Fetal Hypoglycemia Induced by Placental SLC2A3-RNA Interference Alters Fetal Pancreas Development and Transcriptome at Mid-Gestation.

Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to ß cell activity.

Pathogenic Potential of a PCK1 Gene Variant in Cytosolic PEPCK Deficiency: A Compelling Case Study.

BACKGROUND Cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) deficiency is an extremely rare autosomal recessive inherited error of metabolism in which gluconeogenesis is impaired, resulting in life-threatening episodes of hypoglycemia and metabolic acidosis. The diagnosis of gluconeogenesis disorders is challenging. In the diagnostic pathway, the molecular test plays a paramount role. CASE REPORT The aim of the paper is to present the case report of a girl with recurrent episodes of severe hypoglycemia, in whom molecular diagnosis enabled the confirmation of PEPCK - C deficiency. The patient experienced 4 episodes of severe hypoglycemia. Most of them were accompanied by hyperlacticaemia, metabolic acidosis, and elevated liver enzymes. All of the metabolic decompensations were triggered by infectious agents. The episodes resolved after continuous infusion of high-dose glucose. Due to the recurrent character of the disease, a genetic condition was suspected. The differential diagnosis included metabolic and endocrinological causes of hypoglycemia. Two variants in the PCK1 gene were detected: c.265G>A p.(Glu89Lys) in exon 3 and c.925G>A p.(Gly309Arg) in exon 6. As c.925G>A p.(Gly309Arg) is a known pathogenic variant, the second variant was first described in June 2023 in the ClinVar database and described as "with unknown clinical significance". CONCLUSIONS According to the clinical symptoms observed in the presented case, the variant c.265G>A p.(Glu89Lys) in PCK1 gene should be considered likely pathogenic. We suggest considering molecular diagnostics in every patient presented with recurrent, severe hypoglycemia with accompanying liver damage as most accurate, feasible, and reliable method.

Metabolomic associations of impaired awareness of hypoglycaemia in type 1 diabetes.

This study investigates impaired awareness of hypoglycaemia (IAH), a complication of insulin therapy affecting 20-40% of individuals with type 1 diabetes. The exact pathophysiology is unclear, therefore we sought to identify metabolic signatures in IAH to elucidate potential pathophysiological pathways. Plasma samples from 578 individuals of the Dutch type 1 diabetes biomarker cohort, 67 with IAH and 108 without IAH (NAH) were analysed using the targeted metabolomics Biocrates AbsoluteIDQ p180 assay. Eleven metabolites were significantly associated with IAH. Genome-wide association studies of these 11 metabolites identified significant single nucleotide polymorphisms (SNPs) in C22:1-OH and phosphatidylcholine diacyl C36:6. After adjusting for the SNPs, 11 sphingomyelins and phosphatidylcholines were significantly higher in the IAH group in comparison to NAH. These metabolites are important components of the cell membrane and have been implicated to play a role in cell signalling in diabetes. These findings demonstrate the potential role of phosphatidylcholine and sphingomyelins in IAH.

[Clinical and genetic analysis of two children with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency].

OBJECTIVE: To explore the clinical characteristics and genetic variants of two children with 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD). METHODS: Two children with HMGCLD diagnosed at Henan Provincial Children's Hospital respectively in December 2019 and June 2022 were selected as the study subjects. Clinical data and results of laboratory testing were analyzed retrospectively. RESULTS: Both children had manifested with repeated convulsions, severe hypoglycemia, metabolic acidosis and liver dysfunction. Blood amino acids and acylcarnitine analysis showed increased 3-hydroxy-isovalyl carnitine (C5OH) and 3-hydroxy-isovalyl carnitine/capryloyl carnitine ratio (C5OH/C8), and urinary organic acid analysis showed increased 3-hydroxyl-3-methyl glutaric acid, 3-methyl glutaric acid, 3-methyl glutaconic acid, 3-hydroxyisoglycine and 3-methylprotarylglycine. Child 1 was found to harbor homozygous c.722C>T variants of the HMGCL gene, which was rated as uncertain significance (PM2_Supporting+PP3). Child 2 was found to harbor homozygous c.121C>T variants of the HMGCL gene, which was rated as pathogenic variant (PVS1+PM2_Supporting+PP4). CONCLUSION: Acute episode of HMGCLD is usually characterized by metabolic disorders such as hypoglycemia and metabolic acidosis, and elevated organic acids in urine may facilitate the differential diagnosis, though definite diagnosis will rely on genetic testing.

