Evaluation Of Glucagon-Like Peptide-1 Receptor Expression In Nondiabetic And Diabetic Atherosclerotic Mice Using Pet Tracer Ga-68-Nodaga-Exendin-4

Activation of glucagon-like peptide-1 receptor (GLP-1R) signaling attenuates development of atherosclerosis and vascular inflam-mation. However, the expression of GLP-1R in atherosclerotic arteries remains uncertain. We evaluated whether a positron emission tomography (PET) tracer Ga-68-NODAGA-exendin-4 enables detection and imaging of GLP-1R expression in the mouse atherosclerotic aorta. Hypercholesterolemic (LDLR-/-ApoB(100/100)), hypercholesterolemic, diabetic (IGF-II/LDLR-/-ApoB(100/100)), and healthy control (C57BL/6N) mice were used in the study. The uptake of 68Ga-NODAGA-exendin-4 in atherosclerotic lesions was studied by autoradiography of tissue sections followed by immunofluorescence evaluation of inflammatory and vascular cell markers and GLP-1R. A subset of mice was imaged with Ga-68-NODAGA-exendin-4 PET/computed tomography (CT). The aortas of both LDLR--/-ApoB(100/100) and IGF-II/LDLR-/- ApoB(100/100) mice contained prominent, macrophage-rich atherosclerotic lesions. Diabetic mice demonstrated hyperglycemia and glucose intolerance. We found that by autoradiography, Ga-68-NODAGA-exendin-4 uptake was focally increased in macrophage-rich lesion areas compared with corresponding healthy vessel wall (lesion-to-wall ratio 1.6 +/- 0.10, P < 0.0001) in both nondiabetic and diabetic hypercholesterolemic mice. Preinjection of unlabeled exendin-4 peptide significantly reduced cellular uptake of Ga-68-NODAGA-exendin-4. Furthermore, PET/CT imaging showed Ga-68-NODAGA-exendin-4 accumulation in the atherosclerotic aorta. Immunofluorescence stainings demonstrated colocalization of GLP-1R with macrophage-rich areas in atherosclerotic lesions. Tracer uptake was low in the healthy vessel wall of C57BL/6N mice coupled with negative GLP-1R staining. In conclusion, Ga-68-NODAGA-exendin-4 detects GLP-1R expression in atherosclerotic lesions in both nondiabetic and diabetic hypercholesterolemic mice. These results provide evidence that GLP-1R expression is mainly localized in macrophage-rich area in atherosclerotic lesions and may have implications for studies of pharmacological modification of GLP-1R signaling in atherosclerosis.NEW & NOTEWORTHY Cardiovascular effects of glucagon-like peptide-1 receptor (GLP-1R) agonist therapies are potentially mediated by anti-inflammatory effects on atherosclerosis. Our study demonstrates that Ga-68-NODAGA-exendin-4, a radioligand specifically targeting GLP-1R, detects GLP-1R expression in inflamed atherosclerotic lesions in nondiabetic and diabetic hypercholesterolemic mice. Immunofluorescence staining suggests that GLP-1R is primarily localized in M2 macrophages in lesions. This study describes a new potential tool that may have translational relevance for studies of pharmacological modification of GLP-1R signaling in atherosclerosis.