Biomolecules & Therapeutics  
Oral Administration of Glycine and Leucine Dipeptides Improves Skin Hydration and Elasticity in UVB-Irradiated Hairless Mice
Jong Il Park1, Ji Eun Lee1, Hyun Jun Shin1, Soonran Song2, Won Kyung Lee2 and Jae Sung Hwang1,*
1Department of Genetic Engineering & Graduate School of Biotechnology, College of Life Sciences, Kyung Hee University, Yongin 17104, 2LG Household & Healthcare Research Park, Daejeon 34114, Republic of Korea
E-mail: jshwang@khu.ac.kr
Tel: +82-31-201-3797, Fax: +82-31-203-4969
Received: April 13, 2017; Revised: May 10, 2017; Accepted: May 11, 2017; Published online: June 27, 2017.
© The Korean Society of Applied Pharmacology. All rights reserved.

Abstract
Placenta is a special organ that contains many nutrients such as growth factors, minerals, and bioactive peptides. Dipeptides of glycine and leucine are major components of porcine placenta extracts (PPE) that has been used as an alternative of human placenta extracts. In this study, we investigated whether major peptides of PPE, Glycyl-L-Leucine (Gly-Leu), L-Leucyl-Glycine (Leu-Gly), and L-Leucyl-L-Leucine (Leu-Leu), affect skin hydration and elasticity in vitro and in vivo. We found that Gly-Leu and Leu-Gly dipeptides induced the expression of transglutaminase 1 in normal human epidermal keratinocytes (NHEKs) whereas Leu-Leu dipeptides did not. Treatment with Gly-Leu or Leu-Gly significantly increased hyaluronan (HA) synthesis in NHEKs and the upregulation of hyaluronan synthase 2 (HAS2) mRNA level was confirmed. In addition, elastase activity was inhibited in NHEKs treated with Gly-Leu or Leu-Gly dipeptides. Oral administration of Gly-Leu or Leu-Gly dipeptides increased skin hydration and elasticity in UVB-irradiated hairless mice. The significant upregulation of HA in UVB-irradiated hairless mice was observed in response to oral administration of Gly-Leu or Leu-Gly. These results suggest that the major dipeptides of porcine placenta, Gly-Leu and Leu-Gly, are potentially active ingredients for skin moisturization formulations.
Keywords: Gly-Leu, Leu-Gly, Hyaluronan, elasticity, Porcine placenta extract


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