Changes in serum hypoxanthine levels by exercise in obese subjects

To study on effect of obesity on changes in serum hypoxanthine with exercise, exercise stress testing with treadmill was performed on 7 obese subjects (body mass index [BMI], 30.6 +/- 3.2 kg/m(2)) and 16 healthy volunteers (BMI, 21.5 +/- 2.10 kg/m(2)). Expiratory gas analysis during exercise showed that peak Vo(2) was significantly lower in the obese group than in the control group (28.1 +/- 4.0 v 37.1 +/- 4.7 mL/kg/min; P <.001). Furthermore, the obese group had lower anaerobic threshold (AT) values (P <.005), respiratory quotient at AT (P =.003), and exercise capacity reserve (P =.002) than the control group. Baseline serum hypoxanthine levels were significantly higher in the obese group than in the control group (3.46 +/- 3.70 v 1.23 +/- 1.16 micromol/L; P <.05). Exercise induced a pronounced increase in serum hypoxanthine level in the obese group compared with the control group (10.65 +/- 6.81 v 43.86 +/- 4.56 micromol/L; P <.01). Serum levels of uric acid before and after load were also higher in the obese group than in the control group (404 +/- 43 v 302 +/- 77 micromol/L; P <.005). A pronounced increase in hypoxanthine with exercise may result in organ damage caused by free radicals, and intermittent training from mild intensity may be less hazardous for exercise treatment of obesity.