Hold the salt for kidney regeneration.

The macula densa (MD) is a distinct cluster of approximately 20 specialized kidney epithelial cells that constitute a key component of the juxtaglomerular apparatus. Unlike other renal tubular epithelial cell populations with functions relating to reclamation or secretion of electrolytes and solutes, the MD acts as a cell sensor, exerting homeostatic actions in response to sodium and chloride changes within the tubular fluid. Electrolyte flux through apical sodium transporters in MD cells triggers release of paracrine mediators, affecting blood pressure and glomerular hemodynamics. In this issue of the JCI, Gyarmati and authors explored a program of MD that resulted in activation of regeneration pathways. Notably, regeneration was triggered by feeding mice a low-salt diet. Furthermore, the MD cells showed neuron-like properties that may contribute to their regulation of glomerular structure and function. These findings suggest that dietary sodium restriction and/or targeting MD signaling might attenuate glomerular injury.

Self-Performed Dietary Sodium Reduction and Blood Pressure in Patients With Essential Hypertension: A Randomized Clinical Trial.

BACKGROUND: Hypertension is the leading risk factor for cardiovascular disease worldwide. Patients with blood pressure (BP) response to dietary sodium reduction are referred to as "salt sensitive." Salt sensitivity (SS) might be due to differences in sodium storage capacity and the erythrocyte SS examines this capacity of the red blood cells. This study aimed to test the effect of a self-performed sodium reduced diet on BP in patients with essential hypertension and examine whether erythrocyte SS predicts SS. METHODS AND RESULTS: Seventy-two patients with hypertension were included and randomized 2:1 to either sodium reduction or a control group for 4 weeks. Blood samples, 24-hour BP measurement, and 24-hour urine collection were performed before and after. The intervention group received advice on how to lower sodium intake. Urinary sodium excretion decreased 66 mmol (95% CI, -96 to -37 mmol) in the intervention group compared with the control group. Systolic 24-hour BP decreased 9 mm Hg after low-sodium diet compared with the control group (95% CI, -13 to -4 mm Hg). Similarly, the difference in reduction in diastolic BP between the groups was 5 mm Hg (95% CI, -8 to -1 mm Hg). We found no correlation between erythrocyte SS at baseline and decrease in 24-hour BP, neither systolic nor diastolic (P=0.66 and P = 0.84). CONCLUSIONS: Self-performed sodium reduction was feasible and led to decrease in 24-hour BP of 9/5 mm Hg compared with a control group. The erythrocyte SS did not correlate to the change in BP after lowering sodium intake. REGISTRATION: URL: https://clinicaltrials.gov; Unique Identifier: NCT05165823.

The Guidelines for use and promotion of low sodium salt in China.

AIM: Both excessive intake of sodium and inadequate intake of potassium are associated with blood pressure elevation and subsequent increase in the risk of cardiovascular disease, which accounts for the largest number of deaths in China and worldwide. Low sodium salt, a mixture of mainly sodium chloride and potassium chloride, has shown its great potential as a promising population strategy for sodium intake reduction through multiple large-scale, multicenter, randomized controlled trials among populations including patients with cardiovascular disease, individuals with and without hypertension, older and younger adults, and men and women in China and other countries. This Guidelines aims to provide expert recommendations for promotion and use of low sodium salt in China, based on the current available scientific evidence regarding the effectiveness, safety, cost-effectiveness, and acceptability of low sodium salts in various population groups and different application scenarios. The suggestions to key stakeholders are also made. METHODS: A working group, an expert review committee and an advisory committee were established to be responsible for formulating the guidelines' scope and key questions to be addressed, for searching, synthesizing, and evaluating research evidence, proposing and reviewing the recommendations. The consensus on the final recommendations was reached using the GRADE grid method. RESULTS: The working group summarized current available evidence of salt substitution regarding its effectiveness, safety, cost-effectiveness, acceptability, availability, suitability, etc. The Guidelines provided six recommendations advising different populations how to use low sodium salt, four recommendations on the application of low sodium salts in different scenarios, and five suggestions for key stakeholders to promote salt substitution. CONCLUSION: The first evidence-based guidelines on promotion and use of low sodium salts covers all key questions in relevance and would play a critical role in prevention and control of hypertension and cardiovascular disease in China and worldwide.

