Figure 12.

I) A Gd³⁺-based macrocyclic agent that acts as a MRI sensor of free Zn²⁺ ions in vivo. II) Simulation of insulin secretion from pancreatic β-cells by glucose results in co-release of high levels of free Zn²⁺ ions packaged with insulin in β-cell granules. The colored areas shown in these images reflect functional release of Zn²⁺ and insulin in these mice. The mouse on the right was fed a high fat diet for 12 weeks to expand β-cell mass. The expanded colored areas in this image reflect a larger functional pancreas (increased β-cell function) in this animal. This process is known to occur in diet-induced obesity (DIO) mouse models (94). Functional agents such as this may one day allow imaging of β-cell function in humans during development of type II diabetes or as a biomarker to test new drugs designed to improve β-cell function.