Effects of salt supplementation on the albuminuric response to telmisartan with or without hydrochlorothiazide therapy in hypertensive patients with type 2 diabetes are modulated by habitual dietary salt intake

Sodium Management in Kidney Disease: Old Stories, New Tricks

Excessive dietary sodium intake is associated with an increased risk of hypertension, especially in the setting of chronic kidney disease (CKD). Although implementation of a low-sodium diet in patients with CKD generally is recommended, data supporting the efficacy of this practice is mostly opinion-based. Few controlled studies have investigated the specific association of dietary sodium intake and cardiovascular events and mortality in CKD. Furthermore, in epidemiologic studies, the association of sodium intake with CKD progression, cardiovascular risk, and mortality is not homogeneous, and both low- and high-sodium intake has been associated with adverse health outcomes in different studies. In general, the adverse effects of high dietary sodium intake are more apparent in the setting of advanced CKD. However, there is no established definitive target level of dietary sodium intake in different CKD stages based on glomerular filtration rate and albuminuria/proteinuria. This review discusses the current challenges regarding the rationale of sodium restriction, target levels and assessment of sodium intake, and interventions for sodium restrictions in CKD in relation to clinical outcomes.

Altered dietary salt intake for preventing diabetic kidney disease and its progression

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor in the development of increased blood pressure (BP) and that a reduction in our salt intake lowers BP, whether BP levels are normal or raised initially. Effective control of BP in people with diabetes lowers the risk of strokes, heart attacks and heart failure and slows the progression of chronic kidney disease (CKD) in people with diabetes. This is an update of a review first published in 2010.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and of CKD in people with diabetes.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 31 March 2022 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of altered salt intake in individuals with type 1 and type 2 diabetes. Studies were included when there was a difference between low and high sodium intakes of at least 34 mmol/day.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion. We calculated mean effect sizes as mean difference (MD) and 95% confidence intervals (CI) using the random-effects model. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Thirteen RCTs (313 participants), including 21 comparisons (studies), met our inclusion criteria. One RCT (two studies) was added to this review update. Participants included 99 individuals with type 1 diabetes and 214 individuals with type 2 diabetes. Two RCTs (four studies) included some participants with reduced overall kidney function. The remaining studies either reported that participants with reduced glomerular filtration rate (GFR) were excluded from the study or only included participants with microalbuminuria and normal GFR. Five studies used a parallel study design, and 16 used a cross-over design. Studies were at high risk of bias for most criteria. Random sequence generation and allocation concealment were adequate in only three and two studies, respectively. One study was at low risk of bias for blinding of participants and outcome assessment, but no studies were at low risk for selective reporting. Twelve studies reported non-commercial funding sources, three reported conflicts of interest, and eight reported adequate washout between interventions in cross-over studies. The median net reduction in 24-hour urine sodium excretion (24-hour UNa) in seven long-term studies (treatment duration four to 12 weeks) was 76 mmol (range 51 to 124 mmol), and in 10 short-term studies (treatment duration five to seven days) was 187 mmol (range 86 to 337 mmol). Data were only available graphically in four studies. In long-term studies, reduced sodium intake may lower systolic BP (SBP) by 6.15 mm Hg (7 studies: 95% CI -9.27 to -3.03; I² = 12%), diastolic BP (DBP) by 3.41 mm Hg (7 studies: 95% CI -5.56 to -1.27; I² = 41%) and mean arterial pressure (MAP) by 4.60 mm Hg (4 studies: 95% CI -7.26 to -1.94; I² = 28%). In short-term studies, low sodium intake may reduce SBP by 8.43 mm Hg (5 studies: 95% CI -14.37 to -2.48; I² = 88%), DBP by 2.95 mm Hg (5 studies: 95% CI -4.96 to -0.94; I² = 70%) and MAP by 2.37 mm Hg (9 studies: 95% CI -4.75 to -0.01; I² = 65%). There was considerable heterogeneity in most analyses but particularly among short-term studies. All analyses were considered to be of low certainty evidence. SBP, DBP and MAP reductions may not differ between hypertensive and normotensive participants or between individuals with type 1 or type 2 diabetes. In hypertensive participants, SBP, DBP and MAP may be reduced by 6.45, 3.15 and 4.88 mm Hg, respectively, while in normotensive participants, they may be reduced by 8.43, 2.95 and 2.15 mm Hg, respectively (all low certainty evidence). SBP, DBP and MAP may be reduced by 7.35, 3.04 and 4.30 mm Hg, respectively, in participants with type 2 diabetes and by 7.35, 3.20, and 0.08 mm Hg, respectively, in participants with type 1 diabetes (all low certainty evidence). Eight studies provided measures of urinary protein excretion before and after salt restriction; four reported a reduction in urinary albumin excretion with salt restriction. Pooled analyses showed no changes in GFR (12 studies: MD -1.87 mL/min/1.73 m², 95% CI -5.05 to 1.31; I² = 32%) or HbA1c (6 studies: MD -0.62, 95% CI -1.49 to 0.26; I² = 95%) with salt restriction (low certainty evidence). Body weight was reduced in studies lasting one to two weeks but not in studies lasting for longer periods (low certainty evidence). Adverse effects were reported in only one study; 11% and 21% developed postural hypotension on the low-salt diet and the low-salt diet combined with hydrochlorothiazide, respectively.

AUTHORS' CONCLUSIONS

This systematic review shows an important reduction in SBP and DBP in people with diabetes with normal GFR during short periods of salt restriction, similar to that obtained with single drug therapy for hypertension. These data support the international recommendations that people with diabetes with or without hypertension or evidence of kidney disease should reduce salt intake to less than 5 g/day (2 g sodium).

High-Salt Attenuates the Efficacy of Dapagliflozin in Tubular Protection by Impairing Fatty Acid Metabolism in Diabetic Kidney Disease

High-salt intake leads to kidney damage and even limits the effectiveness of drugs. However, it is unclear whether excessive intake of salt affects renal tubular energy metabolism and the efficacy of dapagliflozin on renal function in diabetic kidney disease (DKD). In this study, we enrolled 350 DKD patients and examined the correlation between sodium level and renal function, and analyzed influencing factors. The results demonstrated that patients with macroalbuminuria have higher 24 h urinary sodium levels. After establishment of type 2 diabetes mellitus model, the animals received a high-salt diet or normal-salt diet. In the presence of high-salt diet, the renal fibrosis was aggravated with fatty acid metabolism dysregulation. Furthermore, Na+/K+-ATPase expression was up-regulated in the renal tubules of diabetic mice, while the fatty acid metabolism was improved by inhibiting Na+/K+-ATPase of renal tubular epithelial cells. Of note, the administration with dapagliflozin improved renal fibrosis and enhanced fatty acid metabolism. But high salt weakened the above-mentioned renal protective effects of dapagliflozin in DKD. Similar results were recapitulated in vitro after incubating proximal tubular epithelial cells in high-glucose and high-salt medium. In conclusion, our results indicate that high salt can lead to fatty acid metabolism disorders by increasing Na+/K+-ATPase expression in the renal tubules of DKD. High salt intake diminishes the reno-protective effect of dapagliflozin in DKD.

Effect of a sodium restriction diet on albuminuria and blood pressure in diabetic kidney disease patients: a meta-analysis

BACKGROUND

A sodium restriction diet is a key component of chronic kidney disease (CKD) management. However, the efficacy of its use in patients with diabetic kidney disease (DKD) is uncertain. The present meta-analysis explored the effects of restricting sodium intake on albuminuria and blood pressure in DKD patients with albuminuria.

METHODS

We searched the Cochrane Central Register of Controlled Trials, Web of Science, MEDLINE, and EMBASE for randomized controlled trials, and we reviewed the references of all searched articles to avoid omitting other relevant articles. Our primary endpoints were blood pressure, albumin excretion rate, and plasma renin activity. We assessed pooled data using a random-effects model.

RESULTS

Of the 661 articles identified, a total of 12 articles were included in the meta-analysis. The random-effects model indicated that salt-restriction diet interventions led to a poled - 4.72 mmHg (95% CI - 6.71, - 2.73) difference in systolic blood pressure and that the intervention resulted in a 2.33 mmHg lower diastolic blood pressure (95% CI - 3.61, - 1.05). In patients with microalbuminuria, restricted sodium intake decreased the albumin excretion rate (AER) by 12.62 mg/min (95% CI - 19.64, - 5.60). Furthermore, the AER was 127.69 mg/min lower in patients with macroalbuminuria (95% CI - 189.07, - 66.32).

