JOURNAL OF COSMETIC SCIENCE 426 and are correlated to skin water content. A uniform-pressure sensor probe was placed on the surface of the hand skin for approximately fi ve seconds and a reading was taken. Four measurements were taken at each site at every time point. Measurements were automatically acquired via a computer software package, ensuring standardization of the measurements. STATISTICAL ANALYSIS Data were given as means ± SEM. Excel (Microsoft) software was used to evaluate statistical signifi cance by using the Student’s two-tailed t-test function in the software package. A p value of 0.05, at least, was considered signifi cant. RESULTS IN VITRO EFFECTS OF N-ACETYL-GLUCOSAMINE ON KERATINOCYTES IN CULTURE Human keratinocyte (HaCaT) monolayers were treated with increasing amounts of amino sugars to assess their effect on cellular morphology. HaCaT keratinocytes treated with 50 mM, 125 mM, and 250 mM of NAG appeared to be released from culture dishes and dissociated (Figure 1). Similar effects were observed with other amino sugars such as N-acetylneuraminic acid and N-acetyl-galactosamine (data not shown). Suspension or release of keratinocytes from the substrate has been reported to promote keratinocyte dif- ferentiation (10). We therefore investigated the levels of two different protein markers of keratinocyte differentiation in these N-acetyl-glucosamine treatments. Increasing con- centrations of N-acetyl-glucosamine resulted in increased accumulation of involucrin, keratin K1, and keratin K10 in cultured keratinocytes (Figure 2). These data supported the observation that the keratinocytes had reduced adhesion to the substratum. Figure 1. Effect of NAG on human keratinocyte morphology. HaCaT cells were treated for 24 hours with 50 mM, 125 mM, and 250 mM of NAG in whole media. Cell cultures were then viewed at ×100 magnifi caion by phase contrast and refl ectance microscopy with an Olympus BX60 microscope (Olympus, Melville, NY).

NAG AS EXFOLIATION ENHANCER 427 CLINICAL EFFECTS OF N-ACETYL-GLUCOSAMINE ON SKIN MOISTURATION AND DESQUAMATION Skin moisturization was evaluated using a Nova dermal phase meter (Table I). Moistur- ization was observed to increase by 12% and 18% over controls, at two and four weeks, respectively, in human skin. The two-week change was not statistically signifi cant, but this became signifi cant after four weeks. NAG was tested at 1% vs the placebo, on the back of the hands for their effect on skin desquamation and reduction of skin fl akiness via the D-squame disc method. After two and four weeks of treatment, the group using 1% NAG showed 39% and 38% decreases in fl akiness, whereas the placebo use resulted in a 30% increase (Table II). Table I Effect of 1% NAG on Skin Moisturization via the Dermal Phase Meter DPM values at p values at baseline vs Product Baseline 2 Weeks 4 Weeks 2 Weeks 4 Weeks 1% Glucosamine 145 131 131 0.16 0.11 Untreated control 159 125 116 0.06 0.01 p value (treated vs control) 0.11 0.16 0.009 % Increase (treated–control) 12 18 Four measurements were taken at each site at every time point. Measurements were performed on 45 panelists. Table II Desquamation Effi cacy of NAG in Vehicle via the D-Squame Disk Method % Decrease in fl akiness Product treatment group 2 Weeks 4 Weeks Placebo 6.0 -29.9 1% N-acetyl glucosamine 38.8 38.0 Four D-Squame discs were used on the face and hands of each of 45 panelists. Desquamation was evaluated from the D-Squame discs via image analysis as described in Methods. The average gray value corresponding to the sample density was measured. Figure 2. Protein levels of involucrin and keratin K1 and K10 in human keratinocytes treated with NAG. HaCaT cells were grown in six-well culture dishes to confl uence and treated with 50 mM, 125 mM, and 250 mM NAG for 24 hours. Each dose was run in triplicate. Cells were then scraped and processed as detailed in Methods. Experiments were repeated three times. Data is representative of one experiment.