No association of sequence variants in the neuropeptide Y2 receptor (NPY2R) gene with early onset obesity in Germans.

The neuropeptide Y2 receptor (NPY2R) has been implicated in body weight regulation both in humans and rodents. We investigated if genetic variation in the NPY2R gene is associated with obesity in German extremely obese children and adolescents. The coding sequence and predicted promoter of the NPY2R were screened for variations. Subsequently, case-control (184 extremely obese children and adolescents: mean body mass index [BMI] 35.7+/-6.1 kg/m(2), 277 lean students: mean BMI 18.2+/-1.1 kg/m(2)) and family-based (770 parental pairs with a total of 1081 obese off-spring) association analyses were conducted in independent samples. We identified 14 sequence variants (seven novel variants including two coding variants c.369C >T and c.834G >A), five of which were detected once, each in the heterozygous state. In case-control analyses we did not detect association with obesity for seven common (minor allele frequency >1%) variants (all p >0.16); additional gender-stratified analyses employing several genetic models and haplotype analyses were also nonsignificant. Furthermore, in a family-based association study for coding synonymous SNP rs1047214 (Ile195) we found no evidence for a transmission disequilibrium in the total or in the gender-stratified PDT analyses (all p >0.50). In conclusion, we did not find evidence for an involvement of genetic variation in the NPY2R in early onset obesity in German samples.

A novel mutation Thr162Arg of the melanocortin 4 receptor gene in a Spanish children and adolescent population.

OBJECTIVE: The melanocortin 4 receptor gene (MC4R) is involved in body weight regulation. While many studies associated MC4R mutations with childhood obesity, information on MC4R mutations in Spanish children and adolescents is lacking. Our objective was to screen a population of children and adolescents from the north of Spain (Navarra) for MC4R mutations and to study the phenotypes of carriers and their families. In addition, functional assays were performed for a novel MC4R mutation. METHODS: The study was composed of 451 Spanish children and adolescents (49% boys), aged 5-18 year. According to the International Obesity Task Force (IOTF) criteria, the groups included 160 obese, 132 overweight and 159 normal-weight control subjects. RESULTS: One novel (Thr162Arg) and three known nonsynonymous mutations in the MC4R gene (Ser30Phe, Thr150Ile, Ala244Glu) were detected heterozygously. The MC4R mutations were found in three male (one obese and two overweight) and two female subjects (one obese and one overweight). The novel mutation did not appear to lead to an impaired receptor function. An unequivocal relationship of MC4R mutations with obesity in pedigrees together with an impaired function of the encoded receptor could not be established for any of the mutations. CONCLUSIONS: The presence of heterozygous MC4R mutations in obese and overweight subjects indicates that these mutations may be a susceptibility factor for obesity development, but lifestyle factors, such as exercise or sedentary activities, may modify their effect.

A novel non-synonymous mutation in the melanocortin-4 receptor gene (MC4R) in a 2-year-old Austrian girl with extreme obesity.

BACKGROUND: Functionally relevant mutations in the melanocortin-4 receptor gene ( MC4R) currently display the most common major gene/allele effect on extreme obesity. OBJECTIVE: Mutation screen of the MC4R in consecutively ascertained Austrian children and adolescents with severe obesity, to analyse the phenotype of mutation carriers and to functionally characterise novel mutations. SUBJECTS AND METHODS: 102 unrelated extremely obese children and adolescents (mean BMI 33.5+/-7.1 kg/m(2), >97th centile; mean age 13.8+/-4.1 yr) and 109 parents (79 mothers/30 fathers) of 88 of these patients were studied. The MC4R coding region was screened using denaturing high-performance liquid chromatography (dHPLC); PCR products of aberrant dHPLC pattern were re-sequenced. Signal transduction properties of mutant MC4R was investigated by challenge with the highly potent agonist NDP-alpha-MSH. Cell surface expression was determined by ELISA. Magnetic resonance imaging (MRI) of the central nervous system (CNS) was applied to a 2.3 year old index patient. Body fat and bone mineral content were assessed in three of the five mutation carriers by dual energy x-ray absorptiometry (DEXA). Oral glucose tolerance test (OGTT) was applied to some mutation carriers. RESULTS: Heterozygous carriers of two non-synonymous mutations, two polymorphisms and a silent variation were identified within the study group. (1) A novel MC4R non-synonymous mutation (S136F) was detected in a 2.3 year old girl with extreme obesity (BMI 33.2 kg/m(2), >99th centile); (2) a previously described non-synonymous mutation (V253I) was identified in an obese mother (BMI 28.1 kg/m(2)) who did not transmit this mutation to her extremely obese son; (3) two known polymorphisms (V103I and I251L) were also identified; and (4) one obese mother was carrier of a silent variation (c.594C>T; I198). Co-segregation of S136F with the obesity phenotype was shown for three generations. IN VITRO functional studies revealed a complete loss of signal transduction activity of the mutant receptor while cell surface expression was only slightly reduced compared to the wild-type receptor. CONCLUSIONS: We detected a novel non-synonymous mutation (S136F) that leads to a complete loss of MC4R function IN VITRO.

