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Malavolti M, Naska A, Fairweather-Tait SJ, Malagoli C, Vescovi L, Marchesi C, Vinceti M, Filippini T. Sodium and Potassium Content of Foods Consumed in an Italian Population and the Impact of Adherence to a Mediterranean Diet on Their Intake. Nutrients 2021; 13:nu13082681. [PMID: 34444841 PMCID: PMC8401684 DOI: 10.3390/nu13082681] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 07/20/2021] [Accepted: 07/30/2021] [Indexed: 12/25/2022] Open
Abstract
High sodium and low potassium intakes are associated with increased levels of blood pressure and risk of cardiovascular diseases. Assessment of habitual dietary habits are helpful to evaluate their intake and adherence to healthy dietary recommendations. In this study, we determined sodium and potassium food-specific content and intake in a Northern Italy community, focusing on the role and contribution of adherence to Mediterranean diet patterns. We collected a total of 908 food samples and measured sodium and potassium content using inductively coupled plasma mass spectrometry. Using a validated semi-quantitative food frequency questionnaire, we assessed habitual dietary intake of 719 adult individuals of the Emilia-Romagna region. We then estimated sodium and potassium daily intake for each food based on their relative contribution to the overall diet, and their link to Mediterranean diet patterns. The estimated mean sodium intake was 2.15 g/day, while potassium mean intake was 3.37 g/day. The foods contributing most to sodium intake were cereals (33.2%), meat products (24.5%, especially processed meat), and dairy products (13.6%), and for potassium they were meat (17.1%, especially red and white meat), fresh fruits (15.7%), and vegetables (15.1%). Adherence to a Mediterranean diet had little influence on sodium intake, whereas potassium intake was greatly increased in subjects with higher scores, resulting in a lower sodium/potassium ratio. Although we may have underestimated dietary sodium intake by not including discretionary salt use and there may be some degree of exposure misclassification as a result of changes in food sodium content and dietary habits over time, our study provides an overview of the contribution of a wide range of foods to the sodium and potassium intake in a Northern Italy community and of the impact of a Mediterranean diet on intake. The mean sodium intake was above the dietary recommendations for adults of 1.5–2 g/day, whilst potassium intake was only slightly lower than the recommended 3.5 g/day. Our findings suggest that higher adherence to Mediterranean diet patterns has limited effect on restricting sodium intake, but may facilitate a higher potassium intake, thereby aiding the achievement of healthy dietary recommendations.
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Affiliation(s)
- Marcella Malavolti
- Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (M.M.); (C.M.); (L.V.); (T.F.)
| | - Androniki Naska
- Department of Hygiene, Epidemiology and Medical Statistics, School of Medicine, National and Kapodistrian University of Athens, Mikras Asias 75, 11527 Athens, Greece;
| | - Susan J. Fairweather-Tait
- Norwich Medical School, University of East Anglia, Norwich Research Park, James Watson Road, Norwich NR4 7UQ, UK;
| | - Carlotta Malagoli
- Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (M.M.); (C.M.); (L.V.); (T.F.)
| | - Luciano Vescovi
- Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (M.M.); (C.M.); (L.V.); (T.F.)
| | - Cristina Marchesi
- Head Office, Direzione Generale, Azienda USL-IRCCS di Reggio Emilia, Via Amendola 2, 42122 Reggio Emilia, Italy;
| | - Marco Vinceti
- Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (M.M.); (C.M.); (L.V.); (T.F.)
- Department of Epidemiology, Boston University School of Public Health, 715 Albany Street, Boston, MA 02118, USA
- Correspondence:
| | - Tommaso Filippini
- Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (M.M.); (C.M.); (L.V.); (T.F.)
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Al-Qusairi L, Grimm PR, Zapf AM, Welling PA. Rapid development of vasopressin resistance in dietary K + deficiency. Am J Physiol Renal Physiol 2021; 320:F748-F760. [PMID: 33749322 PMCID: PMC8174811 DOI: 10.1152/ajprenal.00655.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/15/2021] [Accepted: 03/15/2021] [Indexed: 12/27/2022] Open
Abstract
The association between diabetes insipidus (DI) and chronic dietary K+ deprivation is well known, but it remains uncertain how the disorder develops and whether it is influenced by the sexual dimorphism in K+ handling. Here, we determined the plasma K+ (PK) threshold for DI in male and female mice and ascertained if DI is initiated by polydipsia or by a central or nephrogenic defect. C57BL6J mice were randomized to a control diet or to graded reductions in dietary K+ for 8 days, and kidney function and transporters involved in water balance were characterized. We found that male and female mice develop polyuria and secondary polydipsia. Altered water balance coincided with a decrease in aquaporin-2 (AQP2) phosphorylation and apical localization despite increased levels of the vasopressin surrogate marker copeptin. No change in the protein abundance of urea transporter-A1 was observed. The Na+-K+-2Cl- cotransporter decreased only in males. Desmopressin treatment failed to reverse water diuresis in K+-restricted mice. These findings indicate that even a small fall in PK is associated with nephrogenic DI (NDI), coincident with the development of altered AQP2 regulation, implicating low PK as a causal trigger of NDI. We found that PK decreased more in females, and, consequently, females were more prone to develop NDI. Together, these data indicate that AQP2 regulation is disrupted by a small decrease in PK and that the response is influenced by sexual dimorphism in K+ handling. These findings provide new insights into the mechanisms linking water and K+ balances and support defining the disorder as "potassium-dependent NDI."NEW & NOTEWORTHY This study shows that aquaporin-2 regulation is disrupted by a small fall in plasma potassium levels and the response is influenced by sexual dimorphism in renal potassium handling. The findings provided new insights into the mechanisms by which water balance is altered in dietary potassium deficiency and support defining the disorder as "potassium-dependent nephrogenic diabetes insipidus."
