A novel mutation in the ABCC8 gene causing maturity-onset diabetes of the young: A case report

A 34-year-old woman was diagnosed with type 1 diabetes mellitus and treated with insulin for 24 years. The patient has a family history of diabetes in three consecutive generations. Her Whole exon sequencing showed a heterozygous mutation in the ABCC8 gene, and it also found some of her relatives to carry this mutation. She was diagnosed with MODY12 and received glimepiride therapy with the achievement of good glycaemic control.

A multigenerational study on phenotypic consequences of the most common causal variant of HNF1A-MODY

AIMS/HYPOTHESIS

Systematic studies on the phenotypic consequences of variants causal of HNF1A-MODY are rare. Our aim was to assess the phenotype of carriers of a single HNF1A variant and genetic and clinical factors affecting the clinical spectrum.

METHODS

We conducted a family-based multigenerational study by comparing heterozygous carriers of the HNF1A p.(Gly292fs) variant with the non-carrier relatives irrespective of diabetes status. During more than two decades, 145 carriers and 131 non-carriers from 12 families participated in the study, and 208 underwent an OGTT at least once. We assessed the polygenic risk score for type 2 diabetes, age at onset of diabetes and measures of body composition, as well as plasma glucose, serum insulin, proinsulin, C-peptide, glucagon and NEFA response during the OGTT.

RESULTS

Half of the carriers remained free of diabetes at 23 years, one-third at 33 years and 13% even at 50 years. The median age at diagnosis was 21 years (IQR 17-35). We could not identify clinical factors affecting the age at conversion; sex, BMI, insulin sensitivity or parental carrier status had no significant effect. However, for 1 SD unit increase of a polygenic risk score for type 2 diabetes, the predicted age at diagnosis decreased by 3.2 years. During the OGTT, the carriers had higher levels of plasma glucose and lower levels of serum insulin and C-peptide than the non-carriers. The carriers were also leaner than the non-carriers (by 5.0 kg, p=0.012, and by 2.1 kg/m² units of BMI, p=2.2 × 10^-4, using the first adult measurements) and, possibly as a result of insulin deficiency, demonstrated higher lipolytic activity (with medians of NEFA at fasting 621 vs 441 μmol/l, p=0.0039; at 120 min during an OGTT 117 vs 64 μmol/l, p=3.1 × 10^-5).

CONCLUSIONS/INTERPRETATION

The most common causal variant of HNF1A-MODY, p.(Gly292fs), presents not only with hyperglycaemia and insulin deficiency, but also with increased lipolysis and markedly lower adult BMI. Serum insulin was more discriminative than C-peptide between carriers and non-carriers. A considerable proportion of carriers develop diabetes after young adulthood. Even among individuals with a monogenic form of diabetes, polygenic risk of diabetes modifies the age at onset of diabetes.

Transcriptomic analysis of patients with clinical suspicion of maturity-onset diabetes of the young (MODY) with a negative genetic diagnosis

Background

Diagnosis of mature-onset diabetes of the young (MODY), a non-autoimmune monogenic form of diabetes mellitus, is confirmed by genetic testing. However, a positive genetic diagnosis is achieved in only around 50% of patients with clinical characteristics of this disease.

Results

We evaluated the diagnostic utility of transcriptomic analysis in patients with clinical suspicion of MODY but a negative genetic diagnosis. Using Nanostring nCounter technology, we conducted transcriptomic analysis of 19 MODY-associated genes in peripheral blood samples from 19 patients and 8 healthy controls. Normalized gene expression was compared between patients and controls and correlated with each patient’s biochemical and clinical variables. Z-scores were calculated to identify significant changes in gene expression in patients versus controls. Only 7 of the genes analyzed were detected in peripheral blood. HADH expression was significantly lower in patients versus controls. Among patients with suspected MODY, GLIS3 expression was higher in obese versus normal-weight patients, and in patients aged < 25 versus > 25 years at diabetes onset. Significant alteration with respect to controls of any gene was observed in 57.9% of patients.

Conclusions

Although blood does not seem to be a suitable sample for transcriptomic analysis of patients with suspected MODY, in our study, we detected expression alterations in some of the genes studied in almost 58% of patients. That opens the door for future studies that can clarify the molecular cause of the clinic of these patients and thus be able to maintain a more specific follow-up and treatment in each case.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02263-3.

Low genetic confirmation rate in South Indian subjects with a clinical diagnosis of maturity-onset diabetes of the young (MODY) who underwent targeted next-generation sequencing for 13 genes

PURPOSE

To screen for maturity-onset diabetes of the young (MODY) variants in subjects with an early age of onset and positive family history of diabetes mellitus.

METHODS

60 subjects with onset of diabetes between 3 and 30 years of age and parental history (onset < 35 years) of diabetes were recruited after excluding autoimmune, pancreatic and syndromic forms of diabetes. Detailed pedigree chart and clinical data were recorded. MODY genetic testing (MODY 1-13) was performed and variant classification was done adhering to the ACMG guidelines.

