Testing for rare genetic causes of obesity: findings and experiences from a pediatric weight management program

Rare gene variants and weight loss at 10 years after sleeve gastrectomy and gastric bypass - a randomized clinical trial

BACKGROUND

Genetic background of severe obesity is inadequately understood. The effect of genetic factors on weight loss after metabolic bariatric surgery (MBS) has shown inconclusive results.

OBJECTIVES

To determine the prevalence of rare obesity-associated gene variants in a secondary analysis of a randomized clinical trial (RCT) comparing laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB) for the treatment of severe obesity and examine their association with long-term weight loss at 10 years.

SETTING

University Hospital, Finland.

METHODS

Targeted sequencing panel was used to examine variants in 79 obesity-associated genes and 16p11.2 copy number variants. Weight loss was evaluated by percentage total weight loss (%TWL).

RESULTS

Out of 240 patients, 113 patients [mean body mass index 48.4 kg/m2, (6.8 standard deviation [SD]) kg/m2 and median age 49 (range 26-64) years, LSG n = 60, LRYGB n = 53] were available for this post-hoc study. We identified 7 rare heterozygous likely/suspected pathogenic (LP/SP) variants in SH2B1, PCSK1, DNMT3A, BDNF, and AFF4 in 6 patients (5.3%), 5 heterozygous variants of uncertain significance in PLXNA4, PLXNA2, NRP1, and SEMA3D in 5 patients (4.4%), heterozygous Bardet-Biedl syndrome variants in 3 patients (2.7%), and PCKS1 risk allele p.Asn221Asp in 9 patients (8.0%). The patients with LP/SP variants had earlier age of obesity onset (P = .0089) and higher %TWL (P = .0446) compared with patients without LP/SP variants.

CONCLUSIONS

There were LP/SP pathogenic variants in 5% of the patients supporting the potential benefits of genetic testing to optimize targeted therapies in the future. Despite deleterious gene defects the long-term MBS outcome can be favorable.

Integrating Genetic Insights, Technological Advancements, Screening, and Personalized Pharmacological Interventions in Childhood Obesity

Childhood obesity is a significant global health challenge with rising prevalence over the past 50 years, affecting both immediate and long-term health outcomes. The increase in prevalence from 0.7% to 5.6% in girls and 0.9% to 7.8% in boys highlights the urgency of addressing this epidemic. By 2025, it is estimated that 206 million children and adolescents aged 5-19 years will be living with obesity. This review explores the complex interplay of genomics and genetics in pediatric obesity, transitioning from monogenic and polygenic obesity to epigenetics, and incorporating advancements in omics technologies. The evolutionary purpose of adiposity, systemic evaluation of hyperphagia, and the role of various genetic factors are discussed. Technological advancements in genotyping offer new insights and interventions. The integration of genetic screening into clinical practice for early identification and personalized treatment strategies is emphasized.

The expanding landscape of genetic causes of obesity

Obesity and weight regulation disorders are determined by the combined effects of genetics and environment. Polygenic obesity results from the combination of common variants in several genes which predisposes the individual to obesity and its related complications. In contrast, monogenic obesity results from changes in single genes, especially those in leptin-melanocortin pathway, and presents with early onset severe obesity, with or without other syndromic features. Rare variants in melanocortin 4 receptor are the commonest form of monogenic obesity. In addition, structural variation in small or large segments of chromosomes may also present with syndromic forms of obesity. Prader-Willi Syndrome, caused by imprinting errors in chromosome 15q11-13, is the most prevalent genetic cause of severe hyperphagia and obesity. With the advances in technologies, the past decade has witnessed a revolution in the identification of novel genetic causes of obesity, primarily in genes related to the leptin melanocortin pathway. The availability of safe melanocortin analogs holds the potential for targeted therapies for some of these disorders. This review summarizes known and novel rare genetic forms of obesity, along with approaches for the clinical investigation of copy number and sequence variants. The goal is to provide a reference for practicing clinicians to encourage genetic testing in obesity. IMPACT: What does this article add to the existing literature? Genetic obesity is an expanding frontier with potential to change management. Here, we summarize current information on the genetic causes of obesity and provide guidance for genetic testing. Emerging treatments may provide targeted precise treatment and change management practices.

