Potential pathogenetic role of a novel ABCC8 missense variant on both transient neonatal diabetes mellitus and fetal growth restriction: a case report.

BACKGROUND: The diagnosis of neonatal diabetes can be problematic in preterm infants with fetal growth restriction (FGR). Growth restricted fetuses may have impaired insulin production and secretion; low birthweight infants may have a reduced response to insulin. We report a novel missense ABCC8 variant associated with a clinical phenotype compatible with transient neonatal diabetes mellitus (TNDM) in a fetal growth restricted preterm infant. METHODS AND RESULTS: A preterm growth restricted infant experienced hyperglycemia from the first day of life, requiring insulin therapy on the 13th and 15th day of life and leading to the diagnosis of TNDM. Glycemic values normalized from the 35th day of life onwards. Genetic screening was performed by next generation sequencing, using a Clinical Exon panel of 4800 genes, filtered for those associated with the clinical presentation and by means of methylation-specific multiplex ligation-dependent probe amplification analysis to identify chromosomal aberrations at 6q24. Genetic tests excluded defects at 6q24 and were negative for KCNJ11, SLC2A2 (GLUT-2) and HNF1B, but revealed the presence of the heterozygous missense variant c.2959T > C (p.Ser987Pro) in ABCC8 gene. The presence of the variant was excluded in parents' DNA and the proband variant was then considered de novo. CONCLUSIONS: In our infant, the persistence of hyperglycemia beyond 3 weeks of life led us to the diagnosis of TNDM and to hypothesize a possible genetic cause. The genetic variant we found could be, most likely, the main cause of both FGR and TNDM.

Congenital diabetes mellitus.

Congenital diabetes mellitus is a rare disorder characterized by hyperglycemia that occurs shortly after birth. We define "Diabetes of Infancy" if hyperglycemia onset before 6 months of life. From the clinical point of view, we distinguish two main types of diabetes of infancy: transient (TNDM), which remits spontaneously, and permanent (PNDM), which requires lifelong treatment. TNDM may relapse later in life. About 50% of cases are transient (TNDM) and 50% permanent. Clinical manifestations include severe intrauterine growth retardation, hyperglycemia and dehydration. A wide range of different associated clinical signs including facial dysmorphism, deafness and neurological, cardiac, kidney or urinary tract anomalies are reported. Developmental delay and learning difficulties may also be observed. In this paper we review all the causes of congenital diabetes and all genes and syndromes involved in this pathology. The discovery of the pathogenesis of most forms of congenital diabetes has made it possible to adapt the therapy to the diagnosis and in the forms of alteration of the potassium channels of the pancreatic Beta cells the switch from insulin to glibenclamide per os has greatly improved the quality of life. Congenital diabetes, although it is a very rare form, has been at the must of research in recent years especially for pathogenesis and pharmacogenetics. The most striking difference compared to the more frequent autoimmune diabetes in children (type 1 diabetes) is the possibility of treatment with hypoglycemic agents and the apparent lower frequency of chronic complications.

Loss-of-Function Mutations in APPL1 in Familial Diabetes Mellitus.

Diabetes mellitus is a highly heterogeneous disorder encompassing several distinct forms with different clinical manifestations including a wide spectrum of age at onset. Despite many advances, the causal genetic defect remains unknown for many subtypes of the disease, including some of those forms with an apparent Mendelian mode of inheritance. Here we report two loss-of-function mutations (c.1655T>A [p.Leu552(∗)] and c.280G>A [p.Asp94Asn]) in the gene for the Adaptor Protein, Phosphotyrosine Interaction, PH domain, and leucine zipper containing 1 (APPL1) that were identified by means of whole-exome sequencing in two large families with a high prevalence of diabetes not due to mutations in known genes involved in maturity onset diabetes of the young (MODY). APPL1 binds to AKT2, a key molecule in the insulin signaling pathway, thereby enhancing insulin-induced AKT2 activation and downstream signaling leading to insulin action and secretion. Both mutations cause APPL1 loss of function. The p.Leu552(∗) alteration totally abolishes APPL1 protein expression in HepG2 transfected cells and the p.Asp94Asn alteration causes significant reduction in the enhancement of the insulin-stimulated AKT2 and GSK3ß phosphorylation that is observed after wild-type APPL1 transfection. These findings-linking APPL1 mutations to familial forms of diabetes-reaffirm the critical role of APPL1 in glucose homeostasis.

