Increased all-cause and cardiovascular mortality in monogenic diabetes as a result of mutations in the HNF1A gene

A preliminary study to evaluate the strategy of combining clinical criteria and next generation sequencing (NGS) for the identification of monogenic diabetes among multi-ethnic Asians

AIMS

Diabetes is increasing globally and Asia is the epicenter. Among those with young-onset diabetes (<45years), the prevalence of monogenic diabetes is estimated to be non-trivial (∼5%). An accurate diagnosis of monogenic diabetes is important to inform treatment, prognosis and genetic counseling. Therefore, a robust clinical algorithm to identify probands for testing is needed. Our aims are (1) to select probands for genetic testing and variant identification based on their clinical phenotype and (2) to evaluate the MODY probability calculator in our multi-ethnic Asian population.

METHODS

Eighty-four potential probands, identified in accordance with clinical practice guidelines, were subjected to re-sequencing of 16 monogenic diabetes genes and targeted genotyping for mitochondrial 3243A>G point-mutation. Variants, confirmed by bi-directional Sanger sequencing, were classified as pathogenic if they fulfilled the criteria adapted from American College of Medical Genetics. Performance of MODY calculator (with positive-predictive threshold set at >62.4%) for those with diabetes-onset ⩽35years (data input-limit) (n=71) was also evaluated.

RESULTS

Thirteen subjects (15.5%) harbored likely pathogenic/pathogenic variants: 6 (2 novel) in HNF1A (1 subject concomitantly had another HNF4A variant), 1 in HNF4A, 2 in mt3243A>G and 1 each in GCK, KCNJ11 (novel), ABCC8 (novel) and PAX4 (novel). Performance of the MODY calculator was: sensitivity 0.769, specificity 0.603 and negative predictive value 0.921. When analysis was restricted to MODY1-3, the performance was: 0.875, 0.587 and 0.974, respectively.

CONCLUSIONS

The prevalence of MODY is non-trivial (∼15%) among Asians with young-onset diabetes. MODY calculator performs well in our population in nominating probands for genetic testing.

Successful maintenance on sulphonylurea therapy and low diabetes complication rates in a HNF1A-MODY cohort

AIMS

HNF1A gene mutations are the most common cause of maturity-onset diabetes of the young (MODY) in the UK. Persons with HNF1A-MODY display sensitivity to sulphonylurea therapy; however, the long-term efficacy is not established. There is limited literature as to the prevalence of micro- and macrovascular complications in this unique cohort. The aim of this study was to determine the natural progression and clinical management of HNF1A-MODY diabetes in a dedicated MODY clinic.

METHODS

Sixty patients with HNF1A-MODY and a cohort of 60 BMI-, age-, ethnicity- and diabetes duration-matched patients with Type 1 diabetes mellitus participated in the study. All patients were phenotyped in detail. Clinical follow-up of the HNF1A-MODY cohort occurred on a bi-annual basis.

RESULTS

Following a genetic diagnosis of MODY, the majority of the cohort treated with sulphonylurea therapy remained insulin independent at 84-month follow-up (80%). The HbA1c in the HNF1A-MODY group treated with sulphonylurea therapy alone improved significantly over the study period [from 49 (44-63) mmol/mol, 6.6 (6.2-7.9)% to 41 (31-50) mmol/mol, 5.9 (5-6.7)%; P = 0.003]. The rate of retinopathy was significantly lower than that noted in the Type 1 diabetes mellitus group (13.6 vs. 50%; P = 0.0001).There was also a lower rate of microalbuminuria and cardiovascular disease in the HNF1A-MODY group compared with the Type 1 diabetes mellitus group.

CONCLUSIONS

This study demonstrates that the majority of patients with HNF1A-MODY can be maintained successfully on sulphonylurea therapy with good glycaemic control. We note a significantly lower rate of micro- and macrovascular complications than reported previously. The use of appropriate therapy at early stages of the disorder may decrease the incidence of complications.