CONCLUSION

Moderate sodium restriction diets reduce urinary albumin excretion and decrease the level of blood pressure, especially for patients with macro-albuminuria. Thus, it is necessary to strengthen the intervention and health education as well as to provide individualized dietary advice.

Triple combination therapy with telmisartan, amlodipine, and hydrochlorothiazide ameliorates albuminuria in a normotensive rat remnant kidney model

Background

Some types of antihypertensive drugs may have pleiotropic effects in patients with chronic kidney disease (CKD). However, whether triple combination therapy with angiotensin II receptor blockers (ARBs), calcium channel blockers (CCBs), and thiazide diuretics (TZD) confer renoprotective effects in normotensive CKD remains unknown. Thus, we explored this issue using a normotensive rat remnant kidney model.

Methods

Sprague-Dawley rats were randomly allocated into four groups: sham (n = 10), 5/6 nephrectomy (NTx) (n = 9), NTx treated with telmisartan and amlodipine (dual) (n = 8), and NTx treated with telmisartan, amlodipine, and hydrochlorothiazide (triple) (n = 7), and followed for 4 weeks. Blood pressure (BP), blood chemistry including renal function, urinary albumin excretion (UAE), and renal pathology were evaluated in all groups.

Results

There was no significant change in systolic BP among the four groups during the study period. Serum blood urea nitrogen (BUN) was significantly higher, and 24-h creatinine clearance (Ccr) was lower in all NTx groups (p < 0.001). Dual therapy further increased the glomerular diameter in NTx rats (p < 0.001), which was significantly ameliorated by triple therapy (p < 0.001). Triple therapy, but not dual therapy, significantly reduced NTx-induced UAE levels (p < 0.05), whereas BUN, 24-h Ccr, and tubulointerstitial injury scores were comparable among all the NTx groups.

Conclusions

Our results suggest that triple combination therapy with telmisartan, amlodipine, and hydrochlorothiazide could ameliorate glomerular hypertrophy and albuminuria in normotensive CKD rats in a BP-lowering independent manner.

Dietary sodium and potassium intake in people with diabetes: are guidelines being met?

Objective

Despite public health bodies advocating for lowering dietary sodium and increasing potassium intake to improve cardiovascular outcomes, people with diabetes are not meeting these targets. We hypothesize that (i) both at an individual level and within the cohort, there will be a low adherence to the guidelines and (ii) sodium and potassium intake will remain stable over time.

Methods

We conducted this prospective study in a cohort of 904 participants with diabetes who provided 24-h urine collections from 2009 to 2015. Dietary sodium and potassium intake were estimated from 24-h urinary sodium (uNa) and potassium (uK) measurements. Additional data were collected for: 24-h urinary volume (uVol), creatinine (uCr),; serum creatinine, urea, estimated glomerular filtration rate (eGFR), glycated haemoglobin (HbA1c), fasting glucose, lipids); clinical characteristics (age, blood pressure (BP), body mass index (BMI) and duration of diabetes). Adherence to recommended dietary sodium (uNa < 2300 mg/24 h (100mmol/24 h)) and potassium (uK > 4680 mg/24 h(120 mmol/24)) intake were the main outcome measures.

Results

Participants (n = 904) completed 3689 urine collections (average four collections/participant). The mean ± SD (mmol/24 h) for uNa was 181 ± 73 and uK was 76 ± 25. After correcting uNa for uCr, 7% and 5% of participants met dietary sodium and potassium guidelines respectively. Males were less likely to meet sodium guidelines (OR 0.40, p < 0.001) but were more likely to meet potassium guidelines (OR 6.13, p < 0.001). Longer duration of diabetes was associated with higher adherence to sodium and potassium guidelines (OR 1.04, p < 0.001 and OR 0.96, p = 0.006 respectively). Increasing age was significantly associated with adherence to potassium guidelines (OR 0.97, p = 0.007).

Conclusions

People with diabetes do not follow current dietary sodium and potassium guidelines and are less likely to change their dietary intake of sodium and potassium over time.

Body Fluid-Independent Effects of Dietary Salt Consumption in Chronic Kidney Disease

The average dietary salt (i.e., sodium chloride) intake in Western society is about 10 g per day. This greatly exceeds the lifestyle recommendations by the WHO to limit dietary salt intake to 5 g. There is robust evidence that excess salt intake is associated with deleterious effects including hypertension, kidney damage and adverse cardiovascular health. In patients with chronic kidney disease, moderate reduction of dietary salt intake has important renoprotective effects and positively influences the efficacy of common pharmacological treatment regimens. During the past several years, it has become clear that besides influencing body fluid volume high salt also induces tissue remodelling and activates immune cell homeostasis. The exact pathophysiological pathway in which these salt-induced fluid-independent effects contribute to CKD is not fully elucidated, nonetheless it is clear that inflammation and the development of fibrosis play a major role in the pathogenic mechanisms of renal diseases. This review focuses on body fluid-independent effects of salt contributing to CKD pathogenesis and cardiovascular health. Additionally, the question whether better understanding of these pathophysiological pathways, related to high salt consumption, might identify new potential treatment options will be discussed.

Effect of angiotensin II receptor blocker and salt supplementation on short-term blood pressure variability in type 2 diabetes

High blood pressure variability (BPV) has been associated with increased cardiovascular (CV) risk. The effect of dietary salt and renin-angiotensin-aldosterone system (RAAS) activity on short-term BPV in type 2 diabetes mellitus (T2DM) is not well characterised. We aimed to determine the effect of dietary salt (sodium chloride, NaCl) supplementation on 24-h mean arterial BPV (24hBPV) during angiotensin II receptor blocker (telmisartan) use and to evaluate the effects of age, sex, plasma renin activity (PRA) and serum aldosterone on 24hBPV. In a randomised, double-blind, crossover study, patients with T2DM (n = 28), treated with telmisartan received NaCl (100 mmol/24 h) or placebo capsules during 2 weeks of telmisartan. Following a 6-week washout, the protocol was repeated in reverse. 24hBPV was evaluated as a co-efficient of variation [CV (%) = mean/standard deviation] × 100). Twenty-four hour urinary sodium excretion, ambulatory BP and biochemical tests were performed at each phase. Results were analysed using a linear mixed model to generate predicted values for 24hBPV. Predicted 24hBPV was higher with telmisartan vs baseline (p = 0.01), with a trend towards reduced 24hBPV with salt (p = 0.052). Predicted 24hBPV was lower in females (p = 0.017), increasing age (p = 0.001) and increasing PRA (p = 0.011). In patients with T2DM, predicted 24hBPV increased from baseline with telmisartan, but there was no additional increase in predicted 24hBPV with salt supplementation. This suggests that in the short-term, salt supplementation has no apparent deleterious effects on 24hBPV. Long-term studies are required to evaluate the effect of 24hBPV on CV outcomes in patients with T2DM.

Salt-induced effects on microvascular function: A critical factor in hypertension mediated organ damage

Salt has been linked very closely to the occurrence and complications of arterial hypertension. A large percentage of patients with essential hypertension are salt-sensitive; that is, their blood pressure increases with increased salt intake and decreases with its reduction. For this reason, emphasis is placed on reducing salt intake to better regulate blood pressure. In day-to-day clinical practice this is viewed as mandatory for hypertensive patients who are judged to be salt-sensitive. Previous studies have highlighted the negative effect of high-salt diets on macrovascular function, which also affects blood pressure levels by increasing peripheral resistances. More recent studies provide a better overview of the pathophysiology of microvascular disorders and show that they are largely due to the overconsumption of salt. Microvascular lesions, which have a major impact on the functioning of vital organs, are often not well recognized in clinical practice and are not paid sufficient attention. In general, the damage caused by hypertension to the microvascular network is likely to be overlooked, while reversion of the damage is only rarely considered as a therapeutic target by the treating physician. The purpose of this review is to summarize the impact and the harmful consequences of increased salt consumption in the microvascular network, their significance and pathophysiology, and at the same time to place some emphasis on their treatment and reversion, mainly through diet.

