Comprehensive genetic screening: The prevalence of maturity-onset diabetes of the young gene variants in a population-based childhood diabetes cohort

A novel BLK heterozygous mutation (p.Met121lle) in maturity-onset diabetes mellitus: A case report and literature review

Maturity onset diabetes of the young (MODY) is a highly heterogeneous monogenic disease that occurs due to β-cell dysfunction. It is divided into different types depending on the gene mutated, and a total of 16 genes have been found to be associated with MODY. However, due to the current lack of understanding of monogenic diabetes, 90% of MODY is currently misdiagnosed and ignored in clinical practice. In this paper, we report the clinical data of a patient diagnosed with diabetes. Genetic testing revealed a novel BLK heterozygous mutation (c.363G>A) in the patient and in his father and son. He had no islet-specific autoantibodies and showed a reduced meal-induced response of insulin. Precise diagnosis of MODY individuals is important to the treatment.

The Maturity-Onset Diabetes of the Young (MODY) Calculator Overestimates MODY Probability in Hispanic Youth

CONTEXT

The applicability of the MODY risk calculator (Shields et al) to non- White European populations remains unknown.

OBJECTIVE

We aimed to test its real-world application in Hispanic youth.

METHODS

We conducted a retrospective chart review of Hispanic youth (<23 years) with diabetes (n=2033) in a large pediatric tertiary care center in the U.S. We calculated MODY probability for all subjects, splitting them into two cohorts based on the original model: Individuals who were started on insulin within 6 months of diabetes diagnosis (Cohort 1) and those who were not (Cohort 2).

RESULTS

Cohort 1 consisted of 1566 individuals (median age [25p, 75p]: 16 [13, 19] years, 49% female), while Cohort 2 comprised 467 youth (median age [25p, 75p]: 17 [15, 20] years, 62% female). The mean MODY probability was 5.9% and 61.9% in Cohort 1 and Cohort 2, respectively. The mean probability for both cohorts combined was 18.8% suggesting an expected 382 individuals with MODY, which is much higher than previous estimations (1-5%; i.e. 20-102 individuals in this cohort). A total of 18 individuals tested positive for MODY among the limited number of individuals tested based on clinical suspicion and genetic testing availability (n=44 out of 2033 tested, [2.2% of overall cohort]).

CONCLUSIONS

The MODY risk calculator likely overestimates the probability of MODY in Hispanic youth, largely driven by an overestimation in those not early-insulin treated (predominantly young-onset type 2 diabetes). The calculator needs updating to improve its applicability in this population. In addition, further research to help better identify MODY in Hispanic youth.

Clinical characteristics, treatment, and treatment switch after molecular-genetic classification in individuals with maturity-onset diabetes of the young: Insights from the multicenter real-world DPV registry

BACKGROUND

Individuals with maturity-onset diabetes of the young (MODY) are often misdiagnosed as type 1 or type 2 diabetes and receive inappropriate care. We aimed to investigate the characteristics and treatment of all MODY types in a multicenter, real-world setting.

METHODS

Individuals with MODY from the diabetes prospective follow-up (DPV) registry were studied. We compared clinical parameters during the first year of diabetes and the most recent treatment year after MODY diagnosis.

RESULTS

A total of 1640 individuals were identified with GCK-MODY (n = 941) and HNF1A-MODY (n = 417) as the most frequent types. Among these, 912 individuals were available with information during the first and the most recent treatment year (median duration of follow-up: 4.2 years [2.6-6.6]). Positive beta cell autoantibodies were present in 20.6% (15.2% IAA). Median age at diagnosis ranged from 9.9 years in GCK-MODY (Q1-Q3: 6.2-13.1 years) and INS-MODY (2.7-13.7 years) to 14.3 years (5.0-17.1) in KCNJ11-MODY. Frequency of oral antidiabetic agents (OAD) use increased and insulin decreased in HNF4A-MODY (OAD: 18% to 39%, insulin: 34% to 23%) and in HNF1A-MODY (OAD: 18% to 31%, insulin: 35% to 25%). ABCC8-MODY was characterized by a decrement in nonpharmacological treatment (26% to 16%) and "insulin only" treatment (53% to 42%), while the proportion of individuals treated with OAD but no insulin increased from 0% to 21%.

CONCLUSIONS

Our results indicate that some teams caring for individuals with MODY are hesitant with regard to current recommendations. Registries are an essential source of information and provide a basis for discussing treatment guidelines for MODY.

