Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

Clinical characteristics in children with maturity-onset diabetes of the young detected by urine glucose screening at schools in the Tokyo Metropolitan Area

This study aimed to examine the clinical characteristics of young children diagnosed with maturity-onset diabetes (MODY) using urine glucose screening at schools. The study participants were 70 non-obese children who were clinically diagnosed with type 2 diabetes through urine glucose screening at schools in Tokyo between 1974 and 2020. Of these children, 55 underwent genetic testing, and 21 were finally diagnosed with MODY: MODY2 in eight, MODY3 in eight, MODY1 in four and MODY5 in one. A family history of diabetes was found in 76.2% of the patients. Fasting plasma glucose levels did not differ between the different MODY subtypes, while patients with MODY 3, 1, and 5 had significantly higher levels of glycosylated hemoglobin and 2-hour glucose in an oral glucose tolerance test than those with MODY2. In contrast, most patients exhibit mild insulin resistance and sustained β-cell function. In the initial treatment, all patients with MODY2 were well controlled with diet and exercise, whereas the majority of those with MODY3, 1, and 5 required pharmacological treatment within one month of diagnosis. In conclusion, urine glucose screening in schools appears to be one of the best opportunities for early detection of the disease and providing appropriate treatment to patients.

Functional Analysis of a Novel HNF4A Variant Identified in a Patient With MODY1

Context

HNF4A-maturity-onset diabetes of the young (MODY1) is a relatively rare subtype of monogenic diabetes caused by loss of function of the HNF4A gene, which encodes the transcription factor HNF4α. HNF4α is known to form heterodimers, and the various combinations of isoforms that make up these heterodimers have been reported to result in a diversity of targeted genes. However, the function of individual HNF4α variant isoforms and the heterodimers comprising both wild-type (WT) and variant HNF4α have not yet been assessed.

Objective

In this study, we analyzed the functional consequence of the HNF4A D248Y variant in vitro.

Methods

We investigated the case of a 12-year-old Japanese girl who developed diabetes at age 11 years. Genetic sequencing detected a novel heterozygous missense HNF4A variant (c.742G > T, p.Asp248Tyr; referred as "D248Y") in the patient and her relatives who presented with diabetes.

Results

Although the WT HNF4α isoforms (HNF4α2, HNF4α3, HNF4α8, HNF4α9) enhanced the INS gene promoter activity in HepG2 cells, the promoter activity of D248Y was consistently low across all isoforms. The presence of D248Y in homodimers and heterodimers, comprising either HNF4α8 or HNF4α3 or a combination of both isoforms, also reduced the INS promoter activity in Panc-1 cells.

Conclusion

We report the clinical course of a patient with HNF4A-MODY and the functional analysis of novel HNF4A variants, with a focus on the isoforms and heterodimers they form. Our results serve to improve the understanding of the dominant-negative effects of pathogenic HNF4A variants.

Identification of causative gene variants for patients with known monogenic diabetes using a targeted next-generation sequencing panel in a single-center study

Aims

We aimed to verify the usefulness of targeted next-generation sequencing (NGS) technology for diagnosing monogenic diabetes in a single center.

Methods

We designed an amplicon-based NGS panel targeting 34 genes associated with known monogenic diabetes and performed resequencing in 56 patients with autoantibody-negative diabetes mellitus diagnosed at < 50 years who had not been highly obese. By bioinformatic analysis, we filtered significant variants based on allele frequency (< 0.005 in East Asians) and functional prediction. We estimated the pathogenicity of each variant upon considering the family history.

Results

Overall, 16 candidate causative variants were identified in 16 patients. Among them, two previously known heterozygous nonsynonymous single-nucleotide variants associated with monogenic diabetes were confirmed as causative variants: one each in the GCK and WFS1 genes. The former was found in two independent diabetes-affected families. Two novel putatively deleterious heterozygous variants were also assumed to be causative from the family history: one frameshift and one nonsynonymous single-nucleotide variant in the HNF4A gene. Twelve variants remained as candidates associated with the development of diabetes.

Conclusion

Targeted NGS panel testing was useful to diagnose various forms of monogenic diabetes in combination with familial analysis, but additional ingenuity would be needed for practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00669-3.

Partial GCK gene deletion mutations causing maturity-onset diabetes of the young

AIMS

Maturity-onset diabetes of the young (MODY) is an autosomal dominant monogenic form of diabetes, and glucokinase-maturity-onset diabetes of the young (GCK-MODY), or MODY 2, being the most prevalent type. However, the presence of copy number variants (CNVs) may lead to misdiagnoses, as genetic testing for MODY is typically reliant on sequencing techniques. This study aimed to describe the process of diagnosis in a Chinese pedigree with an exon 8-10 deletion of the GCK gene.

METHODS

This study collected clinical data and medical history through direct interviews with the patient and reviewing relevant medical records. Sanger sequencing and whole exome sequencing (WES) were conducted over years of follow up. WES-based CNV sequencing technology was used to detect CNVs and the results were validated by multiplex ligation-dependent amplification dosage assay (MLPA). Additionally, we reviewed the previously reported cases caused by heterozygous exon deletion of the GCK gene.

RESULTS

WES-based CNV detection revealed a heterozygous exon 8-10 deletion in the GCK gene within this particular pedigree after Sanger sequencing and WES failed to find causal variants in single nucleotide variations (SNVs) and small indels. The deletion was considered pathogenic according to ACMG/AMP and ClinGen guidelines. Most of the previously reported cases caused by heterozygous exon deletion or whole gene deletion of the GCK gene present similarly to GCK-MODY caused by SNVs and small indels.

CONCLUSIONS

This study contributed to progress in our comprehension of the mutation spectrum of the GCK gene and underscored the significance of CNV detection in the genetic testing of MODY.

Two novel GCK mutations in Chinese patients with maturity-onset diabetes of the young

PURPOSE

Heterozygous inactivating mutations in the glucokinase (GCK) gene result in the asymptomatic fasting hyperglycemia named as GCK-MODY or MODY2. The genetic testing can effectively avoid the misdiagnosis and inappropriate treatment for GCK-MODY.

METHODS

A total of 25 unrelated families with MODY were screened for mutations in coding region of GCK by using direct sequencing. Three different bioinformatics tools such as PolyPhen2, Mutation Taster and PROVEAN were performed to predict the function of mutant proteins. The glucose profile was recorded by continuous glucose monitoring system (CGMS) to evaluate the glycemic variability for the GCK-MODY patient.

RESULTS

Our study identified five GCK mutations in 24% of the families (6/25): two novel mutations (I126fs and G385A) and three already described mutations (G44S, H50fs and S383L). In silico analyses predicted that these mutations altered structural conformational changes. The values of mean amplitude of glycemic excursions (MAGE), an important index of blood glucose fluctuation in CGMS system, were 0.81 in the first 24 h and 1.61 in the second 24 h record in the patient with GCK-MODY (F3), suggesting little glucose fluctuation.

CONCLUSION

The genetic testing is suggested to be important to differentiate GCK-MODY from other types of diabetes. CGMS might be used to screen GCK-MODY cases prior to genetic testing.

Genetic and Epigenetic Factors in Gestational Diabetes Mellitus Pathology

Gestational diabetes (GDM) is the carbohydrate intolerance occurring during pregnancy. The risk factors of GDM include obesity, advanced maternal age, polycystic ovary syndrome, multigravidity, a sedentary lifestyle, and pre-existing hypertension. Additionally, complex genetic and epigenetic processes are also believed to play a crucial role in the development of GDM. In this narrative review, we discuss the role of genetic and epigenetic factors in gestational diabetes mellitus pathogenesis.

Treatment strategy for maturity-onset diabetes of the young 3 (MODY3): Experience with two sisters and their mother

Maturity onset diabetes of the young (MODY) is a relatively young-onset diabetes mellitus with an autosomal dominant inheritance. Among these phenotypes, MODY3, caused by mutations in HNF1A, is one of the most frequent. Although MODY3 is known to respond markedly to sulfonylureas (SU), many cases require insulin therapy. However, there are no clear guidelines for factors to consider when introducing antidiabetic drugs and insulin. This report describes a familial case in which an older sister was diagnosed with diabetes and subsequently with MODY3, followed by the onset of diabetes in the younger sister and mother. The elder sister initially denied insulin treatment and exhibited a suboptimal response to SU but finally agreed to insulin use. The mother initially selected insulin therapy because of the challenges associated with adherence to strict dietary therapy. Conversely, the younger sister responded positively to SU and maintained effective glycemic control. The management of MODY3, even though they have the same single-gene mutation and similar residual insulin secretion at diagnosis, should be flexibly individualized for each family member to ensure long-term adherence and appropriate glycemic control.

