Dietary sodium restriction: a neglected therapeutic opportunity in chronic kidney disease

Apical tubular complement activation and the loss of kidney function in proteinuric kidney diseases

Many kidney diseases are associated with proteinuria. Since proteinuria is independently associated with kidney function loss, anti-proteinuric medication, often in combination with dietary salt restriction, comprises a major cornerstone in the prevention of progressive kidney failure. Nevertheless, complete remission of proteinuria is very difficult to achieve, and most patients with persistent proteinuria slowly progress toward kidney failure. It is well-recognized that proteinuria leads to kidney inflammation and fibrosis via various mechanisms. Among others, complement activation at the apical side of the proximal tubular epithelial cells is suggested to play a crucial role as a cause of progressive loss of kidney function. However, hitherto limited attention is given to the pathophysiological role of tubular complement activation relative to glomerular complement activation. This review aims to summarize the evidence for tubular epithelial complement activation in proteinuric kidney diseases in relation to loss of kidney function.

Self-Reported Frequency of Adding Salt to Food and Risk of Incident Chronic Kidney Disease

Importance

The self-reported frequency of adding salt to foods could reflect a person's long-term salt taste preference, and salt intake has been associated with increased risk of cardiovascular diseases (CVD). Whether self-reported adding of salt to foods is associated with increased risk of chronic kidney disease (CKD) remains unknown.

Objective

To prospectively examine the association of self-reported frequency of adding salt to foods with incident CKD risk in a general population of adults.

Design, Setting, and Participants

This population-based cohort study evaluated UK Biobank participants aged 37 to 73 years who were free of CKD at baseline. Participants were enrolled from 2006 to 2010 and prospectively followed up for disease diagnosis. Data were analyzed from October 2022 to April 2023.

Exposure

Self-reported frequency of adding salt to foods, categorized into never or rarely, sometimes, usually, and always.

Main Outcome and Measure

Incident CKD cases were defined by diagnostic codes. Hazard ratios (HRs) and 95% CIs were calculated by using Cox proportional hazards models. Models were adjusted for several potential confounders including age, sex, race and ethnicity, Townsend Deprivation Index, estimated glomerular filtration rate (eGFR), body mass index, (BMI), smoking status, alcohol drinking status, regular physical activity, high cholesterol, diabetes, CVD, hypertension, infectious disease, immune disease, and nephrotoxic drugs use at baseline.

Results

Within a cohort of 465 288 individuals (mean [SD] age 56.32 [8.08] years; 255 102 female participants [54.83%]; 210 186 male participants [45.17%]), participants with higher self-reported frequency of adding salt to foods were more likely to have a higher BMI, higher Townsend Deprivation Index score, and diminished baseline eGFR compared with those who reported a lower frequency of adding salt to foods. Participants who added salt to their foods were also more likely than those who did not add salt to their foods to be current smokers and have diabetes or CVD at baseline. During a median (IQR) follow-up of 11.8 (1.4) years, 22 031 incident events of CKD were documented. Higher self-reported frequency of adding salt to foods was significantly associated with a higher CKD risk after adjustment for covariates. Compared with those who reported never or rarely adding salt to foods, those who reported sometimes adding salt to food (adjusted HR [aHR], 1.04; 95% CI, 1.00-1.07), those who reported usually adding salt to food (aHR, 1.07; 95% CI, 1.02-1.11), and those who reported always adding salt to food (aHR, 1.11; 95% CI, 1.05-1.18) had an increased risk of CKD (P for trend < .001). In addition, eGFR, BMI, and physical activity significantly modified the associations, which were more pronounced among participants with a higher eGFR, lower BMI, or lower level of physical activity.

Conclusions and Relevance

In this cohort study of 465 288 individuals, a higher self-reported frequency of adding salt to foods was associated with a higher risk of CKD in the general population. These findings suggest that reducing the frequency of adding salt to foods at the table might be a valuable strategy to lower CKD risk in the general population.

Lifestyle factors related to prevalent chronic disease multimorbidity: A population-based cross-sectional study

BACKGROUND

Multimorbidity is associated with poor quality of life, polypharmacy, health care costs and mortality, with those affected potentially benefitting from a healthy lifestyle. We assessed a comprehensive set of lifestyle factors in relation to multimorbidity with major chronic diseases.

METHODS

This cross-sectional study utilised baseline data for adults from the prospective Lifelines Cohort in the north of the Netherlands (N = 79,345). We defined multimorbidity as the co-existence of two or more chronic diseases (i.e. cardiovascular disease, cancer, respiratory disease, type 2 diabetes) and evaluated factors in six lifestyle domains (nutrition, physical (in)activity, substance abuse, sleep, stress, relationships) among groups by the number of chronic diseases (≥2, 1, 0). Multinomial logistic regression models were created, adjusted for appropriate confounders, and odds ratios (OR) with 95% confidence intervals (95%CI) were reported.

RESULTS

3,712 participants had multimorbidity (4.7%, age 53.5 ± 12.5 years), and this group tended to have less healthy lifestyles. Compared to those without chronic diseases, those with multimorbidity reported physical inactivity more often (OR, 1.15; 95%CI, 1.06-1.25; not significant for one condition), chronic stress (OR, 2.14; 95%CI, 1.92-2.38) and inadequate sleep (OR, 1.70; 95%CI, 1.41-2.06); as expected, they more often watched television (OR, 1.70; 95%CI, 1.42-2.04) and currently smoked (OR, 1.91; 95%CI, 1.73-2.11), but they also had lower alcohol intakes (OR, 0.66; 95%CI, 0.59-0.74).

CONCLUSIONS

Chronic stress and poor sleep, in addition to physical inactivity and smoking, are lifestyle factors of great concern in patients with multimorbidity.

Nutritional Treatment as a Synergic Intervention to Pharmacological Therapy in CKD Patients

Nutritional and pharmacological therapies represent the basis for non-dialysis management of CKD patients. Both kinds of treatments have specific and unchangeable features and, in certain cases, they also have a synergic action. For instance, dietary sodium restriction enhances the anti-proteinuric and anti-hypertensive effects of RAAS inhibitors, low protein intake reduces insulin resistance and enhances responsiveness to epoetin therapy, and phosphate restriction cooperates with phosphate binders to reduce the net phosphate intake and its consequences on mineral metabolism. It can also be speculated that a reduction in either protein or salt intake can potentially amplify the anti-proteinuric and reno-protective effects of SGLT2 inhibitors. Therefore, the synergic use of nutritional therapy and medications optimizes CKD treatment. Quality of care management is improved and becomes more effective when compared to either treatment alone, with lower costs and fewer risks of unwanted side effects. This narrative review summarizes the established evidence of the synergistic action carried out by the combination of nutritional and pharmacological treatments, underlying how they are not alternative but complementary in CKD patient care.