Whole Exome Sequencing in Children With Type 1 Diabetes Before Age 6 Years Reveals Insights Into Disease Heterogeneity

Aims: This study is aimed at comparing whole exome sequencing (WES) data with the clinical presentation in children with type 1 diabetes onset ≤ 5 years of age (EOT1D). Methods: WES was performed in 99 unrelated children with EOT1D with subsequent analysis to identify potentially deleterious rare variants in MODY genes. High-resolution HLA class II haplotyping, SNP genotyping, and T1D-genetic risk score (T1D-GRS) were also evaluated. Results: Eight of the ninety-nine EOT1D participants carried a potentially deleterious rare variant in a MODY gene. Rare variants affected five genes: GCK (n = 1), HNF1B (n = 2), HNF4A (n = 1), PDX1 (n = 2), and RFX6 (n = 2). At diagnosis, these children had a mean age of 3.0 years, a mean HbA1c of 10.5%, a detectable C-peptide in 5/8, and a positive islet autoantibody in 6/7. Children with MODY variants tend to exhibit a lower number of pancreatic autoantibodies and a lower fasting C-peptide compared to EOT1D without MODY rare variants. They also carried at least one high-risk DR3-DQ2 or DR4-DQ8 haplotype and exhibited a T1D-GRS similar to the other individuals in the EOT1D cohort, but higher than healthy controls. Conclusions: WES found potentially deleterious rare variants in MODY genes in 8.1% of EOT1D, occurring in the context of a T1D genetic background. Such genetic variants may contribute to disease precipitation by a β-cell dysfunction mechanism. This supports the concept of different endotypes of T1D, and WES at T1D onset may be a prerequisite for the implementation of precision therapies in children with autoimmune diabetes.

Monogenic diabetes in children: An underdiagnosed and poorly managed clinical dilemma

Monogenic diabetes, constituting 1%-2% of global diabetes cases, arises from single gene defects with distinctive inheritance patterns. Despite over 50 ass-ociated genetic disorders, accurate diagnoses and management of monogenic diabetes remain inadequate, underscoring insufficient clinician awareness. The disease spectrum encompasses maturity-onset diabetes of the young (MODY), characterized by distinct genetic mutations affecting insulin secretion, and neonatal diabetes mellitus (NDM) - a heterogeneous group of severe hyperglycemic disorders in infants. Mitochondrial diabetes, autoimmune monogenic diabetes, genetic insulin resistance and lipodystrophy syndromes further diversify the monogenic diabetes landscape. A tailored approach based on phenotypic and biochemical factors to identify candidates for genetic screening is recommended for suspected cases of MODY. NDM diagnosis warrants immediate molecular genetic testing for infants under six months. Identifying these genetic defects presents a unique opportunity for precision medicine. Ongoing research aimed to develop cost-effective genetic testing methods and gene-based therapy can facilitate appropriate identification and optimize clinical outcomes. Identification and study of new genes offer a valuable opportunity to gain deeper insights into pancreatic cell biology and the pathogenic mechanisms underlying common forms of diabetes. The clinical review published in the recent issue of World Journal of Diabetes is such an attempt to fill-in our knowledge gap about this enigmatic disease.

Comparison of Bayesian approaches for developing prediction models in rare disease: application to the identification of patients with Maturity-Onset Diabetes of the Young

BACKGROUND

Clinical prediction models can help identify high-risk patients and facilitate timely interventions. However, developing such models for rare diseases presents challenges due to the scarcity of affected patients for developing and calibrating models. Methods that pool information from multiple sources can help with these challenges.

METHODS

We compared three approaches for developing clinical prediction models for population screening based on an example of discriminating a rare form of diabetes (Maturity-Onset Diabetes of the Young - MODY) in insulin-treated patients from the more common Type 1 diabetes (T1D). Two datasets were used: a case-control dataset (278 T1D, 177 MODY) and a population-representative dataset (1418 patients, 96 MODY tested with biomarker testing, 7 MODY positive). To build a population-level prediction model, we compared three methods for recalibrating models developed in case-control data. These were prevalence adjustment ("offset"), shrinkage recalibration in the population-level dataset ("recalibration"), and a refitting of the model to the population-level dataset ("re-estimation"). We then developed a Bayesian hierarchical mixture model combining shrinkage recalibration with additional informative biomarker information only available in the population-representative dataset. We developed a method for dealing with missing biomarker and outcome information using prior information from the literature and other data sources to ensure the clinical validity of predictions for certain biomarker combinations.

RESULTS

The offset, re-estimation, and recalibration methods showed good calibration in the population-representative dataset. The offset and recalibration methods displayed the lowest predictive uncertainty due to borrowing information from the fitted case-control model. We demonstrate the potential of a mixture model for incorporating informative biomarkers, which significantly enhanced the model's predictive accuracy, reduced uncertainty, and showed higher stability in all ranges of predictive outcome probabilities.

