Victoria Hiscock Discusses Vitamin a As a Skincare Ingredient

SKIN/DERMATOLOGY VITAMIN A www.aestheticmed.co.uk “A” STA R Victoria Hiscock discusses vitamin A as a skincare ingredient ithout question, the greatest boon to anti- BIO-AVAILABILITY OF RETINOIDS ageing treatments was the introduction of The amount of biological activity will differ with each substrate retinoic acid by Albert M Kligman, MD, PhD in of vitamin A. Retinoic acid is the only form of retinol the body 1986. Since then, the world of vitamin A has can use, therefore, the body uses specialised enzymes in exploded and many new compounds have been the skin cells to convert vitamin A into retinoic acid. Not all Wdeveloped to treat a host of skin conditions. forms of vitamin A are created equally. Some are more easily There are many different types of vitamin A which vary in converted to retinoic acid than others. A typical conversion strength and action. These can be seen in the table below. pathway looks like this: VITAMIN A SUBSTRATES – By strength Retinyl palmitate <=> Retinol <=> Retinaldehyde => Retinoic acid Retinoic Acid Tretinoin It takes two and three metabolic steps, correspondingly, (All-Trans-Retnoic-Acid/ (prescription only) to convert retinol and retinyl palmitate to retinoic acid. ATRA) The overall rate of conversion of retinol to retinoic Retinyl Retinoate Chemically joined Retinoic acid is low and that of retinyl palmitate is lower still. Acid and Retinol Molecules Therefore, a relatively large amount of retinol and Retinal / Retinaldehyde Can convert to Retinoic Acid even larger amount of retinyl palmitate needs to be or Retinol delivered into a cell to boost retinoic acid levels and Retinol Entire Vitamin A Molecule produce clinically meaningful effects. Among retinoid precursors, retinaldehyde Retinyl Palmitate Ester of Retinol & Palmitic (retinal) is the nearest (on the metabolic pathway) Acid (a fatty acid) to retinoic acid and is likely to match its benefits Retinal Acetate Synthetic ester of Retinol more closely. & Acetic Acid (organic Although no one has clinically demonstrated compound) the conversion rate of retinol to retinoic acid, (as Retinyl esters Storage form of a Vitamin it is subjective), it is believed to be roughly about one-tenth the strength of Tretinoin. WHAT IS RETINOL? What is retinol? That is a questions that often gets asked. BIO-CHEMICAL PATHWAY OF RETINOIDS Retinol is a form of vitamin A that is used in skincare to There are several kinds of retinoid receptors, each return the skin to more youthful state by stimulating the affecting different cellular processes. fibroblast cells responsible for collagen, elastin, hydration First, retinol is oxidised to form retinal. Then retinal is and cellular turnover. oxidised to generate retinoic acid, which binds to retinoid Although retinol belongs to the family of chemical compounds receptors of skin cells—a step necessary to allow it to known as retinoids, physiologically speaking, vitamin A is not enter the nucleus and bind with DNA. It is the action a retinoid because it does not interact directly with retinoid of retinoic acid on the DNA that accounts for all the receptors in our skin cells. Cells have to first convert vitamin A biological effects on the skin. to retinoic acid. Retinoic acid regulates the expression Retinoic acid facilitates communication between cells, of cellular genes via the activation of two encouraging ageing cells to continue their renewal process and classes of nuclear retinoid receptors, regenerate collagen and elastin. known as retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Ultimately, these MEASURING RETINOL forms of retinoids carry out many physiological Vitamin preparations are advertised by the percent of vitamin processes, such as cell differentiation, maintenance they contain, but the body uses them in terms of international of cell turnover and certain immunity functions. units, or IU, which are measured in terms of biological activity. The major biological activities of retinol are One IU of vitamin A is equal to 0.3 micrograms of vitamin A. So, the control of epithelial cell proliferation 1 gram of vitamin A would equal 1 million micrograms/0.3 = 3.33 and differentiation, immune modulation, million units of vitamin A. stimulation of the creation of new blood To expand this one step further, 100g of a 1% vitamin A vessels, and production of collagen. Some solution contains 1 gram of vitamin A (or 1 million micrograms) or other functions include inhibition of carcinogenesis, 3.33 million units of vitamin A. absorption of UV light, antioxidant function and pigment > 46 Aesthetic Medicine • November 2016 SKIN/DERMATOLOGY www.aestheticmed.co.uk VITAMIN A Without question, the greatest boon to anti- ageing treatments was the introduction of retinoic acid by Albert M Kligman, MD, PhD in 1986. Since then, the world of vitamin A has exploded and many new compounds have been developed to treat a host of skin conditions Aesthetic Medicine • November 2016 47 