Estimated Impact of Achieving the Australian National Sodium Reduction Targets on Blood Pressure, Chronic Kidney Disease Burden and Healthcare Costs: A Modelling Study

Excess sodium intake raises blood pressure which increases the risk of chronic kidney disease (CKD). We aimed to estimate the impact of reduced sodium intake on future CKD burden in Australia. A multi-cohort proportional multistate lifetable model was developed to estimate the potential impact on CKD burden and health expenditure if the Australian Suggested Dietary Target (SDT) and the National Preventive Health Strategy 2021-2030 (NPHS) sodium target were achieved. Outcomes were projected to 2030 and over the lifetime of adults alive in 2019. Achieving the SDT and NPHS targets could lower population mean systolic blood pressure by 2.1 mmHg and 1.7 mmHg, respectively. Compared to normal routines, attaining the SDT and NPHS target by 2030 could prevent 59,220 (95% UI, 53,140-65,500) and 49,890 (44,377-55,569) incident CKD events, respectively, while postponing 568 (479-652) and 511 (426-590) CKD deaths, respectively. Over the lifetime, this generated 199,488 health-adjusted life years (HALYs) and AUD 644 million in CKD healthcare savings for the SDT and 170,425 HALYs and AUD 514 million for the NPHS. CKD due to hypertension and CKD due to other/unspecified causes were the principal contributors to the HALY gains. Lowering sodium consumption in Australia could deliver substantial CKD health and economic benefits.

Obesity and Chronic Kidney Disease A Current Review

Background

Obesity poses significant challenges to healthcare globally, particularly through its bi-directional relationship with co-morbid metabolic conditions such as type 2 diabetes and hypertension. There is also emerging evidence of an association between obesity and chronic kidney disease (CKD) which is less well characterized.

Methods

A literature search of electronic libraries was conducted to identify and present a narrative review of the interplay between obesity and CKD.

Findings

Obesity may predispose to CKD directly as it is linked to the histopathological finding of obesity-related glomerulopathy and indirectly through its widely recognized complications such as atherosclerosis, hypertension, and type 2 diabetes. The biochemical and endocrine products of adipose tissue contribute to pathophysiological processes such as inflammation, oxidative stress, endothelial dysfunction, and proteinuria. The prevention and management of obesity may prove critical in counteracting both the development and advancement of CKD. Moreover, measures of abdominal adiposity such as waist circumference, are generally associated with worse morbidity and mortality in individuals receiving maintenance hemodialysis.

Conclusion

Obesity is a risk factor for the onset and progression of CKD and should be recognized as a potential target for a preventative public health approach to reduce CKD rates within the general population. Future research should focus on the use of glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors in patients with CKD and obesity due to their multi-faceted actions on major outcomes.

Effects of Oral Bicarbonate Supplementation on the Cardiovascular Risk Factors and Serum Nutritional Markers in Non-Dialysed Chronic Kidney Disease Patients

Background and Objectives: Kidneys play a key role in maintaining the acid−base balance. The aim of this study was to evaluate the effect of a 3-month oral sodium bicarbonate administration on arterial wall stiffness, arterial pressure and serum nutritional markers in non-dialysed patients with chronic kidney disease (CKD) stages 3−5 and metabolic acidosis. Methods: Eighteen CKD patients with eGFR < 45 mL/min/1.73 m2 and capillary blood bicarbonate (HCO3) < 22 mmol/L were enrolled in this single-centre, prospective study. Anthropometric parameters, pulse wave velocity, 24-h ambulatory blood pressure measurements, blood and urine parameters were assessed at the beginning and at the end of the study. The patients received supplementation with 2 g of sodium bicarbonate daily for three months. Results: A significant increase of pH: 7.32 ± 0.06 to 7.36 ± 0.06; p = 0.025, HCO3 from 18.7 mmol/L (17.7−21.3) to 22.2 mmol/L (20.2−23.9); p < 0.001 and a decrease in base excess from −6.0 ± 2.4 to −1.9 ± 3.1 mmol/L; p < 0.001 were found. An increase in serum total protein from 62.7 ± 6.9 to 65.8 ± 6.2; p < 0.013 and albumin from 37.3 ± 5.4 to 39.4 ± 4.8; p < 0.037 but, also, NT-pro-BNP (N-Terminal Pro-B-Type Natriuretic Peptide) from 794.7 (291.2−1819.0) to 1247.10 (384.7−4545.0); p < 0.006, CRP(C Reactive Protein) from 1.3 (0.7−2.9) to 2.8 (1.1−3.1); p < 0.025 and PTH (parathyroid hormone) from 21.5 ± 13.7 to 27.01 ± 16.3; p < 0.006 were observed, as well as an increase in erythrocyte count from 3.4 ± 0.6 to 3.6 ± 0.6; p < 0.004, haemoglobin from 10.2 ± 2.0 to 11.00 ± 1.7; p < 0.006 and haematocrit from 31.6 ± 6.00 to 33.6 ± 4.8; p < 0.009. The mean eGFR during sodium bicarbonate administration did not change significantly: There were no significant differences in pulse wave velocity or in the systolic and diastolic BP values. Conclusion: The administration of sodium bicarbonate in non-dialysed CKD patients in stages 3−5 improves the parameters of metabolic acidosis and serum nutritional markers; however, it does not affect the blood pressure and vascular stiffness.

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25%-35% of phosphorus, 12%-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

Potential Novel Benefits of Sodium Restriction in Chronic Kidney Disease

Chronic kidney disease is a global public health issue, and it has been considered as the epidemic of the 21st century. Therefore, all initiatives addressed to slow down the evolution and complications of this condition should be well received. While the effects of salt reduction on cardiovascular disease have some controversial issues, in chronic kidney disease, such a policy is beneficial in multiple aspects. In chronic kidney disease patients, dietary sodium restriction is regularly recommended to control extracellular fluid expansion, hypertension and cardiovascular risk. Instead, the effects of sodium reduction on chronic kidney disease progression are still controversial. In the last years, potentially beneficial effects of a low sodium diet on chronic kidney disease evolution have emerged. Firstly, recent magnetic resonance-based findings of increased Na depots in skin and muscle associated with renal function, ageing and sodium intake open a vast body of investigation as a potential tool for monitoring effects of sodium restriction. In this narrative review, we also discussed novel aspects of sodium restriction in chronic kidney disease to manage metabolic acidosis as well as renal effects on fibroblast growth factor 23 or gut microbiota. Beyond current evidence, these approaches showed that common findings of kidney failure environment such as sodium -sensitivity, micro-inflammation, arterial stiffness metabolic acidosis and sarcopenia could be delayed controlling dietary sodium. Additional studies are now needed in populations with chronic kidney disease to confirm these new findings, addressed to slow down the evolution and complications of this condition.

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25-35% of phosphorus, 12-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

Dietary satisfaction and quality of life in chronic kidney disease patients on low-protein diets: a multicentre study with long-term outcome data (TOrino-Pisa study)

BACKGROUND

Concerns about adherence and quality of life (QoL) limit the diffusion of low-protein diets (LPDs) as a way to slow chronic kidney disease (CKD) progression and postpone dialysis. The aim of this multicentre study is to assess dietary satisfaction in stable CKD patients.

METHODS

This was a multicentre cross-sectional study with long-term follow-up data. Prevalent patients on LPD for at least 6 months were selected in four Italian centres. QoL was assessed using the World Health Organization Quality of Life questionnaire, and diet satisfaction with the Modification of Diet in Renal Disease satisfaction questionnaire. Comorbidity was assessed by Charlson Comorbidity Index, estimated glomerular filtration rate (eGFR) was calculated by the CKD Epidemiology Collaboration equation and protein intake by Maroni-Mitch formula. Survival was analysed with Kaplan-Meier curves and Cox Proportional Hazard Model.

