Resting metabolic rate, plasma leptin concentrations, leptin receptor expression, and adipose tissue measured by whole-body magnetic resonance imaging in women with Prader-Willi syndrome

Malignancies in Prader-Willi Syndrome: Results From a Large International Cohort and Literature Review

CONTEXT

Prader-Willi syndrome (PWS) is a complex disorder combining hypothalamic dysfunction, neurodevelopmental delay, hypotonia, and hyperphagia with risk of obesity and its complications. PWS is caused by the loss of expression of the PWS critical region, a cluster of paternally expressed genes on chromosome 15q11.2-q13. As life expectancy of patients with PWS increases, age-related diseases like malignancies might pose a new threat to health.

OBJECTIVE

To investigate the prevalence and risk factors of malignancies in patients with PWS and to provide clinical recommendations for cancer screening.

METHODS

We included 706 patients with PWS (160 children, 546 adults). We retrospectively collected data from medical records on past or current malignancies, the type of malignancy, and risk factors for malignancy. Additionally, we searched the literature for information about the relationship between genes on chromosome 15q11.2-q13 and malignancies.

RESULTS

Seven adults (age range, 18-55 years) had been diagnosed with a malignancy (acute lymphoblastic leukemia, intracranial hemangiopericytoma, melanoma, stomach adenocarcinoma, biliary cancer, parotid adenocarcinoma, and colon cancer). All patients with a malignancy had a paternal 15q11-13 deletion. The literature review showed that several genes on chromosome 15q11.2-q13 are related to malignancies.

CONCLUSION

Malignancies are rare in patients with PWS. Therefore, screening for malignancies is only indicated when clinically relevant symptoms are present, such as unexplained weight loss, loss of appetite, symptoms suggestive of paraneoplastic syndrome, or localizing symptoms. Given the increased cancer risk associated with obesity, which is common in PWS, participation in national screening programs should be encouraged.

Hormonal Imbalances in Prader-Willi and Schaaf-Yang Syndromes Imply the Evolution of Specific Regulation of Hypothalamic Neuroendocrine Function in Mammals

The hypothalamus regulates fundamental aspects of physiological homeostasis and behavior, including stress response, reproduction, growth, sleep, and feeding, several of which are affected in patients with Prader-Willi (PWS) and Schaaf-Yang syndrome (SYS). PWS is caused by paternal deletion, maternal uniparental disomy, or imprinting defects that lead to loss of expression of a maternally imprinted region of chromosome 15 encompassing non-coding RNAs and five protein-coding genes; SYS patients have a mutation in one of them, MAGEL2. Throughout life, PWS and SYS patients suffer from musculoskeletal deficiencies, intellectual disabilities, and hormonal abnormalities, which lead to compulsive behaviors like hyperphagia and temper outbursts. Management of PWS and SYS is mostly symptomatic and cures for these debilitating disorders do not exist, highlighting a clear, unmet medical need. Research over several decades into the molecular and cellular roles of PWS genes has uncovered that several impinge on the neuroendocrine system. In this review, we will discuss the expression and molecular functions of PWS genes, connecting them with hormonal imbalances in patients and animal models. Besides the observed hormonal imbalances, we will describe the recent findings about how the loss of individual genes, particularly MAGEL2, affects the molecular mechanisms of hormone secretion. These results suggest that MAGEL2 evolved as a mammalian-specific regulator of hypothalamic neuroendocrine function.

[Energy exchange: how we can personalize obesity therapy]

Obesity is a consequence of chronic energy imbalance when energy intake constantly exceeds expenditure, which leads to excess white adipose tissue accumulation. Effective treatment of obesity requires accurate measure of calories intake and expenditure, as well as related behavior to understand how energy homeostasis is regulated and evaluate the effectiveness of the measures taken. The greatest interest is to study features of energy metabolism in various forms of obesity. It is necessary to create an evidence-based, personalized approach to diet therapy and to increase the effectiveness of weight loss measures. Modern studies have shown that the use of indirect calorimetry in obesity treatment programs leads to greater weight loss compared to traditional diet therapy planning based on calculated formulas.

Obesity in Prader-Willi syndrome: physiopathological mechanisms, nutritional and pharmacological approaches

Prader-Willi syndrome (PWS) is a genetic disorder caused by the lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region. The three main genetic subtypes are represented by paternal 15q11-q13 deletion, maternal uniparental disomy 15, and imprinting defect. Clinical picture of PWS changes across life stages. The main clinical characteristics are represented by short stature, developmental delay, cognitive disability and behavioral diseases. Hypotonia and poor suck resulting in failure to thrive are typical of infancy. As the subjects with PWS age, clinical manifestations such as hyperphagia, temperature instability, high pain threshold, hypersomnia and multiple endocrine abnormalities including growth hormone and thyroid-stimulating hormone deficiencies, hypogonadism and central adrenal insufficiency due to hypothalamic dysfunction occur. Obesity and its complications are the most common causes of morbidity and mortality in PWS. Several mechanisms for the aetiology of obesity in PWS have been hypothesized, which include aberration in hypothalamic pathways of satiety control resulting in hyperphagia, disruption in hormones regulating appetite and satiety and reduced energy expenditure. However, despite the advancement in the research field of the genetic basis of obesity in PWS, there are contradictory data on the management. Although it is mandatory to adopt obesity strategy prevention from infancy, there is promising evidence regarding the management of obesity in adulthood with current obesity drugs along with lifestyle interventions, although the data are limited. Therefore, the current manuscript provides a review of the current evidence on obesity and PWS, covering physiopathological aspects, obesity-related complications and conservative management.

Hypothalamic neuropeptides and neurocircuitries in Prader Willi syndrome

Prader-Willi Syndrome (PWS) is a rare and incurable congenital neurodevelopmental disorder, resulting from the absence of expression of a group of genes on the paternally acquired chromosome 15q11-q13. Phenotypical characteristics of PWS include infantile hypotonia, short stature, incomplete pubertal development, hyperphagia and morbid obesity. Hypothalamic dysfunction in controlling body weight and food intake is a hallmark of PWS. Neuroimaging studies have demonstrated that PWS subjects have abnormal neurocircuitry engaged in the hedonic and physiological control of feeding behavior. This is translated into diminished production of hypothalamic effector peptides which are responsible for the coordination of energy homeostasis and satiety. So far, studies with animal models for PWS and with human post-mortem hypothalamic specimens demonstrated changes particularly in the infundibular and the paraventricular nuclei of the hypothalamus, both in orexigenic and anorexigenic neural populations. Moreover, many PWS patients have a severe endocrine dysfunction, e.g. central hypogonadism and/or growth hormone deficiency, which may contribute to the development of increased fat mass, especially if left untreated. Additionally, the role of non-neuronal cells, such as astrocytes and microglia in the hypothalamic dysregulation in PWS is yet to be determined. Notably, microglial activation is persistently present in non-genetic obesity. To what extent microglia, and other glial cells, are affected in PWS is poorly understood. The elucidation of the hypothalamic dysfunction in PWS could prove to be a key feature of rational therapeutic management in this syndrome. This review aims to examine the evidence for hypothalamic dysfunction, both at the neuropeptidergic and circuitry levels, and its correlation with the pathophysiology of PWS.

Irisin levels in genetic and essential obesity: clues for a potential dual role

Irisin is conventionally regarded as a myokine involved in the browning of white adipose tissue, energy expenditure and glucose tolerance. Its potential link to fat accumulation and metabolic dysfunction is debated. We sought to explore the relationship between circulating irisin and components of body composition in two different phenotypes of severe obesity. For this purpose, 30 obese adults with Prader-Will syndrome (PWS) (age 35.7 ± 1.5 y, BMI 45.5 ± 1.5 kg/m²) and 30 adult controls with common obesity (age 34.9 ± 1.7 y, BMI 46.8 ± 1.4 kg/m²) underwent analysis of irisin levels, metabolic profile, body composition and resting energy expenditure (REE). Normal irisin levels were obtained from a group of 20 lean donors (age 32.4 ± 1.5 y, BMI 23.8 ± 0.8 kg/m²). Expected differences in body composition and metabolic profile existed between study groups. PWS exhibited lower muscle mass (p < 0.001), FFM (p < 0.001), REE (p < 0.001), as well as insulin (p < 0.05), HOMA-IR (p < 0.05) and triglycerides levels (p < 0.05) than controls with common obesity. In PWS, irisin levels were significantly lower and overall less dispersed than in controls with common obesity (p < 0.05), while being similar to values recorded in lean subjects. To explore the relation between irisin and body composition in obesity, univariate correlation analysis in the obese populations as a whole showed positive associations between irisin and muscle mass (p = 0.03) as well as REE (p = 0.01), which disappeared when controlled for the PWS status. Noticeably, a positive association became evident between irisin and %FM after controlling for the PWS status (p = 0.02). Also positive were associations between irisin and insulin (p = 0.02), HOMA-IR (p = 0.02) and triglycerides (p = 0.04). In stepwise multivariable regression analysis, irisin levels were independently predicted by the PWS status (p = 0.001), %FM (p = 0.004) and triglycerides (p = 0.008). Current results suggest that obese adults with PWS harbor lower irisin levels than individuals with common obesity. The divergent models of obesity herein studied suggest a potential link between circulating irisin and muscle mass and metabolic dysfunction relating to adiposity.