CONCLUSION

We have compared several approaches that could be used to develop prediction models for rare diseases. Our findings highlight the recalibration mixture model as the optimal strategy if a population-level dataset is available. This approach offers the flexibility to incorporate additional predictors and informed prior probabilities, contributing to enhanced prediction accuracy for rare diseases. It also allows predictions without these additional tests, providing additional information on whether a patient should undergo further biomarker testing before genetic testing.

Band-shaped keratopathy in HNF4A-related Fanconi syndrome: a case report and review of the literature

BACKGROUND

Fanconi's syndrome (FS) is characterized by type-2 renal tubular acidosis, short stature, and renal rickets, along with glycosuria, aminoaciduria, hypophosphaturia, and urinary bicarbonate wasting. The genetic form of FS has been linked to HNF4A variants. Although additional clinical features such as hearing impairment have recently been associated with HNF4A-linked FS, its ocular manifestation has not been described.

MATERIAL AND METHODS

Presenting a case of a 5-year-old male child with bilateral progressive corneal opacification and the presence of bilateral greyish-white deposits in the interpalpebral region since infancy. A next-generation sequencing (NGS)-based genetic testing was performed for the child followed by parental genetic testing for the identified variant. Furthermore, relevant works of literature were reviewed related to this condition.

RESULTS

Detailed corneal findings showed a bilateral band-shaped keratopathy (BSK) in the patient. Physical and systemic findings showed signs consistent with FS. Sequencing analysis revealed a novel heterozygous c.635C>T, (p.Pro212Leu) variant in the HNF4A gene in the proband and mother, while the father had a normal genotype.

CONCLUSIONS

Our case highlights the occurrence of BSK in an exceptionally rare manifestation of hereditary FS linked to HNF4A gene variant. The variant exists both in proband and asymptomatic mother. Therefore, the variable penetrance which is known to exist in HNF4A is acknowledged in this context. This report suggests the first documented instance establishing a plausible connection between BSK and HNF4A-associated FS, characterized by the variable penetrance attributed to the HNF4A gene.

Development of a clinical calculator to aid the identification of MODY in pediatric patients at the time of diabetes diagnosis

Maturity Onset Diabetes of the Young (MODY) is a young-onset, monogenic form of diabetes without needing insulin treatment. Diagnostic testing is expensive. To aid decisions on who to test, we aimed to develop a MODY probability calculator for paediatric cases at the time of diabetes diagnosis, when the existing "MODY calculator" cannot be used. Firth logistic regression models were developed on data from 3541 paediatric patients from the Swedish 'Better Diabetes Diagnosis' (BDD) population study (n = 46 (1.3%) MODY (HNF1A, HNF4A, GCK)). Model performance was compared to using islet autoantibody testing. HbA1c, parent with diabetes, and absence of polyuria were significant independent predictors of MODY. The model showed excellent discrimination (c-statistic = 0.963) and calibrated well (Brier score = 0.01). MODY probability > 1.3% (ie. above background prevalence) had similar performance to being negative for all 3 antibodies (positive predictive value (PPV) = 10% v 11% respectively i.e. ~ 1 in 10 positive test rate). Probability > 1.3% and negative for 3 islet autoantibodies narrowed down to 4% of the cohort, and detected 96% of MODY cases (PPV = 31%). This MODY calculator for paediatric patients at time of diabetes diagnosis will help target genetic testing to those most likely to benefit, to get the right diagnosis.

Promoting advanced medical services in the framework of 3PM-a proof-of-concept by the "Centro" Region of Portugal

Multidisciplinary team from three universities based in the "Centro" Region of Portugal developed diverse approaches as parts of a project dedicated to enhancing and expanding Predictive, Preventive, and Personalized Medicine (3PM) in the Region. In a sense, outcomes acted as a proof-of-concept, in that they demonstrated the feasibility, but also the relevance of the approaches. The accomplishments comprise defining a new regional strategy for implementing 3PM within the Region, training of human resources in genomic sequencing, and generating good practices handbooks dedicated to diagnostic testing via next-generation sequencing, to legal and ethical concerns, and to knowledge transfer and entrepreneurship, aimed at increasing literacy on 3PM approaches. Further approaches also included support for entrepreneurship development and start-ups, and diverse and relevant initiatives aimed at increasing literacy relevant to 3PM. Efforts to enhance literacy encompassed citizens across the board, from patients and high school students to health professionals and health students. This focus on empowerment through literacy involved a variety of initiatives, including the creation of an illustrated book on genomics and the production of two theater plays centered on genetics. Additionally, authors stressed that genomic tools are relevant, but they are not the only resources 3PM is based on. Thus, they defend that other initiatives intended to enable citizens to take 3PM should include multi-omics and, having in mind the socio-economic burden of chronic diseases, suboptimal health status approaches in the 3PM framework should also be considered, in order to anticipate medical intervention in the subclinical phase.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00353-9.

