Franco Cerutti

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]

Insulin resistance and hyperinsulinemia in homozygous β-thalassemia☆

Abstract Insulin resistance and hyperinsulinemia have been reported in homozygous β-thalassemia before the development of diabetes. However, insulin sensitivity (S l ) has never been studied in normoinsulinemic patients. Furthermore, whether hyperinsulinemia is due to increased β-cell secretion or to decreased hepatic insulin extraction is poorly understood. We estimated S l β-cell secretion, and hepatic insulin extraction using the minimal model analysis of a frequently sampled intravenous glucose tolerance test (2.8 g/m 2 ) in two groups of nondiabetic pubertal patients with homozygous β-thalassemia (seven hyperinsulinemic and seven normoinsulinemic patients) and seven control subjects matched for age, body mass index, and pubertal stage. In both thalassemic groups, S l was reduced by approximately 40% (3.52 ± 0.57 and 3.74 ± 0.66 v 6.89 ± 1.02 10 −4 · min − [μU/mL], P = .011) and was inversely correlated with iron overload ( r = −.707, P = .006). All parameters of β-cell secretion were not significantly different in patients and controls. On the other hand, basal posthepatic insulin delivery (BDR) was more than doubled in hyperinsulinemic patients with respect to normoinsulinemic patients or controls (15.1 ± 2.4 v 6.1 ± 1.1 and 7.5 ± 2.3 pmol/L · min −1 , P = .012), and the same was true for total posthepatic insulin delivery ([TID] 6.3 ± 1.0 v 2.9 ± 0.5 and 2.9 ± 0.7 pmol/L · 240 min −1 , P = .015). Hepatic insulin extraction was significantly lower in hyperinsulinemic patients than in normoinsulinemic patients or controls (49.3% ± 9.4% v 73.0% ± 3.7% and 77.4% ± 3.9%, P = .011), and in patients it was inversely correlated with iron overload ( r = −.829, P = .0001). In conclusion, insulin resistance is present even in normoinsulinemic patients, β-cell responsiveness to glucose is normal, and hyperinsulinemia is mainly due to decreased hepatic insulin extraction. In nondiabetic thalassemic patients, these defects are possibly related to iron overload.

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.

Sulfonylurea treatment outweighs insulin therapy in short-term metabolic control of patients with permanent neonatal diabetes mellitus due to activating mutations of the KCNJ11 (KIR6.2) gene

To the Editor, Activating missense mutations in the gene encoding potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) represent the most common cause (40 to 64%, depending on populations) of permanent neonatal diabetes mellitus in patients diagnosed in the first 6 months of life [1, 2]. In addition, KCNJ11 activating mutations can lead to transient/relapsing neonatal diabetes [3, 4]. The KCNJ11 gene encodes the pore-forming subunit (also known as KIR6.2) of the pancreatic beta cell ATP-sensitive potassium channel (KATP), which exerts a pivotal role in glucose-regulated insulin release. In the beta cell, KIR6.2 forms a hetero-octameric complex (4:4) with the sulfonylurea receptor subtype 1 (SUR1); binding to SUR1 by sulfonylureas determines channel closure and insulin secretion [2]. In previously published cases, seven patients have been reported to respond well to the transfer from insulin to oral hypoglycaemic agents [4–8]. Here we report on the replacement of insulin with sulfonylureas in ten Italian children who have mutations in KCNJ11 (R50P, V59M [x4], K170R, R201C and R201H [x3]) and were followed in nine Diabetologia (2006) 49:2210–2213 DOI 10.1007/s00125-006-0329-x

Mutations at the same residue (R50) of Kir6.2 (KCNJ11) that cause neonatal diabetes produce different functional effects.

