A quantitative trait locus on chromosome 18q for physical activity and dietary intake in Hispanic children.
OBJECTIVE
Genetic components of energy homeostasis contributing to childhood obesity are poorly understood. Genome scans were performed to identify chromosomal regions contributing to physical activity and dietary intake traits in Hispanic children participating in the VIVA LA FAMILIA Study.


METHODS
We report linkage findings on chromosome 18 for physical activity and dietary intake in 1030 siblings from 319 Hispanic families. Measurements entailed physical activity by accelerometry, dietary intake by two 24-hour recalls, and genetic linkage analyses using SOLAR software.


RESULTS
Significant heritabilities were seen for physical activity and dietary intake, ranging from 0.46 to 0.69, except for vigorous activity (h2 = 0.18). Percentage time in sedentary activity mapped to markers D18S1102-D18S64 on chromosome 18 [logarithm of the odds (LOD) score = 4.07], where melanocortin 4 receptor gene (MC4R) resides. Quantitative trait loci (QTLs) for total activity counts, percentage time in light or in moderate activity, and carbohydrate intake and percentage of energy intake from carbohydrates were detected in the same region (LOD = 2.28, 2.79, 2.2, 1.84, and 1.51, respectively). A novel loss of function mutation in MC4R (G55V) was detected in six obese relatives, but not in the rest of the cohort. Removal of these MC4R-deficient subjects from the analysis reduced the LOD score for sedentary activity to 3.94.


CONCLUSIONS
Given its role in the regulation of food intake and energy expenditure, MC4R is a strong positional candidate gene for the QTL on chromosome 18 detected for physical activity and dietary intake in Hispanic children.
Cai
Guowen
G
U.S. Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA. cai@bcm.edu
Cole
Shelley A
SA
Butte
Nancy
N
Bacino
Carlos
C
Diego
Vincent
V
Tan
Karen
K
Göring
Harald H
HH
O'Rahilly
Stephen
S
Farooqi
I Sadaf
IS
Comuzzie
Anthony G
AG
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics*; D015331:Cohort Studies; D004032:Diet; D004034:Diet Surveys; D002149:Energy Intake / Q000235:genetics* / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D008040:Genetic Linkage; D006306:Health Surveys; D006630:Hispanic or Latino / Q000235:genetics*; D006801:Humans; D008126:Lod Score; D008297:Male; D009765:Obesity / Q000453:epidemiology / Q000208:ethnology / Q000235:genetics; D040641:Quantitative Trait Loci; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics
C470072:MC4R protein, human; D044105:Receptor, Melanocortin, Type 4