Effect of the melanocortin-3 receptor Thr6Lys and Val81Ile genetic variants on body composition and substrate oxidation
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ORIGINAL PAPER
Effect of the melanocortin-3 receptor Thr6Lys and Val81Ile genetic variants on body composition and substrate oxidation in Chilean obese children Ana M. Obregón & Erik Diaz & Jose L. Santos
Received: 29 April 2011 / Accepted: 31 August 2011 / Published online: 8 October 2011 # University of Navarra 2011
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 Role of each author Ana M. Obregón carried out the research, obtaining part of funding for its implementation and performed most important part of the laboratory analysis. She conducted the statistical analysis, participated in interpretation of the data results, and generated the first draft of the manuscript. Prof. E. Diaz participated in the generation and collection of the data and support in the academic and technical information concerning substrate oxidation. Prof. J.L. Santos was the leader of this research project, coordinating all aspects of the investigation from study design to data interpretation and manuscript redaction. A. M. Obregón : J. L. Santos (*) Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, Avenida Libertador Bernardo O’Higgins 340, Santiago 8331150, Chile e-mail: [email protected] A. M. Obregón e-mail: [email protected] A. M. Obregón : E. Diaz Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile E. Diaz e-mail: [email protected]
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–gendermatched 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 airdisplacement 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 n
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