Single Gene and Syndromic Causes of Obesity: Illustrative Examples

Treatment of Hypothalamic Obesity With GLP-1 Analogs

Introduction

Congenital and acquired damage to hypothalamic nuclei or neuronal circuits controlling satiety and energy expenditure results in hypothalamic obesity (HO). To date, successful weight loss and satiety has only been achieved in a limited number of affected patients across multiple drug trials. Glucagon-like peptide-1 (GLP-1) acts via central pathways that are independent from the hypothalamus to induce satiety. GLP-1 receptor agonists (GLP-1RAs) may provide an alternative approach to treating HO.

Methods

We performed a comprehensive search in Medline, Google Scholar, and clinical trials registries (ClinicalTrials.gov; clinicaltrialsregister.eur). This nonsystematic literature review was conducted to identify scientific papers published from January 2005 to February 2024 using the Pubmed and Embase databases. Key words used were GLP-1, GLP-1RA, hypothalamic obesity, suprasellar tumor, and craniopharyngioma.

Results

Our search identified 7 case studies, 5 case series, and 2 published clinical trials relating to the use of GLP-1RAs in HO. All case studies demonstrated weight loss and improved metabolic function. In contrast, results from case series were variable, with some showing no weight loss and others demonstrating moderate to significant weight loss and improved metabolic parameters. In the ECHO clinical trial, nearly half the subjects randomized to weekly exenatide showed reduced body mass index (BMI). Paradoxically, BMI reduction was greater in patients with more extensive hypothalamic injuries.

Conclusion

GLP-1RAs potentially offer a new approach to treating HO. There is a need to stratify patients who are more likely to respond. Further randomized controlled trials are required to determine their efficacy either in isolation or combined with other therapies.

Exploring the Interplay of Genetics and Nutrition in the Rising Epidemic of Obesity and Metabolic Diseases

Background: Obesity has become a significant global health issue. This multifaceted condition is influenced by genetic, environmental, and lifestyle factors, significantly influenced by nutrition. Aim: The study's objective is to elucidate the relationship between obesity-related genes, nutrient intake, and the development of obesity and the importance of other metabolic diseases. Methods: A comprehensive literature review spanning the past two decades was conducted to analyze the contributions of genetic variants-including FTO, MC4R, and LEPR-and their associations with dietary habits, highlighting how specific nutrients affect gene expression and obesity risk and how the coexistence of metabolic diseases such as type 2 diabetes and osteoporosis may modulate these factors. Moreover, the role of epigenetic factors, such as dietary patterns that encourage the development of obesity, was explored. Discussion and Conclusions: By understanding the intricate relationships among genetics, nutrients, and obesity development, this study highlights the importance of personalized dietary strategies in managing obesity. Overall, an integrated approach that considers genetic predispositions alongside environmental influences is essential for developing effective prevention and treatment methodologies, ultimately contributing to better health outcomes in diverse populations.

Genotype-phenotype correlation in Prader-Willi syndrome: A large-sample analysis in China

The genotype-phenotype relationship in PWS patients is important for a better understanding of the clinical phenotype and clinical characteristics of different genotypes of PWS in children. We aimed to explore the influence of specific gene changes on the clinical symptoms of PWS and the value of early screening and early intervention of the condition. All data in this study were extracted from the database of the XiaoPang Weili Rare Disease Care Center. The collected information included basic demographics, maternal pregnancy information, endocrine abnormalities, growth and development abnormalities, and other clinical phenotypes. The relationships between genotypes and phenotypes in the major categories of PWS were analyzed. A total of 586 PWS cases with confirmed molecular diagnosis and genotyping were included in this study. Among them, 83.8% belonged to the deletion type, 10.9% the uniparental disomy (UPD) type, and 5.3% the imprinting defect (ID) type. Age-wide comparison among the three groups: The rate of hypopigmentation in the deletion group was higher than that in the UPD group (88.8% vs. 60.9%; p < 0.05); A total of 62 patients (14.2%) had epilepsy; and no statistical significance was found among the three groups (p = 0.110). Age-wide comparison between the deletion and non-deletion types: the rate of skin hypopigmentation and epilepsy in the deletion group was significantly higher than that in the non-deletion group (88.8% vs. 68.4%, p < 0.001; 15.9% vs. 7.6%, p = 0.040). The intergroup comparison for the >2-year age group: there were significant intergroup differences in the language development delay among the three groups (p < 0.001). The incidence of delayed language development was the highest in the deletion group, followed by the UPD group, and the lowest in the ID group. The rates of obesity and hyperphagia in the deletion group were also higher than those in the non-deletion group (71.1% vs. 58.9%, p = 0.041; 75.7% vs. 62.0%, p = 0.016). There are significant differences in the rates of skin hypopigmentation and language developmental delay among the deletion, UPD, and ID genotypes. The patients with deletion type had significantly higher rates of lighter skin color, obesity, hyperphagia, language developmental delay, and epilepsy. The results of this study will help clinicians better understand the impact of different PWS molecular etiologies on specific phenotypes.

Behavioral and Psychiatric Disorders in Syndromic Autism

Syndromic autism refers to autism spectrum disorder diagnosed in the context of a known genetic syndrome. The specific manifestations of any one of these syndromic autisms are related to a clinically defined genetic syndrome that can be traced to certain genes and variants, genetic deletions, or duplications at the chromosome level. The genetic mutations or defects in single genes associated with these genetic disorders result in a significant elevation of risk for developing autism relative to the general population and are related to recurrence with inheritance patterns. Additionally, these syndromes are associated with typical behavioral characteristics or phenotypes as well as an increased risk for specific behavioral or psychiatric disorders and clinical findings. Knowledge of these associations helps guide clinicians in identifying potentially treatable conditions that can help to improve the lives of affected patients and their families.

Hyperphagia and impulsivity: use of self-administered Dykens' and in-house impulsivity questionnaires to characterize eating behaviors in children with severe and early-onset obesity

BACKGROUND

The determinants of early-onset obesity (< 6 years) are not completely elucidated, however eating behavior has a central role. To date no study has explored eating behavior in children with severe, early-onset obesity. Self-administered questionnaire data from these children were examined to evaluate eating behavior and the etiology of early-onset obesity.

METHODS

Children with severe, early-onset obesity (body mass index [BMI] > International Obesity Task Force [IOTF] 30) of different etiologies (hypothalamic obesity [HO], intellectual disability with obesity [IDO], common polygenic obesity [CO]) were prospectively included. BMI history and responses from the Dykens' Hyperphagia Questionnaire and an in-house Impulsivity Questionnaire at first visit were compared between groups.

RESULTS

This cohort of 75 children (39 girls; mean age ± standard deviation [SD] 10.8 ± 4.4 years) had severe, early-onset obesity at an age of 3.8 ± 2.7 years, with a BMI Z-score of 4.9 ± 1.5. BMI history varied between the 3 groups, with earlier severe obesity in the HO group versus 2 other groups (BMI > IOTF40 at 3.4 ± 1.6 vs. 4.6 ± 1.6 and 8.4 ± 4.1 years for the IDO and CO groups, respectively [P < 0.01]). Absence of adiposity rebound was more prevalent in the HO group (87% vs. 63% and 33% for the IDO and CO groups, respectively [P < 0.01]). The Dykens' mean total score for the cohort was 22.1 ± 7.2 with no significant between-group differences. Hyperphagia (Dykens' score > 19) and impulsivity (score > 7) were found in 50 (67%) and 11 children (15%), respectively, with no difference between the HO, IDO and CO groups regarding the number of patients with hyperphagia (10 [67%], 14 [74%], and 26 [63%] children, respectively) or impulsivity (2 [13%], 1 [7%], and 8 [19%] children, respectively). Children with food impulsivity had significantly higher total and severity scores on the Dykens' Questionnaire versus those without impulsivity.

CONCLUSION

The Dykens' and Impulsivity questionnaires can help diagnose severe hyperphagia with/without food impulsivity in children with early-onset obesity, regardless of disease origin. Their systematic use can allow more targeted management of food access control in clinical practice and monitor the evolution of eating behavior in the case of innovative therapeutic targeting hyperphagia.

