Jana Malikova

Novel Insight into Etiology, Diagnosis and Management of Primary Adrenal Insufficiency

Primary adrenal insufficiency (PAI) is a rare condition in childhood which is either inherited (mostly) or acquired. It is characterized by glucocorticoid and maybe mineralocorticoid deficiency. The most common form in children is 21-hydroxylase deficiency, which belongs to the steroid biosynthetic defects causing PAI. Newer forms of complex defects of steroid biosynthesis are P450 oxidoreductase deficiency and (apparent) cortisone reductase deficiency. Other forms of PAI include metabolic disorders, autoimmune disorders and adrenal dysgenesis, e.g. the IMAGe syndrome, for which the underlying genetic defect has been recently identified. Newer work has also expanded the genetic causes underlying isolated, familial glucocorticoid deficiency (FGD). Mild mutations of CYP11A1 or StAR have been identified in patients with FGD. MCM4 mutations were found in a variant of FGD in an Irish travelling community manifesting with PAI, short stature, microcephaly and recurrent infections. Finally, mutations in genes involved in the detoxification of reactive oxygen species were identified in patients with unsolved FGD. Most mutations were found in the enzyme nicotinamide nucleotide transhydrogenase, which uses the mitochondrial proton pump gradient to produce NADPH. NADPH is essential in maintaining high levels of reduced forms of antioxidant enzymes for the reduction of hydrogen peroxide. Similarly, mutations in the gene for TXNRD2 involved in this system were found in FGD patients, suggesting that the adrenal cortex is particularly susceptible to oxidative stress.

Genesis of two most prevalent PROP1 gene variants causing combined pituitary hormone deficiency in 21 populations

Two variants (c.[301_302delAG];[301_302delAG] and c.[150delA];[150delA]) in the PROP1 gene are the most common genetic causes of recessively inherited combined pituitary hormones deficiency (CPHD). Our objective was to analyze in detail the origin of the two most prevalent variants. In the multicentric study were included 237 patients with CPHD and their 15 relatives carrying c.[301_302delAG];[301_302delAG] or c.[150delA];[150delA] or c.[301_302delAG];[ 150delA]. They originated from 21 different countries worldwide. We genotyped 21 single-nucleotide variant markers flanking the 9.6-Mb region around the PROP1 gene that are not in mutual linkage disequilibrium in the general populations – a finding of a common haplotype would be indicative of ancestral origin of the variant. Haplotypes were reconstructed by Phase and Haploview software, and the variant age was estimated using an allelic association method. We demonstrated the ancestral origin of both variants – c.[301_302delAG] was carried on 0.2 Mb-long haplotype in a majority of European patients arising ~101 generations ago (confidence interval 90.1–116.4). Patients from the Iberian Peninsula displayed a different haplotype, which was estimated to have emerged 23.3 (20.1–29.1) generations ago. Subsequently, the data indicated that both the haplotypes were transmitted to Latin American patients ~13.8 (12.2–17.0) and 16.4 (14.4–20.1) generations ago, respectively. The c.[150delA] variant that was carried on a haplotype spanning about 0.3 Mb was estimated to appear 43.7 (38.4–52.7) generations ago. We present strong evidence that the most frequent variants in the PROP1 gene are not a consequence of variant hot spots as previously assumed, but are founder variants.

High Incidence of Heterozygous ABCC8 and HNF1A Mutations in Czech Patients With Congenital Hyperinsulinism

CONTEXT Congenital hyperinsulinism of infancy (CHI) represents a group of heterogeneous disorders characterized by oversecretion of insulin from pancreatic β-cells causing severe hypoglycemia. OBJECTIVE We studied the distribution of genetic causes of CHI in a Czech population. METHODS Countrywide collection of patients with CHI included 40 subjects (12 females, median age of diagnosis, 1 wk [interquartile range, 1-612 wk]). We sequenced the ABCC8, KCNJ11, GLUD1, GCK, HADH, UCP2, SLC16A1, HNF4A, and HNF1A genes and investigated structural changes in the ABCC8 gene. We functionally tested novel variants in the ABCC8 gene by Rb(86+) efflux assay and novel variants in the HNF1A gene by transcriptional activation and DNA-binding tests. RESULTS We found causal mutations in 20 subjects (50%): 19 carried a heterozygous mutation while one patient was homozygous for mutation in the ABCC8 gene. Specifically, we detected 11 mutations (seven novel) in ABCC8, one novel mutation in KCNJ11, five mutations (two novel) in HNF1A, two novel mutations in HNF4A, and one in GCK. We showed a decrease of activation by diazoxide in mutant KATP channels with novel ABCC8 variants by 41-91% (median, 82%) compared with wild-type (WT) channels and reduced transcriptional activity of mutant HNF1A proteins (2.9% for p.Asn62Lysfs93* and 22% for p.Leu254Gln) accompanied by no DNA-binding ability compared with WT HNF1A. CONCLUSION We detected a higher proportion of heterozygous mutations causing CHI compared with other cohorts probably due to lack of consanguinity and inclusion of milder CHI forms. Interestingly, HNF1A gene mutations represented the second most frequent genetic cause of CHI in the Czech Republic. Based on our results we present a genetic testing strategy specific for similar populations.

