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1.
Sodium Abnormalities in Cardiac Surgery With Cardiopulmonary Bypass in Adults: A Narrative Review.
Leong, XF, Cheng, M, Jong, B, Hwang, NC, Roscoe, A
Journal of cardiothoracic and vascular anesthesia. 2021;(11):3374-3384
Abstract
Perioperative sodium abnormalities or dysnatremia is not uncommon in patients presenting for cardiac surgery and is associated with increased morbidity and mortality. Both the disease process of heart failure and its treatment may contribute to abnormalities in serum sodium concentration. Serum sodium is the main determinant of serum osmolality, which in turn affects cell volume. Brain cells are particularly vulnerable to changes in serum osmolality because of the nondistensible cranium. The potentially catastrophic neurologic sequelae of rapidly correcting chronic dysnatremia and the time-sensitive nature of cardiac surgery can make the management of these patients challenging. The use of cardiopulmonary bypass to facilitate surgery adds another layer of complexity in the intraoperative management of sodium and water balance. This narrative review examines the definition and classification of dysnatremia. It also covers the etiology and pathophysiology of dysnatremia, implications during cardiac surgery requiring cardiopulmonary bypass, and the perioperative management of dysnatremia.
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2.
Recent progress in understanding salinity tolerance in plants: Story of Na+/K+ balance and beyond.
Hussain, S, Hussain, S, Ali, B, Ren, X, Chen, X, Li, Q, Saqib, M, Ahmad, N
Plant physiology and biochemistry : PPB. 2021;:239-256
Abstract
High salt concentrations in the growing medium can severely affect the growth and development of plants. It is imperative to understand the different components of salt-tolerant network in plants in order to produce the salt-tolerant cultivars. High-affinity potassium transporter- and myelocytomatosis proteins have been shown to play a critical role for salinity tolerance through exclusion of sodium (Na+) ions from sensitive shoot tissues in plants. Numerous genes, that limit the uptake of salts from soil and their transport throughout the plant body, adjust the ionic and osmotic balance of cells in roots and shoots. In the present review, we have tried to provide a comprehensive report of major research advances on different mechanisms regulating plant tolerance to salinity stress at proteomics, metabolomics, genomics and transcriptomics levels. Along with the role of ionic homeostasis, a major focus was given on other salinity tolerance mechanisms in plants including osmoregulation and osmo-protection, cell wall remodeling and integrity, and plant antioxidative defense. Major proteins and genes expressed under salt-stressed conditions and their role in enhancing salinity tolerance in plants are discussed as well. Moreover, this manuscript identifies and highlights the key questions on plant salinity tolerance that remain to be discussed in the future.
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3.
Plant HKT Channels: An Updated View on Structure, Function and Gene Regulation.
Riedelsberger, J, Miller, JK, Valdebenito-Maturana, B, Piñeros, MA, González, W, Dreyer, I
International journal of molecular sciences. 2021;(4)
Abstract
HKT channels are a plant protein family involved in sodium (Na+) and potassium (K+) uptake and Na+-K+ homeostasis. Some HKTs underlie salt tolerance responses in plants, while others provide a mechanism to cope with short-term K+ shortage by allowing increased Na+ uptake under K+ starvation conditions. HKT channels present a functionally versatile family divided into two classes, mainly based on a sequence polymorphism found in the sequences underlying the selectivity filter of the first pore loop. Physiologically, most class I members function as sodium uniporters, and class II members as Na+/K+ symporters. Nevertheless, even within these two classes, there is a high functional diversity that, to date, cannot be explained at the molecular level. The high complexity is also reflected at the regulatory level. HKT expression is modulated at the level of transcription, translation, and functionality of the protein. Here, we summarize and discuss the structure and conservation of the HKT channel family from algae to angiosperms. We also outline the latest findings on gene expression and the regulation of HKT channels.
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4.
Obesity, Sodium Homeostasis, and Arterial Hypertension in Children and Adolescents.