SKIN/DERMATOLOGY VITAMIN A www.aestheticmed.co.uk control. In addition, since retinoids contain several conjugated double bonds, they can trap free radicals and thus protect DNA, lipid membranes and proteins from UV- induced oxidative stress. At this time, little is known about what regulates the uptake of retinoids by cells. RETINOIDS IN MORE DETAIL RETINOIC ACID Also known by its brand name Tretinoin, retinoid acid is a prescription only substrate of vitamin A. Typical strength of topical Tretinoin creams ranges from 0.025 to 0.1 percent. Side effects are not uncommon and include skin irritation, dryness, peeling and sun sensitivity. With Tretinoin, more is not necessarily better. Studies indicate that 0.025 percent Tretinoin may be almost as effective as 0.05 or 0.1 percent, but with a lower incidence of skin irritation. According to studies, improvement on Tretinoin may continue for up to a year of continued use.1 RETINAL/RETINALDEHYDE Retinaldehyde is easily converted to retinoic acid in the body in just one step. It could conceivably have the same effect effectiveness. Notably, retinyl retinoate is reported to be on acne as directly acting retinoids. Furthermore, since it is more resistant to inactivation by sunlight than retinol and less irritating than retinoids, retinaldehyde may be easier to most other forms of vitamin A. If true, this would make it an combine with other potentially irritating acne treatments, especially practicable choice for skin care formulations. such as alpha-hydroxy acids, beta-hydroxy acids or benzoyl However, vitamin A in all forms is destroyed by UV light— peroxide. In fact, two studies have demonstrated the both the UVB (290–320 nm) and UVA (320–400) spectra so effectiveness of topical 0.1% retinaldehyde combined with night time application is advised. 6% glycolic acid in treating acne. Also, there is evidence that In addition, a study by the National Toxicology Program, retinaldehyde possesses some antimicrobial activity against which is a U.S. government research group, has concluded P. acnes, the bacteria involved in the development of acne.2 that retinyl palmitate and retinoic acid speed the development of skin cancers and tumours when applied RETINYL RETINOATE to the skin in the present of sunlight (NTP 2012). This is yet Retinyl retinoate is a molecule that is produced by chemically another reason for applying retinoids in the evening and joining the molecules of retinoic acid and retinol in the body. washing your face in the morning. Just one metabolic step is required to split it back into retinoic acid and retinol, at which point retinoic acid is immediately CLINICAL APPLICATIONS OF VITAMIN A active, whereas retinol can be converted to additional Vitamin A can be used to treat several clinical conditions, retinoic acid later on. As a result, biological activity of retinyl including acne, ageing skin and hyperpigmentation. Each of retinoate in the skin is reportedly higher than that of retinol the forms of vitamin A—retinol, retinyl acetate and retinyl (and possibly even retinaldehyde) and may be approaching palmitate—has specific reasons why it would be selected for that of retinoic acid itself.3 a particular treatment or patient over the others. Microencapsulation of vitamin A is an effective way to RETINYL ESTERS ensure stability, delivery and efficacy of retinol. A synthetic Retinyl esters are the storage phase of retinol and serve no wax or polymer encases the vitamin A, protects it while on known biological activity other than to store vitamin A. In the shelf and slowly breaks down in the skin. This creates a foods of animal origin, the major form of vitamin A is an ester, time released delivery of retinol leading to less irritation. primarily retinyl palmitate, which is converted to retinol, Because vitamin A is drip fed into the skin in small doses, the which is chemically an alcohol (see pathway above). body can metabolise it over a longer period and more retinol is converted into retinoic acid. AM STABILITY OF VITAMIN A Even if a retinol or retinaldehyde product maintains its 1 - http://www.smartskincare.com/treatments/topical/retinaldehyde.html potency until it is actually used (due to good formulation 2 - http://www.smartskincare.com/treatments/topical/retinaldehyde.html and proper storage), it often gets inactivated by exposure 3 - http://www.smartskincare.com/treatments/topical/retinyl-retinoate.html to sunlight soon after application, which results in reduced Victoria Hiscock is the product and education specialist for Alumier Labs UK and has been educating skin >> care professionals for over a decade. Co-owner of CLINICBEAUTY, a medispa in Southampton, Victoria brings a vast spectrum of knowledge and education based on her hands on experience as well as her time as a trainer. She has a passion for Cosmetic Science and empowering fellow practitioners to develop their profitability through education. 48 Aesthetic Medicine • November 2016.

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