Mutations In Glucokinase Gene Research Articles

Quantitative profiling and diagnostic potential of one-carbon and central metabolism pools in MODY2 and T1DM

BackgroundMaturity-onset diabetes of the young type 2 (MODY2) is a rare genetic disorder characterized as mild fasting hyperglycemia with low risk of vascular complications caused by glucokinase gene mutation. This study aims to investigate metabolites alteration associated with MODY2, exploring possible mechanism underlying characteristic clinical manifestations and low cardiovascular risks of MODY2 and providing serum metabolite biomarkers to facilitating MODY2 diagnosis.MethodsFasting serum samples from MODY2, type 1 diabetes (T1DM) and healthy individuals were collected. By using targeted metabolomics via liquid chromatography–tandem mass spectrometry platform, we quantified the metabolites involved in tricarboxylic acid (TCA) cycle and one-carbon metabolism.ResultsMetabolomic profiling revealed significant difference of intermediates from central metabolism cycle, methionine cycle and several amino acids between MODY2 and T1DM groups. Among these, serum citrate, α-ketoglutaric acid, serine, glycine, glutamine and homocysteine were significantly elevated in MODY2 patients compared with T1DM patients; and compared with healthy subjects, malate and methionine levels were significantly increased in the two groups of diabetic patients. The correlation analysis with clinical indexes showed that α- ketoglutarate, serine, glycine, and glutamine were negatively correlated with blood glucose indicators including fasting blood glucose, HbA1c, and GA, while citrate was positively correlated with C-peptide. And homocysteine displayed positive correlation with HDL and negative with C-reactive protein, which shed light on the mechanism of mild symptoms and low risk of cardiovascular complications in MODY2 patients. A panel of 4 metabolites differentiated MODY2 from T1DM with AUC of 0.924, and a combination of clinical indices and metabolite also gained good diagnostic value with AUC 0.948.ConclusionIn this research, we characterized the metabolite profiles of TCA cycle and one-carbon metabolism in MODY2 and T1DM and identified promising diagnostic biomarkers for MODY2. This study may provide novel insights into the pathogenesis and clinical manifestations of MODY2.

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.

Hepatic energy metabolism in a family with a glucokinase gene mutation and dysglycemia

Carriers heterozygous for the D124N (c.370, GAC > AAC in exon 4) variant of GCK not only exhibit reduced insulin-secretion, but also impaired adipose insulin sensitivity, which may shift fatty acids towards the liver. This could contribute to increased hepatic lipid-accumulation and alterations of liver energy metabolism resulting in dysglycemia.ClinicalTrial.gov registration no: NCT01055093.

TWO OPPOSITE PHENOTYPES OF GLUCOSE DISORDERS IN A FAMILY WITH HETEROZYGOUS P.SER453LEU (C.1358C> T) MUTATION IN THE GLUCOKINASE (GCK) GENE: MATURITY ONSET DIABETES IN YOUNG AND INSULINOMA.

Heterozygous gain-of-function mutations in the glucokinase (GCK) gene cause hyperinsulinaemic hypoglycaemia (GCK-HI), while loss-of-function mutations lead to a monogenic type of diabetes (GCK-MODY). We, herein, report a heterozygous GCK gene mutation in a large family with GCK-MODY and insulinoma in one individual from the same family. The proband, an 11-year-old male, was referred for asymptomatic mild hyperglycemia (fasting glucose:121 mg/dL) and HbA1c of 6.1%. Segregation analysis of the family revealed multiplex members with asymptomatic fasting hyperglycaemia or non-insulin-dependent diabetes and 33-year-old maternal uncle of the proband case had a history of distal pancreatectomy due to the diagnosis of insulinoma. His preoperative investigations were revealed fasting glucose of 31 mg/dL, insulin: 7µU/mL, C-peptide: 2.6 mg/dL, and a low HbA1c(4.0%) which was suggestive for recurring hypoglycaemia episodes. Post-pancreatectomy he developed mild fasting hyperglycemia (115-136 mg/dL). Genetic analysis revealed heterozygous p.Ser453Leu(c.1358C> T) mutation in the GCK gene in the proband. In segregation analysis, the identical heterozygous p.Ser453Leu(c.1358C> T) GCK gene mutation was detected in all of the other affected family members for whom a DNA analysis was applicable. The maternal uncle was first diagnosed with insulinoma and underwent a pancreatectomy. He also had an identical mutation in a heterozygous state. We, to the best of our knowledge, firstly identified these two entirely distinct phenotypes of glucose metabolism, GCK-MODY and GCK-HI, due to an identical heterozygous p.Ser453Leu (c.1358C> T) mutation in the GCK. Further studies required to elucidate this new phenomenon and understanding the genotype-phenotype relationship of GCK gene mutations.

