Effective treatment with oral sulfonylureas in patients with diabetes due to sulfonylurea receptor 1 (SUR1) mutations

Transient diabetes mellitus with ABCC8 variant successfully treated with sulfonylurea: Two case reports and review of literature

BACKGROUND

Transient neonatal diabetes mellitus (TNDM) is a rare form of diabetes mellitus that usually presents within the first 6 mo of life. Patients often enter remission within several months, although relapse can occur later in life. Mutations in the ABCC8 gene, which encodes the sulfonylurea receptor 1 of the ATP-sensitive potassium channel in pancreatic beta cells, are associated with TNDM and permanent neonatal diabetes. This study describes a novel de novo c.3880C>T heterozygous ABCC8 variant that causes TNDM and can be treated with sulf-onylurea therapy.

CASE SUMMARY

We retrospectively analyzed 2 Chinese patients with TNDM who were diagnosed, treated, or referred for follow-up between September 2017 and September 2023. The patients were tested for mutations using targeted next-generation sequencing. Patients with neonatal diabetes mellitus caused by a c.3880C>T heterozygous missense variant in the ABCC8 gene have not been reported before. Both children had an onset of post-infectious diabetic ketoacidosis, which is worth noting. At a follow-up visit after discontinuing insulin injection, oral glyburide was found to be effective with no adverse reactions.

CONCLUSION

Early genetic testing of neonatal diabetes mellitus aids in accurate diagnosis and treatment and helps avoid daily insulin injections that may cause pain.

The Elusive Nature of ABCC8-related Maturity-Onset Diabetes of the Young (ABCC8-MODY). A Review of the Literature and Case Discussion

PURPOSE OF REVIEW

Maturity-onset diabetes of the young (MODY) are monogenic forms of diabetes resulting from genetic defects, usually transmitted in an autosomal dominant fashion, leading to β-cell dysfunction. Due to the lack of homogeneous clinical features and univocal diagnostic criteria, MODY is often misdiagnosed as type 1 or type 2 diabetes, hence its diagnosis relies mostly on genetic testing. Fourteen subtypes of MODY have been described to date. Here, we review ABCC8-MODY pathophysiology, genetic and clinical features, and current therapeutic options.

RECENT FINDINGS

ABCC8-MODY is caused by mutations in the adenosine triphosphate (ATP)-binding cassette transporter subfamily C member 8 (ABCC8) gene, involved in the regulation of insulin secretion. The complexity of ABCC8-MODY genetic picture is mirrored by a variety of clinical manifestations, encompassing a wide spectrum of disease severity. Such inconsistency of genotype-phenotype correlation has not been fully understood. A correct diagnosis is crucial for the choice of adequate treatment and outcome improvement. By targeting the defective gene product, sulfonylureas are the preferred medications in ABCC8-MODY, although efficacy vary substantially. We illustrate three case reports in whom a diagnosis of ABCC8-MODY was suspected after the identification of novel ABCC8 variants that turned out to be of unknown significance. We discuss that careful interpretation of genetic testing is needed even on the background of a suggestive clinical context. We highlight the need for further research to unravel ABCC8-MODY disease mechanisms, as well as to clarify the pathogenicity of identified ABCC8 variants and their influence on clinical presentation and response to therapy.

Genetic perspectives on childhood monogenic diabetes: Diagnosis, management, and future directions

Monogenic diabetes is caused by one or even more genetic variations, which may be uncommon yet have a significant influence and cause diabetes at an early age. Monogenic diabetes affects 1 to 5% of children, and early detection and gene-tically focused treatment of neonatal diabetes and maturity-onset diabetes of the young can significantly improve long-term health and well-being. The etiology of monogenic diabetes in childhood is primarily attributed to genetic variations affecting the regulatory genes responsible for beta-cell activity. In rare instances, mutations leading to severe insulin resistance can also result in the development of diabetes. Individuals diagnosed with specific types of monogenic diabetes, which are commonly found, can transition from insulin therapy to sulfonylureas, provided they maintain consistent regulation of their blood glucose levels. Scientists have successfully devised materials and methodologies to distinguish individuals with type 1 or 2 diabetes from those more prone to monogenic diabetes. Genetic screening with appropriate findings and interpretations is essential to establish a prognosis and to guide the choice of therapies and management of these interrelated ailments. This review aims to design a comprehensive literature summarizing genetic insights into monogenetic diabetes in children and adolescents as well as summarizing their diagnosis and mana-gement.

Precision Medicine in Type 2 Diabetes Mellitus: Utility and Limitations

Type 2 diabetes mellitus (T2DM) is one of the most widespread diseases in Western countries, and its incidence is constantly increasing. Epidemiological studies have shown that in the next 20 years. The number of subjects affected by T2DM will double. In recent years, owing to the development and improvement in methods for studying the genome, several authors have evaluated the association between monogenic or polygenic genetic alterations and the development of metabolic diseases and complications. In addition, sedentary lifestyle and socio-economic and pandemic factors have a great impact on the habits of the population and have significantly contributed to the increase in the incidence of metabolic disorders, obesity, T2DM, metabolic syndrome, and liver steatosis. Moreover, patients with type 2 diabetes appear to respond to antihyperglycemic drugs. Only a minority of patients could be considered true non-responders. Thus, it appears clear that the main aim of precision medicine in T2DM is to identify patients who can benefit most from a specific drug class more than from the others. Precision medicine is a discipline that evaluates the applicability of genetic, lifestyle, and environmental factors to disease development. In particular, it evaluated whether these factors could affect the development of diseases and their complications, response to diet, lifestyle, and use of drugs. Thus, the objective is to find prevention models aimed at reducing the incidence of pathology and mortality and therapeutic personalized approaches, to obtain a greater probability of response and efficacy. This review aims to evaluate the applicability of precision medicine for T2DM, a healthcare burden in many countries.

A beneficial role of GLP-1 receptor agonist therapy in ABCC8-MODY (MODY 12)

Maturity-onset diabetes of the young (MODY) is an inherited form of diabetes resulting from a mutation in a single gene. ABCC8-MODY is caused by mutations in the ABCC8 gene, which encodes sulfonylurea receptor 1 (SUR1), a regulatory component of the ATP-sensitive potassium (KATP) channel found in beta cells. In ABCC8-MODY, mutations in the ABCC8 gene interfere with insulin secretion in response to glucose. Recent evidence suggests that therapy with GLP-1 receptor agonists (GLP-1 RAs) may be beneficial in ABCC8-MODY. This report presents a successful treatment of a 49-year-old woman diagnosed with ABCC8-MODY using the GLP-1 RA semaglutide. The patient, who had been previously receiving insulin therapy, experienced significant improvements in glycemic control and weight loss after transitioning to semaglutide. GLP-1 RAs potentially enhance insulin secretion in ABCC8-MODY by activating multiple signaling pathways involved in insulin secretion. The report highlights the potential of GLP-1 RA therapy as an alternative to sulfonylureas and insulin for individuals with ABCC8-MODY. GLP-1 RAs have previously demonstrated benefits in other forms of MODY. Understanding the molecular mechanisms through which GLP-1 RAs promote insulin secretion, including their effects on KATP channels and activation of PKA and Epac signaling, offers valuable insights into their therapeutic effects.

