GCG and Hyperglycemia: In a glucose tolerance test, intravenous injection into mice of recombinant DPP4 from P. gingivalis, T. forsythia, and Pre. intermedia reduced the plasma GLP‐1 active form and insulin levels, which were accompanied by a substantial elevation in postprandial hyperglycemia together with retardation of the decrease in blood glucose levels (Ohara‐Nemoto et al., 2017).