Beck: Aromatase and Testosterone Administration

ABSTRACT The influence of the aromatase enzyme in androgen-induced bone maintenance following skeletal-maturity remains somewhat unclear. Our purpose was to determine whether aromatase activity is essential to androgen-induced bone maintenance. 10 month old male Fisher 344 rats (n=73) were randomly assigned to receive Sham surgery, orchiectomy (ORX), ORX+anastrozole (AN; aromatase inhibitor), ORX+testosterone-enanthate (TE, 7.0mg/week), ORX+TE+AN, ORX+trenbolone-enanthate (TREN; non-aromatizable, non-estrogenic testosterone analogue; 1.0mg/week), or ORX+TREN+AN. ORX animals exhibited histomorphometric indices of high-turnover osteopenia and reduced cancellous bone volume compared to Shams. Both TE and TREN administration suppressed cancellous bone turnover similarly and fully prevented ORX-induced cancellous bone loss. TE and TREN treated animals also exhibited greater femoral neck shear strength than ORX animals. AN co-administration slightly inhibited the suppression of bone resorption in TE-treated animals, but did not alter TE-induced suppression of bone formation or the osteogenic effects of this androgen. In TREN treated animals, AN co-administration produced no discernible effects on cancellous bone turnover or bone volume. ORX animals also exhibited reduced levator ani/bulbocavernosus (LABC) muscle mass and elevated visceral adiposity. In contrast, TE and TREN produced potent myotrophic effects in the LABC muscle and maintained fat-mass at the level of Shams. AN co-administration did not alter androgen-induced effects on muscle or fat. In conclusion, androgens are able to induce direct effects on musculoskeletal and adipose tissue, independent of aromatase activity.