SEGREGATION ANALYSIS OF ABDOMINAL VISCERAL FAT - THE HERITAGE FAMILY STUDY

A major gene hypothesis for abdominal visceral fat (AVF) level, both b efore and after adjustment for total body fat mass, was investigated i n 86 white families who participated in the HERITAGE Family Study. In this study, sedentary families were tested for a battery of measures ( baseline), endurance exercise trained for 20 weeks, and then remeasure d again, The baseline measures reported here are unique in that the va riance due to a potentially important environmental factor (activity l evel) was limited. AVF area was assessed at L4 to L5 by the use of com puterized tomography scan, and total body fat mass was assessed with u nderwater weighing, For fat mass, a putative locus accounted for 64% o f the variance, but there was no evidence of a multifactorial componen t (i.e., no polygenic and/or common familial environmental effects). F or AVF area, both a major gene effect accounting for 54% of the varian ce and a multifactorial component accounting for 17% of the variance w ere significant. However, after AVF area was adjusted for the effects of total level of body fat, the support for a major gene was reduced, In particular, there was a major effect for fat mass-adjusted AVF area , but it was not transmitted from parents to offspring (i.e., the thre e transmission probabilities were equal). The importance of this study is twofold. First, these results confirm a previous study that sugges ted that there is a putative major locus for AVF and for total body fa t mass, Second, the findings from the HERITAGE Family Study suggest th at the factors underlying AVF area in sedentary families may be simila r to those in the population at large, which includes both sedentary a nd active families. Whether the gene(s) responsible for the high level s of AVF area is the same as that which influences total body fat cont ent remains to be further investigated.