Identifying Glucokinase Monogenic Diabetes in a Multiethnic Gestational Diabetes Mellitus Cohort: New Pregnancy Screening Criteria and Utility of HbA1c

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.

Differential contribution of alpha and beta cell dysfunction to impaired fasting glucose and impaired glucose tolerance

AIMS/HYPOTHESIS

People with isolated impaired fasting glucose (IFG) have normal beta cell function. We hypothesised that an increased glucose threshold for beta cell secretion explains IFG.

METHODS

We used graded glucose infusion to examine the relationship of insulin secretion rate (ISR) and glucagon secretion rate (GSR) with rising glucose. We studied 39 non-diabetic individuals (53 ± 2 years, BMI 30 ± 1 kg/m2), categorised by fasting glucose and glucose tolerance status. After an overnight fast, a variable insulin infusion was used to maintain glucose at ~4.44 mmol/l (07:00 to 08:30 hours). At 09:00 hours, graded glucose infusion commenced at 1 mg kg-1 min-1 and doubled every 60 min until 13:00 hours. GSR and ISR were calculated by nonparametric deconvolution from concentrations of glucagon and C-peptide, respectively.

RESULTS

The relationship of ISR with glucose was linear and the threshold for insulin secretion in isolated IFG did not differ from that in people with normal fasting glucose and normal glucose tolerance. GSR exhibited a single-exponential relationship with glucose that could be characterised by G50, the change in glucose necessary to suppress GSR by 50%. G50 was increased in IFG compared with normal fasting glucose regardless of the presence of impaired or normal glucose tolerance.

CONCLUSIONS/INTERPRETATION

These data show that, in non-diabetic humans, alpha cell dysfunction contributes to the pathogenesis of IFG independently of defects in insulin secretion. We also describe a new index that quantifies the suppression of glucagon secretion by glucose.

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.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Challenges of Treating Glucokinase MODY during Pregnancy: A Review of Maternal and Fetal Outcomes

Background: The optimal treatment strategy for the follow-up and management of women with glucokinase maturity-onset diabetes of the young (GCK−MODY)during pregnancy remains unknown. Data regarding maternal and fetal outcomes are lacking. Aim: This paper summarizes the existing literature regarding the maternal and fetal outcomes of women with glucokinase MODY to guide future treatment strategy. Methods: A literature search was conducted in Pubmed, Embace, and Cochrane library with citation follow-up using the terms: glucokinase, MODY, diabetes, pregnancy, gestation, and outcomes. We searched for articles with known fetal mutational status. Relevant outcomes included: birthweight, large for gestational age (LGA), small for gestational age (SGA), macrosomia, cesarean delivery (CD), shoulder dystocia, congenital anomalies, miscarriages, preterm births, and long-term outcomes. Results: Fourteen relevant manuscripts were identified describing maternal and fetal outcomes. The percentage of LGA and macrosomia in 102 glucokinase -unaffected offspring (GCK−) was significantly higher than in the glucokinase -affected offspring (GCK+) (44% vs. 10%, p < 0.001 and 22% vs. 2%, p < 0.001, respectively). Among the 173 GCK(+) offspring, only 5% were SGA, which can be expected according to the normal distribution. We observed higher rates of CD and shoulder dystocia in the GCK(−) offspring. Conclusions: GCK(−) offspring have significantly higher birthweights and more birth complications. The optimal treatment strategy to guide management should take into consideration multiple variables other than fetal mutational status.

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 Childhood Diabetes: Dissecting Clinical Heterogeneity by Next-Generation Sequencing in Maturity-Onset Diabetes of the Young

