PET imaging of GABAA receptors in pancreatic islets by [11C]flumazenil.

IF 3.1 3区 医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING EJNMMI Research Pub Date : 2024-12-02 DOI:10.1186/s13550-024-01176-5
Faïza Maloum-Rami, Pierre Cheung, Gunnar Antoni, Zhe Jin, Olof Eriksson, Daniel Espes
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引用次数: 0

Abstract

Background: Type 1 diabetes (T1D) is an autoimmune disease characterized by a progressive β-cell destruction. There are no clinically established methods for quantifying endocrine cells of the pancreas and current knowledge is almost exclusively based on autopsy material and functional measurements. Based on the expression of the γ-aminobutyric acid A receptors (GABAARs) in pancreatic islets and the fact that GABAAR agonists are being explored as treatment for T1D, we hypothesized that the positron emission tomography (PET) tracer [11C]flumazenil ([11C]FMZ) could serve as a marker of the endocrine mass of the pancreas. The in vivo uptake of [11C]FMZ in pig pancreas was evaluated by PET/CT, either tracer alone or after blockade of GABAAR by unlabeled flumazenil. The pancreatic binding of [11C]FMZ was investigated in vitro with frozen sections of pig pancreas as well as human organ donors, in addition to isolated mouse and human islets and exocrine preparations. The expression of GABAAR subunits in pig, human and mouse pancreas was explored by immunohistochemistry.

Results: Strong specific in vivo uptake of [11C]FMZ was observed in the pig brain as expected, but in the pancreas the signal was moderate and only partially reduced by blockade. In vitro experiments revealed a positive but weak and variable binding of [11C]FMZ in islets compared to exocrine tissue in the mouse, pig and human pancreas. In pig and mouse pancreatic islets we identified the GABAAR subunits β2 and γ2 but not α2. In the human pancreas from non-diabetic donors, we have identified the α2, β2 (although weak) and γ2 subunits, whereas from a T2D donor the α2 subunit was missing.

Conclusions: Our findings suggest that [11C]FMZ bind to GABAARs in the islets, but not with a sufficient contrast or magnitude to be implemented as an in vivo PET marker for the endocrine mass of the pancreas. However, GABAARs with different subunits are widely expressed in the endocrine cells within the pancreas in pig, human and mouse. Hence, the GABAAR could still be a potential imaging target for the endocrine cells of the pancreas but would require tracers with higher affinity and selectivity for individual GABAAR subunits.

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来源期刊
EJNMMI Research
EJNMMI Research RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING&nb-
CiteScore
5.90
自引率
3.10%
发文量
72
审稿时长
13 weeks
期刊介绍: EJNMMI Research publishes new basic, translational and clinical research in the field of nuclear medicine and molecular imaging. Regular features include original research articles, rapid communication of preliminary data on innovative research, interesting case reports, editorials, and letters to the editor. Educational articles on basic sciences, fundamental aspects and controversy related to pre-clinical and clinical research or ethical aspects of research are also welcome. Timely reviews provide updates on current applications, issues in imaging research and translational aspects of nuclear medicine and molecular imaging technologies. The main emphasis is placed on the development of targeted imaging with radiopharmaceuticals within the broader context of molecular probes to enhance understanding and characterisation of the complex biological processes underlying disease and to develop, test and guide new treatment modalities, including radionuclide therapy.
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