Maturity onset diabetes of the young and pregnancy

Management of monogenic diabetes in pregnancy: A narrative review

Pregnancy in women with monogenic diabetes is potentially complex, with significant implications for both maternal and fetal health. Among these, maturity-onset diabetes of the young (MODY) stands out as a prevalent monogenic diabetes subtype frequently encountered in clinical practice. Each subtype of MODY requires a distinct approach tailored to the pregnancy, diverging from management strategies in non-pregnant individuals. Glucokinase MODY (GCK-MODY) typically does not require treatment outside of pregnancy, but special considerations arise when a woman with GCK-MODY becomes pregnant. The glycemic targets in GCK-MODY pregnancies are not exclusively dictated by the maternal/paternal MODY genotype but are also influenced by the genotype of the developing fetus. During pregnancy, the choice between sulfonylurea or insulin for treating hepatocyte nuclear factor 1-alpha (HNF1A)-MODY and HNF4A-MODY depends on the mother's specific circumstances and the available expertise. Management of other rarer MODY subtypes is individualized, with decisions made on a case-by-case basis. Therefore, a collaborative approach involving expert diabetes and obstetric teams is crucial for the comprehensive management of MODY pregnancies.

Maturity-onset Diabetes of the Young (MODY) in Pregnancy: A Review

Hyperglycaemia in pregnancy is one of the most common complications of pregnancy and is generally diagnosed as gestational diabetes mellitus (GDM). Nevertheless, clinical symptoms of hyperglycaemia in pregnancy in some cases do not match the clinical manifestations of GDM. It is suspected that 1-2 % of women diagnosed with GDM are misdiagnosed maturity-onset diabetes of the young (MODY). MODY often has a subclinical course; thus, it is challenging for clinicians to aptly diagnose monogenic diabetes in pregnancy. Proper diagnosis is crucial for the effective treatment of hyperglycaemia in pregnancy. Many studies revealed that misdiagnosis of MODY increases the rate of complications for both mother and fetus. This literature review reports the current knowledge regarding diagnosis, treatment, and complications of the most common types of MODY in pregnancy.

Screening for monogenic subtypes of gestational diabetes in a high prevalence island population - A whole exome sequencing study

AIMS

The reported frequency of monogenic defects of beta cell function in gestational diabetes (GDM) varies extensively. This study aimed to evaluate the frequency and molecular spectrum of variants in genes associated with monogenic/atypical diabetes in non-obese females of Maltese ethnicity with GDM.

METHODS

50 non-obese females who met the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria for diagnosis of GDM and with a first-degree relative with non-autoimmune diabetes were included in this study. Whole exome capture and high throughput sequencing was carried out. Rare sequence variants were filtered, annotated, and prioritised according to the American College for Medical Genetics guidelines. For selected missense variants we explored effects on protein stability and structure through in-silico tools.

RESULTS

We identified three pathogenic variants in GCK, ABCC8 and HNF1A and several variants of uncertain significance in the cohort. Genotype-phenotype correlations and post-pregnancy follow-up data are described.

CONCLUSIONS

This study provides the first insight into an underlying monogenic aetiology in non-obese females with GDM from an island population having a high prevalence of diabetes. It suggests that monogenic variants constitute an underestimated cause of diabetes detected in pregnancy, and that careful evaluation of GDM probands to identify monogenic disease subtypes is indicated.

Pregnancy in Women With Monogenic Diabetes due to Pathogenic Variants of the Glucokinase Gene: Lessons and Challenges

Heterozygous loss-of-function variants of the glucokinase (GCK) gene are responsible for a subtype of maturity-onset diabetes of the young (MODY). GCK-MODY is characterized by a mild hyperglycemia, mainly due to a higher blood glucose threshold for insulin secretion, and an up-regulated glucose counterregulation. GCK-MODY patients are asymptomatic, are not exposed to diabetes long-term complications, and do not require treatment. The diagnosis of GCK-MODY is made on the discovery of hyperglycemia by systematic screening, or by family screening. The situation is peculiar in GCK-MODY women during pregnancy for three reasons: 1. the degree of maternal hyperglycemia is sufficient to induce pregnancy adverse outcomes, as in pregestational or gestational diabetes; 2. the probability that a fetus inherits the maternal mutation is 50% and; 3. fetal insulin secretion is a major stimulus of fetal growth. Consequently, when the fetus has not inherited the maternal mutation, maternal hyperglycemia will trigger increased fetal insulin secretion and growth, with a high risk of macrosomia. By contrast, when the fetus has inherited the maternal mutation, its insulin secretion is set at the same threshold as the mother's, and no fetal growth excess will occur. Thus, treatment of maternal hyperglycemia is necessary only in the former situation, and will lead to a risk of fetal growth restriction in the latter. It has been recommended that the management of diabetes in GCK-MODY pregnant women should be guided by assessment of fetal growth by serial ultrasounds, and institution of insulin therapy when the abdominal circumference is ≥ 75th percentile, considered as a surrogate for the fetal genotype. This strategy has not been validated in women with in GCK-MODY. Recently, the feasibility of non-invasive fetal genotyping has been demonstrated, that will improve the care of these women. Several challenges persist, including the identification of women with GCK-MODY before or early in pregnancy, and the modalities of insulin therapy. Yet, retrospective observational studies have shown that fetal genotype, not maternal treatment with insulin, is the main determinant of fetal growth and of the risk of macrosomia. Thus, further studies are needed to specify the management of GCK-MODY pregnant women during pregnancy.

