Home blood pressure measurement days and changes in urinary sodium-to-potassium ratio, estimated salt and potassium intakes and blood pressure: 1-year prospective study.

OBJECTIVE: Current international guidelines recommend home blood pressure (BP) measurement and low sodium and high potassium intakes for the management of hypertension. We hypothesized that increased home BP measurement may result in more effective management of sodium and potassium intakes and BP. METHODS: We examined associations of home BP measurement days with changes in the urinary sodium-to-potassium (Na/K) ratio, estimated salt and potassium intakes and BP. We included 209 healthy participants (mean age, 55.9 years; 56.5% women) from a prospective cohort study. We examined 1-year data on self-measured home BP and spot urine samples. RESULTS: Median (interquartile range) days of home BP measurement was 324 (225-358) over 1-year. Baseline mean (SD) Na/K ratio, salt and potassium intakes, morning and evening SBP, and morning and evening DBP were 3.8 (2.3), 8.5 (1.9) g/day, 1833.5 (416.5) mg/day, 120.4 (14.0) mmHg, 118.2 (14.2) mmHg, 79.2 (10.1) mmHg, and 76.2 (10.1) mmHg, respectively. In multivariable-adjusted linear regression , ß (standard error) per 10 days increase in number of home BP measurement were -0.031 (0.017) for Na/K ratio, -0.036 (0.015) for salt intake, -1.357 (2.797) for potassium intake, -0.178 (0.064) for morning SBP, -0.079 (0.041) for morning DBP, -0.109 (0.067) for evening SBP and -0.099 (0.045) for evening DBP. Additionally, relationships persisted for men and women, but changes in salt intake were more pronounced among participants taking antihypertensive medication (interaction P = 0.002). CONCLUSION: Continuous measurement of home BP may lead not only to self-monitoring of BP, but also to declines in salt intakes and some BP indices.

Associations between dietary potassium intake and urinary potassium excretion: a protocol for systematic review and meta-analysis.

BACKGROUND: While numerous studies have reported associations between low dietary potassium intake and adverse clinical outcomes, methods to estimate potassium intake, mainly self-reported dietary measures and urinary potassium excretion, entail certain limitations. Self-reported measures are subject to underreporting and overreporting. Urinary potassium excretion is affected by multiple factors including renal function. Revealing the degree of bias inherent in these measures would help accurately assess potassium intake and its association with disease risk. We aim to summarize evidence on the strength of the associations between potassium intake estimated from 24-h urinary potassium excretion and potassium intake estimated from self-reported dietary measures or objective quantification methods in populations with different kidney function levels and age groups. We also aim to identify factors that affect the association strength. METHODS: We will search for potentially eligible studies that examined associations between self-reported potassium intake, 24-h urinary potassium excretion, and objectively quantified potassium intake, using MEDLINE (PubMed), Embase, Web of Science, and Scopus. Studies on children, adolescents, adults, and the elderly are eligible. Studies of patients on dialysis will be excluded. Collective study results, including a meta-analysis, will be synthesized if an adequate number of studies examining similar dietary potassium intake estimation methods are found. Analyses will be performed separately according to age groups and renal function. For the meta-analysis, fixed-effects or random-effect models will be employed depending on the degree of study heterogeneity to combine across studies the correlation coefficient, ratio, or standardized mean difference for potassium intake, comparing dietary potassium intake based on self-reported or objectively quantified methods and intake based on 24-h urinary potassium excretion. The degree of heterogeneity among included studies will be examined by calculating I2 statistics. To investigate sources of study heterogeneity, random-effects meta-regression analyses will be performed. DISCUSSION: Revealing the strength of the association between dietary and urinary measures in populations with different levels of kidney function and age groups will enhance researchers' and clinicians' ability to interpret studies that utilize these measures and help establish a more solid evidence base for the role of potassium intake in changing chronic disease risk. Identifying factors that modify the associations between these measures may aid in developing predictive models to estimate actual potassium intake. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022357847.

24-h urinary sodium and potassium excretions, plasma metabolomic profiles, and cardiometabolic biomarkers in the United States adults: a cross-sectional study.

