Sonia Toni

Seven mutations in the human insulin gene linked to permanent neonatal/infancy-onset diabetes mellitus

Permanent neonatal diabetes mellitus (PNDM) is a rare disorder usually presenting within 6 months of birth. Although several genes have been linked to this disorder, in almost half the cases documented in Italy, the genetic cause remains unknown. Because the Akita mouse bearing a mutation in the Ins2 gene exhibits PNDM associated with pancreatic beta cell apoptosis, we sequenced the human insulin gene in PNDM subjects with unidentified mutations. We discovered 7 heterozygous mutations in 10 unrelated probands. In 8 of these patients, insulin secretion was detectable at diabetes onset, but rapidly declined over time. When these mutant proinsulins were expressed in HEK293 cells, we observed defects in insulin protein folding and secretion. In these experiments, expression of the mutant proinsulins was also associated with increased Grp78 protein expression and XBP1 mRNA splicing, 2 markers of endoplasmic reticulum stress, and with increased apoptosis. Similarly transfected INS-1E insulinoma cells had diminished viability compared with those expressing WT proinsulin. In conclusion, we find that mutations in the insulin gene that promote proinsulin misfolding may cause PNDM.

High prevalence of glucokinase mutations in Italian children with MODY. Influence on glucose tolerance, first-phase insulin response, insulin sensitivity and BMI

Aims/hypothesis. The aim of this study was to assess the prevalence of glucokinase gene mutations in Italian children with MODY and to investigate genotype/phenotype correlations of the mutants. Methods. Screening for sequence variants in the glucokinase gene was performed by denaturing gradient gel electrophoresis and direct sequencing in 132 children with maturity onset diabetes of the young (MODY) and in 9 children with chronic fasting hyperglycaemia but without laboratory evidence for Type I (insulin-dependent) diabetes mellitus and with normoglycaemic parents (“non-classical” MODY). Results. Altogether 54 mutations were identified in the MODY group (54/132 or 41 %) and 3 among the “non-classical” MODY individuals (3/9 or 33 %). Paternity testing indicated that the latter mutations have arisen de novo. Mean fasting plasma glucose concentrations of the children with the mutant glucokinase was in the expected impaired fasting glucose range. In contrast, results of the oral glucose tolerance test showed a wide range from normal glucose tolerance (Group 1: 2-h OGTT = 6.7 ± 1.1 mmol/l; 11 patients) to diabetes (Group 2: 2-h OGTT = 11.5 ± 0.5 mmol/l; 9 patients), with the remaining in the impaired glucose tolerance range. Disruptive mutations (i. e. nonsense, frameshifts, splice-site) were equally represented in Groups 1 and 2 and were not clearly associated with an impaired first-phase insulin response. Surprisingly, 5 out of 11 children (or 45 %) in Group 1 were found to be overweight but no children in Group 2 were overweight. Sensitivity index (SI), calculated by a recently described method, was found to be significantly lower in Group 2 than in Group 1 (SI Group 2 = 0.0013 ± 0.0009 ml Kg–1 min–1/μU/ml; SI Group 1 = 0.0068 ± 0.0048, p < 0.0035). Conclusion/interpretation. Mutations in glucokinase are the first cause of MODY among Italian children selected through a low threshold limit of fasting plasma glucose (i. e. > 5.5 mmol). The lack of correlation between the molecular severity of glucokinase mutations, insulin secretion at intravenous glucose tolerance test and differences in glucose tolerance suggests that factors outside the beta cell are also involved in determining post-load glucose concentrations in these subjects. Our results seem to indicate that the differences observed in the 2-h responses at the OGTT among children with MODY 2 could be related to individual differences in insulin sensitivity. [Diabetologia (2001) 44: 898–905]

A cross‐sectional international survey of continuous subcutaneous insulin infusion in 377 children and adolescents with type 1 diabetes mellitus from 10 countries

Objective:  To document current practices using continuous subcutaneous insulin infusion (CSII) by downloading electronically the 90‐d pump data held within the pump memory and relating that to clinical data from children and adolescents in different pediatric diabetes centers from Europe and Israel.

Maturity-onset diabetes of the young in children with incidental hyperglycemia: a multicenter Italian study of 172 families

OBJECTIVE To investigate the prevalence of maturity-onset diabetes of the young (MODY) in Italian children with incidental hyperglycemia. RESEARCH DESIGN AND METHODS Among 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. RESULTS We 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. CONCLUSIONS GCK mutations are the prevailing cause of MODY (63.4%) when the index case is recruited in Italian children with incidental hyperglycemia.

Use of integrated real-time continuous glucose monitoring/insulin pump system in children and adolescents with type 1 diabetes: A 3-year follow-up study