Management of Neonatal Diabetes due to a KCNJ11 Mutation with Automated Insulin Delivery System and Remote Patient Monitoring

Neonatal diabetes mellitus (NDM) is a monogenic form of diabetes. Management of hyperglycemia in neonates with subcutaneous insulin is challenging because of frequent feeding, variable quantity of milk intake with each feed, low insulin dose requirements, and high risk for hypoglycemia and associated complications in this population. We present a case of NDM in a proband initially presenting with focal seizures and diabetic ketoacidosis due to a pathologic mutation in the beta cell potassium ATP channel gene KCNJ11 c.679G > A (p.E227K). We describe the use of continuous glucose monitoring (CGM), insulin pump, automated insulin delivery system, and remote patient monitoring technologies to facilitate rapid and safe outpatient cross-titration from insulin to oral sulfonylurea. Our case highlights the safety and efficacy of these technologies for infants with diabetes, including improvements in glycemia, quality of life, and cost-effectiveness by shortening hospital stay.

From target discovery to clinical drug development with human genetics

The substantial investments in human genetics and genomics made over the past three decades were anticipated to result in many innovative therapies. Here we investigate the extent to which these expectations have been met, excluding cancer treatments. In our search, we identified 40 germline genetic observations that led directly to new targets and subsequently to novel approved therapies for 36 rare and 4 common conditions. The median time between genetic target discovery and drug approval was 25 years. Most of the genetically driven therapies for rare diseases compensate for disease-causing loss-of-function mutations. The therapies approved for common conditions are all inhibitors designed to pharmacologically mimic the natural, disease-protective effects of rare loss-of-function variants. Large biobank-based genetic studies have the power to identify and validate a large number of new drug targets. Genetics can also assist in the clinical development phase of drugs-for example, by selecting individuals who are most likely to respond to investigational therapies. This approach to drug development requires investments into large, diverse cohorts of deeply phenotyped individuals with appropriate consent for genetically assisted trials. A robust framework that facilitates responsible, sustainable benefit sharing will be required to capture the full potential of human genetics and genomics and bring effective and safe innovative therapies to patients quickly.

From glucose sensing to exocytosis: takes from maturity onset diabetes of the young

Monogenic diabetes gave us simplified models of complex molecular processes occurring within β-cells, which allowed to explore the roles of numerous proteins from single protein perspective. Constellation of characteristic phenotypic features and wide application of genetic sequencing techniques to clinical practice, made the major form of monogenic diabetes - the Maturity Onset Diabetes of the Young to be distinguishable from type 1, type 2 as well as neonatal diabetes mellitus and understanding underlying molecular events for each type of MODY contributed to the advancements of antidiabetic therapy and stem cell research tremendously. The functional analysis of MODY-causing proteins in diabetes development, not only provided better care for patients suffering from diabetes, but also enriched our comprehension regarding the universal cellular processes including transcriptional and translational regulation, behavior of ion channels and transporters, cargo trafficking, exocytosis. In this review, we will overview structure and function of MODY-causing proteins, alterations in a particular protein arising from the deleterious mutations to the corresponding gene and their consequences, and translation of this knowledge into new treatment strategies.

Case report: Better late than never, but sooner is better: switch from CSII to sulfonylureas in two patients with neonatal diabetes due to KCNJ11 variants

Neonatal diabetes mellitus (NDM) is a rare genetic disease characterized by severe hyperglycemia requiring insulin therapy with onset mostly within the first 6 months and rarely between 6-12 months of age. The disease can be classified into transient (TNDM) or permanent neonatal diabetes mellitus (PNDM), or it can be a component of a syndrome. The most frequent genetic causes are abnormalities of the 6q24 chromosomal region and mutations of the ABCC8 or KCNJ11 genes coding for the pancreatic beta cell's potassium channel (KATP). After the acute phase, patients with ABCC8 or KCNJ11 mutations treated with insulin therapy can switch to hypoglycemic sulfonylureas (SU). These drugs close the KATP channel binding the SUR1 subunit of the potassium channel and restoring insulin secretion after a meal. The timing of this switch can be different and could affect long-term complications. We describe the different management and clinical outcome over the time of two male patients with NDM due to KCNJ11 pathogenetic variants. In both cases, continuous subcutaneous insulin infusion pumps (CSII) were used to switch therapy from insulin to SU, but at different times after the onset. The two patients kept adequate metabolic control after the introduction of glibenclamide; during the treatment, insulin secretion was evaluated with c-peptide, fructosamine, and glycated hemoglobin (HbA1c), which were within the normal range. In neonates or infants with diabetes mellitus, genetic testing is an indispensable diagnostic tool and KCNJ11 variants should be considered. A trial of oral glibenclamide must be considered, switching from insulin, the first line of NDM treatment. This therapy can improve neurological and neuropsychological outcomes, in particular in the case of earlier treatment initiation. A new modified protocol with glibenclamide administered several times daily according to continuous glucose monitoring profile indications, was used. Patients treated with glibenclamide maintain good metabolic control and prevent hypoglycemia, neurological damage, and apoptosis of beta cells during long-term administration.

A Systematic Review of the use of Precision Diagnostics in Monogenic Diabetes

Monogenic forms of diabetes present opportunities for precision medicine as identification of the underlying genetic cause has implications for treatment and prognosis. However, genetic testing remains inconsistent across countries and health providers, often resulting in both missed diagnosis and misclassification of diabetes type. One of the barriers to deploying genetic testing is uncertainty over whom to test as the clinical features for monogenic diabetes overlap with those for both type 1 and type 2 diabetes. In this review, we perform a systematic evaluation of the evidence for the clinical and biochemical criteria used to guide selection of individuals with diabetes for genetic testing and review the evidence for the optimal methods for variant detection in genes involved in monogenic diabetes. In parallel we revisit the current clinical guidelines for genetic testing for monogenic diabetes and provide expert opinion on the interpretation and reporting of genetic tests. We provide a series of recommendations for the field informed by our systematic review, synthesizing evidence, and expert opinion. Finally, we identify major challenges for the field and highlight areas for future research and investment to support wider implementation of precision diagnostics for monogenic diabetes.

ABCC8-related maturity-onset diabetes of the young: switching from insulin to sulphonylurea therapy: how long do we need for a good metabolic control?

OBJECTIVES

Activating variants of the ABCC8 gene cause neonatal diabetes or maturity-onset diabetes of the young (MODY). We report three cases of MODY type 12 caused by variants in the ABCC8 encoding sulphonylurea receptor 1, and the experience of switching from insulin therapy to sulphonylurea therapy.

CASE PRESENTATIONS

We describe a 12.5-year-old girl with permanent neonatal diabetes mellitus, and two diabetes mellitus cases with variants in the ABCC8 gene. Two of these cases were successfully switched from subcutaneous insulin to oral glibenclamide, with a marked improvement in glycemic control. In permanent neonatal diabetes case, glibenclamide dose was progressively increased to achieve a full dose (2 mg/kg/day) in 9 days. Nine months after starting oral sulphonylurea therapy, her blood glucose control dramatically improved and insulin therapy was discontinued.

CONCLUSIONS

We conclude that patients with ABCC8 gene variants can successfully switch from insulin to sulphonylureas.

The Role of ABC Transporters in Skin Cells Exposed to UV Radiation

ABC transporters are expressed in skin cells to protect them against harmful xenobiotics. Moreover, these transmembrane proteins have a number of additional functions that ensure skin homeostasis. This review summarizes the current knowledge about the role of specific ABC proteins in the skin, including multi-drug resistance transporters (MDR1/3), the transporter associated with antigen processing 1/2 (TAP1/2), the cystic fibrosis transmembrane conductance regulator (CFTR), sulfonylurea receptors (SUR1/2), and the breast cancer resistance protein (BCRP). Additionally, the effect of UV radiation on ABC transporters is shown. The exposure of skin cells to UV radiation often leads to increased activity of ABC transporters-as has been observed in the case of MDRs, TAPs, CFTR, and BCRP. A different effect of oxidative stress has been observed in the case of mitochondrial SURs. However, the limited data in the literature-as indicated in this article-highlights the limited number of experimental studies dealing with the role of ABC transporters in the physiology and pathophysiology of skin cells and the skin as a whole. At the same time, the importance of such knowledge in relation to the possibility of daily exposure to UV radiation and xenobiotics, used for both skin care and the treatment of its diseases, is emphasized.

