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Abstract
Excessive salt intake raises blood pressure, but the implications of this observation for human health have remained contentious. It has also been recognized for many years that potassium intake may mitigate the effects of salt intake on blood pressure and possibly on outcomes such as stroke. Recent large randomized intervention trials have provided strong support for the benefits of replacing salt (NaCl) with salt substitute (75% NaCl, 25% KCl) on hard outcomes, including stroke. During the same period of time, major advances have been made in understanding how the body senses and tastes salt, and how these sensations drive intake. Additionally, new insights into the complex interactions between systems that control sodium and potassium excretion by the kidneys, and the brain have highlighted the existence of a potassium switch in the kidney distal nephron. This switch seems to contribute importantly to the blood pressure-lowering effects of potassium intake. In recognition of these evolving data, the United States Food and Drug Administration is moving to permit potassium-containing salt substitutes in food manufacturing. Given that previous attempts to reduce salt consumption have not been successful, this new approach has a chance of improving health and ending the 'Salt Wars'.
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Affiliation(s)
- Robert Little
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- LeDucq Transatlantic Network of Excellence
| | - David H. Ellison
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon, USA
- Oregon Clinical & Translational Research Institute, Oregon Health & Science University, Portland, Oregon, USA
- LeDucq Transatlantic Network of Excellence
- VA Portland Health Care System, Portland, OR
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2
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Yuan Y, Jin A, Zhao MH, Wang H, Feng X, Qiao Q, Zhang R, Gao R, Wu Y. Association of serum potassium level with dietary potassium intake in Chinese older adults: a multicentre, cross-sectional survey. BMJ Open 2023; 13:e077249. [PMID: 38000815 PMCID: PMC10679980 DOI: 10.1136/bmjopen-2023-077249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 10/31/2023] [Indexed: 11/26/2023] Open
Abstract
OBJECTIVES Evidence linking dietary potassium and serum potassium is virtually scarce and inconclusive. The aim of the study was to investigate the association between serum potassium level and potassium intake measured by 24-hour urine. We also explored whether the association differed across health conditions. DESIGN A cross-sectional study conducted from September 2017 to March 2018. SETTING 48 residential elderly care facilities in northern China. PARTICIPANTS Participants aged 55 years and older and with both serum potassium and 24-hour urinary potassium measured were classified as having a low (apparently healthy), moderate (with ≥1 health condition but normal renal function) and high (with ≥1 health condition and abnormal renal function) risk of hyperkalaemia. EXPOSURE Potassium intake is measured by 24-hour urinary potassium. OUTCOMES Serum potassium in association with potassium intake after adjustment for age, sex, region and accounting for the cluster effect. RESULTS Of 962 eligible participants (mean age 69.1 years, 86.8% men), 17.3% were at low risk, 48.4% at moderate risk and 34.3% at high risk of hyperkalaemia. Serum potassium was weakly associated with 24-hour urinary potassium among individuals with moderate (adjusted β=0.0040/L; p=0.017) and high (adjusted β=0.0078/L; p=0.003) but not low (adjusted β=0.0018/L; p=0.311) risk of hyperkalaemia. CONCLUSIONS A weak association between dietary potassium intake and serum potassium level existed only among individuals with impaired renal function or other health conditions but not among apparently healthy individuals. The results imply that increasing dietary potassium intake may slightly increase the risk of hyperkalaemia but may also decrease the risk of hypokalaemia in unhealthy individuals, both of which have important health concerns. TRIAL REGISTRATION NUMBER NCT03290716; Post-results.
