Evidence of coexisting changes in 11 beta-hydroxysteroid dehydrogenase and 5 beta-reductase activity in subjects with untreated essential hypertension

Clinical and cardiac characteristics of primary bilateral macronodular adrenal hyperplasia

Background

Cardiovascular disease is the leading cause of death in Cushingžs syndrome (CS). Primary bilateral macro-nodular adrenal hyperplasia (PBMAH), is a rare cause of CS that is clinically distinct from the other common types of CS, but cardiac characteristics have been poorly studied.

Methods

The clinical data, steroid hormones and echocardiographic variables of 17 patients with PBMAH were collected. Twenty-one CS patients with cortisol-producing adenoma (CPA) were collected as controls. The similarities and differences of clinical and cardiac features between the two groups were compared.

Tissue Glucocorticoid Metabolism in Adrenal Insufficiency: A Prospective Study of Dual-release Hydrocortisone Therapy

BACKGROUND

Patients with adrenal insufficiency (AI) require life-long glucocorticoid (GC) replacement therapy. Within tissues, cortisol (F) availability is under the control of the isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD). We hypothesize that corticosteroid metabolism is altered in patients with AI because of the nonphysiological pattern of current immediate release hydrocortisone (IR-HC) replacement therapy. The use of a once-daily dual-release hydrocortisone (DR-HC) preparation, (Plenadren®), offers a more physiological cortisol profile and may alter corticosteroid metabolism in vivo.

STUDY DESIGN AND METHODS

Prospective crossover study assessing the impact of 12 weeks of DR-HC on systemic GC metabolism (urinary steroid metabolome profiling), cortisol activation in the liver (cortisone acetate challenge test), and subcutaneous adipose tissue (microdialysis, biopsy for gene expression analysis) in 51 patients with AI (primary and secondary) in comparison to IR-HC treatment and age- and BMI-matched controls.

RESULTS

Patients with AI receiving IR-HC had a higher median 24-hour urinary excretion of cortisol compared with healthy controls (72.1 µg/24 hours [IQR 43.6-124.2] vs 51.9 µg/24 hours [35.5-72.3], P = .02), with lower global activity of 11β-HSD2 and higher 5-alpha reductase activity. Following the switch from IR-HC to DR-HC therapy, there was a significant reduction in urinary cortisol and total GC metabolite excretion, which was most significant in the evening. There was an increase in 11β-HSD2 activity. Hepatic 11β-HSD1 activity was not significantly altered after switching to DR-HC, but there was a significant reduction in the expression and activity of 11β-HSD1 in subcutaneous adipose tissue.

CONCLUSION

Using comprehensive in vivo techniques, we have demonstrated abnormalities in corticosteroid metabolism in patients with primary and secondary AI receiving IR-HC. This dysregulation of pre-receptor glucocorticoid metabolism results in enhanced glucocorticoid activation in adipose tissue, which was ameliorated by treatment with DR-HC.

Modulation of 11β-hydroxysteroid dehydrogenase functions by the cloud of endogenous metabolites in a local microenvironment: The glycyrrhetinic acid-like factor (GALF) hypothesis

11β-Hydroxysteroid dehydrogenase (11β-HSD)-dependent conversion of cortisol to cortisone and corticosterone to 11-dehydrocorticosterone are essential in regulating transcriptional activities of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Inhibition of 11β-HSD by glycyrrhetinic acid metabolites, bioactive components of licorice, causes sodium retention and potassium loss, with hypertension characterized by low renin and aldosterone. Essential hypertension is a major disease, mostly with unknown underlying mechanisms. Here, we discuss a putative mechanism for essential hypertension, the concept that endogenous steroidal compounds acting as glycyrrhetinic acid-like factors (GALFs) inhibit 11β-HSD dehydrogenase, and allow for glucocorticoid-induced MR and GR activation with resulting hypertension. Initially, several metabolites of adrenally produced glucocorticoids and mineralocorticoids were shown to be potent 11β-HSD inhibitors. Such GALFs include modifications in the A-ring and/or at positions 3, 7 and 21 of the steroid backbone. These metabolites may be formed in peripheral tissues or by gut microbiota. More recently, metabolites of 11β-hydroxy-Δ4androstene-3,17-dione and 7-oxygenated oxysterols have been identified as potent 11β-HSD inhibitors. In a living system, 11β-HSD isoforms are not exposed to a single substrate but to several substrates, cofactors, and various inhibitors simultaneously, all at different concentrations depending on physical state, tissue and cell type. We propose that this "cloud" of steroids and steroid-like substances in the microenvironment determines the 11β-HSD-dependent control of MR and GR activity. A dysregulated composition of this cloud of metabolites in the respective microenvironment needs to be taken into account when investigating disease mechanisms, for forms of low renin, low aldosterone hypertension.

The Role of Gut Microbiota in Hypertension Pathogenesis and the Efficacy of Antihypertensive Drugs

PURPOSE OF HEADING

To review the relationship between intestinal microbes and hypertension and its impact on the efficacy of antihypertensive drugs, and help to address some of these knowledge gaps.

RECENT FINDINGS

Hypertension is associated with cardiovascular diseases and is the most important modifiable risk factor for all-cause morbidity and mortality worldwide. The pathogenesis of hypertension is complex, including factors such as dietary, environmental and genetics. Recently, the studies have shown that the gut microbiota influences the occurrence and development of hypertension through a variety of ways, including affecting the production of short-chain fatty acids, dysfunction of the brain-gut axis, and changes in serotonin content that cause the imbalance of vagus and sympathetic nerve output associated with hypertension. However, patients with hypertension typically take antihypertensive drugs orally on a long-term basis, and most antihypertensive drugs are absorbed by the gastrointestinal tract. Studies have shown that the pharmacokinetics and metabolism of antihypertensive drugs may be influenced by microbiota, or antihypertensive drugs act directly on the intestinal flora to exert efficacy, including regulation of intestinal microbial metabolism, intestinal inflammation, and intestinal sympathetic nervous system disorders. The intestinal flora can affect the pharmacokinetics and metabolism of antihypertensive drugs in the rats, and intestinal microbiota also can be the target "organ" by antihypertensive drugs.

Sex- and age-specific reference intervals for diagnostic ratios reflecting relative activity of steroidogenic enzymes and pathways in adults

OBJECTIVE

Diagnostic ratios calculated from urinary steroid hormone metabolites are used as a measure for the relative activity of steroidogenic enzymes or pathways in the clinical investigation of steroid metabolism disorders. However, population-based sex- and age-specific reference intervals and day-night differences in adults are lacking.

METHODS

Sixty-five diagnostic ratios were calculated from steroid metabolites measured by GC-MS in day- and night-time and in 24-hour urine from 1128 adults recruited within the Swiss Kidney Project on Genes in Hypertension (SKIPOGH), a population-based, multicenter cohort study. Differences related to sex, age and day- and night-time were evaluated and reference curves in function of age and sex were modelled by multivariable linear mixed regression for diagnostic ratios and were compared to values from the literature.

RESULTS

Most ratios had sex- and age-specific relationships. For each ratio, percentiles were plotted in function of age and sex in order to create reference curves and sex- and age-specific reference intervals derived from 2.5th and 97.5th percentiles were obtained. Most ratios reflected a higher enzyme activity during the day compared to the night.