The Relationship between Low-Sodium Salt Intake and Both Blood Pressure Level and Hypertension in Chinese Residents.

Compared to common salt, low-sodium salt can reduce blood pressure to varying degrees. However, the exact dosage relationship remains unclear. We aimed to investigate the dose-response relationships between low-sodium salt intake and systolic blood pressure (SBP) and diastolic blood pressure (DBP), as well as the risk of hypertension, and to determine the optimal range for low-sodium salt intake. We investigated the basic characteristics and dietary profile of 350 individuals who consumed low-sodium salt. The samples were divided into three groups according to the 33.3rd and 66.6th percentiles of low-sodium salt intake in condiments (Q1: <4.72 g/d, Q2: ≥4.72 g/d, and <6.88 g/d, and Q3: ≥6.88 g/d). The restricted cubic spline results indicated that low-sodium salt intake decreased linearly with SBP and DBP, while low-sodium intake demonstrated a non-linear, L-shaped relationship with the risk of hypertension, with a safe range of 5.81 g to 7.66 g. The multiple linear regression analysis revealed that compared with group Q1, the DBP in group Q2 decreased by 2.843 mmHg (95%CI: -5.552, -0.133), and the SBP in group Q3 decreased by 4.997 mmHg (95%CI: -9.136, -0.858). Exploratory subgroup analyses indicated that low-sodium salt intake had a significant impact on reducing SBP in males, DBP in females, SBP in rural populations, and DBP in urban populations. The intake of low-sodium salt adheres to the principle of moderation, with 5.81-7.66 g potentially serving as a pivotal threshold.

Na and K Intake from Lunches Served in a Japanese Company Cafeteria and the Estimated Improvement in the Dietary Na/K Ratio Using Low-Na/K Seasonings and Dairy to Prevent Hypertension.

The excessive intake of sodium (Na) and insufficient intake of potassium (K) are major concerns in the prevention of hypertension. Using low-Na/K seasonings (reducing 25% of the NaCl and adding K salt) may improve the dietary Na/K ratio and help prevent hypertension. To devise an intervention study using low-Na/K seasonings at a company cafeteria, we calculated the Na and K contents of the meals served at the cafeteria and estimated changes in the intakes when suitable low-Na/K seasonings were used. We also considered using milk as a good source of K. We used an ingredient list of a company cafeteria and calculated Na and K contents in each dish. The average amounts of NaCl and K per use were 5.04 g and 718 mg, respectively. Seasonings contributed 70.9% of the NaCl. With the use of low-Na/K seasonings, an estimated reduction in NaCl of 0.8 g/day and an estimated increase in K of 308 mg/day was achieved. With an additional serving (200 mL) of milk, NaCl was reduced by 0.57 g/day and K was increased by 610 mg/day, with an overall decrease in the dietary Na/K ratio from 3.20 to 2.40. The use of low-Na/K seasonings and dairy may improve the dietary Na/K ratio among cafeteria users and help prevent hypertension.

Croatian Action on Salt and Health (CRASH): On the Road to Success-Less Salt, More Health.

The World Health Organization recommends adjusting salt intake as a part of the nine global targets to reduce premature mortality from non-communicable chronic diseases as a priority and the most cost-effective intervention. In 2006, the main aim of the Croatian Action on Salt and Health was to decrease salt intake by 16% because of its critical intake and consequences on human health. We have organized educative activities to increase awareness on salt harmfulness, define food categories of prime interest, collaborate with industries and determine salt intake (24 h urine sodium excretion). It was determined that the proportion of salt in ready-to-eat baked bread should not exceed 1.4%. In the period 2014-2022, salt in semi-white bread was reduced by 14%, 22% in bakery and 25% in the largest meat industry. Awareness of the harmfulness of salt on health increased from 65.3% in 2008 to 96.9% in 2023 and salt intake was reduced by 15.9-1.8 g/day (22.8% men, 11.7% women). In the last 18 years, a significant decrease in salt intake was achieved in Croatia, awareness of its harmfulness increased, collaboration with the food industry was established and regulatory documents were launched. However, salt intake is still very high, underlying the need for continuation of efforts and even stronger activities.

