SNORD116 and growth hormone therapy impact IGFBP7 in Prader-Willi syndrome.

PURPOSE: Prader-Willi syndrome (PWS) is a neurodevelopmental disorder with hypothalamic dysfunction due to deficiency of imprinted genes located on the 15q11-q13 chromosome. Among them, the SNORD116 gene appears critical for the expression of the PWS phenotype. We aimed to clarify the role of SNORD116 in cellular and animal models with regard to growth hormone therapy (GHT), the main approved treatment for PWS. METHODS: We collected serum and induced pluripotent stem cells (iPSCs) from GH-treated PWS patients to differentiate into dopaminergic neurons, and in parallel used a Snord116 knockout mouse model. We analyzed the expression of factors potentially linked to GH responsiveness. RESULTS: We found elevated levels of circulating IGFBP7 in naive PWS patients, with IGFBP7 levels normalizing under GHT. We found elevated IGFBP7 levels in the brains of Snord116 knockout mice and in iPSC-derived neurons from a SNORD116-deleted PWS patient. High circulating levels of IGFBP7 in PWS patients may result from both increased IGFBP7 expression and decreased IGFBP7 cleavage, by downregulation of the proconvertase PC1. CONCLUSION: SNORD116 deletion affects IGFBP7 levels, while IGFBP7 decreases under GHT in PWS patients. Modulation of the IGFBP7 level, which interacts with IGF1, has implications in the pathophysiology and management of PWS under GHT.

Evolution of Hip Dysplasia in Pediatric Patients With Prader-Willi Syndrome Treated With Growth Hormone Early in Development.

BACKGROUND: Prader-Willi syndrome (PWS) is a rare genetic disorder characterized by obesity, hypotonia, feeding difficulties, obesity, musculoskeletal manifestations including scoliosis, and hip dysplasia (HD). The aim of this study was to characterize the clinical and radiographic evolution of HD in the pediatric PWS population. METHODS: The authors performed a retrospective cohort study of 72 patients (147 anteroposterior pelvic radiographs) between January 2004 and December 2016. Center-edge angle (CEA) of Wiberg, acetabular index (AI), and neck-shaft angle (NSA) were measures in all hips. The relationship between radiographic and demographic parameters of age, sex, and body mass index z-score (BMIzs) were assessed. RESULTS: A total of 274 radiographic measurements were performed and analyzed in 72 patients. The mean CEA, AI, and NSA were 21.8±7.1 degrees (range, 5 to 35 degrees), 16.7±7 degrees (range, 5 to 45 degrees), and 142±8.5 degrees (range, 128 to 165 degrees), respectively. HD was diagnosed in 79 (29%) hip radiographs and varied significantly between the age groups (P<0.01). A statistically significant association was identified between age and CEA [ß coef, 0.80; 95% confidence interval (CI), 0.6-1; P<0.01], AI (ß coef, -0.90; 95% CI, -1.1 to -0.7; P<0.01), and NSA (ß coef, -1.11; 95% CI, -1.4 to -0.9; P<0.01) angles. Sex and BMIzs were not identified as independent predictors of radiographic hip angles (P>0.1). CONCLUSIONS: The present study demonstrated favorable evolution of hip radiographic parameters in the PWS population treated with growth hormone early in development. This finding should prompt orthopedists to consider observation alone in the management algorithm for HD in patients with PWS. LEVELS OF EVIDENCE: Level III-a retrospective comparative study.

Growth Hormone Treatment for Prader-Willi Syndrome.

The European Marketing Authorization for recombinant human growth hormone (rhGH) in children with Prader-Willi syndrome was the first indication for metabolic and body composition effects in children. In the US it is indicated for short stature associated with PWS. Recombinant hGH is the first treatment for the PWS population and radically changed the care of these children by facilitating access to physicians who prescribe rhGH, mainly paediatric endocrinologists, and manage the organization of multidisciplinary care. Recombinant hGH treatment improved linear growth, body composition, and socialization not only in children but also in young adults. The pathophysiology of combined hormonal deficiencies including GH is starting to be unravelled. We now have to focus on co-morbidities that are not modified by rhGH treatment, such as feeding disorders and behaviour problems, to truly change the life of patients. The transition of care from adolescents to young adults also remains a challenge.