Glucokinase Gene Mutations in Subjects with Gestational Diabetes Mellitus from Gaza Strip

Objective: This study was conducted in order to evaluate the frequency of GCK gene mutations in exons 7, 8 & 9 in women with Gestational Diabetes Mellitus (GDM) and their relationship to some biochemical parameters as compared to healthy controls.
 Methods: Samples were collected from 45 GDM women and 42 apparently healthy pregnant women. DNA was extracted and the samples were screened for GCK exons 7, 8 & 9 mutations at positions C.682A>G (p.Thr228Ala); C.895G>C (p.Gly299Arg) and C.1148C>A (p.Ser383X), respectively. The mutations were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methodology. Investigated biochemical features included: fasting blood glucose (FBG), oral glucose tolerance test (OGTT), HbA1c, insulin and the lipid profile.
 Results: The results showed that 9 out of the 45 (i.e., 20%) GDM subjects harbored the exon 8 (895G>C) mutation. Neither exon 7 (c.682A>G) nor exon 9 (c.1148C>A) was encountered in the study population. Moreover, the level of FBG, OGTT and HBA1c were higher in the c.895G>C mutation-positive subjects, as compared to mutation-negative ones.
 Conclusions: The screening of GDM patients for GCK gene mutations allowed for the identification of glucokinase-deficient patients diagnosed as GDM. Therefore, molecular screening is important for the differential diagnosis of GDM and MODY2 and consequently, proper patient management.

A novel mutation in GCK gene: Beware of SGA child with diabetic mother

MODY is a monogenic, autosomal dominant form of diabetes mellitus. MODY can be caused by mutations in several genes; glucokinase (GCK) accounts for 30–50% of the cases. The diagnosis can be suspected in early-onset diabetes with atypical features for type 1/type 2. Treatment is usually not recommended. A 5-year-old girl came to our attention for occasional episodes of hyperglycaemia. She was born at term, her birth weight was small for gestational age. At the beginning of her pregnancy, her mother was already on insulin therapy for impaired fasting glucose levels, detected before conception and confirmed in the first weeks of gestation. She was treated with insulin until the childbirth without further investigations. The patient was asymptomatic and in good clinical condition. Basal blood tests have shown a fasting plasma glucose of 125 mg/dl, an HbA1c of 6.5%. Antibodies against islet cells, anti-GAD and anti-ZNT8 antibodies were all negative. A 2-h oral glucose tolerance test was performed and underlined an impaired glucose tolerance. HLA haplotypes were screened, excluding susceptibility. GCK Sanger Sequencing identified a novel heterozygous variant. It is not described as a classical mutations. The analysis has been extended to the parents, finding out the same variant in her mother. To our knowledge this mutation has not been described previously; we believe that this variant is responsible for MODY2 due to FBG and Hb1Ac of all the affected members of family. We suggest high suspicion of an underlying GCK variant in SGA children with hyperglycaemia born to a diabetic mother.

Glucokinase activating mutation causing hypoglycaemia diagnosed late in adult who fasts for Ramadhan.