CONCLUSIONS

Sex- and age-specific references for 24 hours, day and night urine steroid metabolite ratios may help distinguishing between health and disease when investigating human disorders affecting steroid synthesis and metabolism. The day-night differences observed for most of the diagnostic ratios suggest a circadian rhythm for enzymes involved in human steroid hormones metabolism.

Perceived stress, depressive symptoms, and cortisol-to-cortisone ratio in spot urine in 6878 older adults

BACKGROUND

Late life depression and perceived stress could influence disease pathways via reduced 11β-HSD2 activity, particularly given suggestions that reduced 11β-HSD2 activity, which is reflected in the cortisol-to-cortisone ratio, is a risk factor of disease. To date, however, examination of the relationship between the cortisol-to-cortisone ratio and perceived stress or depressive symptoms is insufficient.

METHODS

We examined the cross-sectional association of the cortisol-to-cortisone ratio with perceived stress and depressive symptoms, and analyzed whether cortisol levels modify this association, in 6878 participants aged 45-74 years. Cortisol and cortisone in spot urine were measured using liquid chromatography-mass spectrometry. Perceived stress during the past year was measured using a self-reported questionnaire. Depressive symptoms were evaluated using the Zung Self-Rating Depression Scale. Analyses were performed with adjustment for age, sex, lifestyle factors (smoking habit, alcohol consumption, physical activity, and sleeping hours), and physical health factors (body mass index [kg/m²] and medical history [diabetes, hypertension, and medication for hyperlipidemia or corticosteroids]).

RESULTS

Cortisol-to-cortisone ratio and cortisol were positively associated with perceived stress (% change: 2.33, P_trend = 0.003; and 4.74, P_trend = 0.001, respectively), but were not significantly associated with depressive symptoms. Further, the relationship between cortisol-to-cortisone ratio and perceived stress was modified by cortisol level and sex: the positive association between perceived stress and the cortisol-to-cortisone ratio was more evident in subjects with lower cortisol levels (P_interaction = 0.009) and in men (P_interaction = 0.026).

CONCLUSIONS

These findings suggest that the cortisol-to-cortisone ratio in spot urine may be a useful marker for non-acute perceived stress in daily life against a possible background of reduced 11β-HSD2 in older adults.

Intestinal Flora Modulates Blood Pressure by Regulating the Synthesis of Intestinal-Derived Corticosterone in High Salt-Induced Hypertension

Rationale:

High-salt diet is one of the most important risk factors for hypertension. Intestinal flora has been reported to be associated with high salt–induced hypertension (hSIH). However, the detailed roles of intestinal flora in hSIH pathogenesis have not yet been fully elucidated.

Objective:

To reveal the roles and mechanisms of intestinal flora in hSIH development.

Methods and Results:

The abovementioned issues were investigated using various techniques including 16S rRNA gene sequencing, untargeted metabolomics, selective bacterial culture, and fecal microbiota transplantation. We found that high-salt diet induced hypertension in Wistar rats. The fecal microbiota of healthy rats could dramatically lower blood pressure (BP) of hypertensive rats, whereas the fecal microbiota of hSIH rats had opposite effects. The composition, metabolism, and interrelationship of intestinal flora in hSIH rats were considerably reshaped, including the increased corticosterone level and reduced Bacteroides and arachidonic acid levels, which tightly correlated with BP. The serum corticosterone level was also significantly increased in rats with hSIH. Furthermore, the above abnormalities were confirmed in patients with hypertension. The intestinal Bacteroides fragilis could inhibit the production of intestinal-derived corticosterone induced by high-salt diet through its metabolite arachidonic acid.

Conclusions:

hSIH could be transferred by fecal microbiota transplantation, indicating the pivotal roles of intestinal flora in hSIH development. High-salt diet reduced the levels of B fragilis and arachidonic acid in the intestine, which increased intestinal-derived corticosterone production and corticosterone levels in serum and intestine, thereby promoting BP elevation. This study revealed a novel mechanism different from inflammation/immunity by which intestinal flora regulated BP, namely intestinal flora could modulate BP by affecting steroid hormone levels. These findings enriched the understanding of the function of intestinal flora and its effects on hypertension.

Low-Renin Hypertension

Low-renin hypertension affects 30% of hypertensive patients. Primary hyperaldosteronism presents with low renin and aldosterone excess. Low-renin, low-aldosterone hypertension represents a wide spectrum of disorders that includes essential low-renin hypertension, hereditary forms of hypertension, and hypertension secondary to endogenous or exogenous factors. This review addresses the different conditions that present with low-renin hypertension, discussing an appropriate diagnostic approach and highlighting the genetic subtypes within familial forms.

Genetics of Hypertension in African Americans and Others of African Descent

Hypertension is the leading cause of cardiovascular disease in the United States, affecting up to one-third of adults. When compared to other ethnic or racial groups in the United States, African Americans and other people of African descent show a higher incidence of hypertension and its related comorbidities; however, the genetics of hypertension in these populations has not been studied adequately. Several genes have been identified to play a role in the genetics of hypertension. They include genes regulating the renin-aldosterone-angiotensin system (RAAS), such as Sodium Channel Epithelial 1 Beta Subunit (SCNN1B), Armadillo Repeat Containing 5 (ARMC5), G Protein-Coupled Receptor Kinase 4 (GRK4), and Calcium Voltage-Gated Channel Subunit Alpha1 D (CACNA1D). In this review, we focus on recent genetic findings available in the public domain for potential differences between African Americans and other populations. We also cover some recent and relevant discoveries in the field of low-renin hypertension from our laboratory at the National Institutes of Health. Understanding the different genetics of hypertension among various groups is essential for effective precision-guided medical therapy of high blood pressure.

Role of gut metabolism of adrenal corticosteroids and hypertension: clues gut-cleansing antibiotics give us

Intestinal bacteria can metabolize sterols, bile acids, steroid hormones, dietary proteins, fiber, foodstuffs, and short chain fatty acids. The metabolic products generated by some of these intestinal bacteria have been linked to a number of systemic diseases including obesity with Type 2 diabetes mellitus, some forms of inflammation, and more recently, systemic hypertension. In this review, we primarily focus on the potential role selected gut bacteria play in metabolizing the endogenous glucocorticoids corticosterone and cortisol. Those generated steroid metabolites, when reabsorbed in the intestine back into the circulation, produce biological effects most notably as inhibitors of 11β-hydroxysteroid dehydrogenase (11β-HSD) types 1 and 2. Inhibition of the dehydrogenase actions of 11β-HSD, particularly in kidney and vascular tissue, allows both corticosterone and cortisol the ability to bind to and activate mineralocorticoid receptors with attended changes in sodium handling and vascular resistance leading to increases in blood pressure. In several animal models of hypertension, administration of gut-cleansing antibiotics results in transient resolution of hypertension and transfer of intestinal contents from a hypertensive animal to a normotensive animal produces hypertension in the recipient. Moreover, fecal samples from hypertensive humans transplanted into germ-free mice resulted in hypertension in the recipient mice. Thus, it appears that the intestinal microbiome may not just be an innocent bystander but certain perturbations in the type and number of bacteria may directly or indirectly affect hypertension and other diseases.

