Editor’s note: Glycation has previously been addressed1 in terms of its impact on skin aging, and several ingredients as well as finished products making anti-glycation related claims have since appeared on the market.2–5 The present article, adapted from Draelos and Pugliese*, provides a review of the chemistry involved in the glycation process to assist formulators in developing topical or nutricosmetic solutions for mature skin care.
Glycation fortunately does not occur largely in the dermis before age 35 but once it begins, along with intrinsic aging, it progresses rapidly. These long-lived tissues are the target of advanced glycation end products (AGEs) that bind tenaciously to collagen and elastin, more avidly to elastin, which can be seen in the upper dermis in the realm of elastin. In fact, a paper by Mizutari et al. showed a section of a skin biopsy from the face of a 91-year-old revealing tangled masses of elastotic material in the upper dermis.6 Elastotic material consists of abnormal elastin fibers and protein and is usually associated with sun damage. It does not function like normal elastin and is quite stiff.
Many of the fine processes involved in glycation remain to be discovered. However, it is known that glucose and other simple sugars combine with proteins as a first step, and that sugars combine with amino acids and other compounds to initiate the process. As an example, fructoselysine, formed by glycation of the amino acid lysine, can be oxidatively cleaved to form smaller reactive compounds such as carboxy-methyl lysine (CML) and pentosidine.7
As consumers age they have a greater risk of glycation-initiated damage and their glucose level is the major culprit in initiating the formation of AGEs and glycation. Glucose, in its common closed-ring form, D-glucopyranose, is a rather unreactive molecule that is an important cellular fuel. It is the only sugar that circulates in abundance and although it is relatively harmless, as noted, it can become harmful through its transformation into an AGE by an intricate random process that occurs in animals and vegetables. This “browning” action requires no enzymes but depends merely upon temperature and an abundance of reactants.