APOE and Impaired glucose tolerance: GCA abundance was lower by 29.7% in the DEM (P = 0.012) group and by 16.2% in the MCI group (P = 0.025) as compared to the NC group when not controlled for sex, ApoE status (E2/E2, E2/E3, E2/E4, E3/E3, E3/E4, or E4/E4), age, or impaired glucose tolerance (IGT) status (impaired or not impaired).