Characterization of alterations in carbohydrate metabolism in children with Prader-Willi syndrome

Metabolomic profiling of Prader-Willi syndrome compared with essential obesity

Introduction

Prader-Willi syndrome (PWS) is a rare disease, which shows a peculiar clinical phenotype, including obesity, which is different from essential obesity (EOB). Metabolomics might represent a valuable tool to reveal the biochemical mechanisms/pathways underlying clinical differences between PWS and EOB. The aim of the present (case-control, retrospective) study was to determine the metabolomic profile that characterizes PWS compared to EOB.

Methods

A validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) targeted metabolomic approach was used to measure a total of 188 endogenous metabolites in plasma samples of 32 patients with PWS (F/M = 23/9; age: 31.6 ± 9.2 years; body mass index [BMI]: 42.1 ± 7.0 kg/m2), compared to a sex-, age- and BMI-matched group of patients with EOB (F/M = 23/9; age: 31.4 ± 6.9 years; BMI: 43.5 ± 3.5 kg/m2).

Results

Body composition in PWS was different when compared to EOB, with increased fat mass and decreased fat-free mass. Glycemia and HDL cholesterol were higher in patients with PWS than in those with EOB, while insulinemia was lower, as well as heart rate. Resting energy expenditure was lower in the group with PWS than in the one with EOB, a difference that was missed after fat-free mass correction. Carrying out a series of Tobit multivariable linear regressions, adjusted for sex, diastolic blood pressure, and C reactive protein, a total of 28 metabolites was found to be associated with PWS (vs. non-PWS, i.e., EOB), including 9 phosphatidylcholines (PCs) ae, 5 PCs aa, all PCs aa, 7 lysoPCs a, all lysoPCs, 4 acetylcarnitines, and 1 sphingomyelin, all of which were higher in PWS than EOB.

Conclusions

PWS exhibits a specific metabolomic profile when compared to EOB, suggesting a different regulation of some biochemical pathways, fundamentally related to lipid metabolism.

Endocrine features of Prader-Willi syndrome: a narrative review focusing on genotype-phenotype correlation

Prader-Willi syndrome (PWS) is a complex genetic disorder caused by three different types of molecular genetic abnormalities. The most common defect is a deletion on the paternal 15q11-q13 chromosome, which is seen in about 60% of individuals. The next most common abnormality is maternal disomy 15, found in around 35% of cases, and a defect in the imprinting center that controls the activity of certain genes on chromosome 15, seen in 1-3% of cases. Individuals with PWS typically experience issues with the hypothalamic-pituitary axis, leading to excessive hunger (hyperphagia), severe obesity, various endocrine disorders, and intellectual disability. Differences in physical and behavioral characteristics between patients with PWS due to deletion versus those with maternal disomy are discussed in literature. Patients with maternal disomy tend to have more frequent neurodevelopmental problems, such as autistic traits and behavioral issues, and generally have higher IQ levels compared to those with deletion of the critical PWS region. This has led us to review the pertinent literature to investigate the possibility of establishing connections between the genetic abnormalities and the endocrine disorders experienced by PWS patients, in order to develop more targeted diagnostic and treatment protocols. In this review, we will review the current state of clinical studies focusing on endocrine disorders in individuals with PWS patients, with a specific focus on the various genetic causes. We will look at topics such as neonatal anthropometry, thyroid issues, adrenal problems, hypogonadism, bone metabolism abnormalities, metabolic syndrome resulting from severe obesity caused by hyperphagia, deficiencies in the GH/IGF-1 axis, and the corresponding responses to treatment.

