Role of Sodium Intake in the Progression of Chronic Kidney Disease

Dietary Intake of Antioxidant Vitamins and Its Relation to the Progression of Chronic Kidney Disease in Adults With Preserved Renal Function

OBJECTIVE

It is expected that antioxidants contribute to slow the progression of chronic kidney disease (CKD). However, there are no data on the protective effect of dietary antioxidant vitamins on CKD. The purpose of study was to evaluate the renoprotective effect of dietary antioxidant vitamins in the general population.

DESIGN AND METHODS

The study participants were 127,081 Korean adults with preserved renal function with estimated glomerular filtration rate ≥60 mL/min/1.73 m2. They were categorized into 3 groups by tertile levels of dietary antioxidant vitamins intake including vitamins C, E, and A. Cox proportional hazard assumption was used to calculate multivariable hazard ratios and 95% confidence interval for the incident moderate to severe CKD (adjusted hazard ratio [95% confidence interval]) according to tertile levels of dietary intake of antioxidant vitamins. Subgroup analysis was conducted to evaluate the risk of progression from normal to mildly decreased renal function, and from mildly decreased renal function to moderate to severe CKD.

RESULTS

The risk of moderate to severe CKD was not significantly associated with the third tertile of dietary antioxidant vitamin intake including vitamin C (1.02 [0.78-1.34]), E (0.96 [0.73-1.27]), and A (0.98 [0.74-1.29]). Additionally, any tertile groups didn't show the significant association with the risk of moderate to severe CKD. Subgroup analysis also didn't show the decreased risk of progression from normal to mildly decreased renal function, and from mildly decreased renal function to moderate to severe CKD in any tertile groups.

CONCLUSION

Dietary intake of vitamins C, E, and A was not significantly associated with the risk of CKD progression.

Hyperosmotic Stress Induces Inflammation and Excessive Th17 Response to Blunt T-Cell Immunity in Tilapia

Despite the advances in study on osmotic physiology in bony fish, the mechanism by which the immune system, especially T-cell immunity, adapts and responds to osmotic stress remains unknown. In the current study, we investigated the response of T cells to hyperosmotic stress in the bony fish Nile tilapia (Oreochromis niloticus). As a euryhaline fish, tilapia was able to adapt to a wide range of salinities; however, hypertonic stress caused inflammation and excessive T-cell activation. Furthermore, hypertonic stress increased the expression of IL-17A in T cells, upregulated the transcription factor RORα, and activated STAT3 signaling, along with IL-6- and TGF-β1-mediated pathways, revealing an enhanced Th17 response in this early vertebrate. These hypertonic stress-induced events collectively resulted in an impaired antibacterial immune response in tilapia. Hypertonic stress elevated the intracellular ROS level, which in turn activated the p38-MK2 signaling pathway to promote IL-17A production by T cells. Both ROS elimination and the p38-MK2 axis blockade diminished the increased IL-17A production in T cells under hypertonic conditions. Moreover, the produced proinflammatory cytokines further amplified the hypertonic stress signaling via the MKK6-p38-MK2 axis-mediated positive feedback loop. To our knowledge, these findings represent the first description of the mechanism by which T-cell immunity responds to hypertonic stress in early vertebrates, thus providing a novel perspective for understanding the adaptive evolution of T cells under environmental stress.

Levels of Salt Reduction in Bread, Acceptability and Purchase Intention by Urban Mozambican Consumers

Excess sodium (Na) consumption is implicated in several health problems, particularly hypertension, and bread is an important dietary source. We aimed to analyze perception of salt, acceptability, and purchase intention of low-salt and unsalted white bread by consumers in Mozambique. Sensory evaluation was performed using a triangular test (N = 42) to perceive if differences in saltiness were detected when comparing low-salt and unsalted with salt-reduced white bread. Nine-point hedonic and five-point purchase intention scales were used to measure acceptability and purchase intention, respectively (N = 120). Difference in saltiness was not detected when fresh white bread with 282 mg Na/100 g vs. 231 mg Na/100 g and 279 mg Na/100 g vs. 123 mg Na/100 g were compared. Difference in saltiness was not detected when comparing unsalted vs. 64 mg Na/100 g, while differences were detected when unsalted vs. 105 mg Na/100 g and unsalted vs. 277 mg Na/100 g were compared. Overall acceptability and purchase intention were not affected by reductions of Na in bread. A reduction of up to more than 50% of Na was not perceived and a small level of Na was not distinguished from unsalted bread. Consumers were shown to accept and be willing to buy both unsalted and salt-reduced bread, suggesting that Na can be reduced from current levels.

