Learning by observation and learning by doing in Prader-Willi syndrome.

BACKGROUND: New competencies may be learned through active experience (learning by doing) or observation of others' experience (learning by observation). Observing another person performing a complex action accelerates the observer's acquisition of the same action, limiting the time-consuming process of learning by doing. Here, we compared learning by observation and learning by doing in individuals with Prader-Willi syndrome (PWS). It is hypothesized that PWS individuals could show more difficulties with learning by observation than learning by doing because of their specific difficulty in interpreting and using social information. METHODS: The performance of 24 PWS individuals was compared with that of 28 mental age (MA)- and gender-matched typically developing (TD) children in tasks of learning a visuo-motor sequence by observation or by doing. To determine whether the performance pattern exhibited by PWS participants was specific to this population or whether it was a nonspecific intellectual disability effect, we compared the PWS performances with those of a third MA- and gender-matched group of individuals with Williams syndrome (WS). RESULTS: PWS individuals were severely impaired in detecting a sequence by observation, were able to detect a sequence by doing, and became as efficient as TD children in reproducing an observed sequence after a task of learning by doing. The learning pattern of PWS children was reversed compared with that of WS individuals. CONCLUSIONS: The observational learning deficit in PWS individuals may be rooted, at least partially, in their incapacity to understand and/or use social information.

Growth hormone response to standard provocative stimuli and combined tests in very young children with Prader-Willi syndrome.

BACKGROUND: In Prader-Willi syndrome (PWS) a reduced growth hormone (GH) response to several stimulators has been documented in many studies, but none have focused on very young children. We evaluated the pattern of GH secretion in very young PWS patients. PATIENTS AND METHODS: Twenty-seven genetically confirmed PWS children (10 females, aged 0.4-5 years, mean: 2.2 ± 1.4 years) were included. All subjects underwent standard provocative tests (clonidine, CLO; and arginine, ARG) and one combined test [growth hormone-releasing hormone (GHRH) plus pyridostigmine (13 patients) or GHRH plus arginine (14 patients)]. Insulin-like growth factor-1 (IGF-1) levels were also measured. RESULTS: While standard tests (CLO and ARG) showed low GH peak in 85.2 and 70.4% of the patients, respectively, the combined test was found to be normal in 85.2%. IGF-1 was low in 66.7% of patients. Out of 27 patients, 3 (11%) showed a normal GH peak with both standard tests (group A), 6 (22%) to one of the standard tests (group B) and 18 (67%) presented a low response to both standard tests (group C). Four subjects showed low response to both the combined and standard tests and reduced IGF-1. CONCLUSION: Our data suggest that very young PWS children seem to have impaired hypothalamic GHRH secretion with a normal GH pituitary reserve.

Central adrenal insufficiency in young adults with Prader-Willi syndrome.

OBJECTIVE: A high prevalence (60%) of central adrenal insufficiency (CAI) has been reported in Prader-Willi syndrome (PWS) using the metyrapone test. We have assessed CAI in adults with PWS using the low-dose short synacthen test (LDSST). DESIGN: Basal cortisol and ACTH, and 30-min cortisol after the administration of 1 µg synacthen, were determined in 53 PWS adults (33 females). A peak cortisol value of ≥500 nmol/l was taken as normal. Hormonal profiles were analysed in relation to gender, genotype and phenotype. Deficient patients were retested by high-dose short synachten test (HDSST) or a repeat LDSST. RESULTS: Mean ± SD basal cortisol and ACTH were 336·6 ± 140·7 nmol/l and 4·4 ± 3·7 pmol/l respectively. Cortisol rose to 615·4 ± 135·0 nmol/l after LDSST. Eight (15·1%) patients had a peak cortisol response <500 nmol/l, with a lower mean ± SD (range) basal cortisol of 184·9 ± 32·0 (138·0-231·7) compared with 364·1 ± 136·6 (149·0-744·5) in normal responders (P < 0·001). Seven of the eight patients underwent retesting, with 4 (7·5%) showing persistent suboptimal responses. Basal and peak cortisol correlated in females (r = 0·781, P < 0·001). Logistic regression revealed that only female gender and baseline cortisol were predictors of cortisol peaks (adjusted R square 0·505). CONCLUSIONS: Although CAI can be part of the adult PWS phenotype, it has a lower prevalence (7·5%) than previously reported. Clinicians are advised to test PWS patient for CAI. Our study also shows that basal cortisol is closely correlated with adrenal response to stimulation, indicating that its measurement may be helpful in selecting patients for LDSST.

Glyburide ameliorates motor coordination and glucose homeostasis in a child with diabetes associated with the KCNJ11/S225T, del226-232 mutation.

