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Ammonium is a major urinary buffer that is necessary for the normal excretion of the daily acid load. Its urinary rate of excretion (UNH

Kidney tubular secretion is an essential mechanism for clearing many common antihypertensive drugs and other metabolites and toxins. It is unknown whether novel measures of tubular secretion are associated with adverse events (AEs) during hypertension treatment.Among 2089 SPRINT (Systolic Blood Pressure Intervention Trial) participants with baseline eGFR60 ml/min per 1.73 mOverall, 30% of participants experienced at least one AE during a median follow-up of 3.0 years. In multivariable models adjusted for eGFR and albuminuria, lower (worse) secretion scores at baseline were associated with greater risk of the composite AE outcome (hazard ratio per 1-SD lower secretion score, 1.16; 95% confidence interval, 1.04 to 1.27). In analyses of the individual AEs, lower secretion score was associated with significantly greater risk of AKI, serious electrolyte abnormalities, and ambulatory hyperkalemia. Associations were similar across randomized treatment assignment groups.Among SPRINT participants with CKD, worse tubular secretion was associated with greater risk of AEs, independent of eGFR and albuminuria.

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.

Background: Individuals with chronic kidney disease (CKD) have a high burden of cardiovascular disease (CVD). Abnormalities in cardiac structure and function represent subclinical CVD and can be assessed by cardiac magnetic resonance imaging (cMRI). Methods: We investigated differences in cMRI parameters in 140 individuals with CKD stages 3b-4 who participated in the CKD Optimal Management with BInders and NicotinamidE (COMBINE) trial and in 24 age-and sex matched healthy volunteers. Among COMBINE participants, we examined the associations of estimated glomerular filtration rate (eGFR), urine albumin-to-creatinine ratio (UACR), phosphate, fibroblast growth factor 23 (FGF23), and parathyroid hormone (PTH) with baseline (N=140) and 12-month change (N=112) in cMRI parameters. Results: Mean (standard deviation [SD]) age of the COMBINE participants and healthy volunteers were 64.9 (11.9) and 60.4 (7.3) years. The mean (SD) baseline eGFR in COMBINE participants was 32.1 (8.0) and 85.9 (16.0) ml/ min/1.73m2 in healthy volunteers. The median (interquartile range [IQR]) UACR in COMBINE participants was 154 (20.3 - 540.0) mg/g. Individuals with CKD had lower mitral valve E/A ratio compared to healthy volunteers (β estimate -0.13 CKD vs. non-CKD, 95% confidence interval [CI] -0.24, -0.012). Among COMBINE participants, multivariable linear regression analyses showed that higher UACR was significantly associated with lower mitral valve E/A ratio (β-estimate per 1 unit increase in natural log UACR -0.06, 95% CI -0.09, -0.03). This finding was preserved among individuals without baseline CVD. UACR was not associated with 12-month change in any cMRI parameter. eGFR, phosphate, FGF23, and PTH were not associated with any cMRI parameter in cross-sectional or change analyses. Conclusions: Individuals with CKD stages 3b-4 have evidence of cMRI abnormalities. Albuminuria was independently associated with diastolic dysfunction assessed by mitral valve E/A ratio in individuals with CKD with and without clinical CVD, but was not associated with change in any cMRI parameter.

RATIONALE AND OBJECTIVE. While low estimated glomerular filtration rate (eGFR) is associated with cardiovascular disease (CVD) events and mortality, the clinical significance of variability in eGFR over time is uncertain. We aimed to evaluate the association between variability in eGFR and the risk of CVD events and all-cause mortality. STUDY DESIGN. Longitudinal analysis of clinical trial participants. SETTINGS AND PARTICIPANTS. 7,520 Systolic Blood Pressure Intervention Trial (SPRINT) participants aged ≥ 50 year with 1 or more CVD risk factors. PREDICTORS. eGFR variability, estimated by the coefficients of variation of eGFR measurements at the 6, 12, and 18-month study visits. OUTCOMES. SPRINT primary CVD composite outcome (myocardial infarction, acute coronary syndrome, stroke, heart failure, or CVD death) and all-cause mortality from month 18 to end of follow-up. ANALYTICAL APPROACH. Cox models evaluated associations between eGFR variability and CVD outcomes and all-cause mortality. Models were adjusted for demographics, randomization arm, CVD risk factors, albuminuria and month 18 eGFR. RESULTS. Mean age was 68±9 years, 65% were men, and 58% were white. The mean eGFR was 73±21 ml/min/1.73m(2) at 6 months. There were 370 CVD events and 154 deaths during a median follow-up of 2.4 years. Greater eGFR variability was associated with higher risk for all-cause mortality (hazard ratio (HR) per standard deviation (SD) greater variability, 1.29; 95% confidence interval (CI) 1.14 to 1.45) but not CVD events (HR 1.05; 95% CI 0.95 to 1.16) after adjusting for albuminuria at baseline, eGFR at month 18, and other CVD risk factors. Associations were similar when stratified by treatment arm and baseline CKD status, when accounting for concurrent systolic BP changes, use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), and diuretic medications during follow-up. LIMITATIONS. Persons with diabetes and proteinuria > 1 g/day were excluded. CONCLUSIONS. In trial participants at high risk for CVD with hypertension, greater eGFR variability was independently associated with all-cause mortality but not CVD events.

