For example, a study from our group showed elevated levels of mIns in APOE ε4 carriers without evidence of Aβ accumulation when compared with non-APOE ε4 carriers,22 in-line with previous studies showing the same association in the context of healthy aging.26,27 However, other studies have found no effect of APOE genotype on the levels of mIns in healthy participants, as well as in patients from the Alzheimer’s disease spectrum.24,28,29. Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.