Diagnostic approach to low-renin hypertension

Renin-angiotensin-aldosterone system (RAAS) plays a crucial role in maintaining water and electrolytes homoeostasis, and its deregulation contributes to the development of arterial hypertension. Since the historical description of the "classical" RAAS, a dramatic increase in our understanding of the molecular mechanisms underlying the development of both essential and secondary hypertension has occurred. Approximatively 25% of the patients affected by arterial hypertension display low-renin levels, a definition that is largely arbitrary and depends on the investigated population and the specific characteristics of the assay. Most often, low-renin levels are expression of a physiological response to sodium-volume overload, but also a significant number of secondary hereditary or acquired conditions falls within this category. In a context of suppressed renin status, the concomitant examination of plasma aldosterone levels (which can be inappropriately elevated, within the normal range or suppressed) and plasma potassium are essential to formulate a differential diagnosis. To distinguish between the different forms of low-renin hypertension is of fundamental importance to address the patient to the proper clinical management, as each subtype requires a specific and targeted therapy. The present review will discuss the differential diagnosis of the most common medical conditions manifesting with a clinical phenotype of low-renin hypertension, enlightening the novelties in genetics of the familial forms.

Glucocorticoids and gut bacteria: "The GALF Hypothesis" in the metagenomic era

A new concept is emerging in biomedical sciences: the gut microbiota is a virtual 'organ' with endocrine function. Here, we explore the literature pertaining to the role of gut microbial metabolism of endogenous adrenocorticosteroids as a contributing factor in the etiology of essential hypertension. A body of literature demonstrates that bacterial products of glucocorticoid metabolism are absorbed into the portal circulation, and pass through the kidney before excretion into urine. Apparent mineralocorticoid excess (AME) syndrome patients were found to have congenital mutations resulting in non-functional renal 11β-hydroxysteroid dehydrogenase-2 (11β-HSD2) and severe hypertension often lethal in childhood. 11β-HSD2 acts as a "guardian" enzyme protecting the mineralocorticoid receptor from excess cortisol, preventing sodium and water retention in the normotensive state. Licorice root, whose active ingredient, glycerrhetinic acid (GA), inhibits renal 11β-HSD2, and thereby causes hypertension in some individuals. Bacterially derived glucocorticoid metabolites may cause hypertension in some patients by a similar mechanism. Parallel observations in gut microbiology coupled with screening of endogenous steroids as inhibitors of 11β-HSD2 have implicated particular gut bacteria in essential hypertension through the production of glycerrhetinic acid-like factors (GALFs). A protective role of GALFs produced by gut bacteria in the etiology of colorectal cancer is also explored.

11-Beta Dehydrogenase Type 2 Activity Is Not Reduced in Treatment Resistant Hypertension

BACKGROUND AND OBJECTIVE

Decreased renal 11-beta dehydrogenase type 2 (11β-HSD2) activity, as reflected by an increased urinary free cortisol to cortisone ratio (UFF/UFE), is associated with having hypertension (HTN). The current study was conducted to determine if reduced 11β-HSD2 activity is also associated with having resistant HTN.

METHOD

We evaluated 55 consecutive patients with RHTN, defined as blood pressure (BP) ≥140/90 mm Hg despite using ≥3 antihypertensive medications including a diuretic, and 38 patients whose BP was controlled on ≤3 medications to serve as a non-RHTN comparator group. All patients underwent biochemical evaluation, including measurement of 24-hour urinary UFF/UFE.

RESULTS

The 2 study groups had similar demographic characteristics. Systolic, diastolic BP, and number of antihypertensive medications were greater in patients with uncontrolled RHTN vs. the control group (167.5 ± 28.2/91.2 ± 18.8 vs. 126.6 ± 11.4/77.8 ± 8.65 mm Hg and 4.31 ± 1.23 vs. 2.74 ± 0.6, respectively). The 24-hour UFF was 13.6 ± 11.8 vs. 14.3 ± 10.7 µg/24 h and UFE was 64.9 ± 36.3 vs. 76.1 ± 44 µg/24 h such that the UFF/UFE was 0.22 ± 0.16 vs. 0.19 ± 0.09 in RHTN vs. the control group. This ratio was not associated to age, race, gender, and body mass index.

CONCLUSION

An elevated UFF/UFE was not present in this large cohort of patients with uncontrolled RHTN. This suggests that reduced conversion of cortisol to cortisone does not contribute to the development of RHTN.

Why do humans have two glucocorticoids: A question of intestinal fortitude

The main purpose of this review article is threefold (a) to try to address the question "why are two adrenal glucocorticoids, cortisol and corticosterone, secreted by humans and other mammalian species?", (b) to outline a hypothesis that under certain physiological conditions, corticosterone has additional biochemical functions over and above those of cortisol, and (c) to emphasize the role of gastrointestinal bacteria in chemically transforming corticosterone into metabolites and that these re-cycled metabolites can be reabsorbed from the enterohepatic circuit. Cortisol and its metabolites are not secreted into the bile and thus are excluded from the enterohepatic circuit. Corticosterone was the first steroid hormone isolated from adrenal gland extracts. Many believe that corticosterone functions identically to cortisol. Yet, corticosterone causes significant sodium retention and potassium secretion in Addisonian patients, unlike cortisol. In humans, corticosterone and its metabolite, 3α,5α-TH-corticosterone, are excreted via the bile in humans where they are transformed in the intestine by anaerobic bacteria into 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones. These metabolites inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase, being many-fold more potent than 3α,5α-TH-cortisol. Corticosterone has significantly lower Km's for both 11β-HSD2 and 11β-HSD1 enzymatic dehydrogenase activity, compared to cortisol. Patients diagnosed with 17α-hydroxylase deficiency have elevated blood pressure and high levels of circulating corticosterone, 3α,5α-TH-corticosterone, and their 21-dehydroxlated corticosterone derivatives. In humans, these 5α-corticosterone metabolites are likely to influence blood pressure regulation and Na(+) retention by inhibiting the rate of deactivation of cortisol by 11β-HSD isoforms.

Pathophysiology, diagnosis, and treatment of mineralocorticoid disorders

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure control, fluid, and electrolyte balance in humans. Chronic activation of mineralocorticoid production leads to dysregulation of the cardiovascular system and to hypertension. The key mineralocorticoid is aldosterone. Hyperaldosteronism causes sodium and fluid retention in the kidney. Combined with the actions of angiotensin II, chronic elevation in aldosterone leads to detrimental effects in the vasculature, heart, and brain. The adverse effects of excess aldosterone are heavily dependent on increased dietary salt intake as has been demonstrated in animal models and in humans. Hypertension develops due to complex genetic influences combined with environmental factors. In the last two decades, primary aldosteronism has been found to occur in 5% to 13% of subjects with hypertension. In addition, patients with hyperaldosteronism have more end organ manifestations such as left ventricular hypertrophy and have significant cardiovascular complications including higher rates of heart failure and atrial fibrillation compared to similarly matched patients with essential hypertension. The pathophysiology, diagnosis, and treatment of primary aldosteronism will be extensively reviewed. There are many pitfalls in the diagnosis and confirmation of the disorder that will be discussed. Other rare forms of hyper- and hypo-aldosteronism and unusual disorders of hypertension will also be reviewed in this article.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones (potent inhibitors of 11β-HSD2 and 11β-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11β-hydroxy-progesterone, and 3α,5α-tetrahydro-11β-hydroxy-progesterone strongly inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

Chronic inhibition of 11 β -hydroxysteroid dehydrogenase type 1 activity decreases hypertension, insulin resistance, and hypertriglyceridemia in metabolic syndrome