Body Fat Distribution Contributes to Defining the Relationship between Insulin Resistance and Obesity in Human Diseases

The risk for metabolic and cardiovascular complications of obesity is defined by body fat distribution rather than global adiposity. Unlike subcutaneous fat, visceral fat (including hepatic steatosis) reflects insulin resistance and predicts type 2 diabetes and cardiovascular disease. In humans, available evidence indicates that the ability to store triglycerides in the subcutaneous adipose tissue reflects enhanced insulin sensitivity. Prospective studies document an association between larger subcutaneous fat mass at baseline and reduced incidence of impaired glucose tolerance. Case-control studies reveal an association between genetic predisposition to insulin resistance and a lower amount of subcutaneous adipose tissue. Human peroxisome proliferator-activated receptorgamma (PPAR-γ) promotes subcutaneous adipocyte differentiation and subcutaneous fat deposition, improving insulin resistance and reducing visceral fat. Thiazolidinediones reproduce the effects of PPAR-γ activation and therefore increase the amount of subcutaneous fat while enhancing insulin sensitivity and reducing visceral fat. Partial or virtually complete lack of adipose tissue (lipodystrophy) is associated with insulin resistance and its clinical manifestations, including essential hypertension, hypertriglyceridemia, reduced HDL-c, type 2 diabetes, cardiovascular disease, and kidney disease. Patients with Prader Willi syndrome manifest severe subcutaneous obesity without insulin resistance. The impaired ability to accumulate fat in the subcutaneous adipose tissue may be due to deficient triglyceride synthesis, inadequate formation of lipid droplets, or defective adipocyte differentiation. Lean and obese humans develop insulin resistance when the capacity to store fat in the subcutaneous adipose tissue is exhausted and deposition of triglycerides is no longer attainable at that location. Existing adipocytes become large and reflect the presence of insulin resistance.

Approach to the Patient With Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a rare, multisystemic, genetic disorder involving the hypothalamus. It is caused by loss of expression of paternally inherited genes in chromosome 15 q11-13 region. The estimated incidence is around 1 in 20.000 births. PWS is characterized by a complex lifelong trajectory involving neurodevelopmental, nutritional, endocrine, metabolic, and behavioral changes. The major symptoms are hypotonia, short stature, hypogonadism, and eating disorders ranging from anorexia in infancy to hyperphagia, a deficit of satiety, and a high risk of severe obesity. The patients display intellectual disability comprising cognitive deficit, delayed motor and language development, learning deficits, impaired social skills, and emotional regulation. Behavioral features including temper outbursts, anxiety, obsessive-compulsive symptoms and rigidity are common and become more apparent with increasing age. Almost all have hypogonadism and growth hormone deficiency. Central adrenal insufficiency is rare whereas central hypothyroidism occurs in up to 30% of children with PWS. The prevalence of obesity increases with age from almost none in early childhood to more than 90% in adulthood. Up to 25% of adults with obesity have type 2 diabetes. Obesity and its complications are the major causes of comorbidity and mortality in PWS. As there is no specific treatment, care consists of comprehensive management of feeding disorders, a restricted, controlled diet, regular exercise, hormone substitution, and screening and treatment of comorbidities. Here we present the course of PWS from birth to adulthood in 2 patients and discuss their symptoms in relation to the literature.

Do patients with Prader-Willi syndrome have favorable glucose metabolism?

Background

In recent years, more studies have observed that patients with Prader–Willi syndrome have lower insulin levels and lower insulin resistance than body mass index-matched controls, which may suggest protected glucose metabolism.

Method

The PubMed and Web of Science online databases were searched to identify relevant studies published in the English language using the terms “Prader–Willi syndrome” with “glucose”, “insulin”, “diabetes mellitus”, “fat”, “adipo*”, “ghrelin”, “oxytocin”, “irisin” or “autonomic nervous system”.

Results

The prevalence of impaired glucose intolerance, type 2 diabetes mellitus and some other obesity-associated complications in patients with Prader–Willi syndrome tends to be lower when compared to that in general obesity, which is consistent with the hypothetically protected glucose metabolism. Factors including adipose tissue, adiponectin, ghrelin, oxytocin, irisin, growth hormone and the autonomic nervous system possibly modulate insulin sensitivity in patients with Prader–Willi syndrome.

