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Abstract
The melanocortin-4 receptor (MC4R) was cloned in 1993 by degenerate PCR; however, its function was unknown. Subsequent studies suggest that the MC4R might be involved in regulating energy homeostasis. This hypothesis was confirmed in 1997 by a series of seminal studies in mice. In 1998, human genetic studies demonstrated that mutations in the MC4R gene can cause monogenic obesity. We now know that mutations in the MC4R are the most common monogenic form of obesity, with more than 150 distinct mutations reported thus far. This review will summarize the studies on the MC4R, from its cloning and tissue distribution to its physiological roles in regulating energy homeostasis, cachexia, cardiovascular function, glucose and lipid homeostasis, reproduction and sexual function, drug abuse, pain perception, brain inflammation, and anxiety. I will then review the studies on the pharmacology of the receptor, including ligand binding and receptor activation, signaling pathways, as well as its regulation. Finally, the pathophysiology of the MC4R in obesity pathogenesis will be reviewed. Functional studies of the mutant MC4Rs and the therapeutic implications, including small molecules in correcting binding and signaling defect, and their potential as pharmacological chaperones in rescuing intracellularly retained mutants, will be highlighted.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology, Auburn University, Alabama 36849-5519, USA.
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102
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Ghoussaini M, Stutzmann F, Couturier C, Vatin V, Durand E, Lecoeur C, Degraeve F, Heude B, Tauber M, Hercberg S, Levy-Marchal C, Tounian P, Weill J, Traurig M, Bogardus C, Baier LJ, Michaud JL, Froguel P, Meyre D. Analysis of the SIM1 contribution to polygenic obesity in the French population. Obesity (Silver Spring) 2010; 18:1670-5. [PMID: 20075856 PMCID: PMC2953787 DOI: 10.1038/oby.2009.468] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
SIM1 (single-minded 1) haploinsufficiency is responsible for obesity in both humans and mice, but the contribution of frequent DNA variation to polygenic obesity is unknown. Sequencing of all exons, exon/intron boundaries, 870 base pairs (bp) of the putative promoter, and 1,095 bp of the 3'UTR of SIM1 gene in 143 obese children and 24 control adults identified 13 common variants. After analysis of the linkage disequilibrium (LD) structure, association study of eight variants was performed in 1,275 obese children and severely obese adults, in 1,395 control subjects, and in 578 obesity-selected pedigrees. A nominal evidence of association was found for the nonsynonymous variant P352T C/A (rs3734354) (P = 0.01, OR = 0.81 (0.70-0.95)), the +2,004 TGA -/insT SNP (rs35180395) (P = 0.02, OR = 1.21 (1.02-1.43)), the +2,215A/G TGA SNP (rs9386126) (P = 0.002, OR = 0.81 (0.71-0.93)), and pooled childhood/adult obesity. Even though transmission disequilibrium test (TDT) further supported the association of P352T and +2,004 -/inst T with obesity, none of these nominal associations remained significant after a multiple testing Bonferroni correction. Therefore, our study excludes a major contribution of SIM1 common variants in exons, 5' and 3' UTR regions in polygenic obesity susceptibility in French Europeans.
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Affiliation(s)
- Maya Ghoussaini
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Fanny Stutzmann
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Cyril Couturier
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Vincent Vatin
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Emmanuelle Durand
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Cécile Lecoeur
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Franck Degraeve
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Barbara Heude
- Epidemiological and Statistical Research, INSERM U780, Villejuif, France
- University Paris-Sud, Orsay, France
| | - Maithé Tauber
- Center of Physiopathology Toulouse Purpan, INSERM U563, Children’s Hospital, CHU, Toulouse, France
| | - Serge Hercberg
- Centre of Research in Nutrition, UMR U557 INSERM, U1125 INRA, CNAM, Université Paris 13, CRNH IdF, Bobigny, France
| | - Claire Levy-Marchal
- Department of Pediatric Endocrinology and Diabetology, INSERM, U690, Paris, France
- University Paris Diderot, Paris, France
| | - Patrick Tounian
- Department of Pediatric Gastroenterology and Nutrition, Armand-Trousseau Hospital, AP-HP, Paris, France
| | - Jacques Weill
- Pediatric Endocrine Unit, Jeanne de Flandre Hospital, Lille, France
| | - Michael Traurig
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona, USA
| | - Clifton Bogardus
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona, USA
| | - Leslie J. Baier
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona, USA
| | | | - Philippe Froguel
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
- Department of Genomic Medicine, Hammersmith Hospital, ‘Imperial College London, London, UK
| | - David Meyre
- Genomics and Molecular Physiology of Metabolic Diseases, CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
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103
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Abstract
The genetic contribution to interindividual variation in common obesity has been estimated at 40-70%. Yet, despite a relatively high heritability, the search for obesity susceptibility genes has been an arduous task. This paper reviews recent progress made in the obesity genetics field with an emphasis on established obesity susceptibility loci identified through candidate gene as well as genome-wide studies. For the last 15 years, candidate gene and genome-wide linkage studies have been the two main genetic epidemiological approaches to identify genetic loci for common traits, yet progress has been slow and success limited. Only recently have candidate gene studies started to succeed; by means of large-scale studies and meta-analyses at least five variants in four candidate genes have been found to be robustly associated with obesity-related traits. Genome-wide linkage studies, however, have so far not been able to pinpoint genetic loci for common obesity. The genome-wide association approach, which has become available in recent years, has dramatically changed the pace of gene discoveries for common disease, including obesity. Three waves of large-scale high-density genome-wide association studies have already discovered at least 15 previously unanticipated genetic loci incontrovertibly associated with body mass index and extreme obesity risk. Although the combined contribution of these loci to the variation in obesity risk at the population level is small and their predictive value is typically low, these recently discovered loci are set to improve fundamentally our insights into the pathophysiology of obesity.
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Affiliation(s)
- Ruth J F Loos
- MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK.
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104
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Abstract
The biological causes of childhood obesity are complex. Environmental factors, such as massive marketing campaigns for food leading to over-nutrition and snacking and the decline in physical activity, have undoubtedly contributed to the increased prevalence of overweight and obesity in children, but these cannot be considered as the only causes. Susceptibility to obesity is also determined to a great extent by genetic factors. Furthermore, molecular mechanisms involved in the regulation of gene expression, such as epigenetic mechanisms, can increase the risk of developing early-onset obesity. There is evidence that early-onset obesity is a heritable disorder, and a range of genetic factors have recently been shown to cause monogenic, syndromic and polygenic forms of obesity, in some cases interacting with environmental exposures. Modifications of the transcriptome can lead to increased adiposity, and the gut microbiome has recently been shown to be key to the genesis of obesity. These new genomic discoveries complement previous knowledge on the development of early-onset obesity and provide new perspectives for research on the complex molecular and physiological mechanisms involved in this disease. Personalized preventive strategies and genomic medicine may become possible in the near future.
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Affiliation(s)
- Hélène Choquet
- CNRS UMR8199, Institute of Biology, Pasteur Institute, 1 Pr Calmette Street, 59000 Lille, France.