The role of genetic and epigenetic GNAS alterations in the development of early-onset obesity

BACKGROUND

GNAS (guanine nucleotide-binding protein, alpha stimulating) is an imprinted gene that encodes Gsα, the α subunit of the heterotrimeric stimulatory G protein. This subunit mediates the signalling of a diverse array of G protein-coupled receptors (GPCRs), including the melanocortin 4 receptor (MC4R) that serves a pivotal role in regulating food intake, energy homoeostasis, and body weight. Genetic or epigenetic alterations in GNAS are known to cause pseudohypoparathyroidism in its different subtypes and have been recently associated with isolated, early-onset, severe obesity. Given the diverse biological functions that Gsα serves, multiple molecular mechanisms involving various GPCRs, such as MC4R, β2- and β3-adrenoceptors, and corticotropin-releasing hormone receptor, have been implicated in the pathophysiology of severe, early-onset obesity that results from genetic or epigenetic GNAS changes.

SCOPE OF REVIEW

This review examines the structure and function of GNAS and provides an overview of the disorders that are caused by defects in this gene and may feature early-onset obesity. Moreover, it elucidates the potential molecular mechanisms underlying Gsα deficiency-induced early-onset obesity, highlighting some of their implications for the diagnosis, management, and treatment of this complex condition.

MAJOR CONCLUSIONS

Gsα deficiency is an underappreciated cause of early-onset, severe obesity. Therefore, screening children with unexplained, severe obesity for GNAS defects is recommended, to enhance the molecular diagnosis and management of this condition.

Increased body weight in mice with fragile X messenger ribonucleoprotein 1 (Fmr1) gene mutation is associated with hypothalamic dysfunction

Mutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene are linked to Fragile X Syndrome, the most common monogenic cause of intellectual disability and autism. People affected with mutations in FMR1 have higher incidence of obesity, but the mechanisms are largely unknown. In the current study, we determined that male Fmr1 knockout mice (KO, Fmr1-/y), but not female Fmr1-/-, exhibit increased weight when compared to wild-type controls, similarly to humans with FMR1 mutations. No differences in food or water intake were found between groups; however, male Fmr1-/y display lower locomotor activity, especially during their active phase. Moreover, Fmr1-/y have olfactory dysfunction determined by buried food test, although they exhibit increased compulsive behavior, determined by marble burying test. Since olfactory brain regions communicate with hypothalamic regions that regulate food intake, including POMC neurons that also regulate locomotion, we examined POMC neuron innervation and numbers in Fmr1-/y mice. POMC neurons express Fmrp, and POMC neurons in Fmr1-/y have higher inhibitory GABAergic synaptic inputs. Consistent with increased inhibitory innervation, POMC neurons in the Fmr1-/y mice exhibit lower activity, based on cFOS expression. Notably, Fmr1-/y mice have fewer POMC neurons than controls, specifically in the rostral arcuate nucleus, which could contribute to decreased locomotion and increased body weight. These results suggest a role for Fmr1 in the regulation of POMC neuron function and the etiology of Fmr1-linked obesity.

Autonomic nervous system dysfunction in Prader-Willi syndrome

INTRODUCTION

Prader-Willi syndrome is a complex neurodevelopmental genetic disorder due to lack of paternal expression of critical imprinted genes in the 15q11.2-q13.1 chromosomal region, generally from a paternal deletion. Predominant features include infantile hypotonia, a poor suck with failure to thrive, craniofacial features, and developmental and behavioral problems including self-injury and childhood onset of obesity. In addition to severe obesity, patients with PWS present with other symptoms of autonomic nervous system dysfunction.

METHODS

We examined the features seen in Prader-Willi syndrome and searched the literature for evidence of autonomic nervous system involvement in this rare obesity-related disorder and illustrative findings possibly due to autonomic nervous system dysfunction. Additionally, we reviewed the literature in relation to childhood obesity syndromes and compared those syndromes to the syndromic obesity found in Prader-Willi syndrome.

RESULTS

We report autonomic nervous system-related symptoms associated with childhood obesity impacting features seen in Prader-Willi syndrome and possibly other obesity-related genetic syndromes. We compiled evidence of both an autonomic route for the obesity seen in PWS and other autonomic nervous system-related dysfunctions. These include decreased salvation, sleep disordered breathing, increased pain and thermal threshold instability, delayed gastric emptying, altered blood pressure readings, and pupillary constriction responses as evidence of autonomic nervous system involvement.

CONCLUSIONS

We summarized and illustrated findings of autonomic nervous system dysfunction in Prader-Willi syndrome and other obesity-related syndromes and genetic factors that may play a causative role in development.

Evaluation of Autonomic Nervous System Dysfunction in Childhood Obesity and Prader-Willi Syndrome

The autonomic nervous system (ANS) may play a role in the distribution of body fat and the development of obesity and its complications. Features of individuals with Prader-Willi syndrome (PWS) impacted by PWS molecular genetic classes suggest alterations in ANS function; however, these have been rarely studied and presented with conflicting results. The aim of this study was to investigate if the ANS function is altered in PWS. In this case-control study, we assessed ANS function in 20 subjects with PWS (6 males/14 females; median age 10.5 years) and 27 body mass index (BMI) z-score-matched controls (19 males/8 females; median age 12.8 years). Standardized non-invasive measures of cardiac baroreflex function, heart rate, blood pressure, heart rate variability, quantitative sudomotor axon reflex tests, and a symptom questionnaire were completed. The increase in heart rate in response to head-up tilt testing was blunted (p < 0.01) in PWS compared to controls. Besides a lower heart rate ratio with Valsalva in PWS (p < 0.01), no significant differences were observed in other measures of cardiac function or sweat production. Findings suggest possible altered sympathetic function in PWS.

Novel therapeutics in rare genetic obesities: A narrative review

The better understanding of the molecular causes of rare genetic obesities and its associated phenotype involving the hypothalamus allows today to consider innovative therapeutics focused on hunger control. Several new pharmacological molecules benefit patients with monogenic or syndromic obesity. They are likely to be among the treatment options for these patients in the coming years, helping clinicians and patients prevent rapid weight progression and eventually limit bariatric surgery procedures, which is less effective in these patients. Their positioning in the management of such patients will be needed to be well defined to develop precision medicine in genetic forms of obesity.

Prader-Willi Syndrome and Chromosome 15q11.2 BP1-BP2 Region: A Review

Prader-Willi syndrome (PWS) is a complex genetic disorder with three PWS molecular genetic classes and presents as severe hypotonia, failure to thrive, hypogonadism/hypogenitalism and developmental delay during infancy. Hyperphagia, obesity, learning and behavioral problems, short stature with growth and other hormone deficiencies are identified during childhood. Those with the larger 15q11-q13 Type I deletion with the absence of four non-imprinted genes (NIPA1, NIPA2, CYFIP1, TUBGCP5) from the 15q11.2 BP1-BP2 region are more severely affected compared with those with PWS having a smaller Type II deletion. NIPA1 and NIPA2 genes encode magnesium and cation transporters, supporting brain and muscle development and function, glucose and insulin metabolism and neurobehavioral outcomes. Lower magnesium levels are reported in those with Type I deletions. The CYFIP1 gene encodes a protein associated with fragile X syndrome. The TUBGCP5 gene is associated with attention-deficit hyperactivity disorder (ADHD) and compulsions, more commonly seen in PWS with the Type I deletion. When the 15q11.2 BP1-BP2 region alone is deleted, neurodevelopment, motor, learning and behavioral problems including seizures, ADHD, obsessive-compulsive disorder (OCD) and autism may occur with other clinical findings recognized as Burnside-Butler syndrome. The genes in the 15q11.2 BP1-BP2 region may contribute to more clinical involvement and comorbidities in those with PWS and Type I deletions.

Clinical Trials in Prader-Willi Syndrome: A Review

Prader-Willi syndrome (PWS) is a complex, genetic, neurodevelopmental disorder. PWS has three molecular genetic classes. The most common defect is due to a paternal 15q11-q13 deletion observed in about 60% of individuals. This is followed by maternal disomy 15 (both 15 s from the mother), found in approximately 35% of cases. the remaining individuals have a defect of the imprinting center that controls the activity of imprinted genes on chromosome 15. Mild cognitive impairment and behavior problems in PWS include self-injury, anxiety, compulsions, and outbursts in childhood, impacted by genetic subtypes. Food seeking and hyperphagia can lead to morbid obesity and contribute to diabetes and cardiovascular or orthopedic problems. The control of hyperphagia and improving food-related behaviors are the most important unmet needs in PWS and could be addressed with the development of a new therapeutic agent, as currently no approved therapeutics exist for PWS treatment. The status of clinical trials with existing results for the management of obesity and hyperphagia in PWS will be discussed in this review, including treatments such as beloranib, setmelanotide, a diazoxide choline controlled-release tablet (DCCR), an unacylated ghrelin analogue, oxytocin and related compounds, glucagon-like peptide 1 receptor agonists, surgical intervention, and transcranial direct-current stimulation.