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.

An educational intervention for improving knowledge, attitude, and practice of dietary salt intake among individuals with hypertension in public sector secondary care facilities, Agra, India, 2021.

We conducted a pre-post intervention study to determine knowledge, attitude, and practice toward dietary salt intake before, immediately, and 1-month after nurse-led one-on-one counseling. We purposively selected three public health facilities in Agra, India, and enrolled all eligible hypertensive patients aged 18-60 under treatment for ≥6 months. Of the 153 patients at the 1-month follow-up, counseling improved knowledge (4% vs. 42%, p < .001), a greater prioritization of a low salt diet (34% vs. 52%, p < .001), and practice of adding less salt to the dough (48% to 41%, p < .001). The counseling intervention improved knowledge, attitude, and practice toward dietary salt intake.

Dissociation of Hypertension and Renal Damage After Cessation of High-Salt Diet in Dahl Rats.

BACKGROUND: Every year, thousands of patients with hypertension reduce salt consumption in an effort to control their blood pressure. However, hypertension has a self-sustaining character in a significant part of the population. We hypothesized that chronic hypertension leads to irreversible renal damage that remains after removing the trigger, causing an elevation of the initial blood pressure. METHODS: Dahl salt-sensitive rat model was used for chronic, continuous observation of blood pressure. Rats were fed a high salt diet to induce hypertension, and then the diet was switched back to normal sodium content. RESULTS: We found that developed hypertension was irreversible by salt cessation: after a short period of reduction, blood pressure grew even higher than in the high-salt phase. Notably, the self-sustaining phase of hypertension was sensitive to benzamil treatment due to sustaining epithelial sodium channel hyperactivity, as shown with patch-clamp analysis. Glomerular damage and proteinuria were also irreversible. In contrast, some mechanisms, contributing to the development of salt-sensitive hypertension, normalized after salt restriction. Thus, flow cytometry demonstrated that dietary salt reduction in hypertensive animals decreased the number of total CD45+, CD3+CD4+, and CD3+CD8+ cells in renal tissues. Also, we found tubular recovery and improvement of glomerular filtration rate in the postsalt period versus a high-salt diet. CONCLUSIONS: Based on earlier publications and current data, poor response to salt restriction is due to the differential contribution of the factors recognized in the developmental phase of hypertension. We suggest that proteinuria or electrolyte transport can be prioritized over therapeutic targets of inflammatory response.

Influence of proteolytic cleavage of ENaC's γ subunit upon Na+ and K+ handling.

The epithelial Na+ channel (ENaC) γ subunit is essential for homeostasis of Na+, K+, and body fluid. Dual γ subunit cleavage before and after a short inhibitory tract allows dissociation of this tract, increasing channel open probability (PO), in vitro. Cleavage proximal to the tract occurs at a furin recognition sequence (143RKRR146, in the mouse γ subunit). Loss of furin-mediated cleavage prevents in vitro activation of the channel by proteolysis at distal sites. We hypothesized that 143RKRR146 mutation to 143QQQQ146 (γQ4) in 129/Sv mice would reduce ENaC PO, impair flow-stimulated flux of Na+ (JNa) and K+ (JK) in perfused collecting ducts, reduce colonic amiloride-sensitive short-circuit current (ISC), and impair Na+, K+, and body fluid homeostasis. Immunoblot of γQ4/Q4 mouse kidney lysates confirmed loss of a band consistent in size with the furin-cleaved proteolytic fragment. However, γQ4/Q4 male mice on a low Na+ diet did not exhibit altered ENaC PO or flow-induced JNa, though flow-induced JK modestly decreased. Colonic amiloride-sensitive ISC in γQ4/Q4 mice was not altered. γQ4/Q4 males, but not females, exhibited mildly impaired fluid volume conservation when challenged with a low Na+ diet. Blood Na+ and K+ were unchanged on a regular, low Na+, or high K+ diet. These findings suggest that biochemical evidence of γ subunit cleavage should not be used in isolation to evaluate ENaC activity. Furthermore, factors independent of γ subunit cleavage modulate channel PO and the influence of ENaC on Na+, K+, and fluid volume homeostasis in 129/Sv mice, in vivo.NEW & NOTEWORTHY The epithelial Na+ channel (ENaC) is activated in vitro by post-translational proteolysis. In vivo, low Na+ or high K+ diets enhance ENaC proteolysis, and proteolysis is hypothesized to contribute to channel activation in these settings. Using a mouse expressing ENaC with disruption of a key proteolytic cleavage site, this study demonstrates that impaired proteolytic activation of ENaC's γ subunit has little impact upon channel open probability or the ability of mice to adapt to low Na+ or high K+ diets.