N-terminal pro-brain natriuretic peptide (NT-proBNP) predicts the cardio-renal response to aliskiren in patients with type 2 diabetes at high renal and cardiovascular risk

Sodium retention and volume overload are the main determinants of poor response to renin-angiotensin-aldosterone system (RAAS) inhibition in patients with diabetes. As volume excess can exist without symptoms, biomarkers are needed to identify a priori which patients are volume overloaded and may experience less benefit from RAAS inhibition. N-terminal pro-brain natriuretic peptide (NT-proBNP) is released in the setting of increased cardiac wall stress and volume overload. We conducted a post hoc analysis among 5081 patients with type 2 diabetes mellitus participating in the ALTITUDE trial to investigate whether NTproBNP can predict the effects of additional therapy with aliskiren on cardio-renal endpoints. Aliskiren compared to placebo reduced the risk of the primary cardio-renal endpoint events by 20% (95% confidence interval [CI] 16 to 61) and 2% (95% CI -42 to 30) in the two lowest NT-proBNP tertiles, and it increased the risk by 25% (95% CI -4 to 96) in the highest NT-proBNP tertile (P value for trend = 0.009). Similar trends were observed for the cardiovascular and end-stage renal disease endpoints. Effects of aliskiren compared to placebo on safety outcomes (hyperkalaemia and hospitalization for acute kidney injury) were independent of NT-proBNP. In conclusion, baseline NT-proBNP may be used as a marker to predict the response to aliskiren with regard to cardio-renal outcomes when added to standard therapy with RAAS inhibition.

Management of patients with diabetes and CKD: conclusions from a "Kidney Disease: Improving Global Outcomes" (KDIGO) Controversies Conference

The prevalence of diabetes around the world has reached epidemic proportions and is projected to increase to 642 million people by 2040. Diabetes is already the leading cause of end-stage kidney disease (ESKD) in most developed countries, and the growth in the number of people with ESKD around the world parallels the increase in diabetes. The presence of kidney disease is associated with a markedly elevated risk of cardiovascular disease and death in people with diabetes. Several new therapies and novel investigational agents targeting chronic kidney disease patients with diabetes are now under development. This conference was convened to assess our current state of knowledge regarding optimal glycemic control, current antidiabetic agents and their safety, and new therapies being developed to improve kidney function and cardiovascular outcomes for this vulnerable population.

Antialbuminuric effect of eplerenone in comparison to thiazide diuretics in patients with hypertension

This study investigated the effects and safety of eplerenone or thiazide diuretics in patients with hypertension and albuminuria (pretreatment urinary albumin/creatinine ratio ≥10 mg/gCr) treated with an angiotensin II receptor blocker. The primary end point was the mean percent change in the urinary albumin/creatinine ratio from baseline to 48 weeks. An efficacy analysis was performed in 195 patients (98 in the eplerenone group and 97 in the thiazide group). Systolic and diastolic blood pressures at 48 weeks were similar in the two groups. The mean percent change in the urinary albumin/creatinine ratio from baseline to 48 weeks was similar in the two groups (P=.804). In the safety analysis, the withdrawal rates for adverse events were similar in both groups. The antialbuminuric effects and safety of eplerenone therapy were similar to those of thiazide diuretics when combined with an angiotensin II receptor blocker in patients with hypertension and albuminuria.

Sodium and Its Role in Cardiovascular Disease - The Debate Continues

Guidelines have recommended significant reductions in dietary sodium intake to improve cardiovascular health. However, these dietary sodium intake recommendations have been questioned as emerging evidence has shown that there is a higher risk of cardiovascular disease with a low sodium diet, including in individuals with type 2 diabetes. This may be related to the other pleotropic effects of dietary sodium intake. Therefore, despite recent review of dietary sodium intake guidelines by multiple organizations, including the dietary guidelines for Americans, American Diabetes Association, and American Heart Association, concerns about the impact of the degree of sodium restriction on cardiovascular health continue to be raised. This literature review examines the effects of dietary sodium intake on factors contributing to cardiovascular health, including left ventricular hypertrophy, heart rate, albuminuria, rennin-angiotensin-aldosterone system activation, serum lipids, insulin sensitivity, sympathetic nervous system activation, endothelial function, and immune function. In the last part of this review, the association between dietary sodium intake and cardiovascular outcomes, especially in individuals with diabetes, is explored. Given the increased risk of cardiovascular disease in individuals with diabetes and the increasing incidence of diabetes worldwide, this review is important in summarizing the recent evidence regarding the effects of dietary sodium intake on cardiovascular health, especially in this population.

Reduction in sodium intake is independently associated with improved blood pressure control in people with chronic kidney disease in primary care

Decreasing sodium intake has been associated with improvements in blood pressure (BP) and proteinuria, two important risk factors for CVD and chronic kidney disease (CKD) progression. We aimed to investigate the role of sodium intake by examining the effect of changes in sodium intake over 1 year on BP and proteinuria in people with early stage CKD. From thirty-two general practices, 1607 patients with previous estimated glomerular filtration rate of 59-30 ml/min per 1.73 m² and mean age of 72.9 (sd 9.0) years were recruited. Clinical assessment, urine and serum biochemistry testing were performed at baseline and after 1 year. Sodium intake was estimated from early morning urine specimens using an equation validated for this study population. We found that compared with people who increased their sodium intake from ≤ 100 to >100 mmol/d over 1 year, people who decreased their intake from >100 to ≤ 100 mmol/d evidenced a greater decrease in all BP variables (Δmean arterial pressure (ΔMAP) = -7.44 (SD 10.1) v. -0.23 (SD 10.4) mmHg; P<0.001) as well as in pulse wave velocity (ΔPWV = -0.47 (SD 1.3) v. 0.08 (SD 1.88) m/s; P<0.05). Albuminuria improved only in albuminuric patients who decreased their sodium intake. BP improved in people who maintained low sodium intake at both times and in those with persistent high intake, but the number of anti-hypertensive increased only in the higher sodium intake group, and PWV improved only in participants with lower sodium intake. Decreasing sodium intake was an independent determinant of ΔMAP. Although more evidence is needed, our results support the benefits of reducing and maintaining sodium intake below 100 mmol/d (2.3-2.4 g/d) in people with early stages of CKD.

Salt Restriction in Diabetes

There are no long-term interventions examining the effects of salt reduction in people with diabetes, and these are urgently required. Sodium reduction is controversial as it appears that an intake below 2.5 g and above 6 g/day of salt is associated with increased cardiovascular disease risk. However, pre-existing illness leading to a lower salt intake may confound the findings. Only a few studies have prospectively collected data on the sodium intake and excretion of people with diabetes and examined hard end points. In addition, future studies need to collect more data on food intake as well as coexistent illnesses to address potential confounding. The World Health Organization recommends a reduction to less than 5 g/day salt in adults. Given that the available evidence suggests that the salt intake of people with type 2 diabetes is generally well above 6 g/day it seems reasonable to ensure individuals with diabetes have an intake below 6 g/day. However, such recommendations need to be individualized.

Meta-Analysis of the Effect of Dietary Sodium Restriction with or without Concomitant Renin-Angiotensin-Aldosterone System-Inhibiting Treatment on Albuminuria

BACKGROUND AND OBJECTIVES

Urinary albumin excretion and/or albumin to creatinine ratio are associated with CKD and higher risk of cardiovascular events. Several studies investigated the effect of reduced dietary sodium intake on urinary albumin excretion and/or albumin to creatinine ratio in adult patient populations, but the majority was inconclusive because of insufficient statistical power. A meta-analysis of the randomized, controlled trials available could overcome this problem and lead to more definitive conclusions.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A systematic search of the online databases available (from 1996 to October of 2014) was conducted of randomized, controlled trials that expressed urinary albumin excretion or albumin to creatinine ratio as the difference between the effects of two different sodium intake regimens. For each study, the mean difference and 95% confidence intervals were pooled using a random effect model. Heterogeneity, publication bias, subgroup, and meta-regression analyses were performed.

RESULTS

Eleven studies met the predefined inclusion criteria and provided 23 cohorts with 516 participants and 1-6 weeks of follow-up time. In the pooled analysis, an average reduction in sodium intake of 92 mmol/d was associated with a 32.1% (95% confidence interval, -44.3 to -18.8) reduction in urinary albumin excretion. The effect of sodium restriction was higher in the cohorts including patients on concomitant renin-angiotensin-aldosterone system-blocking therapy, in the studies with intervention lasting at least 2 weeks, and among participants with evidence of kidney damage. A greater reduction of urinary albumin excretion was associated with a higher decrease in BP during the intervention. The analysis of changes in albumin to creatinine ratio provided similar results.