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Affiliation(s)
- Lama Al-Qusairi
- Departments of Medicine, Nephrology, and Physiology, Johns Hopkins University Medical School, Baltimore, Maryland
| | - P Richard Grimm
- Departments of Medicine, Nephrology, and Physiology, Johns Hopkins University Medical School, Baltimore, Maryland
| | - Ava M Zapf
- Graduate Program in Life Sciences, University of Maryland, Baltimore, Maryland
| | - Paul A Welling
- Departments of Medicine, Nephrology, and Physiology, Johns Hopkins University Medical School, Baltimore, Maryland
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Sun H, Weaver CM. Rise in Potassium Deficiency in the US Population Linked to Agriculture Practices and Dietary Potassium Deficits. J Agric Food Chem 2020; 68:11121-11127. [PMID: 32921052 DOI: 10.1021/acs.jafc.0c05139] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This paper, for the first time, provides evidence that current practices that lead to agricultural crop removal of potassium are unsustainable and likely contributed to the decline in dietary potassium intake and rise in hypokalemia prevalence in the US population. Potassium concentrations in beef, pork, turkey, fruit, vegetables, cereal crops, and so forth decreased between 1999 and 2015 based on the examination of potassium values of food items of USDA standard reference. Ratios of potassium input to removal by crops between 1987 and 2014, potassium in topsoil, and crop-available soil potassium in US farms all declined in recent years. Reported reductions in dietary potassium intake correspond to these decreases in the food supply and to increases in hypokalemia prevalence in the US population. Results of this paper provide new understanding on links between potassium management in agricultural practices and potassium intake deficits, which is needed for combating increasing hypokalemia prevalence in the US population.
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Affiliation(s)
- Hongbing Sun
- GEMS Department, Health Studies Institute, Rider University, 2083 Lawrenceville Road, Lawrenceville, New Jersey 08648, United States
| | - Connie M Weaver
- Weaver & Associates Consulting LLC, West Lafayette, Indiana 47906, United States
- Department of Nutrition Science, Purdue University, 700 W State Street, West Lafayette, Indiana 47907, United States
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Abstract
PURPOSE OF REVIEW Multiple clinical and translational evidence support benefits of high potassium diet; however, there many uncertainties underlying the molecular and cellular mechanisms determining effects of dietary potassium. Kir4.1 and Kir5.1 proteins form a functional heteromer (Kir4.1/Kir5.1), which is the primary inwardly rectifying potassium channel on the basolateral membrane of both distal convoluted tubule (DCT) and the collecting duct principal cells. The purpose of this mini-review is to summarize latest advances in our understanding of the evolution, physiological relevance and mechanisms controlling these channels. RECENT FINDINGS Kir4.1 and Kir5.1 channels play a critical role in determining electrolyte homeostasis in the kidney and blood pressure, respectively. It was reported that Kir4.1/Kir5.1 serves as potassium sensors in the distal nephron responding to variations in dietary intake and hormonal stimuli. Global and kidney specific knockouts of either channel resulted in hypokalemia and severe cardiorenal phenotypes. Furthermore, knock out of Kir5.1 in Dahl salt-sensitive rat background revealed the crucial role of the Kir4.1/Kir5.1 channel in salt-induced hypertension. SUMMARY Here, we focus on reviewing novel experimental evidence of the physiological function, expression and hormonal regulation of renal basolateral inwardly rectifying potassium channels. Further investigation of molecular and cellular mechanisms controlling Kir4.1 and Kir4.1/Kir5.1-mediating pathways and development of specific compounds targeting these channels function is essential for proper control of electrolyte homeostasis and blood pressure.
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Affiliation(s)
- Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226
| | - Oleh Pochynyuk
- Department of Integrative Biology, University of Texas Health Science Center, Houston, TX 77030
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Arnold R, Pianta TJ, Pussell BA, Kirby A, O’Brien K, Sullivan K, Holyday M, Cormack C, Kiernan MC, Krishnan AV. Randomized, Controlled Trial of the Effect of Dietary Potassium Restriction on Nerve Function in CKD. Clin J Am Soc Nephrol 2017; 12:1569-1577. [PMID: 28893921 PMCID: PMC5628705 DOI: 10.2215/cjn.00670117] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 06/26/2017] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES Neuromuscular complications are almost universal in CKD by the time that a patient commences dialysis. Recent studies have indicated that chronic hyperkalemia may contribute to the development of neuropathy in CKD. This study was undertaken to determine whether dietary restriction of potassium intake may be a neuroprotective factor in CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A 24-month prospective, single-blind, randomized, controlled trial was undertaken in 47 consecutively recruited patients with stages 3 and 4 CKD. The intervention arm (n=23) was prescribed a diet focusing on potassium restriction to meet a monthly serum potassium level of ≤4.5 mEq/L, with oral sodium polystyrene sulfonate provided if dietary advice failed to achieve the target. The control arm (n=24) received dietary advice regarding general nutrition. The primary outcome was the change in the total neuropathy score evaluated by a blinded observer. Secondary outcomes included electrolyte levels, gait speed, neurophysiologic parameters, and health-related quality of life scores. Five patients withdrew before initiation of treatment, and final analysis consisted of n=21 in each group. RESULTS There was a greater increase in total neuropathy score from baseline to final assessment in the control arm compared with the intervention arm (6.1±6.2-8.6±7.9 controls; 7.8±7.4-8.2±7.5 intervention; change 2.8±3.3-0.4±2.2, respectively; P<0.01). The intervention significantly reduced mean serum potassium compared with controls (4.6±0.1-4.8±0.1 mEq/L mean recorded every 6 months over the trial duration; P=0.03). There were no adverse changes in other nutritional parameters. Improved gait speed was also noted in the intervention arm compared with the control arm, with a mean increase of 0.15±0.17 m/s in the intervention group versus 0.02±0.16 m/s in the control group (P=0.01). CONCLUSIONS Our results provide important preliminary evidence that dietary potassium restriction confers neuroprotection in CKD and should be confirmed in a larger multicenter trial.