Heterozygous mutations in the human Kir6.2 gene (KCNJ11), the pore-forming subunit of the ATP-sensitive K+ channel (KATP channel), are a common cause of neonatal diabetes. We identified a novel KCNJ11 mutation, R50Q, that causes permanent neonatal diabetes (PNDM) without neurological problems. We investigated the functional effects this mutation and another at the same residue (R50P) that led to PNDM in association with developmental delay. Wild-type or mutant Kir6.2/SUR1 channels were examined by heterologous expression in Xenopus oocytes. Both mutations increased resting whole-cell currents through homomeric and heterozygous KATP channels by reducing channel inhibition by ATP, an effect that was larger in the presence of Mg2+. However the magnitude of the reduction in ATP sensitivity (and the increase in the whole-cell current) was substantially larger for the R50P mutation. This is consistent with the more severe phenotype. Single–R50P channel kinetics (in the absence of ATP) did not differ from wild type, indicating that the mutation primarily affects ATP binding and/or transduction. This supports the idea that R50 lies in the ATP-binding site of Kir6.2. The sulfonylurea tolbutamide blocked heterozygous R50Q (89%) and R50P (84%) channels only slightly less than wild-type channels (98%), suggesting that sulfonylurea therapy may be of benefit for patients with either mutation.

Increasing trend of type I diabetes in children and young adults in the province of Turin (Italy). Analysis of age, period and birth cohort effects from 1984 to 1996.

Aims/hypothesis. This study aimed to determine if the incidence of Type I (insulin-dependent) diabetes mellitus increased over time and if the time trend is attributable to linear trend, calendar period or birth cohort effects.¶Methods. This study was based on a cohort of subjects aged 0–29 years from 1984 to 1996, who resided in the province of Turin, Italy. Poisson regression models were used to estimate the effect of sex, age, calendar time and cohorts on incidence rates.¶Results. The mean incidence rate in the age group of 0 to 29 years was 7.78 of 100,000 person-years (95 % confidence interval: 7.26–8.32), with a lower risk in women than in men [rate ratio (RR): 0.76 (0.67–0.88)]. We found a trend of incidence increasing over time (annual increase of risk 2.25 % a year, 95 % CI 0.44–4.10). In Poisson regression analysis we found that the best model was the one with sex, age and a linear term attributable to either calendar period or cohort effects. The linear term corresponds to a RR of 1.12 (1.02–1.22, p = 0.015) for each 5-year age span.¶Conclusion/interpretation. We found that the time trend in this Mediterranean area was similar in magnitude to that reported in northern European countries. The increase was linear in pattern, each birth cohort and each calendar period showing a higher risk than the preceeding one with some evidence of two steep increases in the incidence of Type I diabetes centered on the years 1964 and 1984. We found that the incidence of diabetes increased in the 0 to 14 age group and also in the older age group of 15 to 29 years and that the age-period models were not statistically significantly better than the age-cohort models. [Diabetologia (2001) 44: 22–25]

Variations of the Perforin Gene in Patients With Type 1 Diabetes

OBJECTIVE—Perforin plays a key role in cell-mediated cytotoxicity. Mutations of its gene, PRF1, cause familial hemophagocytic lymphohistiocytosis but have also been associated with lymphomas and the autoimmune/lymphoproliferative syndrome. The aim of this work was to investigate the role of PRF1 variations in type 1 diabetes. RESEARCH DESIGN AND METHODS—We typed for the N252S and A91V variations in an initial population of 352 type 1 diabetic patients and 816 control subjects and a second population of 365 patients and 964 control subjects. Moreover, we sequenced the coding sequence and intron-exons boundaries in 200 patients and 300 control subjects. RESULTS—In both cohorts, allelic frequency of N252S was significantly higher in patients than in control subjects (combined cohorts: 1.5 vs. 0.4%; odds ratio 6.68 [95% CI 1.83–7.48]). Sequencing of the entire coding region detected one novel mutation in one patient, causing a P477A amino acid change not detected in 199 patients and 300 control subjects. Typing for HLA-DQA1 and DQB1 alleles showed that type 1 diabetes–predisposing DQα/DQβ heterodimers were less frequent in patients carrying N252S or P477A than in those carrying wild-type PRF1. We previously found that natural killer (NK) activity is not decreased in most N252S heterozygotes, but we detected one whose NK activity was normal at the age of 12 but strikingly low in early childhood. Here, we discovered that NK function was low in three heterozygotes in early childhood, one homozygous adult, and in the subject carrying P477A. CONCLUSIONS—These data suggest that N252S and possibly other PRF1 variations are susceptibility factors for type 1 diabetes development.