The Genetic Spectrum of Maturity-Onset Diabetes of the Young (MODY) in Qatar, a Population-Based Study

Maturity-onset diabetes of the young (MODY) is a rare monogenic form of diabetes mellitus. In this study, we estimated the prevalence and genetic spectrum of MODY in the Middle Eastern population of Qatar using whole-genome sequencing (WGS) of 14,364 subjects from the population-based Qatar biobank (QBB) cohort. We focused our investigations on 14 previously identified genes ascribed to the cause of MODY and two potentially novel MODY-causing genes, RFX6 and NKX6-1. Genetic variations within the 16 MODY-related genes were assessed for their pathogenicity to identify disease-causing mutations. Analysis of QBB phenotype data revealed 72 subjects (0.5%) with type 1 diabetes, 2915 subjects (20.3%) with type 2 diabetes and 11,377 (79.2%) without diabetes. We identified 22 mutations in 67 subjects that were previously reported in the Human Genetic Mutation Database (HGMD) as disease-causing (DM) or likely disease causing (DM?) for MODY. We also identified 28 potentially novel MODY-causing mutations, predicted to be among the top 1% most deleterious mutations in the human genome, which showed complete (100%) disease penetrance in 34 subjects. Overall, we estimated that MODY accounts for around 2.2-3.4% of diabetes patients in Qatar. This is the first population-based study to determine the genetic spectrum and estimate the prevalence of MODY in the Middle East. Further research to characterize the newly identified mutations is warranted.

Targeted gene panel analysis of Japanese patients with maturity-onset diabetes of the young-like diabetes mellitus: Roles of inactivating variants in the ABCC8 and insulin resistance genes

AIMS/INTRODUCTION

To investigate the genetic background of Japanese patients with suspected maturity-onset diabetes of the young (MODY).

MATERIALS AND METHODS

On 340 proband patients referred from across Japan, genomic variants were analyzed using a targeted multigene panel analysis combined with the multiplex ligation probe amplification (MLPA) analysis, mitochondrial m.3243A > G analysis and methylation-specific polymerase chain reaction of the imprinted 6q24 locus. Pathogenic/likely pathogenic variants were listed according to the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria. Additionally, variants with a population frequency <0.001 and Combined Annotation Dependent Depletion score >20 (CS >20) were listed as rare variants of uncertain significance-CS >20.

RESULTS

A total of 157 pathogenic/likely pathogenic variants and 44 rare variants of uncertain significance-CS >20 were identified. In the pathogenic/likely pathogenic variants, alterations in the GCK gene were the most common (82, 52.2%) followed by HNF1A (29, 18.5%), HNF4A (13, 8.3%) and HNF1B (13, 8.3%). One patient was a 29.5% mosaic with a truncating INSR variant. In the rare variants of uncertain significance-CS >20, 20 (45.5%) were in the genes coding for the adenosine triphosphate-sensitive potassium channel, KCNJ11 or ABCC8, and four were in the genes of the insulin-signaling pathway, INSR and PIK3R1. Four variants in ABCC8 were previously reported in patients with congenital hyperinsulinism, suggesting the inactivating nature of these variants, and at least two of our patients had a history of congenital hyperinsulinism evolving into diabetes. In two patients with INSR or PIK3R1 variants, insulin resistance was evident at diagnosis.

CONCLUSIONS

Causative genomic variants could be identified in at least 46.2% of clinically suspected MODY patients. ABCC8-MODY with inactivating variants could represent a distinct category of MODY. Genes of insulin resistance should be included in the sequencing panel for MODY.

An effective preselection criterion for MODY with an increasingly positive genetic testing rate by NGS: results from two cohorts of Chinese children

The purpose of this study was to determine the frequency of maturity-onset diabetes of the young (MODY) in two selected cohorts of Chinese children with diabetes and clinically suspected MODY, using next-generation sequencing (NGS). Ninety-three children who met the comprehensive criteria of suspected MODY were enrolled in two cohorts. A custom NGS panel or a whole exon group was used for sequencing. We identified 55/93 (59.1%) children with pathogenic and likely pathogenic MODY variants. Forty-two (76.3%) were confirmed to have the GCK (MODY2) mutation. Additionally, five had the HNF1A (MODY3), two the HNF1B (MODY5), one the 17q12 microdeletion (MODY5), two the HNF4A (MODY1), two the ABCC8 (MODY12), and one the PDX1 mutation (MODY4). Of these, 13 novel variants were detected in different genes. By comparing the gene-positive with gene-negative children, we found that discriminatory factors for MODY at diagnosis included lower HbA1c [7.4% vs. 10.2% (53 vs. 86 mmol/mol); P = 0.002], lower body mass index z score (0.2 vs. 1.0; P = 0.01), lower onset age (8.1 vs. 11.2 years; P = 0.001), and lower C-peptide (1.4 vs. 2.5 ng/mL; P = 0.02). In conclusion, the criteria used in this study for screening MODY are effective, and MODY2 is the most common subtype (76%), followed by MODY3 and MODY5. Some rare MODY subtypes have been reported in Chinese children.NEW & NOTEWORTHY We proved the clinical suspicion of maturity-onset diabetes of the young (MODY) according to the comprehensive criterion for next-generation sequencing testing, which helps to identify both common and rare MODYs, leading to accurate diagnosis and personalized treatment.

A Novel GCK Large Genomic Rearrangement in a Patient with MODY-2 Detected by Clinical Exome Sequencing

Maturity-onset diabetes of the young (MODY) is a rare form of non-autoimmune diabetes with an autosomal dominant inheritance. To date, 14 genes have been reported as genetic basis of MODY. GCK gene, encoding the glucokinase enzyme, was the first MODY gene to be identified. GCK heterozygous inactivating variants cause the GCK-MODY or MODY2 subtype. However, partial or whole gene deletions have been rarely identified, showing it to be a rare cause of GCK-MODY. We reported the molecular evaluation of a Ukrainian patient with clinical diagnosis of MODY2. We performed the Next generation sequencing of the clinical exome using the Clinical Exome Solution® kit (SOPHiA Genetics), followed by the design of a 14 genes virtual panel related to the suggestive diagnosis of MODY. Bioinformatics analysis was performed using the SOPHiA DDM platform (SOPHiA Genetics). The SALSA MLPA kit for MODY (MRC-Holland) was used for relative quantification of GCK exons. From the molecular evaluation, no pathogenic sequence variants were detected in the investigated genes. Copy Number Variation analysis was able to identify a large deletion involving the last three exons of the GCK gene. This result was confirmed by MLPA. To the best of our knowledge, the identified rearrangement has never been reported in the literature.

Precision diabetes: Lessons learned from maturity-onset diabetes of the young (MODY)

Maturity-onset of diabetes of the young (MODY) are monogenic forms of diabetes characterized by early onset diabetes with autosomal dominant inheritance. Since its first description about six decades ago, there have been significant advancements in our understanding of MODY from clinical presentations to molecular diagnostics and therapeutic responses. The prevalence of MODY is estimated as at least 1.1-6.5% of the pediatric diabetes population with a high degree of geographic variability that might arise from several factors in the criteria used to ascertain cases. GCK-MODY, HNF1A-MODY, and HNF4A-MODY account for >90% of MODY cases. While some MODY forms do not require treatment (i.e., GCK-MODY), some others are highly responsive to oral agents (i.e., HNF1A-MODY). The risk of micro- and macro-vascular complications of diabetes also differ significantly between MODY forms. Despite its high clinical impact, 50-90% of MODY cases are estimated to be misdiagnosed as type 1 or type 2 diabetes. Although there are many clinical features suggestive of MODY diagnosis, there is no single clinical criterion. An online MODY Risk Calculator can be a useful tool for clinicians in the decision-making process for MODY genetic testing in some situations. Molecular genetic tests with a commercial gene panel should be performed in cases with a suspicion of MODY. Unresolved atypical cases can be further studied by exome or genome sequencing in a clinical or research setting, as available.