BACKGROUND: High-sodium and low-potassium intakes are associated with a higher risk of hypertension and cardiovascular disease, but there are limited data on the circulating metabolomics profiles of 24-h urinary sodium and potassium excretions in free-living individuals. OBJECTIVES: We aimed to characterize the metabolomics signatures of a high-sodium and low-potassium diet in a cross-sectional study. METHODS: In 1028 healthy older adults from the Women's and Men's Lifestyle Validation Studies, we investigated the association of habitual sodium and potassium intakes measured by 2 to 4 24-h urine samples with plasma metabolites (quantified using liquid chromatography-tandem mass spectrometry) and metabolomic pathways. Our primary exposures were energy-adjusted 24-h urinary sodium excretion, potassium excretion, and sodium-to-potassium ratio, calculated based on energy expenditure derived from the doubly labeled water method. We then assessed the partial correlations of their metabolomics scores, derived from elastic net regressions, with cardiometabolic biomarkers. RESULTS: Higher sodium excretion was associated with 38 metabolites including higher piperine, phosphatidylethanolamine, and C5:1 carnitine. In pathway analysis, higher sodium excretion was associated with enhanced biotin and propanoate metabolism and enhanced degradation of lysine and branched-chain amino acids (BCAAs). Metabolites associated with higher potassium and lower sodium-to-potassium ratio included quinic acid and proline-betaine. After adjusting for confounding factors, the metabolomics score for sodium-to-potassium ratio positively correlated with fasting insulin (Spearman's rank correlation coefficient ρ = 0.27), C-peptide (ρ = 0.30), and triglyceride (ρ = 0.46), and negatively with adiponectin (ρ = -0.40), and high-density lipoprotein cholesterol (ρ = -0.42). CONCLUSIONS: We discovered metabolites and metabolomics pathways associated with a high-sodium diet, including metabolites related to biotin, propanoate, lysine, and BCAA pathways. The metabolomics signature for a higher sodium low-potassium diet is associated with multiple components of elevated cardiometabolic risk.

Impaired distal renal potassium handling in streptozotocin-induced diabetic mice.

Diabetes is closely associated with K+ disturbances during disease progression and treatment. However, it remains unclear whether K+ imbalance occurs in diabetes with normal kidney function. In this study, we examined the effects of dietary K+ intake on systemic K+ balance and renal K+ handling in streptozotocin (STZ)-induced diabetic mice. The control and STZ mice were fed low or high K+ diet for 7 days to investigate the role of dietary K+ intake in renal K+ excretion and K+ homeostasis and to explore the underlying mechanism by evaluating K+ secretion-related transport proteins in distal nephrons. K+-deficient diet caused excessive urinary K+ loss, decreased daily K+ balance, and led to severe hypokalemia in STZ mice compared with control mice. In contrast, STZ mice showed an increased daily K+ balance and elevated plasma K+ level under K+-loading conditions. Dysregulation of the NaCl cotransporter (NCC), epithelial Na+ channel (ENaC), and renal outer medullary K+ channel (ROMK) was observed in diabetic mice fed either low or high K+ diet. Moreover, amiloride treatment reduced urinary K+ excretion and corrected hypokalemia in K+-restricted STZ mice. On the other hand, inhibition of SGLT2 by dapagliflozin promoted urinary K+ excretion and normalized plasma K+ levels in K+-supplemented STZ mice, at least partly by increasing ENaC activity. We conclude that STZ mice exhibited abnormal K+ balance and impaired renal K+ handling under either low or high K+ diet, which could be primarily attributed to the dysfunction of ENaC-dependent renal K+ excretion pathway, despite the possible role of NCC.NEW & NOTEWORTHY Neither low dietary K+ intake nor high dietary K+ intake effectively modulates renal K+ excretion and K+ homeostasis in STZ mice, which is closely related to the abnormality of ENaC expression and activity. SGLT2 inhibitor increases urinary K+ excretion and reduces plasma K+ level in STZ mice under high dietary K+ intake, an effect that may be partly due to the upregulation of ENaC activity.

Analysis of urinary potassium isotopes and association with pancreatic health: healthy, diabetic and cancerous states.