Human NR5A1/SF-1 Mutations Show Decreased Activity on BDNF (Brain-Derived Neurotrophic Factor), an Important Regulator of Energy Balance: Testing Impact of Novel SF-1 Mutations Beyond Steroidogenesis

Context Human NR5A1/SF-1 mutations cause 46,XY disorder of sex development (DSD) with broad phenotypic variability, and rarely cause adrenal insufficiency although SF-1 is an important transcription factor for many genes involved in steroidogenesis. In addition, the Sf-1 knockout mouse develops obesity with age. Obesity might be mediated through Sf-1 regulating activity of brain-derived neurotrophic factor (BDNF), an important regulator of energy balance in the ventromedial hypothalamus. Objective To characterize novel SF-1 gene variants in 4 families, clinical, genetic and functional studies were performed with respect to steroidogenesis and energy balance. Patients 5 patients with 46,XY DSD were found to harbor NR5A1/SF-1 mutations including 2 novel variations. One patient harboring a novel mutation also suffered from adrenal insufficiency. Methods SF-1 mutations were studied in cell systems (HEK293, JEG3) for impact on transcription of genes involved in steroidogenesis (CYP11A1, CYP17A1, HSD3B2) and in energy balance (BDNF). BDNF regulation by SF-1 was studied by promoter assays (JEG3). Results Two novel NR5A1/SF-1 mutations (Glu7Stop, His408Profs*159) were confirmed. Glu7Stop is the 4th reported SF-1 mutation causing DSD and adrenal insufficiency. In vitro studies revealed that transcription of the BDNF gene is regulated by SF-1, and that mutant SF-1 decreased BDNF promoter activation (similar to steroid enzyme promoters). However, clinical data from 16 subjects carrying SF-1 mutations showed normal birth weight and BMI. Conclusions Glu7Stop and His408Profs*159 are novel SF-1 mutations identified in patients with 46,XY DSD and adrenal insufficiency (Glu7Stop). In vitro, SF-1 mutations affect not only steroidogenesis but also transcription of BDNF which is involved in energy balance. However, in contrast to mice, consequences on weight were not found in humans with SF-1 mutations.

Mast cell stabilization with sodium cromoglycate modulates pulmonary vessel wall remodeling during four-day hypoxia in rats

ABSTRACT Aim of the study: In rats, the environment with low content of oxygen induces hypoxic pulmonary hypertension. Remodeling of pulmonary resistance arteries is particularly triggered by the mast cell degranulation products, e.g., rodent-like interstitial collagenase (matrix metalloproteinase 13). Administration of sodium cromoglycate leads to stabilization of mast cell granules, and thus to the modified remodeling process. Materials and Methods: During four-day hypoxia, we treated rats with sodium cromoglycate. Pulmonary vascular remodeling was assessed as well as counts of periarterial pulmonary mast cells, both total and matrix metalloproteinase 13-positive ones. Results: Four-day hypoxia induced remodeling of both resistance arteries and large conduit arteries. We have found increase in the tunica media thickness of resistance arteries. Tunica adventitia thickness of both resistance arteries and large conduit arteries with a diameter of over 300 μm increased as well; the latter ones revealed increase in the number of vasa vasorum in their walls. Mast cell stabilization suppressed hypoxic pulmonary vascular remodeling in resistance pulmonary arteries. Four-day hypoxia led to changes in distribution of toluidine blue-detected and MMP-13 positive periarterial mast cells; this redistribution was also influenced by the administration of sodium cromoglycate. Conclusions: The number of pulmonary periarterial mast cells seemingly decreases during hypoxia due to their degranulation, which disables their identification. Large conduit arteries do not affect final blood pressure in the pulmonary vascular bed; however, their structure changes substantially under hypoxia. Such remodeling changes are not mediated by mast cell products only since they have occurred in spite of stabilization of mast cell granules.

McCune Albright syndrome and bilateral adrenal hyperplasia: the GNAS mutation may only be present in adrenal tissue

OBJECTIVECorticotropin (ACTH)-independent hypercortisolism due to bilateral adrenocortical hyperplasia (BAH) in infancy is an extremely rare condition that is often caused by McCune Albright syndrome (MAS). MAS is caused by an activating mutation of the GNAS gene which leads to increased cyclic (c) adenosine monophosphate (AMP) signaling. Most forms of BAH are linked to increased cAMP signaling. We report the case of an infant with MAS who had BAH.METHODSGenomic DNA fragments from blood and adrenal tissue encompassing regions (exons 8 and 9) with the hot spot activating missense GNAS mutations were amplified by classical bidirectional Sanger sequencing.RESULTSThe infant was found to carry the most common GNAS mutation, in exon 8 (c.602G >A, p. R201H), only in her adrenocortical tissue, despite extensive skin and other findings.CONCLUSIONSWe conclude that infants with MAS, despite absence of the GNAS activating mutation in blood, may still have significant clinical findings, including ACTH-independent hypercortisolism. Molecular confirmation of the diagnosis should be sought at the tissue level in these patients.

Androgen production in pediatric adrenocortical tumors may occur via both the classic and/or the alternative backdoor pathway.

Children with adrenocortical tumors (ACTs) often present with virilization due to high tumoral androgen production, with dihydrotestosterone (DHT) as most potent androgen. Recent work revealed two pathways for DHT biosynthesis, the classic and the backdoor pathway. Usage of alternate routes for DHT production has been reported in castration-resistant prostate cancer, CAH and PCOS. To assess whether the backdoor pathway may contribute to the virilization of pediatric ACTs, we investigated seven children suffering from androgen producing tumors using steroid profiling and immunohistochemical expression studies. All cases produced large amounts of androgens of the classic and/or backdoor pathway. Variable expression of steroid enzymes was observed in carcinomas and adenomas. We found no discriminative pattern. This suggests that enhanced androgen production in pediatric ACTs is the result of deregulated steroidogenesis through multiple steroid pathways. Thus future treatments of ACTs targeting androgen overproduction should consider these novel steroid production pathways.