Molecular Changes in the Glucokinase Gene (GCK) Associated with the Diagnosis of Maturity Onset Diabetes of the Young (MODY) in Pregnant Women and Newborns

BACKGROUND

Diabetes mellitus is the most common metabolic alteration in gestation. Monogenic diabetes or Maturity-Onset Diabetes of the Young (MODY) is a subtype caused by a primary defect in insulin secretion determined by autosomal dominant inheritance.

OBJECTIVES

This study aimed to analyze molecular changes of the Glucokinase gene (GCK) in pregnant women with hyperglycemia during gestation and in their neonates. Case Study and Methods: We collected 201 blood samples, 128 from pregnant patients diagnosed with hyperglycemia and 73 from umbilical cord blood from neonates of the respective patients. DNA extraction and polymerase chain reaction (PCR) were performed to identify molecular changes in the GCK gene.

RESULTS

In a total of 201 samples (128 from mothers and 73 from neonates), we found changes in 21 (10.6%), among which 12 were maternal samples (6.0%) and 9 were neonatal samples (4.5%). DNA sequencing identified two polymorphisms and one deleterious MODY GCK-diagnostic mutation.

CONCLUSION

The prevalence of molecular changes in the Glucokinase gene (GCK) and the deleterious MODY GCK-diagnostic mutation were 9.3% and 0.7%, respectively, in women with hyperglycemia during gestation and 12.5% and 1.3%, respectively, in their neonates. The deleterious MODY GCK mutation identified is associated with a reduction in GCK activity and hyperglycemia. In the other molecular changes identified, it was impossible to exclude phenotypic change despite not having clinical significance. Therefore, these changes may interfere with the management and clinical outcome of the patients.

Monogenic diabetes caused by GCK gene mutation is misdiagnosed as gestational diabetes - A multicenter study in Portugal

AIMS

Monogenic diabetes is an underdiagnosed type of diabetes mellitus, which can be harmful in pregnancy. We aim to estimate the prevalence of diabetes caused by the mutation of the glucokinase gene (GCK-MODY) in pregnant women diagnosed with gestational diabetes mellitus (GDM) and to characterize pregnant women with this suspicion.

METHODS

A multicenter observational study with data prospectively collected from pregnancies with GDM was conducted. Two groups of pregnant women were considered: those with GCK-MODY criteria and those without those criteria.

RESULTS

Of 18421 women with GDM, 3.6% (n = 730) had the GCK-MODY clinical criteria. A prevalence of 1.5% of GCK-MODY is estimated in women with GDM in Portugal, which is higher than in Northern European countries. Suspected GCK-MODY women had statistically higher odds of having neonates below the 25th percentile (OR = 1.23, 95%CI = 1.04-1.46, p = 0.016) and having prediabetes and diabetes in postpartum reclassification (OR = 2.11, 95%CI = 1.55-2.82, p < 0.001 and OR = 5.96, 95%CI = 3.38-10.06, p < 0.001, respectively).

CONCLUSIONS

Higher odds of neonates below the 25th percentile was probably due to excessive insulin treatment in cases where both the mother and the fetus have the mutation. It is essential to consider the diagnosis of GCK-MODY in all women with GDM criteria for better management of diabetes in pregnancy.

Monitoring motherhood: Monitoring and optimizing glycaemia in women with pre-existing diabetes in pregnancy

Despite recent advances in care, women with diabetes in pregnancy are still at increased risk of multiple pregnancy complications. Offspring exposed to hyperglycaemia in utero also experience long-term health sequelae, affecting neurocognitive and cardiometabolic status. Many of these adverse consequences can be prevented or ameliorated with good medical care, specifically to optimize glycaemic control. The accurate assessment of glycaemia in pregnancy is therefore vital to safeguard the health of mother and child. However, there is no consensus about the best method of monitoring glycaemic control in pregnancy. Short-term changes in insulin dosage and lifestyle, with altered appetite, insulin sensitivity and red cell turnover create difficulties in interpretation of standard laboratory measures such as HbA_1c. The ideal marker would provide short-term feedback on daily or weekly glycaemic control, with additional capability to predict pregnancies at high risk of suboptimal outcomes. Several novel biochemical markers are available which allow assessment of dynamic changes in glycaemia over weeks rather than months. Continuous glucose monitoring devices have advanced in accuracy and provide new opportunities for robust assessment of glycaemia in pregnancy. Recent work from the continuous glucose monitoring in pregnant women with type 1 diabetes trial (CONCEPTT) has provided information about the ability of different markers of glycaemia to predict pregnancy outcomes.The aim of this review is to summarize the care for women with pre-existing diabetes in pregnancy and to highlight the important role of glycaemic monitoring in pregnancy.