Diabetes is a common disorder with a heterogeneous clinical presentation and an enormous burden on health care worldwide. About 1-6% of patients with diabetes suffer from maturity-onset diabetes of the young (MODY), the most common form of monogenic diabetes with autosomal dominant inheritance. MODY is genetically and clinically heterogeneous and caused by genetic variations in pancreatic β-cell development and insulin secretion. We report here new findings from targeted next-generation sequencing (NGS) of 13 MODY-related genes. A sample of 22 unrelated pediatric patients with MODY and 13 unrelated healthy controls were recruited from a Turkish population. Targeted NGS was performed with Miseq 4000 (Illumina) to identify genetic variations in 13 MODY-related genes: HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, and KCNJ11. The NGS data were analyzed adhering to the Genome Analysis ToolKit (GATK) best practices pipeline, and variant filtering and annotation were performed. In the patient sample, we identified 43 MODY-specific genetic variations that were not present in the control group, including 11 missense mutations and 4 synonymous mutations. Importantly, and to the best of our knowledge, the missense mutations NEUROD1 p.D202E, KFL11 p.R461Q, BLK p.G248R, and KCNJ11 p.S385F were first associated with MODY in the present study. These findings contribute to the worldwide knowledge base on MODY and molecular correlates of clinical heterogeneity in monogenic childhood diabetes. Further comparative population genetics and functional genomics studies are called for, with an eye to discovery of novel diagnostics and personalized medicine in MODY. Because MODY is often misdiagnosed as type 1 or type 2 diabetes mellitus, advances in MODY diagnostics with NGS stand to benefit diabetes overall clinical care as well.

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.

A Pathophysiology of Type 2 Diabetes Unrelated to Metabolic Syndrome

OBJECTIVE

Clinically, type 2 diabetes mellitus (T2DM) is heterogeneous, but the prevailing pathophysiologic hypothesis nevertheless contends that components of metabolic syndrome are central to all cases of T2DM. Here, we re-evaluated this hypothesis.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional analysis of 138 women from the monocenter, post gestational diabetes study PPSDiab, 73 of which had incident prediabetes or T2DM. Additionally, we examined all the 412 incident cases of T2DM in phases 3 to 9 of the Whitehall II study in comparison to healthy controls. Our analysis included a medical history, anthropometrics, oral glucose tolerance testing, and laboratory chemistry in both studies. Additional analyses from the PPSDiab Study consisted of cardiopulmonary exercise testing, magnetic resonance imaging, auto-antibody testing, and the exclusion of glucokinase maturity-onset diabetes of the young.

RESULTS

We found that 33 (45%) of the women with prediabetes or T2DM in the PPSDiab study displayed no components of metabolic syndrome. They reached no point for metabolic syndrome in the National Cholesterol Education Program Adult Treatment Panel III score other than hyperglycemia and, moreover, had levels of liver fat content, plasma triglycerides, high-density lipoprotein cholesterol, c-reactive protein, and blood pressure that were comparable to healthy controls. In the Whitehall II study, 62 (15%) of the incident T2DM cases fulfilled the same criteria. In both studies, these cases without metabolic syndrome revealed insulin resistance and inadequately low insulin secretion.

CONCLUSIONS

Our results contradict the hypothesis that components of metabolic syndrome are central to all cases of T2DM. Instead, they suggest the common occurrence of a second, unrelated pathophysiology.

Clinical implications of the glucokinase impaired function - GCK MODY today

Heterozygous inactivating mutations of the glucokinase (GCK) gene are causing GCK-MODY, one of the most common forms of the Maturity Onset Diabetes of the Young (MODY). GCK-MODY is characterized by fasting hyperglycemia without apparent worsening with aging and low risk for chronic vascular complications. Despite the mild clinical course, GCK-MODY could be misdiagnosed as type 1 or type 2 diabetes. In the diagnostic process, the clinical suspicion is often based on the clinical diagnostic criteria for GCK-MODY and should be confirmed by DNA analysis. However, there are several issues in the clinical and also in genetic part that could complicate the diagnostic process. Most of the people with GCK-MODY do not require any pharmacotherapy. The exception are pregnant women with a fetus which did not inherit GCK mutation from the mother. Such a child has accelerated growth, and has increased risk for diabetic foetopathy. In this situation the mother should be treated with substitutional doses of insulin. Therefore, distinguishing GCK-MODY from gestational diabetes in pregnancy is very important. For this purpose, special clinical diagnostic criteria for clinical identification of GCK-MODY in pregnancy are used. This review updates information on GCK-MODY and discusses several currently not solved problems in the clinical diagnostic process, genetics, and treatment of this type of monogenic diabetes.

