Gel-Forming of Self-Assembling Peptides Functionalized with Food Bioactive Motifs Modulate DPP-IV and ACE Inhibitory Activity in Human Intestinal Caco-2 Cells

Abstract

Food bioactive peptides are increasingly used for formulating food products, nutraceuticals, and functional food, since they are generally considered safe for human consumption and metabolic syndrome prevention. They are also becoming popular as sustainable sources of novel functional biomaterials such as hydrogels, edible nanonutraceuticals, delivery systems, and packing materials. However, such food peptides are mostly unstable, and degrade during food processing, or in a gastrointestinal environment, thus resulting in low bioavailability precluding their practical applications. Here, we decided to functionalize the well-known and characterized self-assembling peptide RADA16 with two synthetic analogues of food bioactive peptides deriving from the hydrolysis of soybean glycinin and lupin β-conglutin (namely IAVPTGVA and LTFPGSAED) for control of and improvement in their gel-forming nanostructures, biomechanics, and biological features. Extensive characterization was performed via Circular Dichroism (CD) spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), Thioflavin T (ThT) binding assay, rheological measurements, and Atomic Force Microscopy (AFM) analysis. Lastly, since self-assembling peptides (SAPs) can be co-assembled with diluent SAPs (without a bioactive epitope) as an approach to control the density of biological signals and therefore attain enhanced bioactivity, we investigated the effect of the co-assembly of RADA16 and functionalized food bioactive SAPs (dubbed cAP-Soy1 and cAP-Lup1) for the growth of Caco-2 human intestinal cells and contextually we characterized their biological activities as DPP-IV and ACE inhibitors, in order to demonstrate their potential use for the prevention of metabolic syndrome.

Self-assembly and Hydrogelation Properties of Peptides Derived from Peptic Cleavage of Aggregation-prone Regions of Ovalbumin

“…This suggests the formation of larger nuclei, which can serve as a template for further growth of fibrillar structures during the peptide aggregation process [ 11 ]. A similar increase in ThT fluorescence was observed with self-assembling RADA16 peptide, likely also due to conformational changes within the peptide that promoted strong amyloidogenic-like features commonly seen in β-sheet structures [ 25 ]. Compared to the EWP hydrolysates, significantly decreased free sulfhydryl group content was observed in the gel aggregate sample ( Figure 1 F).…”

Enhancement of DPP-IV inhibitory activity and the capacity for enabling GLP-1 secretion through RADA16-assisted molecular designed rapeseed peptide nanogels

“…The main features were high stability and dispersibility in water, and low temperatures (37 °C) hardly destroyed its spatial structure. Differently, Lammi et al developed a method to retain DPP-IV inhibitory peptides 21 and hydrolysates 22 in the structure of RADA16 gel fiber, which was just a physical cross between nanofibrous structures and did not involve chemical bonding. Of course, this peptide-bonded oligopeptide sequence has also been reported, which can self-assemble in a wild environment to form a nanoscale hydrogel.…”

“…Similarly, RADA16-IAVPTGVA and RADA16-LTFPGSAED had the typical profile of soft hydrogels alike RADA16-RAP1 and RADA16-RAP2. 21 In clinical aspect, a variety of peptide nanogels that promote tissue regeneration are self-assembled using ion-complementary peptides such as RADA16. 37,[39][40][41] In order to inject RADA16-RAP1 and RADA16-RAP2 subcutaneously, the study of thixotropy is of great significance.…”

“…Recently, many self-assembling peptides including RADA16 have been used in the delivery and functional enhancement of active oligopeptides because of their native extracellular matrix and favorable three-dimensional microenvironment. 21,22 It has been reported that RADA16 has excellent biocompatibility and low immunogenicity, and its degradation products are amino acids, which do not cause tissue inflammation and do not affect the normal healing of tissues. 23 Nano-gelation of the two active oligopeptides IPQVS and ELHQEEPL can result in many excellent properties such as biocompatibility, stability, and non-toxicity.…”

Self-Assembled Food Peptides: Recent Advances and Perspectives in Food and Health Applications

“…Moreover, a subsequent study reported the dipeptidyl peptidase (DPP)-IV and angiotensin I-converting enzyme (ACE) inhibitory activities of self-assembling peptides derived from the hydrolysis of soybean glycinin and lupin β-conglutin in human intestinal (Caco-2) cells. 23 The results revealed that the self-assembled peptides were more active as ACE inhibitors (52−79% of inhibition) than as DPP-IV inhibitors (28−38% of inhibition). Furthermore, self-assembling peptides from Pacific oyster (Crassostrea gigas) was reported to have scarless healing properties in vivo.…”