Glucokinase Mutations Research Articles

Identification of small molecule glucokinase activators for the treatment of diabetes based on plants from the traditional Chinese medicine: In silico analysis

Mutations in glucokinase (GCK) can either enhance or inhibit insulin secretion, leading to different forms of diabetes, including gestational diabetes. While many glucokinase activators (GKAs) have been explored as treatments, their long-term effectiveness has often been unsatisfactory. However, recent interest has surged with the introduction of dorzagliatin and TTP399. This study investigates the efficacy of four previously studied compounds (Swertiamarin, Apigenin, Mangiferin, and Tatanan A) in activating GCK using computational methods.Initial molecular docking revealed binding affinities ranging from −6.7 to −8.6 kcal/mol. The compounds were then evaluated for drug-likeness and pharmacokinetic properties. Re-docking studies were performed for validation. Based on their favorable binding affinities and compliance with Lipinski's rule and ADMET criteria, three compounds (Swertiamarin, Apigenin, and Tatanan A) were selected for molecular dynamics (MD) simulations.MD simulations demonstrated that Swertiamarin showed excellent stability, as indicated by analyses of RMSD, RMSF, radius of gyration (Rg), hydrogen bonding, and principal component analysis (PCA). These results suggest that Swertiamarin holds promise for further investigation in in vivo and clinical settings to evaluate its potential in enhancing GCK activity and treating diabetes.This study assessed the potential of four compounds as GCK activators using molecular docking, pharmacokinetic profiling, and MD simulations. Swertiamarin, in particular, showed significant stability and adherence to drug-likeness criteria, making it a promising candidate for further research in combating diabetes.

Two novel GCK mutations in Chinese patients with maturity-onset diabetes of the young.

Heterozygous inactivating mutations in the glucokinase (GCK) gene result in the asymptomatic fasting hyperglycemia named as GCK-MODY or MODY2. The genetic testing can effectively avoid the misdiagnosis and inappropriate treatment for GCK-MODY. A total of 25 unrelated families with MODY were screened for mutations in coding region of GCK by using direct sequencing. Three different bioinformatics tools such as PolyPhen2, Mutation Taster and PROVEAN were performed to predict the function of mutant proteins. The glucose profile was recorded by continuous glucose monitoring system (CGMS) to evaluate the glycemic variability for the GCK-MODY patient. Our study identified five GCK mutations in 24% of the families (6/25): two novel mutations (I126fs and G385A) and three already described mutations (G44S, H50fs and S383L). In silico analyses predicted that these mutations altered structural conformational changes. The values of mean amplitude of glycemic excursions (MAGE), an important index of blood glucose fluctuation in CGMS system, were 0.81 in the first 24 h and 1.61 in the second 24 h record in the patient with GCK-MODY (F3), suggesting little glucose fluctuation. The genetic testing is suggested to be important to differentiate GCK-MODY from other types of diabetes. CGMS might be used to screen GCK-MODY cases prior to genetic testing.

SAT163 Title: Adult-onset Hyperinsulinemic Hypoglycemia Due To An Activating Mutation In Glucokinase