RESULTS

Four hundred and twenty-two CKD Stages 3-5 patients were enrolled. Over 95% were on moderately restricted diets (0.6 g/kg/day). Compliance was good (protein intake: 0.59 g/kg/day at baseline, 0.72 at the end of follow-up). Median dietary satisfaction was 4 on a 1-5 scale. QoL was not affected by the type of diet, but was influenced by age, comorbidity and setting of care. Two years later, at the end of follow-up, 66.6% of the patients were still on a diet; the main causes of discontinuation were dialysis and death. The dropout rate was low (5.5%); in Cox analysis, patient and renal survival were influenced by age and eGFR, but not by QoL, setting of care or type of diet.

CONCLUSIONS

LPDs are compatible with high dietary satisfaction and minimal dropout, at least in patients who are able to follow such a diet for at least 6 months.

Results of the CARDIA study suggest that higher dietary potassium may be kidney protective

The association between dietary sodium and potassium intake with the development of kidney disease remains unclear, particularly among younger individuals. Here, we determined whether dietary sodium and potassium intake are associated with incident chronic kidney disease (CKD) using data from 1,030 adults (age 23-35 in 1990-1991) from the Coronary Artery Risk Development In Young Adults study, based on repeated measurements of estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (ACR) from 1995 through 2015. Urinary sodium and potassium excretion (mg/day), calculated from three 24-hour urine collections in 1990-1991, were averaged to measure sodium and potassium intake. Serum creatinine was used to calculate eGFR using the CKD EPI equation; spot urine albumin and creatinine were used to calculate ACR, each at five visits from 1995-1996 through 2015-2016. CKD was defined as decreased eGFR (under 60 ml/min/1.73m2) or the development of albuminuria (ACR over 30 mg/g). We used log binomial regression models adjusted for socio-demographic, behavioral, and clinical factors to determine whether sodium and potassium intake were associated with incident CKD (decreased eGFR or developed albuminuria) among those free of CKD in 1995. Dietary sodium intake was not significantly associated with incident CKD. However, every 1,000 mg/day increment of potassium intake in 1990 was significantly associated with a 29% lower risk of incident albuminuria (relative risk 0.71, 95% confidence interval 0.53, 0.95), but not eGFR. Thus, higher dietary potassium intake may protect against the development of kidney damage, particularly albuminuria.

Advances in management of chronic metabolic acidosis in chronic kidney disease

PURPOSE OF REVIEW

Chronic metabolic acidosis is a common complication of chronic kidney disease (CKD) and is associated with adverse consequences, such as CKD progression and muscle wasting. We review the findings from recent clinical trials that have examined the effects of sodium bicarbonate therapy and veverimer in patients with CKD and chronic metabolic acidosis.

RECENT FINDINGS

There are four recent clinical trials on chronic metabolic acidosis of CKD. In a pilot, cross-over study, 6 weeks of sodium bicarbonate therapy improved vascular endothelial function, measured by brachial artery flow-mediated dilation. In a single-center, randomized, open-label study, 6 months of sodium bicarbonate therapy increased muscle mass and lean body mass, and preserved kidney function. The other two clinical trials (phase 1/2 and phase 3 studies) examined the effects of veverimer, which is a hydrochloric acid binder. The phase 3 study showed that 12-weeks of veverimer increased serum bicarbonate levels and might improve physical function. The effects of veverimer on CKD progression, physical function and cardiovascular endpoints as well as its long-term safety are yet to be determined.

SUMMARY

Recent studies suggest that sodium bicarbonate therapy may improve vascular endothelial function and muscle mass, and preserve renal function. Veverimer increases serum bicarbonate level and could be a potential new therapeutic option for treating chronic metabolic acidosis.

Sodium Intake and Target Organ Damage in Hypertension-An Update about the Role of a Real Villain

Salt intake is too high for safety nowadays. The main active ion in salt is sodium. The vast majority of scientific evidence points out the importance of sodium restriction for decreasing cardiovascular risk. International Guidelines recommend a large reduction in sodium consumption to help reduce blood pressure, organ damage, and cardiovascular risk. Regulatory authorities across the globe suggest a general restriction of sodium intake to prevent cardiovascular diseases. In spite of this seemingly unanimous consensus, some researchers claim to have evidence of the unhealthy effects of a reduction of sodium intake, and have data to support their claims. Evidence is against dissenting scientists, because prospective, observational, and basic research studies indicate that sodium is the real villain: actual sodium consumption around the globe is far higher than the safe range. Sodium intake is directly related to increased blood pressure, and independently to the enlargement of cardiac mass, with a possible independent role in inducing left ventricular hypertrophy. This may represent the basis of myocardial ischemia, congestive heart failure, and cardiac mortality. Although debated, a high sodium intake may induce initial renal damage and progression in both hypertensive and normotensive subjects. Conversely, there is general agreement about the adverse role of sodium in cerebrovascular disease. These factors point to the possible main role of sodium intake in target organ damage and cardiovascular events including mortality. This review will endeavor to outline the existing evidence.

Blood pressure targets in chronic kidney disease: an update on the evidence

PURPOSE OF REVIEW

Hypertension is the leading modifiable cause of cardiovascular events and of mortality and is generally considered as a direct cause of chronic kidney disease. Defining optimal blood pressure targets in patients with chronic kidney disease is therefore of critical importance.

RECENT FINDINGS

Over the recent years, results and post-hoc analyses of several important trials comparing blood pressure targets which included patients with chronic kidney disease have been published. Although these results provide important means to understand the consequences of high blood pressure and to improve the management of hypertension in chronic kidney disease, they led to remarkably different interpretations and recommendations in the current guidelines.

SUMMARY

The present review summarizes the current evidence and areas of controversy for the definition of blood pressure targets in patients with chronic kidney disease.

The renal replacement therapy landscape in 2030: reducing the global cardiovascular burden in dialysis patients

Despite the significant progress made in understanding chronic kidney disease and uraemic pathophysiology, use of advanced technology and implementation of new strategies in renal replacement therapy, the clinical outcomes of chronic kidney disease 5 dialysis patients remain suboptimal. Considering residual suboptimal medical needs of short intermittent dialysis, it is our medical duty to revisit standards of dialysis practice and propose new therapeutic options for improving the overall effectiveness of dialysis sessions and reduce the burden of stress induced by the therapy. Several themes arise to address the modifiable components of the therapy that are aimed at mitigating some of the cardiovascular risks in patients with end-stage kidney disease. Among them, five are of utmost importance and include: (i) enhancement of treatment efficiency and continuous monitoring of dialysis performances; (ii) prevention of dialysis-induced stress; (iii) precise handling of sodium and fluid balance; (iv) moving towards heparin-free dialysis; and (v) customizing electrolyte prescriptions. In summary, haemodialysis treatment in 2030 will be substantially more personalized to the patient, with a clear focus on cardioprotection, volume management, arrhythmia surveillance, avoidance of anticoagulation and the development of more dynamic systems to align the fluid and electrolyte needs of the patient on the day of the treatment to their particular circumstances.

A Self-management Approach for Dietary Sodium Restriction in Patients With CKD: A Randomized Controlled Trial

RATIONALE & OBJECTIVE

Patients with chronic kidney disease (CKD) are particularly sensitive to dietary sodium. We evaluated a self-management approach for dietary sodium restriction in patients with CKD.

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

Nephrology outpatient clinics in 4 Dutch hospitals. 99 adults with CKD stages 1 to 4 or a functioning (estimated glomerular filtration rate≥25mL/min/1.73m²) kidney transplant, hypertension, and sodium intake>130mmol/d.

INTERVENTION

Routine care was compared with routine care plus a web-based self-management intervention including individual e-coaching and group meetings implemented over a 3-month intervention period, followed by e-coaching over a 6-month maintenance period.