Differentiating Among Type 1, Type 2 Diabetes, and MODY: Raising Awareness About the Clinical Implementation of Genetic Testing in Latin America

Objective

To describe a case of maturity-onset diabetes of the young (MODY) to highlight the importance of a correct diabetes diagnosis.

Methods

We describe a Mexican family misdiagnosed with T1D and T2D.

Results

A 36-year-old woman with diabetes and adverse outcomes during 2 pregnancies had been diagnosed with T2D 10 years ago. Genetic testing was performed due to clinical and family history, which showed a pathogenic heterozygous variant c.544G>T (p.Val182Leu) in the GCK gene. This mutation was also confirmed in most of the family members who had been diagnosed with diabetes.

Conclusion

This case highlights the need for a correct diabetes classification. Reassessment of diabetes etiology is justified, especially in individuals with unclear clinical presentation or when family history is suggestive.

Evaluation of pregnancy outcomes in women with GCK-MODY

AIMS

To determine the fetal and maternal outcomes in pregnant women with Glucokinase-Maturity onset diabetes of the young (GCK-MODY).

METHODS

We studied the obstetric and perinatal outcomes in 99 pregnancies of 34 women with GCK-MODY. The mutation status of the offspring was known in 29 and presumed in 33. Clinical outcomes were determined and compared between affected (n = 39) and unaffected (n = 23) offspring.

RESULTS

59% of pregnancies were treated with diet alone and 41% received insulin. Birthweight, percentage of large for gestational age (LGA) and caesarean section (CS) in GCK-unaffected offspring was significantly higher than in GCK-affected offspring (4.0 ± 0.7 vs. 3.4 ± 0.4 kg, p = 0.001), 15 (65%) vs. 5(13%) (p = 0.00006) and 17 (74%) vs. 11 (28%) (p = 0.001), respectively. We observed an earlier gestational age at delivery on insulin in unaffected offspring (38.3 ± 1.0 vs. 39.5 ± 1.5 weeks, p = 0.03) with no significant change in LGA (9 (82%) vs. 6 (50%); p = 0.12), and a higher rate of CS (8 [73%] vs. 3 [11%]; p < 0.001), and no change in small for gestational age (0 [0%] vs. 4 [14%]; p = 0.30) in affected offspring.

CONCLUSION

Insulin therapy in unaffected offspring did not reduce LGA and was associated with earlier gestational age at delivery. Insulin treatment in GCK-affected offspring was associated with an increased incidence of CS, but did not adversely affect fetal outcome. Fetal genotype determines birthweight rather than treatment. Pre-pregnancy diagnosis of GCK-MODY, use of continuous glucose monitoring and non-invasive fetal genotyping may enable further investigation of targeted therapy in this condition.

Precision Therapy for a Chinese Family With Maturity-Onset Diabetes of the Young

OBJECTIVE

To determine the pathogenic gene and explore the clinical characteristics of maturity-onset diabetes of the young type 2 (MODY2) pedigree caused by a mutation in the glucokinase (GCK) gene.

METHODS

Using whole-exome sequencing (WES), the pathogenic gene was detected in the proband-a 20-year-old young man who was accidentally found with hyperglycemia, no ketosis tendency, and a family history of diabetes. The family members of the proband were examined. In addition, relevant clinical data were obtained and genomic DNA from peripheral blood was obtained. Pathologic variants of the candidate were verified by Sanger sequencing technology, and cosegregation tests were conducted among other family members and non-related healthy controls. After adjusting the treatment plan based on the results of genetic testing, changes in biochemical parameters, such as blood glucose levels and HAblc levels were determined.

RESULTS

In the GCK gene (NM_000162) in exon 9, a heterozygous missense mutation c.1160C > T (p.Ala387Val) was found in the proband, his father, uncle, and grandmother. Thus mutation, which was found to co-segregate with diabetes, was the first discovery of such a mutation in the Asian population. After stopping hypoglycemic drug treatment, good glycemic control was achieved with diet and exercise therapy.

CONCLUSION

GCK gene mutation c.1160C > T (p.Ala387Val) is the pathogenic gene in the GCK-MODY pedigree. Formulating an optimized and personalized treatment strategy can reduce unnecessary excessive medical treatment and adverse drug reactions, and maintain a good HbA1c compliance rate.

Approach to the Patient with MODY-Monogenic Diabetes

Maturity-onset diabetes of the young, or MODY-monogenic diabetes, is a not-so-rare collection of inherited disorders of non-autoimmune diabetes mellitus that remains insufficiently diagnosed despite increasing awareness. These cases are important to efficiently and accurately diagnose, given the clinical implications of syndromic features, cost-effective treatment regimen, and the potential impact on multiple family members. Proper recognition of the clinical manifestations, family history, and cost-effective lab and genetic testing provide the diagnosis. All patients must undergo a thorough history, physical examination, multigenerational family history, lab evaluation (glycated hemoglobin A1c [HbA1c], glutamic acid decarboxylase antibodies [GADA], islet antigen 2 antibodies [IA-2A], and zinc transporter 8 [ZnT8] antibodies). The presence of clinical features with 3 (or more) negative antibodies may be indicative of MODY-monogenic diabetes, and is followed by genetic testing. Molecular genetic testing should be performed before attempting specific treatments in most cases. Additional testing that is helpful in determining the risk of MODY-monogenic diabetes is the MODY clinical risk calculator (>25% post-test probability in patients not treated with insulin within 6 months of diagnosis should trigger genetic testing) and 2-hour postprandial (after largest meal of day) urinary C-peptide to creatinine ratio (with a ≥0.2 nmol/mmol to distinguish HNF1A- or 4A-MODY from type 1 diabetes). Treatment, as well as monitoring for microvascular and macrovascular complications, is determined by the specific variant that is identified. In addition to the diagnostic approach, this article will highlight recent therapeutic advancements when patients no longer respond to first-line therapy (historically sulfonylurea treatment in many variants).