Abstract Disclosure: S. Vaid: None. R. Ghosh: None. H. Elenius: None. C. Cochran: None. R. Chang: None. N. Nilubol: None. R. Muniyappa: None. Introduction: Glucokinase (GK), the key β-cell glucose sensor, determines the threshold for glucose-stimulated insulin secretion. Activating mutations of GK are infrequent causes (prevalence of 1.2%) of congenital hyperinsulinemic hypoglycemia (HH). Adult-onset of severe hypoglycemia due to GK-HH is extremely rare. Clinical Case: A 26-year-old well-nourished female (BMI, 27 kg/m2) with a recent history of dizziness, tremulousness, fatigue, sweating, and hunger, associated with weight gain presented for further workup. Hypoglycemia was noted, and Whipple's triad was confirmed. She had no family history of endocrine disease or hypoglycemia. Supervised fasting promptly produced symptomatic hypoglycemia with hyperinsulinemia. Laboratory studies revealed a low glucose level at 44 mg/dL; a plasma insulin level at 93 μIU/mL (<3 μIU/ml); a C-peptide level at 8.1 ng/mL (<0.6 ng/mL); pro-insulin at 266 pmol/L (<5 pmol/L); and beta-hydroxybutyrate <2.7 mmol/L. IGF2/IGF-1 ratio was 3.1 (<10) and renal and liver function was normal. Interestingly, a mixed meal also provoked significant hypoglycemia within an hour of consumption of a meal. Urine for sulfonylurea screen was negative, and so were anti-insulin antibodies. Imaging of the pancreas with computed tomography (CT), magnetic resonance imaging (MRI), and endoscopic ultrasound revealed a 1.2x0.8cm nodule on the superior margin of the body of the pancreas. 68Ga-DOTATATE​​ PET/CT (targeting somatostatin receptors) showed mild uptake coinciding with the nodule on the CT scan. Arteriography with calcium stimulation and venous sampling (ASVS) was non-localizing. The patient subsequently underwent laparoscopic exploration with intraoperative ultrasound (IOUS) of the pancreas followed by the enucleation of the pancreatic nodule. Histopathology of the nodule revealed a normal pancreatic tissue with no evidence of a neuroendocrine tumor. Change to multiple small meals, addition of cornstarch to diet, continuous blood glucose monitoring (CGM), diazoxide (70 mg oral, three times a day), and monthly octreotide LAR (30 mg) has allowed the patient to avoid hypoglycemia. Genetic testing by analysis of the genes known to cause hypoglycemia revealed a heterozygous GCK variant [c.1367C>T (p.Ala456Val), which was predicted to be a pathological mutation. This mutation is known to increase affinity for glucose, which leads to exaggerated insulin secretion. Conclusion: Our study highlights that in adults with non-insulinoma pancreatogenous hypoglycemia, genetic causes of HH should be considered in the differential diagnosis. Presentation: Saturday, June 17, 2023

Phenotypic Characterization of Congenital Hyperinsulinism Due to Novel Activating Glucokinase Mutations.

Our evaluation of six novel and two previously published activating GCK mutations revealed that the detrimental effects of these mutations on glucose homeostasis can be attributed not only to a lowering of the glucose threshold of insulin secretion but also to a decreased counterregulatory glucagon secretory response. These studies provide insights into the pathophysiology of GCK-hyperinsulinism and the dual role of glucokinase in β-cells and α-cells to regulate glucose homeostasis.

1474-P: Identification and Management of MODY2 Pregnancy Patients

Precise differentiation of glucokinase (GCK) monogenic diabetes, MODY2, from gestational diabetes mellitus (GDM) is critical for accurate management of the pregnancy outcome. We screened MODY2 complicating pregnancies in Chinese GDM patients, explored the pathogenesis of novel GCK mutations, and evaluated the patients’ pregnancy outcome and management. The GCK gene from 411 GDM patients was screened with PCR-direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and 15 GCK mutations were identified. We also retrospectively analyzed a total of 65 pregnancies from 21 MODY2 families, wherein 41 were from 15 maternal families and 24 were from six paternal families. Bioinformatic analysis and biochemical functional study were conducted to identify novel GCK mutations. In total, we identified 21 GCK mutations: 15 from the 411 GDM patients and six from 24 fathers. Of the Asp78Asn (GAC → AAC), Met87Arg (ATG → AGG), Leu451Val (CTT → GTT), Leu451Pro (CTG → CCG) and 1019 + 20G > A mutations, five, i.e., were novel and deleterious, with markedly decreased enzyme activity and thermal stability. The unaffected offspring of GCK mutation affected mothers were heavier than affected offspring (p<0.001). Of 21 insulin-treated affected mothers, 10 had maternal hypoglycemia (47.6%) and seven had perinatal complications (33.3%), and the affected offspring of the insulin-treated affected mothers had significantly lower birth weights than that of the 20 diet-control affected mothers (p=0.031). In this study, the prevalence of MODY2 complicating pregnancy in Chinese GDM patients was 3.6% (15/411). The defective GCK may contribute to the hyperglycemia in MODY2. Insulin therapy is not beneficial for MODY2 complicating pregnancy and therefore should not be recommended. Disclosure L.Liu: None. Y.Jiang: None. Y.Chen: None. C.Liu: None. T.Li: None. Funding National Natural Science Foundation of China (81970686, 81770791, 81471012, 82070823, 81270876); Interdisciplinary Program of Shanghai Jiao Tong University (YG2019ZDA08); Shanghai Leading Talent (SLJ15055); National Institutes of Health (SC1DK104821); Tobacco-Related Disease Research Program (T31IR1603)

