title: Sex and genetic effects on upper and lower body fat and associations with diabetes in multigenerational families of African heritage.
abstract: Very few studies have comprehensively defined the genetic and environmental influences on body fat storage in the arms and legs and their association with diabetes, especially in families of African heritage. We analyzed body fat distribution by dual-energy x-ray absorptiometry (percentage total fat, percentage trunk fat, percentage arm fat, and percentage leg fat) and fasting serum glucose in 471 individuals (mean age, 43 years) from 8 multigenerational Afro-Caribbean families (mean family size = 51; 3535 relative pairs). Diabetes was inversely associated with percentage leg fat (P = .009) and, to some extent, positively associated with percentage arm fat independent of age, sex, and body size (P = .08), but not with anthropometric or dual-energy x-ray absorptiometric measures of total and central adiposity. Furthermore, percentage leg fat was inversely, whereas percentage arm fat was positively, associated with body mass index, waist circumference, and serum glucose (P < .01). Residual heritability (h2r) for arm and leg fat was significant (P < .01) and high: 62% (for percentage arm fat) and 40% (for percentage leg fat). Moreover, sex-specific h2r for leg fat was considerably higher (P = .02) in women than in men (h2r values, 58% vs 17%, respectively). Genetic correlation (rho(G)) between arm and leg fat was -0.61 (P < .01), suggesting that only 37% of the covariation between these 2 adipose tissue depots may be due to shared genetic influences. This study provides new evidence for a strong genetic and sex contribution to upper and lower body fat, with relatively little covariation between these traits due to shared genes. Our findings also suggest that, in this population, leg fat is associated with diabetes independent of overall adiposity.
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA. ivm1@pitt.edu
authors.forename: Iva
authors.initials: I
authors.lastname: Miljkovic-Gacic
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wang
authors.forename: Candace M
authors.initials: CM
authors.lastname: Kammerer
authors.forename: Clareann H
authors.initials: CH
authors.lastname: Bunker
authors.forename: Alan L
authors.initials: AL
authors.lastname: Patrick
authors.forename: Victor W
authors.initials: VW
authors.lastname: Wheeler
authors.forename: Lewis H
authors.initials: LH
authors.lastname: Kuller
authors.forename: Rhobert W
authors.initials: RW
authors.lastname: Evans
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zmuda
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000235:genetics*; D000368:Aged; D000369:Aged, 80 and over; D050218:Body Fat Distribution; D015992:Body Mass Index; D003920:Diabetes Mellitus / Q000208:ethnology* / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012727:Sex Characteristics