Age and ethnic variations in sebaceous lipids

Abstract

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), high-resolution 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.

Keywords: age; ethnic; fatty acid; lipid; sebum; skin; squalene.

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.

Figure 2. Quantitative lipid analysis of females segmented by age and ethnic group. Results were expressed as micrograms of fatty acids and were grouped per individual class of lipid. FFA, TG, WE and squalane were graphed as well as total lipid, which was expressed as the sum of all of the aforementioned classes (A) for the total group tested and (B) per age group. Data are shown as mean ± standard deviation. **p < 0.05. Abbreviations: FFA, free fatty acids; TG, triglycerides; Sq, squalene; WE, wax esters.

Figure 3. Correlation of wax ester fraction and hydration values among three ethnic groups of females aged 20‒45 y. Wax ester results and hydration values were grouped by combining females from all ethnic groups and analyzed by one-way analysis of variance and subsequent t-tests. Trends are shown by red arrows. Data are shown as mean ± standard deviation.

Figure 4. Correlation of the most predominant fatty acids from the wax ester fraction among three ethnic groups of females aged 20‒45 y. ^{Statistically significant differences in major sebum fatty acids were observed only in the wax ester fraction (25‒30% of sebum). Data are expressed as µg fatty acid/sebutape/30min.} Results were grouped by combining data from women in all ethnic groups and analyzed by one way analysis of variance and subsequent t-tests. Data are shown as mean ± standard deviation.