Childhood-onset mild diabetes caused by a homozygous novel variant in the glucokinase gene

PURPOSE

Heterozygous loss-of-function mutations in the glucokinase (GCK) gene cause MODY 2, which is characterized by asymptomatic fasting hyperglycemia and does not require insulin treatment. Conversely, homozygous loss-of-function mutations in the same gene give rise to permanent neonatal diabetes mellitus (DM) that appears in the first 6-9 months of life and necessitates lifelong insulin treatment. We aimed to present the genotypic and phenotypic features of a 13-year-old patient diagnosed with DM at the age of 3 years due to a homozygous variant in the GCK gene.

METHODS

The patient's clinical and laboratory findings at follow-up were not consistent with the initial diagnosis of type 1 DM; thus, next-generation sequencing of MODY genes (GCK, HNF1A, HNF1B, and HNF4A genes) was performed to identify monogenic causes of DM.

RESULTS

A novel homozygous variant c.1222 G > T in the GCK gene was revealed. In silico analysis identified it as a pathogenic variant. His mother, father, and brother had the same heterozygous variant in the GCK gene and were diagnosed with MODY 2 (mild fasting hyperglycemia and elevated HbA1c) after genetic counseling.

CONCLUSION

In this case report, a patient with a homozygous variant in the GCK gene, who was diagnosed with DM after the infantile period, was presented, highlighting the fact that cases with homozygous variants in the GCK gene can, though rarely, present at a later age with a milder phenotype.

Identification of Variants Responsible for Monogenic Forms of Diabetes in Brazil

Monogenic forms of diabetes mellitus may affect a significant number of patients of this disease, and it is an important molecular cause to be investigated. However, studies of the genetic causes of monogenic diabetes, especially in populations with mixed ethnic backgrounds, such as the one in Brazil, are scarce. The aim of this study was to screen several genes associated with monogenic diabetes in fifty-seven Brazilian patients with recurrence of the disease in their families and thirty-four relatives. Inclusion criteria were: Age of onset ≤ 40 years old, BMI < 30 kg/m², at least two affected generations and negative anti-GAD and anti-IA2 antibodies. MODY genes HNF4A, GCK, HNF1A, HNF1B, NEUROD1, KLF11, PAX4, INS, KCNJ11, and MT-TL1 were sequenced by Sanger sequencing. We identified a total of 20 patients with variants, 13 GCK-MODY, four HNF1A-MODY, and one variant in each of the following genes, HNF4A, HNF1B and MT-TL1. Segregation analysis was performed in 13 families. Four variants were novel, two in GCK (p.(Met115Val) [c.343A>G] and p.(Asp365GlufsTer95) [c.1094_1095insGCGA]) and two in HNF1A (p.(Tyr163Ter) [c.489C>G] and p.(Val380CysfsTer39) [c.1136_1137insC]). Here we highlight the importance of screening for monogenic diabetes in admixed populations.

Clinical Characteristics of Patients With HNF1-alpha MODY: A Literature Review and Retrospective Chart Review

The clinical manifestation of hepatocyte nuclear factor-1-alpha (HNF1-alpha) maturity-onset diabetes of the young (MODY) is highly variable. This study aims to investigate the clinical characteristics of patients with HNF1-alpha MODY in general, by geographical regions (Asian or non-Asian), HNF1-alpha mutations, and islet autoantibody status. A literature review and a chart review of patients with HNF1-alpha MODY were performed. The means and proportions from studies were pooled using the inverse variance method for pooling, and subgroup analyses were performed. A total of 109 studies involving 1,325 patients [41.5%, 95% confidence interval (CI): 35.2, 48.1; male] were identified. The mean age of diagnosis was 20.3 years (95% CI: 18.3-22.2), and the mean glycated hemoglobin was 7.3% (95% CI: 7.2-7.5). In comparison, Asian patients exhibited significantly higher HbA1c (p = 0.007) and 2-h post-load C-peptide (p = 0.012) levels and lower levels of triglyceride (TG) (p < 0.001), total cholesterol (TC) (p < 0.001), and high-density lipoprotein cholesterol (HDL-c) (p < 0.001) and less often had macrovascular complications (p = 0.014). The age of diagnosis was oldest in patients with mutations in the transactivation domain (p < 0.001). The levels of 2-h post-load C-peptide (p < 0.001), TG (p = 0.007), TC (p = 0.017), and HDL-c (p = 0.001) were highest and the prevalence of diabetic neuropathy was lowest (p = 0.024) in patients with DNA-binding domain mutations. The fasting (p = 0.004) and 2-h post-load glucose (p = 0.003) levels and the prevalence of diabetic neuropathy (p = 0.010) were higher among patients with positive islet autoantibodies. The study demonstrated that the clinical manifestations of HNF1-alpha MODY differed by geographical regions, HNF1-alpha mutations, and islet autoantibody status.

A case report with functional characterization of a HNF1B mutation (p.Leu168Pro) causing MODY5

We previously performed next-generation sequencing-based genetic screening in patients with autoantibody-negative type 1 diabetes, and identified the p.Leu168Pro mutation in HNF1B. Here,we report the clinical course of the patient and the results of functional characterization of this mutation. The proband had bilateral renal hypodysplasia and developed insulin-dependent diabetes during childhood. The pathogenicity of Leu168Pro-HNF1B was evaluated with three-dimensional structure modeling, Western blotting, immunofluorescence analysis and luciferase reporter assays using human embryonic kidney 293 cells. Three-dimensional structure modeling predicted that the Leu168 residue is buried in the DNA-binding Pit-Oct-Unc-specific (POU_S) domain and forms a hydrophobic core. Western blotting showed that the protein expression level of Leu168Pro-HNF1B was lower than that of wild-type (WT) HNF1B. Immunofluorescence staining showed that both WT- and Leu168Pro-HNF1B were normally localized in the nucleus. The cells transfected with WT-HNF1B exhibited 5-fold higher luciferase reporter activity than cells transfected with an empty vector. The luciferase activities were comparable between WT-HNF1B/Leu168Pro-HNF1B and WT-HNF1B/empty vector co-transfection. In conclusion, Leu168Pro is a protein-destabilizing HNF1B mutation, and the destabilization is likely due to the structural changes involving the hydrophobic core of POU_S. The disease-causing Leu168Pro HNF1B mutation is a loss-of-function mutation without a dominant-negative effect.

A Comprehensive Analysis of Hungarian MODY Patients-Part I: Gene Panel Sequencing Reveals Pathogenic Mutations in HNF1A, HNF1B, HNF4A, ABCC8 and INS Genes

Maturity-onset diabetes of the young (MODY) has about a dozen known causal genes to date, the most common ones being HNF1A, HNF4A, HNF1B and GCK. The phenotype of this clinically and genetically heterogeneous form of diabetes depends on the gene in which the patient has the mutation. We have tested 450 Hungarian index patients with suspected MODY diagnosis with Sanger sequencing and next-generation sequencing and found a roughly 30% positivity rate. More than 70% of disease-causing mutations were found in the GCK gene, about 20% in the HNF1A gene and less than 10% in other MODY-causing genes. We found 8 pathogenic and 9 likely pathogenic mutations in the HNF1A gene in a total of 48 patients and family members. In the case of HNF1A-MODY, the recommended first-line treatment is low dose sulfonylurea but according to our data, the majority of our patients had been on unnecessary insulin therapy at the time of requesting their genetic testing. Our data highlights the importance of genetic testing in the diagnosis of MODY and the establishment of the MODY subtype in order to choose the most appropriate treatment.

Maturity Onset Diabetes of the Young-New Approaches for Disease Modelling

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous group of monogenic endocrine disorders that is characterised by autosomal dominant inheritance and pancreatic β-cell dysfunction. These patients are commonly misdiagnosed with type 1 or type 2 diabetes, as the clinical symptoms largely overlap. Even though several biomarkers have been tested none of which could be used as single clinical discriminator. The correct diagnosis for individuals with MODY is of utmost importance, as the applied treatment depends on the gene mutation or is subtype-specific. Moreover, in patients with HNF1A-MODY, additional clinical monitoring can be included due to the high incidence of vascular complications observed in these patients. Finally, stratification of MODY patients will enable better and newer treatment options for MODY patients, once the disease pathology for each patient group is better understood. In the current review the clinical characteristics and the known disease-related abnormalities of the most common MODY subtypes are discussed, together with the up-to-date applied diagnostic criteria and treatment options. Additionally, the usage of pluripotent stem cells together with CRISPR/Cas9 gene editing for disease modelling with the possibility to reveal new pathophysiological mechanisms in MODY is discussed.

