In diabetes, to quantify the mass of pancreatic β-islet cells, a novel tracer, [11C]dihydrotetrabenazine, which targets β-cell vesicular monoamine transporter type II (VMAT2) has been shown to detect pancreatic β-islet cells and reduction in cell mass in streptozotocin-treated and Zucker rat models of diabetes [31] and in human type I diabetics [32]. Here, SLC18A2 is linked to diabetes mellitus.