Background: More than 700 million people worldwide suffer from diseases of the pancreas, such as diabetes, pancreatitis and pancreatic cancer. Often dysregulation of potassium (K+) channels, co-transporters and pumps can promote development and progression of many types of these diseases. The role of K+ transport system in pancreatic cell homeostasis and disease development remains largely unexplored. Potassium isotope analysis (δ41K), however, might have the potential to detect minute changes in metabolic processes relevant for pancreatic diseases. Methods: We assessed urinary K isotope composition in a case-control study by measuring K concentrations and δ41K in spot urines collected from patients diagnosed with pancreatic cancer (n=18), other pancreas-related diseases (n=14) and compared those data to healthy controls (n=16). Results: Our results show that urinary K+ levels for patients with diseased pancreas (benign and pancreatic cancer) are significantly lower than the healthy controls. For δ41K, the values tend to be higher for individuals with pancreatic cancer (mean δ41K = -0.58 ± 0.33‰) than for healthy individuals (mean δ41K = -0.78 ± 0.19‰) but the difference is not significant (p=0.08). For diabetics, urinary K+ levels are significantly lower (p=0.03) and δ41K is significantly higher (p=0.009) than for the healthy controls. These results suggest that urinary K+ levels and K isotopes can help identify K disturbances related to diabetes, an associated factors of all-cause mortality for diabetics. Conclusion: Although the K isotope results should be considered exploratory and hypothesis-generating and future studies should focus on larger sample size and δ41K analysis of other K-disrupting diseases (e.g., chronic kidney disease), our data hold great promise for K isotopes as disease marker.

Effects of salt intake reduction by urinary sodium to potassium ratio self-monitoring method.

Effective and feasible educational methods are needed to control salt intake. We performed a single-center, non-randomized controlled study to investigate the effectiveness and feasibility of self-monitoring using a urinary sodium/potassium (Na/K) ratio-measuring device in patients with difficulty in reducing salt intake. This study included 160 patients with hypertension, chronic kidney disease, or heart disease who were followed up in the outpatient clinic of the Dokkyo Medical University Nikko Medical Center. Urinary Na/K ratio measuring Na/K ratio meter were loaned for 2-6 weeks to the treatment (T) group (n = 80) and not to the patients in the control (C) group (n = 80). In the T group, patients were instructed to measure the urinary Na/K ratio at least three times a day and maintain a Na/K ratio below 2.0. Salt reduction education and home blood pressure measurement guidance continued in both groups. The mean device loan period in the T group was 25.1 days, the mean number of measurements was 3.0 times/day, and the proportion of patients achieving three measurements per day was 48.8% (39/80). Self-monitoring using the urinary Na/K ratio meter successfully reduced salt intake by -1.9 g/day at the second visit (p < 0.001) in the T group. In contrast, no change was observed over time in the C group. Self-monitoring using the urinary Na/K ratio meter successfully reduced salt intake in patients with difficulty reducing salt intake.

24-Hour Urinary Chemistries and Kidney Stone Risk.

RATIONALE & OBJECTIVE: Most previous studies of the relationship between urinary factors and kidney stone risk have either assumed a linear effect of urinary parameters on kidney stone risk or implemented arbitrary thresholds suggesting biologically implausible "all-or-nothing" effects. In addition, little is known about the hierarchy of effects of urinary factors on kidney stone risk. This study evaluated the independent associations between urine chemistries and kidney stone formation and examined their magnitude and shape. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: We analyzed 9,045 24-hour urine collections from 6,217 participants of the Health Professionals Follow-Up Study and Nurses' Health Studies I and II. EXPOSURE: Urine volume and pH, and concentrations of calcium, citrate, oxalate, potassium, magnesium, uric acid, phosphorus, and sodium. OUTCOME: Incident symptomatic kidney stones. ANALYTICAL APPROACH: Multivariable logistic regression analysis incorporating restricted cubic splines to explore potentially nonlinear relationships between urinary factors and the risk of forming a kidney stone. Optimal inflection point analysis was implemented for each factor, and dominance analysis was performed to establish the relative importance of each urinary factor. RESULTS: Each urinary factor was significantly associated with stone formation except for urine pH. Higher urinary levels of calcium, oxalate, phosphorus, and sodium were associated with a higher risk of stone formation whereas higher urine volume, uric acid, citrate, potassium, and magnesium were associated with a lower risk. The relationships were substantially linear for urine calcium, uric acid, and sodium. By contrast, the magnitudes of the relationships were modestly attenuated at levels above the inflection points for urine oxalate, citrate, volume, phosphorus, potassium, and magnesium. Dominance analysis identified 3 categories of factors' relative importance: higher (calcium, volume, and citrate), intermediate (oxalate, potassium, and magnesium), and lower (uric acid, phosphorus, and sodium). LIMITATIONS: Predominantly White participants, lack of information on stone composition. CONCLUSIONS: Urine chemistries have complex relationships and differential relative associations with the risk of kidney stone formation. PLAIN-LANGUAGE SUMMARY: Kidney stones are common and likely to recur. Certain urinary factors play a role in the development of stones, but their independent roles, relative importance, and shapes of association with stone formation are not well-characterized. We analyzed 24-hour urine collections from individuals with and without kidney stones. Stones were less likely in those with higher urine volume, citrate, potassium, magnesium, and uric acid and were more likely in those with higher calcium, oxalate, phosphorus, and sodium. The acidity of the urine was not related to stones. The urinary parameters showed different degrees of relative importance, with calcium, volume, and citrate being greatest. All parameters exhibited a linear or close-to-linear shape of association with stone formation.