Tunisian Maturity-Onset Diabetes of the Young: A Short Review and a New Molecular and Clinical Investigation

INTRODUCTION/AIMS

Maturity-Onset Diabetes of the Young (MODY) is a monogenic non-autoimmune diabetes with 14 different genetic forms. MODY-related mutations are rarely found in the Tunisian population. Here, we explored MODY related genes sequences among seventeen unrelated Tunisian probands qualifying the MODY clinical criteria.

MATERIALS AND METHODS

The GCK and HNF1A genes were systematically analyzed by direct sequencing in all probands. Then, clinical exome sequencing of 4,813 genes was performed on three unrelated patients. Among them, 130 genes have been reported to be involved in the regulation of glucose metabolism, β-cell development, differentiation and function. All identified variants were analyzed according to their frequencies in the GnomAD database and validated by direct sequencing.

RESULTS

We identified the previously reported GCK mutation (rs1085307455) in one patient. The clinical features of the MODY2 proband were similar to previous reports. In this study, we revealed rare and novel alterations in GCK (rs780806456) and ABCC8 (rs201499958) genes with uncertain significance. We also found two likely benign alterations in HNF1A (rs1800574) and KLF11 (rs35927125) genes with minor allele frequencies similar to those depicted in public databases. No pathogenic variants have been identified through clinical exome analysis.

CONCLUSIONS

The most appropriate patients were selected, following a strict clinical screening approach, for genetic testing. However, the known MODY1-13 genes could not explain most of the Tunisian MODY cases, suggesting the involvement of unidentified genes in the majority of Tunisian affected families.

Identification of Novel GCK and HNF4α Gene Variants in Japanese Pediatric Patients with Onset of Diabetes before 17 Years of Age

BACKGROUND

Maturity-onset diabetes of the young (MODY) is commonly misdiagnosed as type 1 or type 2 diabetes. Common reasons for misdiagnosis are related to limitations in genetic testing. A precise molecular diagnosis is essential for the optimal treatment of patients and allows for early diagnosis of their asymptomatic family members.

OBJECTIVE

The aim of this study was to identify rare monogenic variants of common MODY genes in Japanese pediatric patients.

METHODS

We investigated 45 Japanese pediatric patients based on the following clinical criteria: development of diabetes before 17 years of age, a family history of diabetes, testing negative for glutamate decarboxylase-65 (GAD 65) antibodies and insulinoma-2-associated autoantibodies (IA-2A), no significant obesity, and evidence of endogenous insulin production. Genetic screening for MODY1 (HNF4α), MODY2 (GCK), MODY3 (HNF1α), and MODY5 (HNF1β) was performed by direct sequencing followed by multiplex ligation amplification assays.

RESULTS

We identified 22 missense variants (3 novel variants) in 27 patients (60.0%) in the GCK, HNF4α, and HNF1α genes. We also detected a whole exon deletion in the HNF1β gene and an exon 5-6 aberration in the GCK gene, each in one proband (4.4%). There were a total of 29 variations (64.4%), giving a relative frequency of 53.3% (24/45) for GCK, 2.2% (1/45) for HNF4α, 6.7% (3/45) for HNF1α, and 2.2% (1/45) for HNF1β genes.

CONCLUSIONS

Clinicians should consider collecting and assessing detailed clinical information, especially regarding GCK gene variants, in young antibody-negative patients with diabetes. Correct molecular diagnosis of MODY better predicts the clinical course of diabetes and facilitates individualized management.

Monogenic diabetes characteristics in a transnational multicenter study from Mediterranean countries

BACKGROUND

Diagnosis of monogenic diabetes has important clinical implications for treatment and health expenditure. However, its prevalence remains to be specified in many countries, particularly from South Europe, North Africa and Middle-East, where non-autoimmune diabetes in young adults is increasing dramatically.

AIMS

To identify cases of monogenic diabetes in young adults from Mediterranean countries and assess the specificities between countries.

METHODS

We conducted a transnational multicenter study based on exome sequencing in 204 unrelated patients with diabetes (age-at-diagnosis: 26.1 ± 9.1 years). Rare coding variants in 35 targeted genes were evaluated for pathogenicity. Data were analyzed using one-way ANOVA, chi-squared test and factor analysis of mixed data.

RESULTS

Forty pathogenic or likely pathogenic variants, 14 of which novel, were identified in 36 patients yielding a genetic diagnosis rate of 17.6%. The majority of cases were due to GCK, HNF1A, ABCC8 and HNF4A variants. We observed highly variable diagnosis rates according to countries, with association to genetic ancestry. Lower body mass index and HbA1c at study inclusion, and less frequent insulin treatment were hallmarks of pathogenic variant carriers. Treatment changes following genetic diagnosis have been made in several patients.

CONCLUSIONS

Our data from patients in several Mediterranean countries highlight a broad clinical and genetic spectrum of diabetes, showing the relevance of wide genetic testing for personalized care of early-onset diabetes.

Delineation of the genetic and clinical spectrum, including candidate genes, of monogenic diabetes: a multicenter study in South Korea

OBJECTIVES

Monogenic diabetes includes a group of heterogeneous diabetes types. We aimed to identify the frequency, clinical and molecular features of monogenic diabetes in a Korean pediatric cohort.

METHODS

A retrospective cohort and multicenter study of Korean children suspected to have monogenic diabetes, managed by four pediatric endocrine centers in the southeast region of South Korea, from February 2016 to February 2020. We recruited 27 pediatric Korean patients suspected to have monogenic diabetes who had at least two of the following three criteria (age at diagnosis, family history, and clinical presentation). Targeted exome sequencing was conducted in these patients. The functional consequences of the variants were predicted by bioinformatics and protein structure analysis.

RESULTS

Molecular genetic analysis identified 16 patients (59.3%) with monogenic diabetes. We identified a total of eight unique variants, including five novel variants (HNF4A c.1088C>T, CEL c.1627C>T and c.1421C>T, PAX4 c.538+8G>C, INS c.71C>T). We also identified two potential candidate gene variants for monogenic diabetes, namely c.650T>C in the SLC2A2 gene and c.629G>A in the PTF1A gene. Other variants were identified in the WFS1and NPHP3 genes in two rare genetic disorders. Variant-positive individuals had a lower presence of autoantibody positivity at the time of diagnosis and higher glycosylated hemoglobin levels at last follow-up when compared to variant-negative patients (p<0.001 and p=0.029, respectively).

CONCLUSIONS

These results further expand the spectrum of known variants as well as potential candidate gene variants associated with monogenic diabetes in Korea.

Update on Monogenic Diabetes in Korea

Monogenic diabetes, including maturity-onset diabetes of the young, neonatal diabetes, and other rare forms of diabetes, results from a single gene mutation. It has been estimated to represent around 1% to 6% of all diabetes. With the advances in genome sequencing technology, it is possible to diagnose more monogenic diabetes cases than ever before. In Korea, 11 studies have identified several monogenic diabetes cases, using Sanger sequencing and whole exome sequencing since 2001. The recent largest study, using targeted exome panel sequencing, found a molecular diagnosis rate of 21.1% for monogenic diabetes in clinically suspected patients. Mutations in glucokinase (GCK), hepatocyte nuclear factor 1α (HNF1A), and HNF4A were most commonly found. Genetic diagnosis of monogenic diabetes is important as it determines the therapeutic approach required for patients and helps to identify affected family members. However, there are still many challenges, which include a lack of simple clinical criterion for selecting patients for genetic testing, difficulties in interpreting the genetic test results, and high costs for genetic testing. In this review, we will discuss the latest updates on monogenic diabetes in Korea, and suggest an algorithm to screen patients for genetic testing. The genetic tests and non-genetic markers for accurate diagnosis of monogenic diabetes will be also reviewed.

Maturity-Onset diabetes of the young type 5 treated with the glucagon-like peptide-1 receptor agonist: A case report

RATIONALE

Maturity-onset diabetes of the young type 5 (MODY 5) is a form of monogenic diabetes that is often accompanied by pancreatic dysfunction. To date, no cases of MODY 5 treated with glucagon-like peptide-1 receptor agonist (GLP-1RA) have been reported. We present the first case of MODY 5 treated with GLP-1RA.

PATIENT CONCERNS

A 17-year-old woman, with a history of being operated for congenital ileal atresia at birth, was admitted to our hospital due to hyperglycemia. She had been clinically diagnosed with type 1 diabetes 1 month prior, and administered 14 units of insulin glargine 300 U/mL per day.

DIAGNOSIS

She had hypopotassemia, hypomagnesaemia, pancreatic body, and tail defects, multiple renal cysts, and a family history of diabetes, and urogenital anomaly. Genetic testing revealed heterozygous deletion of hepatocyte nuclear transcription factor-1 beta, leading to the diagnosis of MODY 5.

