Age and ethnic variations in sebaceous lipids.

Report Report Dermato-Endocrinology 5:2, 319–324; April/May/June 2013; © 2013 Landes Bioscience Age and ethnic variations in sebaceous lipids Apostolos Pappas,* Jared Fantasia and Theresa Chen Johnson & Johnson Consumer Companies, Inc.; Skillman, NJ USA Keywords: age, ethnic, fatty acid, lipid, sebum, skin, squalene Abbreviations: FFA, free fatty acids; GC-FID, gas chromatography-flame ionization detector; TEWL, transepidermal water loss; TG, triglycerides; TLC, thin layer chromatography; WE, wax esters This study was conducted to compare lipid components of sebum from persons from three ethnic backgrounds— Caucasian, African American and Northern Asian. Men and women with no acne in two age groups (18–25 y and 35–45 y) were recruited. Skin surface hydration (SkiCon 200EX and NovaMeter), barrier function (Delfin VapoMeter), highresolution clinical imaging, self-assessments and two pairs of sebutapes on the forehead that extracted the lipids on the surface of their skin were used. Significant differences (p < 0.05) in skin hydration between African Americans and Caucasians in both age groups were noted, with the order from highest to lowest absolute values: African American > Northern Asian > Caucasian. Transepidermal water loss (TEWL) measurements demonstrated that African Americans and Caucasians were significantly different (p < 0.05), with the trend being the inverse of the hydration trend—Caucasian > Northern Asian > African American, which would indicate better barrier function for African Americans with a lower TEWL. African American women had more total lipid production than Northern Asian or Caucasian women. When analyzing the three lipid classes (free fatty acids, triglycerides and wax esters), the trend became significant (p < 0.05) in the wax ester fraction when directly comparing African Americans with Caucasians. Additionally, six lipids were identified in the wax ester fractions that were significantly different in quantity (p < 0.05) between African Americans and Caucasians. These results identified significant differences in sebaceous lipid profiles across ethnic groups and determined that the differences correlated with skin barrier function. Introduction Previous studies have indicated that different skin types have different levels of skin hydration1 and barrier function2 based on bioinstrumental measures of conductance and transepidermal water loss (TEWL). Another study has indicated that skin hydration and TEWL are age-dependent but linked to ethnic skin type.3,4 However, another major component of skin that has been less investigated due to its complexity, but still contributes significantly to hydration and barrier function, are the sebaceous lipids.5 To investigate this topic further, in vivo biochemical experiments on the skin from different ethnic populations living in the same environment are needed. Several previous studies have focused on dissecting the relationship between sebum output and the pathophysiology of acne. Two recent studies showed a correlation between higher sebum output and acne development.6,7 Most of the published studies assess the total sebum output by instrumental analysis (e.g., the sebumeter), self-evaluation or by using a sebum absorbing adhesive tape (Sebutape), which is a specially designed tape that has been proven to be reproducible and convenient to estimate sebaceous gland output.8 Additionally, Sebutape is used for collecting sebum for further quantitation of its components.8 To our knowledge no study thus far has measured individual sebaceous lipids in search of specific sebaceous lipids that could be uniquely associated with ethnic groups or would be correlated with instrumental parameters. This is likely due to the cumbersome and lengthy tasks associated with the individual extraction,7,8 separation and quantitation of lipids and their corresponding subclasses. To date, a few studies have reported on the correlation of sebaceous lipids and acne status; however, these studies were conducted in diseased (acne) skin and not in healthy skin.7,9,10 Elevated sebum excretion is involved in the pathophysiology of acne,11-13 as body sites that are rich in sebaceous glands are where acne lesions are typically manifested. High levels of sebum are associated with acne in adolescence and may offer a possible benefit by lubricating the skin, contributing to a better skin barrier as well as better skin hydration. Because acne is unique to humans it has been suggested that the unique sebaceous lipids could be associated with this human-specific disease. The accumulation of squalene and the presence of unique fatty acids and waxes are unique manifestations of sebum.14,15 Our study aimed to identify possible lipid components with sebum that could correlate with ethnic skin hydration and barrier and might be associated with age or ethnicity. In the current study we conducted a series of in vivo assessments on the skin of women from three different ethnic populations living in the same environment (i.e., same locale). This *Correspondence to: Apostolos Pappas; Email: Submitted: 03/28/13; Accepted: 06/11/13 http://dx.doi.org/10.4161/derm.25366 www.landesbioscience.com Dermato-Endocrinology 319 Figure 1. Correlation of hydration and TEWL values among three ethnic groups of males and females aged 20–45 y. Hydration and TEWL values were grouped per the total gender and age combined ethnic population examined. Higher SkiCon were value associated with greater hydration (red arrow, left panel). Greater TEWL (blue arrow, right panel) is associated with worse barrier function (red arrow, right panel). Data are shown as mean ± standard deviation. Abbreviation: TEWL, transepidermal water loss. study was conducted to determine what, if any, differences were quantifiable in skin lipid content across age and ethnic skin type composition between females aged 18–25 and 35–45 y with no acne or other chronic skin diseases. Results Extracted lipids from each Sebutape were subjected initially to thin layer chromatography and three major lipid classes were separated: free fatty acids, triglycerides and wax and cholesterol esters. Subsequently, each lipid class was extracted separately from the silica plate and subjected to saponification and derivatization to be prepared for individual fatty acid analysis. This was performed by gas chromatography with fluorescence ionization detector (GC-FID), as previously described.7 We were able to estimate the individual fatty acid population of each of the lipid classes listed above. The initial pilot study involved male and females from three ethnic groups (n = 17–21). Skin hydration and TEWL were assessed. Results showed significant differences (p < 0.05) in skin hydration between African Americans and Caucasians—with the order of African-American > Northern Asian > Caucasian (Fig. 1). The results for TEWL demonstrated that African Americans and Caucasians were again significantly different ( (...truncated)