Myocardial ischemia is a leading cause of cardiovascular morbidity and mortality; however, early and noninvasive diagnosis remains challenging. Conventional diagnostic methods, including electrocardiography, coronary angiography, and myocardial perfusion imaging have limitations in detecting early-stage ischemia. This study aimed to identify plasma metabolite biomarkers associated with early myocardial ischemia using liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF/MS) based metabolomics. Eighty-nine patients with suspected myocardial ischemia hospitalized at Kyungpook National University Hospital were screened. After applying exclusion criteria, 43 patients were enrolled and divided into 2 groups: control (n = 24, no angiographic stenosis) and case (n = 19, >70% stenosis in vessels with a diameter of ≥2.5 mm). All participants underwent an exercise stress test based on the Bruce protocol. Plasma samples were collected before and 10 minutes after exercise. Untargeted LC–QTOF/MS profiling was performed, and multivariate analyses (principal component analysis and orthogonal partial least squares-discriminant analysis) were used to identify differential metabolites. Receiver operating characteristic analysis was conducted to evaluate diagnostic performance. Multivariate modeling revealed distinct metabolic differences between the groups. Thirteen metabolites were significantly altered in both groups, while 9 changed exclusively in the ischemia group following exercise. Notably, several phosphatidylcholine (PC) species – PC (O-18:5/2:0), PC (O-16:0/22:4), PC (O-18:4/18:2), and PC (20:4/20:4) – as well as 13Z-docosenamide, differed significantly between groups. Receiver operating characteristic analysis identified 3 key metabolites – 13Z-docosenamide, PC (16:0/22:5), and PC (18:1/20:4) – with excellent discriminative performance (area under the curve = 0.941; 95% confidence interval: 0.865–1.000; sensitivity, 92%; specificity, 93%). Pathway analysis indicated that exercise-induced ischemia was associated with alterations in phospholipid, sphingolipid, and fatty acid metabolism, reflecting hypoxia-mediated energy shifts and oxidative stress. LC–MS-based metabolomic profiling identified distinct lipid metabolic signatures associated with early myocardial ischemia. The metabolites 13Z-docosenamide, PC (16:0/22:5), and PC (18:1/20:4) demonstrated strong diagnostic potential and may serve as early biomarkers for the noninvasive detection of myocardial ischemia. Further validation in independent cohorts might be required to confirm their clinical applicability.

Background: A plant-based diet is reportedly effective in preventing chronic and metabolic diseases, primarily because of the antioxidant properties of phytochemicals present in vegetables and fruits. However, systematic metabolomics studies investigating the changes in metabolic phenotypes resulting from plant-based diets in adolescents are lacking. Therefore, this study aimed to examine alterations in urinary metabolomic profiles associated with a plant-based diet to explore its beneficial metabolic effects. Methods: Eighteen healthy Korean adolescents participated in an 8-week intervention, in which they modified their dietary patterns to primarily include whole grains, vegetables, and fruits. Urine samples were analyzed using gas chromatography–mass spectrometry, and multivariate analysis was performed to identify statistically significant metabolite alterations following the plant-based dietary intervention. Results: The plant-based diet significantly reduced body weight and body fat mass but increased plasma biological antioxidant potential. Metabolomic profiling revealed a clear distinction between samples collected before and after the 8-week intervention, with R ² Y and Q ² values for the permuted models at 0.906 and 0.635, respectively. Key metabolite changes included increases in L-phenylalanine, L-tyrosine, glutathione, succinic acid, and tartaric acid as well as decreases in L-leucine, glycine, and indoleacetic acid. These changes suggest enhancements of antioxidant capacity, detoxification pathways, and mitochondrial function. Conclusion: This nutritional metabolomics study provides mechanistic insights into the metabolic changes associated with a plant-based diet. Its findings support the integration of plant-based meals into school settings to promote the metabolic health of adolescents and mitigate the risk of chronic disease progression.

Background/Objectives: Vitamin D (VD) is metabolized in the body and plays a crucial role in regulating the antioxidant system. While exposure to heavy metals (HMs) inhibits VD activity, HMs can also be absorbed following VD stimulation. Despite differing views on the interaction between HM and VD activity, the effects of HM exposure on VD-related pathways have not been examined using metabolomics. This study aimed to investigate the impact of HM exposure on VD-related antioxidant activity under VD deficiency conditions using untargeted metabolic profiling. Methods: In this retrospective cohort study, 46 plasma samples were analyzed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS). Metabolic profiling was performed on two groups: individuals with severe VD deficiency and low HM exposure (SVDD–LHM) and those with VD deficiency and high HM exposure (VDD–HHM). Results: As a compensatory response to oxidative stress induced by HMs, VD-related antioxidant pathways may be associated with elevated levels of antioxidants, including bilirubin, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). In-creases in EPA and DHA were also linked to alterations in lipid metabolism, including diacylglycerol and phosphatidylcholine levels. DHA showed an area under the curve (AUC) of 0.850 (95% CI: 0.651–0.990), suggesting that DHA could serve as a potential biomarker for VD activity in response to HM exposure. Conclusions: The identified metabolites and metabolic pathways suggest that HM exposure may stimulate VD-related antioxidant activity, even under VD-deficient conditions.