Colloidal Oatmeal (Avena Sativa) Improves Skin Barrier Through Multi-Therapy Activity

of epidermal differentiation markers involved in cornified envelope formation, transglutaminase-1 (TGM1), and involucrin (IVL) compared with vehicle control (Figure 1A). We also observed an enhancement of mRNA level of claudin-family tight junction (TJ) protein claudin-7 (CLDN7) induced by MCO and ACO. Additionally, mRNA expression of enzyme involved in the synthesis of long chain FFAs, and acyl-ceramide synthesis, elongase of very long chain fatty acids-4 (ELOVL4), was upregulated following treatment with MCO, ACO, and HCO. MCO also resulted in a 3-fold upregulation of involucrin protein levels in primary keratinocytes (Figure 1B).

The pH buffering capacity (BC) of whole colloidal oatmeal water extract and its fractions were investigated (Table 2). The BC of the water extract of colloidal oat was significantly higher (BC=142) than the BC of the native colloidal oat (BC=40.8). The extract is enriched in globulin proteins (20-35 kDa and 50-60 kDa), assessed by protein gel electrophoresis analysis (data not shown) and consistent with previously published data,⁹ and carbohydrates. The >20 kDa fraction, which contains primarily globulins, had a slightly lower BC=114 than the crude water extract. The fraction isolated in the 3-20 kDa range presumably contains the gluteins, as well as some prolamins,⁹ did not significantly contribute to the overall BC of colloidal oat (Table 2). Collectively, the buffering capacity demonstrated that the water extract of colloidal oatmeal possessed effective pH buffering activity, suggesting that colloidal oats can be beneficial for skin by helping to provide a skin barrier with enhanced pH buffering capacity and therefore potentially aid in protection against irritants.

We next analyzed expression of barrier regulatory genes in human skin equivalents after topical application of colloidal oatmeal protectant lotion. The colloidal oatmeal containing lotion significantly induced the expression of TJ genes CLDN7 and CLDN4, and other target genes including TGM1, HMG-CoA reductase (HMGCR - the key enzyme of cholesterol synthesis), and ceramide glucosyltransferase UGCG (which is involved in the initial step of glycosphingolipid synthesis; Figure 2A). Furthermore, an increase in the expression of PPARβ/δ (transcription factor with critical roles in regulating lipid homeostasis) and its direct target protein ANGPLT4-encoding adipocytokine was also observed (Figure 2B). Taken together, these results demonstrate that the colloidal oatmeal up-regulated genes of key biological targets responsible for the functionality of the cellular and lipid skin barrier and therefore can provide overall skin barrier related benefits.