Severe insulin resistance in disguise: A familial case of reactive hypoglycemia associated with a novel heterozygous INSR mutation.

AIM: Hypoglycemia in childhood is very rare and can be caused by genetic mutations or insulin-secreting neoplasms. Postprandial hypoglycemia has previously been associated with insulin receptor (INSR) gene mutations. We aimed to identify the cause of postprandial hypoglycemia in a 10-year-old boy. SUBJECTS: We studied the symptomatic proband and his apparently asymptomatic mother and elder brother. All of them were lean. METHODS: Metabolic screening of the proband included a 5-hour oral glucose tolerance test (OGTT), angio-magnetic resonance imaging, and 18 F-dihydroxyphenylalanine positron emission tomography/computed tomography imaging of the pancreas. INSR gene sequencing and in vitro functional studies of a novel INSR mutation were also undertaken. RESULTS: Fasting hyperinsulinemia was detected during metabolic screening, and 5-hour OGTT showed hypoglycemia at 240' in the proband, his mother, and brother. Pancreatic imaging showed no evidence of neoplasia. Acanthosis nigricans with high fasting insulin levels in the proband suggested severe insulin resistance and prompted INSR gene sequencing, which revealed the novel, heterozygous p.Phe1213Leu mutation in the patient and his family members. In vitro studies showed that this mutation severely impairs insulin receptor function by abolishing tyrosine kinase activity and downstream insulin signaling. CONCLUSIONS: The identification of etiological cause of hypoglycemia in childhood may be challenging. The combination of fasting hyperinsulinemia with acanthosis nigricans in a lean subject with hypoglycemia suggests severe insulin resistance and warrants INSR gene screening.

Focal congenital hyperinsulinism managed by medical treatment: a diagnostic algorithm based on molecular genetic screening.

OBJECTIVE: Congenital hyperinsulinism (CHI) requires rapid diagnosis and treatment to avoid irreversible neurological sequelae due to hypoglycaemia. Aetiological diagnosis is instrumental in directing the appropriate therapy. Current diagnostic algorithms provide a complete set of diagnostic tools including (i) biochemical assays, (ii) genetic facility and (iii) state-of-the-art imaging. They consider the response to a therapeutic diazoxide trial an early, crucial step before proceeding (or not) to specific genetic testing and eventually imaging, aimed at distinguishing diffuse vs focal CHI. However, interpretation of the diazoxide test is not trivial and can vary between research groups, which may lead to inappropriate decisions. Objective of this report is proposing a new algorithm in which early genetic screening, rather than diazoxide trial, dictates subsequent clinical decisions. PATIENTS, METHODS AND RESULTS: Two CHI patients weaned from parenteral glucose infusion and glucagon after starting diazoxide. No hypoglycaemia was registered during a 72-h continuous glucose monitoring (CGMS), or hypoglycaemic episodes were present for no longer than 3% of 72-h. Normoglycaemia was obtained by low-medium dose diazoxide combined with frequent carbohydrate feeds for several years. We identified monoallelic, paternally inherited mutations in KATP channel genes, and (18) F-DOPA PET-CT revealed a focal lesion that was surgically resected, resulting in complete remission of hypoglycaemia. CONCLUSIONS: Although rare, some patients with focal lesions may be responsive to diazoxide. As a consequence, we propose an algorithm that is not based on a 'formal' diazoxide response but on genetic testing, in which patients carrying paternally inherited ABCC8 or KCNJ11 mutations should always be subjected to (18) F-DOPA PET-CT.

Permanent neonatal diabetes-causing insulin mutations have dominant negative effects on beta cell identity.