Effect of the DASH diet on the sodium-chloride cotransporter and aquaporin-2 in urinary extracellular vesicles.

The dietary approach to stop hypertension (DASH) diet combines the antihypertensive effect of a low sodium and high potassium diet. In particular, the potassium component of the diet acts as a switch in the distal convoluted tubule to reduce sodium reabsorption, similar to a diuretic but without the side effects. Previous trials to understand the mechanism of the DASH diet were based on animal models and did not characterize changes in human ion channel protein abundance. More recently, protein cargo of urinary extracellular vesicles (uEVs) has been shown to mirror tissue content and physiological changes within the kidney. We designed an inpatient open label nutritional study transitioning hypertensive volunteers from an American style diet to DASH diet to examine physiological changes in adults with stage 1 hypertension otherwise untreated (Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH; DASH-Sodium Collaborative Research Group. N Engl J Med 344: 3-10, 2001). Urine samples from this study were used for proteomic characterization of a large range of pure uEVs (small to large) to reveal kidney epithelium changes in response to the DASH diet. These samples were collected from nine volunteers at three time points, and mass spectrometry identified 1,800 proteins from all 27 samples. We demonstrated an increase in total SLC12A3 [sodium-chloride cotransporter (NCC)] abundance and a decrease in aquaporin-2 (AQP2) in uEVs with this mass spectrometry analysis, immunoblotting revealed a significant increase in the proportion of activated (phosphorylated) NCC to total NCC and a decrease in AQP2 from day 5 to day 11. This data demonstrates that the human kidney's response to nutritional interventions may be captured noninvasively by uEV protein abundance changes. Future studies need to confirm these findings in a larger cohort and focus on which factor drove the changes in NCC and AQP2, to which degree NCC and AQP2 contributed to the antihypertensive effect and address if some uEVs function also as a waste pathway for functionally inactive proteins rather than mirroring protein changes.NEW & NOTEWORTHY Numerous studies link DASH diet to lower blood pressure, but its mechanism is unclear. Urinary extracellular vesicles (uEVs) offer noninvasive insights, potentially replacing tissue sampling. Transitioning to DASH diet alters kidney transporters in our stage 1 hypertension cohort: AQP2 decreases, NCC increases in uEVs. This aligns with increased urine volume, reduced sodium reabsorption, and blood pressure decline. Our data highlight uEV protein changes as diet markers, suggesting some uEVs may function as waste pathways. We analyzed larger EVs alongside small EVs, and NCC in immunoblots across its molecular weight range.

Dietary sodium and fluid intake in heart failure. A clinical consensus statement of the Heart Failure Association of the ESC.

Sodium and fluid restriction has traditionally been advocated in patients with heart failure (HF) due to their sodium and water avid state. However, most evidence regarding the altered sodium handling, fluid homeostasis and congestion-related signs and symptoms in patients with HF originates from untreated patient cohorts and physiological investigations. Recent data challenge the beneficial role of dietary sodium and fluid restriction in HF. Consequently, the European Society of Cardiology HF guidelines have gradually downgraded these recommendations over time, now advising for the limitation of salt intake to no more than 5 g/day in patients with HF, while contemplating fluid restriction of 1.5-2 L/day only in selected patients. Therefore, the objective of this clinical consensus statement is to provide advice on fluid and sodium intake in patients with acute and chronic HF, based on contemporary evidence and expert opinion.