SummaryActivating mutation of glucokinase gene (GCK) causes resetting of insulin inhibition at a lower glucose threshold causing hyperinsulinaemic hypoglycaemia (GCK-HH). This is the first reported case who tolerated years of regular fasting during Ramadhan, presenting only with seizure and syncope now. We describe a case with GCK gene variant p.T65I diagnosed in a 51-year-old woman with hypoglycaemia unawareness even at glucose level of 1.6 mmol/L. Insulin and C-peptide levels during hypoglycaemia were suggestive of hyperinsulinism, but at a day after intravenous glucagon, hypoglycaemia occurred with low insulin and C-peptide levels, pointing against insulinoma as the underlying aetiology. Imaging studies of the pancreas and calcium arterial stimulation venous sampling were unremarkable. A review of old medical records revealed asymptomatic hypoglycaemia years ago. Genetic testing confirmed activating mutation of GCK. Hypoglycaemia was successfully controlled with a somatostatin analogue. This case highlights the importance of consideration of genetic causes of hypoglycaemia in adulthood, especially when imaging is uninformative.Learning pointsConsider genetic causes of endogenous hyperinsulinism hypoglycaemia in adulthood, especially when imaging is uninformative.Late presentation of activating mutation of GCK can occur because of hypoglycaemia unawareness.Long-acting somatostatin analogue may be useful for the treatment of activating mutation of GCK causing hypoglycaemia.Depending on the glucose level when the blood was taken, and the threshold of glucose-stimulated insulin release (GSIR), the serum insulin and C-peptide levels may be raised (hyperinsulinaemic) or low (hypoinsulinaemic) in patients with activating mutation of GCK.Glucagon may be useful to hasten the process of unmasking the low insulin level during hypoglycaemia below the GSIR level of which insulin released is suppressed.

Maturity onset diabetes of the young type 2 (MODY2): Insight from an extended family

AimsTo assess long-term outcome of patients with maturity onset diabetes of the young, type 2 (MODY2) in a unique large cohort of patients with the same genetic and environmental background. MethodsWe prospectively evaluated 162 patients aged 5 to 82 years, belonging to the same extended family living in the same village. All patients underwent molecular testing for the glucokinase (GCK) gene mutation identified in the proband, and were categorized into three groups (MODY2, type 2 diabetes and controls). ResultsThe 5.5-year-old proband had the c.1278_1286del mutation in the GCK and was diagnosed with MODY2. Forty-two out of 162 participants were positive for the mutation and 39 had type 2 diabetes. Patients were followed for a mean 10.2 ± 3.7 years (range 0–14). Mean fasting blood glucose and HbA1c increased significantly over the years in MODY2 patients (133 vs. 146 mg/dL; 6.9% vs. 8.2%, respectively). Increase in HbA1c occurred only in the obese/overweight subgroups. Twenty-five percent of MODY2 patients developed diabetes complications, all were above 40 years of age. ConclusionsAlthough MODY2 commonly has a benign disease course, weight gain is a risk factor for diabetes complications, requiring life-long follow-up and in some patients, medical intervention.

Genotype-Phenotype Characteristics of Turkish Children With Glucokinase Mutations Associated Maturity-Onset Diabetes of the Young

To investigate phenotype-genotype correlations in Turkish children with glucokinase gene mutations leading to Maturity-onset diabetes in young (GCK-MODY). Retrospective analysis of 40 patients (16 girls) aged under 18 with GCK-MODY. Mean (SD) serum fasting blood glucose level was 6.79 (0.59) mmol/L and the mean (SD) HbA1c level at diagnosis was 6.3% (0.5). Sixteen different variations were detected in the GCK genes of the 40 cases; 33 missense mutations, 6 deletions, and one nonsense mutation. The birthweight of infants with deletion mutation was significantly lower than that of infants with other mutations [2460 (353.66) g vs 2944.11 (502.08) g]. GCK-MODY patients with deletion mutation inherited from mothers had lower birthweight and higher fasting blood glucose than those with other inherited mutations but similar HbA1c values.

Genetic deletion of a short fragment of glucokinase in rabbit by CRISPR/Cas9 leading to hyperglycemia and other typical features seen in MODY-2.