Development and preliminary validation of a prediction formula of sodium and sodium-to-potassium ratio based on multiple regression using 24-h urines.

Accurate measurement of sodium intake in the diet is challenging, and epidemiological studies can be hampered by the attenuation of associations due to measurement error in sodium intake. A prediction formula for habitual 24-h urine sodium excretion and sodium-to-potassium ratio might lead to more reliable conclusions. Five 24-h urinary samples and two Food Frequency Questionnaires (FFQs) were conducted among 244 Japanese participants aged 35-80 years. We conducted multivariate linear regression analysis with urinary excretion as dependent variables and eating behaviour and food frequency as independent variables. Empirical weights of sodium excretion and sodium-to-potassium ratio were extracted. Preliminary validity was also assessed by randomly dividing the subjects into development and validation groups based on the correlation coefficient between estimates by the prediction formula and urinary excretion. Taste preference, soy sauce use at the table, frequency of pickled vegetables intake and number of bowls of miso soup were extracted as determinants of sodium excretion. Correlation coefficients between the estimates and urinary excretion for men and women were 0.42 and 0.43, respectively, for sodium and 0.49 and 0.50, respectively, for sodium-to-potassium ratio. This prediction formula may provide more accurate estimation of sodium intake and sodium-to-potassium ratio than the food composition approach.

No change in 24-h sodium intake estimated from spot urine in Norwegian adults from 2006 to 2019: the population-based Trøndelag Health Study (HUNT).

OBJECTIVE: Monitoring time trends in salt consumption is important for evaluating the impact of salt reduction initiatives on public health outcomes. There has so far not been available data to indicate if salt consumption in Norway has changed during the previous decade. We aimed to assess whether average 24-h salt intake estimated from spot urine samples in the adult population of mid-Norway changed from 2006-2008 to 2017-2019 and to describe variations by sex, age and educational level. DESIGN: Repeated cross-sectional studies. SETTING: The population-based Trøndelag Health Study (HUNT). PARTICIPANTS: In each of two consecutive waves (HUNT3: 2006-2008 and HUNT4: 2017-2019), spot urine samples were collected from 500 men and women aged 25-64 years, in addition to 250 men and women aged 70-79 years in HUNT4. Based on spot urine concentrations of Na, K and creatinine and age, sex and BMI, we estimated 24-h Na intake using the International Cooperative Study on Salt and Blood Pressure (INTERSALT) equation for the Northern European region. RESULTS: Mean (95 % CI) estimated 24-h salt intakes in men were 11·1 (95 % CI 10·8, 11·3) g in HUNT3 and 10·9 (95 % CI 10·6, 11·1) g in HUNT4, P = 0·25. Corresponding values in women were 7·7 (95 % CI 7·5, 7·9) g and 7·7 (95 % CI 7·5, 7·9) g, P = 0·88. Mean estimated salt intake in HUNT4 decreased with increasing age in women, but not in men, and it did not differ significantly across educational level in either sex. CONCLUSIONS: Estimated 24-h salt intake in adult men and women in mid-Norway did not change from 2006-2008 to 2017-2019.

Effects of sex and hydration status on kappa opioid receptor-mediated diuresis in rats.

Understanding the function of the kappa opioid receptor (KOP) is crucial for the development of novel therapeutic interventions that target KOP for the treatment of pain, stress-related disorders and other indications. Activation of KOP produces diuretic effects in rodents and man. Sex is a vital factor to consider when assessing drug response in pre-clinical and clinical studies. In this study, the diuretic effect of the KOP agonist, U50488 (1-10 mg/kg), was investigated in both adult female and male Wistar rats that were either normally hydrated or water-loaded. The KOP antagonist norbinaltorphimine (norBNI, 10 mg/kg) was administered 24 h prior to U50488 to confirm the involvement of KOP. U50488 elicited a significant diuretic response at doses ≥ 3 mg/kg in both female and male rats independent of hydration status. U50488 diuretic effects were inhibited by norBNI pre-administration. Water-loading reduced data variability for urine volume in males, but not in females, compared with normally hydrated rats. Sex differences were also evident in U50488 eliciting a significant increase in sodium and potassium ion excretion only in males. This may suggest different mechanisms of U50488 diuretic action in males where renal excretion mechanisms are directly affected more than in females.

