Effects of Treatment of Metabolic Acidosis in CKD: A Systematic Review and Meta-Analysis

Sodium Zirconium Cyclosilicate in CKD, Hyperkalemia, and Metabolic Acidosis: NEUTRALIZE Randomized Study

Key Points

Background

Metabolic acidosis and hyperkalemia are common in CKD. A potential dual effect of sodium zirconium cyclosilicate (SZC), a selective binder of potassium in the gastrointestinal tract, on serum potassium (sK+) and serum bicarbonate (sHCO3 −) was evaluated in patients with hyperkalemia and metabolic acidosis associated with CKD.

Methods

In the NEUTRALIZE study (NCT04727528), non-dialysis patients with stage 3–5 CKD, hyperkalemia (sK+>5.0 to ≤5.9 mmol/L), and metabolic acidosis (sHCO3 − 16–20 mmol/L) received open-label SZC 10 g three times daily for ≤48 hours. Patients achieving normokalemia (sK+ 3.5–5.0 mmol/L) were randomized 1:1 to SZC 10 g or placebo daily for 4 weeks. The primary end point was patients (%) maintaining normokalemia at the end of treatment (EOT) without rescue. Secondary end points included mean change in sHCO3 − at EOT (day 29) and patients (%) with normokalemia with a ≥3-mmol/L increase in sHCO3 − without rescue.

Results

Of 229 patients screened, 37 were randomized (SZC, n=17; placebo, n=20). High screen failure led to early study termination. At EOT, 88.2% (SZC) versus 20.0% (placebo) of patients maintained normokalemia (odds ratio, 56.2; P = 0.001). Low enrollment rendered secondary end point P values nominal. SZC treatment provided nominally significant increases in sHCO3 – versus placebo from day 15 onward. Patients with normokalemia with a ≥3-mmol/L increase in sHCO3 − without rescue were 35.3% (SZC) and 5.0% (placebo; P < 0.05). No new safety concerns were reported.

Conclusions

SZC effectively lowered sK+ and maintained normokalemia, with nominally significant increases in sHCO3 – observed for SZC versus placebo.

Metabolic Acidosis in CKD: Pathogenesis, Adverse Effects, and Treatment Effects

Metabolic acidosis is a frequent complication of chronic kidney disease and is associated with a number of adverse outcomes, including worsening kidney function, poor musculoskeletal health, cardiovascular events, and death. Mechanisms that prevent metabolic acidosis detrimentally promote further kidney damage, creating a cycle between acid accumulation and acid-mediated kidney injury. Disrupting this cycle through the provision of alkali, most commonly using sodium bicarbonate, is hypothesized to preserve kidney function while also mitigating adverse effects of excess acid on bone and muscle. However, results from clinical trials have been conflicting. There is also significant interest to determine whether sodium bicarbonate might improve patient outcomes for those who do not have overt metabolic acidosis. Such individuals are hypothesized to be experiencing acid-mediated organ damage despite having a normal serum bicarbonate concentration, a state often referred to as subclinical metabolic acidosis. Results from small- to medium-sized trials in individuals with subclinical metabolic acidosis have also been inconclusive. Well-powered clinical trials to determine the efficacy and safety of sodium bicarbonate are necessary to determine if this intervention improves patient outcomes.

Dietary acid load in health and disease

Maintaining an appropriate acid-base equilibrium is crucial for human health. A primary influencer of this equilibrium is diet, as foods are metabolized into non-volatile acids or bases. Dietary acid load (DAL) is a measure of the acid load derived from diet, taking into account both the potential renal acid load (PRAL) from food components like protein, potassium, phosphorus, calcium, and magnesium, and the organic acids from foods, which are metabolized to bicarbonate and thus have an alkalinizing effect. Current Western diets are characterized by a high DAL, due to large amounts of animal protein and processed foods. A chronic low-grade metabolic acidosis can occur following a Western diet and is associated with increased morbidity and mortality. Nutritional advice focusing on DAL, rather than macronutrients, is gaining rapid attention as it provides a more holistic approach to managing health. However, current evidence for the role of DAL is mainly associative, and underlying mechanisms are poorly understood. This review focusses on the role of DAL in multiple conditions such as obesity, cardiovascular health, impaired kidney function, and cancer.

Metabolic acidosis in chronic kidney disease: mere consequence or also culprit?

Metabolic acidosis is a frequent complication in non-transplant chronic kidney disease (CKD) and after kidney transplantation. It occurs when net endogenous acid production exceeds net acid excretion. While nephron loss with reduced ammoniagenesis is the main cause of acid retention in non-transplant CKD patients, additional pathophysiological mechanisms are likely inflicted in kidney transplant recipients. Functional tubular damage by calcineurin inhibitors seems to play a key role causing renal tubular acidosis. Notably, experimental and clinical studies over the past decades have provided evidence that metabolic acidosis may not only be a consequence of CKD but also a driver of disease. In metabolic acidosis, activation of hormonal systems and the complement system resulting in fibrosis have been described. Further studies of changes in renal metabolism will likely contribute to a deeper understanding of the pathophysiology of metabolic acidosis in CKD. While alkali supplementation in case of reduced serum bicarbonate < 22 mmol/l has been endorsed by CKD guidelines for many years to slow renal functional decline, among other considerations, beneficial effects and thresholds for treatment have lately been under intense debate. This review article discusses this topic in light of the most recent results of trials assessing the efficacy of dietary and pharmacological interventions in CKD and kidney transplant patients.

Sodium citrate versus sodium bicarbonate for metabolic acidosis in patients with chronic kidney disease: A randomized controlled trial

BACKGROUND

Metabolic acidosis (MA) is frequently associated with chronic kidney disease (CKD) progression. Our aim was to compare the effect of oral sodium citrate (SC) with that of oral sodium bicarbonate (SB) on renal function and serum bicarbonate correction, as well as to evaluate their safety profile in patients with MA of CKD.

METHODS

We conducted a prospective, single-center, randomized 1:1, parallel, controlled, unblinded clinical trial of 124 patients with MA and CKD stages 3b and 4. The primary outcome was the mean change in estimated glomerular filtration rate (eGFR). The secondary outcomes were mean change in serum bicarbonate level, eGFR decrease by 30%, eGFR decrease by 50%, dialysis, death or prolonged hospitalization, and a combined endpoint.

RESULTS

No significant difference was found between the groups in terms of mean eGFR change [adjusted mean difference = -0.99 mL/min/1.73 m2 (95% CI: -2.51 to 0.93, P = .20)]. We observed a mean serum bicarbonate change of 6.15 mmol/L [(95% CI: 5.55-6.74), P < .001] in the SC group and of 6.19 mmol/L [(95% CI: 5.54-6.83), P < .001] in the SB group, but no significant difference between the 2 groups [adjusted mean difference = 0.31 mmol/L (-0.22 to 0.85), P = .25]. Cox proportional hazard analysis showed similar risks regarding eGFR decrease by 30% (P = .77), eGFR decrease by 50% (P = .50), dialysis (P = .85), death or prolonged hospitalization (P = .29), and combined endpoint (P = .57). Study drug discontinuation due to adverse events was significantly more common in the SB group (17.7% vs 4.8%, P = .02).

CONCLUSIONS

SC and SB have a similar effect on kidney function decline, both improve serum bicarbonate level, but SB is associated with higher rates of medication discontinuation due to adverse events.

Assessment of Dietary Acid Load in Children with Chronic Kidney Disease: An Observational Study

Introduction

Dietary acid load (DAL), which reflects the balance between acid- and alkaline-forming foods, is a modifiable risk factor for metabolic acidosis in CKD. Owing to the paucity of data in the Indian context, we undertook this cross-sectional study to estimate DAL and assess acid and alkaline food consumption in children with CKD2-5D (Chronic kidney disease stage 2 to 5 and 5D-those on hemodialysis).

Methods

Clinical profile, dietary assessment of energy, protein intake/deficits, and macronutrients were noted and computed using software created by the division of nutrition, St John's research institute based on Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines in clinically stable children with CKD2-5D. DAL was estimated using potential renal acid load (PRAL in mEq/day) = (0.49 × protein intake in g/day) + (0.037 × phosphorus-intake in mg/day) - (0.02 × potassium intake in mg/day) - (0.013 × calcium intake in mg/day) - (0.027 × magnesium intake in mg/day). A positive dietary PRAL (>0) favors acidic content and negative (<0) favors alkaline content. PRAL was stratified into quartiles for analysis. The association of various clinical and dietary parameters were analysed across these quartiles.

Results

Eighty-one children [of mean age 122 ± 47 months; 56 (69%) boys, 29 (36%) on dialysis, 62 (77%) non-vegetarians] were studied. Twenty-eight (34%) were on bicarbonate supplements. A positive PRAL (9.97 ± 7.7 mEq/day) was observed in 74/81 (91%) children with comparable proportions in those with CKD2-5 and 5D [47/52 (90%) vs. 27/29 (93%) respectively, P > 0.05]. Protein intake was significantly higher in the highest quartile compared to the lowest quartile of PRAL in CKD2-5 (55 ± 16 g/day vs. 40 ± 14 g/day, P < 0.001) and 5D groups (47 ± 15 g/day vs. 25 ± 11 g/day, P = 0.002). A majority of the participants 60/81 (74%) consumed highly acidic and minimal alkali foods.

Conclusion

In children with CKD2-5D, PRAL estimation revealed high DAL in the majority with a high consumption of acidic foods. These findings provide implications for appropriate dietary counseling in children with CKD.