OBJECTIVE: Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM), requiring insulin therapy similar to T1D. While the negative effects on insulin processing and secretion are known, how dominant insulin mutations result in a continued decline of beta cell function after birth is not well understood. METHODS: We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations using patient-derived iPSCs and mutated hESCs. RESULTS: we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on beta-cell mass and function after transplantation into mice. In addition to anticipated ER stress, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. CONCLUSIONS: These results highlight a novel mechanism, the loss of beta cell identity, contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

A new variant in the GATA6 gene associated with tracheoesophageal fistula, pulmonary vein stenosis and neonatal diabetes.

INTRODUCTION: GATA6 is a gene that encodes a transcription factor with a key role in the development of several organ systems, including the development of the pancreas. It is associated with neonatal diabetes but also with other extra-pancreatic anomalies. CASE PRESENTATION: This report describes the association of tracheoesophageal fistula (TEF), pulmonary vein stenosis (PVS), and neonatal diabetes caused by a novel mutation of the GATA6 gene in a small-for-gestational-age male neonate born at 32 weeks of gestation. Next-Generation Sequencing revealed the novel heterozygous variant c.1502C>G in the GATA6 gene, which determines the introduction of the premature stop codon p.Ser501Ter at the protein level. This de novo nonsense variant was not detected in the analyzed parental DNA samples and has not been previously described in the literature. At about two months of life, a PVS was suspected. The PVS progressively increased with the development of an intramural component, resulting in severe postcapillary pulmonary hypertension. The child died at about 4 months of life. CONCLUSION: TEF can be associated with GATA6 variants. In the case of neonatal diabetes and TEF, neonatologists should be aware of this association and should also investigate the child for complex congenital heart disorders, such as in our case, with a cardiac computed tomography.

The changing landscape of neonatal diabetes mellitus in Italy between 2003-2022.

CONTEXT: In the last decade Sanger method of DNA sequencing has been replaced by next generation sequencing (NGS). NGS is valuable in conditions characterized by high genetic heterogeneity such as neonatal diabetes mellitus (NDM). OBJECTIVE: To compare results of genetic analysis of patients with NDM and congenital severe insulin resistance (c.SIR) identified in Italy in 2003-2012 (Sanger) versus 2013-2022 (NGS). METHODS: We reviewed clinical and genetic records of 104 cases with diabetes onset before 6 months of age (NDM+c.SIR) of the Italian dataset. RESULTS: Fiftyfive patients (50 NDM + 5 c.SIR) were identified during 2003-2012 and 49 (46 NDM + 3 c.SIR) in 2013-2022. Twenty-year incidence was 1:103,340 (NDM) and 1:1,240,082 (c.SIR) live births. Frequent NDM/c.SIR genetic defects (KCNJ11, INS, ABCC8, 6q24, INSR) were detected in 41 and 34 probands during 2003-2012 and 2013-2022, respectively. We identified a pathogenic variant in rare genes in a single proband (GATA4) (1/42 or 2.4%) during 2003-2012 and in 8 infants (RFX6, PDX1, GATA6, HNF1B, FOXP3, IL2RA, LRBA, BSCL2) during 2013-2022 (8/42 or 19%, p= 0.034 vs 2003-2012). Notably, five among rare genes were recessive. Swift and accurate genetic diagnosis led to appropriate treatment: patients with autoimmune NDM (FOXP3, IL2RA, LRBA), were subjected to bone marrow transplant; patients with pancreas agenesis/hypoplasia (RFX6, PDX1) were supplemented with pancreatic enzymes and the individual with lipodystrophy caused by BSCL2 was started on metreleptin. CONCLUSIONS: NGS substantially improved diagnosis and precision therapy of monogenic forms of neonatal diabetes and congenital SIR in Italy.

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.

Monogenic diabetes clinic (MDC): 3-year experience.