Conclusion

Although lower insulin levels, lower IR and protected glucose metabolism are widely reported in PWS patients, the causes are still mysterious. Based on existing knowledge, we cannot determine which factor is of utmost importance and what are the underlying mechanisms, and further research is in urgent need.

Endocrine disorders in Prader-Willi syndrome: a model to understand and treat hypothalamic dysfunction

Prader-Willi syndrome is a rare genetic neurodevelopmental disorder resulting from the loss of expression of maternally imprinted genes located in the paternal chromosomal region, 15q11-13. Impaired hypothalamic development and function is the cause of most of the phenotypes comprising the developmental trajectory of Prader-Willi syndrome: from anorexia at birth to excessive weight gain preceding hyperphagia, and early severe obesity with hormonal deficiencies, behavioural problems, and dysautonomia. Growth hormone deficiency, hypogonadism, hypothyroidism, premature adrenarche, corticotropin deficiency, precocious puberty, and glucose metabolism disorders are the main endocrine dysfunctions observed. Additionally, as a result of hypothalamic dysfunction, oxytocin and ghrelin systems are impaired in most patients. Standard pituitary and gonadal hormone replacement therapies are required. In this Review, we discuss Prader-Willi syndrome as a model of hypothalamic dysfunction, and provide a comprehensive description of the accumulated knowledge on genetics, pathophysiology, and treatment approaches of this rare disorder.

Update on Diabetes Mellitus and Glucose Metabolism Alterations in Prader-Willi Syndrome

PURPOSE OF REVIEW

This review summarizes our current knowledge on type 2 diabetes mellitus (T2DM) and glucose metabolism alterations in Prader-Willi syndrome (PWS), the most common syndromic cause of obesity, and serves as a guide for future research and current best practice.

RECENT FINDINGS

Diabetes occurs in 10-25% of PWS patients, usually in adulthood. Severe obesity is a significant risk factor for developing of T2DM in PWS. Paradoxically, despite severe obesity, a relative hypoinsulinemia, without the expected insulin resistance, is frequently observed in PWS. The majority of PWS subjects with T2DM are asymptomatic and diabetes-related complications are infrequent. Long-term growth hormone therapy does not adversely influence glucose homeostasis in all ages, if weight gain does not occur. Early intervention to prevent obesity and the regular monitoring of glucose levels are recommended in PWS subjects. However, further studies are required to better understand the physiopathological mechanisms of T2DM in these patients.

Prevalence and risk factors for type 2 diabetes mellitus with Prader-Willi syndrome: a single center experience

BACKGROUND

Prader-Willi syndrome (PWS) is often related to severe obesity and type-2 diabetes mellitus (T2DM). However, few studies, and none in Korea, have examined prevalence of T2DM and other variables in PWS. The aim of this study was to identify the prevalence and associated risk factors for T2DM in Korean patients with PWS.

METHODS

We performed a retrospective cohort study of the 84 PWS patients aged 10 or over (10.3-35.8 years of age) diagnosed with PWS at Samsung Medical Center from 1994 to 2016. We estimated occurrence of T2DM according to age (10-18 years versus >18 years), body mass index (BMI), genotype, history of growth hormone therapy, homeostasis model of assessment-insulin resistance (HOMA-IR), and the presence of dyslipidemia, hypogonadism, or central precocious puberty. Additionally, we investigated cutoff values of risk factors for development of T2DM.

RESULTS

Twenty-nine of a total 211 patients, diagnosed with PWS over the study period, were diagnosed as having T2DM (13.7%, mean age 15.9 ± 3.6 years). In the >18 years group, obesity, HOMA-IR, and presence of dyslipidemia, hypogonadism, or central precocious puberty were associated with the occurrence of T2DM in univariate analysis. In multivariate logistic regression analysis, only obesity (p = 0.001) and HOMA-IR (p < 0.001) were significant predictive factors for T2DM. Based on the receiver operating a characteristic curve analysis, the cutoff values of HOMA-IR and BMI for predicting T2DM were >2.7 and >28.49 kg/m2, respectively. Of the 29 patients, seven had ≥1 microvascular complication, with non-proliferative diabetic retinopathy in 6 of 7 cases. Advanced age and HOMA-IR were positively correlated with diabetic microvascular complications (p < 0.05, Spearman correlation coefficient 0.393 and 0.434, respectively).