CONCLUSIONS

This meta-analysis indicates that sodium intake reduction markedly reduces albumin excretion, more so during concomitant renin-angiotensin-aldosterone system-blocking therapy and among patients with kidney damage.

Short-term dietary salt supplementation blunts telmisartan induced increases in plasma renin activity in hypertensive patients with type 2 diabetes mellitus

Current guidelines recommend low dietary salt intake (LDS) in patients with diabetes to reduce blood pressure (BP). However, low salt intake has been associated with higher mortality rates in people with diabetes. Our aim is to examine the effect of angiotensin II receptor blocker (ARB), telmisartan, with and without dietary sodium chloride (NaCl) supplementation, on BP [mean arterial pressure (MAP)], plasma renin activity (PRA), serum aldosterone level and estimated glomerular filtration rate (eGFR) in hypertensive patients with type 2 diabetes. In a randomized, double-blind, placebo-controlled study (RCT), 28 patients with type 2 diabetes, treated with telmisartan (40 mg daily), received 2 weeks of placebo or NaCl capsules (100 mmol/24 h). Following a 6-week washout, the protocol was repeated in reverse. Twenty-four-hour urinary sodium excretion (24hUNa), ambulatory BP (ABP) monitoring and blood tests were performed before and after each study phase. The telmisartan-associated increase in PRA was blunted by approximately 50% during salt supplementation compared with placebo; median PRA was 2.3 μg/l/h with placebo compared with 1.7 μg/l/h with salt (P<0.001). A trend towards blunting of ARB induced increases in serum aldosterone was also demonstrated. Salt supplementation significantly reduced the MAP lowering effects of telmisartan (P<0.05). The present study demonstrates that salt supplementation blunts the telmisartan induced increase in PRA in patients with type 2 diabetes.

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

PURPOSE OF REVIEW

Restriction of dietary sodium is recommended at a population level as well as for groups at high cardiovascular risk, and chronic kidney disease (CKD). This review addresses recent evidence for the protective effect of dietary sodium restriction in CKD patients specifically.

RECENT FINDINGS

Sodium intake in CKD populations is generally high, and often above population average. Recent data demonstrated that moderately lower sodium intake in CKD patients is associated with substantially better long-term outcome of renin-angiotensin-aldosterone system (RAAS)-blockade, in diabetic and nondiabetic CKD, related to better effects of RAAS-blockade on proteinuria, independent of blood pressure. This is in line with better short-term efficacy of RAAS-blockade during moderate sodium restriction in diabetic and nondiabetic CKD. This effect of sodium restriction is likely mediated by its effects on volume status. Sustainable sodium restriction can be achieved by approaches on the basis of behavioral sciences.

SUMMARY

Moderate restriction of dietary sodium can substantially improve the protective effects of RAAS-blockade in CKD, by specific renal effects apparent from proteinuria reduction. The latter precludes straightforward extrapolation of data from nonrenal populations to CKD. Concerns regarding the adverse effects of a very low sodium intake should not distract from the protective effects of moderate sodium restriction. Prospective studies should assess the efficacy and sustainability of different strategies to target high sodium intake in CKD, along with measures at population level.

VIDEO ABSTRACT

http://links.lww.com/CONH/A14.

Effects of intensive low-salt diet education on albuminuria among nondiabetic patients with hypertension treated with olmesartan: a single-blinded randomized, controlled trial

BACKGROUND AND OBJECTIVES

The antiproteinuric effect of a renin-angiotensin-aldosterone system blockade can be magnified by dietary salt restriction. This study sought to determine the effect of intensive low-salt diet education on BP and urine albumin excretion in nondiabetic patients with hypertension and albuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study was conducted between March of 2012 and March of 2013 as an open-label, randomized, controlled trial. After a run-in period of 8 weeks, all patients received the angiotensin II receptor blocker olmesartan (40 mg daily). Patients were then divided into two groups. One group was treated for another 8 weeks with angiotensin II receptor blocker plus conventional low-salt diet education, and the other group was treated for 8 weeks with angiotensin II receptor blocker plus intensive low-salt diet education. The final analyses was performed with 245 completed patients.

RESULTS

The amount of daily albuminuria was significantly decreased from 0 (566.0 [25.0-5398.6] mg/d) to 8 weeks (282.5 [16.1-4898.5] mg/d; P<0.001). From 8 to 16 weeks, the 24-hour urinary sodium excretion was decreased by 36.0±5.9 mmol/d in the intensive education group and 8.8±4.9 mmol/d in the conventional education group (interaction P<0.001). Patients who completed intensive low-salt diet education exhibited greater decreases in urinary albumin excretion than the control group (change in albuminuria from 8 to 16 weeks, -154.0 versus 0.4 mg/d; P=0.01). Urinary albumin excretion tended to decrease as the 24-hour urinary sodium excretion amount decreased (R=0.32; 95% confidence interval, 0.20 to 0.43; P<0.001).

CONCLUSIONS

The 24-hour urinary albumin excretion was decreased more in patients in the intensive low-salt diet education group than patients in the conventional education group. Weekly intensive education on a low-salt diet would be a suitable method for clinical practice.

High sodium intake is associated with important risk factors in a large cohort of chronic kidney disease patients

BACKGROUND/OBJECTIVES

An increased risk of mortality and cardiovascular disease (CVD) is observed in people with chronic kidney disease (CKD) even in early stages. Dietary sodium intake has been associated with important CVD and CKD progression risk factors such as hypertension and proteinuria in this population. We aimed to investigate the relationship between sodium intake and CVD or CKD progression risk factors in a large cohort of patients with CKD stage 3 recruited from primary care.

SUBJECTS/METHODS

A total of 1733 patients with previous estimated glomerular filtration rate (eGFR) of 30-59 ml/min/1.73m(2), with a mean age 72.9±9.0 years, were recruited from 32 general practices in primary care in England. Medical history was obtained and participants underwent clinical assessment, urine and serum biochemistry testing. Sodium intake was estimated from three early-morning urine specimens using an equation validated for this study population.

RESULTS

Sixty percent of participants who had estimated sodium intake above recommendation (>100 mmol/day or 6 g salt/day) also had higher diastolic blood pressure, mean arterial pressure (MAP), urinary albumin-to-creatinine ratio, high-sensitive C-reactive protein and uric acid and used a greater number of anti-hypertensive drugs. In multivariable regression analysis, excessive sodium intake was an independent predictor of MAP (B=1.57, 95% confidence interval (CI) 0.41-2.72; P=0.008) and albuminuria (B=1.35, 95% CI 1.02-1.79; P=0.03).

CONCLUSIONS

High sodium intake was associated with CVD and CKD progression risk factors in patients with predominantly early stages of CKD followed up in primary care. This suggests that dietary sodium intake could afffect CVD risk even in early or mild CKD. Intervention studies are warranted to investigate the potential benefit of dietary advice to reduce sodium intake in this population.

Fibroblast growth factor 23 and the antiproteinuric response to dietary sodium restriction during renin-angiotensin-aldosterone system blockade

BACKGROUND

Residual proteinuria during renin-angiotensin-aldosterone system (RAAS) blockade is a major renal and cardiovascular risk factor in chronic kidney disease. Dietary sodium restriction potentiates the antiproteinuric effect of RAAS blockade, but residual proteinuria remains in many patients. Previous studies linked high fibroblast growth factor 23 (FGF-23) levels with volume overload; others linked higher serum phosphate levels with impaired RAAS-blockade efficacy. We hypothesized that FGF-23 reduces the capacity of dietary sodium restriction to potentiate RAAS blockade, impairing the antiproteinuric effect.

STUDY DESIGN

Post hoc analysis of cohort data from a randomized crossover trial with two 6-week study periods comparing proteinuria after a regular-sodium diet with proteinuria after a low-sodium diet, both during background angiotensin-converting enzyme inhibition.

SETTING & PARTICIPANTS

47 nondiabetic patients with CKD with residual proteinuria (median protein excretion, 1.9 [IQR, 0.8-3.1] g/d; mean age, 50±13 [SD] years; creatinine clearance, 69 [IQR, 50-110] mL/min).

PREDICTOR

Plasma carboxy-terminal FGF-23 levels.

OUTCOMES

Difference in residual proteinuria at the end of the regular-sodium versus low-sodium study period. Residual proteinuria during the low-sodium diet period adjusted for proteinuria during the regular-sodium diet period.

