exercem função importante na tolerância imunológica materna, evitando rejeição fetal e algumas complicações obstétricas. Além disso, o HLA permeia diversas etapas do desenvolvimento conceptual como clivagem, formação do trofoblasto e implantação. Para revisão, foram pesquisados os bancos de dados MEDLINE e LILACS, utilizando os descritores: "HLA antigens"; "pregnancy"; "embryonic development"; "pregnancy complication"; "abortion, habitual"; "pre-eclampsia". O conhecimento sobre a influência do HLA na gravidez é necessário para melhor manejo da gestação e patologias obstétricas auto-imunes, favorecendo intervenções precoces e terapêutica específica, reduzindo a morbimortalidade materna e perinatal.

The presence of gestational diabetes is associated with increased detection of anti-HLA-class II antibodies in the maternal circulation

PROBLEM

Gestational diabetes (GD) may be associated with temporarily reduced immune tolerance toward alloantigens for the time of pregnancy. The aim of this study was to assess anti-HLA-class I and -II antibodies as markers for an aberrant immunostimulation in women with GD.

METHOD OF STUDY

The percentage of anti-HLA-class I and -II antibodies was estimated in women with GD, normal term delivery and fetal distress, which was confirmed by demonstrating low cord blood pH for this patient group. These antibodies may cross the placental barrier and cause interleukin-6 (IL-6) release from fetal monocytes by cross-linking monocytes with antibody-loaded cells. Therefore we estimated the percentage of IL-6-positive monocytes in the fetal circulation of these three patient groups.

RESULTS

We found a significantly increased percentage of anti-HLA-class II in the circulation of women with GD. In comparison with women with normal term delivery, a significantly increased percentage of IL-6-positive monocytes was detected for women with GD and for women with fetal distress. Significantly decreased cord blood pH were detected for neonates born in the presence of fetal distress but not for neonates born in the presence of GD.

CONCLUSIONS

Our results suggest that GD is associated with an increased humoral immune response against HLA-class II antigens.

Different HLA-DR-DQ and MHC class I chain-related gene A (MICA) genotypes in autoimmune and nonautoimmune gestational diabetes in a Swedish population

The genetic susceptibility for gestational diabetes (GDM) was estimated by comparisons of genotypes within human leukocyte antigen (HLA) and major histocompatibility complex class I chain-related gene A (MICA) in 199 women with GDM and 213 healthy women. At least one of ICA, glutamic acid decarboxylase antibodies, or islet cell antigen-2 antibodies/tyrosine phosphatase antibodies was found in 6.0% (12/199) of women with GDM and were considered as autoimmune GDM, whereas the remaining 187 were considered as nonautoimmune GDM. HLA genotyping was done with polymerase chain reaction and sequence-specific oligonucleotides. MICA polymorphism was determined with polymerase chain reaction and fragment size determination. HLA-DR3-DQ2/x or DR4-DQ8/x and MICA5.0/5.1 were more frequent in autoimmune GDM compared with controls; 92% versus 46% and 42% versus 13% and conferred increased risk (odds ratio [OR] = 13; 95% confidence interval [CI] 1.7-104) and (OR = 4.7; 95%CI 1.4-16). Four other genotypes were more frequent in nonautoimmune GDM compared with controls: HLA-DR7-DQ2/y, 24% versus 14%; DR9-DQ9/y, 9.6% versus 1.9%; DR14-DQ5/y, 7.5% versus 0.94%; and MICA5.0/z, 24% versus 13% and gave increased risk: OR = 2.0; 95%CI 1.2-3.4, OR = 5.6; 95%CI 1.8-17, OR = 8.5; 95%CI 1.9-38, and OR = 2.0; 95%CI 1.2-3.4, respectively. We concluded that autoimmune diabetes with onset during pregnancy is associated with the type 1 diabetes-associated genotypes and also with MICA5.0/5.1, whereas DR7-DQ2/y, DR9-DQ9/y, DR14-DQ5/y, and MICA5.0/z are risk factors for nonautoimmune GDM.

