Abstract
The stratum corneum (SC) is the outermost layer of the epidermis and plays an important role in maintaining skin moisture and protecting the skin from the external environment. Ceramide and natural moisturizing factor (NMF) are the major SC components that maintain skin moisture. In this study, we investigated whether the oral intake of enzymatically decomposed AP collagen peptides (APCPs) can improve skin moisture and barrier function by assessing changes in the ceramide and NMF contents in the SC after APCP ingestion with the aim to develop a skin functional food. Fifty participants orally ingested APCP (1000 mg) or placebo for 12 weeks, and then, skin hydration and skin texture were evaluated. SC samples were collected to analyze skin scaling, ceramide, and NMF contents. Participants in the APCP group exhibited improved skin moisture content by 7.33% (p = 0.031) and roughness by −4.09% (p = 0.036) when compared with those in the placebo group. NMF content; the amounts of amino acids (AA), including glycine and proline; and AA derivatives were significantly increased in the APCP group (31.98 μg/mg protein) compared to those in the placebo group (−16.01 μg/mg protein) (p = 0.006). The amounts of total ceramides and ceramide subclasses were significantly higher in the APCP group than in the placebo group (p = 0.014). In conclusion, our results demonstrate that APCP intake improves skin moisture and increase the ceramide and NMF contents in the SC, thereby enhancing the skin barrier function.
Highlights
The skin acts as a primary barrier protecting the body from the external environment and preventing the water loss from the body
natural moisturizing factor (NMF) consists of hydrophilic amino acids (AAs) and their derivatives (AADs), such as pyrrolidone carboxylic acid (PCA) and urocanic acid (UCA), lactic acid, sugars, organic acids, peptides, and urea, which contribute to the establishment of a water gradient in the stratum corneum (SC) [3,4,5]
Of the six participants who were excluded from the final analysis, one participant was excluded owing to abnormal fasting blood sugar level at the end visit, and five participants dropped out
Summary
The skin acts as a primary barrier protecting the body from the external environment and preventing the water loss from the body. Reductions in the NMF and ceramide contents lead to dry skin due to an increase in transepidermal water loss (TEWL) and a decrease in the flexibility of the SC [8,9]. Several studies have shown that the application of products containing humectants, such as urea, glycerol, and physiological lipids of the skin, is helpful in protecting skin that is deficient in ceramides and NMF [15,16,17]. This finding implies that increasing the NMF and ceramide contents helps moisturize the skin. Collagen peptides have been studied as dietary supplements [19,20,21]
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