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1.
Emerging concepts of potassium homeostasis in plants.
Srivastava, AK, Shankar, A, Nalini Chandran, AK, Sharma, M, Jung, KH, Suprasanna, P, Pandey, GK
Journal of experimental botany. 2020;(2):608-619
Abstract
Potassium (K+) is an essential cation in all organisms that influences crop production and ecosystem stability. Although most soils are rich in K minerals, relatively little K+ is present in forms that are available to plants. Moreover, leaching and run-off from the upper soil layers contribute to K+ deficiencies in agricultural soils. Hence, the demand for K fertilizer is increasing worldwide. K+ regulates multiple processes in cells and organs, with K+ deficiency resulting in decreased plant growth and productivity. Here, we discuss the complexity of the reactive oxygen species-calcium-hormone signalling network that is responsible for the sensing of K+ deficiency in plants, together with genetic approaches using K+ transporters that have been used to increase K+ use efficiency (KUE) in plants, particularly under environmental stress conditions such as salinity and heavy metal contamination. Publicly available rice transcriptome data are used to demonstrate the two-way relationship between K+ and nitrogen nutrition, highlighting how each nutrient can regulate the uptake and root to shoot translocation of the other. Future research directions are discussed in terms of this relationship, as well as prospects for molecular approaches for the generation of improved varieties and the implementation of new agronomic practices. An increased knowledge of the systems that sense and take up K+, and their regulation, will not only improve current understanding of plant K+ homeostasis but also facilitate new research and the implementation of measures to improve plant KUE for sustainable food production.
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2.
Doing 'business as usual' comes with a cost: evaluating energy cost of maintaining plant intracellular K+ homeostasis under saline conditions.
Rubio, F, Nieves-Cordones, M, Horie, T, Shabala, S
The New phytologist. 2020;(3):1097-1104
Abstract
Salinization of agricultural lands is a major threat to agriculture. Many different factors affect and determine plant salt tolerance. Nonetheless, there is a consensus on the relevance of maintaining an optimal cytosolic potassium : sodium ion (K+ : Na+ ) ratio for salinity tolerance in plants. This ratio depends on the operation of plasma membrane and tonoplast transporters. In the present review we focus on some aspects related to the energetic cost of maintaining that K+ : Na+ ratio. One of the factors that affect the cost of the first step of K+ acquisition - root K+ uptake through High Affinity K+ transporter and Arabidopsis K+ transport system 1 transport systems - is the value of the plasma membrane potential of root cells, a parameter that may differ amongst plant species. In addition to its role in nutrition, cytosolic K+ also is important for signalling, and K+ efflux through gated outward-rectifying K+ and nonselective cation channels can be regarded as a switch to redirect energy towards defence reactions. In maintaining cytosolic K+ , the great buffer capacity of the vacuole should be considered. The possible role of high-affinity K+ transporters (HKT)2s in mediating K+ uptake under saline conditions and the importance of cycling of K+ throughout the plant also are discussed.
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3.
What is the role of putrescine accumulated under potassium deficiency?
Cui, J, Pottosin, I, Lamade, E, Tcherkez, G
Plant, cell & environment. 2020;(6):1331-1347
Abstract
Biomarker metabolites are of increasing interest in crops since they open avenues for precision agriculture, whereby nutritional needs and stresses can be monitored optimally. Putrescine has the potential to be a useful biomarker to reveal potassium (K+ ) deficiency. In fact, although this diamine has also been observed to increase during other stresses such as drought, cold or heavy metals, respective changes are comparably low. Due to its multifaceted biochemical properties, several roles for putrescine under K+ deficiency have been suggested, such as cation balance, antioxidant, reactive oxygen species mediated signalling, osmolyte or pH regulator. However, the specific association of putrescine build-up with low K+ availability in plants remains poorly understood, and possible regulatory roles must be consistent with putrescine concentration found in plant tissues. We hypothesize that the massive increase of putrescine upon K+ starvation plays an adaptive role. A distinction of putrescine function from that of other polyamines (spermine, spermidine) may be based either on its specificity or (which is probably more relevant under K+ deficiency) on a very high attainable concentration of putrescine, which far exceeds those for spermidine and spermine. putrescine and its catabolites appear to possess a strong potential in controlling cellular K+ and Ca2+ , and mitochondria and chloroplasts bioenergetics under K+ stress.