Glucokinase (GCK) is a key enzyme in glucose sensing and glycemic regulation. In humans, mutations in the GCK gene cause maturity-onset diabetes of the young 2 (MODY-2), a disease that is characterized by an early-onset and persistent hyperglycemia. It is known that Gck knockout (KO) is lethal in mice with Gck KO mice dying within 2weeks after birth. Therefore, Gck KO mice are not suitable for preclinical study and have limited suitability to study the pathophysiological role of glucokinase in vivo. Here, we report the generation of a novel rabbit with a non-frameshift mutation of GCK gene (GCK-NFS) by cytoplasm microinjection of Cas9 mRNA and gRNA. These GCK-NFS rabbits showed typical features of MODY-2 including hyperglycemia and glucose intolerance with similar survival rate and weight compared to wild-type (WT) rabbits. The diabetic phenotype including pancreatic and renal dysfunction was also found in the F1-generation rabbits, indicating that the genetic modification is germline transmissible. Treatment of GCK-NFS rabbit with glimepiride successfully reduced the fasting blood glucose drastically and improved its islet function. In conclusion, this novel GCK mutant rabbit generated with the CRISPR/Cas9 system mimics most, if not all, histopathological and functional defects seen in MODY-2 patients such as hyperglycemia and will be a valuable rabbit model for preclinical studies and drug screening for diabetes as well as for studying the pathophysiological role of glucokinase.

Genetic Factors of Diabetes Mellitus

Diabetes mellitus is a disease in which pancreas fail to perform its work. In this condition, insulin is not produced in the amount as required for the normal function of the body. This led to different complication. And the results of many different diseases like kidney failure, high blood pressure, urination, blindness, stroke, heart attack, muscle dysfunction. Diabetes mellitus has two types: first is known as type 1 diabetes or Insulin-dependent diabetes. Second is known as type 2 diabetes or Non-insulin dependent diabetes mellitus. Most important is genetics which plays an important role in the development of diabetes. Other is environmental factors which are responsible for causing of disease by changing the gene patterns. In genetics, different genes are responsible for the causing of diabetes and these genes are present at a different position on a chromosome. In type 1 diabetes chromosome 6 and HLA complex, viral infection, physiological factors, environmental factors, and 60 genes are identified for causing of this disease. In type 2 diabetes environmental factor, 120 genetic loci, E23K polymorphism in the KCNG11 gene, Glucokinase gene mutation, epigenetics, TCF722, ABCC8, CAPN10, GIUT2, genes are responsible for the causing of disease of type 2 diabetes.

Genetic and clinical characteristics of Chinese children with Glucokinase-maturity-onset diabetes of the young (GCK-MODY)

BackgroundThere is scarcity of information on the clinical features and genetics of glucokinase-maturity-onset diabetes of the young (GCK-MODY) in China. The aim of the study was to investigate the clinical and molecular characteristics of Chinese children with GCK-MODY.MethodsEleven children with asymptomatic hyperglycemia and clinically suspected GCK-MODY were identified from the database of children with diabetes in the biggest children’s hospital in South China. Clinical data were obtained from medical records. Blood was collected from the patients and their parents for glucokinase (GCK) gene analysis. Parents without diabetes were tested for fasting glucose and HbA1c. Clinical information and blood for GCK gene analysis were obtained from grandparents with diabetes. GCK gene mutational analysis was performed by polymerase chain reaction and direct sequencing. Patients without a GCK gene mutation were screened by targeted next-generation sequencing (NGS) technology for other MODY genes.ResultsNine children tested positive for GCK gene mutations while two were negative. The nine GCK-MODY patients were from unrelated families, aged 1 month to 9 years and 1 month at first detection of hyperglycaemia. Fasting glucose was elevated (6.1–8.5 mmol/L), HbA1c 5.2–6.7% (33.3–49.7 mmol/mol), both remained stable on follow-up over 9 months to 5 years. Five detected mutations had been previously reported: p.Val182Met, c.679 + 1G > A, p.Gly295Ser, p.Arg191Gln and p.Met41Thr. Four mutations were novel: c.483 + 2 T > A, p.Ser151del, p.Met57GlyfsX29 and p.Val374_Ala377del. No mutations were identified in the other two patients, who were also tested by NGS.ConclusionsGCK gene mutations are detected in Chinese children and their family members with typical clinical features of GCK-MODY. Four novel mutations are detected.

The prevalence of monogenic diabetes in Australia: the Fremantle Diabetes Study Phase II.