Risks of the ketogenic diet in CKD - the con part

The ketogenic diet is a very low carbohydrate diet that has received a lot of attention for its role in the treatment of type 2 diabetes and obesity. For patients with chronic kidney disease, there is limited evidence on the risks and/or benefits of this diet. However, from the limited evidence that does exist, there are several inferences that can be drawn regarding this diet for patients with kidney disease. The ketogenic diet may not be better than comparator higher carbohydrate diets over the long term. The diet also has low adherence levels in studies lasting ≥12 months. The diet's emphasis on fat, which often comes from animal fat, increases the consumption of saturated fat, which may increase the risk of heart disease. It has the potential to worsen metabolic acidosis by increasing dietary acid load and endogenous acid production through the oxidation of fatty acids. In addition, the diet has been associated with an increased risk of kidney stones in patients using it for the treatment of refractory epilepsy. For these reasons, and for the lack of safety data on it, it is reasonable for patients with kidney disease to avoid utilizing the ketogenic diet as a first-line option given alternative dietary patterns (like the plant-dominant diet) with less theoretical risk for harm. For those adopting the ketogenic diet in kidney disease, a plant-based version of the ketogenic diet may mitigate some of the concerns with animal-based versions of the ketogenic diet.

Association of fresh vegetable and salt-preserved vegetable consumptions with estimated glomerular filtration rate

OBJECTIVE

This study aimed to investigate the relationship between the consumption of fresh and salt-preserved vegetables and the estimated glomerular filtration rate (eGFR), which requires further research.

METHODS

For this purpose, the data of those subjects who participated in the 2011-2012 and 2014 surveys of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and had biomarker data were selected. Fresh and salt-preserved vegetable consumptions were assessed at each wave. eGFR was assessed using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation based on plasma creatinine. Furthermore, a linear mixed model was used to evaluate associations between fresh/salt-preserved vegetables and eGFR.

RESULTS

The results indicated that the median baseline and follow-up eGFRs were 72.47 mL/min/1.73 m² and 70.26 mL/min/1.73 m², respectively. After applying adjusted linear mixed model analysis to the data, the results revealed that compared to almost daily intake, occasional consumption of fresh vegetables was associated with a lower eGFR (β=-2.23, 95% CI: -4.23, -0.23). Moreover, rare or no consumption of salt-preserved vegetables was associated with a higher eGFR (β = 1.87, 95% CI: 0.12, 3.63) compared to individuals who consumed salt-preserved vegetables daily.

CONCLUSION

Fresh vegetable consumption was direct, whereas intake of salt-preserved vegetables was inversely associated with eGFR among the oldest subjects, supporting the potential benefits of diet-rich fresh vegetables for improving eGFR.

Advances in the management of chronic kidney disease

Chronic kidney disease (CKD) represents a global public health crisis, but awareness by patients and providers is poor. Defined as persistent abnormalities in kidney structure or function for more than three months, manifested as either low glomerular filtration rate or presence of a marker of kidney damage such as albuminuria, CKD can be identified through readily available blood and urine tests. Early recognition of CKD is crucial for harnessing major advances in staging, prognosis, and treatment. This review discusses the evidence behind the general principles of CKD management, such as blood pressure and glucose control, renin-angiotensin-aldosterone system blockade, statin therapy, and dietary management. It additionally describes individualized approaches to treatment based on risk of kidney failure and cause of CKD. Finally, it reviews novel classes of kidney protective agents including sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide-1 receptor agonists, non-steroidal selective mineralocorticoid receptor antagonists, and endothelin receptor antagonists. Appropriate, widespread implementation of these highly effective therapies should improve the lives of people with CKD and decrease the worldwide incidence of kidney failure.

Hidden Acid Retention with Normal Serum Bicarbonate Level in Chronic Kidney Disease

Management of metabolic acidosis is crucial for preserving bone, muscle, and renal health, as evidenced by the results of several interventional studies conducted on patients with chronic kidney disease (CKD). Considering the continuity of CKD progression over time, it is reasonable to deduce that a subclinical form of metabolic acidosis may exist prior to the manifestation of overt metabolic acidosis. Covert H⁺ retention with normal serum bicarbonate level in patients with CKD may result in maladaptive responses that contribute to kidney function deterioration, even in the early stages of the disease. The loss of adaptive compensatory mechanisms of urinary acid excretion may be a key factor in this process. Early modulation of these responses could be an important therapeutic strategy in preventing CKD progression. However, to date, the optimal approach for alkali therapy in subclinical metabolic acidosis in CKD remains uncertain. There is a lack of established guidelines on when to initiate alkali therapy, potential side effects of alkali agents, and the optimal blood bicarbonate levels based on evidence-based practices. Therefore, further research is necessary to address these concerns and establish more robust guidelines for the use of alkali therapy in patients with CKD. Herein, we provide an overview of recent developments on this subject and examine the potential therapeutic approaches that interventional treatments may present for patients with hidden H⁺ retention, exhibiting normal serum bicarbonate levels - commonly described as subclinical or eubicarbonatemic metabolic acidosis in patients with CKD.

Serum Bicarbonate Deficiency in Dogs with Acute and Chronic Kidney Disease

Serum bicarbonate deficiency is a disorder frequently found in human patients with acute (AKI) and chronic (CKD) kidney disease, due to abnormalities in kidney generation and reabsorption of bicarbonate. Although alkali supplementation is usually performed in both humans and veterinary CKD patients, data regarding the frequency of bicarbonate disorders in AKI and CKD dogs are scarce. The aim of the present study is to assess the frequency and the severity of bicarbonate deficiency of dogs affected by AKI, acute chronic kidney disease (ACKD), and CKD, and to investigate its possible association with the IRIS grade/stage as well as with disorders of calcium phosphate metabolism. A retrospective evaluation of the serum biochemical panels of all dogs with diagnoses of AKI, ACKD, and CKD referred to the nephrology and urology service of the Veterinary Teaching Hospital of the University of Pisa, between January 2014 and January 2022, was performed. Bicarbonate deficiency was defined as serum bicarbonate < 22 mmol/L and classified as moderate (between 18 and 22 mmol/L) or severe (<18 mmol/L). Serum bicarbonate deficiency was found in 397/521 dogs (76%), of which 142/397 (36%) showed moderate deficiency, and 255/397 (64%) severe deficiency. Dogs with AKI and ACKD showed a significantly higher frequency of bicarbonate deficiency (p = 0.004) and severe forms compared to CKD dogs (p = 0.02). In AKI and ACKD dogs, a negative linear correlation was found between serum bicarbonate and serum creatinine, urea, and phosphate. The frequency of bicarbonate deficiency was higher in the later stages of the disease in both AKI (p = 0.01), ACKD (p = 0.0003), and CKD dogs (p = 0.009). Dogs with serum CaxP ≥ 70 mg²/dL² showed a higher frequency of bicarbonate deficiency (p = 0.01) and showed severe forms (p = 0.01) compared to dogs with CaxP < 70 mg²/dL². Serum bicarbonate deficiency seems to be a very frequent disorder in both AKI, ACKD, and CKD dogs, with an increasing frequency and severity in more advanced stages of kidney disease. The higher frequency and severity of bicarbonate deficiency in AKI and ACKD may be caused by a more severe and sudden loss of kidney function, or extra-renal factors. Finally, the association between frequency and severity of bicarbonate deficiency and abnormal CaxP may suggest a potential connection between metabolic acidosis and bone mineral disorders.

Effect of sodium bicarbonate on cardiovascular outcome and mortality in patients with advanced chronic kidney disease

Background: Metabolic acidosis is a common complication in patients with chronic kidney disease (CKD). Oral sodium bicarbonate is often used to treat metabolic acidosis and prevent CKD progression. However, there is limited information about the effect of sodium bicarbonate on major adverse cardiovascular events (MACE) and mortality in patients with pre-dialysis advanced CKD. Method: 25599 patients with CKD stage V between January 1, 2001 and December 31, 2019 were identified from the Chang Gung Research Database (CGRD), a multi-institutional electronic medical record database in Taiwan. The exposure was defined as receiving sodium bicarbonate or not. Baseline characteristics were balanced using propensity score weighting between two groups. Primary outcomes were dialysis initiation, all-cause mortality, and major adverse cardiovascular events (MACE) (myocardial infarction, heart failure, stroke). The risks of dialysis, MACE, and mortality were compared between two groups using Cox proportional hazards models. In addition, we performed analyzes using Fine and Gray sub-distribution hazard models that considered death as a competing risk. Result: Among 25599 patients with CKD stage V, 5084 patients (19.9%) were sodium bicarbonate users while 20515 (80.1%) were sodium bicarbonate non-users. The groups had similar risk of dialysis initiation (hazard ratio (HR): 0.98, 95% confidence interval (CI): 0.95-1.02, p < 0.379). However, taking sodium bicarbonate was associated with a significantly lower risks of MACE (HR: 0.95, 95% CI 0.92-0.98, p < 0.001) and hospitalizations for acute pulmonary edema (HR: 0.92, 95% CI 0.88-0.96, p < 0.001) compared with non-users. The mortality risks were significantly lower in sodium bicarbonate users compared with sodium bicarbonate non-users (HR: 0.75, 95% CI 0.74-0.77, p < 0.001). Conclusion: This cohort study revealed that in real world practice, use of sodium bicarbonate was associated with similar risk of dialysis compared with non-users among patients with advanced CKD stage V. Nonetheless, use of sodium bicarbonate was associated with significantly lower rate of MACE and mortality. Findings reinforce the benefits of sodium bicarbonate therapy in the expanding CKD population. Further prospective studies are needed to confirm these findings.

