Activity Of 11beta-hydroxysteroid Dehydrogenase Type Research Articles

Does the Caesarean Section Impact on 11β HSD2 and Fetal Cortisol?

Purpose: Comparison of the activity of 11beta-hydroxysteroid dehydrogenase type 2 in the placenta and the umbilical cord blood cortisol level between caesarean sections with or without uterine contraction and vaginal delivery groups. Cortisol is the main stress hormone responsible for the normal adaptation of the neonate to extrauterine life. The disorders resulting from a dysfunction of the 11β-HSD 2–cortisol system can explain the higher risk of developing diseases in children born by caesarean section. Methods: 111 healthy, pregnant women in singular pregnancy at term of delivery were included into the study. The study comprised 11β-HSD 2 in placental tissue from 49 pregnant women delivering by elective caesarean section and 46 pregnant women delivering by vagina. In 16 cases of the elective caesarean section, regular uterine contractions were declared. Cortisol level was estimated in umbilical cord blood directly after delivery. Results: We found no statistically significant differences in the activity of 11β-HSD 2 in placentas delivered via caesarean sections (29.61 on average in elective caesarean sections and 26.65 on average in intrapartum caesarean sections) compared to vaginal deliveries (31.94 on average, p = 0.381), while umbilical cord blood cortisol in the elective caesarean sections group was significantly lower (29.86 on average) compared to the vaginal deliveries (55.50 on average, p < 0.001) and intrapartum caesarean sections (52.27 on average, p < 0.001). Conclusions: The model of placental 11β-HSD 2 activity and umbilical cord blood cortisol concentration seems to be significant in conditions of stress associated with natural uterine contractions in labour.

Demonstration of Proof of Mechanism and Pharmacokinetics and Pharmacodynamic Relationship with 4′-Cyano-biphenyl-4-sulfonic Acid (6-Amino-pyridin-2-yl)-amide (PF-915275), an Inhibitor of 11β-Hydroxysteroid Dehydrogenase Type 1, in Cynomolgus Monkeys

Glucocorticoids, through activation of the glucocorticoid receptor (GR), regulate hepatic gluconeogenesis. Elevated hepatic expression and activity of 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) play a key role in ligand-induced activation of the GR through the production of cortisol. Evidence from genetically modified mice suggests that inhibition of 11betaHSD1 might be a therapeutic approach to treat the metabolic syndrome. We have identified a potent 11betaHSD1 inhibitor, 4'-cyano-biphenyl-4-sulfonic acid (6-amino-pyridin-2-yl)-amide (PF-915275), that is selective for the primate and human enzymes. The objective of this study was to demonstrate target inhibition with PF-915275 and to quantify the relationship between target inhibition and drug exposure in monkeys. We characterized the ability of PF-915275 to inhibit the conversion of prednisone, a synthetic cortisone analog that can be distinguished from the endogenous substrate cortisone, enabling a direct measure of substrate to product conversion without the complication of feedback. Adult cynomolgus monkeys were administered either vehicle or various doses of PF-915275 followed by a 10-mg/kg dose of prednisone. Prednisone conversion to prednisolone and the concentrations of PF-915275 were measured by liquid chromatography/tandem mass spectrometry. PF-915275 dose-dependently inhibited 11betaHSD1-mediated conversion of prednisone to prednisolone, with a maximum of 87% inhibition at a 3-mg/kg dose. An exposure-response relationship was demonstrated, with an estimated EC(50) of 391 nM (total) and 17 nM (free). Insulin levels were also reduced in a dose-related manner. These results should enable the development of a biomarker for evaluating target modulation in humans that will aid in identifying 11betaHSD1 inhibitors to treat diabetes and other related metabolic diseases.

Identification of polymorphisms in the human 11beta‐hydroxysteroid dehydrogenase type 2 gene promoter: functional characterization and relevance for salt sensitivity

Reduced activity of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) plays a role in essential hypertension and the sensitivity of blood pressure to dietary salt. Nonconservative mutations in the coding region are extremely rare and do not explain the variable 11beta-HSD2 activity. We focused therefore on the 5'-regulatory region and identified and characterized the first promoter polymorphisms. Transfections of variants G-209A and G-126A into SW620 cells reduced promoter activity and affinity for activators nuclear factor 1 (NF1) and Sp1. Chromatin immunoprecipitation revealed Sp1, NF1, and glucocorticoid receptor (GR) binding to the HSD11B2 promoter. Dexamethasone induced expression of mRNA and activity of HSD11B2. GR and/or NF1 overexpression increased endogenous HSD11B2 mRNA and activity. GR complexes cooperated with NF1 to activate HSD11B2, an effect diminished in the presence of the G-209A variant. When compared to salt-resistant subjects (96), salt-sensitive volunteers (54) more frequently had the G-209A variant, higher occurrence of alleles A4/A7 of polymorphic microsatellite marker, and higher urinary ratios of cortisol to cortisone metabolites. First, we conclude that the mechanism of glucocorticoid-induced HSD11B2 expression is mainly mediated by cooperation between GR and NF1 on the HSD11B2 promoter and, second, that the newly identified promoter variants reduce activity and cooperation of cognate transcription factors, resulting in diminished HSD11B2 transcription, an effect favoring salt sensitivity.

