RARE DISEASE
Obesity due to melanocortin 4 receptor deficiency
Obesity due to melanocortin 4 receptor deficiency
Obesity due to melanocortin 4 receptor deficiency
Synonyms: MC4R deficiency
Synonyms: MC4R deficiency
Synonyms: MC4R deficiency
Drug discovery
605
papers
On emerging therapies
Overview
Overview of Obesity Due to Melanocortin 4 Receptor Deficiency
MC4R deficiency is the most common monogenic cause of obesity, characterized by severe early-onset hyperphagia, accelerated linear growth in childhood, increased lean mass, and hyperinsulinemia [1][4][10]. It arises from heterozygous or homozygous mutations in the MC4R gene, disrupting hypothalamic appetite regulation. Adults exhibit lower hypertension prevalence but retain metabolic risks like type 2 diabetes and insulin resistance [4][7][9]. Penetrance varies by age, with higher obesity rates in childhood (79%) than older adults (40%) [2][14].
Burden
Comorbidities: Elevated risk of type 2 diabetes (independent of BMI in childhood), hyperleptinemia, and insulin resistance [7][9][16].
Growth and metabolic effects: Increased final adult height, accelerated BMI gain in childhood, and lower blood pressure compared to BMI-matched controls [4][10].
Psychosocial/economic impact: Significant healthcare costs due to early complications (e.g., obstructive sleep apnea, lymphedema) and reduced quality of life [15][16].
Therapies
Lifestyle modifications: Often insufficient due to impaired satiety signaling [4][16].
Pharmacotherapy: GLP-1 agonists (semaglutide, tirzepatide) show efficacy [4]; MC4R agonists (e.g., setmelanotide) are under investigation [8].
Surgery: Roux-en-Y bypass may benefit heterozygous patients but is ineffective in homozygotes [4][16].
Emerging therapies: Preclinical success with BDNF gene therapy targeting MC4R downstream pathways [3][13].
Categories: rare endocrine diseases, rare genetic diseases
Research Papers
605 drug discovery papers about Obesity due to melanocortin 4 receptor deficiency, with 4 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
605 drug discovery papers about Obesity due to melanocortin 4 receptor deficiency, with 4 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
proteins
2026-08-07 | Pharmacogenetic hypersensitivity to somatropin in a child with severe growth hormone deficiency and MC4R p.V166I variant.
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor that regulates energy homeostasis. Pathogenic MC4R variants represent the most common cause of monogenic obesity and are frequently associated with increased linear growth. However, the mechanisms linking MC4R signaling to somatic growth remain incompletely understood. We report a child with severe growth hormone deficiency (GHD) carrying a heterozygous MC4R variant (c.496G>A; p.V166I), in whom recombinant human growth hormone (rhGH) therapy triggered an unexpectedly exaggerated clinical and biochemical response, suggesting a potential pharmacogenetic interaction between MC4R signaling and the GH/IGF-1 axis. The male patient was first evaluated at 1 month of age due to micropenis and diagnosed with multiple pituitary hormone deficiencies. At 57 months of age, his height was 97.3 cm (-2.56 SDS) and annual growth velocity was 4.1 cm/year (<-2 SDS); rhGH (somatropin) therapy was initiated. Despite severe biochemically confirmed GHD, rhGH at 0.03 mg/kg/day triggered an exaggerated response: IGF-1 levels increased from -3.35 SDS to +8.00 SDS. Concurrently, his height velocity accelerated to 16 cm/year, and his bone age rapidly advanced by approximately 4 years over a 23-month period, culminating in mandibular prognathism. The coexistence of severe GHD and an MC4R variant is rarely described, and such a pronounced response to rhGH has not previously been reported. These findings suggest that MC4R p.V166I may modulate peripheral GH/IGF-1 signaling and act as a pharmacogenetic modifier of GH responsiveness. Careful rhGH dose titration with close IGF-1 monitoring may be considered in patients carrying the MC4R p.V166I variant.
2026-07-10 | The application of GLP-1 receptor agonists in obesity due to MC4R deficiency
Although the pathogenesis of genetic obesity is becoming increasingly clear, effective treatments remain lacking, particularly for obesity caused by melanocortin 4 receptor (MC4R) deficiency. The activity of MC4R is strictly regulated by its endogenous ligands: α-melanocyte-stimulating hormone (α-MSH) binds to MC4R and transmits anorexigenic and energy-expenditure signals, whereas agouti-related protein (AgRP) exerts an antagonistic effect by binding to the receptor, competitively inhibiting α-MSH action and promoting appetite. Current options, such as lifestyle modifications and bariatric surgery, have limited efficacy, highlighting the need for accessible pharmacological interventions. This review evaluates glucagon-like peptide-1 (GLP-1) receptor agonists in MC4R-deficient obesity. We conducted a comprehensive literature search across databases, including PubMed and Web of Science, compiling data from clinical trials, case reports, and basic research studies published up to 2025, with a focus on the efficacy, safety, and mechanism of action of drugs such as liraglutide, semaglutide, and tirzepatide in patients with MC4R deficiency. Evidence indicates these agents induce significant weight loss, appetite suppression, and metabolic improvements via mechanisms independent of intact MC4R signaling. Their weight-loss effects are comparable to those seen in common obesity, with additional benefits for comorbidities like insulin resistance and dyslipidemia. These findings support the GLP-1 pathway as an alternative to impaired MC4R, offering a viable treatment. Understanding their efficacy and mechanisms provides new treatment options for this rare condition and offers evidence for genetically specific personalized weight management.
2026-04-02 | Tirzepatide and Metformin Effects on Hunger and BMI in an Adolescent with Hyperphagia and Severe Obesity due to MC4R Deficiency: A Case Report.
Tirzepatide, a dual glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide receptor agonist, is recently approved for the treatment of type 2 diabetes and obesity in adults. Melanocortin-4-receptor (MC4R) deficiency is the most common monogenic cause of obesity and presents with hyperphagia and early onset obesity. While tirzepatide seems to be effective in inducing weight loss in adults with MC4R deficiency, its effects on hyperphagia and weight loss in pediatric patients are unexplored. A 17-year-old girl was admitted to our specialized obesity clinic because of hyperphagia and severe early onset obesity due to MC4R deficiency. She had an extensive history of lifestyle interventions and psychological support and maintained a high level of physical activity. Despite these efforts, she presented with a BMI of 37 kg/m2 (3.68 SDS) and a substantial psychosocial burden. Vital signs and laboratory evaluations revealed no obesity-related complications. Tirzepatide was initiated at a dose of 2.5 mg weekly and slowly titrated to a maximum dose of 12.5 mg weekly. She initially experienced a substantial reduction in hyperphagia and reported less food noise, a reduction in hunger feelings and prolonged postprandial satiety. However, after 12 weeks hunger scores started to increase again, approaching pre-treatment levels at 28 weeks of follow-up. Metformin was added at 28 weeks in an attempt to better manage of hyperphagia, resulting in a reduction in hyperphagia. Despite these increasing hunger feelings from week 12 to 28, substantial weight loss was achieved, and the patient lost -13.9% of her initial body weight at 28 weeks. After addition of metformin, the patient lost an additional -7% of her weight. Total body weight reduction at week 37 was -20.9%. Tirzepatide was well tolerated, with no adverse effects reported at 41 weeks of follow-up. This case report suggests that tirzepatide is effective in reducing body weight in adolescents with MC4R deficiency. However, the question remains what the effect is on hunger and satiety in the long run and at a higher dose. Cohort studies are needed to assess long-term safety and effectiveness of tirzepatide in the pediatric population and in managing hyperphagia.
2026-02-22 | Efficacy of GLP-1 analog peptides, semaglutide, tirzepatide, and retatrutide on MC4R deficient obesity and their comparison.
Melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor expressed in the hypothalamus, playing a key role in regulating feeding behavior and energy homeostasis. MC4R is integral to the POMC-MC4R and leptin-MC4R pathways, which control food intake and body weight. Mutations in the POMC gene lead to severe early-onset obesity and increased food consumption. Recently, glucagon-like peptide-1 (GLP-1) analogs, including semaglutide, tirzepatide, and retatrutide, have been explored as potential anti-obesity therapies. This study aimed to assess and compare the efficacy of these GLP-1 analogs in MC4R knockout (KO) mice, which are deficient in the POMC-MC4R pathway. GLP-1 analogs were administered for 21 days to MC4R KO mice and compared their efficacy. The percentage of body weight reduction was 19.7 ± 4.1% for semaglutide, 31.6 ± 7.6% for tirzepatide, and 24.1 ± 5.8% for retatrutide. Body composition analysis, including fat and lean mass, was performed using the Echo-MRI system, revealing significant suppression of both fat and lean mass by all three GLP-1 analogs. Furthermore, GLP-1 analogs improved plasma insulin levels, HOMA-IR, cholesterol levels, and markers of liver damage (AST and ALT), as well as reduced liver hypertrophy. While GLP-1 analogs suppressed genes related to fatty acid synthesis, they had no significant effect on inflammation-related gene expressions. Additionally, GLP-1 analogs reduced energy expenditure, with only tirzepatide showing a significant decrease in the respiratory quotient (RQ) in MC4R KO mice. Our findings demonstrate that all three GLP-1 analogs, semaglutide, tirzepatide, and retatrutide, exhibit significant anti-obesity effects in MC4R KO mice. These results suggest that GLP-1 analogs may provide an effective treatment option for patients with MC4R-POMC pathway deficiencies. Moreover, the efficacy of these drugs in MC4R KO mice aligns with clinical studies, indicating that MC4R KO mice serve as a reliable animal model for obesity research.
2026-01-05 | Treatment Approaches for Obesity in Children With Heterozygous MC4R Variants.
Melanocortin-4 receptor (MC4R) deficiency is the most common cause of monogenic obesity; yet treatment options for children with MC4R mutations are limited. We describe significant improvement in weight in three patients with pathogenic or likely pathogenic MC4R mutations; two adolescents treated with semaglutide, and a younger child treated with metformin and topiramate. These findings indicate GLP-1 receptor agonists, topiramate and metformin can be helpful in managing obesity associated with MC4R deficiency.
small molecules
2026-06-24 | Cardiometabolic regulation by adipocyte-derived leptin and the brain melanocortin system.
Tonic activation of central nervous system (CNS) leptin receptors (LepRs) and melanocortin 4 receptors (MC4Rs) is critical for maintaining normal cardiometabolic function. Deficiency of CNS LepR or MC4R signaling causes severe obesity and is accompanied by multiple metabolic abnormalities including insulin resistance, glucose intolerance, and hyperlipidemia that are only partially explained by obesity. Defective LepR and MC4R signaling also causes dysfunction of the sympathetic nervous system (SNS) and blood pressure (BP) regulation. Hyperleptinemia and activation of the CNS melanocortin system in obesity are important compensatory mechanisms that attenuate abnormalities of glucose and lipid metabolism but may also contribute to SNS activation and increased BP. Despite potentially adverse effects of increases in SNS activity and BP, pharmacological activation of brain LepRs and MC4Rs may provide an important therapeutic approach for protecting target organs, such as the heart, kidneys, and brain, from ischemic injury by improving mitochondrial function and ATP production. However, additional preclinical studies are needed to address mechanistic questions before clinical studies are begun to test the effectiveness of leptin and MC4R agonists for treating people with ischemic injury of target organs.
2026-05-27 | SKNY-1, a THCV Analog, Produces Weight Loss, Lipid Normalization and Attenuation of Reward-Associated Behaviors in an mc4r(G894C) Zebrafish Model of Obesity.
Obesity resulting from melanocortin-4 receptor (MC4R) dysfunction is characterized by combined metabolic dysregulation and maladaptive reward-related behaviors that limit the durability of existing therapies. The endocannabinoid system is a central regulator of appetite, lipid metabolism, and reward processing; however, first-generation cannabinoid receptor 1 (CB1) antagonists were limited by adverse neuropsychiatric effects. SKNY-1 is an orally active tetrahydrocannabivarin (THCV) analog designed to engage pathway-biased CB1 signaling, modulate cannabinoid receptor 2 (CB2), and selectively inhibit monoamine oxidase B (MAO-B), with the objective of addressing both metabolic and behavioral components of obesity while minimizing central nervous system liability through biased CB1 signaling, CB2 modulation, and potential complementary MAO-B inhibition. Here, we integrated in vitro pharmacological profiling of SKNY-1 with in vivo evaluation in an adult mc4r(G894C) zebrafish model exhibiting obesity-associated metabolic and reward-related phenotypes. In vitro, SKNY-1 displayed low-potency modulation of CB1 cyclic AMP signaling (EC50 ~30 µM) but more potent antagonism of the CB1 β-arrestin pathway (IC50 ~6 µM), consistent with differential CB1 pathway modulation. SKNY-1 acted as a CB2 partial agonist (EC50 ~0.1 µM), with antagonist activity emerging at higher concentrations, and selectively inhibited MAO-B at low affinity with no activity against MAO-A. In vivo, mc4r(G894C) zebrafish mutants exhibited dyslipidemia, hepatic triglyceride accumulation, altered appetite-regulatory gene expression, increased metabolic rate, and enhanced compulsive high-calorie feeding and nicotine-seeking behaviors. Oral administration of SKNY-1 for six days produced dose-dependent effects. Both doses normalized total cholesterol and low-density lipoprotein levels and reduced hepatic triglycerides toward wild-type values without affecting circulating triglycerides. The higher dose (200 ng per fish per day) induced significant body weight reduction while preserving body density and attenuated reward-associated feeding and nicotine-seeking behaviors. The lower dose (20 ng per fish per day) more effectively normalized the leptin a-to-ghrelin expression ratio. Collectively, these findings demonstrate that SKNY-1 engages integrated endocannabinoid and potential dopaminergic mechanisms to improve metabolic parameters and attenuate maladaptive reward-related behaviors in an MC4R-deficient vertebrate model, supporting its further translational investigation for obesity complicated by compulsive eating and substance-seeking behaviors.
2026-04-21 | Mice lacking β-arrestin-2 in melanocortin 4 receptor-expressing neurons show marked metabolic deficits.
Hypothalamic melanocortin 4 receptors (MC4Rs) play a central role in regulating food intake and energy homeostasis. In fact, inactivating mutations in the MC4R gene are the most common form of monogenic obesity. Agonist activation of MC4Rs reduces food intake by modulating hypothalamic signaling circuits. Thus, a detailed understanding of the signaling pathways that regulate MC4R activity is of considerable translational relevance. Ligand-activated MC4Rs not only interact with heterotrimeric G proteins but also can recruit β-arrestin-2 (barr2) to the receptor. The potential functional role of barr2 in regulating the anorectic effects of MC4R signaling remains unexplored. In the present study, we used mutant mouse models to demonstrate MC4R-mediated activation of barr2/ERK signaling in MC4R neurons of the paraventricular nucleus leads to reduced food intake. We also found the appetite-suppressing effect of setmelanotide, an MC4R agonist FDA approved for the treatment of certain types of obesity, requires the presence of barr2 in MC4R-containing neurons. These data suggest that MC4R agonists able to promote MC4R/barr2 interactions with high efficacy may become useful as appetite-suppressing drugs.
2026-04-04 | Bombesin receptor-activated protein homolog deficiency reduces food intake and alleviates metabolic dysfunction in high-fat diet treated mice.
In our previous study, we found that both bombesin receptor-activated protein (BRAP) and its mouse homolog, BC004004, are expressed in the central nervous system, although their functions remain unclear. In feeding experiments, BRAP homolog knockout mice (BC004004-/-) showed reduced preference for a high-fat diet (HFD) compared with wild-type controls. After four months of HFD treatment, BC004004-/- mice had lower food intake and weight gain, along with reduced fasting blood glucose, insulin, triglycerides, and low-density lipoprotein cholesterol levels. Histological analysis revealed less hepatic steatosis, renal injury, and white adipose tissue (WAT) hypertrophy in the BC004004-/- mice. qPCR analysis of inguinal fat tissues showed increased expression of thermogenic markers (UCP1, Prdm16, Tfam) in BC004004-/- mice, indicating enhanced WAT "browning". Oil red O staining showed that overexpression of the BC004004 gene in cultured mouse microglia BV2 cells increased palmitic acid-induced lipid deposition and higher levels of the proinflammatory cytokines IL-1β and TNF-α, as measured by ELISA of culture supernatants. Additionally, qPCR showed lower agouti-related peptide (AgRP) and neuropeptide Y (NPY) expression and higher proopiomelanocortin (POMC) and melanocortin receptors 4 (MC4R) expression in the hypothalamus of BC004004-/- mice, possibly contributed to their reduced food intake and weight gain. These results suggest that BRAP homolog deficiency protects against HFD-induced metabolic dysfunction through multiple mechanisms, including alterations in hypothalamic neuronal circuits and adipose tissue biology.
