Characterisation of HNF1A variants in paediatric diabetes in Norway using functional and clinical investigations to unmask phenotype and monogenic diabetes

AIMS/HYPOTHESIS

Correctly diagnosing MODY is important, as individuals with this diagnosis can discontinue insulin injections; however, many people are misdiagnosed. We aimed to develop a robust approach for determining the pathogenicity of variants of uncertain significance in hepatocyte nuclear factor-1 alpha (HNF1A)-MODY and to obtain an accurate estimate of the prevalence of HNF1A-MODY in paediatric cases of diabetes.

METHODS

We extended our previous screening of the Norwegian Childhood Diabetes Registry by 830 additional samples and comprehensively genotyped HNF1A variants in autoantibody-negative participants using next-generation sequencing. Carriers of pathogenic variants were treated by local healthcare providers, and participants with novel likely pathogenic variants and variants of uncertain significance were enrolled in an investigator-initiated, non-randomised, open-label pilot study (ClinicalTrials.gov registration no. NCT04239586). To identify variants associated with HNF1A-MODY, we functionally characterised their pathogenicity and assessed the carriers' phenotype and treatment response to sulfonylurea.

RESULTS

In total, 615 autoantibody-negative participants among 4712 cases of paediatric diabetes underwent genetic sequencing, revealing 19 with HNF1A variants. We identified nine carriers with novel variants classified as variants of uncertain significance or likely to be pathogenic, while the remaining ten participants carried five pathogenic variants previously reported. Of the nine carriers with novel variants, six responded favourably to sulfonylurea. Functional investigations revealed their variants to be dysfunctional and demonstrated a correlation with the resulting phenotype, providing evidence for reclassifying these variants as pathogenic.

CONCLUSIONS/INTERPRETATION

Based on this robust classification, we estimate that the prevalence of HNF1A-MODY is 0.3% in paediatric diabetes. Clinical phenotyping is challenging and functional investigations provide a strong complementary line of evidence. We demonstrate here that combining clinical phenotyping with functional protein studies provides a powerful tool to obtain a precise diagnosis of HNF1A-MODY.

Molecular diagnosis of maturity onset diabetes of the young in Iranian patients: improving management

Background

The purpose of this study is to identify the mutations of the most common form of maturity-onset diabetes of the young (MODY), also known as MODY3, in diabetic patients suspected of MODY. This can recommend appropriate medical surveillance of at-risk family members of MODY based on the genetic cause.

Methods

We analyzed the clinical course of 19 patients from 12 unrelated Iranian families with diabetes features. The coding regions and intron-exon boundaries of the hepatocyte nuclear factor 1 alpha (HNF1A) gene were studied by polymerase chain reaction (PCR) and sanger sequencing. Also, the detected mutation was analyzed by bioinformatics tools.

Results

One novel frameshift insertion mutation (p.Glu11Argfs*12) was detected in one of the probands and seven other patients of her family with the heterozygote state. The mutation is located in the exon1 of the dimerization domain of the HNF1A gene. According to the In Silico analysis, the detected mutation is predicted as a pathogenic one.

Conclusions

Differential diagnosis between MODY3 and other forms of diabetes can be considered a necessity in terms of overlapping symptoms of MODY3 with type1 or 2 diabetes. Molecular genetic testing can provide an accurate diagnosis for optimal management.

Clinical features, complications and treatment of rarer forms of maturity-onset diabetes of the young (MODY) - A review

Maturity onset diabetes of the young (MODY) is the most common form of monogenic diabetes and is currently believed to have 14 subtypes. While much is known about the common subtypes of MODY (MODY-1, 2, 3 and 5) little is known about its rare subtypes (MODY4, 6-14). With the advent of next-generation sequencing (NGS) there are several reports of the rarer subtypes of MODY emerging from across the world. Therefore, a greater understanding on these rarer subtypes is needed. A search strategy was created, and common databases were searched, and 51 articles finally selected. INS-(MODY10) and ABCC8-(MODY12) mutations were reported in relatively large numbers compared to the other rare subtypes. The clinical characteristics of the rare MODY subtypes exhibited heterogeneity between families reported with the same mutation. Obesity and diabetic ketoacidosis (DKA) were also reported among rarer MODY subtypes which presents as a challenge as these are not part of the original description of MODY by Tattersal and Fajans. The treatment modalities of the rarer subtypes included oral drugs, predominantly sulfonylureas, insulin but also diet alone. Newer drugs like DPP-4 and SGLT2 inhibitors have also been tried as new modes of treatment. The microvascular and macrovascular complications among the patients with various MODY subtypes are less commonly reported. Recently, there is a view that not all the 14 forms of 'MODY' are true MODY and the very existence of some of these rarer subtypes as MODY has been questioned. This scoping review aims to report on the clinical characteristics, treatment and complications of the rarer MODY subtypes published in the literature.

