We predicted that multiple genes in the pancreatic islet network may be involved in modulating plasma insulin levels in the B6XBTBR F2 cross, including App, Gria3, Grb10, Calca, and Ins1. In particular, our pancreatic islet network predicts that the Alzheimer's disease gene, amyloid precursor protein App is a negative regulator of insulin abundance in the plasma. The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.