503-P: Distinct Effects of a Novel GCK-MODY Mutation on Lipid Profiles and Diabetic Complications

Glucokinase (GK) encoded by glucokinase gene (GCK) is the first rate-limiting enzyme in glucose metabolism. The heterozygous inactivating mutations of GCK cause maturity-onset diabetes of the young (GCK-MODY). Unlike other types of diabetes, GCK-MODY is not associated with increased risks of diabetic complications in young patients. However, the long-term effects of mutant GK on lipid profiles and chronic complications in elder patients remain unknown. Herein, we established a knock-in mouse model heterozygeously expressing a novel GCK mutation encoding GK-Q26L that was identified in a Chinese family with early onset diabetes. GK-Q26L mice developed mild early onset diabetes with moderate elevated blood glucose and decreased serum insulin, confirming diabetogenes of GK-Q26L. To determine age- and diet-related diabetic complications and lipid profiles, we have fed the mice with either chow diet or high-fat diet (HFD) for 28, 40, or 60 weeks. We found that, after 28 week of HFD, GK-Q26L alleviated abnormal lipid profiles in plasma and liver, suggesting beneficial effects of GK-Q26L on lipid metabolism. Surprisingly however, those protective effects were disappeared at 40 weeks, and at 60 weeks of HFD, GK-Q26L mice exhibited even more severe abnormal lipid profiles. Consistent with the distinct trends of lipid profiles, HFD-induced kidney injury (increased urinary albumin/creatinine ratio and renal fibrosis) was also alleviated in GK-Q26L mice at 28 weeks of HFD, but aggravated at 60 weeks of HFD. Similar effects on diabetic retinopathy were observed in GK-Q26L mice. These data reveal for the first time that although inactivating GCK mutations have beneficial effects on HFD-induced abnormal lipid metabolism and diabetes related damages of kidney and retina in short-term, it is strongly associated with long-term diabetic nephropathy and retinopathy. This study suggests that more attention should be paid on the long-term chronic complications in elder patients with GCK-MODY. Disclosure Y.Huang: None. Y.Fan: None. X.Li: None. S.Ji: None. S.Chen: None. J.Cui: None. W.Feng: None. H.Shu: None. M.Liu: None. Funding National Natural Science Foundation of China (81830025, 82220108014, 82100865, 81800733, 81900720, 82000796, 82070854); National Key R&D Program of China (2019YFA0802502, 2022YFE0131400); Tianjin Key Medical Discipline Construction Project (TJYXZDXK-030A)

GCK exonic mutations induce abnormal biochemical activities and result in GCK-MODY.