Identification of monogenic diabetes in an Australian cohort using the Exeter maturity-onset diabetes of the young (MODY) probability calculator and next-generation sequencing gene panel testing

AIMS

This study aims to describe the prevalence of monogenic diabetes in an Australian referral cohort, in relation to Exeter maturity-onset diabetes of the young (MODY) probability calculator (EMPC) scores and next-generation sequencing with updated testing where relevant.

METHODS

State-wide 5-year retrospective cohort study of individuals referred for monogenic diabetes genetic testing.

RESULTS

After excluding individuals who had cascade testing for a familial variant (21) or declined research involvement (1), the final cohort comprised 40 probands. Incorporating updated testing, the final genetic result was positive (likely pathogenic/pathogenic variant) in 11/40 (27.5%), uncertain (variant of uncertain significance) in 8/40 (20%) and negative in 21/40 (52.5%) participants. Causative variants were found in GCK, HNF1A, MT-TL1 and HNF4A. Variants of uncertain significance included a novel multi-exonic GCK duplication. Amongst participants with EMPC scores ≥ 25%, a causative variant was identified in 37%. Cascade testing was positive in 9/10 tested relatives with diabetes and 0/6 tested relatives with no history of diabetes.

CONCLUSIONS

Contemporary genetic testing produces a high yield of positive results in individuals with clinically suspected monogenic diabetes and their relatives with diabetes, highlighting the value of genetic testing for this condition. An EMPC score cutoff of ≥ 25% correctly yielded a positive predictive value of ≥ 25% in this multiethnic demographic. This is the first Australian study to describe EMPC scores in the Australian clinic setting, albeit a biased referral cohort. Larger studies may help characterise EMPC performance between ethnic subsets, noting differences in the expected probability of monogenic diabetes relative to type 2 diabetes.

Whole-exome sequencing reveals novel variants of monogenic diabetes in Tunisia: impact on diagnosis and healthcare management

Introduction: Monogenic diabetes (MD) accounts for 3%-6% of all cases of diabetes. This prevalence is underestimated due to its overlapping clinical features with type 1 and type 2 diabetes. Hence, genetic testing is the most appropriate tool for obtaining an accurate diagnosis. In Tunisia, few cohorts of MD have been investigated until now. The aim of this study is to search for pathogenic variants among 11 patients suspected of having MD in Tunisia using whole-exome sequencing (WES). Materials and methods: WES was performed in 11 diabetic patients recruited from a collaborating medical center. The pathogenicity of genetic variation was assessed using combined filtering and bioinformatics prediction tools. The online ORVAL tool was used to predict the likelihood of combinations of pathogenic variations. Then, Sanger sequencing was carried out to confirm likely pathogenic predicted variants among patients and to check for familial segregation. Finally, for some variants, we performed structural modeling to study their impact on protein function. Results: We identified novel variants related to MD in Tunisia. Pathogenic variants are located in several MODY and non-MODY genes. We highlighted the presence of syndromic forms of diabetes, including the Bardet-Biedl syndrome, Alström syndrome, and severe insulin resistance, as well as the presence of isolated diabetes with significantly reduced penetrance for Wolfram syndrome-related features. Idiopathic type 1 diabetes was also identified in one patient. Conclusion: In this study, we emphasized the importance of genetic screening for MD in patients with a familial history of diabetes, mainly among admixed and under-represented populations living in low- and middle-income countries. An accurate diagnosis with molecular investigation of MD may improve the therapeutic choice for better management of patients and their families. Additional research and rigorous investigations are required to better understand the physiopathological mechanisms of MD and implement efficient therapies that take into account genomic context and other related factors.

Increased Liver Enzymes: An Under-Recognized Finding in Maturity-Onset Diabetes of the Young Type 5 (MODY 5)

Maturity-onset diabetes of the young type 5 (MODY 5) is characterized by a single gene mutation in the HNF1B gene. This frequently leads to insulin resistance and presents as young-onset diabetes. Other manifestations can occur in organs expressing hepatocyte nuclear factor-1 beta. This case report highlights family members with MODY 5 presenting with increased liver enzymes with no etiology. The siblings and their mother had a point mutation p.Arg235Trp in HNF1B gene located at 17q12. This variant is associated with autosomal dominant MODY 5 with renal cysts also known as renal cysts and diabetes syndrome.