Sequelae of GH Treatment in Children with PWS.

More than 15 years after rGH was granted marketing authorization for children with PWS, a review of the sequelae, side effects and safety issues of rGH therapy is timely. The publications on issues concerning respiratory function, glucose metabolism, fat mass, and scoliosis at baseline and with rGH treatment are herein presented. We discuss the impact of rGH side effects, make proposals to prevent or treat them, and emphasise the remaining questions and perspectives. As a whole, the benefit /risk ratio is positive, although questions are raised about the role of GH in premature pubarche and its long-term effects, particularly the potential long-term oncogenic risk. The organisation of care in dedicated or reference centres at the national and European level will facilitate the collection and analysis of data and serve as a paradigm for long-term follow-up.

New candidate loci identified by array-CGH in a cohort of 100 children presenting with syndromic obesity.

Syndromic obesity is defined by the association of obesity with one or more feature(s) including developmental delay, dysmorphic traits, and/or congenital malformations. Over 25 syndromic forms of obesity have been identified. However, most cases remain of unknown etiology. The aim of this study was to identify new candidate loci associated with syndromic obesity to find new candidate genes and to better understand molecular mechanisms involved in this pathology. We performed oligonucleotide microarray-based comparative genomic hybridization in a cohort of 100 children presenting with syndromic obesity of unknown etiology, after exhaustive clinical, biological, and molecular studies. Chromosomal copy number variations were detected in 42% of the children in our cohort, with 23% of patients with potentially pathogenic copy number variants. Our results support that chromosomal rearrangements are frequently associated with syndromic obesity with a variety of contributory genes having relevance to either obesity or developmental delay. A list of inherited or apparently de novo duplications and deletions including their enclosed genes and not previously linked to syndromic obesity was established. Proteins encoded by several of these genes are involved in lipid metabolism (ACOXL, MSMO1, MVD, and PDZK1) linked with nervous system function (BDH1 and LINGO2), neutral lipid storage (PLIN2), energy homeostasis and metabolic processes (CDH13, CNTNAP2, CPPED1, NDUFA4, PTGS2, and SOCS6).

Obesity, Overweight, and Pituitary Stalk Interruption Syndrome in Children and Young Adults.

CONTEXT: Pituitary stalk interruption syndrome (PSIS) is rare in the pediatric population. It combines ectopic posterior pituitary stalk interruption and anterior pituitary hypoplasia with hormonal deficiencies. The phenotype is highly heterogeneous and obesity/overweight seems to be underreported in the literature. OBJECTIVE: To identify patients with PSIS and obesity or overweight, describe their phenotype, and compare them with patients with PSIS without overweight/obesity. METHODS: Sixty-nine children and young adults with PSIS in a Toulouse cohort from 1984 to 2019 were studied. We identified 25 obese or overweight patients (OB-OW group), and 44 were nonobese/overweight (NO group). Then the groups were compared. RESULTS: All cases were sporadic. The sex ratio was 1.6. The main reason for consultation in both groups was growth retardation (61% in OB-OW group, 77% in NO group). History of neonatal hypoglycemia was more common in the OB-OW than in the NO group (57% vs 14%, P = .0008), along with extrapituitary malformations (64% vs 20%, P < 0001). The incidence of caesarean section was higher in the OB-OW group (52%) than in the NO group (23%), although not significant (P = .07). CONCLUSION: Patients with PSIS who are obese/overweight display interesting phenotypic differences that suggest hypothalamic defects. Studies are needed that include additional information on hormonal levels, particularly regarding oxytocin and ghrelin.

Longitudinal changes in acylated versus unacylated ghrelin levels may be involved in the underlying mechanisms of the switch in nutritional phases in Prader-Willi syndrome.

