The effect of water loading on serum copeptin and aquaporin 2 levels in overweight and obese individuals

Background and Aim: The water intake has beneficial effects on obesity. Arginine vasopressin hormone regulates body fluid homeostasis. Arginin vasopressin and copeptin derive from the same precursor peptide pre-provasopressin and copeptin is reliably mirrors arjinin vasopressin concentrations in the circulation. Aquaporin 2 is a membrane protein that regulates water reabsorption from the kidneys. In this study, it was aimed to investigate how water loading affects serum copeptin and aquaporrin 2 levels in overweight/obese individuals. Material and Methods: Thirty healthy individuals (15 normal weight and 15 overweight/obese) were included in the study. After 12 hours of fasting and thirst, anthropometric parameters, basal metabolic rates of all volunteers and blood pressure were measured, the 1st blood samples were taken and they were allowed to drink 10 ml/kg of water within 30 minutes. After 90 minutes blood pressure measurement were repeated and 2nd blood sample was taken. Biochemical parameters, copeptin and aquaporin 2 levels were determined in serum samples. Results: Copeptin levels in groups normal weight and overweight/obese after water restriction were similar (5.61±3.93 vs. 4.37±3.13; p=0.351). There was no statistically significant difference in aquaporin 2 levels in the overweight/obese group compared to the normal weight group (8.22±6.58 vs. 12.32±10.27; p=0.206). Both copeptin and aquaporin 2 levels did not change after water loading. When water restriction and water loading periods were compared, differences were detected between groups in insulin, cortisol and glucose values. Conclusion: Evidence has been provided that the amount (10ml/kg) used for water loading does not change the levels of copeptin and aquaporin 2 in the pathogenesis of obesity. Keywords: Copeptin, aquaporin-2, arginine vasopressin, obesity, water loading