Protective Effect of Gamma Aminobutyric Acid against Aggravation of Renal Injury Caused by High Salt Intake in Cisplatin-Induced Nephrotoxicity

Gamma-aminobutyric acid (GABA) is one of the inhibitory neurotransmitters. Several studies have suggested that GABA supplements can reduce blood pressure and modulate the renal immune system in vitro and in vivo. In the present study, we investigated the effect of GABA-enriched salt as an alternative to traditional salt on aggravated renal injury by high salt intake in cisplatin-induced nephrotoxicity mice. High salt intake accelerated the increase of biomarkers, such as blood urea nitrogen and serum creatinine levels for renal injury in cisplatin-induced nephrotoxicity mice. However, oral administration of GABA-contained salt notably suppressed serum BUN and creatinine levels. The efficacy of GABA salt was superior to lacto GABA salt and postbiotics GABA salt. Furthermore, GABA-enriched salt markedly restored histological symptoms of nephrotoxicity including renal hypertrophy, tubular dilation, hemorrhage, and collagen deposition aggravated by salt over-loading in cisplatin-exposed mice. Among them, GABA salt showed a higher protective effect against cisplatin-induced renal histological changes than lacto GABA salt and postbiotics GABA salt. In addition, administration of high salt significantly enhanced expression levels of apoptosis and inflammatory mediators in cisplatin-induced nephrotoxicity mice, while GABA-enriched salt greatly down-regulated the expression of these mediators. Taken together, these results demonstrate the protective effect of GABA against damage caused by high salt intake in cisplatin-induced renal toxicity. Its mechanism may be due to the suppression of hematological and biochemical toxicity, apoptosis, and inflammation. In conclusion, although the protective efficacy of GABA salt on renal injury is different depending on the sterilization and filtration process after fermentation with L. brevis BJ20 and L. plantarum BJ21, our findings suggest that GABA-enriched salt has a beneficial effect against immoderate high salt intake-mediated kidney injury in patients with cisplatin-induced nephrotoxicity.

Altered dietary salt intake for people with chronic kidney disease

BACKGROUND

Evidence indicates that reducing dietary salt may reduce the incidence of heart disease and delay decline in kidney function in people with chronic kidney disease (CKD). This is an update of a review first published in 2015.

OBJECTIVES

To evaluate the benefits and harms of altering dietary salt for adults with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 6 October 2020 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials comparing two or more levels of salt intake in adults with any stage of CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility, conducted risk of bias evaluation and evaluated confidence in the evidence using GRADE. Results were summarised using random effects models as risk ratios (RR) for dichotomous outcomes or mean differences (MD) for continuous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

We included 21 studies (1197 randomised participants), 12 in the earlier stages of CKD (779 randomised participants), seven in dialysis (363 randomised participants) and two in post-transplant (55 randomised participants). Selection bias was low in seven studies, high in one and unclear in 13. Performance and detection biases were low in four studies, high in two, and unclear in 15. Attrition and reporting biases were low in 10 studies, high in three and unclear in eight. Because duration of the included studies was too short (1 to 36 weeks) to test the effect of salt restriction on endpoints such as death, cardiovascular events or CKD progression, changes in salt intake on blood pressure and other secondary risk factors were examined. Reducing salt by mean -73.51 mmol/day (95% CI -92.76 to -54.27), equivalent to 4.2 g or 1690 mg sodium/day, reduced systolic/diastolic blood pressure by -6.91/-3.91 mm Hg (95% CI -8.82 to -4.99/-4.80 to -3.02; 19 studies, 1405 participants; high certainty evidence). Albuminuria was reduced by 36% (95% CI 26 to 44) in six studies, five of which were carried out in people in the earlier stages of CKD (MD -0.44, 95% CI -0.58 to -0.30; 501 participants; high certainty evidence). The evidence is very uncertain about the effect of lower salt intake on weight, as the weight change observed (-1.32 kg, 95% CI -1.94 to -0.70; 12 studies, 759 participants) may have been due to fluid volume, lean tissue, or body fat. Lower salt intake may reduce extracellular fluid volume in the earlier stages of CKD (-0.87 L, 95% CI -1.17 to -0.58; 3 studies; 187 participants; low certainty evidence). The evidence is very uncertain about the effect of lower salt intake on reduction in antihypertensive dose (RR 2.45, 95% CI 0.98 to 6.08; 8 studies; 754 participants). Lower salt intake may lead to  symptomatic hypotension (RR 6.70, 95% CI 2.40 to 18.69; 6 studies; 678 participants; moderate certainty evidence). Data were sparse for other types of adverse events.

AUTHORS' CONCLUSIONS

We found high certainty evidence that salt reduction reduced blood pressure in people with CKD, and albuminuria in people with earlier stage CKD in the short-term. If such reductions could be maintained long-term, this effect may translate to clinically significant reductions in CKD progression and cardiovascular events. Research into the long-term effects of sodium-restricted diet for people with CKD is warranted.

Ex Vivo High Salt Activated Tumor-Primed CD4+T Lymphocytes Exert a Potent Anti-Cancer Response

Simple Summary

Cell based immunotherapy is rapidly emerging as a promising cancer treatment. Salt (sodium chloride) treatment to immune cell cultures is known to induce inflammatory activation. In our current study, we analyzed the anti-cancer ability of salt treatment on immune cells outside the host followed by reinfusion into the host. Using a pre-clinical breast cancer model, we demonstrated that external salt treatment on T-cell subset of immune cells produced a viable anti-cancer response, which may have future human clinical application.