INTRODUCTION: Prader-Willi syndrome (PWS) is characterized by a switch from failure to thrive to excessive weight gain and hyperphagia in early childhood. An elevated, more unfavorable ratio between acylated and unacylated ghrelin (AG/UAG ratio) might play a role in the underlying mechanisms of this switch. We aimed to assess the evolution of the appetite regulating hormones acylated ghrelin (AG) and unacylated ghrelin (UAG) and the AG/UAG ratio and their association with the change in eating behavior in children with PWS, compared to healthy age-matched controls. METHODS: Longitudinal study in 134 children with PWS and 157 healthy controls, from The Netherlands, France and Belgium. Levels of AG and UAG and the AG/UAG ratio were measured and nutritional phases as reported for PWS were scored. RESULTS: The AG/UAG ratio was in the first years of life lower in PWS than in controls and started to increase from the age of 3 years, resulting in a high-normal AG/UAG ratio compared to controls. The AG levels remained stable during the different nutritional phases (p=0.114), while the UAG levels decreased from 290 pg/ml in phase 1a to 137 pg/ml in phase 2b (p<0.001). The AG/UAG ratio increased significantly from 0.81 in phase 2a to 1.24 in phase 2b (p= 0.012). CONCLUSIONS: The change from failure to thrive to excessive weight gain and hyperphagia in infants and children with PWS coincides with an increase in AG/UAG ratio. The increase in AG/UAG ratio occurred during phase 2a, thus before the onset of hyperphagia.

Impact of Deprivation on Obesity in Children with PWS.

Our study aimed to evaluate the social deprivation score in families with a child with Prader-Willi syndrome (PWS) and analyze its impact on the occurrence of obesity in the affected child. We included 147 children with PWS followed in our reference center with Evaluation of the Deprivation and Inequalities of Health in Healthcare Centres by the EPICES score. Deprivation (EPICES ≥ 30) was found in 25.9% of the population. Compared with the non-obese children, children with obesity had more deprived families, 50.0 vs. 18.0% (p = 0.0001); were older, with a median of 10.1 vs. 6.0 years (p = 0.0006); were less frequently treated with growth hormone (GH), 80.6 vs. 91.9% (p = 0.07). The mothers of obese children were more frequently obese, 46.9 vs. 13.3% (p < 0.0001), and achieved high study levels less frequently (≥Bac+2), 40.9 vs. 70.1% (p = 0.012). The multivariate logistic regression indicated that age, living in a deprived family, and having a mother with overweight/obesity were significantly associated with an increased risk of obesity (respectively, OR = 3.31 (1.26−8.73) and OR = 6.76 (2.36−19.37)). The same risk factors of obesity observed in the general population were found in children with PWS. Families at risk, including social deprivation, will require early identification and a reinforced approach to prevent obesity.

What underlies emotion regulation abilities? An innovative programme based on an integrative developmental approach to improve emotional competencies: Promising results in children with Prader-Willi syndrome.

Background: This study aimed to test the effect of a new training programme on emotional competencies, named EMO-T, and to show the value of an integrative developmental approach. This approach postulates that the emotion regulation disturbances commonly observed in neurodevelopmental disorders are the consequence of potential disruptions in the prerequisite emotion skills. This integrative approach is particularly suitable in the case of complex and multidimensional disorders such as Prader-Willi syndrome (PWS), a rare genetic disease. Methods: We examined the emotion expression, recognition, comprehension, and regulation skills in 25 PWS children aged 5-10 and 50 typically developing children (TD) aged 3-10. After a pre-test session, half of the PWS children participated in the EMO-T programme with their regular therapist for 6 weeks, while the other half continued their usual rehabilitation programme. Two post-test sessions were conducted, one at the end of the programme and one 3 months later. Results: At pre-test, PWS children displayed a deficit in the four emotional competencies (EC). PWS children who participated in the EMO-T programme showed a significant and sustainable post-test improvement regarding voluntary expression and emotion recognition abilities, such that the level reached was no longer different from the baseline level of TD children. They also tended to improve in their emotion regulation, although they received no specific training in this skill. Discussion: These results support that emotion regulation abilities require prerequisite emotion skills, which should be more fully considered in current training programmes. Because emotion regulation disorders strongly impact all areas of life, an integrative developmental approach appears crucial especially in the case of neurodevelopmental disorders. Further studies should be conducted to explore this perspective.