Biological behaviors of mutant proinsulin contribute to the phenotypic spectrum of diabetes associated with insulin gene mutations

Insulin gene mutation is the second most common cause of neonatal diabetes (NDM). It is also one of the genes involved in maturity-onset diabetes of the young (MODY). We aim to investigate molecular behaviors of different INS gene variants that may correlate with the clinical spectrum of diabetes phenotypes. In this study, we concentrated on two previously uncharacterized MODY-causing mutants, proinsulin-p.Gly44Arg [G(B20)R] and p.Pro52Leu [P(B28)L] (a novel mutant identified in one French family), and an NDM causing proinsulin-p.(Cys96Tyr) [C(A7)Y]. We find that these proinsulin mutants exhibit impaired oxidative folding in the endoplasmic reticulum (ER) with blocked ER export, ER stress, and apoptosis. Importantly, the proinsulin mutants formed abnormal intermolecular disulfide bonds that not only involved the mutant proinsulin, but also the co-expressed WT-proinsulin, forming misfolded disulfide-linked proinsulin complexes. This impaired the intracellular trafficking of WT-proinsulin and limited the production of bioactive mature insulin. Notably, although all three mutants presented with similar defects in folding, trafficking, and dominant negative behavior, the degrees of these defects appeared to be different. Specifically, compared to MODY mutants G(B20)R and P(B28)L that partially affected folding and trafficking of co-expressed WT-proinsulin, the NDM mutant C(A7)Y resulted in an almost complete blockade of the ER export of WT-proinsulin, decreasing insulin production, inducing more severe ER stress and apoptosis. We thus demonstrate that differences in cell biological behaviors among different proinsulin mutants correlate with the spectrum of diabetes phenotypes caused by the different INS gene mutations.

Role of Gliclazide MR in the Management of Type 2 Diabetes: Report of a Symposium on Real-World Evidence and New Perspectives

In patients with type 2 diabetes mellitus (T2DM) who require additional glucose-lowering on top of first-line metformin monotherapy, sulfonylureas are the most common choice for second-line therapy followed by dipeptidyl peptidase inhibitors (DPP-4i). This article summarises presentations at a symposium entitled "Real-World Evidence and New Perspectives with Gliclazide MR" held at the International Diabetes Federation Congress in Busan, South Korea on 4 December 2019. Although guideline recommendations vary between countries, the guidelines with the highest quality ratings include sulfonylureas as one of the preferred choices as second-line therapy for T2DM. Data from randomised controlled trials (RCTs) have consistently demonstrated that sulfonylureas are effective glucose-lowering agents and that the risk of severe hypoglycaemia with these agents is low. In addition, both RCTs and real-world observational studies have shown no increased risk of mortality or cardiovascular disease with the use of newer-generation sulfonylureas compared with other classes of glucose-lowering treatments. However, differences between sulfonylureas do exist, with gliclazide being associated with a significantly lower risk of mortality or cardiovascular mortality compared with glibenclamide, as well as the lowest incidence of severe hypoglycaemia compared with other agents in this class. Recent real-world studies into the effectiveness and safety of gliclazide appear to confirm these findings, and publication of new data from these studies in patients with T2DM in the UK, and in Muslim patients who are fasting during Ramadan, are awaited with interest. Another study being undertaken with gliclazide is a pan-India study in patients with maturity-onset diabetes of the young (MODY) subtypes 1, 3 and 12. Patients with these MODY subtypes respond particularly well to sulfonylurea treatment, and sulfonylureas are the first-line agents of choice in these patients. These new and ongoing studies will add to the cumulative data on the efficacy and safety of certain sulfonylureas in patients with diabetes.