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Affiliation(s)
- Yifang Yuan
- Peking University Clinical Research Center, Peking University Health Science Center, Beijing, China
| | - Aoming Jin
- Peking University First Hospital, Beijing, China
- Clinical Research Institute, Peking University, Beijing, China
| | - Ming-Hui Zhao
- Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China
| | - Hongxia Wang
- Hohhot Center for Disease Control and Prevention, Inner Mongolia, China
| | | | - Qianku Qiao
- Yangcheng Ophthalmic Hospital, Jincheng, Shanxi, China
| | | | - Runlin Gao
- Fu Wai Hospital, National Center for Cardiovascular Diseases, Beijing, China
| | - Yangfeng Wu
- Peking University First Hospital, Beijing, China
- Department of Epidemiology and Biostatistics, Peking University School of Public Health, Beijing, China
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3
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Wouda RD, Boekholdt SM, Khaw KT, Wareham NJ, de Borst MH, Hoorn EJ, Rotmans JI, Vogt L. Sex-specific associations between potassium intake, blood pressure, and cardiovascular outcomes: the EPIC-Norfolk study. Eur Heart J 2022; 43:2867-2875. [PMID: 35863377 PMCID: PMC9356908 DOI: 10.1093/eurheartj/ehac313] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 05/18/2022] [Accepted: 05/31/2022] [Indexed: 12/12/2022] Open
Abstract
AIMS A potassium replete diet is associated with lower blood pressure (BP) and lower risk of cardiovascular disease (CVD). Whether these associations differ between men and women and whether they depend on daily sodium intake is unknown. METHODS AND RESULTS An analysis was performed in 11 267 men and 13 696 women from the EPIC-Norfolk cohort. Twenty-four hour excretion of sodium and potassium, reflecting intake, was estimated from sodium and potassium concentration in spot urine samples using the Kawasaki formula. Linear and Cox regression were used to explore the association between potassium intake, systolic BP (SBP), and CVD events (defined as hospitalization or death due to CVD). After adjustment for confounders, interaction by sex was found for the association between potassium intake and SBP (P < 0.001). In women, but not in men, the inverse slope between potassium intake and SBP was steeper in those within the highest tertile of sodium intake compared with those within the lowest tertile of sodium intake (P < 0.001 for interaction by sodium intake). Both in men and women, higher potassium intake was associated with a lower risk of CVD events, but the hazard ratio (HR) associated with higher potassium intake was lower in women than in men [highest vs. lowest potassium intake tertile: men: HR 0.93, 95% confidence interval (CI) 0.87-1.00; women: HR 0.89, 95% CI 0.83-0.95, P = 0.033 for interaction by sex]. CONCLUSION The association between potassium intake, SBP, and CVD events is sex specific. The data suggest that women with a high sodium intake in particular benefit most from a higher potassium intake with regard to SBP.
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Affiliation(s)
- Rosa D Wouda
- Department of Internal Medicine, Section of Nephrology, Amsterdam University Medical Centers, Amsterdam Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - S Matthijs Boekholdt
- Department of Cardiology, Amsterdam University Medical Centers, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
| | - Kay Tee Khaw
- Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | | | - Martin H de Borst
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, Groningen, The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Joris I Rotmans
- Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Liffert Vogt
- Department of Internal Medicine, Section of Nephrology, Amsterdam University Medical Centers, Amsterdam Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
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4
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McDonough AA, Fenton RA. Potassium homeostasis: sensors, mediators, and targets. Pflugers Arch 2022; 474:853-867. [PMID: 35727363 PMCID: PMC10163916 DOI: 10.1007/s00424-022-02718-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 06/08/2022] [Accepted: 06/12/2022] [Indexed: 12/16/2022]
Abstract
Transmembrane potassium (K) gradients are key determinants of membrane potential that can modulate action potentials, control muscle contractility, and influence ion channel and transporter activity. Daily K intake is normally equal to the amount of K in the entire extracellular fluid (ECF) creating a critical challenge - how to maintain ECF [K] and membrane potential in a narrow range during feast and famine. Adaptations to maintain ECF [K] include sensing the K intake, sensing ECF [K] vs. desired set-point and activating mediators that regulate K distribution between ECF and ICF, and regulate renal K excretion. In this focused review, we discuss the basis of these adaptions, including (1) potential mechanisms for rapid feedforward signaling to kidney and muscle after a meal (before a rise in ECF [K]), (2) how skeletal muscles sense and respond to changes in ECF [K], (3) effects of K on aldosterone biosynthesis, and (4) how the kidney responds to changes in ECF [K] to modify K excretion. The concepts of sexual dimorphisms in renal K handling adaptation are introduced, and the molecular mechanisms that can account for the benefits of a K-rich diet to maintain cardiovascular health are discussed. Although the big picture of K homeostasis is becoming more clear, we also highlight significant pieces of the puzzle that remain to be solved, including knowledge gaps in our understanding of initiating signals, sensors and their connection to homeostatic adjustments of ECF [K].