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Affiliation(s)
| | - Timothy J. Pianta
- Northern Clinical School, University of Melbourne, Melbourne, Australia
| | - Bruce A. Pussell
- Prince of Wales Clinical School, UNSW Sydney, Sydney, Australia
- Departments of Nephrology and
| | - Adrienne Kirby
- Nutrition and Dietetics, Prince of Wales Hospital, Sydney, Australia; and
| | - Kate O’Brien
- National Health and Medical Research Council Clinical Trials Centre and
| | - Karen Sullivan
- National Health and Medical Research Council Clinical Trials Centre and
| | - Margaret Holyday
- National Health and Medical Research Council Clinical Trials Centre and
| | | | | | - Arun V. Krishnan
- Nutrition and Dietetics, Prince of Wales Hospital, Sydney, Australia; and
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Kim T, Rhee CM, Streja E, Soohoo M, Obi Y, Chou JA, Tortorici AR, Ravel VA, Kovesdy CP, Kalantar-Zadeh K. Racial and Ethnic Differences in Mortality Associated with Serum Potassium in a Large Hemodialysis Cohort. Am J Nephrol 2017; 45:509-521. [PMID: 28528336 PMCID: PMC5546877 DOI: 10.1159/000475997] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 01/14/2017] [Indexed: 12/18/2022]
Abstract
BACKGROUND Hyperkalemia is observed in chronic kidney disease patients and may be a risk factor for life-threatening arrhythmias and death. Race/ethnicity may be important modifiers of the potassium-mortality relationship in maintenance hemodialysis (MHD) patients given that potassium intake and excretion vary among minorities. METHODS We examined racial/ethnic differences in baseline serum potassium levels and all-cause and cardiovascular mortality using Cox proportional hazard models and restricted cubic splines in a cohort of 102,241 incident MHD patients. Serum potassium was categorized into 6 groups: ≤3.6, >3.6 to ≤4.0, >4.0 to ≤4.5 (reference), >4.5 to ≤5.0, >5.0 to ≤5.5, and >5.5 mEq/L. Models were adjusted for case-mix and malnutrition-inflammation cachexia syndrome (MICS) covariates. RESULTS The cohort was composed of 50% whites, 34% African-Americans, and 16% Hispanics. Hispanics tended to have the highest baseline serum potassium levels (mean ± SD: 4.58 ± 0.55 mEq/L). Patients in our cohort were followed for a median of 1.3 years (interquartile range 0.6-2.5). In our cohort, associations between higher potassium (>5.5 mEq/L) and higher mortality risk were observed in African-American and whites, but not Hispanic patients in models adjusted for case-mix and MICS covariates. While in Hispanics only, lower serum potassium (<3.6 mEq/L) levels were associated with higher mortality risk. Similar trends were observed for cardiovascular mortality. CONCLUSIONS Higher potassium levels were associated with higher mortality risk in white and African-American MHD patients, whereas lower potassium levels were associated with higher death risk in Hispanics. Further studies are needed to determine the underlying mechanisms for the differential association between potassium and mortality across race/ethnicity.
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Affiliation(s)
- Taehee Kim
- Harold Simmons Center for Kidney Disease Research and Epidemiology, University of California Irvine, School of Medicine, Orange, CA, USA
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Kumar SA, Magnusson M, Ward LC, Paul NA, Brown L. A green algae mixture of Scenedesmus and Schroederiella attenuates obesity-linked metabolic syndrome in rats. Nutrients 2015; 7:2771-87. [PMID: 25875119 PMCID: PMC4425172 DOI: 10.3390/nu7042771] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/18/2015] [Accepted: 03/31/2015] [Indexed: 12/26/2022] Open
Abstract
This study investigated the responses to a green algae mixture of Scenedesmus dimorphus and Schroederiella apiculata (SC) containing protein (46.1% of dry algae), insoluble fibre (19.6% of dry algae), minerals (3.7% of dry algae) and omega-3 fatty acids (2.8% of dry algae) as a dietary intervention in a high carbohydrate, high fat diet-induced metabolic syndrome model in four groups of male Wistar rats. Two groups were fed with a corn starch diet containing 68% carbohydrates as polysaccharides, while the other two groups were fed a diet high in simple carbohydrates (fructose and sucrose in food, 25% fructose in drinking water, total 68%) and fats (saturated and trans fats from beef tallow, total 24%). High carbohydrate, high fat-fed rats showed visceral obesity with hypertension, insulin resistance, cardiovascular remodelling, and nonalcoholic fatty liver disease. SC supplementation (5% of food) lowered total body and abdominal fat mass, increased lean mass, and attenuated hypertension, impaired glucose and insulin tolerance, endothelial dysfunction, infiltration of inflammatory cells into heart and liver, fibrosis, increased cardiac stiffness, and nonalcoholic fatty liver disease in the high carbohydrate, high fat diet-fed rats. This study suggests that the insoluble fibre or protein in SC helps reverse diet-induced metabolic syndrome.
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Affiliation(s)
- Senthil Arun Kumar
- Centre for Systems Biology, University of Southern Queensland, Toowoomba 4350, Australia.
| | - Marie Magnusson
- MACRO-the Centre for Macroalgal Resources & Biotechnology, College of Marine and Environmental Sciences, James Cook University, Townsville 4811, Australia.
| | - Leigh C Ward
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane 4072, Australia.
| | - Nicholas A Paul
- MACRO-the Centre for Macroalgal Resources & Biotechnology, College of Marine and Environmental Sciences, James Cook University, Townsville 4811, Australia.
| | - Lindsay Brown
- School of Health and Wellbeing, University of Southern Queensland, Toowoomba 4350, Australia.
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Blanch N, Clifton PM, Keogh JB. A systematic review of vascular and endothelial function: effects of fruit, vegetable and potassium intake. Nutr Metab Cardiovasc Dis 2015; 25:253-266. [PMID: 25456155 DOI: 10.1016/j.numecd.2014.10.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 10/02/2014] [Accepted: 10/04/2014] [Indexed: 01/16/2023]
Abstract
AIM To review the relationships between: 1) Potassium and endothelial function; 2) Fruits and vegetables and endothelial function; 3) Potassium and other measures of vascular function; 4) Fruits and vegetables and other measures of vascular function. DATA SYNTHESIS An electronic search for intervention trials investigating the effect of potassium, fruits and vegetables on vascular function was performed in MEDLINE, EMBASE and the Cochrane Library. Potassium appears to improve endothelial function with a dose of >40 mmol/d, however the mechanisms for this effect remain unclear. Potassium may improve measures of vascular function however this effect may be dependent on the effect of potassium on blood pressure. The effect of fruit and vegetables on endothelial function independent of confounding variables is less clear. Increased fruit and vegetable intake may improve vascular function only in high risk populations. CONCLUSION Increasing dietary potassium appears to improve vascular function but the effect of increasing fruit and vegetable intake per se on vascular function is less clear.
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Affiliation(s)
- N Blanch
- School of Pharmacy and Medical Science, University of South Australia, Australia
| | - P M Clifton
- School of Pharmacy and Medical Science, University of South Australia, Australia
| | - J B Keogh
- School of Pharmacy and Medical Science, University of South Australia, Australia.