Monogenic diabetes

Monogenic diabetes includes several clinical conditions generally characterized by early-onset diabetes, such as neonatal diabetes, maturity-onset diabetes of the young (MODY) and various diabetes-associated syndromes. However, patients with apparent type 2 diabetes mellitus may actually have monogenic diabetes. Indeed, the same monogenic diabetes gene can contribute to different forms of diabetes with early or late onset, depending on the functional impact of the variant, and the same pathogenic variant can produce variable diabetes phenotypes, even in the same family. Monogenic diabetes is mostly caused by impaired function or development of pancreatic islets, with defective insulin secretion in the absence of obesity. The most prevalent form of monogenic diabetes is MODY, which may account for 0.5-5% of patients diagnosed with non-autoimmune diabetes but is probably underdiagnosed owing to insufficient genetic testing. Most patients with neonatal diabetes or MODY have autosomal dominant diabetes. More than 40 subtypes of monogenic diabetes have been identified to date, the most prevalent being deficiencies of GCK and HNF1A. Precision medicine approaches (including specific treatments for hyperglycaemia, monitoring associated extra-pancreatic phenotypes and/or following up clinical trajectories, especially during pregnancy) are available for some forms of monogenic diabetes (including GCK- and HNF1A-diabetes) and increase patients' quality of life. Next-generation sequencing has made genetic diagnosis affordable, enabling effective genomic medicine in monogenic diabetes.

Identification of monogenic variants in more than ten per cent of children without type 1 diabetes-related autoantibodies at diagnosis in the Finnish Pediatric Diabetes Register

AIMS/HYPOTHESIS

Monogenic forms of diabetes (MODY, neonatal diabetes mellitus and syndromic forms) are rare, and affected individuals may be misclassified and treated suboptimally. The prevalence of type 1 diabetes is high in Finnish children but systematic screening for monogenic diabetes has not been conducted. We assessed the prevalence and clinical manifestations of monogenic diabetes in children initially registered with type 1 diabetes in the Finnish Pediatric Diabetes Register (FPDR) but who had no type 1 diabetes-related autoantibodies (AABs) or had only low-titre islet cell autoantibodies (ICAs) at diagnosis.

METHODS

The FPDR, covering approximately 90% of newly diagnosed diabetic individuals aged ≤15 years in Finland starting from 2002, includes data on diabetes-associated HLA genotypes and AAB data (ICA, and autoantibodies against insulin, GAD, islet antigen 2 and zinc transporter 8) at diagnosis. A next generation sequencing gene panel including 42 genes was used to identify monogenic diabetes. We interpreted the variants in HNF1A by using the gene-specific standardised criteria and reported pathogenic and likely pathogenic findings only. For other genes, we also reported variants of unknown significance if an individual's phenotype suggested monogenic diabetes.

RESULTS

Out of 6482 participants, we sequenced DNA for 152 (2.3%) testing negative for all AABs and 49 (0.8%) positive only for low-titre ICAs (ICA_low). A monogenic form of diabetes was revealed in 19 (12.5%) of the AAB-negative patients (14 [9.2%] had pathogenic or likely pathogenic variants) and two (4.1%) of the ICA_low group. None had ketoacidosis at diagnosis or carried HLA genotypes conferring high risk for type 1 diabetes. The affected genes were GCK, HNF1A, HNF4A, HNF1B, INS, KCNJ11, RFX6, LMNA and WFS1. A switch from insulin to oral medication was successful in four of five patients with variants in HNF1A, HNF4A or KCNJ11.

CONCLUSIONS/INTERPRETATION

More than 10% of AAB-negative children with newly diagnosed diabetes had a genetic finding associated with monogenic diabetes. Because the genetic diagnosis can lead to major changes in treatment, we recommend referring all AAB-negative paediatric patients with diabetes for genetic testing. Low-titre ICAs in the absence of other AABs does not always indicate a diagnosis of type 1 diabetes.

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.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Diabetes-related antibody-testing is a valuable screening tool for identifying monogenic diabetes - A survey from the worldwide SWEET registry

AIMS

To evaluate access to screening tools for monogenic diabetes in paediatric diabetes centres across the world and its impact on diagnosis and clinical outcomes of children and youth with genetic forms of diabetes.

METHODS

79 centres from the SWEET diabetes registry including 53,207 children with diabetes participated in a survey on accessibility and use of diabetes related antibodies, c-peptide and genetic testing.

RESULTS

73, 63 and 62 participating centres had access to c-peptide, antibody and genetic testing, respectively. Access to antibody testing was associated with higher proportion of patients with rare forms of diabetes identified with monogenic diabetes (54 % versus 17 %, p = 0.01), lower average whole clinic HbA1c (7.7[Q1,Q2: 7.3-8.0]%/61[56-64]mmol/mol versus 9.2[8.6-10.0]%/77[70-86]mmol/mol, p < 0.001) and younger age at onset (8.3 [7.3-8.8] versus 9.7 [8.6-12.7] years p < 0.001). Additional access to c-peptide or genetic testing was not related to differences in age at onset or HbA1c outcome.

