Mutations In Glucokinase Gene Research Articles

Monogenic diabetes and type 1 diabetes mellitus: a challenging combination

AbstractThe co‐existence of maturity onset diabetes of the young (MODY) due to a glucokinase gene (GCK) mutation and type 1 diabetes mellitus (T1DM) is rarely diagnosed. We present a family with GCK mutation, where one member also has T1DM. We highlight the challenges faced in the management of a child with dual diagnosis, due to the higher threshold for activation of counter‐regulatory hormones in GCK mutations. Fluctuations in blood glucose (BG) levels and significant hypoglycaemia on attempts at normalising BG levels complicate management in these patients. Resetting the threshold for hypoglycaemia and target BG, combined with insulin pump therapy, enabled us to significantly reduce hypoglycaemia and improve quality of life. The population prevalence of GCK‐MODY is 1.1 in 1000. T1DM neither predisposes to nor protects from GCK‐MODY; one would therefore expect the prevalence of GCK‐MODY to be the same in T1DM patients.In conclusion, it is important to recognise the co‐existence of T1DM and GCK‐MODY as symptoms of hypoglycaemia at BG levels usually considered ‘within target’ pose management challenges. A combined diagnosis warrants careful consideration of BG target. Copyright © 2014 John Wiley & Sons, Ltd.

Prädisposition und Phänotypen des Gestationsdiabetes

Gestational diabetes (GDM) is defined as glucose intolerance first diagnosed with a 75 gram oral glucose tolerance test based on IADPSG criteria which had been recently adopted by WHO. In industrial countries GDM is one of the most frequent pregnancy complications. In 2012, in Germany GDM had been diagnosed in 4,3 % of all births, overall 27,700 cases. GDM has to be considered as a preliminary stage of type 2 diabetes with insulin resistance and inadequate β-cell-compensation. Additionally, adverse metabolic profile, associations with inflammatory parameters, with D vitamin metabolism, and insufficient decline of renal threshold for glucose had been identified in women with GDM. Within 10 years after GDM roughly 50 % of the women convert to overt diabetes, mostly type 2. GDM and type 2 diabetes share potential candidate genes. In about 1 % of GDM in Caucasian women a mutation in glucokinase gene had been found (GCK-MODY). Predisposition to GDM is predominantly characterized by family history of diabetes, previous GDM in pregnancies, factors of metabolic syndrome, and unfavorable life style. The probability for GDM rises with increasing mother's age and preconceptional BMI. Via fetal programming GDM dispones to offspring obesity as early as school entry. Prevention of GDM focus on regular physical exercise, normalizing body weight before conception, reducing excess intake of animal protein and soft drinks, planning of pregnancy in younger ages, and avoiding pollutant exposition as well as smoking cessation.

Identification and analysis of novel R308K mutation in glucokinase of type 2 diabetic patient and its kinetic correlation

Glucokinase (GK) plays a critical role in glucose homeostasis and the mutations in GK gene result in pathogenic complications known as Maturity Onset Diabetes of the Young 2, an autosomal dominant form of diabetic condition. In the present study, GK was purified from human liver tissue and the pure enzyme showed single band in SDS-PAGE with a molecular weight of 50 kDa. The kinetics of pure GK showed enzyme activity of 0.423±0.02 µM glucose-6-phosphate (G6P)/mL/Min and Km value of 6.66±0.02 µM. These values were compared in the liver biopsy of a clinically proven type 2 diabetic patient, where GK kinetics showed decreased enzyme activity of 0.16±0.025 µM G6P/mL/Min and increased Km of 23±0.9 µM, indicating the hyperglycemic condition in the patient. The genetic analysis of 10th exon of GK gene from this patient showed a R308K mutation. To substantiate these results, comparative molecular dynamics and docking studies were carried out where a higher docking score (-10.218 kcal/mol) was observed in the mutated GK than wild-type GK structure (-12.593 kcal/mol) indicating affinity variations for glucose. During the simulation process, glucose was expelled out from the mutant conformation but not from wild-type GK, making glucose unavailable for phosphorylation. Therefore, these results conclusively explain hyperglycemic condition in this patient.