INTERVENTIONS

The patient was treated with multiple daily insulin injections for 9 days (22 units/d) before administration of GLP-1RA, and then liraglutide was initiated.

OUTCOMES

Liraglutide treatment (0.6 mg/d) alone maintained the patient's glycated hemoglobin level below 7.0% for at least 12 months after discharge. A higher dose, 0.9 mg/d, of liraglutide was not tolerated by the patient due to nausea. Serum levels of C-peptide immunoreactivity were 1.15 ng/mL and 1.91 ng/mL, respectively, after 6 and 12 months of liraglutide therapy.

LESSONS

GLP-1RA might be effective at regulating glucose metabolism by utilizing residual pancreatic endocrine function in patients with MODY 5. Imaging and genetic screening were helpful in the diagnosis of MODY 5.

MODY2 in Asia: analysis of GCK mutations and clinical characteristics

AIMS

Heterozygous inactivating mutations in the GCK gene cause the familial, mild fasting hyperglycaemia named MODY2. Many patients with MODY2 in Asia have delayed timely treatment because they did not receive the correct diagnosis. This study aims to analyze the clinical characteristics and GCK mutations in Asian MODY2.

METHODS

We have collected 110 Asian patients with MODY2 from the PubMed, Embase, Medline, Web of Science, CNKI, and Wanfang with the following search terms: 'maturity-onset diabetes of the young' OR 'MODY' OR 'maturity-onset diabetes of the young type 2' OR 'MODY2' OR 'GCK-DM' OR 'GCK-MODY'. Both mutations of GCK and clinical characteristics of MODY2 were analyzed.

RESULTS

There were 96 different mutations that occurred in coding regions and non-coding regions. Exon 5 and 7 were the most common location in coding regions and missense was the primary mutation type. The proportion of probands younger than 25 was 81.8%, and 81.4% of the probands had family history of hyperglycaemia. Ninety percent and 93% of Asian MODY2 probands exhibited mild elevation in FPG (5.4-8.3 mmol/L) and HbA1c (5.6-7.6%), respectively.

CONCLUSIONS

In most Asian patients, MODY2 occurred due to GCK mutation in coding regions, and exon 5 and 7 were the most common locations. FPG, HbA1c, and familial diabetes were important reference indicators for diagnosing MODY2. Altogether, the study indicates that for the young onset of diabetes with mild elevated blood glucose and HbA1c and family history of hyperglycaemia, molecular genetic testing is suggested in order to differentiate MODY2 from other types of diabetes earlier.

Molecular diagnosis of maturity-onset diabetes of the young in a cohort of Chinese children

OBJECTIVE

The purpose of this study was to investigate the molecular basis of maturity-onset diabetes of the young (MODY) by whole-exome sequencing (WES) and estimate the frequency and describe the clinical characteristics of MODY in southern China.

METHODS

Genetic analysis was performed in 42 patients with MODY aged 1 month to 18 years among a cohort of 759 patients with diabetes, identified with the following four clinical criteria: age of diagnosis ≤18 years; negative pancreatic autoantibodies; family history of diabetes; or persistently detectable C-peptide; or diabetes associated with extrapancreatic features. GCK gene mutations were first screened by Sanger sequencing. GCK mutation-negative patients were further analyzed by WES.

RESULTS

Mutations were identified in 24 patients: 20 mutations in GCK, 1 in HNF4A, 1 in INS, 1 in ABCC8, and a 17q12 microdeletion. Four previously unpublished novel GCK mutations: c.1108G>C in exon 9, and c.1339C>T, c.1288_1290delCTG, and c.1340_1343delGGGGinsCTGGTCT in exon 10 were detected. WES identified a novel missense mutation c.311A>G in exon 3 in the INS gene, and copy number variation analysis detected a 1.4 Mb microdeletion in the long arm of the chromosome 17q12 region. Compared with mutation-negative subjects, the mutation-positive subjects had lower hemoglobin A1c and initial blood glucose levels.

CONCLUSIONS

Most MODY cases in this study were due to GCK mutations, which is in contrast to previous reports in Chinese patients. Diabetes associated with extrapancreatic features should be a clinical criterion for MODY genetic analysis. Mutational analysis by WES provided a precise diagnosis of MODY subtypes. Moreover, WES can be useful for detecting large deletions in coding regions in addition to point mutations.

ABCC8-Related Maturity-Onset Diabetes of the Young (MODY12): A Report of a Chinese Family

Maturity-onset diabetes mellitus of the young (MODY) is a monogenic diabetes characterized by autosomal dominant inheritance. Its atypical clinical features make diagnosis difficult and it can be misdiagnosed as type 1 or type 2 diabetes. Fourteen subtypes of MODY have been diagnosed so far, of which MODY12 is caused by mutation of the ABCC8 (ATP Binding Cassette Subfamily C Member 8) gene, which is rarely reported in China. This paper reports a Chinese family of MODY12 caused by a rare missense mutation on the ABCC8 gene, which has not been reported to be associated with MODY in China or in other countries, with the aim of increasing clinicians' awareness and attention to the disease.

Maturity-Onset Diabetes of the Young Identified Among Algerian Probands with Early-Onset Diabetes

AIM

To investigate the prevalence of variants within selected maturity-onset diabetes of the young (MODY)-genes among Algerian patients initially diagnosed with type 1 diabetes (T1D) or type 2 diabetes (T2D), yet presenting with a MODY-like phenotype.

METHODS

Eight unrelated patients with early-onset diabetes (before 30 years) and six relatives with diabetes were examined by targeted re-sequencing for variants in genes known to be involved in MODY (HNF1A, GCK, HNF4A, HNF1B, INS, ABCC8, KCNJ1). Clinical data for probands were retrieved from hospital records.

RESULTS

A total of 12 variants were identified, of which three were classified as pathogenic and one as a variant of uncertain clinical significance (VUS). Two of the pathogenic variants were found in GCK (p.Gly261Arg and p.Met210Lys, respectively) in one proband each and the remaining pathogenic variant was found in HNF1B (p.Gly76Cys) in a proband also carrying the VUS in HNF1A (p.Thr156Met).

CONCLUSION

Variants in known MODY-genes can be the cause of early-onset diabetes in Algerians diagnosed with T1D or T2D among patients presenting with a MODY-like phenotype; thus, genetic screening should be considered.

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).

Identifying Pathogenic Variants of Monogenic Diabetes Using Targeted Panel Sequencing in an East Asian Population

PURPOSE

Monogenic diabetes is a specific type of diabetes in which precision medicine could be applied. In this study, we used targeted panel sequencing to investigate pathogenic variants in Korean patients clinically suspected to have monogenic diabetes.

METHODS

The eligibility criteria for inclusion were non-type 1 diabetes patients with an age of onset ≤ 30 years and a BMI (body mass index) ≤ 30 kg/m2. Among the 2,090 non-type 1 diabetes patients, 109 were suspected to have monogenic diabetes and subjected to genetic testing. We analyzed 30 monogenic diabetes genes using targeted panel sequencing. The pathogenicity of the genetic variants was evaluated according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines.

RESULTS

Among the 109 suspected monogenic diabetes patients, 23 (21.1%) patients harbored pathogenic/likely pathogenic variants. A total of 14 pathogenic/likely pathogenic variants of common maturity onset diabetes of the young (MODY) genes were identified in GCK, HNF1A, HNF4A, and HNF1B. Other pathogenic/likely pathogenic variants were identified in WFS1, INS, ABCC8 and FOXP3. The mitochondrial DNA 3243 A>G variant was identified in five participants. Patients with pathogenic/likely pathogenic variants had a significantly higher MODY probability, a lower BMI, and a lower C-peptide level than those without pathogenic/likely pathogenic variants (P=0.007, P=0.001, and P=0.012, respectively).

CONCLUSIONS

Using targeted panel sequencing followed by pathogenicity evaluation, we were able to make molecular genetic diagnoses for 23 (21.1%) suspected monogenic diabetes patients. Lower BMI, higher MODY probability, and lower C-peptide levels were characteristics of these participants.

Changes in annual incidence of school children with type 2 diabetes in the Tokyo Metropolitan Area during 1975-2015

OBJECTIVE

To analyze changes in the annual incidence of school students with type 2 diabetes detected by urine glucose screening at schools in the Tokyo Metropolitan Area during 1975-2015.