Liraglutide for Weight Management in Children and Adolescents With Prader-Willi Syndrome and Obesity.

CONTEXT: Prader-Willi syndrome (PWS) is characterized by lack of appetite control and hyperphagia, leading to obesity. Pharmacological options for weight management are needed. OBJECTIVE: To determine whether liraglutide treatment for weight management is superior to placebo/no treatment in pediatric individuals with PWS. METHODS: This was a multicenter, 52-week, placebo-controlled trial with a 16-week double-blinded period. Adolescents (n = 31, aged 12-17 years; Tanner stage 2-5) and children (n = 24, aged 6-11 years; Tanner stage <2) with PWS and obesity were included. Patients were randomized 2:1 to liraglutide 3.0 mg (or maximum-tolerated dose) or placebo for 16 weeks, after which placebo was stopped. Liraglutide was continued for 52 weeks. All patients followed a structured diet and exercise program throughout the trial. The coprimary endpoints were change in body mass index (BMI) standard deviation score (SDS) from baseline to 16 and 52 weeks. Secondary endpoints included other weight-related parameters, hyperphagia, and safety. RESULTS: Change in BMI SDS from baseline to weeks 16 and 52 was not significantly different between treatments in adolescents (estimated treatment difference: -0.07 at week 16 and -0.14 at week 52) and children (-0.06 and -0.07, respectively). Changes in other weight-related parameters between treatments were not significant. At week 52, hyperphagia total and drive scores were lower in adolescents treated with liraglutide vs no treatment. The most common adverse events with liraglutide were gastrointestinal disorders. CONCLUSION: Although the coprimary endpoints were not met, changes in hyperphagia total and drive scores in adolescents warrant further studies on liraglutide in this population.

First step towards a consensus strategy for multi-locus diagnostic testing of imprinting disorders.

BACKGROUND: Imprinting disorders, which affect growth, development, metabolism and neoplasia risk, are caused by genetic or epigenetic changes to genes that are expressed from only one parental allele. Disease may result from changes in coding sequences, copy number changes, uniparental disomy or imprinting defects. Some imprinting disorders are clinically heterogeneous, some are associated with more than one imprinted locus, and some patients have alterations affecting multiple loci. Most imprinting disorders are diagnosed by stepwise analysis of gene dosage and methylation of single loci, but some laboratories assay a panel of loci associated with different imprinting disorders. We looked into the experience of several laboratories using single-locus and/or multi-locus diagnostic testing to explore how different testing strategies affect diagnostic outcomes and whether multi-locus testing has the potential to increase the diagnostic efficiency or reveal unforeseen diagnoses. RESULTS: We collected data from 11 laboratories in seven countries, involving 16,364 individuals and eight imprinting disorders. Among the 4721 individuals tested for the growth restriction disorder Silver-Russell syndrome, 731 had changes on chromosomes 7 and 11 classically associated with the disorder, but 115 had unexpected diagnoses that involved atypical molecular changes, imprinted loci on chromosomes other than 7 or 11 or multi-locus imprinting disorder. In a similar way, the molecular changes detected in Beckwith-Wiedemann syndrome and other imprinting disorders depended on the testing strategies employed by the different laboratories. CONCLUSIONS: Based on our findings, we discuss how multi-locus testing might optimise diagnosis for patients with classical and less familiar clinical imprinting disorders. Additionally, our compiled data reflect the daily life experiences of diagnostic laboratories, with a lower diagnostic yield than in clinically well-characterised cohorts, and illustrate the need for systematising clinical and molecular data.

Prader-Willi syndrome: Hormone therapies.