Abstract

Cell based immunotherapy is rapidly emerging as a promising cancer treatment. A modest increase in salt (sodium chloride) concentration in immune cell cultures is known to induce inflammatory phenotypic differentiation. In our current study, we analyzed the ability of salt treatment to induce ex vivo expansion of tumor-primed CD4 (cluster of differentiation 4)+T cells to an effector phenotype. CD4+T cells were isolated using immunomagnetic beads from draining lymph nodes and spleens from tumor bearing C57Bl/6 mice, 28 days post-injection of Py230 syngeneic breast cancer cells. CD4+T cells from non-tumor bearing mice were isolated from splenocytes of 12-week-old C57Bl/6 mice. These CD4+T cells were expanded ex vivo with five stimulation cycles, and each cycle comprised of treatment with high salt (Δ0.035 M NaCl) or equimolar mannitol controls along with anti-CD3/CD28 monoclonal antibodies for the first 3 days, followed by the addition of interleukin (IL)-2/IL-7 cytokines and heat killed Py230 for 4 days. Ex vivo high salt treatment induced a two-fold higher Th1 (T helper type 1) expansion and four-fold higher Th17 expansion compared to equimolar mannitol treatment. Importantly, the high salt expanded CD4+T cells retained tumor-specificity, as demonstrated by higher in vitro cytotoxicity against Py230 breast cancer cells and reduced in vivo syngeneic tumor growth. Metabolic studies revealed that high salt treatment enhanced the glycolytic reserve and basal mitochondrial oxidation of CD4+T cells, suggesting a role of high salt in enhanced pro-growth anabolic metabolism needed for inflammatory differentiation. Mechanistic studies demonstrated that the high salt induced switch to the effector phenotype was mediated by tonicity-dependent transcription factor, TonEBP/NFAT5. Using a transgenic murine model, we demonstrated that CD4 specific TonEBP/NFAT5 knock out (CD4^cre/creNFAT5^flox/flox) abrogated the induction of the effector phenotype and anti-tumor efficiency of CD4+T cells following high salt treatment. Taken together, our data suggest that high salt-mediated ex vivo expansion of tumor-primed CD4+T cells could induce effective tumor specific anti-cancer responses, which may have a novel cell-based cancer immunotherapeutic application.

At-home determination of 24-h urine sodium excretion: Validation of chloride test strips and multiple spot samples

Sodium intake and compliance with dietary sodium modification are typically assessed using a 24-h urine collection analyzed using flame photometry, but this is inconvenient. Spot urine samples have been investigated as alternatives to 24-h collections, but their accuracy is poor. Since sodium and chloride are present in equal concentrations in dietary salt, chloride test strips may provide a suitable proxy for at-home measurement of urine sodium concentrations. We aimed to determine whether (i) chloride test strips provide a reliable measure of urinary sodium compared to the gold standard flame photometry and (ii) multiple spot samples accurately reflect 24-h urine sodium. We recruited 43 participants (19 males) aged 23.6 ± 0.6 years to complete multiple consecutive spot samples (morning and evening) along with a 24-h urine sodium collection. Urine 24-h sodium estimates using chloride test strips (114.6 ± 7.5 mmol/day) were highly correlated (r = 0.900, p < 0.0001) with flame photometry (121.1 ± 7.7 mmol/day) with a bias of -6.53 ± 22.2 mmol/day. Use of a three-spot sample average (both morning and evening spot samples) with a correction factor applied (122.9 ± 4.1 mmol/day) provided a good approximation of 24-h sodium measured by flame photometry (125.6 ± 9.0 mmol/day), with a bias of -2.55 ± 43.9 mmol/day. Chloride test strips applied to a 24-h urine collection provide a highly accurate measure of urinary sodium excretion, permitting convenient at-home sample collection and analysis. Their application to multiple spot samples provides a reasonable approximation of sodium excretion that can be used to conveniently monitor attempts at dietary sodium manipulation, without the inconvenience of completing a 24-h urine sample.

Locked on salt? Excessive consumption of high-sodium foods during COVID-19 presents an underappreciated public health risk: a review

Abrupt changes in food preferences and eating habits have induced an overlooked health risk during the coronavirus disease pandemic (COVID-19). Indeed, emerging evidence points to a major shift to consumption of high-sodium foods during the pandemic lockdowns in the population from different countries and cultures. High-sodium foods have sodium contents exceeding 500 mg per 100 g, and many processed and preserved foods fall into this category. Excessive dietary sodium intake is associated with chronic diseases including hypertension, cardiovascular diseases, and kidney diseases, and thus poses confounding risks during the pandemic. Here, we review food categories in consumers' shopping lists and food parcels delivered to people who needed assistance during the pandemic, when frozen meals, canned foods, instant foods, snacks, and other high-sodium foods gained substantial popularity. Such change in consumers' behavior is driven by several factors: the perceived risk of viral infection in grocery shopping trips, limited supplies and inflated prices of fresh produce, preference on foods with long shelf lives, and emotional eating. Moreover, the general low awareness of sodium contents in food has contributed to the increased consumption of high-sodium foods during the pandemic. We also discuss the possible effects on COVID-19 infection and severity caused by excessive sodium intake. We conclude that the public should be educated to maintain a healthy sodium intake during the pandemic, and measures should be adopted by governments and private donors in procuring food parcels with more balanced sodium contents to lower the risks of prolonged and excessive sodium intakes in the vulnerable population.

