Role of alpha-lipoic acid in vascular function: A systematic review of human intervention studies

Alpha-lipoic acid (ALA) has long been the focus of interest due to its promising effects on cardiometabolic risk factors. The aim of this systematic review was to summarize findings from existing human intervention studies evaluating the effect of ALA on vascular function. We performed a systematic search in the PubMed, SCOPUS, and Web of science electronic databases from inception until 1 July 2020. A total of 1106 records were identified from the database search, of which 12 were eligible: nine addressed chronic effects and three measured acute effects of ALA on vascular function. Of 11 trials that evaluated endothelial function by methods such as flow-mediated dilation (n = 7), reactive hyperemia (n = 2) and ACh-induced endothelium-dependent vasodilation (n = 2), 10 reported a significant improvement in endothelial function. In contrast, none of six trials examining the response of endothelium-independent vasodilation reported the favorable impact. The effect of ALA on arterial stiffness measures has been poorly studied. ALA appears to improve endothelial function through increasing the bioavailability of endothelium-derived nitric oxide as well as decreasing oxidative stress and inflammation. In conclusion, these results suggest improvement of endothelial function, but not endothelium-independent vasodilation as a potential mechanism by which ALA attenuates cardiovascular diseases.