PhD Thesis / Metabolomics offers a systemic approach to discover clinical biomarkers for early detection of chronic diseases while also revealing underlying mechanisms relevant to human disorders of complex aetiology. Metabolomic studies in support of chronic disease prevention have focused primarily on surrogate biofluids (e.g., serum, plasma) for analysis due to their routine and less invasive sample collection in a clinical setting. However, biofluids are non-organ specific and thus are reflective of confounding biochemical processes within the body that are often difficult to interpret. As a result, it is necessary to assess metabolite changes localized within tissues since they are the direct site of pathogenic processes, in order to obtain more robust and specific biomarkers. This thesis aims to contribute to new advances in biomarker discovery and tissue metabolomic studies using multiplexed separations together with innovative data workflows based on multisegment injection-capillary electrophoresis-mass spectrometry (MSI-CE-MS). Chapter II introduces a high throughput yet targeted screening method for accurate quantification of serum γ‐glutamyl dipeptides from a cohort of overweight Japanese non-alcoholic steatohepatitis (NASH) patients that may allow for better risk assessment of long-term survivorship complementary to histopathology. Chapter III introduces a non-targeted metabolite profiling strategy for fasting plasma samples from prediabetic, older adults undergoing short-term step reduction (<1000 steps/day) in order to identify adaptive metabolic responses to abrupt changes in physical inactivity for early detection of sarcopenia in high-risk older persons. Chapter IV describes the first metabolomics study to characterize the human skeletal muscle metabolome from mass-restricted tissue biopsies together with matching plasma samples, which identified novel metabolic signatures associated with strenuous interval exercise, as well as treatment effects from high-dose bicarbonate pretreatment that delays the onset of muscle fatigue. Lastly, in Chapter V, metabolite coverage was expanded to include fatty acids for comprehensive characterization of murine placental tissue metabolome, which revealed sex-specific metabolic adaptations during gestation from maternal dams fed a standardized diet. In summary, this thesis contributes to new innovations in metabolomics for the discovery of novel biomarkers from blood and/or tissue specimens as required for early detection of chronic diseases relevant to population health, which were also used to validate the efficacy of therapeutic interventions based on physical activity to support healthy ageing. / Thesis / Doctor of Philosophy (PhD)