Treatment options for children with monogenic forms of obesity

Harnessing the melanocortin system in the control of food intake and glucose homeostasis

The central and peripheral melanocortin system, comprising of five receptors and their endogenous ligands, is responsible for a wide array of physiological functions such as skin pigmentation, sexual function and development, and inflammation. A growing body of both clinical and pre-clinical research is demonstrating the relevance of this system in metabolic health. Disruption of hypothalamic melanocortin signalling is the most common cause of monogenic obesity in humans. Setmelanotide, an FDA-approved analogue of alpha-melanocyte stimulating hormone (α-MSH) that functions by restoring central melanocortin signalling, has proven to be a potent pharmacological tool in the treatment of syndromic obesity. As the first effective therapy targeting the melanocortin system to treat metabolic disorders, its approval has sparked research to further harness the links between these melanocortin receptors and metabolic processes. Here, we outline the structure of the central and peripheral melanocortin system, discuss its critical role in the regulation of food intake, and review promising targets that may hold potential to treat metabolic disorders in humans.

Genetic Contributors to Obesity

Genetic forms of obesity contribute to ∼7% of severe obesity in children and adolescents. The exact global prevalence of monogenic and syndromic forms of obesity is not well established, most likely due to missed or delayed diagnosis. The challenge in determining the prevalence can be attributed to the lack of consensus on identifying and evaluating symptoms of genetic defects in a timely manner and hence a vastly undertested patient population. Further large-scale and long-term studies are needed to advance the understanding of this unique phenotype of obesity and effective treatment options."

The role of leptin in patients recovering from Anorexia Nervosa

Introduction: Anorexia nervosa (AN) is a mental disorder with the highest death rate. The characteristic feature of AN is endocrine dysregulations, including changes in adipose-tissue secreted hormones, especially adipokines. The most widely studied of them is leptin whose role in the pathophysiology and prognosis of AN is confirmed in more and more studies. The aim of the study was to summarize the role of endocrine disruptions with particular emphasis on leptin in the pathophysiology of AN.

Material and methods: For the literature review, the electronic databases PubMed, Cochrane and Google Scholar search were used with the following keywords: eating disorders, adipokines, leptin, metreleptin, satiety, hunger, anorexia, obesity, for studies listed from database inception to October 2021.

Results: Leptin, produced mainly by white adipose tissue, inhibits the hunger center in the hypothalamus by negative feedback with ghrelin secreted by the gastrointestinal tract. Leptin is involved in numerous biological functions, including body weight regulation, innate and adaptive immunity regulation, reproduction, and bone formation. Studies confirm decreased leptin levels in AN individuals. In recent years, extensive experience has been gained with leptin as a drug in clinical trials. The studies suggested that treatment can restore menstrual function and bone health and improve mood with unclear body weight effects.

Conclusions: Focusing on leptin-related changes is a promising approach to improve AN management. Assessment of leptin levels in AN patients could be a useful tool for therapy monitoring. Treatment with leptin could reverse unfavourable changes induced by diet restriction, including mood symptoms, loss of bone mass and menstrual function. However, the results of these studies need confirmation on larger groups of patients.

Evaluation and Management of Early Onset Genetic Obesity in Childhood

One in five children and adolescents in the United States are diagnosed with obesity and nearly 6% of them are being classified under the severe obesity category. With over 7% of severe obesity being attributed to genetic disorders, in this review we aim to focus on monogenic and syndromic obesity: its etiology, wide spectrum of clinical presentation, criticalness of early identification, and limited management options. Advanced genetic testing methods including microarray and whole genome sequencing are imperative to identify the spectrum of mutations and develop targeted treatment strategies including personalized multidisciplinary care, use of investigational drugs, and explore surgical options in this unique subset of severe pediatric obesity.

A comprehensive diagnostic approach to detect underlying causes of obesity in adults

Obesity is a worldwide growing problem. When confronted with obesity, many health care providers focus on direct treatment of the consequences of adiposity. We plead for adequate diagnostics first, followed by an individualized treatment. We provide experience-based and evidence-based practical recommendations (illustrated by clinical examples), to detect potential underlying diseases and contributing factors. Adult patients consulting a doctor for weight gain or obesity should first be clinically assessed for underlying diseases, such as monogenetic or syndromic obesity, hypothyroidism, (cyclic) Cushing syndrome, polycystic ovarian syndrome (PCOS), hypogonadism, growth hormone deficiency, and hypothalamic obesity. The most important alarm symptoms for genetic obesity are early onset obesity, dysmorphic features/congenital malformations with or without intellectual deficit, behavioral problems, hyperphagia, and/or striking family history. Importantly, also common contributing factors to weight gain should be investigated, including medication (mainly psychiatric drugs, (local) corticosteroids, insulin, and specific β-adrenergic receptor blockers), sleeping habits and quality, crash diets and yoyo-effect, smoking cessation, and alcoholism. Other associated conditions include mental factors such as chronic stress or binge-eating disorder and depression.Identifying and optimizing the underlying diseases, contributing factors, and other associated conditions may not only result in more effective and personalized treatment but could also reduce the social stigma for patients with obesity.