Divergent phenotypes in siblings with identical novel mutations in the HNF-1α gene leading to maturity onset diabetes of the young type 3

BACKGROUND

Maturity onset diabetes of the young (MODY) is an autosomal dominant form of non-insulin-dependent diabetes mellitus caused by mutations in at least 13 different genes. The hepatocyte nuclear factor (HNF)-1α gene is affected in the most common form (HNF1A-MODY [MODY3]).

CASE PRESENTATION

We describe the co-inheritance of a novel heterozygous missense mutation c.1761C > G (p.Pro588Ala) with a novel complex deletion insertion mutation (c.1765_1766delinsGCCCGfs86*) in the HNF-1α gene among affected members of one family. Both mutations were present in the affected patients and neither was present in unaffected family members. The family had not only inheritance of MODY but also increased susceptibility to type 2 diabetes. Therefore one family member had classical type 2 diabetes including metabolic syndrome aggravated by a genetic predisposition in the form of HNF1A-MODY.

CONCLUSION

The presence of common type 2 diabetes features should not detract from the possibility of MODY in patients with a striking autosomal-dominant family history.

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.

Intima-media thickness and endothelial dysfunction in GCK and HNF1A-MODY patients

OBJECTIVE

Mutations in the glucokinase (GCK) gene, along with hepatocyte nuclear factor 1A (HNF1A) gene mutations, are the most frequent cause of maturity-onset diabetes of the young (MODY). GCK-MODY patients are typically characterized by a moderate fasting hyperglycemia; however, little is known about atherosclerosis and intermediate-related phenotypes in these subjects.

DESIGN

To examine carotid artery intima-media thickness (IMT) and endothelial function assessed by brachial artery flow-mediated dilatation (FMD) in GCK gene mutations carriers and HNF1A-MODY.

METHODS

A total of 64 subjects with GCK gene mutations, and 52 HNF1A gene mutation carriers as well as 53 nondiabetic controls were examined. IMT and FMD were assessed by ultrasonography. Appropriate statistical tests were performed to assess differences between the groups, and multivariate linear regression was done for the association with IMT and FMD.

RESULTS

The clinical characteristics of all groups were similar with the mean age at examination of 35.1, 41.1, and 39.5 years for GCK, HNF1A and the control group respectively. The highest mean IMT value was in the HNF1A-MODY group: 7.0±1.4 mm, whereas it reached 6.3±1.4 mm in GCK mutation carriers and 6.3±1.3 mm in controls (P=0.008). After adjustment for possible clinical and biochemical cofounders, IMT remained higher in HNF1A-MODY patients as compared with GCK-MODY patients (P=0.02) and controls (P=0.0003). FMD was significantly lower in HNF1A (9.9±4.6%) and GCK-MODY (11.1±4.6%) patients in comparison with controls (13.9±4.7%; P=0.0001). After adjustment, FMD remained lower in HNF1A-MODY (P=0.0005) and GCK-MODY patients (P=0.01) as compared with controls.

CONCLUSIONS

Both examined MODY groups demonstrated evidence of endothelial dysfunction. In addition, HNF1-MODY patients seem to be more prone to an early atherosclerotic phenotype.

Many faces of monogenic diabetes

Monogenic diabetes represents a heterogeneous group of disorders resulting from defects in single genes. Defects are categorized primarily into two groups: disruption of β-cell function or a reduction in the number of β-cells. A complex network of transcription factors control pancreas formation, and a dysfunction of regulators high in the hierarchy leads to pancreatic agenesis. Dysfunction among factors further downstream might cause organ hypoplasia, absence of islets of Langerhans or a reduction in the number of β-cells. Many transcription factors have pleiotropic effects, explaining the association of diabetes with other congenital malformations, including cerebellar agenesis and pituitary agenesis. Monogenic diabetes variants are classified conventionally according to age of onset, with neonatal diabetes occurring before the age of 6 months and maturity onset diabetes of the young (MODY) manifesting before the age of 25 years. Recently, certain familial genetic defects were shown to manifest as neonatal diabetes, MODY or even adult onset diabetes. Patients with neonatal diabetes require a thorough genetic work-up in any case, and because extensive phenotypic overlap exists between monogenic, type 2, and type 1 diabetes, genetic analysis will also help improve diagnosis in these cases. Next generation sequencing will facilitate rapid screening, leading to the discovery of digenic and oligogenic diabetes variants, and helping to improve our understanding of the genetics underlying other types of diabetes. An accurate diagnosis remains important, because it might lead to a change in the treatment of affected subjects and influence long-term complications.