CONCLUSIONS

The prevalence of diabetes in Korean PWS was similar to that in previous results. BMI and HOMA-IR were strong predictive factors for the development of T2DM in PWS. We specifically suggest the regular monitoring of glucose homeostasis parameters through a detailed settlement of ethnically specific cutoff values for BMI and HOMA-IR in PWS to prevent progression of T2DM and diabetic microvascular complications.

Disorders of glucose metabolism in Prader-Willi syndrome: Results of a multicenter Italian cohort study

BACKGROUND AND AIMS

Prader-Willi syndrome (PWS) is characterized by a high incidence of altered glucose metabolism (AGM). However, epidemiological data on impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) are still discordant.

METHODS AND RESULTS

We performed a multicenter study based on 274 PWS patients [144 females, aged 20.3 ± 10.4 yrs (range: 8.1-50.1 years)] evaluating the prevalence for AGM in the entire group, and according to age (children <10 yrs; adolescents 10-18 yrs, and adults >18 yrs), Body Mass Index (BMI = kg/m(2)), gender, genotypes (deletion or uniparental disomy for chromosome 15), and GH therapy (GHT) (untreated, previously or currently treated). Altogether, AGM was detected in 67 (24.4%) of patients (0.7% IFG, 10.2% IGT, 13.5% T2DM). The prevalence of AGM was correlated to age (p = 0.001), BMI (p = 0.001) and HOMA-IR (p = 0.001). However, gender, genotype, and GHT did not influence AGM development in univariate analysis. These data were confirmed as positive predictors when inserted in a multivariate analysis model.

CONCLUSION

This study is the first report on the prevalence of AGM in a large population of PWS. Overall, PWS subjects show a high prevalence of AGM that appears more common in obese and adult subjects. Our data confirm the main role of obesity on the individual metabolic risk clustering in PWS, and thus reinforce the concept that improvement in weight control remains the most important goal of any PWS treatment program.

Postprandial metabolism in adults with Prader-Willi syndrome

OBJECTIVE

Individuals with Prader-Willi syndrome (PWS) are commonly restricted to 60-75% of height-appropriate calorie intake because they rapidly become obese on a normal diet. This study measured changes in energy expenditure, glucose and lipid homeostasis, and metabolic flexibility in response to a meal in PWS adults.

METHODS

11 adults with PWS were compared with 12 adiposity-matched and 10 lean subjects. Indirect calorimetry was conducted at baseline and 210 min after a standardized 600 kCal breakfast to assess energy expenditure and substrate utilization. Circulating glucose, insulin, C-peptide, glucagon, nonesterified fatty acids, and triglycerides were measured up to 240 min. Insulin sensitivity and insulin secretion rate were assessed by HOMA-IR and C-peptide deconvolution, respectively. Body composition was determined by dual-energy X-ray absorptiometry.

RESULTS

The PWS group had lower lean mass than the obesity control group. Corrected for lean mass, there were no differences between the PWS and obesity groups in resting metabolic rate or metabolic flexibility. Total and abdominal fat mass, insulin sensitivity, and insulin secretion rate were also similar between these groups.

CONCLUSIONS

This study did not detect an intrinsic metabolic defect in individuals with PWS. Rather, lower lean mass, combined with lower physical activity, may contribute to weight gain on an apparent weight-maintenance diet.

Metabolic syndrome in adult patients with Prader-Willi syndrome

BACKGROUND AND AIMS

Prader-Willi syndrome (PWS), the most common genetic cause of obesity, is characterized by elevated morbility and mortality in all ages. In this context, non-obese PWS children showed low frequency of metabolic syndrome (MetS), while a comparable prevalence was observed in obese PWS and obese controls. Aim of this study was to estimate the occurrence of MetS and its components in a large group of PWS adults, according to obesity status.

