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Background: Eicosapentaenoic acid (EPA) and α-lipoic acid (α-LA) have been investigated for their beneficial effects on obesity and cardiovascular risk factors. In the current research, the goal was to evaluate metabolomic changes following the dietary supplementation of these two lipids, alone or combined in healthy overweight/obese sedentary women following an energy-restricted diet. For this purpose, an untargeted metabolomics approach was conducted on urine samples using liquid chromatography coupled with time of flight mass spectrometry (HPLC-TOF-MS). Methods: This is a short-term double blind placebo-controlled study with a parallel nutritional design that lasted 10 weeks. Participants were assigned to one of the 4 experimental groups [Control, EPA (1.3 g/d), α-LA (0.3 g/d) and EPA+α-LA (1.3 g/d + 0.3 g/d)]. All intervention groups followed an energy-restricted diet of 30% less than total energy expenditure. Clinically relevant biochemical measurements were analyzed. Urine samples (24 h) were collected at baseline and after 10 weeks. Untargeted metabolomic analysis on urine samples was carried out, and principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were performed for the pattern recognition and characteristic metabolites identification. Results: Urine samples were scattered in the PCA scores plots in response to the supplementation with α-LA. Totally, 28 putative discriminant metabolites in positive ionization, and 6 in negative ionization were identified among groups clearly differentiated according to the α-LA administration. Remarkably is the presence of an ascorbate intermediate metabolite (one of the isomers of trihydroxy-dioxohexanoate, or dihydroxy–oxohexanedionate) in the groups supplemented with αLA. This fact might be associated with antioxidant properties of both α-LA and ascorbic acid. Correlations between phenotypical parameters and putative metabolites of provided additional information on whether there is a direct or inverse relationship between them. Especially interesting are the negative correlation between ascorbate intermediate metabolite and asymmetric dimethylarginine (ADMA) and the positive one between superoxide dismutase (SOD) and αLA supplementation. Conclusions: This metabolomic approach supports that the beneficial effects of α-LA administration on body weight reduction may be partly explained by the antioxidant properties of this organosulfur carboxylic acid mediated by isomers of trihydroxy-dioxohexanoate, or dihydroxy–oxohexanedionate.

α-lipoic acid (5-(1,2-dithiolan-3-yl)-pentanoic acid) is a natural occurring compound which possesses antioxidant properties. Moreover, anti-obesity properties in both rodents and humans have been attributed to α-lipoic acid being adipose tissue a target for this compound. In this context, the present study has demonstrated the ability of α-LA to modulate lipid metabolism in both murine and human white adipocytes. Thus, α-LA: 1) Inhibits fatty acids uptake (through CD36 downregulation); 2) Reduces fatty acids esterification into triglycerides (through DGAT1 reduction); 3) Decreases de novo lipogenesis (induced by inhibition of FAS, SCD1 and ACC mediated by AMPK activation); 4) Stimulates lipolysis (mainly mediated by the phosphorylation of HSL through cAMP-mediated activation of PKA, probably through the inhibition of AdPLA and PGE2; 5) Increases fatty acid oxidation machinery (CPT1 and ACOX) in white adipocytes; 6) Promotes mitochondrial biogenesis by the activation of PGC-1α mediated by SIRT1 and AMPK activation; and 7) Induces a brown-like remodelling in white subcutaneous adipocytes from overweight/obese subjects. Taking together all of these facts suggest that α-LA remodels adipocyte metabolism towards oxidation rather than storage, and this could contribute to the anti-obesity properties of α-LA.