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4.
Abnormalities of Potassium in Heart Failure: JACC State-of-the-Art Review.
Ferreira, JP, Butler, J, Rossignol, P, Pitt, B, Anker, SD, Kosiborod, M, Lund, LH, Bakris, GL, Weir, MR, Zannad, F
Journal of the American College of Cardiology. 2020;(22):2836-2850
Abstract
Potassium (K+) is the most abundant cation in humans and is essential for normal cellular function. Alterations in K+ regulation can lead to neuromuscular, gastrointestinal, and cardiac abnormalities. Dyskalemia (i.e., hypokalemia and hyperkalemia) in heart failure is common because of heart failure itself, related comorbidities, and medications. Dyskalemia has important prognostic implications. Hypokalemia is associated with excess morbidity and mortality in heart failure. The lower the K+ levels, the higher the risk, starting at K+ levels below approximately 4.0 mmol/l, with a steep risk increment with K+ levels <3.5 mmol/l. Hyperkalemia (>5.5 mmol/l) has also been associated with increased risk of adverse events; however, this association is prone to reverse-causation bias as stopping renin angiotensin aldosterone system inhibitor therapy in the advent of hyperkalemia likely contributes the observed risk. In this state-of-the-art review, practical and easy-to-implement strategies to deal with both hypokalemia and hyperkalemia are provided as well as guidance for the use of potassium-binders.
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5.
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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6.
Hyperkalemia in heart failure: Foe or friend?
Rakisheva, A, Marketou, M, Klimenko, A, Troyanova-Shchutskaia, T, Vardas, P
Clinical cardiology. 2020;(7):666-675
Abstract
Hyperkalemia is a frequent and sometimes life-threatening condition that may be associated with arrhythmia and cardiac dysfunction in patients with heart failure (HF). High potassium levels in HF represent both a direct risk for cardiovascular complication and an indirect biomarker of the severity of the underlying disease, reflecting neurohormonal activation and renal dysfunction. Evaluating the prevalence and significance of hyperkalemia in HF patients is essential for optimizing the use of potassium sparing agents, such the renin-angiotensin-aldosterone system inhibitors (RAASi) or angiotensin receptor-neprilysin inhibitors and mineralocorticoid receptor antagonists, which represent a well-established cornerstone and life-saving therapy. In this review we discuss recent findings and current concepts related to the epidemiology, pathological mechanisms and implications of hyperkalemia, as well as novel therapeutic approaches to counteract it in patients with HF. The balance between optimizing life-saving potassium sparing medication and minimizing hyperkalemia-associated risk is much needed in patients with HF. Although older potassium-binding agents are associated with serious adverse events, novel potassium-binding drugs are effective in lowering potassium levels and are generally well tolerated. Novel potassium-binding drugs, such as patiromer and sodium zirconium cyclosilicate, may help to optimize therapy in HF and achieve guideline-recommended doses. Hyperkalemia is common in HF patients and is associated with a poorer prognosis and an increased risk of cardiovascular complications: Contrariwise, "moderate" potassium levels go with a better prognosis, while the emergence of new drugs, potassium binders, could allow target doses of RAASi to be achieved.
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7.
Effect of Perioperative Glucose-Insulin-Potassium Therapy in Patients Undergoing On-Pump Cardiac Surgery: A Meta-Analysis.
