Abstract

Obese subjects with impaired glucose tolerance (IGT) are more susceptible than healthy individuals to oxidativestress and cardiovascular disease. This randomised controlled investigation was designed to test the hypothesisthat a-lipoic acid supplementation and exercise training may elicit favourable clinical changes in obese subjectswith IGT. All data were collected from 24 obese (BMI ≥ 30 kg/m2) IGT patients. Following participant randomisationinto two groups, fasting venous blood samples were obtained at baseline, and before and following intervention.The first group consisted of 12 participants who completed a 12 week control phase followed by 12 weeks ofchronic exercise at 65% HRmax for 30 minutes a day, 5 days per week, while ingesting 1 gram per day of a-lipoicacid for 12 weeks. The second group consisted of 12 participants who completed the same 12 week control phase,but this was followed by 12 weeks of 1 gram per day of a-lipoic acid supplementation only (no exercise). Themain findings show a comparatively greater rate of low density lipoprotein (LDL) oxidation in the group consistingof a-lipoic acid only (p < 0.05 vs. pre intervention), although total oxidant status was lower post intervention (p <0.05 vs. baseline) in this group. However, exercise and a-lipoic acid in combination attenuates LDL oxidation.Furthermore, in the a-lipoic acid supplement plus exercise training group, total antioxidant capacity wassignificantly increased (p < 0.05 vs. baseline and pre intervention). Body fat percentage and waist and hipcircumference decreased following exercise training (p < 0.05 vs. post intervention). There were no selectivetreatment differences for a range of other clinical outcomes including glycaemic regulation (p > 0.05). Thesefindings report that a-lipoic acid ingestion may increase the atherogenicity of LDL when ingested in isolation ofexercise, suggesting that in IGT the use of this antioxidant treatment does not ameliorate metabolic disturbances,but instead may detrimentally contribute to the pathogenesis of atherosclerosis and development of CVD.However, when a-lipoic acid is combined with exercise, this atherogenic effect is abolished.