Dietary Protein Intake and Single-Nephron Glomerular Filtration Rate

High protein intake can increase glomerular filtration rate (GFR) in response to excretory overload, which may exacerbate the progression of kidney disease. However, the direct association between glomerular hemodynamic response at the single-nephron level and dietary protein intake has not been fully elucidated in humans. In the present study, we evaluated nutritional indices associated with single-nephron GFR (SNGFR) calculated based on corrected creatinine clearance (SNGFR_Cr). We retrospectively identified 43 living kidney donors who underwent enhanced computed tomography and kidney biopsy at the time of donation at Jikei University Hospital in Tokyo from 2007 to 2018. Total nephron number was estimated with imaging-derived cortical volume and morphometry-derived glomerular density. SNGFR_Cr was calculated by dividing the corrected creatinine clearance by the number of non-sclerosed glomeruli (Nglom_NSG). The mean (± standard deviation) Nglom_NSG/kidney and SNGFR_Cr were 685,000 ± 242,000 and 61.0 ± 23.9 nL/min, respectively. SNGFR_Cr was directly associated with estimated protein intake/ideal body weight (p = 0.005) but not with body mass index, mean arterial pressure, albumin, or sodium intake. These findings indicate that greater protein intake may increase SNGFR and lead to glomerular hyperfiltration.

Phosphorus and sodium contents in commercial wet foods for dogs and cats

It has been reported that wet foods for dogs and cats have high levels of sodium and phosphorus due to their composition. Therefore, this study aimed to evaluate the sodium and phosphorus contents in wet pet foods, and compare it to daily requirements for both species. Twenty‐five commercial wet foods for adult animals were evaluated, 13 for dogs and 12 for cats. The analyses’ results were compared to the European Pet Food Industry Federation (FEDIAF 2018) recommendations. All foods contained phosphorus and sodium amounts above minimum requirements. Three wet foods for dogs exceeded the safe upper limit for phosphorus, and four wet foods for dogs and three for cats exceeded 3.75 g of sodium/1,000 kcal metabolizable energy (ME), considered safe by FEDIAF. No studies were found at the present time evaluating whether higher sodium levels are safe for dogs and cats; however, consumption of high phosphorus diets has been associated with adverse effects on renal function parameters. Therefore, more studies are necessary to investigate the health implications of phosphorus and sodium concentrations observed in some foods evaluated in this research.

It has been reported that wet foods for dogs and cats have high levels of sodium and phosphorus due to their composition. Therefore, this study aimed to evaluate the sodium and phosphorus contents in wet pet foods, and compared to daily requirements for both species.

Role of NFAT5 in the Immune System and Pathogenesis of Autoimmune Diseases

The nuclear factor of activated T cells (NFAT5), also known as a tonicity-responsive enhancer-binding protein, was originally identified as a key transcription factor involved in maintaining cellular homeostasis against hypertonic and hyperosmotic environments. Although NFAT5 has been expressed and studied in various types of hyperosmolar tissues, evidence has emerged that NFAT5 plays a role in the development and activation of immune cells, especially T cells and macrophages. The immune-regulatory function of NFAT5 is achieved by inducing different target genes and different signaling pathways in both tonicity-dependent and -independent manners. Particularly in response to hyperosmotic stress, NFAT5 induces the generation of pathogenic T_H17 cells and pro-inflammatory macrophages, contributing to autoimmune and inflammatory diseases. Meanwhile, with tonicity-independent stimuli, including activation of the Toll-like receptors and inflammatory cytokines, NFAT5 also can be activated and promotes immune cell survival, proliferation, migration, and angiogenesis. Moreover, under isotonic conditions, NFAT5 has been implicated in the pathogenesis of a variety of inflammatory and autoimmune diseases including rheumatoid arthritis. This review describes the current knowledge of NFAT5, focusing on its immune-regulatory functions, and it highlights the importance of NFAT5 as a novel therapeutic target for chronic inflammatory diseases.

Estimating the urinary sodium excretion in patients with chronic kidney disease is not useful in monitoring the effects of a low-salt diet

Background

Several epidemiologic studies have suggested that the urine sodium excretion (USE) can be estimated in lieu of performing 24-hour urine collection. However, this method has not been verified in patients with chronic kidney disease (CKD) or in an interventional study. The purpose of this study was to evaluate the usefulness of estimating USE in a prospective low-salt diet education cohort (ESPECIAL).