Gain-of-function mutations of KCNJ11 can cause permanent neonatal diabetes mellitus, but only rarely after 6 months of age. Specific uncommon mutations KCNJ11give rise to a syndrome defined as developmental delay, epilepsy, and neonatal diabetes (DEND), or - more frequently - to a milder sub-type lacking epilepsy, denoted as intermediate-DEND (iDEND). Our aim was to consider a possible monogenic etiology in a 12-yr-old boy with early onset diabetes and mild neurological features. We studied a subject diagnosed with diabetes at 21 months of age, and negative to type 1 diabetes autoantibodies testing. He had learning difficulties during primary school, and a single episode of seizures at the age of 10 yr. We performed direct DNA sequencing of the KCNJ11 gene with subsequent functional study of mutated channels in COSm6 cells. The patient's clinical response to oral glyburide (Glyb) was assessed. Motor coordination was evaluated before and after 6 and 12 months of Glyb therapy. Sequencing of the KCNJ11 gene detected the novel, spontaneous mutation S225T, combined with deletion of amino acids 226-232. In vitro studies revealed that the mutation results in a K(ATP) channel with reduced sensitivity to the inhibitory action of ATP. Glyb improved diabetes control (hemoglobin A1c on insulin: 52 mmol/mol/6.9%; on Glyb: 36 mmol/mol/5.4%) and also performance on motor coordination tests that were impaired before the switch of therapy. We conclude that KCNJ11/S225T, del226-232 mutation caused a mild iDEND form in our patient. KCNJ11 should be considered as the etiology of diabetes even beyond the neonatal period if present in combination with negative autoantibody testing and even mild neurological symptoms.

Analysis of endothelial protein C receptor gene and metabolic profile in Prader-Willi syndrome and obese subjects.

The endothelial protein C receptor (EPCR) has a critical role in the regulation of anticoagulant and anti-inflammatory functions of activated protein C (APC). Abnormalities in EPCR might be associated with an increased risk of thrombosis. In this respect, a 23 bp insertion in the exon 3 of the EPCR gene predicts a truncated protein which cannot bind APC. High levels of C-reactive protein (CRP), a strong predictor of cardiovascular events, are found both in the obese and in subjects with Prader-Willi syndrome (PWS). Several cardiovascular risk factors are already present in prepubertal PWS children, but it is uncertain which mechanism contributes to the increased risk of cardiovascular disease in PWS. We analyzed the distribution of 23 bp insertion in the EPCR gene in 81 overweight and obese PWS subjects, 52 adults and 29 children, and in 58 overweight and obese children and adolescents (controls). We found that 1/58 (1.7%) of the controls was heterozygous for the 23 bp insertion, while this mutation was never found in PWS subjects. Furthermore, we evaluated CRP levels, glucose, insulin, and lipid profile, and we found higher CRP values in PWS adults with respect to children with PWS and controls, and a better insulin sensitivity in all PWS subjects than in the controls. This study suggests that in PWS subjects there is no predisposition to develop thrombotic events in association with EPCR gene alteration and demonstrates substantial differences regarding metabolic and inflammatory profile between PWS and non-PWS obese children, with further impairment in adults with PWS.

Assessment of central adrenal insufficiency in children and adolescents with Prader-Willi syndrome.

OBJECTIVE: A recent study evidenced by metyrapone test a central adrenal insufficiency (CAI) in 60% of Prader-Willi syndrome (PWS) children. These results were not confirmed in investigations with low [Low-Dose Tetracosactrin Stimulation Test (LDTST), 1 µg] or standard-dose tetracosactrin stimulation tests. We extended the research by LDTST in paediatric patients with PWS. DESIGN: Cross-sectional evaluation of adrenal stress response to LDTST in a PWS cohort of a tertiary care referral centre. PATIENTS: Eighty-four children with PWS. MEASUREMENTS: Assessment of adrenal response by morning cortisol and ACTH dosage, and 1-µg tetracosactrin test. Response was considered appropriate when cortisol reached 500 nm; below this threshold, patients were submitted to a second test. Responses were correlated with the patients' clinical and molecular characteristics to assess genotype-phenotype correlation. RESULTS: Pathological cortisol peak responses to the LDTST were registered in 12 patients (14.3%) who had reduced basal (169.4 ± 83.3 nm) and stimulated (428.1 ± 69.6 nm) cortisol levels compared to patients with normal responses (367.1 ± 170.6 and 775.9 ± 191.3 nm, P < 0.001). Body mass index standard deviation score was negatively correlated with basal and peak cortisol levels (both P < 0.001), and the patients' ages (P < 0.001). In patients with deletion on chromosome 15, the cortisol peak was significantly lower than that in uniparental disomy (UPD) cases (P = 0.030). At multiple regression analysis, the predictors of peak response were basal cortisol, age, and UPD subclass (r(2) = 0.353, P < 0.001). Standard-dose (250 µg) tetracosactrin test confirmed CAI in 4/12 patients (4.8% of the cohort). CONCLUSIONS: Our results support the hypothesis that, albeit rare, CAI may be part of the PWS in childhood.

Central precocious puberty and growth hormone deficiency in a boy with Prader-Willi syndrome.

