title: Effect of the melanocortin-3 receptor Thr6Lys and Val81Ile genetic variants on body composition and substrate oxidation in Chilean obese children.
abstract: Mice genetically deficient in the melanocortin-3 receptor gene are characterized by normal body weight, increased body fat, mild hypophagia, reduced locomotor activity, and increased respiratory quotient compared with wild-type mice. In humans, the 6Lys-81Ile haplotype of melanocortin-3 receptor (MC3R) gene has been associated with childhood obesity, higher body fat percentage, and reduced fat oxidation compared to non-carriers. The aim of this study was to evaluate the association between MC3R 6Lys-81Ile haplotype with body composition and substrate oxidation in response to moderate exercise in obese children. Eight Chilean obese children (aged 8-12) carriers of MC3R 6Lys-81Ile haplotype were compared with eight age-gender-matched obese non-carriers. Children were identified through a previous cross-sectional study on genetic determinants of childhood obesity (n = 229). Genotypes for MC3R Thr6Lys and Val81Ile were determined by polymerase chain reaction-restriction fragment length polymorphism. Body composition was assessed by the four-compartment model (dual-energy X-ray absorptiometry, total body water by the deuterium dilution technique, and total fat mass by air-displacement plethysmography). Substrate oxidation was assessed by indirect calorimetry in response to moderate exercise (60% VO(2 max)). Wilcoxon matched-pairs test was used to compare quantitative variables. No significant differences among carriers and non-carriers were found in anthropometrical and body composition measurements. The Carriers of the 6Lys-81Ile haplotype showed higher respiratory quotient (p = 0.06) and a significantly higher glucose oxidation (p = 0.01) compared with non-carriers after standardization for fat-free mass. Our results are consistent with a possible participation of MC3R 6Lys-81Ile variants in glucose oxidation in response to moderate exercise.
authors: Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, Avenida Libertador Bernardo O'Higgins 340, Santiago 8331150, Chile. aniobregon@gmail.com
authors: Ana M
authors: AM
authors: Obregón
authors: Erik
authors: E
authors: Diaz
authors: Jose L
authors: JL
authors: Santos
mesh_terms: D001823:Body Composition / Q000235:genetics*; D015992:Body Mass Index; D016022:Case-Control Studies; D002648:Child; D002677:Chile; D004734:Energy Metabolism; D056726:Genetic Association Studies; D005947:Glucose / Q000378:metabolism; D006239:Haplotypes; D006579:Heterozygote; D006801:Humans; D020125:Mutation, Missense; D009765:Obesity / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D010084:Oxidation-Reduction; D005082:Physical Exertion; D020641:Polymorphism, Single Nucleotide; D044104:Receptor, Melanocortin, Type 3 / Q000235:genetics*
chemical_list: C505392:MC3R protein, human; D044104:Receptor, Melanocortin, Type 3; D005947:Glucose