A case report of maturity-onset diabetes of the young (MODY12) in a Chinese Han patient with a novel ABCC8 gene mutation

RATIONALE

Maturity onset diabetes of the young (MODY) is the most common type of monogenic diabetes, characterized by autosomal dominant inheritance, the age of onset is often <25 years old, and the clinical manifestations are atypical. MODY12 is caused by a rare missense mutation of adenosine triphosphate (ATP)-binding cassette transporter subfamily C member 8 (ABCC8) gene and more than 50 ABCC8 variants were associated with MODY12.

PATIENT CONCERNS

The patient was a 30-year-old Chinese Han man. He was overweight with a poor control of blood glucose.

DIAGNOSES

The patient was diagnosed with MODY12.

INTERVENTIONS

The patient was given glimepiride (4 mg/d) with diet and exercise therapy to reduce blood glucose and weight.

OUTCOMES

The level of fasting blood glucose and C-peptide was improved after 1 year treatment as well as body weight.

LESSONS

A Chinese Han adult with a heterozygous missense mutation c.3976G > A (p.Glu1326Lys) was diagnosed with MODY12, which was the new pathogenic mutation for the disease. This report expands the spectrum of variants causing MODY12 and reduces misdiagnosis.

Clinical presentation and long-term outcome of patients with KCNJ11/ABCC8 variants: Neonatal diabetes or MODY in the DPV registry from Germany and Austria

OBJECTIVE

To describe clinical presentation/longterm outcomes of patients with ABCC8/KCNJ11 variants in a large cohort of patients with diabetes.

RESEARCH DESIGN AND METHODS

We analyzed patients in the Diabetes Prospective Follow-up (DPV) registry with diabetes and pathogenic variants in the ABCC8/KCNJ11 genes. For patients with available data at three specific time-points-classification as K⁺ -channel variant, 2-year follow-up and most recent visit-the longitudinal course was evaluated in addition to the cross-sectional examination.

RESULTS

We identified 93 cases with ABCC8 (n = 54)/KCNJ11 (n = 39) variants, 63 of them with neonatal diabetes. For 22 patients, follow-up data were available. Of these, 19 were treated with insulin at diagnosis, and the majority of patients was switched to sulfonylurea thereafter. However, insulin was still administered in six patients at the most recent visit. Patients were in good metabolic control with a median (IQR) A1c level of 6.0% (5.5-6.7), that is, 42.1 (36.6-49.7) mmol/mol after 2 years and 6.7% (6.0-8.0), that is, 49.7 (42.1-63.9) mmol/mol at the most recent visit. Five patients were temporarily without medication for a median (IQR) time of 4.0 (3.5-4.4) years, while two other patients continue to be off medication at the last follow-up.

CONCLUSIONS

ABCC8/KCNJ11 variants should be suspected in children diagnosed with diabetes below the age of 6 months, as a high percentage can be switched from insulin to oral antidiabetic drugs. Thirty patients with diabetes due to pathogenic variants of ABCC8 or KCNJ11 were diagnosed beyond the neonatal period. Patients maintain good metabolic control even after a diabetes duration of up to 11 years.

The dynamic interplay of PIP2 and ATP in the regulation of the KATP channel

ATP-sensitive potassium (KATP ) channels couple the intracellular ATP concentration to insulin secretion. KATP channel activity is inhibited by ATP binding to the Kir6.2 tetramer and activated by phosphatidylinositol 4,5-bisphosphate (PIP2 ). Here, we use molecular dynamics simulation, electrophysiology and fluorescence spectroscopy to show that ATP and PIP2 occupy different binding pockets that share a single amino acid residue, K39. When both ligands are present, simulations suggest that K39 shows a greater preference to co-ordinate with PIP2 than with ATP. They also predict that a neonatal diabetes mutation at K39 (K39R) increases the number of hydrogen bonds formed between K39 and PIP2 , potentially accounting for the reduced ATP inhibition observed in electrophysiological experiments. Our work suggests that PIP2 and ATP interact allosterically to regulate KATP channel activity. KEY POINTS: The KATP channel is activated by the binding of phosphatidylinositol 4,5-bisphosphate (PIP2 ) lipids and inactivated by the binding of ATP. K39 has the potential to bind to both PIP2 and ATP. A mutation to this residue (K39R) results in neonatal diabetes. This study uses patch-clamp fluorometry, electrophysiology and molecular dynamics simulation. We show that PIP2 competes with ATP for K39, and this reduces channel inhibition by ATP. We show that K39R increases channel affinity to PIP2 by increasing the number of hydrogen bonds with PIP2 , when compared with the wild-type K39. This therefore decreases KATP channel inhibition by ATP.

Clinical characteristics, growth patterns, and long-term diabetes complications of 24 patients with neonatal diabetes mellitus: A single center experience

OBJECTIVES

Neonatal diabetes mellitus (NDM) is a rare form of monogenic diabetes, diagnosed before age 6 months. We aimed to describe the clinical characteristics, molecular genetics, and long-term follow-up of NDM patients from a single pediatric endocrine center in Israel.

METHODS

Retrospective study (1975-2020) of all patients diagnosed with diabetes before 6 months of age, who tested negative for pancreatic autoantibodies. Medical records were reviewed for demographic, familial and medical history, and clinical and biochemical features; a genetic analysis was performed.

RESULTS

Of 24 patients, nine had transient neonatal diabetes (TNDM) and 15 permanent neonatal diabetes (PNDM), of whom five had rare syndromic causes. Genetic etiology was revealed in 87.5% of the NDM cohort, and the most common causes were ABCC8 mutations in TNDM and KCNJ11 and insulin gene mutations in PNDM. The switch from insulin to off-label sulfonylurea therapy was successful for 5/9 (56%) of the qualifying candidates. Severe hypoglycemia and diabetic ketoacidosis developed in 2 (8%) patients, and chronic diabetes complications in 5 (21%) patients with more than 10 years NDM. At last follow-up, weight and height of all but two syndromic PNDM patients were normal. The median height-SDS of the TNDM subgroup was significantly taller and the mean weight-SDS significantly heavier than those of the PNDM subgroup (-0.52 (-0.67, -0.09) vs. -0.9 (-1.42, -0.3) (p = 0.035) and 0.22 ± 0.69 vs. -0.89 ± 1.21 (p = 0.02), respectively). PNDM patients showed no incremental change in mean weight SDS over the time.

CONCLUSION

The Israeli NDM cohort has clinical and genetic characteristics comparable with other populations. Patients with TNDM were taller and heavier than those diagnosed with PNDM, although both show rapid catch-up growth and reached normal growth parameters. Chronic diabetes complications developed in patients with long-standing NDM.

Role of Actionable Genes in Pursuing a True Approach of Precision Medicine in Monogenic Diabetes

Monogenic diabetes is a genetic disorder caused by one or more variations in a single gene. It encompasses a broad spectrum of heterogeneous conditions, including neonatal diabetes, maturity onset diabetes of the young (MODY) and syndromic diabetes, affecting 1-5% of patients with diabetes. Some of these variants are harbored by genes whose altered function can be tackled by specific actions ("actionable genes"). In suspected patients, molecular diagnosis allows the implementation of effective approaches of precision medicine so as to allow individual interventions aimed to prevent, mitigate or delay clinical outcomes. This review will almost exclusively concentrate on the clinical strategy that can be specifically pursued in carriers of mutations in "actionable genes", including ABCC8, KCNJ11, GCK, HNF1A, HNF4A, HNF1B, PPARG, GATA4 and GATA6. For each of them we will provide a short background on what is known about gene function and dysfunction. Then, we will discuss how the identification of their mutations in individuals with this form of diabetes, can be used in daily clinical practice to implement specific monitoring and treatments. We hope this article will help clinical diabetologists carefully consider who of their patients deserves timely genetic testing for monogenic diabetes.