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Affiliation(s)
- Alicia A McDonough
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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Youn JH, Oh YT, Gili S, McDonough AA, Higgins J. Estimating in vivo potassium distribution and fluxes with stable potassium isotopes. Am J Physiol Cell Physiol 2022; 322:C410-C420. [PMID: 35080924 PMCID: PMC8917925 DOI: 10.1152/ajpcell.00351.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extracellular potassium (K+) homeostasis is achieved by a concerted effort of multiple organs and tissues. A limitation in studies of K+ homeostasis is inadequate techniques to quantify K+ fluxes into and out of organs and tissues in vivo. The goal of the present study was to test the feasibility of a novel approach to estimate K+ distribution and fluxes in vivo using stable K+ isotopes. 41K was infused as KCl into rats consuming control or K+-deficient chow (n = 4 each), 41K-to-39K ratios in plasma and red blood cells (RBCs) were measured by inductively coupled plasma mass spectrometry, and results were subjected to compartmental modeling. The plasma 41K/39K increased during 41K infusion and decreased upon infusion cessation, without altering plasma total K+ concentration ([K+], i.e., 41K + 39K). The time course of changes was analyzed with a two-compartmental model of K+ distribution and elimination. Model parameters, representing transport into and out of the intracellular pool and renal excretion, were identified in each rat, accurately predicting decreased renal K+ excretion in rats fed K+-deficient vs. control diet (P < 0.05). To estimate rate constants of K+ transport into and out of RBCs, 41K/39K were subjected to a simple model, indicating no effects of the K+-deficient diet. The findings support the feasibility of the novel stable isotope approach to quantify K+ fluxes in vivo and sets a foundation for experimental protocols using more complex models to identify heterogeneous intracellular K+ pools and to answer questions pertaining to K+ homeostatic mechanisms in vivo.
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Affiliation(s)
- Jang H. Youn
- 1Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, California
| | - Young Taek Oh
- 1Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, California
| | - Stefania Gili
- 2Department of Geosciences, Princeton University, Princeton, New Jersey
| | - Alicia A. McDonough
- 1Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, California
| | - John Higgins
- 2Department of Geosciences, Princeton University, Princeton, New Jersey
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6
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Wei KY, Gritter M, Vogt L, de Borst MH, Rotmans JI, Hoorn EJ. Dietary potassium and the kidney: lifesaving physiology. Clin Kidney J 2020; 13:952-968. [PMID: 33391739 PMCID: PMC7769543 DOI: 10.1093/ckj/sfaa157] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Indexed: 02/07/2023] Open
Abstract
Potassium often has a negative connotation in Nephrology as patients with chronic kidney disease (CKD) are prone to develop hyperkalaemia. Approaches to the management of chronic hyperkalaemia include a low potassium diet or potassium binders. Yet, emerging data indicate that dietary potassium may be beneficial for patients with CKD. Epidemiological studies have shown that a higher urinary potassium excretion (as proxy for higher dietary potassium intake) is associated with lower blood pressure (BP) and lower cardiovascular risk, as well as better kidney outcomes. Considering that the composition of our current diet is characterized by a high sodium and low potassium content, increasing dietary potassium may be equally important as reducing sodium. Recent studies have revealed that dietary potassium modulates the activity of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule (DCT). The DCT acts as a potassium sensor to control the delivery of sodium to the collecting duct, the potassium-secreting portion of the kidney. Physiologically, this allows immediate kaliuresis after a potassium load, and conservation of potassium during potassium deficiency. Clinically, it provides a novel explanation for the inverse relationship between dietary potassium and BP. Moreover, increasing dietary potassium intake can exert BP-independent effects on the kidney by relieving the deleterious effects of a low potassium diet (inflammation, oxidative stress and fibrosis). The aim of this comprehensive review is to link physiology with clinical medicine by proposing that the same mechanisms that allow us to excrete an acute potassium load also protect us from hypertension, cardiovascular disease and CKD.
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Affiliation(s)
- Kuang-Yu Wei
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Department of Internal Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Liffert Vogt
- Department of Internal Medicine, Division of Nephrology, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Martin H de Borst
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Joris I Rotmans
- Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Hoorn EJ, Gritter M, Cuevas CA, Fenton RA. Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis. Physiol Rev 2020; 100:321-356. [DOI: 10.1152/physrev.00044.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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8
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Abstract
BACKGROUND Hyperkalemia is a common feature of chronic renal insufficiency, usually ascribed to impaired K+ homeostasis. However, various experimental observations suggest that the increase in extracellular [K+] actually functions in a homeostatic fashion, directly stimulating renal K+ excretion through an effect that is independent of, and additive to, aldosterone. METHODS We have reviewed relevant studies in experimental animals and in human subjects that have examined the regulation of K+ excretion and its relation to plasma [K+]. RESULTS Studies indicate that (1) extracellular [K+] in patients with renal insufficiency correlates directly with intracellular K+ content, and (2) hyperkalemia directly promotes K+ secretion in the principal cells of the collecting duct by increasing apical and basolateral membrane conductances. The effect of hyperkalemia differs from that of aldosterone in that K+ conductances are increased as the primary event. The changes in principal cell function and structure induced by hyperkalemia are indistinguishable from the effects seen in adaptation to a high K+ diet. CONCLUSIONS We propose that hyperkalemia plays a pivotal role in K+ homeostasis in renal insufficiency by stimulating K+ excretion. In patients with chronic renal insufficiency, a new steady state develops in which extracellular [K+] rises to the level needed to stimulate K+ excretion so that it again matches intake. When this new steady state is achieved, plasma [K+] remains stable unless dietary intake increases, glomerular filtration rate falls, or drugs are given that disrupt the new balance.
