Evaluation and Management of Early Onset Genetic Obesity in Childhood

Differentiating monogenic and syndromic obesities from polygenic obesity: Assessment, diagnosis, and management

Background

Obesity is a multifactorial neurohormonal disease that results from dysfunction within energy regulation pathways and is associated with increased morbidity, mortality, and reduced quality of life. The most common form is polygenic obesity, which results from interactions between multiple gene variants and environmental factors. Highly penetrant monogenic and syndromic obesities result from rare genetic variants with minimal environmental influence and can be differentiated from polygenic obesity depending on key symptoms, including hyperphagia; early-onset, severe obesity; and suboptimal responses to nontargeted therapies. Timely diagnosis of monogenic or syndromic obesity is critical to inform management strategies and reduce disease burden. We outline the physiology of weight regulation, role of genetics in obesity, and differentiating characteristics between polygenic and rare genetic obesity to facilitate diagnosis and transition toward targeted therapies.

Methods

In this narrative review, we focused on case reports, case studies, and natural history studies of patients with monogenic and syndromic obesities and clinical trials examining the efficacy, safety, and quality of life impact of nontargeted and targeted therapies in these populations. We also provide comprehensive algorithms for diagnosis of patients with suspected rare genetic causes of obesity.

Results

Patients with monogenic and syndromic obesities commonly present with hyperphagia (ie, pathologic, insatiable hunger) and early-onset, severe obesity, and the presence of hallmark characteristics can inform genetic testing and diagnostic approach. Following diagnosis, specialized care teams can address complex symptoms, and hyperphagia is managed behaviorally. Various pharmacotherapies show promise in these patient populations, including setmelanotide and glucagon-like peptide-1 receptor agonists.

Conclusion

Understanding the pathophysiology and differentiating characteristics of monogenic and syndromic obesities can facilitate diagnosis and management and has led to development of targeted pharmacotherapies with demonstrated efficacy for reducing body weight and hunger in the affected populations.

Specificity of Early Childhood Hyperphagia Profiles in Neurogenetic Conditions

Hyperphagia is highly penetrant in Prader-Willi syndrome (PWS) and has increasingly been reported in other neurogenetic conditions (NGC). The Hyperphagia Questionnaire (HQ) was completed by caregivers of 4-8-year-olds with PWS (n = 17), Angelman syndrome (AS; n = 22), Williams syndrome (WS; n = 25), or low-risk controls (LRC; n = 35). All NGC groups were significantly elevated in HQ Total and Behavior scores compared to LRC. Only AS and WS were significantly elevated in the Drive domain, and only PWS in the Severity domain. After controlling for externalizing behavior, HQ Total scores were higher for PWS relative to other groups. Hyperphagic symptoms may not differentiate PWS from other NGCs in early childhood. However, hyperphagic phenotypes may be most severe in PWS. Further investigation of these profiles may inform etiology and syndrome-specific treatments.

The Tip of the Iceberg: Genotype of Puerto Rican Pediatric Obesity

Childhood obesity is a significant public health concern, particularly among Hispanic populations. This study aimed to elucidate the genetic predisposition to obesity in Puerto Rican children of Hispanic descent, addressing a notable gap in existing research. A cohort of 103 children with obesity and hyperphagia underwent genetic screening for rare obesity-related variants. Clinical assessments and family history evaluations were conducted to characterize the demographic and clinical characteristics of the cohort. Genetic testing revealed a high prevalence of variants, with 73% of subjects having at least one reported variant. Pathogenic variants, predominantly associated with obesity-related ciliopathies, were identified in 7% of cases. Additionally, 90% of cases had variants of uncertain significance, highlighting the complexity of genetic contributions to obesity. This study emphasizes the critical need for further investigation into the genetic foundations of obesity, particularly within Hispanic communities. The findings emphasize the importance of early medical evaluation, vigilant monitoring for hyperphagia onset, and targeted interventions tailored to the unique genetic landscape of Puerto Rican children. This research provides a foundational framework for future studies to mitigate the impact of genetic obesity within this population.

The Role of the Pediatrician in the Promotion of Healthy, Active Living

Few children and adolescents meet federal nutrition or physical activity recommendations, and many experience poor or inadequate sleep and negative health effects from screen use and social media. These lifestyle factors exacerbate physical and mental health risks for children and adolescents. This clinical report provides guidance to help pediatricians address the nutritional, physical activity, sleep, media and screen use, and social-emotional factors that affect child and adolescent health and wellness. The recommendations in this clinical report aim to promote health and wellness practices for infants, children, and adolescents across several domains of influence, including the individual, interpersonal, institutional, community, and public policy levels.

Clinical and molecular characterisation of children with monogenic obesity: a case series

INTRODUCTION

To study the clinical profile and molecular diagnosis of children with severe early-onset non-syndromic monogenic obesity.

METHODS

The clinical and molecular data (performed using whole exome sequencing) of 7 children with early-onset (< 5 years) non-syndromic monogenic obesity were extracted from the Obesity Clinic files and analysed retrospectively.