LEARNING OBJECTIVES

Upon completion of this educational activity, participants should be able to.

TARGET AUDIENCE

This continuing medical education activity should be of substantial interest to endocrinologists and all health care professionals who care for people with diabetes mellitus.

MODY2 diagnostic issues in adults

Approximately 90% of all cases of diabetes mellitus in adults involve type 2 diabetes, while the prevalence of maturity-onset diabetes of the young (MODY) remains undetermined leading to inappropriate treatment regimens. One of the most common monogenic forms of diabetes is a disease caused by a mutation in the glucokinase gene, MODY2. Knowledge of the clinical features of the disease allows the selection of patients with a high risk of mutation in the glucokinase gene and verification of diagnosis for molecular genetic research. This paper reflects the clinical features of MODY2 and the difficulties of diagnosis in adults. Furthermore, it presents a clinical case of a patient with MODY2 demonstrating all the features of this type of diabetes. A family member with a mutation in the gene allows to predict the nature of carbohydrate metabolism disorders in first degree relatives. A targeted study of only one part of the glucokinase gene in molecular genetic research is sufficient to confirm the diagnosis in relatives.

Management and Outcomes of Maturity-Onset Diabetes of the Young in Pregnancy

Maturity-onset diabetes of the young (MODY) is a group of monogenic disorders that accounts for 1% to 5% of diabetes. The most common mutations are those in the hepatocyte nuclear factor-1-alpha (HNF-1-alpha) and in the glucokinase (GCK) genes. Although management of MODY is well established, no guidelines currently exist for management during pregnancy. Both maternal glycemic control and fetal mutation status are factors that may influence outcomes during pregnancy. The primary aim of this project was to describe cases of MODY during pregnancy to highlight the clinical implications of management of this disorder during pregnancy. The Ottawa Hospital is the primary referral centre for high-risk obstetrical patients, including those with diabetes in pregnancy, in Ottawa, Canada. Referrals between 2008 and 2018 were reviewed and a case series of three women and five pregnancies is described. Together with the illustrative cases, a literature review of MODY in pregnancy is used to highlight clinical considerations unique to MODY in pregnancy. We describe 5 pregnancies with MODY-2 (GCK mutation) and MODY 3 (HNF-1-alpha mutation). Important issues identified included monitoring of fetal growth and individualization of maternal glycemic control, particularly in cases where fetal mutation status is unknown. Management of MODY in pregnancy is challenging and there is little evidence to guide recommendations. Fetal growth can be used to guide management of maternal glycemic targets when fetal mutation status is unknown.

High frequency of pathogenic and rare sequence variants in diabetes-related genes among Russian patients with diabetes in pregnancy

AIMS

Diabetes in pregnancy may be associated with monogenic defects of beta-cell function, frequency of which depends on ethnicity, clinical criteria for selection of patients as well as methods used for genetic analysis. The aim was to evaluate the contribution and molecular spectrum of mutations among genes associated with monogenic diabetes in non-obese Russian patients with diabetes in pregnancy using the next-generation sequencing (NGS).

METHODS

188 non-obese pregnant women with diabetes during pregnancy were included in the study; among them 57 subjects (30.3%) met the American Diabetes Association (ADA) criteria of preexisting pregestational diabetes (pre-GDM), whereas 131 women (69.7%) fulfilled criteria of gestational diabetes mellitus (GDM). A custom NGS panel targeting 28 diabetes causative genes was used for sequencing. The sequence variants were rated according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

RESULTS

In total, 23 pathogenic, 18 likely pathogenic and 16 variants of uncertain significance were identified in 59/188 patients (31.4%). The majority of variants (38/59) were found in GCK gene. No significant differences in the number of variants among the two study groups (pre-GDM and GDM) were observed.

CONCLUSIONS

The study suggests that frequency of monogenic variants of diabetes might be underestimated, which warrants a broader use of genetic testing, especially in pregnancy.

Identification of an HNF1A p.Gly292fs Frameshift Mutation Presenting as Diabetes During Pregnancy in a Maltese Family

The diagnosis of maturity onset diabetes of the young (MODY) is a challenging process in view of the extensive clinical and genetic heterogeneity of the disease. Mutations in the gene encoding hepatocyte nuclear factor 1α (HNF1A) are responsible for most forms of monogenic diabetes in Northern European populations. Genetic analysis through a combination of whole exome sequencing and Sanger sequencing in three Maltese siblings and their father identified a rare duplication/frameshift mutation in exon 4 of HNF1A that lies within a known mutational hotspot in this gene. In this report, we provide the first description of an HNF1A-MODY3 phenotype in a Maltese family. The findings reported are relevant and new to a regional population, where the epidemiology of atypical diabetes has never been studied before. This report is of clinical interest as it highlights how monogenic diabetes can be misdiagnosed as either type 1, type 2, or gestational diabetes. It also reinforces the need for a better characterisation of monogenic diabetes in Mediterranean countries, particularly in island populations such as Malta with a high prevalence of diabetes.

