Potential roles of gut microbial tryptophan metabolites in the complex pathogenesis of acne vulgaris

Abstract

Acne vulgaris is a chronic inflammatory skin disease in which the influence of gut microbiota has been implicated but without clarification of mechanisms. Gut microbiota may exert such an influence via metabolites, particularly those of tryptophan. End metabolites of tryptophan activate receptors, including aryl hydrocarbon, G protein-coupled, and pregnane X receptors to stabilize the immune microenvironment and intestinal mucosal homeostasis. Any impact on the pathogenesis of acne vulgaris remains unclear. The current review collates recent advances concerning potential roles of tryptophan metabolism in mediating skin inflammation, follicular sebaceous gland function and intestinal permeability, all of which influence the pathogenesis of acne vulgaris. The aim was to improve understanding of the pathogenesis of acne vulgaris and to expose therapeutic opportunities.

Multi‐omics approach to understand the impact of sun exposure on an in vitro skin ecosystem and evaluate a new broad‐spectrum sunscreen

“…38,40 For example, skin microbiota may play a regulatory role in local skin inflammation in the pathogenesis of acne vulgaris or atopic dermatitis via metabolites of tryptophan metabolism. 41 The sequencing data correlates with the metabolomic analyses, showing modulation of the tryptophan pathway that may partly be due to the changes in the microbiota at the skin surface, especially species within the genus Malassezia. Based on sequencing analysis, a decrease of Malassezia was observed after SSR exposure in the absence of SPF50+ sunscreen.…”

“…Tryptophan metabolism end products may activate the immune system through binding to AhR, which is a ligand‐dependent transcription factor shown to have important roles in skin physiology and immune‐inflammatory diseases 38,40 . For example, skin microbiota may play a regulatory role in local skin inflammation in the pathogenesis of acne vulgaris or atopic dermatitis via metabolites of tryptophan metabolism 41 …”

Dual intervention on the gut and skin microbiota attenuates facial cutaneous aging

“…38 Increased intestinal probiotics, such as Bifidobacterium , may generate tryptophan-derived end metabolites which regulate sebum synthesis. 39 Interestingly, this bacterium only enriched after the intervention in group OT. Both the gut and skin possess extensive innervation and vascularization, as they are essential for immune and neuroendocrine functions.…”

Late puberty onset and lack of acne during adolescence reduce high‐grade prostate cancer at adulthood

“…28 Pathogenesis of acne is complex; in addition to the functional alterations of the sebaceous glands and the hormonal microenvironment [6], the inflammation caused by Cutibacterium acnes 29 and alterations of the intestinal microbiota could cause acne. 28 The last two aspects correlate with the role inflammation might have on prostate carcinogenesis. 7 Cutibacterium acnes has been isolated from prostate tissue (prostatectomy); compared to samples with benign hyperplasia, the frequency of this bacteria was higher in samples with prostate cancer.…”

“…Acne vulgaris is a chronic disease affecting mainly facial, chest, and back skin of men between 12 and 24 years old 28 . Pathogenesis of acne is complex; in addition to the functional alterations of the sebaceous glands and the hormonal microenvironment [6], the inflammation caused by Cutibacterium acnes 29 and alterations of the intestinal microbiota could cause acne 28 . The last two aspects correlate with the role inflammation might have on prostate carcinogenesis 7 .…”