Effect of Sodium Bicarbonate on Systolic Blood Pressure in CKD: A Systematic Review and Meta-Analysis

BACKGROUND

Individuals with CKD are at a higher risk of cardiovascular morbidity and mortality. Acidosis is positively correlated with CKD progression and elevated systolic BP. Sodium bicarbonate is an efficacious treatment of acidosis, although this may also increase systolic BP. In this systematic review and meta-analysis, we summarize the evidence evaluating systolic BP and antihypertensive medication change (which may indicate systolic BP change) in response to sodium bicarbonate therapy in individuals with CKD.

METHODS

Medical Literature Analysis and Retrieval System Online, Excerpta Medica database, Cumulative Index to Nursing and Allied Health Literature, Allied and Complementary Medicine Database, Cochrane Central Register of Controlled Trials, and World Health Organization (WHO) trials registry databases were searched for randomized control trials where sodium bicarbonate was compared with placebo/usual care in CKD stage G1-5 non-dialysis-dependent populations. Random effects meta-analyses were used to evaluate changes in systolic BP and BP-modifying drugs after sodium bicarbonate intervention.

RESULTS

Fourteen randomized control trials (2110 individuals, median follow-up 27 [interquartile range 97] weeks, mean age 60 [SD 10] years, mean systolic BP 136 [SD 17] mm Hg, mean eGFR 38 [SD 10] ml/min, mean serum bicarbonate 22 [SD 4] mmol/L) were eligible for inclusion. Meta-analysis suggested that sodium bicarbonate did not influence systolic BP in individuals with CKD stage G1-5. Results were consistent when stratifying by dose of sodium bicarbonate or duration of intervention. Similarly, there was no significant increase in the use of antihypertensive medication or diuretics in individuals taking sodium bicarbonate, whereas there was a greater decrease in antihypertensive medication use in individuals taking sodium bicarbonate compared with controls.

CONCLUSIONS

Our results suggest, with moderate certainty, that sodium bicarbonate supplementation does not adversely affect systolic BP in CKD or negatively influence antihypertensive medication requirements.

Non-Traditional Non-Immunological Risk Factors for Kidney Allograft Loss-Opinion

Rates of late allograft loss have improved slowly in the last decades. Well described traditional risk factors that influence allograft survival include cardiovascular events, rejection, infections and post-transplant neoplasia. Here, we critically evaluate the influence of several non-immunological, non-traditional risk factors and describe their impact on allograft survival and cardiovascular health of kidney transplant recipients. We assessed the following risk factors: arterial stiffness, persistent arteriovenous access, mineral bone disease, immunosuppressive drugs residual levels variability, hypomagnesemia, glomerular pathological alterations not included in Banff criteria, persistent inflammation and metabolic acidosis.

Diet and Metabolism in CKD-Related Metabolic Acidosis

Metabolic acidosis is a common complication in patients with chronic kidney disease that occurs when the daily nonvolatile acid load produced in metabolism cannot be excreted fully by the kidney. A reduction in urine net acid excretion coupled with a high nonvolatile acid load may play a role in its pathogenesis. Diet is important in generation of the nonvolatile acid load. Acids are produced from metabolism of dietary protein and from the endogenous production of organic anions from neutral precursors. Acids can be balanced by alkali precursors ingested in the diet in the form of combustible organic anions. These typically are reflected indirectly by the excess of mineral cations to mineral anions in a food or diet. These principles underscore widely used methods to estimate the nonvolatile acid load from dietary intake using formulas such as the net endogenous acid production equation and the potential renal acid load equation. Empiric data largely validate these paradigms with high net endogenous acid production and potential renal acid load contributed by foods such as protein, grains, and dairy, and low net endogenous acid production and potential renal acid load contributed by fruits and vegetables along with corresponding dietary patterns. Although further studies are needed to understand the health benefits of altering nonvolatile acid load via diet, this review provides a detailed assessment on our current understanding of the role of diet in chronic kidney disease-related acidosis, providing an updated resource for researchers and clinicians.

The Role of Dietary Potassium in the Cardiovascular Protective Effects of Plant-Based Diets

Dietary intervention is an essential factor in managing a multitude of chronic health conditions such as cardiovascular and chronic kidney disease. In recent decades, there has been a host of research suggesting the potential benefit of plant-based diets in mitigating the health outcomes of these conditions. Plant-based diets are rich in vegetables and fruits, while limiting processed food and animal protein sources. The underlying physiological mechanism involves the interaction of several macronutrients and micronutrients such as plant protein, carbohydrates, and dietary potassium. Specifically, plant-based foods rich in potassium provide cardiorenal protective effects to include urinary alkalization and increased sodium excretion. These diets induce adaptive physiologic responses that improve kidney and cardiovascular hemodynamics and improve overall metabolic health. A shift toward consuming plant-based diets even in subjects with cardiorenal decrements may reduce their morbidity and mortality. Nonetheless, randomized controlled trials are needed to confirm the clinical benefits of plant-based diets.

Sodium bicarbonate for kidney transplant recipients with metabolic acidosis in Switzerland: a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial

BACKGROUND

Metabolic acidosis is common in kidney transplant recipients and is associated with declining graft function. Sodium bicarbonate treatment effectively corrects metabolic acidosis, but no prospective studies have examined its effect on graft function. Therefore, we aimed to test whether sodium bicarbonate treatment would preserve graft function and slow the progression of estimated glomerular filtration rate (GFR) decline in kidney transplant recipients.

METHODS

The Preserve-Transplant Study was a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial at three University Hospitals in Switzerland (Zurich, Bern, and Geneva), which recruited adult (aged ≥18 years) male and female long-term kidney transplant recipients if they had undergone transplantation more than 1 year ago. Key inclusion criteria were an estimated GFR between 15 mL/min per 1·73 m2 and 89 mL/min per 1·73 m2, stable allograft function in the last 6 months before study inclusion (<15% change in serum creatinine), and a serum bicarbonate of 22 mmol/L or less. We randomly assigned patients (1:1) to either oral sodium bicarbonate 1·5-4·5 g per day or matching placebo using web-based data management software. Randomisation was stratified by study centre and gender using a permuted block design to guarantee balanced allocation. We did multi-block randomisation with variable block sizes of two and four. Treatment duration was 2 years. Acid-resistant soft gelatine capsules of 500 mg sodium bicarbonate or matching 500 mg placebo capsules were given at an initial dose of 500 mg (if bodyweight was <70 kg) or 1000 mg (if bodyweight was ≥70 kg) three times daily. The primary endpoint was the estimated GFR slope over the 24-month treatment phase. The primary efficacy analyses were applied to a modified intention-to-treat population that comprised all randomly assigned participants who had a baseline visit. The safety population comprised all participants who received at least one dose of study drug. The trial is registered with ClinicalTrials.gov, NCT03102996.

FINDINGS

Between June 12, 2017, and July 10, 2019, 1114 kidney transplant recipients with metabolic acidosis were assessed for trial eligibility. 872 patients were excluded and 242 were randomly assigned to the study groups (122 [50%] to the placebo group and 120 [50%] to the sodium bicarbonate group). After secondary exclusion of two patients, 240 patients were included in the intention-to-treat analysis. The calculated yearly estimated GFR slopes over the 2-year treatment period were a median -0·722 mL/min per 1·73 m2 (IQR -4·081 to 1·440) and mean -1·862 mL/min per 1·73 m2 (SD 6·344) per year in the placebo group versus median -1·413 mL/min per 1·73 m2 (IQR -4·503 to 1·139) and mean -1·830 mL/min per 1·73 m2 (SD 6·233) per year in the sodium bicarbonate group (Wilcoxon rank sum test p=0·51; Welch t-test p=0·97). The mean difference was 0·032 mL/min per 1·73 m2 per year (95% CI -1·644 to 1·707). There were no significant differences in estimated GFR slopes in a subgroup analysis and a sensitivity analysis confirmed the primary analysis. Although the estimated GFR slope did not show a significant difference between the treatment groups, treatment with sodium bicarbonate effectively corrected metabolic acidosis by increasing serum bicarbonate from 21·3 mmol/L (SD 2·6) to 23·0 mmol/L (2·7) and blood pH from 7·37 (SD 0·06) to 7·39 (0·04) over the 2-year treatment period. Adverse events and serious adverse events were similar in both groups. Three study participants died. In the placebo group, one (1%) patient died from acute respiratory distress syndrome due to SARS-CoV-2 and one (1%) from cardiac arrest after severe dehydration following diarrhoea with hypotension, acute kidney injury, and metabolic acidosis. In the sodium bicarbonate group, one (1%) patient had sudden cardiac death.

INTERPRETATION

In adult kidney transplant recipients, correction of metabolic acidosis by treatment with sodium bicarbonate over 2 years did not affect the decline in estimated GFR. Thus, treatment with sodium bicarbonate should not be generally recommended to preserve estimated GFR (a surrogate marker for graft function) in kidney transplant recipients with chronic kidney disease who have metabolic acidosis.

FUNDING

Swiss National Science Foundation.

Increasing Serum Bicarbonate is Associated with Reduced Risk of Adverse Kidney Outcomes in Patients with CKD and Metabolic Acidosis

Introduction

Low serum bicarbonate at a single point in time is associated with accelerated kidney decline in patients with chronic kidney disease (CKD). We modeled how changes in serum bicarbonate over time affect incidence of adverse kidney outcomes.