In Prader-Willi syndrome (PWS) hypothalamic dysfunction is the cause of hormonal disturbances, such as growth hormone deficiency (GHD), hypogonadism, and delayed or incomplete puberty. Only a few cases of central precocious puberty (CPP) have been reported. We describe an 8.8-year-old PWS boy, with microdeletion of chromosome 15q, who developed CPP. On admission, height was 131.1 cm (+0.17 SD), BMI 26.2 kg/m(2), pubic hair (Ph) 2, and testis 4.5 ml. We found increased growth velocity (7 cm/year), high testosterone levels, pubertal response to GnRH test, and advanced bone age (10.6 years). An evaluation of growth hormone (GH) secretion revealed a deficiency. Pituitary MRI was normal. LHRH analogue therapy (Leuproreline 3.75 mg/28 days i.m.) was started at 8.9 years and discontinued at 11.3 years, when the patient had bone age of 13 years. During therapy, growth velocity, testosterone, FSH, and LH peak decreased significantly, with no pubertal progression. Growth hormone therapy (0.24 mg/kg/week) was started at 9.5 years and discontinued at 15.3 years because the patient had bone age of 17 years. After interrupting LHRH therapy the patient demonstrated spontaneous pubertal progression with pubertal gonadotropin and testosterone. At 16.3 years, height was 170 cm (-0.48 SDS), BMI 36.3 kg/m(2), Ph 4, testis volume 10 ml and there was a combined hypothalamic and peripheral hypogonadism hormonal pattern (normal LH even with low testosterone and undetectable inhibin B with high FSH). To our knowledge this is the fourth male patient with genetically-confirmed PWS demonstrating CPP and GHD and the first with a long follow-up to young adulthood.

An observational study comparing continuous subcutaneous insulin infusion (CSII) and insulin glargine in children with type 1 diabetes.

OBJECTIVE: The advantages of continuous subcutaneous insulin infusion (CSII) or insulin glargine have been demonstrated both in adult and paediatric diabetic patients; however, as no data comparing these two approaches during childhood are available, we have examined the efficacy of these two intensive approaches. RESEARCH DESIGN AND METHODS: We retrospectively evaluated data from 36 diabetic children, who had changed their previous insulin regimen [with isophane insulin (NPH) at bedtime] because of HbA1c levels >8.0%. Twenty patients underwent CSII, while the other 16 (significantly younger for age) started insulin glargine at bedtime. RESULTS: At 6 and 12 months, CSII-treated patients showed a significant reduction in HbA1c values from 8.5 +/- 1.8 to 7.4 +/- 1.1% and to 7.6 +/- 1.2%, respectively. The insulin requirement significantly decreased from 0.93 +/- 0.2 IU/kg to 0.73 +/- 0.2 IU/kg of body weight and to 0.74 +/- 0.15 IU/kg of body weight, respectively, while no significant differences were observed for BMI SDS, fructosamine and severe hypoglycaemic events. The patients treated with glargine showed a small decline in HbA1c values from 8.9 +/- 1.7 to 8.3 +/- 0.9% (not significant) in the first 6 months of treatment and to 8.2 +/- 0.9% after 12 months. CONCLUSION: The basal insulin supplementation can be supplied effectively in children with type 1 diabetes by either CSII or insulin glargine. As previously reported for adults, it is confirmed that CSII is the best current intensive approach aimed to the improvement of glycaemic control.

A 2-year pilot trial of continuous subcutaneous insulin infusion versus intensive insulin therapy in patients with newly diagnosed type 1 diabetes (IMDIAB 8).

In a pilot study, the metabolic effects of continuous subcutaneous insulin infusion (CSII) versus intensive subcutaneous insulin therapy (ISIT) started at diagnosis in patients with Type 1 diabetes and continued for a 2-year period were evaluated and compared. Twenty-three patients (between 12 and 35 years old, mean +/- SD 18.4 +/- 9 years) were randomized into two treatment groups (CSII vs. ISIT), and both received supplemental nicotinamide (NA), 25 mg/kg of body weight. CSII was started immediately after admission to the hospital. Parameters of metabolic control [insulin dose, hemoglobin A1c (HbA1c), and C-peptide] were evaluated for a 2-year follow-up period. Data are presented for a total of 19 patients who remained in the study for its duration. Two years after diagnosis, mean +/- SD HbA1c was 6.3 +/- 0.5% and 6.2 +/- 0.3% for the CSII and ISIT groups, respectively (p=not significant). Compared with baseline values, an increase of baseline C-peptide of 38% for the CSII group and 27% for the ISIT group was observed; however, the difference between the groups was not significant. The insulin requirement for the entire duration of the study, but not at entry and 3 months, was significantly higher in CSII compared with ISIT patients (0.62 +/- 0.4 IU/kg/day vs. 0.3 +/- 0.4 IU/kg/day, respectively; p<0.01). After trial completion patients on CSII continued with this mode of therapy. Implementation of CSII as well as ISIT at diagnosis of Type 1 diabetes and continuation for 2 years thereafter achieved similar and optimal metabolic control, but more insulin was required with the CSII group. Both types of intensive insulin therapy combined with NA are able to preserve C-peptide secretion or even increase baseline levels for up to 2 years after diagnosis.