Methods

A new formula was developed on the basis of morning fasting urine samples from 228 CKD patients in the ESPECIAL cohort. This formula was compared to the previous four formulas in the prediction of 24-hour USE after treatment with olmesartan and low-salt diet education.

Results

Most previously reported formulas had low predictability of the measured USE based on the ESPECIAL cohort. Only the Tanaka formula showed a small but significant bias (9.8 mEq/day, P < 0.05) with a low correlation (r = 0.34). In contrast, a new formula showed improved bias (-0.1 mEq/day) and correlation (r = 0.569) at baseline. This formula demonstrated no significant bias (-1.2 mEq/day) with the same correlation (r = 0.571) after 8 weeks of treatment with olmesartan. Intensive low-salt diet education elicited a significant decrease in the measured USE. However, none of the formulas predicted this change in the measured urine sodium after diet adjustment.

Conclusion

We developed a more reliable formula for estimating the USE in CKD patients. Although estimating USE is applicable in an interventional study, it may be unsuitable for estimating the change of individual sodium intake in a low-salt intervention study.

Sodium in feline nutrition

High sodium levels in cat food have been controversial for a long time. Nonetheless, high sodium levels are used to enhance water intake and urine volume, with the main objective of reducing the risk of urolithiasis. This article is a review of current evidence of the putative risks and benefits of high dietary sodium levels. Its secondary aim is to report a possible safe upper limit (SUL) for sodium intake. The first part of the manuscript is dedicated to sodium physiology, with a focus on the mechanisms of sodium homeostasis. In this respect, there is only few information regarding possible interactions with other minerals. Next, the authors address how sodium intake affects sodium balance; knowledge of these effects is critical to establish recommendations for sodium feed content. The authors then review the consequences of changes in sodium intake on feline health, including urolithiasis, blood pressure changes, cardiovascular alterations and kidney disease. According to recent, long-term studies, there is no evidence of any deleterious effect of dietary sodium levels as high as 740 mg/MJ metabolizable energy, which can therefore be considered the SUL based on current knowledge.

Altered dietary salt intake for people with chronic kidney disease

BACKGROUND

Salt intake shows great promise as a modifiable risk factor for reducing heart disease incidence and delaying kidney function decline in people with chronic kidney disease (CKD). However, a clear consensus of the benefits of reducing salt in people with CKD is lacking.

OBJECTIVES

This review evaluated the benefits and harms of altering dietary salt intake in people with CKD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 13 January 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared two or more levels of salt intake in people with any stage of CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility and conducted risk of bias evaluation. Results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Mean effect sizes were calculated using the random-effects models.

MAIN RESULTS

We included eight studies (24 reports, 258 participants). Because duration of the included studies was too short (1 to 26 weeks) to test the effect of salt restriction on endpoints such as mortality, cardiovascular events or CKD progression, changes in salt intake on blood pressure and other secondary risk factors were applied. Three studies were parallel RCTs and five were cross-over studies. Selection bias was low in five studies and unclear in three. Performance and detection biases were low in two studies and unclear in six. Attrition and reporting biases were low in four studies and unclear in four. One study had the potential for high carryover effect; three had high risk of bias from baseline characteristics (change of medication or diet) and two studies were industry funded.There was a significant reduction in 24 hour sodium excretion associated with low salt interventions (range 52 to 141 mmol) (8 studies, 258 participants: MD -105.86 mmol/d, 95% CI -119.20 to -92.51; I(2) = 51%). Reducing salt intake significantly reduced systolic blood pressure (8 studies, 258 participants: MD -8.75 mm Hg, 95% CI -11.33 to -6.16; I(2) = 0%) and diastolic blood pressure (8 studies, 258 participants: MD -3.70 mm Hg, 95% CI -5.09 to -2.30; I(2) = 0%). One study reported restricting salt intake reduced the risk of oedema by 56%. Salt restriction significantly increased plasma renin activity (2 studies, 71 participants: MD 1.08 ng/mL/h, 95% CI 0.51 to 1.65; I(2) = 0%) and serum aldosterone (2 studies, 71 participants: 6.20 ng/dL (95% CI 3.82 to 8.58; I(2) = 0%). Antihypertensive medication dosage was significantly reduced with a low salt diet (2 studies, 52 participants): RR 5.48, 95% CI 1.27 to 23.66; I(2) = 0%). There was no significant difference in eGFR (2 studies, 68 participants: MD -1.14 mL/min/1.73 m(2), 95% CI -4.38 to 2.11; I(2) = 0%), creatinine clearance (3 studies, 85 participants): MD -4.60 mL/min, 95% CI -11.78 to 2.57; I(2) = 0%), serum creatinine (5 studies, 151 participants: MD 5.14 µmol/L, 95% CI -8.98 to 19.26; I(2) = 59%) or body weight (5 studies, 139 participants: MD -1.46 kg; 95% CI -4.55 to 1.64; I(2) = 0%). There was no significant change in total cholesterol in relation to salt restriction (3 studies, 105 participants: MD -0.23 mmol/L, 95% CI -0.57 to 0.10; I(2) = 0%) or symptomatic hypotension (2 studies, 72 participants: RR 6.60, 95% CI 0.77 to 56.55; I(2) = 0%). Salt restriction significantly reduced urinary protein excretion in all studies that reported proteinuria as an outcome, however data could not be meta-analysed.