Diagnosis of obesity and use of obesity biomarkers in science and clinical medicine

The global epidemic of obesity is a major public health problem today. Obesity increases the risk of many chronic diseases, such as type 2 diabetes, coronary heart disease, and certain types of cancer, and is associated with lower life expectancy. The body mass index (BMI), which is currently used to classify obesity, is only an imperfect measure of abnormal or excessive body fat accumulation. Studies have shown that waist circumference as a measure of fat distribution may improve disease prediction. More elaborate techniques such as magnetic resonance imaging are increasingly available to assess body fat distribution, but these measures are not readily available in routine clinical practice, and health-relevant cut-offs not yet been established. The measurement of biomarkers that reflect the underlying biological mechanisms for the increased disease risk may be an alternative approach to characterize the relevant obesity phenotype. The insulin/insulin-like growth factor (IGF) axis and chronic low-grade inflammation have been identified as major pathways. In addition, specific adipokines such as leptin, adiponectin and resistin have been related to obesity-associated health outcomes. This biomarker research, which is currently further developed with the application of high throughput methods, gives important insights in obesity-related disease etiology and pathophysiological pathways and may be used to better characterize obese persons at high risk of disease development and target disease-causing biomarkers in personalized prevention strategies.

Increased brain age in adults with Prader-Willi syndrome

Prader-Willi syndrome (PWS) is the most common genetic obesity syndrome, with associated learning difficulties, neuroendocrine deficits, and behavioural and psychiatric problems. As the life expectancy of individuals with PWS increases, there is concern that alterations in brain structure associated with the syndrome, as a direct result of absent expression of PWS genes, and its metabolic complications and hormonal deficits, might cause early onset of physiological and brain aging. In this study, a machine learning approach was used to predict brain age based on grey matter (GM) and white matter (WM) maps derived from structural neuroimaging data using T1-weighted magnetic resonance imaging (MRI) scans. Brain-predicted age difference (brain-PAD) scores, calculated as the difference between chronological age and brain-predicted age, are designed to reflect deviations from healthy brain aging, with higher brain-PAD scores indicating premature aging. Two separate adult cohorts underwent brain-predicted age calculation. The main cohort consisted of adults with PWS (n = 20; age mean 23.1 years, range 19.8-27.7; 70.0% male; body mass index (BMI) mean 30.1 kg/m2, 21.5-47.7; n = 19 paternal chromosome 15q11-13 deletion) and age- and sex-matched controls (n = 40; age 22.9 years, 19.6-29.0; 65.0% male; BMI 24.1 kg/m2, 19.2-34.2) adults (BMI PWS vs. control P = .002). Brain-PAD was significantly greater in PWS than controls (effect size mean ± SEM +7.24 ± 2.20 years [95% CI 2.83, 11.63], P = .002). Brain-PAD remained significantly greater in PWS than controls when restricting analysis to a sub-cohort matched for BMI consisting of n = 15 with PWS with BMI range 21.5-33.7 kg/m2, and n = 29 controls with BMI 21.7-34.2 kg/m2 (effect size +5.51 ± 2.56 years [95% CI 3.44, 10.38], P = .037). In the PWS group, brain-PAD scores were not associated with intelligence quotient (IQ), use of hormonal and psychotropic medications, nor severity of repetitive or disruptive behaviours. A 24.5 year old man (BMI 36.9 kg/m2) with PWS from a SNORD116 microdeletion also had increased brain PAD of 12.87 years, compared to 0.84 ± 6.52 years in a second control adult cohort (n = 95; age mean 34.0 years, range 19.9-55.5; 38.9% male; BMI 28.7 kg/m2, 19.1-43.1). This increase in brain-PAD in adults with PWS indicates abnormal brain structure that may reflect premature brain aging or abnormal brain development. The similar finding in a rare patient with a SNORD116 microdeletion implicates a potential causative role for this PWS region gene cluster in the structural brain abnormalities associated primarily with the syndrome and/or its complications. Further longitudinal neuroimaging studies are needed to clarify the natural history of this increase in brain age in PWS, its relationship with obesity, and whether similar findings are seen in those with PWS from maternal uniparental disomy.

Prediction of Circulating Adipokine Levels Based on Body Fat Compartments and Adipose Tissue Gene Expression

BACKGROUND

Adipokines are hormones secreted from adipose tissue (AT), and a number of them have been established as risk factors for chronic diseases. However, it is not clear whether and to what extent adiposity, gene expression, and other factors determine their circulating levels.

OBJECTIVES

To assess to what extent adiposity, as measured by the amount of subcutaneous AT (SAT) and visceral AT (VAT) using magnetic resonance imaging, and gene expression levels in SAT determine plasma concentrations of the adipokines adiponectin, leptin, soluble leptin receptor, resistin, interleukin 6, and fatty acid-binding protein 4 (FABP4).

METHODS

We performed a cross-sectional analysis of 156 participants from the EPIC Potsdam cohort study and analyzed multiple regression models and partial correlation coefficients.

RESULTS

For leptin and FABP4 concentrations, 81 and 45% variance were explained by SAT mass, VAT mass, and gene expression in SAT in multivariable regression models. For the remaining adipokines, AT mass and gene expression explained <16% variance of plasma concentrations. Gene expression in SAT was a less important predictor compared to AT mass. SAT mass was a better predictor than VAT mass for leptin (partial correlation r = 0.81, 95% confidence interval 0.75-0.86, vs. r = 0.58, 95% confidence interval 0.46-0.67), while differences between AT compartments were small for the other adipokines.

CONCLUSIONS

While plasma levels of leptin and FABP4 can be explained in a large and medium part by the amount of AT and SAT gene expression, surprisingly, these predictors explained only little variance for all other investigated adipokines.

Body composition, adipokines, bone mineral density and bone remodeling markers in relation to IGF-1 levels in adults with Prader-Willi syndrome

Background

In patients with Prader-Willi syndrome (PWS) body composition is abnormal and alterations in appetite regulating factors, bone mineral density and insulin-like growth factor-1 (IGF-1) levels have been described. Studies in PWS adults are limited. In this study, we investigated body composition, appetite regulating peptides, bone mineral density and markers of bone remodeling in an adult PWS population. Furthermore, we investigated the association between these different parameters and IGF-1 levels because of the described similarities with growth hormone deficient patients.

Methods

In this cross-sectional observational cohort study in a university hospital setting we studied fifteen adult PWS patients. Anthropometric and metabolic parameters, IGF-1 levels, bone mineral density and bone metabolism were evaluated. The homeostasis model assessment of insulin resistance (HOMA2-IR) was calculated. Fourteen healthy siblings served as a control group for part of the measurements.

Results

In the adult PWS patients, height, fat free mass, IGF-1 and bone mineral content were significantly lower when compared to controls; body mass index (BMI), waist, waist-to-hip ratio and fat mass were higher. There was a high prevalence of osteopenia and osteoporosis in the PWS patients. Also, appetite regulating peptides and bone remodelling markers were aberrant when compared to reference values. Measurements of body composition were significantly correlated to appetite regulating peptides and high-sensitive C-reactive protein (hs-CRP), furthermore HOMA was correlated to BMI and adipokines.

Conclusion

In adults with Prader-Willi syndrome alterations in body composition, adipokines, hs-CRP and bone mineral density were demonstrated but these were not associated with IGF-1 levels. Further investigations are warranted to gain more insight into the exact pathophysiology and the role of these alterations in the metabolic and cardiovascular complications seen in PWS, so these complications can be prevented or treated as early as possible.

