Answering Your Questions About Cosmeceutical Peptides

Zoe Draelos

The continuing expansion of peptide use in cosmeceuticals is worthy of notice by the dermatologist. Because peptides facilitate cellular communication, they provide interesting functionality to antiaging topical formulations.

Q: What Are Peptides?

Peptides are composed of amino acids, and the number of amino acids determines the peptide category. For example, 2 amino acids are a dipeptide, 3 amino acids are a tripeptide, 4 amino acids are a tetrapeptide, etc. The term oligopeptide can be used to describe peptides built from 2 to 20 amino acids. The number, type, and order of amino acids determine the properties of the peptide. Peptides can interact with selective skin target sites in extremely low concentration and are short-lived.

Q: What Are the Commonly Used Antioxidant Peptides?

Glutathione and carnosine are the 2 antioxidant peptides commonly used in cosmeceutical formulations. Glutathione is a tripeptide antioxidant that decreases in concentration in the body with aging. Thus, skin application is thought to replenish glutathione stores; however, oral ingestion is probably more effective. Carnosine is a biomimetic antioxidant peptide that can inhibit glycation, the binding of sugars to proteins, which creates advanced glycation end products.

Q: What Are Neuropeptides?

Neuropeptides are intended to act like a local neurotoxin in blocking neurotransmitters at the neuromuscular junction, reducing lines of facial expression, minimizing wrinkle depth, and improving skin roughness without systemic effects. The peptide acetyl octapeptide-3 is an example of a neuropeptide composed of the amino acids aspartic acid, glutamic acid, glutamine, and methionine. Other widely used neuropeptides include acetyl hexapeptide-3 (Argireline), pentapeptide-18 (Leuphasyl), pentapeptide-3 (Vialox), and tripeptide-3 (Syn-Ake).

Q: What Are Signal Peptides, and What Do They Signal?

Signal peptides initiate some biologic signal to include the production of growth factors, collagen, elastin, proteoglycans, and fibronectin. The most widely used signal peptide is lysine-threonine-threonine-lysine-serine (KTTKS). This peptide is part of the sequence of amino acids derived from the procollagen type I C-terminus end. It can be conjugated to palmitic acid to create palmitoyl-KTTKS, enhancing skin penetration that may be limited unless the peptides are very small. In fibroblast culture, this signal peptide can stimulate the production of type I and III collagen and fibronectin. Other similar signal tripeptides include palmitoyl sh-tripeptide-3 amide, palmitoyl sh-tripeptide-1 amide, acetyl tripeptide-54 amide, and acetyl tripeptide-74 amide.

Q: Are There Peptides That Claim to Improve Skin Pigmentation?

Yes, peptides have been developed to modulate pigmentation because melanogenesis is triggered by the α-melanocyte–stimulating hormone (α-MSH) peptide. Many α-MSH peptide fragments have been synthesized, including a tetrapeptide composed of proline-lysine-glutamic acid-lysine. In vitro, this peptide was shown to decrease inflammatory cytokines such as IL-6, IL-8, and TNF-α known to worsen postinflammatory hyperpigmentation.

Q: Can Peptides Be Used in Hair Growth Formulas?

Peptides are commonly found in topical formulations to promote hair growth. The tripeptide glycyl-histidyl-lysine (GHK) is a collagen fragment used not only to stimulate collagen synthesis but also to stimulate hair growth when coupled with biotin (biotinyl-GHK). Biotin apparently strengthens the ability of the tripeptide to bind to the hair keratin. These hair-promoting peptides are used in concentrations of 2 to 5 ppm in commercial formulations. The idea here is that a signal can be presented to the hair that cascades to elicit a far-reaching, broader effect.

Conclusion

The number and type of peptides available for cosmeceutical formulation are ever expanding. Unique claims can be made for proprietary peptide mixtures designed to affect pigmentation, collagen production, and the neuromuscular junction simultaneously. The only limitation here is cost. Peptides are extraordinarily expensive and are thus used at the ppm level in cosmeceutical formulations. Clinical studies are required to validate published findings based on cell culture work.

Zoe Diana Draelos, MD, is a consulting professor of dermatology at Duke University School of Medicine in Durham, North Carolina, and Dermatology Times’ editor in chief emeritus.