Methods

We analyzed data from Optum's deidentified Integrated Claims-Clinical data set of US patients (2007-2019) with ≥1 year of prior medical record data, CKD stages G3 to G5, and metabolic acidosis (i.e., index serum bicarbonate 12 to <22 mmol/l). The primary predictor of interest was the change in serum bicarbonate, evaluated at each postindex outpatient serum bicarbonate test as a time-dependent continuous variable. The primary outcome was a composite of either a ≥40% decline in estimated glomerular filtration rate (eGFR) from index or evidence of dialysis or transplantation, evaluated using Cox proportional hazards models.

Results

A total of 24,384 patients were included in the cohort with median follow-up of 3.7 years. A within-patient increase in serum bicarbonate over time was associated with a lower risk of the composite kidney outcome. The unadjusted hazard ratio (HR) per 1-mmol/l increase in serum bicarbonate was 0.911 (95% confidence interval [CI]: 0.905-0.917; P < 0.001). After adjustment for baseline eGFR and serum bicarbonate, the time-adjusted effect of baseline eGFR and other covariates, the HR per 1-mmol/l increase in serum bicarbonate was largely unchanged (0.916 [95% CI: 0.910-0.922; P < 0.001]).

Conclusion

In a real-world population of US patients with CKD and metabolic acidosis, a within-patient increase in serum bicarbonate over time independent of changes in eGFR, was associated with a lower risk of CKD progression.

Chronic kidney disease-induced muscle atrophy: Molecular mechanisms and promising therapies

Chronic kidney disease (CKD) is a high-risk chronic catabolic disease due to its high morbidity and mortality. CKD is accompanied by many complications, leading to a poor quality of life, and serious complications may even threaten the life of CKD patients. Muscle atrophy is a common complication of CKD. Muscle atrophy and sarcopenia in CKD patients have complex pathways that are related to multiple mechanisms and related factors. This review not only discusses the mechanisms by which inflammation, oxidative stress, mitochondrial dysfunction promote CKD-induced muscle atrophy but also explores other CKD-related complications, such as metabolic acidosis, vitamin D deficiency, anorexia, and excess angiotensin II, as well as other related factors that play a role in CKD muscle atrophy, such as insulin resistance, hormones, hemodialysis, uremic toxins, intestinal flora imbalance, and miRNA. We highlight potential treatments and drugs that can effectively treat CKD-induced muscle atrophy in terms of complication treatment, nutritional supplementation, physical exercise, and drug intervention, thereby helping to improve the prognosis and quality of life of CKD patients.

Sodium zirconium cyclosilicate and metabolic acidosis: Potential mechanisms and clinical consequences

Metabolic acidosis is frequent in chronic kidney disease (CKD) and is associated with accelerated progression of CKD, hypercatabolism, bone disease, hyperkalemia, and mortality. Clinical guidelines recommend a target serum bicarbonate ≥ 22 mmol/L, but metabolic acidosis frequently remains undiagnosed and untreated. Sodium zirconium cyclosilicate (SZC) binds potassium in the gut and is approved to treat hyperkalemia. In clinical trials with a primary endpoint of serum potassium, SZC increased serum bicarbonate, thus treating CKD-associated metabolic acidosis. The increase in serum bicarbonate was larger in patients with more severe pre-existent metabolic acidosis, was associated to decreased serum urea and was maintained for over a year of SZC therapy. SZC also decreased serum urea and increased serum bicarbonate after switching from a potassium-binding resin in normokalemic individuals. Mechanistically, these findings are consistent with SZC binding the ammonium ion (NH₄⁺) generated from urea by gut microbial urease, preventing its absorption and, thus, preventing the liver regeneration of urea and promoting the fecal excretion of H⁺. This mechanism of action may potentially result in benefits dependent on corrected metabolic acidosis (e.g., improved well-being, decreased catabolism, improved CKD mineral bone disorder, better control of serum phosphate, slower progression of CKD) and dependent on lower urea levels, such as decreased protein carbamylation. A roadmap is provided to guide research into the mechanisms and clinical consequences of the impact of SZC on serum bicarbonate and urate.

[Nephrological management and drug dosing in patients with rheumatic diseases and renal insufficiency]

BACKGROUND

In patients with inflammatory rheumatic diseases and renal insufficiency there are two challenges for physicians: to adapt the antirheumatic medication to the renal function and to carry out a nephroprotective treatment that prevents long-term deterioration of renal function and reduces the elevated cardiovascular risk.

METHODS

A literature search (in PubMed) was carried out and the current state of knowledge on nephroprotective treatment strategies and the treatment of rheumatic diseases in the presence of renal insufficiency was collated, evaluated and summarized.

RESULTS

Lifestyle interventions, especially the cessation of smoking and drug treatment strategies form the basis of nephroprotection including the control of diabetes mellitus with metformin, sodium glucose transporter 2 (SGLT2) inhibitors, glucagon-like peptide 1 (GLP1) analogues and control of hypertension with blockade of the renin-angiotensin-aldosterone system (RAAS), hyperlipidemia, hyperphosphatemia and metabolic acidosis. The SGLT2 inhibitors are also effective for nondiabetic nephropathy. The elevated cardiovascular risk is further reduced by effective control of inflammatory rheumatic activity. Numerous conventional disease modifying antirheumatic drugs, especially methotrexate and the Janus kinase (JAK) inhibitors baricitinib and filgotinib, must mostly be adapted to the renal function. In contrast, biologics can be given in standard doses with the exception of anakinra. The increased cardiovascular risk currently limits the use of tofacitinib in patients with renal insufficiency.

CONCLUSION

The antirheumatic medication should be modified and a complex nephroprotective treatment concept is mandatory in the management of patients with rheumatic disease and renal insufficiency, that in the best-case scenario can be guaranteed by a close interdisciplinary cooperation of rheumatologists and nephrologists.

Influence of Microbial Metabolites and Itaconic Acid Involved in Bacterial Inflammation on the Activity of Mitochondrial Enzymes and the Protective Role of Alkalization

Human microbiota produces metabolites that may enter the bloodstream and exert systemic influence on various functions including mitochondrial. Mitochondria are not only a target for microbial metabolites, but also themselves, due to the inhibition of several enzymes, produce metabolites involved in infectious processes and immune response. The influence of indolic acids, microbial derivatives of tryptophan, as well as itaconic acid, formed in the tricarboxylic acid cycle under the action of bacterial lipopolysaccharides, on the activity of mitochondrial enzymes was studied by methyl thiazolyl tetrazolium (MTT), dichlorophenolindophenol (DCPIP) and pyridine nucleotide fluorescence assays. Thus, it was found that indolic acids suppressed succinate and glutamate oxidation, shifting the redox potential of pyridine nucleotides to a more oxidized state. Itaconic acid, in addition to the well-known inhibition of succinate oxidation, also decreased NAD reduction in reactions with glutamate as a substrate. Unlike itaconic acid, indolic acids are not direct inhibitors of succinate dehydrogenase and glutamate dehydrogenase as their effects could be partially eliminated by the thiol antioxidant dithiothreitol (DTT) and the scavenger of lipid radicals butyl-hydroxytoluene (BHT). Alkalization turned out to be the most effective means to decrease the action of these metabolites, including itaconic acid, which is due to the protective influence on redox-dependent processes. Thus, among mitochondrial oxidative enzymes, the most accessible targets of these microbial-related metabolites are succinate dehydrogenase and glutamate dehydrogenase. These are important in the context of the shifting of metabolic pathways involved in bacterial inflammation and sepsis as well as the detection of new markers of these pathologies.

A methodologic survey on use of the GRADE approach in evidence syntheses published in high-impact factor urology and nephrology journals

Background

To identify and describe the use of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach for rating the certainty of systematic reviews (SRs) evidence published in urology and nephrology journals.

Methods

SRs that were published in the top ten "urology and nephrology" journals with the highest impact factor according to the 2020 Journal Citation Reports (covering 2016–2020) were systematically searched and evaluated using the GRADE approach.

Results

A total of 445 SRs were researched. Sixty SRs of randomized control trials (RCTs) and/or non-randomized studies (NRSs) were evaluated using the GRADE approach. Forty-nine SRs (11%) rated the outcome-specific certainty of evidence (n = 29 in 2019–2020). We identified 811 certainty of evidence outcome ratings (n = 544 RCT ratings) as follows: very low (33.0%); low (32.1%); moderate (24.5%); and high (10.4%). Very low and high certainty of evidence ratings accounted for 55.0% and 0.4% of ratings in SRs of NRSs compared to 23.0% and 15.3% in SRs of RCTs. The certainty of evidence for RCTs and NRSs was downgraded most often for risk of bias and imprecision.

Conclusions

We recommend increased emphasis on acceptance of the GRADE approach, as well as optimal use of the GRADE approach, in the synthesis of urinary tract evidence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01701-x.

