Preparation, Characterization, and Application of Biotinylated and Biotin−PEGylated Glucagon-Like Peptide-1 Analogues for Enhanced Oral Delivery
Glucagon-like peptide-1 (GLP-1) (7-36) is a type of incretin hormone with unique antidiabetic potential. The introduction of orally active GLP-1 offers substantial benefits in the treatment of type 2 diabetes over conventional injection-based therapies. Because the intestinal absorption of GLP-1 is restricted by its natural characteristics, we developed a series of GLP-1 analogues via the site-specific conjugation of biotin-NHS and/or of biotin-poly(ethylene glycol)-NHS at Lys 26 and Lys 34 of GLP-1 (7-36), respectively, in order to improve oral delivery. The resultant GLP-1 analogues, Lys 26,34-DiBiotin-GLP-1 (DB-GLP-1) and Lys 26-Biotin-Lys 34-(Biotin-PEG)-GLP-1 (DBP-GLP-1), were prepared and studied in terms of their chemical, structural, and biological properties. DBP-GLP-1 demonstrated superior proteolytic stability against trypsin, intestinal fluid, and the major GLP-1 inactivation enzyme (dipeptidyl peptidase-IV (DPP-IV)) to native GLP-1 or DB-GLP-1 ( p < 0.001). The in vitro insulinotropic effects of DB-GLP-1 and DBP-GLP-1 showed potent biological activity in a dose-dependent manner, which resembled that of native GLP-1 in terms of stimulating insulin secretion in isolated rat islets of Langerhans. Intraperitoneal glucose tolerance tests (IPGTT) after the oral administration of GLP-1 analogues in diabetic db/db mice demonstrated that DB-GLP-1 and DBP-GLP-1 significantly reduced the AUC 0-180 min of glucose for 3 h by 14.9% and 24.5% compared to that of native GLP-1, respectively ( p < 0.01). In particular, DBP-GLP-1 concentration in plasma rapidly increased 30 min after oral administration in rats, presumably due to improved intestinal absorption. These findings revealed that site-specific biotinylated and biotin-PEGylated GLP-1 is absorbed by intestine and that it has biological activity in vivo. Therefore, we propose that this orally active bioconjugated GLP-1 might be considered as a potential oral antidiabetic agent for type 2 diabetes mellitus.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.