INS and type 1 diabetes mellitus: Elevated plasma proinsulin/C-peptide and proIAPP/IAPP ratios are promising biomarkers of beta cell dysfunction, can potentially be used to predict the onset of type 1 diabetes, islet graft failure, and response to immunotherapy [8, 12, 20, 28], and may be associated with loss of PC1/3 expression in islets [9–11].