Reproductive Consequences of Electrolyte Disturbances in Domestic Animals

Electrolyte balance is essential to maintain homeostasis in the body. The most crucial electrolytes are sodium (Na+), potassium (K+), magnesium (Mg2+), chloride (Cl−), and calcium (Ca2+). These ions maintain the volume of body fluids, and blood pressure, participate in muscle contractions, and nerve conduction, and are important in enzymatic reactions. The balance is mainly ensured by the kidneys, which are an important organ that regulates the volume and composition of urine, together with which excess electrolytes are excreted. They are also important in the reproductive system, where they play a key role. In the male reproductive system, electrolytes are important in acrosomal reaction and sperm motility. Sodium, calcium, magnesium, and chloride are related to sperm capacitation. Moreover, Mg2+, Ca2+, and Na+ play a key role in spermatogenesis and the maintenance of morphologically normal spermatozoa. Infertility problems are becoming more common. It is known that disturbances in the electrolyte balance lead to reproductive dysfunction. In men, there is a decrease in sperm motility, loss of sperm capacitation, and male infertility. In the female reproductive system, sodium is associated with estrogen synthesis. In the contraction and relaxation of the uterus, there is sodium, potassium, and calcium. Calcium is associated with oocyte activation. In turn, in women, changes in the composition of the follicular fluid are observed, leading to a restriction of follicular growth. Imbalance of oocyte electrolytes, resulting in a lack of oocyte activation and, consequently, infertility.

Acid-Mediated Kidney Injury Across the Spectrum of Metabolic Acidosis

Metabolic acidosis affects about 15% of patients with chronic kidney disease. As kidney function declines, the kidneys progressively fail to eliminate acid, primarily reflected by a decrease in ammonium and titratable acid excretion. Several studies have shown that the net acid load remains unchanged in patients with reduced kidney function; the ensuing acid accumulation can precede overt metabolic acidosis, and thus, indicators of urinary acid or potential base excretion, such as ammonium and citrate, may serve as early signals of impending metabolic acidosis. Acid retention, with or without overt metabolic acidosis, initiates compensatory responses that can promote tubulointerstitial fibrosis via intrarenal complement activation and upregulation of endothelin-1, angiotensin II, and aldosterone pathways. The net effect is a cycle between acid accumulation and kidney injury. Results from small- to medium-sized interventional trials suggest that interrupting this cycle through base administration can prevent further kidney injury. While these findings inform current clinical practice guidelines, large-scale clinical trials are still necessary to prove that base therapy can limit chronic kidney disease progression or associated adverse events.

Importance of Metabolic Acidosis as a Health Risk in Chronic Kidney Disease

Human kidneys are well adapted to excrete the daily acid load from diet and metabolism in order to maintain homeostasis. In approximately 30% of patients with more advanced stages of CKD, these homeostatic processes are no longer adequate, resulting in metabolic acidosis. Potential deleterious effects of chronic metabolic acidosis in CKD, including muscle wasting, bone demineralization, hyperkalemia, and more rapid progression of CKD, have been well cataloged. Based primarily upon concerns related to nutrition and bone disease, early Kidney Disease Outcomes Quality Initiative guidelines recommended treating metabolic acidosis with alkali therapy targeting a serum bicarbonate ≥22 mEq/L. More recent guidelines have suggested similar targets based upon potential slowing of CKD progression. However, appropriately powered, long-term, randomized controlled trials to study efficacy and safety of alkali therapy for these outcomes are largely lacking. As a result, practice among physicians varies, underscoring the complexity of treatment of chronic metabolic acidosis in real-world CKD practice. Novel treatment approaches and rigorous phase 3 trials may resolve some of this controversy in the coming years. Metabolic acidosis is an important complication of CKD, and where it "falls" in the priority schema of CKD care will depend upon the generation of strong clinical evidence.

Dietary Contributions to Metabolic Acidosis

Eating a net acid-producing diet can produce an "acid stress" of severity proportional to the diet net acid load, as indexed by the steady-state renal net acid excretion rate. Depending on how much acid or base is ingested or produced from endogenous metabolic processes and how well our homeostatic mechanisms can buffer or eliminate the additional acids or bases, we can alter our systemic acid-base balance. With increasing age, the kidney's ability to excrete daily net acid loads declines (a condition similar to that of mild CKD), invoking increased utilization of potential base stores (eg, bone, skeletal muscle) on a daily basis to mitigate the acid accumulation, thereby contributing to development of osteoporosis, loss of muscle mass, and age-related renal insufficiency. Patients suffering from more advanced CKD often present with more severe acid stress or metabolic acidosis, as the kidney can no longer excrete the entire acid load. Alkaline diets based on fruits and vegetables may have a positive effect on long-term preservation of renal function while maintaining nutritional status. This chapter discusses the biochemistry of dietary precursors that affect acid or base production.

Metabolic mechanisms of acute proximal tubular injury

Damage to the proximal tubule (PT) is the most frequent cause of acute kidney injury (AKI) in humans. Diagnostic and treatment options for AKI are currently limited, and a deeper understanding of pathogenic mechanisms at a cellular level is required to rectify this situation. Metabolism in the PT is complex and closely coupled to solute transport function. Recent studies have shown that major changes in PT metabolism occur during AKI and have highlighted some potential targets for intervention. However, translating these insights into effective new therapies still represents a substantial challenge. In this article, in addition to providing a brief overview of the current state of the field, we will highlight three emerging areas that we feel are worthy of greater attention. First, we will discuss the role of axial heterogeneity in cellular function along the PT in determining baseline susceptibility to different metabolic hits. Second, we will emphasize that elucidating insult specific pathogenic mechanisms will likely be critical in devising more personalized treatments for AKI. Finally, we will argue that uncovering links between tubular metabolism and whole-body homeostasis will identify new strategies to try to reduce the considerable morbidity and mortality associated with AKI. These concepts will be illustrated by examples of recent studies emanating from the authors' laboratories and performed under the auspices of the Swiss National Competence Center for Kidney Research (NCCR Kidney.ch).

Modifiable Lifestyle Behaviors and CKD Progression: A Narrative Review

Living a healthy lifestyle is one of the safest and most cost-effective ways to improve one's quality of life and prevent and/or manage chronic disease. As such, current CKD management guidelines recommend that patients adhere to a healthy diet, perform ≥150 minutes per week of physical activity, manage their body weight, abstain from tobacco use, and limit alcohol. However, there are limited studies that investigate the relationship between these lifestyle factors and the progression of CKD among people with established CKD. In this narrative review, we examine the reported frequencies of health lifestyle behavior engagement among individuals with non-dialysis-dependent CKD and the existing literature that examines the influences of diet, physical activity, weight management, alcohol consumption, and tobacco use on the progression of CKD, as measured by decline in GFR, incident ESKD, or elevated proteinuria or albuminuria in individuals with CKD. Many of the available studies are limited by length of follow-up and small sample sizes, and meta-analyses were limited because the studies were sparse and had heterogeneous classifications of behaviors and/or referent groups and of CKD progression. Further research should be done to determine optimal methods to assess behaviors to better understand the levels at which healthy lifestyle behaviors are needed to slow CKD progression, to investigate the effect of combining multiple lifestyle behaviors on important clinical outcomes in CKD, and to develop effective techniques for behavior change. Despite the lack of evidence of efficacy from large trials on the ability of lifestyle behaviors to slow CKD progression, maintaining a healthy lifestyle remains a cornerstone of CKD management given the undisputed benefits of healthy lifestyle behaviors on cardiovascular health, BP control, and survival.

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.

Increased intrarenal post-glomerular blood flow is a key condition for the development of calcineurin inhibitor-induced renal tubular acidosis in kidney transplant recipients

BACKGROUND

Hyperchloremic metabolic acidosis (HCMA) from renal tubular acidosis (RTA) is common in kidney transplant (KT) recipients. Calcineurin inhibitors (CNIs) are a potential cause of RTA, and whether HCMA is a determinant of poor graft prognosis is controversial.

METHODS

The subjects were living-donor KT recipients (LDKTRs, n = 47) and matched donors (n = 43). All cases of rejection, extrarenal causes, and respiratory disorders were excluded. HCMA was defined as having a [Na+] - [Cl-] value of ≤ 34 or starting alkalization. We determined the potential causes of HCMA in LDKTRs at 3 months (m) and 1 year (y) post-KT. We examined renal hemodynamic parameters in 26 LDKTRs at 1 y post-KT: namely, glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF; GFR/RPF) and pre-/post-glomerular vascular resistance (pre-/postVR).

RESULTS

The HCMA incidence in the 3-m post-KT LDKTR group was higher than that of the donors (51.0% vs. 6.9%, p<0.001, adjusted odds ratio: 6.7-15.7). Among adjusted factors, the most dominant HCMA contributor was low hemoglobin concentration (Hb ≤12 g/dL). Compared to non-HCMA cases, HCMA patients had low FF and low post-VR (p = 0.008, 0.003, respectively) suggesting increased intrarenal post-glomerular blood flow. The high pathological score of alternative arteriolar hyalinosis (aah) ≥2 was a significant HCMA risk. The tacrolimus trough level was not high in HCMA but was significantly high in HCMA in the low post-VR setting (p = 0.002).

CONCLUSION

Among LDKTRs, low hemoglobin level is an important contributor to the manifestation of HCMA in the induction period, and increased intrarenal post-glomerular blood flow is a key condition for the development of CNI-induced RTA. This article is protected by copyright. All rights reserved.

Effects of veverimer on serum bicarbonate and physical function in women with chronic kidney disease and metabolic acidosis: a subgroup analysis from a randomised, controlled trial

BACKGROUND

Globally, the prevalence of chronic kidney disease (CKD) is higher in women than in men; however, women have been historically under-represented in nephrology clinical trials. Metabolic acidosis increases risk of progressive loss of kidney function, causes bone demineralization and muscle protein catabolism, and may be more consequential in women given their lower bone and muscle mass. Veverimer, an investigational, non-absorbed polymer that binds and removes gastrointestinal hydrochloric acid, is being developed as treatment for metabolic acidosis.