Novel compound heterozygous mutations of the FBP1 gene in a patient with hypoglycemia and lactic acidosis: A case report.

BACKGROUND: Fructose-1,6-bisphosphatase (FBPase) deficiency, caused by an FBP1 mutation, is an autosomal recessively inherited metabolic disorder characterized by impaired gluconeogenesis. Due to the rarity of FBPase deficiency, the mechanism by which the mutations cause enzyme activity loss still remains unclear. METHODS: We report a pediatric patient with typical FBPase deficiency who presented with hypoglycemia, hyperlactatemia, metabolic acidosis, and hyperuricemia. Whole-exome sequencing was used to search for pathogenic genes, Sanger sequencing was used for verification, and molecular dynamic simulation was used to evaluate how the novel mutation affects FBPase activity and structural stability. RESULTS: Direct and allele-specific sequence analysis of the FBP1 gene (NM_000507) revealed that the proband had a compound heterozygote for the c. 490 (exon 4) G>A (p. G164S) and c. 861 (exon 7) C>A (p. Y287X, 52), which he inherited from his carrier parents. His father and mother had heterozygous G164S and Y287X mutations, respectively, without any symptoms of hypoglycemia. CONCLUSION: Our results broaden the known mutational spectrum and possible clinical phenotype of FBP1.

Diazepam Binding Inhibitor Control of Eu- and Hypoglycemic Patterns of Ventromedial Hypothalamic Nucleus Glucose-Regulatory Signaling.

Pharmacological stimulation/antagonism of astrocyte glio-peptide octadecaneuropeptide signaling alters ventromedial hypothalamic nucleus (VMN) counterregulatory γ-aminobutyric acid (GABA) and nitric oxide transmission. The current research used newly developed capillary zone electrophoresis-mass spectrometry methods to investigate hypoglycemia effects on VMN octadecaneuropeptide content, along with gene knockdown tools to determine if octadecaneuropeptide signaling regulates these transmitters during eu- and/or hypoglycemia. Hypoglycemia caused dissimilar adjustments in the octadecaneuropeptide precursor, i.e., diazepam-binding-inhibitor and octadecaneuropeptide levels in dorsomedial versus ventrolateral VMN. Intra-VMN diazepam-binding-inhibitor siRNA administration decreased baseline 67 and 65 kDa glutamate decarboxylase mRNA levels in GABAergic neurons laser-microdissected from each location, but only affected hypoglycemic transcript expression in ventrolateral VMN. This knockdown therapy imposed dissimilar effects on eu- and hypoglycemic glucokinase and 5'-AMP-activated protein kinase-alpha1 (AMPKα1) and -alpha2 (AMPKα2) gene profiles in dorsomedial versus ventrolateral GABAergic neurons. Diazepam-binding-inhibitor gene silencing up-regulated baseline (dorsomedial) or hypoglycemic (ventrolateral) nitrergic neuron neuronal nitric oxide synthase mRNA profiles. Baseline nitrergic cell glucokinase mRNA was up- (ventrolateral) or down- (dorsomedial) regulated by diazepam-binding-inhibitor siRNA, but knockdown enhanced hypoglycemic profiles in both sites. Nitrergic nerve cell AMPKα1 and -α2 transcripts exhibited division-specific responses to this genetic manipulation during eu- and hypoglycemia. Results document the utility of capillary zone electrophoresis-mass spectrometric tools for quantification of ODN in small-volume brain tissue samples. Data show that hypoglycemia has dissimilar effects on ODN signaling in the two major neuroanatomical divisions of the VMN and that this glio-peptide imposes differential control of glucose-regulatory neurotransmission in the VMNdm versus VMNvl during eu- and hypoglycemia.

Case report: Two unexpected cases of DGUOK-related mitochondrial DNA depletion syndrome presenting with hyperinsulinemic hypoglycemia.

