Apparent mineralocorticoid excess syndrome: an overview. (1/12)

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.  (+info)

Exogenously-induced apparent hypermineralocorticoidism associated with ingestion of "asam boi". (2/12)

A 31-year-old woman presented with a one-week history of headache, generalised lethargy, weakness and poor appetite. Clinical examination showed that her blood pressure was 200/120 mmHg. On an earlier occasion, her blood pressure was found to be normal by a general practitioner whom she last visited three months earlier when she had an upper respiratory tract infection. Investigations showed hypokalaemia, suppressed serum renin and aldosterone. Further history was taken and revealed that she had been craving for guava fruits which she ate with flavoured "asam boi" (containing glycyrrhizic acid) at least three spoonfuls twice a day for the past six weeks. The hypertension and hypokalaemia resolved after two weeks of stopping the "asam boi". Her clinical picture was compatible with exogenously-induced hypermineralocortoidism.  (+info)

The mother or the fetus? 11beta-hydroxysteroid dehydrogenase type 2 null mice provide evidence for direct fetal programming of behavior by endogenous glucocorticoids. (3/12)

Low birth weight associates with increased susceptibility to adult cardiometabolic and affective disorders spawning the notion of fetal "programming." Prenatal exposure to excess glucocorticoids may be causal. In support, maternal stress or treatment during pregnancy with dexamethasone (which crosses the placenta) or inhibitors of fetoplacental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the physiological "barrier" to maternal glucocorticoids, reduces birth weight and programs permanent offspring hypertension, hyperglycemia, and anxiety behaviors. It remains uncertain whether such effects are mediated indirectly via altered maternal function or directly on the fetus and its placenta. To dissect this critical issue, we mated 11beta-HSD2(+/-) mice such that each pregnant female produces +/+, +/-, and -/- offspring and compared them with offspring of homozygous wild-type and -/- matings. We show that 11beta-HSD2(-/-) offspring of either +/- or -/- mothers have lower birth weight and exhibit greater anxiety than 11beta-HSD2(+/+) littermates. This provides clear evidence for the key role of fetoplacental 11beta-HSD2 in prenatal glucocorticoid programming.  (+info)

Apparent mineralocorticoid excess: report of six new cases and extensive personal experience. (4/12)

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.  (+info)

Impaired protein stability of 11beta-hydroxysteroid dehydrogenase type 2: a novel mechanism of apparent mineralocorticoid excess. (5/12)

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.  (+info)

Two elderly patients with mineralocorticoid excess due to 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) impairment. (6/12)

A 75-year-old woman had a low circulating level of aldosterone, despite the mineralocorticoid excess state. These abnormalities were improved by spironolactone administration. The distinct elevation of urinary cortisol/cortisone ratio revealed 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) impairment. Moreover, slight but distinct elevation of the ratio was found in a 95-year-old woman with normotension and normopotassemia. The mineralocorticoid excess state with reduced aldosterone level appeared following with vomiting and diarrhea, exaggerating asymptomatic impairment of 11beta-HSD2 to induce apparent mineralocorticoid excess (AME)-like condition.  (+info)

Apparent mineralocorticoid excess syndrome in a Brazilian boy caused by the homozygous missense mutation p.R186C in the HSD11B2 gene. (7/12)

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In silico structure-function analysis of pathological variation in the HSD11B2 gene sequence. (8/12)

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