Glucokinase (GCK) serves as the pancreatic glucose sensor. Heterozygous inactivating GCK mutations cause hyperglycemia, whereas activating mutations cause hypoglycemia. We studied the GCK V62M mutation identified in two families and co-segregating with hyperglycemia to understand how this mutation resulted in reduced function. Structural modeling locates the mutation close to five naturally occurring activating mutations in the allosteric activator site of the enzyme. Recombinant glutathionyl S-transferase-V62M GCK is paradoxically activated rather than inactivated due to a decreased S 0.5 for glucose compared with wild type (4.88 versus 7.55 mM). The recently described pharmacological activator (RO0281675) interacts with GCK at this site. V62M GCK does not respond to RO0281675, nor does it respond to the hepatic glucokinase regulatory protein (GKRP). The enzyme is also thermally unstable, but this lability is apparently less pronounced than in the proven instability mutant E300K. Functional and structural analysis of seven amino acid substitutions at residue Val 62 has identified a non-linear relationship between activation by the pharmacological activator and the van der Waals interactions energies. Smaller energies allow a hydrophobic interaction between the activator and glucokinase, whereas larger energies prohibit the ligand from fitting into the binding pocket. We conclude that V62M may cause hyperglycemia by a complex defect of GCK regulation involving instability in combination with loss of control by a putative endogenous activator and/or GKRP. This study illustrates that mutations that cause hyperglycemia are not necessarily kinetically inactivating but may exert their effects by other complex mechanisms. Elucidating such mechanisms leads to a deeper understanding of the GCK glucose sensor and the biochemistry of ␤-cells and hepatocytes. Glucokinase (GCK)1 plays a critical role in the regulation of insulin secretion and has been termed the pancreatic ␤-cell glucose sensor on account of its kinetics, which allow the ␤-cells to change glucose phosphorylation rate over a range of physiological glucose concentrations. These kinetic characteristics are the enzyme's low affinity for glucose (S 0.5 ϳ 7.5 mM), cooperativity with glucose (Hill number of ϳ1.7), and lack of inhibition by its product glucose 6-phosphate. Glucokinase plays an important role in glucose sensing not only in the pancreatic ␤-cell but also in the liver and a variety of neural/neuroendocrine cells. These include the pancreatic ␣-cell, L-and K-type gut enterocytes, and certain rare neurons in the central nervous system, mainly in the hypothalamus (1-3). It is the sum of its actions in these multiple sites that ultimately determines the blood glucose concentration. In the liver glucokinase is regulated by glucokinase regulatory protein (GKRP), which acts as a competitive inhibitor with respect to glucose (4, 5). In addition to this role GKRP also determines the subcellular location of glucokinase within the liver cell (6). Glucokinase tra...

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Monogenic diabetes is highly prevalent in patients referred to Italian pediatric diabetes centers. A genetic diagnosis guided the therapeutic decisions, allowed the formulation of a prognosis regarding chronic diabetic complications for a relevant number of patients (i.e.,GCK/MODY), and helped to provide genetic counseling.

BackgroundWolfram Syndrome type 2 (WFS2) is considered a phenotypic and genotypic variant of WFS, whose minimal criteria for diagnosis are diabetes mellitus and optic atrophy. The disease gene for WFS2 is CISD2. The clinical phenotype of WFS2 differs from WFS1 for the absence of diabetes insipidus and psychiatric disorders, and for the presence of bleeding upper intestinal ulcers and defective platelet aggregation. After the first report of consanguineous Jordanian patients, no further cases of WFS2 have been reported worldwide. We describe the first Caucasian patient affected by WFS2.Case presentationThe proband was a 17 year-old girl. She presented diabetes mellitus, optic neuropathy, intestinal ulcers, sensorineural hearing loss, and defective platelet aggregation to ADP. Genetic testing showed a novel homozygous intragenic deletion of CISD2 in the proband. Her brother and parents carried the heterozygous mutation and were apparently healthy, although they showed subclinical defective platelet aggregation. Long runs of homozygosity analysis from SNP-array data did not show any degree of parental relationship, but the microsatellite analysis confirmed the hypothesis of a common ancestor.ConclusionOur patient does not show optic atrophy, one of the main diagnostic criteria for WFS, but optic neuropathy. Since the “asymptomatic” optic atrophy described in Jordanian patients is not completely supported, we could suppose that the ocular pathology in Jordanian patients was probably optic neuropathy and not optic atrophy. Therefore, as optic atrophy is required as main diagnostic criteria of WFS, it might be that the so-called WFS2 could not be a subtype of WFS. In addition, we found an impaired aggregation to ADP and not to collagen as previously reported, thus it is possible that different experimental conditions or inter-patient variability can explain different results in platelet aggregation. Further clinical reports are necessary to better define the clinical spectrum of this syndrome and to re-evaluate its classification.