OUTCOMES

Primary outcomes were sodium excretion after the 3-month intervention and after the 6-month maintenance period. Secondary outcomes were blood pressure, proteinuria, costs, quality of life, self-management skills, and barriers and facilitators for implementation.

RESULTS

Baseline estimated glomerular filtration rate was 55.0±22.0mL/min/1.73m². During the intervention period, sodium excretion decreased in the intervention group from 188±8 (SE) to 148±8mmol/d (P<0.001), but did not change significantly in the control group. At 3 months, mean sodium excretion was 24.8 (95% CI, 0.1-49.6) mmol/d lower in the intervention group (P=0.049). At 3 months, systolic blood pressure (SBP) decreased in the intervention group from 140±3 to 132±3mm Hg (P<0.001), but was unchanged in the control group. Mean difference in SBP across groups was-4.7 (95% CI, -10.7 to 1.3) mm Hg (P=0.1). During the maintenance phase, sodium excretion increased in the intervention group, but remained lower than at baseline at 160±8mmol/d (P=0.01), while it decreased in the control group from 174±9 at the end of the intervention period to 154±9mmol/d (P=0.001). Consequently, no difference in sodium excretion between groups was observed after the maintenance phase. There was no difference in SBP between groups after the maintenance phase.

LIMITATIONS

Limited power, postrandomization loss to follow-up, Hawthorne effect, lack of dietary data, short-term follow-up.

CONCLUSIONS

A coaching intervention reduced sodium intake at 3 months. Efficacy during the maintenance phase was diminished, possibly due to inadvertent adoption of the intervention by the control group.

FUNDING

Grant funding from the Netherlands Organization for Health Research and Development and the Dutch Kidney Foundation.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT02132013.

Could nutritional therapy take us further in our approaches to Fabry disease?

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the GLA gene that result in deficiency of enzyme α-galactosidase A activity. Clinical manifestation varies from mild to severe depending on the phenotype. The main clinical manifestations are cutaneous (angiokeratomas), neurologic (acroparesthesias), gastrointestinal (nausea, diarrhea, and abdominal pain), renal (proteinuria and kidney failure), cardiovascular (cardiomyopathy and arrhythmias), and cerebrovascular (stroke). Enzyme replacement therapy with recombinant human α-galactosidase is currently the therapeutic option for FD. Although enzyme replacement therapy has changed the natural history of disease, many clinical aspects of FD require an additional specific treatment. Nutritional approach is mostly indicated in case of nephropathy and gastrointestinal symptoms. Specific dietary interventions can modulate some pathogenetic mechanisms of the disease, such as the inflammation, oxidative stress, and autophagic disorders. However, to our knowledge, limited attention has been given to the nutritional aspects of FD. The aim of this review is to examine nutritional strategies that might interfere with several pathophysiologic aspects of FD, including inflammation and oxidative stress. A dietary approach should be part of the basic treatment in renal manifestations of FD. Dietary measures recommended for irritable bowel syndrome could be recommended for gastrointestinal symptoms. Dietary factors can modulate the inflammation, oxidative stress, and autophagy involved in FD. Polyphenols, ω-3 fatty acids, microbiota, and specific dietary patterns can interfere with inflammation/oxidative stress and autophagy mechanisms and could also contribute to the slowing of FD progression.

Chronic kidney disease progression in kidney transplant recipients: A focus on traditional risk factors

Kidney transplant recipients are a subset of patients with chronic kidney disease (CKD) that remain at high risk for progression to dialysis and mortality. Recent advances in immunosuppression have only partially improved long-term graft and patient survival. Discovery of new immunosuppressive regimens is a slow and resource-intensive process. Hence, recognition and management of modifiable allogeneic and non-allogeneic risk factors for progression to CKD among kidney transplant recipients is of major interest for improving long-term outcomes. Graft survival is mainly determined by the quality of the allograft and by the patient's alloimmune response, which is influenced by human leukocyte antigen matching and the presence of donor-specific antibodies. Alloimmune responses manifest as acute and chronic forms of cell- and antibody-mediated rejection, which can be worsened by patient non-adherence or under-immunosuppression. However, donor and patient ages, glomerular disease recurrence, time on dialysis, pre-existing cardiovascular burden, medication side-effects and traditional risk factors, such as hypertension, proteinuria, anaemia, dyslipidaemia, diabetes and bone mineral disorder, which can ultimately lead to severe endothelial derangement, also contribute to graft loss and mortality. These traditional risk factors, common to pre-dialysis patients, often are considered of secondary importance when compared to alloimmunity and immunosuppression concerns. In this review article, we focus on the epidemiological, pathophysiological and therapeutic features of non-allogeneic traditional risk factors for CKD. We also discuss the benefit of adopting a multidisciplinary approach to pursue the same therapeutic targets recommended for pre-dialysis patients.

Salt-deficient diet exacerbates cystogenesis in ARPKD via epithelial sodium channel (ENaC)

Background

Autosomal Recessive Polycystic Kidney Disease (ARPKD) is marked by cyst formation in the renal tubules, primarily in the collecting duct (CD) system, ultimately leading to end-stage renal disease. Patients with PKD are generally advised to restrict their dietary sodium intake. This study was aimed at testing the outcomes of dietary salt manipulation in ARPKD.

Methods

PCK/CrljCrlPkhd1pck/CRL (PCK) rats, a model of ARPKD, were fed a normal (0.4% NaCl; NS), high salt (4% NaCl; HS), and sodium-deficient (0.01% NaCl; SD) diets for 8 weeks. Immunohistochemistry, GFR measurements, balance studies, and molecular biology approaches were applied to evaluate the outcomes of the protocol. Renin-angiotensin-aldosterone system (RAAS) levels were assessed using LC-MS/MS, and renal miRNA profiles were studied.

Findings

Both HS and SD diets resulted in an increase in cystogenesis. However, SD diet caused extensive growth of cysts in the renal cortical area, and hypertrophy of the tissue; RAAS components were enhanced in the SD group. We observed a reduction in epithelial Na⁺ channel (ENaC) expression in the SD group, accompanied with mRNA level increase. miRNA assay revealed that renal miR-9a-5p level was augmented in the SD group; we showed that this miRNA decreases ENaC channel number in CD cells.

Interpretation

Our data demonstrate a mechanism of ARPKD progression during salt restriction that involves activity of ENaC. We further show that miR-9a-5p potentially implicated in this mechanism and that miR-9a-5p downregulates ENaC in cultured CD cells. Our findings open new therapeutic possibilities and highlight the importance of understanding salt reabsorption in ARPKD.

Tolerance to Sodium in Patients With CKD-Induced Metabolic Acidosis: Does the Accompanying Anion Matter?

Patients with chronic kidney disease (CKD) continue to produce endogenous acids but have a reduction in net acid excretion, resulting in a primary decrease in serum bicarbonate concentration, which is termed chronic metabolic acidosis. Recent prospective studies, along with retrospective cohort analyses, demonstrate a higher risk for CKD progression with untreated metabolic acidosis. To normalize serum bicarbonate levels, acidemic patients are often treated with sodium bicarbonate (NaHCO₃) or sodium citrate, which have been shown to slow the progression of CKD. However, studies using this approach have routinely excluded patients with common sodium-sensitive comorbid conditions, such as poorly controlled hypertension, congestive heart failure, volume overload, or edema. This article examines the effect of the anion that accompanies sodium delivered with these therapies. Do the negative effects on blood pressure (BP) and sodium retention, as measured by an increase in edema, weight gain, and congestive heart failure, observed with oral administration of sodium chloride (NaCl) differ when a similar amount of sodium is given with bicarbonate or citrate in this patient population? A review of the literature suggests that NaHCO₃ does not increase BP or sodium retention when administered to patients with CKD during a concurrent severe NaCl dietary restriction (∼10 mEq/d). However, this degree of NaCl restriction is feasible only under strict control in clinical research environments. In contrast, when NaHCO₃ is given to patients without severe dietary NaCl restriction, there is an increase in BP and sodium retention. Thus, unless patients with CKD can tolerate a diet virtually devoid of NaCl, additional sodium, regardless of the accompanying anion, appears to increase BP and sodium retention.

