Apparent mineralocorticoid excess syndrome in a Brazilian boy caused by the homozygous missense mutation p.R186C in the HSD11B2 gene

Apparent mineralocorticoid excess: comprehensive overview of molecular genetics

Apparent mineralocorticoid excess is an autosomal recessive form of monogenic disease characterized by juvenile resistant low-renin hypertension, marked hypokalemic alkalosis, low aldosterone levels, and high ratios of cortisol to cortisone metabolites. It is caused by defects in the HSD11B2 gene, encoding the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which is primarily involved in the peripheral conversion of cortisol to cortisone. To date, over 50 deleterious HSD11B2 mutations have been identified worldwide. Multiple molecular mechanisms function in the lowering of 11β-HSD2 activity, including damaging protein stability, lowered affinity for the substrate and cofactor, and disrupting the dimer interface. Genetic polymorphism, environmental factors as well as epigenetic modifications may also offer an implicit explanation for the molecular pathogenesis of AME. A precise diagnosis depends on genetic testing, which allows for early and specific management to avoid the morbidity and mortality from target organ damage. In this review, we provide insights into the molecular genetics of classic and non-classic apparent mineralocorticoid excess and aim to offer a comprehensive overview of this monogenic disease.

Canonical and Noncanonical Androgen Metabolism and Activity

Androgens are critical drivers of prostate cancer. In this chapter we first discuss the canonical pathways of androgen metabolism and their alterations in prostate cancer progression, including the classical, backdoor and 5α-dione pathways, the role of pre-receptor DHT metabolism, and recent findings on oncogenic splicing of steroidogenic enzymes. Next, we discuss the activity and metabolism of non-canonical 11-oxygenated androgens that can activate wild-type AR and are less susceptible to glucuronidation and inactivation than the canonical androgens, thereby serving as an under-recognized reservoir of active ligands. We then discuss an emerging literature on the potential non-canonical role of androgen metabolizing enzymes in driving prostate cancer. We conclude by discussing the potential implications of these findings for prostate cancer progression, particularly in context of new agents such as abiraterone and enzalutamide, which target the AR-axis for prostate cancer therapy, including mechanisms of response and resistance and implications of these findings for future therapy.

Beyond T and DHT - novel steroid derivatives capable of wild type androgen receptor activation

While androgen deprivation therapy (ADT) remains the primary treatment for metastatic prostate cancer (PCa), castration does not eliminate androgens from the prostate tumor microenvironment, and residual intratumoral androgens are implicated in nearly every mechanism by which androgen receptor (AR)-mediated signaling promotes castration-resistant disease. The uptake and intratumoral (intracrine) conversion of circulating adrenal androgens such as dehydroepiandrosterone sulfate (DHEA-S) to steroids capable of activating the wild type AR is a recognized driver of castration resistant prostate cancer (CRPC). However, less well-characterized adrenal steroids, including 11-deoxcorticosterone (DOC) and 11beta-hydroxyandrostenedione (11OH-AED) may also play a previously unrecognized role in promoting AR activation. In particular, recent data demonstrate that the 5α-reduced metabolites of DOC and 11OH-AED are activators of the wild type AR. Given the well-recognized presence of SRD5A activity in CRPC tissue, these observations suggest that in the low androgen environment of CRPC, alternative sources of 5α-reduced ligands may supplement AR activation normally mediated by the canonical 5α-reduced agonist, 5α-DHT. Herein we review the emerging data that suggests a role for these alternative steroids of adrenal origin in activating the AR, and discuss the enzymatic pathways and novel downstream metabolites mediating these effects. We conclude by discussing the potential implications of these findings for CRPC progression, particularly in context of new agents such as abiraterone and enzalutamide which target the AR-axis for prostate cancer therapy.

Variants of 11β-hydroxysteroid dehydrogenase (HSD11B) gene type 1 and 2 in Chinese obese adolescents

OBJECTIVE

To investigate the relationship between 11β-hydroxysteroid dehydrogenase (HSD11B) gene type 1 and 2 and obesity in Chinese children.

METHODS

A total of 400 obese and 200 healthy adolescents were enrolled as obese and control groups. Seven SNPs in HSD11B1 (rs4393158, rs2235543, rs10082248, rs10863782, rs2236903, rs2298930, rs4545339) and four variants in HSD11B2 gene (rs28934592, rs28934591, rs28934594 and rs28934593) were measured by automated platform MassArray.

RESULTS

The rs28934592 in HSD11B2 and rs10863782 in HSD11B1 were excluded as false positive or HWE P < 0.05. Moreover, one allele type was found in the other three locations of HSD11B2. The minor allele frequency of rs2235543 and rs10082248 was higher in patients than that in controls (P = 0.045, P = 0.041, respectively). The rs10082248, rs2298930 and rs4545339 were associated with the risk of obesity in the recessive model (P < 0.05, respectively). Moreover, the total cholesterol in patients with GG or AG genotype was significantly higher than that in patients with AA genotype in rs10082248. The rs4393158 was associated with the hypertension in log-additive model test (P = 0.037), and glucose abnormal and hypercholesteremia in dominant model test (P < 0.05, respectively), while the rs2235543 was associated with hypercholesteremia in overdominant model test (P = 0.017).

CONCLUSIONS

The polymorphism of HSD11B1 may be a cause of childhood obesity, or even associated with the complication of childhood obesity. However, variants of HSD11B2 may be not a cause of obesity.

Inherited forms of mineralocorticoid hypertension

PURPOSE OF REVIEW

Inherited forms of mineralocorticoid hypertension are a group of monogenic disorders that, although rare, have enlightened our understanding of normal physiology, and subsequent processes implicated in the pathogenesis of 'essential' hypertension. They often present in early life and can be a cause of major morbidity and mortality that can be effectively treated with simple but targeted pharmacological therapy. Interestingly, all the conditions centre on the regulation of sodium transport through its epithelial channel, either directly or through mediators that act via the mineralocorticoid receptor.

RECENT FINDINGS

In recent years, molecular mechanisms of these conditions and their functional consequences have been elucidated. Diagnosis has been facilitated by plasma and urinary biomarkers.

SUMMARY

We provide an overview and diagnostic approach to apparent mineralocorticoid excess, glucocorticoid remediable aldosteronism, familial hyperaldosteronism type 2, Liddle's syndrome, Gordon's syndrome, activating mutations of the mineralocorticoid receptor, generalized glucocorticoid resistance and hypertensive forms of congenital adrenal hyperplasia.

In silico structure-function analysis of pathological variation in the HSD11B2 gene sequence

11beta-Hydroxysteroid dehydrogenase type 2 (11betaHSD2) is a short-chain dehydrogenase/reductase (SDR) responsible for inactivating cortisol and preventing its binding to the mineralocorticoid receptor (MR). Nonfunctional mutations in HSD11B2, the gene encoding 11betaHSD2, cause the hypertensive syndrome of apparent mineralocorticoid excess (AME). Like other such Mendelian disorders, AME is rare but has nevertheless helped to illuminate principles fundamental to the regulation of blood pressure. Furthermore, polymorphisms in HSD11B2 have been associated with salt sensitivity, a major risk factor for cardiovascular mortality. It is therefore highly likely that sequence variation in HSD11B2, having subtle functional ramifications, will affect blood pressure in the wider population. In this study, a three-dimensional homology model of 11betaHSD2 was created and used to hypothesize the functional consequences in terms of protein structure of published mutations in HSD11B2. This approach underscored the strong genotype-phenotype correlation of AME: severe forms of the disease, associated with little in vivo enzyme activity, arise from mutations occurring in invariant alignment positions. These were predicted to exert gross structural changes in the protein. In contrast, those mutations causing a mild clinical phenotype were in less conserved regions of the protein that were predicted to be relatively more tolerant to substitution. Finally, a number of pathogenic mutations are shown to be associated with regions predicted to participate in dimer formation, and in protein stabilization, which may therefore suggest molecular mechanisms of disease.