Genetic and Environmental Influences on Children's Dietary Intakes, Growth and Health During Puberty: A Population-Based Twin Study in China
2219.ris
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Background. The relative genetic and environmental influences on children's dietary intakes, body composition (BC) and pubertal insulin resistance (IR) are poorly understood, especially among Asians. This thesis examined the influences of genetic and environmental factors on usual dietary intakes, BC phenotypes and the association between sexual maturation (SM) and IR among Chinese children. Methods. We surveyed 622 Chinese twins (162 monozygotic (MZ) pairs and 149 dizygotic (DZ) pairs, 298 boys and 324 girls) aged 7-15 y and their mothers between Dec. 2009 and Jan. 2010. Child dietary intakes were assessed using a validated 145-item food frequency questionnaire. Anthropometric and laboratory measures included height, weight, waist circumference, fasting glucose and insulin. Body fat percentage (BF%) was measured by bioelectric impedance analysis. SM (Tanner stages) was assessed by pediatricians. Results. In boys, genetic contributions to dietary intake ranged 18.8%-58.4% for nutrients and 1.1%-86.9% for food groups. In girls, they were 5.1%-38.7% and 12.6%-94.6%, respectively. Five food patterns were obtained in each sex and their genetic components were moderate or strong (32.5%-67.9% in boys, 53.1%-89.8% in girls). Estimated heritabilities for anthropometric and BC measures ranged from 16.3% (waist-to-height-ratio) to 28.4% (BMI), 35.3% (BF%) and 68.0% (fat mass). After additional adjustment for physical activity and dietary intake factors, the additive genetic factors remained statistically significant for BC indices (p<0.05), except for fat-free mass index and waist-to-height-ratio. Girls undergoing early SM had higher BMI, BF% and IR, but not boys. Half of the effects of early SM on IR were mediated through adiposity. The heritability of HOMA-IR was much higher in females who underwent early SM (72.6%) than females with normal SM (0%). A significant relationship between SM and IR existed both within and between twin pairs among girls, but only between pairs among boys. Conclusions. Genetic factors affected usual dietary intake of nutrients and food groups, as well as BC and IR phenotypes among Chinese children. Early SM magnified genetic effects on IR among girls. Associations between SM and IR were affected by individual and shared environments in girls, shared environments in boys, and appeared to be mediated through genetic factors in both sexes.
THES
Li, Ji
Wang, Youfa Beaty Terri
2011
3483273
246
The Johns Hopkins University
Ann Arbor
2219