Perceived Sodium Reduction Barriers Among Patients with Chronic Kidney Disease: Which Barriers Are Important and Which Patients Experience Barriers?

PURPOSE

The purposes of this study were to assess the importance of perceived sodium reduction barriers among patients with chronic kidney disease (CKD) and identify associated sociodemographic, clinical, and psychosocial factors.

METHOD

A total of 156 patients with CKD completed a questionnaire assessing sodium reduction barriers (18 self-formulated items), depressive symptoms (Beck Depression Inventory), perceived autonomy support (Modified Health Care Climate Questionnaire), and self-efficacy (Partners in Health Questionnaire). Factor analysis was used to identify barrier domains. Correlation coefficients were computed to examine relationships between barrier domains and patient characteristics.

RESULTS

Nine barrier domains were identified. Barriers perceived as important were as follows: high sodium content in products, lack of sodium feedback, lack of goal setting and discussing strategies for sodium reduction, and not experiencing CKD-related symptoms (mean scores > 3.0 on 5-point scales, ranging from 1 'no barrier' to 5 'very important barrier'). Other barriers (knowledge, attitude, coping skills when eating out, and professional support) were rated as moderately important (rated around midpoint), and the barrier 'intrinsic motivation' was rated as somewhat important (mean score = 1.9). Sodium reduction barrier domains were not associated with gender and kidney function, but were associated with age, level of education, number of comorbidities, perceived autonomy support, depressive symptoms, and self-efficacy (range r = 0.17-0.35). Patients with lower self-efficacy and perceived autonomy support scores experienced most sodium reduction barriers.

CONCLUSION

Patients with CKD experience multiple important sodium reduction barriers and could benefit from support strategies that target various sodium reduction barriers and strengthen beliefs regarding self-efficacy and autonomy support. Additionally, environmental interventions should be implemented to reduce sodium levels in processed foods.

Public health relevance of drug-nutrition interactions

The public health relevance of drug–nutrition interactions is currently highly undervalued and overlooked. This is particularly the case for elderly persons where multi-morbidity and consequently polypharmacy is very common. Vitamins and other micronutrients have central functions in metabolism, and their interactions with drugs may result in clinically relevant physiological impairments but possibly also in positive effects. On 12 April 2016, the University Medical Center Groningen (The Netherlands), as part of its Healthy Ageing program, organized a workshop on the public health relevance of drug–nutrient interactions. In this meeting, experts in the field presented results from recent studies on interactions between pharmaceuticals and nutrients, and discussed the role of nutrition for elderly, focusing on those persons receiving pharmaceutical treatment. This paper summarizes the proceedings of the symposium and provides an outlook for future research needs and public health measures. Since food, pharma and health are closely interconnected domains, awareness is needed in the medical community about the potential relevance of drug–nutrition interactions. Experts and stakeholders should advocate for the integration of drug–nutrition evaluations in the drug development process. Strategies for the individual patients should be developed, by installing drug review protocols, screening for malnutrition and integrating this topic into the general medical advice.

Nutritional treatment of advanced CKD: twenty consensus statements

The Italian nephrology has a long tradition and experience in the field of dietetic-nutritional therapy (DNT), which is an important component in the conservative management of the patient suffering from a chronic kidney disease, which precedes and integrates the pharmacological therapies. The objectives of DNT include the maintenance of an optimal nutritional status, the prevention and/or correction of signs, symptoms and complications of chronic renal failure and, possibly, the delay in starting of dialysis. The DNT includes modulation of protein intake, adequacy of caloric intake, control of sodium and potassium intake, and reduction of phosphorus intake. For all dietary-nutritional therapies, and in particular those aimed at the patient with chronic renal failure, the problem of patient adherence to the dietetic-nutritional scheme is a key element for the success and safety of the DNT and it can be favored by an interdisciplinary and multi-professional approach of information, education, dietary prescription and follow-up. This consensus document, which defines twenty essential points of the nutritional approach to patients with advanced chronic renal failure, has been written, discussed and shared by the Italian nephrologists together with representatives of dietitians (ANDID) and patients (ANED).

Evaluation of the Pharmacodynamic Effects of the Potassium Binder RDX7675 in Mice

INTRODUCTION

Hyperkalemia is a common complication in patients with heart failure or chronic kidney disease, particularly those who are taking inhibitors of the renin-angiotensin-aldosterone system. RDX7675, the calcium salt of a reengineered polystyrene sulfonate-based resin, is a potassium binder that is being investigated as a novel treatment for hyperkalemia. This study evaluated the pharmacodynamic effects of RDX7675 in mice, compared to 2 current treatments, sodium polystyrene sulfonate (SPS) and patiromer.

METHODS

Seven groups of 8 male CD-1 mice were given either standard chow (controls) or standard chow containing 4.0% or 6.6% active moiety of RDX7675, patiromer, or SPS for 72 hours. Stool and urine were collected over the final 24 hours of treatment for ion excretion analyses.

RESULTS

RDX7675 increased stool potassium (mean 24-hour excretion: 4.0%, 9.19 mg; 6.6%, 18.11 mg; both P < .0001) compared with controls (4.47 mg) and decreased urinary potassium (mean 24-hour excretion: 4.0%, 12.05 mg, P < .001; 6.6%, 6.68 mg, P < .0001; vs controls, 20.38 mg). The potassium-binding capacity of RDX7675 (stool potassium/gram of resin: 4.0%, 1.14 mEq/g; 6.6%, 1.32 mEq/g) was greater (all P < .0001) than for patiromer (4.0%, 0.63 mEq/g; 6.6%, 0.48 mEq/g) or SPS (4.0%, 0.73 mEq/g; 6.6% 0.55 mEq/g). RDX7675 and patiromer decreased urinary sodium (mean 24-hour excretion: 0.07-1.38 mg; all P < .001) compared to controls (5.01 mg). In contrast, SPS increased urinary sodium excretion (4.0%, 13.31 mg; 6.6%, 17.60 mg; both P < .0001) compared to controls.

CONCLUSIONS

RDX7675 reduced intestinal potassium absorption and had a greater potassium-binding capacity than patiromer or SPS in mice. The calcium-based resins RDX7675 and patiromer reduced intestinal sodium absorption, unlike sodium-based SPS. These results support further studies in humans to confirm the potential of RDX7675 for the treatment of patients with hyperkalemia.

