Hydroxytyrosol Modulates Arachidonic Acid Metabolism and Purine Catabolism in Individuals with Prediabetes: An Untargeted Metabolomics Study in a Randomized Controlled Trial

Background: Hydroxytyrosol (HT) is a phenolic compound found in extra virgin olive oil that modulates oxidative and inflammatory status. However, clinical trials evaluating HT as a stand-alone supplement remain scarce, and its underlying mechanisms and pathway modulation are not yet fully understood. This study aimed to investigate the metabolic effects of HT supplementation in individuals with overweight and prediabetes using an untargeted metabolomics approach. Methods: An untargeted liquid chromatography–mass spectrometry (LC–MS)-based metabolomics analysis was performed on serum samples from 49 participants with overweight and prediabetes enrolled in a randomized controlled trial. Participants received either HT (15 mg/day for 16 weeks; n = 24) or placebo (n = 25). Global metabolomic profiling was used to compare metabolic changes between the two groups. Results: HT supplementation induced a distinct metabolic profile compared with placebo. Participants in the HT group showed reduced levels of nitrogenous base derivatives and arachidonic acid, together with increased concentrations of phosphatidylcholines, lysophosphatidylcholines and sphingomyelins. These alterations suggest modulation of two key metabolic pathways including purine degradation and arachidonic acid metabolism. Conclusions: These findings provide mechanistic insights into the biological effects of HT and support the integration of metabolomics and multi-omics approaches in future clinical studies to validate these pathways in larger populations.