2026-02-09 | Monogenic and syndromic obesity in children: Clinical recognition, genetics, and precision management
ABSTRACT Obesity is increasingly being recognized as a heterogeneous condition with strong genetic underpinnings. Monogenic obesity, caused by single‐gene mutations, primarily affects the leptin–melanocortin pathway, which regulates hunger and satiety. Mutations in genes, such as LEP , LEPR , POMC , PCSK1 , and MC4R , lead to hyperphagia, early onset severe obesity, and metabolic dysregulation. LEP and LEPR mutations impair leptin signaling, resulting in defective appetite suppression, whereas POMC and PCSK1 deficiencies disrupt prohormone processing. MC4R mutations, the most common cause of monogenic obesity, impair satiety signaling and are linked to rapid weight gain. Syndromic obesity, including the Bardet‐Biedl and Alström syndromes, involves ciliary dysfunction, leading to developmental abnormalities alongside obesity. Other genes such as SH2B1 , SIM1 , and BDNF play crucial roles in hypothalamic development and energy regulation. Advances in genomic sequencing have improved the recognition of genetic etiologies; however, many patients remain undiagnosed due to limited testing availability and a lack of clinician awareness. Precision therapies, including set‐melanotide for specific melanocortin pathway defects, demonstrate the promise of targeted treatments. However, management must extend beyond pharmacology; lifestyle interventions, psychosocial support, and family‐centered care remain essential, especially when intellectual disability or behavioral challenges complicate adherence. Ethical considerations surrounding access and equity are critical, as high‐cost therapies and the limited availability of genetic testing risk widening disparities between health systems. Polygenic risk scores and multi‐omics approaches may expand precision medicine beyond rare genetic syndromes to common obesity, highlighting the importance of integrating genetics, psychosocial care, and policy advocacy in the management of pediatric obesity.
gene therapies
2024-03-06 | Hypothalamic POMC neuron-specific knockout of MC4R affects insulin sensitivity by regulating Kir2.1
Abstract Background Imbalance in energy regulation is a major cause of insulin resistance and diabetes. Melanocortin-4 receptor (MC4R) signaling at specific sites in the central nervous system has synergistic but non-overlapping functions. However, the mechanism by which MC4R in the arcuate nucleus (ARC) region regulates energy balance and insulin resistance remains unclear. Methods The MC4R flox/flox mice with proopiomelanocortin (POMC) -Cre mice were crossed to generate the POMC-MC4R flox/+ mice. Then POMC-MC4R flox/+ mice were further mated with MC4R flox/flox mice to generate the POMC-MC4R flox/flox mice in which MC4R is selectively deleted in POMC neurons. Bilateral injections of 200 nl of AAV-sh-Kir2.1 (AAV-sh-NC was used as control) were made into the ARC of the hypothalamus. Oxygen consumption, carbon dioxide production, respiratory exchange ratio and energy expenditure were measured by using the CLAMS; Total, visceral and subcutaneous fat was analyzed using micro-CT. Co-immunoprecipitation assays (Co-IP) were used to analyze the interaction between MC4R and Kir2.1 in GT1-7 cells. Results POMC neuron-specific ablation of MC4R in the ARC region promoted food intake, impaired energy expenditure, leading to increased weight gain and impaired systemic glucose homeostasis. Additionally, MC4R ablation reduced the activation of POMC neuron, and is not tissue-specific for peripheral regulation, suggesting the importance of its central regulation. Mechanistically, sequencing analysis and Co-IP assay demonstrated a direct interaction of MC4R with Kir2.1. Knockdown of Kir2.1 in POMC neuron-specific ablation of MC4R restored the effect of MC4R ablation on energy expenditure and systemic glucose homeostasis, indicating by reduced body weight and ameliorated insulin resistance. Conclusion Hypothalamic POMC neuron-specific knockout of MC4R affects energy balance and insulin sensitivity by regulating Kir2.1. Kir2.1 represents a new target and pathway that could be targeted in obesity.
2023-11-13 | Melanocortin-4 receptor in macrophages attenuated angiotensin II-induced abdominal aortic aneurysm in mice
Abstract Obesity is recognized as an independent risk factor for abdominal aortic aneurysm (AAA). While mutations in the melanocortin-4 receptor ( MC4R ) gene is the most common cause of obesity caused by mutations in a single gene, the link between MC4R function and vascular disease has still remained unclear. Here, by using melanocortin-4 receptor (MC4R) deficient mice, we confirmed MC4R deficiency promotes AAA and atherosclerosis. We demonstrated the contribution of two novel factors towards vascular vulnerability in this model: leptin signaling in vascular smooth muscle cells (VSMCs) and loss of MC4R signaling in macrophages. Leptin was shown to promote vascular vulnerability via PI3K-dependent upregulation of Spp1 expression in VSMC. Additionally, Ang II-induced AAA incidence was significantly reduced when MC4R gene expression was myeloid cell-specifically rescued in MC4R deficient (MC4R TB/TB ) mice. Ex vivo analysis showed a suppression in NF-κB activity in bone marrow-derived macrophages from LysM(+);MC4R TB/TB mice compared to LysM(−);MC4R TB/TB mice, which exaggerates with endogenous MC4R ligand treatment; α-MSH. These results suggest that MC4R signaling in macrophages attenuates AAA by inhibiting NF-κB activity and subsequent vascular inflammation.
2023-06-17 | Understanding the Genetics of Early-Onset Obesity in a Cohort of Children From Qatar
Monogenic obesity is a rare form of obesity due to pathogenic variants in genes implicated in the leptin-melanocortin signaling pathway and accounts for around 5% of severe early-onset obesity. Mutations in the genes encoding the MC4R, leptin, and leptin receptor are commonly reported in various populations to cause monogenic obesity. Determining the genetic cause has important clinical benefits as novel therapeutic interventions are now available for some forms of monogenic obesity.To unravel the genetic causes of early-onset obesity in the population of Qatar.In total, 243 patients with early-onset obesity (above the 95% percentile) and age of onset below 10 years were screened for monogenic obesity variants using a targeted gene panel, consisting of 52 obesity-related genes.Thirty rare variants potentially associated with obesity were identified in 36 of 243 (14.8%) probands in 15 candidate genes (LEP, LEPR, POMC, MC3R, MC4R, MRAP2, SH2B1, BDNF, NTRK2, DYRK1B, SIM1, GNAS, ADCY3, RAI1, and BBS2). Twenty-three of the variants identified were novel to this study and the rest, 7 variants, were previously reported in literature. Variants in MC4R were the most common cause of obesity in our cohort (19%) and the c.485C>T p.T162I variant was the most frequent MC4R variant seen in 5 patients.We identified likely pathogenic/pathogenic variants that seem to explain the phenotype of around 14.8% of our cases. Variants in the MC4R gene are the commonest cause of early-onset obesity in our population. Our study represents the largest monogenic obesity cohort in the Middle East and revealed novel obesity variants in this understudied population. Functional studies will be required to elucidate the molecular mechanism of their pathogenicity.
2022-01-14 | Oestrogen engages brain MC4R signalling to drive physical activity in female mice.
Oestrogen depletion in rodents and humans leads to inactivity, fat accumulation and diabetes1,2, underscoring the conserved metabolic benefits of oestrogen that inevitably decrease with age. In rodents, the preovulatory surge in 17β-oestradiol (E2) temporarily increases energy expenditure to coordinate increased physical activity with peak sexual receptivity. Here we report that a subset of oestrogen-sensitive neurons in the ventrolateral ventromedial hypothalamic nucleus (VMHvl)3-7 projects to arousal centres in the hippocampus and hindbrain, and enables oestrogen to rebalance energy allocation in female mice. Surges in E2 increase melanocortin-4 receptor (MC4R) signalling in these VMHvl neurons by directly recruiting oestrogen receptor-α (ERα) to the Mc4r gene. Sedentary behaviour and obesity in oestrogen-depleted female mice were reversed after chemogenetic stimulation of VMHvl neurons expressing both MC4R and ERα. Similarly, a long-term increase in physical activity is observed after CRISPR-mediated activation of this node. These data extend the effect of MC4R signalling - the most common cause of monogenic human obesity8 - beyond the regulation of food intake and rationalize reported sex differences in melanocortin signalling, including greater disease severity of MC4R insufficiency in women9. This hormone-dependent node illuminates the power of oestrogen during the reproductive cycle in motivating behaviour and maintaining an active lifestyle in women.