Wójcik, M, Kozioł-Kozakowska, A
Nutrients. 2021;(11)
Abstract
BACKGROUND The relationship between obesity, arterial hypertension, and excessive salt intake has been known for a long time; however, the mechanism of this relationship remains not clear. METHODS The paper presents a current literature review on the relationship between salt consumption and the development of arterial hypertension in children and adolescents with obesity. RESULTS In addition to the traditional theory of hypertension development due to the increase in intravascular volume and disturbances of sodium excretion, recent studies indicate the existence of a complex mechanism related to excessive, pathological secretory activity of adipocytes, insulin resistance, and impaired function of the renin-angiotensin-aldosterone axis. That makes obese children and adolescents particularly vulnerable to the development of salt-sensitive arterial hypertension. Studies performed in many countries have shown that children and adolescents consume more sodium than recommended. It is worth noting, however, that the basis for these recommendations was the extrapolation of data from studies conducted on adults. Moreover, more important than sodium intake is the Na/K ratio and water consumption. CONCLUSION Regardless of the population-wide recommendations on reducing salt intake in children, specific recommendations for overweight and obese patients should be developed.
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5.
[Sodium metabolism: An update in 2019].
Robert, A, Cheddani, L, Ebel, A, Vilaine, E, Seidowsky, A, Massy, Z, Essig, M
Nephrologie & therapeutique. 2020;(2):77-82
Abstract
The classical theory of sodium metabolism considers mostly its role on the extracellular volume according to a daily response to the variations of salt intake, correlated to the variations of water volume. Recent works consider sodium tissular storage. This non-osmotic pool could play a role in blood pressure regulation and in immunity mechanisms. The regulation modalities could be more complex, organised over the long term, with a modification of the sodium-water relationship. The aim of this article is to give a new insight on sodium metabolism, based on recent works, especially on the role and regulation of non osmotic tissular sodium.
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6.
Dietary potassium restriction attenuates urinary sodium wasting in the generalized form of pseudohypoaldosteronism type 1.
Adachi, M, Tajima, T, Muroya, K
CEN case reports. 2020;(2):133-137
Abstract
Owing to its rarity and severe nature, the treatment for generalized pseudohypoaldosteronism type 1 (PHA1), a genetic disorder in the epithelial sodium channel (ENaC), is exclusively experience-based. In particular, the usefulness of dietary potassium restriction in PHA1 remains unclear with the absence of theoretical background to elucidate its utility. First, we demonstrated the effect of potassium restriction in a 13-month-old patient with ENaC γ-subunit gene mutations via a retrospective chart review; reduction of daily dietary potassium intake from 40 to 20 mEq induced rapid restoration of volume depletion, as evidenced by weight gain, elevation of the serum sodium level from 133 to 141 mEq/L, decreased urinary sodium excretion, and normalized renin activity. The serum potassium level decreased from 5.6 to 4.5 mEq/L. Next, we attempted to elucidate the pathophysiological basis of the usefulness of potassium restriction, leveraged by the increased knowledge regarding the roles of with-no-lysine kinases (WNKs) in the distal nephron. When potassium is restricted, the WNK signal will turn "on" in the distal nephron via reduction in the intracellular chloride level. Consequently, the sodium reabsorption from the Na+Cl- cotransporter (NCC) in the distal convoluted tubule and possibly from pendrin in the β-intercalated cell will increase. Thus, potassium restriction causes NCC and pendrin to compensate for the non-functional ENaC in the collecting duct. In conclusion, dietary potassium restriction is one of the indispensable treatments for generalized PHA1.
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7.
Vasopressin receptor subtypes and renal sodium transport.
Natochin, YV, Golosova, DV
Vitamins and hormones. 2020;:239-258
Abstract
In mammals, three subtypes of V-receptors have been identified in the kidney. The effects of vasopressin, a hormone synthesized in the hypothalamus, are triggered by three distinct receptor isoforms: V2, V1a, and V1b. Stimulation of V2-receptors regulates urine osmotic concentration by increasing sodium reabsorption in the thick ascending limb of the loop of Henle and enhancing osmotic permeability of the epithelium cells in the collecting duct. Stimulation of V1a-receptors inhibits renal sodium reabsorption and induces natriuresis, comparable to the effect of the diuretic furosemide, in the thick ascending limb of the loop of Henle. Stimulation of V1b-receptors induces potassium secretion in the final parts of the distal segments and initial parts of the collecting ducts. In this review, we discuss the role of vasopressin and its interaction with V-receptor subtypes in natriuresis and for stabilizing the physicochemical parameters of the internal environment and water-salt homeostasis in humans. A better understanding of these systems and their regulation is necessary to facilitate identification of additional system components and mechanisms, clarify their contribution during various normal and pathological functional states, and suggest novel strategies for the development of therapeutic interventions.
