Adipose aromatase gene expression is greater in older women and is unaffected by postmenopausal estrogen therapy.
ABSTRACT Although natural menopause is associated with loss of ovarian estrogen production, this life phase is followed by a significant increase in estrogen-related cancers, namely breast and endometrial cancer. These tissues, as well as adipose, skeletal, and vascular tissues and the brain are important sites of postmenopausal estrogen production. Circulating C19 steroid precursors are essential substrates for extragonadal estrogen synthesis; however, the levels of these androgenic precursors decline markedly with advancing age. This implies an increase in capacity for extragonadal tissues to produce estrogen with age.
To explore this, and the effects of the menopause transition and postmenopausal estrogen therapy on extragonadal estrogen biosynthesis, we have compared the expression of the aromatase gene and estrogen (ER) and androgen receptors (AR) in subcutaneous abdominal and gluteal fat taken from premenopausal (group 1: n = 11), postmenopausal (group 2: n = 10), and postmenopausal women taking estrogen therapy (group 3: n = 10). All subjects were of normal body mass index, euglycemic, and normolipemic.
The postmenopausal women were older (group 1, 43.1 +/- 5.0 vs groups 2 and 3, 57.9 +/- 7.4 years, P < 0.001 and 56.1 +/- 4.5 years, P < 0.001, respectively) and had lower serum estradiol levels (group 2, 22.2 +/- 3.2 vs group 1, 442.5 +/- 248.2 pmol/L, P < 0.05), which were restored to premenopausal levels with estrogen therapy. Expression analysis revealed that levels of transcripts encoding aromatase were greater in gluteal than abdominal depots in each group in postmenopausal versus premenopausal women (P < 0.05). Use of hormone therapy did not influence aromatase gene expression in either depot. No differences were detected in the expression of ER or AR between groups of between tissue depots.
Thus, the capacity of adipose tissue to produce estrogen seems to increase significantly with age at the time of menopause and to be unaltered by exogenous estrogen therapy. This difference in extragonadal estrogen production with age may play a pivotal role in the increase in estrogen-dependent malignancies in the postmenopausal years.
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ABSTRACT: The objective was to provide guidelines for the therapeutic use of androgens in women. The Task Force was composed of a chair, selected by the Clinical Guidelines Subcommittee (CGS) of The Endocrine Society, six additional experts, a methodologist, and a medical writer. The Task Force received no corporate funding or remuneration. The Task Force used systematic reviews of available evidence to inform its key recommendations. The Task Force used consistent language and graphical descriptions of both the strength of recommendation and the quality of evidence, using the recommendations of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) group. The strength of a recommendation is indicated by the number 1 (strong recommendation, associated with the phrase "we recommend") or 2 (weak recommendation, associated with the phrase "we suggest"). The quality of the evidence is indicated by cross-filled circles, such that [1 cross-filled circle, 3 empty circles] denotes very-low-quality evidence, [2 cross-filled circles, 2 empty circles] low quality, [3 cross-filled circles, 1 empty circle] moderate quality, and [4 cross-filled circles] high quality. Each recommendation is followed by a description of the evidence. Consensus was guided by systematic reviews of evidence and discussions during one group meeting, several conference calls, and e-mail communications. The drafts prepared by the task force with the help of a medical writer were reviewed successively by The Endocrine Society's CGS, Clinical Affairs Committee (CAC), and Executive Committee. The version approved by the CGS and CAC was placed on The Endocrine Society's web site for comments by members. At each stage of review, the Task Force received written comments and incorporated needed changes. We recommend against making a diagnosis of androgen deficiency in women at present because of the lack of a well-defined clinical syndrome and normative data on total or free testosterone levels across the lifespan that can be used to define the disorder. Although there is evidence for short-term efficacy of testosterone in selected populations, such as surgically menopausal women, we recommend against the generalized use of testosterone by women because the indications are inadequate and evidence of safety in long-term studies is lacking. A review of the data currently available is presented, and areas of future research are outlined. To formulate clinical guidelines for use of testosterone in women, additional information will be necessary. This includes defining conditions that, when not treated with androgens, have adverse health consequences to women; defining clinical and laboratory parameters that distinguish those with these conditions; and assessing the efficacy and long-term safety of androgen administration on outcomes that are important to women diagnosed with these conditions. This necessary clinical research cannot occur until the biological, physiological, and psychological underpinnings of the role of androgens in women and candidate disorders are further elucidated.Journal of Clinical Endocrinology & Metabolism 11/2006; 91(10):3697-710. · 6.50 Impact Factor
