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: Ana M Obregón, Erik Diaz, Jose L Santos
• Journal: Journal of physiology and biochemistry (J Physiol Biochem) Vol. 68 Issue 1 Pg. 71-6 (Mar 2012) ISSN: 1877-8755 [Electronic] Spain
• PMID: 21983807 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• MC3R protein, human
• Receptor, Melanocortin, Type 3
• Glucose

Topics

• Body Composition (genetics)
• Body Mass Index
• Case-Control Studies
• Child
• Chile
• Energy Metabolism
• Genetic Association Studies
• Glucose (metabolism)
• Haplotypes
• Heterozygote
• Humans
• Mutation, Missense
• Obesity (genetics, metabolism, physiopathology)
• Oxidation-Reduction
• Physical Exertion
• Polymorphism, Single Nucleotide
• Receptor, Melanocortin, Type 3 (genetics)