CONCLUSIONS

Clinical suspicion and antibody testing are related to identification of different types of diabetes. Implementing access to comprehensive antibody screening may provide important information for selecting individuals for further genetic evaluation. In addition, worse overall clinical outcomes in centers with limited diagnostic capabilities indicate they may also need support for individualized diabetes management.

TRIAL REGISTRATION

NCT04427189.

Study of ten causal genes in Turkish patients with clinically suspected maturity-onset diabetes of the young (MODY) using a targeted next-generation sequencing panel

BACKGROUND

Maturity-onset diabetes of the young (MODY), which is the most common cause of monogenic diabetes, has an autosomal dominant pattern of inheritance and exhibits marked clinical and genetic heterogeneity. The aim of the current study was to investigate molecular defects in patients with clinically suspected MODY using a next-generation sequencing (NGS)-based targeted gene panel.

METHODS

Candidate patients with clinical suspicion of MODY and their parents were included in the study. Molecular genetic analyses were performed on genomic DNA by using NGS. A panel of ten MODY-causal genes involving GCK, HNF1A, HNF1B, HNF4A, ABCC8, CEL, INS, KCNJ11, NEUROD1, PDX1 was designed and subsequently implemented to screen 40 patients for genetic variants.

RESULTS

Ten different pathogenic or likely pathogenic variants were identified in MODY-suspected patients, with a diagnostic rate of 25%. Three variants of uncertain significance were also detected in the same screen. A novel pathogenic variant in the gene HNF1A (c.505_506delAA [p.Lys169AlafsTer18]) was described for the first time in this report. Intriguingly, we were able to detect variants associated with rare forms of MODY in our study population.

CONCLUSIONS

Our results suggest that in heterogenous diseases such as MODY, NGS analysis enables accurate identification of underlying molecular defects in a timely and cost-effective manner. Although MODY accounts for 2-5% of all diabetic cases, molecular genetic diagnosis of MODY is necessary for optimal long-term treatment and prognosis as well as for effective genetic counseling.

Improvements in Awareness and Testing Have Led to a Threefold Increase Over 10 Years in the Identification of Monogenic Diabetes in the U.K

OBJECTIVE

Maturity-onset diabetes of the young (MODY) is a rare monogenic form of diabetes. In 2009, >80% of U.K. cases were estimated to be misdiagnosed. Since then, there have been a number of initiatives to improve the awareness and detection of MODY, including education initiatives (Genetic Diabetes Nurse [GDN] project), the MODY probability calculator, and targeted next-generation sequencing (tNGS). We examined how the estimated prevalence of MODY and other forms of monogenic diabetes diagnosed outside the neonatal period has changed over time and how the initiatives have impacted case finding.

RESEARCH DESIGN AND METHODS

U.K. referrals for genetic testing for monogenic diabetes diagnosed >1 year of age from 1 January 1996 to 31 December 2019 were examined. Positive test rates were compared for referrals reporting GDN involvement/MODY calculator use with those that did not.

RESULTS

A diagnosis of monogenic diabetes was confirmed in 3,860 individuals, more than threefold higher than 2009 (1 January 1996 to 28 February 2009, n = 1,177). Median age at diagnosis in probands was 21 years. GDN involvement was reported in 21% of referrals; these referrals had a higher positive test rate than those without GDN involvement (32% vs. 23%, P < 0.001). MODY calculator usage was indicated in 74% of eligible referrals since 2014; these referrals had a higher positive test rate than those not using the calculator (33% vs. 25%, P = 0.001). Four hundred ten (10.6%) cases were identified through tNGS. Monogenic diabetes prevalence was estimated to be 248 cases/million (double that estimated in 2009 because of increased case finding).

CONCLUSIONS

Since 2009, referral rates and case diagnosis have increased threefold. This is likely to be the consequence of tNGS, GDN education, and use of the MODY calculator.

Frequency and spectrum of glucokinase mutations in an adult Maltese population

AIM

To investigate the frequency and spectrum of glucokinase (GCK) mutations in a cohort of adults from an island population having a high prevalence of diabetes mellitus (DM).

METHODS

A single-centre cohort study was conducted, including 145 non-obese adults of Maltese-Caucasian ethnicity with impaired fasting glycaemia (IFG) or non-autoimmune diabetes diagnosed before the age of 40 years. Bidirectional sequencing of the GCK coding regions was performed. Genotype-phenotype associations and familial segregation were explored and the effects of missense variants on protein structure were evaluated using computational analysis.

RESULTS

Three probands with pathogenic/likely pathogenic GCK variants in the heterozygous state having clinical features consistent with GCK-diabetes were detected. The missense variants have structurally destabilising effects on protein structure. GCK variant carriers exhibited a significantly lower body mass index and serum triglyceride levels when compared to GCK variant non-carriers.