AUTHORS' CONCLUSIONS

We found a critical evidence gap in long-term effects of salt restriction in people with CKD that meant we were unable to determine the direct effects of sodium restriction on primary endpoints such as mortality and progression to end-stage kidney disease (ESKD). We found that salt reduction in people with CKD reduced blood pressure considerably and consistently reduced proteinuria. If such reductions could be maintained long-term, this effect may translate to clinically significant reductions in ESKD incidence and cardiovascular events. Research into the long-term effects of sodium-restricted diet for people with CKD is warranted, as is investigation into adherence to a low salt diet.

When to increase or reduce sodium loading in the management of fluid volume status during acute decompensated heart failure

Sodium restriction has been believed to be indispensible to manage fluid overload during acute decompensated heart failure (ADHF). However, recently, it was reported that a change in aggression of sodium and water restriction did not affect the outcome of ADHF. In contrast, current data suggest that small amount of hypertonic saline solution with high-dose furosemide produces an improvement in haemodynamic and clinical parameters without any severe adverse effects. In this perspective, first, we are going to describe the effects of sodium loading on neurohormonal activation, body's sodium balance, and renal function in chronic heart failure and the efficacy of loop diuretics in ADHF. Then, we are going to explain the possible mechanisms by which sodium loading enhances the efficacy of loop diuretics and about the clinical conditions during which sodium loading should be avoided.

Association of urinary sodium and potassium excretion with blood pressure

BACKGROUND

Higher levels of sodium intake are reported to be associated with higher blood pressure. Whether this relationship varies according to levels of sodium or potassium intake and in different populations is unknown.

METHODS

We studied 102,216 adults from 18 countries. Estimates of 24-hour sodium and potassium excretion were made from a single fasting morning urine specimen and were used as surrogates for intake. We assessed the relationship between electrolyte excretion and blood pressure, as measured with an automated device.

RESULTS

Regression analyses showed increments of 2.11 mm Hg in systolic blood pressure and 0.78 mm Hg in diastolic blood pressure for each 1-g increment in estimated sodium excretion. The slope of this association was steeper with higher sodium intake (an increment of 2.58 mm Hg in systolic blood pressure per gram for sodium excretion >5 g per day, 1.74 mm Hg per gram for 3 to 5 g per day, and 0.74 mm Hg per gram for <3 g per day; P<0.001 for interaction). The slope of association was steeper for persons with hypertension (2.49 mm Hg per gram) than for those without hypertension (1.30 mm Hg per gram, P<0.001 for interaction) and was steeper with increased age (2.97 mm Hg per gram at >55 years of age, 2.43 mm Hg per gram at 45 to 55 years of age, and 1.96 mm Hg per gram at <45 years of age; P<0.001 for interaction). Potassium excretion was inversely associated with systolic blood pressure, with a steeper slope of association for persons with hypertension than for those without it (P<0.001) and a steeper slope with increased age (P<0.001).

CONCLUSIONS

In this study, the association of estimated intake of sodium and potassium, as determined from measurements of excretion of these cations, with blood pressure was nonlinear and was most pronounced in persons consuming high-sodium diets, persons with hypertension, and older persons. (Funded by the Heart and Stroke Foundation of Ontario and others.).

Development and validation of a dietary screening tool for high sodium consumption in Australian renal patients

OBJECTIVE

The study objective was to develop and evaluate the feasibility and validity of a self-administered Scored Sodium Questionnaire (SSQ) for use in the routine clinical care of Australian chronic kidney disease (CKD) patients.

DESIGN AND METHODS

The study took place in community-based outreach clinics using a multidisciplinary model of care. Assessment of sources of dietary sodium intake in the target population used comprehensive diet history interviews (Phase 1) to inform development of a 10-item food frequency questionnaire that was scored and validated using 24-hour urinary sodium and 2 alternative dietary intake methods (Phase 2). Subjects were adults with CKD Stages 3 to 5 (Phase 1 n = 30; Phase 2 n = 47).

INTERVENTION

On a single day, participants (n = 47) completed the SSQ, feasibility survey, 24-hour urine collection, and 24-hour food record. A diet history interview was also conducted to confirm sodium intake on the day of data collection reflected habitual intake.

MAIN OUTCOME MEASURE

Validity of the SSQ score was confirmed by correlation with 24-hour urine sodium. Validity of a cutpoint on the SSQ score to correctly identify high- versus low-sodium consumers was confirmed by receiver operating characteristic curve analysis: area under the curve, sensitivity, and specificity.