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Affiliation(s)
- F John Gennari
- Fletcher Allen Health Care, University of Vermont College of Medicine, Burlington, VT 05401, USA.
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9
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Abstract
Although only 2% of the body potassium is present in the extracellular space, its concentration is finely regulated by the internal balance, or distribution of potassium between the intracellular and extracellular compartments, and by the external balance, or difference between intake and output of potassium. Internal balance is modulated by a host of factors, including insulin, epinephrine, extracellular pH and plasma tonicity. Potassium output from the body is mainly determined by renal excretion. Renal secretion of potassium takes place predominantly in the principal cells of late distal and cortical collecting tubules, by a process involving the accumulation of potassium in the cell by the activity of the basolateral Na+,K(+)-ATPase and its exit through luminal conductive channels. The factors regulating renal potassium secretion are potassium intake, rate of tubular fluid flow, distal sodium delivery, acid-base status and aldosterone. Hypokalaemia may result from a low potassium intake, excessive gastrointestinal, cutaneous or renal losses and altered body distribution. Aetiological diagnosis and therapy are best accomplished when the acid-base status is assessed at the same time. Before establishing the diagnosis of hyperkalaemia, spurious hyperkalaemia due to haemolysis or release of potassium from cells during clot retraction (pseudohyperkalaemia) should be ruled out. Hyperkalaemia may result from exogenous or endogenous loading, decreased renal output and altered body distribution. Acute hyperkalaemia represents an emergency situation which requires immediate therapy.
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Affiliation(s)
- J Rodríguez-Soriano
- Department of Paediatrics, Hospital de Cruces and Basque University School of Medicine, Bilbao, Spain
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10
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Krishna GG, Kapoor SC. Potassium supplementation ameliorates mineralocorticoid-induced sodium retention. Kidney Int 1993; 43:1097-103. [PMID: 8510388 DOI: 10.1038/ki.1993.154] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Potassium depletion induced by dietary potassium restriction causes sodium retention while potassium supplementation augments urinary sodium excretion. The role of external potassium balance in modulating mineralocorticoid-induced sodium retention in humans is unknown. Accordingly, eight healthy subjects were studied at the Clinical Research Center receiving a constant diet providing (per kg body wt) sodium 2.5 mmol, potassium 1.1 mmol daily. After establishing basal sodium and potassium balance over three days, each subject received 9 alpha-fludrocortisone 0.4 mg/day for 10 days. Subjects were studied twice, four to eight weeks apart, in a double blind, randomized crossover design receiving either placebo or additional KCl (80 mmol/day) over the 10 day study period. Serum potassium concentrations were unchanged from basal values on KCl while the values fell (4.1 +/- 0.1 vs. 3.4 +/- 0.1 mmol/liter, P = 0.01) on placebo. Urinary sodium excretion decreased with fludrocortisone administration in both groups, but this decrease reached significance only in the placebo group. Furthermore, during fludrocortisone administration the sodium excretion rates on KCl were significantly higher compared to the values noted on placebo (134 +/- 8 vs. 112 +/- 13 mmol/day, P = 0.01). Body weight recorded after 10 days of fludrocortisone administration was higher on placebo compared to KCl (72.3 +/- 2.8 vs. 71.6 +/- 2.8 kg, P = 0.01). Plasma renin activity, and aldosterone concentrations decreased on fludrocortisone while atrial natriuretic peptide levels increased. These studies suggest that amelioration of hypokalemia attenuates mineralocorticoid-induced sodium retention. Therefore, potassium depletion may contribute to the mineralocorticoid-induced sodium retention.
