Functional properties of the stratum corneum in patients with diabetes mellitus: Similarities to senile xerosis

Background: Although diabetes mellitus is known to induce many pathophysiological changes in the skin, none of the earlier studies has focused on the state of the stratum corneum (SC) in patients with diabetes. In our previous report on a diabetic mouse model, we described a decreased SC hydration state and abnormalities in the function of the sebaceous gland together with a normally retained barrier function of the SC. Objectives: To examine the functional changes of the SC in patients with diabetes. Methods: The following values were measured in 49 patients with diabetes: fasting plasma glucose (FPG) and haemoglobin A_1c (HbA_1c); skin surface lipid level on the forehead; and high-frequency conductance (HFC) and transepidermal water loss (TEWL) of the SC of the volar forearm and extensor surface of the lower leg. These functions of the SC were compared in two pairs of patient groups, i.e. between groups with high and low FPG, and between groups with high and low HbA_1c. Results: The HFC levels on the extensor leg and volar forearm were significantly lower in the group with high FPG (FPG > 110 mg dL ^-1) than in the group with low FPG (FPG < 110 mg dL^-1), although TEWL values were almost the same in these two groups. The skin surface lipids on the forehead were significantly lower in the former than in the latter. The HFC did not differ significantly between the group with high HbA_1c (HbA_1c>5.8%) and the group with low HbA _1c (HbA_1c<5.8%), whereas the TEWL of the volar forearm was slightly lower in the former than in the latter. Conclusions: These new results as well as our earlier results with diabetic mice suggest that patients with diabetes mellitus tend to show a reduced hydration state of the SC together with decreased sebaceous gland activity, without any impairment of the SC barrier function.