Why is it so difficult to measure glucagon-like peptide-1 in a mouse?

Aims/hypothesis In humans, glucagon-like peptide-1 (GLP-1) is rapidly degraded by dipeptidyl peptidase-4 to a relatively stable metabolite, GLP-1(9–36)NH2, which allows measurement of GLP-1 secretion. However, little is known about the kinetics of the GLP-1 metabolite in mice. We hypothesised that the GLP-1 metabolite is rapidly degraded in this species by neutral endopeptidase(s) (NEP[s]).