Metabolic syndrome is a constellation of risk factors including hypertension, dyslipidemia, insulin resistance, and obesity that promote the development of cardiovascular disease. Metabolic syndrome has been associated with changes in the secretion or metabolism of glucocorticoids, which have important functions in adipose, liver, kidney, and vasculature. Tissue concentrations of the active glucocorticoid cortisol are controlled by the conversion of cortisone to cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Because of the various cardiovascular and metabolic activities of glucocorticoids, we tested the hypothesis that 11β-HSD1 is a common mechanism in the hypertension, dyslipidemia, and insulin resistance in metabolic syndrome. In obese and lean SHR/NDmcr-cp (SHR-cp), cardiovascular, metabolic, and renal functions were measured before and during four weeks of administration of vehicle or compound 11 (10 mg/kg/d), a selective inhibitor of 11β-HSD1. Compound 11 significantly decreased 11β-HSD1 activity in adipose tissue and liver of SHR-cp. In obese SHR-cp, compound 11 significantly decreased mean arterial pressure, glucose intolerance, insulin resistance, hypertriglyceridemia, and plasma renin activity with no effect on heart rate, body weight gain, or microalbuminuria. These results suggest that 11β-HSD1 activity in liver and adipose tissue is a common mediator of hypertension, hypertriglyceridemia, glucose intolerance, and insulin resistance in metabolic syndrome.

HSD11B2 CA-repeat and sodium balance

Type 2 11β-hydroxysteroid dehydrogenase encoded by the HSD11B2 gene converts cortisol to inactive cortisone and thus protects the mineralocorticoid receptor from cortisol exposure. Impaired activity of this enzyme leads to mineralocorticoid excess, suggesting HSD11B2 as a candidate locus for patients at risk of developing low renin or salt-sensitive essential hypertension. In the present study, we searched for frequent polymorphisms in 155 Japanese subjects but detected none in the proximal promoter or coding regions of HSD11B2. Following this result, we genotyped a highly polymorphic CA-repeat polymorphism within the first intron in 848 normotensive and 430 hypertensive Japanese patients, and we then analyzed its association with disease and clinical parameters. We confirmed 12 alleles (12, 15-25 CA repeats) in the population and found no significant difference in the distribution of the allele length between normotensive and hypertensive patients. In 174 normal subjects without medication, urinary cortisol excretion was higher in subjects with more CA repeats in the shorter allele, but the ratio of urinary cortisone to cortisol, a reliable marker of renal HSD11B2 activity, did not differ. However, longer CA-repeat length was positively correlated with 24-h urinary sodium excretion, fractional sodium excretion and potassium clearance, and this observation was confirmed when the longer CA-repeat length was dichotomized. Thus, HSD11B2 CA-repeat genotype is not associated with hypertension itself, but with renal sodium excretion, probably through salt intake/appetite.

Role of 11βHSD type 2 enzyme activity in essential hypertension and children with chronic kidney disease (CKD)

BACKGROUND

The mineralocorticoid receptor is protected from excess of glucocorticoids by conversion of active cortisol to inactive cortisone by enzyme 11β-hydroxysteroid dehydrogenase type 2 present in the kidney. The metabolites of cortisol and cortisone are excreted in the urine as tetrahydrocortisol (5αTHF+5βTHF) and tetrahydrocortisone (THE), respectively.

HYPOTHESIS

Patients with chronic kidney disease (CKD) and essential hypertension have a functional defect in their ability to convert cortisol to cortisone, thus leading to the activation of mineralocorticoid receptor.

OBJECTIVE

The objective of the investigation was to study the ratio of urinary steroids (5αTHF+5βTHF) to THE in patients with CKD, postrenal transplant, and essential hypertension and to compare the ratio with controls.

DESIGN/METHODS

We enrolled 44 patients (17 with CKD, eight postrenal transplant, 19 with essential hypertension) and 12 controls. We measured spot urinary 5α-THF, 5β-THF, THE, free active cortisol and inactive cortisone by gas chromatography/mass spectrometry. We collected data on age, sex, cause of kidney disease, height, weight, body mass index, blood pressure, serum electrolytes, aldosterone, and plasma renin activity. Blood pressure percentiles and z-scores were calculated. The glomerular filtration rate was calculated using the modified Schwartz formula.

RESULTS

The ratios of 5αTHF+5βTHF to THE were significantly higher in patients with CKD [mean±sd score (SDS)=1.31±1.07] as compared with essential hypertension (mean±SDS=0.59±0.23; P=0.02) and controls (mean±SDS=0.52±0.25; P=0.01). In the postrenal transplant group, the ratio was not significantly different (mean±SDS=0.71±0.55). The urinary free cortisol to free cortisone ratios were significantly higher in the hypertension and CKD groups as compared with the controls. The 5αTHF+5βTHF to THE ratio negatively correlated with the glomerular filtration rate and positively correlated with systolic and diastolic blood pressure z-scores. The correlation of the blood pressure z-scores with ratios was stronger in the CKD group than the essential hypertension and posttransplant groups.

CONCLUSIONS

We have elucidated a functional deficiency of 11β-hydroxysteroid dehydrogenase type 2 in children with CKD and a subset of essential hypertension. Urinary 5α-THF, 5β-THF, and THE analysis by gas chromatography/mass spectrometry should be a part of routine work-up of CKD and hypertensive patients.

Physiological concentrations of serum cortisol are related to vascular risk markers in prepubertal children

There is increasing evidence that cortisol contributes to cardiovascular risk. It is unclear whether physiological concentrations of serum cortisol are related to vascular risk markers in children. The cross-sectional associations between morning serum cortisol and cardiovascular risk markers: blood pressure (BP) and carotid intima-media thickness (IMT), were examined in a sample of healthy prepubertal children (age, 6.8 ± 0.1 y) attending primary care clinics. Serum cortisol was associated with increased systolic BP (SBP; n = 223; p < 0.001) and carotid IMT (n = 91; p < 0.0001). These associations were independent from age, BMI, body fat, waist, insulin resistance, serum lipids, and heart rate (HR). No gender interactions were apparent in these associations. In summary, a higher morning serum cortisol within the physiological range is in prepubertal children associated with vascular risk markers. Because childhood risk factors predict adult risk for cardiovascular disease, these observations may have implications in the prevention of cardiovascular disease early in life.

11β-Hydroxysteroid dehydrogenase type-2 and type-1 (11β-HSD2 and 11β-HSD1) and 5β-reductase activities in the pathogenia of essential hypertension

Cortisol availability is modulated by several enzymes: 11β-HSD2, which transforms cortisol (F) to cortisone (E) and 11β-HSD1 which predominantly converts inactive E to active F. Additionally, the A-ring reductases (5α- and 5β-reductase) inactivate cortisol (together with 3α-HSD) to tetrahydrometabolites: 5αTHF, 5βTHF, and THE. The aim was to assess 11β-HSD2, 11β-HSD1, and 5β-reductase activity in hypertensive patients. Free urinary F, E, THF, and THE were measured by HPLC-MS/MS in 102 essential hypertensive patients and 18 normotensive controls. 11β-HSD2 enzyme activity was estimated by the F/E ratio, the activity of 11β-HSD1 in compare to 11β-HSD2 was inferred by the (5αTHF + 5βTHF)/THE ratio and 5β-reductase activity assessed using the E/THE ratio. Activity was considered altered when respective ratios exceeded the maximum value observed in the normotensive controls. A 15.7% of patients presented high F/E ratio suggesting a deficit of 11β-HSD2 activity. Of the remaining 86 hypertensive patients, two possessed high (5αTHF + 5βTHF)/THE ratios and 12.8% had high E/THE ratios. We observed a high percentage of alterations in cortisol metabolism at pre-receptor level in hypertensive patients, previously misclassified as essential. 11β-HSD2 and 5β-reductase decreased activity and imbalance of 11β-HSDs should be considered in the future management of hypertensive patients.