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Lennon-Edwards S, Ramick MG, Matthews EL, Brian MS, Farquhar WB, Edwards DG. Salt loading has a more deleterious effect on flow-mediated dilation in salt-resistant men than women. Nutr Metab Cardiovasc Dis 2014; 24:990-995. [PMID: 24989702 PMCID: PMC4195435 DOI: 10.1016/j.numecd.2014.05.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 04/15/2014] [Accepted: 05/05/2014] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND AIMS Dietary sodium loading has been shown to adversely impact endothelial function independently of blood pressure (BP). However, it is unknown whether dietary sodium loading impacts endothelial function differently in men as compared to women. The aim of this study was to test the hypothesis that endothelial-dependent dilation (EDD) would be lower in men as compared to women in response to a high sodium diet. METHODS AND RESULTS Thirty subjects (14F, 31±2y; 16M, 29±2y) underwent a randomized, crossover, controlled diet study consisting of 7 days of low sodium (LS; 20 mmol/day) and 7 days of high sodium (HS; 300-350 mmol/day). Salt-resistance was determined by a change in 24-hr mean arterial pressure (MAP) ≤ 5 mm Hg between HS and LS as assessed on day 7 of each diet. Blood and 24-hr urine were also collected and EDD was assessed by brachial artery flow-mediated dilation (FMD). By design, MAP was not different between LS and HS conditions and urinary sodium excretion increased on HS diet (P < 0.01). FMD did not differ between men and women on the LS diet (10.2 ± 0.65 vs. 10.7 ± 0.83; P > 0.05) and declined in both men and women on HS (P < 0.001). However, FMD was lower in men as compared to women on HS (5.7 ± 0.5 vs. 8.6 ± 0.86; P < 0.01). CONCLUSIONS HS reduced FMD in both men and women. In response to an HS diet, FMD was lower in men compared to women suggesting a greater sensitivity of the vasculature to high sodium in men.
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Affiliation(s)
- S Lennon-Edwards
- Department of Behavioral Health and Nutrition, University of Delaware, Newark, DE, USA; Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.
| | - M G Ramick
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
| | - E L Matthews
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
| | - M S Brian
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
| | - W B Farquhar
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA; Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - D G Edwards
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA; Department of Biological Sciences, University of Delaware, Newark, DE, USA
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Abstract
The distal nephron is composed of two main cell types: principal cells and intercalated cells. These cells have distinct morphologic features that allow them to be readily distinguished by light microscopy, as well as distinct suites of proteins that facilitate cell-specific transport properties. In this issue of the JCI, Gueutin and colleagues describe a new mechanism by which β-intercalated cells, via release of ATP and prostaglandin E2 (PGE2), influence the activity of transporters in principal cells.
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Gueutin V, Vallet M, Jayat M, Peti-Peterdi J, Cornière N, Leviel F, Sohet F, Wagner CA, Eladari D, Chambrey R. Renal β-intercalated cells maintain body fluid and electrolyte balance. J Clin Invest 2013; 123:4219-31. [PMID: 24051376 DOI: 10.1172/jci63492] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 06/28/2013] [Indexed: 12/11/2022] Open
Abstract
Inactivation of the B1 proton pump subunit (ATP6V1B1) in intercalated cells (ICs) leads to type I distal renal tubular acidosis (dRTA), a disease associated with salt- and potassium-losing nephropathy. Here we show that mice deficient in ATP6V1B1 (Atp6v1b1-/- mice) displayed renal loss of NaCl, K+, and water, causing hypovolemia, hypokalemia, and polyuria. We demonstrated that NaCl loss originated from the cortical collecting duct, where activity of both the epithelial sodium channel (ENaC) and the pendrin/Na(+)-driven chloride/bicarbonate exchanger (pendrin/NDCBE) transport system was impaired. ENaC was appropriately increased in the medullary collecting duct, suggesting a localized inhibition in the cortex. We detected high urinary prostaglandin E2 (PGE2) and ATP levels in Atp6v1b1-/- mice. Inhibition of PGE2 synthesis in vivo restored ENaC protein levels specifically in the cortex. It also normalized protein levels of the large conductance calcium-activated potassium channel and the water channel aquaporin 2, and improved polyuria and hypokalemia in mutant mice. Furthermore, pharmacological inactivation of the proton pump in β-ICs induced release of PGE2 through activation of calcium-coupled purinergic receptors. In the present study, we identified ATP-triggered PGE2 paracrine signaling originating from β-ICs as a mechanism in the development of the hydroelectrolytic imbalance associated with dRTA. Our data indicate that in addition to principal cells, ICs are also critical in maintaining sodium balance and, hence, normal vascular volume and blood pressure.
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Donfrancesco C, Ippolito R, Lo Noce C, Palmieri L, Iacone R, Russo O, Vanuzzo D, Galletti F, Galeone D, Giampaoli S, Strazzullo P. Excess dietary sodium and inadequate potassium intake in Italy: results of the MINISAL study. Nutr Metab Cardiovasc Dis 2013; 23:850-856. [PMID: 22835983 DOI: 10.1016/j.numecd.2012.04.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 04/18/2012] [Accepted: 04/18/2012] [Indexed: 12/25/2022]
Abstract
OBJECTIVE As excess sodium and inadequate potassium intake are causally related to hypertension and cardiovascular disease, the MINISAL-GIRCSI Program aimed to provide reliable estimates of dietary sodium and potassium intake in representative samples of the Italian population. DESIGN AND METHODS Random samples of adult population were collected from 12 Italian regions, including 1168 men and 1112 women aged 35-79 yrs. Electrolyte intake was estimated from 24 hour urine collections and creatinine was measured to estimate the accuracy of the collection. Anthropometric indices were measured with standardised procedures. RESULTS The average sodium excretion was 189 mmol (or 10.9 g of salt/day) among men and 147 mmol (or 8.5 g) among women (range 27-472 and 36-471 mmol, respectively). Ninety-seven % of men and 87% of women had a consumption higher than the WHO recommended target of 5g/day. The 24 h average potassium excretion was 63 and 55 mmol, respectively (range 17-171 and 20-126 mmol), 96% of men and 99% of women having an intake lower than 100 mmol/day (European and American guideline recommendation). The mean sodium/potassium ratio was 3.1 and 2.8 respectively, i.e. over threefold greater than the desirable level of 0.85. The highest sodium intake was observed in Southern regions. Sodium and potassium excretion were both progressively higher the higher the BMI (p < 0.0001). CONCLUSIONS These MINISAL preliminary results indicate that in all the Italian regions thus far surveyed dietary sodium intake was largely higher and potassium intake lower than the recommended intakes. They also highlight the critical association between overweight and excess salt intake.