[A three-year follow-up observation of a pedigree of maturity onset diabetes of the young caused by a novel mutation of glucokinase and literature review]

Objective: To explore the clinical characteristics and follow-up outcomes of a pedigree of maturity onset diabetes of the young (MODY) induced by a novel mutation of glucokinase (GCK). Methods: The clinical features and laboratory data of a pedigree diagnosed with GCK-MODY in Peking Union Medical College Hospital was analyzed. Genomic DNA was extracted, and Sanger sequencing was performed to detect the gene mutation of the family members. The proband and her father were followed up for 3 years. Wanfang and PubMed were used to search literatures on follow-up studies for treatment of GCK-MOYD. Results: Both the proband and her father were found to have a novel mutation on the GCK gene located in exo10 c.1348G.T (p. Ala450Thr). The proband was treated with diet and exercise control only. At the end of the follow-up, her fasting plasma glucose (FPG, 6.8 mmol/L), 2 h postprandial plasma glucose (2hPG, 7.4 mmol/L), and glycated hemoglobin (HbA1c, 6.3%) were all within the control targets. Additionally, the levels homeostasis model assessment of insulin resistance (HOMA-IR) tended to improved comparing to that at baseline (4.09 to 2.32), and glucose disposition index (DI) was improved compared with baseline (16.22 to 20.05). As to the proband's father, the treatment with insulin plus acarbose was converted to sulfonylureas monotherapy. His FPG and 2hPG mostly were within the target range, and the levels of HbA1c were significantly reduced by 0.5%-0.7% when compared to that at baseline. The HOMA-IR or islet beta cell function was comparable to those at baseline. Conclusions: Screening patients whose clinical performance meets GCK-MODY and their family members with proper genetic testing is of great importance to reduce misdiagnosis of GCK-MODY, so as to obtain a better glucose control without unnecessary over-treatment and protect islet beta cell function.

Autoimmune Thyroid Diseases in Children and Adolescents with Maturity Onset Diabetes of the Young Type 2

BACKGROUND/AIM

The relationship between type 1 diabetes mellitus (T1DM) and autoimmune thyropathies is well known and has been described in the literature. Based on present knowledge, the relationship between thyropathies and other forms of diabetes, such as monogenic diabetes, has not been investigated. The aim of our study was to assess the prevalence of autoimmune thyroid diseases (ATD) in children and adolescents with maturity onset diabetes of the young type 2 (MODY2) in comparison with patients with T1DM and a control group.

PATIENTS AND METHODS

We examined 23 children and adolescents with MODY2 (11 F/12 M; 13.5 ± 5.3 years) and 166 patients with T1DM (80 F/86 M; 14.0 ± 4.7 years). The control group consisted of 62 age-matched healthy subjects (34 F/28 M). ATD diagnosis was based on the finding of one or more positive thyroid autoantibodies and characteristic thyroid ultrasound lacking homogeneity, with a hypogenic or mixed echo pattern.

RESULTS

ATD was diagnosed in 15 (10.5%; 9 F/6 M) patients with T1DM, in 4 with MODY2 (17.4%; 4 F), and in 1 (1.6%) control. A significantly higher ATD prevalence was detected in T1DM and MODY2 compared to the control subjects (p = 0.02), without differences between T1DM and MODY2 (p = 0.26). There were no gender differences noted in T1DM (p = 0.42); on the contrary, in MODY2 a higher prevalence was noted in females (p = 0.04). Celiac disease and a positive family history of ATD were not detected in subjects with MODY2.

CONCLUSION

Our study showed an increased prevalence of ATD in patients with MODY2. Therefore, a careful follow-up of all children with MODY2 is recommended in order to assess the presence of thyroid disorders.

Hyperglycemia in pediatric age: could it be maturity onset diabetes of the young? Case reports and review of the literature

Maturity Onset Diabetes of the Young (MODY) includes a clinically and genetically heterogeneous group of diabetes subtypes with MODY-2 being the second most prevalent form. We report 2 cases of MODY-2 identified during the investigation of asymptomatic hyperglycemia. A 12-year-old girl with a familiar history of diabetes (mother, maternal aunt, and maternal grandfather) was referred due to hypercholesterolemia, abnormal fasting glucose (114 mg/dL), and increased levels of glycated haemoglobin (HbA1c) (6%) presenting with negative β-cell antibodies. A glucokinase (GCK) heterozygous missense mutation c.364C>T (p.Leu122Phe) in exon 4 was identified in the index patient and in the 3 family members. An obese 9-year-old boy was investigated for elevated fasting glycemic levels (99-126 mg/dL), HbA1c rise (6.6%-7.6%), and negative β-cell antibodies. The patient's father, paternal aunt, and paternal grandfather had a history of diabetes during their childhood. A GCK heterozygous missense mutation c.698G>A (p.Cys233Tyr) in exon 7 was identified in the index patient. This variant was only described in another family strongly affected by both MODY and classic autoimmune mediated diabetes, contrary to our case. MODY-2 should be suspected in the presence of early onset of persistent mild fasting hyperglycemia and negative β-cell antibodies associated with a positive family history of diabetes. These cases illustrate the challenging aspects of MODY diagnosis due to possible phenotypic overlap with other types of diabetes. The diagnosis requires a high level of suspicion and GCK genetic screening should be performed in the presence of compatible features. An early diagnosis allows for appropriate management, genetic counselling, and the identification of affected family members.

