Maturity-onset diabetes of the young as a model for elucidating the multifactorial origin of type 2 diabetes mellitus

Association between the type of family history of diabetes and the risk and age at onset of diabetes in the Japanese general population

Aim

The objective of this cross-sectional study was to clarify the relationship between the type of first-degree family history of diabetes (FHD) and the presence and age at onset of diabetes (AOD) in the Japanese general population.

Material and methods

Using anonymized processed data collected from community-based health checkups, we classified 10,691 subjects into 5 groups according to the type of FHD as follows: (1) no FHD; (2) diabetes only in a sibling (sFHD); (3) diabetes only in the mother (mFHD); (4) diabetes only in the father (pFHD); and (5) diabetes in ≥ 2 family members, e.g., one parent plus a sibling or both parents (FHD in ≥ 2 family members).

Result

Results of multivariate logistic regression analysis performed using the no FHD group as reference revealed a significant association between a positive FHD and the presence of diabetes (odds ratio: sFHD, 3.67; mFHD, 3.70; pFHD, 2.88; FHD in ≥ 2 family members, 6.35; P < 0.0001 for all). Moreover, the AOD was significantly younger in all the four groups with FHD than in the group without FHD (P < 0.01), being the youngest in the group of FHD in ≥ 2 family members.

Conclusion

Our results revealed that the degree of associations between a positive FHD and the presence of diabetes and AOD differ according to the type of FHD. In particular, FHD in ≥ 2 family members appears to be especially strongly associated with a high risk of diabetes and a younger AOD.

Case-based learning: a case of maturity-onset diabetes of the young 5 (MODY5) due to 17q12 microdeletion with a diminished plasma glucagon level

Maturity-onset diabetes of the young type 5 (MODY5), causally associated with loss-of-function of the HNF1B gene, is a rare form of monogenic diabetes that has been underdiagnosed in part because microdeletions of chromosome 17q12 encompassing the HNF1B gene cannot be detected by sequencing-based approaches, which accounts for about 50% of MODY5 cases. We herein describe a 37-year-old Japanese woman who manifested diabetic ketosis at the onset. The coexistence of features associated with MODY5, including abnormal renal function, impaired insulin secretion, pancreatic hypoplasia and hypomagnesemia, prompted us to decode her genomic information using whole-exome sequencing, where we were not able to identify any pathogenic HNF1B gene mutations. We further examined her genomic integrity using multiplex ligation probe amplification (MLPA) analysis, leading to identification of the 17q12 microdeletion which was further supported by array comparative genomic hybridization (array-CGH). Her insulin secretory capacity was insufficient, whereas her total daily dose of insulin was 11 U/day (0.25 U/Kg/day), indicating that she was relatively sensitive to insulin. As a possible explanation, we found that her plasma glucagon level was below the detection limit. Since inactivation of acetyl-CoA carboxylase 1 (ACACA), encoded in close proximity to the HNF1B gene, was reported to blunt glucagon secretion, the concurrent deletion of the ACACA gene may be in part responsible for this manifestation. In conclusion, the genetic analyses of MODY5 cases require the judicious use of appropriate genetic technologies. In addition, alpha-cell dysfunction may at least in part account for the variable clinical manifestations of MODY5.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-025-00804-2.

Exon Sequencing of HNF1β in Chinese Patients with Early-Onset Diabetes

BACKGRUOUND

Maturity-onset diabetes of the young (MODY) due to variants of hepatocyte nuclear factor 1-beta (HNF1β) (MODY5) has not been well studied in the Chinese population. This study aimed to estimate its prevalence and evaluate the application of a clinical screening method (Faguer score) in Chinese early-onset diabetes (EOD) patients.

METHODS

Among 679 EOD patients clinically diagnosed with type 2 diabetes mellitus (age at diagnosis ≤40 years), the exons of HNF1β were sequenced. Functional impact of rare variants was evaluated using a dual-luciferase reporter system. Faguer scores ≥8 prompted multiplex ligation-dependent probe amplification (MLPA) for large deletions. Pathogenicity of HNF1β variants was assessed following the American College of Medical Genetics and Genomics (ACMG) guidelines.

RESULTS

Two rare HNF1β missense mutations (E105K and G454R) were identified by sequencing in five patients, showing functional impact in vitro. Another patient was found to have a whole-gene deletion by MLPA in 22 patients with the Faguer score above 8. Following ACMG guidelines, six patients carrying pathogenic or likely pathogenic variant were diagnosed with MODY5. The estimated prevalence of MODY5 in Chinese EOD patients was approximately 0.9% or higher.

CONCLUSION

MODY5 is not uncommon in China. The Faguer score is helpful in deciding whether to perform MLPA analysis on patients with negative sequencing results.

A case report of a MODY6 patient coexistence with Charcot-Marie-Toothe 1A syndrome

Monogenic diabetes, which encompasses neonatal diabetes (NDM), maturity onset diabetes of the young (MODY), and several diabetes-associated syndromes, primarily arises from impaired function or abnormal development of the islets of Langerhans, particularly pancreatic β-cells responsible for insulin secretion. This condition is typically associated with a single pathogenic genetic mutation. Charcot-Marie-Tooth disease type 1A (CMT1A) is a hereditary demyelinating neuropathy that is caused by a duplication of the PMP22 gene located on chromosome 17. Herein, we report a case of a young Chinese patient with MODY6 harboring a novel mutation (c. 317C>T, p. Ala106Val) in the NEUROD1 gene. Additionally, this patient concurrently presents with CMT1A, which is characterized by a large segmental duplication within the exon of the PMP22 gene and its adjacent regions. Considering the patient's compromised islet function, we treat him with insulin and oral hypoglycemic agents (metformin, acarbose). This represents the first reported instance of a patient with NEUROD1-MODY coexisting with CMT1A.

Maturity-Onset Diabetes of the Young (MODY) With HNF1B p.Glu105Lys Mutation Achieving Significant Insulin Reduction on Tirzepatide: A Case Report

This report describes the first case of maturity-onset diabetes in young (MODY) with HNF1B mutation started administration of the dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, tirzepatide. A 26-year-old female with a 15-year history of diabetes mellitus was diagnosed with MODY, which is characterized by decreased insulin secretion. She was treated with tirzepatide, which significantly improved her glycemic management; insulin secretion increased the fasting serum C-peptide immunoreactivity from 0.36 to 1.09 ng/mL. The patient discontinued glimepiride, and her total daily insulin dose was reduced from 88 to 4 units. This report highlights the glucose-lowering effects of tirzepatide in a patient with MODY who has the HNF1B p.Glu105Lys mutation.

Diabetes and gut microbiome

Diabetes mellitus represents a significant global health problem. The number of people suffering from this metabolic disease is constantly rising and although the incidence is heterogeneous depending on region, country, economic situation, lifestyle, diet and level of medical care, it is increasing worldwide, especially among youths and children, mainly due to lifestyle and environmental changes. The pathogenesis of the two most common subtypes of diabetes mellitus, type 1 (T1DM) and type 2 (T2DM), is substantially different, so each form is characterized by a different causation, etiology, pathophysiology, presentation, and treatment. Research in recent decades increasingly indicates the potential role of the gut microbiome in the initiation, development, and progression of this disease. Intestinal microbes and their fermentation products have an important impact on host metabolism, immune system, nutrient digestion and absorption, gut barrier integrity and protection against pathogens. This review summarizes the current evidence on the changes in gut microbial populations in both types of diabetes mellitus. Attention is focused on changes in the abundance of specific bacterial groups at different taxonomic levels in humans, and microbiome shift is also assessed in relation to geographic location, age, diet and antidiabetic drug. The causal relationship between gut bacteria and diabetes is still unclear, and future studies applying new methodological approaches to a broader range of microorganisms inhabiting the digestive tract are urgently needed. This would not only provide a better understanding of the role of the gut microbiome in this metabolic disease, but also the use of beneficial bacterial species in the form of probiotics for the treatment of diabetes.