Objective: Glucokinase-maturity-onset diabetes of the young (GCK-MODY; MODY2) is a rare genetic disorder caused by mutations in the glucokinase (GCK) gene. It is often under- or misdiagnosed in clinical practice, but correct diagnosis can be facilitated by genetic testing. In this study, we examined the genes of three patients diagnosed with GCK-MODY and tested their biochemical properties, such as protein stability and half-life, to explore the function of the mutant proteins and identify the pathogenic mechanism of GCK-MODY. Methods: Three patients with increased blood glucose levels were diagnosed with MODY2 according to the diagnostic guidelines of GCK-MODY proposed by the International Society for Pediatric and Adolescent Diabetes (ISPAD) in 2018. Next-generation sequencing (whole exome detection) was performed to detect gene mutations. The GCK gene and its mutations were introduced into the pCDNA3.0 and pGEX-4T-1 vectors. Following protein purification, enzyme activity assay, and protein immunoblotting, the enzyme activity of GCK was determined, along with the ubiquitination level of the mutant GCK protein. Results: Genetic testing revealed three mutations in the GCK gene of the three patients, including c.574C>T (p.R192W), c.758G>A (p.C253Y), and c.794G>A (p.G265D). The biochemical characteristics of the protein encoded by wild-type GCK and mutant GCK were different, compared to wild-type GCK, the enzyme activity encoded by the mutant GCK was reduced, suggesting thermal instability of the mutant GST-GCK. The protein stability and expression levels of the mutant GCK were reduced, and the enzyme activity of GCK was negatively correlated with the levels of fasting blood glucose and HbA1c. In addition, ubiquitination of the mutant GCK protein was higher than that of the wild-type, suggesting a higher degradation rate of mutant GCK than WT-GCK. Conclusion: GCK mutations lead to changes in the biochemical characteristics of its encoded proteins. The enzyme activities, protein expression, and protein stability of GCK may be reduced in patients with GCK gene mutations, which further causes glucose metabolism disorders and induces MODY2.

Glucokinase maturity-onset diabetes of the young as a mimicker of stress hyperglycemia: a case report

Febrile seizures are frequently accompanied by stress-induced hyperglycemia. Herein, we report the case of a 1.5-yr-old girl with hyperglycemia during febrile seizures who was subsequently diagnosed with glucokinase (GCK) maturity-onset diabetes of the young (MODY), considering its distinction from stress hyperglycemia. Following the development of febrile seizures owing to adenovirus infection, the patient presented a casual blood glucose level was 185 mg/dL. She had a multigenerational family history of diabetes and a hemoglobin A1c (HbA1c) level of 6.4%. Owing to the persistent glucose intolerance until the age of 5 years, genetic testing was performed, which revealed a heterozygous mutation in GCK, and the patient was diagnosed with GCK-MODY. Precise diagnosis of GCK-MODY individuals is important to avoid administering unnecessary antidiabetic medications. Even during hyperglycemia under stress, multigenerational diabetes and mildly elevated HbA1c levels can suggest GCK-MODY.

A clinical mutation in glucokinase causing maturity-onset diabetes in the young type 2 increases enzyme activity.

Glucokinase (GCK) is the pancreatic β-cell glucose sensor, and its kinetics are key to that purpose. A slow transition step, displayed as non-hyperbolic kinetics, and a low affinity for glucose characterize GCK. Mutations in GCK associated with maturity-onset diabetes of the young type 2 (MODY2) previously describedreduce the functionality of the human pancreatic β-cell, leading to diabetic clinical phenotypes. We present a kinetic characterization of the G448D mutation identified in a MODY2 patient, which is one of the first mutations to exhibit increased functionality. This mutant displays increased activity, high affinity for both Mg2+ -ATP and glucose, hyperbolic kinetics and increased phosphorylation potential. Hyperbolic kinetics and assays in the presence of glycerol indicate that G448D lacks the slow transition step crucial for the pancreatic β-cell glucose sensor function.

