Diabetes is the result of the reduction in the number of islet beta cells in the pancreas, which leads to insufficient insulin secretion and high blood glucose levels (hyperglycemia). Currently, insulin secretion is used as a surrogate measure of beta cell mass but however, serum insulin concentrations provide an imprecise measure of beta cell mass and no reliable non-invasive measure of beta cell mass has been available. But a recent study report that positron emission tomography (PET)-based quantization of pancreatic radio-labeled VMAT2 receptors in diabetic rats is a reliable and non-invasive way to measure beta cell mass.
Paul Harris and colleagues from Columbia University in New York exploited the finding that type 2 vesicular monoamine transporters (VMAT2) are expressed in human islet beta cells within the pancreas. It is also expressed in tissues of the
central nervous system. Currently used in clinical imaging of the brain, the radioligand [11C]Dihydrotetrabenazine (DTBZ) binds specifically to VMAT2. Then the researchers were able to use DTBZ to estimate beta cell mass in rats with type 1 diabetes. In longitudinal PET studies, Harris and his colleagues saw a significant decline in pancreatic uptake of DTBZ that preceded the loss of
glycemic control in the diabetic rat. The result suggest that PET-based quantization of VMAT2 receptors could provide a non-invasive measurement of beta cell mass. This could be used to study the pathogenesis of diabetes and to monitor therapeutic interventions.