Monogenic diabetes

Diseases in which genetic factors contribute to nearly 100% of the causation by single-gene mutations are referred to as monogenic disorders or Mendelian genetic diseases. These include neonatal diabetes mellitus (NDM), presenting within the first six months of life, maturity-onset diabetes of the young (MODY), developing later in childhood or adolescence, mitochondrial diabetes (MIDD), and insulin-resistant disorders, etc. On the other hand, common lifestyle-related diseases such as type 2 diabetes (T2DM), hypertension and dyslipidemia are multifactorial, emerging through complex interplay of genetic and environmental factors. The identification of causative genes for diabetes resulting from single-gene abnormalities not only unveils previously unknown mechanisms of insulin secretion and sensitivity at the molecular level but also reveals novel targets for drug development. Moreover, monogenic diabetes in which insulin secretion is impaired serve to clarify the pathophysiology and suggest therapeutic targets for the common multifactorial type 2 diabetes mellitus prevalent in the Japanese population, which is characterized by impaired insulin secretion. In this study, we characterize the various monogenic subtypes of diabetes so far identified.

A Korean Family Presenting with Renal Cysts and Maturity-Onset Diabetes of the Young Caused by a Novel In-Frame Deletion of HNF1B

Maturity-onset diabetes of the young (MODY; OMIM # 606391) comprises a cluster of inherited disorders within non-autoimmune diabetes mellitus (DM), typically emerging during adolescence or young adulthood. We report a novel in-frame deletion of HNF1B in a family with renal cysts and MODY, furthering our understanding of HNF1B-related phenotypes. We conducted sequential genetic testing to investigate the glucose intolerance, renal cysts, hepatic cysts, and agenesis of the dorsal pancreas observed in the proband. A comprehensive clinical exome sequencing approach using a Celemics G-Mendeliome Clinical Exome Sequencing Panel was employed. Considering the clinical manifestations observed in the proband, gene panel sequencing identified a heterozygous HNF1B variant, c.36_38delCCT/p.(Leu13del) (reference transcript ID: NM_000458.4), as the most likely cause of MODY in the proband. The patient's clinical presentation was consistent with MODY caused by the HNF1B variant, showing signs of glucose intolerance, renal cysts, hepatic cysts, and agenesis of the dorsal pancreas. Sanger sequencing confirmed the same HNF1B variant and established the paternally inherited autosomal dominant status of the heterozygous variant in the patient, as well as in his father and sister. The presence of early-onset diabetes, renal cysts, a family history of the condition, and nephropathy appearing before or after the diagnosis of diabetes mellitus (DM) suggests a diagnosis of HNF1B-MODY5. Early diagnosis is crucial for preventing complications of DM, enabling family screening, providing pre-conceptional genetic counseling, and monitoring kidney function decline.

High prevalence of copy number variations in the Japanese participants with suspected MODY

Maturity-Onset Diabetes of the Young (MODY) is a diabetes mellitus subtype caused by a single gene. The detection rate of the responsible gene is 27% in the United Kingdom, indicating that the causative gene remains unknown in the majority of clinically diagnosed MODY cases. To improve the detection rate, we applied comprehensive genetic testing using whole exome sequencing (WES) followed by Multiplex Ligation-dependent Probe Amplification (MLPA) and functional analyses. Twenty-one unrelated Japanese participants with MODY were enrolled in the study. To detect copy number variations (CNVs), WES was performed first, followed by MLPA analysis for participants who were negative on the basis of WES. Undetermined variants were analyzed according to their functional properties. WES identified 7 pathogenic and 3 novel likely pathogenic variants in the 21 participants. Functional analyses revealed that 1 in 3 variants was pathogenic. MLPA analysis applied to the remaining 13 undetermined samples identified 4 cases with pathogenic CNVs: 3 in HNF4A and 1 in HNF1B. Pathogenic variants were identified in 12 participants (12/21, 57.1%) - relatively high rate reported to date. Notably, one-third of the participants had CNVs in HNF4A or HNF1B, indicating a limitation of WES-only screening.

HNF1β, LHX1, and GGNBP2 deletion contributed to kidney and reproductive dysfunction in 17q12 deletion syndrome: evidence from a case report

17q12 deletion syndrome is a chromosomal abnormality, where there is a small missing piece (deletion) of genetic material on the long arm (q) of chromosome 17. Sign and symptoms can vary widely among different patients. Recently, a patient was diagnosed with 17q12 deletion syndrome in our hospital, and the clinical characteristics presented as absence of the right kidney, compensatory hypertrophy of the left kidney, multiple small cysts in the left kidney, pancreatic atrophy, hypomagnesemia, bowed uterus, multiple follicular cysts in both lobes of the thyroid gland, and maturity-onset diabetes of the young type 5 (MODY-5). A 1.5-Mb deletion with haploinsufficiency for 20 genes within the 17q12 region was found through copy number variation (CNV) analysis based on metagenomic next-generation sequencing (mNGS) technology. In addition to HNF1B absence, the LIM-class homeobox 1 transcription factor (LHX1) and GGNBP2 absence was also involved in regulation of kidney development and the reproductive system through bioinformatics analysis. The inheriting risk of 17q12 deletion syndrome is about 50%, and it is recommended to provide genetic counseling to all patients who are suspected or diagnosed with the syndrome.

MODY Only Monogenic? A Narrative Review of the Novel Rare and Low-Penetrant Variants

Maturity-onset diabetes of the young (MODY) represents the most frequent form of monogenic diabetes mellitus (DM), currently classified in 14 distinct subtypes according to single gene mutations involved in the differentiation and function of pancreatic β-cells. A significant proportion of MODY has unknown etiology, suggesting that the genetic landscape is still to be explored. Recently, novel potentially MODY-causal genes, involved in the differentiation and function of β-cells, have been identified, such as RFX6, NKX2.2, NKX6.1, WFS1, PCBD1, MTOR, TBC1D4, CACNA1E, MNX1, AKT2, NEUROG3, EIF2AK3, GLIS3, HADH, and PTF1A. Genetic and clinical features of MODY variants remain highly heterogeneous, with no direct genotype-phenotype correlation, especially in the low-penetrant subtypes. This is a narrative review of the literature aimed at describing the current state-of-the-art of the novel likely MODY-associated variants. For a deeper understanding of MODY complexity, we also report some related controversies concerning the etiological role of some of the well-known pathological genes and MODY inheritance pattern, as well as the rare association of MODY with autoimmune diabetes. Due to the limited data available, the assessment of MODY-related genes pathogenicity remains challenging, especially in the setting of rare and low-penetrant subtypes. In consideration of the crucial importance of an accurate diagnosis, prognosis and management of MODY, more studies are warranted to further investigate its genetic landscape and the genotype-phenotype correlation, as well as the pathogenetic contribution of the nongenetic modifiers in this cohort of patients.

A Case of 17q12 Microdeletion Syndrome in a MODY5 Type Diabetes with HNF-1β Gene Mutation Accompanied

Maturity Onset Diabetes of the Young (MODY) is an autosomal dominant inherited disorder prevalent among adolescents. Typically, it manifests with hyperglycemia before the age of 25. MODY5 is attributed to a mutation in the Hepatocyte Nuclear Factor-1β (HNF-1β) gene. A complete absence of HNF-1β is observed in 50% of those with MODY5. The 17q12 microdeletion syndrome closely linked with MODY5. Its incidence in the general population is around 1 in 14,500 and is linked with facial deformities, diabetes, polycystic kidneys, pancreatic hypertrophy, liver anomalies, and neuropsychological impairments. The most primary clinical signs are predominantly associated with the HNF-1β gene deletion. We chronicle the case of a male of 19 years of age diagnosed with diabetes, who, alongside persistent liver damage and polycystic kidneys, was referred from a community hospital to the Xuzhou Central Hospital. His clinical presentation included diabetes, liver dysfunction, polycystic kidneys, lipid irregularities, insulin resistance, and fatty atrophy. Subsequent genetic screening unveiled a 17q12 chromosomal deletion and an absence of the Hepatocyte Nuclear Factor-1β (HNF-1β) gene. Hence, for adolescent patients lacking a familial diabetes history but exhibiting symptoms like polycystic kidneys, liver damage, lipid irregularities, and fatty atrophy, a thorough assessment for the 17q12 microdeletion syndrome becomes imperative.