Li, Q, Yang, J, Zhang, J, Yang, C, Fan, Z, Yang, Y, Zheng, T, Yang, J
The heart surgery forum. 2020;(1):E063-E069
Abstract
OBJECTIVE The role of glucose-insulin-potassium (GIK) infusion during cardiac surgery has held interest for so many years without a clear answer. The aim of this meta-analysis was to evaluate the effect of GIK therapy on outcomes in patients undergoing on-pump cardiac surgery. METHODS A comprehensive online review was performed in The Web of Science, Embase, Medline, PubMed, and The Cochrane Library databases from 2000 to 2019. Eligible studies included randomized controlled trials (RCTs) that compared GIK treatment with placebo or standard care during on-pump cardiac surgery. Risk ratios (RR) were used for binary outcomes and mean difference (MD) was used for continuous variables; both with their 95% confidence intervals (CI). RESULTS A total of 18 RCTs involving 2,131 patients met the inclusion criteria. Compared with the control group, the GIK treatment significantly reduced in-hospital mortality (RR = 0.56, 95% CI: 0.32-0.97; P = .04), postoperative myocardial infarctions (MI) (RR = 0.71, 95% CI: 0.56-0.91; P = .006), the use of inotropic support (RR = 0.53, 95% CI: 0.45-0.63; P < .00001), and length of stay in the intensive care unit (ICU) (MD = -0.33, 95% CI: -0.52--0.14; P = .0007). Moreover, GIK treatment seemed to be associated with fewer postoperative atrial fibrillation (AF) (RR = 0.81, 95% CI: 0.64-1.03; P = .09). CONCLUSIONS In patients undergoing on-pump cardiac surgery, GIK infusion has a beneficial role in mortality during hospital stay and demonstrates superior efficacy versus standard care for reduction in postoperative MI, AF, ICU length of stay as well as inotropic agent requirements.
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8.
A Brief Review of the Pharmacology of Hyperkalemia: Causes and Treatment.
Wooten, JM, Kupferman, FE, Kupferman, JC
Southern medical journal. 2019;(4):228-233
Abstract
Hyperkalemia is a common problem in both inpatients and outpatients. Many disease states (eg, chronic kidney disease) and medications may precipitate hyperkalemia. There are several drugs now available to treat hyperkalemia. Many of these drugs are relatively new. This review provides information regarding drug-induced causes of hyperkalemia and provides detailed information on the medications used to treat this problem.
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9.
Pivotal clinical trials, meta-analyses and current guidelines in the treatment of hyperkalemia.
Bianchi, S, Regolisti, G
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association. 2019;(Suppl 3):iii51-iii61
Abstract
Hyperkalemia (HK) is the most common electrolyte disturbance observed in patients with advanced stages of chronic kidney disease (CKD), is a potentially life-threatening clinical condition due to an increased risk of fatal arrhythmias, and strongly impacts the quality of life and prognosis of CKD patients. Moreover, while renin-angiotensin-aldosterone system inhibitors (RAASIs) represent the most cardio-nephro-protective drugs used in clinical practice, the treatment with these drugs per se increases serum potassium (sK) values, particularly when heart failure and diabetes mellitus coexist. In fact, the onset or recurrence of HK is frequently associated with not starting, down-titrating or withdrawing RAASIs, and is an indication to begin renal replacement treatment in end-stage renal disease. Current strategies aimed at preventing and treating chronic HK are still unsatisfactory, as evidenced by the relatively high prevalence of HK also in patients under stable nephrology care, and even in the ideal setting of randomized clinical trials. Indeed, dietary potassium restriction, the use of sodium bicarbonate or diuretics, the withdrawal or down-titration of RAASIs, or the administration of old potassium binders, namely sodium polystyrene sulphonate and calcium polystyrene sulphonate, have limited efficacy and are poorly tolerated; therefore, these strategies are not suitable for long-term control of sK. As such, there is an important unmet need for novel therapeutic options for the chronic management of patients at risk for HK. The development of new potassium binders may change the treatment landscape in the near future. This review summarizes the current evidence on the treatment of chronic HK in cardio-renal patients.
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10.
Chronic Hyperkalemia in Cardiorenal Patients: Risk Factors, Diagnosis, and New Treatment Options.
Di Lullo, L, Ronco, C, Granata, A, Paoletti, E, Barbera, V, Cozzolino, M, Ravera, M, Fusaro, M, Bellasi, A
Cardiorenal medicine. 2019;(1):8-21
Abstract
Chronic hyperkalemia (HK) is a serious medical condition that often manifests in patients with chronic kidney disease (CKD) and heart failure (HF) leading to poor outcomes and necessitating careful management by cardionephrologists. CKD, HF, diabetes, and renin-angiotensin-aldosterone system inhibitors use is known to induce HK. Current therapeutic options are not optimal, as pointed out by a large number of CKD and HF patients with HK. The following review will focus on the main risk factors for developing HK and also aims to provide a guide for a correct diagnosis and present new approaches to therapy.