Dipeptidyl peptidase IV (DPP-IV) inhibitory properties of camel milk protein hydrolysates generated with trypsin

Dipeptidyl peptidase IV (DPP-IV) inhibitory properties of a camel whey protein enriched hydrolysate preparation

Camel milk proteins contain dipeptidyl peptidase IV (DPP-IV) inhibitory peptides. A camel whey protein concentrate (WPC, 44.7 ± 3.4% (w/w) protein) was prepared and subsequently hydrolysed with trypsin at different temperatures, enzyme to substrate (E:S) ratios and hydrolysis times yielding fifteen hydrolysates (H1-H15). Their DPP-IV half maximal inhibitory concentrations (IC₅₀) ranged from 0.55 ± 0.05 to 1.52 ± 0.16 mg L^-1 for H8 and H6, respectively. E:S was the only factor having a significant effect on the DPP-IV IC₅₀ value (p < 0.05). Relatively potent α-lactalbumin-derived DPP-IV inhibitory peptides (LAHKPL and ILDKEGIDY) were detected in selected hydrolysates. Additionally, three potent β-CN-derived peptides, VPV, YPI and VPF having DPP-IV IC₅₀ values of 6.6 ± 0.5, 35.0 ± 2.0 and 55.1 ± 5.8 µM, respectively, were identified. After IPI, VPV is the second most potent DPP-IV inhibitory peptide identified to date, which supports the role of camel milk as an antidiabetic agent.

The molecular basis of the anti-diabetic properties of camel milk

Over the years, strong evidence have been accumulated in favor of the beneficial effects of camel milk on glucose homeostasis with significant anti-diabetic properties in both human and animal diabetic models. However, the cellular and molecular mechanisms involved in such effects remain not understood. In this review, we speculated about the potential mechanisms and summarized few mechanistic-based studies that investigated the biological activity of camel milk and its protein components on the different aspects that may be involved in the anti-diabetic effects. A special emphasis is given to the molecular events engaged by camel milk proteins/peptides on two key aspects: insulin secretion and insulin receptor activity. Thus, the review gives a molecular rationale to the anti-diabetic effects of camel milk. This will help to identify the anti-diabetic agent(s) contained in camel milk and to understand better its mechanism of action in order to use it for the management of diabetes mellitus.

In Silico Approaches Applied to the Study of Peptide Analogs of Ile-Pro-Ile in Relation to Their Dipeptidyl Peptidase IV Inhibitory Properties

Inhibition of dipeptidyl peptidase IV (DPP-IV) may be exploited to maintain the incretin effect during the postprandial phase. As a result, glycemic regulation and energy homeostasis may be improved. Food protein-derived peptides have been identified as natural agents capable of inhibiting DPP-IV. Ile-Pro-Ile is the most potent DPP-IV inhibitory peptide identified to date. A minimum analog peptide set approach was used to study peptide analogs of Ile-Pro-Ile. The DPP-IV half maximal inhibitory concentration (IC50) values of the 25 peptides evaluated ranged from 3.9 ± 1.0 µM (Ile-Pro-Ile) to 247.0 ± 32.7 µM (Phe-Pro-Phe). The presence of Pro at position 2 of tripeptides was required to achieve high DPP-IV inhibition. Most peptides behaved as competitive inhibitors of DPP-IV with the exception of peptides with a N-terminal Trp, which were mixed-type inhibitors. While possessing the structure of preferred DPP-IV substrates, most peptides studied were particularly stable during 30 min incubation with DPP-IV. Molecular docking revealed that Ile-Pro-Ile and its peptide analogs interacted in a very similar manner with the active site of DPP-IV. In addition, no correlation was found between the Hydropathic INTeraction score and the DPP-IV IC50 values of the peptides studied. This outcome suggests that free energy may not be directly responsible for enzyme inhibition by the peptides. Finally, novel DPP-IV inhibitory peptides were identified using the strategy employed herein. These results may be relevant for the development of food protein-derived peptides with serum glucose lowering and food intake regulatory properties in humans.