METHODS

This was a Phase 3, multicenter, randomised, blinded, placebo-controlled trial in 196 patients with CKD (eGFR: 20-40 mL/min/1.73 m2) and metabolic acidosis who were treated for up to 1 year with veverimer or placebo. We present the findings from a pre-specified subgroup analysis evaluating the effects of veverimer on metabolic acidosis and physical function among women (N = 77) enrolled in this trial.

RESULTS

At week 52, women treated with veverimer had a greater increase in mean (± standard error) serum bicarbonate than the placebo group (5.4 [0.5] vs. 2.2 [0.6] mmol/L; P < 0.0001). Physical Function reported by patients on the Kidney Disease and Quality of Life - Physical Function Domain, a measure that includes items related to walking, stair climbing, carrying groceries and other activities improved significantly in women randomized to veverimer vs placebo (+ 13.2 vs. -5.2, respectively, P < 0.0031). Objectively measured performance time on the repeated chair stand test also improved significantly in the veverimer group vs. placebo (P = 0.0002).

CONCLUSIONS

Veverimer was effective in treating metabolic acidosis in women with CKD, and significantly improved how they felt and functioned.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03390842 . Registered on January 4, 2018.

Effects of oral alkali drug therapy on clinical outcomes in pre-dialysis chronic kidney disease patients: a systematic review and meta-analysis

BACKGROUND

Metabolic acidosis accelerates the progression of chronic kidney disease (CKD) and increases the mortality rate. Whether oral alkali drug therapy benefits pre-dialysis CKD patients is controversial. We performed a meta-analysis of the effects of oral alkali drug therapy on major clinical outcomes in pre-dialysis CKD patients.

METHODS

We systematically searched MEDLINE using the Ovid, EMBASE, and Cochrane Library databases without language restriction. We included all eligible clinical studies that involved pre-dialysis CKD adults and compared those who received oral alkali drug therapy with controls.

RESULTS

A total of 18 eligible studies, including 14 randomized controlled trials and 4 cohort studies reported in 19 publications with 3695 participants, were included. Oral alkali drug therapy led to a 55% reduction in renal failure events (relative risk [RR]: 0.45; 95% confidence interval [CI]: 0.25-0.82), a rate of decline in the estimated glomerular filtration rate (eGFR) of 2.59 mL/min/1.73 m² per year (95% CI, 0.88-4.31). There was no significant effect on decline in eGFR events (RR: 0.34; 95% CI: 0.09-1.23), proteinuria (standardized mean difference: -0.32; 95% CI: -1.08 to 0.43), all-cause mortality events (RR: 0.90; 95% CI: 0.40-2.02) and cardiovascular (CV) events (RR: 1.03; 95% CI: 0.32-3.37) compared with the control groups.

CONCLUSION

Based on the available and low-to-moderate certainty evidence, oral alkali drug therapy might potentially reduce the risk of kidney failure events, but no benefit in reducing all-cause mortality events, CV events, decline in eGFR and porteninuria.

Acid-base effects of combined renal deletion of NBCe1-A and NBCe1-B

The molecular mechanisms regulating ammonia metabolism are fundamental to acid-base homeostasis. Deletion of the A splice variant of Na+-bicarbonate cotransporter, electrogenic, isoform 1 (NBCe1-A) partially blocks the effect of acidosis to increase urinary ammonia excretion, and this appears to involve the dysregulated expression of ammoniagenic enzymes in the proximal tubule (PT) in the cortex but not in the outer medulla (OM). A second NBCe1 splice variant, NBCe1-B, is present throughout the PT, including the OM, where NBCe1-A is not present. The purpose of the present study was to determine the effect of combined renal deletion of NBCe1-A and NBCe1-B on systemic and PT ammonia metabolism. We generated NBCe1-A/B deletion using Cre-loxP techniques and used Cre-negative mice as controls. As renal NBCe1-A and NBCe1-B expression is limited to the PT, Cre-positive mice had PT NBCe1-A/B deletion [PT-NBCe1-A/B knockout (KO)]. Although on a basal diet, PT-NBCe1-A/B KO mice had severe metabolic acidosis, yet urinary ammonia excretion was not changed significantly. PT-NBCe1-A/B KO decreased the expression of phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase and increased the expression of glutamine synthetase, an ammonia-recycling enzyme, in PTs in both the cortex and OM. Exogenous acid loading increased ammonia excretion in control mice, but PT-NBCe1-A/B KO prevented any increase. PT-NBCe1-A/B KO significantly blunted acid loading-induced changes in phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and glutamine synthetase expression in PTs in both the cortex and OM. We conclude that NBCe1-B, at least in the presence of NBCe1-A deletion, contributes to PT ammonia metabolism in the OM and thereby to systemic acid-base regulation.NEW & NOTEWORTHY The results of the present study show that combined deletion of both A and B splice variants of electrogenic Na+-bicarbonate cotransporter 1 from the proximal tubule impairs acid-base homeostasis and completely blocks changes in ammonia excretion in response to acidosis, indicating that both proteins are critical to acid-base homeostasis.

Increased Body Fat and Organic Acid Anions Production Are Associated with Larger Kidney Size in ADPKD

Background and Objectives: A high body mass index (BMI) is associated with the progression of autosomal dominant polycystic kidney disease (ADPKD). However, body fat (BF), which is another adiposity marker, has not yet been studied. Excessive weight may promote elevation in the endogenous synthesis of organic acid (OA) anions. Accordingly, we aimed to investigate the possible association of the aforementioned markers with kidney volume and renal function in patients with ADPKD. Materials and Methods: We conducted a retrospective cohort study of adult ADPKD outpatients involving clinical, serum, and urinary laboratorial data and body composition assessments retrieved from their medical records. BF was estimated by skinfold thickness (mm) on the non-dominant arm and was considered as normal or high for each sex. Total kidney volume (TKV) and height-adjusted volume (htTKV) were measured by magnetic resonance imaging. The annual estimated glomerular filtration rate (eGFR) slope was analyzed during a median follow-up time of 6 (5.0–7.0) years to calculate rapid progression (decline in renal function ≥2.5 mL/min/year over 5 years). Results: A total of 104 patients were included (41.9 ± 11.9 years old, 38.5% men), with 62.5% of the patients classified as high BF. The High BF group presented higher levels of OA, glycosylated hemoglobin (HbA1c), C-reactive protein (CRP), 24 h urinary sodium (UNa), and htTKV, and lower eGFR than those with a normal BF. In the multivariate linear regression, the associated variables with TKV were high BF, OA and BMI (std. β 0.47, p < 0.05; std. β 0.36, p = 0.001; std. β 0.25, p = 0.01, respectively). In the binary logistic regression, when adjusted for potential confounders, UNa was the only parameter associated with an increased risk of eGFR decline ≥2.5 mL/min/year (OR 1.02, 95% CI 1.01–1.03, p = 0.02). Conclusions: Increased body fat and endogenous production of organic acid anions are associated with larger kidney size in ADPKD but not with a decline in renal function.

The Effects of Oral Sodium Bicarbonate on Renal Function and Cardiovascular Risk in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Oral sodium bicarbonate is often used to correct acid-base disturbance in patients with chronic kidney disease (CKD). However, there is little evidence on patient-level benign outcomes to support the practice.

METHODS

We conducted a systematic review and meta-analysis to examine the efficacy and safety of oral sodium bicarbonate in CKD patients. A total of 1853 patients with chronic metabolic acidosis or those with low-normal serum bicarbonate (22-24 mEq/L) were performed to compare the efficacy and safety of oral sodium bicarbonate in patients with CKD.

RESULTS

There was a significant increase in serum bicarbonate level (MD 2.37 mEq/L; 95% CI, 1.03 to 3.72) and slowed the decline in estimated glomerular filtration rate (eGFR) (MD -4.44 mL/min per 1.73 m2, 95% CI, -4.92 to -3.96) compared with the control groups. The sodium bicarbonate lowered T50-time, an indicator of vascular calcification (MD -20.74 min; 95% CI, -49.55 to 8.08); however, there was no significant difference between the two groups. In addition, oral sodium bicarbonate dramatically reduced systolic blood pressure (MD -2.97 mmHg; 95% CI, -5.04 to -0.90) and diastolic blood pressure (MD -1.26 mmHg; 95% CI, -2.33 to -0.19). There were no statistically significant body weight, urine pH and mean mid-arm muscle circumference.

CONCLUSION

Treatment of metabolic acidosis with sodium bicarbonate may slow the decline rate of kidney function and potentially significantly improve vascular endothelial function in patients with CKD.

PROSPERO REGISTRATION NUMBER

CRD42020207185.

Serum bicarbonate is associated with kidney outcomes in autosomal dominant polycystic kidney disease

BACKGROUND

Metabolic acidosis accelerates progression of chronic kidney disease, but whether this is also true for autosomal dominant polycystic kidney disease (ADPKD) is unknown.

METHODS

Patients with ADPKD from the DIPAK (Developing Interventions to halt Progression of ADPKD) trial were included [n = 296, estimated glomerular filtration rate (eGFR) 50 ± 11 mL/min/1.73 m2, 2.5 years follow-up]. Outcomes were worsening kidney function (30% decrease in eGFR or kidney failure), annual eGFR change and height-adjusted total kidney and liver volumes (htTKV and htTLV). Cox and linear regressions were adjusted for prognostic markers for ADPKD [Mayo image class and predicting renal outcomes in ADPKD (PROPKD) scores] and acid-base parameters (urinary ammonium excretion).