Glucokinase Gene Mutations (MODY 2) in Asian Indians

Heterozygous inactivating mutations in the glucokinase (GCK) gene cause a hyperglycemic condition termed maturity-onset diabetes of the young (MODY) 2 or GCK-MODY. This is characterized by mild, stable, usually asymptomatic, fasting hyperglycemia that rarely requires pharmacological intervention. The aim of the present study was to screen for GCK gene mutations in Asian Indian subjects with mild hyperglycemia. Of the 1,517 children and adolescents of the population-based ORANGE study in Chennai, India, 49 were found to have hyperglycemia. These children along with the six patients referred to our center with mild hyperglycemia were screened for MODY 2 mutations. The GCK gene was bidirectionally sequenced using BigDye(®) Terminator v3.1 (Applied Biosystems, Foster City, CA) chemistry. In silico predictions of the pathogenicity were carried out using the online tools SIFT, Polyphen-2, and I-Mutant 2.0 software programs. Direct sequencing of the GCK gene in the patients referred to our Centre revealed one novel mutation, Thr206Ala (c.616A>G), in exon 6 and one previously described mutation, Met251Thr (c.752T>C), in exon 7. In silico analysis predicted the novel mutation to be pathogenic. The highly conserved nature and critical location of the residue Thr206 along with the clinical course suggests that the Thr206Ala is a MODY 2 mutation. However, we did not find any MODY 2 mutations in the 49 children selected from the population-based study. Hence prevalence of GCK mutations in Chennai is <1:1,517. This is the first study of MODY 2 mutations from India and confirms the importance of considering GCK gene mutation screening in patients with mild early-onset hyperglycemia who are negative for β-cell antibodies.

The spectrum ofHNF1Agene mutations in Greek patients with MODY3: relative frequency and identification of seven novel germline mutations

Maturity-Onset Diabetes of the Young (MODY) is the most common type of monogenic diabetes accounting for 1-2% of the population with diabetes. The relative incidence of HNF1A-MODY (MODY3) is high in European countries; however, data are not available for the Greek population. The aims of this study were to determine the relative frequency of MODY3 in Greece, the type of the mutations observed, and their relation to the phenotype of the patients. Three hundred ninety-five patients were referred to our center because of suspected MODY during a period of 15 yr. The use of Denaturing Gradient Gel Electrophoresis of polymerase chain reaction amplified DNA revealed 72 patients carrying Glucokinase gene mutations (MODY2) and 8 patients carrying HNF1A gene mutations (MODY3). After using strict criteria, 54 patients were selected to be further evaluated by direct sequencing or by multiplex ligation probe amplification (MLPA) for the presence of HNF1A gene mutations. In 16 unrelated patients and 13 of their relatives, 15 mutations were identified in the HNF1A gene. Eight of these mutations were previously reported, whereas seven were novel. Clinical features, such as age of diabetes at diagnosis or severity of hyperglycemia, were not related to the mutation type or location. In our cohort of patients fulfilling strict clinical criteria for MODY, 12% carried an HNF1A gene mutation, suggesting that defects of this gene are responsible for a significant proportion of monogenic diabetes in the Greek population. No clear phenotype-genotype correlations were identified.

Structural Variations of Human Glucokinase Glu256Lys in MODY2 Condition Using Molecular Dynamics Study

Glucokinase (GK) is the predominant hexokinase that acts as glucose sensor and catalyses the formation of Glucose-6-phosphate. The mutations in GK gene influence the affinity for glucose and lead to altered glucose levels in blood causing maturity onset diabetes of the young type 2 (MODY2) condition, which is one of the prominent reasons of type 2 diabetic condition. In view of the importance of mutated GK resulting in hyperglycemic condition, in the present study, molecular dynamics simulations were carried out in intact and 256 E-K mutated GK structures and their energy values and conformational variations were correlated. Energy variations were observed in mutated GK (3500 Kcal/mol) structure with respect to intact GK (5000 Kcal/mol), and it showed increased γ-turns, decreased β-turns, and more helix-helix interactions that affected substrate binding region where its volume increased from 1089.152 Å2 to 1246.353 Å2. Molecular docking study revealed variation in docking scores (intact = −12.199 and mutated = −8.383) and binding mode of glucose in the active site of mutated GK where the involvement of A53, S54, K56, K256, D262 and Q286 has resulted in poor glucose binding which probably explains the loss of catalytic activity and the consequent prevailing of high glucose levels in MODY2 condition.

