Aerobic exercise and bone mineral density in middle-aged finnish men: a controlled randomized trial with reference to androgen receptor, aromatase, and estrogen receptor α gene polymorphisms

Abstract

Our aim was to investigate associations of the polymorphic loci of androgen receptor (AR), aromatase CYP19, and estrogen receptor α (ERα) genes with bone mineral density (BMD) in a four-year controlled randomized exercise intervention trial in Finnish middle-aged men. Additionally, we studied whether the gene polymorphisms affect circulating testosterone (T), estradiol (E 2), and sex hormone-binding globulin concentrations. The polymorphic CAG repeat of the AR gene, the TTTA repeat of the human aromatase gene, and the PvuII site of the ERα gene were analyzed. BMDs of the lumbar spine (L2–L4), femoral neck, and total proximal femur were measured with a dual-energy X-ray absorptiometry (DXA). In the exercise group, the subjects with the ERα gene PP or Pp genotypes showed an increase (+6.5 and +5.1%, respectively) in lumbar spine BMDs ( P = 0.007; repeated measures ANOVA) during intervention, while there was no change in the subjects with the pp genotype. The long TTTA repeat (TTTA 9–12) in aromatase gene was associated with greater height ( P = 0.026) and lower BMI ( P = 0.029) values than the short TTTA repeat (TTTA 6–8). With regard to the AR gene, no statistically significant differences in bone properties were found between the genotypes. There were no significant associations of any analyzed polymorphic sites with the serum sex steroid hormone concentrations in the exercise or reference group. In conclusion, the Finnish middle-aged men with ERα PP or Pp genotypes appear to have increased BMD values in the lumbar spine. This increase may reflect a predisposition to age-related degenerative changes in the spine. In addition, the AR CAG repeat and aromatase TTTA repeat do not modify the effect of regular aerobic exercise on BMD.