RESULTS

Baseline characteristics of subjects were as follows: mean age of onset of diabetes 19.9 ± 7 years, mean duration of diabetes 6.3 ± 6.8 years, BMI 23.3 ± 3 kg/m² and C-peptide 1.56 ± 1.06 nmol/l. Four out of sixty (6.6%) were positive for variants classifiable as pathogenic/likely pathogenic: one patient with HNF4Ac.691C > T, (p.Arg231Trp), two with HNF 1A c.746C > A(p.Ser249Ter) and c.1340C > T(p.Pro447Leu), and one with ABCC8 c.4544C > T (p.Thr1515Met). MODY 1 and MODY 3 variants were documented in the paediatric age group (< 18 years).

CONCLUSION

A genetic diagnosis of MODY could be confirmed in only 6.6% (4/60) of patients clinically classifiable as MODY. This is less than that reported in clinically diagnosed MODY subjects of European descent. Newly published population data and more stringent criteria for assessment of pathogenicity and younger age of onset of type 2 diabetes in Indians could have contributed to the lower genetic confirmation rate. Apart from variants in the classical genes (HNF1A, HNF4A), a likely pathogenic variant in a non-classical gene (ABCC8) was noted in this study.

A case report of Maturity-onset diabetes of the young 12: large fragment deletion in ABCC8 gene with literature review

Background

Maturity-onset diabetes of the young (MODY) is one type of monogenic diabetes that is often misdiagnosed. The case refers to a case of maturity-onset diabetes of the young 12 (MODY12) who was misdiagnosed with type 1 diabetes (T1DM), and this was the first case of MODY12 induced by a large deletion of the ATP-binding cassette transporter C8 gene (ABCC8). Additionally, a literature review was conducted regarding the pathological mechanisms, clinical manifestations, diagnosis, and treatment of ABCC8-mutated diabetes.

Case Description

A 22 years old, male patient had been misdiagnosed with T1DM for 4 years and had experienced poor glucose control with multiple daily insulin injections. Their glycated hemoglobin (HbA1c) was 12.9% at the time of admission and they had been experiencing frequent hypoglycemia. Next-generation sequencing found that the chr11p15.1 region had large fragment heterozygous deletion of exon 17 of the ABCC8 gene. According to the genetic test results, the patient was diagnosed as MODY12, insulin treatment was gradually stopped and converted to glimepiride for oral administration, and HbA1c decreased to 6.1%. After oral treatment for 8 months, the glimepride was stopped; however, HbA1c was 5.9% after 6 months of drug withdrawal and C-peptide level became elevated [fasting C-peptide (FCP) increase from 0.8 to 7.5 ng/mL, and 2 h postprandial C-peptide increase from 0.7 to. 4.1 ng/mL].

Conclusions

It is easy for underweight MODY patients to be misdiagnosed with T1DM. For T1DM patients with poor insulin treatment effects, repeated hypoglycemia, and persistent insulin secretion level, ABCC8 or other genes related to monogenic diabetes should be screened. An early diagnosis and transition of treatment can help improve prognosis.

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.

Overview of Atypical Diabetes

Although type 1 diabetes mellitus and, to a lesser extent, type 2 diabetes mellitus, are the prevailing forms of diabetes in youth, atypical forms of diabetes are not uncommon and may require etiology-specific therapies. By some estimates, up to 6.5% of children with diabetes have monogenic forms. Mitochondrial diabetes and cystic fibrosis related diabetes are less common but often noted in the underlying disease. Atypical diabetes should be considered in patients with a known disorder associated with diabetes, aged less than 25 years with nonautoimmune diabetes and without typical characteristics of type 2 diabetes mellitus, and/or with comorbidities associated with atypical diabetes.

Analysis of the promoter regions of disease-causing genes in maturity-onset diabetes of the young patients

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes caused by the variants in MODY-related genes. In addition to coding variants, variants in the promoter region of MODY-related genes can cause the disease as well. In this study, we screened the promoter regions of the most common MODY-related genes GCK, HNF1A, HNF4A and HNF1B in our cohort of 29 MODY patients. We identified one genetic variant in the HNF1A gene, a 7 bp insertion c.-154-160insTGGGGGT, and three variants in the GCK gene, -282C>T; -194A>G; 402C>G appearing as set. Chloramphenicol acetyltransferase (CAT) assay was performed to test the effect of the 7 bp insertion and the variant set on the activity of the reporter gene in HepG2 and RIN-5F cell, respectively, where a decreasing trend was observed for both variants. In silico analysis and electrophoretic mobility shift assay showed that the 7 bp insertion did not create the binding site for new transcriptional factors, but gave rise to additional binding sites for the existing ones. Results from our study indicated that the 7 bp insertion in the HNF1A gene could be associated with the patient's diabetes. As for the GCK variant set, it is probably not associated with diabetes in patients, but it may modify the fasting glucose level by causing small elevation in variant set carriers. We have presented two promoter variants in MODY-related genes. Variant in the HNF1A gene is presumed to be disease-causing and the GCK promoter variant set could be a phenotype modifier.