Treatment of Diabetic Kidney Disease With Hypertension Control and Renin Angiotensin System Inhibition

The global incidence and prevalence of diabetes continues to expand due primarily to the influences of obesity and the contribution of obesity to the progression of type 2 diabetes mellitus. The rising prevalence of type 2 diabetes has driven an increase in rates of CKD in the past 3 decades in the United States. In turn, so have the rates for complications related to type 2 diabetes including CKD, eg, diabetic kidney disease (DKD). Although incident rates for DKD have stabilized in the recent years, diabetes continues to be the leading cause of ESRD in the United States. The United Kingdom Prospective Diabetes Study data and other population-level studies support that lowering blood pressure reduces kidney disease and cardiovascular disease in patients with type 2 diabetes. Furthermore, strategies targeting renin-angiotensin-aldosterone system interruption have shown to improve DKD outcomes to a greater extent than other classes of antihypertensive regimens.

CE: Improving Outcomes for Patients with Chronic Kidney Disease: Part 1

: The burden of chronic kidney disease (CKD) is rising both in this country and worldwide. An estimated 10% to 15% of U.S. adults are currently living with CKD. Reducing the CKD burden requires a systematic, interdisciplinary approach to care. The greatest opportunities to reduce the impact of CKD arise early, when most patients are being followed in primary care; yet many clinicians are inadequately educated on this disease. Nurses are well positioned to facilitate the implementation of collaborative care. This two-part article aims to provide nurses with the basic information necessary to assess and manage patients with CKD. Part 1 offers an overview of the disease, describes identification and etiology, and discusses ways to slow disease progression. Part 2, which will appear next month, addresses disease complications and treatment of kidney failure.

High sodium diet converts renal proteoglycans into pro-inflammatory mediators in rats

BACKGROUND

High dietary sodium aggravates renal disease by affecting blood pressure and by its recently shown pro-inflammatory and pro-fibrotic effects. Moreover, pro-inflammatory modification of renal heparan sulfate (HS) can induce tissue remodeling. We aim to investigate if high sodium intake in normotensive rats converts renal HS into a pro-inflammatory phenotype, able to bind more sodium and orchestrate inflammation, fibrosis and lymphangiogenesis.

METHODS

Wistar rats received a normal diet for 4 weeks, or 8% NaCl diet for 2 or 4 weeks. Blood pressure was monitored, and plasma, urine and tissue collected. Tissue sodium was measured by flame spectroscopy. Renal HS and tubulo-interstitial remodeling were studied by biochemical, immunohistochemical and qRT-PCR approaches.

RESULTS

High sodium rats showed a transient increase in blood pressure (week 1; p<0.01) and increased sodium excretion (p<0.05) at 2 and 4 weeks compared to controls. Tubulo-interstitial T-cells, myofibroblasts and mRNA levels of VCAM1, TGF-β1 and collagen type III significantly increased after 4 weeks (all p<0.05). There was a trend for increased macrophage infiltration and lymphangiogenesis (both p = 0.07). Despite increased dermal sodium over time (p<0.05), renal concentrations remained stable. Renal HS of high sodium rats showed increased sulfation (p = 0.05), increased L-selectin binding to HS (p<0,05), and a reduction of sulfation-sensitive anti-HS mAbs JM403 (p<0.001) and 10E4 (p<0.01). Hyaluronan expression increased under high salt conditions (p<0.01) without significant changes in the chondroitin sulfate proteoglycan versican. Statistical analyses showed that sodium-induced tissue remodeling responses partly correlated with observed HS changes.

CONCLUSION

We show that high salt intake by healthy normotensive rats convert renal HS into high sulfated pro-inflammatory glycans involved in tissue remodeling events, but not in increased sodium storage.

A phase 1 study of the safety, tolerability, pharmacodynamics, and pharmacokinetics of tenapanor in healthy Japanese volunteers

BACKGROUND

Tenapanor (RDX5791, AZD1722), a small molecule with minimal systemic availability, is an inhibitor of the sodium/hydrogen exchanger isoform 3 (NHE3). Tenapanor acts locally in the gut to reduce absorption of sodium and phosphate. It is being developed for the treatment of patients with hyperphosphatemia in CKD requiring dialysis and patients with constipation-predominant irritable bowel syndrome. We report the safety, pharmacodynamics, and pharmacokinetics of tenapanor in Japanese volunteers.

METHODS

In this phase 1, double-blind study (NCT02176252), healthy Japanese adults (aged 20-45 years) received single-dose tenapanor 180 mg (n = 6), repeated-dose tenapanor 15, 30, 60, or 90 mg twice daily (n = 12 each) for 7 days, or placebo (n = 14). All participants received a standardized diet.

RESULTS

Single and repeated doses of tenapanor resulted in higher mean stool sodium content vs. placebo (single dose, 41.9 mmol/day; repeated dose, range of means 21.3-32.2 mmol/day; placebo, 4.1 mmol/day) accompanied by lower urinary sodium content (single dose, 110 mmol/day; repeated dose, 101-112 mmol/day; placebo, 143 mmol/day). Additionally, stool phosphorus content was increased (single dose, 31.0 mmol/day; repeated dose, 17.6-24.8 mmol/day; placebo, 16.8 mmol/day) and urinary phosphorus content decreased (single dose, 18.7 mmol/day; repeated dose, 15.3-19.4 mmol/day; placebo, 25.5 mmol/day). Tenapanor had minimal systemic exposure, provided a softer stool consistency, and was well tolerated.

CONCLUSIONS

Tenapanor treatment reduced absorption of intestinal sodium and phosphate from the gut in Japanese adults. Tenapanor had minimal systemic exposure and was well tolerated. Further research into the clinical benefits of tenapanor is warranted.

Risk factors for chronic kidney disease among patients at Olabisi Onabanjo University Teaching Hospital in Sagamu, Nigeria: A retrospective cohort study

BACKGROUND

Chronic kidney disease (CKD) is common and often goes undetected and undiagnosed until the disease is well advanced and kidney failure is imminent. It is estimated that approximately 36 million Nigerians suffer from different stages of CKD, as one in seven Nigerians has kidney disease.

METHODS

This research was a retrospective cohort study of 150 cases and 300 controls. Selection of subjects was by a retrospective review of records of in-patients from 2010-2013 in a state teaching hospital. Data was analyzed using Chi-square at 5% level of significance.

RESULTS

Majority of subjects were between ages 20 - 29 years. The mean (SD) age of the cases was 40.6 (14.4) and controls was 38.6 (15.8). Ninety (60%) of the cases and 212(70.7%) of the controls were males (p= 0.023). Almost 87% of the cases and 42% of the controls ingest herbal concoction. Use of bleaching substances was more among the cases 20(13.4%) compared with the controls 2(0.7%), ( p= 0.001). Eight (5.3%) of the cases had family history of CKD while only 1(0.3%) of the control had similar history (p= 0.001). There were more cases (10.7%) with diabetic mellitus compared with the controls (2.7%), (p= 0.001). The number of cases with high blood pressure was more than the number of controls, (p-value <0.001). Sixty-four percent of the cases had history of chronic use of analgesic compared with 10.3% of the controls (p < 0.001).

CONCLUSIONS

CKD is mostly found among men in their productive age, who were either diabetic or hypertensive with history of ingestion of herbal concoction and chronic use of analgesic. Individual should engage in regular medical check, modify their life style while government and health care providers increase awareness and campaign on the causes and risk factors of CKD.

