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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

11 Beta-hydroxysteroid dehydrogenases type 1 and 2 (11 beta-HSD1 and 11 beta-HSD2) are microsomal enzymes responsible for the interconversion of cortisol into the inactive form cortisone and vice versa. 11 beta-HSD1 is mainly present in the liver, and has predominantly reductase activity although its function has not yet been elucidated. 11 beta-HSD2, present in mineralocorticoid target tissues such as the kidney, converts cortisol into cortisone. Reduced activity due to inhibition or mutations of 11 beta-HSD2 leads to hypertension and hypokalemia resulting in the Apparent Mineralocorticoid Excess Syndrome (AMES). Like humans, cats are highly susceptible for hypertension. As large species differences exist with respect to the kinetic parameters (K(m) and V(max)) and amino acid sequences of both enzymes, we determined these characteristics in the cat. Both enzyme types were found in the kidneys. 11 beta-HSD1 in the feline kidney showed bidirectional activity with predominantly dehydrogenase activity (dehydrogenase: K(m) 1959+/-797 nM, V(max) 766+/-88 pmol/mg*min; reductase: K(m) 778+/-136 nM, V(max) 112+/-4 pmol/mg*min). 11 beta-HSD2 represents a unidirectional dehydrogenase with a higher substrate affinity (K(m) 184+/-24 nM, V(max) 74+/-3 pmol/mg*min). In the liver, only 11 beta-HSD1 is detected exerting reductase activity (K(m) 10462 nM, V(max) 840 pmol/mg*min). Sequence analysis of conserved parts of 11 beta-HSD1 and 11 beta-HSD2 revealed the highest homology of the feline enzymes with the correspondent enzymes found in man. This suggests that the cat may serve as a suitable model species for studies directed to the pathogenesis and treatment of human diseases like AMES and hypertension.
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PMID:Characterisation of 11 beta-hydroxysteroid dehydrogenases in feline kidney and liver. 1473 82

The enzyme 11-beta hydroxysteroid dehydrogenase type 2 plays a major role in blood pressure regulation. It metabolizes glucocorticoid hormones into derivatives with low affinity for the mineralocorticoid receptor, preventing its permanent occupancy by circulating cortisol, which is 100- to 1000-fold more abundant than aldosterone in the plasma. Inactivating mutations of the enzyme result in severe hypertension, as seen in children with apparent mineralocorticoid excess syndrome. In patients with essential hypertension, however, attempts to evidence enzyme deficiency have been inconclusive. In this pilot study, its catalytic activity was measured directly in aldosterone-sensitive sweat gland ducts collected from skin biopsy samples of 10 male normotensive subjects and 10 subjects with essential hypertension (more than 140 to 90 mm Hg) with no sign of hypermineralocorticism. Isolated ducts were assayed for nicotinamide-dinucleotide-dependent dehydrogenase activity (transformation of tritiated corticosterone into tritiated-11 dehydrocorticosterone, as measured by high-pressure liquid chromatography). Hypertensive patients exhibited significantly lower 11-beta hydroxysteroid dehydrogenase type 2 activity (9.7+/-4.7 femtomoles per 3 mm length of duct and per 10 minutes incubation, median+/-SD) than did normotensive subjects (15.9+/-2.6). Such defect was undetectable using the classical urinary corticosteroid metabolism indexes, probably because of compensatory mechanisms. Relations between these findings and blood pressure levels should benefit from direct enzyme measurements in the vasculature. In conclusion, this cross-sectional study points to partial 11-beta hydroxysteroid dehydrogenase type 2 deficiency as a novel feature of essential hypertension, which should stimulate search for new signaling pathways and therapeutical targets.
Hypertension 2004 Apr
PMID:Impaired 11-beta hydroxysteroid dehydrogenase type 2 activity in sweat gland ducts in human essential hypertension. 1498 Oct 55

