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Chemical Reaction: Age, Rage and Wrinkles
By: Steve Herman
Posted: August 26, 2008, from the September 2007 issue of GCI Magazine.
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For example, the aldehyde group of a glucose molecule will combine with the amino group of a lysine molecule to form an imine, which is a double bond between the carbon atom of the glucose and the nitrogen atom of the lysine. The Amadori product is a rearrangement from the Schiff base wherein the hydrogen atom from the hydroxyl group adjacent to the carbon-nitrogen double bond moves to bond to the nitrogen, leaving a ketone. When the Amadori product is oxidized, most often by transition metal catalysis, an advanced glycation end product (AGE) is formed. The first two steps in this reaction are both reversible; the last step is irreversible.
Pentosidine levels increase with age, and collagen has a long life in the skin. Even though the nonenzymatic process is slow, it accumulates relentlessly as we grow older.
Sugar and the Skin
Many cells in the body bear RAGE, which, when binding with AGEs, contributes to age-related, chronic inflammatory effects. RAGE is also able to bind other ligands, and is wthus as a pattern-recognition receptor. There may be some chemicals, such as aminoguanidine, that limit the formation of AGEs. AGE and RAGE have been extensively studied in diabetics, where the excess sugar accentuates the skin aging process in afflicted patients. Varieties of the RAGE protein that lack the transmembrane and the signalling domain are referred to as soluble RAGE or sRAGE. They may counteract the negative effect of the full-length receptor and provide a means to cure RAGE-associated diseases.
In the skin of healthy individuals, AGEs were reported to accumulate in dermal elastin and collagen and to interact with the cell membrane of dermal fibroblasts. In human fibroblasts, AGE and RAGE interactions may influence the process of skin aging through stimulation of extracellular matrix gene expression. Self-tanning products that employ dihydroxyacetone (DHA), a three-carbon sugar, produce brown color through a Maillard reaction with protein in the skin. Any DHA penetrating beyond the statum corneum will encourage glycation.