Treatment Options for MODY Patients: A Systematic Review of Literature

Maturity-onset diabetes of the young (MODY) is an unusual form of diabetes with specific features that distinguish it from type 1 and type 2 diabetes. There are 14 known subtypes of MODY, and mutations in three genes (HNF1A, HNF4A, GCK) account for about 95% of all MODY cases. Diagnosis usually occurs before the age of 25 years, although less frequent forms may occur more often-but not necessarily-later in life. The molecular diagnosis may tailor the choice of the most appropriate treatment, with the aim to optimize blood glucose control, reduce the risk of hypoglycemic events and long-term complications, and enable proper genetic counseling. Treatment is usually unnecessary for patients with mutations in the GCK gene, while oral hypoglycemic agents (generally sulphonylureas) are recommended for patients with mutations in the HNF4A and HNF1A genes. More recent data show that other glucose-lowering agents can be effective in the latter patients, and additional and alternative therapies have been proposed. Proper management guidelines during pregnancy have been developed for carriers of GCK gene mutations, but such guidelines are still a subject of debate in other cases, although some recommendations are available. The other subtypes of MODY are even more rare, and very little data are available in the literature. In this review we summarize the most pertinent findings and recommendations on the treatment of patients with the different subtypes of MODY. Our aim is to provide the reader with an easy-to-read update that can be used to drive the clinician's therapeutical approach to these patients after the molecular diagnosis.

Identification of MODY among patients screened for gestational diabetes: a clinician's guide

PURPOSE

Screening of gestational diabetes/GDM (although different in different countries) represents a standard procedure allowing to identify women with pregnancy-associated diabetes. Some of the women with GDM (up to 5%) may, however, suffer from previously undiagnosed MODY (Maturity-Onset Diabetes of the Young). Currently, no international or local guidelines focused on the identification of MODY among GDM exist. Thus, the aim of this manuscript is to propose a clear guide for clinicians on how to detect MODY among pregnant women with gestational diabetes.

METHODS

Based on the available literature about diagnosis (in general population) of MODY and management of MODY (both, in general population and in pregnant women), we propose a clear clinical guide on how to diagnose and manage MODY in pregnancy.

RESULTS

The manuscript suggests a feasible clinical approach how to recognize MODY among patients with GDM and how to manage pregnancy of women with three most common MODY subtypes.

CONCLUSION

A correct classification of diabetes is, nonetheless, essential, particularly in case of MODY, as the management of pregnant women with MODY is different and the correct diagnosis of MODY enables individualized treatment with regard to optimal pregnancy outcomes.

Increased levels of glycosylated hemoglobin, microalbuminuria and serum cystatin C predict adverse outcomes in high-risk pregnancies with gestational diabetes mellitus

In the present study, the predictive value of glycosylated hemoglobin (HbA1c), microalbuminuria (24 h mAlb) and serum cystatin C (Cys-C) levels on the outcome of pregnancy in patients with gestational diabetes mellitus (GDM) was investigated. Samples of 144 females with GDM and 117 normal pregnant females as controls were selected for retrospective analysis. The following parameters were compared between the two groups: Levels of HbA1c, Cys-C and 24 h mAlb, maternal pregnancy outcome and adverse pregnancy rate. The predictive value of elevated 24 h mAlb, HbA1c and Cys-C regarding an adverse pregnancy outcome was then determined. Cys-C, 24 h mAlb and HbA1c levels in the GDM group were significantly higher than those in the control group (P<0.001). The adverse pregnancy rate in the GDM group was significantly higher than that in the control group (40.97 vs. 16.24%; P<0.001). Logistic regression and receiver operating characteristics (ROC) analyses indicated that, in subjects with GDM, HbA1c, Cys-C and 24 h mAlb levels were closely associated with adverse pregnancy outcomes (P<0.050) and may be considered as predictors for an adverse pregnancy outcome (risk ratio >1). Linear correlation analyses indicated that HbA1c, Cys-C and 24 h mAlb were negatively correlated with the neonatal Apgar scores (r=-0.509, -0.954 and -0.954, respectively; P<0.001). According to ROC analysis, the combined predictive sensitivity of HbAlc, Cys-C and 24 h mAlb for adverse pregnancy outcome in patients with GDM was 96.49% and the specificity was 77.19%. The increase in HbAlc, Cys-C and 24 h mAlb levels is expected to be an effective predictor of adverse pregnancy outcomes in high-risk pregnant women.