Timely diagnosis of persistent neonatal hypoglycemia is critical to prevent neurological sequelae, but diagnosis is complicated by the heterogenicity of the causes. We discuss two cases at separate institutions in which clinical management was fundamentally altered by the results of molecular genetic testing. In both patients, critical samples demonstrated hypoketotic hypoglycemia and a partial glycemic response to glucagon stimulation, thereby suggesting hyperinsulinism (HI). However, due to rapid genetic testing, both patients were found to have deoxyguanosine kinase (DGUOK)-related mitochondrial DNA depletion syndrome, an unexpected diagnosis. Patients with this disease typically present with either hepatocerebral disease in the neonatal period or isolated hepatic failure in infancy. The characteristic features involved in the hepatocerebral form of the disease include lactic acidosis, hypoglycemia, cholestasis, progressive liver failure, and increasing neurologic dysfunction. Those with isolated liver involvement experience hepatomegaly, cholestasis, and liver failure. Although liver transplantation is considered, research has demonstrated that for patients with DGUOK-related mitochondrial DNA depletion syndrome and neurologic symptoms, early demise occurs. Our report advocates for the prompt initiation of genetic testing in patients presenting with persistent neonatal hypoglycemia and for the incorporation of mitochondrial DNA depletion syndromes in the differential diagnosis of HI.

A splice-switching oligonucleotide treatment ameliorates glycogen storage disease type 1a in mice with G6PC c.648G>T.

Glycogen storage disease type 1a (GSD1a) is caused by a congenital deficiency of glucose-6-phosphatase-α (G6Pase-α, encoded by G6PC), which is primarily associated with life-threatening hypoglycemia. Although strict dietary management substantially improves life expectancy, patients still experience intermittent hypoglycemia and develop hepatic complications. Emerging therapies utilizing new modalities such as adeno-associated virus and mRNA with lipid nanoparticles are under development for GSD1a but potentially require complicated glycemic management throughout life. Here, we present an oligonucleotide-based therapy to produce intact G6Pase-α from a pathogenic human variant, G6PC c.648G>T, the most prevalent variant in East Asia causing aberrant splicing of G6PC. DS-4108b, a splice-switching oligonucleotide, was designed to correct this aberrant splicing, especially in liver. We generated a mouse strain with homozygous knockin of this variant that well reflected the pathophysiology of patients with GSD1a. DS-4108b recovered hepatic G6Pase activity through splicing correction and prevented hypoglycemia and various hepatic abnormalities in the mice. Moreover, DS-4108b had long-lasting efficacy of more than 12 weeks in mice that received a single dose and had favorable pharmacokinetics and tolerability in mice and monkeys. These findings together indicate that this oligonucleotide-based therapy could provide a sustainable and curative therapeutic option under easy disease management for GSD1a patients with G6PC c.648G>T.

Deficiency of the metabolic enzyme SCHAD in pancreatic ß-cells promotes amino acid-sensitive hypoglycemia.

Congenital hyperinsulinism of infancy (CHI) can be caused by a deficiency of the ubiquitously expressed enzyme short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD). To test the hypothesis that SCHAD-CHI arises from a specific defect in pancreatic ß-cells, we created genetically engineered ß-cell-specific (ß-SKO) or hepatocyte-specific (L-SKO) SCHAD knockout mice. While L-SKO mice were normoglycemic, plasma glucose in ß-SKO animals was significantly reduced in the random-fed state, after overnight fasting, and following refeeding. The hypoglycemic phenotype was exacerbated when the mice were fed a diet enriched in leucine, glutamine, and alanine. Intraperitoneal injection of these three amino acids led to a rapid elevation in insulin levels in ß-SKO mice compared to controls. Consistently, treating isolated ß-SKO islets with the amino acid mixture potently enhanced insulin secretion compared to controls in a low-glucose environment. RNA sequencing of ß-SKO islets revealed reduced transcription of ß-cell identity genes and upregulation of genes involved in oxidative phosphorylation, protein metabolism, and Ca2+ handling. The ß-SKO mouse offers a useful model to interrogate the intra-islet heterogeneity of amino acid sensing given the very variable expression levels of SCHAD within different hormonal cells, with high levels in ß- and δ-cells and virtually absent α-cell expression. We conclude that the lack of SCHAD protein in ß-cells results in a hypoglycemic phenotype characterized by increased sensitivity to amino acid-stimulated insulin secretion and loss of ß-cell identity.

A narrative review on pathogenetic mechanisms of hyperinsulinemic hypoglycemia in Kabuki syndrome.