SUMOylation of Pancreatic Glucokinase Regulates Its Cellular Stability and Activity*[S

Glucokinase is the predominant hexokinase expressed in hepatocytes and pancreatic β-cells, with a pivotal role in regulating glucose-stimulated insulin secretion, illustrated by glucokinase gene mutations causing monogenic diabetes and congenital hyperinsulinemic hypoglycemia. A complex tissue-specific network of mechanisms regulates this enzyme, and a major unanswered question in glucokinase biology is how post-translational modifications control the function of the enzyme. Here, we show that the pancreatic isoform of human glucokinase is SUMOylated in vitro, using recombinant enzymes, and in insulin-secreting model cells. Three N-terminal lysines unique for the pancreatic isoform (Lys-12/Lys-13 and/or Lys-15) may represent one SUMOylation site, with an additional site (Lys-346) common for the pancreatic and the liver isoform. SUMO-1 and E2 overexpression stabilized preferentially the wild-type human pancreatic enzyme in MIN6 β-cells, and SUMOylation increased the catalytic activity of recombinant human glucokinase in vitro and also of glucokinase in target cells. Small ubiquitin-like modifier conjugation represents a novel form of post-translational modification of the enzyme, and it may have an important regulatory function in pancreatic β-cells.

Analysis of the glucokinase gene in Iranian families with maturity onset diabetes of the young

Non insulin dependent diabetes mellitus (NIDDM) as a most common form of diabetes is a major public health problem; there is a subgroup of NIDDM patients who develop the disease at an early age and show a dominant mode of inheritance. This type is nominates Maturity onset diabetes of the young (MODY). The prevalence of MODY is difficult to access, and patients with MODY genes mutations are often identified during routine screening for other purposes. MODY2 was linked to glucokinase gene (GCK) mutations, and accounted for 8% to 56% of MODY, with the highest prevalence found in the southern Europe. The aim of this study was to examine the prevalence and nature of mutations in GCK gene in Iranian paients. We have screened GCK mutations by polymerase chain reaction (PCR); single stranded conformation polymorphism (SSCP) technique in 12 Iranian families with clinical diagnosis of MODY, included 30 patients (8 males and 22 females) and their 21 family members. PCR products with abnormal mobility in denaturing gradient gel electrophoresis (DGGE) were directly sequenced. We identified 6 novel mutations in GCK gene in Iranian families (corresponding to 36.6% prevalence). Our findings and the last study on MODY1 highlight that in addition to GCK, other MODY genes such as MODY3 and MODYX may play a significant role in diabetes characterized by monogenic autosomal dominant transmission. There is an important point that the genetic recognation can be used to pre-symptomatically identify family members at risk for developing MODY.

MODY 2: Mutation identification and molecular ancestry in a Brazilian family

Maturity Onset Diabetes of the Young (MODY) is a heterogeneous group of genetic diseases characterized by a primary defect in insulin secretion and hyperglycemia, non-ketotic disease, monogenic autosomal dominant mode of inheritance, age at onset less than 25years, and lack of auto-antibodies. It accounts for 2–5% of all cases of non-type 1 diabetes. MODY subtype 2 is caused by mutations in the glucokinase (GCK) gene. In this study, we sequenced the GCK gene of two volunteers with clinical diagnosis for MODY2 and we were able to identify four mutations including one for a premature stop codon (c.76C>T). Based on these results, we have developed a specific PCR-RFLP assay to detect this mutation and tested 122 related volunteers from the same family. This mutation in the GCK gene was detected in 21 additional subjects who also had the clinical features of this genetic disease. In conclusion, we identified new GCK gene mutations in a Brazilian family of Italian descendance, with one due to a premature stop codon located in the second exon of the gene. We also developed a specific assay that is fast, cheap and reliable to detect this mutation. Finally, we built a molecular ancestry model based on our results for the migration of individuals carrying this genetic mutation from Northern Italy to Brazil.

