Search

Abstract: Objective: Evidence of a genetic basis of metabolic risk factors (MRFs) is growing. Studies examining the genetic and environmental basis of the clustering of MRFs, grouped together in the metabolic syndrome (MetS), are however sparse. The aim of this study therefore was to study the heritabilities of the MRFs and the genetic and environmental correlations between the MRFs. Methods: Study participants were 768 Caucasian twins coming from 418 pairs (18–34 years). MRFs were those included in the National Cholesterol Education Program Adult Treatment Panel III definition of the MetS. Multivariate path analysis on the continuous MRFs of the MetS was implemented. Results: Heritabilities ranged between 47.0% and 80.2% (men) and 58.5% and 77.9% (women) for the individual MRFs. Evidence was found for overarching genetic (A) and environmental (E) sources of variance, both however loading mainly on waist circumference. Furthermore, the model included a ‘lipids’ and a ‘blood pressure’-factor both in part attributable to A and E. The majority of the variance however was MRF-specific. Conclusion: Based on our sample of young adults with a low prevalence of the MetS, it can be concluded that both genes and environment contribute significantly to the clustering of the MRFs although the majority of the variation is MRF-specific. Therefore, future QTL searches in young adults may want to focus on MRF-specific loci, rather than ‘cluster-phenotypes’ such as the MetS. [Copyright &y& Elsevier]

The purpose of this study was to determine whether the observed phenotypic stability in static strength during adolescence, as measured by interage correlations in arm pull, is mainly caused by genetic and/or environmental factors. Subjects were from the Leuven Longitudinal Twin Study (n = 105 pairs, equally divided over 5 zygosity groups). Arm-pull data were aligned on age at peak height velocity to attenuate the temporal fluctuations in interage correlations caused by differences in timing of the adolescent growth spurt. Developmental genetic models were fitted using structural equation modeling. After the data were aligned on age at peak height velocity, the annual interage correlations conformed to a quasi-simplex structure over a 4-yr interval. The best-fitting models included additive genetic and unique environmental sources of variation. Additive genetic factors that already explained a significant amount of variation at previous measurement occasions explained 44.3 and 22.5% of the total variation at the last measurement occasion in boys and girls, respectively. Corresponding values for unique environmental sources of variance are 31.2 and 44.5%, respectively. In conclusion, the observed stability of static strength during adolescence is caused by both stable genetic influences and stable unique environmental influences in boys and girls. Additive genetic factors seem to be the most important source of stability in boys, whereas unique environmental factors appear to be more predominant in girls. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether the observed phenotypic stability in explosive strength during adolescence, as measured by inter-age correlations in vertical jump (VTJ), is mainly caused by genetic and/or environmental factors. Methods: Subjects are from the Leuven Longitudinal Twin Study (LLTS) ( n = 105 pairs, equally divided over five zygosity groups). VTJ data were aligned on age at peak height velocity (APHV) to attenuate the temporal fluctuations in inter-age correlations caused by differences in timing of the adolescent growth spurt. Simplex models were fitted using structural equation modelling. Results: After aligning the data on APHV, the annual inter-age correlations show a clear simplex structure over a 4 year interval. The best fitting models included additive genetic and unique environmental sources of variation. Heritability estimates ranged between 60.8% (CI 37.7%–77.2%) and 87.3% (CI 74.2%–94.0%) for boys and between 76.5% (CI 56.7%–89.0%) and 88.6% (CI 77.8%–94.1%) for girls. Up to 56.4% and 62.8% of the total variation at the last measurement occasion is explained by additive genetic factors that already explained a significant amount of variation at previous measurement occasions in boys and girls respectively. It thus can be concluded that the observed stability of explosive strength during adolescence is mainly caused by a stable genetic influence in boys and girls. Conclusions: Additive genetic factors seem to be the main cause of the observed phenotypic stability in VTJ performance in boys and girls during adolescence. [ABSTRACT FROM AUTHOR]