Predominant genetic mutations leading to or predisposing diabetes progress: A Review

Diabetes mellitus (DM) arises following poor capacity to generate or secrete insulin or insulin resistance; hence insulin production impairment creates the illness. Individuals can control their weight, impulsivity, blood pressure, and blood lipids at the commencement of the disease. A single genetic mutation affects nearly 3% of people with diabetes. Surprisingly, beta cell function is regulated by more than 20 genes. Benefits of genetic diagnosis include improved therapy, better prediction of illness prognosis and progression, genetic counseling, and possibly prevention. Alpha HNF1 mutations in the early stages may respond to the regimen. Still, most patients need it because they control their blood glucose and will be subject to microvascular or macrovascular complications. In cases where insulin does not control sugar, using low-dose sulfonylureas would be beneficial and lower four times the glucose metabolism of metformin. These patients are susceptible to sulfonylureas and may be treated for years in case of no blood glucose attack complications. The drug will start at one-fourth of the adult dose: MODY1. It is caused by a mutation in the alpha-HNF 4 gene and is relatively uncommon. The same is true, but the threshold for renal excretion is not low, and the incidence of upward alpha-HNF 4 mutations in cases where there is a robust clinical panel for alpha HNF 1 but not confirmed by genetic sequencing should be considered. The disease is also susceptible to sulfonylureas: MODY4 with a mutation in the MODY6 gene, IPF1, with a mutation in MODY7, NeuroD1 is characterized by a carboxy sterilise mutation, which is not common: MODY2. In children and adolescents, an increment in fasting blood glucose of 100 to 150 mg/dl is not typical. The incidence of this condition is usually considered to be type 1 or 2 diabetes, but a large percentage of the above patients are heterozygote individuals, the glucokinase mutations. Specific mutations, including those rare variants in WFS1 and ABCC8 genes, insulin receptor (IR), fructose 6-phosphate aminotransferase (GFPT2), and nitric oxide synthase (eNOS), as well as mouse pancreatic β‐cell lines (Min6 and SJ cells), showed that the HDAC4 variant (p. His227Arg) had been directly linked with T2DM. Keywords: type-2 diabetes, genetic mutations, risk factors

Window of opportunity: screening for GCK monogenic diabetes in the antenatal diabetes clinic

Abstract Monogenic diabetes (MODY) is a rare, inherited form of diabetes, of which glucokinase (GCK) mutation is one of the most common forms. Correct diagnosis is important, particularly during pregnancy, as treatment should be tailored accordingly. In our antenatal diabetes clinic, we audited those eligible for genetic screening over a one‐year period as per European Best Practice guidelines (2008) and new NHS England criteria (2021), as well as those identified with the mutation. Our audit recorded a significant drop in the number of eligible women identified using new criteria (2.6% vs 5.2%), with a notable reduction in women of African ethnicity (15.2% vs 29.2%). The audit highlighted the need for increased health care professional awareness and the implementation of clear pathways within the antenatal diabetes service to facilitate identification of women for genetic screening and subsequent appropriate management. It also underlined the importance of ongoing assessment of the clinical performance of the new screening criteria. Copyright © 2022 John Wiley & Sons.

A-267 Pediatric Neuropsychology Genetic Consultation: Rare de novo GCK Mutation with Severe Persistent Congenital Hyperinsulinemia (CH/CHI)

Abstract Objective: Chromosomal abnormalities may result in neurodevelopmental delay. Mutations in the gene encoding the enzyme glucokinase (GCK) have been shown to result in congenital hyperinsulinemia (CH/CHI) and hyperglycemia (Galcheva et al., 2019). GCK is important for both glucose metabolism and homeostasis (Kraslow et al., 2021). Methods: The present case involves a 5-year-old, right-handed, Caucasian male, with a history of chromosomal abnormalities. DNA sequence analysis performed by PCR amplification of highly purified genomic DNA, followed by automated bi-directional DNA sequencing of coding regions of the genes revealed: GCK Variant 1: Transition T>C; Nucleotide position: 295; Codon position: 99; Amino acid change: Tryptophan>Arginine; DNA variant type: Disease-associated mutation, heterozygous; Inheritance: Autosomal Dominant; and Phenotype: CH. The patient had a history of severe persistent CH/CHI, obstructive sleep apnea, congenital chordee, cholelithiasis, and gross motor delay. He was referred for neuropsychological testing to ascertain the extent of his neurodevelopmental issues. Results: Neuropsychological testing revealed a diagnosis of a neurodevelopmental disorder characterized by an attention-deficit/hyperactivity disorder—combined type, dysexecutive syndrome/executive functioning disorder, below average general intellectual functioning and retention of new information, and severe behavioral dysregulation. Conclusion: Rare de novo GCK mutations with severe persistent CH/CHI are uncommon (Kraslow et al., 2021). According to Roper et al. (2020), roughly up to 48% of neonates affected with CH/CHI may exhibit sequelae of neurodevelopmental delay and intellectual disabilities. Analyses of GCK mutations and resultant neuropsychological deficits are rarely reported. Our case highlights the importance of pediatric neuropsychology genetic consultation in elucidating neurodevelopmental sequelae and academic and rehabilitation recommendations.