Cortisol–cortisone ratios in small for gestational age (SGA) children without postnatal catch‐up growth

Low birthweight is a risk factor for metabolic and cardiovascular disorders in later adult life. Changes in the activity of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) and the consequent disequilibrium between cortisol (F) and cortisone (E) are thought to be a key mechanism for these effects. We investigated whether prenatal programming leads to alterations in F/E ratios on a systemic level. In a cross-sectional, retrospective study we analysed sera of 132 children born small for gestational age (SGA) (aged 2-13 years) with persistent short stature [< -2 standard deviation score (SDS)] and of 25 children born appropriate for gestational age (AGA) (aged 4-11 years) with normal body height. Thirty-one per cent of the SGA and 44% of the AGA children were born preterm. Serum E and F concentrations were measured using tandem mass spectrometry. To exclude species-specific effects, we studied the 11beta-HSD system by measuring the ratio of corticosterone (B) to dehydrocorticosterone (11OH-B) in rats that were born SGA after protein restriction of the female dams during pregnancy. F, E and the F/E ratio in serum did not differ in these children when comparing SGA to children who were born AGA and had normal height. The concentrations were independent of weight and length SDS at birth as well as gestational age. In rats born SGA, the B/11OH-B ratio was not different to that in normal control animals at 6, 11 and 15 weeks of life. We found no alterations in systemic cortisol-cortisone conversion either in short children born SGA or in SGA rats. However, local modifications of the 11beta-HSD system may be possible.

Sex‐specific Difference in the Interconversion of Cortisol and Cortisone in Men and Women

Our objective was to demonstrate that the smaller oxoreductase activity of 11beta-HSD1 in women would shift the interconversion of cortisol and cortisone toward cortisone, resulting in a larger amount of generated labeled cortisone in healthy women than in healthy men. Using mass spectrometry, the amount of cortisone generated from a continuous infusion (8 am to 6 pm) of stable-labeled cortisol (1alpha,2alpha-d-cortisol) was determined in non-obese and in obese (BMI>35 kg/m2) men and women during steady-state conditions (from 2 pm to 6 pm). In this setting, the amount of generated labeled cortisone (expressed as % of the achieved steady-state concentrations of labeled cortisol) reflects the sum of the bi-directional conversion of cortisol into cortisone (and vice versa) by 11beta-hydroxysteroid dehydrogenase. The amount of generated labeled cortisone was higher in men than in women (p<0.0001). This sex difference was higher in obese than in non-obese patients (p=0.0062). The interconversion of cortisol and cortisone during steady-state conditions is shifted toward cortisol in men as compared with women. This suggests a higher overall oxoreductase activity of 11beta-hydroxysteroid dehydrogenase type 1 in men than in women. This sex-specific difference is maintained in obesity.

Impaired Protein Stability of 11β-Hydroxysteroid Dehydrogenase Type 2

Apparent mineralocorticoid excess (AME) is a severe form of hypertension that is caused by impaired activity of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), which converts biologically active cortisol into inactive cortisone. Mutations in HSD11B2 result in cortisol-induced activation of mineralocorticoid receptors and cause hypertension with hypokalemia, metabolic alkalosis, and suppressed circulating renin and aldosterone concentrations. This study uncovered the first patient with AME who was described in the literature, identified the genetic defect in HSD11B2, and provided evidence for a novel mechanism of reduced 11beta-HSD2 activity. This study identified a cluster of amino acids (335 to 339) in the C-terminus of 11beta-HSD2 that are essential for protein stability. The cluster includes Tyr(338), which is mutated in the index patient, and Arg(335) and Arg(337), previously reported to be mutated in hypertensive patients. It was found that wild-type 11beta-HSD2 is a relatively stable enzyme with a half-life of 21 h, whereas that of Tyr(338)His and Arg(337)His was 3 and 4 h, respectively. Enzymatic activity of Tyr(338)His was partially retained at 26 degrees C or in the presence of the chemical chaperones glycerol and dexamethasone, indicating thermodynamic instability and misfolding. The results provide evidence that the degradation of both misfolded mutant Tyr(338)His and wild-type 11beta-HSD2 occurs through the proteasome pathway. Therefore, impaired 11beta-HSD2 protein stability rather than reduced gene expression or loss of catalytic activity seems to be responsible for the development of hypertension in some individuals with AME.