Chromosomal Microarray Study in Prader-Willi Syndrome

A high-resolution chromosome microarray analysis was performed on 154 consecutive individuals enrolled in the DESTINY PWS clinical trial for Prader-Willi syndrome (PWS). Of these 154 PWS individuals, 87 (56.5%) showed the typical 15q11-q13 deletion subtypes, 62 (40.3%) showed non-deletion maternal disomy 15 and five individuals (3.2%) had separate unexpected microarray findings. For example, one PWS male had Klinefelter syndrome with segmental isodisomy identified in both chromosomes 15 and X. Thirty-five (40.2%) of 87 individuals showed typical larger 15q11-q13 Type I deletion and 52 individuals (59.8%) showed typical smaller Type II deletion. Twenty-four (38.7%) of 62 PWS individuals showed microarray patterns indicating either maternal heterodisomy 15 subclass or a rare non-deletion (epimutation) imprinting center defect. Segmental isodisomy 15 was seen in 34 PWS subjects (54.8%) with 15q26.3, 15q14 and 15q26.1 bands most commonly involved and total isodisomy 15 seen in four individuals (6.5%). In summary, we report on PWS participants consecutively enrolled internationally in a single clinical trial with high-resolution chromosome microarray analysis to determine and describe an unbiased estimate of the frequencies and types of genetic defects and address potential at-risk genetic disorders in those with maternal disomy 15 subclasses in the largest PWS cohort studied to date.

Syndromic and Nonsyndromic Obesity: Underlying Genetic Causes in Humans

Growing evidence supports syndromic and nonsyndromic causes of obesity, including genome-wide association studies, candidate gene analysis, advanced genetic technology using next-generation sequencing (NGS), and identification of copy number variants. Identification of susceptibility genes impacts mechanistic understanding and informs precision medicine. The cause of obesity is heterogeneous with complex biological processes playing a role by controlling peptides involved in regulating appetite and food intake, cellular energy, and metabolism. Evidence for heritability shows genetic components contributing to 40%-70% of obesity. Monogenic causes and obesity-related syndromes are discussed and illustrated as well as biological pathways, gene interactions, and factors contributing to the obesity phenotype. Over 550 obesity-related single genes have been identified and summarized in tabular form with approximately 20% of these genes have been added to obesity gene panels for testing by commercially available laboratories. Early studies show that about 10% of patients with severe obesity using NGS testing have a pathogenic gene variant. Discussion to help characterize gene-gene interactions and disease mechanisms for early diagnosis, treatment, and risk factors contributing to disease is incorporated in this review.

Genetics of Obesity in Humans: A Clinical Review

Obesity is a complex multifactorial disorder with genetic and environmental factors. There is an increase in the worldwide prevalence of obesity in both developed and developing countries. The development of genome-wide association studies (GWAS) and next-generation sequencing (NGS) has increased the discovery of genetic associations and awareness of monogenic and polygenic causes of obesity. The genetics of obesity could be classified into syndromic and non-syndromic obesity. Prader-Willi, fragile X, Bardet-Biedl, Cohen, and Albright Hereditary Osteodystrophy (AHO) syndromes are examples of syndromic obesity, which are associated with developmental delay and early onset obesity. Non-syndromic obesity could be monogenic, polygenic, or chromosomal in origin. Monogenic obesity is caused by variants of single genes while polygenic obesity includes several genes with the involvement of members of gene families. New advances in genetic testing have led to the identification of obesity-related genes. Leptin (LEP), the leptin receptor (LEPR), proopiomelanocortin (POMC), prohormone convertase 1 (PCSK1), the melanocortin 4 receptor (MC4R), single-minded homolog 1 (SIM1), brain-derived neurotrophic factor (BDNF), and the neurotrophic tyrosine kinase receptor type 2 gene (NTRK2) have been reported as causative genes for obesity. NGS is now in use and emerging as a useful tool to search for candidate genes for obesity in clinical settings.

The Efficacy, Safety, and Pharmacology of a Ghrelin O-Acyltransferase Inhibitor for the Treatment of Prader-Willi Syndrome

CONTEXT

Acylated ghrelin (AG) stimulates appetite and is elevated compared to its unacylated (UAG) counterpart in Prader-Willi syndrome (PWS). GLWL-01 is a selective, reversible inhibitor of ghrelin O-acyltransferase (GOAT), the enzyme that converts UAG into AG.

OBJECTIVE

This work aimed to assess the efficacy, pharmacokinetics, pharmacodynamics, and safety of GLWL-01 in the treatment of PWS patients.

METHODS

A double-blind, placebo-controlled, phase 2 crossover study was conducted with 2 active treatment periods of 28 days in 19 patients (aged 16-65 years; body mass index (BMI) ≥ 28) with genetically confirmed PWS. The study took place in 7 hospital-based study centers in the United States and Canada. Patients received placebo or GLWL-01 (450 mg twice daily) orally after lead-in placebo and washout periods. The Hyperphagia Questionnaire for Clinical Trials and Caregiver Global Impression of Change were used to measure reductions in hyperphagia. Plasma concentrations of AG and UAG were evaluated as correlates.

RESULTS

Treatment resulted in statistically significant differences compared to placebo in plasma AG (P = .0002), UAG (P = .0488), and AG/UAG (P = .0003). GLWL-01 did not statistically significantly reduce hyperphagia-related behavior or bring about changes in global clinical end points, as assessed by caregivers. Anthropometric and clinical parameters correlated with obesity did not statistically significantly change in response to treatment. Less than half of patients reported a treatment-emergent adverse event (TEAE). No deaths, serious adverse events, or severe TEAEs were reported.

CONCLUSION

GLWL-01 is safe and well tolerated. Pharmacological parameters confirmed the inhibition of GOAT following administration of GLWL-01. Patients' eating behaviors, BMI, blood glucose, and total cholesterol, among other similar measures, were not modified.

Critical review of bariatric surgical outcomes in patients with Prader-Willi syndrome and other hyperphagic disorders

OBJECTIVE

The aim of this study was to review bariatric procedure outcomes among patients with Prader-Willi syndrome (PWS), melanocortin 4 receptor (MC4R) mutations, Bardet-Biedl syndrome, and hypothalamic obesity.

METHODS

Systematic published literature review used the following search terms: "Prader-Willi syndrome," "Bardet-Biedl syndrome," "hyperphagia," "bariatric surgery," "MC4R"/"melanocortin 4 receptor", "hypothalamic obesity," and "bariatric procedure." Information collected included demographics, genetics, anthropometry, procedure type, outcomes, and complications, with inclusion of case series and clinical reports given the rarity of the disorders. For PWS, postoperative weight-change percentage and BMI up to 14 years following surgery were analyzed using general linear mixed models, with descriptive outcomes for other conditions.

RESULTS

A total of 54 publications were identified, with variable follow-up periods for 202 patients (114 with PWS, 43 with MC4R mutations, 7 with Bardet-Biedl syndrome, and 38 with hypothalamic obesity) among bariatric procedures. Weight loss of patients with PWS was greatest within 1 year of surgery, with weight-change percentage not significantly different from 0 at 5 years. Long-term results in other conditions were variable and featured suboptimal weight loss and increased reoperation risk.

CONCLUSIONS

Bariatric procedures among hyperphagic individuals, including those with PWS, report variable results and outcomes. Benefits of bariatric surgery may be less durable in hyperphagic disorders in comparison with other patients with severe obesity.

Genetic conditions of short stature: A review of three classic examples

Noonan, Turner, and Prader-Willi syndromes are classical genetic disorders that are marked by short stature. Each disorder has been recognized for several decades and is backed by extensive published literature describing its features, genetic origins, and optimal treatment strategies. These disorders are accompanied by a multitude of comorbidities, including cardiovascular issues, endocrinopathies, and infertility. Diagnostic delays, syndrome-associated comorbidities, and inefficient communication among the members of a patient's health care team can affect a patient's well-being from birth through adulthood. Insufficient information is available to help patients and their multidisciplinary team of providers transition from pediatric to adult health care systems. The aim of this review is to summarize the clinical features and genetics associated with each syndrome, describe best practices for diagnosis and treatment, and emphasize the importance of multidisciplinary teams and appropriate care plans for the pediatric to adult health care transition.