Human Delta4-3-oxosteroid 5beta-reductase (AKR1D1) deficiency and steroid metabolism

Conclusive in vivo evidence regarding the enzyme responsible for steroid hormone 5beta-reduction has not been obtained, although studies have suggested it may be the same enzyme as that utilized for cholic acid and chenodeoxycholic bile-acid synthesis. We have recorded the steroid metabolome of a patient with a defect in the "bile-acid" 5beta-reductase (AKR1D1) and from this confirm that this enzyme is additionally responsible for steroid hormone metabolism. The 13-year old patient has been investigated since infancy because of a cholestasis phenotype caused by bile-acid insufficiency. Several years ago it was shown that she had a 662C>T missense mutation in AKR1D1 causing a Pro198Leu substitution. It was found that the patient had an almost total absence of 5beta-reduced metabolites of corticosteroids and severely reduced production of 5beta-reduced metabolites of other steroids. The patient is healthy in spite of her earlier hepatic failure and is on no treatment. All her vital signs were normal, as were results of many biochemical analyses. She had normal pubertal changes and experiences regular menstrual cycles. There was no evidence for any clinical condition that could be attributed to attenuated ability to metabolize steroids in normal fashion. Both parents were heterozygous for the mutation but the steroid excretion was entirely normal, although an older female sibling showed definitive evidence for attenuated 5beta-reduction of cortisol. A younger brother had a normal steroid metabolome. The sibling genotypes were not available.

Glucocorticoids and cardiovascular disease

Chronic excessive activation of glucocorticoid receptors induces obesity, insulin resistance, glucose intolerance, dyslipidaemia and hypertension. Subtle abnormalities of the hypothalamic-pituitary-adrenal axis and/or of tissue sensitivity to glucocorticoids are also associated with these cardiovascular risk factors in patients with the metabolic syndrome. Furthermore, glucocorticoids have direct effects on the heart and blood vessels, mediated by both glucocorticoid and mineralocorticoid receptors and modified by local metabolism of glucocorticoids by the 11beta-hydroxysteroid dehydrogenase enzymes. These effects influence vascular function, atherogenesis and vascular remodelling following intra-vascular injury or ischaemia. This article reviews the systemic and cardiovascular effects of glucocorticoids, and the evidence that glucocorticoids not only promote the incidence and progression of atherogenesis but also modify the recovery from occlusive vascular events and intravascular injury. The conclusion is that manipulation of glucocorticoid action within metabolic and cardiovascular tissues may provide novel therapeutic avenues to combat cardiovascular disease.

Diagnosis and treatment of low-renin hypertension

Plasma renin levels can be used to classify hypertension. A significant proportion of hypertensive individuals display a low-renin profile and thus low-renin hypertension (LRH) requires appropriate diagnosis and treatment. LRH includes essential, secondary and genetic forms, the most common of which are low-renin essential hypertension and primary aldosteronism. Several studies have investigated the relationship between PRA status and clinical response to different antihypertensive therapies. The present review will discuss the differential diagnosis of LRH subtypes and the most appropriate treatment options based on the pathophysiological background of this condition.

Evidence for altered hypothalamus-pituitary-adrenal axis functioning in systemic hypertension: blunted cortisol response to awakening and lower negative feedback sensitivity

BACKGROUND

Hypothalamus-pituitary-adrenal (HPA) axis functioning in systemic hypertension is not fully understood. We explored HPA axis activity and feedback sensitivity to oral administration of dexamethasone in systemic hypertension via assessment of the cortisol awakening response (CAR) and the circadian cortisol profile.

METHODS

The CAR and circadian cortisol profile were assessed in 20 unmedicated and otherwise healthy middle-aged hypertensive men and in 22 normotensive male controls. Salivary free cortisol measures for the CAR were obtained immediately after awakening and 15, 30, 45, and 60 min thereafter. Circadian cortisol secretion was sampled at 08:00, 11:00, 15:00, and 20:00 h. Assessment of the CAR was repeated on the next day after administration of 0.5mg dexamethasone at 23:00 h on the previous night.

RESULTS

Hypertensives had a significantly lower CAR (p<0.02) and significantly reduced suppression of the CAR after dexamethasone administration (p<0.01) than normotensive controls. There were no significant differences in cortisol levels at awakening and in circadian cortisol profiles between hypertensives and normotensives.

CONCLUSION

We found evidence for altered HPA axis activity in men with systemic hypertension evident with the CAR. Hypertensives showed relative attenuation in the CAR and in the HPA axis feedback sensitivity following dexamethasone suppression. Such alterations in HPA axis regulation might contribute to the atherosclerotic risk in hypertensive individuals.

Endogenous inhibitors (GALFs) of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2: derivatives of adrenally produced corticosterone and cortisol

Two isoforms of 11beta-HSD exist; 11beta-HSD1 is bi-directional (the reductase usually being predominant) and 11beta-HSD2 functions as a dehydrogenase, conferring kidney mineralocorticoid specificity. We have previously described endogenous substances in human urine, "glycyrrhetinic acid-like factors (GALFs)", which like licorice, inhibit the bi-directional 11beta-HSD1 enzyme as well as the dehydrogenase reaction of 11beta-HSD2. Many of the more potent GALFs are derived from two major families of adrenal steroids, corticosterone and cortisol. For example, 3alpha5alpha-tetrahydro-corticosterone, its derivative, 3alpha5alpha-tetrahydro-11beta-hydroxy-progesterone (produced by 21-deoxygenation of corticosterone in intestinal flora); 3alpha5alpha-tetrahydro-11beta-hydroxy-testosterone (produced by side chain cleavage of cortisol); are potent inhibitors of 11beta-HSD1 and 11beta-HSD2-dehydrogenase, with IC50's in range 0.26-3.0 microM, whereas their 11-keto-3alpha5alpha-tetrahydro-derivatives inhibit 11beta-HSD1 reductase, with IC50's in range 0.7-0.8 microM (their 3alpha5beta-derivatives being completely inactive). Inhibitors of 11beta-HSD2 increase local cortisol levels, permitting it to act as a mineralocorticoid in kidney. Inhibitors of 11beta-HSD1 dehydrogenase/11beta-HSD1 reductase serve to adjust the set point of local deactivation/reactivation of cortisol in vascular and other glucocorticoid target tissues, including adipose, vascular, adrenal tissue, and the eye. These adrenally derived 11-oxygenated C21- and C19 -steroidal substances may serve as 11beta-HSD1- or 11beta-HSD2-GALFs. We conclude that adrenally derived products are likely regulators of local cortisol bioactivity in humans.

Cardiovascular consequences of cortisol excess

Cushing's syndrome is a consequence of primary or, more commonly, secondary oversecretion of cortisol. Cardiovascular disease is the major cause of morbidity and mortality in Cushing's syndrome, and excess risk remains even in effectively treated patients. The cardiovascular consequences of cortisol excess are protean and include, inter alia, elevation of blood pressure, truncal obesity, hyperinsulinemia, hyperglycemia, insulin resistance, and dyslipidemia. This review analyses the relationship of cortisol excess, both locally and at tissue level, to these cardiovascular risk factors, and to putative mechanisms for hypertension. Previous studies have examined correlations between cortisol, blood pressure, and other parameters in the general population and in Cushing's syndrome. This review also details changes induced by short-term cortisol administration in normotensive healthy men.

