Gender differences in the regulation of P450 aromatase expression and activity in human adipose tissue

OBJECTIVE: To investigate the hormonal regulation of P450 aromatase activity (responsible for the conversion of C19 androgens to C18 oestrogens) in human adipose tissue from men and pre- and post-menopausal women. SUBJECTS: Subcutaneous abdominal adipose tissue was obtained from 19 subjects: six pre-menopausal females (mean age 41.8 +/- (s.e.m.) 2.5; mean weight 76.01 +/- 5.6 kg), eight post-menopausal females (mean age 59.9 +/- 2.0; mean weight 63.5 +/- 2.6 kg), and five males (mean age 35.8 +/- 8.8; mean weight 78.5 +/- 7.8 kg) undergoing elective or cosmetic surgery. MEASUREMENTS: Cell viability and cell size were determined using staining techniques. RT-PCR was used to confirm the presence of aromatase, The regulation of aromatase activity was characterized using androstenedione as a substrate in a tritiated water release assay. Aromatase activity was analysed in abdominal subcutaneous stromal cells (ASC) and mature adipocytes (AD) cultured in serum-free medium with cortisol (10(-6)-10(-7) M), insulin (500 nM) or a combination of both. RESULTS: In ASC aromatase activity increased in females from 14.5 +/- 1.7 to 29.3 +/- 2.6 pmol/mg/h (n = 14, P < 0.05) and to 25.2 +/- 2.1 pmol/mg/h with cortisol (10(-7) M) and insulin, respectively (P<0.05). In males ASC basal aromatase activity (20.5 +/- 4.2 pmol/mg/h; n = 5) was inhibited by cortisol (10(-7) M) alone (12.3 +/- 1.8 pmol/mg/h) and in combination with insulin (6.6 +/- 1.2 pmol/mg/h; men vs women, P < 0.005). Aromatase activity in mature adipocytes was stimulated by cortisol plus insulin (P < 0.05) with no gender-specific differences. Treatment of ASC from both pre- and post-menopausal females with cortisol alone (10(-6)M; 10(-7)M) or in combination with insulin demonstrated significantly different aromatase regulation compared with male aromatase stromal cell regulation (P < 0.05); however there were no differences in aromatase regulation between pre- and post-menopausal females either in stromal cells or adipocytes. CONCLUSION: This study shows intrinsic gender differences in the regulation of aromatase, suggesting that differential enzyme regulation may affect sex steroid metabolism to alter the pattern of fat distribution between the sexes.