METHODS

Trend in temporal changes in the annual incidence rate were analyzed using a joinpoint regression model and the joinpoints. Annual percent change (APC) was calculated for each segmented line regression. Average annual percent change (AAPC) was also calculated for the whole period analyzed.

RESULTS

In total, 301 students, including 64 primary school students and 237 junior high school students, were diagnosed with type 2 diabetes. The overall incidence of type 2 diabetes (per 100 000/year) during the entire study period was 2.58 in all students, 0.80 in primary school students, and 6.41 in junior high school students. AAPC during the entire study period was estimated at -1.5 (not significant), and the incidence significantly increased during 1975-1982 (APC = 17.49, P < 0.05), but tended to decrease during 1982-2015 (APC = -1.01). In primary school students, the incidence significantly increased during1975-2010 (APC = 3.30, P < 0.05), and tended to decrease during 2010-2015 (APC = -29.61). In junior high school students, the incidence did not significantly change during the entire study period (APC = 0.06).

CONCLUSIONS

We found increasing trend in the overall incidence of school students with type 2 diabetes during 1975-1982, but a decreased tendency in recent years. This could be due to changes observed during the same time period in the primary school students. Lifestyle changes might contribute to improved incidence of childhood type 2 diabetes.

Insights into pathogenesis of five novel GCK mutations identified in Chinese MODY patients

OBJECTIVE

Heterozygous inactivating mutations in GCK are associated with defects in pancreatic insulin secretion and/or hepatic glycogen synthesis leading to mild chronic hyperglycaemia of maturity onset diabetes of young type 2 (MODY2). However, the effect of naturally occurring GCK mutations on the pathogenesis for MODY2 hyperglycaemia remains largely unclear, especially in the Asian population. The aim of this study is to explore the potential pathogenicity of novel GCK mutations related to MODY2.

METHODS

Genetic screening for GCK mutations from 96 classical MODY families was performed, and structure-function characterization and clinical profile of identified GCK mutations were conducted.

RESULTS

Five novel (F195S, I211T, V222D, E236G and K458R) and five known (T49N, I159V, R186X, A188T and M381T) mutations were identified and co-segregated with hyperglycaemia in their pedigrees. R186X generates non-functional truncated form and V222D and E236G fully inactivate glucokinase due to severe structure disruptions. The other seven GCK mutations exhibited marked reductions in catalytic efficiency and thermo-stability; notably, the interaction with GKRP was significantly enhanced in I211T, I159V, T49N and K458R, reduced in F195S and M381T, and completely lost with A188T. 31% (17/55) of MODY2 patients showed signs of insulin resistance. Conventional hypoglycaemia treatment did not improve the HbA1C in MODY2 patients when insulin resistance is not present.

CONCLUSIONS

Five novel GCK mutations have been identified in Chinese MODY. The defects in enzymatic activity and protein stability, together with alteration of GKRP binding on GCK mutants may synergistically contribute to the development of MODY2 hyperglycaemia. No treatment should be prescribed to MODY2 patients when insulin resistance is not present.

Genetic basis of early-onset, maturity-onset diabetes of the young-like diabetes in Japan and features of patients without mutations in the major MODY genes: Dominance of maternal inheritance

BACKGROUND

Causative mutations cannot be identified in the majority of Asian patients with suspected maturity-onset diabetes of the young (MODY).

OBJECTIVES

To elucidate the genetic basis of Japanese patients with MODY-like diabetes and gain insight into the etiology of patients without mutations in the major MODY genes.

SUBJECTS

A total of 263 Japanese patients with early-onset, non-obese, MODY-like diabetes mellitus referred to Osaka City General Hospital for diagnosis.

METHODS

Mutational analysis of the four major MODY genes (GCK, HNF1A, HNF4A, HNF1B) by Sanger sequencing. Mutation-positive and mutation-negative patients were further analyzed for clinical features.

RESULTS

Mutations were identified in 103 (39.2%) patients; 57 mutations in GCK; 29, HNF1A; 7, HNF4A; and 10, HNF1B. Contrary to conventional diagnostic criteria, 18.4% of mutation-positive patients did not have affected parents and 8.2% were in the overweight range (body mass index [BMI] >85th percentile). HOMA-IR at diagnosis was elevated (>2) in 15 of 66 (22.7%) mutation-positive patients. Compared with mutation-positive patients, mutation-negative patients were significantly older (P = 0.003), and had higher BMI percentile at diagnosis (P = 0.0006). Interestingly, maternal inheritance of diabetes was significantly more common in mutation-negative patients (P = 0.0332) and these patients had significantly higher BMI percentile as compared with mutation-negative patients with paternal inheritance (P = 0.0106).

CONCLUSIONS

Contrary to the conventional diagnostic criteria, de novo diabetes, overweight, and insulin-resistance are common in Japanese patients with mutation-positive MODY. A significant fraction of mutation-negative patients had features of early-onset type 2 diabetes common in Japanese, and non-Mendelian inheritance needs to be considered for these patients.

Traditional clinical criteria outperform high-sensitivity C-reactive protein for the screening of hepatic nuclear factor 1 alpha maturity-onset diabetes of the young among young Asians with diabetes

BACKGROUND

Young adults with diabetes in Asia represent a heterogeneous group. Using traditional clinical criteria to preselect individuals for testing for maturity-onset diabetes of the young (MODY) may exclude a large proportion from testing. High-sensitivity C-reactive protein (hs-CRP) has shown promise as a biomarker to differentiate hepatic nuclear factor 1 alpha (HNF1A)-MODY from type 2 diabetes. We aimed to compare the use of hs-CRP as a biomarker versus traditional criteria, to guide testing for HNF1A-MODY among a cohort of young adults with diabetes in Singapore.

METHODS

A total of 252 adults (age of onset ⩽45 years) and 20 children with diabetes were recruited. Using traditional criteria (family history of diabetes and onset of diabetes ⩽25 years) and an hs-CRP cut off of ⩽0.5 mg/l, 125 and 37 adults, respectively, were identified for HNF1A gene testing. All children underwent HNF1A gene testing.

RESULTS

Five adults (5/143, 3.5%) with HNF1A-MODY were identified. There were no HNF1A gene mutations among the children. Traditional criteria correctly identified all five HNF1A-MODY individuals (5/125, 4%), while applying an hs-CRP level of ⩽0.5 mg/l selected just 1 of these 5 for HNF1A gene testing (1/37, 2.7%). None of those with a positive GAD antibody or undetectable C-peptide level had HNF1A-MODY.

CONCLUSION

The use of hs-CRP to guide screening for HNF1A-MODY among Asian young adults with diabetes did not improve the diagnostic yield. Applying a combination of age of onset of diabetes under 25 years and a family history of diabetes alone could guide targeted HNF1A-MODY screening in Asians, with an expected yield of 4% diagnosed with HNF1A-MODY among those screened.

A Novel p.L145Q Mutation in the HNF1B Gene in a Case of Maturity-onset Diabetes of the Young Type 5 (MODY5)

Maturity-onset diabetes of the young (MODY) is an autosomal dominant form of early onset diabetes. The hepatocyte nuclear factor-1-beta (HNF1B) gene is responsible for MODY type 5 (MODY5) with distinctive clinical features, including pancreatic atrophy and renal disease. We herein report a Japanese case of young-onset diabetes with typical phenotypes of MODY5 and a novel heterozygous missense mutation (p.L145Q) in the HNF1B gene. The mutation was located in the Pit-Oct-Unc (POU)-specific domain, and the amino acid residue L145 was highly conserved among species. It is strongly suggested that this mutation explains the phenotypes of MODY5.

Maturity-onset diabetes of the young as a model for elucidating the multifactorial origin of type 2 diabetes mellitus

Maturity‐onset diabetes of the young (MODY) is a form of diabetes classically characterized as having autosomal dominant inheritance, onset before the age of 25 years in at least one family member and partly preserved pancreatic β‐cell function. The 14 responsible genes are reported to be MODY type 1~14, of which MODY 2 and 3 might be the most common forms. Although MODY is currently classified as diabetes of a single gene defect, it has become clear that mutations in rare MODYs, such as MODY 5 and MODY 6, have small mutagenic effects and low penetrance. In addition, as there are differences in the clinical phenotypes caused by the same mutation even in the same family, other phenotypic modifying factors are thought to exist; MODY could well have characteristics of type 2 diabetes mellitus, which is of multifactorial origin. Here, we outline the effects of genetic and environmental factors on the known phenotypes of MODY, focusing mainly on the examples of MODY 5 and 6, which have low penetrance, as suggestive models for elucidating the multifactorial origin of type 2 diabetes mellitus.