Impaired protein stability of 11beta-hydroxysteroid dehydrogenase type 2: a novel mechanism of apparent mineralocorticoid excess

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.

Tissue Production of Cortisol by 11beta-Hydroxysteroid Dehydrogenase Type 1 and Metabolic Disease

Activation of intracellular glucocorticoid receptors is determined not only by the plasma concentrations of cortisol, under the influence of the hypothalamic-pituitary-adrenal (HPA) axis, but also by 11HSD enzymes within the target cell which interconvert cortisol with its inert metabolite cortisone. Data from cells in culture, isolated tissues, and transgenic mouse models have established that 11HSD type 1 regenerates glucocorticoids and amplifies glucocorticoid receptor activation. In humans, the rate of cortisol regeneration in peripheral tissues is of similar magnitude to adrenal secretion of cortisol at most times of day, and occurs principally in the splanchnic circulation. Approximately two-thirds of the splanchnic activity appears to reside in visceral adipose tissue, sufficient to allow visceral adipose tissue to "deliver" cortisol to the liver via the portal vein. In obesity, 11HSD1 activity in subcutaneous adipose tissue is increased, putatively explaining the link between obesity and other features of the metabolic syndrome. The regulation of 11HSD1, and the basis for its upregulation in obesity, are now being explored. Against this background, inhibition of 11HSD1 has become a major therapeutic target in metabolic syndrome. Preclinical results with novel selective 11HSD1 inhibitors are encouraging, and clinical proof of principle has been achieved with the nonselective inhibitor carbenoxolone. Although the parallels between metabolic syndrome and Cushing's syndrome were originally drawn with reference to patients with elevated plasma cortisol concentrations, it now appears that manipulating tissue concentrations of cortisol will allow the subtle level of control required for long-term therapy to reduce the risks of cardiovascular disease.

Apparent Mineralocorticoid Excess: Report of Six New Cases and Extensive Personal Experience

In mineralocorticoid target tissues such as the cortical collecting duct in the kidney, the enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) is responsible for the peripheral inactivation of cortisol to cortisone, thereby protecting the mineralocorticoid receptor from inappropriate activation by cortisol. Mutations in the HSD11B2 gene cause the syndrome of apparent mineralocorticoid excess, an autosomal recessive form of inherited hypertension in which cortisol acts as a potent mineralocorticoid. Herein are described six new families with mutations in the HSD11B2 gene causing hypokalemic hypertension, with low plasma aldosterone and low renin levels in affected individuals, indicating mineralocorticoid hypertension. Profiling of urinary steroid metabolites showed decreased cortisol inactivation, with urinary tetrahydrocortisol and tetrahydrocortisone ratio (THF + 5alphaTHF)/THE ranging 2.4 to 40 and nearly absent urinary free cortisone in all but one case. Genetic analysis of the HSD11B2 gene from these patients with apparent mineralocorticoid excess revealed distinct homozygous point mutations in four families, a compound heterozygous mutation in one family, and a large 23-bp exonic insert with frameshift and disruption of the amino acid sequence in another family. Expression studies of mutants that were expressed in HEK-293 cells showed marked reduction or abolition of 11betaHSD2 enzymatic activity. These cases are reviewed along with previous ones from the authors' extensive personal experience to highlight the importance of 11betaHSD2 in the understanding of a new biologic principle in hormone action, demonstrating that local metabolism of the glucocorticoid hormones into inactive derivatives by the enzyme 11betaHSD2 is one of the mechanisms that intervene to allow specific aldosterone regulatory effects.

Cortisol metabolism in hypertension

Corticosteroids are critically involved in blood pressure regulation. Lack of adrenal steroids in Addison's disease causes life-threatening hypotension, whereas glucocorticoid excess in Cushing's syndrome invariably results in high blood pressure. At a pre-receptor level, glucocorticoid action is modulated by 11beta-hydroxysteroid dehydrogenases (11beta-HSDs). 11Beta-HSD1 activates cortisone to cortisol to facilitate glucocorticoid receptor (GR)-mediated action. By contrast, 11beta-HSD2 plays a pivotal role in aldosterone target tissues where it catalyses the opposite reaction (i.e. inactivation of cortisol to cortisone) to prevent activation of the mineralocorticoid receptor (MR) by cortisol. Mutations in the 11beta-HSD2 gene cause a rare form of inherited hypertension, the syndrome of apparent mineralocorticoid excess (AME), in which cortisol activates the MR resulting in severe hypertension and hypokalemia. Ingestion of competitive inhibitors of 11beta-HSD2 such as liquorice and carbenoxolone result in a similar but milder clinical phenotype. Epidemiological data suggests that polymorphic variability in the HSD11B2 gene determines salt sensitivity in the general population, which is a key predisposing factor to adult onset hypertension in some patients. Extrarenal sites of glucocorticoid action and metabolism that might impact on blood pressure include the vasculature and the central nervous system. Intriguingly, increased exposure to glucocorticoids during fetal life promotes high blood pressure in adulthood suggesting an early programming effect. Thus, metabolism and action in many peripheral tissues might contribute to the pathophysiology of human hypertension.

Enhanced 11beta-hydroxysteroid dehydrogenase activity, the metabolic syndrome, and systemic hypertension

Metabolic syndrome, with its attendant cardiovascular complications, is reaching epidemic proportions worldwide; hence, there is intense interest in understanding the pathogenesis of and developing therapy for these common disorders. Recent studies have suggested that metabolic syndrome may be a stress response, with an underlying abnormality in the enzyme 11beta-hydroxysteroid dehydrogenase. At the cellular level, the enzyme hydroxysteroid dehydrogenase type 1 (HSD1) locally regenerates active cortisol from inactive cortisone, amplifying glucocorticoid receptor activation and promoting preadipocyte differentiation and adipocyte hypertrophy. Although initial studies in transgenic mice and humans are encouraging, more data are required to conclusively prove the hypothesis that the adipose-tissue-specific overexpression of HSD1 and the resultant increase in tissue-specific cortisol concentrations result in human obesity, insulin resistance, high blood pressure, and metabolic syndrome. Currently, selective inhibitors of HSD1 are not available for human use; however, their development is under way. The use of potent and selective HSD1 inhibitors will finally confirm or refute this hypothesis and may turn out to be an effective strategy for combating these common maladies.

Comprehensive study of urinary cortisol metabolites in hyperthyroid and hypothyroid patients

OBJECTIVE

To further analyse the significance and mutual relationship of thyroid function-linked alterations in cortisol metabolism that have been separately and variously reported.

PATIENTS AND MEASUREMENTS

Twenty-four-hour urine samples from 21 patients with hyperthyroidism (Graves' disease), 16 patients with hypothyroidism (Hashimoto's thyroiditis), 21 healthy age- and sex-matched controls for hyperthyroidism, and 16 healthy age- and sex-matched controls for hypothyroidism were evaluated for 6beta-hydroxycortisol (6beta-OHF), tetrahydrocortisol (THF), tetrahydrocortisone (THE), allo-tetrahydrocortisol (allo-THF), urinary free cortisol (UFF), urinary free cortisone (UFE) and 17-hydroxycorticosteroid (17-OHCS).

