Effects of thyroid hormone (thyroxine) and testosterone on hepatic 11beta-hydroxysteroid dehydrogenase mRNA and activity in pubertal hypothyroid male rats

Steroid hormones related to 11beta-hydroxysteroid dehydrogenase type 1 in treated obesity

The local concentration of glucocorticoids is intensively regulated by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD 1). Human 11beta-HSD 1 also reversibly catalyzes the inter-conversion of 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) into 7-oxo-DHEA. The cohort of 282 obese adolescents, 154 girls (median age 15.31 years, range 14.17-16.68 years) and 128 boys (median age 14.95 years, range 13.87-16.16 years), BMI (Body Mass Index) >90th percentile was examined. In samples collected before and after one month of reductive diet therapy, circulating levels of steroids were analyzed by liquid chromatography-tandem mass spectrometry and radioimmunoassay methods. The model of the treatment efficacy prediction was calculated. A significant reduction in circulating levels of cortisone, E2 and increased levels of 7beta-hydroxy-DHEA after the reductive treatment was observed. Levels of cortisol, DHEA, DHT sustained without any significant change. The predictive Orthogonal Projections to Latent Structures (OPLS) model explained 20.1 % of variability of BMI, z-score change by the basal levels of 7alpha-hydroxy-DHEA, DHEA, cortisol and E2 as the strongest predictors. Reduced levels of circulating cortisone and reduced ratios of oxygenated/reduced metabolites reflect increased reductase activity of 11beta-HSD 1 with reduced BMI, z-score. We hypothesize whether these changes can be attributed to the altered activity of 11beta-HSD 1 in the liver.

Is there sufficient evidence to consider the use of 11β-hydroxysteroid dehydrogenase type 1 inhibition in children?

Manifestations of the metabolic syndrome [obesity, dyslipidaemia, hypertension, blood glucose derangements including prediabetes or type 2 diabetes mellitus (T2DM)] in juvenile populations are becoming increasingly prevalent throughout the world and are at the point of being a global public health concern. Derangements in cortisol regeneration seem to be involved in the pathophysiology. Treatment with selective 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) inhibitors could be a therapeutic strategy in paediatric patients with manifestations of the metabolic syndrome. Based on preclinical and clinical data regarding development of the 11β-HSD1 enzyme, it appears that maturation occurs within the first year of life. Different changes in biomarkers for assessing the efficacy and safety of 11β-HSD1 inhibitors are to be expected in paediatric patients compared to adults, reflecting differences in metabolism. The effect of 11β-HSD1 treatment in children on bone differentiation and development as well as adrenocorticotropic hormone (ACTH), circulating and local cortisol tissue concentrations, androgens and respective stress response is not yet known. Based on current literature, the concept of inhibition of 11β-HSD1 is considered a potentially effective mean to regulate local cortisol levels in the paediatric population, and 11β-HSD1 inhibitors may provide a valuable target and treatment option for the metabolic syndrome in paediatric patients. However, the uncertainty over effects on the developing skeleton combined with mild increases in adrenal androgen levels raises potential concerns regarding growth as well as onset of puberty as to their future use in children. Future clinical studies are needed to thoroughly assess the risks and benefits of this new class of drugs in the paediatric population.

Changes in Gene Expression during Wolffian Duct Development

BACKGROUND

Wolffian ducts (WDs) are the embryonic precursors of the male reproductive tract. Their development is induced by testosterone, which interacts with the androgen receptor (AR). The molecular pathways underlying androgen-dependent WD development are largely unknown. We aimed to identify AR target genes important in this process.

METHODS

RNA was isolated from rat WDs at E17.5 and E20.5. Affymetrix GeneChip expression arrays were used to identify transcripts up- or downregulated more than 2-fold. Regulation of seven transcripts was confirmed using quantitative PCR.

RESULTS

Transcripts from 76 known genes were regulated, including modulators of insulin-like growth factor and transforming growth factor-beta signalling. By controlling these modulators, androgens may indirectly affect growth factor signalling pathways important in epithelial-mesenchymal interactions and organ development. Caveolin-1, also upregulated, may play a role in modifying as well as mediating AR signalling. Differentiation of WD epithelium and smooth muscle, innervation and extracellular matrix synthesis were reflected in regulation of other transcripts. Several genes were previously suggested to be regulated by androgens or contained functional or putative androgen/glucocorticoid response elements, indicating they may be direct targets of androgen signalling.

CONCLUSION

Our results suggest novel cohorts of signals that may contribute to androgen-dependent WD development and provide hypotheses that can be tested by future studies.

Cortisol metabolism and the role of 11beta-hydroxysteroid dehydrogenase

Two isoforms of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD) interconvert the active glucocorticoid, cortisol, and inactive cortisone. 11beta-HSD1 is believed to act in vivo predominantly as an oxo-reductase using NADP(H) as a cofactor to generate cortisol. In contrast, 11beta-HSD2 acts exclusively as an NAD-dependent dehydrogenase inactivating cortisol to cortisone, thereby protecting the mineralocorticoid receptor from occupation by cortisol. In peripheral tissues, both enzymes serve to control the availability of cortisol to bind to the corticosteroid receptors. Defective expression of 11beta-HSD2 is implicated in patients with hypertension and intra-uterine growth retardation, while 11beta-HSD1 appears to be intricately involved in the conditions of apparent cortisone reductase deficiency, insulin resistance and visceral obesity. The ability of peripheral tissues to regulate corticosteroid concentrations through 11beta-HSD isozymes is established as an important mechanism in the pathogenesis of diverse human diseases. Modulation of enzyme activity may offer a novel therapeutic approach to treating human disease while circumventing the consequences of systemic glucocorticoid excess or deficiency.

Effects of spironolactone on systolic blood pressure in experimental diabetic rats

BACKGROUND

Mineralocorticoid hormones, which maintain electrolyte balance and blood pressure, are thought to be associated not only with the expression of renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), but also with that of intracellular mineralocorticoid receptors (MRs). The present study was designed to test whether the mineralocorticoid action of glucocorticoid corticosterone on renal MR is involved in the development of diabetes-associated hypertension by measuring the alterations of renal 11beta-HSD2.

METHOD

We measured the mean systolic blood pressure, renal 11beta-HSD1, and mRNA levels in streptozotocin (STZ)-induced diabetic rats that received spironolactone, insulin, or no treatment, and in nondiabetic controls that received spironolactone.

RESULTS

Four weeks after an injection of STZ, the renal 11beta-HSD2 and mRNA levels were significantly lower in diabetic rats than in control rats, and the mean systolic blood pressure was 14.8% higher in diabetic rats than in controls. Subcutaneous injections of spironolactone into diabetic rats for three weeks partially reversed the decrease in renal 11beta-HSD2 activity and gene expression, and prevented the mean systolic blood pressure elevation. Spironolactone treatment for one week also resulted in a significant reduction in mean systolic blood pressure during the development of diabetic hypertension. However, treatment with STZ did not significantly decrease the renal 11beta-HSD1 activity and mRNA expression, and spironolactone treatment did not exert a significant effect on this enzyme in STZ-induced diabetic rats.

CONCLUSION

In the development of diabetes-induced hypertension, the effect of spironolactone on mean systolic blood pressure may be associated with the mineralocorticoid effects of corticosterone on renal MR, as well as an alteration of renal 11beta-HSD2 activity and its mRNA expression in insulin-dependent diabetic rats.