Prediction of endogenous mineralocorticoid receptor activity by depressor effects of mineralocorticoid receptor antagonists in patients with primary aldosteronism.

Patients with primary aldosteronism have an increased risk of developing cardiovascular disease. The response to mineralocorticoid receptor antagonists varies among individuals, indicating diverse mineralocorticoid receptor activities in these patients. This study explored the factors linked to the efficacy of blood pressure reduction through mineralocorticoid receptor antagonists in patients with primary aldosteronism. We examined the relationship between the reduction in blood pressure and patient characteristics in a group of 41 patients with primary aldosteronism (24 males, mean age 55 ± 13 years, including 34 patients diagnosed with bilateral primary aldosteronism) before and after undergoing treatment with mineralocorticoid receptor antagonists. Significant reductions in office blood pressure were observed 3 and 6 months after treatment initiation. Single correlation analyses showed that the urinary chloride-to-potassium ratio displayed the strongest positive association with blood pressure reduction, surpassing plasma aldosterone concentration, plasma renin activity, and urinary sodium-to-potassium ratio, at 3 and 6 months. Multiple correlation analyses revealed a consistent and independent positive correlation between the urinary chloride-to-potassium ratio and blood pressure reduction at 3 and 6 months. The optimal threshold for the urinary chloride-to-potassium ratio with respect to its ability to lower blood pressure, was determined as 3.18. These results imply that the urinary chloride-to-potassium ratio may be independently associated with the effectiveness of blood pressure reduction facilitated by mineralocorticoid receptor antagonists. Moreover, it could potentially serve as a valuable predictor of the effectiveness of these agents and function as an indicator of endogenous mineralocorticoid receptor activity in patients with primary aldosteronism.

Genetic Determinants of Thiazide-Induced Hyperuricemia, Hyperglycemia, and Urinary Electrolyte Disturbances - A Genome-Wide Evaluation of the UK Biobank.

Thiazide diuretics, widely used in hypertension, cause a variety of adverse reactions, including hyperglycemia, hyperuricemia, and electrolyte abnormalities. In this study, we aimed to identify genetic variants that interact with thiazide-use to increase the risk of these adverse reactions. Using UK Biobank data, we first performed genomewide variance quantitative trait locus (vQTL) analysis of ~ 6.2 million SNPs on 95,493 unrelated hypertensive White British participants (24,313 on self-reported bendroflumethiazide treatment at recruitment) for 2 blood (glucose and urate) and 2 urine (potassium and sodium) biomarkers. Second, we conducted direct gene-environment interaction (GEI) tests on the significant (P < 2.5 × 10-9) vQTLs, included a second UK Biobank cohort comprising 13,647 unrelated hypertensive White British participants (3,478 on thiazides other than bendroflumethiazide) and set significance at P = 0.05 divided by the number of vQTL SNPs tested for GEIs. The vQTL analysis identified eight statistically significant SNPs for blood glucose (5 SNPs) and serum urate (3 SNPs), with none being identified for the urinary biomarkers. Two of the SNPs (1 glucose SNP: CDKAL1 intron rs35612982, GEI P = 6.24 × 10-3; and 1 serum urate SNP: SLC2A9 intron rs938564, GEI P = 4.51 × 10-4) demonstrated significant GEI effects in the first, but not the second, cohort. Both genes are biologically plausible candidates, with the SLC2A9-mediated interaction having been previously reported. In conclusion, we used a two-stage approach to detect two biologically plausible genetic loci that can interact with thiazides to increase the risk of thiazide-associated biochemical abnormalities. Understanding how environmental exposures (including medications such as thiazides) and genetics interact, is an important step toward precision medicine and improved patient outcomes.

Urinary Biomarkers in Screening for the Usual Intake of Fruit and Vegetables, and Sodium, Potassium, and the Sodium-to-Potassium Ratio: Required Number and Accuracy of Measurements.