CONCLUSIONS

The frequency of GCK-diabetes is approximately 2% in non-obese Maltese adults with diabetes or prediabetes. This study broadens the mutational spectrum of GCK and highlights clinical features that could be useful in discriminating GCK-DM from type 2 DM or prediabetes. It reinforces the need for increased molecular testing in young adults with diabetes having a suspected monogenic aetiology.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

First Japanese Family With PDX1-MODY (MODY4): A Novel PDX1 Frameshift Mutation, Clinical Characteristics, and Implications

CONTEXT

The PDX1 gene encodes pancreatic and duodenal homeobox, a critical transcription factor for pancreatic β-cell differentiation and maintenance of mature β-cells. Heterozygous loss-of-function mutations cause PDX1-MODY (MODY4).

CASE DESCRIPTION

Our patient is an 18-year-old lean man who developed diabetes at 16 years of age. Given his early-onset age and leanness, we performed genetic testing. Targeted next-generation sequencing and subsequent Sanger sequencing detected a novel heterozygous frameshift mutation (NM_00209.4:c.218delT. NP_000200.1: p.Leu73Profs*50) in the PDX1 transactivation domain that resulted in loss-of-function and was validated by an in vitro functional study. The proband and his 56-year-old father, who had the same mutation, both showed markedly reduced insulin and gastric inhibitory polypeptide (GIP) secretion compared with the dizygotic twin sister, who was negative for the mutation and had normal glucose tolerance. The proband responded well to sitagliptin, suggesting its utility as a treatment option. Notably, the proband and his father showed intriguing phenotypic differences: the proband had been lean for his entire life but developed early-onset diabetes requiring an antihyperglycemic agent. In contrast, his father was overweight, developed diabetes much later in life, and did not require medication, suggesting the oligogenic nature of PDX1-MODY. A review of all reported cases of PDX1-MODY also showed heterogeneous phenotypes regarding onset age, obesity, and treatment, even in the presence of the same mutation.

CONCLUSIONS

We identified the first Japanese family with PDX1-MODY. The similarities and differences found among the cases highlight the wide phenotypic spectrum of PDX1-MODY.

Clinical and genetic features of maturity-onset diabetes of the young in pediatric patients: a 12-year monocentric experience

BACKGROUND

A retrospective observational study was conducted to assess the prevalence of maturity onset diabetes of the young (MODY) in a large paediatric population of Southern Italy newly diagnosed with diabetes. Clinical and genetic features of the identified MODY patients were also described.

METHODS

Genetic testing was performed in children and adolescents newly diagnosed with diabetes who presented autoantibody negativity and fasting C-peptide levels ≥ 0.8 ng/mL. Patients with a low insulin daily dose and optimal glycaemic control after two years from diabetes onset were also investigated for monogenic diabetes, regardless of their autoimmunity status and/or C-peptide levels.

RESULTS

A prevalence of 6.5% of MODY was found. In particular, glucokinase-MODY was the most common type of MODY. The mean age at diagnosis was 9.1 years. Clinical presentation and biochemical data were heterogeneous also among patients belonging to the same MODY group.

CONCLUSIONS

We found a relatively high prevalence of MODY among paediatric patients with a new diagnosis of diabetes in comparison to literature data. Our findings highlight that a more detailed clinical evaluation along with easier and less expensive approachability to genetic testing may allow diagnosing an increasing number of MODY cases. A correct, prompt diagnosis is crucial to choose the most appropriate treatment and offer adequate genetic counselling.

A KCNK16 mutation causing TALK-1 gain of function is associated with maturity-onset diabetes of the young

Maturity-onset diabetes of the young (MODY) is a heterogeneous group of monogenic disorders of impaired pancreatic β cell function. The mechanisms underlying MODY include β cell KATP channel dysfunction (e.g., KCNJ11 [MODY13] or ABCC8 [MODY12] mutations); however, no other β cell channelopathies have been associated with MODY to date. Here, we have identified a nonsynonymous coding variant in KCNK16 (NM_001135105: c.341T>C, p.Leu114Pro) segregating with MODY. KCNK16 is the most abundant and β cell-restricted K+ channel transcript, encoding the two-pore-domain K+ channel TALK-1. Whole-cell K+ currents demonstrated a large gain of function with TALK-1 Leu114Pro compared with TALK-1 WT, due to greater single-channel activity. Glucose-stimulated membrane potential depolarization and Ca2+ influx were inhibited in mouse islets expressing TALK-1 Leu114Pro with less endoplasmic reticulum Ca2+ storage. TALK-1 Leu114Pro significantly blunted glucose-stimulated insulin secretion compared with TALK-1 WT in mouse and human islets. These data suggest that KCNK16 is a previously unreported gene for MODY.

