Interestingly, IAPP levels were close to significantly higher in AD patients compared with NC in APOE4 non-carriers (319.37 ± 182.17 vs. 219.27 ± 107.80, respectively, p = 0.061), while IAPP levels in APOE4-carrying AD patients and NC were unchanged (315.72 ± 153.68 vs. 328.70 ± 217.18, respectively, p = 0.751). Here, IAPP is linked to Alzheimer disease.