Objective. Kabuki syndrome (KS) is associated with hyperinsulinemic hypoglycemia (HH) in 0.3-4% of patients, thus exceeding the prevalence in the general population. HH association is stronger for KS type 2 (KDM6A-KS, OMIM #300867) than KS type 1 (KMT2D-KS, OMIM #147920). Both the disease-associated genes, KMD6A and KMT2D, modulate the chromatin dynamic. As such, KS is considered to be the best characterized pediatric chromatinopathy. However, the exact pathogenetic mechanisms leading to HH in this syndrome remain still unclear. Methods. We selected on the electronic database PubMed all articles describing or hypothesizing the mechanisms underlying the dysregulated insulin secretion in KS. Results. The impact on the gene expression due to the KDM6A or KMT2D function loss may lead to a deregulated pancreatic ß-cell differentiation during embryogenesis. Moreover, both KMT2D gene and KDM6A gene are implicated in promoting the transcription of essential pancreatic ß-cell genes and in regulating the metabolic pathways instrumental for insulin release. Somatic KMT2D or KDM6A mutations have also been described in several tumor types, including insulinoma, and have been associated with metabolic pathways promoting pancreatic cell proliferation. Conclusions. The impact of pathogenic variants in KDM6A and KDM2D genes on ß-cell insulin release remains to be fully clarified. Understanding this phenomenon may provide valuable insight into the physiological mechanisms of insulin release and into the pathological cascade causing hyperinsulinism in KS. The identification of these molecular targets may open new therapeutic opportunities based on epigenetic modifiers.

Tmem117 in AVP neurons regulates the counterregulatory response to hypoglycemia.

The counterregulatory response to hypoglycemia (CRR), which ensures a sufficient glucose supply to the brain, is an essential survival function. It is orchestrated by incompletely characterized glucose-sensing neurons, which trigger a coordinated autonomous and hormonal response that restores normoglycemia. Here, we investigate the role of hypothalamic Tmem117, identified in a genetic screen as a regulator of CRR. We show that Tmem117 is expressed in vasopressin magnocellular neurons of the hypothalamus. Tmem117 inactivation in these neurons increases hypoglycemia-induced vasopressin secretion leading to higher glucagon secretion in male mice, and this effect is estrus cycle phase dependent in female mice. Ex vivo electrophysiological analysis, in situ hybridization, and in vivo calcium imaging reveal that Tmem117 inactivation does not affect the glucose-sensing properties of vasopressin neurons but increases ER stress, ROS production, and intracellular calcium levels accompanied by increased vasopressin production and secretion. Thus, Tmem117 in vasopressin neurons is a physiological regulator of glucagon secretion, which highlights the role of these neurons in the coordinated response to hypoglycemia.

Ghrelin does not impact the blunted counterregulatory response to recurrent hypoglycemia in mice.

Introduction: Recurrent episodes of insulin-induced hypoglycemia in patients with diabetes mellitus can result in hypoglycemia-associated autonomic failure (HAAF), which is characterized by a compromised response to hypoglycemia by counterregulatory hormones (counterregulatory response; CRR) and hypoglycemia unawareness. HAAF is a leading cause of morbidity in diabetes and often hinders optimal regulation of blood glucose levels. Yet, the molecular pathways underlying HAAF remain incompletely described. We previously reported that in mice, ghrelin is permissive for the usual CRR to insulin-induced hypoglycemia. Here, we tested the hypothesis that attenuated release of ghrelin both results from HAAF and contributes to HAAF. Methods: C57BL/6N mice, ghrelin-knockout (KO) + control mice, and GhIRKO (ghrelin cell-selective insulin receptor knockout) + control mice were randomized to one of three treatment groups: a "Euglycemia" group was injected with saline and remained euglycemic; a 1X hypoglycemia ("1X Hypo") group underwent a single episode of insulin-induced hypoglycemia; a recurrent hypoglycemia ("Recurrent Hypo") group underwent repeated episodes of insulin-induced hypoglycemia over five successive days. Results: Recurrent hypoglycemia exaggerated the reduction in blood glucose (by ~30%) and attenuated the elevations in plasma levels of the CRR hormones glucagon (by 64.5%) and epinephrine (by 52.9%) in C57BL/6N mice compared to a single hypoglycemic episode. Yet, plasma ghrelin was equivalently reduced in "1X Hypo" and "Recurrent Hypo" C57BL/6N mice. Ghrelin-KO mice exhibited neither exaggerated hypoglycemia in response to recurrent hypoglycemia, nor any additional attenuation in CRR hormone levels compared to wild-type littermates. Also, in response to recurrent hypoglycemia, GhIRKO mice exhibited nearly identical blood glucose and plasma CRR hormone levels as littermates with intact insulin receptor expression (floxed-IR mice), despite higher plasma ghrelin in GhIRKO mice. Conclusions: These data suggest that the usual reduction of plasma ghrelin due to insulin-induced hypoglycemia is unaltered by recurrent hypoglycemia and that ghrelin does not impact blood glucose or the blunted CRR hormone responses during recurrent hypoglycemia.