PHIP gene variants with protein modeling, interactions, and clinical phenotypes

Variants in the pleckstrin homology domain-interacting protein (PHIP) gene are implicated in the clinical phenotype of Chung-Jansen syndrome, which includes dysmorphic features, cognitive dysfunction, aberrant behavior, and childhood onset obesity. Following a systematic literature review, 35 patients are reported to have unique PHIP variants impacting the encoded protein product. We summarize the status and frequency of these variants and relationship to clinical presentation. We also describe an additional patient with a rare, pathogenic variant due to a five base pair deletion leading to an altered codon at I307 but with a stop codon at 22 codons downstream; notably, a variant was identified at the same location as seen previously at protein position I307 in one other subject and a frameshift change at that protein position. We compare the clinical characteristics between the two patients and analyze whether certain types of gene defects impact clinical presentation in previously reported individuals. In addition, we predict structural protein models, which yielded unique differences between the wild-type and I307P-related mutant truncated proteins. Protein-protein interactions indicate involvement of POMC and related proteins with potential contribution to obesity, congenital, neuromuscular, and lipid disorders with heart, gastrointestinal, and rheumatoid diseases. With its surrounding proline-rich region, the I307P point mutation increases susceptibility to conformational rigidity and thermodynamic stability, ultimately impacting function as well as a stop codon downstream. Furthermore, the frameshift mutation seen in our patient may result in a truncated protein with a short abnormal region prior to the stop codon due to a five base pair deletion at I307 or target the protein for nonsense-mediated mRNA decay.

Expert opinion on the preoperative medical optimization of adults with diabetes undergoing metabolic surgery

Diabetes mellitus (DM) and obesity are interrelated in a complex manner, and their coexistence predisposes patients to a plethora of medical problems. Metabolic surgery has evolved as a promising therapeutic option for both conditions. It is recommended that patients, particularly those of Asian origin, maintain a lower body mass index threshold in the presence of uncontrolled DM. However, several comorbidities often accompany these chronic diseases and need to be addressed for successful surgical outcome. Laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) are the most commonly used bariatric procedures worldwide. The bariatric benefits of RYGB and LSG are similar, but emerging evidence indicates that RYGB is more effective than LSG in improving glycemic control and induces higher rates of long-term DM remission. Several scoring systems have been formulated that are utilized to predict the chances of remission. A glycemic target of glycated hemoglobin < 7% is a reasonable goal before surgery. Cardiovascular, pulmonary, gastrointestinal, hepatic, renal, endocrine, nutritional, and psychological optimization of surgical candidates improves perioperative and long-term outcomes. Various guidelines for preoperative care of individuals with obesity have been formulated, but very few specifically focus on the concerns arising from the presence of concomitant DM. It is hoped that this statement will lead to the standardization of presurgical management of individuals with DM undergoing metabolic surgery.

A Streamlined Approach to Prader-Willi and Angelman Syndrome Molecular Diagnostics

Establishing or ruling out a molecular diagnosis of Prader–Willi or Angelman syndrome (PWS/AS) presents unique challenges due to the variety of different genetic alterations that can lead to these conditions. Point mutations, copy number changes, uniparental isodisomy (i-UPD) 15 of two subclasses (segmental or total isodisomy), uniparental heterodisomy (h-UPD), and defects in the chromosome 15 imprinting center can all cause PWS/AS. Here, we outline a combined approach using whole-exome sequencing (WES) and DNA methylation data with methylation-sensitive multiplex ligation-dependent probe amplification (MLPA) to establish both the disease diagnosis and the mechanism of disease with high sensitivity using current standard of care technology and improved efficiency compared to serial methods. The authors encourage the use of this approach in the clinical setting to confirm and establish the diagnosis and genetic defect which may account for the secondary genetic conditions that may be seen in those with isodisomy 15, impacting surveillance and counseling with more accurate recurrence risks. Other similarly affected individuals due to other gene disorders or cytogenetic anomalies such as Rett syndrome or microdeletions would also be identified with this streamlined approach.

Measurement of Serum Chemerin, Oxidized LDL, and Vitamin D Levels in Prader–Willi Syndrome: A Cross-Sectional Study in Pediatric Egyptian Patients

Prader–Willi syndrome (PWS) is the commonest genetic cause of obesity. Oxidative stress and chronic low-grade inflammation play a crucial role in the pathogenesis of obesity. Alterations of vitamin D (25-OHD) levels are commonly encountered with obesity. The aim of this study was to analyze serum chemerin, oxidized low-density lipoprotein (ox-LDL), and 25-OHD values in pediatric PWS patients in comparison with obese healthy children and nonobese control groups, highlighting possible correlations with body mass index (BMI) and obesity. Twenty-six PWS Egyptian patients and 26 obese healthy individuals referred to the outpatient clinic of the Clinical Genetics Department, National Research Centre, Cairo, Egypt, and 20 control patients with matching age and sex were enrolled in the study. Patients were clinically diagnosed and confirmed by routine cytogenetic and fluorescence in-situ hybridization analysis. Anthropometric measurements were performed, and BMI was calculated by weight/height2 (kg/m2), and BMI z score was also determined. Serum chemerin, ox-LDL, and vitamin D were determined by enzyme-linked immunosorbent assay. Chemerin levels, which reflected chronic inflammation, were significantly elevated as compared with obese and nonobese controls (p ≤ 0.0001). Concerning oxidative damage, children with PWS showed higher Ox-LDL levels compared with obese and nonobese controls (p < 0.0001). Vitamin D levels were significantly lower in PWS patients compared with obese and nonobese controls (p ≤ 0.0001). Our data showed that obesity in PWS is associated with oxidative stress and chronic low-grade inflammation. Ox-LDL is a good indicator of oxidative stress, and chemerin could be used as a biomarker for the chronic inflammatory state. Furthermore, vitamin D supplementation is recommended in PWS patients

Cardiac autonomic control during non-REM and REM sleep stages in paediatric patients with Prader-Willi syndrome

Cardiac death is the second most prevalent cause in Prader-Willi syndrome (PWS). Paediatric patients with PWS often present cardiac autonomic dysfunction during wakefulness, obesity and sleep-disordered breathing. However, the extent of cardiac autonomic modulation during sleep in PWS has not been documented. The objective of this study was to assess alterations in cardiac autonomic modulation of paediatric patients with PWS during different sleep stages. Thirty-nine participants in three groups: 14 PWS, 13 sex and age-matched lean controls (LG) and 12 obese-matched controls (OB). All participants underwent overnight polysomnography, including continuous electrocardiogram recordings. Heart rate variability (HRV) was analysed during representative periods of each sleep stage through time and frequency domains calculated across 5-min periods. Between-within ANOVAs were employed (p < .05). The results show that total HRV was lower in PWS than OB and LG during slow-wave sleep (SWS) (standard deviation of all NN intervals [SDNN] ms, p = .006). Parasympathetic modulation assessed by time-domain analysis was lower during SWS in PWS compared to both OB and LG (square root of the mean of the sum of the squares of differences between adjacent NN intervals [RMSSD] ms, p = .004; SDSD, standard deviation of differences between adjacent NN intervals [SDSD] ms, p = .02; number of adjacent NN intervals differing by >50 ms [NN50] ms, p = .03; proportion of adjacent NN intervals differing by >50 ms [pNN50] ms, p = .01). Sympathovagal balance assessed by frequency-domain analysis was lower during both N2 and SWS than during the rapid eye movement (REM) sleep stage, but not different among groups. In conclusion, this group of paediatric patients with PWS had impaired cardiac autonomic balance due to reduced parasympathetic modulation during SWS. This result could imply an underlying increased cardiovascular risk in PWS even during early age and independent of obesity.