In Vitro Functional Analysis Can Aid Precision Diagnostics of HNF1B-MODY

Precision medicine relies on accurate and consistent classification of sequence variants. A correct diagnosis of hepatocyte nuclear factor (HNF) 1B maturity-onset diabetes of the young, caused by pathogenic variants in the HNF1B gene, is important for optimal disease management and prognosis, and it has implications for genetic counseling and follow-up of at-risk family members. We hypothesized that the functional characterization could provide valuable information to assist the interpretation of pathogenicity of HNF1B variants. Using different in vitro functional assays, variants identified among 313 individuals, suspected to have monogenic diabetes with or without kidney disease, were characterized. The data from the functional assays were subsequently conjugated with obtained clinical, biochemical, and in silico data. Two variants (p.A167P, p.H336Pfs∗22) showed severe loss of function due to impaired transactivation, reduced DNA binding (p.A167P), and mRNA instability (p.A167P). Although both these variant carriers were diagnosed with diabetes, the p.H336Pfs∗22 carrier also had congenital absence of a kidney, which is a characteristic trait for HNF1B maturity-onset diabetes of the young. Functional analysis of the p.A167P variant revealed damaging effects on HNF-1B protein function, which may warrant imaging of the kidneys and/or pancreas. In addition, the current study has generated important data, including evidence supporting the benign functional impact of five variants (p.D82N, p.T88A, p.N394D, p.V458G, and p.T544A), and piloting new approaches that will prove critical for the growth of HNF1B-diabetes diagnosis.

Perspectives on genetic studies of type 2 diabetes from the genome-wide association studies era to precision medicine

Genome-wide association studies (GWAS) have facilitated a substantial and rapid increase in the number of confirmed genetic susceptibility variants for complex diseases. Approximately 700 variants predisposing individuals to the risk for type 2 diabetes have been identified through GWAS until 2023. From 2018 to 2022, hundreds of type 2 diabetes susceptibility loci with smaller effect sizes were identified through large-scale GWAS with sample sizes of 200,000 to >1 million. The clinical translation of genetic information for type 2 diabetes includes the development of novel therapeutics and risk predictions. Although drug discovery based on loci identified in GWAS remains challenging owing to the difficulty of functional annotation, global efforts have been made to identify novel biological mechanisms and therapeutic targets by applying multi-omics approaches or searching for disease-associated coding variants in isolated founder populations. Polygenic risk scores (PRSs), comprising up to millions of associated variants, can identify individuals with higher disease risk than those in the general population. In populations of European descent, PRSs constructed from base GWAS data with a sample size of approximately 450,000 have predicted the onset of diseases well. However, European GWAS-derived PRSs have limited predictive performance in non-European populations. The predictive accuracy of a PRS largely depends on the sample size of the base GWAS data. The results of GWAS meta-analyses for multi-ethnic groups as base GWAS data and cross-population polygenic prediction methodology have been applied to establish a universal PRS applicable to small isolated ethnic populations.

Identification of causative gene variants for patients with known monogenic diabetes using a targeted next-generation sequencing panel in a single-center study

Aims

We aimed to verify the usefulness of targeted next-generation sequencing (NGS) technology for diagnosing monogenic diabetes in a single center.

Methods

We designed an amplicon-based NGS panel targeting 34 genes associated with known monogenic diabetes and performed resequencing in 56 patients with autoantibody-negative diabetes mellitus diagnosed at < 50 years who had not been highly obese. By bioinformatic analysis, we filtered significant variants based on allele frequency (< 0.005 in East Asians) and functional prediction. We estimated the pathogenicity of each variant upon considering the family history.

Results

Overall, 16 candidate causative variants were identified in 16 patients. Among them, two previously known heterozygous nonsynonymous single-nucleotide variants associated with monogenic diabetes were confirmed as causative variants: one each in the GCK and WFS1 genes. The former was found in two independent diabetes-affected families. Two novel putatively deleterious heterozygous variants were also assumed to be causative from the family history: one frameshift and one nonsynonymous single-nucleotide variant in the HNF4A gene. Twelve variants remained as candidates associated with the development of diabetes.

Conclusion

Targeted NGS panel testing was useful to diagnose various forms of monogenic diabetes in combination with familial analysis, but additional ingenuity would be needed for practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00669-3.

Hepatocyte nuclear factor 1B deletion, but not intragenic mutation, might be more susceptible to hypomagnesemia

AIMS

HNF1B syndrome is caused by defects in the hepatocyte nuclear factor 1B (HNF1B) gene, which leads to maturity-onset diabetes of the young type 5 and congenital organ malformations. This study aimed to identify a gene defect in a patient presenting with diabetes and severe diarrhea, while also analyzing the prevalence of hypomagnesemia and its correlation with the HNF1B genotype.

MATERIALS AND METHODS

Whole exome sequencing was used to identify responsible point mutations and small indels in the proband and their family members. Multiplex ligation-dependent probe amplification was carried out to identify HNF1B deletions. Furthermore, an analysis of published data on 539 cumulative HNF1B cases, from 29 literature sources, was carried out to determine the correlation between the HNF1B genotype and the phenotype of serum magnesium status.

RESULTS

Using multiplex ligation-dependent probe amplification, we identified a de novo heterozygous HNF1B deletion in the patient, who showed dorsal pancreas agenesis and multiple kidney cysts, as detected by magnetic resonance imaging. Magnesium supplementation effectively alleviated the symptoms of diarrhea. Hypomagnesemia was highly prevalent in 192 out of 354 (54.2%) patients with HNF1B syndrome. Compared with patients with intragenic mutations, those with HNF1B deletions were more likely to suffer from hypomagnesemia, with an odds ratio of 3.1 (95% confidence interval 1.8-5.4).

CONCLUSIONS

Hypomagnesemia is highly prevalent in individuals with HNF1B syndrome, and those with HNF1B deletion are more susceptible to developing hypomagnesemia compared with those with intragenic mutations. The genotype-phenotype associations in HNF1B syndrome have significant implications for endocrinologists in terms of genotype detection, treatment decisions and prognosis assessment.

Japanese 17q12 Deletion Syndrome with Complex Clinical Manifestations

17q12 deletion syndrome is a rare chromosomal anomaly with variable phenotypes, caused by the heterozygous deletion of chromosome 17q12. We herein report a 35-year-old Japanese patient with chromosomal 17q12 deletion syndrome identified by de novo deletion of the 1.46 Mb segment at the 17q12 band by genetic analyses. He exhibited a wide range of phenotypes, such as maturity-onset diabetes of the young (MODY) type 5, structural or functional abnormalities of the kidney, liver, and pancreas; facial dysmorphic features, electrolyte disorders; keratoconus, and acquired perforating dermatosis. This case report provides valuable resources concerning the clinical spectrum of rare 17q12 deletion syndrome.