Maturity-onset diabetes of the young: From a molecular basis perspective toward the clinical phenotype and proper management

Maturity-onset diabetes of the young (MODY) comprises a heterogeneous group of monogenic disorders characterized by primary defect in pancreatic β-cell function, early onset and autosomal dominant inheritance, accounting for about 1-5% of all diabetes diagnoses. Mutations in 14 genes are responsible for the majority of all MODY cases described so far. The clinical phenotype relies on genetic defects, with important implications in the optimal treatment and prognosis definition. MODY's early diagnosis remains a challenge, since this group of inherited disorders comprises a large clinical spectrum and it usually overlaps with other types of diabetes, requiring a high index of suspicion even if the definitive statement demands a molecular genetic study. Recent advances on the genetic determinants and pathophysiology of MODY have allowed a better understanding of its underlying molecular mechanisms, providing a proper genetic counseling and early diagnosis. These new management insights will make possible to set up new therapeutic strategies, with drugs able to prevent, correct or at least delay the decline of pancreatic β-cell function, thus affording for a more personalized treatment and, ultimately, for a better patient care.

A UK nationwide prospective study of treatment change in MODY: genetic subtype and clinical characteristics predict optimal glycaemic control after discontinuing insulin and metformin

AIMS/HYPOTHESIS

Treatment change following a genetic diagnosis of MODY is frequently indicated, but little is known about the factors predicting future treatment success. We therefore conducted the first prospective study to determine the impact of a genetic diagnosis on individuals with GCK-, HNF1A- or HNF4A-MODY in the UK, and to identify clinical characteristics predicting treatment success (i.e. HbA_1c ≤58 mmol/mol [≤7.5%]) with the recommended treatment at 2 years.

METHODS

This was an observational, prospective, non-selective study of individuals referred to the Exeter Molecular Genetic Laboratory for genetic testing from December 2010 to December 2012. Individuals from the UK with GCK- or HNF1A/HNF4A-MODY who were not on recommended treatment at the time of genetic diagnosis, and who were diagnosed below the age of 30 years and were currently aged less than 50 years, were eligible to participate.

RESULTS

A total of 44 of 58 individuals (75.9%) changed treatment following their genetic diagnosis. Eight individuals diagnosed with GCK-MODY stopped all diabetes medication without experiencing any change in HbA_1c (49.5 mmol/mol [6.6%] both before the genetic diagnosis and at a median of 1.25 years' follow-up without treatment, p = 0.88). A total of 36 of 49 individuals (73.5%) diagnosed with HNF1A/HNF4A-MODY changed treatment; however, of the 21 of these individuals who were being managed with diet or sulfonylurea alone at 2 years, only 13 (36.1% of the population that changed treatment) had an HbA_1c ≤58 mmol/mol (≤7.5%). These individuals had a shorter diabetes duration (median 4.6 vs 18.1 years), lower HbA_1c (58 vs 73 mmol/mol [7.5% vs 8.8%]) and lower BMI (median 24.2 vs 26.0 kg/m²) at the time of genetic diagnosis, compared with individuals (n = 23/36) with an HbA_1c >58 mmol/mol (>7.5%) (or <58 mmol/mol [<7.5%] on additional treatment) at the 2 year follow-up. Overall, 64% (7/11) individuals with a diabetes duration of ≤11 years and an HbA_1c of ≤69 mmol/mol (≤8.5%) at time of the genetic test achieved good glycaemic control (HbA_1c ≤58 mmol/mol [≤7.5%]) with diet or sulfonylurea alone at 2 years, compared with no participants with a diabetes duration of >11 years and an HbA_1c of >69 mmol/mol (>8.5%) at the time of genetic diagnosis.

CONCLUSIONS/INTERPRETATION

In participants with GCK-MODY, treatment cessation was universally successful, with no change in HbA_1c at follow-up. In those with HNF1A/HNF4A-MODY, a shorter diabetes duration, lower HbA_1c and lower BMI at genetic diagnosis predicted successful treatment with sulfonylurea/diet alone, supporting the need for early genetic diagnosis and treatment change. Our study suggests that, in individuals with HNF1A/HNF4A-MODY with a longer duration of diabetes (>11 years) at time of genetic test, rather than ceasing current treatment, a sulfonylurea should be added to existing therapy, particularly in those who are overweight or obese and have a high HbA_1c.