Energy Metabolism Profile in Individuals with Prader-Willi Syndrome and Implications for Clinical Management: A Systematic Review

Prader-Willi syndrome (PWS) is a rare genetic disorder associated with excessive weight gain. Hyperphagia associated with PWS may result in higher energy intake, but alterations in energy expenditure may also contribute to energy imbalance. The purpose of this critical literature review is to determine the presence of alterations in energy expenditure in individuals with PWS. Ten studies that measured total energy expenditure (TEE), resting energy expenditure (REE), sleep energy expenditure (SEE), activity energy expenditure (AEE), and diet induced thermogenesis (DIT) were included in this review. The studies provided evidence that absolute TEE, REE, SEE, and AEE are lower in individuals with PWS than in age-, sex-, and body mass index-matched individuals without the syndrome. Alterations in lean body mass and lower physical activity amounts appear to be responsible for the lower energy expenditure in PWS rather than metabolic differences. Regardless of the underlying mechanism for lower TEE, the estimation of energy requirements with the use of equations derived for the general population would result in weight gain in individuals with PWS. The determination of energy requirements for weight management in individuals with PWS requires a more comprehensive understanding of energy metabolism. Future studies should aim to comprehensively profile all specific components of energy expenditure in individuals with PWS with the use of appropriately matched controls and gold standard methods to measure energy metabolism and body composition. One component of energy expenditure that is yet to be explored in detail in PWS is DIT. A reduced DIT (despite differences in fat free mass), secondary to hormonal dysregulation, may be present in PWS individuals, leading to a reduced overall energy expenditure. Further research exploring DIT in PWS needs to be conducted. Dietary energy recommendations for weight management in PWS have not yet been clearly established.

Concentrations of leptin, adiponectin and other metabolic parameters in non-obese children with Down syndrome

BACKGROUND

Recent data indicates that adults with Down syndrome (DS) are at increased risk for cardiovascular disease (CVD) that significantly contributes to their morbidity and mortality. Although identification of cardiometabolic risk factors during childhood is desirable to design preventive interventions, the data on such risk factors in children with DS is scarce. The aim of this study was to study the cardiometabolic risk factors such as insulin resistance (IR), leptin and adiponectin concentrations, lipid abnormalities and leptin resistance in non-obese children with DS.

METHODS

This cross-sectional case control study included karyotype confirmed trisomy-21 DS children aged 2-12 years and their matched healthy controls. After detailed anthropometry, weight, height and body mass index (BMI) standard deviation scores (SDSs) were calculated with reference data. Laboratory evaluation included determination of fasting lipid parameters, insulin, glucose, leptin and adiponectin concentrations. The homeostasis model assessment method (HOMA-IR) was used to assess IR and the ratio of leptin to BMI was used as an index of leptin resistance.

RESULTS

Seventy-seven children (39 with DS and 38 controls) comprised the study cohort. The anthropometric parameters were similar in the two groups. Children with DS showed significantly higher mean leptin concentrations (2.098±1.68 ng/mL vs. 1.44±0.52 ng/mL, p-value: 0.00) and higher indices of leptin resistance (0.127±0.085 vs. 0.09±0.03, p-value: 0.001) as compared to controls. Fasting adiponectin concentrations were lower (20.64±19.87 ng/mL vs. 32.58±34.25 ng/mL, p-value: 0.21) and fasting glucose higher (89.25±8.12 mg/dL vs. 85.71±5.52 mg/dL, p-value: 0.06) in the DS group as compared to the controls but the differences did not reach statistical significance. The concentrations of insulin, various lipid parameters and calculated HOMA-IR values were similar in the two groups. In the DS group, five children were identified to have high (>75th centile) leptin levels and four as impaired fasting glucose as compared to none in the controls.

CONCLUSIONS

Alterations of several cardiometabolic risk factors, in particular, leptin concentrations and leptin resistance are present in children with DS. The presence of hyperleptinemia without hyperinsulinemia suggests a probable inherent genetic basis for increased leptin resistance in patients with DS. There is a need for larger studies to further understand increased leptin resistance in DS that may contribute to increased CVD related morbidity and mortality in these patients.

Appetite Regulation: Hormones, Peptides, and Neurotransmitters and Their Role in Obesity

Understanding body weight regulation will aid in the development of new strategies to combat obesity. This review examines energy homeostasis and food intake behaviors, specifically with regards to hormones, peptides, and neurotransmitters in the periphery and central nervous system, and their potential role in obesity. Dysfunction in feeding signals by the brain is a factor in obesity. The hypothalamic (arcuate nucleus) and brainstem (nucleus tractus solitaris) areas integrate behavioral, endocrine, and autonomic responses via afferent and efferent pathways from and to the brainstem and peripheral organs. Neurons present in the arcuate nucleus express pro-opiomelanocortin, Neuropeptide Y, and Agouti Related Peptide, with the former involved in lowering food intake, and the latter two acutely increasing feeding behaviors. Action of peripheral hormones from the gut, pancreas, adipose, and liver are also involved in energy homeostasis. Vagal afferent neurons are also important in regulating energy homeostasis. Peripheral signals respond to the level of stored and currently available fuel. By studying their actions, new agents maybe developed that disable orexigenic responses and enhance anorexigenic signals. Although there are relatively few medications currently available for obesity treatment, a number of agents are in development that work through these pathways.

Cellular and disease functions of the Prader-Willi Syndrome gene MAGEL2

Melanoma antigen L2 (MAGEL2 or MAGE-L2) is a member of the MAGE family of ubiquitin ligase regulators. It is maternally imprinted and often paternally deleted or mutated in the related neurodevelopmental syndromes, Prader-Willi Syndrome (PWS) and Schaaf-Yang Syndrome (SHFYNG). MAGEL2 is highly expressed in the hypothalamus and plays an important role in a fundamental cellular process that recycles membrane proteins from endosomes through the retromer sorting pathway. MAGEL2 is part of a multi-subunit protein complex consisting of MAGEL2, the TRIM27 E3 ubiquitin ligase, and the USP7 deubiquitinating enzyme. The MAGEL2-USP7-TRIM27 (or MUST) complex facilitates the retromer recycling pathway through ubiquitination and activation of the WASH actin nucleation promoting factor. This review provides an overview of the MAGE protein family of ubiquitin ligases regulators and details the molecular and cellular role of MAGEL2 in ubiquitination, actin regulation and endosomal sorting processes, as well as MAGEL2 implications in PWS and SHFYNG disorders. The physiological functions of MAGEL2, elucidated through the study of Magel2 knockout mouse models, are also discussed.

Circulating angiopoietin-like 8 (ANGPTL8) is a marker of liver steatosis and is negatively regulated by Prader-Willi Syndrome

ANGPTL8 is a liver-derived protein related to insulin-sensitivity. Its relationship with obesity and liver function in Prader-Willi syndrome (PWS) is unknown. The present study investigated circulating ANGPTL8 in PWS and controls with common obesity, assessing its association to liver steatosis. For this purpose, 20 obese PWS and 20 controls matched for body mass index (BMI), sex and age underwent analysis of ANGPTL8 levels, glucose and lipid metabolism. Liver function tests and degree of liver steatosis by ultrasonography (US), fat-free mass (FFM) and fat mass (FM) by dual-energy x-ray absorptiometry (DEXA) were also assessed. In comparison to controls, obese PWS showed lower values of FFM (p < 0.0001) and higher FM (p = 0.01), while harbouring higher HDL cholesterol, lower triglycerides and OGTT-derived insulin levels, as well as a lower prevalence and severity of liver steatosis. With respect to obese controls, ANGPTL8 levels were significantly lower in PWS (p = 0.007) and overall correlated with transaminase levels and the severity of liver steatosis, as well as FFM (p < 0.05 for all). By a stepwise multivariable regression analysis, ANGPTL8 levels were independently predicted by PWS status (p = 0.01) and liver steatosis (p < 0.05). In conclusion, ANGPTL8 levels are lower in PWS than obese controls and are inversely associated with the severity of liver steatosis. Further studies should investigate the potential genetic basis for this observation.

Targeting the endocannabinoid/CB1 receptor system for treating obesity in Prader-Willi syndrome

Objective

Extreme obesity is a core phenotypic feature of Prader–Willi syndrome (PWS). Among numerous metabolic regulators, the endocannabinoid (eCB) system is critically involved in controlling feeding, body weight, and energy metabolism, and a globally acting cannabinoid-1 receptor (CB₁R) blockade reverses obesity both in animals and humans. The first-in-class CB₁R antagonist rimonabant proved effective in inducing weight loss in adults with PWS. However, it is no longer available for clinical use because of its centrally mediated, neuropsychiatric, adverse effects.

Methods

We studied eCB ‘tone’ in individuals with PWS and in the Magel2-null mouse model that recapitulates the major metabolic phenotypes of PWS and determined the efficacy of a peripherally restricted CB₁R antagonist, JD5037 in treating obesity in these mice.

Results

Individuals with PWS had elevated circulating levels of 2-arachidonoylglycerol and its endogenous precursor and breakdown ligand, arachidonic acid. Increased hypothalamic eCB ‘tone’, manifested by increased eCBs and upregulated CB₁R, was associated with increased fat mass, reduced energy expenditure, and decreased voluntary activity in Magel2-null mice. Daily chronic treatment of obese Magel2-null mice and their littermate wild-type controls with JD5037 (3 mg/kg/d for 28 days) reduced body weight, reversed hyperphagia, and improved metabolic parameters related to their obese phenotype.

