Silventoinen Karri, Magnusson Patrik K E, Tynelius Per, Kaprio Jaakko, Rasmussen Finn
Department of Public Health, University of Helsinki, Helsinki, Finland.
Genet Epidemiol. 2008 May;32(4):341-9. doi: 10.1002/gepi.20308.
Moderate heritability for skeletal muscle strength has been reported in twin studies, but genetic co-variation between muscle strength at different parts of body and body size is not well known. Further, representativeness of twin cohorts needs to be critically evaluated. Height, weight, elbow flexion, hand grip and knee extension strength were measured in young adulthood in 1,139,963 Swedish men born between 1951 and 1976. We identified 154,970 full-brother pairs and 1582 monozygotic (MZ) and 1864 same-sex dizygotic (DZ) complete twin pairs. The data were analyzed using quantitative genetic modeling for twin and family data. Twins compared to singletons and MZ twins compared to DZ twins were shorter, lighter and had lower muscle strength. In singletons, there was more variation in weight and the strength measures compared to twins with known zygosity but not when compared to twins with unknown zygosity. Full-sib correlations for these traits were lower than DZ correlations. Additive genetic factors explained 81% of variation in height, 59% in body mass index and 50-60% in the strength measures. Additive genetic correlations varied from 0.13 between height and elbow flexion strength to 0.78 between elbow flexion and hand grip strength. Our results suggest that extra variation may exist in general populations not found in twin samples, probably because of selection due to non-participation. This may have inflated heritability estimates in previous twin studies. Nonetheless, we showed that genetic factors affect muscle strength and part of these genes are common to different strength indicators and body size.
双胞胎研究报告了骨骼肌力量的中度遗传力，但身体不同部位的肌肉力量与体型之间的遗传协变尚不清楚。此外，双胞胎队列的代表性需要进行严格评估。对1951年至1976年出生的1139963名瑞典男性在青年期测量了身高、体重、肘部屈曲、握力和膝关节伸展力量。我们识别出154970对全兄弟对以及1582对同卵双胞胎（MZ）和1864对同性异卵双胞胎（DZ）完整双胞胎对。使用双胞胎和家庭数据的定量遗传模型对数据进行分析。与单胎相比，双胞胎以及与DZ双胞胎相比，MZ双胞胎更矮、更轻且肌肉力量更低。在单胎中，与已知合子性的双胞胎相比，体重和力量测量值的变异更大，但与合子性未知的双胞胎相比则不然。这些性状的全同胞相关性低于DZ相关性。加性遗传因素解释了身高变异的81%、体重指数变异的59%以及力量测量值变异的50 - 60%。加性遗传相关性从身高与肘部屈曲力量之间的0.13到肘部屈曲与握力之间的0.78不等。我们的结果表明，一般人群中可能存在双胞胎样本中未发现的额外变异，这可能是由于不参与导致的选择所致。这可能在先前的双胞胎研究中夸大了遗传力估计值。尽管如此，我们表明遗传因素会影响肌肉力量，并且这些基因中的一部分对于不同的力量指标和体型是共有的。
