NTN1 and Alzheimer disease: As presented in Figure 1A and Table 2, serum netrin-1 levels showed a statistically significant decrease in AD (492.80 ± 135.51 pg/ml, P < 0.001) and MCI (553.33 ± 94.24 pg/ml, P = 0.013) patients as compared with controls (656.17 ± 161.41 pg/ml).