Conclusions

Dysregulation of the eCB/CB₁R system may contribute to hyperphagia and obesity in Magel2-null mice and in individuals with PWS. Our results demonstrate that treatment with peripherally restricted CB₁R antagonists may be an effective strategy for the management of severe obesity in PWS.

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Circulating levels of endocannabinoids are increased in individuals with PWS.

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Magel2 is a negative regulator of hypothalamic endocannabinoid ‘tone’.

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Peripherally-restricted CB1 receptor blockade reverses obesity in Magel2-null mice.

Prediction of basal metabolic rate in patients with Prader-Willi syndrome

BACKGROUND/OBJECTIVES

The objective of this study was to develop new equations for predicting basal metabolic rate (BMR) in Prader-Willi syndrome (PWS) subjects and to compare their accuracy with commonly used equations developed by Lazzer (2007), Livingston (2005), Huang (2004), Nelson (1992), Mifflin (1990), Owen (1987), WHO (1985), Bernstein (1983) and Harris-Benedict (1919), using the Bland-Altman method.

SUBJECTS/METHODS

BMR was measured by indirect calorimetry and fat-free mass (FFM) and fat mass (FM) by a tetrapolar impedancemeter in 80 Caucasian PWS patients (mean body mass index: 39.1 kg/m(2); 17-50 years). Equations were derived by stepwise multiple regression analysis using a calibration group (n:50) and tested against the validation group (n:30).

RESULTS

Two new equations, based on anthropometric (BMR=body mass × 0.052+sex × 0.778-age × 0.033+2.839 (R(2)adj=0.61, s.e.=0.89 MJ per day)) or body composition (BMR=FFMx0.074+FMx0.042+sexx0.636-agex0.037+2.515 (R(2)adj=0.69, s.e.=0.82 MJ per day)), were generated. Predicted BMR (PBMR) was not significantly different from the measured BMR (<3.3%), and was accurate in 59% and 62% of patients, respectively. Nevertheless, significant magnitude bias was found for both equations (P<0.001, R(2)=0.36). The Owen (1987), Mifflin (1990), Huang (2004) and Lazzer (2007) equations showed mean differences <5% and PBMR was accurate in ~50% of patients. The Livingston (2005), WHO (1985) and Harris-Benedict (1919) equations showed a PBMR overestimation >7% and were accurate in <50% of patients. The Nelson (1992) and Bernstein (1983) equations showed a greater PBMR underestimation in >60% of subjects.

CONCLUSIONS

The new prediction equations showed significantly higher accuracy compared with equations tested, with exception of Lazzer (2007) and Livingston (2005) equations, and result in lower mean differences and lower limits of agreement compared with the equations tested.

Glucose homeostasis in adults with Prader-Willi syndrome during treatment with growth hormone: results from a 12-month prospective study

OBJECTIVES

To investigate glucose homeostasis in relation to body mass index (BMI) in adults with PWS before and after GH therapy.

DESIGN

We prospectively investigated the effects of a 12-month GH treatment on body composition and glucose homeostasis in relation to BMI in 39 adults, mean (±SD) age=28.6 (6.5) years with genetically verified PWS. We compared the results for different BMI categories (<25 kg/m²; 25-30 kg/m²; >30 kg/m²) and performed a regression analysis to detect predictors for homeostasis model of assessment-insulin resistance (HOMA-IR).

RESULTS

The baseline HOMA-IR was higher, with BMI of >30 kg/m². Our main findings were as follows: i) GH treatment (mean final dose, 0.6 (0.25) mg) was associated with small increases in fasting p-glucose, 2-h p-glucose by oral glucose load tolerance test, HOMA-IR and lean mass, and a reduction in fat mass. ii) Whereas the baseline HOMA-IR was associated with increased BMI (>30 kg/m²), we found no differences in HOMA-IR among the BMI categories after 12 months of GH. iii) Stepwise linear regression identified the triglyceride level as the strongest predictor of HOMA-IR at baseline, whereas an increase in VAT was the strongest predictor of the increase in HOMA-IR after therapy.

CONCLUSIONS

GH treatment for 12 months in adults with PWS resulted in an increase in HOMA-IR, irrespective of BMI, confirming that control of HbA1c is essential during GH treatment in PWS.

Whole body fat: content and distribution

Obesity and its co-morbidities, including type II diabetes, insulin resistance and cardiovascular diseases, have become one of the biggest health issues of present times. The impact of obesity goes well beyond the individual and is so far-reaching that, if it continues unabated, it will cause havoc with the economies of most countries. In order to be able to fully understand the relationship between increased adiposity (obesity) and its co-morbidity, it has been necessary to develop proper methodology to accurately and reproducibly determine both body fat content and distribution, including ectopic fat depots. Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) have recently emerged as the gold-standard for accomplishing this task. Here, we will review the use of different MRI techniques currently being used to determine body fat content and distribution. We also discuss the pros and cons of MRS to determine ectopic fat depots in liver, muscle, pancreas and heart and compare these to emerging MRI techniques currently being put forward to create ectopic fat maps. Finally, we will discuss how MRI/MRS techniques are helping in changing the perception of what is healthy and what is normal and desirable body-fat content and distribution.

Two years of growth hormone treatment in adults with Prader-Willi syndrome do not improve the low BMD

BACKGROUND

Bone mineral density (BMD) in adult patients with Prader-Willi syndrome (PWS) might be low due to high bone turnover.

OBJECTIVES

The objective of the study was to investigate bone mass in a group of adult PWS subjects and study the effects of GH treatment on BMD and markers of bone turnover.

DESIGN

Forty-six adults with genetically verified PWS were randomized to GH or placebo for 12 months, followed by open prospective GH for 24 additional months. BMD at the lumbar spine (LS) L1-4, the total hip, and the total body was assessed by dual-energy x-ray absorptiometry at baseline and every 12th month thereafter. Markers of bone turnover were measured at baseline and at the end of the controlled study.

RESULTS

In this cohort of adult subjects with PWS, baseline BMD was reduced in all compartments compared with the reference (Z-scores). Men had lower Z-scores BMD than women in LS and total body (P < .05). With 12 months of GH, LS-BMD was significantly reduced compared with placebo. No changes in BMD were observed with continuous GH treatment for 24 months. The bone formation markers increased with GH therapy compared with placebo, whereas the resorption marker did not change.

CONCLUSIONS

Adult PWS subjects, especially the men, have low bone mass that was not improved with GH treatment for 2 years. Because PWS subjects are short, BMD might be underestimated and should be adjusted for. Further studies, with adequate GH and sex hormone replacement throughout puberty and early adult life, are needed to better characterize PWS.

Comparison of body composition, basal metabolic rate and metabolic outcomes of adults with Prader Willi syndrome or lesional hypothalamic disease, with primary obesity

CONTEXT

The care of patients with hypothalamic obesity is challenging.

OBJECTIVE

To compare body composition, basal metabolic rate (BMR) and metabolic outcomes of adults, with lesional or genetic hypothalamic obesity, with obese patients suffering from primary obesity, once matched for body mass index (BMI).

DESIGN AND PATIENTS

Adults with hypothalamic obesity of genetic origin (Prader Willi syndrome (PWS)) or acquired hypothalamic damage (HD), such as craniopharygioma, were compared with obese control candidates awaiting bariatric surgery (C), with a BMI between 35 and 65 kg m(-)(2), and aged between 18 and 50 years.

MAIN OUTCOME MEASURES

Body composition measured by whole-body dual-energy X-ray absorptiometry scanning, BMR using indirect calorimetry, hormonal and metabolic assessments.

RESULTS

A total of 27 adults with a genetic diagnosis of PWS, 15 obese subjects with HD and 206 obese controls with similar BMI were studied. Compared with the control group, PWS patients had an increased percentage of fat mass (FM), and a decreased percentage of android FM. The BMR of PWS patients was significantly lower than controls and highly correlated with lean body mass in PWS and C patients. Body composition of HD was similar with those of obese patients. A trend toward an increased prevalence of diabetes in HD patients and of cytolysis in PWS was observed in comparison with primary obese patients.

CONCLUSION

Genetic and lesional hypothalamic obesities have different consequences for phenotypic features such as body composition or BMR compared with primary obese patients. The mechanisms of adipose tissue development and metabolic complications may be different between genetic and lesional obesities.