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8.
Evolution and evolving resolution of controversy over existence and prevalence of cerebral/renal salt wasting.
Maesaka, JK, Imbriano, LJ, Miyawaki, N
Current opinion in nephrology and hypertension. 2020;(2):213-220
Abstract
PURPOSE OF REVIEW The topic of hyponatremia is in a state of flux. We review a new approach to diagnosis that is superior to previous methods. It simplifies identifying the causes of hyponatremia, the most important issue being the differentiation of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) from cerebral/renal salt wasting (RSW). We also report on the high prevalence of RSW without cerebral disease in the general wards of the hospital. RECENT FINDINGS We applied our new approach to hyponatremia by utilizing sound pathophysiologic criteria in 62 hyponatremic patients. Seventeen (27%) had SIADH, 19 (31%) had a reset osmostat, 24 (38%) had RSW with 21 having no evidence of cerebral disease, 1 had Addison's disease, and 1 was because of hydrochlorothiazide. Many had urine sodium concentrations (UNa) less than 30 mmol/l. SUMMARY RSW is much more common than perceived in the general wards of the hospital. It is important to change the terminology from cerebral to RSW and to differentiate SIADH from RSW. These changes will improve clinical outcomes because of divergent therapeutic goals of water-restricting in SIADH and administering salt and water to a dehydrated patient with RSW. The present review will hopefully spur others to reflect and act on the new findings and different approaches to hyponatremia.
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9.
The challenges of diagnosis and management of Gitelman syndrome.
Urwin, S, Willows, J, Sayer, JA
Clinical endocrinology. 2020;(1):3-10
Abstract
Gitelman syndrome is an inherited tubulopathy characterized by renal salt wasting from the distal convoluted tubule. Defects in the sodium chloride cotransporter (encoded by SLC12A3) underlie this autosomal recessive condition. This article focuses on the specific challenges of diagnosing and treating Gitelman syndrome, with use of an illustrative case report. Symptoms relate to decreased serum potassium and magnesium levels, which include muscle weakness, tetany, fatigue and palpitations. Sudden cardiac deaths have been reported. Making a diagnosis may be difficult given its rarity but is important. A knowledge of the serum and urine biochemical picture is vital to distinguish it from a broad differential diagnosis, and application of genetic testing can resolve difficult cases. There is a group of Gitelman syndrome heterozygous carriers that experience symptoms and electrolyte disturbance and these patients should be managed in a similar way, though here genetic investigations become key in securing a difficult diagnosis. Potassium and magnesium replacement is the cornerstone of treatment, though practically this can be hard for patients to manage and often does not fully relieve symptoms even when serum levels are normalized. Challenges arise due to the lack of randomized controlled trials focussing on treatment of this rare disease; hence, clinicians endorse strategies in line with correction of the underlying pathophysiology such as sodium loading or pharmacological treatments, which seem to help some patients. Focussed dietary advice and knowing the best tolerated preparations of potassium and magnesium medications are useful tools for the physician, as well as an awareness of the specific burdens that this patient group face in order to signpost appropriate support.
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10.
Clinical impact of tissue sodium storage.
Olde Engberink, RHG, Selvarajah, V, Vogt, L
Pediatric nephrology (Berlin, Germany). 2020;(8):1373-1380
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Abstract
In recent times, the traditional nephrocentric, two-compartment model of body sodium has been challenged by long-term sodium balance studies and experimental work on the dermal interstitium and endothelial surface layer. In the new paradigm, sodium can be stored without commensurate water retention in the interstitium and endothelial surface layer, forming a dynamic third compartment for sodium. This has important implications for sodium homeostasis, osmoregulation and the hemodynamic response to salt intake. Sodium storage in the skin and endothelial surface layer may function as a buffer during periods of dietary depletion and excess, representing an extra-renal mechanism regulating body sodium and water. Interstitial sodium storage may also serve as a biomarker for sodium sensitivity and cardiovascular risk, as well as a target for hypertension treatment. Furthermore, sodium storage may explain the limitations of traditional techniques used to quantify sodium intake and determine infusion strategies for dysnatraemias. This review is aimed at outlining these new insights into sodium homeostasis, exploring their implications for clinical practice and potential areas for further research for paediatric and adult populations.