2021-03-09 | Neuroanatomical organization and functional roles of PVN MC4R pathways in physiological and behavioral regulations
ABSTRACT Objective The paraventricular nucleus of hypothalamus (PVN) is an integrative center in the brain orchestrating a wide range of physiological and behavioral responses. While the PVN melanocortin 4 receptor (MC4R) signaling (PVN MC4R+ ) is undoubtedly involved in feeding regulation, the neuroanatomical organization of PVN MC4R+ pathway and its role in diverse physiological and behavioral regulations have not been fully understood. Here we aimed to better characterize the input-output organization of PVN MC4R+ neurons and further test their potential functional roles beyond feeding. Methods Using a combination of viral tools, we performed a comprehensive mapping of PVN MC4R+ circuits and tested the effects of chemogenetic activation of PVN MC4R+ neurons on thermogenesis, cardiovascular control and other behavioral regulations beyond feeding. Results We found that PVN MC4R+ neurons broadly innervate many different brain regions known to be important not only for feeding but also for neuroendocrine and autonomic control of thermogenesis and cardiovascular function, including but not limited to preoptic area, median eminence, parabrachial nucleus, locus coeruleus, nucleus of solitary tract, ventrolateral medulla and thoracic spinal cord. Contrary to broad efferent projections, PVN MC4R+ neurons receive monosynaptic inputs from limited brain regions, including medial preoptic nucleus, arcuate and dorsomedial hypothalamic nuclei, and supraoptic nucleus. Consistent with broad efferent projections, chemogenetic activation of PVN MC4R+ neurons not only suppressed feeding but also led to an apparent increase in heart rate, blood pressure and brown adipose tissue thermogenesis. Strikingly, these physiological changes accompanied an unexpected repetitive bedding-removing behavior followed by hypoactivity and resting-like behavior. Conclusions Our results clarify the neuroanatomical organization of PVN MC4R+ circuits and shed new light on the roles of PVN MC4R+ pathways in autonomic control of thermogenesis, cardiovascular function and other behavioral regulations.
oligonucleotides
2022-09-29 | MicroRNA-7 regulates melanocortin circuits involved in mammalian energy homeostasis
MicroRNAs (miRNAs) modulate physiological responses by repressing the expression of gene networks. We found that global deletion of microRNA-7 (miR-7), the most enriched miRNA in the hypothalamus, causes obesity in mice. Targeted deletion of miR-7 in Single-minded homolog 1 (Sim1) neurons, a critical component of the hypothalamic melanocortin pathway, causes hyperphagia, obesity and increased linear growth, mirroring Sim1 and Melanocortin-4 receptor (MC4R) haplo-insufficiency in mice and humans. We identified Snca (α-Synuclein) and Igsf8 (Immunoglobulin Superfamily Member 8) as miR-7 target genes that act in Sim1 neurons to regulate body weight and endocrine axes. In humans, MIR-7-1 is located in the last intron of HNRNPK, whose promoter drives the expression of both genes. Genetic variants at the HNRNPK locus that reduce its expression are associated with increased height and truncal fat mass. These findings demonstrate that miR-7 suppresses gene networks involved in the hypothalamic melanocortin pathway to regulate mammalian energy homeostasis.
2022-05-25 | Obesity and the role of genetic polymorphism: A review of genes as the risk of obesity
Obesity can be caused by environmental factors, which are higher energy input or lower energy expenditure. Environmental factors supported by genetic factors cause a person to have a different risk for developing obesity from to another. Genetics factors cause obesity through several pathways, which are impaired regulation in the hypothalamus and the regulation of energy expenditure. Obesity may be caused by one gene as monogenic-associated obesity, however, commonly caused by several genes together with environmental factors as the main multi-factorial risk of obesity. Obesity causes inflammation which leads to metabolic diseases. Many efforts are performed to prevent or treat obesity through the intervention to environmental and or genetic factors. Many attempts to reduce the prevalence of obesity were performed by influencing the environmental risk factors or the genetic risk factors. In this review, we identified the main genes which influence obesity. The genetic risks of obesity may be different from one to another country or between ethnic groups. Therefore, a better treatment approach should consider the differences role of genes in obesity rather than only changes in lifestyle. Nutrigenetic approach by considering the difference role of gens in responding to nutrients or drugs is recommended in individualized treatment plans.
2020-07-25 | Function of Dicer with regard to Energy Homeostasis Regulation, Structural Modification, and Cellular Distribution
As a type III ribonuclease (RNase III) specifically cleaving double-stranded RNA substrates into short fragments, Dicer is indispensable in a range of physi/pathologic processes, e.g., nutrient deprivation, hypoxia, or DNA damage. Therefore, much interest has been paid to the research of this protein as well as its products like microRNAs (miRNAs). The close relationship between Dicer levels and fluctuations of nutrient availability suggests that the protein participates in the regulation of systemic energy homeostasis. Through miRNAs, Dicer regulates the hypothalamic melanocortin-4 system and central autophagy promoting energy expenditure. Moreover, by influencing canonical energy sensors like adenosine monophosphate-activated protein kinase (AMPK) or mammalian target of rapamycin (mTOR), Dicer favors catabolism in the periphery. Taken together, Dicer might be targeted in the control of energy dysregulation. However, factors affecting its RNase activity should be noted. Firstly, modulation of structural integrity affects its role as a ribonuclease. Secondly, although previously known as a cytosolic endoribonuclease, evidence suggests Dicer can relocalize into the nucleus where it could also produce small RNAs. In this review, we probe into involvement of Dicer in energy homeostasis as well as its structural integrity or cellular distribution which affects its ability to produce miRNAs, in the hope of providing novel insights into its mechanism of action for future application.
2018-11-02 | MicroRNAs are involved in the hypothalamic leptin sensitivity
The central nervous system monitors modifications in metabolic parameters or hormone levels (leptin) and elicits adaptive responses such as food intake and glucose homeostasis regulation. Particularly, within the hypothalamus, pro-opiomelanocortin (POMC) neurons are crucial regulators of energy balance. Consistent with a pivotal role of the melanocortin system in the control of energy homeostasis, disruption of the Pomc gene causes hyperphagia and obesity. Pomc gene expression is tightly controlled by different mechanisms. Interestingly, recent studies pointed to a key role for micro ribonucleic acid (miRNAs) in the regulation of gene expression. However, the role of miRNAs in the leptin sensitivity in hypothalamic melanocortin system has never been assessed. We developed a transgenic mouse model (PDKO) with a partial deletion of the miRNA processing enzyme DICER specifically in POMC neurons. PDKO mice exhibited a normal body weight but a decrease of food intake. Interestingly, PDKO mice had decreased metabolic rate by reduction of VO2 consumption and CO2 production which could explain that PDKO mice have normal weight while eating less. Interestingly, we observed an increase of leptin sensitivity in the POMC neurons of PDKO mice which could explain the decrease of food intake in this model. We also observed an increase in the expression of genes involved in the function of brown adipose tissue that is in polysynaptic contact with the POMC neurons. In summary, these results support the hypothesis that Dicer-derived miRNAs may be involved in the effect of leptin on POMC neurons activity.
2016-12-01 | A compendium of human genes regulating feeding behavior and body weight, its functional characterization and identification of GWAS genes involved in brain-specific PPI network
Obesity is heritable. It predisposes to many diseases. The objectives of this study were to create a compendium of genes relevant to feeding behavior (FB) and/or body weight (BW) regulation; to construct and to analyze networks formed by associations between genes/proteins; and to identify the most significant genes, biological processes/pathways, and tissues/organs involved in BW regulation. The compendium of genes controlling FB or BW includes 578 human genes. Candidate genes were identified from various sources, including previously published original research and review articles, GWAS meta-analyses, and OMIM (Online Mendelian Inheritance in Man). All genes were ranked according to knowledge about their biological role in body weight regulation and classified according to expression patterns or functional characteristics. Substantial and overrepresented numbers of genes from the compendium encoded cell surface receptors, signaling molecules (hormones, neuropeptides, cytokines), transcription factors, signal transduction proteins, cilium and BBSome components, and lipid binding proteins or were present in the brain-specific list of tissue-enriched genes identified with TSEA tool. We identified 27 pathways from KEGG, REACTOME and BIOCARTA whose genes were overrepresented in the compendium. Networks formed by physical interactions or homological relationships between proteins or interactions between proteins involved in biochemical/signaling pathways were reconstructed and analyzed. Subnetworks and clusters identified by the MCODE tool included genes/proteins associated with cilium morphogenesis, signal transduction proteins (particularly, G protein–coupled receptors, kinases or proteins involved in response to insulin stimulus) and transcription regulation (particularly nuclear receptors). We ranked GWAS genes according to the number of neighbors in three networks and revealed 22 GWAS genes involved in the brain-specific PPI network. On the base of the most reliable PPIs functioning in the brain tissue, new regulatory schemes interpreting relevance to BW regulation are proposed for three GWAS genes (ETV5, LRP1B, and NDUFS3). A compendium comprising 578 human genes controlling FB or BW was designed, and the most significant functional groups of genes, biological processes/pathways, and tissues/organs involved in BW regulation were revealed. We ranked genes from the GWAS meta-analysis set according to the number and quality of associations in the networks and then according to their involvement in the brain-specific PPI network and proposed new regulatory schemes involving three GWAS genes (ETV5, LRP1B, and NDUFS3) in BW regulation. The compendium is expected to be useful for pathology risk estimation and for design of new pharmacological approaches in the treatment of human obesity.
proteins
2026-08-07 | Pharmacogenetic hypersensitivity to somatropin in a child with severe growth hormone deficiency and MC4R p.V166I variant.
