Evidence of defective fattyacidome and aminoacidome in sebaceous and non sebaceous skin areas in atopic dermatitis

Atopic dermatitis (AD) is a composite disease characterized by derangement of the skin permeability barrier (SPB). Little is known on the role played by the sebaceous gland (SG) activity in the SPB integrity in AD. Our objective was to investigate lipidomics profiles of sebaceous-type and epidermal-type free fatty acids (FFAs), together with levels of squalene, cholesterol, triglycerides (TGs), and wax esters (WEs) in sebum and stratum corneum (SC) specimens obtained from seborrheic and non-seborrheic areas in healthy and AD adults. Aminoacidome was investigated in SC. Controls (44 unaffected subjects: 27F, 17M) and 54 AD patients, which included 20 with uninvolved face (fnAD: 11F, 9M) and 34 with involved face (fyAD: 16F, 18M), were enrolled. Sebum and SC were sampled from SG-dense areas (forehead and cheek). SC was sampled also from SG-deprived regions (arm). Integrity of SPB was verified on the same areas by assessing TEWL and skin hydration before sampling. Sebometry was inferred from weighed sebum. FFAs, aminoacids, squalene, and cholesterol were quantified by GCMS, whereas total TGs and WEs were determined by TLC. Multivariate ANOVA-simultaneous component analysis (ASCA) proved the multiple sources of deranged sebogenesis in adult AD. Declined sebometry and disruption of the SBP were associated with decreased levels of lipids of both sebaceous and epidermal types, including straight and terminally branched C15:0, and very long straight chain C24:0, respectively. Lipid derangement in fyAD was more pronounced than that observed for fnAD, independently on the site. Aminoacid signature was altered on the forehead in both fnAD and fyAD groups. Sebum bio-signatures associated with aminoacidome, and skin physical properties may serve the definition of phenotype clusters that associate with AD severity.