Experience with enteral sulfonylurea monotherapy for extremely low birth weight infants with hyperglycemia

Limited data are available on the effects of enteral sulfonylurea (SU) monotherapy in extremely low birth weight infants (ELBWIs) with hyperglycemia. Therefore, we report our experience with enteral SU monotherapy for hyperglycemic ELBWIs. We retrospectively evaluated 11 hyperglycemic ELBWIs (seven male infants, median gestational age = 24.9 wk) who received SU between January 2016 and December 2019. Blood glucose (BG) levels were monitored before and after SU initiation and evaluated for the occurrence of adverse effects. We administered SU at a median of 15 d (interquartile range [IQR]: 12–20 d) after birth, with the median maximum dose of 0.2 mg/kg/d (IQR: 0.125–0.3 mg/kg/d). Hyperglycemia improved in all patients, and the target BG levels were achieved without severe side effects at a median of 6 d (IQR: 4–8.5 d) after initiation of treatment. The incidence of hypoglycemia during SU treatment was observed in 18 events per 1000 patient hours; however, the patients were asymptomatic. Based on these results, enteral SU monotherapy may be considered as an option for hyperglycemic ELBWIs.

Novel perspectives of super-high dose sulfonylurea and high-dose oral prednisolone in an infant with DEND syndrome due to V64M heterozygote KCNJ11 mutation

AIMS

To report a novel mutation associated with developmental delay, epilepsy, and neonatal diabetes-DEND Syndrome, responsive to a novel management combination.

METHODS

We describe the investigation, treatment, and genetic diagnosis of a newborn diagnosed with DEND syndrome.

RESULTS

The patient was found to be de-novo heterozygous for pathogenic KCNJ11 missense variant: c.190G > A, p. (Val64Met), associated with DEND syndrome, responsive to a combination of super high doses of sulfonylurea (SU) and oral high-dose steroids. A single case was reported so far due to this mutation, presenting with severe DEND syndrome, treated by insulin only. His phenotypic description and management during 18 months, demonstrates this mutation is responsive to super-high doses of SU combined with high dose 6 weeks steroids protocol.

CONCLUSIONS

We have identified a heterozygous missense mutation as the etiology for severe DEND syndrome in a one-day old neonate, presenting with asymptomatic hyperglycemia, responsive to a novel management combination.

Genetic and clinical heterogeneity of permanent neonatal diabetes mellitus: a single tertiary centre experience

AIMS

Neonatal diabetes mellitus (NDM) is a rare disease where diabetes presents during the first six months of life. There are two types of this disorder: permanent neonatal diabetes (PNDM) and transient neonatal diabetes mellitus (TNDM). PNDM occurs due to mutations in genes involved in either beta-cell survival, insulin regulation, and secretion. This study aims to define the genetic aetiology and clinical phenotypes of PNDM in a large Egyptian cohort from a single centre.

METHODS

Patients with PNDM who were diagnosed, treated, or referred for follow-up between January 2002 and January 2021 were identified and clinically phenotyped. All patients were tested for mutations in EIF2AK3, KCNJ11, ABCC8, INS, FOXP3, GATA4, GATA6, GCK, GLIS3, HNF1B, IER3IP1, PDX1, PTF1A, NEUROD1, NEUROG3, NKX2-2, RFX6, SLC2A2, SLC19A2, STAT3, WFS1, ZFP57 using targeted next-generation sequencing (NGS) panel. INSR gene mutation was tested in one patient who showed clinical features of insulin resistance.

RESULTS

Twenty-nine patients from twenty-six families were diagnosed with PNDM. Pathogenic variants were identified in 17/29 patients (59%). EIF2AK3, INS, and K_ATP channel mutations were the commonest causes with frequency of 17%, 17%, and 14%, respectively. Patients with ABBC8 and KCNJ11 mutations were successfully shifted to sulfonylureas (SU). Paired data of glycosylated haemoglobin before and after SU transfer showed improved glycaemic control; 9.6% versus 7.1%, P = 0.041.

CONCLUSIONS

PNDM is a heterogenous disease with variable genotypes and clinical phenotypes among Egyptian patients. EIF2AK3, INS, ABCC8, and KCNJ11 mutations were the commonest causes of PNDM in the study cohort. All patients with K_ATP channel mutations were effectively treated with glyburide, reflecting the fact that genetic testing for patients with NDM is not only important for diagnosis but also for treatment plan and prognosis.

ABCC8 variants in MODY12: Review of the literature and report of a case with severe complications

More than 1000 variants of the ATP-binding cassette transporter subfamily C member 8 (ABCC8) gene have been reported in neonatal diabetes mellitus. Up to now only 55 ABCC8 variants were associated with Maturity-Onset Diabetes of the Young 12 (MODY12). We present a c.3544C>T p.(Arg1182Trp) ABCC8 variant in a 35-year-old women who had pronounced microvascular diabetic complications and a charcot arthropathy necessitating a lower limb amputation. The unusual severity of the disease course prompted us to perform a systematic review of all genetic variants in MODY12. The present mutation has mostly been associated with neonatal diabetes and in only three papers reporting a MODY12. The 55 MODY12 variants show a large clinical heterogeneity, even in relatives with the same mutation, ranging from mild impaired glucose tolerance to severe insulin-dependent diabetes mellitus. HbA1c at diagnosis ranged from 5% to 14% and age at diagnosis ranged from 2 to 53 years. However, several case reports lack documentation of diabetic complications. Hence, more detailed reports remain necessary to improve insight in MODY12 pathophysiology and outcome. In this article current data regarding therapeutic management are provided, and key points to consider for the individual patient affected by MODY12 are presented.

Monogenic diabetes mellitus and clinical implications of genetic diagnosis

Monogenic diabetes mellitus, which is diabetes caused by a defect in a single gene that is associated with β cell function or insulin action, accounts for 1% to 6% of all pediatric diabetes cases. Accurate diagnosis is important, as the effective treatment differs according to genetic etiology in some types of monogenic diabetes: high-dose sulfonylurea treatment in neonatal diabetes caused by activating mutations in KCNJ11 or ABCC8; low-dose sulfonylurea treatment in HNF1A/HNF4A-diabetes; and no treatment in GCK diabetes. Monogenic diabetes should be suspected by clinicians for certain combinations of clinical features and laboratory results, and approximately 80% of monogenic diabetes cases are misdiagnosed as type 1 diabetes or type 2 diabetes. Here, we outline the types of monogenic diabetes and the clinical implications of genetic diagnosis.

Identification of GCK-maturity-onset diabetes of the young in cases of neonatal hyperglycemia: A case series and review of clinical features

Heterozygous mutations in GCK result in a persistent, mildly raised glucose from birth, but it is usually diagnosed in adulthood as maturity-onset diabetes of the young (MODY), where hyperglycemia is often an incidental finding. The hyperglycemia of GCK-MODY is benign and does not require treatment, but is important to be aware of, particularly in females where it has implications for managing pregnancy. We present three cases of neonatal hyperglycemia resulting from a heterozygous mutation in GCK, illustrating its clinical presentation and evolution in early life. In summary, as with adults, neonatal hyperglycemia is an incidental finding, does not require treatment and has no adverse consequences for health. Neonates and their parents should be referred for genetic testing to confirm the diagnosis, avoid a label of diabetes and enable pregnancy counseling for females found to be affected.

