Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Bartter and Gitelman Syndromes: A Primer for Clinicians.

Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies.

A life-threatening case of pseudo-aldosteronism secondary to excessive liquorice ingestion.

BACKGROUND: Liquorice is found in many food products, soft drinks, and herbal medicines. Liquorice ingestion is an uncommon cause of apparent mineralocorticoid excess or pseudo-aldosteronism. The mechanism involves the inhibition of 11-beta-hydroxysteroid dehydrogenase type-2 by the active ingredient called glycyrrhizin. This leads to the uninhibited activation of mineralocorticoid receptors by cortisol. Confectionary products that contain liquorice are readily available in many countries around the world. CASE PRESENTATION: We report a case of severe refractory hypokalaemia with hypertensive crisis and acute pulmonary oedema due to excessive liquorice consumption. A 79-year-old female presented to the emergency department following a road traffic accident. She described feeling weak and dizzy while driving before the collision. She attended her general practitioner (GP) several weeks earlier for fatigue and was being managed for hypokalaemia on oral potassium supplements. Investigations revealed hypertension (BP 180/69 mmHg), severe hypokalaemia (K 2.2 mmol/l), normal renal function, normal serum magnesium with metabolic alkalosis. Spot urinary potassium was 22 mmol/l. The patient denied taking medications including over-the-counter or herbal medication that can cause hypokalaemia. Hypokalaemia persisted despite aggressive intravenous (i.v.) and oral potassium replacement. She later developed a hypertensive crisis (BP 239/114 mmHg) with pulmonary oedema. She required admission to the intensive care unit and was managed with intravenous furosemide infusion and isosorbide dinitrate infusion. On further discussion, our patient admitted to struggling with nicotine cravings since quitting smoking two months earlier. She began eating an excessive amount of liquorice sweets to manage her cravings. Suppression of plasma renin and aldosterone supported the diagnosis of apparent mineralocorticoid excess secondary to excessive liquorice consumption. Her symptoms and hypokalaemia resolved after stopping liquorice intake. CONCLUSIONS: This case highlights the life-threatening and refractory nature of hypokalaemia secondary to excessive liquorice consumption. This case also emphasizes the importance of comprehensive history taking including dietary habits. Increased awareness among the public is required regarding the potential health hazards of excessive liquorice consumption.

Endothelial progenitor cells in primary aldosteronism: a biomarker of severity for aldosterone vasculopathy and prognosis.

CONTEXT: Primary aldosteronism (PA) is associated with a higher incidence of cardiovascular events, probably through mineralocorticoid receptor (MR)-dependent endothelial cell dysfunction, in comparison with essential hypertension (EH). OBJECTIVE: Our objective was to investigate the number and function of endothelial progenitor cells (EPC) in PA and the relationship with arterial stiffness and disease progression. DESIGN AND SETTING: We conducted a prospective study of the change of EPC number and outcome of PA patients after treatment at a tertiary medical center. PRIMARY OUTCOMES: Changes in arterial stiffness and EPC number after treatment and the curability of hypertension were assessed. PATIENTS: A total of 113 PA patients (87 patients diagnosed with aldosterone-producing adenoma, 26 with idiopathic hyperaldosteronism) and 55 patients with EH participated. RESULTS: PA patients had higher arterial stiffness than EH patients (P = 0.006), with a lower numbers of circulating EPC and endothelial colony-forming units (P < 0.05). The differences were ameliorated at 6 months after unilateral adrenalectomy or treatment with spironolactone. Expression of MR was identified in the EPC. The number of circulating EPC was inversely correlated with the plasma aldosterone concentration (P = 0.021), arterial stiffness (P = 0.029) and serum high-sensitivity C-reactive protein (P = 0.03). High-dose aldosterone (10(-5) and 10(-6) m) attenuated EPC proliferation and angiogenesis in vitro. Among the 45 patients who underwent unilateral adrenalectomy, 32 (71%) were cured of hypertension. The preoperative number of EPC [log(EPC number percent) >-3.6] predicted the curability of hypertension after adrenalectomy (P = 0.003). CONCLUSIONS: The relative deficiency of EPC in PA patients may contribute to aldosterone vasculopathy, which can be reversed by adrenalectomy and spironolactone. High aldosterone levels attenuated EPC proliferation and angiogenesis. Circulating EPC number may be a valuable biomarker to identify PA patients with a high incidence of arterial stiffness and to predict postoperative residual hypertension of aldosterone-producing adenoma.

Bartter- and Gitelman-like syndromes: salt-losing tubulopathies with loop or DCT defects.

