Peptides

In some of our products, we use peptides to achieve specific results. You’ll find peptides in the following products:

EGF Peptide Repair Serum contains Oligopeptide-1, -2 and -5. These peptides have not only been shown to reduce wrinkles and pore size while improving the skin barrier, they also minimise scarring and help rehabilitate acne-plagued skin. Argireline Serum contains Acetyl Hexapeptide-8, which works similarly to Botox (Botulinum neurotoxin) by preventing muscles from contracting, thereby reducing expression lines like worry lines or crow’s feet. Eyelash Serum and Eyebrow Serum contain Myristoyl Pentapeptide-17, which can stimulate expression of the gene for keratin, a very important structural protein in hair. This peptide is especially common in products stimulating eyelash and eyebrow growth.

Below you can read more about peptides and learn why they are so effective in skin care.

PEPTIDES, PROTEINS AND AMINO ACIDS

Peptides are short chains of amino acids that can have a wide range of different and potent properties. Some can transport important trace elements into the skin; others can provide important signals that e.g. can stimulate collagen production and still others can inhibit neurotransmitters or enzymes. Many peptides are interesting in anti-aging products which should help against e.g. wrinkles and uneven skin tone.

“Peptide” comes from the Greek word “peptós”, which means “digested”, as peptides can be formed by breaking down proteins. Peptides are just like proteins chains of amino acids, bound together by peptide bonds. A peptide bond is an amide bond between the acid group on one amino acid and the amine group on another amino acid. Compared to proteins, peptides are usually shorter chains and can be divided into oligopeptides, which are chains consisting of 2 to about 20 amino acids and polypeptides, which consist of more than 20 amino acids. The boundary between what is called oligopeptide and polypeptide has not been fully established in the literature but is somewhere between 10 and 50 amino acids. Cyclic peptides also exist.

Proteins usually consist of over 100 amino acids in a chain and can consist of several chains of amino acids, which are folded together in a very special way. However, the smallest natural protein consists of only 46 amino acids, while the largest consists of 38,138 amino acids. Proteins are vital to life in general and have many different functions. They can be seen as the primary cellular means of communication that is essential in great many processes. They are receptors, enzymes, hormones, antibodies, carriers and structural molecules. A few examples of proteins in the body are the hormone insulin, the structural proteins collagen, keratin and elastin and the enzymes that break down the food you eat and thus provide energy to the body.

Like proteins, peptides are vital for life. They can have many different properties. Some are, for example, antimicrobial, antiviral, immunomodulatory and anti-inflammatory – properties that are also interesting in medicines. There are drugs based on peptides and new ones are constantly being developed. Many of them are signaling molecules and also the “building blocks” for the formation of proteins together with the amino acids.

There are 20 standard amino acids that proteins and peptides are made of – 9 of these are essential amino acids, which means that the human body cannot synthesize them, thus these must be supplied by the diet. An amino acid consists of an amino group and a carboxylic acid group and between these two groups there is a side chain (often referred to as “R” in figures in the literature as the figure below), which is the part that makes the amino acids different. When writing down a sequence of amino acids, a 3- or 1-letter abbreviation is often used for each amino acid (e.g. Leu or L for Leucine) and the sequence is usually written so that the N-terminus (the end with the unbound amino group) is first and the C-terminus (the end with the unbound carboxylic acid group) is at the end. The importance of amino acids cannot be overstated because without amino acids, peptides and proteins cannot be build and fulfill all the vital functions they have. Some amino acids also have an important role to play in themselves as they can be converted into other important substances in the body – they are precursors. An example is the essential amino acid phenylalanine, which can be converted to the amino acid tyrosine and afterwards by a series of biosynthetic steps become the hormones adrenaline and noradrenaline, the neurotransmitter dopamine and via coupling to the amino acid cysteine ​​and some other biosynthetic steps become the melanin pigment pheomelanin – one of the substances that give the skin light protection and color.

Figure 1. A peptide chain (and proteins) consists of amino acids in a chain - like beads on a string. (Figure from Wikipedia)

PEPTIDES IN COSMETICS

Peptides are a relatively new ingredient in cosmetics but have been used for over 20 years and their use is increasing – especially in anti-aging products. And with good reason, because there are many studies that document interesting effects – but there are also many you do not know and many peptides that you do not have good in vivo studies on – so the clinical evidence for effect is not so strong on some peptides. The effects peptides for the skin especially are attributed to have are: Stimulation of collagen production, wound healing, antimicrobial effect, reduction of wrinkles and more even skin tone.

