A tetrapeptide used as an anti-ageing active may work through its ability to regulate collagen binding, according to scientists at ingredients supplier Lipotec.
Tripeptide-10 Citrulline, which appears in two of the company's anti-aging actives, can help to regulate the uniformity of the collagen fibrils which in turn may lead to increased skin suppleness, according to research published in this month's International Journal of Cosmetic Science.
The tetrapeptide mimics the function of a naturally occurring proteoglycan called decorin, the action of which declines as skin ages.
Collagen forms fibrils regulated by decorin
Collagen fibres in the skin are mostly composed of the fibrillar type I collagen.
The polypeptide chains of this type of collagen are synthesized as a triple helix with loose ends that are then removed by enzymes before the shortened molecules can assemble into ordered polymers called fibrils - a process called fibrillogenesis.
The regulation of fibrillogenesis is controlled by a number of molecules one of which is called decorin.
However, in mature skin a fragmented form of decorin is present which does not have the necessary regions which would normally bind to collagen.
The researchers suggest that the presence of this fragmented form of the molecule may explain some of the differences between old and young skin.
In addition, decorin-deficient mice have skin with reduced tensile strength and a thinner than normal dermis, further suggesting a role for the molecule in skin elasticity.
The tetrapeptide mimics decorin
The researchers screened a number of tetrapeptides for their influence on fibrillogenesis, selecting Tripeptide-10 Citrulline from the results of the in-vitro tests.
According to the scientists, experimentation with skin models showed that collagen fibres treated with Tripeptide-10 Citrulline were more uniform with a decreased diameter.
Furthermore, application of a formulation containing 0.01 per cent tripeptide-10 citrulline to the face of three volunteers over a two month period was found to make the collagen fibres more uniform.
The same cream was applied to 22 female volunteers, while 21 were treated with a placebo cream. The application of the peptide resulted in a 54 per cent increase in skin suppleness, according to the team.
The researchers concluded that the peptide mimics decorin activity, interacts with collagen fibrils to establish and maintain skin mechanical properties and morphology.
Source: International Journal of Cosmetic Science
Volume 30, pages 97-104
"Decorin-like tetrapeptide for optimal organization of collagen fibres"
A. Puig, J. M. Garcia Anton and M. Mangues (Lipotec)