title: An Investigation into the Gastrointestinal Stability of Exenatide in the Presence of Pure Enzymes, Everted Intestinal Rings and Intestinal Homogenates.
abstract: The purpose of this study was to investigate the gastrointestinal stability of exenatide to determine the key factor(s) contributing to peptide degradation during the oral delivery process. The effects of pH and various digestive enzymes on the degradation kinetics of exenatide were determined. Moreover, the degradation clearances of peptide were also examined using rat everted intestinal rings and intestinal homogenates from various intestinal locations. Exenatide was comparatively stable within a pH range of 1.2-8. However, obvious degradation was observed in the presence of digestive enzymes. The order of enzymes, in terms of ability to degradate exenatide, was chymotrypsin>aminopeptidase N>carboxypeptidase A>trypsin>pepsin. Chymotrypsin showed the greatest ability to degrade exenatide (half-life t1/2, 5.784×10(-2) h), whereas aminopeptidase N and carboxylpeptidase A gave t1/2 values of 3.53 and 10.16 h, respectively. The degradation of exenatide was found to be peptide concentration- and intestinal site-dependent, with a lower clearance in the upper part of the duodenum and the lower part of the ileum. When using intestinal homogenates as enzyme sources, the order, in terms of peptide degradation ability, was ileum>jejunum>duodenum. However, no significant difference was observed in the remaining peptide concentrations throughout 2 h of incubation, which may be due to the involvement of cytosolic enzymes. These results revealed key factors contributing to peptide degradation, and suggest that the inhibition of chymotrypsin and site-specific delivery of exenatide might be advantageous in overcoming metabolic obstacles during its oral delivery.
authors.affiliation: National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Sun
authors.forename: Mengshu
authors.initials: M
authors.lastname: Wang
authors.forename: Bingxue
authors.initials: B
authors.lastname: Sun
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Shubo
authors.initials: S
authors.lastname: Liu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Kong
mesh_terms: D000818:Animals; D004798:Enzymes / Q000378:metabolism*; D000077270:Exenatide; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000502:physiology*; D008297:Male; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014688:Venoms / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004798:Enzymes; D010455:Peptides; D014688:Venoms; D000077270:Exenatide