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor that regulates energy homeostasis. Pathogenic MC4R variants represent the most common cause of monogenic obesity and are frequently associated with increased linear growth. However, the mechanisms linking MC4R signaling to somatic growth remain incompletely understood. We report a child with severe growth hormone deficiency (GHD) carrying a heterozygous MC4R variant (c.496G>A; p.V166I), in whom recombinant human growth hormone (rhGH) therapy triggered an unexpectedly exaggerated clinical and biochemical response, suggesting a potential pharmacogenetic interaction between MC4R signaling and the GH/IGF-1 axis. The male patient was first evaluated at 1 month of age due to micropenis and diagnosed with multiple pituitary hormone deficiencies. At 57 months of age, his height was 97.3 cm (-2.56 SDS) and annual growth velocity was 4.1 cm/year (<-2 SDS); rhGH (somatropin) therapy was initiated. Despite severe biochemically confirmed GHD, rhGH at 0.03 mg/kg/day triggered an exaggerated response: IGF-1 levels increased from -3.35 SDS to +8.00 SDS. Concurrently, his height velocity accelerated to 16 cm/year, and his bone age rapidly advanced by approximately 4 years over a 23-month period, culminating in mandibular prognathism. The coexistence of severe GHD and an MC4R variant is rarely described, and such a pronounced response to rhGH has not previously been reported. These findings suggest that MC4R p.V166I may modulate peripheral GH/IGF-1 signaling and act as a pharmacogenetic modifier of GH responsiveness. Careful rhGH dose titration with close IGF-1 monitoring may be considered in patients carrying the MC4R p.V166I variant.
2026-07-10 | The application of GLP-1 receptor agonists in obesity due to MC4R deficiency
Although the pathogenesis of genetic obesity is becoming increasingly clear, effective treatments remain lacking, particularly for obesity caused by melanocortin 4 receptor (MC4R) deficiency. The activity of MC4R is strictly regulated by its endogenous ligands: α-melanocyte-stimulating hormone (α-MSH) binds to MC4R and transmits anorexigenic and energy-expenditure signals, whereas agouti-related protein (AgRP) exerts an antagonistic effect by binding to the receptor, competitively inhibiting α-MSH action and promoting appetite. Current options, such as lifestyle modifications and bariatric surgery, have limited efficacy, highlighting the need for accessible pharmacological interventions. This review evaluates glucagon-like peptide-1 (GLP-1) receptor agonists in MC4R-deficient obesity. We conducted a comprehensive literature search across databases, including PubMed and Web of Science, compiling data from clinical trials, case reports, and basic research studies published up to 2025, with a focus on the efficacy, safety, and mechanism of action of drugs such as liraglutide, semaglutide, and tirzepatide in patients with MC4R deficiency. Evidence indicates these agents induce significant weight loss, appetite suppression, and metabolic improvements via mechanisms independent of intact MC4R signaling. Their weight-loss effects are comparable to those seen in common obesity, with additional benefits for comorbidities like insulin resistance and dyslipidemia. These findings support the GLP-1 pathway as an alternative to impaired MC4R, offering a viable treatment. Understanding their efficacy and mechanisms provides new treatment options for this rare condition and offers evidence for genetically specific personalized weight management.
2026-04-02 | Tirzepatide and Metformin Effects on Hunger and BMI in an Adolescent with Hyperphagia and Severe Obesity due to MC4R Deficiency: A Case Report.
Tirzepatide, a dual glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide receptor agonist, is recently approved for the treatment of type 2 diabetes and obesity in adults. Melanocortin-4-receptor (MC4R) deficiency is the most common monogenic cause of obesity and presents with hyperphagia and early onset obesity. While tirzepatide seems to be effective in inducing weight loss in adults with MC4R deficiency, its effects on hyperphagia and weight loss in pediatric patients are unexplored. A 17-year-old girl was admitted to our specialized obesity clinic because of hyperphagia and severe early onset obesity due to MC4R deficiency. She had an extensive history of lifestyle interventions and psychological support and maintained a high level of physical activity. Despite these efforts, she presented with a BMI of 37 kg/m2 (3.68 SDS) and a substantial psychosocial burden. Vital signs and laboratory evaluations revealed no obesity-related complications. Tirzepatide was initiated at a dose of 2.5 mg weekly and slowly titrated to a maximum dose of 12.5 mg weekly. She initially experienced a substantial reduction in hyperphagia and reported less food noise, a reduction in hunger feelings and prolonged postprandial satiety. However, after 12 weeks hunger scores started to increase again, approaching pre-treatment levels at 28 weeks of follow-up. Metformin was added at 28 weeks in an attempt to better manage of hyperphagia, resulting in a reduction in hyperphagia. Despite these increasing hunger feelings from week 12 to 28, substantial weight loss was achieved, and the patient lost -13.9% of her initial body weight at 28 weeks. After addition of metformin, the patient lost an additional -7% of her weight. Total body weight reduction at week 37 was -20.9%. Tirzepatide was well tolerated, with no adverse effects reported at 41 weeks of follow-up. This case report suggests that tirzepatide is effective in reducing body weight in adolescents with MC4R deficiency. However, the question remains what the effect is on hunger and satiety in the long run and at a higher dose. Cohort studies are needed to assess long-term safety and effectiveness of tirzepatide in the pediatric population and in managing hyperphagia.
2026-02-22 | Efficacy of GLP-1 analog peptides, semaglutide, tirzepatide, and retatrutide on MC4R deficient obesity and their comparison.
Melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor expressed in the hypothalamus, playing a key role in regulating feeding behavior and energy homeostasis. MC4R is integral to the POMC-MC4R and leptin-MC4R pathways, which control food intake and body weight. Mutations in the POMC gene lead to severe early-onset obesity and increased food consumption. Recently, glucagon-like peptide-1 (GLP-1) analogs, including semaglutide, tirzepatide, and retatrutide, have been explored as potential anti-obesity therapies. This study aimed to assess and compare the efficacy of these GLP-1 analogs in MC4R knockout (KO) mice, which are deficient in the POMC-MC4R pathway. GLP-1 analogs were administered for 21 days to MC4R KO mice and compared their efficacy. The percentage of body weight reduction was 19.7 ± 4.1% for semaglutide, 31.6 ± 7.6% for tirzepatide, and 24.1 ± 5.8% for retatrutide. Body composition analysis, including fat and lean mass, was performed using the Echo-MRI system, revealing significant suppression of both fat and lean mass by all three GLP-1 analogs. Furthermore, GLP-1 analogs improved plasma insulin levels, HOMA-IR, cholesterol levels, and markers of liver damage (AST and ALT), as well as reduced liver hypertrophy. While GLP-1 analogs suppressed genes related to fatty acid synthesis, they had no significant effect on inflammation-related gene expressions. Additionally, GLP-1 analogs reduced energy expenditure, with only tirzepatide showing a significant decrease in the respiratory quotient (RQ) in MC4R KO mice. Our findings demonstrate that all three GLP-1 analogs, semaglutide, tirzepatide, and retatrutide, exhibit significant anti-obesity effects in MC4R KO mice. These results suggest that GLP-1 analogs may provide an effective treatment option for patients with MC4R-POMC pathway deficiencies. Moreover, the efficacy of these drugs in MC4R KO mice aligns with clinical studies, indicating that MC4R KO mice serve as a reliable animal model for obesity research.