RESULTS

Higher baseline FGF-23 level was associated with reduced antiproteinuric response to dietary sodium restriction (standardized β=-0.46; P=0.001; model R(2)=0.71). For every 100-RU/mL increase in FGF-23 level, the antiproteinuric response to dietary sodium restriction was reduced by 10.6%. Higher baseline FGF-23 level was a determinant of more residual proteinuria during the low-sodium diet (standardized β=0.27; P=0.003) in linear regression analysis adjusted for baseline proteinuria (model R(2)=0.71). There was no interaction with creatinine clearance (P interaction=0.5). Baseline FGF-23 level did not predict changes in systolic or diastolic blood pressure upon intensified antiproteinuric treatment.

LIMITATIONS

Observational study, limited sample size.

CONCLUSIONS

FGF-23 levels are associated independently with impaired antiproteinuric response to sodium restriction in addition to RAAS blockade. Future studies should address whether FGF-23-lowering strategies may further optimize proteinuria reduction by RAAS blockade combined with dietary sodium restriction.

Effects of sodium restriction and hydrochlorothiazide on RAAS blockade efficacy in diabetic nephropathy: a randomised clinical trial

BACKGROUND

Reduction of dietary sodium intake or diuretic treatment increases renin-angiotensin-aldosterone system (RAAS) blockade efficacy in non-diabetic nephropathy. We aimed to investigate the effect of sodium restriction and the diuretic hydrochlorothiazide, separately and in combination, added to RAAS blockade on residual albuminuria in patients with type 2 diabetic nephropathy.

METHODS

In this multicentre, double-blind, placebo-controlled, crossover randomised trial, we included patients with type 2 diabetic nephropathy. Main entry criteria were microalbuminaria or macroalbuminuria, and creatinine clearance of 30 mL/min or higher with less than 6 mL/min decline in the previous year. We tested the separate and combined effects of sodium restriction (dietary counselling in the outpatient setting) and hydrochlorothiazide (50 mg daily), added to standardised maximal angiotensin-converting enzyme (ACE) inhibition (lisinopril 40 mg daily), on albuminuria (primary endpoint). Patients were given hydrochlorothiazide (50 mg per day) or placebo during four treatment periods of 6 weeks. Both treatments were combined with regular sodium diet or sodium restriction (target sodium intake 50 mmol Na(+) per day). The 6-week treatment periods were done consecutively in a random order. Patients were randomised in blocks of two patients. The trial was analysed by intention to treat. The trial is registered with TrialRegister.nl, number 2366.

FINDINGS

Of 89 eligible patients, 45 were included in the study. Both sodium restriction and hydrochlorothiazide significantly reduced albuminuria, irrespective of treatment sequence. Residual geometric mean albuminuria with baseline treatment was 711 mg per day (95% CI 485-1043); it was significantly reduced by sodium restriction (393 mg per day [258-599], p=0·0002), by hydrochlorothiazide (434 mg per day [306-618], p=0·0003), and to the greatest extent by their combination (306 mg per day [203-461], p<0·0001). Orthostatic complaints were present in two patients (4%) during baseline treatment, five (11%) during addition of sodium restriction, five (11%) during hydrochlorothiazide treatment, and 12 (27%) during combination treatment. No serious adverse events occurred.

INTERPRETATION

We conclude that sodium restriction is an effective non-pharmacological intervention to increase RAAS blockade efficacy in type 2 diabetic nephropathy.

FUNDING

None.

Release from glomerular overload by the addition of low-dose thiazide in patients with angiotensin receptor blocker-resistant hypertension

BACKGROUND/AIMS

This multicenter, prospective, observational study assessed the renoprotective effects of losartan/thiazide combination therapy in terms of lowering the estimated glomerular filtration rate (eGFR).

METHODS

Adult patients with angiotensin receptor blocker (ARB)-resistant essential hypertension (n = 104) were enrolled and switched to combination therapy with losartan (50 mg/day) and hydrochlorothiazide (12.5 mg/day).

RESULTS

eGFR values declined significantly during the first 3 months, and changes in eGFR were assessed according to tertiles of the eGFR decrease ratio at 3 months. Only the high eGFR decrease (1st tertile) group showed significantly greater decreases in baseline eGFR and albumin-to-creatinine ratio (ACR) during the first 3 months. Additionally, the assessment according to tertiles of the baseline eGFR showed a signifcant decrease in eGFR and ACR during the first 3 months in the high baseline eGFR (1st tertile) group, but not in the moderate (2nd tertile) and low baseline eGFR (3rd tertile) groups.

CONCLUSION

The present results revealed that losartan/thiazide combination therapy attenuated glomerular overload, indicating that this therapy may provide glomerular protection in patients with an elevated GFR without causing prolonged damage to renal function.

Relationship between urinary sodium excretion and serum aldosterone in patients with diabetes in the presence and absence of modifiers of the renin-angiotensin-aldosterone system

Although low dietary salt intake has beneficial effects on BP (blood pressure), low 24hUNa (24 h urinary sodium excretion), the most accurate estimate of dietary salt intake, is associated with increased mortality in people with diabetes. In the non-diabetic population, low salt intake is associated with increased RAAS (renin-angiotensin-aldosterone system) activity. In this cross-sectional study, we examined the relationship between 24hUNa, PRA (plasma renin activity), serum aldosterone and BNP (brain natriuretic peptide) in patients with diabetes. Clinical characteristics, 24hUNa, PRA, serum aldosterone and BNP were recorded in 222 consecutive patients (77% with Type 2 diabetes) attending a diabetes clinic at a tertiary hospital. The relationship between 24hUNa, serum aldosterone, PRA, BNP, urinary potassium excretion, serum potassium, serum sodium, eGFR (estimated glomerular filtration rate), urinary albumin excretion and HbA1c (glycated haemoglobin) was examined by a multivariable regression model. Levels of 24hUNa significantly predicted serum aldosterone in a linear fashion (R²=0.20, P=0.002). In the subgroup of patients (n=46) not taking RAAS-modifying agents, this relationship was also observed (R²=0.10, P=0.03), and the effect of 24hUNa on serum aldosterone was found to be more pronounced than in the whole cohort (coefficient=-0.0014, compared with -0.0008). There was no demonstrable relationship between 24hUNa and PRA or BNP. Low 24hUNa is associated with increased serum aldosterone in people with diabetes, in the presence and absence of RAAS-modifying agents. This raises the possibility that stimulation of the RAAS may be a mechanism that contributes to adverse outcomes observed in patients with low 24hUNa.

Association between dietary sodium and potassium intake with chronic kidney disease in US adults: a cross-sectional study

BACKGROUND/AIMS

Clinical guidelines recommend a diet low in sodium and high in potassium to reduce blood pressure and cardiovascular events. Little is known about the relationship between dietary sodium and potassium intake and chronic kidney disease (CKD).

METHODS

13,917 participants from the National Health and Nutrition Examination Survey (2001-2006) were examined. Sodium and potassium intake were calculated from 24-hour recall and evaluated in quartiles. CKD was defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) or eGFR ≥60 ml/min/1.73 m(2) with albuminuria (>30 mg/g creatinine).

RESULTS

The mean (SE) age and eGFR of participants were 45.0 ± 0.4 years and 88.0 ± 0.60 ml/min/1.73 m(2), respectively. 2,333 (14.2%) had CKD: 1,146 (7.3%) had an eGFR <60 ml/min/1.73 m(2) and 1,514 (8.4%) had an eGFR ≥60 ml/min/1.73 m(2) and albuminuria. After adjustment for age, sex, race, BMI, diabetes, hypertension, cardiovascular disease and congestive heart failure, subjects in the highest quartile of sodium intake had lower odds of CKD compared to subjects in the lowest quartile (adjusted OR: 0.79; 95% CI: 0.66-0.96; p < 0.016). Compared to the highest quartile, the odds of CKD increased 44% for participants in the lowest quartile of potassium intake (adjusted OR: 1.44; 95% CI: 1.16-1.79; p = 0.0011).

CONCLUSIONS

Higher intake of sodium and potassium is associated with lower odds of CKD among US adults. These results should be corroborated through longitudinal studies and clinical trials designed specifically to examine the effects of dietary sodium and potassium intake on kidney disease and its progression.

