Abstract
The delivery of therapeutic peptides via the oral route remains one of biggest challenges in the pharmaceutical industry. Recently, we have described an alternative improved drug delivery system for peptide delivery via the oral route, consisting of a lipidic nanocapsule. Despite the striking effects observed, it is still essential to develop strategies to strengthen the nanocarriers' glucagon-like peptide-1 (GLP-1) secretory effect of the nanocarrier and/or prolong its antidiabetic effect in vivo to facilitate its translation into the clinic. For this purpose, we developed and compared different fatty acid-targeted lipid and polymeric nanoparticles and evaluated the L cell stimulation induced by the nanocarriers in murine L cells in vitro and in normal healthy mice in vivo. We further examined the antidiabetic effect in vivo in an obese/diabetic mouse model induced by high-fat diet feeding and examined the effect of the oral administration frequency. Among the tested nanocarriers, only lipid-based nanocarriers that were surface-modified with DSPE-PEG2000 on the surface were able to significantly strengthen the biological effect of the nanocarriers. They increased endogenous GLP-1 levels up to 8-fold in vivo in normoglycemic mice. Moreover, they effectively prolonged the in vivo antidiabetic effect by normalizing the plasma glucose levels in obese/diabetic mice following long-term treatment (one month). Ultimately, the targeted nanocarriers were as effective when the administration frequency was reduced from once daily to once every other day.