AIM: In the pediatric diabetes clinic, patients with type 1 diabetes mellitus (T1D) account for more than 90% of cases, while monogenic forms represent about 6%. Many monogenic diabetes subtypes may respond to therapies other than insulin and have chronic diabetes complication prognosis that is different from T1D. With the aim of providing a better diagnostic pipeline and a tailored care for patients with monogenic diabetes, we set up a monogenic diabetes clinic (MDC). METHODS: In the first 3 years of activity 97 patients with non-autoimmune forms of hyperglycemia were referred to MDC. Genetic testing was requested for 80 patients and 68 genetic reports were available for review. RESULTS: In 58 subjects hyperglycemia was discovered beyond 1 year of age (Group 1) and in 10 before 1 year of age (Group 2). Genetic variants considered causative of hyperglycemia were identified in 25 and 6 patients of Group 1 and 2, respectively, with a pick up rate of 43.1% (25/58) for Group 1 and 60% (6/10) for Group 2 (global pick-up rate: 45.5%; 31/68). When we considered probands of Group 1 with a parental history of hyperglycemia, 58.3% (21/36) had a positive genetic test for GCK or HNF1A genes, while pick-up rate was 18.1% (4/22) in patients with mute family history for diabetes. Specific treatments for each condition were administered in most cases. CONCLUSION: We conclude that MDC may contribute to provide a better diabetes care in the pediatric setting.

Permanent Neonatal diabetes-causing Insulin mutations have dominant negative effects on beta cell identity.

Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM) that results from beta cell failure. We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations. Using b and mutated hESCs, we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on the in vivo performance of patient-derived SC-beta cells after transplantation into NSG mice. These insulin mutations derange endoplasmic reticulum (ER) homeostasis, and result in the loss of beta-cell mass and function. In addition to anticipated apoptosis, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. These results highlight both known and novel mechanisms contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

Glyburide ameliorates motor coordination and glucose homeostasis in a child with diabetes associated with the KCNJ11/S225T, del226-232 mutation.

Gain-of-function mutations of KCNJ11 can cause permanent neonatal diabetes mellitus, but only rarely after 6 months of age. Specific uncommon mutations KCNJ11give rise to a syndrome defined as developmental delay, epilepsy, and neonatal diabetes (DEND), or - more frequently - to a milder sub-type lacking epilepsy, denoted as intermediate-DEND (iDEND). Our aim was to consider a possible monogenic etiology in a 12-yr-old boy with early onset diabetes and mild neurological features. We studied a subject diagnosed with diabetes at 21 months of age, and negative to type 1 diabetes autoantibodies testing. He had learning difficulties during primary school, and a single episode of seizures at the age of 10 yr. We performed direct DNA sequencing of the KCNJ11 gene with subsequent functional study of mutated channels in COSm6 cells. The patient's clinical response to oral glyburide (Glyb) was assessed. Motor coordination was evaluated before and after 6 and 12 months of Glyb therapy. Sequencing of the KCNJ11 gene detected the novel, spontaneous mutation S225T, combined with deletion of amino acids 226-232. In vitro studies revealed that the mutation results in a K(ATP) channel with reduced sensitivity to the inhibitory action of ATP. Glyb improved diabetes control (hemoglobin A1c on insulin: 52 mmol/mol/6.9%; on Glyb: 36 mmol/mol/5.4%) and also performance on motor coordination tests that were impaired before the switch of therapy. We conclude that KCNJ11/S225T, del226-232 mutation caused a mild iDEND form in our patient. KCNJ11 should be considered as the etiology of diabetes even beyond the neonatal period if present in combination with negative autoantibody testing and even mild neurological symptoms.

Lack of the architectural factor HMGA1 causes insulin resistance and diabetes in humans and mice.

Type 2 diabetes mellitus is a widespread disease, affecting millions of people globally. Although genetics and environmental factors seem to have a role, the cause of this metabolic disorder is largely unknown. Here we report a genetic flaw that markedly reduced the intracellular expression of the high mobility group A1 (HMGA1) protein, and adversely affected insulin receptor expression in cells and tissues from four subjects with insulin resistance and type 2 diabetes. Restoration of HMGA1 protein expression in subjects' cells enhanced INSR gene transcription, and restored cell-surface insulin receptor protein expression and insulin-binding capacity. Loss of Hmga1 expression, induced in mice by disrupting the Hmga1 gene, considerably decreased insulin receptor expression in the major targets of insulin action, largely impaired insulin signaling and severely reduced insulin secretion, causing a phenotype characteristic of human type 2 diabetes.

