Which peptides are studied in relation to the skin microbiome?

Peptides studied in relation to the skin microbiome include cathelicidin (LL-37), a host-defence antimicrobial peptide, and the structural proteins of vernix caseosa, a naturally occurring substance that covers newborn skin at birth. The research centres on the skin barrier and innate immune signalling, particularly the relationship between barrier integrity, microbial colonisation, and inflammatory skin disease.

Cathelicidin is an antimicrobial peptide expressed in skin; its precursor is hCAP18, and the active form is LL-37. Vernix caseosa is a white, creamy substance that forms during the last trimester of pregnancy and covers the skin of newborns at birth. No sequence, formula, or molecular weight is given in the evidence for either. The pathway under study is the innate immune response of the skin, including protease activity and antimicrobial peptide expression, and its interaction with the skin microbiome.

Research Studies

Cathelicidin and the skin microbiome in rosacea

A single-site, 16-week open-label study at the University of California, San Diego, assessed the effect of topical ivermectin 1% cream on protease and antimicrobial peptide expression and on the skin microbiome in rosacea [4]. The investigators measured serine protease activity, cathelicidin, and the skin microbiome of all subjects before treatment. All subjects then received ivermectin topical cream and were instructed to apply it daily for 12 weeks. Participants returned for monthly visits during which clinical symptoms of facial redness and the number of facial papules were scored. The study evaluated markers of rosacea-specific inflammation in humans.

Vernix caseosa retention and atopic dermatitis prevention in newborns

A clinical trial examined the retention of vernix caseosa in newborns for the primary prevention of atopic dermatitis [1]. Atopic dermatitis is a chronic inflammatory skin disease that usually begins in infancy and causes itching, discomfort, and sleep disturbance. It affects up to one in five children worldwide. Genetic and environmental factors contribute to its development, especially those related to skin-barrier integrity and the skin microbiome during early life. Preventing atopic dermatitis before it starts—known as primary prevention—has become an important goal. The study population was newborns.

Skin barrier function, inflammation, and the skin microbiome in ageing

A randomized, investigator-blinded, self-controlled pilot study—the BIA Study—examined the physiologic response to topical moisturizers among older adults with dry skin [3]. The overarching hypothesis was that skin barrier decline is an important source of chronic inflammation, and that skin barrier restoration with moisturizers can reduce serum biomarkers of inflammation. The primary objective was to determine the feasibility for a larger trial. Secondary objectives were to determine the extent to which measures of serum inflammation, skin barrier function, and the skin microbiome change in response to moisturizers. Participants were asked to apply one of two topical moisturizers that are widely available. The study population was older adults with dry skin.

Th2-related inflammation and lymphatic biology in lymphedema

An observational, cross-sectional study characterized the biological profile of primary and secondary lymphedema by investigating five interconnected biological domains: T helper 2 (Th2)-related inflammation, endothelial activation, metabolic dysfunction, lymphatic biology, and tissue fibrosis [2]. Lymphedema is traditionally considered a disorder of impaired lymphatic drainage resulting in the accumulation of interstitial fluid. However, increasing evidence suggests that its development and progression involve chronic inflammation, endothelial dysfunction, metabolic alterations, abnormal lymphatic signalling, adipose tissue accumulation, and progressive tissue fibrosis. The study population was individuals with primary or secondary lymphedema. No peptide is named in the evidence for this study.

Comparison of study designs and populations

Antimicrobial peptide expression and protease activity in rosacea

The rosacea study measured serine protease activity and cathelicidin before and during treatment with topical ivermectin 1% cream [4]. The study assessed the role of topical ivermectin on protease and antimicrobial peptide expression and on the skin microbiome. The microorganisms that live on the skin were evaluated as part of the study. The work was conducted in humans with rosacea.

Skin microbiome changes in response to moisturizers in older adults

The BIA Study measured the skin microbiome as a secondary objective, alongside serum inflammation and skin barrier function, in older adults with dry skin who applied one of two widely available topical moisturizers [3]. The hypothesis was that skin barrier decline is an important source of chronic inflammation and that barrier restoration can reduce serum biomarkers of inflammation. The study was a pilot to determine feasibility for a larger trial.

Vernix caseosa and early-life skin microbiome

Vernix caseosa forms during the last trimester and covers the skin of newborns at birth [1]. The trial examined retention of vernix caseosa for primary prevention of atopic dermatitis. The evidence states that genetic and environmental factors contribute to atopic dermatitis development, especially those related to skin-barrier integrity and the skin microbiome during early life. The study population was newborns.

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Sources

• [1] Retention of Vernix Caseosa in Newborns for Primary Prevention of Atopic Dermatitis — ClinicalTrials.gov
• [2] Biological Profile of Primary and Secondary Lymphedema: Inflammatory, Endothelial, Metabolic, Lymphatic, and Fibrotic Markers — ClinicalTrials.gov
• [3] Skin Barrier Function and Inflammation in Aging: The BIA Study — ClinicalTrials.gov
• [4] Evaluation of the Inhibitory Effects of Topical Ivermectin on Markers of Rosacea Specific Inflammation. — ClinicalTrials.gov