To determine the prevalence of monogenic diabetes in an Australian community. Longitudinal observational study of a cohort recruited between 2008 and 2011. Urban population of 157 000 people (Fremantle, Western Australia). 1668 (of 4639 people with diabetes) who consented to participation (36.0% participation). Prevalence of maturity-onset diabetes of the young (MODY) and permanent neonatal diabetes in patients under 35 years of age, from European and non-European ethnic backgrounds, who were at risk of MODY according to United Kingdom risk prediction models, and who were then genotyped for relevant mutations. Twelve of 148 young participants with European ethnic backgrounds (8%) were identified by the risk prediction model as likely to have MODY; four had a glucokinase gene mutation. Thirteen of 45 with non-European ethnic backgrounds (28%) were identified as likely to have MODY, but none had a relevant mutation (DNA unavailable for one patient). Two patients with European ethnic backgrounds (one likely to have MODY) had neonatal diabetes. The estimated MODY prevalence among participants with diagnosed diabetes was 0.24% (95% confidence interval [CI], 0.08-0.66%), an overall population prevalence of 89 cases per million; the prevalence of permanent neonatal diabetes was 0.12% (95% CI, 0.02-0.48%) and the population prevalence 45 cases per million. One in 280 Australians diagnosed with diabetes have a monogenic form; most are of European ethnicity. Diagnosing MODY and neonatal diabetes is important because their management (including family screening) and prognosis can differ significantly from those for types 1 and 2 diabetes.

Glucokinase mutations in pediatric patients with impaired fasting glucose.

Our aim was to detect the frequency of glucokinase (GCK) gene mutations in a cohort of patients with impaired fasting glucose and to describe the clinical manifestations of identified variants. We also aimed at predicting the effect of the novel missense mutations by computational approach. Overall 100 unrelated Italian families with impaired fasting glucose were enrolled and subdivided into two cohorts according to strict and to mild criteria for diagnosis of maturity-onset diabetes of the young (MODY). GCK gene sequencing was performed in all participants. Fifty-three Italian families with 44 different mutations affecting the GCK and co-segregating with the clinical phenotype of GCK/MODY were identified. All mutations were in heterozygous state. In Sample 1, GCK defects were found in 32/36 (88.9%) subjects selected with strict MODY diagnostic criteria, while in Sample 2 GCK defects were found in 21/64 (32.8%) subjects selected with mild MODY diagnostic criteria. Our study enlarged the wide spectrum of GCK defects by adding 9 novel variants. The application of strict recruitment criteria resulted in 88.9% incidence of GCK/MODY, which confirmed it as the commonest form of MODY in the Italian population. In order to avoid misdiagnosis of GCK/MODY, it could be useful to perform molecular screening even if one or more clinical parameters for the diagnosis of MODY are missing. Computational analysis is useful to understand the effect of GCK defect on protein functionality, especially when the novel identified variant is a missense mutation and/or parents' DNA is not available.

An analysis of the sequence of the BAD gene among patients with maturity-onset diabetes of the young (MODY).

Monogenic diabetes is a rare disease caused by single gene mutations. Maturity onset diabetes of the young (MODY) is one of the major forms of monogenic diabetes recognised in the paediatric population. To date, 13 genes have been related to MODY development. The aim of the study was to analyse the sequence of the BCL2-associated agonist of cell death (BAD) gene in patients with clinical suspicion of GCK-MODY, but who were negative for glucokinase (GCK) gene mutations. A group of 122 diabetic patients were recruited from the "Polish Registry for Paediatric and Adolescent Diabetes - nationwide genetic screening for monogenic diabetes" project. The molecular testing was performed by Sanger sequencing. A total of 10 sequence variants of the BAD gene were identified in 122 analysed diabetic patients. Among the analysed patients suspected of MODY, one possible pathogenic variant was identified in one patient; however, further confirmation is required for a certain identification.

Diabetes in Pregnancy - Type 1/Type 2 Diabetes Mellitus and Gestational Diabetes Mellitus

In Germany in 5.5% of all births diabetes is registered. In patients with type 1 and type 2 diabetes planning pregnancy, preconception counseling, diabetologic care with optimized periconceptional metabolic control and folic acid supplementation are essential for good pregnancy outcome. Gestational diabetes (GDM) should be diagnosed timely and managed according to existing guidelines. GDM is treated with insulin in approximately 20%. In 1-2% of GDM cases a glucokinase gene mutation is present (MODY 2). Pregnancies after bariatric-metabolic surgery are increasing and show high risks.