Glucokinase Variant Proteins Are Resistant to Fasting-Induced Uridine Diphosphate Glucose-Dependent Degradation in Maturity-Onset Diabetes of the Young Type 2 Patients

We previously reported that glucokinase undergoes ubiquitination and subsequent degradation, a process mediated by cereblon, particularly in the presence of uridine diphosphate glucose (UDP-glucose). In this context, we hereby present evidence showcasing the resilience of variant glucokinase proteins of maturity-onset diabetes of the young type 2 (MODY2) against degradation and, concomitantly, their influence on insulin secretion, both in cell lines and in the afflicted MODY2 patient. Hence, glucose-1-phodphate promotes UDP-glucose production by UDP-glucose pyrophosphorylase 2; consequently, UDP-glucose-dependent glucokinase degradation may occur during fasting. Next, we analyzed glucokinase variant proteins from MODY2 or persistent hyperinsulinemic hypoglycemia in infancy (PHHI). Among the eleven MODY2 glucokinase-mutated proteins tested, those with a lower glucose-binding affinity exhibited resistance to UDP-glucose-dependent degradation. Conversely, the glucokinaseA456V-mutated protein from PHHI had a higher glucose affinity and was sensitive to UDP-glucose-dependent degradation. Furthermore, in vitro studies involving UDP-glucose-dependent glucokinase variant proteins and insulin secretion during fasting in Japanese MODY2 patients revealed a strong correlation and a higher coefficient of determination. This suggests that UDP-glucose-dependent glucokinase degradation plays a significant role in the pathogenesis of glucose-homeostasis-related hereditary diseases, such as MODY2 and PHHI.

Loss of CtBP2 may be a mechanistic link between metabolic derangements and progressive impairment of pancreatic β cell function

The adaptive increase in insulin secretion in early stages of obesity serves as a safeguard mechanism to maintain glucose homeostasis that cannot be sustained, and the eventual decompensation of β cells is a key event in the pathogenesis of diabetes. Here we describe a crucial system orchestrated by a transcriptional cofactor CtBP2. In cultured β cells, insulin gene expression is coactivated by CtBP2. Global genomic mapping of CtBP2 binding sites identifies a key interaction between CtBP2 and NEUROD1 through which CtBP2 decompacts chromatin in the insulin gene promoter. CtBP2 expression is diminished in pancreatic islets in multiple mouse models of obesity, as well as human obesity. Pancreatic β cell-specific CtBP2-deficient mice manifest glucose intolerance with impaired insulin secretion. Our transcriptome analysis highlights an essential role of CtBP2 in the maintenance of β cell integrity. This system provides clues to the molecular basis in obesity and may be targetable to develop therapeutic approaches.

Incomplete penetrance and variable expressivity in monogenic diabetes; a challenge but also an opportunity

Monogenic Forms of Diabetes (MFD) account for about 3% of all diabetes, and their accurate diagnosis often results in life-changing therapeutic reassignment for the patients. Like other Mendelian diseases, reduced penetrance and variable expressivity are often seen in several different types of MFD, where symptoms develop only in a portion of the persons who carry the pathogenic variant or vary widely in symptom severity and age of onset. This complicates diagnosis and disease management in MFD. In addition to its clinical importance, knowledge of genetic modifiers that confer penetrance and expressivity variability opens possibilities to identify protective genetic variants which may help probe the mechanisms of more common forms of diabetes and shed light in new therapeutic strategies. In this review, we will mainly address penetrance and expressivity variation in different types of MFD, factors that confer such variations and opportunities that come with such knowledge. Related literature was searched in PubMed, Medline and Embase. Papers with publication year from 1974 to 2023 are included. Data are either sourced from literatures or from OMIM, Clinvar and 1000 genome browser.

Targeted gene panel analysis of Japanese patients with maturity-onset diabetes of the young-like diabetes mellitus: Roles of inactivating variants in the ABCC8 and insulin resistance genes

AIMS/INTRODUCTION

To investigate the genetic background of Japanese patients with suspected maturity-onset diabetes of the young (MODY).

MATERIALS AND METHODS

On 340 proband patients referred from across Japan, genomic variants were analyzed using a targeted multigene panel analysis combined with the multiplex ligation probe amplification (MLPA) analysis, mitochondrial m.3243A > G analysis and methylation-specific polymerase chain reaction of the imprinted 6q24 locus. Pathogenic/likely pathogenic variants were listed according to the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria. Additionally, variants with a population frequency <0.001 and Combined Annotation Dependent Depletion score >20 (CS >20) were listed as rare variants of uncertain significance-CS >20.

RESULTS

A total of 157 pathogenic/likely pathogenic variants and 44 rare variants of uncertain significance-CS >20 were identified. In the pathogenic/likely pathogenic variants, alterations in the GCK gene were the most common (82, 52.2%) followed by HNF1A (29, 18.5%), HNF4A (13, 8.3%) and HNF1B (13, 8.3%). One patient was a 29.5% mosaic with a truncating INSR variant. In the rare variants of uncertain significance-CS >20, 20 (45.5%) were in the genes coding for the adenosine triphosphate-sensitive potassium channel, KCNJ11 or ABCC8, and four were in the genes of the insulin-signaling pathway, INSR and PIK3R1. Four variants in ABCC8 were previously reported in patients with congenital hyperinsulinism, suggesting the inactivating nature of these variants, and at least two of our patients had a history of congenital hyperinsulinism evolving into diabetes. In two patients with INSR or PIK3R1 variants, insulin resistance was evident at diagnosis.

CONCLUSIONS

Causative genomic variants could be identified in at least 46.2% of clinically suspected MODY patients. ABCC8-MODY with inactivating variants could represent a distinct category of MODY. Genes of insulin resistance should be included in the sequencing panel for MODY.

Maturity-Onset Diabetes of the Young: Mutations, Physiological Consequences, and Treatment Options

Maturity-Onset Diabetes of the Young (MODY) is a rare form of diabetes which affects between 1% and 5% of diagnosed diabetes cases. Clinical characterizations of MODY include onset of diabetes at an early age (before the age of 30), autosomal dominant inheritance pattern, impaired glucose-induced secretion of insulin, and hyperglycemia. Presently, 14 MODY subtypes have been identified. Within these subtypes are several mutations which contribute to the different MODY phenotypes. Despite the identification of these 14 subtypes, MODY is often misdiagnosed as type 1 or type 2 diabetes mellitus due to an overlap in clinical features, high cost and limited availability of genetic testing, and unfamiliarity with MODY outside of the medical profession. The primary aim of this review is to investigate the genetic characterization of the MODY subtypes. Additionally, this review will elucidate the link between the genetics, function, and clinical manifestations of MODY in each of the 14 subtypes. In providing this knowledge, we hope to assist in the accurate diagnosis of MODY patients and, subsequently, in ensuring they receive appropriate treatment.

UDP-Glucose: A Cereblon-Dependent Glucokinase Protein Degrader

We previously reported that glucokinase is ubiquitinated and degraded by cereblon with an unknown endogenous glucokinase protein degrader. Here, we show that UDP-glucose is a glucokinase protein degrader. We identified that both glucose and UDP-glucose bind to glucokinase and that both uridine and UDP-glucose bind to cereblon in a similar way to thalidomide. From these results, UDP-glucose was identified as a molecular glue between cereblon and glucokinase. Glucokinase produces glucose-6-phosphate in the pancreas and liver. Especially in β-cells, glucokinase is the main target of glucose for glucose-induced insulin secretion. UDP-glucose administration ubiquitinated and degraded glucokinase, lowered glucose-6-phosphate production, and then reduced insulin secretion in β-cell lines and mice. Maturity-onset diabetes of the young type 2 (MODY2) glucokinase^E256K mutant protein was resistant to UDP-glucose induced ubiquitination and degradation. Taken together, glucokinase ubiquitination and degradation signaling might be impaired in MODY2 patients.