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ABSTRACT: Aromatase, the key enzyme in estrogen biosynthesis, is encoded by the Cyp19a1 gene. Thus far, 3 unique untranslated first exons associated with distinct promoters in the mouse Cyp19a1 gene have been described (brain, ovary, and testis-specific). It remains unknown whether aromatase is expressed in other mouse tissues via novel and tissue-specific promoters. Real-time PCR was used to examine the aromatase expression levels in various C57BL/6 mouse tissues. 5'-rapid amplification of cDNA ends (5'-RACE) was used to determine the transcriptional start sites of Cyp19a1 transcripts. Promoter activity was measured using serial deletion mutants of DNA fused to the luciferase reporter gene. Primary mouse adipose fibroblasts were isolated and cultured from 16-week-old mouse gonadal fat pads. We systematically analyzed Cyp19a1 expression in a large number of mouse tissues, and demonstrated for the first time that aromatase was expressed in the male but not female gonadal fat pad. Subcutaneous and brown adipose tissue did not contain detectable Cyp19a1 mRNA. We used 5'-RACE to clone a novel gonadal fat-specific untranslated first exon, which is spliced onto a common junction 15 bp upstream of the translation start site. This adipose-specific first exon was mapped to approximately 75 kb upstream of the translation start site. Transfection of luciferase reporter gene plasmids containing the promoter region upstream of the adipose-specific first exon into murine 3T3-L1 adipose fibroblasts demonstrated significant basal promoter activity conferred primarily by the sequence located at -343/-1 bp. Dexamethasone significantly induced activity of this adipose-specific promoter region. Adipose-specific Cyp19a1 mRNA was expressed in primary mouse adipose fibroblasts and significantly induced by dexamethasone alone or serum plus dexamethasone. Taken together, this research identified a novel, adipose-specific first exon of Cyp19a1 and its hormonally regulated promoter region in male murine gonadal fat. These results expand the known 5'-regulatory region of the murine Cyp19a1 gene to 75 kb upstream of the translation start site. Cyp19a1 expression in mouse adipose tissue may play an important role in reproductive biology and lipid metabolism.Reproductive Biology and Endocrinology 05/2009; 7:37. · 2.05 Impact Factor
Article: Tissue-specific increases in 11beta-hydroxysteroid dehydrogenase type 1 in normal weight postmenopausal women.[show abstract] [hide abstract]
ABSTRACT: With age and menopause there is a shift in adipose distribution from gluteo-femoral to abdominal depots in women. Associated with this redistribution of fat are increased risks of type 2 diabetes and cardiovascular disease. Glucocorticoids influence body composition, and 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) which converts inert cortisone to active cortisol is a putative key mediator of metabolic complications in obesity. Increased 11betaHSD1 in adipose tissue may contribute to postmenopausal central obesity. We hypothesized that tissue-specific 11betaHSD1 gene expression and activity are up-regulated in the older, postmenopausal women compared to young, premenopausal women. Twenty-three pre- and 23 postmenopausal, healthy, normal weight women were recruited. The participants underwent a urine collection, a subcutaneous adipose tissue biopsy and the hepatic 11betaHSD1 activity was estimated by the serum cortisol response after an oral dose of cortisone. Urinary (5alpha-tetrahydrocortisol+5beta-tetrahydrocortisol)/tetrahydrocortisone ratios were higher in postmenopausal women versus premenopausal women in luteal phase (P<0.05), indicating an increased whole-body 11betaHSD1 activity. Postmenopausal women had higher 11betaHSD1 gene expression in subcutaneous fat (P<0.05). Hepatic first pass conversion of oral cortisone to cortisol was also increased in postmenopausal women versus premenopausal women in follicular phase of the menstrual cycle (P<0.01, at 30 min post cortisone ingestion), suggesting higher hepatic 11betaHSD1 activity. In conclusion, our results indicate that postmenopausal normal weight women have increased 11betaHSD1 activity in adipose tissue and liver. This may contribute to metabolic dysfunctions with menopause and ageing in women.PLoS ONE 01/2009; 4(12):e8475. · 4.09 Impact Factor