Polymorphism of the GLIS3 gene in a Caucasian population and among individuals with carbohydrate metabolism disorders in Russia

Objective

Earlier, GLIS3 gene polymorphisms have been shown to be associated with the development of maturity onset diabetes of the young (MODY). We screened GLIS3 gene sequences among patients with MODY to identify probably pathogenic variants by whole-exome sequencing. We estimated frequency of rare single-nucleotide variants in the coding region of GLIS3 in a Caucasian population and among individuals with carbohydrate metabolism disorders in Russia.

Results

We identified 15 single-nucleotide variants in GLIS3. Three rare variants (minor allele frequency < 1%) rs806052, rs143051164, and rs149840771 were genotyped in 126 cases of MODY, in 188 patients with type 2 diabetes mellitus (DM2), and 564 randomly selected Caucasian individuals in Russia. A heterozygous rs806052 variant was identified in one patient with DM2; c.1270T frequency was 0.003. Prevalence of rs143051164 c.844G was 0.003 in the control population and 0.004 and 0.003 in MODY and DM2 samples, respectively. Prevalence of rs149840771 c.2096A was 0.003 and 0.004 in the control population and among MODY patients, respectively. In DM2 patients, rs149840771 c.2096A was not identified. We did not detect any associations of rs806052, rs143051164, and rs149840771 with carbohydrate metabolism disorders among patients with MODY and DM2 in Russia.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3338-1) contains supplementary material, which is available to authorized users.

A Case of Maturity Onset Diabetes of the Young (MODY3) in a Family with a Novel HNF1A Gene Mutation in Five Generations

Diabetes mellitus with autosomal dominant inheritance, i.e., maturity-onset diabetes of the young (MODY), is a genetic form of diabetes mellitus. The MODY phenotype is associated with gene mutations leading to pancreatic β-cell dysfunction. Here, we present the clinical case of a 50-year-old proband with familial diabetes mellitus in five generations (proband, her mother, grandmother, great-grandfather, and son). This disease is most likely associated with the novel Ser6Arg mutation in the HNF1A gene, which was identified in four family members. The mutation was not detected in MODY patients (126 subjects), in patients with type 2 diabetes mellitus (188 subjects), and in a general population sample (564 subjects).

Precision diabetes: learning from monogenic diabetes

The precision medicine approach of tailoring treatment to the individual characteristics of each patient or subgroup has been a great success in monogenic diabetes subtypes, MODY and neonatal diabetes. This review examines what has led to the success of a precision medicine approach in monogenic diabetes (precision diabetes) and outlines possible implications for type 2 diabetes. For monogenic diabetes, the molecular genetics can define discrete aetiological subtypes that have profound implications on diabetes treatment and can predict future development of associated clinical features, allowing early preventative or supportive treatment. In contrast, type 2 diabetes has overlapping polygenic susceptibility and underlying aetiologies, making it difficult to define discrete clinical subtypes with a dramatic implication for treatment. The implementation of precision medicine in neonatal diabetes was simple and rapid as it was based on single clinical criteria (diagnosed <6 months of age). In contrast, in MODY it was more complex and slow because of the lack of single criteria to identify patients, but it was greatly assisted by the development of a diagnostic probability calculator and associated smartphone app. Experience in monogenic diabetes suggests that successful adoption of a precision diabetes approach in type 2 diabetes will require simple, quick, easily accessible stratification that is based on a combination of routine clinical data, rather than relying on newer technologies. Analysing existing clinical data from routine clinical practice and trials may provide early success for precision medicine in type 2 diabetes.

Towards a systematic nationwide screening strategy for MODY

MODY is an early-onset monogenic form of diabetes. Correctly identifying MODY is of considerable importance as diagnosing the specific genetic subtype can inform the optimal treatment, with many patients being able to discontinue unnecessary insulin treatment. Diagnostic molecular genetic testing to confirm MODY is expensive, so screening strategies are required to identify the most appropriate patients for testing. In this issue of Diabetologia, Johansson and colleagues (DOI 10.1007/s00125-016-4167-1 ) describe a nationwide systematic screening approach to identify individuals with MODY in the paediatric age range. They focused testing on patients negative for both GAD and islet antigen 2 (IA-2) islet autoantibodies, thereby ruling out those with markers of type 1 diabetes, the most common form of diabetes in this age group. This commentary discusses the advantages and limitations of the approach, and the caution required when interpreting variants of uncertain pathogenicity identified from testing whole populations rather than targeting only patients with a strong MODY phenotype.