GENETIC PLEIOTROPY FOR RESTING METABOLIC-RATE WITH FAT-FREE MASS AND FAT MASS - THE QUEBEC FAMILY STUDY

Shared genetic and familial environmental causes for the associations among resting metabolic rate (RMR), fat-free mass (FFM), and fat mass (FM) were investigated in families participating in phase 2 of the Que bec Family Study, A multivariate familial correlation model assessing the pattern of significant cross-trait correlations between family mem bers (e.g., RMR in parents with FFM in offspring) was used to infer th e etiology of the associations, For each of FM and FFM with RMR, signi ficant sibling, parent-offspring, and intraindividual cross-trait corr elations suggest the associations are familial, Furthermore, the lack of significant spouse cross-trait correlations suggests that the famil ial aggregation is primarily genetic, Bivariate heritability estimates suggest that as much as 45% to 50% of the shared variance between FFM and RMR may be genetic, and as much as 28% to 34% for FM and RMR, Thi s study supports the notion that the gene(s) affecting each of FFM and FM also influence the RMR, Moreover, the lack of any familial associa tions between FFM and FM suggests that the effects of each body size c omponent on RMR are independent, i.e., more than one genetic source on the RMR-body size association, The possibility that RMR is an oligoge nic trait (i.e., more than one underlying genetic etiology) should be further investigated using more complex multivariate segregation metho ds until specific genes can be tested.