RESULTS

Total SSQ score correlated significantly with 24-hour urine sodium (r = 0.371; P = .031). Correlation between 24-hour food record and diet history sodium confirmed consumption on the data collection day reflected habitual intake (r = 0.701; P ≤ .001). A cutpoint of 65 or greater on the SSQ score was confirmed as valid to identify high-sodium consumers: area under the curve 0.713, sensitivity 61%, and specificity 82%.

CONCLUSION

The SSQ is feasible and valid to assess habitual sodium intake in the Australian CKD population and to identify high-sodium consumers for referral to individualized counseling on a low-sodium diet.

The comparison of 24-hour urinary sodium, albumin, and protein excretion in chronic kidney disease patients with type 2 diabetes mellitus using insulin detemir or insulin glargine

BACKGROUND AND OBJECTIVE

Insulin detemir induces bodyweight loss or less weight gain in patients with type 2 diabetes mellitus. However, in contrast to insulin detemir, insulin glargine has no weight loss effect. Increased sodium excretion has been speculated to be one of the mechanisms of weight loss by insulin detemir. However, there are no studies in the literature comparing sodium excretion between patients using insulin detemir and those using insulin glargine. There are also no studies comparing the excretion of urinary albumin and urinary protein in chronic kidney disease (CKD) patients using insulin detemir or insulin glargine. Thus, the aim of the current study was to compare the effects of insulin detemir and insulin glargine on sodium, albumin, and protein excretion in patients with various stages of CKD and concomitant type 2 diabetes.

METHODS

Demographic, clinical, and laboratory data were evaluated for all patients. Hypoglycemic attacks, appetite score, 24-h urinary sodium, albumin, and protein excretion were also measured.

RESULTS

A total of 47 patients (23 taking insulin detemir, 24 taking insulin glargine) were included in the study. There were no differences with respect to 24-h sodium (p = 0.694), albumin (p = 0.297), or protein excretion (p = 0.202) between patient groups. Appetite and hypoglycemic attacks also did not differ between groups. Use of insulin detemir or insulin glargine was not related to sodium, albumin, and protein excretion in stepwise regression analysis.

CONCLUSION

There was no difference between insulin detemir and insulin glargine with respect to sodium, albumin, and protein excretion in type 2 diabetic CKD patients. Studies are needed both in CKD patients and those with normal renal function to highlight mechanisms regarding the weight loss effect unique to insulin detemir.

Sodium recommendations for special populations and the resulting implications

Based on the most recent Dietary Guidelines for Americans, sodium recommendations are set at 2,300 mg for the general population and 1,500 mg for special populations. However, sodium intake among adults has been shown to be much higher than this; on average 3,436 mg. The Centers for Disease Control and Prevention notes that special populations (those with hypertension, African Americans, and those 40 years of age and older) make up 70% of adults in the United States. Excess sodium in the diet has been shown to contribute to problems such as blood pressure abnormalities, kidney function problems, and congestive heart failure, which account for a large sum of health care costs in the United States. The purpose of this review and accompanying three case studies was to explore if adherence to the sodium recommendations for special populations is feasible. Current literature shows that while a food industry-wide sodium reduction would help reduce overall sodium intake, adherence to low-sodium diets is difficult for the majority of individuals. Three case studies were completed which looked at subjects with a sodium recommendation of 1,500 mg. None of the participants met the recommendation, were aware of their daily sodium intake or knew how much they should be consuming. The snapshot provided by these case studies suggests further research is warranted. Because of the current state of sodium in the American diet, a combination of personal interventions coupled with widespread industry sodium reduction would be the most beneficial way to reduce dietary sodium for most individuals.

High-salt diet increases glomerular ACE/ACE2 ratio leading to oxidative stress and kidney damage

BACKGROUND

Angiotensin II (AngII) contributes to salt-driven kidney damage. In this study, we aimed at investigating whether and how the renal damage associated with a high-salt diet could result from changes in the ratio between angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2).

METHODS

Forty-eight rats randomly allocated to three different dietary contents of salt were studied for 4 weeks after undergoing a left uninephrectomy. We focussed on kidney functional, structural and molecular changes. At the same time, we studied kidney molecular changes in 20 weeks old Ace2-knockout mice (Ace2KO), with and without ACE inhibition.

RESULTS

A high salt content diet significantly increased the glomerular ACE/ACE2 ratio. This was associated with increased oxidative stress. To assess whether these events were related, we measured renal oxidative stress in Ace2KO, and found that the absence of ACE2 promoted oxidative stress, which could be prevented by ACE inhibition.

CONCLUSION

One of the mechanisms by which a high-salt diet leads to renal damage seems to be the modulation of the ACE/ACE2 ratio which in turn is critical for the cause of oxidative stress, through AngII.