Glucokinase deficit and birthweight: does maternal hyperglycemia always meet fetal needs?

AIMS

Many authors do not recommend hypoglycemic treatment during pregnancy in women affected by monogenic diabetes due to heterozygous glucokinase (GCK) mutations (MODY 2) in case of affected fetus, because maternal hyperglycemia would be necessary to achieve a normal birthweight. We aimed to evaluate differences in birthweight between MODY 2 affected children according to the parent who carried the mutation.

METHODS

We retrospectively studied 48 MODY 2 affected children, whose mothers did not receive hypoglycemic treatment during pregnancy, divided into two groups according to the presence of the mutation in the mother (group A) or in the father (group B). Data were extracted from the database of the Regional Centre of Pediatric Diabetology of the University of Campania, Naples, collected from 1996 to 2016. We analyzed birthweight and centile birthweight.

RESULTS

Percentage of small for gestational age was significantly higher in group B than in group A. We found three large for gestational age in the group that inherited the deficit from the mother, all with the same novel GCK mutation (p.Lys458-Cys461del).

CONCLUSIONS

We hypothesize that not all MODY 2 affected fetuses need the same levels of hyperglycemia to have an appropriate growth, maybe because different kinds of GCK mutations may result in different phenotypes. Consequently, a "tailored therapy" of maternal hyperglycemia, based on fetal growth frequently monitored through ultrasounds, is essential in MODY 2 pregnancies.

Clinical Management of Women with Monogenic Diabetes During Pregnancy

PURPOSE OF REVIEW

Monogenic diabetes accounts for 1-2% of all diabetes cases, but is frequently misdiagnosed as type 1, type 2, or gestational diabetes. Accurate genetic diagnosis directs management, such as no pharmacologic treatment for GCK-MODY, low-dose sulfonylureas for HNF1A-MODY and HNF4A-MODY, and high-dose sulfonylureas for K_ATP channel-related diabetes. While diabetes treatment is defined for the most common causes of monogenic diabetes, pregnancy poses a challenge to management. Here, we discuss the key issues in pregnancy affected by monogenic diabetes.

RECENT FINDINGS

General recommendations for pregnancy affected by GCK-MODY determine need for maternal insulin treatment based on fetal mutation status. However, a recent study suggests macrosomia and miscarriage rates may be increased with this strategy. Recent demonstration of transplacental transfer of sulfonylureas also raises questions as to when insulin should be initiated in sulfonylurea-responsive forms of monogenic diabetes. Pregnancy represents a challenge in management of monogenic diabetes, where factors of maternal glycemic control, fetal mutation status, and transplacental transfer of medication must all be taken into consideration. Guidelines for pregnancy affected by monogenic diabetes will benefit from large, prospective studies to better define the need for and timing of initiation of insulin treatment.

Paul T, Jose R, Regi A, Lionel J, Jeyaseelan L, Mathew J, Thomas N. Comprehensive Maturity Onset Diabetes of the Young (MODY) Gene Screening in Pregnant Women with Diabetes in India

Pregnant women with diabetes may have underlying beta cell dysfunction due to mutations/rare variants in genes associated with Maturity Onset Diabetes of the Young (MODY). MODY gene screening would reveal those women genetically predisposed and previously unrecognized with a monogenic form of diabetes for further clinical management, family screening and genetic counselling. However, there are minimal data available on MODY gene variants in pregnant women with diabetes from India. In this study, utilizing the Next generation sequencing (NGS) based protocol fifty subjects were screened for variants in a panel of thirteen MODY genes. Of these subjects 18% (9/50) were positive for definite or likely pathogenic or uncertain MODY variants. The majority of these variants was identified in subjects with autosomal dominant family history, of whom five were in women with pre-GDM and four with overt-GDM. The identified variants included one patient with HNF1A Ser3Cys, two PDX1 Glu224Lys, His94Gln, two NEUROD1 Glu59Gln, Phe318Ser, one INS Gly44Arg, one GCK, one ABCC8 Arg620Cys and one BLK Val418Met variants. In addition, three of the seven offspring screened were positive for the identified variant. These identified variants were further confirmed by Sanger sequencing. In conclusion, these findings in pregnant women with diabetes, imply that a proportion of GDM patients with autosomal dominant family history may have MODY. Further NGS based comprehensive studies with larger samples are required to confirm these finding.

