LB1742 Profiling of the skin surface metabolome, an essential bridge linking skin microbiome and skin phenome

The skin is a complex ecosystem harboring millions of microorganisms. Resource availability (nutrients) is considered a crucial selection pressure shaping the system, which can be assessed by skin surface metabolome. Skin surface metabolome is also essential for addressing the underlying mechanism between microbe-host interaction. Here, we first review metabolites on the skin from various metabolome studies. We next detected and quantified metabolites through our samples from healthy human forearm skin using five analytical approaches: quantitative lipidomics, widely targeted lipidomics, widely targeted metabolomics, and targeted 500 metabolomics and oxidized lipidomics. Our results showed that the diverse substances present on the skin surface, derived from the host (stratum corneum, skin appendages and plasma), environment (xenobiotics) and microbial metabolism, mainly comprised of lipids, amino acids, sugars, peptides, vitamins, hormones, pheromones, and other xenobiotics. Our samples showed free fatty acids (FFAs) and triglycerides (TGs) are the core lipids on the skin surface, accounting for approximately 90% of individual total lipids, with FFAs being the most abundant subclass (55%) and TGs are the most diverse subclass. In addition, the polar compounds on the skin primarily comprise amino acids, organic acids and their derivatives, nucleotides and their metabolites, and hormones and hormone-related compounds. Overall, our study provides a comprehensive overview of the skin surface metabolome that will facilitate future studies for skin microbiome-host interaction.