N-acetylglucosamine (NAG) (Fig. 7) is a water-soluble, neutral compound that can easily be incorporated into skin care formulations. It is found naturally occurring as a repeating unit of the abundantly available material known as chitin (e. g., shrimp shells). In human skin, it is a natural component of GAGs, glycolipids, and membrane glycoproteins. Along with glucuronic acid (a polyhydroxy acid), NAG is a one of the repeating, alternating units in hyaluronic acid, the prominent GAG of skin (29).
NAG represents a new class of anti-aging and exfoliation compounds. Its reported beneficial effects on exfoliation occur as a result of its interaction with CD44 receptors on corneocytes, which prevents cross-linking between cells (58,59). Topical application of NAG has been shown to induce desquamation and epidermal cell turnover, as well as increase epidermal differentiation. In a pilot (n = 9) dansyl chloride exfoliation study of NAG (8% cream, native pH 4.9) in comparison to glycolic acid (8%, pH 3.7) and an untreated control, NAG significantly reduced mean fluorescence scores significantly compared to the untreated control (82% and 62%, respectively), but not as effectively as the tested glycolic acid formulation (92%), p<0.05 (60).
NAG also provides moisturizing and anti-aging benefits to skin. As a component molecule in hyaluronic acid and a potential precursor to its synthesis, NAG has been shown to stimulate synthesis of hyaluronan in fibroblasts and keratinocytes (61-62).
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Oral supplementation of NAG (1 g orally per day vs. placebo for 60 days) reportedly reduced skin dryness and roughness, and increased moisturization (63).
Topical evaluation of 8% NAG was shown to provide significant, clinically-assessed improvements on mild to moderate photodamage with substantial improvements in skin firmness and skin thickness. The latter effect is thought to be due to an increase in the production of GAGs, which increases skin volume through water binding and plumping (64). In addition to its desirable cosmetic effects, NAG was shown to be well tolerated on skin (64), and therefore represents a desirable new class of compounds in the growing exfoliation and anti-aging ingredient technology market.
Dermatologists and patients are inundated with products and devices to assist the skin in its natural exfoliation process. The purest form of exfoliation is achieved through use of physically abrasive implements on skin. These devices, such as loofahs, buff puffs, and mesh poofs, can provide light exfoliation on a daily basis to slough away excess layers of stratum corneum, helping to keep the skin smooth and luminous. Additional clinical benefits to skin are few, if any, and have not been well documented. Microdermabrasion elevates the physical exfoliation process to the next level. Depending on how it is used, this procedure can simply provide mild exfoliation or, when used as part of a comprehensive skin care regimen, it can help the clinician to achieve meaningful cosmetic outcomes.
Chemical exfoliants have more to offer the dermatologist and patient in terms of flexibility and patient outcomes. When properly formulated for optimal bioavailability and safety, these agents penetrate the skin and disrupt binding between stratum corneum cells to facilitate exfoliation. This effect is beneficial in the treatment of various hyperkeratotic disorders including acne and dry skin. Some chemical exfoliants also provide significant anti-aging effects leading to smoother skin with the reduced appearance of fine lines and wrinkles and an increase in skin firmness. Careful selection of a chemical exfoliant facilitates customization of the formulation to skin condition including oily, dry, and sensitive skin. Furthermore, the chemical exfoliants can be readily formulated into products that can be used at home or in physicians’ offices and spas/salons. The use of exfoliating procedures, including topical peels and microdermabrasion, is frequently combined with home application of skin benefit ingredients to achieve significant therapeutic outcomes.