2026-01-05 | Treatment Approaches for Obesity in Children With Heterozygous MC4R Variants.
Melanocortin-4 receptor (MC4R) deficiency is the most common cause of monogenic obesity; yet treatment options for children with MC4R mutations are limited. We describe significant improvement in weight in three patients with pathogenic or likely pathogenic MC4R mutations; two adolescents treated with semaglutide, and a younger child treated with metformin and topiramate. These findings indicate GLP-1 receptor agonists, topiramate and metformin can be helpful in managing obesity associated with MC4R deficiency.
small molecules
2026-06-24 | Cardiometabolic regulation by adipocyte-derived leptin and the brain melanocortin system.
Tonic activation of central nervous system (CNS) leptin receptors (LepRs) and melanocortin 4 receptors (MC4Rs) is critical for maintaining normal cardiometabolic function. Deficiency of CNS LepR or MC4R signaling causes severe obesity and is accompanied by multiple metabolic abnormalities including insulin resistance, glucose intolerance, and hyperlipidemia that are only partially explained by obesity. Defective LepR and MC4R signaling also causes dysfunction of the sympathetic nervous system (SNS) and blood pressure (BP) regulation. Hyperleptinemia and activation of the CNS melanocortin system in obesity are important compensatory mechanisms that attenuate abnormalities of glucose and lipid metabolism but may also contribute to SNS activation and increased BP. Despite potentially adverse effects of increases in SNS activity and BP, pharmacological activation of brain LepRs and MC4Rs may provide an important therapeutic approach for protecting target organs, such as the heart, kidneys, and brain, from ischemic injury by improving mitochondrial function and ATP production. However, additional preclinical studies are needed to address mechanistic questions before clinical studies are begun to test the effectiveness of leptin and MC4R agonists for treating people with ischemic injury of target organs.
2026-05-27 | SKNY-1, a THCV Analog, Produces Weight Loss, Lipid Normalization and Attenuation of Reward-Associated Behaviors in an mc4r(G894C) Zebrafish Model of Obesity.
Obesity resulting from melanocortin-4 receptor (MC4R) dysfunction is characterized by combined metabolic dysregulation and maladaptive reward-related behaviors that limit the durability of existing therapies. The endocannabinoid system is a central regulator of appetite, lipid metabolism, and reward processing; however, first-generation cannabinoid receptor 1 (CB1) antagonists were limited by adverse neuropsychiatric effects. SKNY-1 is an orally active tetrahydrocannabivarin (THCV) analog designed to engage pathway-biased CB1 signaling, modulate cannabinoid receptor 2 (CB2), and selectively inhibit monoamine oxidase B (MAO-B), with the objective of addressing both metabolic and behavioral components of obesity while minimizing central nervous system liability through biased CB1 signaling, CB2 modulation, and potential complementary MAO-B inhibition. Here, we integrated in vitro pharmacological profiling of SKNY-1 with in vivo evaluation in an adult mc4r(G894C) zebrafish model exhibiting obesity-associated metabolic and reward-related phenotypes. In vitro, SKNY-1 displayed low-potency modulation of CB1 cyclic AMP signaling (EC50 ~30 µM) but more potent antagonism of the CB1 β-arrestin pathway (IC50 ~6 µM), consistent with differential CB1 pathway modulation. SKNY-1 acted as a CB2 partial agonist (EC50 ~0.1 µM), with antagonist activity emerging at higher concentrations, and selectively inhibited MAO-B at low affinity with no activity against MAO-A. In vivo, mc4r(G894C) zebrafish mutants exhibited dyslipidemia, hepatic triglyceride accumulation, altered appetite-regulatory gene expression, increased metabolic rate, and enhanced compulsive high-calorie feeding and nicotine-seeking behaviors. Oral administration of SKNY-1 for six days produced dose-dependent effects. Both doses normalized total cholesterol and low-density lipoprotein levels and reduced hepatic triglycerides toward wild-type values without affecting circulating triglycerides. The higher dose (200 ng per fish per day) induced significant body weight reduction while preserving body density and attenuated reward-associated feeding and nicotine-seeking behaviors. The lower dose (20 ng per fish per day) more effectively normalized the leptin a-to-ghrelin expression ratio. Collectively, these findings demonstrate that SKNY-1 engages integrated endocannabinoid and potential dopaminergic mechanisms to improve metabolic parameters and attenuate maladaptive reward-related behaviors in an MC4R-deficient vertebrate model, supporting its further translational investigation for obesity complicated by compulsive eating and substance-seeking behaviors.
2026-04-21 | Mice lacking β-arrestin-2 in melanocortin 4 receptor-expressing neurons show marked metabolic deficits.
Hypothalamic melanocortin 4 receptors (MC4Rs) play a central role in regulating food intake and energy homeostasis. In fact, inactivating mutations in the MC4R gene are the most common form of monogenic obesity. Agonist activation of MC4Rs reduces food intake by modulating hypothalamic signaling circuits. Thus, a detailed understanding of the signaling pathways that regulate MC4R activity is of considerable translational relevance. Ligand-activated MC4Rs not only interact with heterotrimeric G proteins but also can recruit β-arrestin-2 (barr2) to the receptor. The potential functional role of barr2 in regulating the anorectic effects of MC4R signaling remains unexplored. In the present study, we used mutant mouse models to demonstrate MC4R-mediated activation of barr2/ERK signaling in MC4R neurons of the paraventricular nucleus leads to reduced food intake. We also found the appetite-suppressing effect of setmelanotide, an MC4R agonist FDA approved for the treatment of certain types of obesity, requires the presence of barr2 in MC4R-containing neurons. These data suggest that MC4R agonists able to promote MC4R/barr2 interactions with high efficacy may become useful as appetite-suppressing drugs.
2026-04-04 | Bombesin receptor-activated protein homolog deficiency reduces food intake and alleviates metabolic dysfunction in high-fat diet treated mice.
In our previous study, we found that both bombesin receptor-activated protein (BRAP) and its mouse homolog, BC004004, are expressed in the central nervous system, although their functions remain unclear. In feeding experiments, BRAP homolog knockout mice (BC004004-/-) showed reduced preference for a high-fat diet (HFD) compared with wild-type controls. After four months of HFD treatment, BC004004-/- mice had lower food intake and weight gain, along with reduced fasting blood glucose, insulin, triglycerides, and low-density lipoprotein cholesterol levels. Histological analysis revealed less hepatic steatosis, renal injury, and white adipose tissue (WAT) hypertrophy in the BC004004-/- mice. qPCR analysis of inguinal fat tissues showed increased expression of thermogenic markers (UCP1, Prdm16, Tfam) in BC004004-/- mice, indicating enhanced WAT "browning". Oil red O staining showed that overexpression of the BC004004 gene in cultured mouse microglia BV2 cells increased palmitic acid-induced lipid deposition and higher levels of the proinflammatory cytokines IL-1β and TNF-α, as measured by ELISA of culture supernatants. Additionally, qPCR showed lower agouti-related peptide (AgRP) and neuropeptide Y (NPY) expression and higher proopiomelanocortin (POMC) and melanocortin receptors 4 (MC4R) expression in the hypothalamus of BC004004-/- mice, possibly contributed to their reduced food intake and weight gain. These results suggest that BRAP homolog deficiency protects against HFD-induced metabolic dysfunction through multiple mechanisms, including alterations in hypothalamic neuronal circuits and adipose tissue biology.
