Urinary Catalytic Iron in Obesity

INTRODUCTION Obesity precedes the development of many cardiovascular disease risk factors, including type 2 diabetes mellitus (DM), hypertension, and chronic kidney disease. Catalytic iron, which has been associated with these chronic diseases, may be one of the links between obesity and these multifactorial diverse disorders. OBJECTIVE We investigated whether urinary catalytic iron is increased in obese individuals without DM and overt kidney disease. STUDY DESIGN We measured urinary catalytic iron using established methods in 200 randomly selected individuals without DM [100 who were obese (body mass index ≥30 kg/m2) and 100 who were nonobese (body mass index ≤27)]. Participants were selected from an outpatient clinic and community setting and were part of an ongoing cross-sectional study of obesity in individuals between the ages of 18 and 70 years. RESULTS There was a significant difference in mean (95% CI) urinary catalytic iron excretion between the obese participants and the nonobese participants, 463 (343–582) nmol/mg [52.3 (38.8–65.8) nmol/μmol] vs 197 (141–253) nmol/mg [22.3 (15.9–28.6) nmol/μmol]; P < 0.001. The significant predictors of increased urinary catalytic iron were obesity (P = 0.001) and waist-to-hip ratio (P = 0.03). CONCLUSIONS Our study results demonstrate that obesity and waist-to-hip ratio are associated with increased urinary catalytic iron, which may be a useful marker of oxidative stress. Additional studies are needed to determine the role of catalytic iron in increased cardiovascular disease and chronic kidney disease associated with obesity.