The 15q11.2 BP1-BP2 Microdeletion (Burnside-Butler) Syndrome: In Silico Analyses of the Four Coding Genes Reveal Functional Associations with Neurodevelopmental Phenotypes

The 15q11.2 BP1-BP2 microdeletion (Burnside–Butler) syndrome is emerging as the most frequent pathogenic copy number variation (CNV) in humans associated with neurodevelopmental disorders with changes in brain morphology, behavior, and cognition. In this study, we explored functions and interactions of the four protein-coding genes in this region, namely NIPA1, NIPA2, CYFIP1, and TUBGCP5, and elucidate their role, in solo and in concert, in the causation of neurodevelopmental disorders. First, we investigated the STRING protein-protein interactions encompassing all four genes and ascertained their predicted Gene Ontology (GO) functions, such as biological processes involved in their interactions, pathways and molecular functions. These include magnesium ion transport molecular function, regulation of axonogenesis and axon extension, regulation and production of bone morphogenetic protein and regulation of cellular growth and development. We gathered a list of significantly associated cardinal maladies for each gene from searchable genomic disease websites, namely MalaCards.org: HGMD, OMIM, ClinVar, GTR, Orphanet, DISEASES, Novoseek, and GeneCards.org. Through tabulations of such disease data, we ascertained the cardinal disease association of each gene, as well as their expanded putative disease associations. This enabled further tabulation of disease data to ascertain the role of each gene in the top ten overlapping significant neurodevelopmental disorders among the disease association data sets: (1) Prader–Willi Syndrome (PWS); (2) Angelman Syndrome (AS); (3) 15q11.2 Deletion Syndrome with Attention Deficit Hyperactive Disorder & Learning Disability; (4) Autism Spectrum Disorder (ASD); (5) Schizophrenia; (6) Epilepsy; (7) Down Syndrome; (8) Microcephaly; (9) Developmental Disorder, and (10) Peripheral Nervous System Disease. The cardinal disease associations for each of the four contiguous 15q11.2 BP1-BP2 genes are NIPA1- Spastic Paraplegia 6; NIPA2—Angelman Syndrome and Prader–Willi Syndrome; CYFIP1—Fragile X Syndrome and Autism; TUBGCP5—Prader–Willi Syndrome. The four genes are individually associated with PWS, ASD, schizophrenia, epilepsy, and Down syndrome. Except for TUBGCP5, the other three genes are associated with AS. Unlike the other genes, TUBGCP5 is also not associated with attention deficit hyperactivity disorder and learning disability, developmental disorder, or peripheral nervous system disease. CYFIP1 was the only gene not associated with microcephaly but was the only gene associated with developmental disorders. Collectively, all four genes were associated with up to three-fourths of the ten overlapping neurodevelopmental disorders and are deleted in this most prevalent known pathogenic copy number variation now recognized among humans with these clinical findings.

Prader-Willi syndrome: endocrine manifestations and management

Prader-Willi syndrome (PWS) is a genetic disorder caused by the absence of gene expression in the 15q11.2-q13 paternal chromosome. Patients with PWS develop hypothalamic dysfunction that can lead to various endocrine changes such as: obesity, growth hormone deficiency, hypogonadism, hypothyroidism, adrenal insufficiency and low bone mineral density. In addition, individuals with PWS have increased risk of developing type 2 diabetes mellitus. This review summarizes and updates the current knowledge about the prevention, diagnosis and treatment of endocrine manifestations associated with Prader Willi syndrome, especially diagnosis of growth hormone deficiency, management and monitoring of adverse effects; diagnosis of central adrenal insufficiency and management in stressful situations; screening for central hypothyroidism; research and treatment of hypogonadism; prevention and treatment of disorders of glucose metabolism. Careful attention to the endocrine aspects of PWS contributes significantly to the health of these individuals. Arch Endocrinol Metab. 2020;64(3):223-34.

Age Distribution, Comorbidities and Risk Factors for Thrombosis in Prader-Willi Syndrome

Prader–Willi syndrome (PWS) is an imprinting disorder caused by lack of expression of the paternally inherited 15q11.2–q13 chromosome region. The risk of death from obesity-related complications can worsen with age, but survival trends are improving. Comorbidities and their complications such as thrombosis or blood clots and venous thromboembolism (VTE) are uncommon but reported in PWS. Two phases of analyses were conducted in our study: unadjusted and adjusted frequency with odds ratios and a regression analysis of risk factors. Individuals with PWS or non-PWS controls with exogenous obesity were identified by specific International Classification of Diseases (ICD)-9 diagnostic codes reported on more than one occasion to confirm the diagnosis of PWS or exogenous obesity in available national health claims insurance datasets. The overall average age or average age per age interval (0–17 year, 18–64 year, and 65 year+) and gender distribution in each population were similar in 3136 patients with PWS and 3945 non-PWS controls for comparison purposes, with exogenous obesity identified from two insurance health claims dataset sources (i.e., commercial and Medicare advantage or Medicaid). For example, 65.1% of the 3136 patients with PWS were less than 18 years old (subadults), 33.2% were 18–64 years old (adults), and 1.7% were 65 years or older. After adjusting for comorbidities that were identified with diagnostic codes, we found that commercially insured PWS individuals across all age cohorts were 2.55 times more likely to experience pulmonary embolism (PE) or deep vein thrombosis (DVT) than for obese controls (p-value: 0.013; confidence interval (CI): 1.22–5.32). Medicaid-insured individuals across all age cohorts with PWS were 0.85 times more likely to experience PE or DVT than obese controls (p-value: 0.60; CI: 0.46–1.56), with no indicated age difference. Age and gender were statistically significant predictors of VTEs, and they were independent of insurance coverage. There was an increase in occurrence of thrombotic events across all age cohorts within the PWS patient population when compared with their obese counterparts, regardless of insurance type.

Chromosome 15 Imprinting Disorders: Genetic Laboratory Methodology and Approaches

Chromosome 15 imprinting disorders include Prader-Willi (PWS) and Angelman (AS) syndromes, which are caused by absent expression from the paternal and maternal alleles in the chromosome 15q11. 2-q13 region, respectively. In addition, chromosome 15q duplication caused by the presence of at least one additional maternally derived copy of the 15q11.2-q13 region can lead to seizures, cognitive and behavioral problems. We focus on PWS and AS in the report, and expand the discussion of clinical care and description with genetic testing to include high-resolution studies to more specifically characterize the molecular mechanisms of disease. The importance of early diagnosis with the necessity for accurate molecular characterization through a step-wise algorithm is emphasized in an era of targeted therapeutic interventions. We present a flowchart to aid in ordering specialized genetic testing as several methods are available for patients presenting with features of PWS and/or AS.

Early Diagnosis in Prader-Willi Syndrome Reduces Obesity and Associated Co-Morbidities

Prader–Willi syndrome (PWS) is an imprinting genetic disorder characterized by lack of expression of genes on the paternal chromosome 15q11–q13 region. Growth hormone (GH) replacement positively influences stature and body composition in PWS. Our hypothesis was that early diagnosis delays onset of obesity in PWS. We studied 352 subjects with PWS, recruited from the NIH Rare Disease Clinical Research Network, to determine if age at diagnosis, ethnicity, gender, and PWS molecular class influenced the age they first become heavy, as determined by their primary care providers, and the age they first developed an increased appetite and began seeking food. The median ages that children with PWS became heavy were 10 years, 6 years and 4 years for age at diagnosis < 1 year, between 1 and 3 years, and greater than 3 years of age, respectively. The age of diagnosis and ethnicity were significant factors influencing when PWS children first became heavy (p < 0.01), however gender and the PWS molecular class had no influence. Early diagnosis delayed the onset of becoming heavy in individuals with PWS, permitting early GH and other treatment, thus reducing the risk of obesity-associated co-morbidities. Non-white individuals had an earlier onset of becoming heavy.

Impact of genetic subtypes of Prader-Willi syndrome with growth hormone therapy on intelligence and body mass index

Prader-Willi syndrome (PWS) is a genomic imprinting disorder characterized by infantile hypotonia with a poor suck and failure to thrive, hypogenitalism/hypogonadism, behavior and cognitive problems, hormone deficiencies, hyperphagia, and obesity. The Stanford Binet and Wechsler (WAIS-R; WISC-III) intelligence (IQ) tests were administered on 103 individuals with PWS from two separate cohorts [University of California, Irvine (UCI) (N = 56) and Vanderbilt University (N = 47)] and clinical information obtained including growth hormone (GH) treatment, PWS molecular classes, weight and height. Significantly higher IQ scores (p < .02) were found representing the vocabulary section of the Stanford Binet test in the growth hormone (GH) treated group when compared with non-GH treatment in the pediatric-based UCI PWS cohort with a trend for stabilization of vocabulary IQ scores with age in the GH treated maternal disomy (UPD) 15 subject group. Significant differences (p = .05) were also found in the adult-based Vanderbilt PWS cohort with 15q11-q13 deletion subjects having lower Verbal IQ scores compared with UPD 15. No difference in body mass index was identified based on the PWS molecular class or genetic subtype. Medical care and response to treatment with growth hormone may influence intelligence impacted by PWS genetic subtypes and possibly age, but more studies are needed.