Prader-Willi syndrome (PWS) is a rare genetic neurodevelopmental disorder linked to the lack of expression of specific maternally imprinted genes located in the chromosomal region 15q11-q13. Impaired hypothalamic development and function explain most of the phenotype that is characterized by a specific trajectory from anorexia at birth to excessive weight gain at later ages, which is accompanied by hyperphagia and early severe obesity, as well as by other hormonal deficiencies, behavioral deficits, and dysautonomia. In almost all patients, their endocrine dysfunction involves growth hormone deficiency and hypogonadism, which originate from a combination of both peripheral and hypothalamic origin, central hypothyroidism in 40%, precocious adrenarche in 30% of the cases, and in rare cases, also adrenocorticotropin deficiency and precocious puberty. In addition, the oxytocin (OXT) and ghrelin systems are impaired in most patients and involved in a poor suckling response at birth, and hyperphagia with food addiction, poor social skills, and emotional dysregulation. Current hormonal replacement treatments are the same as used in classical hormonal deficiencies, and recombinant human GH treatment is registered since 2000 and has dramatically changed the phenotype of these children. OXT and OXT analogue treatments are currently investigated as well as new molecules targeting the ghrelin system. The severe condition of PWS can be seen as a model to improve the fine description and treatments of hypothalamic dysfunction.

Diabetes Mellitus in Prader-Willi Syndrome: Natural History during the Transition from Childhood to Adulthood in a Cohort of 39 Patients.

Type 2 diabetes mellitus (T2DM) affects 20% of patients with Prader-Willi syndrome (PWS), with many cases diagnosed during the transition period. Our aim was to describe the natural history of T2DM in patients with PWS before the age of 25 years and to develop screening and preventive strategies. Thirty-nine patients followed in the French PWS Reference Center were included (median age 25.6 years [23.7; 31.7]). Twenty-one had been treated with growth hormone (GH), fifteen had not, and three had an unknown status. The median age at T2DM diagnosis was 16.8 years (11-24) and the median BMI was 39 kg/m2 [34.6; 45], with 34/35 patients living with obesity. The patients displayed frequent psychiatric (48.3% hospitalization,) and metabolic (56.4% hypertriglyceridemia,) comorbidities and a parental history of T2DM (35.7%) or overweight (53.6%) compared to the PWS general population. There was no difference in BMI and metabolic complications between the GH-treated and non-GH-treated groups at T2DM diagnosis. Patients with PWS who develop early T2DM have severe obesity, a high frequency of psychiatric and metabolic disorders, and a family history of T2DM and overweight. These results underline the need for early identification of patients at risk, prevention of obesity, and repeated blood glucose monitoring during the transition period.

Paradoxical low severity of COVID-19 in Prader-Willi syndrome: data from a French survey on 647 patients.

BACKGROUND: Patients with Prader-Willi syndrome (PWS) often have comorbidities, especially obesity, that may constitute a risk factor for severe forms of COVID-19. We aimed to assess prevalence and medical course of SARS-CoV-2 infection in children and adults with PWS. From November 2020 to January 2021, we performed a detailed medical survey on 342 adults and 305 children with PWS followed in the French reference center. RESULTS: We obtained responses from 288 adults (84%) and 239 children (78%). From March 2020 to January 2021, 38 adults (13.2%) and 13 children (5.4%) with PWS had SARS-CoV-2 infection. Mean age of adults was 34.1 ± 11.9 years and mean body mass index was 40.6 ± 12.7 kg/m2; 82% had obesity and 37% had diabetes. Only 3 children (23%) had obesity and none had diabetes. Similar to the general population, the most frequent symptoms of COVID-19 were asthenia, fever, cough, headache and shortness of breath. All patients had a favorable outcome. CONCLUSION: PWS itself is not a risk factor for severe COVID-19 in children and adults. On the contrary, evolution of SARS-CoV-2 infection in adults with PWS seems more favorable than expected, given their comorbidities.

Is ghrelin a biomarker of early-onset scoliosis in children with Prader-Willi syndrome?

