INS and type 1 diabetes mellitus: Despite the significant depletion of the beta-cells, beta-cell exocytosis and both first- and second-phase GSIS largely remain preserved in T1D when assessed from donor intact islets or pancreatic slices [230,231,232,233], but secrete less insulin when compared to non-diabetic islets (~1/60th of normal non-diabetic islets) due to their lower insulin content [234,235].