ORIGINAL ARTICLE Longer duration of obesity is associated with a reduction in urinary angiotensinogen in prepubertal children Manuela Morato 1,2,3,4 & Liane Correia-Costa 5,6,7 & Teresa Sousa 1,3 & Dina Cosme 1,5 & Franz Schaefer 8 & José Carlos Areias 9 & António Guerra 7,10,11 & Alberto Caldas Afonso 5,6,7 & Henrique Barros 5,12 & Ana Azevedo 5,12 & António Albino-Teixeira 1,3 Received: 29 July 2016 /Revised: 27 February 2017 /Accepted: 27 February 2017 /Published online: 23 March 2017 # IPNA 2017 Abstract Background We aimed to study the impact of obesity on uri- nary excretion of angiotensinogen (U-AGT) in prepubertal children, focusing on the duration of obesity and gender. Also, we aimed to evaluate whether plasma angiotensinogen (P-AGT) and hydrogen peroxide (H 2 O 2 ) play a role in the putative association. Methods Cross-sectional evaluation of 305 children aged 8– 9 years (160 normal weight, 86 overweight, and 59 obese). Anthropometric measurements and 24-h ambulatory blood pressure monitoring were performed. Angiotensinogen (AGT) was determined by a commercial enzyme-linked im- munosorbent assay (ELISA) kit and H 2 O 2 by a microplate fluorometric assay. Results U-AGT and P-AGT levels were similar across body mass index (BMI) groups and between sexes. However, boys who were overweight/obese since the age of 4 years presented lower levels of U-AGT compared with those of normal weight at the same age. In children who were overweight/obese since the age of 4, urinary H 2 O 2 decreased with P-AGT. Conclusions A higher duration of obesity was associated with decreased U-AGT in boys, thus reflecting decreased intrarenal activity of the renin–angiotensin system. Also, children with a Manuela Morato and Liane Correia-Costa contributed equally as first authors to this paper. Ana Azevedo and António Albino-Teixeira contributed equally to the supervision and scientific revision of this paper. * Manuela Morato mmorato@ff.up.pt 1 Department of Pharmacology and Therapeutics, Faculty of Medicine of University of Porto, Porto, Portugal 2 Department of Drug Sciences, Laboratory of Pharmacology, Faculty of Pharmacy of the University of Porto, Rua Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal 3 MedInUP - Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal 4 Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy of University of Porto, Porto, Portugal 5 EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal 6 Division of Pediatric Nephrology, Integrated Pediatric Hospital, Centro Hospitalar São João, Porto, Portugal 7 Department of Pediatrics, Faculty of Medicine of University of Porto, Porto, Portugal 8 Division of Pediatric Nephrology, Center for Pediatrics and Adolescent Medicine, University of Heidelberg, Heidelberg, Germany 9 Division of Pediatric Cardiology, Integrated Pediatric Hospital, Centro Hospitalar São João, Porto, Portugal 10 Division of Pediatric Nutrition, Integrated Pediatric Hospital, Centro Hospitalar São João, Porto, Portugal 11 CINTESIS - Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Porto, Portugal 12 Department of Clinical Epidemiology, Predictive Medicine and Public Health, Faculty of Medicine of University of Porto, Porto, Portugal Pediatr Nephrol (2017) 32:1411–1422 DOI 10.1007/s00467-017-3639-y