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105
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Hebebrand J, Bammann K, Hinney A. Genetische Ursachen der Adipositas. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2010; 53:674-80. [DOI: 10.1007/s00103-010-1078-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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106
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Abstract
Melanocortin peptides, derived from POMC (pro-opiomelanocortin) are produced in the ARH (arcuate nucleus of the hypothalamus) neurons and the neurons in the commissural NTS (nucleus of the solitary tract) of the brainstem, in anterior and intermediate lobes of the pituitary, skin and a wide range of peripheral tissues, including reproductive organs. A hypothetical model for functional roles of melanocortin receptors in maintaining energy balance was proposed in 1997. Since this time, there has been an extraordinary amount of knowledge gained about POMC-derived peptides in relation to energy homoeostasis. Development of a Pomc-null mouse provided definitive proof that POMC-derived peptides are critical for the regulation of energy homoeostasis. The melanocortin system consists of endogenous agonists and antagonists, five melanocortin receptor subtypes and receptor accessory proteins. The melanocortin system, as is now known, is far more complex than most of us could have imagined in 1997, and, similarly, the importance of this system for regulating energy homoeostasis in the general human population is much greater than we would have predicted. Of the known factors that can cause human obesity, or protect against it, the melanocortin system is by far the most significant. The present review is a discussion of the current understanding of the roles and mechanism of action of POMC, melanocortin receptors and AgRP (agouti-related peptide) in obesity and Type 2 diabetes and how the central and/or peripheral melanocortin systems mediate nutrient, leptin, insulin, gut hormone and cytokine regulation of energy homoeostasis.
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107
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Wang D, Ma J, Zhang S, Hinney A, Hebebrand J, Wang Y, Wang HJ. Association of the MC4R V103I polymorphism with obesity: a Chinese case-control study and meta-analysis in 55,195 individuals. Obesity (Silver Spring) 2010; 18:573-9. [PMID: 19696756 DOI: 10.1038/oby.2009.268] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recently, large-scaled studies suggested a negative association of the infrequent allele of the melanocortin-4 receptor (MC4R) V103I polymorphism with obesity. We conducted a Chinese case-control study, meta-analysis in East Asians and in all populations, in order to further assess the association between the V103I polymorphism and reduced body weight and to explore whether the association varies among different ethnic groups. We conducted a case-control study to analyze this polymorphism in 2,012 children of two independent study groups from Beijing, China, no association was found between the V103I polymorphism and obesity or obesity-related phenotypes (P > 0.10). In the meta-analysis of 3,526 individuals from six East Asian studies, I103 carriers had a 31% lower risk for obesity (odds ratio (OR) = 0.69, 95% confidence interval (CI): 0.50-0.94, P = 0.02). Subsequently, we performed a large meta-analysis of the six East Asian studies and 31 studies of other ethnic groups, involving 55,195 individuals with 19,822 obese cases and 35,373 nonobese controls. In total, the individuals with I103 allele had a 21% lower risk for obesity (OR = 0.79, 95% CI: 0.71-0.88, P < 0.0001). In conclusion, this study confirmed and extended the previous findings, suggesting the MC4R V103I polymorphism is negatively associated with human obesity. It provides significant evidence for the association in East Asian populations. Further large-scaled studies in East Asian populations are needed to validate the association.
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Affiliation(s)
- Du Wang
- Division of Maternal and Child Health, School of Public Health, Peking University Health Science Center, Beijing, China
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108
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Abstract
The prevalence of obesity and diabetes, which are heritable traits that arise from the interactions of multiple genes and lifestyle factors, continues to rise worldwide, causing serious health problems and imposing a substantial economic burden on societies. For the past 15 years, candidate gene and genome-wide linkage studies have been the main genetic epidemiological approaches to identify genetic loci for obesity and diabetes, yet progress has been slow and success limited. The genome-wide association approach, which has become available in recent years, has dramatically changed the pace of gene discoveries. Genome-wide association is a hypothesis-generating approach that aims to identify new loci associated with the disease or trait of interest. So far, three waves of large-scale genome-wide association studies have identified 19 loci for common obesity and 18 for common type 2 diabetes. Although the combined contribution of these loci to the variation in obesity and diabetes risk is small and their predictive value is typically low, these recently identified loci are set to substantially improve our insights into the pathophysiology of obesity and diabetes. This will require integration of genetic epidemiological methods with functional genomics and proteomics. However, the use of these novel insights for genetic screening and personalised treatment lies some way off in the future.
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109
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Mountjoy KG. Distribution and function of melanocortin receptors within the brain. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 681:29-48. [PMID: 21222258 DOI: 10.1007/978-1-4419-6354-3_3] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Biological responses to pro-opiomelanocortin (POMC)-derived peptides administered in the brain were documented in the 1950s but their molecular mechanisms of action only began to be resolved with the mapping of melanocortin receptor subtypes to specific brain regions in the 1990s. Out of the five melanocortin receptor subtypes, MC3R and MC4R are widely recognised as 'neural' melanocortin receptors. In situ hybridization anatomical mapping of these receptor subtypes to distinct hypothalamic nuclei first indicated their roles in energy homeostasis, roles that were later confirmed with the obese phenotypes exhibited by Mc3R and Mc4R knockout mice. It is perhaps less well known however, that all five melanocortin receptor subtypes have been detected in developing and/or adult brains of various species. This chapter provides a comprehensive summary of the detection and mapping of each melanocortin receptor subtype in mammalian, chicken and fish brains and relates the sites of expression to functions that are either known or proposed for each receptor subtype.
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Affiliation(s)
- Kathleen G Mountjoy
- Departments of Physiology and Molecular Medicine and Pathology, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, 1023, New Zealand.
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110
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Cole SA, Butte NF, Voruganti VS, Cai G, Haack K, Kent JW, Blangero J, Comuzzie AG, McPherson JD, Gibbs RA. Evidence that multiple genetic variants of MC4R play a functional role in the regulation of energy expenditure and appetite in Hispanic children. Am J Clin Nutr 2010; 91:191-9. [PMID: 19889825 PMCID: PMC2793108 DOI: 10.3945/ajcn.2009.28514] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 10/12/2009] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Melanocortin-4-receptor (MC4R) haploinsufficiency is the most common form of monogenic obesity; however, the frequency of MC4R variants and their functional effects in general populations remain uncertain. OBJECTIVE The aim was to identify and characterize the effects of MC4R variants in Hispanic children. DESIGN MC4R was resequenced in 376 parents, and the identified single nucleotide polymorphisms (SNPs) were genotyped in 613 parents and 1016 children from the Viva la Familia cohort. Measured genotype analysis (MGA) tested associations between SNPs and phenotypes. Bayesian quantitative trait nucleotide (BQTN) analysis was used to infer the most likely functional polymorphisms influencing obesity-related traits. RESULTS Seven rare SNPs in coding and 18 SNPs in flanking regions of MC4R were identified. MGA showed suggestive associations between MC4R variants and body size, adiposity, glucose, insulin, leptin, ghrelin, energy expenditure, physical activity, and food intake. BQTN analysis identified SNP 1704 in a predicted micro-RNA target sequence in the downstream flanking region of MC4R as a strong, probable functional variant influencing total, sedentary, and moderate activities with posterior probabilities of 1.0. SNP 2132 was identified as a variant with a high probability (1.0) of exerting a functional effect on total energy expenditure and sleeping metabolic rate. SNP rs34114122 was selected as having likely functional effects on the appetite hormone ghrelin, with a posterior probability of 0.81. CONCLUSION This comprehensive investigation provides strong evidence that MC4R genetic variants are likely to play a functional role in the regulation of weight, not only through energy intake but through energy expenditure.
