Hempseed peptide-based hydrogels: new nano-nutraceutical formulations with antidiabetic activity

Introduction: The anti-diabetic activity of hempseed peptides was investigated by measuring their effect on DPPIV. Then, to overcome the usual limitations of food peptides, i.e. the stability and bioavailability, a self-assembled peptide (SAP) hydrogel was combined with hempseed peptides, for obtaining new nano-nutraceutical formulations, with better DPPIV inhibitory activities than the original peptide mixtures. Methods: The peptide RADA16 was assembled with hempseed tryptic (HT) and peptic (HP) peptides obtaining hempseed-based nano-hydrogels that were characterized using FTIR, Thioflavin T spectroscopy assays, and AFM tests. The inhibitory activity of these materials on DPPIV were compared with those of the parent HT and HP peptides, in vitro on the purified enzyme, in situ on Caco-2 cells, and ex vivo on human serum samples. Results: The parent hydrolysates HT and HP (1.0 mg mL-1) inhibited in vitro the activity of purified DPPIV by 17.5% and 32.0%, respectively. In order to check their stability towards intestinal proteases as well as to test their inhibitory activity on DPPIV, a novel cell-based assay based Caco-2 cells was developed. Indeed, HT and HP were able to inhibit the DPPIV activity at cellular level by 15.5% and 22.5%, respectively, whereas, the activity was lost when HT and HP were tested on human serum samples that naturally contains DPPIV. The results obtained using the nano-gels suggested that these materials greatly improved the resistance of HT and HP peptides to proteases hydrolysis, since they were 2- and 2.5 folds, respectively, more active than the original peptide mixtures even on serum circulating DPPIV. Conclusions: Bioactive peptides from protein hydrolysis represent a fast developing area in functional foods. The main limitation of this approach consists of the low stability of peptides. For the first time, our approach could offer a new route for the formulation of nano-nutraceuticals entirely made of SAP based-hydrogel and bioactive protein hydrolysates useful for anti-diabetic applications.