A Comprehensive Analysis of Hungarian MODY Patients-Part I: Gene Panel Sequencing Reveals Pathogenic Mutations in HNF1A, HNF1B, HNF4A, ABCC8 and INS Genes

Maturity-onset diabetes of the young (MODY) has about a dozen known causal genes to date, the most common ones being HNF1A, HNF4A, HNF1B and GCK. The phenotype of this clinically and genetically heterogeneous form of diabetes depends on the gene in which the patient has the mutation. We have tested 450 Hungarian index patients with suspected MODY diagnosis with Sanger sequencing and next-generation sequencing and found a roughly 30% positivity rate. More than 70% of disease-causing mutations were found in the GCK gene, about 20% in the HNF1A gene and less than 10% in other MODY-causing genes. We found 8 pathogenic and 9 likely pathogenic mutations in the HNF1A gene in a total of 48 patients and family members. In the case of HNF1A-MODY, the recommended first-line treatment is low dose sulfonylurea but according to our data, the majority of our patients had been on unnecessary insulin therapy at the time of requesting their genetic testing. Our data highlights the importance of genetic testing in the diagnosis of MODY and the establishment of the MODY subtype in order to choose the most appropriate treatment.

Genetic variants of ABCC8 and phenotypic features in Chinese early onset diabetes

BACKGROUND

ABCC8 variants cause neonatal diabetes, maturity onset diabetes of the young (MODY), and hyperinsulinemic hypoglycemia because of activating or inactivating variants. In this study we used targeted exon sequencing to investigate genetic variants of ABCC8 and phenotypic features in Chinese patients with early onset diabetes (EOD).

METHODS

A cross-sectional study of 543 Chinese patients with EOD was recruited and the exons of them were conducted targeted sequencing. The pathogenicity of ABCC8 variants was defined according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology guideline. The phenotypes of patients owing to ABCC8 variants (ABCC8-MODY) were characterized.

RESULTS

Among the 543 participants, eight (1.5%) patients with ABCC8-MODY were identified. They harbored eight missense ABCC8 variants (p.R306C, p.E1326K, and p.R1379H, previously reported; p.R298C, p.F1176C, p.R1221W, p.K1358R, and p.I1404V) classified as likely pathogenic. Two family members with ABCC8-MODY were also confirmed. The average diagnosed age of the 10 patients was 26.8 ± 12.9 years. The majority of them had unsatisfactory glucose control, 80% of them had diabetic kidney disease, and neurological features were not observed.

CONCLUSION

Using targeted exon sequencing followed by pathogenicity analysis, we could be able to make genetic diagnoses for eight (1.5%) patients with ABCC8-MODY. The phenotype was variable with higher risk of diabetic microvascular complications. Genetic diagnosis is conducive for facilitating the personalized treatment of ABCC8-MODY.

Treatable inherited metabolic disorders causing intellectual disability: 2021 review and digital app

BACKGROUND

The Treatable ID App was created in 2012 as digital tool to improve early recognition and intervention for treatable inherited metabolic disorders (IMDs) presenting with global developmental delay and intellectual disability (collectively 'treatable IDs'). Our aim is to update the 2012 review on treatable IDs and App to capture the advances made in the identification of new IMDs along with increased pathophysiological insights catalyzing therapeutic development and implementation.

METHODS

Two independent reviewers queried PubMed, OMIM and Orphanet databases to reassess all previously included disorders and therapies and to identify all reports on Treatable IDs published between 2012 and 2021. These were included if listed in the International Classification of IMDs (ICIMD) and presenting with ID as a major feature, and if published evidence for a therapeutic intervention improving ID primary and/or secondary outcomes is available. Data on clinical symptoms, diagnostic testing, treatment strategies, effects on outcomes, and evidence levels were extracted and evaluated by the reviewers and external experts. The generated knowledge was translated into a diagnostic algorithm and updated version of the App with novel features.

RESULTS

Our review identified 116 treatable IDs (139 genes), of which 44 newly identified, belonging to 17 ICIMD categories. The most frequent therapeutic interventions were nutritional, pharmacological and vitamin and trace element supplementation. Evidence level varied from 1 to 3 (trials, cohort studies, case-control studies) for 19% and 4-5 (case-report, expert opinion) for 81% of treatments. Reported effects included improvement of clinical deterioration in 62%, neurological manifestations in 47% and development in 37%.

CONCLUSION

The number of treatable IDs identified by our literature review increased by more than one-third in eight years. Although there has been much attention to gene-based and enzyme replacement therapy, the majority of effective treatments are nutritional, which are relatively affordable, widely available and (often) surprisingly effective. We present a diagnostic algorithm (adjustable to local resources and expertise) and the updated App to facilitate a swift and accurate workup, prioritizing treatable IDs. Our digital tool is freely available as Native and Web App (www.treatable-id.org) with several novel features. Our Treatable ID endeavor contributes to the Treatabolome and International Rare Diseases Research Consortium goals, enabling clinicians to deliver rapid evidence-based interventions to our rare disease patients.

Genetic Spectrum of Neonatal Diabetes

Neonatal diabetes (ND) appears during the first months of life and is caused by a single gene mutation. It is heterogenous and very different compared to other forms of multi-factorial or polygenic diabetes. Clinically, this form is extremely severe, however, early genetic diagnosis is pivotal for successful therapy. A large palette of genes is demonstrated to be a cause of ND, however, the mechanisms of permanent hyperglycemia are different. This review will give an overview of more frequent genetic mutations causing ND, including the function of the mutated genes and the specific therapy for certain sub-forms.

Phenotype of a transient neonatal diabetes point mutation (SUR1-R1183W) in mice

Background: The K ATP channel plays a key role in glucose homeostasis by coupling metabolically generated changes in ATP to insulin secretion from pancreatic beta-cells.  Gain-of-function mutations in either the pore-forming (Kir6.2) or regulatory (SUR1) subunit of this channel are a common cause of transient neonatal diabetes mellitus (TNDM), in which diabetes presents shortly after birth but remits within the first few years of life, only to return in later life. The reasons behind this time dependence are unclear. Methods: In an attempt to understand the mechanism behind diabetes remission and relapse, we generated mice expressing the common TNDM mutation SUR1-R1183W. We employed Cre/LoxP technology for both inducible and constitutive expression of SUR1-R1183W specifically in mouse beta-cells, followed by investigation of their phenotype using glucose tolerance tests and insulin secretion from isolated islets.  Results: We found that the R1183W mutation impaired inhibition of K ATP channels by ATP when heterologously expressed in human embryonic kidney cells. However, neither induced nor constitutive expression of SUR1-R1183W in mice resulted in changes in blood glucose homeostasis, compared to littermate controls. When challenged with a high fat diet, female mice expressing SUR1-R1183W showed increased weight gain, elevated blood glucose and impaired glycaemic control, but glucose-stimulated insulin secretion from pancreatic islets appeared unchanged. Conclusions: The mouse model of TNDM did not recapitulate the human phenotype. We discuss multiple potential reasons why this might be the case. Based on our findings, we recommend future TNDM mouse models employing a gain-of-function SUR1 mutation should be created using the minimally invasive CRISPR/Cas technology, which avoids many potential pitfalls associated with the Cre/LoxP system.