A case of early-onset diabetes with impaired insulin secretion carrying a PAX6 gene Gln135* mutation

Summary

A paired homeodomain transcription factor, PAX6 (paired-box 6), is essential for the development and differentiation of pancreatic endocrine cells as well as ocular cells. Despite the impairment of insulin secretion observed in PAX6-deficient mice, evidence implicating causal association between PAX6 gene mutations and monogenic forms of human diabetes is limited. We herein describe a 33-year-old Japanese woman with congenital aniridia who was referred to our hospital because of her uncontrolled diabetes with elevated hemoglobin A1c (13.1%) and blood glucose (32.5 mmol/L) levels. Our biochemical analysis revealed that her insulin secretory capacity was modestly impaired as represented by decreased 24-h urinary C-peptide levels (38.0 μg/day), primarily explaining her diabetes. Intriguingly, there was a trend toward a reduction in her serum glucagon levels as well. Based on the well-recognized association of PAX6 gene mutations with congenital aniridia, we screened the whole PAX6 coding sequence, leading to an identification of a heterozygous Gln135* mutation. We tested our idea that this mutation may at least in part explain the impaired insulin secretion observed in this patient. In cultured pancreatic β-cells, exogenous expression of the PAX6 Gln135* mutant produced a truncated protein that lacked the transcriptional activity to induce insulin gene expression. Our observation together with preceding reports support the recent attempt to include PAX6 in the growing list of genes causally responsible for monogenic diabetes. In addition, since most cases of congenital aniridia carry PAX6 mutations, we may need to pay more attention to blood glucose levels in these patients.

Learning points

PAX6 Gln135* mutation may be causally associated not only with congenital aniridia but also with diabetes. Blood glucose levels may deserve more attention in cases of congenital aniridia with PAX6 mutations. Our case supports the recent attempt to include PAX6 in the list of MODY genes, and Gln135* may be pathogenic.

Early Signs of Molecular Defects in iPSC-Derived Neural Stems Cells from Patients with Familial Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder, classically associated with extensive loss of dopaminergic neurons of the substantia nigra pars compacta. The hallmark of the disease is the accumulation of pathogenic conformations of the presynaptic protein, α-synuclein (αSyn), and the formation of intraneuronal protein aggregate inclusions. Neurodegeneration of dopamine neurons leads to a prominent dopaminergic deficiency in the basal ganglia, responsible for motor disturbances. However, it is now recognized that the disease involves more widespread neuronal dysfunction, leading to early and late non-motor symptoms. The development of in vitro systems based on the differentiation of human-induced pluripotent stem cells provides us the unique opportunity to monitor alterations at the cellular and molecular level throughout the differentiation procedure and identify perturbations that occur early, even at the neuronal precursor stage. Here we aim to identify whether p.A53T-αSyn induced disturbances at the molecular level are already present in neural precursors. Towards this, we present data from transcriptomics analysis of control and p.A53T-αSyn NPCs showing altered expression in transcripts involved in axon guidance, adhesion, synaptogenesis, ion transport, and metabolism. The comparative analysis with the transcriptomics profile of p.A53T-αSyn neurons shows both distinct and overlapping pathways leading to neurodegeneration while meta-analysis with transcriptomics data from both neurodegenerative and neurodevelopmental disorders reveals that p.A53T-pathology has a significant overlap with the latter category. This is the first study showing that molecular dysregulation initiates early at the p.A53T-αSyn NPC level, suggesting that synucleinopathies may have a neurodevelopmental component.

Glucokinase-maturity onset diabetes mellitus in the young suggested by factory-calibrated glucose monitoring data: a case report

Glucokinase has an important role in regulating glycolysis as a glucose sensor in liver and pancreatic β cells. Glucokinase-maturity onset diabetes in young (GCK-MODY also known as MODY2) is caused by autosomal dominant gene mutation of the GCK gene; it is characterized by mild fasting hyperglycemia and small 2-h glucose increment during 75 g-oral glucose tolerance test (OGTT) as well as near-normal postprandial glucose variabilities. A 10-year-old girl with family history of diabetes visited her physician after being found positive for urinary glucose by school medical checkup. She received a diagnosis of diabetes based on the laboratory data: 75 g-OGTT (mild fasting hyperglycemia and small 2-h glucose increment) and factory-calibrated glucose monitoring (mild elevation of average glucose level and near-normal glycemic variability), which raised suspicion of GCK-MODY. She was then referred to our institution for genetic examination, which revealed a GCK heterozygous mutation (NM_000162: exon10: c.1324G>T: p.E442X) in the proband as well as in her mother and maternal grandmother, who had been receiving anti-diabetes medications without knowing that they had GCK-MODY specifically. GCK-MODY cases show incidence of microvascular and macrovascular diseases similar to that of normal subjects, and their glucose levels are adequately controlled without anti-diabetes drug use. Thus, early and definitive diagnosis of MODY2 by genetic testing is important to avoid unnecessary medication.

An HNF1α truncation associated with maturity-onset diabetes of the young impairs pancreatic progenitor differentiation by antagonizing HNF1β function

The HNF1α^p291fsinsC truncation is the most common mutation associated with maturity-onset diabetes of the young 3 (MODY3). Although shown to impair HNF1α signaling, the mechanism by which HNF1α^p291fsinsC causes MODY3 is not fully understood. Here we use MODY3 patient and CRISPR/Cas9-engineered human induced pluripotent stem cells (hiPSCs) grown as 3D organoids to investigate how HNF1α^p291fsinsC affects hiPSC differentiation during pancreatic development. HNF1α^p291fsinsC hiPSCs shows reduced pancreatic progenitor and β cell differentiation. Mechanistically, HNF1α^p291fsinsC interacts with HNF1β and inhibits its function, and disrupting this interaction partially rescues HNF1β-dependent transcription. HNF1β overexpression in the HNF1α^p291fsinsC patient organoid line increases PDX1⁺ progenitors, while HNF1β overexpression in the HNF1α^p291fsinsC patient iPSC line partially rescues β cell differentiation. Our study highlights the capability of pancreas progenitor-derived organoids to model disease in vitro. Additionally, it uncovers an HNF1β-mediated mechanism linked to HNF1α truncation that affects progenitor differentiation and could explain the clinical heterogeneity observed in MODY3 patients.

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MODY3 patient and CRISPR/Cas9 HNF1α^p291fsinsC mutated iPSC lines are generated

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Mutant iPSCs show deficient pancreatic progenitor and β cell differentiation

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Mutant truncated HNF1α protein binds wild-type HNF1β protein to hinder its function

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HNF1β overexpression in MODY3 iPSC line partially rescues β cell differentiation

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.

Maturity-onset diabetes of the young (MODY) type 5, presenting as diabetic ketoacidosis with alkalemia - A report of a case

A 34-year-old man visited our hospital because of dry mouth and weight loss. His plasma glucose level was 32.8 mmol/L and serum levels of ketone bodies were increased, but with metabolic alkalemia. He was also suffering from renal tubular hypomagnesemia and hypokalemia. Abdominal CT revealed bilateral renal cysts. These findings were suggestive of maturity-onset diabetes of the young (MODY) type5. Genetic testing revealed heterozygous hepatocyte nuclear factor 1 beta (HNF1B) gene deletion. In the present case, it seemed reasonable to view HNF1B gene deletion as the common cause of MODY5-associated diabetic ketoacidosis and tubular malfunction-induced hypokalemic alkalosis. This case exemplifies an importance of HNF1B gene abnormality as a potential cause of diabetic ketoacidosis with alkalemia.