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Affiliation(s)
- Shelley A Cole
- Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, TX, USA
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111
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Hinney A, Vogel CIG, Hebebrand J. From monogenic to polygenic obesity: recent advances. Eur Child Adolesc Psychiatry 2010; 19:297-310. [PMID: 20127379 PMCID: PMC2839509 DOI: 10.1007/s00787-010-0096-6] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Accepted: 01/14/2010] [Indexed: 12/18/2022]
Abstract
The heritability of obesity and body weight in general is high. A small number of confirmed monogenic forms of obesity-the respective mutations are sufficient by themselves to cause the condition in food abundant societies-have been identified by molecular genetic studies. The elucidation of these genes, mostly based on animal and family studies, has led to the identification of important pathways to the disorder and thus to a deeper understanding of the regulation of body weight. The identification of inborn deficiency of the mostly adipocyte-derived satiety hormone leptin in extremely obese children from consanguineous families paved the way to the first pharmacological therapy for obesity based on a molecular genetic finding. The genetic predisposition to obesity for most individuals, however, has a polygenic basis. A polygenic variant by itself has a small effect on the phenotype; only in combination with other predisposing variants does a sizeable phenotypic effect arise. Common variants in the first intron of the 'fat mass and obesity associated' gene (FTO) result in an elevated body mass index (BMI) equivalent to approximately +0.4 kg/m(2) per risk allele. The FTO variants were originally detected in a genome wide association study (GWAS) pertaining to type 2 diabetes mellitus. Large meta-analyses of GWAS have subsequently identified additional polygenic variants. Up to December 2009, polygenic variants have been confirmed in a total of 17 independent genomic regions. Further study of genetic effects on human body weight regulation should detect variants that will explain a larger proportion of the heritability. The development of new strategies for diagnosis, treatment and prevention of obesity can be anticipated.
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Affiliation(s)
- Anke Hinney
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, Virchowstrasse 174, Essen, Germany.
| | - Carla I. G. Vogel
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, Virchowstrasse 174, 45147 Essen, Germany
| | - Johannes Hebebrand
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, Virchowstrasse 174, 45147 Essen, Germany
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112
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Meyre D, Proulx K, Kawagoe-Takaki H, Vatin V, Gutiérrez-Aguilar R, Lyon D, Ma M, Choquet H, Horber F, Van Hul W, Van Gaal L, Balkau B, Visvikis-Siest S, Pattou F, Farooqi IS, Saudek V, O'Rahilly S, Froguel P, Sedgwick B, Yeo GS. Prevalence of loss-of-function FTO mutations in lean and obese individuals. Diabetes 2010; 59:311-8. [PMID: 19833892 PMCID: PMC2797938 DOI: 10.2337/db09-0703] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Single nucleotide polymorphisms (SNPs) in intron 1 of fat mass- and obesity-associated gene (FTO) are strongly associated with human adiposity, whereas Fto(-/-) mice are lean and Fto(+/-) mice are resistant to diet-induced obesity. We aimed to determine whether FTO mutations are disproportionately represented in lean or obese humans and to use these mutations to understand structure-function relationships within FTO. RESEARCH DESIGN AND METHODS We sequenced all coding exons of FTO in 1,433 severely obese and 1,433 lean individuals. We studied the enzymatic activity of selected nonsynonymous variants. RESULTS We identified 33 heterozygous nonsynonymous variants in lean (2.3%) and 35 in obese (2.4%) individuals, with 8 mutations unique to the obese and 11 unique to the lean. Two novel mutations replace absolutely conserved residues: R322Q in the catalytic domain and R96H in the predicted substrate recognition lid. R322Q was unable to catalyze the conversion of 2-oxoglutarate to succinate in the presence or absence of 3-methylthymidine. R96H retained some basal activity, which was not enhanced by 3-methylthymidine. However, both were found in lean and obese individuals. CONCLUSIONS Heterozygous, loss-of-function mutations in FTO exist but are found in both lean and obese subjects. Although intron 1 SNPs are unequivocally associated with obesity in multiple populations and murine studies strongly suggest that FTO has a role in energy balance, it appears that loss of one functional copy of FTO in humans is compatible with being either lean or obese. Functional analyses of FTO mutations have given novel insights into structure-function relationships in this enzyme.
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Affiliation(s)
- David Meyre
- CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Karine Proulx
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Hiroko Kawagoe-Takaki
- Cancer Research U.K. London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire, U.K
| | - Vincent Vatin
- CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | | | - Debbie Lyon
- Cancer Research U.K. London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire, U.K
| | - Marcella Ma
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Helene Choquet
- CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
| | - Fritz Horber
- Klinik Lindberg, Winterthur, and University of Berne, Berne, Switzerland
| | - Wim Van Hul
- Department of Medical Genetics, University of Antwerp and Antwerp University Hospital, Antwerp, Belgium
| | - Luc Van Gaal
- Department of Endocrinology, Diabetology and Metabolism, Antwerp University Hospital, Edegem, Belgium
| | - Beverley Balkau
- INSERM U780, Villejuif, France, and University Paris-Sud, Orsay, France
| | | | - François Pattou
- INSERM U859, CHRU Lille, Lille North of France University, Lille, France
| | - I. Sadaf Farooqi
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Vladimir Saudek
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Stephen O'Rahilly
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Philippe Froguel
- CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France
- Section of Genomic Medicine, Hammersmith Hospital, Imperial College London, London, U.K
| | - Barbara Sedgwick
- Cancer Research U.K. London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire, U.K
| | - Giles S.H. Yeo
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
- Corresponding author: Giles Yeo,
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113
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van Vliet-Ostaptchouk JV, Hofker MH, van der Schouw YT, Wijmenga C, Onland-Moret NC. Genetic variation in the hypothalamic pathways and its role on obesity. Obes Rev 2009; 10:593-609. [PMID: 19712437 DOI: 10.1111/j.1467-789x.2009.00597.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Over recent decades, the prevalence of obesity has increased dramatically worldwide. Although this epidemic is mainly attributable to modern (western) lifestyle, multiple twin and adoption studies indicate the significant role of genes in the individual's predisposition to becoming obese. As the hypothalamus plays a central role in controlling body weight, its regulatory circuits may represent a crucial system in the pathogenesis of the disorder. Genetic variations in genes in the hypothalamic pathways may therefore contribute to the susceptibility for obesity in humans and animals. We summarize current knowledge on the physiological role of the hypothalamus in body-weight regulation and review genetic studies on the hypothalamic candidate genes in relation to obesity. Together, data from functional and genetic studies as well as the new, common, obesity loci identified in genome-wide association scans support an important role for the hypothalamic genes in predisposing to obesity. However, findings are still inconclusive for many candidate genes. To improve our understanding of the genetic architecture of common obesity, we suggest that specific obesity phenotypes should be considered and different analytical approaches used. Such studies should consider multiple genes from the same physiological pathways, together with environmental risk factors.
