Activation of the hypothalamic-pituitary-adrenal axis in adults with mineralocorticoid receptor haploinsufficiency

Wildfire-related smoke inhalation worsens cardiovascular risk in sleep disrupted rats

Introduction

As a lifestyle factor, poor sleep status is associated with increased cardiovascular morbidity and mortality and may be influenced by environmental stressors, including air pollution.

Methods

To determine whether exposure to air pollution modified cardiovascular effects of sleep disruption, we evaluated the effects of single or repeated (twice/wk for 4 wks) inhalation exposure to eucalyptus wood smoke (ES; 964 μg/m3 for 1 h), a key wildland fire air pollution source, on mild sleep loss in the form of gentle handling in rats. Blood pressure (BP) radiotelemetry and echocardiography were evaluated along with assessments of lung and systemic inflammation, cardiac and hypothalamic gene expression, and heart rate variability (HRV), a measure of cardiac autonomic tone.

Results and Discussion

GH alone disrupted sleep, as evidenced by active period-like locomotor activity, and increases in BP, heart rate (HR), and hypothalamic expression of the circadian gene Per2. A single bout of sleep disruption and ES, but neither alone, increased HR and BP as rats transitioned into their active period, a period aligned with a critical early morning window for stroke risk in humans. These responses were immediately preceded by reduced HRV, indicating increased cardiac sympathetic tone. In addition, only sleep disrupted rats exposed to ES had increased HR and BP during the final sleep disruption period. These rats also had increased cardiac output and cardiac expression of genes related to adrenergic function, and regulation of vasoconstriction and systemic blood pressure one day after final ES exposure. There was little evidence of lung or systemic inflammation, except for increases in serum LDL cholesterol and alanine aminotransferase. These results suggest that inhaled air pollution increases sleep perturbation-related cardiovascular risk, potentially in part by increased sympathetic activity.

Aldosterone signaling defect in young infants: single-center report and review

BACKGROUND

Aldosterone (Ald) is a crucial factor in maintaining electrolyte and water homeostasis. Defect in either its synthesis or function causes salt wasting (SW) manifestation. This disease group is rare, while most reported cases are sporadic. This study aimed to obtain an overview of the etiology and clinical picture of patients with the above condition and report our rare cases.

METHODS

A combination of retrospective review and case studies was conducted at the Pediatric Endocrine unit of The First Affiliated Hospital Sun Yat Sen University from September 1989 to June 2020.

RESULTS

A total of 187 patients with SW were enrolled, of which 90.4% (n = 169) were diagnosed with congenital adrenal hyperplasia (CAH). SW type 21-hydroxylase deficiency accounted for 98.8% (n = 167) of CAH diagnosis, while 1.2% (n = 2) was of lipoid CAH. Non-CAH comprised 9.6% (n = 18) of the total patients whose etiologies included SF-1 gene mutation (n = 1), X-linked adrenal hypoplasia congenita (n = 9), aldosterone synthase deficiency (ASD, n = 4), and pseudo-hypoaldosteronism type 1 (PHA1, n = 1). Etiologies were not identified in three patients. All of patients with ASD and PHA1 exhibited SW syndrome in their early neonatal period. DNA sequencing showed mutations of CYP11B2 for P1-P4 and NR3C2 for P5. P1 and P2 were sibling brothers affected by compound heterozygous mutations of c.1121G > A (p.R374Q) and c.1486delC p.(L496fs); likewise, P4 was identified with compound heterozygous mutations of c.1200 + 1G > A and c.240-1 G > T; meanwhile P3 demonstrated c.1303G > A p.(G435S) homozygous mutation in CYP11B2 gene. Lastly, P5 showed c.1768 C > T p.(R590*) heterozygous mutation in the NR3C2 gene.

CONCLUSION

Etiology of infant with aldosterone defect was mostly congenital. Renal and adrenal imaging are recommended to exclude renal causes. If clinical picture is suggestive, normal plasma Ald in early infancy cannot rule out aldosterone insufficiency.

Renin-aldosterone system evaluation over four decades in an extended family with autosomal dominant pseudohypoaldosteronism due to a deletion in the NR3C2 gene

Renal pseudohypoaldosteronism (PHA1) is a mild form of an aldosterone-resistance syndrome caused by mutations in the NR3C2 gene that codes for the mineralocorticoid receptor (MR). The disease is inherited as an autosomal dominant trait characterized by signs and symptoms of salt-losing in infancy. Disease manifestations could be severe in infancy but improve after the age of 1-3 years. Some affected members are asymptomatic and remain so life-long. In this study, we report the identification of a large deletion in the NR3C2 gene (c.1897+1_1898-1)_(c.*2955+?)del in renal PHA1 patients from an extended family spanning four generations. We prospectively evaluated the plasma renin activity and serum aldosterone profiles over four decades in symptomatic and asymptomatic affected family members. The benefits of early diagnosis on the clinical outcome were assessed as well. The long-term follow-up showed an age-dependent decrease in both plasma renin activity and serum aldosterone levels over the years. However, aldosterone levels remain high life-long. Thus, levels of aldosterone are a reliable marker to detect asymptomatic family members. The diagnosis of the proposita led to early diagnosis and therapy in other affected family members, significantly mitigating the clinical course. Despite the extremely elevated serum aldosterone levels during pregnancy, affected pregnant women did not experience any ill effects. However, this should be verified by observations in other adult patients.