2026-02-09 | Monogenic and syndromic obesity in children: Clinical recognition, genetics, and precision management
ABSTRACT Obesity is increasingly being recognized as a heterogeneous condition with strong genetic underpinnings. Monogenic obesity, caused by single‐gene mutations, primarily affects the leptin–melanocortin pathway, which regulates hunger and satiety. Mutations in genes, such as LEP , LEPR , POMC , PCSK1 , and MC4R , lead to hyperphagia, early onset severe obesity, and metabolic dysregulation. LEP and LEPR mutations impair leptin signaling, resulting in defective appetite suppression, whereas POMC and PCSK1 deficiencies disrupt prohormone processing. MC4R mutations, the most common cause of monogenic obesity, impair satiety signaling and are linked to rapid weight gain. Syndromic obesity, including the Bardet‐Biedl and Alström syndromes, involves ciliary dysfunction, leading to developmental abnormalities alongside obesity. Other genes such as SH2B1 , SIM1 , and BDNF play crucial roles in hypothalamic development and energy regulation. Advances in genomic sequencing have improved the recognition of genetic etiologies; however, many patients remain undiagnosed due to limited testing availability and a lack of clinician awareness. Precision therapies, including set‐melanotide for specific melanocortin pathway defects, demonstrate the promise of targeted treatments. However, management must extend beyond pharmacology; lifestyle interventions, psychosocial support, and family‐centered care remain essential, especially when intellectual disability or behavioral challenges complicate adherence. Ethical considerations surrounding access and equity are critical, as high‐cost therapies and the limited availability of genetic testing risk widening disparities between health systems. Polygenic risk scores and multi‐omics approaches may expand precision medicine beyond rare genetic syndromes to common obesity, highlighting the importance of integrating genetics, psychosocial care, and policy advocacy in the management of pediatric obesity.
gene therapies
2024-03-06 | Hypothalamic POMC neuron-specific knockout of MC4R affects insulin sensitivity by regulating Kir2.1
Abstract Background Imbalance in energy regulation is a major cause of insulin resistance and diabetes. Melanocortin-4 receptor (MC4R) signaling at specific sites in the central nervous system has synergistic but non-overlapping functions. However, the mechanism by which MC4R in the arcuate nucleus (ARC) region regulates energy balance and insulin resistance remains unclear. Methods The MC4R flox/flox mice with proopiomelanocortin (POMC) -Cre mice were crossed to generate the POMC-MC4R flox/+ mice. Then POMC-MC4R flox/+ mice were further mated with MC4R flox/flox mice to generate the POMC-MC4R flox/flox mice in which MC4R is selectively deleted in POMC neurons. Bilateral injections of 200 nl of AAV-sh-Kir2.1 (AAV-sh-NC was used as control) were made into the ARC of the hypothalamus. Oxygen consumption, carbon dioxide production, respiratory exchange ratio and energy expenditure were measured by using the CLAMS; Total, visceral and subcutaneous fat was analyzed using micro-CT. Co-immunoprecipitation assays (Co-IP) were used to analyze the interaction between MC4R and Kir2.1 in GT1-7 cells. Results POMC neuron-specific ablation of MC4R in the ARC region promoted food intake, impaired energy expenditure, leading to increased weight gain and impaired systemic glucose homeostasis. Additionally, MC4R ablation reduced the activation of POMC neuron, and is not tissue-specific for peripheral regulation, suggesting the importance of its central regulation. Mechanistically, sequencing analysis and Co-IP assay demonstrated a direct interaction of MC4R with Kir2.1. Knockdown of Kir2.1 in POMC neuron-specific ablation of MC4R restored the effect of MC4R ablation on energy expenditure and systemic glucose homeostasis, indicating by reduced body weight and ameliorated insulin resistance. Conclusion Hypothalamic POMC neuron-specific knockout of MC4R affects energy balance and insulin sensitivity by regulating Kir2.1. Kir2.1 represents a new target and pathway that could be targeted in obesity.
2023-11-13 | Melanocortin-4 receptor in macrophages attenuated angiotensin II-induced abdominal aortic aneurysm in mice
Abstract Obesity is recognized as an independent risk factor for abdominal aortic aneurysm (AAA). While mutations in the melanocortin-4 receptor ( MC4R ) gene is the most common cause of obesity caused by mutations in a single gene, the link between MC4R function and vascular disease has still remained unclear. Here, by using melanocortin-4 receptor (MC4R) deficient mice, we confirmed MC4R deficiency promotes AAA and atherosclerosis. We demonstrated the contribution of two novel factors towards vascular vulnerability in this model: leptin signaling in vascular smooth muscle cells (VSMCs) and loss of MC4R signaling in macrophages. Leptin was shown to promote vascular vulnerability via PI3K-dependent upregulation of Spp1 expression in VSMC. Additionally, Ang II-induced AAA incidence was significantly reduced when MC4R gene expression was myeloid cell-specifically rescued in MC4R deficient (MC4R TB/TB ) mice. Ex vivo analysis showed a suppression in NF-κB activity in bone marrow-derived macrophages from LysM(+);MC4R TB/TB mice compared to LysM(−);MC4R TB/TB mice, which exaggerates with endogenous MC4R ligand treatment; α-MSH. These results suggest that MC4R signaling in macrophages attenuates AAA by inhibiting NF-κB activity and subsequent vascular inflammation.
2023-06-17 | Understanding the Genetics of Early-Onset Obesity in a Cohort of Children From Qatar
Monogenic obesity is a rare form of obesity due to pathogenic variants in genes implicated in the leptin-melanocortin signaling pathway and accounts for around 5% of severe early-onset obesity. Mutations in the genes encoding the MC4R, leptin, and leptin receptor are commonly reported in various populations to cause monogenic obesity. Determining the genetic cause has important clinical benefits as novel therapeutic interventions are now available for some forms of monogenic obesity.To unravel the genetic causes of early-onset obesity in the population of Qatar.In total, 243 patients with early-onset obesity (above the 95% percentile) and age of onset below 10 years were screened for monogenic obesity variants using a targeted gene panel, consisting of 52 obesity-related genes.Thirty rare variants potentially associated with obesity were identified in 36 of 243 (14.8%) probands in 15 candidate genes (LEP, LEPR, POMC, MC3R, MC4R, MRAP2, SH2B1, BDNF, NTRK2, DYRK1B, SIM1, GNAS, ADCY3, RAI1, and BBS2). Twenty-three of the variants identified were novel to this study and the rest, 7 variants, were previously reported in literature. Variants in MC4R were the most common cause of obesity in our cohort (19%) and the c.485C>T p.T162I variant was the most frequent MC4R variant seen in 5 patients.We identified likely pathogenic/pathogenic variants that seem to explain the phenotype of around 14.8% of our cases. Variants in the MC4R gene are the commonest cause of early-onset obesity in our population. Our study represents the largest monogenic obesity cohort in the Middle East and revealed novel obesity variants in this understudied population. Functional studies will be required to elucidate the molecular mechanism of their pathogenicity.
2022-01-14 | Oestrogen engages brain MC4R signalling to drive physical activity in female mice.
Oestrogen depletion in rodents and humans leads to inactivity, fat accumulation and diabetes1,2, underscoring the conserved metabolic benefits of oestrogen that inevitably decrease with age. In rodents, the preovulatory surge in 17β-oestradiol (E2) temporarily increases energy expenditure to coordinate increased physical activity with peak sexual receptivity. Here we report that a subset of oestrogen-sensitive neurons in the ventrolateral ventromedial hypothalamic nucleus (VMHvl)3-7 projects to arousal centres in the hippocampus and hindbrain, and enables oestrogen to rebalance energy allocation in female mice. Surges in E2 increase melanocortin-4 receptor (MC4R) signalling in these VMHvl neurons by directly recruiting oestrogen receptor-α (ERα) to the Mc4r gene. Sedentary behaviour and obesity in oestrogen-depleted female mice were reversed after chemogenetic stimulation of VMHvl neurons expressing both MC4R and ERα. Similarly, a long-term increase in physical activity is observed after CRISPR-mediated activation of this node. These data extend the effect of MC4R signalling - the most common cause of monogenic human obesity8 - beyond the regulation of food intake and rationalize reported sex differences in melanocortin signalling, including greater disease severity of MC4R insufficiency in women9. This hormone-dependent node illuminates the power of oestrogen during the reproductive cycle in motivating behaviour and maintaining an active lifestyle in women.