Circulating miR-330-3p in Late Pregnancy is Associated with Pregnancy Outcomes Among Lean Women with GDM

Gestational Diabetes Mellitus (GDM) is characterised by insulin resistance accompanied by reduced beta-cell compensation to increased insulin demand, typically observed in the second and third trimester and associated with adverse pregnancy outcomes. There is a need for a biomarker that can accurately monitor status and predict outcome in GDM, reducing foetal-maternal morbidity and mortality risks. To this end, circulating microRNAs (miRNAs) present themselves as promising candidates, stably expressed in serum and known to play crucial roles in regulation of glucose metabolism. We analysed circulating miRNA profiles in a cohort of GDM patients (n = 31) and nondiabetic controls (n = 29) during the third trimester for miRNA associated with insulin-secretory defects and glucose homeostasis. We identified miR-330-3p as being significantly upregulated in lean women with GDM compared to nondiabetic controls. Furthermore, increased levels of miR-330-3p were associated with better response to treatment (diet vs. insulin), with lower levels associated with exogenous insulin requirement. We observed miR-330-3p to be significantly related to the percentage of caesarean deliveries, with miR-330-3p expression significantly higher in spontaneously delivered GDM patients. We report this strong novel association of circulating miR-330-3p with risk of primary caesarean delivery as a pregnancy outcome linked with poor maternal glycaemic control, strengthening the growing body of evidence for roles of diabetes-associated miRNAs in glucose homeostasis and adaptation to the complex changes related to pregnancy.

Glucokinase Deficit Prevalence in Women With Diabetes in Pregnancy: A Matter of Screening Selection

Introduction: The prevalence among pregnant women with diabetes of monogenic diabetes due to glucokinase deficit (GCK-MODY) varies from 0 to 80% in different studies, based on the chosen selection criteria for genetic test. New pregnancy-specific Screening Criteria (NSC), validated on an Anglo-Celtic pregnant cohort, have been proposed and include pre-pregnancy BMI <25 kg/m² and fasting glycemia >99 mg/dl. Our aim was to estimate the prevalence of GCK-MODY and to evaluate the diagnostic performance of NSC in our population of women with diabetes in pregnancy. Patients and Methods: We retrospectively selected from our database of 468 diabetic pregnant patients in Sant'Andrea Hospital, in Rome, from 2010 to 2018, all the women who received a genetic test for GCK deficit because of specific clinical features. We estimated the prevalence of GCK-MODY among tested women and the minimum prevalence in our entire population with non-autoimmune diabetes. We evaluated diagnostic performance of NSC on the tested cohort and estimated the eligibility to genetic test based on NSC in the entire population. Results: A total of 409 patients had diabetes in pregnancy, excluding those with autoimmune diabetes; 21 patients have been tested for GCK-MODY, 8 have been positive and 13 have been negative (2 of them had HNF1-alfa mutations and 1 had HNF4-alfa mutation). We found no significant differences in clinical features between positive and negative groups except for fasting glycemia, which was higher in the positive group. The minimum prevalence of monogenic diabetes in our population was 2.4%. The minimum prevalence of GCK-MODY was 1.95%. In the tested cohort, the prevalence of GCK-MODY was 38%. In this group, NSC sensitivity is 87% and specificity is 30%, positive predictive value is 43%, and negative predictive value is 80%. Applying NSC on the entire population of women with non-autoimmune diabetes in pregnancy, 41 patients (10%) would be eligible for genetic test; considering a fasting glycemia >92 mg/dl, 85 patients (20.7%) would be eligible. Discussion: In our population, NSC have good sensitivity but low specificity, probably because there are many GDM with GCK-MODY like features. It is mandatory to define selective criteria with a good diagnostic performance on Italian population, to avoid unnecessary genetic tests.

How can maturity-onset diabetes of the young be identified among more common diabetes subtypes?