Fine particulate matter 2.5 ) air pollution is implicated in global mortality, especially from cardiovascular causes. A large body of evidence suggests a link between PM 2.5 and elevation in blood pressure (BP), with the latter implicated as a potential mediator of cardiovascular events. We sought to determine if the outcomes of intensive BP lowering (systolic BP 2.5 exposure in the SPRINT (Systolic BP Intervention Trial). We linked annual PM 2.5 exposure estimates derived from an integrated model to subjects participating in SPRINT. We evaluated the effect of intensive BP lowering by PM 2.5 exposure on the primary outcome in SPRINT using cox-proportional hazard models. A total of 9286 participants were linked to PM 2.5 levels (mean age 68±9 years). Intensive BP-lowering decreased risk of the primary outcome more among patients exposed to higher PM 2.5 ( P interaction =0.047). The estimate for lowering of primary outcome was numerically lower in the highest than in the lower quintiles. The benefits of intensive BP-lowering were larger among patients chronically exposed to PM 2.5 levels above US National Ambient Air Quality Standards of 12 µg/m 3 (hazard ratio, 0.47 [95% CI, 0.29–0.74]) compared with those living in cleaner locations (hazard ratio, 0.81 [95% CI, 0.68–0.97]), P interaction =0.037. This exploratory nonprespecified post hoc analysis of SPRINT suggests that the benefits of intensive BP lowering on the primary outcome was greater in patients exposed to higher PM 2.5 , suggesting that the magnitude of benefit may depend upon the magnitude of antecedent PM 2.5 exposure.

Causes of secondary oxalate nephropathy include enteric dysfunction and excessive intake of oxalate or oxalate precursors. During the COVID-19 pandemic, there has been a dramatic rise in sales of supplements and vitamin C, during which time we observed an apparent increase in the proportion of ingestion-associated oxalate nephropathy.We retrospectively reviewed secondary oxalate nephropathy and compared pre-pandemic (2018-2019) and pandemic (2020-early 2022) time periods.We identified 35 patients with kidney biopsy proven (30 native, 5 allograft) oxalate nephropathy at a single academic institution. Supplement-associated oxalate nephropathy comprised a significantly higher proportion of cases during COVID-19 pandemic compared with the preceding 2 years (44% vsThere was a shift toward supplements rather than enteric hyperoxaluria as a leading cause of secondary oxalate nephropathy during the COVID-19 pandemic. Kidney outcomes are better than those observed for enteric hyperoxaluria, if the offending agent is identified and removed.