RESULTS

The median (IQR) age at presentation was 18 (10.5-27) months. Of the 7 patients, 5 were boys, 3 had a history of parental consanguinity, and 4 had a family history of severe early-onset obesity. All patients exhibited hyperphagia and showed signs of insulin resistance. Dyslipidaemia and fatty liver were observed in 4. The variants identified in 6 patients included 2 in leptin receptor, and one each in melanocortin 4 receptor, pro-opiomelanocortin, leptin, and neurotrophic tyrosine kinase receptor type 2 genes. Notably, 4 of these variants were novel.

CONCLUSIONS

This case series provides valuable insights into the spectrum of genetic mutations associated with non-syndromic monogenic obesity in North Indian children. The findings underscore the significance of next-generation sequencing in identifying the aetiology of severe early-onset obesity.

A comprehensive review of genetic causes of obesity

BACKGROUND

Obesity is a multifactorial chronic disease with a high, increasing worldwide prevalence. Genetic causes account for 7% of the cases in children with extreme obesity.

DATA SOURCES

This narrative review was conducted by searching for papers published in the PubMed/MEDLINE, Embase and SciELO databases and included 161 articles. The search used the following search terms: "obesity", "obesity and genetics", "leptin", "Prader-Willi syndrome", and "melanocortins". The types of studies included were systematic reviews, clinical trials, prospective cohort studies, cross-sectional and prospective studies, narrative reviews, and case reports.

RESULTS

The leptin-melanocortin pathway is primarily responsible for the regulation of appetite and body weight. However, several important aspects of the pathophysiology of obesity remain unknown. Genetic causes of obesity can be grouped into syndromic, monogenic, and polygenic causes and should be assessed in children with extreme obesity before the age of 5 years, hyperphagia, or a family history of extreme obesity. A microarray study, an analysis of the melanocortin type 4 receptor gene mutations and leptin levels should be performed for this purpose. There are three therapeutic levels: lifestyle modifications, pharmacological treatment, and bariatric surgery.

CONCLUSIONS

Genetic study technologies are in constant development; however, we are still far from having a personalized approach to genetic causes of obesity. A significant proportion of the affected individuals are associated with genetic causes; however, there are still barriers to its approach, as it continues to be underdiagnosed. Video Abstract (MP4 1041807 KB).

High Prevalence of Positive Genetic Obesity Variants in Postoperative Bariatric Surgery Patients with Weight Regain Presenting for Medical Obesity Intervention

INTRODUCTION

Genetic obesity susceptibility in postoperative bariatric surgery weight regain (PBSWR) remains largely unexplored.

METHODS

A retrospective case series of adult (N = 27) PBSWR patients who had undergone genetic obesity testing was conducted between Sept. 2020 and March 2022.

PRIMARY OUTCOME

frequency of genetic variants in patients experiencing weight regain following bariatric surgery.

SECONDARY OUTCOMES

prevalence of obesity-related comorbidities, nadir BMI achieved post-bariatric surgery, and percent total body weight loss (%TBWL) achieved with obesity pharmacotherapies.

RESULTS

Heterozygous mutations were identified in 22 (81%) patients, with the most prevalent mutations occurring in CEP290, RPGR1P1L, and LEPR genes (3 patients each). Median age was 56 years (interquartile range (IQR) 46.8-65.5), 88% female. Types of surgery were 67% RYGB, 19% SG, 4% gastric band, and 13% revisions. Median nadir BMI postoperatively was 34.0 kg/m2 (IQR 29.0-38.5). A high prevalence of metabolic derangements was noted; patients presented median 80 months (IQR 39-168.5) postoperative for medical weight management with 40% weight regain. BMI at initiation of anti-obesity medication (AOMs) was 41.7 kg/m2 (36.8-44.4). All received AOM and required at least 3 AOMs for weight regain. Semaglutide (N = 21), topiramate (N = 14), and metformin (N = 12) were most prescribed. Median %TBWL for the cohort at the first, second, and third visit was 1.7, 5.0, and 6.5 respectively. Fourteen (52%) achieved 5%TBWL, 10 (37%) achieved 10%TBWL, and 4 (15%) achieved 15%TBWL with combination AOMs and supervised medical intervention.

CONCLUSION

An unusually high prevalence of genetic obesity variants in PBSWR was found, warranting further research.

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.