Genetic and clinical characteristics of Chinese children with Glucokinase-maturity-onset diabetes of the young (GCK-MODY)

Background

There is scarcity of information on the clinical features and genetics of glucokinase-maturity-onset diabetes of the young (GCK-MODY) in China. The aim of the study was to investigate the clinical and molecular characteristics of Chinese children with GCK-MODY.

Methods

Eleven children with asymptomatic hyperglycemia and clinically suspected GCK-MODY were identified from the database of children with diabetes in the biggest children’s hospital in South China. Clinical data were obtained from medical records. Blood was collected from the patients and their parents for glucokinase (GCK) gene analysis. Parents without diabetes were tested for fasting glucose and HbA1c. Clinical information and blood for GCK gene analysis were obtained from grandparents with diabetes. GCK gene mutational analysis was performed by polymerase chain reaction and direct sequencing. Patients without a GCK gene mutation were screened by targeted next-generation sequencing (NGS) technology for other MODY genes.

Results

Nine children tested positive for GCK gene mutations while two were negative. The nine GCK-MODY patients were from unrelated families, aged 1 month to 9 years and 1 month at first detection of hyperglycaemia. Fasting glucose was elevated (6.1–8.5 mmol/L), HbA1c 5.2–6.7% (33.3–49.7 mmol/mol), both remained stable on follow-up over 9 months to 5 years. Five detected mutations had been previously reported: p.Val182Met, c.679 + 1G > A, p.Gly295Ser, p.Arg191Gln and p.Met41Thr. Four mutations were novel: c.483 + 2 T > A, p.Ser151del, p.Met57GlyfsX29 and p.Val374_Ala377del. No mutations were identified in the other two patients, who were also tested by NGS.

Conclusions

GCK gene mutations are detected in Chinese children and their family members with typical clinical features of GCK-MODY. Four novel mutations are detected.

Comprehensive screening for monogenic diabetes in 89 Japanese children with insulin-requiring antibody-negative type 1 diabetes

BACKGROUND

Mutations in causative genes for neonatal diabetes or maturity-onset diabetes of the young have been identified in multiple patients with autoantibody-negative type 1 diabetes (T1D).

OBJECTIVES

We aimed to clarify the prevalence and phenotypic characteristics of monogenic abnormalities among 89 children with autoantibody-negative insulin-requiring T1D.

METHODS

Mutations in 30 genes were screened using next-generation sequencing, and copy-number alterations of 4 major causative genes were examined using multiplex-ligation-dependent probe amplification. We compared the clinical characteristics between mutation carriers and non-carriers.

RESULTS

We identified 11 probable pathogenic substitutions (6 in INS , 2 in HNF1A , 2 in HNF4A , and 1 in HNF1B ) in 11 cases, but no copy-number abnormalities. Only 2 mutation carriers had affected parents. De novo occurrence was confirmed for 3 mutations. The non-carrier group, but not the carrier group, was enriched with susceptible HLA alleles. Mutation carriers exhibited comparable phenotypes to those of non-carriers, except for a relatively normal body mass index (BMI) at diagnosis.

CONCLUSIONS

This study demonstrated significant genetic overlap between autoantibody-negative T1D and monogenic diabetes. Mutations in INS and HNF genes, but not those in GCK and other monogenic diabetes genes, likely play critical roles in children with insulin-requiring T1D. This study also suggests the relatively high de novo rates of INS and HNF mutations, and the etiological link between autoimmune abnormalities and T1D in the non-carrier group. Carriers of monogenic mutations show non-specific phenotypes among all T1D cases, although they are more likely to have a normal BMI at diagnosis than non-carriers.

MODY in Ukraine: genes, clinical phenotypes and treatment

BACKGROUND

Maturity-onset diabetes of the young (MODY) has not been previously studied in Ukraine. We investigated the genetic etiology in a selected cohort of patients with diabetes diagnosed before 18 years of age, and in their family members.

METHODS

Genetic testing of the most prevalent MODY genes (GCK, HNF1A, HNF4A, HNF1B and INS) was undertaken for 36 families (39 affected individuals) by Sanger or targeted next generation sequencing.

RESULTS

A genetic diagnosis of MODY was made in 15/39 affected individuals from 12/36 families (33%). HNF1A and HNF4A MODY were the most common subtypes, accounting for 9/15 of MODY cases. Eight patients with HNF1A or HNF4A MODY and inadequate glycemic control were successfully transferred to sulfonylureas. Median HbA1c decreased from 67 mmol/mol (range 58-69) to 47 mmol/mol (range 43-50) (8.3% [7.5-8.5] to 6.4% [6.1-6.7]) 3 months after transfer (p=0.006).

CONCLUSIONS

Genetic testing identified pathogenic HNF1A and HNF4A variants as the most common cause of MODY in Ukraine. Transfer to sulfonylureas substantially improved the glycemic control of these patients.

Efficacy and safety of alogliptin in a pediatric patient with maturity-onset diabetes of the young type 1

The first-line pharmacological treatment for patients with maturity-onset diabetes of the young type 1 (MODY1) and maturity-onset diabetes of the young type 3 (MODY3) are sulfonylureas (SUs) or insulin. However, several reports have suggested the possibility of using incretin-associated drugs, including dipeptidyl-peptidase-4 (DPP-4) inhibitors, for the treatment of patients with these types of MODY. Here we report a case of a pediatric patient with MODY1 who was successfully treated with a DPP-4 inhibitor, alogliptin. A 13-yr-old Japanese girl with diabetes was initially treated with insulin for 5 mo. After diagnosis of MODY1, confirmed via a genetic analysis, treatment was changed from insulin to alogliptin. SUs were prescribed temporarily, but monotherapy with alogliptin finally resulted in good glycemic control. After changing to alogliptin, the patient maintained optimal glycemic control with glycated hemoglobin levels of 6.3–7.0% while maintaining substantial β-cell function. No adverse events associated with alogliptin were observed. These results suggest that DPP-4 inhibitors may be a potential treatment for patients with MODY1 at the early stage of the disease when residual insulin secretion is still being sustained.

Systematic Population Screening, Using Biomarkers and Genetic Testing, Identifies 2.5% of the U.K. Pediatric Diabetes Population With Monogenic Diabetes

OBJECTIVE

Monogenic diabetes is rare but is an important diagnosis in pediatric diabetes clinics. These patients are often not identified as this relies on the recognition of key clinical features by an alert clinician. Biomarkers (islet autoantibodies and C-peptide) can assist in the exclusion of patients with type 1 diabetes and allow systematic testing that does not rely on clinical recognition. Our study aimed to establish the prevalence of monogenic diabetes in U.K. pediatric clinics using a systematic approach of biomarker screening and targeted genetic testing.

RESEARCH DESIGN AND METHODS

We studied 808 patients (79.5% of the eligible population) <20 years of age with diabetes who were attending six pediatric clinics in South West England and Tayside, Scotland. Endogenous insulin production was measured using the urinary C-peptide creatinine ratio (UCPCR). C-peptide-positive patients (UCPCR ≥0.2 nmol/mmol) underwent islet autoantibody (GAD and IA2) testing, with patients who were autoantibody negative undergoing genetic testing for all 29 identified causes of monogenic diabetes.

RESULTS

A total of 2.5% of patients (20 of 808 patients) (95% CI 1.6-3.9%) had monogenic diabetes (8 GCK, 5 HNF1A, 4 HNF4A, 1 HNF1B, 1 ABCC8, 1 INSR). The majority (17 of 20 patients) were managed without insulin treatment. A similar proportion of the population had type 2 diabetes (3.3%, 27 of 808 patients).

CONCLUSIONS

This large systematic study confirms a prevalence of 2.5% of patients with monogenic diabetes who were <20 years of age in six U.K. clinics. This figure suggests that ∼50% of the estimated 875 U.K. pediatric patients with monogenic diabetes have still not received a genetic diagnosis. This biomarker screening pathway is a practical approach that can be used to identify pediatric patients who are most appropriate for genetic testing.

GCK gene mutations are a common cause of childhood-onset MODY (maturity-onset diabetes of the young) in Turkey

OBJECTIVE

Inactivating heterozygous mutations in the GCK gene are a common cause of MODY and result in mild fasting hyperglycaemia, which does not require treatment. We aimed to identify the frequency, clinical and molecular features of GCK mutations in a Turkish paediatric cohort.