Characterization of fat distribution in Prader-Willi syndrome: relationships with adipocytokines and influence of growth hormone treatment

Marked anthropometric changes are seen in Prader-Willi syndrome (PWS). Emaciation is observed during infancy, whereas severe obesity is found in older children and adults. Growth hormone (GH) treatment modifies the anthropometric changes in PWS patients. In this study, we examined changes in the body composition of 51 PWS patients (age range, 6-54 years; median, 16.5 years), with a focus on the amount of abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), VAT/SAT ratio, and serum levels of adipocytokines (adiponectin, leptin, and resistin). The relationships between VAT, SAT, and adipocytokines, and lipid abnormalities and type 2 diabetes in 24 patients with obese PWS were also evaluated. With increasing age, SAT and VAT both increased markedly, but in 18 patients receiving GH treatment, VAT remained low at ≤30 cm(2) . In the GH-completed patients (n = 19), VAT and SAT increased with age to levels similar to those in non-GH-treated patients (n = 14). In the obese group, adiponectin decreased as VAT increased (r = -0.35, P = 0.11). Leptin (r = 0.67, P < 0.001) and resistin (r = 0.45, P = 0.04) showed positive correlations with SAT. Total cholesterol, low-density lipoprotein, and triglyceride levels correlated negatively with adiponectin (r = -0.59, r = -0.56, r = -0.56, respectively, P < 0.05) and hemoglobin A1c (r = -0.42, P = 0.08). To maintain lower VAT and prevent cardiovascular disease risk factors, GH treatment may be advisable even in adult patients with PWS.

Excess body fat in obese and normal-weight subjects

Excess body adiposity, especially abdominal obesity and ectopic fat accumulation, are key risk factors in the development of a number of chronic diseases. The advent of in vivo imaging methodologies that allow direct assessment of total body fat and its distribution have been pivotal in this process. They have helped to identify a number of sub-phenotypes in the general population whose metabolic risk factors are not commensurate with their BMI. At least two such sub-phenotypes have been identified: subjects with normal BMI, but excess intra-abdominal (visceral) fat (with or without increased ectopic fat) and subjects with elevated BMI (> 25 kg/m(2)) but low visceral and ectopic fat. The former sub-phenotype is associated with adverse metabolic profiles, while the latter is associated with a metabolically normal phenotype, despite a high BMI. Here, examples of these phenotypes are presented and the value of carrying out enhanced phenotypical characterisation of subjects in interventional studies discussed.

Appetite hormones and the transition to hyperphagia in children with Prader-Willi syndrome

OBJECTIVE

Prader-Willi syndrome (PWS) is a genetic neurodevelopmental disorder with several nutritional phases during childhood proceeding from poor feeding, through normal eating without and with obesity, to hyperphagia and life-threatening obesity, with variable ages of onset. We investigated whether differences in appetite hormones may explain the development of abnormal eating behaviour in young children with PWS.

SUBJECTS

In this cross-sectional study, children with PWS (n=42) and controls (n=9) aged 7 months-5 years were recruited. Mothers were interviewed regarding eating behaviour, and body mass index (BMI) was calculated. Fasting plasma samples were assayed for insulin, leptin, glucose, peptide YY (PYY), ghrelin and pancreatic polypeptide (PP).

RESULTS

There was no significant relationship between eating behaviour in PWS subjects and the levels of any hormones or insulin resistance, independent of age. Fasting plasma leptin levels were significantly higher (mean ± s.d.: 22.6 ± 12.5 vs 1.97 ± 0.79 ng ml(-1), P=0.005), and PP levels were significantly lower (22.6 ± 12.5 vs 69.8 ± 43.8 pmol l(-1), P<0.001) in the PWS group compared with the controls, and this was independent of age, BMI, insulin resistance or IGF-1 levels. However, there was no significant difference in plasma insulin, insulin resistance or ghrelin levels between groups, though PYY declined more rapidly with age but not BMI in PWS subjects.

CONCLUSION

Even under the age of 5 years, PWS is associated with low levels of anorexigenic PP, as in older children and adults. Hyperghrelinaemia or hypoinsulinaemia was not seen in these young children with PWS. Change in these appetite hormones was not associated with the timing of the transition to the characteristic hyperphagic phase. However, abnormal and/or delayed development or sensitivity of the effector pathways of these appetitive hormones (for example, parasympathetic and central nervous system) may interact with low PP levels, and later hyperghrelinaemia or hypoinsulinaemia, to contribute to hyperphagia in PWS.

Autonomic nervous system dysfunction in obesity and Prader-Willi syndrome: current evidence and implications for future obesity therapies

The autonomic nervous system (ANS) controls essential functions like breathing, heart rate, digestion, body temperature and hormone levels. Evidence suggests that ANS dysfunction is associated with adult and childhood obesity and plays a role in the distribution of total body fat and the development of obesity-related complications in humans. This review summarizes our current understanding of ANS involvement in the pathogenesis of obesity and Prader-Willi syndrome. Available evidence of ANS dysfunction in the control of energy balance is limited and, in some cases, contradictory. Further investigation in this area is warranted in order to better understand the important contributions of the ANS to regulation of body fat, development of obesity and its comorbidities. Results from these studies will guide the development of novel obesity therapeutics targeting specific ANS dysfunction.

The relationship between IGF-I concentration, cognitive function and quality of life in adults with Prader-Willi syndrome

Mental retardation is one of the clinical characteristics of Prader-Willi syndrome (PWS) and in part of the patients growth hormone deficiency is demonstrable. Cognitive function seems to be influenced by insulin-like growth factor I (IGF-I); however, little is known about cognitive function in relation to IGF-I levels in PWS adults. The aim of the present study was to evaluate cognitive function in adult PWS patients in comparison to healthy siblings and to investigate whether there is a correlation between cognitive function and IGF-I levels. Anthropometric measurements, IGF-I levels, quality of life (QoL), Appetite Assessment Score, IQ (GIT and Raven) and cognitive function (by four subtests of the Cambridge Neuropsychological Automated Testing Battery, CANTAB) were evaluated in PWS patients and their healthy siblings served as control group. PWS patients had significantly lower IGF-I levels, IQ and QoL when compared to controls. Reaction times were longer and performance was worse on CANTAB subtests in PWS adults. IGF-I on one hand and IQ, Appetite Assessment Score and cognitive performance on the other hand seem to be correlated in PWS patients. In conclusion, IGF-I levels, IQ and QoL are significantly lower in PWS subjects when compared to healthy siblings. In PWS adults, temporal as well as prefrontal cognitive functions are impaired. Higher IGF-I levels appear to be related to better intellectual skills and faster temporal memory processing in PWS patients.

Psychiatric adverse effects of rimonobant in adults with Prader Willi syndrome

BACKGROUND

Prader Willi syndrome (PWS) without strict environmental modifications can lead to obesity associated with significant morbidity and mortality. In addition to increased appetite, these individuals have decreased energy expenditure with lower insulin like growth factor 1 (IGF1), which contributes to adiposity. No effective treatment is available for this condition. Endocannabinoid receptor CB1 antagonist, rimonobant, has been effective for treatment of obesity in adult subjects. Rimonabant promotes weight loss by multiple proposed mechanisms, including decreased appetite and lipogenesis, and increased energy expenditure. Therefore, we conducted this pilot study to evaluate the effect of rimonabant on body weight and composition of adults with PWS.

METHOD

This was a double blind placebo controlled study. Body weight, total fat mass, fasting ghrelin, leptin, IGF1 and insulin like growth factor binding protein (IGFBP-3) were collected at baseline, and after 90 and 180 days of treatment with placebo or 20 mg of rimonabant.

RESULTS

Due to psychiatric adverse effects, 50% of subjects in the rimonabant group withdrew, and the study was terminated early (N=10) for safety concerns. There was a trend for weight loss, lower fat mass and higher IGF1 level at the end of study in this group. Leptin followed the fat mass and decreased with rimonabant treatment.

CONCLUSION

Rimonabant administration may be efficacious for weight loss in adults with PWS; unfortunately it is associated with an unacceptably high risk of psychiatric side effects. Future CB1 antagonists will need a better psychiatric profile before considered in the treatment of obesity in this genetic condition.

Food addiction and obesity: evidence from bench to bedside

Obesity has become a major health problem and epidemic. However, much of the current debate has been fractious and etiologies of obesity have been attributed to eating behavior or fast food, personality issues, depression, addiction, or genetics. One of the interesting new hypotheses for epidemic obesity is food addiction, which is associated with both substance-related disorder and eating disorder. Accumulating evidences have shown that there are many shared neural and hormonal pathways as well as distinct differences that may help researchers find why certain individuals overeat and become obese. Functional neuroimaging studies have further revealed that good or great smelling, looking, tasting, and reinforcing food has characteristics similar to that of drugs of abuse. Many of the brain changes reported for hedonic eating and obesity are also seen in various forms of addictions. Most importantly, overeating and obesity may have an acquired drive like drug addiction with respect to motivation and incentive; craving, wanting, and liking occur after early and repeated exposures to stimuli. The acquired drive for great food and relative weakness of the satiety signal would cause an imbalance between the drive and hunger/reward centers in the brain and their regulation.