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Affiliation(s)
- C Donfrancesco
- Cardiovascular Epidemiology Observatory, Istituto Superiore di Sanità, Rome, Italy.
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O’Neil CE, Nicklas TA, Rampersaud GC, Fulgoni III VL. 100% orange juice consumption is associated with better diet quality, improved nutrient adequacy, decreased risk for obesity, and improved biomarkers of health in adults: National Health and Nutrition Examination Survey, 2003-2006. Nutr J 2012; 11:107. [PMID: 23234248 PMCID: PMC3545988 DOI: 10.1186/1475-2891-11-107] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 11/30/2012] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Consumption of 100% orange juice (OJ) has been positively associated with nutrient adequacy and diet quality, with no increased risk of overweight/obesity in children; however, no one has examined these factors in adults. The purpose of this study was to examine the association of 100% OJ consumption with nutrient adequacy, diet quality, and risk factors for metabolic syndrome (MetS) in a nationally representative sample of adults. METHODS Data from adults 19+ years of age (n = 8,861) participating in the National Health and Nutrition Examination Survey 2003-2006 were used. The National Cancer Institute method was used to estimate the usual intake (UI) of 100% OJ consumption, selected nutrients, and food groups. Percentages of the population below the Estimated Average Requirement (EAR) or above the Adequate Intake (AI) were determined. Diet quality was measured by the Healthy Eating Index-2005 (HEI-2005). Covariate adjusted logistic regression was used to determine if consumers had a lower odds ratio of being overweight or obese or having risk factors of MetS or MetS. RESULTS Usual per capita intake of 100% OJ was 50.3 ml/d. Among consumers (n = 2,310; 23.8%), UI was 210.0 ml/d. Compared to non-consumers, consumers had a higher (p < 0.05) percentage (% ± SE) of the population meeting the EAR for vitamin A (39.7 ± 2.5 vs 54.0 ± 1.2), vitamin C (0.0 ± 0.0 vs 59.0 ± 1.4), folate (5.8 ± 0.7 vs 15.1 ± 0.9), and magnesium (51.6 ± 1.6 vs 63.7 ± 1.2). Consumers were also more likely to be above the AI for potassium (4.1 ± 0.8 vs 1.8 ± 0.2). HEI-2005 was significantly (p < 0.05) higher in consumers (55.0 ± 0.4 vs 49.7 ± 0.3). Consumers also had higher intakes of total fruit, fruit juice, whole fruit, and whole grain. Consumers had a lower (p < 0.05) mean body mass index (27.6 ± 0.2 vs 28.5 ± 0.1), total cholesterol levels (197.6 ± 1.2 vs 200.8 ± 0.75 mg/dL), and low density lipoprotein-cholesterol levels (112.5 ± 1.4 vs 116.7 ± 0.93 mg/dL). Finally, compared to non-consumers of 100% OJ, consumers were 21% less likely to be obese and male consumers were 36% less likely to have MetS. CONCLUSION The results suggest that moderate consumption of 100% OJ should be encouraged to help individuals meet the USDA daily recommendation for fruit intake and as a component of a healthy diet.
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Affiliation(s)
- Carol E O’Neil
- Louisiana State University Agricultural Center, 261 Knapp Hall, Baton Rouge, Louisiana, 70803, USA
| | - Theresa A Nicklas
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, 77030, USA
| | - Gail C Rampersaud
- Food Science and Human Nutrition Department, University of Florida, Gainesville, Florida, 32611, USA
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Rechkalov AV, Gorshkova NE. [Biochemical indicators of blood at sportsmen at joint application of muscular and food loading]. Fiziol Cheloveka 2011; 37:65-71. [PMID: 21950088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The results of a blood biochemical testing among highly skilled sportsmen, coaching under different power conditions accompanied by veloergometer dosed stress and a trial carbohydrate breakfast are considered in the research. The quantity of glucose, crude protein, albumines, calcium, magnesium, potassium, chlorine and sodium were difined in the blood serum. Essential differences in the indices of glucose, magnesium, sodium, chlorine among skilled and non-skilled sportsmen were taped. The results got testify about the presence of expressed alterations in a power and water-salt interacting at trainings under different power conditions.
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Phakdeekitcharoen B, Kittikanokrat W, Kijkunasathian C, Chatsudthipong V. Aldosterone increases Na+ -K+ -ATPase activity in skeletal muscle of patients with Conn's syndrome. Clin Endocrinol (Oxf) 2011; 74:152-9. [PMID: 21044117 DOI: 10.1111/j.1365-2265.2010.03912.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE In Conn's syndrome, hypokalaemia normally results from renal potassium loss because of the effect of excess aldosterone on Na(+) -K(+) -ATPase in principal cells. Little is known about the effect of aldosterone on cellular potassium redistribution in skeletal muscle. Our study determined the effect of aldosterone on muscle Na(+) -K(+) -ATPase. DESIGN Muscle biopsies were taken from six patients immediately before and 1 month after adrenalectomy. Ten age-matched subjects with normal levels of circulating aldosterone served as controls. RESULTS Average plasma aldosterone was significantly higher in presurgery (235·0 ± 51·1 pg/ml) than postsurgery (64·5 ± 25·1 pg/ml) patients. Similarly, Na(+) -K(+) -ATPase activity, relative mRNA expression of α(2) (not α(1) or α(3) ) and β(1) (not β(2) or β(3) ), and protein abundance of α(2) and β(1) subunits were greater in pre- than postsurgery samples (128·7 ± 12·3 vs 79·4 ± 13·3 nmol·mg/protein/h, 2·45 ± 0·31 vs 1·04 ± 0·17, 1·92 ± 0·22 vs1·02 ± 0·14, 2·17 ± 0·33 vs 0·98 ± 0·09 and 1·70 ± 0·17 vs 0·90 ± 0·17, respectively, all P<0·05). The activity and mRNA expression of the α(2) and β(1) subunits correlated well with plasma aldosterone levels (r = 0·71, r = 0·75 and r = 0·78, respectively, all P < 0·01). CONCLUSIONS Our study provides the first evidence in human skeletal muscle that increased plasma aldosterone leads to increased Na(+) -K(+) -ATPase activity via increases in α(2) and β(1) subunit mRNAs and their protein expressions. The increased activity may contribute in part to the induction of hypokalaemia in patients with Conn's syndrome.