Maturity onset diabetes of the young (MODY) represents a diabetes type which has an enormous clinical impact. It significantly alters treatment, refines a patient's prognosis and enables early detection of diabetes in relatives. Nevertheless, when diabetes is manifested the vast majority of MODY patients are not correctly diagnosed, but mostly falsely included among patients with type 1 or type 2 diabetes, in many cases permanently. The aim of this article is to offer a simple and comprehensible guide for recognizing individuals with MODY hidden among adult patients with another type of long-term diabetes and in women with gestational diabetes.

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.

Maturity-onset diabetes of the young (MODY): current perspectives on diagnosis and treatment

Maturity-onset diabetes of the young (MODY) is characterized by autosomal dominant inheritance, onset before 25 years of age, absence of β-cell autoimmunity, and sustained pancreatic β-cell function. To date, mutations have been identified in at least 14 different genes, including six genes encoding proteins that, respectively, correspond to MODY subtypes 1-6: hepatocyte nuclear factor (HNF) 4α (HNF4α), glucokinase (GCK), HNF1α (HNF1 α), pancreatic and duodenal homeobox 1 (PDX1), HNF1β (HNF1 β), and neurogenic differentiation 1 (NEUROD1). Diagnostic tools based on currently available genetic tests can facilitate the correct diagnosis and appropriate treatment of patients with MODY. Candidates for genetic testing include nonobese subjects with hyperglycemia, no evidence of β-cell autoimmunity, sustained β-cell function, and a strong family history of similar-type diabetes among first-degree relatives. Moreover, identification of the MODY subtype is important, given the subtype-related differences in the age of onset, clinical course and progression, type of hyperglycemia, and response to treatment. This review discusses the current perspectives on the diagnosis and treatment of MODY, particularly with regard to the six major subtypes (MODY 1-6).

Characterization of Glucokinase Catalysis from a Pseudo-Dimeric View

Glucose phosphorylation by glucokinase exhibits a sigmoidal dependency on substrate concentration regardless of its simple structure. Dimorph mechanism suggested the existence of two enzymatic states with different catalytic properties, which has been shown to be plausible by structural analysis. However, the dimorph mechanism gives rise to a complicated or non-explicit non-closed mathematical form. It is neither feasible to apply the dimorph mechanism in effector characterizations. To improve the area of glucokinase study with stronger theoretical support and less complication in computation, we proposed the investigation of the enzyme from a pseudo-dimeric angle. The proposed mechanism started from the idealization of two monomeric glucokinase as a dimeric complex, which significantly simplified the glucose phosphorylation kinetics, while the differences in enzyme reconfiguration caused by variable substrates and effectors have been successfully characterized. The study presented a simpler and more reliable way in studying the properties of glucokinase and its effectors, providing guidelines of effector developments for hyperglycemia and hypoglycemia treatment.

Management and pregnancy outcomes of women with GCK-MODY enrolled in the US Monogenic Diabetes Registry

AIMS

GCK-MODY is characterized by mild hyperglycemia. Treatment is not required outside of pregnancy. During pregnancy, insulin treatment is recommended if second trimester fetal ultrasound monitoring shows macrosomia, suggesting the fetus has not inherited the GCK gene. There are limited data about GCK-MODY management in pregnancy. The aim of this study was to examine clinical management and pregnancy outcomes amongst women with a known diagnosis of GCK-MODY.

METHODS

In this observational, cross-sectional study, a survey was distributed via Redcap to women ≥ 18 years enrolled in the University of Chicago Monogenic Diabetes Registry (n = 94). All or part of the survey was completed by 54 women (128 pregnancies).

RESULTS

There were 78 term births (61%), 15 pre-term births (12%), and 24 miscarriages (19%). Of the 39 pregnancies where insulin was given, 22 (56%) had occasional or frequent hypoglycemia including 9 with severe hypoglycemia. Average birth weight for full-term GCK-affected infants was significantly less in cases of maternal insulin treatment versus no treatment (2967 and 3725 g, p = 0.005). For GCK-unaffected infants, conclusions are limited by small sample size but large for gestational age (LGA) was common with maternal insulin treatment (56%) and no treatment (33%), p = 0.590.

