Effects of Water Loading on Observed and Predicted Plasma Sodium, and Fluid and Urine Cation Excretion in Healthy Individuals

Rationale & Objective: The discovery of sodium storage without concurrent water retention suggests the presence of an additional compartment for sodium distribution in the body. The osmoregulatory role of this compartment under hypotonic conditions is not known. Study Design: Experimental interventional study. Setting & Participants: Single-center study of 12 apparently healthy men. Intervention: To investigate whether sodium can be released from its nonosmotic stores after a hypotonic fluid load, a water-loading test (20 mL water/kg in 20 minutes) was performed. Outcomes: During a 240-minute follow-up, we compared the observed plasma sodium concentration ([Na + ]) and fluid and urine cation excretion with values predicted by the Barsoum-Levine and Nguyen-Kurtz formulas. These formulas are used for guidance of fluid therapy during dysnatremia, but do not account for nonosmotic sodium stores. Results: 30 minutes after water loading, mean plasma [Na + ] decreased 3.2 ± 1.6 (SD) mmol/L, after which plasma [Na + ] increased gradually. 120 minutes after water loading, plasma [Na + ] was significantly underestimated by the Barsoum-Levine (−1.3 ± 1.4 mmol/L; P = 0.05) and Nguyen-Kurtz (−1.5 ± 1.5 mmol/L; P = 0.03) formulas. In addition, the Barsoum-Levine and Nguyen-Kurtz formulas overestimated urine volume, while cation excretion was significantly underestimated, with a cation gap of 57 ± 62 (P = 0.009) and 63 ± 63 mmol (P = 0.005), respectively. After 240 minutes, this gap was 28 ± 59 (P = 0.2) and 34 ± 60 mmol (P = 0.08), respectively. Limitations: The compartment from which the mobilized sodium originated was not identified, and heterogeneity in responses to water loading was observed across participants. Conclusions: These data suggest that healthy individuals are able to mobilize osmotically inactivated sodium after an acute hypotonic fluid load. Further research is needed to expand knowledge about the compartment of osmotically inactivated sodium and its role in osmoregulation and therapy for dysnatremias. Funding: This investigator-initiated study was partly supported by a grant from Unilever Research and Development Vlaardingen, The Netherlands B.V. (MA-2014-01914)

Urinary metabolites associate with the rate of kidney function decline in patients with autosomal dominant polycystic kidney disease.

BACKGROUND:The variable course of autosomal dominant polycystic kidney disease (ADPKD), and the advent of renoprotective treatment require early risk stratification. We applied urinary metabolomics to explore differences associated with estimated glomerular filtration rate (eGFR; CKD-EPI equation) and future eGFR decline. METHODS:Targeted, quantitative metabolic profiling (1H NMR-spectroscopy) was performed on baseline spot urine samples obtained from 501 patients with ADPKD. The discovery cohort consisted of 338 patients (56% female, median values for age 46 [IQR 38 to 52] years, eGFR 62 [IQR 45 to 85] ml/min/1.73m2, follow-up time 2.5 [range 1 to 3] years, and annual eGFR slope -3.3 [IQR -5.3 to -1.3] ml/min/1.73m2/year). An independent cohort (n = 163) was used for validation. Multivariate modelling and linear regression were used to analyze the associations between urinary metabolites and eGFR, and eGFR decline over time. RESULTS:Twenty-nine known urinary metabolites were quantified from the spectra using a semi-automatic quantification routine. The model optimization routine resulted in four metabolites that most strongly associated with actual eGFR in the discovery cohort (F = 128.9, P = 7×10-54, R2 = 0.724). A model using the ratio of two other metabolites, urinary alanine/citrate, showed the best association with future annual change in eGFR (F = 51.07, P = 7.26×10-12, R2 = 0.150). This association remained significant after adjustment for clinical risk markers including height-adjusted total kidney volume (htTKV). Results were confirmed in the validation cohort. CONCLUSIONS:Quantitative NMR profiling identified urinary metabolic markers that associated with actual eGFR and future rate of eGFR decline. The urinary alanine/citrate ratio showed additional value beyond conventional risk markers

Lanreotide Reduces Liver Growth In Patients With Autosomal Dominant Polycystic Liver and Kidney Disease

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Effect of Lanreotide on Kidney Function in Patients With Autosomal Dominant Polycystic Kidney Disease:The DIPAK 1 Randomized Clinical Trial

Importance: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation in both kidneys and loss of renal function, eventually leading to a need for kidney replacement therapy. There are limited therapeutic management options. Objective: To examine the effect of the somatostatin analogue lanreotide on the rate of kidney function loss in patients with later-stage ADPKD. Design, Setting, and Participants: An open-label randomized clinical trial with blinded end point assessment that included 309 patients with ADPKD from July 2012 to March 2015 at 4 nephrology outpatient clinics in the Netherlands. Eligible patients were 18 to 60 years of age and had an estimated glomerular filtration rate (eGFR) of 30 to 60 mL/min/1.73 m2. Follow-up of the 2.5-year trial ended in August 2017. Interventions: Patients were randomized to receive either lanreotide (120 mg subcutaneously once every 4 weeks) in addition to standard care (n = 153) or standard care only (target blood pressure <140/90 mm Hg; n = 152). Main Outcomes and Measures: Primary outcome was annual change in eGFR assessed as slope through eGFR values during the 2.5-year treatment phase. Secondary outcomes included change in eGFR before vs after treatment, incidence of worsening kidney function (start of dialysis or 30% decrease in eGFR), change in total kidney volume and change in quality of life (range: 1 [not bothered] to 5 [extremely bothered]). Results: Among the 309 patients who were randomized (mean [SD] age, 48.4 [7.3] years; 53.4% women), 261 (85.6%) completed the trial. Annual rate of eGFR decline for the lanreotide vs the control group was -3.53 vs -3.46 mL/min/1.73 m2 per year (difference, -0.08; [95% CI, -0.71 to 0.56]; P = .81). There were no significant differences for incidence of worsening kidney function (hazard ratio, 0.87 [95% CI, 0.49 to 1.52]; P = .87), change in eGFR (-3.58 vs -3.45; difference, -0.13 mL/min/1.73 m2 per year [95% CI, -1.76 to 1.50]; P = .88), and change in quality of life (0.05 vs 0.07; difference, -0.03 units per year [95% CI, -0.13 to 0.08]; P = .67). The rate of growth in total kidney volume was lower in the lanreotide group than the control group (4.15% vs 5.56%; difference, -1.33% per year [95% CI, -2.41% to -0.24%]; P = .02). Adverse events in the lanreotide vs control group included injection site discomfort (32% vs 0.7%), injection site papule (5.9% vs 0%), loose stools (91% vs 6.6%), abdominal discomfort (79% vs 20%), and hepatic cyst infections (5.2% vs 0%). Conclusions and Relevance: Among patients with later-stage autosomal dominant polycystic kidney disease, treatment with lanreotide compared with standard care did not slow the decline in kidney function over 2.5 years of follow-up. These findings do not support the use of lanreotide for treatment of later-stage autosomal dominant polycystic kidney disease. Trial Registration: ClinicalTrials.gov Identifier: NCT01616927