Anoctamin 4 channel currents activate glucose-inhibited neurons in the mouse ventromedial hypothalamus during hypoglycemia.

Glucose is the basic fuel essential for maintenance of viability and functionality of all cells. However, some neurons - namely, glucose-inhibited (GI) neurons - paradoxically increase their firing activity in low-glucose conditions and decrease that activity in high-glucose conditions. The ionic mechanisms mediating electric responses of GI neurons to glucose fluctuations remain unclear. Here, we showed that currents mediated by the anoctamin 4 (Ano4) channel are only detected in GI neurons in the ventromedial hypothalamic nucleus (VMH) and are functionally required for their activation in response to low glucose. Genetic disruption of the Ano4 gene in VMH neurons reduced blood glucose and impaired counterregulatory responses during hypoglycemia in mice. Activation of VMHAno4 neurons increased food intake and blood glucose, while chronic inhibition of VMHAno4 neurons ameliorated hyperglycemia in a type 1 diabetic mouse model. Finally, we showed that VMHAno4 neurons represent a unique orexigenic VMH population and transmit a positive valence, while stimulation of neurons that do not express Ano4 in the VMH (VMHnon-Ano4) suppress feeding and transmit a negative valence. Together, our results indicate that the Ano4 channel and VMHAno4 neurons are potential therapeutic targets for human diseases with abnormal feeding behavior or glucose imbalance.

Carnitine-acylcarnitine translocase deficiency caused by SLC25A20 gene heterozygous variants in twins: a case report.

The current case report describes the clinical, biochemical and genetic characteristics of carnitine-acylcarnitine translocase deficiency (CACTD) in infant male and female twins that presented with symptoms shortly after elective caesarean delivery. The clinical manifestations were neonatal hypoglycaemia, arrhythmia and sudden death. The age of onset was 1.5 days and the age of the death was 1.5-3.5 days. Dried blood filter paper analysis was used for the detection of acylcarnitine. Peripheral venous blood and skin samples were used for next-generation sequencing. The twins and their parents underwent gene analysis and whole exome sequencing analyses of the solute carrier family 25 member 20 (SLC25A20; also known as carnitine-acylcarnitine translocase) gene. Both infants carried compound heterozygous variants of the SLC25A20 gene: variant M1:c.706_707insT:p.R236L fs*12 and variant M2:c.689C>G:p.P230R. The M1 variant was paternal and had not been previously reported regarding CACTD. The M2 variant was maternal. CACTD has severe clinical manifestations and a poor prognosis, which is manifested as hypoketotic hypoglycaemia, hyperammonaemia, liver function damage and elevated creatine kinase.

Hypoglycemia in Patients With LAMA2-CMD.

BACKGROUND: Hypoglycemia has been reported in patients with LAMA2-CMD, but the frequency, risk factors, and correlation to genotype/phenotype have not been systematically assessed to date. METHODS: A retrospective cohort study was performed on 48 patients with LAMA2-CMD. Patients were divided into two groups: a hypoglycemic group, with at least one episode of hypoglycemia, and a nonhypoglycemic group. The groups were compared according to gait function, epilepsy, intellectual disability, constipation, gastroesophageal reflux, gastrostomy, weight percentile, scoliosis, the use of a ventilator device, the use of a feeding device, neuromuscular disease swallowing status scale, and type of mutation. RESULTS: Fifteen patients (31.2%) presented with at least one episode of symptomatic hypoglycemia and eight (16.6% of the cohort) had two or more episodes. All patients who had hypoglycemia were in the nonambulant group. We observed a correlation between gait, the use of ventilator and feeding devices, and swallow function with hypoglycemia. Patients with extremely low weight were five times more likely to have recurrent episodes of hypoglycemia. The presence of at least one missense variant appears to be associated with a lower risk of hypoglycemia. CONCLUSION: Patients with LAMA2-CMD are at risk of hypoglycemia. The risk is more relevant in patients with severe phenotype and patients with loss-of-function variants. For patients with extremely low weight, the risk is higher. Blood glucose should be actively measured in patients who are fasting or have infections, and health care providers should be prepared to identify and treat these patients.