Birth seasonality studies in a large Prader-Willi syndrome cohort

Prader‐Willi syndrome (PWS) is generally due to sporadic paternal deletions of the chromosome 15q11‐q13 region followed by maternal disomy 15. Advanced maternal age is more commonly seen in those with maternal disomy 15. Environmental factors (e.g., drug use, occupational chemical exposure, infectious agents, and irradiation) could account for chromosome changes. Previous evidence of differences in male and female gametogenesis could suggest an environmental role in the causation of the paternal 15q11‐q13 deletion seen in PWS. Certain occupations such as hydrocarbon‐exposing occupations (e.g., landscaping, farming, and painting) and viral exposure (e.g., human coronavirus 229E causing upper respiratory infections in adults with an incorporation site in the human genome at chromosome 15q11) can be seasonal in nature and contribute to chromosome damage. To assess, we reviewed birth seasonality data in a large cohort of individuals with PWS recruited nationally (N = 355) but no significant differences were seen by month between those with the 15q11‐q13 deletion compared with maternal disomy 15 when analyzing quarterly seasonal patterns. Although early evidence supported birth seasonality differences in PWS, a larger number of individuals in our recent study using advanced genetic testing methods did not find this observation.

Magnesium Supplement and the 15q11.2 BP1-BP2 Microdeletion (Burnside-Butler) Syndrome: A Potential Treatment?

The 15q11.2 BP1–BP2 microdeletion (Burnside–Butler) syndrome is an emerging disorder that encompasses four genes (NIPA1, NIPA2, CYFIP1, and TUBGCP5). When disturbed, these four genes can lead to cognitive impairment, language and/or motor delay, psychiatric/behavioral problems (attention-deficit hyperactivity, autism, dyslexia, schizophrenia/paranoid psychosis), ataxia, seizures, poor coordination, congenital anomalies, and abnormal brain imaging. This microdeletion was reported as the most common cytogenetic finding when using ultra-high- resolution chromosomal microarrays in patients presenting for genetic services due to autism with or without additional clinical features. Additionally, those individuals with Prader–Willi or Angelman syndromes having the larger typical 15q11–q13 type I deletion which includes the 15q11.2 BP1–BP2 region containing the four genes, show higher clinical severity than those having the smaller 15q11–q13 deletion where these four genes are intact. Two of the four genes (i.e., NIPA1 and NIPA2) are expressed in the brain and encode magnesium transporters. Magnesium is required in over 300 enzyme systems that are critical for multiple cellular functions, energy expenditure, protein synthesis, DNA transcription, and muscle and nerve function. Low levels of magnesium are found in those with seizures, depression, and acute or chronic brain diseases. Anecdotally, parents have administered magnesium supplements to their children with the 15q11.2 BP1–BP2 microdeletion and have observed improvement in behavior and clinical presentation. These observations require more attention from the medical community and should include controlled studies to determine if magnesium supplements could be a treatment option for this microdeletion syndrome and also for a subset of individuals with Prader–Willi and Angelman syndromes.

Analysis of the Prader-Willi syndrome imprinting center using droplet digital PCR and next-generation whole-exome sequencing

BACKGROUND

Detailed analysis of imprinting center (IC) defects in individuals with Prader-Willi syndrome (PWS) is not readily available beyond chromosomal microarray (MA) analysis, and such testing is important for a more accurate diagnosis and recurrence risks. This is the first feasibility study of newly developed droplet digital polymerase chain reaction (ddPCR) examining DNA copy number differences in the PWS IC region of those with IC defects.

METHODS

The study cohort included 17 individuals without 15q11-q13 deletions or maternal disomy but with IC defects as determined by genotype analysis showing biparental inheritance. Seven sets of parents and two healthy, unrelated controls were also analyzed.

RESULTS

Copy number differences were distinguished by comparing the number of positive droplets detected by IC probes to those from a chromosome 15 reference probe, GABRβ3. The ddPCR findings were compared to results from other methods including MA, and whole-exome sequencing (WES) with 100% concordance. The study also estimated the frequency of IC microdeletions and identified gene variants by WES that may impact phenotypes including CPT2 and NTRK1 genes.

CONCLUSION

Droplet digital polymerase chain reaction is a cost-effective method that can be used to confirm the presence of microdeletions in PWS with impact on genetic counseling and recurrence risks for families.

Prader-Willi Syndrome - Clinical Genetics, Diagnosis and Treatment Approaches: An Update

BACKGROUND

Prader-Willi Syndrome (PWS) is a neurodevelopmental genomic imprinting disorder with lack of expression of genes inherited from the paternal chromosome 15q11-q13 region usually from paternal 15q11-q13 deletions (about 60%) or maternal uniparental disomy 15 or both 15s from the mother (about 35%). An imprinting center controls the expression of imprinted genes in the chromosome 15q11-q13 region. Key findings include infantile hypotonia, a poor suck, failure to thrive and hypogonadism/hypogenitalism. Short stature and small hands/feet due to growth and other hormone deficiencies, hyperphagia and marked obesity occur in early childhood, if uncontrolled. Cognitive and behavioral problems (tantrums, compulsions, compulsive skin picking) are common.

OBJECTIVE

Hyperphagia and obesity with related complications are major causes of morbidity and mortality in PWS. This report will describe an accurate diagnosis with determination of specific genetic subtypes, appropriate medical management and best practice treatment approaches.

METHODS AND RESULTS

An extensive literature review was undertaken related to genetics, clinical findings and laboratory testing, clinical and behavioral assessments and summary of updated health-related information addressing the importance of early PWS diagnosis and treatment. A searchable, bulleted and formatted list of topics is provided utilizing a Table of Contents approach for the clinical practitioner.

CONCLUSION

Physicians and other health care providers can use this review with clinical, genetic and treatment summaries divided into sections pertinent in the context of clinical practice. Frequently asked questions by clinicians, families and other interested participants or providers will be addressed.

Preliminary observations of mitochondrial dysfunction in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex multisystem disorder because of errors in genomic imprinting with severe hypotonia, decreased muscle mass, poor suckling, feeding problems and failure to thrive during infancy, growth and other hormone deficiency, childhood-onset hyperphagia, and subsequent obesity. Decreased energy expenditure in PWS is thought to contribute to reduced muscle mass and physical activity but may also relate to cellular metabolism and disturbances in mitochondrial function. We established fibroblast cell lines from six children and adults with PWS and six healthy controls for mitochondrial assays. We used Agilent Seahorse XF extracellular flux technology to determine real-time measurements of several metabolic parameters including cellular substrate utilization, Adenosine Triphosphate (ATP)-linked respiration, and mitochondrial capacity in living cells. Decreased mitochondrial function was observed in the PWS patients compared to the healthy controls with significant differences in basal respiration, maximal respiratory capacity, and ATP-linked respiration. These results suggest disturbed mitochondrial bioenergetics in PWS although the low number of studied subjects will require a larger subject population before a general consensus can be reached to identify if mitochondrial dysfunction is a contributing factor in PWS.

STARTLE RESPONSE ANALYSIS OF FOOD-IMAGE PROCESSING IN PRADER-WILLI SYNDROME

BACKGROUND

Prader-Willi syndrome (PWS) is a complex genetic neurodevelopmental disorder with endocrine disturbances, hyperphagia and often life-threatening obesity as key features. We investigated emotional-processing of food and eating behavior in PWS using startle response-modulation. Startle eyeblink response is an involuntary reflex activated by the autonomic nervous system in response to sudden or disturbing auditory/visual stimuli which may be modulated by the emotional valence of concurrently viewed visual stimuli.

METHODOLOGY

Differences in affective modulation of startle reflex were recorded in 13 individuals with PWS versus 8 healthy controls when viewing standard neutral, negative, positive and food-derived images. Electromyogram (EMG) of the orbicularis oculi muscle was measured in response to binaural white noise before and after consumption of a standard 500 Kcal meal. Participants reported their perceived emotional valence for each image, pre- and post-meal, using a 1-10 Likert rating scale.

RESULTS

Subjective ratings of food images and urge to eat were significantly higher in PWS than controls and did not significantly decline post-meal. Acoustic startle responding was detected in PWS but was significantly lower than control participants under all conditions. Startle responses to food images in PWS were attenuated relative to other picture types with potentially abnormal emotional modulation of responses to non-food images which contrasted self-reported picture ratings. A stable positive emotional valence to food images was observed pre- and post-feeding with a sustained urge to consume food in PWS.

CONCLUSIONS

Emotional processing measured using startle modulation in response to non-food images was abnormal in PWS which may reflect unique physiological attributes such as hypotonia and abnormal skin conductivity due to increased fat mass. Alternatively, disruption of autonomic or sympathetic nervous system functioning reported in PWS may impact on hunger and/or food drive states. Our findings parallel attentional/processing attributes of affective stimuli reported in autism spectrum disorder and support the feasibility of eyeblink startle modulation to assess food motivation in PWS and provide preliminary data to optimize methodological parameters.