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Affiliation(s)
- Bunyong Phakdeekitcharoen
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Bangkok, Thailand.
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16
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High sodium-to-potassium ratio increases cardiac event risk. Study underscore the importance of balanced mineral intake. Heart Advis 2009; 12:5. [PMID: 20383901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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17
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Potassium and sodium out of balance. Too little potassium and too much sodium is bad for the heart and general health. Harv Heart Lett 2009; 19:4-5. [PMID: 19681200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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18
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Kalhoff H, Manz F, Kiwull P, Kiwull-Schöne H. Food mineral composition and acid-base balance in preterm infants. Eur J Nutr 2007; 46:188-95. [PMID: 17479211 DOI: 10.1007/s00394-007-0646-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 01/23/2007] [Indexed: 11/25/2022]
Abstract
BACKGROUND Due to a transient age-related low renal capacity for net acid excretion, preterm infants fed formula are at a considerable risk of spontaneously developing incipient late metabolic acidosis, clinically characterized by e.g., disturbed bone mineralization and impaired growth. AIM OF THE STUDY From acid-base data in blood and urine under different diets of modified human milk or preterm formulas is attempted to explore the impact of food mineral (and protein) composition on renal regulation and systemic acid-base balance in preterm infants. PATIENTS AND METHODS Data were collected from 48 infants fed their own mother's milk (28 native human milk, 20 enriched with fortifier) and 34 patients on formula (23 on a standard batch, 11 on a modified batch with reduced acid load). Intake of food was measured and acid-base data were determined in blood and timed-urine (8-12 h) samples. RESULTS Differences in mineral composition of the diets led to considerable differences of daily "alkali-intake", without significant effects on non-respiratory (base excess, BE) and respiratory (PCO(2)) acid-base data in the blood. In contrast, a highly significant proportionality between individual dietary alkali intake and daily renal base (Na(+) + K(+)-Cl(-)) excretion was observed (y = 0.32x-0.70, n = 80, r = 0.77, P < 0.0001), irrespective of the type of the diet. CONCLUSION Renal base saving mechanisms are normally effective in preterm infants to compensate for differences in dietary acid-base load. Generally, nutritional acid-base challenges can be judged much earlier and more safely by urinary than by blood acid-base analysis. Taking into account the age specific low capacity for renal NAE, the relatively high nutritional acid load of preterm standard formula should be reduced.
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MESH Headings
- Acid-Base Equilibrium
- Body Weight/physiology
- Calcium, Dietary/administration & dosage
- Calcium, Dietary/blood
- Calcium, Dietary/urine
- Chlorides/administration & dosage
- Chlorides/blood
- Chlorides/urine
- Diet/methods
- Dietary Supplements
- Energy Intake/physiology
- Food, Fortified
- Humans
- Infant Formula/chemistry
- Infant Formula/metabolism
- Infant Nutritional Physiological Phenomena
- Infant, Low Birth Weight
- Infant, Newborn
- Infant, Premature
- Kidney/metabolism
- Magnesium/administration & dosage
- Magnesium/blood
- Magnesium/urine
- Milk Proteins/administration & dosage
- Milk Proteins/blood
- Milk Proteins/urine
- Milk, Human/chemistry
- Milk, Human/metabolism
- Minerals/administration & dosage
- Minerals/blood
- Minerals/urine
- Phosphorus, Dietary/administration & dosage
- Phosphorus, Dietary/blood
- Phosphorus, Dietary/urine
- Potassium, Dietary/administration & dosage
- Potassium, Dietary/blood
- Potassium, Dietary/urine
- Sodium, Dietary/administration & dosage
- Sodium, Dietary/blood
- Sodium, Dietary/urine
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19
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Hess TM, Kronfeld DS, Williams CA, Waldron JN, Graham-Thiers PM, Greiwe-Crandell K, Lopes MA, Harris PA. Effects of oral potassium supplementation on acid-base status and plasma ion concentrations of horses during endurance exercise. Am J Vet Res 2005; 66:466-73. [PMID: 15822592 DOI: 10.2460/ajvr.2005.66.466] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To compare effects of oral supplementation with an experimental potassium-free sodium-abundant electrolyte mixture (EM-K) with that of oral supplementation with commercial potassium-rich mixtures (EM+K) on acid-base status and plasma ion concentrations in horses during an 80-km endurance ride. ANIMALS 46 healthy horses. PROCEDURE Blood samples were collected before the ride; at 21-, 37-, 56-, and 80-km inspection points; and during recovery (ie, 30-minute period after the ride). Consumed electrolytes were recorded. Blood was analyzed for pH, PvCO2, and Hct, and plasma was analyzed for Na+, K+, Cl-, Ca2+, Mg2+, lactate, albumin, phosphate, and total protein concentrations. Plasma concentrations of H+ and HCO3-, the strong ion difference (SID), and osmolarity were calculated. RESULTS 34 (17 EM-K and 17 EM+K treated) horses finished the ride. Potassium intake was 33 g less and Na+ intake was 36 g greater for EM-K-treated horses, compared with EM+K-treated horses. With increasing distance, plasma osmolarity; H+, Na+, K+, Mg2+, phosphate, lactate, total protein, and albumin concentrations; and PvCO2 and Hct were increased in all horses. Plasma HCO3-, Ca2+, and Cl- concentrations were decreased. Plasma H+ concentration was significantly lower in EM-K-treated horses, compared with EM+K-treated horses. Plasma K+ concentrations at the 80-km inspection point and during recovery were significantly less in EM-K-treated horses, compared with EM+K-treated horses. CONCLUSIONS AND CLINICAL RELEVANCE Increases in plasma H+ and K+ concentrations in this endurance ride were moderate and unlikely to contribute to signs of muscle fatigue and hyperexcitability in horses.