Mutations in GCK May Lead to MODY2 by Reducing Glycogen Synthesis.

Dysfunction of glucokinase (GCK) caused by mutations in the GCK gene is the main cause of maturity-onset diabetes of the young type-2 (MODY2, also known as GCK-MODY), which is usually present in adolescence or young adulthood. MODY2 is characterized by mild, stable fasting hyperglycemia that presents at birth, usually 5.4-8.3mmolL-1 , and rarely develops complications from diabetes. The treatment of MODY2 prefers a manageable diet rather than the use of insulin. Previous studies have identified GCK mutations only by online software prediction or enzyme kinetic analysis and thermolability assays which are complicated to be conducted. In this study, six mutations in the GCK gene, including four novel mutations and two mutations that are previously reported, are identified. All the six locations are highly conserved according to the sequencing alignment. Moreover, missense mutations are strongly predicted to be pathogenic using online programs. Functional studies show that mutations in GCK mutation do not affect insulin secretion but affect glycogen synthesis. These findings demonstrate that GCK mutations decrease glycogen synthesis, which leads to hyperglycemia in MODY2. Meanwhile, this study provides a new perspective and methods for identifying pathogenic mutations in GCK.

Pregnancy outcome with maternal HNF1B gene mutations and 17q12 deletions.

There is an increasing body of literature regarding monogenic diabetes, particularly the more common forms of glucokinase and HNF1-alpha mutations (MODY2 and MODY3). There is relatively little published literature regarding rarer mutations. HNF1-beta mutations and 17q12 deletions may be associated with a broad range of organ dysfunction, renal disease and diabetes in particular resulting in high-risk pregnancies. This manuscript describes pregnancy outcomes in a woman with an HNF1-beta mutation and 2 women with an HNF1B/17q12 deletion and reviews the previously published literature. It highlights the significant rate of adverse maternal and fetal outcomes, and the maternal features suggestive of the diagnosis which should be considered in preconception counselling.

1342-P: Reduction of Glucokinase and Glucokinase Regulatory Protein Expression by siRNA Is Associated with the Reduction of Lactate and Pyruvate Export from Canine Hepatocytes