METHODS AND RESULTS

A cross-sectional study was performed in 108 PWS aged 18.0-43.2 years (87 obese and 21 non-obese) and in 85 controls with nonsyndromic obesity matched for age, gender, and BMI with obese PWS. Non-obese PWS showed lower waist circumference, insulin, HOMA-index, triglycerides, diastolic blood pressure, and higher HDL-C than both obese PWS and obese controls (p < 0.017). Obese PWS showed higher glucose and systolic blood pressure than both non-obese PWS and obese controls (p < 0.017). MetS was found in 1/21 (4.8%) non-obese PWS, 36/87 (41.4%) obese PWS and 39/85 (45.9%) obese controls. Non-obese PWS showed lower frequency for each MetS component as compared with obese PWS and obese controls. PWS patients with deletion of the chromosome 15q11-13 showed a lower risk for low HDL-C (p < 0.01) and a trend towards a lower MetS risk (p < 0.06) compared to subjects without deletion.

CONCLUSION

Our findings suggest the main role that obesity status plays on the individual metabolic risk clustering in PWS adults. Early identification of MetS could be helpful to improve morbidity and prevent mortality in such patients.

Endocrine manifestations and management of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex genetic disorder, caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13. In infancy it is characterized by hypotonia with poor suck resulting in failure to thrive. As the child ages, other manifestations such as developmental delay, cognitive disability, and behavior problems become evident. Hypothalamic dysfunction has been implicated in many manifestations of this syndrome including hyperphagia, temperature instability, high pain threshold, sleep disordered breathing, and multiple endocrine abnormalities. These include growth hormone deficiency, central adrenal insufficiency, hypogonadism, hypothyroidism, and complications of obesity such as type 2 diabetes mellitus. This review summarizes the recent literature investigating optimal screening and treatment of endocrine abnormalities associated with PWS, and provides an update on nutrition and food-related behavioral intervention. The standard of care regarding growth hormone therapy and surveillance for potential side effects, the potential for central adrenal insufficiency, evaluation for and treatment of hypogonadism in males and females, and the prevalence and screening recommendations for hypothyroidism and diabetes are covered in detail. PWS is a genetic syndrome in which early diagnosis and careful attention to detail regarding all the potential endocrine and behavioral manifestations can lead to a significant improvement in health and developmental outcomes. Thus, the important role of the provider caring for the child with PWS cannot be overstated.

The incidence, clinical features, and treatment of type 2 diabetes in children <15 yr in a population-based cohort from Auckland, New Zealand, 1995–2007

BACKGROUND

The incidence of type 2 diabetes mellitus (T2DM) is increasing in adolescents in most western countries. The time-course of glycemic control and impact of early treatment remain poorly understood.

OBJECTIVES

To determine the change in incidence of T2DM, and the time-course of glycemic control in a regional pediatric cohort with T2DM.

METHODS

Retrospective analysis of prospectively collected data on 52 patients with T2DM from a population-based treatment referral cohort from 1 January 1995 to 31 December 2007.

RESULTS

The annual incidence of new cases of T2DM in children <15 yr increased fivefold in the Auckland region of New Zealand from 1995 [0.5/100,000; 95% confidence interval (CI) 0.0–2.2] to 2007 (2.5/100,000; 95% CI 1.0–5.5). The average annual incidence per 100,000 over the entire period was 1.3 (95% CI 1.0–1.8) overall, 0.1 (0.0–0.4) in Europeans, and 3.4 in both Maori (2.0–5.3) and Pacifica (2.2–5.0). Fifty-seven percent of children were symptomatic at presentation. Fifty-eight percent of patients were treated with insulin from diagnosis, most of whom were symptomatic (p = 0.003). Follow-up data were available for 48 patients with a mean of 2.4 yr. Although insulin therapy was associated with a greater fall in HbA1c values in the first 12 months of treatment (to a nadir of 7.1 vs. 8.1%, p < 0.05), there was a rapid deterioration after 12 months, and subsequent mean HbA1c values were >9% in both groups. Therapy did not affect body mass index standard deviation score (BMI SDS).