Sensor-Augmented Pump Therapy in Very Young Children with Type 1 Diabetes: An Efficacy and Feasibility Observational Study

BACKGROUND Efficacy and feasibility of sensor-augmented pump (SAP) therapy were evaluated in very young children with type 1 diabetes (T1D). SUBJECTS AND METHODS SAP (Dexcom [San Diego, CA] Seven Plus™ usage combined with insulin pump) therapy was retrospectively evaluated in 28 children (15 boys) younger than 7 years (mean age, 5.8 ± 1.2 years; range, 3-7 years), with T1D. Glycosylated hemoglobin (HbA1c) was evaluated at baseline and at the end of the study, as were efficacy and feasibility of the system, using a rating scale (with 3 being the most positive). RESULTS SAP has been used for at least 6 months by 85% of patients, with an overall good satisfaction (92%). The greatest perceived benefit was the reduced fear of hypoglycemia (score of 3, 81%). HbA1c significantly improved only in patients with baseline HbA1c >7.5% (P = 0.026). CONCLUSIONS SAP therapy is effective and feasible in preschool children with T1D. In patients with high HbA1c at baseline it provide a 0.9% decrease, sustained for at least 6 months.

Short-term mortality risk in children and young adults with type 1 diabetes: the population-based Registry of the Province of Turin, Italy.

Short-term mortality risk in young diabetic people is an indicator of quality of care. We assessed this in the Italian incident population-based registry of Turin. The study base included 1210 incident cases (n=677 aged 0-14 years and n=533 aged 15-29 years) with diabetes, onset period 1974-2000 in the Province of Turin, Italy. The relevant timescale for analysis was the time since the onset of diabetes to death, or till 31 December 2003. Standardized mortality ratio (SMR) for all-cause mortality was computed using the Italian population as a standard, by 5 years, age group, sex, and calendar period. Mean attained age of the incident cohort was 29.7 years (range 5.2-49.7 years). During a mean follow-up period of 15.8 years (range 2.0-29.9 years), there were 19 deaths in 15,967. Nine person-years of observation (n=9.5 expected deaths), giving an all-cause mortality rate of 1.19/1000 person-years (95% CI 0.76-1.87) and an SMR of 1.96 (1.25-3.08). In no cases did death occur at the onset of diabetes or in childhood. Out of 19 deaths, 9 were diabetes related (n=6 coma and n=3 end-stage renal disease). In Cox regression analysis, the hazard ratio (HR) was higher in adult-onset than in childhood-onset diabetes (HR=3.90, 95% CI 1.14-13.39), independently of calendar period and gender. (1) Children and young adults with type 1 diabetes experienced a two-fold higher short-term mortality risk than Italian people of similar age and sex and (2) the risk was higher in adult-onset than in childhood-onset diabetes. The quality of diabetes care should be improved to prevent early deaths.

Insulin secretion and hepatic insulin clearance as determinants of hyperinsulinaemia in normotolerant grossly obese adolescents.

Obesity is characterized by variable degrees of hyperinsulinaemia, which has been attributed to either β‐cell hypersecretion or reduced hepatic insulin extraction, or both. To investigate this controversial issue, a 4‐h frequently sampled i.v. glucose tolerance test (glucose dose 12.8 g m‐2) was performed in 13 normotolerant, grossly obese adolescents (10 F/3 M; 13 ± 1 y; body mass index 32 ± 0.9; pubertal stage 4–5; obesity duration 7.8 ± 3 y) and in a comparable group of 8 healthy, normal‐weight subjects. Glucose, insulin and C‐peptide time‐course were analysed by the minimal model technique, which estimates β‐cell secretion, insulin sensitivity (Si), glucose effectiveness (SG) and hepatic insulin extraction (HE). Despite similar fasting and after load glucose patterns (SG similar in the two groups), obese adolescents showed sustained peripheral hyperinsulinaemia (total insulin area under the concentration curve 67.2 ± 10.8 vs 19.1 ± 1.2 pmol l‐1 in 240 min; p < 0:002) and a 71% reduction in Si (2.02 ± 0.33 vs 6.95 ± 1.03±104 min‐1 (μU ml‐1);p < 0:001). Compared with control subjects, the total amounts of prehepatic insulin secretion and posthepatic insulin delivery were also increased significantly in obese adolescents by 30% and 46%, respectively; HE was reduced by 15% during the first 30 min of the test, but recovered within the normal range during the rest of the test. In conclusion, severely obese adolescents are insulin resistant and their hyperinsulinaemia is primarily caused by β‐cell hypersecretion, whereas the reduction in insulin hepatic extraction is a transient metabolic phenomenon.