Effect of longer-term modest salt reduction on blood pressure

BACKGROUND

A reduction in salt intake lowers blood pressure (BP) and, thereby, reduces cardiovascular risk. A recent meta-analysis by Graudal implied that salt reduction had adverse effects on hormones and lipids which might mitigate any benefit that occurs with BP reduction. However, Graudal's meta-analysis included a large number of very short-term trials with a large change in salt intake, and such studies are irrelevant to the public health recommendations for a longer-term modest reduction in salt intake. We have updated our Cochrane meta-analysis.

OBJECTIVES

To assess (1) the effect of a longer-term modest reduction in salt intake (i.e. of public health relevance) on BP and whether there was a dose-response relationship; (2) the effect on BP by sex and ethnic group; (3) the effect on plasma renin activity, aldosterone, noradrenaline, adrenaline, cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglycerides.

SEARCH METHODS

We searched MEDLINE, EMBASE, Cochrane Hypertension Group Specialised Register, Cochrane Central Register of Controlled Trials, and reference list of relevant articles.

SELECTION CRITERIA

We included randomised trials with a modest reduction in salt intake and duration of at least 4 weeks.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two reviewers. Random effects meta-analyses, subgroup analyses and meta-regression were performed.

MAIN RESULTS

Thirty-four trials (3230 participants) were included. Meta-analysis showed that the mean change in urinary sodium (reduced salt vs usual salt) was -75 mmol/24-h (equivalent to a reduction of 4.4 g/d salt), the mean change in BP was -4.18 mmHg (95% CI: -5.18 to -3.18, I (2)=75%) for systolic and -2.06 mmHg (95% CI: -2.67 to -1.45, I (2)=68%) for diastolic BP. Meta-regression showed that age, ethnic group, BP status (hypertensive or normotensive) and the change in 24-h urinary sodium were all significantly associated with the fall in systolic BP, explaining 68% of the variance between studies. A 100 mmol reduction in 24 hour urinary sodium (6 g/day salt) was associated with a fall in systolic BP of 5.8 mmHg (95%CI: 2.5 to 9.2, P=0.001) after adjusting for age, ethnic group and BP status. For diastolic BP, age, ethnic group, BP status and the change in 24-h urinary sodium explained 41% of the variance between studies. Meta-analysis by subgroup showed that, in hypertensives, the mean effect was -5.39 mmHg (95% CI: -6.62 to -4.15, I (2)=61%) for systolic and -2.82 mmHg (95% CI: -3.54 to -2.11, I (2)=52%) for diastolic BP. In normotensives, the mean effect was -2.42 mmHg (95% CI: -3.56 to -1.29, I (2)=66%) for systolic and -1.00 mmHg (95% CI: -1.85 to -0.15, I (2)=66%) for diastolic BP. Further subgroup analysis showed that the decrease in systolic BP was significant in both whites and blacks, men and women. Meta-analysis of hormone and lipid data showed that the mean effect was 0.26 ng/ml/hr (95% CI: 0.17 to 0.36, I (2)=70%) for plasma renin activity, 73.20 pmol/l (95% CI: 44.92 to 101.48, I (2)=62%) for aldosterone, 31.67 pg/ml (95% CI: 6.57 to 56.77, I (2)=5%) for noradrenaline, 6.70 pg/ml (95% CI: -0.25 to 13.64, I (2)=12%) for adrenaline, 0.05 mmol/l (95% CI: -0.02 to 0.11, I (2)=0%) for cholesterol, 0.05 mmol/l (95% CI: -0.01 to 0.12, I (2)=0%) for LDL, -0.02 mmol/l (95% CI: -0.06 to 0.01, I (2)=16%) for HDL, and 0.04 mmol/l (95% CI: -0.02 to 0.09, I (2)=0%) for triglycerides.

AUTHORS' CONCLUSIONS

A modest reduction in salt intake for 4 or more weeks causes significant and, from a population viewpoint, important falls in BP in both hypertensive and normotensive individuals, irrespective of sex and ethnic group. With salt reduction, there is a small physiological increase in plasma renin activity, aldosterone and noradrenaline. There is no significant change in lipid levels. These results provide further strong support for a reduction in population salt intake. This will likely lower population BP and, thereby, reduce cardiovascular disease. Additionally, our analysis demonstrates a significant association between the reduction in 24-h urinary sodium and the fall in systolic BP, indicating the greater the reduction in salt intake, the greater the fall in systolic BP. The current recommendations to reduce salt intake from 9-12 to 5-6 g/d will have a major effect on BP, but are not ideal. A further reduction to 3 g/d will have a greater effect and should become the long term target for population salt intake.

Nebivolol reduces cardiac angiotensin II, associated oxidative stress and fibrosis but not arterial pressure in salt-loaded spontaneously hypertensive rats

OBJECTIVES

Increased sympathetic outflow, renin-angiotensin system (RAS) activity, and oxidative stress are critical mechanisms underlying the adverse cardiovascular effects of dietary salt excess. Nebivolol is a third-generation, highly selective β1-receptor blocker with RAS-reducing effects and additional antioxidant properties. This study evaluated the hypothesis that nebivolol reduces salt-induced cardiac remodeling and dysfunction in spontaneous hypertensive rats (SHRs) by suppressing cardiac RAS and oxidative stress.

METHODS

Male SHRs (8 weeks of age) were given an 8% high salt diet (HSD; n = 22), whereas their age-matched controls (n = 10) received standard chow. In a subgroup of HSD rats (n = 11), nebivolol was given at a dose of 10 mg/kg per day by gastric gavage.

RESULTS

After 5 weeks, HSD exacerbated hypertension as well as increased left-ventricular weight and collagen deposition while impairing left-ventricular relaxation. Salt-induced cardiac remodeling and dysfunction were associated with increased plasma renin concentration (PRC), cardiac angiotensin II immunostaining, and angiotensin-converting enzyme (ACE)/ACE2 mRNA and activity ratio. HSD also increased cardiac 3-nitrotyrosine staining indicating enhanced oxidative stress. Nebivolol treatment did not alter the salt-induced increase in arterial pressure, left-ventricular weight, and cardiac dysfunction but reduced PRC, cardiac angiotensin II immunostaining, ACE/ACE2 ratio, oxidative stress, and fibrosis.

CONCLUSIONS

Our data suggest that nebivolol, in a blood pressure-independent manner, ameliorated cardiac oxidative stress and associated fibrosis in salt-loaded SHRs. The beneficial effects of nebivolol may be attributed, at least in part, to the decreased ACE/ACE2 ratio and consequent reduction of cardiac angiotensin II levels.

Improving the efficacy of RAAS blockade in patients with chronic kidney disease

Reduction of blood pressure and proteinuria by blockade of the renin-angiotensin-aldosterone system (RAAS) has been the cornerstone of renoprotective intervention for patients with chronic kidney disease (CKD) for many years. Despite the proven efficacy of RAAS blockade, however, the reduction in proteinuria is insufficient in many patients, and does not prevent further deterioration of renal function. Short-term studies have shown that a variety of treatment intensification strategies have a beneficial effect on blood pressure and proteinuria, including RAAS blockade using either dose escalation or multiple drugs, and restriction of dietary sodium. Large clinical trials have shown that RAAS blockade with multiple drugs does not improve patients' long-term renal or cardiovascular outcome. By contrast, two post-hoc analyses of landmark trials in nephrology show beneficial renal and cardiovascular effects from avoiding excessive dietary sodium intake during single-agent RAAS blockade therapy. The effects of dietary sodium restriction on renal or cardiovascular outcome still require prospective confirmation. However, current data support the implementation of lifestyle changes to reduce dietary sodium intake in combination with single-agent RAAS blockade, rather than dual-agent RAAS blockade, as a potent and feasible strategy to mitigate the burden of renal and cardiovascular disease in patients with CKD.

Moderation of dietary sodium potentiates the renal and cardiovascular protective effects of angiotensin receptor blockers

Dietary sodium restriction has been shown to enhance the short-term response of blood pressure and albuminuria to angiotensin receptor blockers (ARBs). Whether this also enhances the long-term renal and cardiovascular protective effects of ARBs is unknown. Here we conducted a post-hoc analysis of the RENAAL and IDNT trials to test this in patients with type 2 diabetic nephropathy randomized to ARB or non-renin-angiotensin-aldosterone system (non-RAASi)-based antihypertensive therapy. Treatment effects on renal and cardiovascular outcomes were compared in subgroups based on dietary sodium intake during treatment, measured as the 24-h urinary sodium/creatinine ratio of 1177 patients with available 24-h urinary sodium measurements. ARB compared to non-RAASi-based therapy produced the greatest long-term effects on renal and cardiovascular events in the lowest tertile of sodium intake. Compared to non-RAASi, the trend in risk for renal events was significantly reduced by 43%, not changed, or increased by 37% for each tertile of increased sodium intake, respectively. The trend for cardiovascular events was significantly reduced by 37%, increased by 2% and 25%, respectively. Thus, treatment effects of ARB compared with non-RAASi-based therapy on renal and cardiovascular outcomes were greater in patients with type 2 diabetic nephropathy with lower than higher dietary sodium intake. This underscores the avoidance of excessive sodium intake, particularly in type 2 diabetic patients receiving ARB therapy.

