방사선의학 웹진

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Abstract
Reactive astrogliosis is a hallmark of Alzheimer's disease (AD). However, a clinically validated neuroimaging probe to visualize the reactive astrogliosis is yet to be discovered. Here, we show that PET imaging with 11C-acetate and 18F-fluorodeoxyglucose (18F-FDG) functionally visualizes the reactive astrocyte-mediated neuronal hypometabolism in the brains with neuroinflammation and AD. To investigate the alterations of acetate and glucose metabolism in the diseased brains and their impact on the AD pathology, we adopted multifaceted approaches including microPET imaging, autoradiography, immunohistochemistry, metabolomics, and electrophysiology. Two AD rodent models, APP/PS1 and 5xFAD transgenic mice, one adenovirus-induced rat model of reactive astrogliosis, and post-mortem human brain tissues were used in this study. We further curated a proof-of-concept human study that included 11C-acetate and 18F-FDG PET imaging analyses along with neuropsychological assessments from 11 AD patients and 10 healthy control subjects. We demonstrate that reactive astrocytes excessively absorb acetate through elevated monocarboxylate transporter-1 (MCT1) in rodent models of both reactive astrogliosis and AD. The elevated acetate uptake is associated with reactive astrogliosis and boosts the aberrant astrocytic GABA synthesis when amyloid-β is present. The excessive astrocytic GABA subsequently suppresses neuronal activity, which could lead to glucose uptake through decreased glucose transporter-3 in the diseased brains. We further demonstrate that 11C-acetate uptake was significantly increased in the entorhinal cortex, hippocampus and temporo-parietal neocortex of the AD patients compared to the healthy controls, while 18F-FDG uptake was significantly reduced in the same regions. Additionally, we discover a strong correlation between the patients' cognitive function and the PET signals of both 11C-acetate and 18F-FDG. We demonstrate the potential value of PET imaging with 11C-acetate and 18F-FDG by visualizing reactive astrogliosis and the associated neuronal glucose hypometablosim for AD patients. Our findings further suggest that the acetate-boosted reactive astrocyte-neuron interaction could contribute to the cognitive decline in AD.

Affiliations

Min-Ho Nam 1 2, Hae Young Ko 3, Dongwoo Kim 3, Sangwon Lee 3, Yongmin Mason Park 4 5, Seung Jae Hyeon 1, Woojin Won 4, Jee-In Chung 3, Seon Yoo Kim 3, Han Hee Jo 3, Kyeong Taek Oh 6, Young-Eun Han 1, Gwan-Ho Lee 7, Yeon Ha Ju 1 4 5, Hyowon Lee 1, Hyunjin Kim 1 2, Jaejun Heo 1, Mridula Bhalla 4 5, Ki Jung Kim 4, Jea Kwon 4, Thor D Stein 8, Mingyu Kong 9, Hyunbeom Lee 9, Seung Eun Lee 7, Soo-Jin Oh 1, Joong-Hyun Chun 3, Mi-Ae Park 10, Ki Duk Park 1, Hoon Ryu 1 8, Mijin Yun 3, C Justin Lee 4 5
1Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
2Department of KHU-KIST Convergence Science and Technology, Kyung Hee University, Seoul 02447, Republic of Korea.
3Department of Nuclear Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
4Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Republic of Korea.
5IBS School, University of Science and Technology, Daejeon 34126, Republic of Korea.
6Department of Medical Engineering, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
7Research Resources Division, KIST, Seoul 02792, Republic of Korea.
8Boston University Alzheimer's Disease Research Center and Department of Pathology, Chobanian and Avedisian Boston University School of Medicine, Boston, MA 02130, USA.
9Molecular Recognition Research Center, KIST, Seoul 02792, Republic of Korea.
10Department of Radiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.