Exploring Genetic Testing for Rare Disorders of Obesity: Experience and Perspectives of Pediatric Weight Management Providers

Background: This study describes experiences and perspectives of pediatric weight management (PWM) providers on the implementation of genetic testing for rare causes of obesity. Methods: Purposive and snowball sampling recruited PWM providers via email to complete a 23-question survey with multiple choice and open-ended questions. Analyses include descriptive statistics, Fisher's exact test, one-way ANOVA with Tukey's post hoc test, and qualitative analysis. Results: Of the 55 respondents, 80% reported ordering genetic testing. Respondents were primarily physicians (82.8%) in practice for 11-20 years (42%), identified as female (80%), White (76.4%), and non-Hispanic (92.7%) and provided PWM care 1-4 half day sessions per week. Frequently reported patient characteristics that prompted testing did not vary by provider years of experience (YOE). These included obesity onset before age 6, hyperphagia, dysmorphic facies, and developmental delays. The number of patient characteristics that prompted testing varied by YOE (p = 0.03); respondents with 6-10 YOE indicated more patient characteristics than respondents with >20 YOE (mean 10.3 vs. mean 6.2). The reported primary benefit of testing was health information for patients/families; the primary drawback was the high number of indeterminate tests. Ethical concerns expressed were fear of increasing weight stigma, discrimination, and impact on insurance coverage. Respondents (42%) desired training and guidance on interpreting results and counseling patients and families. Conclusions: Most PWM providers reported genetic testing as an option for patient management. Provider training in genetics/genomics and research into provider and family attitudes on the genetics of obesity and the value of genetic testing are next steps to consider.

Updates on Rare Genetic Variants, Genetic Testing, and Gene Therapy in Individuals With Obesity

PURPOSE OF REVIEW

The goal of this paper is to aggregate information on monogenic contributions to obesity in the past five years and to provide guidance for genetic testing in clinical care.

RECENT FINDINGS

Advances in sequencing technologies, increasing awareness, access to testing, and new treatments have increased the utilization of genetics in clinical care. There is increasing recognition of the prevalence of rare genetic obesity from variants with mean allele frequency < 5% -new variants in known genes as well as identification of novel genes- causing monogenic obesity. While most of these genes are in the leptin melanocortin pathway, those in adipocytes may also contribute. Common variants may contribute either to higher lifetime tendency for weight gain or provide protection from monogenic obesity. While specific genetic mutations are rare, these segregate in individuals with early-onset severe obesity; thus, collectively genetic etiologies are not as rare. Some genetic conditions are amenable to targeted treatment. Research into the discovery of novel genetic causes as well as targeted treatment is growing over time. The utility of therapeutic strategies based on the genetic risk of obesity is an advancing frontier.

Identification of KSR2 Variants in Pediatric Patients with Severe Early-Onset Obesity from Qatar

The kinase suppressor of Ras 2 (KSR2) gene is associated with monogenic obesity, and loss-of-function variants in KSR2 have been identified in individuals with severe early-onset obesity. This study investigated KSR2 variants in 9 pediatric patients with severe early-onset obesity in Qatar using whole genome sequencing among a cohort of 240 individuals. We focused on KSR2 variants with a minor allele frequency (MAF) below 1% and a Combined Annotation Dependent Depletion (CADD) score above 13 to identify potential causative variants. Our analysis identified four KSR2 variants: one intronic (c.1765-8G>A) and three missense variants (c.1057G>A, c.1673G>A, and c.923T>C) in nine patients. The intronic variant c.1765-8G>A was the most frequent (seen in six individuals) and had a CADD score of 21.10, suggesting possible pathogenicity. This variant showed a significantly higher allele frequency in the Qatari population compared to the Genome Aggregation Database (gnomAD), indicating a possible founder effect. Molecular modeling of the missense variants revealed structural changes in the protein structure. The study concludes that these four KSR2 variants are associated with monogenic obesity, with an autosomal dominant inheritance pattern. The c.1765-8G>A variant's prevalence in Qatar underscores its importance in genetic screening for severe obesity. This research advances the understanding of genetic factors in severe early-onset obesity and may inform better management strategies.