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Affiliation(s)
- J V van Vliet-Ostaptchouk
- Molecular Genetics, Medical Biology Section, Department of Pathology and Medical Biology, University Medical Center and University of Groningen, Groningen, the Netherlands.
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114
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Gallicchio L, Chang HH, Christo DK, Thuita L, Huang HY, Strickland P, Ruczinski I, Clipp S, Helzlsouer KJ. Single nucleotide polymorphisms in obesity-related genes and all-cause and cause-specific mortality: a prospective cohort study. BMC MEDICAL GENETICS 2009; 10:103. [PMID: 19818126 PMCID: PMC2763854 DOI: 10.1186/1471-2350-10-103] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 10/09/2009] [Indexed: 01/06/2023]
Abstract
Background The aim of this study was to examine the associations between 16 specific single nucleotide polymorphisms (SNPs) in 8 obesity-related genes and overall and cause-specific mortality. We also examined the associations between the SNPs and body mass index (BMI) and change in BMI over time. Methods Data were analyzed from 9,919 individuals who participated in two large community-based cohort studies conducted in Washington County, Maryland in 1974 (CLUE I) and 1989 (CLUE II). DNA from blood collected in 1989 was genotyped for 16 SNPs in 8 obesity-related genes: monoamine oxidase A (MAOA), lipoprotein lipase (LPL), paraoxonase 1 and 2 (PON1 and PON2), leptin receptor (LEPR), tumor necrosis factor-α (TNFα), and peroxisome proliferative activated receptor-γ and -δ (PPARG and PPARD). Data on height and weight in 1989 (CLUE II baseline) and at age 21 were collected from participants at the time of blood collection. All participants were followed from 1989 to the date of death or the end of follow-up in 2005. Cox proportional hazards regression was used to obtain the relative risk (RR) estimates and 95% confidence intervals (CI) for each SNP and mortality outcomes. Results The results showed no patterns of association for the selected SNPs and the all-cause and cause-specific mortality outcomes, although statistically significant associations (p < 0.05) were observed between PPARG rs4684847 and all-cause mortality (CC: reference; CT: RR 0.99, 95% CI 0.89, 1.11; TT: RR 0.60, 95% CI 0.39, 0.93) and cancer-related mortality (CC: reference; CT: RR 1.01, 95% CI 0.82, 1.25; TT: RR 0.22, 95% CI 0.06, 0.90) and TNFα rs1799964 and cancer-related mortality (TT: reference; CT: RR 1.23, 95% CI 1.03, 1.47; CC: RR 0.83, 95% CI 0.54, 1.28). Additional analyses showed significant associations between SNPs in LEPR with BMI (rs1137101) and change in BMI over time (rs1045895 and rs1137101). Conclusion Findings from this cohort study suggest that the selected SNPs are not associated with overall or cause-specific death, although several LEPR SNPs may be related to BMI and BMI change over time.
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Affiliation(s)
- Lisa Gallicchio
- The Prevention and Research Center, The Weinberg Center for Women's Health & Medicine, Mercy Medical Center, Baltimore, Maryland 21202, USA.
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115
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de Krom M, Bauer F, Collier D, Adan RAH, la Fleur SE. Genetic variation and effects on human eating behavior. Annu Rev Nutr 2009; 29:283-304. [PMID: 19400703 DOI: 10.1146/annurev-nutr-080508-141124] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Feeding is a physiological process, influenced by genetic factors and the environment. In recent years, many studies have been performed to unravel the involvement of genetics in both eating behavior and its pathological forms: eating disorders and obesity. In this review, we provide a condensed introduction on the neurological aspects of eating and we describe the current status of research into the genetics of eating behavior, primarily focused on specific traits such as taste, satiation, and hunger. This is followed by an overview on the genetic studies done to unravel the heritable background of obesity and eating disorders. We examine the discussion currently taking place in the field of genetics of complex disorders and phenotypes on how to perform good and powerful studies, with the use of large-scale whole-genome association studies as one of the possible solutions. In the final part of this review, we give our view on the latest developments, including endophenotype approaches and animal studies. Studies of endophenotypes of eating behavior may help to identify core traits that are genetically influenced. Such studies would yield important knowledge on the underlying biological scaffold on which diagnostic criteria for eating disorders could be based and would provide information to influence eating behavior toward healthier living.
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Affiliation(s)
- Mariken de Krom
- Rudolf Magnus Institute of Neuroscience, Department of Neuroscience & Pharmacology, UMC Utrecht, Utrecht, The Netherlands.
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Blakemore AIF, Meyre D, Delplanque J, Vatin V, Lecoeur C, Marre M, Tichet J, Balkau B, Froguel P, Walley AJ. A rare variant in the visfatin gene (NAMPT/PBEF1) is associated with protection from obesity. Obesity (Silver Spring) 2009; 17:1549-53. [PMID: 19300429 DOI: 10.1038/oby.2009.75] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Visfatin was recently reported as a novel adipokine encoded by the NAMPT (PBEF1) gene. This study was aimed at investigation of the possibility that single-nucleotide polymorphisms (SNPs) in the visfatin gene are associated with either obesity or type 2 diabetes (T2D). A set of eight "tag-SNPs" were selected and ABI SNPlex assays designed for genotyping purposes. A total of 1,709 severely obese subjects were typed (896 class III obese adults and 813 children) together with 2,367 T2D individuals and 2,850 controls. For quantitative trait analysis, an additional 2,362 subjects were typed for rs10487818 from a general population sample. One rare SNP, rs10487818, located in intron 4 of NAMPT was associated with severe obesity, with a minor allele frequency of 1.6% in controls, 0.4% in the class III obese adults and, remarkably, 0% in the severely obese children. A highly significant association was observed for the presence or absence of the rare allele, i.e., (A,A) vs. (A,T + T,T) genotypes, in children (P = 6 x 10(-9)) and in adults (P = 8 x 10(-5)). No other significant (P < 0.05) association was observed with obesity or T2D for this or any other SNP. No association with BMI or waist-to-hip ratio was observed in a general population sample (n = 5,212). This is one of the first rare SNPs shown to be protective against a common polygenic disease and provides further evidence that rare alleles of strong effect can contribute to complex diseases such as severe obesity.
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Abstract
The last few years have seen major advances in common non-syndromic obesity research, much of it the result of genetic studies. This Review outlines the competing hypotheses about the mechanisms underlying the genetic and physiological basis of obesity, and then examines the recent explosion of genetic association studies that have yielded insights into obesity, both at the candidate gene level and the genome-wide level. With obesity genetics now entering the post-genome-wide association scan era, the obvious question is how to improve the results obtained so far using single nucleotide polymorphism markers and how to move successfully into the other areas of genomic variation that may be associated with common obesity.