Associations between stool micro-transcriptome, gut microbiota, and infant growth

Rapid infant growth increases the risk for adult obesity. The gut microbiome is associated with early weight status; however, no study has examined how interactions between microbial and host ribonucleic acid (RNA) expression influence infant growth. We hypothesized that dynamics in infant stool micro-ribonucleic acids (miRNAs) would be associated with both microbial activity and infant growth via putative metabolic targets. Stool was collected twice from 30 full-term infants, at 1 month and again between 6 and 12 months. Stool RNA were measured with high-throughput sequencing and aligned to human and microbial databases. Infant growth was measured by weight-for-length z-score at birth and 12 months. Increased RNA transcriptional activity of Clostridia (R = 0.55; Adj p = 3.7E-2) and Burkholderia (R = -0.820, Adj p = 2.62E-3) were associated with infant growth. Of the 25 human RNAs associated with growth, 16 were miRNAs. The miRNAs demonstrated significant target enrichment (Adj p < 0.05) for four metabolic pathways. There were four associations between growth-related miRNAs and growth-related phyla. We have shown that longitudinal trends in gut microbiota activity and human miRNA levels are associated with infant growth and the metabolic targets of miRNAs suggest these molecules may regulate the biosynthetic landscape of the gut and influence microbial activity.

Maturity-Onset Diabetes of Young Type 5: Diabetes with Extrapancreatic Features

Objective

This case involves a new-onset diabetes patient diagnosed during pregnancy with the congenital dysplastic right kidney. Case Report. Clinical presentation, biochemical features, imaging in a patient with diabetes diagnosed during pregnancy, and congenital dysplastic right kidney. Discussion. We present a case of a 22-year-old female with the congenital dysplastic right kidney diagnosed with gestational diabetes mellitus after failing a 1-hour oral glucose tolerance test, requiring insulin during pregnancy. Because of the family history of diabetes and morphologic renal abnormalities at young ages on the maternal side of the family, our patient was evaluated for maturity-onset diabetes of adult and was found to have HNF-1β mutation.

Conclusion

This case highlights the importance of considering the diagnosis of maturity-onset diabetes of young and particularly MODY-5 in individuals with extrapancreatic features. MODY-5 should also be considered in a patient undergoing renal transplant at young ages with a family history of morphologic renal abnormalities.

A novel RFX6 heterozygous mutation (p.R652X) in maturity-onset diabetes mellitus: A case report

Heterozygous RFX6 mutation has emerged as a potential cause of maturity-onset diabetes mellitus of the young (MODY). A 16-year-old female was diagnosed with diabetes by her family doctor and was referred to our institution for genetic examination. Genetic testing revealed a novel RFX6 heterozygous mutation (NM_173560: exon17: c.1954C>T: p.R652X) in the patient and in her mother and brother. She had no islet-specific autoantibodies and showed a reduced meal-induced response of insulin, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide-1, which is consistent with the phenotype of MODY due to heterozygous RFX6 mutation. In conclusion, we report a case of MODY due to a novel heterozygous mutation, p.R652X.

Deep embedded clustering with multiple objectives on scRNA-seq data

In recent years, single-cell RNA sequencing (scRNA-seq) technologies have been widely adopted to interrogate gene expression of individual cells; it brings opportunities to understand the underlying processes in a high-throughput manner. Deep embedded clustering (DEC) was demonstrated successful in high-dimensional sparse scRNA-seq data by joint feature learning and cluster assignment for identifying cell types simultaneously. However, the deep network architecture for embedding clustering is not trivial to optimize. Therefore, we propose an evolutionary multiobjective DEC by synergizing the multiobjective evolutionary optimization to simultaneously evolve the hyperparameters and architectures of DEC in an automatic manner. Firstly, a denoising autoencoder is integrated into the DEC to project the high-dimensional sparse scRNA-seq data into a low-dimensional space. After that, to guide the evolution, three objective functions are formulated to balance the model's generality and clustering performance for robustness. Meanwhile, migration and mutation operators are proposed to optimize the objective functions to select the suitable hyperparameters and architectures of DEC in the multiobjective framework. Multiple comparison analyses are conducted on twenty synthetic data and eight real data from different representative single-cell sequencing platforms to validate the effectiveness. The experimental results reveal that the proposed algorithm outperforms other state-of-the-art clustering methods under different metrics. Meanwhile, marker genes identification, gene ontology enrichment and pathology analysis are conducted to reveal novel insights into the cell type identification and characterization mechanisms.

Autosomal Dominant Tubulointerstitial Kidney Disease HNF1B With Maturity-Onset Diabetes of the Young: A Case Report With Kidney Biopsy

Autosomal dominant tubulointerstitial kidney disease subtype hepatocyte nuclear factor 1β (ADTKD-HNF1B) is a hereditary disease caused by variants of HNF1B that is characterized by a family history of tubulointerstitial nephropathy with concomitant diabetes mellitus. We report on a Japanese man in his early 40s who had ADTKD-HNF1B diagnosed. He had a reduced glomerular filtration rate, borderline diabetes mellitus, multiple small cysts in his bilateral kidneys, and pancreatic hypoplasia. He also had a family history of diabetes and kidney cystic lesions. These phenotypes represent ADTKD-HNF1B and genetic analysis revealed a missense variant of HNF1B. Kidney biopsy demonstrated not only tubulointerstitial fibrosis but also abnormal mitochondrial morphology in tubular cells, a novel finding.

A heterozygous protein-truncating RFX6 variant in a family with childhood-onset, pregnancy-associated and adult-onset diabetes

BACKGROUND

Recently, heterozygous RFX6 mutations including p.Arg377Ter were identified in individuals with maturity-onset diabetes of the young (MODY). Clinical analysis of 36 individuals suggested that RFX6 mutation-induced MODY is characterized by low penetrance and relatively late onset. However, given the small number of previous reports and the limited clinical information of each case, further studies are necessary to clarify the phenotypic characteristics of RFX6 mutations.

CASE REPORT

We identified a previously reported p.Arg377Ter variant of RFX6 in a three-generation family with diabetes. The variant was detected through mutation screening for 30 diabetes-associated genes. The variant was not found in public databases and was predicted to encode a truncated protein or undergo nonsense-mediated mRNA decay. The proband showed glycosuria from 8 years of age and was diagnosed with MODY at 10 years of age, before the onset of puberty. She received basal and bolus insulin injection as initial therapy. The proband's mother exhibited glycosuria at 26 years of age when she conceived the first child. The mother was treated with insulin, oral hypoglycaemic drugs and diet. The proband and her mother were negative for islet cell autoantibodies. The maternal grandmother showed glycosuria around 50 years of age and was treated with oral hypoglycaemic drugs alone.

CONCLUSION

This study provides supporting evidence for the causal relationship between heterozygous RFX6 mutations and MODY. Furthermore, our results indicate that phenotypic consequences of RFX6 mutations are highly variable even within a single family, and possibly include childhood-onset and pregnancy-associated non-autoimmune diabetes.

A case of MODY5-like manifestations without mutations or deletions in coding and minimal promoter regions of the HNF1B gene

Pancreatic tail hypoplasia is a common manifestation of maturity onset diabetes of the young (MODY) 5 that can cause reno-genito-urinary malformations such as renal cysts and bicornuate uterus. A 69-year-old female was admitted to our hospital for consultation on her relatively high HbA1c value. At age 20, she was diagnosed with uterus bicornis. At age 68, she was diagnosed with pancreas tail hypoplasia, renal cysts and non-functioning pancreatic neuroendocrine tumor (NET) in addition to right hydronephrosis due to multiple ureteral bladder carcinomas. She received total right nephrectomy, ureterectomy and partial cystectomy for multiple ureteral bladder carcinomas [non-invasive papillary urothelial carcinoma, low grade (G1), pTa, LV10, u-rtx, RM0, and pN0 (0/8)]. She also received distal pancreatomy for pancreatic NET [NET G1]. She then was referred to our department at age 69 due to increase in her HbA1c value from 6.2 to 7.2%; 75 g oral glucose tolerance test revealed impaired glucose tolerance. Her clinical characteristics (uterus bicornis, pancreas hypoplasia, and renal cysts) closely resembled the phenotype of MODY5, in which mutations in the HNF1B gene have been reported. Our genetic testing failed to detect any mutation or microdeletion in the coding or minimal promoter regions of the HNF1B gene. Although there remains a possibility that genetic mutations in introns and regulatory regions of the HNF1B gene might cause the MODY5-like manifestations in this patient, these results might suggest involvement of genes other than HNF1B in the pathogenesis of our patient's disease.

