Molecular Diagnosis of Monogenic Diabetes and Their Clinical/Laboratory Features in Turkish Children

Clinical and Laboratory Characteristics of MODY Cases, Genetic Mutation Spectrum and Phenotype-genotype Relationship

Objective

Maturity onset diabetes of the young (MODY) occurs due to mutations in genes involved in pancreatic beta cell function and insulin secretion, has heterogeneous clinical and laboratory features, and account for 1-5% of all diabetes cases. The prevalence and distribution of MODY subtypes vary between countries. The aim of this study was to evaluate the clinical and laboratory characteristics, mutation distribution, and phenotype-genotype relationship in a large case series of pediatric Turkish patients genetically diagnosed with MODY.

Methods

MODY cases from 14 different pediatric endocrinology departments were included. Diagnosis, treatment, follow-up data, and results of genetic analysis were evaluated.

Results

A total of 224 patients were included, of whom 101 (45%) were female, and the mean age at diagnosis was 9.4±4.1 years. Gene variant distribution was: 146 (65%) GCK; 43 (19%) HNF1A; 8 (3.6%) HNF4A, 8 (3.6%) KLF11 and 7 (3.1%) HNF1B. The remaining 12 variants were: PDX (n=1), NEUROD1 (n=3), CEL (n=1), INS (n=3), ABCC8 (n= 3) and KJNC11 (n=1). Of the cases, 197 (87.9%) were diagnosed with incidental hyperglycemia, 16 with ketosis (7%) and 7 (3%) with diabetic ketoacidosis (DKA), while 30% presented with classical symptoms of diabetes. Two-hundred (89%) had a family history of diabetes. Anti-GAD antibody was detected in 13 cases, anti-islet antibody in eight and anti-insulin antibody in four. Obesity was present in 16. Distribution of therapy was: 158 (71%) diet only; 23 (11%) intensive insulin treatment; 17 (7.6%) sulfonylureas; 10 (4.5%) metformin; and 6 (2.7%) insulin and oral anti-diabetic treatment.

Conclusion

This was the largest genetically diagnosed series from Turkey. The most common gene variants were GCK and HNF1A with much lower proportions for other MODY types. Hyperglycemia was the most common presenting symptom while 11% of patients had diabetes-associated autoantibodies and 7% were obese. The majority of patients received dietary management only.

VARIATIONS IN MONOGENIC DIABETES AND DIABETES SUSCEPTIBILITY GENES IN PEDIATRIC CASES: SINGLE CENTER EXPERIENCE

Context

Diabetes is a chronic disorder with a complex pathogenetic background including monogenic, polygenic, and environmental causes.

Objective

The aim of the present paper is to share the information related to genetic and clinical data of large pediatric diabetes cohort.

Design

The present study retrospectively analyzes genetic and clinical findings of subjects diagnosed with diabetes under the age of 18 year and are in follow-up in a pediatric diabetes referral center.

Subjects and Methods

Out of 1205 children with diabetes (902 treated with insulin) 246 underwent genetic tests on the basis of clinical selection criteria since 2007.

Results

One hundred and ten variants related to diabetes were found in 89 of them. Age at presentation was 9.5±4.02 years (F/M 44/45). In total 49 pathogenic and likely pathogenic, 11 "hot and warm" of unknown significance variants were found in fourteen MODY and fifteen non-MODY genes according to criteria developed by American College of Medical Genetics. Thirty novel mutations were found. GCK (26.6%) and ABCC8 (10%) were two most frequently affected genes. Antibody testing revealed negative results in 80% of cases.

Conclusions

Genetic interpretation in selected cases is important to understand the nature of the disease better. Improvement in testing opportunity and awareness might increase the prevalence of genetically explained diabetes cases. The distribution of subtypes differs between countries and even regions of the same country.

Hemoglobin A1C can differentiate subjects with GCK mutations among patients suspected to have MODY

OBJECTIVES

The aim of this study is to determine the clinical and molecular characteristics enabling differential diagnosis in a group of Turkish children clinically diagnosed with MODY and identify the cut-off value of HbA_1c, which can distinguish patients with GCK variants from young-onset type 1 and type 2 diabetes.

METHODS

The study included 49 patients from 48 unrelated families who were admitted between 2018 and 2020 with a clinical diagnosis of MODY. Clinical and laboratory characteristics of the patients at the time of the diagnosis were obtained from hospital records. Variant analysis of ten MODY genes was performed using targeted next-generation sequencing (NGS) panel and the variants were classified according to American Collage of Medical Genetics and Genomics (ACMG) Standards and Guidelines recommendations.

RESULTS

A total of 14 (28%) pathogenic/likely pathogenic variants were detected among 49 patients. 11 variants in GCK and 3 variants in HNF1A genes were found. We identified four novel variants in GCK gene. Using ROC analysis, we found that best cut-off value of HbA_1c at the time of diagnosis for predicting the subjects with a GCK variant among patients suspected to have MODY was 6.95% (sensitivity 90%, specificity 86%, AUC 0.89 [95% CI: 0.783-1]). Most of the cases without GCK variant (33/38 [86%]) had an HbA_1c value above this cutoff value. We found that among participants suspected of having MODY, family history, HbA_1c at the time of diagnosis, and not using insulin therapy were the most differentiating variables of patients with GCK variants.

CONCLUSIONS

Family history, HbA_1c at the time of diagnosis, and not receiving insulin therapy were found to be the most distinguishing variables of patients with GCK variants among subjects suspected to have MODY.

Meta-analysis of HNF1A-MODY3 variants among human population

Background

Previously, numerous case-control studies have highlighted variants responsible for Maturity onset diabetes of young (MODY). However, these studies have been conducted among diverse populations and hence yielded contradictory results. We, therefore, performed a meta-analysis to precisely find the association of SNPs with the disease for the HNF1A gene.

Objective

Meta-analysis of clinically defined studies deciphering mutations in the HNF1A gene responsible for the development of MODY3 was conducted among various populations to determine associations using statistical approaches.

Methods

The curation of 505 research articles published between the years 2000-2021 was carried out. Visualization of data-related protocols and statistical-analysis were conducted, which led to the identification of highly prevalent mutations among different populations (majorly Europe). Further comparison between the frequencies of the control (healthy population) and test (diseased population) dataset generated through curation was performed.

Results

We identified nine MODY3 mutations (rs587776825, rs1169288, rs1800574, rs2464196, rs137853244, rs137853238, rs587780357, rs137853240 and rs137853243) at the genome-wide significance level ( p < 5.0 × 10^-8). The present study confirmed that the data does not follow a normal distribution. Further, the data was confirmed to be a more homogenous type with frequencies having a significant association with the disease.

Conclusion

This meta-analysis found significant associations of mutations in HNF1A with MODY3, consistent with previous studies. Our findings should help elucidate the mutations in a compiled form responsible for causing MODY3.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-022-00975-8.