Aromatase activity in human adipose tissue stromal cells: effect of growth factors

Adipose tissue is a major, nonglandular site for the aromatization of androgens to estrogens. In this tissue, the aromatase activity resides primarily in the stromal cells, and we have used cultures of stromal cells to study the effects of insulin and insulin-like growth factor I (IGF-I) on aromatase activity. Adipose tissue, obtained during indicated surgery, was digested with collagenase, and the stromal cells were isolated and cultured. Aromatase activity was determined by measuring the tritiated water (3H2O) in the medium after incubating stromal cells with [1 beta-3H]androstenedione. Insulin and IGF-I had no effect on the aromatase activity in cultured adipose stromal cells at concentrations of 10 to 1,000 microU/ml. However, insulin (100 to 1,000 microU/ml) and IGF-I (500 ng/ml) markedly attenuated the stimulatory effect of (Bu)2cAMP, but significantly augmented the dexamethasone-stimulated aromatase activity. The greater effects of IGF-I compared with the effect of insulin are compatible with both effects being mediated through the IGF-I compared with the effect of insulin are compatible with both effects being mediated through the IGF-I receptor. In addition, the effects of insulin in attenuating the aromatase activity in adipose tissue could potentiate its role in hyperandrogenic syndromes in women.