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Bartter and Gitelman syndromes: Questions of class.
Besouw, MTP, Kleta, R, Bockenhauer, D
Pediatric nephrology (Berlin, Germany). 2020;(10):1815-1824
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Abstract
Bartter and Gitelman syndromes are rare inherited tubulopathies characterized by hypokalaemic, hypochloraemic metabolic alkalosis. They are caused by mutations in at least 7 genes involved in the reabsorption of sodium in the thick ascending limb (TAL) of the loop of Henle and/or the distal convoluted tubule (DCT). Different subtypes can be distinguished and various classifications have been proposed based on clinical symptoms and/or the underlying genetic cause. Yet, the clinical phenotype can show remarkable variability, leading to potential divergences between classifications. These problems mostly relate to uncertainties over the role of the basolateral chloride exit channel CLCNKB, expressed in both TAL and DCT and to what degree the closely related paralogue CLCNKA can compensate for the loss of CLCNKB function. Here, we review what is known about the physiology of the transport proteins involved in these disorders. We also review the various proposed classifications and explain why a gene-based classification constitutes a pragmatic solution.
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Association Between Estimated 24-h Urinary Sodium Excretion and Metabolic Syndrome in Korean Adults: The 2009 to 2011 Korea National Health and Nutrition Examination Survey.
Won, JC, Hong, JW, Noh, JH, Kim, DJ
Medicine. 2016;(15):e3153
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Abstract
High sodium intake is 1 of the modifiable risk factors for cardiovascular disease, but in Korea, daily sodium intake is estimated to be double the level recommended by World Health Organization. We investigated the association between the estimated 24-h urinary sodium excretion (24hUNaE) and metabolic syndrome using nationwide population data. In total, 17,541 individuals (weighted n = 33,200,054; weighted men, 52.5% [95% confidence interval, CI = 51.8-53.3]; weighted age, 45.2 years [44.7-45.7]) who participated in the Korean Health and Nutrition Examination Survey 2009 to 2011 were investigated. NCEP-ATP III criteria for metabolic syndrome were used, and sodium intake was estimated by 24hUNaE using Tanaka equation with a spot urine sample. The weighted mean 24hUNaE values were 3964 mg/d (95% CI = 3885-4044) in men and 4736 mg/d (4654-4817) in women. The weighted age-adjusted prevalence of metabolic syndrome was 22.2% (21.4-23.0), and it increased with 24hUNaE quartile in both men and women (mean ± standard error of the mean; men: 22.5 ± 1.0%, 23.0 ± 1.0%, 26.0 ± 1.2%, and 26.0 ± 1.2%; P = 0.026; women: 19.4 ± 0.8%, 17.7 ± 0.8%, 19.8 ± 1.0%, and 23.0 ± 1.1%; P = 0.002, for quartiles 1-4, respectively). Even after adjustment for age, daily calorie intake, heavy alcohol drinking, regular exercise, college graduation, and antihypertensive medication, the weighted prevalence of metabolic syndrome increased with the increase in 24hUNaE in men and women. The weighted 24hUNaE was positively associated with the number of metabolic syndrome components after adjustment for confounding factors in men and women. In subjects without antihypertensive medication, the odds ratio for metabolic syndrome in quartile 4 of 24hUNaE compared with quartile 1 was 1.56 (1.33-1.84, P < 0.001) in the total population, 1.66 (1.34-2.06, P < 0.001) in men, and 1.94 (1.49-2.53, P < 0.001) in women. In this nationwide population study, we observed a significant independent association between high sodium intake, estimated by spot urine sodium excretion, and the presence of metabolic syndrome in men and women.
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Correction of hyponatremia and osmotic demyelinating syndrome: have we neglected to think intracellularly?