CONCLUSIONS

The observed miscarriage rate was comparable to the background US population rate (15-20%). Patients treated with insulin experienced a 23% incidence of severe hypoglycemia and lower birth weights were observed in the insulin-treated, GCK-affected neonates. These data support published guidelines of no treatment if the fetus is suspected to have inherited GCK-MODY and highlight the importance of additional studies to determine optimal pregnancy management for GCK-MODY, particularly among unaffected fetuses.

Diagnosis and management of glucokinase monogenic diabetes in pregnancy: current perspectives

Glucokinase-maturity-onset diabetes of the young (GCK-MODY) is an autosomal dominant disorder caused by heterozygous inactivating GCK gene mutations. GCK-MODY is one the most common MODY subtypes, affecting 0.1% of the population and 0.4-1% of women with gestational diabetes mellitus. Glucokinase is predominantly expressed in pancreatic beta cells and catalyzes the phosphorylation of glucose to glucose-6-phosphate. The unique kinetics of glucokinase enable it to change the rate of glucose phosphorylation according to the glucose concentration, thereby regulating insulin secretion. Individuals with GCK-MODY have mildly elevated fasting blood glucose levels (5.5-8.0 mmol/L) and regulate glucose perturbations to a higher set-point, resulting in a relatively flat glucose profile on a 75 g oral glucose tolerance test. The hyperglycemia is usually subclinical and may only be detected on incidental glucose testing. It is important to correctly identify GCK-MODY as the clinical course and management differs substantially from other types of diabetes. Diabetes-related complications are relatively uncommon, so glucose-lowering treatment is not usually required. The exception is pregnancy, where fetal growth and therefore glucose-lowering treatment are predominantly determined by whether or not the fetus inherits the GCK mutation. The fetal genotype is not usually known but can be inferred from serial fetal ultrasound measurements. If there is evidence of accelerating fetal abdominal circumference on serial ultrasounds, the fetus is assumed to not have the GCK mutation and treatment of maternal hyperglycemia is indicated to reduce the risk of macrosomia, Caesarean section and neonatal hypoglycemia. If there is no evidence of accelerating fetal growth, the fetus is assumed to have inherited the GCK mutation and will have a similarly elevated glucose set-point as their mother, so maternal hyperglycemia is not treated. With recent advances in genetic technology, such as next-generation sequencing and noninvasive fetal genotyping, the detection and management of GCK-MODY in pregnancy should continue to improve.

Monogenic Forms of Diabetes Mellitus

In addition to the common types of diabetes mellitus, two major monogenic diabetes forms exist. Maturity-onset diabetes of the young (MODY) represents a heterogenous group of monogenic, autosomal dominant diseases. MODY accounts for 1-2% of all diabetes cases, and it is not just underdiagnosed but often misdiagnosed to type 1 or type 2 diabetes. More than a dozen MODY genes have been identified to date, and their molecular classification is of great importance in the correct treatment decision and in the judgment of the prognosis. The most prevalent subtypes are HNF1A, GCK, and HNF4A. Genetic testing for MODY has changed recently due to the technological advancements, as contrary to the sequential testing performed in the past, nowadays all MODY genes can be tested simultaneously by next-generation sequencing. The other major group of monogenic diabetes is neonatal diabetes mellitus which can be transient or permanent, and often the diabetes is a part of a syndrome. It is a severe monogenic disease appearing in the first 6 months of life. The hyperglycemia usually requires insulin. There are two forms, permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). In TNDM, the diabetes usually reverts within several months but might relapse later in life. The incidence of NDM is 1:100,000-1:400,000 live births, and PNDM accounts for half of the cases. Most commonly, neonatal diabetes is caused by mutations in KCNJ11 and ABCC8 genes encoding the ATP-dependent potassium channel of the β cell. Neonatal diabetes has experienced a quick and successful transition into the clinical practice since the discovery of the molecular background. In case of both genetic diabetes groups, recent guidelines recommend genetic testing.