Congenital Leptin Deficiency and Leptin Gene Missense Mutation Found in Two Colombian Sisters with Severe Obesity

Background: Congenital leptin deficiency is a recessive genetic disorder associated with severe early-onset obesity. It is caused by mutations in the leptin (LEP) gene, which encodes the protein product leptin. These mutations may cause nonsense-mediated mRNA decay, defective secretion or the phenomenon of biologically inactive leptin, but typically lead to an absence of circulating leptin, resulting in a rare type of monogenic extreme obesity with intense hyperphagia, and serious metabolic abnormalities. Methods: We present two severely obese sisters from Colombia, members of the same lineal consanguinity. Their serum leptin was measured by MicroELISA. DNA sequencing was performed on MiSeq equipment (Illumina) of a next-generation sequencing (NGS) panel involving genes related to severe obesity, including LEP. Results: Direct sequencing of the coding region of LEP gene in the sisters revealed a novel homozygous missense mutation in exon 3 [NM_002303.3], C350G>T [p.C117F]. Detailed information and clinical measurements of these sisters were also collected. Their serum leptin levels were undetectable despite their markedly elevated fat mass. Conclusions: The mutation of LEP, absence of detectable leptin, and the severe obesity found in these sisters provide the first evidence of monogenic leptin deficiency reported in the continents of North and South America.

Genetic and Syndromic Causes of Obesity and its Management

The aim of this article is to provide an in depth review of the rare genetic and syndromic forms of childhood obesity. The authors demonstrate the complexity and inter-relationships of the leptin-melanocortin signaling pathway and its central nervous system and systemic effects. Authors highlight the clinical distinctive features of genetic/syndromic causes for childhood obesity, in particular, relative shorter height to their genetic potential, developmental challenges and in some instances, ophthalmological and retina changes. They outline specific genetic testing and treatment options available for these conditions.

Early-onset severe obesity due to complete deletion of the leptin gene in a boy

BACKGROUND

Monogenic obesity results from single gene mutations. Extreme obesity starting at an early age, especially in infancy, which is associated with endocrinopathy and metabolic disturbances is key to the diagnosis of monogenic obesity.

CASE PRESENTATION

A 6-month-old boy was admitted to our clinic with severe obesity and food craving. He was born with a birth weight of 3400 g to first-cousin parents. He started to gain weight at an abnormal rate at the age of 2 months. He had hyperinsulinemia, dyslipidemia and grade 2 hepatosteatosis. He had a 7-year-old, healthy brother with a normal body weight. Because of severe early-onset obesity and abnormal food addiction, his leptin level was measured and found to be 0.55 ng/mL (normal range for his age and sex is 0.7-21 ng/mL). A LEP gene mutation was screened for and a gross leptin gene deletion was detected. To date, no report on a gross deletion of the LEP gene has been published in the literature.

CONCLUSIONS

To the best of our knowledge, a gross deletion of the LEP gene has not been reported so far in the literature. Here we report a unique case with congenital leptin deficiency. Thus, clinicians should search for monogenic obesity in patients with early-onset severe obesity and endocrinopathy. Measuring the leptin level could aid clinicians to identify children with monogenic obesity.

Food reward system: current perspectives and future research needs

This article reviews current research and cross-disciplinary perspectives on the neuroscience of food reward in animals and humans, examines the scientific hypothesis of food addiction, discusses methodological and terminology challenges, and identifies knowledge gaps and future research needs. Topics addressed herein include the role of reward and hedonic aspects in the regulation of food intake, neuroanatomy and neurobiology of the reward system in animals and humans, responsivity of the brain reward system to palatable foods and drugs, translation of craving versus addiction, and cognitive control of food reward. The content is based on a workshop held in 2013 by the North American Branch of the International Life Sciences Institute.

Obesity and genomics: role of technology in unraveling the complex genetic architecture of obesity

Obesity is a complex and multifactorial disease that occurs as a result of the interaction between "obesogenic" environmental factors and genetic components. Although the genetic component of obesity is clear from the heritability studies, the genetic basis remains largely elusive. Successes have been achieved in identifying the causal genes for monogenic obesity using animal models and linkage studies, but these approaches are not fruitful for polygenic obesity. The developments of genome-wide association approach have brought breakthrough discovery of genetic variants for polygenic obesity where tens of new susceptibility loci were identified. However, the common SNPs only accounted for a proportion of heritability. The arrival of NGS technologies and completion of 1000 Genomes Project have brought other new methods to dissect the genetic architecture of obesity, for example, the use of exome genotyping arrays and deep sequencing of candidate loci identified from GWAS to study rare variants. In this review, we summarize and discuss the developments of these genetic approaches in human obesity.