Glycyrrhizic acid (GA) inhibits the activity of 11beta-hydroxysteroid dehydrogenase type 2 in the kidney, with the resulting increase in intrarenal cortisol concentration leading to hypertension and suppression of the renin-aldosterone system. In this paper we describe an interesting case of pseudoaldosteronism, associated with hypocalcemia and an exaggerated ACTH response. A 72-year-old woman was referred to our department for further evaluation of hypokalemia and hypocalcemia. The patient had been taking GA (150 mg/day) for the previous year for treatment of liver damage. Plasma renin activity and aldosterone concentration were both within lower normal limits. Urinary excretion of potassium and calcium was within the upper limit of the normal range and increased with administration of supplements. Plasma ACTH levels increased markedly in response to an intravenous injection of CRH. Cessation of GA and the potassium and calcium supplements on admission, led to a gradual normalization of serum potassium and calcium levels and blood pressure. The hypocalcaemia in our patient was related to decreased tubular reabsorption of calcium as a consequence of renal corticoid excess. It is possible that an increase in the number of CRH receptors in the pituitary following GA treatment caused the exaggerated ACTH response in association with pseudoaldosteronism. The existence of hypocalcemia and an exaggerated ACTH response should be observed carefully when managing pseudoaldosteronism.
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PMID:A case of pseudoaldosteronism, accompanied with hypocalcemia and exaggerated ACTH response. 1500 13

Glucocorticoids play important roles in organ development and 'fetal programming'. Fetal exposure to excess glucocorticoids reduces birth weight and causes later hypertension. To investigate these processes further we have determined the detailed ontogeny in the mouse of the glucocorticoid receptor (GR) and 11beta-hydroxysteroid dehydrogenase type-1 (11beta-HSD1), which amplifies glucocorticoid levels locally; the ontogeny was determined using in situ hybridisation from embryonic day 9.5 (E9.5, term=E19) until after birth. At E9.5 fetal GR mRNA levels are very low, except in fetal placenta. GR gene expression rises during gestation with striking tissue-specific differences in timing and extent. Before E13.5, an increase is clear in gastrointestinal (GI) and upper respiratory tracts, discrete central nervous system (CNS) regions, precartilage and especially in the liver (E10.5-E12). Later, further increases occur in lung, GI and upper respiratory tracts, muscle, pituitary and thymus. In a few tissues such increases are temporary, e.g. ureteric ducts (E13.5-E16.5) and pancreas (E14.5-E16.5, expression later falling sharply). Fetal 11beta-HSD1 mRNA expression is first clearly observed at E14.5-E15, initially in the fetal placenta then in the umbilical cord. Later, 11beta-HSD1 expression is seen as follows: (i) from E15 in lung and liver, rising strongly; (ii) thymus, from E15 (lower level); (iii) at low levels in a few brain regions, including the hippocampus (E16.5+); and (iv) in muscle group fascial planes and tendon insertions. This is the first detailed study of the ontogeny of these two genes and, in combination with previous work on the ontogeny of 11beta-HSD2 and the mineralocorticoid receptor, suggests potential critical periods of glucocorticoid sensitivity during development for several organ systems.
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PMID:Ontogeny of glucocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type-1 gene expression identifies potential critical periods of glucocorticoid susceptibility during development. 1507 71

Apparent mineralocorticoid excess syndrome (AME) is an autosomal recessive disorder that results in low renin hypertension and other characteristic clinical features. Typical patients present with severe hypertension, hypokalemia, and undetectable aldosterone. Most patients also have low birth weight, failure to thrive, and nephrocalcinosis. The 11betahydroxysteroid dehydrogenase type 2 (11betaHSD2) defect is documented by demonstrating a failure to convert cortisol to cortisone. Here, we report a patient with typical phenotypic features of AME who does not carry any of the previously described mutations in the HSD11B2 gene. This female patient from a consanguineous Pakistani family presented at age 9 yr. She had a low birth weight compared with her siblings and presented with hypertension (225/120 mm Hg), low plasma renin activity, hypokalemic metabolic alkalosis, suppressed aldosterone, and bilateral nephrocalcinosis. Echocardiogram did not reveal left ventricular hypertrophy, and baseline ophthalmological evaluation did not demonstrate hypertensive retinopathy. However, at age 12 yr, she developed mild to moderate hypertensive retinopathy. Biochemical analysis showed an elevated urinary cortisol to cortisone metabolites ratio (tetrahydrocortisol and 5alpha-tetrahydrocortisol/tetrahydrocortisone) of 28 (normal, 0.66-2.44). She had a cortisol secretion rate of 0.43 mg/d (normal, 5-25 mg/d). Sequence analysis of the HSD11B2 gene revealed a novel homozygous delta299 mutation in exon 5. In vitro expression in Chinese hamster ovary cells revealed that this mutation resulted in no activity.
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PMID:In vitro expression studies of a novel mutation delta299 in a patient affected with apparent mineralocorticoid excess. 1512 15