Cooperativity between 11β-Hydroxysteroid Dehydrogenase Type 1 and Hexose-6-phosphate Dehydrogenase in the Lumen of the Endoplasmic Reticulum

The functional coupling of 11beta-hydroxysteroid dehydrogenase type 1 and hexose-6-phosphate dehydrogenase was investigated in rat liver microsomal vesicles. The activity of both enzymes was latent in intact vesicles, indicating the intraluminal localization of their active sites. Glucose-6-phosphate, a substrate for hexose-6-phosphate dehydrogenase, stimulated the cortisone reductase activity of 11beta-hydroxysteroid dehydrogenase type 1. Inhibition of glucose-6-phosphate uptake by S3483, a specific inhibitor of the microsomal glucose-6-phosphate transporter, decreased this effect. Similarly, cortisone increased the intravesicular accumulation of radioactivity upon the addition of radiolabeled glucose-6-phosphate, indicating the stimulation of hexose-6-phosphate dehydrogenase activity. A correlation was shown between glucose-6-phosphate-dependent cortisone reduction and cortisone-dependent glucose-6-phosphate oxidation. The results demonstrate a close cooperation of the enzymes based on co-localization and the mutual generation of cofactors for each other.

Tissue-specific glucocorticoid reactivating enzyme, 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1)--a promising drug target for the treatment of metabolic syndrome.

Obesity is closely associated with the Metabolic Syndrome, which includes insulin resistance, glucose intolerance, dyslipidemia and hypertension. The best predictor of these morbidities is not the total body fat mass but the quantity of visceral (e.g. omental, mesenteric) fat. Glucocorticoids play a pivotal role in regulating fat metabolism, function and distribution. Indeed, patients with Cushing-s syndrome (a rare disease characterized by systemic glucocorticoid excess originating from the adrenal or pituitary tumors) or receiving glucocorticoid therapy develop reversible visceral fat obesity. The role of glucocorticoids in prevalent forms of human obesity, however, has remained obscure, because circulating glucocorticoid concentrations are not elevated in the majority of obese subjects. Glucocorticoid action on target tissue depends not only on circulating levels but also on intracellular concentration. Locally enhanced action of gluccorticoids in adipose tissue and skeletal muscle has been demonstrated in the Metabolic Syndrome. Evidence has accumulated that enzyme activity of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which regenerates active glucocorticoids from inactive forms and plays a central role in regulating intracellular glucocorticoid concentration, is commonly elevated in fat depots from obese individuals. This suggests a role for local glucocorticoid reactivation in obesity and the Metabolic Syndrome. 11beta-HSD1 knockout mice resist visceral fat accumulation and insulin resistance even on a high-fat diet. Furthermore, fat-specific 11beta-HSD1 transgenic mice, those have increased enzyme activity to a similar extent seen in obese humans, develop visceral obesity with insulin and leptin resistance, dyslipidemia and hypertension. In adipocytes, both antidiabetic PPARgamma agonists and LXRalpha agonists significantly reduce 11beta-HSD1 mRNA and enzyme activity, suggesting that suppression of 11beta-HSD1 in adipose tissue may be one of the mechanisms by which these drugs exert beneficial metabolic effects. Recently reported selective inhibitors of 11beta-HSD1 can ameliorate severe hyperglycemia in the genetically diabetic obese mice. In summary, 11beta-HSD1 is a promising pharmaceutical target for the treatment of the Metabolic Syndrome.

Functional adrenocorticotropic hormone receptor in cultured human vascular endothelial cells : possible role in control of blood pressure.

Hypertension is a prominent feature of patients with Cushing's disease and ectopic adrenocorticotropic hormone (ACTH) syndrome, who have elevated ACTH levels. Chronic administration of ACTH (1-24) also raises blood pressure in humans. This effect has been postulated to be due to ACTH-induced increases in cortisol secretion in the adrenal gland. It is well known that cortisol increases vascular tone by potentiating the vasoconstrictor action of a number of pressor hormones. In the present study, we show direct evidence that human aortic endothelial cells possess the ACTH receptor. 11beta-Dehydrogenation, converting cortisol to its inactive metabolite, cortisone, mediated by vascular 11beta-hydroxysteroid dehydrogenase type 2 is essential for the control of vascular tone, and the reduced activity may be relevant to the pathogenesis of hypertension. We found that ACTH (1-24) dose-dependently decreased the gene expression and enzyme activity of 11beta-hydroxysteroid dehydrogenase type 2 in these cells, and the decrease was partially abolished by a selective ACTH receptor antagonist. This may indicate that ACTH potentiates the action of cortisol through its direct effect on the vasculature. Therefore, the present study provides important information for understanding the mechanism of ACTH-induced hypertension.