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Polymorphism Val103Ile of the melanocortin-4 receptor gene in the Serbian population. Mol Biol Rep 2009; 37:33-7. [DOI: 10.1007/s11033-009-9500-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Accepted: 03/02/2009] [Indexed: 10/21/2022]
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Zobel DP, Andreasen CH, Grarup N, Eiberg H, Sørensen TIA, Sandbaek A, Lauritzen T, Borch-Johnsen K, Jørgensen T, Pedersen O, Hansen T. Variants near MC4R are associated with obesity and influence obesity-related quantitative traits in a population of middle-aged people: studies of 14,940 Danes. Diabetes 2009; 58:757-64. [PMID: 19073769 PMCID: PMC2646077 DOI: 10.2337/db08-0620] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Variants downstream of the melanocortin-4 receptor gene (MC4R) have been reported to associate with obesity. We examined rs17782313, rs17700633, rs12970134, rs477181, rs502933, and rs4450508 near MC4R for association with obesity-related quantitative traits, obesity, and type 2 diabetes in Danish individuals. RESEARCH DESIGN AND METHODS The variants were investigated for association with obesity-related quantitative traits in 5,807 population-based sampled individuals, obesity in 14,940 individuals, and type 2 diabetes in 8,821 individuals. RESULTS The minor risk alleles of rs17782313, rs17700633, and rs12970134 were associated with BMI (effect per allele 0.25 kg/m2, P = 0.01; 0.23, P = 0.01; and 0.31, P = 7 x 10(-4), respectively), waist circumference (0.67 cm, P = 0.006; 0.53, P = 0.02; and 0.85, P = 3 x 10(-4)), and body weight (1.04 kg, P = 6 x 10(-4); 0.71, P = 0.01; and 1.16, P = 8 x 10(-5)). In case-control studies of obesity defined by BMI, the minor C-allele of rs17782313 was associated with overweight/obesity and obesity (odds ratio [OR] 1.09, P = 0.006 and OR 1.12, P = 0.003, respectively). Similarly, the minor A-allele of rs17700633 was associated with overweight/obesity and obesity (1.12, P = 8 x 10(-5) and 1.16, P = 2 x 10(-5)), and the minor A-allele of rs12970134 was also associated with overweight/obesity and obesity (1.13, P = 2 x 10(-5) and 1.15, P = 6 x 10(-5)). rs477181, rs502933, and rs4450508 were not significantly associated with obesity in the Danish population. The frequency of the minor risk alleles of rs17782313 and rs12970134 was higher among patients with type 2 diabetes than among glucose-tolerant individuals (OR 1.08, P = 0.08 and 1.08, P = 0.06, respectively); however, these borderline associations were abolished after adjustment for BMI. CONCLUSIONS rs17782313, rs17700633, and rs12970134 near MC4R associate with measures of obesity in Danish individuals.
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Reinehr T, Hebebrand J, Friedel S, Toschke AM, Brumm H, Biebermann H, Hinney A. Lifestyle intervention in obese children with variations in the melanocortin 4 receptor gene. Obesity (Silver Spring) 2009; 17:382-9. [PMID: 18997677 DOI: 10.1038/oby.2008.422] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Because information on weight changes after lifestyle intervention in children with mutations in the melanocortin 4 receptor (MC4R) gene is scarce, we compared weight changes after lifestyle intervention between children with and without MC4R variations. A group of 514 overweight children (aged 5-16 years), who presented to participate in a 1-year lifestyle intervention based on exercise, behavior, and nutrition therapy were screened for MC4R mutations. For comparison, children with MC4R mutations leading to reduced receptor function (group A) were each of them randomly matched with five children of same age and gender without MC4R mutations (group B). Changes of weight status were analyzed as change of BMI standard deviation scores (BMI-SDSs). Furthermore, 16 children (3.1%) harbored MC4R mutations leading to reduced receptor function, and 17 (3.3%) children carried variations not leading to reduced receptor function. Children with and without MC4R mutations reduced their overweight at the end of intervention to a similar degree (P = 0.318 between groups based on an intention-to-treat analysis). The maintenance of weight loss after intervention among children with MC4R mutations leading to reduced receptor function failed in contrast to children without such mutations (P < 0.001 adjusted for BMI-SDS at baseline, age, and gender in an intention-to-treat analysis). In conclusion, children with MC4R mutations leading to reduced receptor function were able to lose weight in a lifestyle intervention but had much greater difficulties to maintain this weight loss supporting the impact of these mutations on weight status.
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Affiliation(s)
- Thomas Reinehr
- Department of Pediatric Nutrition Medicine, Vestische Hospital for Children and Adolescents Datteln, University of Witten/Herdecke, Datteln, Germany.
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Yurtcu E, Yilmaz A, Ozkurt Z, Kolukisa E, Yilmaz M, Keles H, Ergun MA, Yetkin I, Menevse A. Melanocortin-4 Receptor Gene Polymorphisms in Obese Patients. Biochem Genet 2009; 47:295-300. [DOI: 10.1007/s10528-009-9228-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 07/21/2008] [Indexed: 11/30/2022]
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Common genetic variation near MC4R is associated with eating behaviour patterns in European populations. Int J Obes (Lond) 2009; 33:373-8. [PMID: 19153581 DOI: 10.1038/ijo.2008.279] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Both rs17782313 (near MC4R) and rs1421085 (FTO) polymorphisms have been consistently associated with increased risk of obesity and with body mass index (BMI) variation. An effect of both polymorphisms on satiety has recently been suggested. We genotyped rs17782313 and rs1421085 in 5764 relatives from 1109 French pedigrees with familial obesity, 1274 Swiss class III obese adults as well as in 4877 French adults and 5612 Finnish teenagers from two randomly selected population cohorts. In all subjects, eating behaviour traits were documented through questionnaires. We first assessed the association of both single nucleotide polymorphisms with BMI and then studied eating behaviour. Under an additive model, the rs17782313-C MC4R allele showed a trend towards higher percentages of snacking in both French obese children (P=0.01) and Swiss obese adults (P=0.04) as well as in adolescents from the Finnish general population (P=0.04). In French adults with familial obesity, this allele tended to be also associated with a higher Stunkard hunger score (P=0.02) and in obese children with a higher prevalence of eating large amounts of food (P=0.04). However, no consistent association of the FTO rs1421085-C allele and available eating behaviour trait was found in our studied populations. The rs17782313-C allele nearby MC4R may modulate eating behaviour-related phenotypes in European obese and randomly selected populations, in both children and adults, supporting a regulatory role of this genetic variant on eating behaviour, as previously shown for MC4R non-synonymous loss-of-function mutations. The potential effect of the obesity-associated FTO gene on eating behaviour deserves additional investigation.
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Gueorguiev M, Lecoeur C, Benzinou M, Mein CA, Meyre D, Vatin V, Weill J, Heude B, Grossman AB, Froguel P, Korbonits M. A Genetic Study of the Ghrelin and Growth Hormone Secretagogue Receptor (GHSR) Genes and Stature. Ann Hum Genet 2009; 73:1-9. [DOI: 10.1111/j.1469-1809.2008.00484.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Because of its high prevalence and the associated medical and psychosocial risks, research into the causes of childhood obesity has experienced a tremendous upswing. Formal genetic data based on twin, adoption, and family studies lead to the conclusion that at least 50% of the interindividual variance of the body mass index (BMI; defined as weight in kilograms divided by height in meters squared) is due to genetic factors. As a result of the recent advent of genome-wide association studies, the first polygenes involved in body weight regulation have been detected. Each of the predisposing alleles explain a few hundred grams of body weight. More polygenes will be detected in the near future, thus for the first time allowing in-depth analyses of gene-gene and gene-environment interactions. They also will enable developmental studies to assess the effect of such alleles throughout childhood and adulthood. The recent increase in obesity prevalence rates illustrates the extreme relevance of environmental factors for body weight. Similar to polygenes, the effect sizes of most such environmental factors are likely to be small, thus rendering their detection difficult. In addition, the validation of the true causality of such factors is not a straightforward task. Important factors are socioeconomic status and television consumption. The authors conclude by briefly assessing implications for treatment and prevention of childhood obesity.