CONCLUSIONS

The incidence of T2DM in childhood or adolescence increased markedly over a 13-yr period in the Auckland region. Long-

Global deficits in development, function, and gene expression in the endocrine pancreas in a deletion mouse model of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a multisystem disorder caused by genetic loss of function of a cluster of imprinted, paternally expressed genes. Neonatal failure to thrive in PWS is followed by childhood-onset hyperphagia and obesity among other endocrine and behavioral abnormalities. PWS is typically assumed to be caused by an unknown hypothalamic-pituitary dysfunction, but the underlying pathogenesis remains unknown. A transgenic deletion mouse model (TgPWS) has severe failure to thrive, with very low levels of plasma insulin and glucagon in fetal and neonatal life prior to and following onset of progressive hypoglycemia. In this study, we tested the hypothesis that primary deficits in pancreatic islet development or function may play a fundamental role in the TgPWS neonatal phenotype. Major pancreatic islet hormones (insulin, glucagon) were decreased in TgPWS mice, consistent with plasma levels. Immunohistochemical analysis of the pancreas demonstrated disrupted morphology of TgPWS islets, with reduced α- and β-cell mass arising from an increase in apoptosis. Furthermore, in vivo and in vitro studies show that the rate of insulin secretion is significantly impaired in TgPWS β-cells. In TgPWS pancreas, mRNA levels for genes encoding all pancreatic hormones, other secretory factors, and the ISL1 transcription factor are upregulated by either a compensatory response to plasma hormone deficiencies or a primary effect of a deleted gene. Our findings identify a cluster of imprinted genes required for the development, survival, coordinate regulation of genes encoding hormones, and secretory function of pancreatic endocrine cells, which may underlie the neonatal phenotype of the TgPWS mouse model.

Delayed response of amylin levels after an oral glucose challenge in children with Prader-Willi syndrome

PURPOSE

Amylin secretion is increased parallel to insulin in obese subjects. Despite their marked obesity, a state of relative hypoinsulinemia occurs in children with Prader-Willi syndrome (PWS). Based on the hypothesis that amylin levels may be relatively low in PWS children, contributing to their excessive appetite, we studied amylin levels after oral glucose loading in children with PWS and overweight controls.

MATERIALS AND METHODS

Plasma levels of amylin, glucagon, insulin, and glucose were measured at 0, 30, 60, 90, and 120 min after a glucose challenge in children with PWS (n = 18) and overweight controls (n = 25); the relationships among the variables were investigated in these two groups.

RESULTS

Amylin levels were significantly correlated with insulin during fasting and during the oral glucose tolerance test in both groups. Amylin levels between 0 and 60 min after glucose loading were statistically different between the two groups. They were lower in children with PWS than in the controls between 0 and 30 min after glucose loading.

CONCLUSION

The relatively low levels of amylin, compared to those in overweight controls, during the early phase of glucose loading in patients with PWS, may contribute, in part, to the excessive appetite of PWS patients as compared to the overweight controls.

The metabolic phenotype of Prader-Willi syndrome (PWS) in childhood: heightened insulin sensitivity relative to body mass index

CONTEXT

Insulin sensitivity is higher in patients with Prader-Willi syndrome (PWS) than in body mass index-matched obese controls (OCs). Factors contributing to the heightened insulin sensitivity of PWS remain obscure. We compared the fasting levels of various hormones, cytokines, lipids, and liver function tests in 14 PWS patients and 14 OCs with those in 14 age- and gender-matched lean children (LC). We hypothesized that metabolic profiles of children with PWS are comparable with those of LC, but different from those of OCs.

