The effects of caffeine and adenosine on the microbiome and lipidome of the scalp.

Hair loss is a complex multifactorial process. The mechanisms by which caffeine and adenosine act against hair loss have been extensively researched, but little is known about their effects on the microbiome and lipidome of the scalp. Hair loss may be associated with the status of scalp microbiota and lipids. Further investigation is warranted to determine whether caffeine and adenosine can regulate scalp microbiota and lipids and thus help to prevent hair loss. The objective of this study was to assess the effect of shampoo containing caffeine and adenosine on the scalp microbiome and lipidome in subjects experiencing hair loss who were aged between 18 and 60 years. The study was a randomized, single-blind and parallel comparison trial involving full scalp treatment, which was conducted among 30 subjects experiencing hair loss. Samples were collected from subjects at baseline and at 12 weeks (±3 days). Microbiomes were analysed via 16S rDNA and ITS1 sequencing. Lipidome analysis was carried out using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). At 12 weeks, significant clinical characteristics indicating an anti-hair loss effect were evident. Abundances of Pseudomonas, Escherichia-Shigella and Malassezia all decreased in the experimental group, whereas those of Talaromyces and Cutibacterium increased. In addition, levels of triglyceride (TG), diglyceride (DG), ceramide (Cer) and ceramide-1-phosphate (CerP) were all significantly impacted in the experimental group. Furthermore, abundances of lipid metabolites were tightly correlated with those of Escherichia-Shigella and Talaromyces. Caffeine and adenosine may enhance the anti-hair loss process through their effects on the lipidome and microbiome of the scalp.