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Affiliation(s)
- Tanja M Hess
- Department of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
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20
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Michea L, Vukusich A, González M, Zehnder C, Marusic ET. Effect of spironolactone on K(+) homeostasis and ENaC expression in lymphocytes from chronic hemodialysis patients. Kidney Int 2005; 66:1647-53. [PMID: 15458462 DOI: 10.1111/j.1523-1755.2004.00931.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Cardiac disease is the major cause of death in hemodialysis patients (HD). It is now clear that aldosterone has deleterious effects in the cardiovascular system. In the present study, we evaluated the effects of an aldosterone-antagonist, spironolactone, on the extrarenal regulation of potassium in HD patients. Furthermore, to validate the effectiveness of the spironolactone dose-design, we measured the expression of Na(+)-channel (ENaC alpha subunit) in peripheral blood mononuclear cells (PBMC), before and after a two-week course of spironolactone. METHODS The study design included a two-week baseline period, followed by spironolactone treatment (50 mg three times weekly for 15 days), and by a two-week washout period and then a two-week placebo period. An oral K(+) load (0.3 mEq/K(+) kg body weight plus carbohydrates) was administered at the end of each period, and time-course of plasma potassium was evaluated. ENaC expression in PBMC was assessed before and after spironolactone. RESULTS The maximal increase in plasma potassium after the K(+) carbohydrate load was: control 5.33 +/- 0.88 mEq K(+)/L; spironolactone 5.23 +/- 0.68 mEq K(+)/L; placebo 5.38 +/- 0.61 mEq K(+)/L (N= 9). No patients developed hyperkalemia during the spironolactone treatment period. ENaC expression was significantly higher in all six HD patients studied, compared to control subjects (P < 0.05). Treatment with spironolactone in HD patients reduced alpha subunit mRNA expression to values similar to those of normal subjects. CONCLUSION Spironolactone may be considered for the treatment of selected chronic HD patients. The effect of the drug on a known target of aldosterone, the ENaC, demonstrates the effectiveness of the drug to block aldosterone effects in nonepithelial tissues.
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Affiliation(s)
- Luis Michea
- Department of Medicine, Faculty of Medicine, Universidad Los Andes, Santiago, Chile.
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21
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Abstract
BACKGROUND Numerous studies have found that low potassium intake and low serum potassium are associated with increased stroke mortality, but data regarding stroke incidence have been limited. Serum potassium levels, dietary potassium intake, and diuretic use in relation to risk for stroke in a prospectively studied cohort were investigated. METHODS The study comprised 5,600 men and women older than 65 years who were free of stroke at enrollment. Baseline data included serum potassium level, dietary potassium intake, and diuretic use. Participants were followed for 4 to 8 years, and the incidence and types of strokes were recorded. Low serum potassium was defined as less than 4.1 mEq/L, and low potassium intake as less than 2.4 g/d. RESULTS Among diuretic users, there was an increased risk for stroke associated with lower serum potassium (relative risk [RR]: 2.5, p < 0.0001). Among individuals not taking diuretics, there was an increased risk for stroke associated with low dietary potassium intake (RR: 1.5, p < 0.005). The small number of diuretic users with lower serum potassium and atrial fibrillation had a 10-fold greater risk for stroke compared with those with higher serum potassium and normal sinus rhythm. CONCLUSIONS A lower serum potassium level in diuretic users, and low potassium intake in those not taking diuretics were associated with increased stroke incidence among older individuals. Lower serum potassium was associated with a particularly high risk for stroke in the small number of diuretic users with atrial fibrillation. Further study is required to determine if modification of these factors would prevent strokes.
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Affiliation(s)
- D M Green
- Neuroscience Institute, The Queen's Medical Center, 1301 Punchbowl Street, Honolulu, HI 96813, USA.
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22
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Suga SI, Phillips MI, Ray PE, Raleigh JA, Vio CP, Kim YG, Mazzali M, Gordon KL, Hughes J, Johnson RJ. Hypokalemia induces renal injury and alterations in vasoactive mediators that favor salt sensitivity. Am J Physiol Renal Physiol 2001; 281:F620-9. [PMID: 11553508 DOI: 10.1152/ajprenal.2001.281.4.f620] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the hypothesis that hypokalemia might induce renal injury via a mechanism that involves subtle renal injury and alterations in local vasoactive mediators that would favor sodium retention. To test this hypothesis, we conducted studies in rats with diet-induced K+ deficiency. We also determined whether rats with hypokalemic nephropathy show salt sensitivity. Twelve weeks of hypokalemia resulted in a decrease in creatinine clearance, tubulointerstitial injury with macrophage infiltration, interstitial collagen type III deposition, and an increase in osteopontin expression (a tubular marker of injury). The renal injury was greatest in the outer medulla with radiation into the cortex, suggestive of an ischemic etiology. Consistent with this hypothesis, we found an increased uptake of a hypoxia marker, pimonidazole, in the cortex. The intrarenal injury was associated with increased cortical angiontensin-converting enzyme (ACE) expression and continued cortical angiotensin II generation despite systemic suppression of the renin-angiotensin system, an increase in renal endothelin-1, a decrease in renal kallikrein, and a decrease in urinary nitrite/nitrates and prostaglandin E(2) excretion. At 12 wk, hypokalemic rats were placed on a normal-K+ diet with either high (4%)- or low (0.01%)-NaCl content. Despite correction of hypokalemia and normalization of renal function, previously hypokalemic rats showed an elevated blood pressure in response to a high-salt diet compared with normokalemic controls. Hypokalemia is associated with alterations in vasoactive mediators that favor intrarenal vasoconstriction and an ischemic pattern of renal injury. These alterations may predispose the animals to salt-sensitive hypertension that manifests despite normalization of the serum K+.
