Differential effects of blood insulin and HbA1c on cerebral amyloid burden and neurodegeneration in nondiabetic cognitively normal older adults

• Published in: Neurobiology of aging 2017-11, Vol.59, p.15-21
• Main Authors: Byun, Min Soo, Kim, Hyun Jung, Yi, Dahyun, Choi, Hyo Jung, Baek, Hyewon, Lee, Jun Ho, Choe, Young Min, Sohn, Bo Kyung, Lee, Jun-Young, Lee, Younghwa, Ko, Hyunwoong, Kim, Yu Kyeong, Lee, Yun-Sang, Sohn, Chul-Ho, Woo, Jong Inn, Lee, Dong Young
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Alzheimer Disease - diagnosis; Alzheimer Disease - diagnostic imaging; Alzheimer Disease - etiology; Amyloid beta-Peptides - metabolism; Biomarkers - blood; Biomarkers - metabolism; Brain - diagnostic imaging; Brain - metabolism; Cerebral amyloid burden; Female; Glycated hemoglobin; Glycated Hemoglobin A - metabolism; Humans; Insulin; Insulin - blood; Magnetic Resonance Imaging; Male; Middle Aged; Neurodegeneration; Neurodegenerative Diseases - diagnosis; Neurodegenerative Diseases - diagnostic imaging; Neurodegenerative Diseases - etiology; Neuroimaging; Positron-Emission Tomography; Preclinical Alzheimer's disease
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2017.07.004

We tested the hypothesis that lower insulin or higher glycated hemoglobin (HbA1c) levels in blood are associated with increased cerebral beta amyloid (Aβ) deposition and neurodegeneration in nondiabetic cognitively normal (CN) older adults. A total of 205 nondiabetic CN older adults underwent comprehensive clinical assessment, [11C]Pittsburgh compound B (PiB)-positron emission tomography (PET), [18F]fluorodeoxyglucose-PET, magnetic resonance imaging, and blood sampling for fasting insulin and HbA1c measurement. Lower blood insulin was significantly associated with increased Aβ positivity rates and decreased cerebral glucose metabolism in the AD-signature region. In contrast, higher HbA1c levels were not associated with Aβ positivity rates but were significantly associated with higher rates of having neurodegeneration in the AD-signature regions. Our results suggest different roles of insulin and HbA1c in AD pathogenesis, in that decreased blood insulin below optimal levels may contribute to increasing cerebral Aβ deposition and neurodegeneration whereas impaired glycemic control may aggravate neurodegeneration through a nonamyloid mechanism in nondiabetic CN older adults.