Molecular genetic classification in Prader-Willi syndrome: a multisite cohort study

BACKGROUND

Prader-Willi syndrome (PWS) is due to errors in genomic imprinting. PWS is recognised as the most common known genetic cause of life-threatening obesity. This report summarises the frequency and further characterises the PWS molecular classes and maternal age effects.

METHODS

High-resolution microarrays, comprehensive chromosome 15 genotyping and methylation-specific multiplex ligation probe amplification were used to describe and further characterise molecular classes of maternal disomy 15 (UPD15) considering maternal age.

RESULTS

We summarised genetic data from 510 individuals with PWS and 303 (60%) had the 15q11-q13 deletion; 185 (36%) with UPD15 and 22 (4%) with imprinting defects. We further characterised UPD15 findings into subclasses based on the presence (size, location) or absence of loss of heterozygosity (LOH). Additionally, significantly older mothers (mean age=32.5 years vs 27.7 years) were found in the UPD15 group (n=145) compared with the deletion subtype (n=200).

CONCLUSIONS

We report on molecular classes in PWS using advanced genomic technology in the largest cohort to date. LOH patterns in UPD15 may impact the risk of having a second genetic condition if the mother carries a recessive mutant allele in the isodisomic region on chromosome 15. The risk of UPD15 may also increase with maternal age.

Growth hormone receptor (GHR) gene polymorphism and scoliosis in Prader-Willi syndrome

OBJECTIVE

A growth hormone receptor (GHR) gene polymorphism impacts sensitivity to endogenous and exogenous growth hormone (GH) to moderate growth and development. Increased sensitivity may accelerate spinal growth and contribute to scoliosis, particularly in GH-deficient and treated populations such as Prader-Willi syndrome (PWS). Therefore, we examined the relationship between GHR genotype and scoliosis (case and control) in PWS cohorts.

DESIGN

We utilized a case-control design in a study of 73 subjects (34M; 39F) with genetically confirmed PWS in 32 individuals previously diagnosed with moderate to severe scoliosis (mean age=16.9±10.2years; age range of 1 to 41years) and 41 adults with no evidence of scoliosis (mean age=30.8±9.7years; age range of 18 to 56years). The GHR gene polymorphism was determined using PCR specific primers to capture the two recognized GHR gene fragment sizes [i.e., full length (fl) or exon 3 deletions (d3)].

RESULTS

Twenty-three (72%) of the 32 case subjects with scoliosis required surgical correction with an approximately equal balance for gender and PWS genetic subtype among cases and 41 control subjects without scoliosis. The GHR d3/d3 genotype was identified in N=2 of 8 (25%) cases with scoliosis and the d3/fl genotype was identified in N=11 of 25 (44%) cases with scoliosis but the distribution difference did not statistically differ. The GHR fl/fl genotype was correlated with a significantly faster rate and heavier weight gain among case subjects.

CONCLUSION

Our examination of demographic and genetic markers associated with scoliosis and surgical repair in PWS found no evidence to support differences in gender, PWS genetic subtype or GHR d3 allele distributions among the case vs control groups. Those with fl/fl alleles were heavier than those with d3/d3 or d3/fl genotypes and warrant further study with a larger sample size and possibly to include other vulnerable populations requiring growth hormone treatment.

Prader-Willi syndrome genetic subtypes and clinical neuropsychiatric diagnoses in residential care adults

The historical diagnosis of Prader-Willi syndrome (PWS), a complex genetic disorder, in adults is often achieved by clinical presentation rather than by genetic testing and thus limited genetic subtype-specific psychometric investigations and treatment options. Genetic testing and clinical psychiatric evaluation using Diagnostic and Statistical Manual (DSM)-IV-TR criteria were undertaken on 72 adult residents (34 M; 38 F) from the Prader-Willi Homes of Oconomowoc (PWHO), a specialty PWS group home system. Methylation specific-multiplex ligation probe amplification and high-resolution microarrays were analyzed for methylation status, 15q11-q13 deletions and maternal uniparental disomy 15 (mUPD15). Seventy (33M; 37F) of 72 residents were genetically confirmed and 36 (51%) had Type I or Type II deletions; 29 (42%) with mUPD15 and 5 (7%) with imprinting defects from three separate families. Psychiatric comorbidities were classified as anxiety disorder (38%), excoriation (skin picking) (33%), intermittent explosive disorder ([30%-predominantly among males at 45% compared with females at 16% [OR = 4.3, 95%CI 1.4-13.1, P < 0.008]) and psychotic features (23%). Psychiatric diagnoses did not differ between mUPD15 vs deletion, but a greater number of psychiatric diagnoses were observed for the larger Type I (4.3) vs smaller Type II (3.6) deletions when age was controlled (F = 5.0, P < 0.04). Adults with PWS presented with uniformly higher rates of psychiatric comorbidities which differed by genetic subtype with gender-specific trends.

Prader-Willi syndrome and early-onset morbid obesity NIH rare disease consortium: A review of natural history study

We describe the National Institutes of Health rare disease consortium for Prader-Willi syndrome (PWS) developed to address concerns regarding medical care, diagnosis, growth and development, awareness, and natural history. PWS results from errors in genomic imprinting leading to loss of paternally expressed genes due to 15q11-q13 deletion, maternal disomy 15 or imprinting defects. The 8 year study was conducted at four national sites on individuals with genetically confirmed PWS and early-onset morbid obesity (EMO) with data accumulated to gain a better understanding of the natural history, cause and treatment of PWS. Enrollment of 355 subjects with PWS and 36 subjects with EMO began in September 2006 with study completion in July 2014. Clinical, genetic, cognitive, behavior, and natural history data were systematically collected along with PWS genetic subtypes, pregnancy and birth history, mortality, obesity, and cognitive status with study details as important endpoints in both subject groups. Of the 355 individuals with PWS, 217 (61%) had the 15q11-q13 deletion, 127 (36%) had maternal disomy 15, and 11 (3%) had imprinting defects. Six deaths were reported in our PWS cohort with 598 cumulative years of study exposure and one death in the EMO group with 42 years of exposure. To our knowledge, this description of a longitudinal study in PWS represents the largest and most comprehensive cohort useful for investigators in planning comparable studies in other rare disorders. Ongoing studies utilizing this database should have a direct impact on care and services, diagnosis, treatment, genotype-phenotype correlations, and clinical outcomes in PWS.

Effects of MetAP2 inhibition on hyperphagia and body weight in Prader-Willi syndrome: A randomized, double-blind, placebo-controlled trial

AIMS

There are no treatments for the extreme hyperphagia and obesity in Prader-Willi syndrome (PWS). The bestPWS clinical trial assessed the efficacy, safety and tolerability of the methionine aminopeptidase 2 (MetAP2) inhibitor, beloranib.

MATERIALS AND METHODS

Participants with PWS (12-65 years old) were randomly assigned (1:1:1) to biweekly placebo, 1.8 mg beloranib or 2.4 mg beloranib injection for 26 weeks at 15 US sites. Co-primary endpoints were the changes in hyperphagia [measured by Hyperphagia Questionnaire for Clinical Trials (HQ-CT); possible score 0-36] and weight by intention-to-treat. ClinicalTrials.gov registration: NCT02179151.

RESULTS

One-hundred and seven participants were included in the intention-to-treat analysis: placebo (n = 34); 1.8 mg beloranib (n = 36); or 2.4 mg beloranib (n = 37). Improvement (reduction) in HQ-CT total score was greater in the 1.8 mg (mean difference -6.3, 95% CI -9.6 to -3.0; P = .0003) and 2.4 mg beloranib groups (-7.0, 95% CI -10.5 to -3.6; P = .0001) vs placebo. Compared with placebo, weight change was greater with 1.8 mg (mean difference - 8.2%, 95% CI -10.8 to -5.6; P < .0001) and 2.4 mg beloranib (-9.5%, 95% CI -12.1 to -6.8; P < .0001). Injection site bruising was the most frequent adverse event with beloranib. Dosing was stopped early due to an imbalance in venous thrombotic events in beloranib-treated participants (2 fatal events of pulmonary embolism and 2 events of deep vein thrombosis) compared with placebo.

CONCLUSIONS

MetAP2 inhibition with beloranib produced statistically significant and clinically meaningful improvements in hyperphagia-related behaviours and weight loss in participants with PWS. Although investigation of beloranib has ceased, inhibition of MetAP2 is a novel mechanism for treating hyperphagia and obesity.

