Lipidomics of facial sebum in the comparison between acne and non-acne adolescents with dark skin

Abstract

Lipidomics is advantageous in the study of sebum perturbations occurring in acne. An extended evaluation of the sebum lipid profiles in acne-prone sebaceous areas is lacking in dark skin. Yet, there is a void space in understanding how the building blocks of sebum lipids, i.e. individual fatty acids (FAs), are intertwined with acne-prone skin. We aimed to determine the sebum lipidome in facial areas of adolescents with and without acne in Nigeria. A cross-sectional analytical study was conducted in 60 adolescents/young adults divided in 30 acne patients (15F, 15M) and 30 age and sex-matched controls. Sebum samples obtained from foreheads and cheeks were analysed separately by gas chromatography-mass spectrometry (GCMS) and thin layer chromatography (HPTLC). Distributions of sebum components were investigated with multivariate ANOVA-simultaneous component analysis (ASCA). Sebum incretion in acne was paralleled by significantly higher abundance of triglycerides, wax esters, and squalene together with monounsaturated FAs (MUFAs), and straight chain saturated FAs (SFAs), especially those with odd-carbon chain, i.e. C13:0, C15:0, and C17:0. Profiling weight/weight percentage of individual components revealed that, in acne, the free FAs (FFAs) array was shifted towards higher relative abundance of the SFAs C15:0, C16:0, and C17:0 and lower percentage of the anteiso-branched FFAs with 12, 14, 16, and 18 carbons. In acne patients, MUFAs and PUFAs were quantitatively increased and decreased on foreheads and cheeks, respectively. Relative abundance of fatty alcohols was decreased in acne independent on the site. The results indicated that acne associates with site-specific derangement of the pathways regulating the balance among odd straight-chain and branched-chain SFAs, MUFAs, which included sapienate (C16:1n-10), PUFAs, and squalene.

Figure 1

Heatmaps of amounts in µg of lipids quantified in sebum sampled with Sebutape patches on foreheads (A) and cheeks (B). Triglycerides (TGs), wax esters (WEs), and cholesterol esters (CEs) were quantified by HPTLC, whereas free fatty acids (FFAs), fatty alcohols (FOHs), squalene and cholesterol were quantified by GCMS. The total sebum amounts were obtained by summing the quantitative data obtained by HPTLC and GCMS. The heatmaps were generated by running custom Python code that uses the open source Matplotlib library. Significant differences were determined with Mann–Whitney test. *p ≤ 0.05, **p < 0.001, ***p < 0.005, ****p < 0.0001.

Figure 2

SCA analysis on the effect matrix (normalized quantities) for acne condition investigated in sebum from foreheads (A–C) and from cheeks (B–D). (A,B) Scores plots after projection of the residuals onto the space spanned by the only significant PC; legend: blue = non-acne; red = acne. (A) and (B) plots refer to the scores of foreheads and cheeks, respectively. (C,D) Variable loadings on SC1, together with their confidence interval (red and blue bars indicate significantly and not significantly contributing descriptors, respectively). (C) and (D) bar graphs refer to the loadings on the SC1 of individual lipids in foreheads and cheeks, respectively.