Because of within-individual variation, surveys to estimate an individual's usual food intake must be conducted over many days, in general. Here, using non-invasive biomarkers, we examined the number of measurements required to screen for the usual intake of fruit and vegetables, in addition to sodium, potassium, and the sodium-to-potassium (Na/K) ratio. Participants were 202 subjects aged 40-74 years from five areas of Japan who completed weighed food records (WFR) and five 24-hour urinary collections (24-h UCs) between 2012 and 2013. The number of 24-h UCs required to screen for intake that deviated from guidelines estimated by the WFR and their accuracies were assessed by the area under the curve (AUC) in a receiver-operating characteristics (ROC) analysis. The single urinary excretion of sodium, potassium, and the Na/K ratio showed moderate performance (AUC value: >0.7) in discriminating deviations from their criteria by respective intake based on the WFR. Urinary potassium excretion also showed moderate performance (AUC value: >0.7) in estimating the intake of vegetables but could not be used to estimate fruit intake even after five collections. The non-invasive measurement of biomarkers in a single 24-h UC showed moderate performance in screening the usual intake of vegetables, as measured based on the 12-day WFR, as well as of sodium, potassium, and the Na/K ratio.

Relationship between traditional risk factors for hypertension and systolic blood pressure in the Tohoku Medical Megabank Community-based Cohort Study.

Risk factors for hypertension have been emphasized in the Japanese Society of Hypertension Guidelines for the Management of Hypertension. However, large-scale studies on the association of smoking, potassium excretion, and gamma-glutamyl transferase level with BP in the Japanese population are limited. We conducted a cross-sectional study to examine the association between hypertension risk factors and systolic blood pressure in the Tohoku Medical Megabank Community-based Cohort Study (23,446 men and 38,921 women aged ≥20 years). A model adjusted for age, body mass index, smoking status, drinking status, estimated daily salt intake, potassium excretion, (or urinary sodium-to-potassium ratio), gamma-glutamyl transferase, physical activity, education level, status of damage to homes during the Great East Japan Earthquake, and residential areas was used. The average age and systolic blood pressure were 62.5 (10.3) years for men and 59.6 (11.3) years for women, 128.9 (16.7) mmHg for men and 124.7 (17.5) mmHg for women, respectively. Body mass index estimated daily salt intake, urinary sodium-to-potassium ratio and gamma-glutamyl transferase levels were positively associated with systolic blood pressure. Compared with never-drinkers, current drinkers who consumed 23-45 g/day and ≥46.0 g/day had significantly increased systolic blood pressure. Conversely, current smokers (1-10 cigarettes/day and 11-20 cigarettes/day) were inversely associated with systolic blood pressure compared to never-smokers. Overall, systolic blood pressure was associated with gamma-glutamyl transferase and hypertension risk factors, including body mass index, alcohol consumption, estimated daily salt intake, urinary sodium-to-potassium ratio, and potassium excretion. Our findings support the notion that lifestyle modifications should be attempted to prevent hypertension.

The contribution of sodium reduction and potassium increase to the blood pressure lowering observed in the Salt Substitute and Stroke Study.

The Salt Substitute and Stroke Study (SSaSS) demonstrated significant reductions in systolic blood pressure (SBP), and the risk of stroke, major cardiovascular events and total mortality with the use of potassium-enriched salt. The contribution of sodium reduction versus potassium increase to these effects is unknown. We identified four different data sources describing the association between sodium reduction, potassium supplementation and change in SBP. We then fitted a series of models to estimate the SBP reductions expected for the differences in sodium and potassium intake in SSaSS, derived from 24-h urine collections. The proportions of the SBP reduction separately attributable to sodium reduction and potassium supplementation were calculated. The observed SBP reduction in SSaSS was -3.3 mmHg with a corresponding mean 15.2 mmol reduction in 24-h sodium excretion and a mean 20.6 mmol increase in 24-h potassium excretion. Assuming 90% of dietary sodium intake and 70% of dietary potassium intake were excreted through urine, the models projected falls in SBP of between -1.67 (95% confidence interval: -4.06 to +0.73) mmHg and -5.33 (95% confidence interval: -8.58 to -2.08) mmHg. The estimated proportional contribution of sodium reduction to the SBP fall ranged between 12 and 39% for the different models fitted. Sensitivity analyses assuming different proportional urinary excretion of dietary sodium and potassium intake showed similar results. In every model, the majority of the SBP lowering effect in SSaSS was estimated to be attributable to the increase in dietary potassium rather than the fall in dietary sodium.