Long-Term Effect of Salt Substitution for Cardiovascular Outcomes : A Systematic Review and Meta-analysis.

BACKGROUND: Salt substitution is a simple yet increasingly promising strategy to improve cardiovascular outcomes. PURPOSE: To evaluate the long-term effects of salt substitution on cardiovascular outcomes. DATA SOURCES: PubMed, EMBASE, Cochrane CENTRAL, and CINAHL searched from inception to 23 August 2023. Trial registries, citation analysis, and hand-search were also done. STUDY SELECTION: Randomized controlled trials (RCTs) comparing provision of or advice to use a salt substitute with no intervention or use of regular salt among adults for 6 months or longer in total study duration. DATA EXTRACTION: Two authors independently screened articles, extracted data, and assessed risk of bias. Primary outcomes include mortality, major cardiovascular events (MACE), and adverse events at 6 months or greater. Secondary and post hoc outcomes include blood pressure, cause-specific mortality, and urinary excretion at 6 months or greater. Random-effects meta-analyses were done and certainty of effect estimates were assessed using GRADE (Grading of Recommendations Assessment, Development and Evaluation). DATA SYNTHESIS: Of the 16 included RCTs, 8 reported on primary outcomes. Most (n = 7 of 8) were done in China or Taiwan, 3 were done in residential facilities, and 7 included populations of older age (average 62 years) and/or with higher-than-average cardiovascular risk. In this population, salt substitute may reduce risk for all-cause mortality (6 RCTs; 27 710 participants; rate ratio [RR], 0.88 [95% CI, 0.82 to 0.93]; low certainty) and cardiovascular mortality (4 RCTs; 25 050 participants; RR, 0.83 [CI, 0.73 to 0.95]; low certainty). Salt substitute may result in a slight reduction in MACE (3 RCTs; 23 215 participants; RR, 0.85 [CI, 0.71 to 1.00]; very low certainty), with very low-certainty evidence of serious adverse events (6 RCTs; 27 995 participants; risk ratio, 1.04 [CI, 0.87 to 1.25]). LIMITATIONS: The evidence base is dominated by a single, large RCT. Most RCTs were from China or Taiwan and involved participants with higher-than-average cardiovascular risk; therefore, generalizability to other populations is very limited. CONCLUSION: Salt substitution may reduce all-cause or cardiovascular mortality, but the evidence for reducing cardiovascular events and for not increasing serious adverse events is uncertain, particularly for a Western population. The certainty of evidence is higher among populations at higher cardiovascular risk and/or following a Chinese diet. PRIMARY FUNDING SOURCE: National Health and Medical Research Council. (PROSPERO: CRD42022327566).

Utilizing Quality of Life Adjusted Days Alive and Out of Hospital in Heart Failure Clinical Trials.