RESULTS

Leptin levels were comparable in PWS patients and OCs, suggesting comparable degrees of adiposity. Glucose levels were comparable among groups. However, fasting insulin concentrations and homeostasis model assessment insulin resistance index were lower in PWS patients than in OCs (P < 0.05) and similar to LC. Moreover, high-density lipoprotein levels were lower and triglycerides higher in OCs (P < 0.05) but not PWS patients. Total adiponectin, high-molecular-weight (HMW) adiponectin and the HMW to total adiponectin ratio were higher in PWS patients (P < 0.05) than in OCs and similar to LC. High-sensitivity C-reactive protein and IL-6 levels were higher in OCs than in PWS patients or LC (P < 0.05). Nevertheless, PAI-1 levels were elevated in both OC and PWS patients. There were no group differences in glucagon-like peptide-1, macrophage chemoattractant protein-1, TNFα, IL-2, IL-8, IL-10, IL-12p40, IL-18, resistin, total or low-density lipoprotein cholesterol, aspartate aminotransferase, or alanine aminotransferase.

CONCLUSIONS

The heightened insulin sensitivity of PWS patients relative to OCs is associated with higher levels of adiponectin and lower levels of high-sensitivity C-reactive protein and IL-6. Future studies will determine whether PWS children are protected from obesity comorbidities such as type 2 diabetes, hyperlipidemia, and nonalcoholic fatty liver disease.

Ghrelin concentrations in Prader-Willi syndrome (PWS) infants and children: changes during development

BACKGROUND

Prader-Willi syndrome (PWS) is associated with failure to thrive in infancy and progressive hyperphagia and obesity in childhood. This progressive weight gain is associated with hyperghrelinaemia and increased insulin sensitivity. The role of ghrelin excess in the pathogenesis of obesity is unclear.

OBJECTIVE

To determine if high ghrelin levels precede the onset of obesity in young PWS children.

DESIGN AND METHODS

A cross-sectional study of 33 infants with PWS and 28 healthy control subjects (C). Fasting ghrelin and other satiety hormones were measured.

RESULTS

Median total serum ghrelin in young children with PWS trended higher, but did not differ significantly from those in C of similar age, weight-for-age z-score and sex. However, there was more variability in ghrelin concentrations of young PWS. Eleven of 33 PWS subjects had ghrelin levels greater than the 95th percentile for ghrelin values in the C subjects (> 2871 pg/ml). Six of the PWS subjects with high ghrelin levels had weight-for-age z-scores < 0. Ghrelin concentrations in PWS and C infants exceeded those in older children. In youngsters with PWS, leptin was higher, suggesting a relative excess of fat to lean body mass and plasma adiponectin was increased.

CONCLUSIONS

Young infants with PWS who have not yet developed hyperphagia or obesity have median fasting ghrelin levels similar to controls. However, a subset (33%) of young PWS is hyperghrelinaemic; approximately one-half of those with hyperghrelinaemia have BMI z-score < 0. The age-related decline in ghrelin is blunted in PWS.

Uso de hormônio de crescimento na síndrome de Prader-Willi

A síndrome de Prader-Willi (PWS), com prevalência de 60:1.000.000, é o resultado da perda de parte do cromossomo 15 paterno, em razão da deleção em 56% dos casos, dissomia uniparental materna em 24% dos casos, ou por causa da metilação, fenômeno epigenético, em 18% dos casos. O quadro clínico inicia-se com profunda hipotonia que, especialmente no primeiro ano de vida, torna difícil a alimentação da criança. Conforme melhora a hipotonia, nos primeiros dois anos, por volta do quarto ano de vida, um apetite insaciável advém, o que leva tais crianças à obesidade extrema, com hipoventilação alveolar que põe em risco sua sobrevivência. Dessa forma, paradoxalmente, a PWS ameaça a vida dos pacientes, em um primeiro momento, por inanição e, em uma fase posterior, pelo excesso de peso. O uso de hormônio de crescimento (hrGH) nessas crianças tem por objetivo primário a mudança da composição corpórea e a melhora da atividade física e da qualidade de vida. Por outro lado, muitos pacientes com PWS são, de fato, deficientes em GH, ocorrendo melhora no padrão de crescimento com o tratamento. Tem-se de ser cuidadoso, no entanto, ao iniciar o tratamento com hrGH, com zelosa avaliação da apnéia do sono (polissonografia) e da permeabilidade das vias aéreas, tendo em vista que o tratamento com hrGH pode piorar o padrão respiratório em alguns pacientes.