BACKGROUND: Adolescents with idiopathic scoliosis display high ghrelin levels. As hyperghrelinemia is found in patients with PWS and early-onset scoliosis (EOS) is highly prevalent in these patients, our aims were to explore (1) whether ghrelin levels differ between those with and without EOS and correlate with scoliosis severity, and (2) whether ghrelin levels in the first year of life are associated with the later development of EOS. METHODS: We used a case control study design for the first question and a longitudinal design for the second. Patients with PWS having plasma ghrelin measurements recorded between 2013 and 2018 in our database were selected and 30 children < 10 years old with EOS and 30 age- and BMI-matched controls without EOS were included. The Cobb angle at diagnosis was recorded. In addition, 37 infants with a ghrelin measurement in the first year of life were followed until 4 years of age and assessed for EOS. Total ghrelin (TG), acylated (AG) and unacylated ghrelin (UAG), and the AG/UAG ratio were analyzed. RESULTS: EOS children had an AG/UAG ratio statistically significantly lower than controls. The Cobb angle was positively correlated with TG and UAG. TG and AG in the first year of life were higher in infants who later develop EOS without reaching a statistically significant difference. CONCLUSIONS: Our results suggest that ghrelin may play a role in the pathophysiology of EOS in PWS. Higher ghrelinemia in the first year of life required careful follow-up for EOS.

Low bone mass in Noonan syndrome children correlates with decreased muscle mass and low IGF-1 levels.

Although musculoskeletal abnormalities have long been described in patients with Noonan syndrome (NS), only a few studies have investigated the bone status of these patients. The aim of this retrospective observational study was to describe the bone health of children with NS. Thirty-five patients with a genetically confirmed diagnosis of NS were enrolled. We analyzed the axial skeleton (lumbar spine) using dual energy X-ray absorptiometry and the appendicular skeleton (hand) with the BoneXpert system. Bone metabolism markers, including mineral homeostasis parameters, serum 25-hydroxy vitamin D (25-OHD) levels and markers of bone formation and resorption were also reported. Compared to the general population, axial and appendicular bone mass was significantly decreased in children with NS (p < 0.0001). Serum 25-OHD levels were low in about half of the patients and were negatively correlated with age (r = -0.52; p < 0.0001). Patients with NS exhibited reduced bone formation marker levels and increased bone resorption marker levels (p < 0.0001). No gender difference or genotype-phenotype correlations were found for the different bone parameters. Muscle mass and, to a lesser extent, serum insulin-like growth factor 1 (IGF-1) levels were independent predictors of whole-body bone mineral content (p < 0.0001 for both parameters; adjusted R2 = 0.97). In conclusion, bone mass is reduced in children with NS and correlates with decreased muscle mass and low serum IGF-1 levels. These data justify addressing all potential threats to bone health including sufficient calcium and vitamin D intake, regular physical exercise, and hormone replacement therapy.

Equivocal expression of emotions in children with Prader-Willi syndrome: what are the consequences for emotional abilities and social adjustment?

BACKGROUND: People with Prader-Willi Syndrome (PWS) experience great difficulties in social adaptation that could be explained by disturbances in emotional competencies. However, current knowledge about the emotional functioning of people with PWS is incomplete. In particular, despite being the foundation of social adaptation, their emotional expression abilities have never been investigated. In addition, motor and cognitive difficulties - characteristic of PWS - could further impair these abilities. METHOD: To explore the expression abilities of children with PWS, twenty-five children with PWS aged 5 to 10 years were assessed for 1) their emotional facial reactions to a funny video-clip and 2) their ability to produce on demand the facial and bodily expressions of joy, anger, fear and sadness. Their productions were compared to those of two groups of children with typical development, matched to PWS children by chronological age and by developmental age. The analyses focused on the proportion of expressive patterns relating to the target emotion and to untargeted emotions in the children's productions. RESULTS: The results showed that the facial and bodily emotional expressions of children with PWS were particularly difficult to interpret, involving a pronounced mixture of different emotional patterns. In addition, it was observed that the emotions produced on demand by PWS children were particularly poor and equivocal. CONCLUSIONS: As far as we know, this study is the first to highlight the existence of particularities in the expression of emotions in PWS children. These results shed new light on emotional dysfunction in PWS and consequently on the adaptive abilities of those affected in daily life.

Necdin plays a role in the serotonergic modulation of the mouse respiratory network: implication for Prader-Willi syndrome.

