Alpha-lipoic acid does not acutely affect resistance and conduit artery function or oxidative stress in healthy men

Aims: Alpha-lipoic acid (ALA) is a thiol compound with antioxidant properties used in the treatment of diabetic polyneuropathy. ALA may also improve arterial function, but there have been scant human trials examining this notion. This project aimed to investigate the effects of oral and intra-arterial ALA on changes in systemic and regional haemodynamics, respectively. Methods: In study 1, 16 healthy older men aged 58 ± 7 years (mean ± SD) received 600 mg of ALA or placebo, on two occasions 1 week apart, in a randomized cross-over design. Repeated measures of peripheral and central haemodynamics were then obtained for 90 min. Central blood pressure and indices of arterial stiffness [augmentation index (Alx) and estimated aortic pulse wave velocity] were recorded non-invasively using pulse wave analysis. Blood samples obtained pre- and post-treatments were analysed for erythrocyte antioxidant enzyme activity, plasma nitrite and malondialdehyde. In study 2 the effects of incremental cumulative doses (0.5, 1.0, 1.5 and 2.0 mg ml ^-1 min ^-1) of intra-arterial ALA on forearm blood flow (FBF) were assessed in eight healthy subjects (aged 31 ± 5 years) by conventional venous occlusion plethysmography. Results: There were no significant changes on any of the central or peripheral haemodynamic measures after either oral or direct arterial administration of ALA. Plasma ALA was detected after oral supplementation (95% confidence intervals 463, 761 ng ml ^-1), but did not alter cellular or plasma measures of oxidative stress. Conclusions: Neither oral nor intra-arterial ALA had any effect on regional and systemic haemodynamics or measures of oxidative stress in healthy men.