Reducing the costs of chronic kidney disease while delivering quality health care: a call to action

The treatment of chronic kidney disease (CKD) and of end-stage renal disease (ESRD) imposes substantial societal costs. Expenditure is highest for renal replacement therapy (RRT), especially in-hospital haemodialysis. Redirection towards less expensive forms of RRT (peritoneal dialysis, home haemodialysis) or kidney transplantation should decrease financial pressure. However, costs for CKD are not limited to RRT, but also include nonrenal health-care costs, costs not related to health care, and costs for patients with CKD who are not yet receiving RRT. Even if patients with CKD or ESRD could be given the least expensive therapies, costs would decrease only marginally. We therefore propose a consistent and sustainable approach focusing on prevention. Before a preventive strategy is favoured, however, authorities should carefully analyse the cost to benefit ratio of each strategy. Primary prevention of CKD is more important than secondary prevention, as many other related chronic diseases, such as diabetes mellitus, hypertension, cardiovascular disease, liver disease, cancer, and pulmonary disorders could also be prevented. Primary prevention largely consists of lifestyle changes that will reduce global societal costs and, more importantly, result in a healthy, active, and long-lived population. Nephrologists need to collaborate closely with other sectors and governments, to reach these aims.

Low-sodium diet induces atherogenesis regardless of lowering blood pressure in hypertensive hyperlipidemic mice

This study investigated the influence of sodium restriction and antihypertensive drugs on atherogenesis utilizing hypertensive (H) low-density lipoprotein-receptor knockout mice treated or not with losartan (Los) or hydralazine (Hyd) and fed low-sodium (LS) or normal-sodium (NS) chow. Despite reducing the blood pressure (BP) of H-LS mice, the LS diet caused arterial lipid infiltration due to increased plasma total cholesterol (TC) and triglycerides (TG). Los and Hyd reduced the BP of H-LS mice, and Los effectively prevented arterial injury, likely by reducing plasma TG and nonesterified fatty acids. Aortic lipid infiltration was lower in Los-treated H-LS mice (H-LS+Los) than in normotensive (N)-LS and H-LS mice. Aortic angiotensin II type 1 (AT1) receptor content was greater in H-NS than H-LS mice and in H-LS+Hyd than H-LS+Los mice. Carboxymethyl-lysine (CML) and receptor for advanced glycation end products (RAGE) immunostaining was greater in H-LS than H-NS mice. CML and RAGE levels were lower in LS animals treated with antihypertensive drugs, and Hyd enhanced the AT1 receptor level. Hyd also increased the gene expression of F4/80 but not tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-10, intercellular adhesion molecule-1 or cluster of differentiation 66. The novelty of the current study is that in a murine model of simultaneous hypertension and hyperlipidemia, the pleiotropic effect of chronic, severe sodium restriction elicited aortic damage even with reduced BP. These negative effects on the arterial wall were reduced by AT1 receptor antagonism, demonstrating the influence of angiotensin II in atherogenesis induced by a severely LS diet.

Dietary Modeling of Foods for Advanced CKD Based on General Healthy Eating Guidelines: What Should Be on the Plate?

Chronic kidney disease (CKD) is a major public health problem with significant clinical, societal, and psychosocial burdens. Nutrition therapy has been an integral part of the medical management of patients with CKD for more than a century, with the main goals of preserving kidney function and preventing complications. Nutrition abnormalities may emerge well before dialysis therapy is initiated and are associated with poor outcomes. It is therefore important to revisit nutrition management in the advanced stages of CKD to gain a broader insight into its role and effect on patient outcomes. Traditionally, nutrition recommendations have focused on the prescription of energy (calories) and macro- and micronutrients. Today, dietary modeling also focuses on the evidence for food consumption on health. This review argues that advanced non-dialysis-dependent CKD nutrition requirements to a large extent align with healthy eating guidelines for the general population and should not be based on deprivation or be unusually restrictive. The best currently available evidence for the CKD diet is likely to be derived from CKD nutrition prescriptions in conjunction with evidence underpinning national dietary guidelines and evidence of healthy dietary patterns, such as Mediterranean-style and Dietary Approaches to Stop Hypertension (DASH)-style eating. Positive messages from these dietary patterns should improve acceptance of CKD dietary interventions among patients.

Dietary salt restriction is beneficial to the management of autosomal dominant polycystic kidney disease

The CRISP study of polycystic kidney disease (PKD) found that urinary sodium excretion associated with the rate of total kidney volume increase. Whether sodium restriction slows the progression of Autosomal Dominant PKD (ADPKD) is not known. To evaluate this we conducted a post hoc analysis of the HALT-PKD clinical trials of renin-angiotensin blockade in patients with ADPKD. Linear mixed models examined whether dietary sodium affected rates of total kidney volume or change in estimated glomerular filtration rate (eGFR) in patients with an eGFR over 60 ml/min/1.73 m² (Study A) or the risk for a composite endpoint of 50% reduction in eGFR, end-stage renal disease or death, or the rate of eGFR decline in patients with an eGFR 25-60 ml/min/1.73 m² (Study B) all in patients initiated on an under100 mEq sodium diet. During the trial urinary sodium excretion significantly declined by an average of 0.25 and 0.41 mEq/24 hour per month in studies A and B, respectively. In Study A, averaged and time varying urinary sodium excretions were significantly associated with kidney growth (0.43%/year and 0.09%/year, respectively, for each 18 mEq urinary sodium excretion). Averaged urinary sodium excretion was not significantly associated with faster eGFR decline (-0.07 ml/min/1.73m²/year for each 18 mEq urinary sodium excretion). In Study B, the averaged but not time-varying urinary sodium excretion significantly associated with increased risk for the composite endpoint (hazard ratio 1.08 for each 18 mEq urinary sodium excretion) and a significantly faster eGFR decline (-0.09 ml/min/1.73m²/year for each mEq 18 mEq urinary sodium excretion). Thus, sodium restriction is beneficial in the management of ADPKD.

Response of fibroblast growth factor 23 to volume interventions in arterial hypertension and diabetic nephropathy

Fibroblast growth factor 23 (FGF-23) rises progressively in chronic kidney disease and is associated with adverse cardiovascular outcomes. FGF-23 putatively induces volume retention by upregulating the sodium-chloride cotransporter (NCC). We studied whether, conversely, interventions in volume status affect FGF-23 concentrations.We performed a post hoc analysis of 1) a prospective saline infusion study with 12 patients with arterial hypertension who received 2 L of isotonic saline over 4 hours, and 2) a randomized controlled trial with 45 diabetic nephropathy (DN) patients on background angiotensin-converting enzyme -inhibition (ACEi), who underwent 4 6-week treatment periods with add-on hydrochlorothiazide (HCT) or placebo, combined with regular sodium (RS) or low sodium (LS) diet in a cross-over design. Plasma C-terminal FGF-23 was measured by ELISA (Immutopics) after each treatment period in DN and before and after saline infusion in hypertensives.The patients with arterial hypertension were 45 ± 13 (mean ± SD) years old with an estimated glomerular filtration rate (eGFR) of 101 ± 18 mL/min/1.73 m. Isotonic saline infusion did not affect FGF-23 (before infusion: 68 median [first to third quartile: 58-97] relative unit (RU)/mL, after infusion: 67 [57-77] RU/mL, P = 0.37). DN patients were 65 ± 9 years old. During ACEi + RS treatment, eGFR was 65 ± 25 mL/min/1.73 m and albuminuria 649 mg/d (230-2008 mg/d). FGF23 level was 94 (73-141) RU/mL during ACEi therapy. FGF-23 did not change significantly by add-on HCT (99 [74-148] RU/mL), LS diet (99 [75-135] RU/mL), or their combination (111 [81-160] RU/mL, P = 0.15).Acute and chronic changes in volume status did not materially change FGF-23 in hypertensive patients and DN, respectively. Our data do not support a direct feedback loop between volume status and FGF-23 in hypertension or DN.