A novel splice-site mutation of the HNF1B gene in a family with maturity onset diabetes of the young type 5 (MODY5)

SUMMARY

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes mellitus characterised by early onset and dominant inheritance. Delayed diagnosis or misdiagnosis as type 1 or type 2 diabetes mellitus is common. Definitive genetic diagnosis is essential for appropriate treatment of patients with MODY. The hepatocyte nuclear factor 1-beta (HNF1B) gene is responsible for MODY type 5 (MODY5), which has distinctive clinical features including renal disease. MODY5 should always be considered by clinicians in patients with early onset diabetes and renal anomalies. We report a case of a 30-year-old Japanese male with early-onset diabetes mellitus, renal anomalies and family history of diabetes that was suggestive of MODY5. Renal histology showed no evidence of diabetic nephropathy. Genetic testing revealed a novel heterozygous splice-site mutation of the HNF1B gene in the family members. It was strongly suggested that the mutation could underlie our patient's MODY5.

LEARNING POINTS

Genetic diagnosis of MODY is relevant for appropriate treatment. Dominantly inherited early-onset diabetes mellitus with renal cysts suggests MODY5. Scanning the non-coding regions is important for not missing a mutation in HNF1B.

Recognition of maturity-onset diabetes of the young in China

Aims/Introduction

Given that mutations related to maturity‐onset diabetes of the young (MODY) are rarely found in Chinese populations, we aim to characterize the mutation spectrum of MODY pedigrees.

Materials and Methods

Maturity‐onset diabetes of the young candidate gene‐ or exome‐targeted capture sequencing was carried out in 76 probands from unrelated families fulfilling the clinical diagnostic criteria for MODY. MAF <0.01 in the GnomAD or ExAC database was used to filter significant variants. Sanger sequencing was then carried out to validate findings. Function prediction by SIFT, PolyPhen‐2 and PROVEAN or CADD was carried out in missense mutations.

Results

A total of 32 mutations in six genes were identified in 31 families, accounting for 40.79% of the potential MODY families. The MODY subtype detection rate was 18.42% for GCK, 15.79% for HNF1A, 2.63% for HNF4A, and 1.32% for KLF11, PAX4 and NEUROG3. Seven nonsense/frameshift mutations and four missense mutations with damaging prediction were newly identified novel mutations. The clinical features of MODY2, MODY3/1 and MODYX are similar to previous reports. Clinical phenotype of NEUROG3 p.Arg55Glufs*23 is characterized by hyperglycemia and mild intermittent abdominal pain.

Conclusions

This study adds to the emerging pattern of MODY epidemiology that the proportion of MODY explained by known pathogenic genes is higher than that previously reported, and found NEUROG3 as a new causative gene for MODY.

L-Arginine prevents cereblon-mediated ubiquitination of glucokinase and stimulates glucose-6-phosphate production in pancreatic β-cells

We sought to determine a mechanism by which L-arginine increases glucose-stimulated insulin secretion (GSIS) in β-cells by finding a protein with affinity to L-arginine using arginine-immobilized magnetic nanobeads technology. Glucokinase (GCK), the key regulator of GSIS and a disease-causing gene of maturity-onset diabetes of the young type 2 (MODY2), was found to bind L-arginine. L-Arginine stimulated production of glucose-6-phosphate (G6P) and induced insulin secretion. We analyzed glucokinase mutants and identified three glutamate residues that mediate binding to L-arginine. One MODY2 patient with GCK^E442* demonstrated lower C-peptide-to-glucose ratio after arginine administration. In β-cell line, GCK^E442* reduced L-arginine-induced insulin secretion compared with GCK^WT. In addition, we elucidated that the binding of arginine protects glucokinase from degradation by E3 ubiquitin ligase cereblon mediated ubiquitination. We conclude that L-arginine induces insulin secretion by increasing G6P production by glucokinase through direct stimulation and by prevention of degradation.

Using arginine-immobilized magnetic nanobeads, Cho et al. show that glucokinase, the key regulator of glucose-stimulated insulin secretion, binds L-arginine, which protects glucokinase from ubiquitination-mediated degradation while inducing insulin secretion. This study provides mechanistic insights into how L-arginine increases insulin production.

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.

Family history of diabetes in both parents is strongly associated with impaired residual β-cell function in Japanese type 2 diabetes patients

AIMS/INTRODUCTION

The objective of the present study was to clarify the association of the type and number of first-degree family history of diabetes (FHD) with the clinical characteristics, especially with residual β-cell function, in type 2 diabetes patients.

MATERIALS AND METHODS

A total of 1,131 type 2 diabetes patients were recruited and divided into four groups according to FHD information as follows: (i) patients without FHD (FHD-); (ii) those with at least one sibling who had diabetes without parental diabetes (FHD+); (iii) those with one parent (FHD++); or (iv) those with both parents (FHD+++) who had diabetes with or without a sibling with diabetes.

RESULTS

The percentages of the FHD-, FHD+, FHD++ and FHD+++ groups were 49.4%, 13.4%, 34.0% and 3.2%, respectively. Patients in the FHD++ and FHD+++ groups were significantly younger at the time of diabetes diagnosis (P < 0.001) than those in the FHD- and FHD+ groups, even after adjusting for confounding factors. In addition, the levels of insulin secretion were significantly lower in the patients in the FHD+, FHD++ and FHD+++ groups than those in the FHD- group (P < 0.05) after adjusting for confounding factors, and the patients in the FHD+++ group presented with the lowest levels of insulin secretion among the four groups.

CONCLUSIONS

Our results showed that in type 2 diabetes patients, the degree of the associations between FHD and clinical characteristics differs according to the number and the type of FHD. In particular, FHD in both parents is most strongly associated with impaired residual β-cell function.

Clinical manifestations of a sporadic maturity-onset diabetes of the young (MODY) 5 with a whole deletion of HNF1B based on 17q12 microdeletion

We report a sporadic case of maturity-onset diabetes of the young type 5 (MODY5) with a whole-gene deletion of the hepatocyte nuclear factor-1beta (HNF1B) gene. A 44-year-old Japanese man who had been diagnosed with early-onset non-autoimmune diabetes mellitus at the age of 23 was examined. He showed multi-systemic symptoms, including a solitary congenital kidney, pancreatic hypoplasia, pancreatic exocrine dysfunction, elevation of the serum levels of liver enzymes, hypomagnesemia, and hyperuricemia. These clinical characteristics, in spite of the absence of a family history of diabetes, prompted us to make the diagnosis of maturity-onset diabetes of the young 5 (MODY 5). One allele deletion of the entire HNF1B gene revealed by multiplex ligation-dependent probe amplification (MLPA) led us to the diagnoses of 17q12 microdeletion syndrome even though there were negative chromosomal analyses with array comparative genomic hybridization (CGH). 17q12 microdeletion syndrome, which is not rare especially in sporadic cases since 17q12 is a typical hot spot for chromosomal deletion, could have complicated the clinical heterogeneity of MODY5.

Maturity-onset diabetes of the young type 5 uncovered during pregnancy with a long-term diagnosis of type 1 diabetes

We report a case of missed diagnosis of maturity-onset diabetes of the young type 5 uncovered during pregnancy with a previous diagnosis of type 1 diabetes. Maturity-onset diabetes of the young type 5 cannot be excluded in early-onset diabetes with positive islet-related autoantibodies and type 1 diabetes-prone human leukocyte antigen subtypes. Abdominal ultrasound should be used in all patients with pre-gestational diabetes, and maturity-onset diabetes of the young type 5 should be considered when renal abnormality is presented.

