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

Prevalence, clinical characteristics and HLA genotypes of idiopathic type 1 diabetes: A cross-sectional study

AIMS

Idiopathic type 1 diabetes (T1D) is a neglected subtype of T1D. Our aim was to investigate the frequency, clinical characteristics, and human leucocyte antigen (HLA) genotypes of idiopathic T1D.

METHODS

We enrolled 1205 newly diagnosed T1D patients in our analysis. To exclude monogenic diabetes in autoantibody-negative patients, we utilised a custom monogenic diabetes gene panel. Individuals negative for autoantibodies and subsequently excluded for monogenic diabetes were diagnosed with idiopathic T1D. We collected clinical characteristics, measured islet autoantibodies by radioligand assay and obtained HLA data.

RESULTS

After excluding 11 patients with monogenic diabetes, 284 cases were diagnosed with idiopathic T1D, accounting for 23.8% (284/1194) of all newly diagnosed T1D cases. When compared with autoimmune T1D, idiopathic T1D patients showed an older onset age, higher body mass index among adults, lower haemoglobin A1c, higher levels of fasting C-peptide and 2-h postprandial C-peptide, and were likely to have type 2 diabetes (T2D) family history and carry 0 susceptible HLA haplotype (all p < 0.01). A lower proportion of individuals carrying 2 susceptible HLA haplotypes in idiopathic T1D was observed in the adult-onset subgroup (15.7% vs. 38.0% in child-onset subgroup, p < 0.001) and in subgroup with preserved beta-cell function (11.0% vs. 30.1% in subgroup with poor beta-cell function, p < 0.001). Multivariable correlation analyses indicated that being overweight, having T2D family history and lacking susceptible HLA haplotypes were associated with negative autoantibodies.

CONCLUSIONS

Idiopathic T1D represents about 1/4 of newly diagnosed T1D, with adult-onset and preserved beta-cell function patients showing lower HLA susceptibility and more insulin resistance.

Next Generation Sequencing (NGS) Target Approach for Undiagnosed Dysglycaemia

Next-generation sequencing (NGS) has revolutionized the field of genomics and created new opportunities for basic research. We described the strategy for the NGS validation of the "dysglycaemia panel" composed by 44 genes related to glucose metabolism disorders (MODY, Wolfram syndrome) and familial renal glycosuria using Ion AmpliSeq technology combined with Ion-PGM. Anonymized DNA of 32 previously genotyped cases with 33 different variants were used to optimize the methodology. Standard protocol was used to generate the primer design, library, template preparation, and sequencing. Ion Reporter tool was used for data analysis. In all the runs, the mean coverage was over 200×. Twenty-nine out of thirty three variants (96.5%) were detected; four frameshift variants were missed. All point mutations were detected with high sensitivity. We identified three further variants of unknown significance in addition to pathogenic mutations previously identified by Sanger sequencing. The NGS panel allowed us to identify pathogenic variants in multiple genes in a short time. This could help to identify several defects in children and young adults that have to receive the genetic diagnosis necessary for optimal treatment. In order not to lose any pathogenic variants, Sanger sequencing is included in our analytical protocol to avoid missing frameshift variants.

Prevalence and characteristics of misdiagnosed adult-onset type 1 diabetes mellitus in Thai people by random plasma C-peptide testing

Background

It is critical to determine the exact type of diabetes because misclassification led to inappropriate treatments. The classification of DM can be aided by the measurement of pancreatic autoantibodies and plasma C-peptide levels. Previous studies suggested that random plasma C-peptide testing in those with clinically diagnosed adult T1DM of at least 3 years duration has led to reclassification in some cases.

Aim

This study aimed to assess the prevalence and characteristics of misdiagnosed adult-onset type 1 diabetes mellitus in Thai people by random plasma C-peptide testing.

Methods

A cross-sectional study of adult Thai patients diagnosed with clinically diagnosed T1DM and DM duration of at least 3 years at Theptarin Hospital, a diabetes center in Bangkok, Thailand was studied. Clinically misdiagnosis of T1DM was defined by preserved endogenous insulin secretion. Characteristics of the misdiagnosed patients were compared with definite T1DM patients.

Results

A total of 73 patients (females 52.1%, mean age 42.2 ± 12.5 years, duration of DM 20.3 ± 11.3 years) were studied. The prevalence of available anti-GAD and anti-IA2 were 53.3% and 20.8%, respectively. Preserved endogenous insulin secretion evaluated by random C-peptide or stimulated C-peptide was found in 8 patients (11.0%). The misdiagnosed patients had higher prevalence of hypertension and diabetic complications. Three patients were suspected to have monogenic diabetes and five patients were reclassified as possible T2DM.

Conclusions

Approximately one-tenth of adult T1DM patients were misdiagnosed. Random plasma C-peptide testing at least 3 years after a diagnosis of T1DM was superior to the measurement of pancreatic autoantibodies. Our present study highlights the need to increase accuracy in the diagnosis of T1DM patients by re-assessing endogenous insulin production with measurement of random plasma C-peptide levels.