Sulfonylurea-responsive neonatal diabetes mellitus diagnosed through molecular genetics in two children and in one adult after a long period of insulin treatment.

A permanent neonatal diabetes mellitus has finally been diagnosed through molecular genetics in two children and one adult after 9 to 35 years of uninterrupted insulin treatment. These patients developed diabetes before 6 months of age and were autoantibody negative. In one boy, a mutation in the KCNJ11 gene was identified at 9 years of age. In the other two patients (daughter and father, 12.6 and 25 years old respectively) the new gene variant (ABCC8/L213P) was found. Switching from insulin to sulfonylurea treatment leads to the definitive discontinuance of insulin therapy, improving metabolic control as well as the amelioration of the associated neurodevelopmental disabilities in the young girl in which an intermediate Development Delay, Epilepsy, Neonatal Diabetes syndrome was diagnosed.

The application of precision medicine in monogenic diabetes.

INTRODUCTION: Monogenic diabetes, a form of diabetes mellitus, is caused by a mutation in a single gene and may account for 1-2% of all clinical forms of diabetes. To date, more than 40 loci have been associated with either isolated or syndromic monogenic diabetes. AREAS COVERED: While the request of a genetic test is mandatory for cases with diabetes onset in the first 6 months of life, a decision may be difficult for childhood or adolescent diabetes. In an effort to assist the clinician in this task, we have grouped monogenic diabetes genes according to the age of onset (or incidental discovery) of hyperglycemia and described the additional clinical features found in syndromic diabetes. The therapeutic options available are reviewed. EXPERT OPINION: Technical improvements in DNA sequencing allow for rapid, simultaneous analysis of all genes involved in monogenic diabetes, progressively shrinking the area of unsolved cases. However, the complexity of the analysis of genetic data requires close cooperation between the geneticist and the diabetologist, who should play a proactive role by providing a detailed clinical phenotype that might match a specific disease gene.

SGLT2i Improves Glycemic Control in Patients With Congenital Severe Insulin Resistance.

Insulin-resistant diabetes in Rabson-Mendenhall syndrome (RMS) is relatively unresponsive to first-line antidiabetic treatments, including metformin and insulin. We report 2 patients with RMS treated with 2 different sodium-glucose cotransporter inhibitors 2: empagliflozin in an 11-year-old boy and dapagliflozin in a 12-year-old girl. In the first patient, we began empagliflozin at 2.5 mg/day and increased the dose to 10 mg/day over 3 months. During treatment with empagliflozin, the amount of time during which the patient maintained serum glucose in the 70 to 180 mg/dL target range increased by 2 hours per day. Hemoglobin A1C dropped from >14% to 11.9%, urinary calcium increased almost twofold, and ß-hydroxybutyrate remained <2.5 mmol/L. Because glycemic control did not further improve with dose escalation, we reverted to the 2.5 mg/day dose. We initiated dapagliflozin in a second patient at 5 mg/day and witnessed a reduction of hemoglobin A1C from 8.5% to 6.2% after 6 months and a mild increase in urinary excretion of phosphorus but not calcium. Insulin levels fell by >50%. In 2 patients with RMS, empagliflozin and dapagliflozin were well tolerated and improved glycemic control without significantly increasing ketonemia. Renal calcium excretion should be carefully monitored.

Very low birth weight newborn with diabetes mellitus due to pancreas agenesis managed with insulin pump reservoir filled with undiluted insulin: 16-month follow-up.

BACKGROUND: When very low doses of insulin are used insulin dilution, a procedure prone to errors, is recommended. CASE PRESENTATION: We managed a neonate with pancreas agenesis with insulin pump therapy from the first days of life to 16 months of age without insulin dilution. Predictive low glucose suspend mode first and then closed loop control were used. No episodes of severe hypoglycemia were observed. CONCLUSIONS: Though limited to a single patient with pancreas agenesis we believe that the use of pump should be warranted in patients with permanent neonatal diabetes mellitus and intestinal malabsorption, even with undiluted insulin.