The Association between Urinary Sodium-Potassium Ratio, Kidney Function, and Blood Pressure in a Cohort from the General Population.

INTRODUCTION: Subclinical kidney dysfunction may contribute to salt-sensitive hypertension. We assessed the association between the urinary sodium-potassium ratio (Na/K ratio) and blood pressure (BP) in a general population cohort without diabetes, chronic kidney disease, cardiovascular disease, or treated hypertension. We investigated whether any such association was mediated by the kidney function markers measured glomerular filtration rate (mGFR), urinary albumin-creatinine ratio (ACR), and urinary epidermal growth factor-creatinine ratio (EGF-Cr). METHODS: The Tromsø Study is a population-based study of inhabitants of the municipality of Tromsø, Northern Norway. Participants aged 50-62 years, without diabetes, chronic kidney disease, or cardiovascular disease, were invited to the substudy Renal Iohexol Clearance Survey in Tromsø 6 (RENIS-T6; 2007-09). For the present study, we excluded participants reporting the use of 1 or more antihypertensive agents, leaving 1,311 RENIS-T6 participants for a cross-sectional analysis. We measured office BP, 24-h ambulatory blood pressure (ABP), and mGFR using iohexol clearance. Na/K ratio, ACR, and EGF-Cr were measured in morning urine samples. RESULTS: Urinary Na/K ratio was significantly associated with systolic office BP and ABP independently of cardiovascular risk factors and kidney function markers. A one-standard deviation unit increase in the Na/K ratio was associated with increased systolic ABP by 1.0 (0.3-1.6) mm Hg. Urinary Na/K ratio showed a stronger association with office BP than ABP. EGF-Cr, ACR, and mGFR did not mediate the relationship between urinary Na/K ratio and systolic BP. CONCLUSIONS: In a representative sample of the middle-aged North-European population without diabetes, chronic kidney disease, cardiovascular disease, or treated hypertension, there was a consistent association between urinary Na/K ratio and BP. The association with BP was not mediated through kidney function measures, suggesting a relationship between a diet with high sodium and low potassium and higher BP regardless of kidney function.

Can sodium and potassium measured in timed voids be used as reference instruments for validating self-report instruments? Results from a urine calibration study.

BACKGROUND: Sodium and potassium measured in 24-h urine collections are often used as reference measurements to validate self-reported dietary intake instruments. OBJECTIVES: To evaluate whether collection and analysis of a limited number of urine voids at specified times during the day ("timed voids") can provide alternative reference measurements, and to identify their optimal number and timing. METHODS: We used data from a urine calibration study among 441 adults aged 18-39 y. Participants collected each urine void in a separate container for 24 h and recorded the collection time. For the same day, they reported dietary intake using a 24-h recall. Urinary sodium and potassium were analyzed in a 24-h composite sample and in 4 timed voids (morning, afternoon, evening, and overnight). Linear regression models were used to develop equations predicting log-transformed 24-h urinary sodium or potassium levels using each of the 4 single timed voids, 6 pairs, and 4 triples. The equations also included age, sex, race, BMI (kg/m2), and log creatinine. Optimal combinations minimizing the mean squared prediction error were selected, and the observed and predicted 24-h levels were then used as reference measures to estimate the group bias and attenuation factors of the 24-h dietary recall. These estimates were compared. RESULTS: Optimal combinations found were as follows: single voids-evening; paired voids-afternoon + overnight (sodium) and morning + evening (potassium); and triple voids-morning + evening + overnight (sodium) and morning + afternoon + evening (potassium). Predicted 24-h urinary levels estimated 24-h recall group biases and attenuation factors without apparent bias, but with less precision than observed 24-h urinary levels. To recover lost precision, it was estimated that sample sizes need to be increased by ∼2.6-2.7 times for a single void, 1.7-2.1 times for paired voids, and 1.5-1.6 times for triple voids. CONCLUSIONS: Our results provide the basis for further development of new reference biomarkers based on timed voids. CLINICAL TRIAL REGISTRY: clinicaltrials.gov as NCT01631240.

KS-WNK1 is required for the renal response to extreme changes in potassium intake.