Sodium intake, ACE inhibition, and progression to ESRD

High sodium intake limits the antihypertensive and antiproteinuric effects of angiotensin-converting enzyme (ACE) inhibitors in patients with CKD; however, whether dietary sodium also associates with progression to ESRD is unknown. We conducted a post hoc analysis of the first and second Ramipril Efficacy in Nephropathy trials to evaluate the association of sodium intake with proteinuria and progression to ESRD among 500 CKD patients without diabetes who were treated with ramipril (5 mg/d) and monitored with serial 24-hour urinary sodium and creatinine measurements. Urinary sodium/creatinine excretion defined low (<100 mEq/g), medium (100 to <200 mEq/g), and high (≥200 mEq/g) sodium intake. During a follow-up of >4.25 years, 92 individuals (18.4%) developed ESRD. Among those with low, medium, and high sodium intakes, the incidence of ESRD was 6.1 (95% confidence interval [95% CI], 3.8-9.7), 7.9 (95% CI, 6.1-10.2), and 18.2 (95% CI, 11.3-29.3) per 100 patient-years, respectively (P<0.001). Patients with high dietary sodium exhibited a blunted antiproteinuric effect of ACE inhibition despite similar BP among groups. Each 100-mEq/g increase in urinary sodium/creatinine excretion associated with a 1.61-fold (95% CI, 1.15-2.24) higher risk for ESRD; adjusting for baseline proteinuria attenuated this association to 1.38-fold (95% CI, 0.95-2.00). This association was independent from BP but was lost after adjusting for changes in proteinuria. In summary, among patients with CKD but without diabetes, high dietary salt (>14 g daily) seems to blunt the antiproteinuric effect of ACE inhibitor therapy and increase the risk for ESRD, independent of BP control.

Elevated N-terminal pro-brain natriuretic peptide levels predict an enhanced anti-hypertensive and anti-proteinuric benefit of dietary sodium restriction and diuretics, but not angiotensin receptor blockade, in proteinuric renal patients

BACKGROUND

Renin-angiotensin aldosterone system (RAAS) blockade only partly reduces blood pressure, proteinuria and renal and cardiovascular risk in chronic kidney disease (CKD) but often requires sodium targeting [i.e. low sodium diet (LS) and/or diuretics] for optimal efficacy. However, both under- and overtitration of sodium targeting can easily occur. We evaluated whether N-terminal pro-brain natriuretic peptide (NT-proBNP), a biomarker of volume expansion, predicts the benefits of sodium targeting in CKD patients.

METHODS

In a cross-over randomized controlled trial, 33 non-diabetic CKD patients (proteinuria 3.8 ± 0.4 g/24 h, blood pressure 143/86 ± 3/2 mmHg, creatinine clearance 89 ± 5 mL/min) were treated during 6-week periods with placebo, angiotensin receptor blockade (ARB; losartan 100 mg/day) and ARB plus diuretics (losartan 100 mg/day plus hydrochlorothiazide 25 mg/day), combined with LS (93 ± 52 mmol Na(+)/24 h) and regular sodium diet (RS; 193 ± 62 mmol Na(+)/24 h, P < 0.001 versus LS), in random order. As controls, 27 healthy volunteers were studied.

RESULTS

NT-proBNP was elevated in patients during placebo + RS [90 (60-137) versus 35 (27-45) pg/mL in healthy controls, P = 0.001]. NT-proBNP was lowered by LS, ARB and diuretics and was normalized by ARB + diuretic + LS [39 (26-59) pg/mL, P = 0.65 versus controls]. NT-proBNP levels above the upper limit of normal (>125 pg/mL) predicted a larger reduction of blood pressure and proteinuria by LS and diuretics but not by ARB, during all steps of the titration regimen.

CONCLUSIONS

Elevated NT-proBNP levels predict an enhanced anti-hypertensive and anti-proteinuric benefit of sodium targeting, but not RAAS blockade, in proteinuric CKD patients. Importantly, this applies to the untreated condition, as well as to the subsequent treatment steps, consisting of RAAS blockade and even RAAS blockade combined with diuretics. NT-proBNP can be a useful tool to identify CKD patients in whom sodium targeting can improve blood pressure and proteinuria.

Moderate dietary sodium restriction added to angiotensin converting enzyme inhibition compared with dual blockade in lowering proteinuria and blood pressure: randomised controlled trial

OBJECTIVE

To compare the effects on proteinuria and blood pressure of addition of dietary sodium restriction or angiotensin receptor blockade at maximum dose, or their combination, in patients with non-diabetic nephropathy receiving background treatment with angiotensin converting enzyme (ACE) inhibition at maximum dose.

DESIGN

Multicentre crossover randomised controlled trial.

SETTING

Outpatient clinics in the Netherlands.

PARTICIPANTS

52 patients with non-diabetic nephropathy.

INTERVENTIONS

All patients were treated during four 6 week periods, in random order, with angiotensin receptor blockade (valsartan 320 mg/day) or placebo, each combined with, consecutively, a low sodium diet (target 50 mmol Na(+)/day) and a regular sodium diet (target 200 mmol Na(+)/day), with a background of ACE inhibition (lisinopril 40 mg/day) during the entire study. The drug interventions were double blind; the dietary interventions were open label.

MAIN OUTCOME MEASURES

The primary outcome measure was proteinuria; the secondary outcome measure was blood pressure.

RESULTS

Mean urinary sodium excretion, a measure of dietary sodium intake, was 106 (SE 5) mmol Na(+)/day during a low sodium diet and 184 (6) mmol Na(+)/day during a regular sodium diet (P<0.001). Geometric mean residual proteinuria was 1.68 (95% confidence interval 1.31 to 2.14) g/day during ACE inhibition plus a regular sodium diet. Addition of angiotensin receptor blockade to ACE inhibition reduced proteinuria to 1.44 (1.07 to 1.93) g/day (P=0.003), addition of a low sodium diet reduced it to 0.85 (0.66 to 1.10) g/day (P<0.001), and addition of angiotensin receptor blockade plus a low sodium diet reduced it to 0.67 (0.50 to 0.91) g/day (P<0.001). The reduction of proteinuria by the addition of a low sodium diet to ACE inhibition (51%, 95% confidence interval 43% to 58%) was significantly larger (P<0.001) than the reduction of proteinuria by the addition of angiotensin receptor blockade to ACE inhibition (21%, (8% to 32%) and was comparable (P=0.009, not significant after Bonferroni correction) to the reduction of proteinuria by the addition of both angiotensin receptor blockade and a low sodium diet to ACE inhibition (62%, 53% to 70%). Mean systolic blood pressure was 134 (3) mm Hg during ACE inhibition plus a regular sodium diet. Mean systolic blood pressure was not significantly altered by the addition of angiotensin receptor blockade (131 (3) mm Hg; P=0.12) but was reduced by the addition of a low sodium diet (123 (2) mm Hg; P<0.001) and angiotensin receptor blockade plus a low sodium diet (121 (3) mm Hg; P<0.001) to ACE inhibition. The reduction of systolic blood pressure by the addition of a low sodium diet (7% (SE 1%)) was significantly larger (P=0.003) than the reduction of systolic blood pressure by the addition of angiotensin receptor blockade (2% (1)) and was similar (P=0.14) to the reduction of systolic blood pressure by the addition of both angiotensin receptor blockade and low sodium diet (9% (1)), to ACE inhibition.

CONCLUSIONS

Dietary sodium restriction to a level recommended in guidelines was more effective than dual blockade for reduction of proteinuria and blood pressure in non-diabetic nephropathy. The findings support the combined endeavours of patients and health professionals to reduce sodium intake. Trial registration Netherlands Trial Register NTR675.

