Lipidomic and Metagenomic Profiling of Chinese Female Emerging Adults With Oily Scalp

BACKGROUND: Excessive sebum secretion leads to oily scalps, which can disturb microbial homeostasis and cause various scalp issues, such as sensitive scalp, dandruff, and seborrheic dermatitis. AIMS: This study aimed to investigate the characteristics of scalp lipids and microbiota in a group of females with excessive sebum secretion using omics technology, and to identify important relationships between feature lipids and dominant functional microbes on oily scalp. METHODS: Through comparison of three lipidomic sampling methods, we first selected absorbent paper (AP) as a cost-effective and practical method for untargeted lipidomic profiling. Using this method, we then collected scalp surface lipids from 85 Chinese female emerging adults with varying degrees of excessive sebum and performed internal standard quantified lipidomic profiling using UPLC-QE Plus-MS equipped with LipidSearch software version 5.1. Simultaneously, we collected and analyzed scalp microorganisms using PE150 pair-end metagenomic sequencing on the Illumina NovaSeq platform followed by taxonomic and functional annotation with bioinformatic tools and databases. Afterwards, multivariate statistical analysis and bioinformatics were used to identify feature lipids related to high sebum levels, discern the roles of dominant microbes involved in lipid metabolism, and explore potential correlations between feature lipids and dominant functional microbes of oily scalp. RESULTS: After comparison of three lipidomic sampling materials, absorbent paper (AP) was selected to collect scalp surface lipids from 85 volunteers. A total of 13 lipid classes were annotated and the most abundant in ESI (+) mode was triacylglycerol (TG, 99.18%) whereas in ESI (-) mode were fatty acid (FA, 56.94%) and O-acyl-(gamma-hydroxy) FA (OAHFA, 34.15%). We identified 27 TGs and 3 FAs as the major lipid molecules contributing to high sebum levels. Seventy percent of these TGs were unsaturated (33% monounsaturated, 26% diunsaturated, 11% triunsaturated), and 30% were saturated. Meanwhile, we found that although the dominant microorganisms, Cutibacterium, Lawsonella, Malassezia, and Staphylococcus were all involved in lipid metabolism on the scalp, only some of them were related to the degree of sebum level and also displayed species-specific preferences for lipids. Among them, Lawsonella clevelandensis and Malassezia globosa were weakly negatively associated with both unsaturated and saturated TGs, while Malassezia restricta and Cutibacterium granulosum were only weakly negatively correlated with saturated TGs, and Cutibacterium namnetense was weakly positively correlated with FA (26:0). CONCLUSIONS: This study describes relevant lipid molecules contributing to higher sebum production, and reveals that L. clevelandensis, M. restricta, M. globosa, C. namnetense, and C. granulosum on the scalp are closely correlated with these lipids, showing species-specific preference. These findings provide new insights into the interaction between key surface lipids and dominant functional microorganisms on oily scalps.