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Affiliation(s)
- Johannes Hebebrand
- Department of Child and Adolescent Psychiatry, Rheinische Kliniken Essen, University of Duisburg-Essen, Virchowstr, 174, D-45147 Essen, Germany
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Affiliation(s)
- Anke Hinney
- *PD Dr. Anke Hinney, Department of Child and Adolescent Psychiatry, University of Duisburg-Essen, Virchowstraβe 174, 45147 Essen, Germany, Tel. +49 201-9597025, Fax -7227302,
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Hughes DA, Hinney A, Brumm H, Wermter AK, Biebermann H, Hebebrand J, Stoneking M. Increased constraints on MC4R during primate and human evolution. Hum Genet 2009; 124:633-47. [PMID: 19011902 PMCID: PMC9947067 DOI: 10.1007/s00439-008-0591-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Accepted: 11/07/2008] [Indexed: 02/02/2023]
Abstract
The melanocortin 4 receptor (MC4R) is routinely investigated for the role it plays in human obesity, as mutations in MC4R are the most common dominantly inherited form of the disease. As little is known about the evolutionary history of this locus, we investigated patterns of variation at MC4R in a worldwide sample of 1,015 humans from 51 populations, and in 8 central chimpanzees. There is a significant paucity of diversity at MC4R in humans, but not in chimpanzees. The spectrum of mutations in humans, combined with the overall low level of diversity, suggests that most (if not all) of the observed non-synonymous polymorphisms are likely to be transient deleterious mutations. The MC4R coding region was resequenced in 12 primate species and sequences from an additional 29 vertebrates were included in molecular evolutionary analyses. MC4R is highly conserved throughout vertebrate evolution, and has apparently been subject to high levels of continuous purifying selection that increased approximately threefold during primate evolution. Furthermore, the strong selection extends to codon usage bias, where most silent mutations are expected to be either quickly fixed or removed from the population, which may help explain the unusually low levels of silent polymorphisms in humans. Finally, there is a significant tendency for non-synonymous mutations that impact MC4R function to occur preferentially at sites that are identified by evolutionary analyses as being subject to very strong purifying selection. The information from this study should help inform future epidemiological investigations of MC4R.
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Affiliation(s)
- David A Hughes
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
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Tao Y. Chapter 6 Mutations in Melanocortin‐4 Receptor and Human Obesity. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 88:173-204. [DOI: 10.1016/s1877-1173(09)88006-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Abstract
PURPOSE OF REVIEW Advances in genetics are occurring at a rapid pace. It will ultimately be the primary care pediatrician who assimilates this knowledge and applies it to patient care. This article is written in a patient encounter format with which the pediatrician is familiar. The vignettes are from the author's own experiences in 13 years of general pediatric practice. RECENT FINDINGS The current literature reinforces the idea that changes in the complexity of the diagnostic evaluation and the time spent explaining the recommended testing will be required by the pediatrician. With this responsibility comes the need of new training strategies for medical students and established pediatricians. SUMMARY Pediatricians will be called upon to incorporate new genetic findings into patient care. This task will ultimately be no different than it was for past pediatricians to incorporate new immunizations or antibiotics into the care plan for each patient. Patient care will improve because therapy will be tailor-made for both the disease and the patient.
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Agurs-Collins T, Khoury MJ, Simon-Morton D, Olster DH, Harris JR, Milner JA. Public health genomics: translating obesity genomics research into population health benefits. Obesity (Silver Spring) 2008; 16 Suppl 3:S85-94. [PMID: 19037221 PMCID: PMC2736102 DOI: 10.1038/oby.2008.517] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We examine how a public health genomics framework can be used to move genomic discoveries into clinical and public health practice for obesity prevention and treatment. There are four phases of translational research: T1: discovery to candidate health application; T2: health application to evidence-based practice guidelines; T3: practice guidelines to health practice; and T4: practice to population health impact. Types of multidisciplinary research and knowledge synthesis needed for each phase, as well as the importance of developing and disseminating evidence-based guidelines, are discussed. Because obesity genomics research is mostly in the discovery phase or in the very early phases of translation (T1), the authors present this framework to illustrate the range of translation activities needed to move genomic discoveries in obesity to actual applications that reduce the burden of obesity at the population level.
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Affiliation(s)
- Tanya Agurs-Collins
- Division of Cancer Control and Population Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
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Krakoff J, Ma L, Kobes S, Knowler WC, Hanson RL, Bogardus C, Baier LJ. Lower metabolic rate in individuals heterozygous for either a frameshift or a functional missense MC4R variant. Diabetes 2008; 57:3267-72. [PMID: 18835933 PMCID: PMC2584132 DOI: 10.2337/db08-0577] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Accepted: 09/17/2008] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Humans with functional variants in the melanocortin 4 receptor (MC4R) are obese, hyperphagic, and hyperinsulinemic but have been reported to have no difference in energy expenditure. RESEARCH DESIGN AND METHODS We investigated the association of two MC4R variants, Arg165Gln (R165Q) and A insertion at nucleotide 100 (NT100), with adiposity in 3,074 full-heritage Pima Indians, a subset of whom had metabolic measures including 24-h energy expenditure (n = 252) and resting metabolic rate (RMR) (n = 364). RESULTS Among the 3,074 subjects, 43 were heterozygous for R165Q and 14 for NT100 (frequency = 0.007 and 0.002). Mean (+/- SD) BMI was higher among subjects with R165Q (39.3 +/- 8.6 kg/m(2)) or NT100 (41.2 +/- 7.8) than subjects without either variant (37.1 +/- 8.4) (P = 0.04 and 0.02, adjusted for age, sex, and birth year and accounting for family membership). The 24-h energy expenditure (four with NT100; three with R165Q) or RMR (six with NT100; two with R165Q) was lower in heterozygous subjects but only met statistical significance when heterozygous subjects were combined and compared with subjects without either variant: least-squares means, 2,163 kcal/24 h (95% CI 2,035-2,291) vs. 2,307 kcal/24 h (2,285-2,328), P = 0.03 for 24-h energy expenditure, and 1,617 kcal/24 h (1,499-1,734) vs. 1,754 kcal/24 h (1,736-1,772), P = 0.02 for RMR; adjusted for age, sex, fat-free mass, and fat mass). For RMR, this difference persisted, even after accounting for family membership. CONCLUSIONS Pima Indians heterozygous for R165Q or NT100 in MC4R have higher BMIs and lower energy expenditure (by approximately 140 kcal/day), indicating that lower energy expenditure was a component of the increased adiposity.