Altered distribution of adiponectin isoforms in children with Prader-Willi syndrome (PWS): association with insulin sensitivity and circulating satiety peptide hormones

OBJECTIVE

Prader-Willi syndrome (PWS) is a genetic syndrome characterized by relative hypoinsulinaemia and normal or increased insulin sensitivity despite profound obesity. We hypothesized that this increased insulin sensitivity is mediated by increased levels of total and high molecular weight adiponectin and associated with changes in levels of satiety hormones.

DESIGN, PATIENTS AND MEASUREMENTS

We measured total adiponectin and its isoforms [high molecular weight (HMW), middle molecular weight (MMW) and low molecular weight (LMW) adiponectin] and satiety hormones in 14 children with PWS [median age 11.35 years, body mass index (BMI) Z-score 2.15] and 14 BMI-matched controls (median age 11.97 years, BMI Z-score 2.34).

RESULTS

Despite comparable BMI Z-scores and leptin levels, the PWS children exhibited lower fasting insulin and HOMA-IR (homeostasis model assessment of insulin resistance) scores compared to obese controls. For any given BMI Z-score, the PWS children showed higher concentrations of fasting total and HMW adiponectin and higher HMW/total adiponectin ratios. The HMW/total adioponectin ratio was preserved in children with PWS at high degrees of obesity. In PWS children, fasting plasma total adiponectin, HMW adiponectin and HMW/total adiponectin ratio correlated negatively with age (P < 0.05), HOMA-IR (P < 0.01), BMI Z-score (P < 0.05), insulin (P < 0.01) and leptin (P < 0.05). In addition to higher fasting ghrelin concentrations, the PWS children showed significantly higher fasting levels of total peptide YY (PYY) and gastric inhibitory polypeptide (GIP) compared to obese controls.

CONCLUSIONS

Relative to controls of similar age and BMI Z-score, the PWS children had significantly higher levels of total and HMW adiponectin, and increased ratios of HMW/total adiponectin. These findings may explain in part the heightened insulin sensitivity of PWS children relative to BMI-matched controls.

Clinical-etiologic correlation in children with Prader-Willi syndrome (PWS): An interdisciplinary study

Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes within chromosome 15q11-q13. Most cases are due to paternal deletion of this region; the remaining cases result from maternal uniparental disomy (UPD) and imprinting defects. To better understand the phenotypic variability of PWS, a genotype-phenotype correlation study was performed in 91 children with PWS. Patients were diagnosed by Southern Blot Methylation assay and genetic subtypes were established using FISH and microsatellite analyses. Fifty-nine subjects with deletion (31/28 males/females; mean age 3.86 years), 30 with UPD (14/16 males/females; mean age 3.89 years) and 2 girls with a presumed imprinting defect (mean age 0.43 yrs) were identified. For correlation purposes patients were grouped as "deleted" and "non-deleted." An increased maternal age was found in the UPD group. Four of Holm's criteria were more frequently present in the deleted group: need for special feeding techniques, sleep disturbance, hypopigmentation, and speech articulation defects. Concerning cognitive assessments, only 9.52% of subjects with deletion had Full-Scale IQ (FSIQ) > or =70, while 61.53% of subjects without deletion had FSIQ > or =70. Similar results were found in behavioral measures. Sleep disorders and carbohydrate metabolism were systematically assessed. Polysomnoghaphic studies revealed a higher frequency of central events with desaturations > or =10% in the deleted group (P = 0.020). In summary, the phenotype was significantly different between both groups in certain parameters related to the CNS. These results might be related to the differences in brain gene expression of the genetic subtypes.