Precision Medicine: A New Paradigm in Therapeutics

A key goal of clinical care is to treat patients as individuals and to approach therapeutics in such a way that it has optimal efficacy and minimal toxicity. With swift technological advances, such as genomic sequencing and molecular targeted drug exploitation, the concept of precision medicine has been robustly promoted in recent years. Precision medicine endeavors to demarcate diseases using multiple data sources from genomics to digital health metrics in order to facilitate an individualized yet "evidence-based" decision regarding diagnostic and therapeutic approaches. In this way, therapeutics can be centered toward patients based on their molecular presentation rather than grouping them into broad categories with a "one size fits all" approach. This review article is aimed to provide a broad overview of the advent and emergence of precision medicine in view of its current implications.

Monogenic diabetes: a gateway to precision medicine in diabetes

Monogenic diabetes refers to diabetes mellitus (DM) caused by a mutation in a single gene and accounts for approximately 1%-5% of diabetes. Correct diagnosis is clinically critical for certain types of monogenic diabetes, since the appropriate treatment is determined by the etiology of the disease (e.g., oral sulfonylurea treatment of HNF1A/HNF4A-diabetes vs. insulin injections in type 1 diabetes). However, achieving a correct diagnosis requires genetic testing, and the overlapping of the clinical features of monogenic diabetes with those of type 1 and type 2 diabetes has frequently led to misdiagnosis. Improvements in sequencing technology are increasing opportunities to diagnose monogenic diabetes, but challenges remain. In this Review, we describe the types of monogenic diabetes, including common and uncommon types of maturity-onset diabetes of the young, multiple causes of neonatal DM, and syndromic diabetes such as Wolfram syndrome and lipodystrophy. We also review methods of prioritizing patients undergoing genetic testing, and highlight existing challenges facing sequence data interpretation that can be addressed by forming collaborations of expertise and by pooling cases.

Molecular Genetics, Clinical Characteristics, and Treatment Outcomes of KATP-Channel Neonatal Diabetes Mellitus in Vietnam National Children's Hospital

BACKGROUND

Neonatal diabetes mellitus (NDM) is defined as insulin-requiring persistent hyperglycemia occurring within the first 6 months of life, which can result from mutations in at least 25 different genes. Activating heterozygous mutations in genes encoding either of the subunits of the ATP-sensitive K⁺ channel (K_ATP channel; KCNJ11 or ABCC8) of the pancreatic beta cell are the most common cause of permanent NDM and the second most common cause of transient NDM. Patients with NDM caused by K_ATP channel mutations are sensitive to sulfonylurea (SU) treatment; therefore, their clinical management can be improved by replacing insulin with oral agents.

PATIENTS AND METHODS

Seventy patients were diagnosed with NDM between May 2008 and May 2021 at Vietnam National Children's Hospital, and molecular genetic testing for all genes known to cause NDM was performed at the Exeter Genomic Laboratory, UK. Patients with ABCC8 or KCNJ11 mutations were transferred from insulin to oral SU. Clinical characteristics, molecular genetics, and annual data relating to glycemic control, SU dose, severe hypoglycemia, and side effects were collected. The main outcomes of interest were SU dose, SU failure (defined as permanent reintroduction of daily insulin), and glycemic control (HbA1c).

RESULTS

Fifty-four of 70 patients (77%) with NDM harbored a genetic mutation and of these; 27 (50%) had activating heterozygous mutations in ABCC8 or KCNJ11. A total of 21 pathogenic mutations were identified in the 27 patients, including 13 mutations in ABCC8 and 8 mutations in KCNJ11. Overall, 51% had low birth weight (below 3rd percentile), 23 (85%) were diagnosed before 3 months of age, and 23 (85%) presented with diabetic ketoacidosis. At diagnosis, clinical and biochemical findings (mean ± SD) were pH 7.16 ± 0.16; HCO3- , 7.9 ± 7.4 mmol/L; BE, -17.9 ± 9.1 mmol/L; HbA1C, 7.98% ± 2.93%; blood glucose, 36.2 ± 12.3 mmol/L; and C-peptide median, 0.09 (range, 0-1.61 nmol/l). Twenty-six patients were successfully transferred from insulin to SU therapy. In the remaining case, remission of diabetes occurred prior to transfer. Glycemic control on SU treatment was better than on insulin treatment: HbA1c and blood glucose level decreased from 7.58% ± 4.63% and 19.04 ± 14.09 mmol/L when treated with insulin to 5.8 ± 0.94% and 6.87 ± 3.46 mmol/L when treated with SU, respectively.

CONCLUSIONS

This is the first case series of NDM patients with ABCC8/KCNJ11 mutations reported in Vietnam. SU is safe in the short term for these patients and more effective than insulin therapy, consistent with all studies to date. This is relevant for populations where access to and cost of insulin are problematic, reinforcing the importance of genetic testing for NDM.

Long-term Follow-up of Glycemic and Neurological Outcomes in an International Series of Patients With Sulfonylurea-Treated ABCC8 Permanent Neonatal Diabetes

OBJECTIVE

ABCC8 mutations cause neonatal diabetes mellitus that can be transient (TNDM) or, less commonly, permanent (PNDM); ∼90% of individuals can be treated with oral sulfonylureas instead of insulin. Previous studies suggested that people with ABCC8-PNDM require lower sulfonylurea doses and have milder neurological features than those with KCNJ11-PNDM. However, these studies were short-term and included combinations of ABCC8-PNDM and ABCC8-TNDM. We aimed to assess the long-term glycemic and neurological outcomes in sulfonylurea-treated ABCC8-PNDM.

RESEARCH DESIGN AND METHODS

We studied all 24 individuals with ABCC8-PNDM diagnosed in the U.K., Italy, France, and U.S. known to transfer from insulin to sulfonylureas before May 2010. Data on glycemic control, sulfonylurea dose, adverse effects including hypoglycemia, and neurological features were analyzed using nonparametric statistical methods.

RESULTS

Long-term data were obtained for 21 of 24 individuals (median follow-up 10.0 [range 4.1-13.2] years). Eighteen of 21 remained on sulfonylureas without insulin at the most recent follow-up. Glycemic control improved on sulfonylureas (presulfonylurea vs. 1-year posttransfer HbA1c 7.2% vs. 5.7%, P = 0.0004) and remained excellent long-term (1-year vs. 10-year HbA1c 5.7% vs. 6.5%, P = 0.04), n = 16. Relatively high doses were used (1-year vs. 10-year dose 0.37 vs. 0.25 mg/kg/day glyburide, P = 0.50) without any severe hypoglycemia. Neurological features were reported in 13 of 21 individuals; these improved following sulfonylurea transfer in 7 of 13. The most common features were learning difficulties (52%), developmental delay (48%), and attention deficit hyperactivity disorder (38%).

CONCLUSIONS

Sulfonylurea treatment of ABCC8-PNDM results in excellent long-term glycemic control. Overt neurological features frequently occur and may improve with sulfonylureas, supporting early, rapid genetic testing to guide appropriate treatment and neurodevelopmental assessment.

Clinical and Genetic Characteristics of ABCC8 Nonneonatal Diabetes Mellitus: A Systematic Review

OBJECTIVES

Diabetes mellitus (DM) is a major chronic metabolic disease in the world, and the prevalence has been increasing rapidly in recent years. The channel of K_ATP plays an important role in the regulation of insulin secretion. The variants in ABCC8 gene encoding the SUR1 subunit of K_ATP could cause a variety of phenotypes, including neonatal diabetes mellitus (ABCC8-NDM) and ABCC8-induced nonneonatal diabetes mellitus (ABCC8-NNDM). Since the features of ABCC8-NNDM have not been elucidated, this study is aimed at concluding the genetic features and clinical characteristics.

METHODS

We comprehensively reviewed the literature associated with ABCC8-NNDM in the following databases: MEDLINE, PubMed, and Web of Science to investigate the features of ABCC8-NNDM.