ENDOCRINOLOGY OF PREGNANCY: Gestational diabetes mellitus: definition, aetiological and clinical aspects

Gestational diabetes (GDM) is defined as a glucose intolerance resulting in hyperglycaemia of variable severity with onset during pregnancy. This review aims to revisit the pathogenesis and aetiology of GDM in order to better understand its clinical presentation and outcomes. During normal pregnancy, insulin sensitivity declines with advancing gestation. These modifications are due to placental factors, progesterone and estrogen. In a physiological situation, a compensatory increase in insulin secretion maintains a normal glucose homeostasis. GDM occurs if pancreatic β-cells are unable to face the increased insulin demand during pregnancy. GDM is most commonly a forerunner of type 2 diabetes (T2D) - the most prevalent form of diabetes. These women share similar characteristics with predisposed subjects to T2D: insulin resistance before and after pregnancy, and carry more T2D risk alleles. Auto-immune and monogenic diabetes are more rare aetiologies of GDM. Adverse pregnancy outcomes of GDM are mainly related to macrosomia caused by fetal hyperinsulinism in response to high glucose levels coming from maternal hyperglycaemia. Screening recommendations and diagnosis criteria of GDM have been recently updated. High risk patients should be screened as early as possible using fasting plasma glucose, and if normal, at 24-28 weeks of gestation using 75 g oral glucose tolerance test. The treatment of GDM is based on education with trained nurses and dieticians, and if necessary insulin therapy.

The clinical management of hyperglycemia in pregnancy complicated by maturity-onset diabetes of the young

OBJECTIVE

Women with maturity-onset diabetes of the young (MODY) are often first identified and diagnosed with diabetes during pregnancy. Genetics and hyperglycemia play an important role in determining fetal size in MODY pregnancies. The principal objective of the current study is to determine the outcomes and clinical management of hyperglycemia in pregnancies complicated by glucokinase gene (GCK) and hepatocyte nuclear factor (HNF)-1α MODY mutations.

STUDY DESIGN

A retrospective chart review of 37 women with a GCK/HNF-1α mutation was conducted. Data on variables such as birthweight, mode of delivery, and the treatment of hyperglycemia were available on 89 pregnancies.

RESULTS

The birthweight in unaffected GCK offspring was significantly higher than in the affected GCK offspring (4.8 [4.1-5.2] kg vs 3.2 [3.1-3.7] kg; P = .01). Seven-point home blood glucose monitoring over a 7-day period in each trimester demonstrated higher fasting and postprandial glycemic excursions in the first trimester of GCK pregnancies when compared to HNF-1α pregnancies (fasting 104 [90-115] mg/dL vs 84 [77-88] mg/dL; P = .01 and postprandial 154 [135-196] mg/dL vs 111 [100-131] mg/dL; P = .04) despite insulin treatment. There was a higher percentage of miscarriages in the GCK group when compared to the HNF-1α MODY group (33.3% vs 14%; P = .07), which was similar to the background population. Insulin initiated at an early gestation appeared to lower the incidence of macrosomia in GCK unaffected offspring.

CONCLUSION

Hyperglycemia in HNF-1α pregnancies is easily managed with current insulin protocols; in contrast, glycemic excursions are difficult to manage in GCK pregnancies. There was an increased percentage of miscarriages in GCK pregnancies highlighting the importance of a diagnosis of GCK-MODY in women prior to conception and the necessity for preconception care.

Maturity-onset diabetes of the young (MODY): an update

Maturity-onset diabetes of the young (MODY) is a group of monogenic disorders characterized by autosomal dominantly inherited non-insulin dependent form of diabetes classically presenting in adolescence or young adults before the age of 25 years. MODY is a rare cause of diabetes (1% of all cases) and is frequently misdiagnosed as Type 1 diabetes (T1DM) or Type 2 diabetes (T2DM). A precise molecular diagnosis is essential because it leads to optimal treatment of the patients and allows early diagnosis for their asymptomatic family members. Mutations in the glucokinase (GCK) (MODY 2) and hepatocyte nuclear factor (HNF)1A/4A (MODY 3 and MODY 1) genes are the most common causes of MODY. GCK mutations cause a mild, asymptomatic, and stable fasting hyperglycemia usually requiring no specific treatment. However, mutations in the HNF1A and HNF4A cause a progressive pancreatic β-cell dysfunction and hyperglycemia that can result in microvascular complications. Sulfonylureas are effective in these patients by acting on adenosine triphosphate (ATP)-sensitive potassium channels, although insulin therapy may be required later in life. Mutations in the HNF1B (MODY 5) is associated with pancreatic agenesis, renal abnormalities, genital tract malformations, and liver dysfunction. Compared to MODY 1, 2, 3, and 5, the remaining subtypes of MODY have a much lower prevalence. In this review, we summarize the main clinical and laboratory characteristics of the common and rarer causes of MODY.

Diabetes and pregnancy: perspectives from Asia

There has been a marked increase in the prevalence of diabetes in Asia over recent years. Diabetes complicating pregnancy, in particular gestational diabetes, has also increased markedly in the region. Multi-ethnic studies have highlighted the increased risk of gestational diabetes mellitus among the different Asian populations. Prevalence of gestational diabetes in Asian countries varies substantially according to the screening strategy and diagnostic criteria applied, and ranges from 1% to 20%, with evidence of an increasing trend over recent years. The International Association for Diabetes in Pregnancy Study group criteria have been adopted by some Asian countries, although they present significant challenges in implementation, especially in low-resource settings. Studies on offspring of mothers with gestational diabetes have reported adverse cardiometabolic profiles and increased risk of diabetes and obesity. Gestational diabetes is likely to be a significant factor contributing to the epidemic of diabetes and other non-communicable diseases in the Asian region. In recognition of this, several large-scale prevention and intervention programmes are currently being implemented in different Asian countries in order to improve glucose control during pregnancy, as well as overall maternal health. Lessons emerging from gestational diabetes studies in Asia may help inform and provide insights on the overall burden and treatment strategies to target gestational diabetes, with the ultimate aim to reduce its adverse short- and long-term consequences.