Recent advances in information and communication technology allow the design and testing of new models of diabetes management, which are able to provide assistance to patients regardless of their distance from the health care providers. The M2DM project, funded by the European Commission, has the specific aim to investigate the potential of novel telemedicine services in diabetes management. A multi-access system based on the integration of Web access, telephone access through interactive voice response systems, and the use of palmtops and smart modems for data downloading has been implemented. The system is based on a technological platform that allows a tight integration between the access modalities through a middle layer called the multi-access organizer. Particular attention has been devoted to the design of the evaluation scheme for the system: A randomized controlled study has been defined, with clinical, organizational, economic, usability, and users' satisfaction outcomes. The evaluation of the system started in January 2002. The system is currently used by 67 patients and seven health care providers in five medical centers across Europe. After 6 months of usage of the system no major technical problems have been encountered, and the majority of patients are using the Web and data downloading modalities with a satisfactory frequency. From a clinical viewpoint, the hemoglobin A1c (HbA1c) of both active patients and controls decreased, and the variance of HbA1c in active patients is significantly lower than the control ones. The M2DM system allows for the implementation of an easy-to-use, user-tailored telemedicine system for diabetes management. The first clinical results are encouraging and seem to substantiate the hypothesis of its clinical effectiveness.

OBJECTIVETo investigate the prevalence of maturity-onset diabetes of the young (MODY) in Italian children with incidental hyperglycemia.RESEARCH DESIGN AND METHODSAmong 748 subjects age 1–18 years with incidental hyperglycemia, minimal diagnostic criteria for MODY were met by 172 families. Mutational analyses of the glucokinase (GCK) and hepatocyte nuclear factor 1α (HNF1Α) genes were performed.RESULTSWe identified 85 GCK gene mutations in 109 probands and 10 HNF1Α mutations in 12 probands. In GCK patients, the median neonatal weight and age at the first evaluation were lower than those found in patients with HNF1A mutations. Median fasting plasma glucose and impaired fasting glucose/impaired glucose tolerance frequency after oral glucose tolerance testing were higher in GCK patients, who also showed a lower frequency of diabetes than HNF1A patients.CONCLUSIONSGCK mutations are the prevailing cause of MODY (63.4%) when the index case is recruited in Italian children with incidental hyperglycemia.

Coeliac disease (CD) is heterogeneous in its clinical presentation and pathological expression. Silent, latent and potential forms represent the submerged part of the so-called "coeliac iceberg". The association of insulin-dependent diabetes mellitus (IDDM) and CD has been widely reported. For the screening of CD in diabetic patients, anti-reticulin R1 (ARA-R1) and anti-endomysium (AEA) antibodies are more reliable markers than anti-gliadin (AGA) antibodies. Recent studies have reported an increased prevalence of CD in children with IDDM. In our experience intestinal biopsy confirmed a diagnosis of CD in 6 out of 172 diabetic patients, with a prevalence of 3.5%. Only occasionally does CD precede the onset of IDDM; more often CD is diagnosed shortly or sometimes years after the onset of diabetes. Typical gastrointestinal complaints of CD (such as diarrhoea, abdominal distension) are rare in IDDM patients, while atypical isolated signs or symptoms of CD are more common, in particular sideropenic anemia, short stature, delayed puberty, epilepsy, hypertransaminasemia, dyspeptic symptoms, herpetiform dermatitis, and recurrent aphthous stomatitis. It is recommended that all diabetic children, even those asymptomatic, should be screened yearly for CD, using a combination of AGA plus ARA-R1 and AEA.

Diabetic patients have increased chances of developing autoimmune thyroid disease. Thyroid autoantibodies (Th-AAb) are more frequent in IDDM children than in the general population, ranging between 7 and 40%. As markers of thyroid autoimmunity, we assessed Th-AAb (MsA and TgA) cross-sectionally in 212 children and adolescents (93 girls and 119 boys) aged 1.2-21 years with IDDM from 0-18 years, and longitudinally in 90/212 (43 girls and 47 boys) at diagnosis and during a 3-10 year follow-up. In the cross-sectional study Th-AAb were found in 22/93 girls (23.7%) and 13/119 boys (10.9%). In the longitudinal study Th-AAb were observed at diagnosis in 6 patients, and during the follow-up in 9 girls. In 11/15 Th-AAb positive patients anti-nuclear antibodies were also present. Hormonal assessment revealed hypothyroidism in 3 girls (afterwards on replacement therapy), thyroid ultrasonography showed abnormal patterns in 5 girls, fine needle aspiration biopsy confirmed Hashimoto's thyroiditis in 9 (8 girls and 1 boy), with a higher frequency than that reported among healthy subjects (1-2%). Thyrotoxicosis also occurs with increased frequency in diabetic children than in the general population. We observed Graves' disease in only 1/212 IDDM patients, a 13 year-old boy in whom thyrotoxicosis developed 4 years after diabetes was diagnosed. The high prevalence of thyroid autoimmunity in our patients, particularly in females, suggests that diabetic children and adolescents should be screened for thyroid autoimmunity even if asymptomatic for hypo- or hyperthyroidism. Patients with IDDM and autoimmune thyroid disease should be evaluated for autoantibodies against other organs, such as adrenal glands and gastric mucosa. It is known that patients affected by type 1 (insulin-dependent) diabetes mellitus (IDDM) may have autoantibodies against different organs, such as thyroid, adrenal glands, gastric mucosa, parathyroid, with or without evident dysfunction of the target organ /1-8/. Among organ-specific disorders, autoimmune thyroid disease (ATD) is frequently associated with IDDM and the presence of thyroid autoantibodies (Th-AAb) has been considered a risk factor for the development of hypo- or hyperthyroidism /9/.