An autoradiographic study of [(18)F]FDG uptake to islets of Langerhans in NOD mouse.

To evaluate the potential of in vivo imaging of accumulation of lymphocytes to islets of Langerhans (insulitis), we compared 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) uptake in the pancreas and pancreatic islets of healthy BALB/c mice, phenotypically healthy NOD mice with insulitis and diabetic NOD mice. [(18)F]FDG was injected i.v. to 14 female BALB/c mice (age 13+/-3 weeks, plasma glucose 8+/-2 mmol/l) and 21 age-matched female NOD mice (plasma glucose 8+/-4 mmol/l, p=0.06). The mice were killed 90-min post injection and distribution of radioactivity was analysed using digital autoradiography. There was no correlation of plasma glucose concentration with the [(18)F]FDG uptake values. Uptake of radioactivity in NOD mice to the islets affected by insulitis was up to 2.3 times higher (p=0.001) than that to unaffected islets in the same pancreas. Uptake to NOD islets with insulitis was also clearly enhanced (1.0-2.3 times higher) compared to the islets in the BALB/c mice. In conclusion, NOD mouse islets with insulitis accumulate [(18)F]FDG markedly more than islets without insulitis or BALB/c islets. However, the relatively small difference in the [(18)F]FDG intensity between healthy and diseased islets, combined with the limited resolution ability of the positron emission tomography (PET), probably prevent the use of [(18)F]FDG in PET studies aiming at in vivo documentation of onset and progression of insulitis and prediabetes in mouse and man.