The unique clinical spectrum of maturity onset diabetes of the young type 3

Phenotypic variability in maturity-onset diabetes of the young (MODY) makes screening criteria for genomic analysis challenging. We describe the clinical spectrum in a large pedigree with HNF1A-MODY; as generations progressed, the course and outcome became poorer. Although uncommon, pancreatic autoantibodies and diabetes ketoacidosis should not exclude the diagnosis of MODY.

Studies of genetic variability of the hepatocyte nuclear factor-1α gene in an Indian maturity-onset diabetes of the young family

Maturity-onset diabetes of the young (MODY), one of the specific types of diabetes mellitus, is a monogenetic disorder characterized by an autosomal dominant (AD) inheritance and β-cell dysfunction. To study an Indian family with clinical diagnosis of MODY and detect the genetic mutations in the aspect of molecular mechanism, seven blood samples were obtained from the diabetic patients of this pedigree and genomic DNA was extracted from peripheral leukocytes. The exon1, exon2 and exon4 of hepatocyte nuclear factor-1α (HNF-1α) gene were amplified by polymerase chain reaction. Then the products were sequenced and compared with standard sequences on gene bank. As a result, two mutations were detected in exon1. That was CTC → CTG (Leu → Leu) in codon17 and ATC → CTC (Ile → Leu) in codon27. I27L was speculated to have a close relationship with the glycometabolism and the pathogenesis of diabetes mellitus together with the putative novel mutation existed in this Indian pedigree. Meanwhile, one mutation of GGG → GGC (Gly → Gly) in codon288 of exon4 was detected in the proband. No mutations were found in exon2 but a G → T base substitution in the intron4 region among all seven samples was detected. It may have some potential effects on the onset of diabetes in this family, but we do not have any evidence right now. Although it requires further investigation on the function of mutations found in the intron region, our research may provide some clue for this issue and it deserves more attention.

A Single Nucleotide Variant in HNF-1β is Associated with Maturity-Onset Diabetes of the Young in a Large Chinese Family

BACKGROUND

Maturity-onset diabetes of the young (MODY) is a heterogeneous entity of monogenic disorders characterized by autosomal dominant inheritance. Eleven genes were related, including HNF4α, GCK, HNF1α, IPF1, and HNF-1β, and various mutations are being reported.

METHODS

To help the overall understanding of MODY-related pathologic mutations, we studied a large MODY family found in 2012, in Shandong, China, which contained 9 patients over 3 generations. DNA was extracted from the periphery blood samples of (i) 9 affected members, (ii) 17 unaffected members, and (iii) 1000 healthy controls. Three pooled samples were obtained by mixing equal quantity of DNA of each individual within the each group. Totally 400 microsatellite markers across the whole genome were genotyped by capillary electrophoresis. The known MODY-related gene near the identified marker was sequenced to look for putative risk variants.

RESULTS

Allelic frequency of marker D17S798 on chromosome 17q11.2 were significantly different (P<0.001) between the affected vs. unaffected members and the affected vs. healthy controls, but not between the unaffected members vs. healthy controls. MODY5-related gene, hepatocyte nuclear factor-1β (HNF-1β) on 17q12 near D17S798 became the candidate gene. A single nucleotide variant (SNV) of C77T in the non-coding area of exon 1 of HNF-1β was found to be related to MODY5.

CONCLUSION

This novel SNV of HNF-1β contributes to the diabetes development in the family through regulating gene expression most likely. The findings help presymptomatic diagnosis, and imply that mutations in the non-coding areas, as well as in the exons, play roles in the etiology of MODY.

Monogenic diabetes and pregnancy

Monogenic diabetes is frequently mistakenly diagnosed as either type 1 or type 2 diabetes, yet accounts for approximately 1-2% of diabetes. Identifying monogenic forms of diabetes has practical implications for specific therapy, screening of family members and genetic counselling. The most common forms of monogenic diabetes are due to glucokinase (GCK), hepatocyte nuclear factor (HNF)-1A and HNF-4A, HNF-1B, m.3243A>G gene defects. Practical aspects of their recognition, diagnosis and management are outlined, particularly as they relate to pregnancy. This knowledge is important for all physicians managing diabetes in pregnancy, given this is a time when previously unrecognised monogenic diabetes may be uncovered with careful attention to atypical features of diabetes misclassified as type 1, type 2, or gestational diabetes.

Three unreported glucokinase (GCK) missense mutations detected in the screening of thirty-two Brazilian kindreds for GCK and HNF1A-MODY

Thirty-two Brazilian families with MODY phenotype were screened for GCK and HNF1A mutations. GCK mutations were found in 8 families, all patients with mild asymptomatic hyperglycaemia; 3 of them are novel: p.Asp365Asn, p.Gly81Asp and p.Val253Leu. Previously described mutations in HNF1A were found in 2 families.