Background and objectives Kidney functional magnetic resonance imaging (MRI) requires further investigation to enhance the noninvasive identification of patients at high risk of CKD progression. Design, setting, participants, & measurements In this exploratory study, we obtained baseline diffusion-weighted and blood oxygen level–dependent MRI in 122 participants of the CKD Optimal Management with Binders and Nicotinamide trial, which was a multicenter, randomized, double-blinded, 12-month, four-group parallel trial of nicotinamide and lanthanum carbonate versus placebo conducted in individuals with eGFR 20–45 ml/min per 1.73 m2. Lower values of apparent diffusion coefficient (ADC) on diffusion-weighted MRI may indicate increased fibrosis, and higher values of relaxation rate (R2*) on blood oxygen level–dependent MRI may represent decreased oxygenation. Because there was no effect of active treatment on eGFR over 12 months, we tested whether baseline kidney functional MRI biomarkers were associated with eGFR decline in all 122 participants. In a subset of 87 participants with 12-month follow-up MRI data, we evaluated whether kidney functional MRI biomarkers change over time. Results Mean baseline eGFR was 32±9 ml/min per 1.73 m2, and mean annual eGFR slope was −2.3 (95% confidence interval [95% CI], −3.4 to −1.1) ml/min per 1.73 m2 per year. After adjustment for baseline covariates, baseline ADC was associated with change in eGFR over time (difference in annual eGFR slope per 1 SD increase in ADC: 1.3 [95% CI, 0.1 to 2.5] ml/min per 1.73 m2 per year, ADC×time interaction P=0.04). This association was no longer significant after further adjustment for albuminuria (difference in annual eGFR slope per 1 SD increase in ADC: 1.0 (95% CI, −0.1 to 2.2) ml/min per 1.73 m2 per year, ADC×time interaction P=0.08). There was no significant association between baseline R2* and change in eGFR over time. In 87 participants with follow-up functional MRI, ADC and R2* values remained stable over 12 months (intraclass correlation: 0.71 and 0.68, respectively). Conclusions Baseline cortical ADC was associated with change in eGFR over time, but this association was not independent of albuminuria. Kidney functional MRI biomarkers remained stable over 1 year. Clinical Trial registry name and registration number CKD Optimal Management with Binders and Nicotinamide (COMBINE), NCT02258074.

Background and objectives In early-phase studies of individuals with hypertensive CKD and normal serum total CO2, sodium bicarbonate reduced urinary TGF-β1 levels and preserved kidney function. The effect of sodium bicarbonate on kidney fibrosis and injury markers in individuals with diabetic kidney disease and normal serum total CO2 is unknown. Design, setting, participants, & measurements We conducted a randomized, double-blinded, placebo-controlled study in 74 United States veterans with type 1 or 2 diabetes mellitus, eGFR of 15–89 ml/min per 1.73 m2, urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, and serum total CO2 of 22–28 meq/L. Participants received oral sodium bicarbonate (0.5 meq/kg lean body wt per day; n=35) or placebo (n=39) for 6 months. The primary outcome was change in urinary TGF-β1-to-creatinine from baseline to months 3 and 6. Secondary outcomes included changes in urinary kidney injury molecule-1 (KIM-1)-to-creatinine, fibronectin-to-creatinine, neutrophil gelatinase-associated lipocalin (NGAL)-to-creatinine, and UACR from baseline to months 3 and 6. Results Key baseline characteristics were age 72±8 years, eGFR of 51±18 ml/min per 1.73 m2, and serum total CO2 of 24±2 meq/L. Sodium bicarbonate treatment increased mean total CO2 by 1.2 (95% confidence interval [95% CI], 0.3 to 2.1) meq/L, increased urinary pH by 0.6 (95% CI, 0.5 to 0.8), and decreased urinary ammonium excretion by 5 (95% CI, 0 to 11) meq/d and urinary titratable acid excretion by 11 (95% CI, 5 to 18) meq/d. Sodium bicarbonate did not significantly change urinary TGF-β1/creatinine (difference in change, 13%, 95% CI, −10% to 40%; change within the sodium bicarbonate group, 8%, 95% CI, −10% to 28%; change within the placebo group, −4%, 95% CI, −19% to 13%). Similarly, no significant effect on KIM-1-to-creatinine (difference in change, −10%, 95% CI, −38% to 31%), fibronectin-to-creatinine (8%, 95% CI, −15% to 37%), NGAL-to-creatinine (−33%, 95% CI, −56% to 4%), or UACR (1%, 95% CI, −25% to 36%) was observed. Conclusions In nonacidotic diabetic kidney disease, sodium bicarbonate did not significantly reduce urinary TGF-β1, KIM-1, fibronectin, NGAL, or UACR over 6 months.