Association of the melanocortin 4 receptor with feed intake and daily gain in F2 Mangalitsa x Piétrain pigs.

The melanocortin 4 receptor (MC4R) is a key factor in the regulation of energy balance and body weight. Hence it is a candidate for feed intake and energy homeostasis-related traits. Studies in humans and swine have revealed several sequence variants in the gene that are associated with some of these traits. In pigs the coding non-synonymous missense variant Asp298Asn in MC4R has been associated with feed intake, fatness and growth. Here we confirm the association of this Piétrain-derived polymorphism with feed intake and daily gain in the F2 generation of a Mangalitsa x Piétrain cross. In one Piétrain founder animal, we detected an additional non-synonymous missense variant Arg236His. Thus, the MC4R gene could be a useful marker for increased growth in the relatively slow-growing Piétrain breed.

Mutation screen of the brain derived neurotrophic factor gene (BDNF): identification of several genetic variants and association studies in patients with obesity, eating disorders, and attention-deficit/hyperactivity disorder.

Several lines of evidence indicate an involvement of brain derived neurotrophic factor (BDNF) in body weight regulation and activity: heterozygous Bdnf knockout mice (Bdnf(+/-)) are hyperphagic, obese, and hyperactive; furthermore, central infusion of BDNF leads to severe, dose-dependent appetite suppression and weight loss in rats. We searched for the role of BDNF variants in obesity, eating disorders, and attention-deficit/hyperactivity disorder (ADHD). A mutation screen (SSCP and DHPLC) of the translated region of BDNF in 183 extremely obese children and adolescents and 187 underweight students was performed. Additionally, we genotyped two common polymorphisms (rs6265: p.V66M; c.-46C > T) in 118 patients with anorexia nervosa, 80 patients with bulimia nervosa, 88 patients with ADHD, and 96 normal weight controls. Three rare variants (c.5C > T: p.T2I; c.273G > A; c.*137A > G) and the known polymorphism (p.V66M) were identified. A role of the I2 allele in the etiology of obesity cannot be excluded. We found no association between p.V66M or the additionally genotyped variant c.-46C > T and obesity, ADHD or eating disorders. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html.

Binge-eating episodes are not characteristic of carriers of melanocortin-4 receptor gene mutations.

Recently, Branson and coworkers reported a strong association between binge-eating disorder (BED) and variants in the melanocortin-4 receptor gene (MC4R). In the current study, we compared the eating behavior of 43 obese probands with functionally relevant MC4R mutations and of 35 polymorphism carriers (V103I or I251L) with wild-type carriers. The module for eating disorders of the Composite International Diagnostic Interview was used to identify binge-eating behavior. The Three-Factor Eating Questionnaire and the Leeds Food Frequency Questionnaire were used to assess restrained eating, disinhibition, hunger and percent total energy intake as fat. No significant differences between carriers of MC4R variants and wild-type carriers were detected. In particular, we found no evidence for an increased rate of binge-eating behavior in obese carriers of MC4R variants. Our findings do not support the strong association between BED and MC4R carrier status.