BACKGROUND Insulin pumps and real-time continuous glucose monitoring devices have recently been combined into the sensor-augmented pump (SAP) system. The objective of this study was the evaluation of the clinical use of SAP in a large series of children with type 1 diabetes using insulin pump therapy. METHODS A questionnaire was administered in all pediatric diabetologic centers in Italy; data were analyzed only regarding patients 18 years old or younger and using SAP for 6 months or more. RESULTS Among all patients using an insulin pump, 129 (13.5 ± 3.8 years old, with a disease duration of 6.3 ± 3.4 years) have been using SAP for 1.4 ± 0.7 years. Four hundred ninety-three patients (12.9 ± 3.4 years old, with a disease duration of 6.2 ± 3.3 years) using conventional insulin pump therapy for 1.7 ± 0.5 years have been evaluated as the control group. After 0.5-3 years of using SAP or conventional insulin pump therapy, glycosylated hemoglobin significantly improved (8.0 ± 1.5% vs. 7.4 ± 0.8% [P = 0.002] and 8.0 ± 1.6% vs. 7.7 ± 1.1% [P = 0.006], respectively); the improvement was higher with SAP (P = 0.005). Insulin requirement showed a significant decrease only in SAP patients (0.88 ± 0.25 vs. 0.7 ± 0.23 U/kg/day, P = 0.003). Body mass index did not change during the observation period. No diabetic ketoacidosis episodes were observed during the follow-up, and severe hypoglycemia significantly decreased in SAP patients (P = 0.04). CONCLUSIONS The increased availability of continuous glucose sensors is likely to have a significant impact on pediatric diabetes therapy and education in the near future. In daily settings, patients using SAP can achieve a better control than patients using conventional insulin pump.

Blood ketone bodies in patients with recent‐onset type 1 diabetes (a multicenter study)

Background:  Insulin deficiency with glucagon excess leads to the release of ketone bodies (KBs) by the liver and excretion in the urine. So far, only KB monitoring in urine has been used during assessment of children with diabetes. Currently used nitroprusside strips for urine KB detection react only with acetoacetate (AcAc) and not with the most prevalent KB moiety – 3β‐hydroxybutyrate (3HB) – that is in equilibrium with AcAc (up to 10:1 ratio).

Type 1 diabetes and measles, mumps and rubella childhood infections within the Italian Insulin-dependent Diabetes Registry

Diabet. Med. 29, 761–766 (2012)

Opposite clinical phenotypes of glucokinase disease: Description of a novel activating mutation and contiguous inactivating mutations in human glucokinase (GCK) gene

Glucokinase is essential for glucose-stimulated insulin release from the pancreatic beta-cell, serving as glucose sensor in humans. Inactivating or activating mutations of glucokinase lead to different forms of glucokinase disease, i.e. GCK-monogenic diabetes of youth, permanent neonatal diabetes (inactivating mutations), and congenital hyperinsulinism, respectively. Here we present a novel glucokinase gene (GCK)-activating mutation (p.E442K) found in an infant with neonatal hypoglycemia (1.5 mmol/liter) and in two other family members suffering from recurrent hypoglycemic episodes in their childhood and adult life. In contrast to the severe clinical presentation in the index case, functional studies showed only a slight activation of the protein (relative activity index of 3.3). We also report on functional studies of two inactivating mutations of the GCK (p.E440G and p.S441W), contiguous to the activating one, that lead to monogenic diabetes of youth. Interestingly, adult family members carrying the GCK pE440G mutation show an unusually heterogeneous and progressive diabetic phenotype, a feature not typical of GCK-monogenic diabetes of youth. In summary, we identified a novel activating GCK mutation that although being associated with severe neonatal hypoglycemia is characterized by the mildest activation of the glucokinase enzyme of all previously reported.

Insulin Pump Therapy Management in Very Young Children with Type 1 Diabetes Using Continuous Subcutaneous Insulin Infusion

BACKGROUND Compared to older children and adolescents very young patients with type 1 diabetes represent a unique population. We analyzed the age-dependent characteristics and parameters of continuous subcutaneous insulin infusion (CSII) in children under 6 years of age with type 1 diabetes. METHODS We evaluated metabolic control and pump-dependent characteristics in 46 children with type 1 diabetes after 0.89 +/- 0.62 years of CSII. RESULTS Metabolic control significantly improved after CSII initiation (glycosylated hemoglobin, 8.12 +/- 1.24% vs. 7.30 +/- 0.67%; P < 0.05), without increased risk for diabetic ketoacidosis or hypoglycemia. Interestingly, very young patients required bigger boluses than expected, especially in the morning and at the afternoon snack. CONCLUSIONS These data support the need to personalize pump-dependent characteristics, especially in very young children with type 1 diabetes, in order to optimize CSII therapy in this unique age group of patients.

The role of joint mobility in evaluating and monitoring the risk of diabetic foot ulcer

AIMS Evaluation of how ankle joint mobility (AJM) can be useful in the identification of patients with diabetes at risk of foot ulcer (FU). METHODS Plantar and dorsal flexion of foot were evaluated using an inclinometer in 87 patients (54 type 2 and 33 type 1), and 35 healthy sex- and age-matched control subjects. Patients with diabetes were followed up for diagnosis of FU over the next 8 years and subsequently, patients were subdivided into: those without a history of FU (18 type 1 and 33 type 2), those who had a history of FU detected before baseline evaluation (14 type 2) and those who had history of first ulceration detected by the 8th year of the evaluation period (7 type 2). RESULTS Aging and diabetes caused a significant reduction in mobility of each of the movements investigated (p<0.001), whereas after adjusting for the confounding effect of age, diabetes specifically reduced plantar flexion (p<0.0001). AJM was significantly lower in those with history of previous FU compared to all the other groups (p<0.001). The first ulceration was detected in the same foot presenting lower AJM in 17 of the 22 subjects with diabetes with history of ulcer (77.27%). CONCLUSIONS Diabetes and aging reduce AJM although diabetes seems to reduce plantar flexion to a more specific extent. Reduced AJM is mostly associated with a previous history of FU. The evaluation of AJM is a valid and reliable ulcer risk scale that indicates which foot is at higher ulcer risk.