RESULTS

Urinary 17-OHCS, THE and allo-THF levels increased considerably in hyperthyroid patients compared to the controls, while UFF and THF showed no difference between the two groups. Urinary 6beta-OHF was significantly lower in the hyperthyroid patients than in the controls. Both the urinary allo-THF + THF/THE and the UFF/UFE ratios were significantly lower in the hyperthyroid patients than in the controls, whereas only the former was significantly higher in the hypothyroid patients than in the controls. The urinary allo-THF/THF ratio was significantly higher in the hyperthyroid patients and significantly lower in the hypothyroid patients than in the controls. In an analysis of pooled subjects including all groups (n = 64), free T4 levels correlated negatively (P < 0.0001) with the urinary allo-THF + THF/THE ratio but not with the UFF/UFE ratio. The serum levels of free T4 correlated positively (P < 0.0001) with the urinary allo-THF/THF ratio.

CONCLUSION

The thyroid hormones seem to affect the total 11beta-HSD activity (allo-THF + THF/THE) more strongly than the renal 11beta-HSD2 activity (UFF/UFE). 5alpha-reductase activity (allo-THF/THF) is also enhanced in hyperthyroidism, while the reduction of urinary 6beta-OHF in hyperthyroidism might be a secondary effect of the altered activity of the total 11beta-HSD and 5alpha-reductase.

Endogenous selective inhibitors of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2 of adrenal origin

In earlier studies [Latif, S.A., Sheff, M.F., Ribeiro, C.E., Morris, D.J., 1997. Selective inhibition of sheep kidney 11beta-hydroxysteroid-dehydrogenase isoform 2 activity by 5alpha-reduced (but not 5beta) derivatives of adrenocorticosteroids. Steroids 62, 230-237], only derivatives of steroid hormones possessing the 5alpha-Ring A-reduced configuration selectively inhibited 11beta-HSD2-dehydrogenase, whereas their 5beta-derivatives were inactive. This present study focuses on an expanded group of endogenous 11-oxygenated, 5alpha and 5beta-Ring A-reduced metabolites of adrenocorticosteroids, and progestogen and androgen steroid hormones. These substances were tested for their inhibitory properties against 11beta-HSD2, 11beta-HSD1-dehydrogenase and 11beta-HSD1 reductase. The present studies showed that the following compounds stand out as potent inhibitors. These are 5alpha-DH-corticosterone, 3alpha,5alpha-TH-corticosterone, 11beta-OH-progesterone, 11beta-OH-allopregnanolone, 11beta-OH-testosterone, and 11beta-OH-androstanediol, inhibitors of 11beta-HSD1-dehydrogenase; 3alpha,5alpha-TH-11-dehydro-corticosterone, 11-keto-progesterone, 11-keto-allopregnanolone, and 11-keto-3beta,5alpha-TH-testosterone, inhibitors of 11beta-HSD1 reductase; 3alpha,5alpha-TH-aldosterone, 5alpha-DH-corticosterone, 3alpha,5alpha-TH-corticosterone,11-dehydro-corticosterone, 3alpha,5alpha-TH-11-dehydro-corticosterone, 11beta-OH-progesterone, 11-keto-progesterone, 11beta-OH-allopregnanolone, 11-keto-allopregnanolone, 11beta-OH-testosterone, and 11-keto-testosterone, inhibitors of 11beta-HSD2. All of these substances have the potential to be derived from adrenally synthesized corticosteroids. Substances with similar structures to those described may help in the design of exogenous agents for the management of a variety of disease states involving 11beta-HSD isoenzymes.

Expression of renal 11beta-hydroxysteroid dehydrogenase type 2 is decreased in patients with impaired renal function

OBJECTIVE

Renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) enables selective access of aldosterone to the mineralocorticoid receptor (MR). Impaired 11beta-HSD2 activity has been suggested in patients with hypertension as well as in patients with renal disease, where it may contribute to sodium retention, oedema and hypertension. To date, these studies have relied upon urinary cortisol (F) metabolite levels as surrogate markers of renal 11beta-HSD2 activity.

METHODS

We have directly analysed renal 11beta-HSD2 mRNA expression in 95 patients undergoing kidney biopsy using TaqMan real-time PCR. Serum and 24-h urine samples were used to document underlying renal function and endocrine parameters. Urinary F and cortisone (E) metabolites were analysed using gas chromatography/mass spectrometry.

RESULTS

Expression of 11beta-HSD2 did not correlate with blood pressure or urinary Na/K ratio, but a significant positive correlation with creatinine clearance was observed (r = 0.284; P < 0.01). Immunofluorescence and confocal laser microscopy confirmed decreased 11beta-HSD2 expression in patients with impaired renal function. For the first time, we showed that 11beta-HSD2 mRNA expression correlated negatively with the urinary free (UF) F/E (UFF/UFE) ratio (r = 0.276; P < 0.05) as well as with the urinary tetrahydrocortisol + 5alpha-tetrahydrocortisol/tetrahydrocortisone ((THF + alphaTHF)/THE) ratio (r = 0.256; P < 0.05). No difference in 11beta-HSD2 mRNA expression or in the UFF/UFE ratio was found between groups with no proteinuria, microalbuminuria, moderate or severe proteinuria. In contrast, the urinary (THF + alphaTHF)/THE ratio increased significantly (P < 0.05) in patients with severe albuminuria, suggesting increased hepatic 11beta-HSD1 in those patients.

CONCLUSIONS

These data suggest that renal 11beta-HSD2 expression may be represented only marginally better, if at all, by the UFF/UFE than by the (THF + alphaTHF)/THE ratio. Reduced renal 11beta-HSD2 expression may lead to occupancy of the MR by glucocorticoids such as cortisol and may contribute to the increased sodium retention seen in patients with impaired renal function.

Biochemical and genetic characterization of 11 beta-hydroxysteroid dehydrogenase type 2 in low-renin essential hypertensives

BACKGROUND

The 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) catalyzes the conversion of cortisol (F) to cortisone (E), avoiding the interaction of cortisol with the mineralocorticoid receptor. If it fails, cortisol will stimulate sodium and water reabsorption, increasing the intravascular volume that suppresses renin and secondarily increase the blood pressure.

OBJECTIVE

To look for the possible contribution of a decreased ability of 11betaHSD2 to convert cortisol to its inactive metabolite cortisone in the pathogenesis of low renin hypertension (LREH).

PATIENTS AND METHODS

We studied 64 LREH patients (plasma renin activity, PRA < 1 ng/ml per h), eighty normo-renin essential hypertensives (NREH) (PRA: 1-2.5 ng/ml per h) and 74 normotensives. Serum aldosterone (SA), F, E and serum F/E ratio was determined in all patients. A serum F/E ratio was considered high when it was higher than X + 2SD from the normotensive value. Cytosine-adenine (CA)-repeat microsatellite region in intron 1 of HSD11B2 gene was genotyped in all patients and normotensives volunteers. In 13 LREH with high F/E ratio we performed HSD11B2 gene sequencing.

RESULTS

LREH had serum F/E ratio higher than NREH and normotensive controls (3.6 (2.9-4.3) versus 2.9 (2.2-4.3) versus 3.0 (2.4-3.7) (P = 0.004), respectively). We observed an inverse relation between F/E ratio and SA and PRA. In NREH and normotensives we did not find correlation between these variables. In the LREH subset the longer 155 bp CA-allele showed the highest serum F/E ratio. No mutations in coding region or short introns were found in LREH patients.