Glucokinase (GCK) mediates hepatic glucose uptake during hyperglycemia and is crucial for the regulation of glucose-responsive glycolysis genes. Mutations in GCK are responsible for maturity-onset diabetes of the young, and glucokinase regulatory protein (GKRP) , the regulator of hepatic GCK, is also a diabetes susceptibility locus. Recently in in vivo experiments, we used hepatic lactate export as a surrogate for GCK activity, which was a measure of “glucose effectiveness.” We hypothesized that in vitro GCK and GKRP suppression in hepatocytes promotes a reduction in lactate and pyruvate export from the liver. We used cryopreserved canine hepatocytes and knocked down GCK and GKRP via lipid delivery of siRNA. A control group did not receive siRNA. We measured lactate dehydrogenase D (LDHD) and pyruvate kinase (PK) gene expression and lactate and pyruvate release into the medium 24 and 48 h after siRNA delivery. Selective blocking of GCK and GKRP did not change cell proliferation but reduced the expression of these genes by 90% and 85%, respectively (P<0.0vs. controls; n=4) . GCK and GKRP knockdown reduced LDHD by 71% and 74%, respectively (P<0.001) ; similarly, PK was reduced by 84% and 82%, respectively (P<0.001) . Lactate exported into the medium was reduced by 36% (P<0.001) and 26% (P<0.05) by GCK and GKRP siRNA, respectively, after 48 h of hepatocyte culture. However, pyruvate was reduced by 17% only after 48 h culture of GCK siRNA (P<0.05) . Thus, we showed that direct suppression of GCK and GKRP genes by siRNA in vitro affects glucose-responsive glycolysis genes, consequently reducing lactate export which can be used as a surrogate for reduced glucokinase activity in hepatocytes. The use of antisense oligonucleotides or CRISPR gene-editing methods in animals will be useful methods to study the glucose-lactate relationship in vivo and will evaluate the role of glucose effectiveness in the pathogenesis of type 2 diabetes. Disclosure M.Kabir: None. M.Ader: None. R.N.Bergman: Consultant; Fractyl Health, Inc., Novo Nordisk, Research Support; AstraZeneca, Janssen Research & Development, LLC. Funding National Institutes of Health R01- DK027619-28

The Genetics of Type 2 Diabetes in Youth: Where We Are and the Road Ahead

The Genetics of Type 2 Diabetes in Youth: Where We Are and the Road Ahead

Identification and management of GCK-MODY complicating pregnancy in Chinese patients with gestational diabetes.

Precise differentiation of glucokinase (GCK) monogenic diabetes from gestational diabetes mellitus (GDM) is critical for accurate management of the pregnancy outcome. We screened GCK-MODY complicating pregnancies in Chinese GDM patients, explored the pathogenesis of novel GCK mutations, and evaluated the patients' pregnancy outcome and management. The GCK gene from 411 GDM patients was screened with PCR-direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and 15 GCK mutations were identified. We also retrospectively analyzed a total of 65 pregnancies from 21 GCK-MODY families, wherein 41 were from 15 maternal families and 24 were from six paternal families. Bioinformatic analysis and biochemical functional study were conducted to identify novel GCK mutations. In total, we identified 21 GCK mutations: 15 from the 411 GDM patients and six from 24 fathers. Of th Asp78Asn (GAC → AAC), Met87Arg (ATG → AGG), Leu451Val (CTT → GTT), Leu451Pro (CTG → CCG) and 1019 + 20G > A e mutations, five, i.e., were novel and deleterious, with markedly decreased enzyme activity and thermal stability. The unaffected offspring of GCK mutation-affected mothers were heavier than affected offspring (p < 0.001). Of 21 insulin-treated affected mothers, 10 had maternal hypoglycemia (47.6%) and seven had perinatal complications (33.3%), and the affected offspring of the insulin-treated affected mothers had significantly lower birth weights than that of the 20 diet-control affected mothers (p = 0.031). In this study, the prevalence of GCK-MODY complicating pregnancy in Chinese GDM patients was 3.6% (15/411). The defective GCK may contribute to the hyperglycemia in GCK-MODY. Insulin therapy is not beneficial for GCK-MODY complicating pregnancy and therefore should not be recommended.

Frequency and spectrum of glucokinase mutations in an adult Maltese population.

To investigate the frequency and spectrum of glucokinase (GCK) mutations in a cohort of adults from an island population having a high prevalence of diabetes mellitus (DM). A single-centre cohort study was conducted, including 145 non-obese adults of Maltese-Caucasian ethnicity with impaired fasting glycaemia (IFG) or non-autoimmune diabetes diagnosed before the age of 40years. Bidirectional sequencing of the GCK coding regions was performed. Genotype-phenotype associations and familial segregation were explored and the effects of missense variants on protein structure were evaluated using computational analysis. Three probands with pathogenic/likely pathogenic GCK variants in the heterozygous state having clinical features consistent with GCK-diabetes were detected. The missense variants have structurally destabilising effects on protein structure. GCK variant carriers exhibited a significantly lower body mass index and serum triglyceride levels when compared to GCK variant non-carriers. The frequency of GCK-diabetes is approximately 2% in non-obese Maltese adults with diabetes or prediabetes. This study broadens the mutational spectrum of GCK and highlights clinical features that could be useful in discriminating GCK-DM from type 2 DM or prediabetes. It reinforces the need for increased molecular testing in young adults with diabetes having a suspected monogenic aetiology.

