title: Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents.
abstract: This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were obtained by dual-energy X-ray absorptiometry. Multiple linear regression models were used to assess the PFM-bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age- and gender-specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole-body-less-head BA (WB-BA), lumbar spine BA (L(2)-L(4)-BA), total-hip BA (TH-BA), total-hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB-BA and L2-L(4)-BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM-bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors.
authors.affiliation: Mary Ann and J Milburn Smith Child Health Research Program, Department of Pediatrics, Northwestern University Feinberg School of Medicine and Children's Memorial Hospital and Children's Memorial Research Center, Chicago, IL 60614, USA.
authors.forename: Xiumei
authors.initials: X
authors.lastname: Hong
authors.forename: Lester M
authors.initials: LM
authors.lastname: Arguelles
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Hui-Ju
authors.initials: HJ
authors.lastname: Tsai
authors.forename: Yi-Hsiang
authors.initials: YH
authors.lastname: Hsu
authors.forename: Binyan
authors.initials: B
authors.lastname: Wang
authors.forename: Shanchun
authors.initials: S
authors.lastname: Zhang
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Li
authors.forename: Gengfu
authors.initials: G
authors.lastname: Tang
authors.forename: Xue
authors.initials: X
authors.lastname: Liu
authors.forename: Jianhua
authors.initials: J
authors.lastname: Yang
authors.forename: Xiping
authors.initials: X
authors.lastname: Xu
authors.forename: Craig
authors.initials: C
authors.lastname: Langman
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Wang
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000033:anatomy & histology*; D000293:Adolescent; D015519:Bone Density; D001842:Bone and Bones / Q000033:anatomy & histology*; D002681:China; D015331:Cohort Studies; D005260:Female; D006615:Hip / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D012424:Rural Population; D055815:Young Adult