CONCLUSION

In this study we show that low-renin essential hypertensives had increased serum cortisol/cortisone ratios as compared with normotensive subjects. This suggest that some essential hypertensives, with suppressed renin activity, may have an impairment in the cortisol inactivation catalyzed by the enzyme 11betaHSD2, whose low activity in LREH patients could be associated with the length of CA-repeat microsatellite in intron 1 of the HSD11B2 gene.

Apparent mineralocorticoid excess syndrome: an overview

Apparent mineralocorticoid excess (AME) syndrome results from defective 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). This enzyme is co-expressed with the mineralocorticoid receptor (MR) in the kidney and converts cortisol (F) to its inactive metabolite cortisone (E). Its deficiency allows the unmetabolized cortisol to bind to the MR inducing sodium retention, hypokalemia, suppression of PRA and hypertension. Mutations in the gene encoding 11beta-HSD2 account for the inherited form, but a similar clinical picture to AME occurs following the ingestion of bioflavonoids, licorice and carbenoxolone, which are competitive inhibitors of 11beta-HSD2. Reduced 11beta-HSD2 activity may explain the increased sodium retention in preeclampsia, renal disease and liver cirrhosis. Relative deficiency of 11beta-HSD2 activity can occur in Cushing's syndrome due to saturation of the enzyme and explains the mineralocorticoid excess state that characterizes ectopic ACTH syndrome. Reduced placental 11beta-HSD2 expression might explain the link between reduced birth weight and adult hypertension. Polymorphic variability in the HSD11B2 gene in part determines salt sensitivity, a forerunner for adult hypertension onset. AME represents a spectrum of mineralocorticoid hypertension with severity reflecting the underlying genetic defect in the 11beta-HSD2; although AME is a genetic disorder, several exogenous compounds can bring about the symptoms by inhibiting 11beta-HSD2 enzyme. Substrate excess as seen in Cushing's syndrome and ACTH ectopic production can overwhelm the capacity of 11beta-HSD2 to convert F to E, leading up to an acquired form of AME.

Role of HSD11B2 polymorphisms in essential hypertension and the diuretic response to thiazides

BACKGROUND

The renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta HSD2) enzyme inactivates 11-hydroxy steroids in the kidney, thereby protecting the nonselective mineralocorticoid (MR) receptor from occupation by glucocorticoids. Loss-of-function mutations in the gene encoding 11beta HSD2 (HSD11B2) result in overstimulation of the MR and cause salt-sensitive hypertension.

METHODS

We have investigated the role of HSD11B2 in hypertension in 377 genetically homogeneous essential hypertensives from North Sardinia.

RESULTS

Thirty of these patients displayed increased urinary cortisol metabolite ratios (greater than or equal to 2) (tetrahydrocortisol [THF]+allotetrahydrocortisol [aTHF]/tetrahydrocortisone [THE]) reflecting a mild reduction in 11beta HSD2 activity. No mutations in HSD11B2 were detected in these patients. All 377 patients were genotyped for a CA repeat microsatellite in intron 1 of HSD11B2 and a G534A polymorphism in exon 3 of HSD11B2. CA repeat length was associated with the (THF+aTHF)/THE ratio, which in turn was significantly related to PRA levels. No associations were found between the G354A polymorphism and the other parameters. There were no differences in blood pressure (BP) levels between HSD11B2 genotypes, but in a subgroup of 91 patients that underwent diuretic therapy, CA repeat length was strongly associated with the BP response to hydrochlorothiazide.

CONCLUSION

This study highlights the role of this HSD11B2 polymorphism in sodium handling and is consistent with a role in the BP response to thiazide diuretics.

11β-Hydroxysteroid dehydrogenase type 2 activity is associated with left ventricular mass in essential hypertension

AIMS

Left ventricular mass (LVM) is under the control of aldosterone and angiotensin II in experimental hypertension, but the effect of aldosterone on LVM is controversial in essential hypertension (EH). Some EH patients show a mild impairment of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity without clinical features of the syndrome of apparent mineralocorticoid excess, where the incomplete cortisol-to-cortisone conversion leads to glucocorticoid-mediated mineralocorticoid effects. The mineralocorticoid receptor and 11beta-HSD2 are co-expressed in human heart. We investigated whether LVM may be regulated by glucocorticoids in EH patients.

METHODS AND RESULTS

The ratio between 24 h urinary tetrahydro derivatives of cortisol and cortisone (THFs/THE), plasma renin activity, 24 h urinary aldosterone, blood pressure, and LVM indexed for height(2.7) (LVMh(2.7)) were analysed in 493 never-treated hypertensives and 98 normotensives. THFs/THE was associated with LVMh(2.7) in hypertensives and normotensives (r=0.32, P<0.001, and r=0.17, P=0.04, respectively) and persisted after adjusting for confounders (multiple regression analysis). Body mass index, sex, recumbent plasma renin activity, and THFs/THE accounted for 26.1% of LVMh(2.7) variation. Urinary aldosterone was not correlated with LVMh(2.7).

CONCLUSION

We suggest that glucocorticoids may take part in the regulation of LVM in EH patients as a function of 11beta-HSD2 activity, and contribute to the target organ damage associated with essential hypertension.

Forms of mineralocorticoid hypertension

Hypertension with hypokalemia, metabolic alkalosis, and suppressed plasma renin activity defines mineralocorticoid hypertension. Mineralocorticoid hypertension is the consequence of an overactivity of the epithelial sodium channel expressed at the apical membrane of renal cells in the distal nephron. This is usually the case when the mineralocorticoid receptor is activated by its physiologic substrate aldosterone. The best known form of mineralocorticoid hypertension is an aldosterone-producing adrenal tumor leading to primary aldosteronism. Primary aldosteronism can also be caused by unilateral or bilateral adrenal hyperplasia and rarely adrenal carcinoma. Interestingly, most of the inherited monogenic disorders associated with hypertension involve an excessive activation of the mineralocorticoid axis. In some of these disorders, mineralocorticoid hypertension results from activation of the mineralocorticoid receptor by other steroids (cortisol, deoxycorticosterone), by primary activation of the receptor itself, or by constitutive overactivity of the renal epithelial sodium channel. The present review addresses the physiology and significance of the key players of the mineralocorticoid axis, placing emphasis on the conditions leading to mineralocorticoid hypertension.

Pseudohyperaldosteronism: pathogenetic mechanisms

Pseudohyperaldosteronism is characterized by a clinical picture of hyperaldosteronism with suppression of plasma renin activity and aldosterone. Pseudohyperaldosteronism can be due to a direct mineralocorticoid effect, as with desoxycorticosterone, fluorohydrocortisone, fluoroprednisolone, estrogens, and the ingestion of high amounts of glycyrrhetinic acid. A block of 11-hydroxysteroid-dehydrogenase type 2 (11HSD2), the enzyme that converts cortisol into cortisone, at the level of epithelial target tissues of aldosterone, is involved in other cases. This mechanism is related either to a mutation of the gene, which encodes 11HSD2 (apparent mineralocorticoid excess syndrome and some cases of low renin hypertension) or to an acquired reduction of the activity of the enzyme due to glycyrrhetinic acid, carbenoxolone, and grapefruit juice. In other cases saturation of 11HSD2 may be involved as in severe Cushing's syndrome and chronic therapy with some corticosteroids. Recently, an activating mutation of the mineralocorticoid receptor gene has been described. Another genetic cause of pseudohyperaldosteronism is the syndrome of Liddle, which is due to a mutation of the gene encoding for beta and gamma subunits of the sodium channels.