In general, peptides are relatively specific, which is an advantage as it reduces the risk of side effects. Often studies show that they are very potent, so large concentrations are not needed to achieve an effect. In addition, the peptides are usually made up of natural amino acids, so they are not completely “foreign” to the body. This has the disadvantage that they are also often relatively easily broken down by the enzymes you have in and on the skin. As with proteins, there is a – at least theoretical – risk of allergy (especially with larger peptides, but it depends on many factors). Other disadvantages are that the peptides are often quite expensive raw materials, and the peptides are relatively large molecules and hydrophilic, so they have difficulty getting into the skin. These two topics will be elaborated a little more.

The reason for the relatively high price can be found in particular in the manufacturing methods, which are more complex than for most cosmetic raw materials. There are two methods of chemical peptide synthesis: In liquid phase or solid phase. The liquid phase method is mostly used for small peptides consisting of up to about 4 amino acids (tetrapeptides). This method requires some steps of purification by chromatography. In the solid phase method, the first amino acid is firmly anchored by the carboxylic acid group to a solid, after which amino acids are coupled to the growing chain one by one and then finally the peptide is decoupled from the solid to which it was anchored. For both of these methods, special coupling reagents and other reagents are used, of which some have adverse properties in relation to the environment. With these methods, it is relatively straightforward to design the peptides as you want and modify them in different ways – for example, to achieve a higher skin penetration. Another way to make peptides is by hydrolyzing (breaking down) proteins. It is a less controlled process but can be a natural method of peptide production. The method can, for example, take place via fermentation with microorganisms or extracts from microorganisms with a mix of these enzymes or it can be done by using specific enzymes (proteases). This will result in a mix of different peptides and free amino acids – so there is often some purification afterwards, using fractionation techniques to separate the peptides and the rest from each other and then more purification. The source of the proteins is often leftovers from the food industry. Recombinant DNA technology, in which genes are inserted into e.g. microorganisms so that they can produce proteins, is generally not used to produce peptides.

An example of a raw material produced by hydrolysis is peptides and proteins from oats (Avena Sativa), where an extraction of oat kernels has been made, starch has been removed and proteins and peptides has been purified together with beta-Glucan (polysaccharides). In a study, this raw material has shown wrinkle-reducing, moisturizing and antioxidative properties.

In relation to the challenge of getting peptides into the skin, various techniques have been developed. Absorption-enhancing substances (e.g. alcohol) can be used in the formulation. These are substances that affect the skin barrier so that more penetrates – which may be inappropriate in some contexts. One method that is already used for some peptides is to modify their chemical structure – often by adding a fatty acid – making the molecule becomes a little more lipophilic, so that it binds better to the skin. Another method is to encapsulate the peptides in small particles, the “shell” of which may be formed of different materials. For example, liposomes, which primarily consist of fats that are already present in the skin; niosomes, which consist of a bilayer of nonionic surfactants and ethosomes, which are phospholipid-based small particles with a normally ethanol-rich interior.

Peptides for cosmetic use are often divided into the following categories: Carrier peptides; signal peptides, neurotransmitter-inhibiting peptides, and enzyme-inhibiting peptides. In the following, these categories will be described.

CARRIER PEPTIDES

These are peptides that can transport small substances – typically the metal copper – into the skin. Copper is an absolutely essential metal in the body, as it i.a. is involved in many enzymes and thus many processes – e.g. wound healing and blood vessel formation. Copper is part of the enzyme superoxide dismutase (SOD), which is a very important antioxidant distributed throughout the body and the lysyl oxidase enzyme which plays an important role in the synthesis of collagen and elastin.

Copper Tripeptide-1 (often abbreviated Cu-GHK) is a natural copper complex that is categorized as a carrier peptide – and in fact also as a signal peptide. It consists of the amino acid sequence: Glycine-Histidine-Lysine and spontaneously forms complexes with copper. It is found naturally in the body (was first isolated from plasma in 1973) and is one of the most well-studied peptides. Of interesting properties may be mentioned, for example, that it promotes the synthesis of collagen, elastin, proteoglycan and glycosaminoglycan; contributes to the anti-inflammatory and antioxidant response and increases the expression of a number of “repair genes” in our DNA. Studies have shown that Copper Tripeptide-1 can improve the skin’s overall appearance, firmness, elasticity, thickness, moisture, light damage, barrier, wound healing and suppress scar-forming proteins – and stimulate hair growth. Several of the studies performed with this peptide on humans show a significant improvement in the appearance of the skin after just 12 weeks.