Mutational analysis uncovers monogenic bone disorders in women with pregnancy-associated osteoporosis: three novel mutations in LRP5, COL1A1, and COL1A2

Pregnancy was found to be a skeletal risk factor promoting the initial onset of previously unrecognized monogenic bone disorders, thus explaining a proportion of cases with pregnancy-associated osteoporosis. Therapeutic measures should focus in particular on the normalization of the disturbed calcium homeostasis in order to enable the partial skeletal recovery.

INTRODUCTION

Pregnancy-associated osteoporosis (PAO) is a rare skeletal condition, which is characterized by a reduction in bone mineral density (BMD) in the course of pregnancy and lactation. Typical symptoms include vertebral compression fractures and transient osteoporosis of the hip. Since the etiology is not well understood, this prospective study was conducted in order to elucidate the relevance of pathogenic gene variants for the development of PAO.

METHODS

Seven consecutive cases with the diagnosis of PAO underwent a skeletal assessment (blood tests, DXA, HR-pQCT) and a comprehensive genetic analysis using a custom-designed gene panel.

RESULTS

All cases showed a reduced BMD (DXA T-score, lumbar spine - 3.2 ± 1.0; left femur - 2.2 ± 0.5; right femur - 1.9 ± 0.5), while the spine was affected more severely (p < 0.05). The trabecular and cortical thickness was overall reduced in HR-pQCT, while the trabecular number showed no alterations in most cases. The genetic analysis revealed three novel mutations in LRP5, COL1A1, and COL1A2.

CONCLUSION

Our data show that previously unrecognized monogenic bone disorders play an important role in PAO. Pregnancy should be considered a skeletal risk factor, which can promote the initial clinical onset of such skeletal disorders. The underlying increased calcium demand is essential in terms of prophylactic and therapeutic measures, which are especially required in individuals with a genetically determined low bone mass. The implementation of this knowledge in clinical practice can enable the partial recovery of the skeleton. Consistent genetic studies are needed to analyze the frequency of pathogenic variants in women with PAO.

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.

Use of oral antidiabetic drugs in the treatment of maturity-onset diabetes of the young: A mini review

MODY (maturity-onset diabetes of the young) is a genetically linked group of clinically heterogeneous subtypes of diabetes. Roughly 5% of people with diabetes mellitus diagnosed prior to age 45 have MODY diabetes. Most of them have been erroneously diagnosed as patients with either type 1 or type 2 diabetes and, as a result, have been improperly treated. Genetic identification of MODY diabetes and its subtypes allows proper treatment and enables clinicians to switch many patients to oral antidiabetic agents, mainly sulphonylureas. However, some new classes of oral antidiabetic drugs have also been tested and found to be effective in MODY patients. We have searched for research articles and case reports written in full-text English or with an English abstract, using the following keywords: MODY and oral antidiabetic* in the databases Cochrane Library, PubMed, and Science Direct. Therapeutic options using currently standardized oral antidiabetic drugs (mainly sulphonylureas), as well as more experimental treatment with other classes of oral antidiabetic drugs in different types of MODY, are discussed, with special focus on the therapy of the most common MODY subtypes, including specific conditions such as pregnancy. This review article summarizes the currently available information about oral antidiabetic treatment of patients with MODY diabetes.

High Prevalence of Diabetes-Predisposing Variants in MODY Genes Among Danish Women With Gestational Diabetes Mellitus

Context:

Gestational diabetes mellitus (GDM), defined as any degree of glucose intolerance with first recognition during pregnancy, is a heterogeneous form of diabetes characterized by various degrees of β-cell dysfunction.

Objectives:

We aimed to estimate the prevalence of possibly pathogenic variants in the maturity-onset diabetes of the young genes GCK, HNF1A, HNF4A, HNF1B, and INS among women with GDM. Furthermore, we examined the glucose tolerance status in variant carriers vs noncarriers at follow-up.

Design, Setting, and Patients:

We sequenced the coding regions and intron/exon boundaries of GCK, HNF1A, HNF4A, HNF1B, and INS using targeted region capture and next-generation sequencing in 354 Danish women with diet-treated GDM. Glucose tolerance was examined at follow-up 10 years after the index pregnancy.

Main Outcome Measures:

The prevalence of possibly pathogenic variants in GCK, HNF1A, HNF4A, HNF1B, and INS was estimated, and differences in anthropometric traits, high-sensitivity C-Reactive Protein (CRP), and glucose metabolism were measured.