RESULTS

Based on a comprehensive literature search, we found that 87 probands with ABCC8-NNDM carried 71 ABCC8 genetic variant alleles, 24% of whom carried inactivating variants, 24% carried activating variants, and the remaining 52% carried activating or inactivating variants. Nine of these variants were confirmed to be activating or inactivating through functional studies, while four variants (p.R370S, p.E1506K, p.R1418H, and p.R1420H) were confirmed to be inactivating. The phenotypes of ABCC8-NNDM were variable and could also present with early hyperinsulinemia followed by reduced insulin secretion, progressing to diabetes later. They had a relatively high risk of microvascular complications and low prevalence of nervous disease, which is different from ABCC8-NDM.

CONCLUSIONS

Genetic testing is essential for proper diagnosis and appropriate treatment for patients with ABCC8-NNDM. And further studies are required to determine the complex mechanism of the variants of ABCC8-NNDM.

Recent Developments in Medicinal Chemistry of Allosteric Activators of Human Glucokinase for Type 2 Diabetes Mellitus Therapeutics

BACKGROUND

Glucokinase (GK), a cytoplasmic enzyme catalyzes the metabolism of glucose to glucose- 6-phosphate with the help of ATP and aids in the controlling of blood glucose levels within the normal range in humans. In pancreatic β-cells, it plays a chief role by controlling the glucose-stimulated secretion of insulin and in liver hepatocyte cells, it controls the metabolism of carbohydrates. GK acts as a promising drug target for the pharmacological treatment of patients with type 2 diabetes mellitus (T2DM) as it plays an important role in the control of carbohydrate metabolism.

METHODS

Data used for this review was based on the search from several science databases as well as various patent databases. The main data search terms used were allosteric GK activators, diabetes mellitus, type 2 diabetes, glucokinase, glucokinase activators and human glucokinase.

RESULTS

This article discusses an overview of T2DM, the biology of GK, the role of GK in T2DM, recent updates in the development of small molecule GK activators reported in recent literature, mechanism of action of GK activators and their clinical status.

CONCLUSION

GK activators are the novel class of pharmacological agents that enhance the catalytic activity of GK enzyme and display their antihyperglycemic effects. Broad diversity of chemical entities including benzamide analogues, carboxamides, acrylamides, benzimidazoles, quinazolines, thiazoles, pyrimidines, pyridines, orotic acid amides, amino acid derivatives, amino phosphates and urea derivatives have been synthesized in past two decades as potent allosteric activators of GK. Presently, the pharmaceutical companies and researchers are focusing on the design and development of liver-selective GK activators for preventing the possible adverse effects associated with GK activators for the long-term treatment of T2DM.

Parental experiences of a diagnosis of neonatal diabetes and perceptions of newborn screening for glucose: a qualitative study

Neonatal diabetes presents <6 months of life but delays in recognition result in presentation with life-threatening hyperglycaemia/diabetic ketoacidosis. Early identification and rapid genetic diagnosis is crucial and ensures correct treatment/management. Adding 'glucose' to newborn bloodspot screening (NBS) could aid prompt detection but requires evidence of parental acceptance.

OBJECTIVES

Increase understanding of parental experience of presentation/recognition of neonatal diabetes and perceptions of glucose testing within NBS.

SETTING

UK families confirmed with a genetic diagnosis of neonatal diabetes, November 2014-2018, were invited to participate.

PARTICIPANTS

In-depth qualitative interviews were conducted with 10 parents of 14 children. 8 had transient neonatal diabetes: KCNJ11 (n=5), ABCC8 (n=1), 6q24 (n=2), 6 had permanent neonatal diabetes: KCNJ11 (n=4), INS (n=1), homozygous GCK (n=1).

PRIMARY AND SECONDARY OUTCOME MEASURES

Interviews audio recorded, transcribed and subjected to thematic content analysis.

RESULTS

3 key themes emerged:Babies were extremely ill at hospital admission, with extended stays in intensive care required.Identification of diabetes was not 'standardised' and perceived a 'chance' finding.Adding glucose to NBS was universally considered extremely positive.

CONCLUSIONS

Diagnosis of neonatal diabetes is frequently delayed, resulting in critically ill presentation with prolonged intensive care support, additional healthcare costs and familial distress. Potential to detect hyperglycaemia earlier was universally endorsed by parents with no negative consequences identified. Although further study including a larger number of individuals is needed to confirm our findings this study provides the first evidence of acceptability of glucose testing fulfilling Wilson-Jungner criteria for implementation within the NBS programme.

Neonatal diabetes due to potassium channel mutation: Response to sulfonylurea according to the genotype

OBJECTIVE

A precision medicine approach is used to improve treatment of patients with monogenic diabetes. Herein, we searched SU efficiency according to the genotype-phenotype correlation, dosage used, and side effects.

RESEARCH DESIGN AND METHODS

Systematic review conducted according the PRISMA control criteria identifying relevant studies evaluating the in vivo and in vitro sensitivity of ATP-dependent potassium channels according to the characteristics of genetic mutation.

RESULTS

Hundred and three selected articles with complete data in 502 cases in whom 413 (82.3%) had mutations in KCNJ11 (#64) and 89 in ABCC8 (# 56). Successful transfer from insulin to SU was achieved in 91% and 86.5% patients, respectively, at a mean age of 36.5 months (0-63 years). Among patients with KCNJ11 and ABCC8 mutations 64 and 46 were associated with constant success, 5 and 5 to constant failure, and 10 and 4 to variable degrees of reported success rate, respectively. The glibenclamide dosage required for each genotype ranged from 0.017 to 2.8 mg/kg/day. Comparing both the in vivo and in vitro susceptibility results, some mutations appear more sensitive than others to sulfonylurea treatment. Side effects were reported in 17/103 of the included articles: mild gastrointestinal symptoms and hypoglycaemia were the most common. One premature patient had an ulcerative necrotizing enterocolitis which association with SU is difficult to ascertain.

CONCLUSIONS

Sulfonylureas are an effective treatment for monogenic diabetes due to KCNJ11 and ABCC8 genes mutations. The success of the treatment is conditioned by differences in pharmacogenetics, younger age, pharmacokinetics, compliance, and maximal dose used.

Treatment Options for MODY Patients: A Systematic Review of Literature

Maturity-onset diabetes of the young (MODY) is an unusual form of diabetes with specific features that distinguish it from type 1 and type 2 diabetes. There are 14 known subtypes of MODY, and mutations in three genes (HNF1A, HNF4A, GCK) account for about 95% of all MODY cases. Diagnosis usually occurs before the age of 25 years, although less frequent forms may occur more often-but not necessarily-later in life. The molecular diagnosis may tailor the choice of the most appropriate treatment, with the aim to optimize blood glucose control, reduce the risk of hypoglycemic events and long-term complications, and enable proper genetic counseling. Treatment is usually unnecessary for patients with mutations in the GCK gene, while oral hypoglycemic agents (generally sulphonylureas) are recommended for patients with mutations in the HNF4A and HNF1A genes. More recent data show that other glucose-lowering agents can be effective in the latter patients, and additional and alternative therapies have been proposed. Proper management guidelines during pregnancy have been developed for carriers of GCK gene mutations, but such guidelines are still a subject of debate in other cases, although some recommendations are available. The other subtypes of MODY are even more rare, and very little data are available in the literature. In this review we summarize the most pertinent findings and recommendations on the treatment of patients with the different subtypes of MODY. Our aim is to provide the reader with an easy-to-read update that can be used to drive the clinician's therapeutical approach to these patients after the molecular diagnosis.