Circulating CD36 is reduced in HNF1A-MODY carriers

INTRODUCTION

Premature atherosclerosis is a significant cause of morbidity and mortality in type 2 diabetes mellitus. Maturity onset diabetes of the young (MODY) accounts for approximately 2% of all diabetes, with mutations in the transcription factor; hepatocyte nuclear factor 1 alpha (HNF1A) accounting for the majority of MODY cases. There is somewhat limited data available on the prevalence of macrovascular disease in HNF1A-MODY carriers with diabetes. Marked insulin resistance and the associated dyslipidaemia are not clinical features of HNF1A-MODY carriers. The scavenger protein CD36 has been shown to play a substantial role in the pathogenesis of atherosclerosis, largely through its interaction with oxidised LDL. Higher levels of monocyte CD36 and plasma CD36(sCD36) are seen to cluster with insulin resistance and diabetes. The aim of this study was to determine levels of sCD36 in participants with HNF1A-MODY diabetes and to compare them with unaffected normoglycaemic family members and participants with type 2 diabetes mellitus.

METHODS

We recruited 37 participants with HNF1A-MODY diabetes and compared levels of sCD36 with BMI-matched participants with type 2 diabetes mellitus and normoglycaemic HNF1A-MODY negative family controls. Levels of sCD36 were correlated with phenotypic and biochemical parameters.

RESULTS

HNF1A-MODY participants were lean, normotensive, with higher HDL and lower triglyceride levels when compared to controls and participants with type 2 diabetes mellitus. sCD36 was also significantly lower in HNF1A-MODY participants when compared to both the normoglycaemic family controls and to lean participants with type 2 diabetes mellitus.

CONCLUSION

In conclusion, sCD36 is significantly lower in lean participants with HNF1A-MODY diabetes when compared to weight-matched normoglycaemic familial HNF1A-MODY negative controls and to lean participants with type 2 diabetes mellitus. Lower levels of this pro-atherogenic marker may result from the higher HDL component in the lipid profile of HNF1A-MODY participants.

Development of an economic evaluation of diagnostic strategies: the case of monogenic diabetes

OBJECTIVES

To describe the development process for defining an appropriate model structure for the economic evaluation of test-treatment strategies for patients with monogenic diabetes (caused by mutations in the GCK, HNF1A or HNF4A genes).

DESIGN

Experts were consulted to identify and define realistic test-treatment strategies and care pathways. A systematic assessment of published diabetes models was undertaken to inform the model structure.

SETTING

National Health Service in England and Wales.

PARTICIPANTS

Experts in monogenic diabetes whose collective expertise spans the length of the patient care pathway.

PRIMARY AND SECONDARY OUTCOMES

A defined model structure, including the test-treatment strategies, and the selection of a published diabetes model appropriate for the economic evaluation of strategies to identify patients with monogenic diabetes.

RESULTS

Five monogenic diabetes test-treatment strategies were defined: no testing of any kind, referral for genetic testing based on clinical features as noted by clinicians, referral for genetic testing based on the results of a clinical prediction model, referral for genetic testing based on the results of biochemical and immunological tests, referral for genetic testing for all patients with a diagnosis of diabetes under the age of 30 years. The systematic assessment of diabetes models identified the IMS CORE Diabetes Model (IMS CDM) as a good candidate for modelling the long-term outcomes and costs of the test-treatment strategies for monogenic diabetes. The short-term test-treatment events will be modelled using a decision tree which will feed into the IMS CDM.