Pham, PM, Pham, PA, Pham, SV, Pham, PT, Pham, PT, Pham, PC
Clinical and experimental nephrology. 2015;(3):489-95
Abstract
BACKGROUND Osmotic demyelination syndrome (ODS) is a complication generally associated with overly rapid correction of hyponatremia. Traditionally, nephrologists have been trained to focus solely on limiting the correction rate. However, there is accumulating evidence to suggest that the prevention of ODS is beyond achieving slow correction rates. METHODS We (1) reviewed the literature for glial intracellular protective alterations during hyperosmolar stress, a state presumed equivalent to the rapid correction of hyponatremia, and (2) analyzed all available hyponatremia-associated ODS cases from PubMed for possible contributing factors including correction rates and concurrent metabolic disturbances involving hypokalemia, hypophosphatemia, hypomagnesemia, and/or hypoglycemia. RESULTS In response to acute hyperosmolar stress, glial cells undergo immediate extracellular free water shift, followed by active intracellular Na(+), K(+) and amino acid uptake, and eventual idiogenic osmoles synthesis. At minimum, protective mechanisms require K(+), Mg(2+), phosphate, amino acids, and glucose. There were 158 cases of hyponatremia-associated ODS where both correction rates and other metabolic factors were documented. Compared with the rapid correction group (>0.5 mmol/L/h), the slow correction group (≤0.5 mmol/L/h) had a greater number of cases with concurrent hypokalemia (49.4 vs. 33.3 %, p = 0.04), and a greater number of cases with any concurrent metabolic derangements (55.8 vs. 38.3 %, p = 0.03). CONCLUSION Glial cell minimizes volume changes and injury in response to hyperosmolar stress via mobilization and/or utilization of various electrolytes and metabolic factors. The prevention of ODS likely requires both minimization of correction rate and optimization of intracellular response during the correction phase when a sufficient supply of various factors is necessary.
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Atrial natriuretic peptide and renal dopaminergic system: a positive friendly relationship?
Choi, MR, Rukavina Mikusic, NL, Kouyoumdzian, NM, Kravetz, MC, Fernández, BE
BioMed research international. 2014;:710781
Abstract
Sodium metabolism by the kidney is accomplished by an intricate interaction between signals from extrarenal and intrarenal sources and between antinatriuretic and natriuretic factors. Renal dopamine plays a central role in this interactive network. The natriuretic hormones, such as the atrial natriuretic peptide, mediate some of their effects by affecting the renal dopaminergic system. Renal dopaminergic tonus can be modulated at different steps of dopamine metabolism (synthesis, uptake, release, catabolism, and receptor sensitization) which can be regulated by the atrial natriuretic peptide. At tubular level, dopamine and atrial natriuretic peptide act together in a concerted manner to promote sodium excretion, especially through the overinhibition of Na+, K+-ATPase activity. In this way, different pathological scenarios where renal sodium excretion is dysregulated, as in nephrotic syndrome or hypertension, are associated with impaired action of renal dopamine and/or atrial natriuretic peptide, or as a result of impaired interaction between these two natriuretic systems. The aim of this review is to update and comment on the most recent evidences demonstrating how the renal dopaminergic system interacts with atrial natriuretic peptide to control renal physiology and blood pressure through different regulatory pathways.
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Monogenic forms of hypertension.
Simonetti, GD, Mohaupt, MG, Bianchetti, MG
European journal of pediatrics. 2012;(10):1433-9
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Abstract
Arterial hypertension in childhood is less frequent as compared to adulthood but is more likely to be secondary to an underlying disorder. After ruling out more obvious causes, some patients still present with strongly suspected secondary hypertension of yet unknown etiology. A number of these children have hypertension due to single gene mutations inherited in an autosomal dominant or recessive fashion. The finding of abnormal potassium levels (low or high) in the presence of suppressed renin secretion, and metabolic alkalosis or acidosis should prompt consideration of these familial diseases. However, mild hypertension and the absence of electrolyte abnormalities do not exclude hereditary conditions. In monogenic hypertensive disorders, three distinct mechanisms leading to the common final pathway of increased sodium reabsorption, volume expansion, and low plasma renin activity are documented. The first mechanism relates to gain-of-function mutations with a subsequent hyperactivity of renal sodium and chloride reabsorption leading to plasma volume expansion (e.g., Liddle's syndrome, Gordon's syndrome). The second mechanism involves deficiencies of enzymes that regulate adrenal steroid hormone synthesis and deactivation (e.g., subtypes of congenital adrenal hyperplasia, apparent mineralocorticoid excess (AME)). The third mechanism is characterized by excessive aldosterone synthesis that escapes normal regulatory mechanisms and leading to volume-dependent hypertension in the presence of suppressed renin release (glucocorticoid remediable aldosteronism). Hormonal studies coupled with genetic testing can help in the early diagnosis of these disorders.