11beta-Hydroxysteroid dehydrogenase type 2 (11beta-HSD2) plays a crucial role in converting hormonally active cortisol to inactive cortisone, thereby conferring specificity upon the mineralocorticoid receptor (MR). Mutations in the gene encoding 11beta-HSD2 (HSD11B2) account for an inherited form of hypertension, the syndrome of "Apparent Mineralocorticoid Excess" (AME) where cortisol induces hypertension and hypokalaemia. We report five different mutations in the HSD11B2 gene in four families from Oman with a total of 9 affected children suffering from AME. Sequence data demonstrate the previously described L114Delta6nt mutation in exon 2 and new mutations in exon 3 (A221V), exon 5 (V322ins9nt) and for the first time in exon 1 (R74G and P75Delta1nt) of the HSD11B2 gene. These additional mutations provide further insight into AME and the function of the 11beta-HSD2 enzyme. The prevalence of monogenic forms of hypertension such as AME remains uncertain. However, our data suggests AME may be a relevant cause of hypertension in certain ethnic groups, such as the Oman population.
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PMID:Molecular basis for the apparent mineralocorticoid excess syndrome in the Oman population. 1513 13

11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) plays a crucial role in converting hormonally active cortisol into inactive cortisone, conferring specificity onto the human mineralocorticoid receptor (MR). Progesterone binds with even higher affinity to the MR, but acts as an MR antagonist. How aldosterone is able to keep its function as predominant MR ligand in clinical situations with high progesterone concentrations, such as pregnancy, is not clear. We have shown in vitro that the human kidney possesses an effective enzyme system that metabolizes progesterone to inactive metabolites in a process similar to the inactivation of cortisol by 11beta-HSD2. In studies on patients with adrenal insufficiency, we have shown that the in vivo anti-mineralocorticoid activity of progesterone is diminished by inactivating metabolism of progesterone, local formation of the deoxycorticosterone mineralocorticoid from progesterone, and inhibition of 11beta-HSD2 by progesterone and its metabolites resulting in decreased inactivation of cortisol and hence increased MR binding by cortisol. The enzymes involved in progesterone metabolism are also responsible for the capability of the human kidney to convert pregnenolone to DHEA and androstenedione leading to the formation of active androgens, testosterone and 5alpha-DH-testosterone. Locally produced androgens might be responsible for the observed difference in blood pressure between men and women and higher susceptibility to hypertension in men.
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PMID:The role of progesterone metabolism and androgen synthesis in renal blood pressure regulation. 1524 28

