APOE and Alzheimer disease: Interestingly, MCTs appear to be altered early in patients at risk for developing AD since young asymptomatic adult carriers of the apolipoproteins E ε4 allele (APOE4), who are at high risk for developing AD, have increased expression of MCT2 and decreased expression of MCT4 in posterior cingulate cortex, as measured by Western blot analysis (Perkins et al., 2016).