Therapeutic Peptides in Aged Skin

By: Farzam Gorouhi, MD, and Howard I. Maibach, MD, University of California School of Medicine

Posted: August 28, 2009, from the September 2009 issue of Cosmetics & Toiletries.

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Overall, topical peptides and proteins have successfully and widely been used. However, note that in the only published systematic review⁶ on interventions for photodamaged skin, no peptide therapy was included. Here, published work on peptides and proteins, their characteristics, and randomized efficacy data are examined.

Material and Methods
In an effort to examine different types of peptides and their efficacy in topical skin treatments, PubMed, Embase and Scopus were systematically searched within a date range of 1974 to June 15, 2008. Different search terms were used to locate peptides or proteins, to find all possible topical therapies, to locate all cosmeceutical-related papers, and to rule out irrelevant papers. All references of relevant articles were screened to find other eligible resources. In addition, some in vitro and in vivo data was collected from pharmaceutical company Web sites. For efficacy data, only randomized trials were included.

Results and Discussion
Surprisingly, scarce data regarding the permeation abilities of topical peptides was found. Only the permeation coefficients for three widely used topical cosmeceutical peptides—copper tripeptide-1 (GHK)⁷, glutathione (GSH)⁷ and melanocyte-stimulating hormone (MSH)^8,9; some mono-peptides^10,11 and their copper complexes were reported. Table 1 summarizes the randomized trials referenced.

GHK: Glycyl-L-histadyl-L-lysine or GHK is primarily known as a carrier peptide but it also acts as a signal peptide mainly to help stabilize and deliver copper. Signal peptides refer to all peptides that stimulate matrix protein production in general, specifically collagen synthesis. These peptides may be produced by growth and stimulation of different skin cells such as human skin fibroblasts. Signal peptides can also increase elastin, proteoglycan, glycosaminoglycans and fibronectin. By increasing matrix cell activities and therefore collagen production, the peptides make skin look firmer and younger.

In a randomized, double blind, placebo-controlled study of 67 volunteers, GHK-Cu and a placebo were applied twice daily for 12 weeks on facial skin.¹² GHK-Cu improved skin laxity, clarity and appearance; reduced fine lines, coarse wrinkles and mottled hyperpigmentation; and increased skin density and thickness.