儿童青少年双生子瘦素遗传度估计及影响因素分析

Heritability of leptin among child and adolescent twins and the analysis of associated factors

目的分析影响儿童青少年瘦素的遗传因素和环境因素,探讨性别、年龄和体质量指数(BMI)的作用,为儿童肥胖早期预防提供依据。方法选择6～18岁同性别双生子337对,平均年龄(12.3±3.5)岁,其中同卵双生子257对,异卵双生子80对。采用DNA微卫星多态性鉴定卵性。应用Mx结构方程模型分别计算年龄和BMI调整前后瘦素的遗传度,并检验性别、年龄和BMI对于模型的作用。结果不同性别间身高、体重和瘦素水平差异均有统计学意义(P值均<0.05)。相关分析显示,瘦素水平与性别、年龄和BMI相关(P值均<0.01)。遗传分析发现,调整前年龄方差在女生中影响较大,而男生则受共同环境方差影响较大。调整后男生特异性性别方差降低,最适模型为ACE(scale)模型。男、女生瘦素遗传模型一致,遗传度为20%。结论儿童青少年人群中瘦素水平与性别、年龄和BMI相关。瘦素受遗传和环境因素共同影响。调整年龄及BMI后,瘦素遗传度不受性别影响。

Objective To study the contribution of genetic and environmental factors on the variation of leptin, and the effect of sex, age and body mass index （ BMI ）. Methods A total of 337 healthy same-sex twin pairs were studied, including 257 monozygotic （ MZ ） and 80 dizygotic （DZ） twin pairs aged 6-18, mean age was （ 12.3±3.5 ） years. Microsatellite polymm＇phism was used to diagnose zygosity of twins. Model-fitting method using Mx package was performed to analyze the genetic and environmental variance of leptin, before and after adjusting age and BMI. The effect of sex, age and BMI on the model was tested. Results There was statistical significant differences between genders on height, weight and leptin levels（ P〈0.05 ）. Correlative analysis indicated that leptin level was correlated with sex, age and BMI（ P〈0.01 ）. Genetic analysis showed that the age variance contributed a lot in the total leptin variance among girls while the environmental variance contributed a lot among boys before the adjustment for age and BMI. After the adjustment the sex-specific additive genetic variance in male decreased and the best-fit model was ACE （scale） among both boys and girls. The heritability of leptin was 20%. Conclusion Leptin level is associated with sex, age and BMI among child and adolescent. Gene and environment influenced leptin together while environment seemed play a more important role relatively. The heritability of leptin is not affected by sex after the adjustment for age and BMI.