Androgens ➔ Estrogens
aromatase enzyme
Aromatase is responsible for the production of 18-carbon estrogens from 19-carbon androgen steroids:TESTOSTERONE and ANDROSTENEDIONE - the gene CYP19 encodes the aromatase enzyme (a member of the Cytochrome P450 enzyme superfamily).
(In the female, FSH increases aromatase activity, enhancing this conversion)
Different body tissues produce estrogen via aromatase response to different activating promoters - tissue-specific regulation of CYP19 (aromatase gene) expression is achieved through the use of distinct promoters controlled by hormones and other factors, including:
• Glucocorticoids (E.g. CORTISOL, the drug prednisone),
• Class 1 cytokines: E.g. IFN-γ, IL-2, IL-6, IL-11, and TNF-α(present in infection);
• Retinoids. E.g. vitamin A
• FSH
Aromatase Gene (CYP19) Expression Regulators |
||
|
Location |
Promoter |
Promoter regulated by: |
|
Ovaries |
Cyclic AMP via the proximal promoter II |
FSH |
|
Placenta |
distal promoter I.1 |
Retinoids |
|
Adipose tissue, skin fibroblasts, bone |
distal promoter I.4 |
Glucocorticoids and class 1 cytokines E.g. tumor-derived PGE2 is the major factor stimulating local aromatase expression in the breast fat of cancer patients. |
- Tissues having beneficial estrogen presence - includes gonads, brain, adipose tissue (E.g. found in the breast), placenta, blood vessels, skin, bone, and endometrium.
- Health conditions where inappropriately high levels of aromatase are present in tissues - endometriosis, uterine fibroids, breast cancer(enhanced aromatase activity found in breast fat)and endometrial cancer.
Aromatase inhibitor examples:
- Nettle root
- PROGESTERONE
- Drugs: MEHP (monoethylhexylphthalate); fenarimol; substituted analogs of ANDROSTENEDIONE, e.g., C-10 substituted (19R-10 β-oxiranyl-), or C-4 substituted (OH-, formestone), or C-7 substituted (7 α-SC6H4-p-NH2-), or 2 β, 19 bridged (2 β, 19-methylene-), fadrazole, letrozole, and arimidex,
Aromatase ACTIVITY is▲Enhanced by:
• Age;
• Obesity;
• INSULIN;
• Gonadotropin hormones (E.g. FSH, LH, hCG);
• Alcohol.
• Location in certain estrogen-dependent local tissue E.g. next to breast tissue
• Endometrial cancer, endometriosis, and uterine fibroids.
Aromatase ACTIVITY is ▼Reduced by:
• PROLACTIN (stimulates milk production for breast-feeding);
• Smoking;
• Anti-mullerian hormone (AMH). Produced by reproductive tissues. Inhibits the development of the Mullerian ducts in the male embryo, which develop into reproductive organs in females.
• Drugs (post-menopausal only) Letrozole (Femara®), anastrozole (Arimidex®), and exemestane (Aromasin®).
Aromatase conversion pathway directly affected by:
- Flavonoids and lignans (both polyphenols). Enterolactones are lignan precursors found in E.g.flaxseed;
- Drugs. Aminoglutethimide, MEHP, Fenarimol, Fadrazole, Letrozole, Anastrozole, Arimidex, Prochloraz, Enconazole/miconazole/ketoconazole, Imizolil, 4-hydroxyANDROSTENEDIONE, 10-propargylestr-4-ene-3,17-dione