RESULTS

Patients in the lowest tertile of baseline serum bicarbonate (23.1 ± 1.6 mmol/L) had a significantly greater risk of worsening kidney function [hazard ratio = 2.95, 95% confidence interval (CI) 1.21-7.19] compared with patients in the highest tertile (serum bicarbonate 29.0 ± 1.3 mmol/L). Each mmol/L decrease in serum bicarbonate increased the risk of worsening kidney function by 21% in the fully adjusted model (hazard ratio = 1.21, 95% CI 1.06-1.37). Each mmol/L decrease of serum bicarbonate was also associated with further eGFR decline (-0.12 mL/min/1.73 m2/year, 95% CI -0.20 to -0.03). Serum bicarbonate was not associated with changes in htTKV or htTLV growth.

CONCLUSIONS

In patients with ADPKD, a lower serum bicarbonate within the normal range predicts worse kidney outcomes independent of established prognostic factors for ADPKD and independent of urine ammonium excretion. Serum bicarbonate may add to prognostic models and should be explored as a treatment target in ADPKD.

Thinking Outside the Box: Novel Kidney Protective Strategies in Kidney Transplantation

Despite the reduction in the incidence of acute rejection, a major risk factor for graft loss, there has been only modest improvement in long-term graft survival. Most cases of kidney graft loss have an identifiable cause that is not idiopathic fibrosis/atrophy or calcineurin inhibitor nephrotoxicity. Distinct immunologic and nonimmunologic factors conspire to lead to a common pathway of allograft fibrosis. It remains plausible that mitigating nonimmunologic damage using strategies proven effective in native kidney disease may yield benefit in kidney transplantation. In this review, we will focus on nonimmunologic aspects of kidney transplant care that may prove to be valuable adjuncts to a well-managed immunosuppression regimen. Topics to be addressed include the roles of hypertension and agents used to treat it, lipid lowering, sodium and water intake, elevated uric acid, metabolic acidosis, and the use of sodium-glucose cotransporter 2 inhibitors on long-term kidney transplant health.

Validation of a Novel Predictive Algorithm for Kidney Failure in Patients Suffering from Chronic Kidney Disease: The Prognostic Reasoning System for Chronic Kidney Disease (PROGRES-CKD)

Current equation-based risk stratification algorithms for kidney failure (KF) may have limited applicability in real world settings, where missing information may impede their computation for a large share of patients, hampering one from taking full advantage of the wealth of information collected in electronic health records. To overcome such limitations, we trained and validated the Prognostic Reasoning System for Chronic Kidney Disease (PROGRES-CKD), a novel algorithm predicting end-stage kidney disease (ESKD). PROGRES-CKD is a naïve Bayes classifier predicting ESKD onset within 6 and 24 months in adult, stage 3-to-5 CKD patients. PROGRES-CKD trained on 17,775 CKD patients treated in the Fresenius Medical Care (FMC) NephroCare network. The algorithm was validated in a second independent FMC cohort (n = 6760) and in the German Chronic Kidney Disease (GCKD) study cohort (n = 4058). We contrasted PROGRES-CKD accuracy against the performance of the Kidney Failure Risk Equation (KFRE). Discrimination accuracy in the validation cohorts was excellent for both short-term (stage 4-5 CKD, FMC: AUC = 0.90, 95%CI 0.88-0.91; GCKD: AUC = 0.91, 95% CI 0.86-0.97) and long-term (stage 3-5 CKD, FMC: AUC = 0.85, 95%CI 0.83-0.88; GCKD: AUC = 0.85, 95%CI 0.83-0.88) forecasting horizons. The performance of PROGRES-CKD was non-inferior to KFRE for the 24-month horizon and proved more accurate for the 6-month horizon forecast in both validation cohorts. In the real world setting captured in the FMC validation cohort, PROGRES-CKD was computable for all patients, whereas KFRE could be computed for complete cases only (i.e., 30% and 16% of the cohort in 6- and 24-month horizons). PROGRES-CKD accurately predicts KF onset among CKD patients. Contrary to equation-based scores, PROGRES-CKD extends to patients with incomplete data and allows explicit assessment of prediction robustness in case of missing values. PROGRES-CKD may efficiently assist physicians' prognostic reasoning in real-life applications.

Association of serum bicarbonate with graft survival and mortality in kidney transplant recipients

BACKGROUND

Metabolic acidosis is an independent risk factor for kidney disease progression with a high prevalence after kidney transplantation (KTx). Remarkably, it is still unclear if there is an impact of metabolic acidosis on graft function and death after KTx. Thus, we wanted to investigate if serum bicarbonate is associated with long-term graft outcome and mortality after KTx.

METHODS

We performed a single-center retrospective study including adult de novo KTx patients between 1999 and 2015. Cox proportional hazard model was used to analyze a possible association between time-dependent serum bicarbonate measurements and graft failure or death.

RESULTS

Four hundred thirty KTRs were included in the analysis with a mean age of 50.9 ± 13.4 years. Mean observation time was 4.7 ± 2.8 years. Two hundred eighty-four (66%) patients were male and 318 (74%) had received a deceased donor kidney transplant. Mean bicarbonate and eGFR levels 1 year post-transplant amounted to 22.9 ± 3.1 mEq/L and 61 ± 26 ml/min/1.73 m², respectively. Prevalence of metabolic acidosis was 31% 1 year after transplantation. Fourteen (3%) patients died and 31 (7%) suffered from graft failure. Higher bicarbonate levels were associated with significantly lower hazards for graft failure (Hazard Ratio (HR) = 0.88; 95% Confidence Interval (CI): 0.79-0.98) and mortality (HR = 0.79; 95% CI 0.66-0.93) after adjusting for potential confounders such as age, donor type and time-varying eGFR.

CONCLUSIONS

Our analysis showed that higher serum bicarbonate levels are positively associated with long-term graft and patient survival in kidney transplant recipients. Thus, serum bicarbonate may serve as a predictor and independent risk factor for graft and patient outcome after KTx as has been previously shown for patients with CKD.

Metabolic Acidosis and Cardiovascular Disease in CKD

Rationale & Objective

Metabolic acidosis related to chronic kidney disease (CKD) is associated with an accelerated decline in glomerular filtration rate (GFR) and the development of end-stage kidney disease. Whether metabolic acidosis is associated with cardiovascular (CV) events in patients with CKD is unclear.

Study Design

Retrospective cohort study.

Setting & Participants

The Optum De-identified Electronic Health Records Dataset, 2007–2017, was used to generate a cohort of patients with non-dialysis-dependent CKD who had at least 3 estimated GFR < 60 mL/min/1.73 m². Patients with metabolic acidosis (serum bicarbonate 12 to <22 mEq/L) or normal serum bicarbonate (22‒29 mEq/L) at baseline were identified by 2 consecutive measurements 28‒365 days apart.

Predictor

Serum bicarbonate as a continuous variable.

Outcome

Primary outcome was a composite of major adverse cardiovascular events (MACE+). Secondary outcomes included individual components of the composite outcome.

Analytical Approach

Cox proportional hazards models to evaluate the association between 1-mEq/L increments in serum bicarbonate and MACE+.

Results

A total of 51,558 patients were evaluated, 34% had metabolic acidosis. The median follow-up period was 3.9–4.5 years, depending on the outcome assessed. The adjusted hazard ratio (HR) for MACE+ was 0.964 (95% CI, 0.961–0.968). For the individual components of incident heart failure (HF), stroke, myocardial infarction (MI), and CV death, HRs were 0.98 (95% CI, 0.97–0.98), 0.98 (95% CI, 0.97–0.99), 0.96 (95% CI, 0.96–0.97), and 0.94 (95% CI, 0.93–0.94), respectively, for every 1-mEq/L increase in serum bicarbonate.

Limitations

Possible residual confounding.

Conclusions

Metabolic acidosis in CKD is associated with an increased risk of MACE+ as well as the individual components of incident HF, stroke, MI, and CV death. Randomized controlled trials evaluating treatments for the correction of metabolic acidosis in CKD to prevent CV events are needed.

Oral sodium bicarbonate in people on haemodialysis: a randomised controlled trial

Background

Adverse events and mortality tend to cluster around dialysis sessions, potentially due to the impact of the saw-toothed profile of uraemic toxins such as potassium, peaking pre-dialysis and rapidly dropping during dialysis. Acidosis could be contributing to this harm by exacerbating a rise in potassium. The objectives of this study were to investigate the effects of oral bicarbonate treatment on reducing inter-dialytic potassium gain as well as other clinical consequences of preserving muscle mass and function and reducing intradialytic arrhythmia risk in people on haemodialysis.

Methods

Open-label randomised controlled trial in a single-centre (London, UK). Forty-three clinically stable adults on haemodialysis were recruited, with a 6 month average pre-dialysis serum bicarbonate level < 22 mmol/l and potassium > 4 mmol/l. Thirty-three participants completed the study. Oral sodium bicarbonate tablets titrated up to a maximum of 3 g bd (6 g total) in intervention group for 12 weeks versus no treatment in the control group. Outcomes compared intervention versus non-intervention phases in the treated group and equivalent time points in the control group: pre- and post-dialysis serum potassium; nutritional assessments: muscle mass and handgrip strength and electrocardiograms (ECGs) pre and post dialysis.