BACKGROUND: Sulfur is an important mineral element whose principal source is animal protein. Animal protein contributes to the daily acid load, which is associated with poor outcomes in individuals with chronic kidney disease (CKD). We hypothesized that higher urinary sulfate, as a reflection of the daily acid load, is associated with a greater risk of death and CKD progression. METHODS: Urinary sulfate was measured in 1057 African American Study of Kidney Disease and Hypertension (AASK) participants at baseline. Participants were categorized by tertiles of daily sulfate excretion. The longitudinal outcome of interest was the composite of death, dialysis, or 50% reduction in measured glomerular filtration rate (GFR). Multivariable adjusted Cox regression models were fit to relate the composite outcome to daily sulfate excretion using the lowest tertile as the reference. RESULTS: Participants in the highest urinary sulfate tertile were more likely to be men and have a higher body mass index, protein intake, measured GFR, and urinary ammonium and phosphate excretion, and lower urinary protein/creatinine. Compared with those in the lowest tertile of sulfate, those in the highest tertile had a 44% lower hazard (95% CI, 0.37 to 0.84), and those in the middle tertile had a 27% lower hazard (95% CI, 0.55 to 0.96) of death, dialysis, or 50% reduction in measured GFR during follow-up after adjusting for demographics, GFR, protein intake, and other potential confounders. Protein intake was not associated with risk of these events. CONCLUSIONS: Higher urinary sulfate excretion is associated with more favorable outcomes in Blacks who have CKD attributed to hypertension.

Rational & objectiveMany drugs, metabolites, and toxins are cleared by the kidneys via tubular secretion. Whether novel endogenous measures of tubular secretion provide information about kidney, cardiovascular, and mortality risk is uncertain.Study designLongitudinal subgroup analysis of clinical trial participants.Setting & participants2,089 Systolic Blood Pressure Intervention Trial participants with estimated glomerular filtration rate (eGFR)1 g/d were excluded.ConclusionsAmong SPRINT participants with CKD, lower estimated tubular secretion was associated with faster eGFR decline, independent of baseline eGFR and albuminuria, but not with CKD progression, CVD, or mortality.

Serum concentrations of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) are elevated in patients with CKD, and higher concentrations are well established as risk factors for cardiovascular disease and death ([1][1]). In the Systolic Blood Pressure Intervention Trial (SPRINT)

BACKGROUND: Oral sodium bicarbonate (NaHCO(3)) may preserve kidney function in CKD, even if initiated when serum bicarbonate concentration is normal. Adequately powered trials testing this hypothesis have not been conducted, partly because the best dose for testing is unknown. METHODS: This multicenter pilot trial assessed the safety, tolerability, adherence, and pharmacodynamics of two doses of NaHCO(3) over 28 weeks in adults with eGFR 20–44 or 45–59 ml/min per 1.73 m(2) with urinary albumin/creatinine (ACR) ≥50 mg/g and serum bicarbonate 20–28 meq/L. We randomly assigned 194 participants from ten clinical sites to receive higher-dose (HD-NaHCO(3); 0.8 meq/kg of lean body wt per day; n=90) or lower-dose (LD-NaHCO(3); 0.5 meq/kg of lean body wt per day; n=52) NaHCO(3) or matching placebo (n=52). The dose was adjusted depending on side effects. The prescribed dose at week 28 was the primary outcome; a dose was considered acceptable for a full-scale trial if ≥67% of participants were on full-dose and ≥80% were on ≥25% of the per-protocol dose. RESULTS: Mean±SD baseline eGFR was 36±9 ml/min per 1.73 m(2), serum bicarbonate was 24±2 meq/L, and median (IQR) ACR was 181 (25–745) mg/g. Both doses were well tolerated without significant changes in BP, weight, or serum potassium. The proportions of adverse events and hospitalizations were similar across the groups. Consequently, 87% in HD-NaHCO(3), 96% in LD-NaHCO(3), and 87% in placebo were on full dose at week 28; and 91% in HD-NaHCO(3), 98% in LD-NaHCO(3), and 92% in placebo were on ≥25% of the per-protocol dose. Mean urinary ammonium excretion was 25% lower and serum bicarbonate concentration was 1.3 meq/L higher in HD-NaHCO(3) compared with LD-NaHCO(3) at week 28. However, mean ACR increased by 12% in the lower-dose group and 30% in the higher-dose group. CONCLUSIONS: Both NaHCO(3) doses were well tolerated over 28 weeks with no significant difference in adverse events or hospitalization compared with placebo. The higher dose lowered urinary ammonium excretion and increased serum bicarbonate more than the lower dose but was associated with a greater increase in ACR. The higher 0.8 meq/kg of lean body wt per day dose of NaHCO(3) may be a reasonable choice for future trials.