Mechanisms and risk factors of metabolic syndrome in children and adolescents

Metabolic syndrome (MetS) is a complex disorder characterized by abdominal obesity, elevated blood pressure, hyperlipidemia, and elevated fasting blood glucose levels. The diagnostic criteria for MetS in adults are well-established, but there is currently no consensus on the definition in children and adolescents. The etiology of MetS is believed to involve a complex interplay between genetic predisposition and environmental factors. While genetic predisposition explains only a small part of MetS pathogenesis, modifiable environmental risk factors play a significant role. Factors such as maternal weight during pregnancy, children's lifestyle, sedentariness, high-fat diet, fructose and branched-chain amino acid consumption, vitamin D deficiency, and sleep disturbances contribute to the development of MetS. Early identification and treatment of MetS in children and adolescents is crucial to prevent the development of chronic diseases later in life. In this review we discuss the latest research on factors contributing to the pathogenesis of MetS in children, focusing on non-modifiable and modifiable risk factors, including genetics, dysbiosis and chronic low-grade inflammation.

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.

Targeted gene panel provides advantages over whole-exome sequencing for diagnosing obesity and diabetes mellitus

A small fraction of patients diagnosed with obesity or diabetes mellitus has an underlying monogenic cause. Here, we constructed a targeted gene panel consisting of 83 genes reported to be causative for monogenic obesity or diabetes. We performed this panel in 481 patients to detect causative variants and compared these results with whole-exome sequencing (WES) data available for 146 of these patients. The coverage of targeted gene panel sequencing was significantly higher than that of WES. The diagnostic yield in patients sequenced by the panel was 32.9% with subsequent WES leading to three additional diagnoses with two novel genes. In total, 178 variants in 83 genes were detected in 146 patients by targeted sequencing. Three of the 178 variants were missed by WES, although the WES-only approach had a similar diagnostic yield. For the 335 samples only receiving targeted sequencing, the diagnostic yield was 32.2%. In conclusion, taking into account the lower costs, shorter turnaround time, and higher quality of data, targeted sequencing is a more effective screening method for monogenic obesity and diabetes compared to WES. Therefore, this approach could be routinely established and used as a first-tier test in clinical practice for specific patients.

Obesity Characteristics Are Poor Predictors of Genetic Mutations Associated with Obesity

BACKGROUND

The genetic contribution to obesity is substantial and may underpin the altered pathophysiology. One such pathway involves melanocortin signaling in the hypothalamus. Genetic variants can cause dysregulation in the central melanocortin pathway that can result in early onset of hyperphagia and obesity. Clinically identifying patients who are at risk of known genetic mutations is challenging. The main purpose of this study was to identify associations between the clinico-demographical characteristics and the presence of a genetic mutation associated with obesity.

METHODS

We tested samples from 238 adult patients with class III obesity between October 2021 to February 2023 using next-generation sequencing (NGS) (Illumina, NovaSeq 6000 Sequencing System). The results were classified as "no variant identified" or "variant identified".

RESULTS

107 patients (45%) had one or more gene mutation in the leptin-melanocortin pathway. All variants were heterozygous. The patients with a gene mutation had a BMI of 48.4 ± 0.8 kg/m2 (mean ± SEM), and those without a gene mutation had a BMI of 49.4 ± 0.7 kg/m2 (p = 0.4). The mean age of onset of obesity in patients with a gene mutation was 13.9 ± 1.3 years and for those without gene mutations was 11.5 ± 0.9 years (p = 0.1). The incidence of hyperphagia as a child was also not predictive (p = 0.4).

CONCLUSIONS

Gene mutations associated with obesity in patients with a BMI > 40 kg/m2 are common. However, a patient's BMI, age of onset of obesity, or age of onset of hyperphagia did not help to differentiate which patients may be more likely to have genetic mutations associated with obesity.

Social consequences and genetics for the child with overweight and obesity: An obesity medicine association (OMA) clinical practice statement 2022

Background

This Obesity Medicine Association (OMA) clinical practice statement (CPS) covers two topics: 1) genetics and 2) social consequences for the child with overweight and obesity. This CPS is intended to provide clinicians with an overview of clinical practices applicable to children and adolescents with body mass indices greater than or equal to the 85th percentile for their ages, particularly those with adverse consequences resulting from increased body mass. The information in this CPS is based on scientific evidence, supported by the medical literature, and derived from the clinical experiences of members of the OMA.

Methods

The scientific information and clinical guidance in this CPS is based upon referenced evidence and derived from the clinical perspectives of the authors.

Results

This OMA clinical practice statement details two topics: 1) genetics and 2) social consequences for the child with overweight and obesity.

Conclusions

This OMA clinical practice statement on genetics and social consequences for the child with overweight and obesity is an overview of current literature. The literature provides a roadmap to the improvement of the health of children and adolescents with obesity, especially those with metabolic, physiological, and psychological complications.