Establishing a biomonitoring baseline by characterizing the hair metabolome across age and sex using high-resolution mass spectrometry

Hair provides an excellent matrix for long-term biomonitoring due to its chemical accumulation during growth. Despite recent uses of hair for biomonitoring to characterize the chemical exposome across demographics, no established baseline exists for the hair metabolome based on age and sex. This study aimed to establish a baseline for the hair metabolome influenced by age and sex, utilizing an Orbitrap mass spectrometer, a high-resolution mass spectrometry (HRMS) technique. We collected hair samples from 48 participants divided by age and sex into four groups: elderly males, elderly females, young males, and young females. Metabolic profiling was conducted using ultrahigh-performance liquid chromatography coupled with Q ExactiveTM Plus Orbitrap mass spectrometer. Our analysis revealed significant age- and sex-dependent variations in metabolite profiles. Volcano plots highlighted the differential metabolic features between groups, with age showing a stronger influence on metabolic variations in females and sex in younger individuals. We identified 205 chemical compounds affected by age and/or sex, with a significant portion showing overlap in their influence. Pathway enrichment analysis pinpointed perturbations in 41 metabolic pathways, including those involved in lipid metabolism, amino acid turnover, and hormone-associated pathways. Notably, the pathways of arachidonic acid metabolism and fatty acid biosynthesis were consistent with known age and sex influences. Our findings underscore the potential of using hair metabolomics for comprehensive environmental exposure assessment and health research, offering insights into the biological impact of age and sex on the human metabolome.