Lapauw B, Goemaere S, Crabbe P, Kaufman J M, Ruige J B
Department of Endocrinology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
Eur J Endocrinol. 2007 Mar;156(3):395-401. doi: 10.1530/EJE-06-0607.
The androgen receptor (AR) gene contains a CAG repeat polymorphism coding for a polyglutamine chain, the length of which is inversely correlated with AR transcriptional activity. We explored whether this polymorphism modulates the activities of testosterone (T) related to body composition in elderly men.
We performed cross-sectional analyses using data from a 4-year follow-up study in community-dwelling men aged 75-89 years (n=159).
Body composition was assessed by dual-energy X-ray absorptiometry and its relation with T and the AR gene CAG repeat length was assessed by multiple linear regression analyses, adjusting for confounding and exploring effect modification.
AR gene CAG repeat length was not directly related to body composition, either with or without adjustment for confounding variables like age, weight, total T or sex hormone binding globulin (SHBG) levels. However, exploration of effect modification showed that CAG repeat length modulated the relation between T and body composition (standardized regression coefficients of interaction term: beta=0.12, P<0.01 and beta=-0.09, P<0.05 for fat-free mass and fat mass respectively). These results were confirmed using similar models and data of mean T, SHBG and weight of the 2 years' preceding body composition assessment instead of data of the same year (beta=0.09, P<0.05 and beta=-0.09, P<0.05 respectively).
These findings suggest that the AR gene CAG polymorphism contributes, albeit modestly, to the between-subject variation of T action on body composition in community-dwelling elderly men.
雄激素受体（AR）基因包含一个编码聚谷氨酰胺链的CAG重复多态性，其长度与AR转录活性呈负相关。我们探讨了这种多态性是否调节老年男性中与身体成分相关的睾酮（T）活性。
我们使用了一项针对75 - 89岁社区居住男性（n = 159）的4年随访研究数据进行横断面分析。
通过双能X线吸收法评估身体成分，并通过多元线性回归分析评估其与T以及AR基因CAG重复长度的关系，对混杂因素进行调整并探索效应修正。
无论是否对年龄、体重、总T或性激素结合球蛋白（SHBG）水平等混杂变量进行调整，AR基因CAG重复长度均与身体成分无直接关系。然而，效应修正探索表明，CAG重复长度调节了T与身体成分之间的关系（交互项的标准化回归系数：无脂肪量和脂肪量的β分别为0.12，P < 0.01和β = -0.09，P < 0.05）。使用类似模型以及身体成分评估前两年的平均T、SHBG和体重数据而非同年数据，这些结果得到了证实（β分别为0.09，P < 0.05和β = -0.09，P < 0.05）。
这些发现表明，AR基因CAG多态性尽管作用不大，但对社区居住老年男性中T对身体成分作用的个体间差异有贡献。
