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.

Early Postnatal Use of Glibenclamide in Permanent Neonatal Diabetes Secondary to Antenatally Diagnosed KJCN11 Mutation

INTRODUCTION

Heterozygous activating mutations in KCNJ11 cause both permanent and transient neonatal diabetes. A minority of patients also have neurological features. Early genetic diagnosis has important therapeutic implications as treatment with sulfonylurea provides good metabolic control and exerts a protective effect on neuromuscular function.

CASE PRESENTATION

A term female infant with normal birth weight (2.73 kg, z-score: -1.69) was admitted to the Neonatal Unit at Addenbrookes Hospital. She had been antenatally diagnosed with KCNJ11 mutation-R201C inherited from her glibenclamide-treated mother who continued sulfonylurea treatment throughout pregnancy. A continuous glucose-monitoring system inserted at 20 h of age showed progressive rise of blood glucose concentrations, prompting treatment with glibenclamide on day 2 of life. Initial attempts to treat with an extemporaneous solution of glibenclamide (starting dose 0.2 mg/kg/day) resulted in inconsistent response and significant hypoglycaemia and hyperglycaemia. A licenced liquid formulation of glibenclamide (AMGLIDIA) at a starting dose of 0.05 mg/kg/day was used with stabilization of blood glucose profile within 24 h. Other than a mild transient elevation in transaminase, treatment was well tolerated. At most recent review (age 12 months), the patient remains well with age-appropriate neurodevelopment. Overall glucose control is reasonable with estimated HbA1c of 7.6% (59.9 mmol/mol).

CONCLUSION

Early postnatal glibenclamide treatment of insulin-naive patients with KATP-dependent neonatal diabetes is safe, provides good metabolic control, and has a potential protective effect on neurological function. The formulation of the medicine needs to be carefully considered in the context of the very small doses required in this age group.

Childhood-onset mild diabetes caused by a homozygous novel variant in the glucokinase gene

PURPOSE

Heterozygous loss-of-function mutations in the glucokinase (GCK) gene cause MODY 2, which is characterized by asymptomatic fasting hyperglycemia and does not require insulin treatment. Conversely, homozygous loss-of-function mutations in the same gene give rise to permanent neonatal diabetes mellitus (DM) that appears in the first 6-9 months of life and necessitates lifelong insulin treatment. We aimed to present the genotypic and phenotypic features of a 13-year-old patient diagnosed with DM at the age of 3 years due to a homozygous variant in the GCK gene.

METHODS

The patient's clinical and laboratory findings at follow-up were not consistent with the initial diagnosis of type 1 DM; thus, next-generation sequencing of MODY genes (GCK, HNF1A, HNF1B, and HNF4A genes) was performed to identify monogenic causes of DM.

RESULTS

A novel homozygous variant c.1222 G > T in the GCK gene was revealed. In silico analysis identified it as a pathogenic variant. His mother, father, and brother had the same heterozygous variant in the GCK gene and were diagnosed with MODY 2 (mild fasting hyperglycemia and elevated HbA1c) after genetic counseling.

CONCLUSION

In this case report, a patient with a homozygous variant in the GCK gene, who was diagnosed with DM after the infantile period, was presented, highlighting the fact that cases with homozygous variants in the GCK gene can, though rarely, present at a later age with a milder phenotype.

Sulfonylurea-Insensitive Permanent Neonatal Diabetes Caused by a Severe Gain-of-Function Tyr330His Substitution in Kir6.2

BACKGROUND/AIMS

Mutations in KCNJ11, the gene encoding the Kir6.2 subunit of pancreatic and neuronal KATP channels, are associated with a spectrum of neonatal diabetes diseases.

METHODS

Variant screening was used to identify the cause of neonatal diabetes, and continuous glucose monitoring was used to assess effectiveness of sulfonylurea treatment. Electrophysiological analysis of variant KATP channel function was used to determine molecular basis.

RESULTS

We identified a previously uncharacterized KCNJ11 mutation, c.988T>C [p.Tyr330His], in an Italian child diagnosed with sulfonylurea-resistant permanent neonatal diabetes and developmental delay (intermediate DEND). Functional analysis of recombinant KATP channels reveals that this mutation causes a drastic gain-of-function, due to a reduction in ATP inhibition. Further, we demonstrate that the Tyr330His substitution causes a significant decrease in sensitivity to the sulfonylurea, glibenclamide.

CONCLUSIONS

In this subject, the KCNJ11 (c.988T>C) mutation provoked neonatal diabetes, with mild developmental delay, which was insensitive to correction by sulfonylurea therapy. This is explained by the molecular loss of sulfonylurea sensitivity conferred by the Tyr330His substitution and highlights the need for molecular analysis of such mutations.

A family with permanent neonatal diabetes due to a novel mutation in INS gene

In this report we present a family with permanent neonatal diabetes, heterozygous for a novel INS gene missense mutation, p.A24V, manifested with marked hyperglycemia and ketoacidosis, unstable glycemic control, requiring insulin therapy, rapid progression of long-term complications and accompanying physical pathological signs and brain lesions.

Successful transition to sulfonylurea in neonatal diabetes, developmental delay, and seizures (DEND syndrome) due to R50P KCNJ11 mutation

Mutations in KCNJ11 cause majority of cases of permanent neonatal diabetes (PND). Multiple reports of PND with successful transitioning to oral sulfonylurea had been reported except for those with DEND syndrome. This case report highlights a case of successful sulfonylurea treatment in a patient with DEND syndrome.

Permanent neonatal diabetes misdiagnosed as type 1 diabetes in a 28-year-old female: a life-changing diagnosis

Many patients with monogenic diabetes are missed or misclassified. Herein, we report a 28-year-old Indian female who developed diabetes at the age of 3 months. An audit of our type 1 diabetes database led to her genetic testing. A KCNJ11 mutation was identified and she was successfully switched to sulphonylurea.