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Affiliation(s)
- Jonathan Krakoff
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Disease, Phoenix, AZ, USA.
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Pichler M, Kollerits B, Heid IM, Hunt SC, Adams TD, Hopkins PN, Kronenberg F. Association of the melanocortin-4 receptor V103I polymorphism with dietary intake in severely obese persons. Am J Clin Nutr 2008; 88:797-800. [PMID: 18779298 PMCID: PMC3246117 DOI: 10.1093/ajcn/88.3.797] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Several studies have reported that carriers of the 103I allele of the melanocortin-4 receptor (MC4R) gene had lower body weight than did persons with the wild-type genotype. A recent study found an association of the MC4R 103I variant with carbohydrate intake, which may mediate some of the association of this variant with leanness. OBJECTIVE The purpose of the study was to investigate the association between the MC4R V103I polymorphism and the dietary intake of persons with severe obesity, which was derived by using the Willett food-frequency questionnaire. DESIGN The MC4R V103I polymorphism was genotyped in a group of 1029 severely obese white subjects with an average body mass index (BMI; in kg/m(2)) of 46.0 (range: 33-92). RESULTS Carriers of the 103I allele had significantly higher daily energy (364 kcal/d or 19%; P = 0.03) and carbohydrate (57 g/d or 27%; P = 0.01) intakes than did noncarriers, but there was no relation with BMI. No notable association of this polymorphism with lipid and glucose variables of the metabolic syndrome was observed. CONCLUSIONS The higher dietary intake of carbohydrates in severely obese persons with the MC4R 103I variant is in line with previous findings. It may indicate a differential effect on body size measures in extremely obese subjects as compared with the general population.
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Affiliation(s)
- Michaela Pichler
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
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Stutzmann F, Tan K, Vatin V, Dina C, Jouret B, Tichet J, Balkau B, Potoczna N, Horber F, O'Rahilly S, Farooqi IS, Froguel P, Meyre D. Prevalence of melanocortin-4 receptor deficiency in Europeans and their age-dependent penetrance in multigenerational pedigrees. Diabetes 2008; 57:2511-8. [PMID: 18559663 PMCID: PMC2518504 DOI: 10.2337/db08-0153] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2008] [Accepted: 06/05/2008] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Melanocortin-4 receptor (MC4R) deficiency is the most frequent genetic cause of obesity. However, there is uncertainty regarding the degree of penetrance of this condition, and the putative impact of the environment on the development of obesity in MC4R mutation carriers is unknown. RESEARCH DESIGN AND METHODS We determined the MC4R sequence in 2,257 obese individuals and 2,677 nonobese control subjects of European origin and established the likely functional impact of all variants detected. We then included relatives of probands carriers and studied 25 pedigrees, including 97 carriers and 94 noncarriers from three generations. RESULTS Of the MC4R nonsynonymous mutations found in obese subjects, 68% resulted in a loss of function in vitro. They were found in 1.72% of obese versus 0.15% of nonobesed subjects (P = 6.9 x 10(-10)). Among the families, abnormal eating behavior was more frequent in both MC4R-deficient children and adults than in noncarriers. Although BMI was inversely associated with educational status in noncarrier adults, no such relationship was seen in MC4R mutation carriers. We observed a generational effect, with a penetrance of 40% in MC4R-deficient adults aged >52 years, 60% in 18- to 52-year-old adults, and 79% in children. The longitudinal study of adult carriers showed an increasing age-dependent penetrance (37% at 20 years versus 60% at >40 years). CONCLUSIONS We have established a robust estimate of age-related penetrance for MC4R deficiency and demonstrated a generational effect on penetrance, which may relate to the development of an "obesogenic" environment. It remains to be seen whether appropriate manipulation of environmental factors may contribute to preventing the development of obesity even in those strongly genetically predisposed to it.
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Affiliation(s)
- Fanny Stutzmann
- Centre National de la Recherche Scientifique-8090, Institute of Biology, Pasteur Institute, Lille, France
| | - Karen Tan
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Vincent Vatin
- Centre National de la Recherche Scientifique-8090, Institute of Biology, Pasteur Institute, Lille, France
| | - Christian Dina
- Centre National de la Recherche Scientifique-8090, Institute of Biology, Pasteur Institute, Lille, France
| | - Béatrice Jouret
- Institut National de la Santé et de la Recherche Médicale U563, Children's Hospital, Toulouse, France
| | - Jean Tichet
- Institut inter Régional pour la Santé, La Riche, France
| | - Beverley Balkau
- Institut National de la Santé et de la Recherche Médicale U780-IFR69, Villejuif, Université Paris-Sud, Orsay, France
| | - Natascha Potoczna
- Klinik Lindberg, Winterthur, and University of Berne, Berne, Switzerland
| | - Fritz Horber
- Klinik Lindberg, Winterthur, and University of Berne, Berne, Switzerland
| | - Stephen O'Rahilly
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - I. Sadaf Farooqi
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Philippe Froguel
- Centre National de la Recherche Scientifique-8090, Institute of Biology, Pasteur Institute, Lille, France
- Department of Genomic Medicine, Hammersmith Hospital, Imperial College London, London, U.K
| | - David Meyre
- Centre National de la Recherche Scientifique-8090, Institute of Biology, Pasteur Institute, Lille, France
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Tao YX. Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. Pharmacol Ther 2008; 120:129-48. [PMID: 18768149 DOI: 10.1016/j.pharmthera.2008.07.005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 07/22/2008] [Indexed: 01/17/2023]
Abstract
The existence of constitutive activity for G protein-coupled receptors (GPCRs) was first described in 1980s. In 1991, the first naturally occurring constitutively active mutations in GPCRs that cause diseases were reported in rhodopsin. Since then, numerous constitutively active mutations that cause human diseases were reported in several additional receptors. More recently, loss of constitutive activity was postulated to also cause diseases. Animal models expressing some of these mutants confirmed the roles of these mutations in the pathogenesis of the diseases. Detailed functional studies of these naturally occurring mutations, combined with homology modeling using rhodopsin crystal structure as the template, lead to important insights into the mechanism of activation in the absence of crystal structure of GPCRs in active state. Search for inverse agonists on these receptors will be critical for correcting the diseases cause by activating mutations in GPCRs. Theoretically, these inverse agonists are better therapeutics than neutral antagonists in treating genetic diseases caused by constitutively activating mutations in GPCRs.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, 212 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
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Abstract
PURPOSE OF REVIEW These last months, the wave of genome-wide association scans finally reached the shores of body weight and obesity complex trait. In parallel, thanks to the increasing sequencing and genotyping capacities, large studies on rare mutations can now be carried out. RECENT FINDINGS In this review, I tried to cover the most recent findings in genome-wide association analyses, the outcome of conclusions subsequently not replicated, and the weight of rare mutations with strong effects on common obesity. The strongest predictor of obesity, FTO, is responsible for 1% of the total heritability, and results from other genome-wide scans do not provide, so far, any clue of other variants of this effect size. Thus, monogenic obesity studies might well reinstall the importance of rare nonsynonymous mutations of already known genes, especially melanocortin-4 receptor gene, in the general population. Nevertheless, additional genome-wide association analyses and replication are expected to confirm these first intuitions. SUMMARY Initial results both support the common variant-common disease hypothesis because at least one such variant exists in FTO, and also tone down its importance because such variants may be fewer than expected. Moreover, having a polymorphism associated with body weight is clearly not the end but rather the beginning of a long search for the gene function and pathway.