Salt-Losing Tubulopathies in Children: What's New, What's Controversial?

Renal tubulopathies provide insights into the inner workings of the kidney, yet also pose therapeutic challenges. Because of the central nature of sodium in tubular transport physiology, disorders of sodium handling may affect virtually all aspects of the homeostatic functions of the kidney. Yet, owing to the rarity of these disorders, little clinical evidence regarding treatment exists. Consequently, treatment can vary widely between individual physicians and centers and is based mainly on understanding of renal physiology, reported clinical observations, and individual experiences. Salt-losing tubulopathies can affect all tubular segments, from the proximal tubule to the collecting duct. But the more frequently observed disorders are Bartter and Gitelman syndrome, which affect salt transport in the thick ascending limb of Henle's loop and/or the distal convoluted tubule, and these disorders generate the greatest controversies regarding management. Here, we review clinical and molecular aspects of salt-losing tubulopathies and discuss novel insights provided mainly by genetic investigations and retrospective clinical reviews. Additionally, we discuss controversial topics in the management of these disorders to highlight areas of importance for future clinical trials. International collaboration will be required to perform clinical studies to inform the treatment of these rare disorders.

Clinical features and molecular basis of pseudohypoaldosteronism type 1

Pseudohypoaldosteronism (PHA) type 1 is a disease showing mineralocorticoid resistance in the kidney and/or other mineralocorticoid target tissues. Patients with PHA1 present very high plasma aldosterone and renin levels, but they develop excessive salt wasting. There are three types of PHA1. The systemic form of PHA1 is inherited in an autosomal recessive manner and causes severe life-long salt loss in multiple target tissues, such as sweat glands, salivary glands, the colonic epithelium, and the lung. In the systemic form of PHA1, life-long salt supplementation is necessary. The second type is the renal form, where aldosterone resistance is shown only in the kidney, and its inheritance is autosomal dominant. In the renal form of PHA1, salt supplementation generally becomes unnecessary by 1-3 yr of age. The third type is the secondary PHA1, which is strongly associated with urinary tract infections and/or urinary tract malformations. This review summarizes the clinical features and molecular basis of PHA1. Understanding of its pathogenesis can be helpful for the early diagnosis and clinical care of affected children with PHA1.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: Mineralocorticoid receptor mutations

Aldosterone and the mineralocorticoid receptor (MR) are key elements for maintaining fluid and electrolyte homeostasis as well as regulation of blood pressure. Loss-of-function mutations of the MR are responsible for renal pseudohypoaldosteronism type 1 (PHA1), a rare disease of mineralocorticoid resistance presenting in the newborn with weight loss, failure to thrive, vomiting and dehydration, associated with hyperkalemia and metabolic acidosis, despite extremely elevated levels of plasma renin and aldosterone. In contrast, a MR gain-of-function mutation has been associated with a familial form of inherited mineralocorticoid hypertension exacerbated by pregnancy. In addition to rare variants, frequent functional single nucleotide polymorphisms of the MR are associated with salt sensitivity, blood pressure, stress response and depression in the general population. This review will summarize our knowledge on MR mutations in PHA1, reporting our experience on the genetic diagnosis in a large number of patients performed in the last 10 years at a national reference center for the disease. We will also discuss the influence of rare MR variants on blood pressure and salt sensitivity as well as on stress and cognitive functions in the general population.

Two Japanese patients with the renal form of pseudohypoaldosteronism type 1 caused by mutations of NR3C2

Pseudohypoaldosteronism type 1 (PHA1) is a disease characterized by neonatal salt loss due to aldosterone resistance. Two types of PHA1 are known: an autosomal recessive systemic form and an autosomal dominant renal form. The cause of the renal form of PHA1 is heterozygous mutations in NR3C2, which encodes the mineralocorticoid receptor (MR). We encountered two female Japanese infants with the renal form of PHA1 and analyzed NR3C2. The two patients had poor weight gain, and one was developmentally delayed. Genetic analysis identified one novel mutation (c.492_493insTT, p.Met166LeufsX8) and one previously reported mutation (p.R861X). The two produced a premature stop codon, resulting in haploinsufficiency of the MR. In conclusion, genetic analysis of NR3C2 is useful for diagnosis and planning therapeutic strategies.