Impaired fasting glucose is associated with increased regional cerebral amyloid

Abstract

The Alzheimer's disease risk gene apolipoprotein E epsilon 4 (APOE ε4) is associated with increased cerebral amyloid. Although impaired glucose metabolism is linked to Alzheimer's disease risk, the relationship between impaired glycemia and cerebral amyloid is unclear. To investigate the independent effects of APOE ε4 and impaired glycemia on cerebral amyloid, we stratified nondemented subjects (n = 73) into 4 groups: normal glucose, APOE ε4 noncarrier (control [CNT]; n = 31), normal glucose, APOE ε4 carrier (E4 only; n = 14) impaired glycemia, APOE ε4 noncarrier (IG only; n = 18), and impaired glycemia, APOE ε4 carrier (IG+E4; n = 10). Cerebral amyloid differed both globally (p = 0.023) and regionally; precuneus (p = 0.007), posterior cingulate (PCC; p = 0.020), superior parietal cortex (SPC; p = 0.029), anterior cingulate (p = 0.027), and frontal cortex (p = 0.018). Post hoc analyses revealed that E4 only subjects had increased cerebral amyloid versus CNT globally and regionally in the precuneus, PCC, SPC, anterior cingulate, and frontal cortex. In IG only subjects, increased cerebral amyloid compared with CNT was restricted to precuneus, PCC, and SPC. IG+E4 subjects exhibited higher cerebral amyloid only in the precuneus relative to CNT. These results indicate that impaired glycemia and APOE ε4 genotype are independent risk factors for regional cerebral amyloid deposition. However, APOE ε4 and impaired glycemia did not have an additive effect on cerebral amyloid.

Keywords: Alzheimer's disease; Amyloid; Apolipoprotein E; Dementia; Impaired fasting glucose; Insulin; Metabolism.