The 0.1% of the population with glucokinase monogenic diabetes can be recognized by clinical characteristics in pregnancy: the Atlantic Diabetes in Pregnancy cohort

OBJECTIVE

Identifying glucokinase monogenic diabetes (GCK-MODY) in pregnancy is important, as management is different from management for other forms of gestational diabetes mellitus (GDM) and there is no increased maternal risk of type 2 diabetes. We calculated the population prevalence of GCK-MODY in pregnancy and determined the clinical characteristics that differentiate pregnant women with GCK-MODY from those with GDM.

RESEARCH DESIGN AND METHODS

We calculated the population prevalence of GCK-MODY in pregnancy by testing a subset of patients from the population-based Atlantic Diabetes in Pregnancy (Atlantic DIP) study (n = 5,500). We sequenced for GCK mutations in 247 women with a fasting glucose ≥5.1 mmol/L and 109 randomly selected control subjects with normal fasting glucose. Using data from the cases found and 40 previously identified GCK-MODY pregnancies, we analyzed whether clinical criteria could be used to differentiate GCK-MODY from GDM.

RESULTS

Four women with fasting glucose ≥5.1 mmol/L were diagnosed with GCK-MODY. No cases were identified with normal fasting glucose. The population prevalence of GCK-MODY is 1.1 in 1,000 (95% CI 0.3-2.9 in 1,000) and prevalence in GDM is 0.9% (95% CI 0.3-2.3). Fasting glucose and BMI significantly differentiate GCK-MODY from GDM (P < 0.0001). Combined criteria of BMI <25 kg/m(2) and fasting glucose ≥5.5 mmol/L has a sensitivity 68%, specificity 96%, and number needed to test of 2.7 women with GDM to find one case of GCK-MODY.

CONCLUSIONS

Our large population cohort of pregnant women tested estimates the population prevalence of GCK-MODY of 1.1 in 1,000. We have shown routine clinical criteria that can identify which women should be tested for GCK-MODY in pregnancy.

Monogenic diabetes: a diagnostic algorithm for clinicians

Monogenic forms of beta cell diabetes account for approximately 1%-2% of all cases of diabetes, yet remain underdiagnosed. Overlapping clinical features with common forms of diabetes, make diagnosis challenging. A genetic diagnosis of monogenic diabetes in many cases alters therapy, affects prognosis, enables genetic counseling, and has implications for cascade screening of extended family members. We describe those types of monogenic beta cell diabetes which are recognisable by distinct clinical features and have implications for altered management; the cost effectiveness of making a genetic diagnosis in this setting; the use of complementary diagnostic tests to increase the yield among the vast majority of patients who will have commoner types of diabetes which are summarised in a clinical algorithm; and the vital role of cascade genetic testing to enhance case finding.

Family history in the diagnosis of monogenic diabetes "leads and misleads"

Always granting that de novo mutations are possible, family history and biological characteristics are nonetheless crucial for the diagnosis of monogenic diabetes. We report here the case of two patients with monogenic diabetes in which the initial family history misled the diagnostic work-up and did not support the diagnosis. Family history details changed substantially after the molecular diagnosis was established.

Pathogenesis of the metabolic syndrome: insights from monogenic disorders

Identifying rare human metabolic disorders that result from a single-gene defect has not only enabled improved diagnostic and clinical management of such patients, but also has resulted in key biological insights into the pathophysiology of the increasingly prevalent metabolic syndrome. Insulin resistance and type 2 diabetes are linked to obesity and driven by excess caloric intake and reduced physical activity. However, key events in the causation of the metabolic syndrome are difficult to disentangle from compensatory effects and epiphenomena. This review provides an overview of three types of human monogenic disorders that result in (1) severe, non-syndromic obesity, (2) pancreatic beta cell forms of early-onset diabetes, and (3) severe insulin resistance. In these patients with single-gene defects causing their exaggerated metabolic disorder, the primary defect is known. The lessons they provide for current understanding of the molecular pathogenesis of the common metabolic syndrome are highlighted.

The glucokinase mutation p.T206P is common among MODY patients of Jewish Ashkenazi descent

BACKGROUND

Maturity-onset diabetes of the young (MODY) is characterized by an autosomal dominant mode of inheritance; a primary defect in insulin secretion with non-ketotic hyperglycemia, age of onset under 25 yr; and lack of autoantibodies. Heterozygous mutations in glucokinase (GCK) are associated with mild fasting hyperglycemia and gestational diabetes mellitus while homozygous or compound heterozygous GCK mutations result in permanent neonatal diabetes mellitus. Given that both the Israeli-Arabic and the various Israeli-Jewish communities tend to maintain ethnic seclusion, we speculated that it would be possible to identify a relatively narrow spectrum of mutations in the Israeli population.

