Twin Study On Physical Development Of Children And Adolescents

Children and adolescents are in the critical periods for the physical development.To investigate the genetic and environmental influences on the physical development of children and adolescents,and to assess the characteristic of gender,age and pubertal development,and to analyze the effect of the polymorphism of DRD4 gene exon III 48 bp VNTR on it,499 pairs of minimum samples and 1033 pairs of maximum samples aged 6 to 18 years old twins were enrolled in Beijing,Hohhot and Baotou of Inner Mongolia.The physical index included a total of 36 items,i.e.the original measurement items and the derivative index,and the Heath-Carter somatotype related index.According to the characteristics of the growth spurt,the samples were divided into four age groups.Zygosity identification was conducted using STR technique.The optimal model fitted by the Mx software was used to estimate the heritability of each index in different age groups.The DRD4 gene exon III 48 bp VNTR was divided by the PCR technique.The correlation between the polymorphism of DRD4 gene exon III 48 bp VNTR and each index was analyzed using GEE model.The results showed that:(1)All the physical index of children and adolescents in different age groups were fitted with ACES model except for the biepicondylar breadth of humeral and biepicondylar breadth of femur.For the most of index,age effect of three age groups twins before 15 years old(0.10-0.38)were more obvious than that of the 15-18 years old twins(0.00-0.08).(2)In the original measurement items,after adjustment for age,the heritabilities(0.63-0.79)of height,sitting height,lower limb length,upper limb length and body weight of 15-18 years old group twins showed generally higher than those of(0.31-0.71)other low age groups.For the each circumference index,the triceps skinfolds and scapular skinfolds,the heritability(0.29-0.65)of the 12-14 years old and 15-18 years old age groups twins showed lower than the twins of low age groups(0.30-0.87).(3)In the derivative index,after adjustment for age,the heritability of BMI(male 0.75,female 0.71),STR(male 0.72,female 0.69),and LBM(male 0.90,female 0.82)showed higher in the 15-18 years old age group,and the Iac(0.05-0.32),BF%(0.23-0.58),body fat(0.18-0.60)and WHR(0.04-0.29)showed a low heritability in each age group.The heritability of the Islel was relatively low(0.16-0.57)except for that of the 9-11 years old group twins(male 0.82,female 0.71).(4)After adjustment for age,the heritabilities of endomorphy,mesomorphy and ectonmorphy were increased with age(0.31-0.91).Except for the endomorphy of the 9-11 years old age group,the heritability of each somatotype factor of the female was lower than those of the male in each age group.(5)The polymorphism of DRD4 gene exon III 48 bp VNTR was correlated significantly with BMI,WHR,body weight,Cw,Ch,BF%,BF and endomorphy(P<0.05).The mean values of the above index of individuals carrying DRD4/5R+ were higher than those with other genotypes.All in all,the genetic effect of most physical index seems to be exerted when one person approaches the maturity.The development of body fat was influenced by environmental factors during the whole childhood and adolescence.The heritabilities of physical index of different developmental stages have differences.There might be a certain correlation between DRD4 gene polymorphism and the development of body fat in the twins.In this study,a large sample size of twins was enrolled as the subjects for the first time to investigate the effects of genetic and environmental factors on the physical development index of children and adolescents at different developmental stages.These results are important to reveal the influencing factors of physical development in children and adolescents and to make corresponding intervention measures for preventing obesity.It can also provide a scientific basis for the research and application of the related fields in the future.