HbA1c‐based diabetes diagnosis among patients with glucokinase mutation (GCK‐MODY) is affected by a genetic variant of glucose‐6‐phosphatase (G6PC2)

Genetic variation at the rs560887 locus of the glucose-6-phosphatase, catalytic 2 gene (G6PC2) is known to affect regulation of fasting glycaemia. We determined the rs560887 genotype of patients with monogenic diabetes and glucokinase gene mutations (GCK-MODY) and correlated the genotypes with HbA(1c) levels. Patients from families with GCK-MODY were recruited from two large cohorts from Poland (n = 128) and the Czech Republic (n = 154). Genotypes at the rs560887 polymorphic site in G6PC2 were examined using real-time quantitative polymerase chain reaction. The effect of rs560887 genotype on age at diagnosis of GCK-MODY and initial HbA(1c) levels were evaluated separately within both cohorts. Following that, a meta-analysis of rs560887 genotype-HbA(1c) associations of both Polish and Czech cohorts was performed to confirm homogeneity of findings and validate cohort-specific results. GG homozygosity at rs560887 was associated with marginally elevated HbA(1c) levels (P = 0.07 in both cohorts). The effects observed in both groups were very homogeneous (Q = 0.18; P = 0.68). Meta-analysis showed that GG homozygosity at rs560887 was associated with mean HbA(1c) levels higher by 2.4 mmol/mol (0.24%), 95% CI 0.5-4.4 mmol/mol (0.05-0.44%) than in individuals with other genotypes. Additionally, meta-analysis of both cohorts showed that GG homozygous individuals had higher odds of reaching the 48 mmol/mol (6.5%) diagnostic threshold of diabetes; (odds ratio 1.90; 95% CI 1.07-3.36; P = 0.03). No such effects were observed for age at diagnosis of diabetes. Variation at the rs560887 locus of G6PC2 is associated with worse glycated haemoglobin levels in individuals with GCK mutations; GG homozygotes are more likely to meet diagnostic criteria for diabetes based on HbA(1c) level.

English

Background: Mutations in glucokinase (GK) gene results in maturity onset diabetes of the young 2 (MODY2). It has been observed that GK activators (GKAs) can activate GK structure and promote glucose phosphorylation and bring blood glucose levels to normal condition. The present study is aimed to identify the binding mode of pyridone derivatives (PDs) as GKAs through molecular docking study. Methods: GK structure was retrieved from the Protein Data Bank (PDB), protonated and energy minimized. A database was constructed with 29 PDs and docked into the allosteric site specified with Y61, R63, S69 and Y215 residues using Molecular Operating Environment (MOE) software. Docking conformations were generated using triangle match algorithm and ranked by London dG scoring function. The binding orientations and strength of interactions were evaluated by ligand interaction module of MOE. Results: Molecular docking of 29 PDs in allosteric site of GK gave reliable docking scores, interestingly arene cationic interactions were observed with the compounds PD1, PD12, PD20 and PD21. R63 residue of allosteric site played a predominant role in binding with PDs. Conclusions: PDs can be potentially useful agents in future management strategies of type 2 diabetes mellitus.

Gestational Diabetes Mellitus: Primum Non Nocere

Maturity-onset diabetes of the young (MODY) encompasses a collection of distinct forms of diabetes, which are inherited in an autosomal-dominant mode from the maternal or paternal side of the family or occasionally occur as a de novo mutation. All the genes involved affect either β-cell sensing or insulin secretion (1). The clinical presentations of MODY are heterogeneous, reflecting the different gene mutations involved, and the glucose dysregulation observed ranges from a relatively innocent rise in the fasting glucose to frank diabetes with neurological involvement (2,3). An exact MODY prevalence within the general diabetes population has proven difficult to assess because of underrecognition and lack of routinely available and affordable diagnostic tools. A further confounder is that the reported regional prevalence of specific MODY mutations varies considerably (4). Conservative estimates suggest that between 0.14–1.8% of all cases of diabetes could be attributable to MODY (4). It is to be expected that among women screened for gestational diabetes mellitus (GDM) the prevalence of MODY will be higher, reflecting both the proportionately lower prevalence of type 2 diabetes in women of this age group and the probability that those with undiagnosed MODY will screen positive (5). From the few population studies reported, mutations in the hepatocyte nuclear factor 1 α ( HNF1a ) gene (MODY 3) and glucokinase ( GCK ) gene (MODY 2) account for the majority of cases (6). MODY 2 is characterized by its high penetrance, early onset, and lifelong fasting hyperglycemia. It is due to mutations in the pancreatic GCK gene, which acts as the β-cell glucose sensor, setting the glucose threshold at which amplification of insulin …