Epidemiology of gestational diabetes mellitus and its association with Type 2 diabetes

Gestational diabetes (GDM) is defined as carbohydrate intolerance that begins or is first recognized during pregnancy. Although it is a well-known cause of pregnancy complications, its epidemiology has not been studied systematically. Our aim was to review the recent data on the epidemiology of GDM, and to describe the close relationship of GDM to prediabetic states, in addition to the risk of future deterioration in insulin resistance and development of overt Type 2 diabetes. We found that differences in screening programmes and diagnostic criteria make it difficult to compare frequencies of GDM among various populations. Nevertheless, ethnicity has been proven to be an independent risk factor for GDM, which varies in prevalence in direct proportion to the prevalence of Type 2 diabetes in a given population or ethnic group. There are several identifiable predisposing factors for GDM, and in the absence of risk factors, the incidence of GDM is low. Therefore, some authors suggest that selective screening may be cost-effective. Importantly, women with an early diagnosis of GDM, in the first half of pregnancy, represent a high-risk subgroup, with an increased incidence of obstetric complications, recurrent GDM in subsequent pregnancies, and future development of Type 2 diabetes. Other factors that place women with GDM at increased risk of Type 2 diabetes are obesity and need for insulin for glycaemic control. Furthermore, hypertensive disorders in pregnancy and afterwards may be more prevalent in women with GDM. We conclude that the epidemiological data suggest an association between several high-risk prediabetic states, GDM, and Type 2 diabetes. Insulin resistance is suggested as a pathogenic linkage. It is possible that improving insulin sensitivity with diet, exercise and drugs such as metformin may reduce the risk of diabetes in individuals at high risk, such as women with polycystic ovary syndrome, impaired glucose tolerance, and a history of GDM. Large controlled studies are needed to clarify this issue and to develop appropriate diabetic prevention strategies that address the potentially modifiable risk factors.

High birth weight is associated with human leukocyte antigen (HLA) DRB1*13 in full-term infants

In cord blood banking, substantial amounts of data on infants and cord blood are gathered at high cost, including birth weights and human leukocyte antigen (HLA) genotypes. As certain HLA alleles have been associated with protective host responses, it is possible that an HLA allele, or another factor linked to it, might even affect normal intrauterine growth. We explored cord blood bank data (n = 1381 infants) to elucidate whether there is an association between birth weight and HLA class II (DRB1) alleles. HLA DRB1 data were available from 1263 infants. We observed an association between birth weight and HLA DRB1*13, which was over-represented among full-term infants with the highest birth weights. The association remained when the birth weight was corrected for varying gestational age (relative birth weight) according to gender (P = 0.015). After correction of the P-value for multiple comparisons, the association was not statistically significant. However, when the birth weights of all infants were analysed for the effect of DRB1*13, infants positive for HLA DRB1*13 (n = 319) were found to have higher birth weights than infants negative for this allele (n = 944; median 3690 g vs. 3650 g, respectively; P = 0.044). Although the difference in median birth weight was only 40 g, it may be considered significant because it appeared after segregation of the infants into two groups according to the single HLA class II allele group earlier associated with protection against, for example, childhood type 1 diabetes and certain infectious diseases. The present finding may thus suggest identification of a new factor affecting normal intrauterine growth.

Autoimmune gestational diabetes mellitus: a distinct clinical entity?

This review gives an update of the present knowledge on what is defined here as autoimmune gestational diabetes mellitus (GDM). Autoimmune phenomena associated with type 1 diabetes mellitus (DM) can be detected in a subgroup of women with GDM. Islet autoantibodies are present in sera from women with GDM with variable frequency. Distinct phenotypic and genotypic features may be recognised in this subset of women with GDM, which are representative of a distinct clinical entity. Furthermore, these women are at increased risk of developing type 1 DM after pregnancy. However, the eventual progression of the autoimmune destruction of beta-cells in these subjects may follow different time-course patterns thus leading to variable forms of presentation of autoimmune DM. As a high-risk group for type 1 diabetes, women with previous autoimmune GDM may be candidates for potential immune intervention strategies.