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Affiliation(s)
- G G Krishna
- Renal Electrolyte Section, University of Pennsylvania, Philadelphia
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11
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Skøtt P, Vaag A, Bruun NE, Hother-Nielsen O, Gall MA, Beck-Nielsen H, Parving HH. Effect of insulin on renal sodium handling in hyperinsulinaemic type 2 (non-insulin-dependent) diabetic patients with peripheral insulin resistance. Diabetologia 1991; 34:275-81. [PMID: 2065862 DOI: 10.1007/bf00405088] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The sodium retaining effect of insulin was studied in ten Type 2 (non-insulin-dependent) diabetic patients (mean age 56 (43-73) years, mean body mass index 29.5 (24.2-33.7) kg/m2) and eight age-matched control subjects (mean age 57 (43-68) years, mean body mass index 23.4 (20.8-26.6) kg/m2). The renal clearances of 99mTc-DTPA, lithium, sodium and potassium were measured over a basal period of 90 min. Then insulin was infused at a rate of 40 mU.min-1.m-2. After an equilibration period of 90 min, the clearance measurements were repeated during a new 90 min period. Blood glucose was clamped at the basal level (diabetic patients: 9.9 +/- 3.5, control subjects: 5.3 +/- 0.5 mmol/l) by a variable glucose infusion. Basal plasma insulin concentration was elevated in the diabetic patients (0.12 +/- 0.05 vs 0.05 +/- 0.02 pmol/ml, p less than 0.01). Insulin infusion resulted in comparable absolute increments in plasma insulin concentrations in the diabetic group and in the control group (0.44 +/- 0.13 vs 0.36 +/- 0.07 pmol/ml, NS). The metabolic clearance rate of glucose during the last 30 min of insulin infusion was lower in the diabetic patients (155 +/- 62 vs 320 +/- 69 ml.min-1.m-2, p less than 0.01), reflecting peripheral insulin resistance. The decline in sodium clearance during insulin infusion was similar in diabetic subjects (1.8 +/- 1.1 vs 0.7 +/- 0.4 ml.min-1.1.73 m-2, p less than 0.01) and in control subjects (1.7 +/- 0.3 vs 0.8 +/- 0.3 ml.min-1.1.73 m-2, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P Skøtt
- Hvidøre Hospital, Klampenborg, Denmark
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12
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Friedberg CE, Koomans HA, Bijlsma JA, Rabelink TJ, Dorhout Mees EJ. Sodium retention by insulin may depend on decreased plasma potassium. Metabolism 1991; 40:201-4. [PMID: 1988777 DOI: 10.1016/0026-0495(91)90175-v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Evidence is accumulating that insulin is a hypertensive factor in humans. The involved mechanism may be its sodium-retaining effect. We examined whether insulin causes sodium retention through a direct action on the kidney, as is generally assumed, or indirectly through hypokalemia. Insulin was infused (euglycemic clamp technique) with and without potassium infusion to prevent hypokalemia in six healthy subjects. Without potassium infusion, insulin caused a marked decrease in plasma potassium (-0.75 mmol/L), and decreased urinary sodium and potassium excretions by, approximately 38% and 65%, respectively. Simultaneous potassium infusion largely prevented the decrease in plasma potassium, as well as the decrease in urinary sodium and potassium excretions. These data suggest that the acute antinatriuretic effect of insulin may be largely mediated in an indirect way, ie, through hypokalemia.
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Affiliation(s)
- C E Friedberg
- Department of Nephrology, University Hospital Utrecht, The Netherlands
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13
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Rabelink TJ, Koomans HA, Hené RJ, Dorhout Mees EJ. Early and late adjustment to potassium loading in humans. Kidney Int 1990; 38:942-7. [PMID: 2266680 DOI: 10.1038/ki.1990.295] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We studied the adaptation to early (72 hr) and late (20 days) K loading (400 mmol/day, 4 equal meals every 6 hour) in six healthy humans. Throughout the study, each single K meal was followed by an acute transient rise in plasma K, aldosterone and kaliuresis. "K balance" (urinary K excretion approximately 80% of intake) was achieved in the second 24 hour period of K loading. This was associated with elevated plasma K and aldosterone, slightly negative sodium (Na) balance and stimulated plasma renin activity. At 20 days of K loading Na loss had been compensated. Plasma renin activity and aldosterone had returned to baseline, although the latter kept increasing after each single K meal. Compared to the first K meal, the K meals at 72 hours and 20 days of K loading were followed by more kaliuresis, while the natriuretic effect had disappeared. Abrupt discontinuation of K loading was followed by negative K balance, lasting only 24 hour, and by Na retention, lasting 72 hours. In conclusion, switching to a high K diet in humans is immediately followed by increased renal K excretion, and by Na loss. K excretion increases over a few days, while Na loss is halted. This can be explained by the rise in plasma aldosterone, secondary to elevated plasma K and renin activity. After weeks, renal adaptation forms an additional factor promoting K excretion and preventing natriuresis. The latter appears specifically from the Na retention which occurs after discontinuation of K loading in the absence of persistent aldosterone stimulation.
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Affiliation(s)
- T J Rabelink
- Department of Nephrology and Hypertension, University Hospital Utrecht, The Netherlands
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