Glucokinase (GCK) mutations and their characterization in MODY2 children of southern Italy.

Type 2 Maturity Onset Diabetes of the Young (MODY2) is a monogenic autosomal disease characterized by a primary defect in insulin secretion and hyperglycemia. It results from GCK gene mutations that impair enzyme activity. Between 2006 and 2010, we investigated GCK mutations in 66 diabetic children from southern Italy with suspected MODY2. Denaturing High Performance Liquid Chromatography (DHPLC) and sequence analysis revealed 19 GCK mutations in 28 children, six of which were novel: p.Glu40Asp, p.Val154Leu, p.Arg447Glyfs, p.Lys458_Cys461del, p.Glu395_Arg397del and c.580-2A>T. We evaluated the effect of these 19 mutations using bioinformatic tools such as Polymorphism Phenotyping (Polyphen), Sorting Intolerant From Tolerant (SIFT) and in silico modelling. We also conducted a functional study to evaluate the pathogenic significance of seven mutations that are among the most severe mutations found in our population, and have never been characterized: p.Glu70Asp, p.His137Asp, p.Phe150Tyr, p.Val154Leu, p.Gly162Asp, p.Arg303Trp and p.Arg392Ser. These seven mutations, by altering one or more kinetic parameters, reduced enzyme catalytic activity by >40%. All mutations except p.Glu70Asp displayed thermal-instability, indeed >50% of enzyme activity was lost at 50°C/30 min. Thus, these seven mutations play a pathogenic role in MODY2 insurgence. In conclusion, this report revealed six novel GCK mutations and sheds some light on the structure-function relationship of human GCK mutations and MODY2.

Low prevalence of glucokinase gene mutations in gestational diabetic patients with good glycemic control

Glucokinase (GCK) plays a key role in glucose homeostasis. Gestational diabetes mellitus increases the risk of gestational complications in pregnant women and fetuses. We screened for mutations in coding and flanking regions of the GCK gene in pregnant women with or without gestational diabetes in a Brazilian population. A sample of 200 pregnant women classified as healthy (control, N = 100) or with gestational diabetes (N = 100) was analyzed for mutations in the GCK gene. All gestational diabetes mellitus patients had good glycemic control maintained by diet alone and no complications during pregnancy. Mutations were detected by single-strand conformation polymorphism and DNA sequencing. Thirteen of the 200 subjects had GCK gene mutations. The mutations detected were in intron 3 (c.43331A>G, new), intron 6 (c.47702T>C, rs2268574), intron 9 (c.48935C>T, rs2908274), and exon 10 (c.49620G>A, rs13306388). None of these GCK mutations were found to be significantly associated with gestational diabetes mellitus. In summary, we report a low frequency of GCK mutations in a pregnant Brazilian population and describe a new intronic variation (c.43331A>G, intron 3). We conclude that mutations in GCK introns and in non-translatable regions of the GCK gene do not affect glycemic control and are not correlated with gestational diabetes mellitus.

Variability in the age at diagnosis of diabetes in two unrelated patients with a homozygous glucokinase gene mutation

Homozygous mutations in the glucokinase gene (GCK) result in a complete deficiency of the GCK enzyme, which leads to permanent neonatal diabetes mellitus. Whilst there has been one report of a patient (with a homozygous p.T168A) who was diagnosed with diabetes at the age of 2 months, all other cases were diagnosed with diabetes within the first 2 weeks of life. We now report a second unrelated patient with the same p.T168A GCK mutation who was diagnosed with diabetes at the age of 9 months. We conclude that the specific GCK mutation, as yet unidentified genetic modifiers, and/or environmental factors might have different effects on pancreatic beta-cell functions, causing variability in the age at diagnosis of diabetes.

