The effects of aerobic exercise training at two different intensities in obesity and type 2 diabetes: implications for oxidative stress, low-grade inflammation and nitric oxide production

Aims To investigate the effect of 16 weeks of aerobic training performed at two different intensities on nitric oxide (tNOx) availability and iNOS/nNOS expression, oxidative stress (OS) and inflammation in obese humans with or without type 2 diabetes mellitus (T2DM). Methods Twenty-five sedentary, obese (BMI > 30 kg/m(2)) males (52.8 +/- 7.2 years); 12 controls versus 13 T2DM were randomly allocated to four groups that exercised for 30 min, three times per week either at low (Fat-Max; 30-40 % VO2max) or moderate (T-vent; 55-65 % VO2max) intensity. Before and after training, blood and muscle samples (v. lateralis) were collected. Results Baseline erythrocyte glutathione was lower (21.8 +/- 2.8 vs. 32.7 +/- 4.4 nmol/ml) and plasma protein oxidative damage and IL-6 were higher in T2DM (141.7 +/- 52.1 vs. 75.5 +/- 41.6 nmol/ml). Plasma catalase increased in T2DM after T-vent training (from 0.98 +/- 0.22 to 1.96 +/- 0.3 nmol/min/ml). T2DM groups demonstrated evidence of oxidative damage in response to training (elevated protein carbonyls). Baseline serum tNOx were higher in controls than T2DM (18.68 +/- 2.78 vs. 12.34 +/- 3.56 mu mol/l). Training at T-vent increased muscle nNOS and tNOx in the control group only. Pre-training muscle nNOS was higher in controls than in T2DMs, while the opposite was found for iNOS. No differences were found after training for plasma inflammatory markers. Conclusion Exercise training did not change body composition or aerobic fitness, but improved OS markers, especially when performed at T-vent. Non-diabetics responded to T-vent training by increasing muscle nNOS expression and tNOx levels in skeletal muscle while these parameters did not change in T2DM, perhaps due to higher insulin resistance (unchanged after intervention).