Prader-Willi syndrome is associated with activation of the innate immune system independently of central adiposity and insulin resistance

BACKGROUND

Subjects with Prader-Willi syndrome (PWS) have a reduced life expectancy due to cardiovascular disease. Increased systemic low-grade inflammation is postulated as a contributor, despite reported lower visceral fat mass and increased insulin sensitivity.

OBJECTIVES

Our aim was to compare inflammatory markers and arterial stiffness in PWS and adiposity-matched obese control subjects.

DESIGN

We conducted a cross-sectional cohort study comparing 12 PWS subjects, 12 obese subjects matched for percentage body fat and central abdominal fat mass, and 10 healthy normal-weight subjects.

MAIN OUTCOME MEASURES

Dual-energy x-ray absorptiometry was used to assess body composition, flow cytometry to quantify activation markers on immun e cells, and ELISA for measurement of C-reactive protein, adiponectin, and IL-6. Insulin resistance was estimated by homeostasis model assessment and arterial stiffness by applanation tonometry.

RESULTS

PWS and obese subjects had similarly increased homeostasis model assessment and arterial stiffness. Nevertheless, PWS subjects showed significantly higher IL-6 (4.9 + or - 1.0 vs. 2.5 + or - 0.4 pg/ml; P = 0.02) and nonsignificantly higher C-reactive protein (10.5 + or - 3.2 vs. 4.0 + or - 1.0 ng/ml; P = 0.08). Neutrophil activation markers CD66b and CD11b were higher in PWS compared to obese subjects (P < 0.01), reflecting an activated innate immune system. These markers were positively related to central adiposity in lean and obese subjects (r = 0.49; P < 0.05), but not in PWS subjects.

CONCLUSIONS

PWS subjects compared to adiposity-matched obese subjects demonstrate similar insulin resistance but increased low-grade inflammation. The dissociation of inflammation and central adiposity suggests that activation of innate immunity may be either a specific genetic feature of PWS or linked to the commonly associated obstructive sleep apnea syndrome, and might offer a treatment target to reduce cardiovascular disease.

Body composition, endocrine and metabolic profiles in adults with Prader-Willi syndrome

OBJECTIVE

Prader-Willi syndrome (PWS) is a complex genetic disease associated with hypothalamic-pituitary dysfunction and severe obesity. The aim of the present study was to describe the relationships between body composition, metabolic and hormonal profiles in PWS adults.

METHOD

Forty six adults with genetically verified PWS, 25 women and 21 men, median age 28 years were studied. Body composition was evaluated by standard anthropometric procedures and with computed tomography (CT) of the abdomen and at the mid-femur level. CT of abdomen was compared to 22 healthy, unmatched adults. Circulating lipids were measured and oral glucose tolerance test (OGTT) and hormonal screening including GH secretory capacity (GHRH/arginine test) was carried out.

RESULTS

Median body mass index (BMI) was 27.2 kg/m(2), with women being more obese than men. Sixteen patients had dyslipidaemia, 10 impaired glucose tolerance and seven had diabetes. Fifty percent were hypogonadal and six fulfilled BMI related criteria for growth hormone deficiency (GHD). Visceral to subcutaneous abdominal fat ratio was reduced in PWS. Visceral abdominal fat fraction correlated with both subcutaneous fat, BMI and peak GH-response. Thigh muscle volume was about half of the thigh fat volume. Beneficial effects of sex-steroid replacement on body composition were not observed.

CONCLUSIONS

Body fat was primarily located subcutaneously and metabolic consequences of obesity limited. The abnormal body composition similar to that in non-PWS GHD adults increases the interest of GH treatment in the prevention of obesity in adults with PWS.

Body fat excess and stimulated growth hormone levels in adult patients with Prader-Willi syndrome

It has been suggested that reduced GH secretion in Prader-Willi syndrome (PWS) may simply reflect their excessive fat body mass. However, the GH response to standard provocative tests is significantly lower in PWS adults than obese controls with similar body mass index (BMI). Nevertheless, BMI is an inadequate measure of body composition, because PWS harbor a higher percentage of fat body mass (FM%) than simple obesity, under the same degree of weight excess. This study evaluated either the GH response to combined GHRH + arginine administration and the FM%, by DEXA, in 11 PWS adults (8 females, aged 20.1-41.1 years, BMI 43.6 +/- 1.8, FM% 53.0 +/- 1.5), in comparison to those obtained in 10 patients with essential obesity (8 females, aged 23.5-45.8 years), matched for BMI and FM% (42.9 +/- 0.4 and 51.5 +/- 1.0, respectively). Moreover, IGF-I levels were measured in both groups. The GH response to GHRH + arginine was significantly lower in PWS patients (GH peak 5.4 +/- 1.3 microg/L; area under the curve (AUC) 311.2 +/- 72.5 microg/L/hr) than obese controls (GH peak 21.0 +/- 4.1 microg/L, P < 0.005; AUC 1241.1 +/- 272.8 microg/L/hr; P < 0.01), as well as IGF-I values (110.5 +/- 16.7 microg/L vs. 242.1 +/- 31 microg/L, P < 0.005). The GHRH + arginine induced GH rise in patients with del15q11-q13 was significantly higher than subjects with UPD15 (GH peak 7.7 +/- 1.7 microg/L vs. 2.7 +/- 1.0 microg/L, P < 0.05; AUC 458.5 +/- 91.0 microg/L/hr vs. 134.4 +/- 46.0 microg/L/hr, P < 0.02). These findings suggested that stimulated GH levels are significantly lower in PWS adults when compared to obese controls and that GH response to GHRH + arginine is different in PWS individuals having separate genetic subtypes.

Nutrition and adults with intellectual or developmental disabilities: systematic literature review results

Approximately 4.5 million Americans have an intellectual or developmental disability. Concern is increasing about these individuals' nutrition-related behavior and its implications for their health. This article reports on a systematic search of the current literature listed in the PsycINFO and PubMed databases related to nutritional status of adults with intellectual or developmental disabilities. The authors used key terms for nutrition, secondary conditions, and intellectual and developmental disability and categorized literature pertaining to nutrition-related studies of adults with intellectual or developmental disabilities as follows: dietary intake studies, anthropometric assessments of nutritional risks, biochemical indexes, and clinical evaluations.

The Italian National Survey for Prader-Willi syndrome: an epidemiologic study

Twenty-five medical centers and the Prader-Willi Syndrome (PWS) Association collaborated on a study which attempted to identify all people with genetically confirmed diagnosis of PWS living in Italy. Investigators of the participating centers contacted PWS subjects and/or their family, filled in a specially developed form with the required data and forwarded this information by email. The study identified 425 subjects (209 males and 216 females, between the ages of 0.4-46.7). Two hundred thirty-eight patients had del15, 104 had UPD15, 4 demonstrated a translocation affecting chromosome 15 and 79 showed a positive methylation test. There were fewer subjects found over the age of 35, probably due to the low rate of identification of older PWS patients as well as the high mortality rate. There were a greater number of male children and adolescents with PWS whilst, amongst adults, there were more females. As expected, the majority of subjects with PWS were obese, especially in adult life. Nevertheless, it is noteworthy that 26% of patients aged between 6 and 17 were normal weight. A total of 212 subjects had received GH treatment, of which 141 were still receiving therapy, while the remaining 71 had stopped. In children and adolescents (233 cases), 89 subjects had never undergone GH therapy. Eighteen PWS patients had died in the past 20 years. Obesity-related cardiovascular and respiratory diseases were the cause of death, both during childhood and after 18 years of age. Three children died suddenly whilst undergoing GH therapy. Respiratory infection and cardiac illness were the causes of death in two cases. There was no definitive cause of death found in the third case. Overall, there was no increase in number of deaths during GH treatment, suggesting that GH administration in patients with PWS, as a group, does not increase the risk of death.

Frontal behavioral syndromes in Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a genetically determined neurodevelopmental disorder presenting with behavioral problems including hyperphagia, emotional aberration, and compulsion-like behaviors. This combination of behavioral problems is likely to be caused by damage to the orbitofrontal cortices and anterior temporal lobes or to circuits involving them.

OBJECTIVES

To investigate the prevalence of eating and non-eating behavioral disturbances in PWS by using assessment tools developed originally for patients with frontotemporal dementia and with frontal lobe injury.

METHOD

The questionnaire consisted of 35 questions related to three categories of behavior: eating behaviors (including four domains: appetite, food preference, eating habits, and other oral behaviors), stereotypy (including four domains: roaming, speaking, movements, and daily rhythm), and collecting behaviors. It was administered in Japan to the parents of 250 individuals aged 1-42 years with a clinical diagnosis of PWS.

