Influence of Hydration Status and Plasma Copeptin on Ambulatory Blood Pressure in Healthy Young Adults

Abstract

BACKGROUND: Adequate hydration is essential for regulating various physiological systems and may influence blood pressure (BP). Hypohydration is linked with elevated copeptin (surrogate of arginine vasopressin), which is associated with elevated cardiovascular disease risk. However, there is limited information on the influence of hydration and copeptin on ambulatory BP measures in young adults. Therefore, we sought to investigate associations between hydration, copeptin, and ambulatory BP. METHODS: We studied 41 participants (19 M/22 F, 24 White/17 Black, age 21±1 years, body mass index 26±5 kg/m 2 , screening BP 111± 10/67±8 mmHg; Mean ± SD) who provided a 24-hour urine sample. We measured urine specific gravity (USG), urine osmolality (OSM), and plasma copeptin as biomarkers of hydration. We used ambulatory BP monitoring (Suntech Oscar2) to assess BP during daytime (1000-2000) and nighttime (0000-0600). Our primary outcomes were plasma copeptin (pmol/L) and night-to-day BP dip ratio (nighttime/daytime BP) in dehydrated (USG >1.020 or OSM >800 mOsm/kg) vs euhydrated participants. Statistical procedures included Student’s t-tests and Mann-Whitney U tests. We also used Spearman’s rho correlation (controlling for BMI, sex, and race). We set α at ≤0.05. RESULTS: Copeptin concentration was elevated in dehydrated compared with euhydrated participants (USG: 6.6±2.9 vs 4.3±2.0 pmol/L, p<0.005; OSM: 6.6±2.7 vs 4.1±2.0 pmol/L, p<0.001). After controlling for BMI, sex, and race, copeptin was associated with USG (rho=0.44, p=0.005) and OSM (rho=0.51, p=0.001). Systolic and diastolic BP dip ratios did not differ by hydration status for either USG or OSM ( ps>0.179). Additionally, adjusted BP dip ratios were not correlated with OSM or USG ( ps>0.149). Plasma copeptin was not associated with BP dip ratios ( ps>0.155) but was associated with absolute nocturnal systolic (rho=-0.34, p=0.036) and diastolic BP dip (rho=-0.33, p=0.041). When we split participants by low and high copeptin concentration (median split), higher copeptin was associated with a lower (i.e., worse) systolic BP dip ratio (0.87±0.06 vs 0.90±0.06, p=0.048) and lower absolute nocturnal systolic and diastolic BP dip ( ps<0.01). CONCLUSIONS: Hydration biomarkers were correlated with plasma copeptin, but not ambulatory BP. The significance of our findings are that higher copeptin was associated with blunted nocturnal BP dipping in younger adults, which could predispose them to increased future cardiovascular disease risk. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.