SIGNAL PEPTIDES

This category of peptides contains many different peptides and constitutes the largest group of peptides used in cosmetics. Signal peptides are also sometimes called matricin peptides and are known to trigger various signal cascades – especially cascades that promote the synthesis of extracellular proteins – particularly collagen. Matricin peptides are small peptides derived from proteolytic degradation of extracellular matrix proteins that stimulate fibroblasts to produce these extracellular matrix proteins.

One of the most widely used signal peptides in cosmetics is Palmitoyl Tetrapeptide-7, which is a fragment of immunoglobulin G (IgG), which reduces the secretion of the pro-inflammatory Interleukin-6 (IL-6), which for example contributes to the inflammation UVB can cause. Another example is Myristoyl Pentapeptide-17, which can stimulate the expression of the gene for keratin, which is a very important structural protein in hair – this peptide is used especially in eyelash and eyebrow stimulating products. In the category of signal peptides there are also a number of peptides, which have been given the INCI names Oligopeptide-1, -2 and -5, which, for example in vivo, have shown reduction of skin pore size and wrinkles and improvement of the skin barrier after 8 weeks.

NEUROTRANSMITTER-INHIBITING PEPTIDES

Neurotransmitters are signal molecules that transmit the signal in the space between two neurons (the synaptic cleft). When an electrical impulse in a nerve cell reaches the end of the axon of the nerve cell, neurotransmitters are released to the synaptic cleft, where they diffuse over to the adjacent neighboring nerve cell, where they bind to specific receptor molecules. This triggers a cascade of reactions, which results in the opening of certain ion channels in the membrane of the nerve cell, thereby initiating an electrical impulse in this nerve cell and continuing the signal. In the same way, the signal can be transmitted via neurotransmitters from a nerve cell to a muscle or gland cell. This very complex process is the basis of all neurological processes – e.g. pain signals, vision signals, signals to and from the internal organs and signals that a muscle must contract. The latter is particularly interesting in relation to the use of signal peptides on the skin, because expression wrinkles are precisely due to the fact that muscles in the skin are repeatedly contracted.

One of the best-known neurotransmitter-inhibiting peptides for cosmetics is the synthetic Acetyl Hexapeptide-8 (which is also known under the trade name Argireline® and previously had the INCI name Acetyl Hexapeptide-3). The sequence of this 6-amino acid-long peptide, which is produced by the solid-phase method, is Glutamic acid-Glutamic acid-Methionine-Glutamine-Arginine-Arginine and it is modified by coupling an actyl group to the C-terminus. This amino acid sequence is a copy of the N-terminus of the SNAP-25 protein, which together with two other proteins in the nerve cell forms the SNARE complex, which determines whether the neurotransmitter acetylcholine is released from the nerve cell to the synaptic cleft that connects the nerve cell and a muscle cell. The mechanism of action of Acetyl Hexapeptide-8 is, in short, that the peptide destabilizes the SNARE complex by competing with SNAP-25 for the position in the SNARE complex. Acetyl Hexapeptide-8 positions itself in the complex instead of SNAP-25 and thus the complex does not work as it should, resulting in acetylcholine not being released to the synaptic cleft and thus the signal that the adjacent muscle cell must contract is not passed on. Acetyl Hexapeptide-8 thus acts very similar to Botox (Botulinium neurotoxin): The muscle does not contract (but the botox mechanism of action and effectiveness are different) and by this can reduce e.g. expression wrinkles; which in vivo studies have shown.

ENZYME-INHIBITING PEPTIDES

This category of peptides directly or indirectly inhibits enzymes. There are great many different enzymes in the body with very different functions, but common to them is that they are proteins and catalyze a certain chemical reaction in the body – e.g. the breakdown of collagen. In this category of peptides are, for example, soybean peptides, some of which inhibit Matrix MetalloProteinases (MMPs), which break down collagen; as well as silk peptides and certain oligopeptides, which inhibit Tyrosinase, which participates in the biosynthesis of melanin, which gives the skin color.

One could also mention the group of antimicrobial peptides (AMPs), which have been shown to help the skin’s immune response by inhibiting certain microorganisms that try to invade the skin. They can act in the “front line” and break down the outer membrane of bacteria and also stimulate other parts of the immune system. These antimicrobial peptides are therefore particularly interesting in connection with skin problems where the microbiome is out of balance.

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