Rare genetic forms of obesity in childhood and adolescence, a comprehensive review of their molecular mechanisms and diagnostic approach

Obesity represents a major health problem in the pediatric population with an increasing prevalence worldwide, associated with cardiovascular and metabolic disorders, and due to both genetic and environmental factors. Rare forms of obesity are mostly monogenic, and less frequently due to polygenic influence. Polygenic form of obesity is usually the common obesity with single gene variations exerting smaller impact on weight and is commonly non-syndromic.Non-syndromic monogenic obesity is associated with variants in single genes typically related to the hypothalamic leptin-melanocortin signalling pathway, which plays a key role in hunger and satiety regulation, thus body weight control. Patients with these genetic defects usually present with hyperphagia and early-onset severe obesity. Significant progress in genetic diagnostic testing has recently made for early identification of patients with genetic obesity, which guarantees prompt intervention in terms of therapeutic management of the disease. What is Known: • Obesity represents a major health problem among children and adolescents, with an increasing prevalence worldwide, associated with cardiovascular disease and metabolic abnormalities, and it can be due to both genetic and environmental factors. • Non-syndromic monogenic obesity is linked to modifications in single genes usually involved in the hypothalamic leptin-melanocortin signalling pathway, which plays a key role in hunger and satiety regulation. What is New: • The increasing understanding of rare forms of monogenic obesity has provided significant insights into the genetic causes of pediatric obesity, and our current knowledge of the various genes associated with childhood obesity is rapidly expanding. • A useful diagnostic algorithm for early identification of genetic obesity has been proposed, which can ensure a prompt intervention in terms of therapeutic management of the disease and an early prevention of the development of associated metabolic conditions.

Towards precision medicine in bariatric surgery prescription

Obesity is a complex, multifactorial and chronic disease. Bariatric surgery is a safe and effective treatment intervention for obesity and obesity-related diseases. However, weight loss after surgery can be highly heterogeneous and is not entirely predictable, particularly in the long-term after intervention. In this review, we present and discuss the available data on patient-related and procedure-related factors that were previously appointed as putative predictors of bariatric surgery outcomes. In addition, we present a critical appraisal of the available evidence on which factors could be taken into account when recommending and deciding which bariatric procedure to perform. Several patient-related features were identified as having a potential impact on weight loss after bariatric surgery, including age, gender, anthropometrics, obesity co-morbidities, eating behavior, genetic background, circulating biomarkers (microRNAs, metabolites and hormones), psychological and socioeconomic factors. However, none of these factors are sufficiently robust to be used as predictive factors. Overall, there is no doubt that before we long for precision medicine, there is the unmet need for a better understanding of the socio-biological drivers of weight gain, weight loss failure and weight-regain after bariatric interventions. Machine learning models targeting preoperative factors and effectiveness measurements of specific bariatric surgery interventions, would enable a more precise identification of the causal links between determinants of weight gain and weight loss. Artificial intelligence algorithms to be used in clinical practice to predict the response to bariatric surgery interventions could then be created, which would ultimately allow to move forward into precision medicine in bariatric surgery prescription.

Genetic Obesity-Causes and Treatments

Genetic abnormalities are responsible for up to 70% of severe, early onset obesity. With recent advances in genetic testing, more individuals with genetic etiology of excessive weight are being identified. However, treatment will need to be individualized based on the cause and underlying pathophysiology. Several treatment options are being investigated, and there are several treatment options now commercially available for some of these genetic conditions. [Pediatr Ann. 2023;52(2):e57-e61.].

Quality of life improvements following one year of setmelanotide in children and adult patients with Bardet-Biedl syndrome: phase 3 trial results

BACKGROUND

Bardet-Biedl syndrome is a rare genetic disease associated with hyperphagia and early-onset, severe obesity. There is limited evidence on how hyperphagia and obesity affect health-related quality of life in patients with Bardet-Biedl syndrome, and on how management of these symptoms may influence disease burden. This analysis evaluated changes in health-related quality of life in adults and children with Bardet-Biedl syndrome in a Phase 3 trial following 1 year of setmelanotide treatment (ClinicalTrials.gov identifier: NCT03746522).

METHODS

Patients with Bardet-Biedl syndrome and obesity received 52 weeks of treatment with setmelanotide and completed various self-reported health-related quality of life measures. Patients aged < 18 years or their caregiver completed the Pediatric Quality of Life Inventory (PedsQL; meaningful improvement, 4.4-point change); adults aged ≥ 18 years completed the Impact of Weight on Quality of Life Questionnaire-Lite (IWQOL-Lite; meaningful improvement range, 7.7-12-point change). Descriptive outcomes were reported in patients with data both at active treatment baseline and after 52 weeks of treatment.

RESULTS

Twenty patients (< 18 years, n = 9; ≥ 18 years, n = 11) reported health-related quality of life at baseline and 52 weeks. For children and adolescents, PedsQL score mean change from baseline after 52 weeks was + 11.2; all patients with PedsQL impairment at baseline (n = 4) experienced clinically meaningful improvement. In adults, IWQOL-Lite score mean change from baseline was + 12.0. Of adults with IWQOL-Lite impairment at baseline (n = 8), 62.5% experienced clinically meaningful improvement. In adults, IWQOL-Lite score was significantly correlated with changes in percent body weight (P = 0.0037) and body mass index (P = 0.0098).

CONCLUSIONS

After 1 year of setmelanotide, patients reported clinically meaningful improvements across multiple health-related quality of life measures. This study highlights the need to address the impaired health-related quality of life in Bardet-Biedl syndrome, and supports utility of setmelanotide for reducing this burden. Trial Registration NCT03746522. Registered November 19, 2018, https://clinicaltrials.gov/ct2/show/NCT03746522 .