2021-03-09 | Neuroanatomical organization and functional roles of PVN MC4R pathways in physiological and behavioral regulations
ABSTRACT Objective The paraventricular nucleus of hypothalamus (PVN) is an integrative center in the brain orchestrating a wide range of physiological and behavioral responses. While the PVN melanocortin 4 receptor (MC4R) signaling (PVN MC4R+ ) is undoubtedly involved in feeding regulation, the neuroanatomical organization of PVN MC4R+ pathway and its role in diverse physiological and behavioral regulations have not been fully understood. Here we aimed to better characterize the input-output organization of PVN MC4R+ neurons and further test their potential functional roles beyond feeding. Methods Using a combination of viral tools, we performed a comprehensive mapping of PVN MC4R+ circuits and tested the effects of chemogenetic activation of PVN MC4R+ neurons on thermogenesis, cardiovascular control and other behavioral regulations beyond feeding. Results We found that PVN MC4R+ neurons broadly innervate many different brain regions known to be important not only for feeding but also for neuroendocrine and autonomic control of thermogenesis and cardiovascular function, including but not limited to preoptic area, median eminence, parabrachial nucleus, locus coeruleus, nucleus of solitary tract, ventrolateral medulla and thoracic spinal cord. Contrary to broad efferent projections, PVN MC4R+ neurons receive monosynaptic inputs from limited brain regions, including medial preoptic nucleus, arcuate and dorsomedial hypothalamic nuclei, and supraoptic nucleus. Consistent with broad efferent projections, chemogenetic activation of PVN MC4R+ neurons not only suppressed feeding but also led to an apparent increase in heart rate, blood pressure and brown adipose tissue thermogenesis. Strikingly, these physiological changes accompanied an unexpected repetitive bedding-removing behavior followed by hypoactivity and resting-like behavior. Conclusions Our results clarify the neuroanatomical organization of PVN MC4R+ circuits and shed new light on the roles of PVN MC4R+ pathways in autonomic control of thermogenesis, cardiovascular function and other behavioral regulations.
oligonucleotides
2022-09-29 | MicroRNA-7 regulates melanocortin circuits involved in mammalian energy homeostasis
MicroRNAs (miRNAs) modulate physiological responses by repressing the expression of gene networks. We found that global deletion of microRNA-7 (miR-7), the most enriched miRNA in the hypothalamus, causes obesity in mice. Targeted deletion of miR-7 in Single-minded homolog 1 (Sim1) neurons, a critical component of the hypothalamic melanocortin pathway, causes hyperphagia, obesity and increased linear growth, mirroring Sim1 and Melanocortin-4 receptor (MC4R) haplo-insufficiency in mice and humans. We identified Snca (α-Synuclein) and Igsf8 (Immunoglobulin Superfamily Member 8) as miR-7 target genes that act in Sim1 neurons to regulate body weight and endocrine axes. In humans, MIR-7-1 is located in the last intron of HNRNPK, whose promoter drives the expression of both genes. Genetic variants at the HNRNPK locus that reduce its expression are associated with increased height and truncal fat mass. These findings demonstrate that miR-7 suppresses gene networks involved in the hypothalamic melanocortin pathway to regulate mammalian energy homeostasis.
2022-05-25 | Obesity and the role of genetic polymorphism: A review of genes as the risk of obesity
Obesity can be caused by environmental factors, which are higher energy input or lower energy expenditure. Environmental factors supported by genetic factors cause a person to have a different risk for developing obesity from to another. Genetics factors cause obesity through several pathways, which are impaired regulation in the hypothalamus and the regulation of energy expenditure. Obesity may be caused by one gene as monogenic-associated obesity, however, commonly caused by several genes together with environmental factors as the main multi-factorial risk of obesity. Obesity causes inflammation which leads to metabolic diseases. Many efforts are performed to prevent or treat obesity through the intervention to environmental and or genetic factors. Many attempts to reduce the prevalence of obesity were performed by influencing the environmental risk factors or the genetic risk factors. In this review, we identified the main genes which influence obesity. The genetic risks of obesity may be different from one to another country or between ethnic groups. Therefore, a better treatment approach should consider the differences role of genes in obesity rather than only changes in lifestyle. Nutrigenetic approach by considering the difference role of gens in responding to nutrients or drugs is recommended in individualized treatment plans.
2020-07-25 | Function of Dicer with regard to Energy Homeostasis Regulation, Structural Modification, and Cellular Distribution
As a type III ribonuclease (RNase III) specifically cleaving double-stranded RNA substrates into short fragments, Dicer is indispensable in a range of physi/pathologic processes, e.g., nutrient deprivation, hypoxia, or DNA damage. Therefore, much interest has been paid to the research of this protein as well as its products like microRNAs (miRNAs). The close relationship between Dicer levels and fluctuations of nutrient availability suggests that the protein participates in the regulation of systemic energy homeostasis. Through miRNAs, Dicer regulates the hypothalamic melanocortin-4 system and central autophagy promoting energy expenditure. Moreover, by influencing canonical energy sensors like adenosine monophosphate-activated protein kinase (AMPK) or mammalian target of rapamycin (mTOR), Dicer favors catabolism in the periphery. Taken together, Dicer might be targeted in the control of energy dysregulation. However, factors affecting its RNase activity should be noted. Firstly, modulation of structural integrity affects its role as a ribonuclease. Secondly, although previously known as a cytosolic endoribonuclease, evidence suggests Dicer can relocalize into the nucleus where it could also produce small RNAs. In this review, we probe into involvement of Dicer in energy homeostasis as well as its structural integrity or cellular distribution which affects its ability to produce miRNAs, in the hope of providing novel insights into its mechanism of action for future application.
2018-11-02 | MicroRNAs are involved in the hypothalamic leptin sensitivity
The central nervous system monitors modifications in metabolic parameters or hormone levels (leptin) and elicits adaptive responses such as food intake and glucose homeostasis regulation. Particularly, within the hypothalamus, pro-opiomelanocortin (POMC) neurons are crucial regulators of energy balance. Consistent with a pivotal role of the melanocortin system in the control of energy homeostasis, disruption of the Pomc gene causes hyperphagia and obesity. Pomc gene expression is tightly controlled by different mechanisms. Interestingly, recent studies pointed to a key role for micro ribonucleic acid (miRNAs) in the regulation of gene expression. However, the role of miRNAs in the leptin sensitivity in hypothalamic melanocortin system has never been assessed. We developed a transgenic mouse model (PDKO) with a partial deletion of the miRNA processing enzyme DICER specifically in POMC neurons. PDKO mice exhibited a normal body weight but a decrease of food intake. Interestingly, PDKO mice had decreased metabolic rate by reduction of VO2 consumption and CO2 production which could explain that PDKO mice have normal weight while eating less. Interestingly, we observed an increase of leptin sensitivity in the POMC neurons of PDKO mice which could explain the decrease of food intake in this model. We also observed an increase in the expression of genes involved in the function of brown adipose tissue that is in polysynaptic contact with the POMC neurons. In summary, these results support the hypothesis that Dicer-derived miRNAs may be involved in the effect of leptin on POMC neurons activity.
2016-12-01 | A compendium of human genes regulating feeding behavior and body weight, its functional characterization and identification of GWAS genes involved in brain-specific PPI network
Obesity is heritable. It predisposes to many diseases. The objectives of this study were to create a compendium of genes relevant to feeding behavior (FB) and/or body weight (BW) regulation; to construct and to analyze networks formed by associations between genes/proteins; and to identify the most significant genes, biological processes/pathways, and tissues/organs involved in BW regulation. The compendium of genes controlling FB or BW includes 578 human genes. Candidate genes were identified from various sources, including previously published original research and review articles, GWAS meta-analyses, and OMIM (Online Mendelian Inheritance in Man). All genes were ranked according to knowledge about their biological role in body weight regulation and classified according to expression patterns or functional characteristics. Substantial and overrepresented numbers of genes from the compendium encoded cell surface receptors, signaling molecules (hormones, neuropeptides, cytokines), transcription factors, signal transduction proteins, cilium and BBSome components, and lipid binding proteins or were present in the brain-specific list of tissue-enriched genes identified with TSEA tool. We identified 27 pathways from KEGG, REACTOME and BIOCARTA whose genes were overrepresented in the compendium. Networks formed by physical interactions or homological relationships between proteins or interactions between proteins involved in biochemical/signaling pathways were reconstructed and analyzed. Subnetworks and clusters identified by the MCODE tool included genes/proteins associated with cilium morphogenesis, signal transduction proteins (particularly, G protein–coupled receptors, kinases or proteins involved in response to insulin stimulus) and transcription regulation (particularly nuclear receptors). We ranked GWAS genes according to the number of neighbors in three networks and revealed 22 GWAS genes involved in the brain-specific PPI network. On the base of the most reliable PPIs functioning in the brain tissue, new regulatory schemes interpreting relevance to BW regulation are proposed for three GWAS genes (ETV5, LRP1B, and NDUFS3). A compendium comprising 578 human genes controlling FB or BW was designed, and the most significant functional groups of genes, biological processes/pathways, and tissues/organs involved in BW regulation were revealed. We ranked genes from the GWAS meta-analysis set according to the number and quality of associations in the networks and then according to their involvement in the brain-specific PPI network and proposed new regulatory schemes involving three GWAS genes (ETV5, LRP1B, and NDUFS3) in BW regulation. The compendium is expected to be useful for pathology risk estimation and for design of new pharmacological approaches in the treatment of human obesity.
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