Duplication of 19p13.3 in 11-Year-Old Male Patient with Dysmorphic Features and Intellectual Disability: A Review

We present a clinical report of an 11-year-old male patient with an interstitial duplication of 19p13.3 (829 kb in size) at genomic coordinates 3,804,495-4,033,722 bp (hg19) identified by chromosomal microarray analysis and review the literature from nine published reports adding knowledge regarding this chromosomal anomaly and clinical outcomes. The size of the duplication ranged from 0.83 to 8.9 Mb in the nine individuals. The young boy in our report was dysmorphic with microcephaly, abnormal craniofacial features, intellectual disability, aggression, and a heart murmur. All patients were found to have a psychomotor developmental delay and/or intellectual disability with the majority having microcephaly, intrauterine growth retardation, and hypotonia. Common craniofacial findings included a tall, prominent forehead, an elongated face, epicanthal folds, hypertelorism, prominent low-set ears, philtrum anomaly, and a small mouth. Other less common features included abnormal digits, sparse hair, and cardiac defects. Clinical features, chromosome duplication sizes, locations, and the number of genes will be summarized in a tabular form.

Survival trends from the Prader-Willi Syndrome Association (USA) 40-year mortality survey

Background

Prader-Willi syndrome (PWS) is a complex genetic disorder characterized by hyperphagia and morbid obesity with increased cardiopulmonary and hyperphagia-related mortality. Survival trends in PWS were evaluated to assess the impact of modern interventions on mortality risk.

Methods

The PWSA (USA) 40-year mortality syndrome-specific database of 486 death reports was utilized to examine survival trends in PWS and cohort effects for recent deaths (years 2000–2015, N=331) relative to deaths prior to 2000 (N=94). Cox Proportional Hazards regression modeling was applied to generate log rank statistics and Kaplan-Meier curves examining sex, cause of death and cohort.

Results

Risk for all-cause mortality in PWS was 1.5 (95%CI=1.2–1.9) times higher for the Early than the Recent era cohort reflected in female cardiac failure (HR=1.8; 95%CI=1.3–2.6), pulmonary embolism (HR=6.1; 95%CI=1.7–22), and GI-related (HR=3.2; 95%CI=1.1–7.4) causes. Accidental deaths in males increased in the Recent era cohort (HR=5.7; 95%CI=1.2–27.1) possibly due to enhanced weight management and mobility. Risk of death from respiratory failure was unchanged.

Conclusions

We report measurable increases in survival effecting cardiovascular and GI-related causes in PWS most likely attributable to earlier diagnosis and proactive interventions to prevent morbid obesity. More research is needed to address underlying vulnerability to respiratory failure, an unchanged mortality risk in PWS.

Clinical and genetic aspects of the 15q11.2 BP1-BP2 microdeletion disorder

BACKGROUND

The 15q11.2 BP1-BP2 microdeletion (Burnside-Butler susceptibility locus) is an emerging condition with over 200 individuals reported in the literature. TUBGCP5, CFYIP1, NIPA1 and NIPA2 genes are located in this chromosome 15 region and when disturbed individually are known to cause neurological, cognitive or behavioural problems as well as playing a role in both Prader-Willi and Angelman syndromes. These syndromes were the first examples in humans of genomic imprinting and typically caused by a deletion but involving the distal chromosome 15q11-q13 breakpoint BP3 and proximally placed breakpoints BP1 or BP2 of different parental origin. The typical 15q11-q13 deletion involves BP1 and BP3 and the typical type II deletion at BP2 and BP3. Several studies have shown that individuals with the larger type I deletion found in both Prader-Willi and Angelman syndromes are reported with more severe neurodevelopmental symptoms compared to those individuals with the smaller type II deletion.

METHODS

The literature was reviewed and clinical and cytogenetic findings summarised in 200 individuals with this microdeletion along with the role of deleted genes in diagnosis, medical care and counseling of those affected and their family members.

RESULTS

Reported findings in this condition include developmental delays (73% of cases) and language impairment (67%) followed by motor delay (42%), attention deficit disorder/attention deficit hyperactivity disorder (35%) and autism spectrum disorder (27%). The de novo deletion frequency has been estimated at 5 to 22% with low penetrance possibly related to subclinical manifestation or incomplete clinical information on family members. A prevalence of 0.6 to 1.3% has been identified in one study for patients with neurological or behavioural problems presenting for genetic services and chromosomal microarray analysis.

CONCLUSIONS

The summarised results indicate that chromosome 15q11.2 BP1-BP2 microdeletion is emerging as one of the most common cytogenetic abnormalities seen in individuals with intellectual impairment, autism spectrum disorder and other related behavioural or clinical findings, but more research is needed.

Causes of death in Prader-Willi syndrome: Prader-Willi Syndrome Association (USA) 40-year mortality survey

BACKGROUND

Prader-Willi syndrome (PWS) is a rare, complex, neurodevelopmental genetic disorder that is associated with hyperphagia and morbid obesity in humans and leads to a shortened life expectancy. This report summarizes the primary causes of death and evaluates mortality trends in a large cohort of individuals with PWS.

METHODS

The US Prader-Willi Syndrome Association (PWSA (USA)) syndrome-specific database of death reports was collected through a cursory bereavement program for PWSA (USA) families using a brief survey created in 1999. Causes of death were descriptively characterized and statistically examined using Cox proportional hazards.

RESULTS

A total of 486 deaths were reported (263 males, 217 females, 6 unknown) between 1973 and 2015, with mean age of 29.5 ± 16 years (2 months-67 years); 70% occurred in adulthood. Respiratory failure was the most common cause, accounting for 31% of all deaths. Males were at increased risk for presumed hyperphagia-related accidents/injuries and cardiopulmonary factors compared to females. PWS maternal disomy 15 genetic subtype showed an increased risk of death from cardiopulmonary factors compared to the deletion subtype.

CONCLUSIONS

These findings highlight the heightened vulnerability to obesity and hyperphagia-related mortality in PWS. Future research is needed to address critical vulnerabilities such as gender and genetic subtype in the cause of death in PWS.Genet Med advance online publication 17 November 2016.

Benefits and limitations of prenatal screening for Prader-Willi syndrome

This review summarizes the status of genetic laboratory testing in Prader-Willi syndrome (PWS) with different genetic subtypes, most often a paternally derived 15q11-q13 deletion and discusses benefits and limitations related to prenatal screening. Medical literature was searched for prenatal screening and genetic laboratory testing methods in use or under development and discussed in relationship to PWS. Genetic testing includes six established laboratory diagnostic approaches for PWS with direct application to prenatal screening. Ultrasonographic, obstetric and cytogenetic reports were summarized in relationship to the cause of PWS and identification of specific genetic subtypes including maternal disomy 15. Advances in genetic technology were described for diagnosing PWS specifically DNA methylation and high-resolution chromosomal SNP microarrays as current tools for genetic screening and incorporating next generation DNA sequencing for noninvasive prenatal testing (NIPT) using cell-free fetal DNA. Positive experiences are reported with NIPT for detection of numerical chromosomal problems (aneuploidies) but not for structural problems (microdeletions). These reports will be discussed along with future directions for genetic screening of PWS. In summary, this review describes and discusses the status of established and ongoing genetic testing options for PWS applicable in prenatal screening including NIPT and future directions for early diagnosis in PWS. © 2016 John Wiley & Sons, Ltd.

Prader-Willi syndrome and atypical submicroscopic 15q11-q13 deletions with or without imprinting defects

We report a 20 year follow up on a Caucasian female, now 26 years of age, with Prader-Willi syndrome (PWS) harboring an atypical 15q11-q13 submicroscopic deletion of 100-200 kb in size first detected in 1996 involving the imprinting center, SNRPN gene and surrounding region. PWS is a rare complex disorder caused by the loss of paternally expressed genes in the 15q11-q13 region. With high resolution chromosomal microarray and methylation - specific MLPA analysis, we updated the genetic findings on our patient and found a 209,819bp deletion including the SNURF-SNRPN gene complex which includes the imprinting center and the SNORD116 region. We compared with four other similarly reported individuals in the literature with atypical submicroscopic deletions within this region but without imprinting center involvement to better characterize the specific genetic lesions causing PWS clinical findings. Clinically, our patient met the diagnostic criteria of PWS including infantile hypotonia, a poor suck with feeding difficulties, global developmental delays and later food foraging, childhood obesity, small hands and skin picking. Small atypical deletions of comparable sizes were seen in the 15q11-q13 region in all five cases and similar behavioral/physical characteristics were found despite an imprinting defect in our patient. These results further support an overlapping critical deletion region involving the non-coding snoRNA SNORD116 in common in the five individuals playing a key role in contributing to the PWS phenotype.