Results

Participants took an average of 3.7 ± 0.5 g sodium bicarbonate a day. In the intervention group, inter-dialytic potassium gain was reduced from 1.90 ± 0.60 to 1.69 ± 0.49 mmol/l (p = 0.032) and pre-dialysis potassium was reduced from 4.96 ± 0.62 to 4.79 ± 0.49 mmol/l without dietary change. Pre-dialysis bicarbonate increased from 18.15 ± 1.35 to 20.27 ± 1.88 mmol/l, however with an increase in blood pressure. Nutritionally, lean tissue mass was reduced in the controls suggesting less catabolism in the intervention group. There was no change in ECGs. Limitations are small sample size and unblinded study design lacking a placebo, with several participants failing to achieve the target of 22 mmol/l serum bicarbonate levels due mainly to tablet burden.

Conclusion

Oral sodium bicarbonate reduced bicarbonate loss and potassium gain in the inter-dialytic period, and may also preserve lean tissue mass.

Trial registration

The study was registered prospectively on 06/08/2015 with EU Clinical Trials Register EudraCT number 2015-001439-20.

Sodium Bicarbonate Prescription and Extracellular Volume Increase: Real-world Data Results from the AlcalUN Study

Oral alkalization with sodium bicarbonate (NaHCO₃ ) or citrate is prescribed for conditions ranging from metabolic acidosis to nephrolithiasis. Although most nephrologists/urologists use this method routinely, extracellular volume (ECV) increase is the main feared adverse event reported for NaHCO₃ . Thus far, no trial has specifically studied this issue in a real-world setting. AlcalUN (NCT03035812) is a multicentric, prospective, open-label cohort study with nationwide (France) enrollment in 18 (public and private) nephrology/urology units. Participants were adult outpatients requiring chronic (>1 month) oral alkalization by either NaHCO₃ -containing or no-NaHCO₃ -containing agents. The ECV increase (primary outcome) was judged based on body weight increase (ΔBW), blood pressure increase (ΔBP), and/or new-onset edema at the first follow-up visit (V1). From February 2017 to February 2020, 156 patients were enrolled. After a median 106 days of treatment, 91 (72%) patients reached the primary outcome. They had lower systolic (135 (125, 141) vs. 141 (130, 150), P = 0.02) and diastolic (77 (67, 85) vs. 85 (73, 90), P = 0.03) BP values, a higher plasma chloride (106.0 (105.0, 109.0) vs. 105.0 (102.0, 107.0), P = 0.02) at baseline, and a less frequent history of nephrolithiasis (32 vs. 56%, P = 0.02). Patients experienced mainly slight ΔBP (< 10 mmHg). The primary outcome was not associated (P = 0.79) with the study treatment (129 received NaHCO₃ and 27 received citrate). We subsequently developed three different models of propensity score matching; each confirmed our results. Chronic oral alkalization with NaHCO₃ is no longer associated with an ECV increase compared to citrate in real-life settings.

Effect of Oral Sodium Bicarbonate Treatment on 24-Hour Ambulatory Blood Pressure Measurements in Patients With Chronic Kidney Disease and Metabolic Acidosis

Background: Sodium bicarbonate supplementation is a mainstay in the treatment of metabolic acidosis in patients with chronic kidney disease (CKD). Recent studies showed reduction of progression of CKD and reduced all-cause mortality. However, additional sodium loading could worsen arterial hypertension, a well-known contributor to progression of CKD. This patient-relevant and economically negative side effect is under-studied in prospective studies up until now.

Objective: The aim of this study was to analyze the effect of sodium bicarbonate treatment on arterial blood pressure at baseline and after 8 weeks.

Methods: The SoBic study is an ongoing randomized controlled trial, in which patients with CKD receive either a high dose of oral sodium bicarbonate or a rescue treatment, if necessary. We used standardized office blood pressure and 24-hour ambulatory blood pressure monitoring (24h-ABPM). Regression models were adjusted for estimated glomerular filtration rate and change of antihypertensives.

Results: 47 subjects were enrolled and the mean age was 57 (±14.6) years and 18 (38%) were female. In 43 randomized subjects with sufficiently performed 24h-ABPM neither systolic 24h-ABPM (2.522; 95%CI: −2.364, 7.408; mmHg) nor diastolic 24h-ABPM (0.868; 95%CI: −2.411, 4.147; mmHg) was affected by study group allocation. When looking at the effect of individual sodium bicarbonate dose on 24h-ABPM, the fully adjusted model suggested an increase of 0.047 (95%CI: −0.026, 0.119) mmHg by each mg/kg per day increase of sodium bicarbonate dose.

Conclusion: Sodium bicarbonate supplementation over 8 weeks did not significantly increase blood pressure measured by 24h-ABPM in CKD patients.

Trial Registration: EUDRACT Number: 2012-001824-36; 12/07/2012 (https://www.clinicaltrialsregister.eu).

Fatigue in CKD: Epidemiology, Pathophysiology, and Treatment

Fatigue is a commonly reported and debilitating symptom among patients with CKD, yet little is known about its epidemiology, pathogenesis, and treatment. Various measurement tools have been used in published studies to identify and quantify fatigue. These include several single-item measures embedded in longer questionnaires for assessing depression, quality of life, or symptom burden in patients with kidney disease. Approximately 70% of patients with CKD report fatigue, with up to 25% reporting severe symptoms. Patient-reported fatigue is associated with death, dialysis initiation, and hospitalization among individuals with CKD. The pathophysiology is multifactorial and likely includes decreased oxygen delivery and increased reliance on anaerobic metabolism, thus generating lactic acidosis in response to exertion; the effects of chronic metabolic acidosis and hyperphosphatemia on skeletal muscle myocytes; protein-energy wasting and sarcopenia; and depression. Physical activity has been shown to improve fatigue in some small but promising trials, and so should be recommended, given the additional benefits of exercise. Targeting higher hemoglobin levels with erythropoiesis-stimulating agents may improve fatigue, but potential adverse cardiovascular effects preclude their use to solely treat fatigue without the presence of another indication. Current guidelines recommend cautious individualization of hemoglobin targets for those at low cardiovascular risk who still experience fatigue or functional limitation despite a hemoglobin level of 10 g/dl. Sodium bicarbonate supplementation for the treatment of metabolic acidosis may also improve functional status. Selective serotonin reuptake inhibitors have not been consistently shown to improve fatigue in patients with kidney disease, but an ongoing trial will evaluate the effect of alternative antidepressant drug and behavioral activation therapy on fatigue in patients with CKD. Overall, more research is needed to further clarify underlying mechanisms of fatigue and identify effective, targeted treatments for patients with CKD.

Chronic kidney disease

Chronic kidney disease is a progressive disease with no cure and high morbidity and mortality that occurs commonly in the general adult population, especially in people with diabetes and hypertension. Preservation of kidney function can improve outcomes and can be achieved through non-pharmacological strategies (eg, dietary and lifestyle adjustments) and chronic kidney disease-targeted and kidney disease-specific pharmacological interventions. A plant-dominant, low-protein, and low-salt diet might help to mitigate glomerular hyperfiltration and preserve renal function for longer, possibly while also leading to favourable alterations in acid-base homoeostasis and in the gut microbiome. Pharmacotherapies that alter intrarenal haemodynamics (eg, renin-angiotensin-aldosterone pathway modulators and SGLT2 [SLC5A2] inhibitors) can preserve kidney function by reducing intraglomerular pressure independently of blood pressure and glucose control, whereas other novel agents (eg, non-steroidal mineralocorticoid receptor antagonists) might protect the kidney through anti-inflammatory or antifibrotic mechanisms. Some glomerular and cystic kidney diseases might benefit from disease-specific therapies. Managing chronic kidney disease-associated cardiovascular risk, minimising the risk of infection, and preventing acute kidney injury are crucial interventions for these patients, given the high burden of complications, associated morbidity and mortality, and the role of non-conventional risk factors in chronic kidney disease. When renal replacement therapy becomes inevitable, an incremental transition to dialysis can be considered and has been proposed to possibly preserve residual kidney function longer. There are similarities and distinctions between kidney-preserving care and supportive care. Additional studies of dietary and pharmacological interventions and development of innovative strategies are necessary to ensure optimal kidney-preserving care and to achieve greater longevity and better health-related quality of life for these patients.

Calcium phosphate microcrystals in the renal tubular fluid accelerate chronic kidney disease progression

The Western pattern diet is rich not only in fat and calories but also in phosphate. The negative effects of excessive fat and calorie intake on health are widely known, but the potential harms of excessive phosphate intake are poorly recognized. Here, we show the mechanism by which dietary phosphate damages the kidney. When phosphate intake was excessive relative to the number of functioning nephrons, circulating levels of FGF23, a hormone that increases the excretion of phosphate per nephron, were increased to maintain phosphate homeostasis. FGF23 suppressed phosphate reabsorption in renal tubules and thus raised the phosphate concentration in the tubule fluid. Once it exceeded a threshold, microscopic particles containing calcium phosphate crystals appeared in the tubule lumen, which damaged tubule cells through binding to the TLR4 expressed on them. Persistent tubule damage induced interstitial fibrosis, reduced the number of nephrons, and further boosted FGF23 to trigger a deterioration spiral leading to progressive nephron loss. In humans, the progression of chronic kidney disease (CKD) ensued when serum FGF23 levels exceeded 53 pg/mL. The present study identified calcium phosphate particles in the renal tubular fluid as an effective therapeutic target to decelerate nephron loss during the course of aging and CKD progression.