Familial resemblance for plasma leptin: sample homogeneity across adiposity and ethnic groups.
OBJECTIVE
Previous studies show a wide range in the percentage of variance in leptin levels attributable to genetic factors. These studies differ markedly with respect to ethnicity, study design, and statistical methodology. Therefore, the purpose of this study was to investigate heterogeneity hypotheses across ethnic groups and by adiposity level, using the same statistical methods.


METHODS
Samples included black vs. white (HERITAGE Family Study) and random vs. obese (Québec Family Study) individuals from 432 families (1432 individuals). Heritability for leptin, alternatively adjusted for age and sex and then for age, sex, and adiposity was estimated with the use of familial correlations. Heterogeneity in the magnitude of the familial resemblance between samples and the effect of adjusting for adiposity was explored.


RESULTS
Heritability did not vary across samples stratified by adiposity level or ethnic group or across adjustment schemes. Maximal heritability, the percentage of additive phenotypic variability due to all familial sources, was 32%.


CONCLUSIONS
Whereas leptin and adiposity were highly correlated within individuals, removing the effects of adiposity did not significantly alter the magnitude of the familial component for leptin. Moreover, this effect did not vary as a function of ethnicity (black vs. white) or adiposity level. Thus, no evidence for heterogeneity was detected. However, a comparison among previous studies raises questions concerning possible genetic heterogeneity in other ethnic groups in which complex interactions among leptin, adiposity, and diabetes status may be important.
Rice
Treva
T
Division of Biostatistics, Departments of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA. treva@wubios.wustl.edu
Chagnon
Yvon C
YC
Borecki
Ingrid B
IB
Pérusse
Louis
L
Collier
Greg
G
Gagnon
Jacques
J
Leon
Arthur S
AS
Skinner
James S
JS
Wilmore
Jack H
JH
Bouchard
Claude
C
Rao
D C
DC
D000273:Adipose Tissue; D000328:Adult; D044383:Black People; D001823:Body Composition / Q000235:genetics*; D005190:Family; D005215:Fasting; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000235:genetics; D010641:Phenotype; D044469:Racial Groups; D012727:Sex Characteristics; D012885:Skinfold Thickness; D044465:White People
D007328:Insulin; D020738:Leptin