Ketogenic diet as elective treatment in patients with drug-unresponsive hyperinsulinemic hypoglycemia caused by glucokinase mutations

BackgroundHyperinsulinemic hypoglycemia (HI) is the most frequent cause of recurrent hypoglycemia in children. Despite diagnostic and therapeutic advances, it remains an important cause of morbidity, leading to neurological complications, such as psychomotor retardation and epilepsy. Patients with diffuse drug-unresponsive HI manifest neurological impairment and neurobehavioral problems, even though surgically treated with a near-total pancreatectomy. Based on the analogies between HI and GLUT1 deficiency, both presenting with neuroglycopenia and lack of alternative cerebral energy sources, we administered a ketogenic diet (KD) in three drug-unresponsive GCK-HI patients with the aim of preserving neurodevelopment and avoiding the need of a near-total pancreatectomy. They presented recurrent symptomatic hypoglycemia, intellectual disability and refractory epilepsy. Patients were treated with classical KD for 79, 27 and 18 months, respectively.ResultsAll patients became asymptomatic in a few days and showed an important improvement of the alert state. Epilepsy disappeared and no appearance of novel hypoglycemic lesions was detected with a brain MRI. Cognitive and adaptive abilities rapidly improved and normalized. IQ rose significantly from 81 to 111 (p = 0.04) in patient 1, from 82 vs 95 (p = 0.04) in patient 2, from 60 to 90 (p = 0.04) in patient 3.ConclusionsWe demonstrated the safety and efficacy of KD in the treatment of drug-unresponsive GCK-HI at a short and long-term. The neuroprotective effects of KD determined the recovery from epilepsy and intellectual disabilities and averted the need of a near-total pancreatectomy. All patients and their families reported an improvement of physical and psychosocial well-being, with a substantial improvement of their quality of life. These results might change the course and the quality of life of these patients and their families, having a relevant impact on human lives. Therefore, KD might be considered the elective treatment in unresponsive forms of GCK-HI.

Permanent Neonatal Diabetes Mellitus in an Indian Infant Due to a Novel Mutation in the Glucokinase Gene

Background: Neonatal diabetes mellitus (NDM) is a rare condition, usually genetic in etiology, that presents with hyperglycemia requiring insulin within the first 6 months of life. Most cases of permanent NDM are caused by mutations in the KCNJ11 or ABCC8 gene, which are involved in the potassium adenosine triphosphate channels. Clinical Description: A 1.88 kg female infant product of a consanguineous marriage was delivered at term by cesarean section for oligohydramnios and intrauterine growth retardation. There was a strong family history of DM involving the mother, father, and grandparents. Clinical examination was normal. Routine blood sugar monitoring identified hyperglycemia at 1 and 3 h. There was no clinical or laboratory evidence of sepsis. Management: Persistent hyperglycemia continued that necessitated the administration of insulin from the 1st day onward. The abdominal ultrasonogram was normal. C-peptide was low, indicating poor endogenous insulin production. Genetic analysis revealed a novel mutation in the glucokinase (GCK) gene (p. Glu178Asp). A brief trial of sulfonylureas (glibenclamide) was ineffective. The infant attained control, although with considerable difficulty, on a mixture of NPH and long-acting insulin. After 5 months of follow-up, she is thriving well. Conclusion: GCK mutation is a rare but important cause of NDM. To the best of our knowledge, this is the first Indian infant to be reported with a GCK gene mutation.