Aquaporins: Stimulation by Vitamins, Steroids and Sugar Alcohols

By: Bud Brewster, C&T magazine

Posted: October 30, 2008, from the November 2008 issue of Cosmetics & Toiletries.

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“Various glyceryl glucosides were designed and synthesized by Beiersdorf to confer specific structural and osmotic properties in regard to their potential to stimulate AQP3 mRNA expression leading to an improved moisturization of the skin,” explained Ute Breitenbach, PhD, one of the inventors and a lab manager of the Laboratory of Dry Skin/Skin Care at Beiersdorf’s Research Center in Hamburg.

“In a large screen of actives using human keratinocytes we analyzed the AQP3 stimulation potential of glyceryl glucoside in relation to glycerol because we were trying to identify new active moisturizers better than glycerol,” Breitenbach said. “We observed a significant increase in AQP3 mRNA levels by the application of glyceryl glucoside” (see Figure 2).

“These glyceryl glucosides were not new to Beiersdorf. They had been in the company patent literature since 1997 as agents that enhance skin moistness,” Breitenbach said, referring to an earlier patent.¹³ “But their potential of stimulating AQP3 expression and thereby the activating the skin’s own water channels from within was a discovery.”

Preparations according to the invention preferably contain 0.1–5% by weight of the glyceryl glycoside. Osmotic stress is known to upregulate AQP3 expression.¹⁴ By adding substances to trigger osmotic stress—substances such as inorganic salts, and salts of the naturally occurring skin acids or weak carboxylic acids—the AQP3 stimulation capacity can be further increased.

Comment
This “Bench & Beyond” column and the three that preceded it focused on compounds that can be introduced into the skin to stimulate AQP3 expression. These compounds work directly on the aquaporin, and there are numerous examples—caffeine, sugars, vitamins—that work in this way. Much rarer in the literature are compounds—such as certain salts and acids—that stimulate AQP3 expression by the indirect route of osmotic stress. Only one such paper¹⁴ was found in the research for this column. Perhaps studies on the means of more precisely regulating osmotic stress in the skin will be the next frontier in aquaporin research.