OBJECTIVE

To characterize the genetic basis of GCK-MODY in the different ethnic groups of the Israeli population.

SUBJECTS

Patients with clinically identified GCK-MODY and their first degree family members.

METHODS

Molecular analysis of GCK was performed on genomic DNA using polymerase chain reaction, denaturing gradient gel electrophoresis (DGGE), and sequencing. Bioinformatic model was preformed using the NEST program.

RESULTS

Mutations in GCK were identified in 25 families and were all family-specific, except c.616A>C. p.T206P. This mutation was identified in six unrelated families, all patients from a Jewish-Ashkenazi descent, thus indicating an ethno-genetic correlation. A simple, fast, and relatively cheap DGGE/restriction-digestion assay was developed.

CONCLUSIONS

The high incidence of the mutant allele in GCK-MODY patients of Jewish-Ashkenazi descent suggests a founder effect. We propose that clinically identified GCK-MODY patients of Jewish-Ashkenazi origin be first tested for this mutation.

Antenatal diagnosis of fetal genotype determines if maternal hyperglycemia due to a glucokinase mutation requires treatment

OBJECTIVE

In women with hyperglycemia due to heterozygous glucokinase (GCK) mutations, the fetal genotype determines its growth. If the fetus inherits the mutation, birth weight is normal when maternal hyperglycemia is not treated, whereas intensive treatment may adversely reduce fetal growth. However, fetal genotype is not usually known antenatally, making treatment decisions difficult.

HISTORY AND EXAMINATION

We report two women with gestational diabetes mellitus resulting from GCK mutations with hyperglycemia sufficient to merit treatment.

INVESTIGATION

In both women, DNA from chorionic villus sampling, performed after high-risk aneuploidy screening, showed the fetus had inherited the GCK mutation. Therefore, maternal hyperglycemia was not treated. Both offspring had a normal birth weight and no peripartum complications.

CONCLUSIONS

In pregnancies where the mother has hyperglycemia due to a GCK mutation, knowing the fetal GCK genotype guides the management of maternal hyperglycemia. Fetal genotyping should be performed when fetal DNA is available from invasive prenatal diagnostic testing.

Glucokinase (GCK) mutations and their characterization in MODY2 children of southern Italy

Type 2 Maturity Onset Diabetes of the Young (MODY2) is a monogenic autosomal disease characterized by a primary defect in insulin secretion and hyperglycemia. It results from GCK gene mutations that impair enzyme activity. Between 2006 and 2010, we investigated GCK mutations in 66 diabetic children from southern Italy with suspected MODY2. Denaturing High Performance Liquid Chromatography (DHPLC) and sequence analysis revealed 19 GCK mutations in 28 children, six of which were novel: p.Glu40Asp, p.Val154Leu, p.Arg447Glyfs, p.Lys458_Cys461del, p.Glu395_Arg397del and c.580-2A>T. We evaluated the effect of these 19 mutations using bioinformatic tools such as Polymorphism Phenotyping (Polyphen), Sorting Intolerant From Tolerant (SIFT) and in silico modelling. We also conducted a functional study to evaluate the pathogenic significance of seven mutations that are among the most severe mutations found in our population, and have never been characterized: p.Glu70Asp, p.His137Asp, p.Phe150Tyr, p.Val154Leu, p.Gly162Asp, p.Arg303Trp and p.Arg392Ser. These seven mutations, by altering one or more kinetic parameters, reduced enzyme catalytic activity by >40%. All mutations except p.Glu70Asp displayed thermal-instability, indeed >50% of enzyme activity was lost at 50°C/30 min. Thus, these seven mutations play a pathogenic role in MODY2 insurgence. In conclusion, this report revealed six novel GCK mutations and sheds some light on the structure-function relationship of human GCK mutations and MODY2.

Mechanisms in the adaptation of maternal β-cells during pregnancy

Pancreatic β-cell mass adapts to changing insulin demands in the body. One of the most amazing reversible β-cell adaptations occurs during pregnancy and postpartum conditions. During pregnancy, the increase in maternal insulin resistance is compensated by maternal β-cell hyperplasia and hyperfunctionality to maintain normal blood glucose. Although the cellular mechanisms involved in maternal β-cell expansion have been studied in detail in rodents, human studies are very sparse. A summary of these studies in rodents and humans is described below. Since β-cell mass expands during pregnancy, unraveling the endocrine/paracrine/autocrine molecular mechanisms responsible for these effects can be of great importance for predicting and treating gestational diabetes and for finding new cues that induce β-cell regeneration in diabetes. In addition to the well known implication of lactogens during maternal β-cell expansion, additional participants are being discovered such as serotonin and HGF. Transcription factors, such as hepatocyte nuclear factor-4α and the forkhead box protein-M1, and cell cycle regulators, such as menin, p27 and p18, are important intracellular signals responsible for these effects. In this article, we summarize and discuss novel studies uncovering molecular mechanisms involved in the maternal β-cell adaptive expansion during pregnancy.