A Novel SCNN1A Variation in a Patient with Autosomal-recessive Pseudohypoaldosteronism Type 1

Pseudohypoaldosteronism Type 1B and Cohen Syndrome: Novel Mutation, Unusual Combination, and Presentation

Pseudohypoaldosteronism type 1 (PHA1) is a rare inherited disorder of resistance to aldosterone and presents with hyponatremia, hyperkalemia, and metabolic acidosis. Cohen syndrome (CS) is another rare inherited disease. Concurrent presentation with pseudohypoaldosteronism makes it so extraordinary and implies more challenges for clinicians. We report a case of a female with Cohen syndrome (novel mutation) and systemic pseudohypoaldosteronism, as well as the challenges we have encountered in the management of this patient.

The Epithelial Sodium Channel-An Underestimated Drug Target

Epithelial sodium channels (ENaC) are part of a complex network of interacting biochemical pathways and as such are involved in several disease states. Dependent on site and type of mutation, gain- or loss-of-function generated symptoms occur which span from asymptomatic to life-threatening disorders such as Liddle syndrome, cystic fibrosis or generalized pseudohypoaldosteronism type 1. Variants of ENaC which are implicated in disease assist further understanding of their molecular mechanisms in order to create models for specific pharmacological targeting. Identification and characterization of ENaC modifiers not only furthers our basic understanding of how these regulatory processes interact, but also enables discovery of new therapeutic targets for the disease conditions caused by ENaC dysfunction. Numerous test compounds have revealed encouraging results in vitro and in animal models but less in clinical settings. The EMA- and FDA-designated orphan drug solnatide is currently being tested in phase 2 clinical trials in the setting of acute respiratory distress syndrome, and the NOX1/ NOX4 inhibitor setanaxib is undergoing clinical phase 2 and 3 trials for therapy of primary biliary cholangitis, liver stiffness, and carcinoma. The established ENaC blocker amiloride is mainly used as an add-on drug in the therapy of resistant hypertension and is being studied in ongoing clinical phase 3 and 4 trials for special applications. This review focuses on discussing some recent developments in the search for novel therapeutic agents.

Mineralocorticoid Receptor Activation in Vascular Insulin Resistance and Dysfunction

Systemic insulin resistance is characterized by reduced insulin metabolic signaling and glucose intolerance. Mineralocorticoid receptors (MRs), the principal receptors for the hormone aldosterone, play an important role in regulating renal sodium handling and blood pressure. Recent studies suggest that MRs also exist in tissues outside the kidney, including vascular endothelial cells, smooth muscle cells, fibroblasts, perivascular adipose tissue, and immune cells. Risk factors, including excessive salt intake/salt sensitivity, hypertension, and obesity, can lead to the activation of vascular MRs to promote inflammation, oxidative stress, remodeling, and fibrosis, as well as cardiovascular stiffening and microcirculatory impairment. These pathophysiological changes are associated with a diminished ability of insulin to initiate appropriate intracellular signaling events, resulting in a reduced glucose uptake within the microcirculation and related vascular insulin resistance. Therefore, the pharmacological inhibition of MR activation provides a potential therapeutic option for improving vascular function, glucose uptake, and vascular insulin sensitivity. This review highlights recent experimental and clinical data that support the contribution of abnormal MR activation to the development of vascular insulin resistance and dysfunction.