KLF11 variant in a family clinically diagnosed with early childhood-onset type 1B diabetes

KLF11 is the causative gene for maturity-onset diabetes of the young 7 (MODY7). KLF11 regulates insulin gene expression through binding to the GC box in the promoter. To date, only two KLF11 mutations have been identified in three families with early-onset type 2 diabetes. Here, we report a novel KLF11 variant associated with early childhood-onset type 1B diabetes. The proband and his younger sister exhibited hyperglycemia at age 1 year, and their mother developed diabetes at age 4 years. These three individuals required insulin injection from the initial phase of the disease. Being negative for islet cell autoantibodies, they were diagnosed with type 1B diabetes. Mutation screening for 30 diabetes-associated genes identified a heterozygous KLF11 variant (p.His418Gln) in the proband and his sister. The variant was also detected in the affected mother, as well as in the allegedly unaffected maternal grandmother. In silico analyses indicated that this variant involves a highly conserved histidine residue in the first C₂ H₂ zinc finger domain which ligates a zinc ion. In vitro analyses showed that expression levels and intracellular localization of His418Gln-KLF11 were comparable to those of wildtype (WT)-KLF11. Luciferase assays demonstrated that while WT-KLF11 suppressed the activity of a 6 × GC box-containing reporter, His418Gln-KLF11 lacked the suppressive effect. Notably, His418Gln-KLF11 canceled the suppressive effect of co-transfected WT-KLF11. Such a dominant-negative effect was absent in the previously reported Ala347Ser-KLF11 variant. These results indicate that specific variants of KLF11 (MODY7) with a dominant-negative effect underlie early childhood-onset type 1B diabetes with incomplete penetrance. This study documents a novel monogenic mutation associated with diabetes in children.

Modeling Monogenic Diabetes using Human ESCs Reveals Developmental and Metabolic Deficiencies Caused by Mutations in HNF1A

Human monogenic diabetes, caused by mutations in genes involved in beta cell development and function, has been a challenge to study because multiple mouse models have not fully recapitulated the human disease. Here, we use genome edited human embryonic stem cells to understand the most common form of monogenic diabetes, MODY3, caused by mutations in the transcription factor HNF1A. We found that HNF1A is necessary to repress an alpha cell gene expression signature, maintain endocrine cell function, and regulate cellular metabolism. In addition, we identified the human-specific long non-coding RNA, LINKA, as an HNF1A target necessary for normal mitochondrial respiration. These findings provide a possible explanation for the species difference in disease phenotypes observed with HNF1A mutations and offer mechanistic insights into how the HNF1A gene may also influence type 2 diabetes.

Transcriptional profiling of the zebrafish proximal tubule

The hepatocyte nuclear factor-1β (Hnf1b) transcription factor is a key regulator of kidney tubule formation and is associated with a syndrome of renal cysts and early onset diabetes. To further our understanding of Hnf1b in the developing zebrafish kidney, we performed RNA sequencing analysis of proximal tubules from hnf1b-deficient larvae. This analysis revealed an enrichment of gene transcripts encoding transporters of the solute carrier (SLC) superfamily, including multiple members of slc2 and slc5 glucose transporters. An investigation of expression of slc2a1a, slc2a2, and slc5a2 as well as a poorly studied glucose/mannose transporter encoded by slc5a9 revealed that these genes undergo dynamic spatiotemporal changes during tubule formation and maturation. A comparative analysis of zebrafish SLC genes with those expressed in mouse proximal tubules showed a substantial overlap at the level of gene families, indicating a high degree of functional conservation between zebrafish and mammalian proximal tubules. Taken together, our findings are consistent with a role for Hnf1b as a critical determinant of proximal tubule transport function by acting upstream of a large number of SLC genes and validate the zebrafish as a physiologically relevant model of the mammalian proximal tubule.

Evaluation of a rare glucose-dependent insulinotropic polypeptide receptor variant in a patient with diabetes

AIMS

Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone that augments insulin secretion in pancreatic β-cells via its glucose-dependent insulinotropic polypeptide receptor (GIPR). Recent genome-wide association studies identified a single nucleotide variant (SNV) in the GIPR encoding gene (GIPR), rs1800437, that is associated with obesity and insulin resistance. In the present study, we tested whether GIPR variants contribute to obesity and disturb glucose homeostasis or diabetes in specific patient populations.

MATERIALS AND METHODS

Exon sequencing of GIPR was performed in 164 children with obesity and insulin resistance and in 80 children with paediatric-onset diabetes of unknown origin. The Study of Health in Pomerania (SHIP) cohort, comprising 8320 adults, was screened for the GIPR variant Arg217Leu. GIPR variants were expressed in COS-7 cells and cAMP production was measured upon stimulation with GIP. Cell surface expression was determined by ELISA. Protein homology modelling of the GIPR variants was performed to extract three-dimensional information of the receptor.

RESULTS

A heterozygous missense GIPR variant Arg217Leu (rs200485112) was identified in a patient of Asian ancestry. Functional characterization of Arg217Leu revealed reduced surface expression and signalling after GIP challenge. The homology model of the GIPR structure supports the observed functional relevance of Arg217Leu.

CONCLUSION

In vitro functional studies and protein homology modelling indicate a potential relevance of the GIPR variant Arg217Leu in receptor function. The heterozygous variant displayed partial co-segregation with diabetes. Based on these findings, we suggest that GIPR variants may play a role in disturbed glucose homeostasis and may be of clinical relevance in homozygous patients.

In silico and in vitro analyses of the pathological relevance of the R258H mutation of hepatocyte nuclear factor 4α identified in maturity-onset diabetes of the young type 1

Mutations of the hepatocyte nuclear factor 4α (HNF4α) gene give rise to maturity-onset diabetes of the young type 1. Although many such mutations have been identified in affected individuals, part of these mutations has been characterized with regard to their pathological relevance. We here identified a missense mutation (c.773G>A, p.R258H) of HNF4A in a mother and daughter with early-onset diabetes and impaired insulin secretion. In silico simulation and in vitro luciferase reporter analyses showed that the mutation impairs the stability of self-dimerization and the transactivation activity of HNF4α. Although arginine-258 does not appear to participate directly in dimerization, its mutation alters the electrostatic surface potential of the dimer interface. Our results thus suggest that this mutation impairs the function of HNF4α and thereby contributes to the pathogenesis of maturity-onset diabetes of the young type 1.

Body mass index and C-peptide are important for the promptly differential diagnosis of maturity-onset diabetes from familial type 2 diabetes in outpatient clinic

Type 2 diabetic patients are becoming younger and having a tendency to family aggregation, they are easily suspected as maturity-onset diabetes of young (MODY) in the outpatient clinic and send to genetic testing. 9 diabetic families were compared in our outpatient clinic who met the primary diagnosis criteria of MODY. Detailed clinical features and laboratory data including gene sequence were collected and analyzed. The patients met the primary clinical diagnostic criteria of MODY for genetic testing at the first look. However, members of families A1 to A3 had normal Body mass index (BMI) and a lower C-peptide level which indicated impaired pancreatic islet function. In contrast, the members with diabetes of families B1 to B6 had normal or increased C-peptide level which indicated insulin resistance and were overweight with BMI. Genetic testing showed that the mutations in HNF1A, INS, KCNJ11 and so on in families A were consistent with the diagnosis of MODY. No pathogenic mutation was found in the members of families B which were diagnosed with familial T2D. Before the clinical laboratory testing and the further gene test, BMI and the concentration of C-peptide are important for the promptly differential diagnosis of MODY from familial type 2 diabetes and medication instruction in the outpatient clinic which could help to alleviate the burden of genetic testing for them.