Salt-losing tubulopathies with secondary hyperaldosteronism (SLT) comprise a set of well-defined inherited tubular disorders. Two segments along the distal nephron are primarily involved in the pathogenesis of SLTs: the thick ascending limb of Henle's loop, and the distal convoluted tubule (DCT). The functions of these pre- and postmacula densa segments are quite distinct, and this has a major impact on the clinical presentation of loop and DCT disorders - the Bartter- and Gitelman-like syndromes. Defects in the water-impermeable thick ascending limb, with its greater salt reabsorption capacity, lead to major salt and water losses similar to the effect of loop diuretics. In contrast, defects in the DCT, with its minor capacity of salt reabsorption and its crucial role in fine-tuning of urinary calcium and magnesium excretion, provoke more chronic solute imbalances similar to the effects of chronic treatment with thiazides. The most severe disorder is a combination of a loop and DCT disorder similar to the enhanced diuretic effect of a co-medication of loop diuretics with thiazides. Besides salt and water supplementation, prostaglandin E2-synthase inhibition is the most effective therapeutic option in polyuric loop disorders (e.g., pure furosemide and mixed furosemide-amiloride type), especially in preterm infants with severe volume depletion. In DCT disorders (e.g., pure thiazide and mixed thiazide-furosemide type), renin-angiotensin-aldosterone system (RAAS) blockers might be indicated after salt, potassium, and magnesium supplementation are deemed insufficient. It appears that in most patients with SLT, a combination of solute supplementation with some drug treatment (e.g., indomethacin) is needed for a lifetime.

Downregulation of renal TRPM7 and increased inflammation and fibrosis in aldosterone-infused mice: effects of magnesium.

Hyperaldosteronism is associated with hypertension, cardiovascular fibrosis, and electrolyte disturbances, including hypomagnesemia. Mechanisms underlying aldosterone-mediated Mg(2+) changes are unclear, but the novel Mg(2+) transporters TRPM6 and TRPM7 may be important. We examined whether aldosterone influences renal TRPM6/7 and the TRPM7 downstream target annexin-1 and tested the hypothesis that Mg(2+) administration ameliorates aldosterone-induced cardiovascular and renal injury and prevents aldosterone-associated hypertension. C57B6 mice were studied (12 weeks, n=8 to 9/group); (1) control group (0.2% dietary Mg(2+)), (2) Mg(2+) group (0.75% dietary Mg(2+)), (3) aldosterone group (Aldo, 400 microg/kg/min and 0.9% NaCl drinking water), and (4) Aldo+Mg(2+) group. Blood pressure was unaltered by aldosterone and was similar in all groups throughout the experiment. Serum Na(+) was increased and serum K(+) and Mg(2+) decreased in the Aldo group. Aldo mice had hypomagnesuria and proteinuria, and renal, cardiac, and aortic fibrosis, which were normalized by Mg(2+) supplementation. Renal and cardiovascular expression of interleukin-6, VCAM1 and COX2 was increased in the Aldo group. Magnesium attenuated renal and cardiac interleukin-6 content and decreased renal VCAM1 and cardiac COX2 expression (P<0.05). Aldosterone decreased expression of renal TRPM7 and the downstream target annexin-1 (P<0.05) without effect on TRPM6. Whereas Mg(2+) increased mRNA expression of TRPM6 and TRPM7, it had no effect on TRPM7 and annexin-1 protein content. Our data demonstrate that aldosterone mediates blood pressure-independent renal and cardiovascular fibrosis and inflammation through Mg(2+)-sensitive pathways. We suggest that altered Mg(2+) metabolism in hyperaldosteronism may relate to TRPM7 downregulation and that Mg(2+) protects against cardiovascular and renal damaging actions of aldosterone.

An additional child case of an aldosterone-producing adenoma with an atypical presentation of peripheral paralysis due to hypokalemia.

Aldosterone-producing adenoma, which is characterized by hypertension, hypokalemia, and elevated aldosterone levels with suppressed plasma renin activity, is a rare condition during childhood and is also potentially curable. To the best of our knowledge, nearly 25 cases of childhood aldosterone-secreting adenoma have been reported in the literature to date. Here we describe a 13-yr-old girl with primary hyperaldosteronism secondary to aldosterone-secreting adenoma. The patient was admitted to our hospital with the neuromuscular complaints of muscle weakness and inability to walk due to hypokalemia. She had been misdiagnosed as having hypokalemic periodic paralysis 2 months before admission and her symptoms had radically improved with potassium supplementation. However, her blood pressure levels had increased and her symptoms reappeared 2 days prior to being observed during hospitalization in our institution. Laboratory examinations revealed hypokalemia (2.1 mEq/l), and increased serum aldosterone levels with suppressed plasma renin activity. Abdominal ultrasonography and abdominal magnetic resonance imaging revealed left adrenal mass. Laparoscopic adrenalectomy was performed and histopathological examinations showed benign adrenal adenoma. Serum aldosterone levels and blood pressure levels returned to normal after surgical intervention. This case demonstrates the importance of a systemic evaluation including blood pressure monitorization of children with hypokalemia as intermittent hypertension episodes may be seen; cases without hypertension may be misdiagnosed as rheumatological or neurological disorders such as hypokalemic periodic paralysis, as in our case.