BACKGROUND: In heart failure (HF) trials, there has been an emphasis on utilizing more patient-centered outcomes, including quality of life (QoL) and days alive and out of hospital. We aimed to explore the impact of QoL adjusted days alive and out of hospital as an outcome in 2 HF clinical trials. METHODS: Using data from 2 trials in HF (Guiding Evidence Based Therapy Using Biomarker Intensified Treatment in Heart Failure [GUIDE-IT] and Study of Dietary Intervention under 100 mmol in Heart Failure [SODIUM-HF]), we determined treatment differences using percentage days alive and out of hospital (%DAOH) adjusted for QoL at 18 months as the primary outcome. For each participant, %DAOH was calculated as a ratio between days alive and out of hospital/total follow-up. Using a regression model, %DAOH was subsequently adjusted for QoL measured by the Kansas City Cardiomyopathy Questionnaire Overall Summary Score. RESULTS: In the GUIDE-IT trial, 847 participants had a median baseline Kansas City Cardiomyopathy Questionnaire Overall Summary Score of 59.0 (interquartile range, 40.8-74.3), which did not change over 18 months. %DAOH was 90.76%±22.09% in the biomarker-guided arm and 88.56%±25.27% in the usual care arm. No significant difference in QoL adjusted %DAOH was observed (1.09% [95% CI, -1.57% to 3.97%]). In the SODIUM-HF trial, 796 participants had a median baseline Kansas City Cardiomyopathy Questionnaire Overall Summary Score of 69.8 (interquartile range, 49.3-84.3), which did not change over 18 months. %DAOH was 95.69%±16.31% in the low-sodium arm and 95.95%±14.76% in the usual care arm. No significant difference was observed (1.91% [95% CI, -0.85% to 4.77%]). CONCLUSIONS: In 2 large HF clinical trials, adjusting %DAOH for QoL was feasible and may provide complementary information on treatment effects in clinical trials.

Non-pharmacological interventions to reduce thirst in patients with heart failure or hemodialysis: A systematic review and meta-analysis.

BACKGROUND: Thirst is a frequent and burdening symptom in many patients, especially in patients with chronic heart failure (CHF) and/or receiving hemodialysis (HD). As drug therapies are not feasible, non-pharmacological strategies are needed to reduce thirst and thirst-related burden. OBJECTIVES: To identify non-pharmacological interventions aiming to reduce thirst in patients with CHF and/ or HD, to describe intervention components, and to evaluate the effectiveness of these interventions. METHODS: In February 2024, we completed a systematic search in MEDLINE via PubMed, Livivo, CINAHL, Cochrane Library and Web of Science. Two reviewers independently screened titles, abstracts, and full texts, performed critical appraisal and data extraction. We checked risk of bias with the checklists of the Joanna Briggs Institute and the Cochrane Risk of Bias tool and calculated meta-analyses for sufficiently homogeneous studies using fixed-effects models. RESULTS: We included 15 intervention studies applying non-pharmacological interventions including chewing gum (n = 8), low-sodium diet (n = 2), acupressure (n = 1), frozen strawberries (n = 1), fluid timetables (n = 1), ice cubes and mouthwash (n = 1), and a psychological intervention (n = 1). Sample sizes varied between 11 and 88 participants. Eleven intervention studies showed a reduction of thirst as intervention effect. Meta-analyses for chewing gum showed no significant effect on thirst using a visual analogue scale (IV: -2,32 [-10.37,5.73]; p = 0.57) or the dialysis thirst inventory (IV: -0.26 [- 1.83, 1.30]; p = 0.74). Quality of studies was moderate to low. CONCLUSION: Results indicate that various non-pharmacological interventions could be helpful to reduce thirst in patients with CHF or HD, but important uncertainty remains.

Dietary Fructose and Sodium Consumed during Early Mid-Life Are Associated with Hypertensive End-Organ Damage by Late Mid-Life in the CARDIA Cohort.

We aimed to investigate how dietary fructose and sodium impact blood pressure and risk of hypertensive target organ damage 10 years later. Data from n = 3116 individuals were obtained from the Coronary Artery Risk Development in Young Adults (CARDIA) study. Four groups were identified based on the four possible combinations of the lower and upper 50th percentile for sodium (in mg) and fructose (expressed as percent of total daily calories). Differences among groups were ascertained and logistic regression analyses were used to assess the risk of hypertensive target organ damage (diastolic dysfunction, coronary calcification and albuminuria). Individuals in the low-fructose + low-sodium group were found to have lower SBP compared to those in the low-fructose + high-sodium and high-fructose + high-sodium groups (p < 0.05). The highest risk for hypertensive target organ damage was found for albuminuria only in the high-fructose + high-sodium group (OR = 3.328, p = 0.006) while female sex was protective across all groups against coronary calcification. Our findings highlight that sodium alone may not be the culprit for hypertension and hypertensive target organ damage, but rather when combined with an increased intake of dietary fructose, especially in middle-aged individuals.