Jansen, Lisa T.

The reference values for daily total water intake from fluids and foods (TWI) from the Institute of Medicine (IOM) are 2.7 and 3.7 liters for females and males, respectively. Recent studies suggest that for optimal water intake 24h urine osmolality should be maintained below 500 mmol·kg −1 . Purpose To determine the total water intake requirement for healthy adults to maintain 24h urine osmolality below 500 mmol·kg −1 . Methods Urinary concentration was assessed in 48 men and 50 women (age: 41±14 y, body mass index: 26.2±5.1 kg·m −2 ) via urine osmolality from 24h samples (UOsm). TWI was assessed via water turnover using the deuterium dilution (D 2 O) method throughout a 7‐day time period, corrected for metabolic water production. The diagnostic accuracy of TWI to identify UOsm ≤ 500 mmol·kg −1 was evaluated using receiver operating characteristic (ROC) analysis in men and women separately. Results UOsm was 511±232 and 402±203 mmol·kg −1 and TWI was 3.54±1.08 L·d −1 and 3.20±1.27 L·d −1 in men and women, respectively. 32% of men and 55% of women met IOM guidelines for TWI. ROC analysis for TWI detecting UOsm ≤ 500 mmol·kg −1 in men yielded an area under the curve (AUC) of 77.4% with sensitivity, specificity, and threshold values of 83.3%, 64.5%, and 3.39 L·d −1 , respectively. In women, the AUC was 82.4% with sensitivity, specificity, and threshold values of 85.7%, 72.1%, and 2.61 L·d −1 , respectively. Conclusion Considering threshold values in men and women of 3.39 L·d −1 and 2.61 L·d −1 , respectively, maintaining TWI in line with IOM guidelines of 3.7 L·d −1 in men and 2.7 L·d −1 in women should be sufficient for most individuals to maintain 24h urine osmolality less than 500 mmol·kg −1 . Support or Funding Information This research was supported by Danone Research. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Copeptin, a c‐terminal segment of arginine vasopressin (AVP) prohormone, has equimolar secretion to AVP in response to osmotic, stress‐related, and hemodynamic stimulation. For this reason, and because of the difficulties in measuring AVP directly linked to its short half‐life, copeptin has been used as a stable and sensitive surrogate marker for AVP for various clinical indications. However, the plasma copeptin response to osmotic stimulation remains poorly documented. PURPOSE Examine the plasma copeptin response to plasma hyperosmolality induced by hypertonic saline infusion. METHODS Sixty healthy adults (50% male, age: 30±1 y, weight: 78.2±15.2 kg, body mass index: 26.9±4.0 kg·m −2 ) were infused intravenously with 3% (HYPER) or 0.9% (ISO) NaCl for 2 h (0.1 ml·kg −1 ·min −1 ) in a counterbalanced, cross‐over design. Blood samples were collected every 30 minutes. Plasma osmolality (P Osm ), copeptin (P Cop ; BRAHAMS copeptin proAVP, Thermo Fisher Scientific, Germany), and sodium (P Na ) were measured, and changes in plasma volume (PV) were calculated from hematocrit and hemoglobin using the Dill & Costill equation. RESULTS Following the HYPER trial, P Na increased from 136±2 mmol ·L −1 to 146.5±3 mmol ·l −1 ( P < 0.001), with PV expansion of 18.7±7.3% ( P < 0.001). Both P Osm and P Cop increased significantly (0 min: 286±3 mmol·kg −1 and 4.5±3.7 pmol·L −1 ; 120 min: 305±4 mmol·kg −1 and 20.4±12.8 pmol·L −1 , respectively, P < 0.001). Mean (95% CI) P Cop increased with increasing P Osm : 3.2 (2.5–3.8) pmol·L −1 for P Osm ≤ 284.9 mmol·kg −1 ; 5.4 (3.8–7.0) pmol·L −1 for P Osm 285–289.9; 6.2 (4.3–8.0) pmol·L −1 for P Osm 290–294.9; 8.5 (7.1–9.9) pmol·L −1 for P Osm 295–299.9; 12.3 (10.2–14.4) pmol·L −1 for P Osm 300–304.9; and 19.2 (16.3–22.2) pmol·L −1 for P Osm ≥ 305 mmol·kg −1 . In contrast, during the ISO trial P Na remained unchanged during the 2‐h infusion (135.9±1.9 vs. 137.6±1.6 mmol·L −1 ), while PV expanded by 10.5±4.4% ( P < 0.001 compared to baseline; P < 0.001 compared to HYPER). Neither P Osm (0 min: 285±4,120 min: 287±3 mmol·kg −1 ) nor P Cop (0 min: 4.1±1.8, 120 min: 3.8±3.0 pmol·L −1 ) were affected during the ISO trial. CONCLUSION Plasma copeptin was stimulated by increased plasma osmolality during a hypertonic infusion. Support or Funding Information This research was supported by Danone Research This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .