111In-exendin uptake in the pancreas correlates with the beta cell mass and not with the alpha cell mass

M. Brom, L. Joosten, C. Frielink, O. Boerman and M. Gotthardt

Department of Radiology and Nuclear Medicine, Radboud university medical center, Nijmegen, The Netherlands.
Nov, 2015



Targeting of the Glucagon-like peptide 1 receptor with (111)In-labeled exendin is an attractive approach to determine the beta cell mass (BCM). Preclinical studies as well as a proof-of-concept study in type 1 diabetic patients and healthy subjects showed a direct correlation between BCM and radiotracer uptake. Despite these promising initial results, the influence of alpha cells on the uptake of the radiotracer remains a matter of debate. In this study we determined the correlation between pancreatic tracer uptake and beta and alpha cell mass in a rat model for beta cell loss. The uptake of (111)In-exendin (\%ID/g) showed a strong positive linear correlation with the BCM (Pearson r = 0.82). The fraction of glucagon positive cells in the total endocrine mass was increased after alloxan treatment (26\% ± 4\%, 43\% ± 8\%, and 69\% ±21\% for 0, 45 and 60 mg/kg alloxan, respectively). The uptake of (111)In-exendin showed a negative linear correlation with the alpha cell fraction (Pearson r = -0.76). These data clearly indicate towards specificity of (111)In-exendin for beta cells and that the influence of the alpha cells on (111)In-exendin uptake is negligible.