Walk into any beauty shop in Birmingham and the word is everywhere. Serums, eye creams and night treatments all shout about peptides, usually in bold type and rarely with an explanation. It is quite similar to the collagen hype that also happened in the most recent years.
Behind the marketing lies a serious area of science, and a whole field of peptides research is devoted to understanding how these tiny molecules behave in cells.
However, it is good to start from basics, what is a peptide, and what do we actually know about them?
A peptide is a short chain of amino acids, the same building blocks that make up proteins.
Short chains are usually called peptides and much longer ones are classed as proteins, although the boundary is a convention rather than a hard rule.
The human body naturally produces and contains thousands of different peptides at any given time (with scientists estimating around 7,000 or more).
Skin is full of protein, with collagen the best known, so it is no surprise that cosmetic chemists took an interest in these smaller pieces.
Peptides in skincare?
One idea behind many beauty peptides is signalling.
When collagen breaks down, small fragments are released, and some researchers think cells may read those fragments as a cue that repair is needed.
Ingredients sold as signal peptides are designed around that logic. It is a hypothesis rather than a settled rule, and the evidence varies a great deal from one ingredient to the next.
GHK-Cu: Copper peptide in skin and ageing research!
One of the best studied copper peptides is GHK-Cu. A 2018 review by Dr Loren Pickart, who first identified the peptide, and Anna Margolina, pulled together decades of work on it.
The authors explain that GHK is a naturally occurring tripeptide found in human blood plasma that readily binds copper to form GHK-Cu. They also report that circulating GHK levels are higher in younger individuals and decline with age.
What makes it interesting is that it does not appear to act through a single pathway. The authors describe GHK-Cu as a biological signalling molecule involved in repair, regeneration and protection.
Skin and connective tissue are the best-known areas of study.
The paper discusses how GHK-Cu may support collagen, elastin, glycosaminoglycans, fibroblast function and remodelling of the extracellular matrix. These are the structures and cell activities involved in skin firmness, wound repair and tissue quality.
The gene expression data adds a further dimension. The review suggests that GHK can influence a large number of genes, including those involved in inflammation, antioxidant protection, tissue remodelling and protein clearance.
Rather than a simple collagen booster, this points to a molecule that may help regulate the wider repair environment, although the authors acknowledge that this analysis is computational and needs supporting biological evidence.
How to read the evidence
It is worth being clear about how much weight these results can bear. The paper is a review rather than a new trial, and its authors are affiliated with a company in the skin biology field, so the findings are best read with that in mind.
Much of the evidence comes from cell cultures and animal studies, which cannot show that the same effects occur in the body.
The gene data is computational, and the authors themselves note that tools of this sort often lack supporting biological data.
They also acknowledge that copper alone does not explain the effects on gene activity, and that the peptide can be broken down by enzymes in wound fluid.
Beauty trends come and go, but curiosity about how the smallest ingredients work keeps laboratories busy long after a product has left the shelf.
The next time a peptide catches your eye in a shop, it is a good reason to keep asking questions about what the label really tells you.