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The skin barrier of melasma is involved in the pathogenesis of melasma. Previous studies have shown that there are differences in the expression of epidermal lipid genes in melasma, but little is known about the epidermis lipid composition of melasma. Compared with the non‐lesional skin, the content of total lipids, phosphatidic acid, phosphatidylserine, and ceramide (Cer) increased significantly in the lesional skin. Multivariate data analysis indicated that 40 individual Cer lipid species were responsible for the discrimination. In terms of acyl chain length in Cer, the expressions of very long chain (VLC) (C20–C26) and ultra‐long chain (ULC) (>C26) increased significantly in the lesional skin. However, Cer[AH] had negative correlations with the activation of melanocytes in the lesional skin. Some lipid species had lower expression in lesional skin with high activation of melanocytes, as well as the high darkness. The epidermal thickness of lesional skin was higher compared with the non‐lesional skin. These results suggest that Cer increased significantly in the lesional skin of melasma, possibly as a compensatory mechanism to maintain skin barrier function. Between different groups of darkness and activation of melanocytes, the change of ceramides might have correlation with the pigmentation progress of melasma. [ABSTRACT FROM AUTHOR]

Background: Pregnancy is a complex physiological state and its unique changes in skin state have been discussed. Skin surface lipid (SSL) is an important molecular basis for this skin condition, and it affects skin condition in a number of ways, but there are no complete research data on it. Objectives: To analyze the lipidome profiles of SSL in pregnancies and controls in order to understand SSL changes in pregnancy. It will provide theoretical data of SSL on skin care and prevention of skin diseases during pregnancy. Methods: Ultra‐high performance liquid chromatography quadrupole time‐of‐flight mass spectrometry (UPLC‐QTOF‐MS) and multivariate statistics were used to investigate the changes of SSL in pregnancy. Results: Results showed that there were significant differences (P <.05) in the lipidome between pregnancies and controls. Multivariate data analysis indicated that there were 20 important individual lipid species identified, and triglycerides (TGs) were the majority of differentiating lipid species. Conclusions: The increase of estrogen level in pregnancies antagonizes and inhibits the regulation of androgen on sebaceous gland, resulting in the decrease of sebum secretion and the weakening of skin barrier function. Besides, the decrease of saturated fatty acid content may be the main factor of the decrease of skin barrier function during pregnancy. Additionally, skin cells perform their self‐regulation function to reduce or counteract abnormal state of the skin during pregnancy through the synthesis and secretion of more glycerophospholipids and ceramides. [ABSTRACT FROM AUTHOR]

Background: Infantile acne refers to a skin disease that usually occurs on the face from 6 weeks to 1 year old, and the etiology of infantile acne is different from that of puberty acne. The change of skin surface lipid (SSL) is an important factor in the occurrence of acne. Objectives: Comparison of facial skin lipid changes in healthy and acne‐prone infants, screening for possible groupings of substances, to explore factors associated with the development of acne in infants, such as gender and frequency of face washing. Methods: A questionnaire was used to obtain information about the infant, facial lipids were affixed with adhesive tape, and the samples were analyzed using Ultraperformance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (UPLC‐QTOF‐MS), with subsequent data analyzed by single‐factor and multifactor analysis. Results: It was observed that some lipids followed the trend of lipid master classes, subclasses and were significantly different. Galactosylceramides, glycosylceramides and phosphatidylethanolamine were screened as the majority of differentiating lipid species. Additionally, it was emphasized that the frequency of face washing and parent's acne was independent with the severity of acne in infant by clinical characteristics, whereas the skin type and gender can affect the severity of acne statistically. Conclusions: Facial lipids change significantly between infantile acne and healthy infants, suggesting that qualitative and quantitative changes in lipids are strongly associated with the development of acne and may exacerbate the environment in which acne occurs. [ABSTRACT FROM AUTHOR]

Background: Fatty acids are common raw materials in cosmetics and also are an important component of skin surface lipids, and their composition and amount affect the skin condition. Aims: The purpose of this article was to review the results of basic research on fatty acids as skin surface lipids. Methods: An extensive literature search was conducted using PubMed, Web of Science, and other databases for articles on fatty acids from 1993 to 2020. Results: This article provides an overview of the mechanisms of fatty acid synthesis and its metabolic pathways as skin surface lipids in the context of sebaceous and intercellular lipids. The three mechanisms by which fatty acids affect the skin condition are also reviewed. Conclusions: This information will aid further understanding of the mechanism of the fatty acid role in skin function maintenance and provide new perspectives for the management of skin health. [ABSTRACT FROM AUTHOR]

Background: Regional differences in skin characteristics are well known. Significant differences in skin physiology between the forehead and cheek have also been reported. However, there are few studies based on lipidomics at the molecular level. Additionally, there is no study focusing on the lipid profile variations of skin surface lipid (SSL) in forehead and cheek. Purpose: This study analyzed the differences in facial SSL between forehead and cheek of men aged 18‐25 years to explain the distinct physiological parameters between forehead and cheek resulting in different skin status. Methods: Facial SSL was identified by ultra‐performance liquid chromatography‐quadrupole time of flight‐mass spectrometry (UPLC‐QTOF‐MS). Multivariate data analysis was used to investigate the SSL difference in forehead and cheek. Results: Significant differences in facial SSL composition were detected between the forehead and cheek. Multivariate data analysis suggested that 21 entities contributed most significantly toward the discrimination and phosphatidylserines (PS) constituted the majority of differentiating lipid species. Subsequent analysis showed a marked increase in the amounts of unsaturated and saturated free fatty acids (FFAs), and a significant increase in average FFAs chain length in the forehead as compared to that in the cheek. Conclusions: Phosphatidylserines exposure might be one of the most important reasons for the increased amount of forehead SSL secretion. The different FFAs chain length and FFAs content lead to altered skin barrier functions in forehead and cheek, consequently resulting in altered trans‐epidermal water loss (TEWL) and pH at the two anatomical sites. [ABSTRACT FROM AUTHOR]

Background: The circadian rhythm is an endogenous clock that governs a wide range of physiological functions. In the skin, rhythmic changes in skin barrier function have been investigated at the physiological level; however, few studies at the molecular level have been reported. Additionally, there is no study on lipidomic profile variations of skin surface lipid (SSL), which could potentially explain the rhythmic changes in skin status. Objectives: The SSL profile of healthy young women was analysed to assess SSL variations and to assess the skin status during the circadian cycle. Methods: Ultra performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry and multivariate data analysis were performed to assess SSL variations. Results: The lipidomic profile showed significant differences with the circadian rhythm. Multivariate data analysis indicated that glycerolipids were the lipids majorly affected by the circadian rhythm. Additionally, in the SSL profile, both the average chain length and the content of free fatty acids (FFAs) were higher at 20:00 than at 08:00. Conclusions: The SSL profile significantly varied with respect to the circadian rhythm. The rhythm‐altered triacylglycerol level, FFA chain length and FFA content resulted in rhythmic changes in skin barrier function, including transepidermal water loss alteration and pH variation. [ABSTRACT FROM AUTHOR]