DESIGN AND PATIENTS

Fifty-four unrelated probands were selected based on the following criteria: age of diagnosis ≤17 years, family history of diabetes in at least two generations, anti-GAD/ICA negative, BMI<95.p and follow-up with diet, oral antidiabetic drug or low-dose insulin treatment (≤0·5U/kg/d). A MODY probability score (www.diabetesgenes.org) was calculated and 21 patients with a score ≥75%, HbA1c levels ≤7·5% (58·5 mmol/mol) and fasting blood glucose (FBG) levels 99-145 mg/dl (5·5-8·0 mmol/l) were selected for Sanger sequencing of the GCK gene. Targeted next-generation sequencing for all known monogenic diabetes genes was undertaken for any patient without a GCK gene mutation.

RESULTS

GCK gene mutations (pathogenic or likely pathogenic variants) and a novel intronic variant of uncertain significance (c.208 + 3A>T) were identified in 13/54 probands (24%). Twelve of these patients had a MODY probability score ≥75%. FBG level and 2-h glucose level in OGTT were 123 ± 14 mg/dl (6·8 ± 0·7 mmol/l) (107-157 mg/dl) and 181 ± 30 mg/dl (10·1 ± 1·6 mmol/l) (136-247 mg/dl), respectively. Average of glucose increment in OGTT was 58 ± 27 mg/dl (3·2 ± 1·5 mmol/l) (19-120 mg/dl), and mean HbA1c level was 6·5 ± 0·5% (47·5 ± 5·5 mmol/mol) (5·9-7·6%). Five novel missense mutations were identified (p.F123S, p.L58P, p.G246A, p.F419C, and p.S151C). Two patients treated with low-dose insulin before the molecular analysis were able to stop treatment.

CONCLUSIONS

Approximately 1 in 4 MODY cases in this Turkish paediatric cohort have a GCK mutation. Selection of patients for GCK gene analysis using the MODY probability score was an effective way of identifying most (11/12) patients with a GCK mutation.

Mody-3: novel HNF1A mutation and the utility of glucagon-like peptide (GLP)-1 receptor agonist therapy

OBJECTIVE

An estimated 1 to 2% of cases of diabetes mellitus have a monogenic basis; however, delayed diagnosis and misdiagnosis as type 1 and 2 diabetes are common. Correctly identifying the molecular basis of an individual's diabetes may significantly alter the management approach to both the patient and his or her relatives. We describe a case of mature onset diabetes of the young (MODY) with sufficient evidence to support the classification of a novel HNF1A (hepatocyte nuclear factor-1-α) mutation as a cause of MODY-3.

METHODS

A 21-year-old Caucasian female presented to our office with a diagnosis of noninsulin-dependent diabetes mellitus (NIDDM) at age 10; glycemia was initially managed with oral antidiabetic (OAD) agents and insulin detemir. The patient reported a strong family history of early-onset NIDDM in both her mother and maternal grandmother, both of whom eventually required insulin therapy to control glycemia. The patient's medical and family history were highly suggestive of maturity-onset diabetes of the young (MODY), and genetic testing was performed.

RESULTS

Genetic screening detected a mutation p. Arg200Trp in the HNF1A gene in the patient, her mother, and maternal grandmother, suggesting a diagnosis of MODY-3. This finding resulted in a change of antidiabetic therapy in all 3 patients, including the addition of once-daily liraglutide therapy, which helped improve their glycemic control.

CONCLUSION

Our case report supports the classification of the p. Arg200Trp mutation as a cause of MODY-3. The findings also suggest that glucagon-like peptide-1 (GLP-1) receptor agonist therapy may be of value in managing glycemia in patients with MODY-3.

GCK mutations in Chinese MODY2 patients: a family pedigree report and review of Chinese literature

BACKGROUND

Maturity-onset diabetes of the young type 2 (MODY2) is caused by mutations in the glucokinase (GCK) gene and is rare in the Chinese population. We report three Chinese families with MODY2 and the sequencing of the GCK gene.

METHODS

Three unrelated Chinese families with MODY2 and their pedigrees were investigated. In Family 1, the proband was a 7-year-old girl with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT). Her mother and maternal grandfather had IFG. In Family 2, the proband was a boy who had diabetes mellitus at 11 years. His sister had IFG. His father and grandmother had diabetes mellitus at 22 and 25 years, respectively. In Family 3, the proband was a boy who had IFG and IGT at 12 years. His sister had diabetes mellitus at 8 years. His father and grandfather had IFG and/or IGT. The GCK gene was directly sequenced.

RESULTS

Diabetes mellitus or IFG/IGT was found among three consecutive generations in three families. One novel nonsense heterozygous mutation in exon 5 (c.556 C>T, p.Arg 186 stop) was detected in Family 1. Another novel frameshift mutation in exon 4 (c.367-374dupTTCGACTA, p.Ile 126 fs) was found in Family 2. A previously reported, a missense heterozygous mutation in exon 5 (c.571 C>T, p.Arg 191Trp) was detected in Family 3.

CONCLUSIONS

The thorough investigation of three Chinese families with MODY2 revealed two novel mutations and one known mutation. GCK gene sequencing helps in MODY2, especially when there is uncertain IFG or IGT.

Undiagnosed MODY: Time for Action

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes that accounts for at least 1 % of all cases of diabetes mellitus. MODY classically presents as non-insulin-requiring diabetes in lean individuals typically younger than 25 with evidence of autosomal dominant inheritance, but these criteria do not capture all cases and can also overlap with other diabetes types. Genetic diagnosis of MODY is important for selecting the right treatment, yet ~95 % of MODY cases in the USA are misdiagnosed. MODY prevalence and characteristics have been well-studied in some populations, such as the UK and Norway, while other ethnicities, like African and Latino, need much more study. Emerging next-generation sequencing methods are making more widespread study and clinical diagnosis increasingly feasible; at the same time, they are detecting other mutations in the same genes of unknown clinical significance. This review will cover the current epidemiological studies of MODY and barriers and opportunities for moving toward a goal of access to an appropriate diagnosis for all affected individuals.

Maturity-Onset Diabetes of the Young: What Do Clinicians Need to Know?

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes that is characterized by an early onset, autosomal dominant mode of inheritance and a primary defect in pancreatic β-cell function. MODY represents less than 2% of all diabetes cases and is commonly misdiagnosed as type 1 or type 2 diabetes mellitus. At least 13 MODY subtypes with distinct genetic etiologies have been identified to date. A correct genetic diagnosis is important as it often leads to personalized treatment for those with diabetes and enables predictive genetic testing for their asymptomatic relatives. Next-generation sequencing may provide an efficient method for screening mutations in this form of diabetes as well as identifying new MODY genes. In this review, I discuss a current update on MODY in the literatures and cover the studies that have been performed in Korea.

Recognition and Management of Individuals With Hyperglycemia Because of a Heterozygous Glucokinase Mutation

Glucokinase-maturity-onset diabetes of the young (GCK-MODY), also known as MODY2, is caused by heterozygous inactivating mutations in the GCK gene. GCK gene mutations are present in ∼1 in 1,000 of the population, but most are not diagnosed. They are common causes of MODY (10-60%): persistent incidental childhood hyperglycemia (10-60%) and gestational diabetes mellitus (1-2%). GCK-MODY has a unique pathophysiology and clinical characteristics, so it is best considered as a discrete genetic subgroup. People with GCK-MODY have a defect in glucose sensing; hence, glucose homeostasis is maintained at a higher set point resulting in mild, asymptomatic fasting hyperglycemia (5.4-8.3 mmol/L, HbA1c range 5.8-7.6% [40-60 mmol/mol]), which is present from birth and shows slight deterioration with age. Even after 50 years of mild hyperglycemia, people with GCK-MODY do not develop significant microvascular complications, and the prevalence of macrovascular complications is probably similar to that in the general population. Treatment is not recommended outside pregnancy because glucose-lowering therapy is ineffective in people with GCK-MODY and there is a lack of long-term complications. In pregnancy, fetal growth is primarily determined by whether the fetus inherits the GCK gene mutation from their mother. Insulin treatment of the mother is only appropriate when increased fetal abdominal growth on scanning suggests the fetus is unaffected. The impact on outcome of maternal insulin treatment is limited owing to the difficulty in altering maternal glycemia in these patients. Making the diagnosis of GCK-MODY through genetic testing is essential to avoid unnecessary treatment and investigations, especially when patients are misdiagnosed with type 1 or type 2 diabetes.