Changes in blood glucose level observed with oral glucose tolerance test (OGTT). OGTT results after 4 weeks of treatment show differences in blood glucose levels in non-diabetic controls (Control), non-diabetic mice treated with DF (Control+DF), STZ-induced diabetes mellitus mice (DM), DM mice treated with acarbose (DM+Acarbose), DM mice treated with low-dose DF peptide (DM+DF-L), DM mice treated with high-dose DF peptide (DM+DF-H), and DM mice treated with APPH peptide (DM+APPH) after 15 min, 30 min, 60 min, and 120 min of oral glucose administration. ** = p < 0.01 and *** = p < 0.001 indicate significant difference in DM group with respect to the control group; κκ = p < 0.01 indicates significant difference in DM+DF-L group with respect to the DM group. δδ = p < 0.01 and δδδ = p < 0.001 indicate significant difference in DM+DF-H group with respect to the DM group. ∆∆ = p < 0.01 and ∆∆∆ = p < 0.001 indicate significant difference with respect to the DM group.