Prader-Willi syndrome is a neurogenetic disease resulting from the absence of paternal expression of several imprinted genes, including NECDIN. Prader-Willi children and adults have severe breathing defects with irregular rhythm, frequent sleep apneas, and blunted respiratory regulations. For the first time, we show that Prader-Willi infants have sleep apneas already present at birth. In parallel, in wild-type and Necdin-deficient mice, we studied the respiratory system with in vivo plethysmography, in vitro electrophysiology, and pharmacology. Because serotonin is known to contribute to CNS development and to affect maturation and function of the brainstem respiratory network, we also investigated the serotonergic system with HPLC, immunohistochemistry, Rabies virus tracing approaches, and primary culture experiments. We report first that Necdin-deficiency in mice induces central respiratory deficits reminiscent of Prader-Willi syndrome (irregular rhythm, frequent apneas, and blunted respiratory regulations), second that Necdin is expressed by medullary serotonergic neurons, and third that Necdin deficiency alters the serotonergic metabolism, the morphology of serotonin vesicles in medullary serotonergic neurons but not the number of these cells. We also show that Necdin deficiency in neonatal mice alters the serotonergic modulation of the respiratory rhythm generator. Thus, we propose that the lack of Necdin expression induces perinatal serotonergic alterations that affect the maturation and function of the respiratory network, inducing breathing deficits in mice and probably in Prader-Willi patients.

Prader-Willi syndrome: A model for understanding the ghrelin system.

Subsequent to the discovery of ghrelin as the endogenous ligand of growth hormone secretagogue receptor 1a, this unique gut peptide has been found to exert numerous physiological effects, such as appetite stimulation and lipid accumulation via the central regulating mechanisms in the hypothalamus, stimulation of gastric motility, regulation of glucose metabolism and brown fat thermogenesis, and modulation of stress, anxiety, taste sensation, reward-seeking behaviour and the sleep/wake cycle. Prader-Willi syndrome (PWS) has been described as a unique pathological state characterised by severe obesity and high circulating levels of ghrelin. It was hypothesised that hyperghrelinaemia would explain at least a part of the feeding behaviour and body composition of PWS patients, who are characterised by hyperphagia, an obsession with food and food-seeking, and increased adiposity. Initially, the link between hyperghrelinaemia and growth hormone deficiency, which is observed in 90% of the children with PWS, was not fully understood. Over the years, however, the increasing knowledge on ghrelin, PWS features and the natural history of the disease has led to a more comprehensive description of the abnormal ghrelin system and its role in the pathophysiology of this rare and complex neurodevelopmental genetic disease. In the present study, we (a) present the current view of PWS; (b) explain its natural history, including recent data on the ghrelin system in PWS patients; and (c) discuss the therapeutic approach of modulating the ghrelin system in these patients and the first promising results.

Causes of death in Prader-Willi syndrome: lessons from 11 years' experience of a national reference center.

BACKGROUND: In the last 20 years, substantial improvements have been made in the diagnosis, treatment and management of patients with Prader-Willi syndrome (PWS). Few data on causes of death are available since those improvements were made. Our study assessed the causes of death among French patients with PWS over the first 11 years of experience of the nationwide French Reference Center for PWS (FRC-PWS). METHODS: Our study relied on two sources of mortality information at national level between 2004 and 2014: The French Epidemiological Centre for the Medical Causes of Death (CépiDc) Registry and the FRC-PWS database. Causes of death were classified into seven categories: respiratory, cardiovascular, gastrointestinal, severe infection, sudden death, other causes, and unknown. Descriptive statistics were calculated separately for children (< 18 years-old) and adults (≥18 years-old). RESULTS: One hundred and four deaths were identified in France from 2004 to 2014. The median age at death was 30 years, ranging from less than 1 month to 58 years. Seventeen deaths occurred in patients under 18 years, with 70% of them in children under 2 years. Respiratory causes accounted for more than 50% of the deaths in patients with PWS in both children and adults. Both cause and age of death did not significantly differ according to gender or genetic subtype. CONCLUSIONS: Patients with PWS die prematurely due to a respiratory cause in most cases at all ages. In those adult patients with data on obesity, 98% were reported to be obese.