Impact of Polymorphism in the ß2-Receptor Gene on the Metabolic Response to Epinephrine After Repeated Hypoglycemia.

The ß2-receptor mediates the metabolic response to epinephrine. This study investigates the impact of the ß2-receptor gene (ADRB2) polymorphism Gly16Arg on the metabolic response to epinephrine before and after repetitive hypoglycemia. Twenty-five healthy men selected according to ADRB2 genotype being homozygous for either Gly16 (GG) (n = 12) or Arg16 (AA) (n = 13) participated in 4 trial days (D1-4): D1pre and D4post with epinephrine 0.06 µg kg-1 ⋅ min-1 infusion and D2hypo1-2 and D3hypo3 with three periods of hypoglycemia by an insulin-glucose clamp. At D1pre, the insulin (mean ± SEM of area under the curve 44 ± 8 vs. 93 ± 13 pmol ⋅ L-1 h; P = 0.0051), glycerol (79 ± 12 vs. 115 ± 14 µmol ⋅ L-1 h; P = 0.041), and free fatty acid (724 ± 96 vs. 1,113 ± 140 µmol ⋅ L-1 h; P = 0.033) responses to epinephrine were decreased in AA participants compared with GG participants but without a difference in glucose response. There were no differences in response to epinephrine between genotype groups after repetitive hypoglycemia at D4post. The metabolic substrate response to epinephrine was decreased in AA participants compared with GG participants but without a difference between genotype groups after repetitive hypoglycemia. ARTICLE HIGHLIGHTS: This study investigates the impact of the ß2-receptor gene (ADRB2) polymorphism Gly16Arg on the metabolic response to epinephrine before and after repetitive hypoglycemia. Healthy men homozygous for either Gly16 (n = 12) or Arg16 (n = 13) participated in the study. Healthy people with the Gly16 genotype have increased metabolic response to epinephrine compared with the Arg16 genotype but without a difference between genotypes after repetitive hypoglycemia.

Hyperinsulinemic Hypoglycemia Diagnosed in Childhood Can Be Monogenic.

CONTEXT: Congenital hyperinsulinism (HI) is characterized by inappropriate insulin secretion despite low blood glucose. Persistent HI is often monogenic, with the majority of cases diagnosed in infancy. Less is known about the contribution of monogenic forms of disease in those presenting in childhood. OBJECTIVE: We investigated the likelihood of finding a genetic cause in childhood-onset HI and explored potential factors leading to later age at presentation of disease. METHODS: We screened known disease-causing genes in 1848 individuals with HI, referred for genetic testing as part of routine clinical care. Individuals were classified as infancy-onset (diagnosed with HI < 12 months of age) or childhood-onset (diagnosed at age 1-16 years). We assessed clinical characteristics and the genotypes of individuals with monogenic HI diagnosed in childhood to gain insights into the later age at diagnosis of HI in these children. RESULTS: We identified the monogenic cause in 24% (n = 42/173) of the childhood-onset HI cohort; this was significantly lower than the proportion of genetic diagnoses in infancy-onset cases (74.5% [n = 1248/1675], P < 0.00001). Most (75%) individuals with genetically confirmed childhood-onset HI were diagnosed before 2.7 years, suggesting these cases represent the tail end of the normal distribution in age at diagnosis. This is supported by the finding that 81% of the variants identified in the childhood-onset cohort were detected in those diagnosed in infancy. CONCLUSION: We have shown that monogenic HI is an important cause of hyperinsulinism presenting outside of infancy. Genetic testing should be considered in children with persistent hyperinsulinism, regardless of age at diagnosis.