The impact of family history of type 2 diabetes on clinical heterogeneity in idiopathic type 1 diabetes

AIM

To investigate the impact of family history of type 2 diabetes (T2D) on the clinical phenotypes of patients with idiopathic type 1 diabetes (T1D).

METHODS

In clinically diagnosed T1D cases, a total of 335 idopathic T1D patients were included in the study, after excluding autoimmune T1D using islet autoantibody testing and monogenic diabetes using a custom monogenic diabetes gene panel obtained from clinically diagnosed T1D cases. A semi-structured questionnaire was used to collect information on the presence of T2D in first-degree relatives. The demographic and metabolic markers of idiopathic T1D patients were analysed. Subgroup analysis was performed to investigate potential interactions between T2D family history and human leukocyte antigen (HLA) genotypes.

RESULTS

A total of 18.2% of individuals with idiopathic T1D had a T2D family history, and these individuals were more likely to have features associated with T2D, such as older age of onset, higher body mass index at diagnosis, lower insulin dosage and better beta-cell function, as indicated by higher levels of fasting C-peptide and 2-hour postprandial C-peptide (all P < 0.05). Additionally, regardless of HLA susceptible genotypes, the impact of family history of T2D was consistently observed in idiopathic T1D patients. Multivariable analyses showed that T2D family history was negatively correlated with the risk of beta-cell function failure in idiopathic T1D patients (P < 0.05).

CONCLUSIONS

Family history of T2D may be implicated in the heterogeneity of idiopathic T1D patients.

The Mutation Spectrum of Rare Variants in the Gene of Adenosine Triphosphate (ATP)-Binding Cassette Subfamily C Member 8 in Patients with a MODY Phenotype in Western Siberia

During differential diagnosis of diabetes mellitus, the greatest difficulties are encountered with young patients because various types of diabetes can manifest themselves in this age group (type 1, type 2, and monogenic types of diabetes mellitus, including maturity-onset diabetes of the young (MODY)). The MODY phenotype is associated with gene mutations leading to pancreatic-β-cell dysfunction. Using next-generation sequencing technology, targeted sequencing of coding regions and adjacent splicing sites of MODY-associated genes (HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, KCNJ11, ABCC8, and APPL1) was carried out in 285 probands. Previously reported missense variants c.970G>A (p.Val324Met) and c.1562G>A (p.Arg521Gln) in the ABCC8 gene were found once each in different probands. Variant c.1562G>A (p.Arg521Gln) in ABCC8 was detected in a compound heterozygous state with a pathogenic variant of the HNF1A gene in a diabetes patient and his mother. Novel frameshift mutation c.4609_4610insC (p.His1537ProfsTer22) in this gene was found in one patient. All these variants were detected in available family members of the patients and cosegregated with diabetes mellitus. Thus, next-generation sequencing of MODY-associated genes is an important step in the diagnosis of rare MODY subtypes.

Demographic and diagnostic markers in new onset pediatric type 1 and type 2 diabetes: differences and overlaps

PURPOSE

Type 1 diabetes (T1D) is the most common type of diabetes in children, but the frequency of type 2 diabetes (T2D) is increasing rapidly. Classification of diabetes is based on a constellation of features that vary by type. We aimed to compare demographic, clinical, and laboratory characteristics at diagnosis of pediatric T1D and T2D.

METHODS

We studied children who visited a large academic hospital in Houston, Texas (USA) with a new diagnosis of T2D (n=753) or T1D (n=758). We compared age, sex, race/ethnicity, presence of obesity, glucose, hemoglobin A1c, islet autoantibody positivity, C-peptide, and presence of diabetic ketoacidosis (DKA) at diabetes diagnosis.

RESULTS

At diagnosis, children with T2D, compared with those with T1D, were older (13.6 years vs. 9.7 years), more likely female (63.2% vs. 47.8%), of racial/ethnic minority (91.1% vs. 42.3%), and obese (90.9% vs. 19.4%) and were less likely to have DKA (7.8% vs. 35.0%) and diabetes autoantibodies (5.5% vs. 95.4%). Children with T2D also had significantly lower glucose, lower hemoglobin A1c and lower C-peptide level (all comparisons, p<0.0001). In multiple logistic regression analysis, older age, racial/ethnic minority, obesity, higher C-peptide, and negative islet autoantibodies were independently associated with T2D (all, p<0.05), while sex, glucose, hemoglobin A1c, and DKA were not (model p<0.0001).

CONCLUSION

There are important demographic, clinical, and laboratory differences between T1D and T2D in children. However, none of the characteristics were unique to either diabetes type, which poses challenges to diabetes classification at diagnosis.

Next- generation sequencing is an effective method for diagnosing patients with different forms of monogenic diabetes

AIM

Monogenic diabetes (MD) represents 5-7% of antibody-negative diabetes cases and is a heterogeneous group of disorders.