Kidney-specific with-no-lysine kinase 1 (KS-WNK1) is an isoform of WNK1 kinase that is predominantly found in the distal convoluted tubule of the kidney. The precise physiological function of KS-WNK1 remains unclear. Some studies have suggested that it could play a role in regulating potassium renal excretion by modulating the activity of the Na+-Cl- cotransporter (NCC). However, changes in the potassium diet from normal to high failed to reveal a role for KS-WNK1, but under a normal-potassium diet, the expression of KS-WNK1 is negligible. It is only detectable when mice are exposed to a low-potassium diet. In this study, we investigated the role of KS-WNK1 in regulating potassium excretion under extreme changes in potassium intake. After following a zero-potassium diet (0KD) for 10 days, KS-WNK1-/- mice had lower plasma levels of K+ and Cl- while exhibiting higher urinary excretion of Na+, Cl-, and K+ compared with KS-WNK1+/+ mice. After 10 days of 0KD or normal-potassium diet (NKD), all mice were challenged with a high-potassium diet (HKD). Plasma K+ levels markedly increased after the HKD challenge only in mice previously fed with 0KD, regardless of genotype. KSWNK1+/+ mice adapt better to HKD challenge than KS-WNK1-/- mice after a potassium-retaining state. The difference in the phosphorylated NCC-to-NCC ratio between KS-WNK1+/+ and KS-WNK1-/- mice after 0KD and HKD indicates a role for KS-WNK1 in both NCC phosphorylation and dephosphorylation. These observations show that KS-WNK1 helps the distal convoluted tubule to respond to extreme changes in potassium intake, such as those occurring in wildlife.NEW & NOTEWORTHY The findings of this study demonstrate that kidney-specific with-no-lysine kinase 1 plays a role in regulating urinary electrolyte excretion during extreme changes in potassium intake, such as those occurring in wildlife. .

Association between sodium and potassium excretion estimated from spot urine and socioeconomic status among primary school children and their mothers in Okinawa, Japan.

Hypertension is the greatest and the most preventable risk factor for cardiovascular disease. Excessive sodium (Na) intake and insufficient potassium (K) intake have been identified as risk factors for hypertension. Socioeconomic status (SES) may be related to diet quality. In Japan, few studies have examined the relationship between urinary Na and K excretion and SES in adults, and there are no studies in children. In 2014, 1944 children (1382 households) in all public elementary schools in Yaese town, Okinawa, Japan were recruited to participate in a study. Casual urine specimens were collected to estimate 24-h urinary Na and K excretion and urinary Na/K ratio. Mother's educational background and household incomes were assessed and used as indicators of SES. A total of 236 pairs of children and their mothers were analyzed in this study. Urinary Na and K excretion were not significantly related to educational levels of mothers and household incomes in children. On the other hand, in mothers, lower household income group had higher 24-h estimated urinary Na excretion and urinary Na/K ratio than other groups. There was no significant difference between urinary excretion and educational levels in mothers. Household income disparities in urinary levels seen in mothers were not seen in children. There may be some factors that moderate the dietary inequalities in children.

Relationship between urinary potassium excretion, serum potassium levels and cardiac injury in non-dialysis chronic kidney disease: KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD).

Although the cardiovascular benefits of an increased urinary potassium excretion have been suggested, little is known about the potential cardiac association of urinary potassium excretion in patients with chronic kidney disease. In addition, whether the cardiac association of urinary potassium excretion was mediated by serum potassium levels has not been studied yet. We reviewed the data of 1633 patients from a large-scale multicentre prospective Korean study (2011-2016). Spot urinary potassium to creatinine ratio was used as a surrogate for urinary potassium excretion. Cardiac injury was defined as a high-sensitivity troponin T ≥ 14 ng/l. OR and 95 % (CI for cardiac injury were calculated using logistic regression analyses. Of 1633 patients, the mean spot urinary potassium to creatinine ratio was 49·5 (sd 22·6) mmol/g Cr and the overall prevalence of cardiac injury was 33·9 %. Although serum potassium levels were not associated with cardiac injury, per 10 mmol/g Cr increase in the spot urinary potassium to creatinine ratio was associated with decreased odds of cardiac injury: OR 0·917 (95 % CI 0·841, 0·998), P = 0·047) in multivariate logistic regression analysis. In mediation analysis, approximately 6·4 % of the relationship between spot urinary potassium to creatinine ratio and cardiac injury was mediated by serum potassium levels, which was not statistically significant (P = 0·368). Higher urinary potassium excretion was associated with lower odds of cardiac injury, which was not mediated by serum potassium levels.