Diagnosis, treatment and genetic analysis of a case of hypoglycemia caused by glucokinase gene mutation.

Congenital hyperinsulinemia (CHI) is a disease phenotype characterized by persistent or recurrent hypoglycemia due to abnormal secretion of insulin by ß cells of the pancreas. CHI induced by activation mutation of a single allele of glucokinase (GCK) is the rarest type. In this paper, the clinical data of a patient with hypoglycemia of unknown cause were collected without obvious clinical symptoms. And a heterozygous missense mutation (c.295T> C:p.W99R) was detected in exon 3 of the GCK gene. The mutation was found in both the son and daughter of the proband, and the blood glucose level was low, while the others were normal. By summarizing and analyzing the characteristics of this case and the genetic pedigree of the family, the possibility of congenital hyperinsulinemia caused by a single gene mutation should be considered for hypoglycemia whose etiology is difficult to be determined clinically. This case also provides new clinical data for subsequent genetic studies of the disease.

SIRT3 alleviates mitochondrial dysfunction induced by recurrent low glucose and improves the supportive function of astrocytes to neurons.

Hypoglycemia is an independent risk factor of cognitive impairment in patients with diabetes. Our previous study indicated that dysfunction of astrocytic mitochondria induced by recurrent low glucose (RLG) may account for hypoglycemia-associated neuronal injury and cognitive decline. Sirtuin 3 (SIRT3) is a key deacetylase for mitochondrial proteins and has recently been demonstrated to be an important regulator of mitochondrial function. However, whether mitochondrial dysfunction due to hypoglycemia is associated with astrocytic SIRT3 remains unclear, and few studies have focused on the impact of astrocytic SIRT3 on neuronal survival. In the present work, primary mouse cortical astrocytes cultured in normal glucose (5.5 mM) and high glucose (16.5 mM) were treated with five rounds of RLG (0.1 mM). The results showed that RLG suppressed SIRT3 expression in a glucose-dependent manner. High-glucose culture considerably increased the vulnerability of SIRT3 to RLG, leading to disrupted mitochondrial morphology in astrocytes. Overexpression of SIRT3 markedly improved astrocytic mitochondrial function and reduced RLG-induced oxidative stress. Moreover, SIRT3 suppressed a shift towards a neuroinflammatory A1-like reactive phenotype of astrocytes in response to RLG with reduced IL-1ß, IL-6, and TNFα levels. Furthermore, it elevated brain-derived neurotrophic factor (BDNF) levels and promoted neurite growth by activating BDNF/TrkB signaling in the co-cultured neurons. The present study reveals the probable crosstalk between neurons and astrocytes after hypoglycemic exposure and provides a potential target in treating hypoglycemia-associated neuronal injury.

Severe neuroglycopenic symptoms due to nonketotic hypoglycemia in children with cardio-facio-cutaneous syndrome.

Cardio-facio-cutaneous syndrome (CFC) (OMIM 115150) is a congenital disease caused by constitutive activation of the Raf/MEK/ERK signaling cascade. Unlike aspects of morphological anomalies, metabolic functions related to the disease have garnered little attention. We present severe neuroglycopenic symptoms due to nonketotic hypoglycemia in two children with CFC (Case 1, a 4-year-old male with c.389A > G heterozygous variant in MAP2K1; Case 2, a 3-year-old male with c.770A > G heterozygous variant in BRAF). Case 1 exhibited a nonketotic hypoglycemic coma and clustered left-hemispheric convulsions despite receiving infusion therapy, leading to severe sequelae with choreoathetosis. Brain magnetic resonance imaging of Case 1 showed T2-elongation with restricted diffusion on the bilateral basal ganglia and thalamus, with the dominance of the right putamen. Case 2 presented a prolonged generalized seizure as an initial clinical symptom but fully recovered. The presence of growth hormone and cortisol deficiency was ruled out in both cases. Blood spots acylcarnitine profiles excluded the co-occurrence of mitochondrial HMG-CoA synthase deficiency and HMG-CoA lyase deficiency. These cases demonstrate the potential vulnerability to nonketotic hypoglycemia, especially during lipid shortages. As children with CFC frequently have difficulties feeding, we suggest great attention should be paid to the potential risk of severe nonketotic hypoglycemia.