Therapeutic approaches in lowering albuminuria: travels along the renin-angiotensin-aldosterone-system pathway

Achieving optimal blood pressure and albuminuria control is a major therapeutic treatment goal in patients with renal insufficiency. Angiotensin-converting enzyme-inhibitors (ACEIs) and angiotensin-receptor blockers (ARB) are the mainstay of therapy in these patients. However, despite these therapies many patients remain at high risk of renal or cardiovascular disease that shows a relationship with albuminuria. Various approaches have been tested to maximize the efficacy of ACEI and ARB. Increasing the dose of an ACEI or ARB beyond the maximal registered antihypertensive dose causes a distinct decrease in albuminuria without additional effects on blood pressure. The combination of an ACEI and ARB is another possibility to further reduce albuminuria. However, the alleged beneficial effects on hard renal and cardiovascular outcome are not unambiguously demonstrated. Adding a direct renin inhibitor to an ACEI or ARB has been shown to lower albuminuria in patients with and without diabetes. Long-term trials are currently under way to determine the effects of direct renin inhibition on clinical outcomes. Volume excess has been shown to blunt the blood pressure and albuminuria response to ACEI or ARB therapy. Intervening in volume status by means of restricting dietary sodium intake or diuretic therapy has convincingly been shown to lower blood pressure and albuminuria. Whether this strategy translates into a reduction in the risk of renal or cardiovascular events has not (yet) been investigated in prospective randomized trials. Various options are at hand which have been shown to maximize the blood pressure and albuminuria response to ACEI and ARB treatment. However, long-term studies supporting the benefits of these strategies on hard renal and cardiovascular outcomes are warranted.

Interaction of ACE and CYP11B2 genes on blood pressure response to hydrochlorothiazide in Han Chinese hypertensive patients

To valuate whether angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and aldosterone synthase (CYP11B2) gene -344T/C polymorphism are associated with individual response to hydrochlorothiazide (HCTZ) in the Han Chinese population with essential hypertension. We enrolled 829 mild/moderate hypertensive patients and 12.5 mg of HCTZ was given daily. After 6 weeks, the results showed that the ACE I/D polymorphism, not the CYP11B2 -344T/C polymorphism, was associated with systolic blood pressure (SBP) response to HCTZ (P = 0.009) in the Han Chinese population with essential hypertension, with no interaction.

High sodium and low potassium intake in patients with Type 2 diabetes

AIMS

To document dietary sodium and potassium intake and adherence to the Australian National Heart Foundation (NHF) guidelines in patients with Type 2 diabetes mellitus attending an Australian tertiary referral and university teaching hospital.

METHODS

In a longitudinal study, 24h urinary sodium (uNa), potassium (uK), creatinine (uCr), urea (uUrea) and glucose (uGlu) excretions, urine volume (uVol) and body mass index were recorded in 122 regular attenders over an 8 year period (2001-2008; mean of 1.9 samples/patient/year). In a cross-sectional study, the same measurements were recorded in patients providing urine samples in the month of June from 2001 to 2009 (782 patients, averaging 87/year).

RESULTS

In the longitudinal study, uNa (mmol/24 h) was 170 ± 53 (mean ± SD) in males and 142 ± 51 in females, whereas uK (mmol/24 h) was 75 ± 22 in males and 62 ± 18 in females. Once adjusted for insensible losses, only 3% of males and 14% of females met the NHF dietary sodium intake guidelines, and 14% of males and 3% of female patients met the NHF dietary potassium guidelines. Body mass index, uUrea, uVol and uGlu were independent predictors of uNa (adjusted r(2) =0.57, P<0.0001). The mean intra-individual coefficient of variation of the corrected uNa was 21 ± 1%. The cross-sectional study confirmed these findings, and no temporal trends were observed. There was no correlation with glycated haemoglobin to suggest natriuresis with hyperglycaemia.

CONCLUSIONS

Most patients with Type 2 diabetes mellitus do not meet NHF sodium or potassium intake guidelines. A diet high in sodium and low in potassium may contribute to the development of hypertension and to resistance to blood-pressure-lowering therapies.

Salt supplementation blunts the blood pressure response to telmisartan with or without hydrochlorothiazide in hypertensive patients with type 2 diabetes

AIMS/HYPOTHESIS

We assessed the effects of sodium chloride (NaCl) supplementation on the blood pressure response to treatment with telmisartan with or without hydrochlorothiazide in hypertensive patients with type 2 diabetes and habitually high (HDS, sodium excretion >200 mmol/24 h on two out of three consecutive occasions) or low (LDS, sodium excretion <100 mmol/24 h on two out of three consecutive occasions) salt intake.

METHODS

Patients received 4 weeks of telmisartan followed by 4 weeks of telmisartan plus hydrochlorothiazide. In a double-blind randomised fashion, patients received sodium chloride (NaCl, 100 mmol/24 h) or placebo capsules in addition to their habitual salt intake during the last 2 weeks of telmisartan and telmisartan plus hydrochlorothiazide therapy. The protocol was repeated with NaCl and placebo capsules administered in reverse order to allow each participant to act as his or her own control. At 0, 4, 8, 14, 18 and 22 weeks, 24 h ambulatory blood pressure (ABP) and 24 h urine collections were performed.

RESULTS

No statistically significant differences were seen in the ABP response in the LDS vs HDS groups to any of the interventions (p = 0.58). NaCl supplementation reduced the effect of telmisartan with or without hydrochlorothiazide on systolic BP by approximately 50% (-5.8 mmHg during NaCl supplementation vs -11.3 mmHg during placebo, mean difference 5.6 mmHg [95% CI 1.7-9.4 mmHg], p = 0.005), irrespective of habitual salt intake. By contrast, addition of hydrochlorothiazide increased the antihypertensive effect of telmisartan on systolic BP by approximately 35% (p = 0.048) in both groups of patients.

CONCLUSIONS/INTERPRETATION

NaCl supplementation blunts the effectiveness of telmisartan with or without hydrochlorothiazide in hypertensive patients with type 2 diabetes, independently of habitual low or high salt intake.

Dietary sodium in chronic kidney disease: a comprehensive approach

Despite existing guidelines, dietary sodium intake among people worldwide often exceeds recommended limits. Research evidence is growing in both animal and human studies showing indirect and direct adverse consequences of high dietary sodium on the kidney. In patients with kidney disease, dietary sodium may have important effects on proteinuria, efficacy of antiproteinuric pharmacologic therapy, hypertension control, maintaining an optimal volume status, and immunosuppressant therapy. Dietary sodium intake is an important consideration in patients with all stages of chronic kidney disease, including those receiving dialysis therapy or those who have received a kidney transplant. We review in detail the dietary sodium recommendations suggested by various organizations for patients with kidney disease. Potential barriers to successfully translating current sodium intake guidelines into practice include poor knowledge about the sodium content of food among both patients and providers, complex labeling information, patient preferences related to taste, and limited support for modifications in public policy. Finally, we offer existing and potential solutions that may assist providers in educating and empowering patients to effectively manage their dietary sodium intake.

The RAAS in the pathogenesis and treatment of diabetic nephropathy

Angiotensin II and other components of the renin-angiotensin-aldosterone system (RAAS) have a central role in the pathogenesis and progression of diabetic renal disease. A study in patients with type 1 diabetes and overt nephropathy found that RAAS inhibition with angiotensin-converting-enzyme (ACE) inhibitors was associated with a reduced risk of progression to end-stage renal disease and mortality compared with non-RAAS-inhibiting drugs. Blood-pressure control was similar between groups and proteinuria reduction was responsible for a large part of the renoprotective and cardioprotective effect. ACE inhibitors can also prevent microalbuminuria in patients with type 2 diabetes who are hypertensive and normoalbuminuric; in addition, ACE inhibitors are cardioprotective even in the early stages of diabetic renal disease. Angiotensin-II-receptor blockers (ARBs) are renoprotective (but not cardioprotective) in patients with type 2 diabetes and overt nephropathy or microalbuminuria. Studies have evaluated the renoprotective effect of other RAAS inhibitors, such as aldosterone antagonists and renin inhibitors, administered either alone or in combination with ACE inhibitors or ARBs. An important task for the future will be identifying which combination of agents achieves the best renoprotection (and cardioprotection) at the lowest cost. Such findings will have major implications, particularly in settings where money and facilities are limited and in settings where renal replacement therapy is not available and the prevention of kidney failure is life saving.