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Affiliation(s)
- Christian Dina
- CNRS 8090-Institute of Biology, Pasteur Institute, Lille, France.
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Loos RJF, Lindgren CM, Li S, Wheeler E, Zhao JH, Prokopenko I, Inouye M, Freathy RM, Attwood AP, Beckmann JS, Berndt SI, Jacobs KB, Chanock SJ, Hayes RB, Bergmann S, Bennett AJ, Bingham SA, Bochud M, Brown M, Cauchi S, Connell JM, Cooper C, Smith GD, Day I, Dina C, De S, Dermitzakis ET, Doney ASF, Elliott KS, Elliott P, Evans DM, Sadaf Farooqi I, Froguel P, Ghori J, Groves CJ, Gwilliam R, Hadley D, Hall AS, Hattersley AT, Hebebrand J, Heid IM, Lamina C, Gieger C, Illig T, Meitinger T, Wichmann HE, Herrera B, Hinney A, Hunt SE, Jarvelin MR, Johnson T, Jolley JDM, Karpe F, Keniry A, Khaw KT, Luben RN, Mangino M, Marchini J, McArdle WL, McGinnis R, Meyre D, Munroe PB, Morris AD, Ness AR, Neville MJ, Nica AC, Ong KK, O'Rahilly S, Owen KR, Palmer CNA, Papadakis K, Potter S, Pouta A, Qi L, Randall JC, Rayner NW, Ring SM, Sandhu MS, Scherag A, Sims MA, Song K, Soranzo N, Speliotes EK, Syddall HE, Teichmann SA, Timpson NJ, Tobias JH, Uda M, Vogel CIG, Wallace C, Waterworth DM, Weedon MN, Willer CJ, Wraight, Yuan X, Zeggini E, Hirschhorn JN, Strachan DP, Ouwehand WH, Caulfield MJ, Samani NJ, Frayling TM, Vollenweider P, Waeber G, Mooser V, Deloukas P, McCarthy MI, Wareham NJ, Barroso I, Jacobs KB, Chanock SJ, Hayes RB, Lamina C, Gieger C, Illig T, Meitinger T, Wichmann HE, Kraft P, Hankinson SE, Hunter DJ, Hu FB, Lyon HN, Voight BF, Ridderstrale M, Groop L, Scheet P, Sanna S, Abecasis GR, Albai G, Nagaraja R, Schlessinger D, Jackson AU, Tuomilehto J, Collins FS, Boehnke M, Mohlke KL. Common variants near MC4R are associated with fat mass, weight and risk of obesity. Nat Genet 2008; 40:768-75. [PMID: 18454148 DOI: 10.1038/ng.140] [Citation(s) in RCA: 927] [Impact Index Per Article: 57.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Accepted: 02/19/2008] [Indexed: 01/15/2023]
Abstract
To identify common variants influencing body mass index (BMI), we analyzed genome-wide association data from 16,876 individuals of European descent. After previously reported variants in FTO, the strongest association signal (rs17782313, P = 2.9 x 10(-6)) mapped 188 kb downstream of MC4R (melanocortin-4 receptor), mutations of which are the leading cause of monogenic severe childhood-onset obesity. We confirmed the BMI association in 60,352 adults (per-allele effect = 0.05 Z-score units; P = 2.8 x 10(-15)) and 5,988 children aged 7-11 (0.13 Z-score units; P = 1.5 x 10(-8)). In case-control analyses (n = 10,583), the odds for severe childhood obesity reached 1.30 (P = 8.0 x 10(-11)). Furthermore, we observed overtransmission of the risk allele to obese offspring in 660 families (P (pedigree disequilibrium test average; PDT-avg) = 2.4 x 10(-4)). The SNP location and patterns of phenotypic associations are consistent with effects mediated through altered MC4R function. Our findings establish that common variants near MC4R influence fat mass, weight and obesity risk at the population level and reinforce the need for large-scale data integration to identify variants influencing continuous biomedical traits.
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Affiliation(s)
- Ruth J F Loos
- MRC Epidemiology Unit, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
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Abstract
PURPOSE OF REVIEW Over the past two decades serious efforts has been invested in the search for genes that predispose to common obesity, but progress has been slow and success limited. Genome-wide association, however, has revived optimism. Here we review recent advances in the field of obesity genetics and discuss the most important findings of candidate gene, genome-wide linkage studies and genome-wide association studies. We conclude by speculating about the way forward in the near future. RECENT FINDINGS Although large-scale candidate gene studies have placed MC4R more firmly on the human obesity map, the major breakthrough in obesity genetics was the discovery of FTO through genome-wide association. Variants located in the first intron of FTO were unequivocally associated with a 1.67-fold increased risk for obesity and a 0.40-0.66 kg/m2 increase in body mass index. SUMMARY Genome-wide association promises to enhance greatly our understanding of the genetic basis of common obesity, although candidate gene studies will remain a valuable approach because they allow more detailed analyses of biologically relevant candidates. A key factor contributing to continued success lies in large-scale data integration through international collaboration, which will provide the sample sizes required to identify genetic association with conclusive evidence.
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Affiliation(s)
- Shengxu Li
- Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, UK
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Abstract
The molecular genetic analysis of obesity has led to the identification of a limited number of confirmed major genes. While such major genes have a clear influence on the development of the phenotype, the underlying mutations are however (extremely) infrequent and thus of minor clinical importance only. The genetic predisposition to obesity must thus be polygenic; a number of such variants should be found in most obese subjects; however, these variants predisposing to obesity are also found in normal weight and even lean individuals. Therefore, a polygene can only be identified and validated by statistical analyses: the appropriate gene variant (allele) occurs more frequently in obese than in non-obese subjects. Each single polygene makes only a small contribution to the development of obesity. The 103Ile allele of the Val103Ile single nucleotide polymorphism (SNP) of the melanocortin-4 receptor gene (MC4R) was the first confirmed polygenetic variant with an influence on the body mass index (BMI); the more common Val103 allele is more frequent in obese individuals. As determined in a recent, large-scaled meta-analysis the effect size of this allele on mean BMI was approximately -0.5 kg/m(2). The first genome-wide association study (GWA) for obesity, based on approximately 100,000 SNPs analyzed in families of the Framingham study, revealed that a SNP in the proximity of the insulin-induced gene 2 (INSIG2) was associated with obesity. The positive result was replicated in independent samples; however, some other study groups detected no association. Currently, a meta-analysis is ongoing; its result will contribute to the evaluation of the importance of the INSIG2 polymorphism in body weight regulation. SNP alleles in intron 1 of the fat mass and obesity associated gene (FTO) confer the most relevant polygenic effect on obesity. In the first GWA for extreme early onset obesity we substantiated that variation in FTO strongly contributes to early onset obesity.
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Affiliation(s)
- Anke Hinney
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, Essen, Germany.
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