Social Determinants of Racial Disparities in CKD

Significant disparities in CKD rates and outcomes exist between black and white Americans. Health disparities are defined as health differences that adversely affect disadvantaged populations, on the basis of one or more health outcomes. CKD is the complex result of genetic and environmental factors, reflecting the balance of nature and nurture. Social determinants of health have an important role as environmental components, especially for black populations, who are disproportionately disadvantaged. Understanding the social determinants of health and appreciating the underlying differences associated with meaningful clinical outcomes may help nephrologists treat all their patients with CKD in an optimal manner. Altering the social determinants of health, although difficult, may embody important policy and research efforts, with the ultimate goal of improving outcomes for patients with kidney diseases, and minimizing the disparities between groups.

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.

Concordance of dietary sodium intake and concomitant phosphate load: Implications for sodium interventions

BACKGROUND AND AIMS

Both a high dietary sodium and high phosphate load are associated with an increased cardiovascular risk in patients with chronic kidney disease (CKD), and possibly also in non-CKD populations. Sodium and phosphate are abundantly present in processed food. We hypothesized that (modulation of) dietary sodium is accompanied by changes in phosphate load across populations with normal and impaired renal function.

METHODS AND RESULTS

We first investigated the association between sodium and phosphate load in 24-h urine samples from healthy controls (n = 252), patients with type 2 diabetes mellitus (DM, n = 255) and renal transplant recipients (RTR, n = 705). Secondly, we assessed the effect of sodium restriction on phosphate excretion in a nondiabetic CKD cohort (ND-CKD: n = 43) and a diabetic CKD cohort (D-CKD: n = 39). Sodium excretion correlated with phosphate excretion in healthy controls (R = 0.386, P < 0.001), DM (R = 0.490, P < 0.001), and RTR (R = 0.519, P < 0.001). This correlation was also present during regular sodium intake in the intervention studies (ND-CKD: R = 0.491, P < 0.001; D-CKD: R = 0.729, P < 0.001). In multivariable regression analysis, sodium excretion remained significantly correlated with phosphate excretion after adjustment for age, gender, BMI, and eGFR in all observational cohorts. In ND-CKD and D-CKD moderate sodium restriction reduced phosphate excretion (31 ± 10 to 28 ± 10 mmol/d; P = 0.04 and 26 ± 11 to 23 ± 9 mmol/d; P = 0.02 respectively).

CONCLUSIONS

Dietary exposure to sodium and phosphate are correlated across the spectrum of renal function impairment. The concomitant reduction in phosphate intake accompanying sodium restriction underlines the off-target effects on other nutritional components, which may contribute to the beneficial cardiovascular effects of sodium restriction. (f) Registration numbers: Dutch Trial Register NTR675, NTR2366.

Factors impacting sodium restriction in patients with chronic kidney disease: a cohort study from a Chinese center

PURPOSE

Sodium restriction is important for the management of chronic kidney disease (CKD). The present study evaluated the factors impacting dietary sodium restriction in a cohort of Chinese patients with CKD.

METHODS

A questionnaire on dietary sodium restriction was administered to patients with non-dialysis CKD who visited our CKD clinic from September 2014 to March 2015. Twenty-four-hour urinary sodium excretion (24-h UNa) was measured. Logistic regression was performed to examine the association between patient characteristics and sodium restriction.

RESULTS

Two hundred and twenty-nine patients were included in the final analysis. Most of the patients (97.7 %) declared their awareness of the necessity of sodium restriction, but 27.3 % of them chose an incorrect sodium restriction limit. Most of the patients (85.2 %) also reported that they had taken actions to reduce their sodium consumption, with intolerance of sodium restriction as the most common reason for taking no actions. Only 42 patients (18.3 %) had a 24-h UNa of <100 mmol. Multivariable logistic regression showed that age and the use of condiments were independently associated with successful sodium restriction [odds ratio (95 % confidence interval) 1.04 (1.01-1.07), p = 0.006 and 0.38 (0.16-0.88), p = 0.023, respectively]. Most of the patients (83.0 %) did not know how to estimate their sodium intake from condiments.

CONCLUSIONS

This study indicates that there is much room for improvement in dietary sodium restriction in Chinese patients with CKD. Condiments as a hidden source of sodium intake should be stressed in the education of these patients.

Melatonin prevents kidney injury in a high salt diet-induced hypertension model by decreasing oxidative stress

Melatonin, a potent antioxidant molecule, plays a role in blood pressure regulation. We hypothesized that melatonin may generate a protective effect in a high salt diet (HSD) rodent model mediated by decreasing renal oxidative stress. Dahl salt-sensitive rats were divided into three groups according to diet: normal chow (control); HSD; HSD with melatonin [30/mg/kg/day]) placed in their water (HSD + Mel) over an 8-wk period. Blood pressure was measured by the tail cuff method. Kidney injury was evaluated by 24 H urine protein excretion. Glomerular injury index (GII) (fibrotic glomeruli/100 glomeruli) was evaluated from a Masson's trichrome-stained section. Kidney oxidative stress was determined by superoxide production via dihydroethidium staining. Expression of oxidative stress-related genes was measured by reverse transcriptase-qPCR. Melatonin had no effect on blood pressure increase induced by HSD and attenuated proteinuria induced by HSD (HSD--50.7 ± 12, HSD + Mel--22.3 ± 4.3, controls--6.5 ± 1.0 gram protein/gram creatinine, P < 0.001). HSD-induced glomerular damage was significantly diminished by melatonin (GII in HSD--24 ± 6, HSD + Mel--3.6 ± 0.8, controls--0.8 ± 0.5, P < 0.05). Superoxide production was significantly higher in kidneys of HSD fed rats than the controls (99 ± 9 versus 60 ± 7 relative fluorescent units (RFU)/μm(2), respectively, P < 0.05). Melatonin also decreased superoxide production (74 ± 5 RFU/μm(2), P < 0.05). The expression of kidney inducible nitric oxide synthase and p67(phox) mRNA was significantly higher in HSD than in the controls and HSD + Mel rats. Treatment with melatonin eliminated the deleterious effect of HSD in the kidneys of Dahl salt-sensitive rats. The beneficial effect of melatonin is not mediated by lowering blood pressure but by a direct antioxidative effect.

Association between sodium intakes with the risk of chronic kidney disease: evidence from a meta-analysis

OBJECTIVE

Inconsistent results regarding the association between sodium intake and the risk of chronic kidney disease (CKD) have been reported. Thus, we conducted a meta-analysis to summarize the evidence from epidemiological studies of sodium with the risk of CKD.

METHODS

Pertinent studies were identified by searching of PubMed and Web of Science. The random effect model was used to combine the results. Meta-regression and subgroups analyses were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Egger's regression asymmetry test.

RESULTS

Finally, 9 articles involving 5638 CKD cases were included in this meta-analysis. Pooled results suggested that highest sodium intake level versus lowest level was significantly associated with the risk of CKD [summary relative risk (RR) = 1.088, 95% CI = 1.009-1.193, I(2) = 78.1%], especially among Europe [summary RR = 1.097, 95% CI = 1.009-1.205], but not in the America. The association was also found in the prospective studies [summary RR = 1.096, 95% CI = 1.007-1.192], but not in the cross-sectional studies. No evidence of significant publication bias was found.

CONCLUSIONS

Higher sodium intake might increase the risk of CKD.