Doubling the referral rate of monogenic diabetes through a nationwide information campaign - update on glucokinase gene mutations in a Polish cohort

In order to improve recruitment efficiency of patients with monogenic diabetes in Poland, in September 2010 a nationwide advertising campaign was launched to inform multiple target groups interested or participating in pediatric diabetologic care. Promotional actions aimed at informing physicians, patients, parents and educators were carried out through nationwide newspapers, medical and patient-developed websites and educational conference presentations. Recruitment efficiency was compared between September 2010 (publication of the first report on project's results) and the following 12 months. The number of families and patients referred to genetic screening was increased by 92% and 96% respectively nearly reaching the numbers recruited throughout the initial 4 years of the project. Participation of non-academic centers was also significantly increased from 2.3% to 7.5% (p = 0.0005). DNA sequencing and Multiplex Ligation-dependant Probe Amplification of the glucokinase gene resulted in finding 50 different mutations. Among those mutations, 19 were novel variants, which included: 17 missense mutations (predicted to be pathogenic according to bioinformatic analysis), 1 nonsense mutation and 1 mutation affecting a consensus intronic splice site. Advertising actions directed at increasing recruitment efficiency are a powerful and possibly neglected tool in screening for rare genetic disorders with a clinically defined phenotype.

Onset of type 1 diabetes mellitus in two patients with maturity onset diabetes of the young

The association between maturity onset diabetes of the young (MODY) and type 1 diabetes mellitus (T1DM) has been rarely described. We report two patients affected by MODY who developed T1DM. Case 1: a 4-yr-old girl referred for glycosuria presented hemoglobin A1c (HbA1c) of 6.6%. Islet cell antibodies (ICA) and anti-glutamic acid decarboxylase (GADA) were initially negative. As her father, uncle and grandmother showed mild hyperglycemia, they were screened for MODY 2. A novel mutation in glucokinase gene was found in the family. Few months later, her glycemic control worsened consistently and she required insulin treatment. A high titer of GADA and ICA was then detected. Six years afterwards insulin requirement is 0.8 U/kg and HbA1c 6.7%. Case 2: a 15-yr-old boy treated for growth hormone deficiency was found with a blood glucose level of 106 mg/dL. HbA1c was 7.2%, ICA and GADA were negative. Family history was positive for autoimmune diseases and type 2 diabetes mellitus. The patient was investigated for MODY 2 and MODY 3, and a mutation of hepatocyte nuclear factor-1 alpha gene was found. The same mutation was found in the mother who had never been referred for hyperglycemia. After 1 yr, due to an unjustified worsening of the metabolic control, autoimmunity was again investigated and a mild positivity was found. He then required insulin therapy and after 5 yr current HbA1c was 8.2%. The diagnosis of MODY does not exclude the risk of developing T1DM. Therefore autoimmunity should be investigated when ordinary treatments fail and metabolic control unexpectedly worsens.

67 Spontaneous cardiac hypertrophy and adverse LV remodelling in a novel human relevant mouse model of diabetes; a mechanistic insight