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Affiliation(s)
- S I Suga
- Division of Nephrology, University of Washington Medical Center, Seattle, WA 98195, USA
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23
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Abstract
The renal concentrating defect typical for chronic K depletion has been ascribed to malfunction of renomedullary cells caused by inadequate accumulation of organic osmolytes. A reduction in intracellular ionic strength, which is believed to influence decisively the accumulation of organic osmolytes, has been held responsible for insufficient osmolyte accumulation. To test this hypothesis, intra- and extracellular Na, Cl and K concentrations, the major determinants of ionic strength, were measured in the papilla by electron microprobe analysis and organic osmolytes (glycerophosphorylcholine, betaine, sorbitol, myo-inositol, free amino acids) in inner-medullary tissue by HPLC in antidiuretic rats kept on either a control (normal-K) or a K-deplete (low-K) diet and in euhydrated rats with free access to water and control diet. K depletion was associated with a reduced urine concentrating ability. Papillary interstitial ionic strength (sum of Na, Cl and K) in antidiuretic low-K rats was significantly reduced compared with antidiuretic normal-K rats (688+/-19 vs. 971+/-61 mmol/kg wet wt) but was similar to that in euhydrated normal-K rats (643+/-35 mmol/kg wet wt). The lower interstitial ionic strength in antidiuretic low-K and euhydrated normal-K rats was associated with a lower total content of organic osmolytes in the inner medulla (365+/-14 and 381+/-20, respectively, vs. 465+/-11 mmol/kg protein in antidiuretic normal-K rats). Intracellular ionic strength (sum of Na, Cl and K) of papillary collecting duct cells, however, was similar in antidiuretic normal-K and euhydrated normal-K rats (171+/-5 and 179+/-11 mmol/kg wet wt) but lower in antidiuretic low-K rats (138+/-9 mmol/kg wet wt). These results do not support the view that, in the steady state of osmotic adaptation of renomedullary cells in situ, intracellular ionic strength is the decisive factor for maintaining high levels of organic osmolytes. During chronic K depletion, reduced osmolyte accumulation by renomedullary cells may be the consequence, rather than the cause, of lower medullary interstitial tonicity.
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MESH Headings
- Amino Acids/analysis
- Animals
- Betaine/analysis
- Chlorides/analysis
- Chlorides/blood
- Chlorides/urine
- Chromatography, High Pressure Liquid
- Electrolytes/analysis
- Electrolytes/blood
- Electrolytes/urine
- Electron Probe Microanalysis
- Glycerylphosphorylcholine/analysis
- Inositol/analysis
- Kidney Concentrating Ability/physiology
- Kidney Medulla/chemistry
- Kidney Medulla/physiology
- Kidney Tubules, Collecting/chemistry
- Kidney Tubules, Collecting/metabolism
- Male
- Potassium, Dietary/analysis
- Potassium, Dietary/blood
- Potassium, Dietary/urine
- Rats
- Rats, Wistar
- Sodium, Dietary/analysis
- Sodium, Dietary/blood
- Sodium, Dietary/urine
- Sorbitol/analysis
- Urea/analysis
- Urea/metabolism
- Water-Electrolyte Balance/physiology
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Affiliation(s)
- F X Beck
- Physiologisches Institut der Universität München, Munich, Germany.
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24
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Abstract
UNLABELLED NH4+ secretion in inner medullary collecting duct in potassium deprivation: Role of colonic H+-K+-ATPase. BACKGROUND In K+ deprivation (KD), gastric (g) H+-K+-ATPase (HKA) is suppressed, whereas colonic (c) HKA is induced in the terminal inner medullary collecting duct (IMCD). We hypothesized that in KD, cHKA is induced and can mediate the secretion of NH4+. METHODS Rats were sacrificed after 2, 3, 6, or 14 days on regular (NML) or K+-free (KD) diet. mRNA expression of HKA isoforms in terminal inner medulla was examined and correlated with NH4+ secretion in perfused IMCD in vitro. RESULTS Urinary NH4+ excretion increased after K+-free diet for six days. In terminal inner medulla, cHKA expression was strongly induced, whereas gHKA expression was decreased. NH4+ secretion increased by 62% in KD (JtNH4+ 0.57 vs. 0.92 pmol/min/mm tubule length, P < 0.001). Ouabain (1 mM) in perfusate inhibited NH4+ secretion in KD by 45% (P < 0.002) but not in NML. At luminal pH 7.7, which inhibits NH3 diffusion, NH4+ secretion in IMCD was 140% higher in KD (0.36 vs. 0.15, P < 0.03) and was sensitive to ouabain. ROMK-1 mRNA expression was induced in parallel with cHKA in inner medulla. CONCLUSIONS These data suggest that in KD, cHKA replaces gHKA and mediates enhanced secretion of NH4+ (and H+) into the lumen facilitated by K+ recycling through ROMK-1.
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MESH Headings
- Acid-Base Equilibrium/physiology
- Acidosis, Renal Tubular/metabolism
- Animals
- Blotting, Northern
- Colon/enzymology
- Gene Expression Regulation, Enzymologic
- H(+)-K(+)-Exchanging ATPase/genetics
- H(+)-K(+)-Exchanging ATPase/metabolism
- Hypokalemia/metabolism
- Kidney Medulla/chemistry
- Kidney Medulla/enzymology
- Kidney Medulla/metabolism
- Kidney Tubules, Collecting/chemistry
- Kidney Tubules, Collecting/enzymology
- Kidney Tubules, Collecting/metabolism
- Kidney Tubules, Proximal/metabolism
- Male
- Potassium Channels/genetics
- Potassium Channels/metabolism
- Potassium Channels, Inwardly Rectifying
- Potassium, Dietary/blood
- Potassium, Dietary/pharmacology
- Quaternary Ammonium Compounds/urine
- RNA, Messenger/analysis
- Rats
- Rats, Sprague-Dawley
- Sodium/metabolism
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25
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Abstract
The effect of a low Na+, high K+ diet on Na+,K(+)-ATPase levels in cochlear lateral wall tissues was investigated in laboratory rats by using an enzyme-linked immunosorbent assay. The low Na+, high K+ diet induced high aldosterone plasma levels in the animals as well as changes in plasma cation levels. Animals that received a low Na+, high K+ diet demonstrated a statistically significant (97%) increase in Na+,K(+)-ATPase levels in the stria vascularis when compared to animals that received a control diet. This increase in strial Na+,K(+)-ATPase levels was blocked only 70% by administration of the aldosterone antagonist, spironolactone. Findings therefore indicate that strial Na+,K(+)-ATPase may be modulated by both aldosterone and Na+,K+ plasma levels. Na+,K(+)-ATPase levels in the spiral ligament were not affected by the experimental treatment. These findings suggest that spiral ligament Na+,K(+)-ATPase levels may be regulated by factors other than aldosterone and Na+,K+ plasma levels. This study provides further insight into the mechanisms of the beneficial effects of salt restriction and potassium loading in patients with Méniére's disease.
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Affiliation(s)
- W J ten Cate
- Department of Anatomy, College of Medicine, University of Florida, Gainesville 32610
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