CONCLUSIONS

Defining a model structure for any economic evaluation requires decisions to be made. Expert consultation and the explicit use of critical appraisal can inform these decisions. Although arbitrary choices have still been made, decision modelling allows investigation into such choices and the impact of assumptions that have to be made due to a lack of data.

Mutations in the genes encoding the transcription factors hepatocyte nuclear factor 1 alpha and 4 alpha in maturity-onset diabetes of the young and hyperinsulinemic hypoglycemia

Maturity-onset diabetes of the young (MODY) is a monogenic disorder characterized by autosomal dominant inheritance of young-onset (typically <25 years), noninsulin-dependent diabetes due to defective insulin secretion. MODY is both clinically and genetically heterogeneous with mutations in at least 10 genes. Mutations in the HNF1A gene encoding hepatocyte nuclear factor-1 alpha are the most common cause of MODY in most adult populations studied. The number of different pathogenic HNF1A mutations totals 414 in 1,247 families. Mutations in the HNF4A gene encoding hepatocyte nuclear factor-4 alpha are a rarer cause of MODY with 103 different mutations reported in 173 families to date. Sensitivity to treatment with sulfonylurea tablets is a feature of both HNF1A and HNF4A mutations. The HNF4A MODY phenotype has been expanded by the reports of macrosomia in ∼50% of babies, and more rarely, neonatal hyperinsulinemic hypoglycemia. The identification of an HNF1A or HNF4A gene mutation has important implications for clinical management in diabetes and pregnancy, but MODY is significantly underdiagnosed. Current research is focused on identifying biomarkers and developing probability models to identify those patients most likely to have MODY, until next generation sequencing technology enables cost-effective gene analysis for all patients with young onset diabetes.

Exome sequencing and genetic testing for MODY

CONTEXT

Genetic testing for monogenic diabetes is important for patient care. Given the extensive genetic and clinical heterogeneity of diabetes, exome sequencing might provide additional diagnostic potential when standard Sanger sequencing-based diagnostics is inconclusive.

OBJECTIVE

The aim of the study was to examine the performance of exome sequencing for a molecular diagnosis of MODY in patients who have undergone conventional diagnostic sequencing of candidate genes with negative results.

RESEARCH DESIGN AND METHODS

We performed exome enrichment followed by high-throughput sequencing in nine patients with suspected MODY. They were Sanger sequencing-negative for mutations in the HNF1A, HNF4A, GCK, HNF1B and INS genes. We excluded common, non-coding and synonymous gene variants, and performed in-depth analysis on filtered sequence variants in a pre-defined set of 111 genes implicated in glucose metabolism.

RESULTS

On average, we obtained 45 X median coverage of the entire targeted exome and found 199 rare coding variants per individual. We identified 0-4 rare non-synonymous and nonsense variants per individual in our a priori list of 111 candidate genes. Three of the variants were considered pathogenic (in ABCC8, HNF4A and PPARG, respectively), thus exome sequencing led to a genetic diagnosis in at least three of the nine patients. Approximately 91% of known heterozygous SNPs in the target exomes were detected, but we also found low coverage in some key diabetes genes using our current exome sequencing approach. Novel variants in the genes ARAP1, GLIS3, MADD, NOTCH2 and WFS1 need further investigation to reveal their possible role in diabetes.

CONCLUSION

Our results demonstrate that exome sequencing can improve molecular diagnostics of MODY when used as a complement to Sanger sequencing. However, improvements will be needed, especially concerning coverage, before the full potential of exome sequencing can be realized.

Clinical features and treatment of maturity onset diabetes of the young (MODY)

Maturity onset diabetes of the young (MODY) is a heterogeneous group of disorders that result in β-cell dysfunction. It is rare, accounting for just 1%-2% of all diabetes. It is often misdiagnosed as type 1 or type 2 diabetes, as it is often difficult to distinguish MODY from these two forms. However, diagnosis allows appropriate individualized care, depending on the genetic etiology, and allows prognostication in family members. In this review, we discuss features of the common causes of MODY, as well as the treatment and diagnosis of MODY.