New insights into KATP channel gene mutations and neonatal diabetes mellitus

The ATP-sensitive potassium channel (K_ATP channel) couples blood levels of glucose to insulin secretion from pancreatic β-cells. K_ATP channel closure triggers a cascade of events that results in insulin release. Metabolically generated changes in the intracellular concentrations of adenosine nucleotides are integral to this regulation, with ATP and ADP closing the channel and MgATP and MgADP increasing channel activity. Activating mutations in the genes encoding either of the two types of K_ATP channel subunit (Kir6.2 and SUR1) result in neonatal diabetes mellitus, whereas loss-of-function mutations cause hyperinsulinaemic hypoglycaemia of infancy. Sulfonylurea and glinide drugs, which bind to SUR1, close the channel through a pathway independent of ATP and are now the primary therapy for neonatal diabetes mellitus caused by mutations in the genes encoding K_ATP channel subunits. Insight into the molecular details of drug and nucleotide regulation of channel activity has been illuminated by cryo-electron microscopy structures that reveal the atomic-level organization of the K_ATP channel complex. Here we review how these structures aid our understanding of how the various mutations in the genes encoding Kir6.2 (KCNJ11) and SUR1 (ABCC8) lead to a reduction in ATP inhibition and thereby neonatal diabetes mellitus. We also provide an update on known mutations and sulfonylurea therapy in neonatal diabetes mellitus.

Phenotype, genotype and glycaemic variability in people with activating mutations in the ABCC8 gene: response to appropriate therapy

AIMS

To examine the phenotypic features of people identified with ABCC8-maturity-onset diabetes of the young (MODY) who were included in the adult 'Mater MODY' cohort and to establish their response to sulfonylurea therapy.

METHODS

Ten participants with activating ABCC8 mutations were phenotyped in detail. A 2-hour oral glucose tolerance test was performed to establish glycaemic tolerance, with glucose, insulin and C-peptide measurements taken at baseline and 30-min intervals. Insulin was discontinued and sulfonylurea therapy initiated after genetic diagnosis of ABCC8-MODY. A blinded continuous glucose monitoring sensor was used to establish glycaemic control on insulin vs a sulfonylurea.

RESULTS

The mean age at diagnosis of diabetes was 33.8 ± 11.1 years, with fasting glucose of 18.9 ± 11.5 mmol/l and a mean (range) HbA_1c of 86 (51,126) mmol/mol [10.0 (6.8,13.7)%]. Following a genetic diagnosis of ABCC8-MODY three out of four participants discontinued insulin (mean duration 10.6 ± 1.69 years) and started sulfonylurea treatment. The mean (range) HbA_1c prior to genetic diagnosis was 52 (43,74) mmol/mol (6.9%) and the post-treatment change was 44 (30,57) mmol/mol (6.2%; P=0.16). Retinopathy was the most common microvascular complication in this cohort, occurring in five out of 10 participants.

CONCLUSIONS

Low-dose sulfonylurea therapy resulted in stable glycaemic control and the elimination of hypoglycaemic episodes attributable to insulin therapy. The use of appropriate therapy at the early stages of diabetes may decrease the incidence of complications and reduce the risks of hypoglycaemia associated with insulin therapy.

Neonatal diabetes caused by the heterozygous Pro1198Leu mutation in the ABCC8 gene in a male infant: 6-year clinical course

Neonatal diabetes is a rare disease, often caused by a monogenic abnormality. A male infant patient developed diabetic ketoacidosis at 2 months-of-age due to the heterozygous ABCC8 gene mutation (p.Pro1198Leu). After genetic diagnosis, insulin therapy was successfully transitioned to oral sulfonylurea therapy. For >6 years, oral sulfonylurea therapy has been safe and effective, and the required amount of sulfonylureas has progressively decreased. The mutation was transmitted in an autosomal-dominant fashion across three generations of his family, but the severity of diabetes varied among members from neonatal diabetes to mild diabetes. One family member had normal glucose tolerance despite having the mutation. This case presentation could help in the understanding of neonatal diabetes caused by the ABCC8 gene mutation.

Update of variants identified in the pancreatic β-cell KATP channel genes KCNJ11 and ABCC8 in individuals with congenital hyperinsulinism and diabetes

The most common genetic cause of neonatal diabetes and hyperinsulinism is pathogenic variants in ABCC8 and KCNJ11. These genes encode the subunits of the β-cell ATP-sensitive potassium channel, a key component of the glucose-stimulated insulin secretion pathway. Mutations in the two genes cause dysregulated insulin secretion; inactivating mutations cause an oversecretion of insulin, leading to congenital hyperinsulinism, whereas activating mutations cause the opposing phenotype, diabetes. This review focuses on variants identified in ABCC8 and KCNJ11, the phenotypic spectrum and the treatment implications for individuals with pathogenic variants.

Phenotype of a transient neonatal diabetes point mutation (SUR1-R1183W) in mice

Background: The K ATP channel plays a key role in glucose homeostasis by coupling metabolically generated changes in ATP to insulin secretion from pancreatic beta-cells.  Gain-of-function mutations in either the pore-forming (Kir6.2) or regulatory (SUR1) subunit of this channel are a common cause of transient neonatal diabetes mellitus (TNDM), in which diabetes presents shortly after birth but remits within the first few years of life, only to return in later life. The reasons behind this time dependence are unclear. Methods: In an attempt to understand the mechanism behind diabetes remission and relapse, we generated mice expressing the common TNDM mutation SUR1-R1183W. We employed Cre/LoxP technology for both inducible and constitutive expression of SUR1-R1183W specifically in mouse beta-cells, followed by investigation of their phenotype using glucose tolerance tests and insulin secretion from isolated islets.  Results: We found that the R1183W mutation impaired inhibition of K ATP channels by ATP when heterologously expressed in human embryonic kidney cells. However, neither induced nor constitutive expression of SUR1-R1183W in mice resulted in changes in blood glucose homeostasis, compared to littermate controls. When challenged with a high fat diet, female mice expressing SUR1-R1183W showed increased weight gain, elevated blood glucose and impaired glycaemic control, but glucose-stimulated insulin secretion from pancreatic islets appeared unchanged. Conclusions: The mouse model of TNDM did not recapitulate the human phenotype. We discuss multiple potential reasons why this might be the case. Based on our findings, we recommend future TNDM mouse models employing a gain-of-function SUR1 mutation should be created using the minimally invasive CRISPR/Cas technology, which avoids many potential pitfalls associated with the Cre/LoxP system.

Diagnosis and management of neonatal diabetes mellitus: A survey of physicians' perceptions and practices in ASPED countries

AIM

To ascertain the awareness and practice of neonatal diabetes mellitus (NDM) among paediatricians in Arab countries.

METHODS

An online questionnaire was distributed to physicians associated with the Arab Society for Paediatric Endocrinology and Diabetes (ASPED).

RESULTS

We received 126 replies, from 16 countries. All except one classified the survey's case scenario as NDM and 94% agreed that NDM patients should have detailed assessment to identify extra-pancreatic features. Although 92% felt that genetic testing is necessary, only 72% requesting them routinely and 32% unaware of the availability of free genetic testing. Insulin is considered the initial therapy for 93% and 80% diluted insulin to deliver accurate doses. Basal-bolus regimen was preferred by 36% and similar percentage used insulin pump. The remaining 28% favour long acting insulin alone. Oral sulfonylureas would be tried empirically by 34% and 69% would do so if genetic testing is unavailable. Whilst 70% have no local NDM management guidelines, 41% are unaware of any international guidelines.

CONCLUSIONS

The ASPED surveyed clinicians have good awareness of NDM diagnosis with marked variation in their practice raising the need to establish management guideline for the condition. The survey highlights areas to focus on in developing consensus and educational activities.