Potentially modifiable factors affecting the progression of autosomal dominant polycystic kidney disease

BACKGROUND AND OBJECTIVES

The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) was created to identify markers of disease progression in patients with autosomal dominant polycystic kidney disease (ADPKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Linear mixed models were utilized to model effects of baseline parameters on changes in natural-log (ln)-transformed total kidney volume (TKV) and iothalamate clearance (GFR) across time in CRISP participants (creatinine clearance at entry >70 ml/min). Stepwise selection was used to obtain a final main effect model.

RESULTS

TKV increased from year to year, whereas GFR uncorrected for body surface area (BSA) decreased only at year 6. Higher lnTKV and urine sodium excretion (U(Na)V), lower serum HDL-cholesterol, and younger age at baseline associated with greater lnTKV growth from baseline to year 3 and to year 6. Higher lnTKV at baseline associated with greater GFR decline from year 1 to year 3 and to year 6. Higher BSA and 24-hour urine osmolality at baseline associated with greater GFR decline from year 1 to year 6. Higher U(Na)V and lower serum HDL-cholesterol at baseline associated with greater GFR decline from year 1 to year 6 by univariate analysis only. Associations seen during year 1 to year 6 (not seen during year 1 to year 3) reflect the time lag between structural and functional disease progression.

CONCLUSIONS

Serum HDL-cholesterol, U(Na)V, and 24-hour urine osmolality likely affect ADPKD progression. To what extent their modification may influence the clinical course of ADPKD remains to be determined.

Disparate effects of eplerenone, amlodipine and telmisartan on podocyte injury in aldosterone-infused rats

BACKGROUND

Several studies in patients with primary aldosteronism (PA) have suggested that aldosterone (ALD) is directly contributing to albuminuria. However, there are limited data pertaining to the direct role of ALD in in vivo models in regard to the induction of renal injury and the involved mechanisms. In the present study, we established a high-dose ALD-infused rat model to evaluate urinary albumin excretion rate (UAER) and podocyte damage. Moreover, we studied the effect of eplerenone (EPL), telmisartan (TEL) and amlodipine (AML) on ALD-induced renal structural and functional changes.

METHODS

Immunohistochemical and real-time PCR analyses, and TUNEL assays were performed to evaluate nephrin expression and podocyte injury.

RESULTS

ALD-receiving rats (ARR) showed a progressive increase in BP, UAER and proteinuria when compared with control rats (CR). Conversely, BP was significantly reduced in ALD + EPL (A/ERR)-, ALD + AML (A/ARR)- and ALD + TEL (A/TRR)-treated rats. However, UAER and proteinuria were decreased only in A/ERR and A/TRR, but not in A/ARR. Only EPL administration provided protection against ALD-induced podocyte apoptosis. Renal tissue of ARR revealed enhanced expression of nephrin protein and mRNA. This effect of ALD was inhibited by EPL, but not by TEL or AML. Conclusions. ALD induces direct glomerular injury independent of its haemodynamic effects; this effect of ALD is, at least in part, mediated through activation of the mineralocorticoid receptor.

Workers intake too much salt from dishes of eating out and food service cafeterias; direct chemical analysis of sodium content

The average sodium intake of Koreans was reported to be 5,279.9 mg/day, which is one of the highest intake levels worldwide. The average Koreans intake 19.6% of sodium from kimchi, showing kimchi as the main contributor of sodium in this country (Ministry of Health and Welfare, 2005). The sodium content of dishes that are frequently chosen by workers, and which were served by foodservice cafeterias were chemically analyzed. The average sodium content of one meal provided by 10 foodservice cafeterias was 2,777.7 mg. Twenty-one, one-dish-meals, frequently chosen by workers for a lunch menu, were collected at 4 different restaurants for each menu by one male, aged in the twenties and analyzed chemically also. Workers who eat lunch at a workplace cafeteria everyday could intake about 8 g of salt at a one-time meal and those who eat out for a one-dish-meal would intake 3-8 g of salt without counting sodium content from the side dishes. From these study results, one could estimate that over 10 g of salt could be possible for a single meal for workers who eat out everyday. A nationwide nutrition campaign and education for low salt diets for restaurant owners and foodservice providers should be seriously considered.

Mineralocorticoid receptor blockers and chronic kidney disease

The increasing prevalence of chronic kidney disease (CKD) and the public health initiatives for detection and slowing its progression have placed special emphasis on controlling proteinuria and the renin-angiotensin-aldosterone system (RAAS). In addition to the traditional blockers of angiotensin-converting enzyme and angiotensin receptors, mineralocorticoid receptor blockers (MRBs) have come into focus as anti-proteinuric agents with moderate anti-hypertensive effects. The beneficial effects of MRBs on mortality in patients with cardiac disease have been well described. We review the role of aldosterone in end-organ damage, the rationales for using MRBs as adjuncts to angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in treating CKD, and the adverse effects that may occur when these agents are used in combination. Suggestions are included for avoiding serious adverse events in CKD patients treated with MRBs. There is a clearly defined need for prospective outcome studies focused on cardiovascular mortality as well as progression of CKD in patients treated with MRBS and other inhibitors of the RAAS.