CLDN1 and Alzheimer disease: Combining the results of Biotin-556-TJ barrier function in correlation to Cldn-1 levels in SG for healthy, non-lesional and lesional AD skin, led to the observation of an overall correlation with good fit to a logarithmic curve (Fig. 3f, Coefficient of determination (R2) = 0.56, Spearman′s correlation coefficient (rS) = 0.74, p < 0.01).