METHODS

We used targeted next-generation sequencing (NGS) on Illumina NextSeq 550 platform involving the SureSelect assay to perform genetic and clinical characteristics of a study group of 684 individuals, including 542 patients referred from 12 Polish Diabetes Centers with suspected MD diagnosed between December 2016 and December 2019 and their 142 family members (FM).

RESULTS

In 198 probands (36.5%) and 66 FM (46.5%) heterozygous causative variants were confirmed in 11 different MD-related genes, including 31 novel mutations, with the highest number in the GCK gene (206/264), 22/264 in the HNF1A gene and 8/264 in the KCNJ11 gene. Of the 183 probands with MODY1-5 diabetes, 48.6% of them were diagnosed at the pre-diabetes stage and most of them (68.7%) were on diet only at the time of genetic diagnosis, while 31.3% were additionally treated with oral hypoglycaemic drugs and/or insulin.

CONCLUSIONS

In summary, the results obtained confirm the efficacy of targeted NGS method in the molecular diagnosis of patients with suspected MD and broaden the spectrum of new causal variants, while updating our knowledge of the clinical features of patients defined as having MD.

Diabetes Mellitus Diagnosed in Childhood and Adolescence With Negative Autoimmunity: Results of Genetic Investigation

Monogenic diabetes is a rare form of diabetes, accounting for approximately 1% to 6% of pediatric diabetes patients. Some types of monogenic diabetes can be misdiagnosed as type 1 diabetes in children or adolescents because of similar clinical features. Identification of the correct etiology of diabetes is crucial for clinical, therapeutic, and prognostic issues. Our main objective was to determine the prevalence of monogenic diabetes in patients with diabetes mellitus, diagnosed in childhood or in adolescence, and negative autoimmunity. We retrospectively analyzed clinical data of 275 patients diagnosed with insulin-dependent diabetes at age <18yr in the last 10 years. 8.4% of subjects has negative autoimmunity. Their DNA was sequenced by NGS custom panel composed by 45 candidate genes involved in glucose metabolism disorder. Two novel heterozygous pathogenic or likely pathogenic variants (10,5% of autoantibody negative subjects) were detected: the frameshift variant c.617_618insA in NEUROD1 exon 2 and the missense change c.116T>C in INS exon 2. Our study corroborates previous results of other reports in literature. NGS assays are useful methods for a correct diagnosis of monogenic diabetes, even of rarest forms, highlighting mechanisms of pediatric diabetes pathogenesis.

A case of digenic maturity onset diabetes of the young with heterozygous variants in both HNF1Α and HNF1Β genes

BACKGROUND

Maturity onset diabetes of the young (MODY) is the most commonly reported form of monogenic diabetes in the pediatric population. Only a few cases of digenic MODY have been reported up to now.

CASE REPORT

A female patient was diagnosed with diabetes at the age of 7 years and was treated with insulin. A strong family history of diabetes was present in the maternal side of the family. The patient also presented hypomagnesemia, glomerulocystic kidney disease and a bicornuate uterus. Genetic testing of the patient revealed that she was a double heterozygous carrier of HNF1A gene variant c.685C > T; (p.Arg229Ter) and a whole gene deletion of the HNF1B gene. Her mother was a carrier of the same HNF1A variant.

CONCLUSION

Digenic inheritance of MODY pathogenic variants is probably more common than currently reported in literature. The use of Next Generation Sequencing panels in testing strategies for MODY could unmask such cases that would otherwise remain undiagnosed.

The Mutation Spectrum of Maturity Onset Diabetes of the Young (MODY)-Associated Genes among Western Siberia Patients

Maturity onset diabetes of the young (MODY) is a congenital form of diabetes characterized by onset at a young age and a primary defect in pancreatic-β-cell function. Currently, 14 subtypes of MODY are known, and each is associated with mutations in a specific gene: HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, KCNJ11, ABCC8, and APPL1. The most common subtypes of MODY are associated with mutations in the genes GCK, HNF1A, HNF4A, and HNF1B. Among them, up to 70% of cases are caused by mutations in GCK and HNF1A. Here, an analysis of 14 MODY genes was performed in 178 patients with a MODY phenotype in Western Siberia. Multiplex ligation-dependent probe amplification analysis of DNA samples from 50 randomly selected patients without detectable mutations did not reveal large rearrangements in the MODY genes. In 38 patients (37% males) among the 178 subjects, mutations were identified in HNF4A, GCK, HNF1A, and ABCC8. We identified novel potentially causative mutations p.Lys142*, Leu146Val, Ala173Glnfs*30, Val181Asp, Gly261Ala, IVS7 c.864 -1G>T, Cys371*, and Glu443Lys in GCK and Ser6Arg, IVS 2 c.526 +1 G>T, IVS3 c.713 +2 T>A, and Arg238Lys in HNF1A.