RESULTS

The prevalence rates of symptoms in all categories were high. Each domain involved in eating behaviors was significantly correlated with stereotypy and collecting behaviors. The prevalence rates and severity scores of some eating and non-eating behaviors were higher in the older groups.

CONCLUSION

Abnormal eating behaviors, stereotyped behaviors, and collecting behaviors were common in the PWS subjects. There was also a potential link between abnormal eating and non-eating behaviors related to frontal behavioral syndromes. It is likely that these behavioral abnormalities reflect dysfunction of the orbitofrontal cortices and anterior temporal lobes.

Imprinted genes and neuroendocrine function

Imprinted genes are monoallelically expressed in a parent-of-origin dependent manner. Whilst the full functional repertoire of these genes remains obscure, they are generally highly expressed in the brain and are often involved in fundamental neural processes. Besides influencing brain neurochemistry, imprinted genes are important in the development and function of the hypothalamus and pituitary gland, key sites of neuroendocrine regulation. Moreover, imprinted genes may directly modulate hormone-dependent signalling cascades, both in the brain and elsewhere. Much of our knowledge about imprinted gene function has come from studying knockout mice and human disorders of imprinting. One such disorder is Prader-Willi syndrome, a neuroendocrine disorder characterised by hypothalamic abnormalities and aberrant feeding behaviour. Through examining the role of imprinted genes in neuroendocrine function, it may be possible to shed light on the neurobiological basis of feeding and aspects of social behaviour and underlying cognition, and to provide insights into disorders where these functions go awry.

Cross-cultural comparisons of obesity and growth in Prader-Willi syndrome

Introduction The present study reports cross-cultural comparisons of body mass index (BMI) and growth in Prader-Willi syndrome, a neurodevelopmental disorder associated with obesity, growth restriction and mild learning disability. Our objectives were to: (1) compare rates of obesity in adults with Prader-Willi syndrome (PWS) in France, with data available from Belgium, the UK and the USA; (2) compare growth of French children with PWS with their counterparts in Germany and the USA; and (3) evaluate the contribution of genetic, medical and social parameters to obesity outcome in French children and adults with PWS. Method (1) Cross-sectional comparison of BMI of 40 French adults, 38 Belgian adults, 46 British adults and 292 North American adults; (2) Construction of growth curves for French children aged 2-20 years from longitudinal data for 150 individuals with PWS, and comparison with published growth curves from Germany and the USA; and (3) Longitudinal regression analysis of 141 French children and adults to determine the factors contributing to obesity outcome. Results A total of 82.5% French adults with PWS have BMI > 30 compared with 65.8% in Belgium (n.s.), 58.2% in the USA (P < 0.005), and 54.3% in the UK (P < 0.01). Higher rates of obesity in females vs. males were found in the USA sample (P < 0.001) but not in the other samples. In contrast to adults, growth curves for French children with PWS show similar rates of growth compared with children with PWS in Germany and the USA. The principal determining factors of BMI status in the French PWS population are age (P < 0.0001), cohort (born within the last 15 years vs. born over 15 years ago, P < 0.0002) and growth hormone replacement therapy (P < 0.0002). Significant subsidiary effects include domestic situation (P < 0.0001), genetic diagnosis (P < 0.0001) and age of diagnosis (P < 0.0001). Conclusions French adults with PWS have significantly higher rates of obesity than adults in the UK and the USA, but growth in French children with PWS is similar to the USA and Germany. Clinical management has a greater impact on obesity outcome in PWS than cultural factors.

Leptin levels among prepubertal children with Down syndrome compared with their siblings

OBJECTIVES

To compare levels of leptin and other obesity-related hormones in prepubertal children with Down syndrome (DS), a population at high obesity risk, and those in unaffected siblings to better understand the pathophysiology of obesity in children with DS.

STUDY DESIGN

This was a cross-sectional study of 35 children with DS and 33 control siblings, ages 4 to 10 years, with a fasting blood sample and anthropometric measurements to estimate body composition. Generalized estimating equations were used to account for the lack of independence between siblings.

RESULTS

In addition to having higher body mass index and percent body fat, children with DS had higher leptin levels than unaffected siblings, even after adjustment for age, sex, race, and ethnicity (difference, 5.8 ng/mL; 95% CI, 2.4-9.3; P = .001) and further adjustment for percent body fat (difference, 2.7 ng/mL; 95% CI, 0.08-5.40, P = .04). Leptin and percent body fat were positively associated in both groups (P < .0001), but with a significantly greater positive association in the DS group, suggesting a significant effect modification (P < .0001).

CONCLUSIONS

This group of children with DS had increased leptin levels for percent body fat than their unaffected siblings. This difference may contribute to the increased risk for obesity in children with DS.

Adult subjects with Prader-Willi syndrome show more low-grade systemic inflammation than matched obese subjects

AIM

Adult subjects with Prader-Willi syndrome (PWS) may show several conditions that are associated with an activation of innate immunity such as obesity, deficient GH secretion or hypogonadism. Our aim was to study whether obese adult PWS subjects show an additional low-grade systemic inflammation (LGSI) in relation to obese adult non-PWS subjects and lean healthy control subjects before and after a standardized liquid meal.

METHODS

Seven obese adult PWS subjects, 7 matched obese non-PWS subjects and 7 lean healthy control subjects were studied for 6 h from the administration of a standard liquid meal.

RESULTS

Compared to non-PWS, PWS subjects showed higher plasma concentrations of C-reactive protein (CRP) (p=0.030), complement component C3 (p=0.018), interleukin(IL)-18 (p=0.048), and IL-6 (p=0.041) that persisted post-prandially elevated for CRP (p<0.0001), C3 (p=0.015), and IL-18 (p=0.003). Tumor necrosis factor(TNF)-alpha did not differ between the 3 groups. These results were independent from IGF-I levels, homeostasis model assessment index, and body mass index (BMI). In male subjects with PWS, testosterone levels correlated to IL-18 (r=-0,646, p=0.041).

CONCLUSIONS

Compared to matched non-PWS subjects, the obese PWS subjects in this study showed an additional LGSI that persisted postprandially and was independent from BMI, insulin resistance, and deficient GH secretion. However, in PWS males, high IL-18 levels were related to low testosterone concentrations.

Clinical evidence of intrauterine disturbance in Prader-Willi syndrome, a genetically imprinted neurodevelopmental disorder

BACKGROUND

Imprinted genes are considered to play an important role in growth and early development but much of the research is based on animal studies.

AIM

This study reports clinical data from a French population concerning prenatal, perinatal and postnatal complications in Prader-Willi syndrome (PWS), a genetically imprinted neurodevelopmental disorder associated with growth retardation, intellectual impairment and obesity.

STUDY DESIGN

Data from family health records concerning prenatal, perinatal and postnatal complications were collected from 52 French people with the deletion form (DEL), and 34 French people with the maternal disomy form of PWS (UPD) and compared against national norms and between groups.

RESULTS

Significant findings include: a history of miscarriage, high rate of polyhydramnios (12/34 UPD, 11/52 DEL), a high rate of induced labour, a high rate of Caesarian section (20/34 UPD, 26/52 DEL), small gestational age (10/34 UPD, 22/52 DEL), hypotonia (34/34 UPD, 49/52 DEL), and suckling deficit (25/34 UPD, 46/52 DEL). Significant differences between genetic subtypes include a higher rate of induced labour in UPD (27/34 UPD, 25/52 DEL), an increased risk of premature term in UPD (9/34 UPD vs. 4/52 DEL), raised maternal age in UPD (36.4 years vs. 29.3 years), low birth weight for newborns with a deletion form of PWS (girls 2.8 kg, boys 2.7 kg), a positive correlation between parental weight and offspring birth weight only for patients with UPD (UPD maternal: r=0.62, paternal: r=0.51).

CONCLUSION

The results indicate significant intrauterine disturbance in PWS, particularly in PWS due to UPD, but a more significant weight disturbance for PWS due to deletion.

Enhanced activation of reward mediating prefrontal regions in response to food stimuli in Prader-Willi syndrome

BACKGROUND

Individuals with Prader-Willi syndrome (PWS) exhibit severe disturbances in appetite regulation, including delayed meal termination, early return of hunger after a meal, seeking and hoarding food and eating of non-food substances. Brain pathways involved in the control of appetite in humans are thought to include the hypothalamus, frontal cortex (including the orbitofrontal, ventromedial prefrontal, dorsolateral prefrontal and anterior cingulate areas), insula, and limbic and paralimbic areas. We hypothesised that the abnormal appetite in PWS results from aberrant reward processing of food stimuli in these neural pathways.

METHODS

We compared functional MRI blood oxygen level dependent (BOLD) responses while viewing pictures of food in eight adults with PWS and eight normal weight adults after ingestion of an oral glucose load.