Results:

At baseline, 17 possibly disease-causing variants were found in 21 women, revealing a combined GCK, HNF1A, HNF4A, HNF1B, and INS variant prevalence of 5.9% (95% confidence interval: 3.5% to 8.4%). At follow-up, 15 out of 135 women with diabetes (11%) were carriers of variants in GCK, HNF1A, HNF4A, HNF1B, or INS.

Conclusions:

Almost 6% of Danish women with diet-treated GDM have possibly pathogenic variants in GCK, HNF1A, HNF4A, HNF1B, or INS. These women are at high risk of developing diabetes after pregnancy. Thus screening for variants in GCK, HNF1A, HNF4A, HNF1B, and INS should be considered among women with GDM.

The Genetic Architecture of Diabetes in Pregnancy: Implications for Clinical Practice

The genetic architecture of diabetes mellitus in general and in pregnancy is complex, owing to the multiple types of diabetes that comprise both complex/polygenic forms and monogenic (largely caused by a mutation in a single gene) forms such as maturity-onset diabetes of the young (MODY). Type 1 diabetes (T1D) and type 2 diabetes (T2D) have complex genetic etiologies, with over 40 and 90 genes/loci, respectively, implicated that interact with environmental/lifestyle factors. The genetic etiology of gestational diabetes mellitus has largely been found to overlap that of T2D. Genetic testing for complex forms of diabetes is not currently useful clinically, but genetic testing for monogenic forms, particularly MODY, has important utility for determining treatment, managing risk in family members, and pregnancy management. In particular, diagnosing MODY2, caused by GCK mutations, indicates that insulin should not be used, including during pregnancy, with the possible exception of an unaffected pregnancy during the third trimester to prevent macrosomia. A relatively simple method for identifying women with MODY2 has been piloted. MODY1, caused by HNF4A mutations, can paradoxically cause neonatal hyperinsulinemic hypoglycemia and macrosomia, indicating that detecting these cases is also clinically important. Diagnosing all MODY types provides opportunities for diagnosing other family members.

Monogenic Diabetes: What It Teaches Us on the Common Forms of Type 1 and Type 2 Diabetes

To date, more than 30 genes have been linked to monogenic diabetes. Candidate gene and genome-wide association studies have identified > 50 susceptibility loci for common type 1 diabetes (T1D) and approximately 100 susceptibility loci for type 2 diabetes (T2D). About 1-5% of all cases of diabetes result from single-gene mutations and are called monogenic diabetes. Here, we review the pathophysiological basis of the role of monogenic diabetes genes that have also been found to be associated with common T1D and/or T2D. Variants of approximately one-third of monogenic diabetes genes are associated with T2D, but not T1D. Two of the T2D-associated monogenic diabetes genes-potassium inward-rectifying channel, subfamily J, member 11 (KCNJ11), which controls glucose-stimulated insulin secretion in the β-cell; and peroxisome proliferator-activated receptor γ (PPARG), which impacts multiple tissue targets in relation to inflammation and insulin sensitivity-have been developed as major antidiabetic drug targets. Another monogenic diabetes gene, the preproinsulin gene (INS), is unique in that INS mutations can cause hyperinsulinemia, hyperproinsulinemia, neonatal diabetes mellitus, one type of maturity-onset diabetes of the young (MODY10), and autoantibody-negative T1D. Dominant heterozygous INS mutations are the second most common cause of permanent neonatal diabetes. Moreover, INS gene variants are strongly associated with common T1D (type 1a), but inconsistently with T2D. Variants of the monogenic diabetes gene Gli-similar 3 (GLIS3) are associated with both T1D and T2D. GLIS3 is a key transcription factor in insulin production and β-cell differentiation during embryonic development, which perturbation forms the basis of monogenic diabetes as well as its association with T1D. GLIS3 is also required for compensatory β-cell proliferation in adults; impairment of this function predisposes to T2D. Thus, monogenic forms of diabetes are invaluable "human models" that have contributed to our understanding of the pathophysiological basis of common T1D and T2D.