Hypersecretion of cortisol is associated with hypertension. In addition, an abnormal cortisol metabolism may play a role in the pathogenesis of hypertension. The 11beta-hydroxysteroid dehydrogenase (11beta-HSD) isozymes catalyze interconversion of cortisol and cortisone and play an important role in the regulation of the effects of cortisol. Activity of 11beta-HSD type 2, converting active cortisol in inactive cortisone, is crucial in preventing access of cortisol to the renal mineralocorticoid receptors (MRs). Decreased activity of this isozyme in the kidney, either congenitally in Apparent Mineralocorticoid Excess syndrome or acquired following licorice consumption, allows cortisol access to the MRs, resulting in hypokalemic hypertension. In normotensive subjects, an association has been demonstrated between blood pressure increase on a high-salt diet and a mild decrease of renal 11beta-HSD2 activity. In ectopic adrenocorticotropic hormone (ACTH), plasma cortisol levels are very high, resulting in mineralocorticoid hypertension caused by saturation of the available renal 11beta-HSD2 capacity. Activity of the 11beta-HSDs has also been demonstrated in many extrarenal sites. Several studies have demonstrated extrarenal effects of cortisol on blood pressure, as well as a possible role for altered extrarenal 11beta-HSD activities in the pathogenesis of hypertension. More studies are needed to clarify the role of 11beta-HSDs in the pathogenesis of hypertension.
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PMID:Cortisol, 11beta-hydroxysteroid dehydrogenases, and hypertension. 1547 32

The enzyme 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta HSD2) is selectively expressed in aldosterone target tissues, where it confers aldosterone selectivity for the mineralocorticoid receptor by inactivating 11 beta-hydroxyglucocorticoids. Variable activity of 11 beta HSD2 is relevant for blood pressure control and hypertension. The present investigation aimed to elucidate whether an epigenetic mechanism, DNA methylation, accounts for the rigorous control of expression of the gene encoding 11 beta HSD2, HSD11B2. CpG islands covering the promoter and exon 1 of HSD11B2 were found to be densely methylated in tissues and cell lines with low expression but not those with high expression of HSD11B2. Demethylation induced by 5-aza-2'-deoxycytidine and procainamide enhanced the transcription and activity of the 11 beta HSD2 enzyme in human cells in vitro and in rats in vivo. Methylation of HSD11B2 promoter-luciferase constructs decreased transcriptional activity. Methylation of recognition sequences of transcription factors, including those for Sp1/Sp3, Arnt, and nuclear factor 1 (NF1) diminished their DNA-binding activity. Herein NF1 was identified as a strong HSD11B2 stimulatory factor. The effect of NF1 was dependent on the position of CpGs and the combination of CpGs methylated. A methylated-CpG-binding protein complex 1 transcriptional repression interacted directly with the methylated HSD11B2 promoter. These results indicate a role for DNA methylation in HSD11B2 gene repression and suggest an epigenetic mechanism affecting this gene causally linked with hypertension.
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PMID:Epigenetic regulation of 11 beta-hydroxysteroid dehydrogenase type 2 expression. 1548 62

Epidemiological evidence suggests that low birth weight is associated with an increased risk of cardiovascular, metabolic and neuroendocrine disorders in adult life. Glucocorticoid administration during pregnancy reduces offspring birth weight and alters the maturation of the lung and other organs. We hypothesised that prenatal exposure to excess glucocorticoids or stress might represent a mechanism linking foetal growth with adult pathophysiology. In rats, birth weight is reduced following prenatal exposure to the synthetic steroid dexamethasone, which readily crosses the placenta, or to carbenoxolone, which inhibits 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the physiological feto-placental 'barrier' to maternal glucocorticoids. As adults, the offspring exhibit permanent hypertension, hyperglycaemic, increased hypothalamic-pituitary-adrenal (HPA) axis activity and behaviour reminiscent of anxiety. Physiological variations in placental 11beta-HSD2 activity correlate directly with foetal weight. In humans, 11beta-HSD2 gene mutations cause low birth weight. Moreover, low-birth-weight babies have higher plasma cortisol levels throughout adult life, indicating HPA axis programming. The molecular mechanisms may reflect permanent changes in the expression of specific transcription factors, key among which is the glucocorticoid receptor (GR) itself. The differential programming of the GR in different tissues reflects effects upon one or more of the multiple tissue-specific alternate first exons/promoters of the GR gene. Overall, the data suggest that both pharmacological and physiological exposure prenatally to excess glucocorticoids programmes cardiovascular, metabolic and neuroendocrine disorders in adult life.
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PMID:Prenatal glucocorticoids and long-term programming. 1555 87


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