CROSS-TRAIT FAMILIAL RESEMBLANCE FOR BODY-FAT AND BLOOD-PRESSURE - FAMILIAL CORRELATIONS IN THE QUEBEC FAMILY STUDY

Cross-trait resemblance between body fat and blood pressure (BP) was e xamined among families in the Quebec Family Study by using a bivariate familial correlation model assessing both intraindividual (e.g., comp arison of father's body fat with his own BP) and interindividual (e.g. , comparison of father's body fat with son's BP) cross-trait correlati ons. Each of six body-fat measures-(i) percent body fat, (ii) body-mas s index, (iii) the sum of six skinfolds, (iv) the ratio of the sum of six skinfolds to total fat mass, (v) the ratio of the trunk skinfold s um to the extremity skinfold sum, and (vi) the regression of the trunk -extremity skinfold ratio on the sum of six skinfolds-was analyzed sep arately with systolic BP and with diastolic BP. Results showed that (1 ) upper-body fat was the strongest interindividual correlate of BP (es pecially the correlation of trunk-extremity ratio with diastolic BP), suggesting shared pleiotropic genetic and/or common familial environme ntal effects; (2) summary body-fat measures either were inconsistent ( in the case of both percent body fat and sum of six skinfolds) or gave no evidence of interindividual cross-trait resemblance skinfolds and BP largely vanished once the skinfold sum was adjusted for fat mass, s uggesting that the intraindividual association may be mediated largely by the absolute amount of subcutaneous fat rather than by the subcuta neous proportion. Finally, the magnitude of the spouse resemblance for the trunk-extremity ratio with diastolic BP suggests that a significa nt proportion of the resemblance may be due to environmental influence s, In summary, our investigation confirms a heritable link between BP and truncal-abdominal fat as predicted by the metabolic-syndrome hypot hesis. That this result is obtained in primarily normotensive, nonobes e families, suggests the connection involves normal metabolic paths.