Estrogen and Glucocorticoid Metabolism
Sammanfattning: Background: Cardiovascular disease (CVD) is the leading cause of death among women in Sweden. The risk of CVD increases rapidly after the menopause. A major contributing factor may be the redistribution of adipose tissue, from the peripheral to central depots, associated with menopause. This change in body composition is commonly attributed to declining estrogen levels but may also be affected by tissue-specific alterations in exposure to other steroid hormones, notably glucocorticoids – mainly cortisol in humans. Indeed, adipose tissue-specific overexpression of the glucocorticoid-activating enzyme 11?-hydroxysteroid dehydrogenase type 1 (11?HSD1) induces central obesity, insulin resistance and hypertension in mice. Interestingly, estrogen may regulate this enzyme. The aim of this thesis was to investigate putative links between estrogen and glucocorticoid activation by 11?HSD1. Materials and Methods: 11?HSD1 expression and/or activity in adipose tissue and liver, and adipose estrogen receptor ? and ? (ER? and ER?) gene expression, were investigated in lean pre- and postmenopausal women and ovariectomized rodents with and without estrogen supplementation. In lean women measures of 11?HSD1 were correlated to risk markers for CVD. The association between adipose 11?HSD1 and ER mRNA expression was investigated in both lean women and rats and in an additional cohort of obese premenopausal women. In vitro experiments with adipocyte cell lines were used to explore possible pathways for estrogen regulation of 11?HSD1. Results: Subcutaneous adipose tissue transcript levels and hepatic activity of 11?HSD1 were higher in postmenopausal vs. premenopausal women. In rodents, estrogen treatment to ovariectomized rats decreased visceral adipose tissue 11?HSD1, resulting in a shift towards higher subcutaneous (vs. visceral) 11?HSD1 mRNA expression/activity. Increased adipose and hepatic 11?HSD1 were associated with increased blood pressure and a disadvantageous blood lipid profile in humans. We found significant positive associations between 11?HSD1 and ER? transcript levels in adipose tissue. The in vitro experiments showed upregulation of 11?HSD1 mRNA expression and activity with estrogen or ER?-agonist treatment at low (corresponding to physiological) concentrations. Conclusions: Our studies show for the first time increased local tissue glucocorticoid activation with menopause/age in women. This may contribute to an increased risk of CVD. Estrogen treatment in rodents induces a shift in 11?HSD1 activity towards the subcutaneous adipose tissue depots, which may direct fat accumulation to this metabolically “safer” depot. The in vitro studies suggest that low-dose estrogen treatment upregulates 11?HSD1 via ER?. In summary, estrogen - glucocorticoid metabolism interactions may be key in the development of menopause-related metabolic dysfunction and in part mediate the beneficial effects of postmenopausal estrogen treatment on body fat distribution.
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