Screening for Glucokinase (GCK) Gene Mutation in Gestational Diabetes Women in Western Region of Saudi Arabia

Screening for Glucokinase (GCK) Gene Mutation in Gestational Diabetes Women in Western Region of Saudi Arabia

Circulating ghrelin level is higher in HNF1A-MODY and GCK-MODY than in polygenic forms of diabetes mellitus.

Ghrelin is a hormone that regulates appetite. It is likely to be involved in the pathophysiology of varying forms of diabetes. In animal studies, the ghrelin expression was regulated by the hepatocyte nuclear factor 1 alpha (HNF1A). Mutations of the HNF1A gene cause maturity onset diabetes of the young (MODY). We aimed to assess the circulating ghrelin levels in HNF1A–MODY and in other types of diabetes and to evaluate its association with HNF1A mutation status. Our cohort included 46 diabetic HNF1A gene mutation carriers, 55 type 2 diabetes (T2DM) subjects, 42 type 1 diabetes (T1DM) patients, and 31 glucokinase (GCK) gene mutation carriers with diabetes as well as 51 healthy controls. Plasma ghrelin concentration was measured using the immunoenzymatic assay with polyclonal antibody against the C-terminal fragment of its acylated and desacylated forms. Ghrelin concentrations were 0.75 ± 0.32, 0.70 ± 0.21, 0.50 ± 0.20, and 0.40 ± 0.16 ng/ml in patients with HNF1A–MODY, GCK–MODY, T1DM, and T2DM, respectively. The ghrelin levels were higher in HNF1A–MODY and GCK–MODY than in T1DM and T2DM (p < 0.001 for all comparisons) but lower than in non-diabetic controls (1.02 ± 0.29 ng/ml, p < 0.001 for both comparisons). In the multivariate linear model, the differences between both MODY groups and common diabetes types remained significant. Analysis by a HNF1A mutation type indicated that ghrelin concentration is similar in patients with different types of sequence differences. Plasma ghrelin level is higher in HNF1A–MODY and GCK–MODY than in the common polygenic forms of diabetes.

Intima-media thickness and endothelial dysfunction in GCK and HNF1A-MODY patients.

Mutations in the glucokinase (GCK) gene, along with hepatocyte nuclear factor 1A (HNF1A) gene mutations, are the most frequent cause of maturity-onset diabetes of the young (MODY). GCK-MODY patients are typically characterized by a moderate fasting hyperglycemia; however, little is known about atherosclerosis and intermediate-related phenotypes in these subjects. To examine carotid artery intima-media thickness (IMT) and endothelial function assessed by brachial artery flow-mediated dilatation (FMD) in GCK gene mutations carriers and HNF1A-MODY. A total of 64 subjects with GCK gene mutations, and 52 HNF1A gene mutation carriers as well as 53 nondiabetic controls were examined. IMT and FMD were assessed by ultrasonography. Appropriate statistical tests were performed to assess differences between the groups, and multivariate linear regression was done for the association with IMT and FMD. The clinical characteristics of all groups were similar with the mean age at examination of 35.1, 41.1, and 39.5 years for GCK, HNF1A and the control group respectively. The highest mean IMT value was in the HNF1A-MODY group: 7.0±1.4 mm, whereas it reached 6.3±1.4 mm in GCK mutation carriers and 6.3±1.3 mm in controls (P=0.008). After adjustment for possible clinical and biochemical cofounders, IMT remained higher in HNF1A-MODY patients as compared with GCK-MODY patients (P=0.02) and controls (P=0.0003). FMD was significantly lower in HNF1A (9.9±4.6%) and GCK-MODY (11.1±4.6%) patients in comparison with controls (13.9±4.7%; P=0.0001). After adjustment, FMD remained lower in HNF1A-MODY (P=0.0005) and GCK-MODY patients (P=0.01) as compared with controls. Both examined MODY groups demonstrated evidence of endothelial dysfunction. In addition, HNF1-MODY patients seem to be more prone to an early atherosclerotic phenotype.

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 &amp; Sons, Ltd.