RESULTS

Subjects with PWS demonstrated significantly greater BOLD activation in the ventromedial prefrontal cortex than controls when viewing food pictures. No significant differences were found in serum insulin, glucose or triglyceride levels between the groups at the time of the scan.

CONCLUSIONS

Individuals with PWS had an increased BOLD response in the ventromedial prefrontal cortex compared with normal weight controls when viewing pictures of food after an oral glucose load. These findings suggest that an increased reward value for food may underlie the excessive hunger in PWS, and support the significance of the frontal cortex in modulating the response to food in humans. Our findings in the extreme appetite phenotype of PWS support the importance of the neural pathways that guide reward related behaviour in modulating the response to food in humans.

A lesser postprandial suppression of plasma ghrelin in Prader-Willi syndrome is associated with low fasting and a blunted postprandial PYY response

OBJECTIVE

Ghrelin and polipeptide YY (PYY) are involved in the regulation of food intake. We evaluated these two peptides and their possible relationship in adult patients with Prader-Willi syndrome (PWS).

PATIENTS

Seven patients with PWS, 16 age-sex-BMI matched obese and 42 age-sex matched lean subjects.

DESIGN AND MEASUREMENTS

Fasting plasma PYY and ghrelin levels were measured in all subjects and, postprandially until 6 h, in seven matched subjects of each group.

RESULTS

Fasting ghrelin levels were higher in PWS than in the other two groups. Fasting PYY levels were lower in patients with PWS than in lean subjects but similar to those in obese subjects. The postprandial decrease in ghrelin concentrations was lower in PWS as compared to the other two groups and therefore the 6-h-postprandial area under the curve (AUC) for ghrelin was higher in PWS than in obese subjects. PYY response after the meal was blunted in patients with PWS, but not in the other two groups that showed a peak at 60 min The AUC for PYY was lower in PWS as compared to the other two groups. Fasting PYY levels correlated negatively with fasting ghrelin levels and with ghrelin AUC and they were the only predictor for ghrelin AUC (beta = -0.464, P = 0.034). The increase in PYY correlated negatively with the decrease in ghrelin at times 60 min and 120 min in PWS.

CONCLUSIONS

In PWS, the low decrease in postprandial ghrelin levels could be related to the low fasting PYY concentrations and their blunted postprandial response.

Validation of three predictive equations for basal metabolic rate in adults

Objective

To cross-validate three predictive set of equations for basal metabolic rate (BMR) developed by Schofield (Schofield database), Henry (Oxford database) and Cole (Oxford database) using mean values for age, weight, height and BMR of published studies.

Design

Literature review of studies published from 1985 to March 2002.

Setting

All studies selected used appropriate methods and followed conditions that met the criteria established for basal metabolism, were performed in healthy adults, and were not part of the Schofield or Oxford database.

Subjects

A total of 261 groups of men and women from 175 studies were selected and categorised in three age groups (18.5–29.9, 30.0–59.9, ≥60 years old) and three body mass index (BMI) groups (normal weight, overweight and obese).

Results

Linear regression and concordance correlation analysis showed that the three sets of equations had the same association and agreement with measured BMR, across gender, age, and BMI groups. The agreement of all equations was moderate for men and poor for women. The lowest mean squared prediction errors (MSPRs) were given by Henry equations in men and Cole equations in women. Henry and Cole equations gave lower values than Schofield equations, except for men over 60 years of age. Henry equations were the most accurate in men. None of the three equations performed consistently better in women.

Conclusion

These results support the use of Henry equations in men with a wide range of age and BMI. None of the proposed predictive equations seem to be appropriate to estimate BMR in women.

Body composition and fatness patterns in Prader-Willi syndrome: comparison with simple obesity

OBJECTIVE

To characterize the body composition of Prader-Willi syndrome (PWS) subjects and compare with simple obesity.

RESEARCH METHODS AND PROCEDURES

Seventy-two individuals (27 PWS deletion, 21 PWS uniparental disomy, and 24 obese controls) 10 to 49 years old were studied with the use of DXA. Body composition measures were obtained, and regional fat and lean mass patterns were characterized. Significant differences were assessed with Student's t test and ANOVA adjusting for age, gender, and BMI.

RESULTS

Significant differences between the PWS and obese groups were found for lean measures of the arms, legs, and trunk. Total lean mass was significantly lower in PWS than in obese subjects for arms, trunk, and especially legs. Furthermore, two body regions (legs and trunk) showed significant differences for fat and lean measures between PWS and obese males. However, significant differences between PWS and obese females for these measures were found only for the legs. No significant differences were identified between PWS deletion and uniparental disomy subjects.

DISCUSSION

Our results demonstrate that PWS individuals do, in fact, have an unusual body composition and fatness patterns, characterized by reduced lean tissue and increased adiposity, with PWS males contributing most with fat patterns more similar to females.

Characterization of cis- and trans-acting elements in the imprinted human SNURF-SNRPN locus

The imprinted SNRPN locus is a complex transcriptional unit that encodes the SNURF and SmN polypeptides as well as multiple non-coding RNAs. SNRPN is located within the Prader-Willi and Angelman syndrome (PWS/AS) region that contains multiple imprinted genes, which are coordinately regulated by a bipartite imprinting center (IC). The SNRPN 5′ region co-localizes with the PWS-IC and contains two DNase I hypersensitive sites, DHS1 at the SNRPN promoter, and DHS2 within intron 1, exclusively on the paternally inherited chromosome. We have examined DHS1 and DHS2 to identify cis- and trans-acting regulatory elements within the endogenous SNRPN 5′ region. Analysis of DHS1 by in vivo footprinting and chromatin immunoprecipitation identified allele-specific interaction with multiple regulatory proteins, including NRF-1, which regulates genes involved in mitochondrial and metabolic functions. DHS2 acted as an enhancer of the SNRPN promoter and contained a highly conserved region that showed allele-specific interaction with unphosphorylated RNA polymerase II, YY1, Sp1 and NRF-1, further suggesting a key role for NRF-1 in regulation of the SNRPN locus. We propose that one or more of the regulatory elements identified in this study may also contribute to PWS-IC function.

Molecular physiology of syndromic obesities in humans

Obesity has become an increasingly prevalent public health problem and represents the complex interaction of genetic, developmental, behavioral and environmental influences. Although rare, the study of syndromic forms of obesity provides insight into underlying molecular and physiological mechanisms by which adiposity is regulated through food intake, energy expenditure and partitioning of stored calories.

Prader-Willi syndrome: clinical genetics, cytogenetics and molecular biology

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder that arises from lack of expression of paternally inherited genes known to be imprinted and located in the chromosome 15q11-q13 region. PWS is considered the most common syndromal cause of life-threatening obesity and is estimated at 1 in 10,000 to 20,000 individuals. A de novo paternally derived chromosome 15q11-q13 deletion is the cause of PWS in about 70% of cases, and maternal disomy 15 accounts for about 25% of cases. The remaining cases of PWS result either from genomic imprinting defects (microdeletions or epimutations) of the imprinting centre in the 15q11-q13 region or from chromosome 15 translocations. Here, we describe the clinical presentation of PWS, review the current understanding of causative cytogenetic and molecular genetic mechanisms, and discuss future directions for research.

Correlation of the dysmetabolic risk factors with different anthropometric measurements

Metabolic syndrome is a common disorder in Taiwan. For this study 431 subjects were randomly selected from visitors to the Department of Health Management. Blood pressure, blood glucose, lipid, uric acid levels and anthropometric measurements with immunoreactive insulin (IRI) and leptin levels were all correlated. We randomly selected 431 subjects who visited the Department of Health Management. Whole body three-dimensional (3-D) laser scanner scans were employed for the anthropometric measurements. The metabolic index (MI) was designed using anthropometric parameters. Of the 431 subjects, 50% had displayed a body mass index (BMI) equal to or exceeding 25 kg/m2. Pearson correlation coefficient and multiple regression analysis revealed that MI constituted another index for correlating metabolic parameters by comparing MI with BMI and waist circumference to hip circumference ratio (WHR). Most data related to metabolic syndrome showed statistically significant differences between high and low IRI groups, comprising uric acid, total cholesterol, fasting plasma glucose, triglyceride, LDL, Chol/HDL ratio, and LDL/HDL ratio. Both IRI and leptin revealed statistical association with BMI, WHR, waist cross section area to hip cross section area ratio (WHAR), and MI in the study. Hypercholesterolemia appeared in 14.6% of the subjects. Elevated low-density lipoprotein (> or = 130 mg/dL) affected 36.9% of the subjects. In conclusion, MI calculated from 3-D body scanner correlated with many important metabolic risk factors and associated with clinical disorders like DM, hyperlipidemia, hyperuricemia and hypertension.