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  • Systematic Review
  • Published:

Association between FDG- and TSPO-PET signals across human and animal studies investigating neurodegenerative conditions: a systematic review

Abstract

Background

Fluorodeoxyglucose (FDG)-PET hypometabolism is considered a biomarker of neurodegeneration. However, recent evidence revealed that glial cells contribute to the FDG-PET signal. In this context, microglial changes have been evaluated with 18-kDa translocator protein (TSPO)-PET radiopharmaceuticals. While several studies have concomitantly conducted FDG- and TSPO-PET imaging, their associations remain controversial.

Objective

We systematically revised multi-tracer preclinical and clinical studies using FDG- and TSPO-PET to investigate neurodegenerative conditions.

Results

From 401 studies, 14 preclinical studies, 7 clinical studies and 1 study including both met the inclusion criteria. The preclinical studies included mouse models of amyloid, tau, and neurotoxins, whereas the clinical studies investigated Alzheimer’s disease, Parkinson’s disease and frontotemporal lobar degeneration. Most clinical studies found a negative association between FDG- and TSPO-PET signals, whereas animal studies showed mixed results being highly dependent on the radiotracer used.

Discussion

Our findings support the connection between glial and metabolic changes in the brain while highlighting glial heterogeneity between species and the specificities of TSPO-PET radiotracers. To better understand the dynamic associations between FDG- and TSPO-PET, it is essential to conduct longitudinal studies during the early stages of neurodegenerative disorders, along with the use of novel mouse models that more accurately represent these conditions.

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Fig. 1: TSPO-PET radiopharmaceuticals.
Fig. 2
Fig. 3: Summary of brain FDG- and TSPO-PET preclinical studies with animal models of neurodegenerative disorders.
Fig. 4: Summary of brain FDG- and TSPO-PET clinical studies with neurodegenerative disorders’ individuals.

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Acknowledgements

LSM is supported by Anna-Lisa och Bror Björnsons Stiftelse. MM is funded by Race Against Dementia Alzheimer’s Research UK (ARUK-RADF2021A-010), and the National Institute for Health Research (NIHR) Cambridge Biomedical Research Centre (NIHR203312: the views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care). HZ is a Wallenberg Scholar supported by grants from the Swedish Research Council (#2023-00356; #2022-01018 and #2019-02397), the European Union’s Horizon Europe research and innovation programme under grant agreement No 101053962, Swedish State Support for Clinical Research (#ALFGBG-71320), the Alzheimer Drug Discovery Foundation (ADDF), USA (#201809-2016862), the AD Strategic Fund and the Alzheimer’s Association (#ADSF-21-831376-C, #ADSF-21-831381-C, #ADSF-21-831377-C, and #ADSF-24-1284328-C), the Bluefield Project, Cure Alzheimer’s Fund, the Olav Thon Foundation, the Erling-Persson Family Foundation, Stiftelsen för Gamla Tjänarinnor, Hjärnfonden, Sweden (#FO2022-0270), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860197 (MIRIADE), the European Union Joint Programme – Neurodegenerative Disease Research (JPND2021-00694), the National Institute for Health and Care Research University College London Hospitals Biomedical Research Centre, and the UK Dementia Research Institute at UCL (UKDRI-1003). AS-P is funded by the Harrison Gardner Jr. Innovation Award, the Karen Toffler Charitable Trust, and the Massachusetts Center for Alzheimer Therapeutics Science (MassCATS). PRN is supported by the Weston Brain Institute, Canadian Institutes of Health Research (CIHR) [MOP-11-51-31; RFN 152985, 159815, 162303], Canadian Consortium of Neurodegeneration and Aging (CCNA; MOP-11-51-31 -team 1), Brain Canada Foundation (CFI Project 34874; 33397), the Fonds de Recherche du Québec – Santé (FRQS; Chercheur Boursier, 2020-VICO-279314). ERZ is supported by CAPES (#88881.996985/2024-01), CNPq (#12410/2018-2, #435642/2018-9, #312306/2021-0, #409066/2022-2, #447074/2023-7, #409595/2023-3, and #444880/2024-0), Instituto Nacional Saúde em Excitotoxicidade Neuroproteção (#465671/2014-4), Instituto Nacional Saúde Cerebral (#406020/2022-1), Instituto Serrapilheira (#Serra-1912-31365; and #R-2401-47242), FAPERGS (#21/2551-0000673-0 and #85053.824.30451.24062024), Alzheimer’s Association (#21-850670; #22-928689; #23-1148735; and #BFECAA2024), National Academy of Neuropsychology and Alzheimer’s Association (#22-92838), Michael J. Fox Foundation (#MJFF-023158), and the Ministério da Saúde (#00030420240118-003490).

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Study conception and design: LSM and ERZ. Article screening and data extraction: LSM, PV, CL, LM, AR, and LP. Risk of bias assessment: LSM and PV. Data preparation: LSM. Data interpretation: LSM, AS-P, PR-N and ERZ. Manuscript preparation and figure elaboration: LSM. Intellectual content: all authors. All authors revised and approved the final version of the manuscript.

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Correspondence to Eduardo R. Zimmer.

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Competing interests

HZ has served at scientific advisory boards and/or as a consultant for Abbvie, Acumen, Alector, Alzinova, ALZPath, Annexon, Apellis, Artery Therapeutics, AZTherapies, Cognito Therapeutics, CogRx, Denali, Eisai, Merry Life, Nervgen, Novo Nordisk, Optoceutics, Passage Bio, Pinteon Therapeutics, Prothena, Red Abbey Labs, reMYND, Roche, Samumed, Siemens Healthineers, Triplet Therapeutics, and Wave, has given lectures in symposia sponsored by Alzecure, Biogen, Cellectricon, Fujirebio, Lilly, and Roche, and is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures Incubator Program (outside submitted work). KB has served as a consultant and at advisory boards for Acumen, ALZPath, AriBio, BioArctic, Biogen, Eisai, Lilly, Moleac Pte. Ltd, Novartis, Ono Pharma, Prothena, Roche Diagnostics, and Siemens Healthineers; has served at data monitoring committees for Julius Clinical and Novartis; has given lectures, produced educational materials and participated in educational programs for AC Immune, Biogen, Celdara Medical, Eisai, and Roche Diagnostics; and is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures Incubator Program, outside the work presented in this paper. AS-P reports on a material transfer agreement with Ionis Pharmaceuticals, Inc. PRN has served on the scientific advisory board of Novonordisk, Eisai, and Ely Lilly. He has also served as a consultant to Eisai, and Cerveau radiopharmaceuticals. ERZ has served on the scientific advisory board, as a consultant or speaker for Nintx, Novo Nordisk, Biogen, Lilly and Magdalena Biosciences. He is also a co-founder and a minority shareholder at masima. Other authors declare no conflict of interest.

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Machado, L.S., Vidor, P., Perquim, L. et al. Association between FDG- and TSPO-PET signals across human and animal studies investigating neurodegenerative conditions: a systematic review. Mol Psychiatry (2025). https://doi.org/10.1038/s41380-025-03160-4

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