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.

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.

Absence of Islet Autoantibodies and Modestly Raised Glucose Values at Diabetes Diagnosis Should Lead to Testing for MODY: Lessons From a 5-Year Pediatric Swedish National Cohort Study

OBJECTIVE

Identifying maturity-onset diabetes of the young (MODY) in pediatric populations close to diabetes diagnosis is difficult. Misdiagnosis and unnecessary insulin treatment are common. We aimed to identify the discriminatory clinical features at diabetes diagnosis of patients with glucokinase (GCK), hepatocyte nuclear factor-1A (HNF1A), and HNF4A MODY in the pediatric population.

RESEARCH DESIGN AND METHODS

Swedish patients (n = 3,933) aged 1-18 years, diagnosed with diabetes May 2005 to December 2010, were recruited from the national consecutive prospective cohort Better Diabetes Diagnosis. Clinical data, islet autoantibodies (GAD insulinoma antigen-2, zinc transporter 8, and insulin autoantibodies), HLA type, and C-peptide were collected at diagnosis. MODY was identified by sequencing GCK, HNF1A, and HNF4A, through either routine clinical or research testing.

RESULTS

The minimal prevalence of MODY was 1.2%. Discriminatory factors for MODY at diagnosis included four islet autoantibody negativity (100% vs. 11% not-known MODY; P = 2 × 10^-44), HbA_1c (7.0% vs. 10.7% [53 vs. 93 mmol/mol]; P = 1 × 10^-20), plasma glucose (11.7 vs. 26.7 mmol/L; P = 3 × 10^-19), parental diabetes (63% vs. 12%; P = 1 × 10^-15), and diabetic ketoacidosis (0% vs. 15%; P = 0.001). Testing 303 autoantibody-negative patients identified 46 patients with MODY (detection rate 15%). Limiting testing to the 73 islet autoantibody-negative patients with HbA_1c <7.5% (58 mmol/mol) at diagnosis identified 36 out of 46 (78%) patients with MODY (detection rate 49%). On follow-up, the 46 patients with MODY had excellent glycemic control, with an HbA_1c of 6.4% (47 mmol/mol), with 42 out of 46 (91%) patients not on insulin treatment.

CONCLUSIONS

At diagnosis of pediatric diabetes, absence of all islet autoantibodies and modest hyperglycemia (HbA_1c <7.5% [58 mmol/mol]) should result in testing for GCK, HNF1A, and HNF4A MODY. Testing all 12% patients negative for four islet autoantibodies is an effective strategy for not missing MODY but will result in a lower detection rate. Identifying MODY results in excellent long-term glycemic control without insulin.

Negative autoimmunity in a Spanish pediatric cohort suspected of type 1 diabetes, could it be monogenic diabetes?

Objective

Monogenic diabetes can be misdiagnosed as type 1 or type 2 diabetes in children. The right diagnosis is crucial for both therapeutic choice and prognosis and influences genetic counseling. The main objective of this study was to search for monogenic diabetes in Spanish pediatric patients suspected of type 1 diabetes with lack of autoimmunity at the onset of the disease. We also evaluated the extra value of ZnT8A in addition to the classical IAA, GADA and IA2A autoantibodies to improve the accuracy of type 1 diabetes diagnosis.

Methods

Four hundred Spanish pediatric patients with recent-onset diabetes (mean age 8.9 ± 3.9 years) were analyzed for IAA, GADA, IA2A and ZnT8A pancreatic-autoantibodies and HLA-DRB1 alleles. Patients without autoimmunity and those with only ZnT8A positive were screened for 12 monogenic diabetes genes by next generation sequencing.

Results

ZnT8A testing increased the number of autoantibody-positive patients from 373 (93.3%) to 377 (94.3%). An isolated positivity for ZnT8A allowed diagnosing autoimmune diabetes in 14.8% (4/27) of pediatric patients negative for the rest of the antibodies tested. At least 2 of the 23 patients with no detectable autoimmunity (8%) carried heterozygous pathogenic variants: one previously reported missense variant in the INS gene (p.Gly32Ser) and one novel frameshift variant (p.Val264fs) in the HNF1A gene. One variant of uncertain significance was also found. Carriers of pathogenic variants had HLA-DRB1 risk alleles for autoimmune diabetes and clinical characteristics compatible with type 1 diabetes except for the absence of autoimmunity.

Conclusion

ZnT8A determination improves the diagnosis of autoimmune diabetes in pediatrics. At least 8% of pediatric patients suspected of type 1 diabetes and with undetectable autoimmunity have monogenic diabetes and can benefit from the correct diagnosis of the disease by genetic study.