A new technique for in vivo imaging of specific GLP-1 binding sites: first results in small rodents

Area of Science:

• Nuclear Medicine
• Molecular Imaging
• Endocrinology

Background:

• In vivo imaging of tissues expressing the glucagon-like peptide-1 (GLP-1) receptor is crucial for understanding physiological and pathological processes.
• The GLP-1 analog Exendin 4 serves as a basis for developing targeted radiolabeled compounds.

Purpose of the Study:

• To develop and evaluate a novel radiolabeled compound, DTPA-Lys40-Exendin 4, for specific targeting and imaging of GLP-1 receptors in vivo.
• To assess the feasibility of detecting GLP-1 receptor-positive tissues using biodistribution and small animal imaging studies.

Main Methods:

• Development of a radiolabeled compound, DTPA-Lys40-Exendin 4, based on Exendin 4.
• High-specific-activity labeling of the compound with 111In.
• In vivo small animal imaging using a high-resolution multi-pinhole SPECT system fused with MRI.
• Biodistribution studies in rats and mice.

Main Results:

• DTPA-Lys40-Exendin 4 was successfully labeled with 111In with high specific activity (>40 GBq/micromol) and radiochemical purity (>95%).
• Biodistribution studies and in vivo imaging revealed specific GLP-1 binding sites in the stomach, pancreas, lung, adrenals, and pituitary.
• High-resolution SPECT imaging achieved a resolution of less than 1 mm, enabling clear visualization of receptor-positive tissues.

Conclusions:

• The developed DTPA-Lys40-Exendin 4 technique enables highly sensitive in vivo imaging of GLP-1 receptor-positive tissues.
• This method facilitates intra-individual follow-up studies of GLP-1 receptor expression in vivo.