<h3></h3> Heart failure (HF) is one of the commonest cardiovascular complications of Diabetes Mellitus (DM) with the prevalence of DM reported at around 30% in many pivotal heart failure studies. DM is an independent predictor of mortality in patients with HF, however molecular mechanisms that contribute to HF development in the diabetic population are poorly understood. Using a novel human relevant mouse model of DM (GENA348), identified through the MRC mouse mutagenesis programme with a point mutation in the pancreatic glucokinase (GLK) gene we investigate the molecular mechanisms that contribute to the HF phenotype in DM. GLK is the glucose sensor which regulates insulin secretion and GLK activity is reduced by 90% by the GENA348 point mutation resulting in severe hyperglycaemia. Similar mutations underlie Maturity Onset Diabetes of the Young Type 2 (MODY 2) in humans. Mean random blood glucose was found to be increased in the GENA348 mutant (HO) mice compared to wild type (WT) littermates (WT 6.9±0.3 mmol/l vs HO 20.6±0.8 mmol/l, p&lt;0.001). Serial echocardiography was performed, at 3, 6 and 12 months. No significant changes in echocardiographic parameters were observed at 3 months, although by 6 months development of significant cardiac hypertrophy in HO mice was observed. At 12 months of age left ventricular dilatation was evident, characterised by an 8% increase in diastolic diameter (WT 4.08±0.10 vs HO 4.41±0.12, p&lt;0.05). Systolic function was preserved although significant diastolic dysfunction was evident at 6 and 12 months with a 31% reduction in the E:A ratio. Histological staining illustrated significant cellular hypertrophy with real time PCR data demonstrating a relative 150% increase in the hypertrophic marker BNP. Hypertrophic pathways were examined through western blot analysis revealing an age dependant increase in Akt phosphorylation (3 months- no increase, 6 months-140%, 12 months-460%). Serum levels of advanced glycation end products (AGE) were also elevated by 86% (WT 21±3.5 ng/ml vs HO 39±8.3 ng/ml, p&lt;0.05) as was the protein expression level of the receptor for AGEs (RAGE). In vitro cellular experiments also revealed AGEs directly activate Akt through phosphorylation and increase levels of the receptor RAGE. AGE induced phosphorylation of Akt is inhibited in the presence of wortmannin, suggesting a PI3K dependent signalling mechanism. This was further confirmed in vivo where a bolus injection of wortmannin in 6-month old mutant mice returned Akt phosphorylation levels to those seen in WT mice. In conclusion, using the first human relevant mouse model of diabetes, GENA348 we demonstrate the development of a progressive cardiac phenotype including cardiac hypertrophy, LV dilatation and diastolic dysfunction similar to the clinical manifestations of diabetic cardiomyopathy. We propose that the RAGE/PI3K/Akt pathway contributes to the molecular mechanisms associated with the cardiac phenotype.

Novel glucokinase mutations in patients with monogenic diabetes - clinical outline of GCK-MD and potential for founder effect in Slavic population

Glucokinase (GCK) gene mutations are the causative factor of GCK-MD (monogenic diabetes) characterized by a mild clinical phenotype and potential for insulin withdrawal. This study presents the results of a nationwide genetic screening for GCK-MD performed in Poland. A group of 194 patients with clinical suspicion of GCK-MD and 17 patients with neonatal diabetes were subjected to GCK sequencing. Patients negative for GCK mutations were subjected to multiplex ligation-dependent probe amplification (MLPA) to detect deletions or insertions. A total of 44 GCK heterozygous mutations were found in 68 probands (35%). Among those, 20 mutations were novel ones: A282fs, D198V, E158X, G246V, G249R, I348N, L165V, L315Q, M115I, N254S, P284fs, Q338P, R377L, R43C, R46S, S212fs, S212P, T255N, V406A and Y214D. No abnormalities were detected in MLPA analysis. Homozygous D278E mutation was found in one patient with neonatal diabetes. The most frequently observed combinations of symptoms typical for GCK-MD were mild diabetes and/or fasting hyperglycaemia (98.3%), positive C-peptide at diagnosis (76%) and dominant mode of inheritance (59%). This study outlines numerous novel mutations of the GCK gene present in white Caucasians of Slavic origin. Thorough clinical assessment of known factors associated with GCK-MD may facilitate patient selection.

Transient neonatal diabetes with two novel mutations in the KCNJ11 gene and response to sulfonylurea treatment in a preterm infant

Neonatal diabetes mellitus (NDM) is a rare condition that can be either transient or permanent. K(ATP) channel (Kir6.2 or SUR1) mutation, chromosome 6 abnormalities, insulin, or glucokinase gene mutations can lead to isolated NDM. Cases caused by Kir6.2 mutation usually result in permanent NDM (PNDM) rather than transient NDM (TNDM). The majority of patients with the Kir6.2 or SUR1 mutation can be successfully managed with a sulfonylurea agent, without the need for insulin. We report a preterm male with NDM having two novel missense mutations, E322A and D352H, in the KCNJ11 gene. At 2 months of age, successful transition from insulin to glibenclamide (glyburide) therapy of the patient was managed. At 5 months of age, his diabetes went in to remission.