Characterization and identification of novel antidiabetic and anti-obesity peptides from camel milk protein hydrolysates

In-vitro inhibitory properties of peptides released from camel milk proteins against dipeptidyl peptidase-IV (DPP-IV), porcine pancreatic α-amylase (PPA), and porcine pancreatic lipase (PPL) were studied. Results revealed that upon hydrolysis by different enzymes, camel milk proteins displayed dramatic increase in inhibition of DPP-IV and PPL, but slight improvement in PPA inhibition was noticed. Peptide sequencing revealed a total of 20 and 3 peptides for A9 and B9 hydrolysates respectively, obtained the score of 0.8 or more on peptide ranker and were categorized as potential DPP-IV inhibitory peptides. KDLWDDFKGL in A9 and MPSKPPLL in B9 were identified as most potent PPA inhibitory peptide. For PPL inhibition only 7 and 2 peptides qualified as PPL inhibitory peptides from hydrolysates A9 and B9, respectively. The present study report for the first time PPA and PPL inhibitory and only second for DPP-IV inhibitory potential of protein hydrolysates from camel milk.

Generation of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides during the enzymatic hydrolysis of tropical banded cricket (Gryllodes sigillatus) proteins

Cricket (Gryllodes sigillatus) protein hydrolysates inhibit dipeptidyl peptidase IV (DPP-IV) in vitro.

Enhancing bioactive peptide release and identification using targeted enzymatic hydrolysis of milk proteins

Milk proteins have been extensively studied for their ability to yield a range of bioactive peptides following enzymatic hydrolysis/digestion. However, many hurdles still exist regarding the widespread utilization of milk protein-derived bioactive peptides as health enhancing agents for humans. These mostly arise from the fact that most milk protein-derived bioactive peptides are not highly potent. In addition, they may be degraded during gastrointestinal digestion and/or have a low intestinal permeability. The targeted release of bioactive peptides during the enzymatic hydrolysis of milk proteins may allow the generation of particularly potent bioactive hydrolysates and peptides. Therefore, the development of milk protein hydrolysates capable of improving human health requires, in the first instance, optimized targeted release of specific bioactive peptides. The targeted hydrolysis of milk proteins has been aided by a range of in silico tools. These include peptide cutters and predictive modeling linking bioactivity to peptide structure [i.e., molecular docking, quantitative structure activity relationship (QSAR)], or hydrolysis parameters [design of experiments (DOE)]. Different targeted enzymatic release strategies employed during the generation of milk protein hydrolysates are reviewed herein and their limitations are outlined. In addition, specific examples are provided to demonstrate how in silico tools may help in the identification and discovery of potent milk protein-derived peptides. It is anticipated that the development of novel strategies employing a range of in silico tools may help in the generation of milk protein hydrolysates containing potent and bioavailable peptides, which in turn may be used to validate their health promoting effects in humans. Graphical abstract The targeted enzymatic hydrolysis of milk proteins may allow the generation of highly potent and bioavailable bioactive peptides.

Features of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from dietary proteins

Dipeptidyl peptidase IV (DPP-IV) is involved in incretin hormone processing and therefore plays a key role in glycemic regulation. This review summarizes the latest developments in food protein-derived DPP-IV inhibitory peptides. The in silico approaches currently used to develop targeted strategies for the enzymatic release of DPP-IV inhibitory peptides from food proteins are outlined. The features within the primary sequences of potent DPP-IV inhibitory di-, tri-, and larger peptides, having half maximal inhibitory activity (IC₅₀ ) < 100 µM, were evaluated and the outcomes are presented herein. It is proposed that detailed analysis of those food derived peptides identified in humans following ingestion may constitute a practical strategy for the targeted identification of novel bioavailable DPP-IV inhibitory peptides. Human intervention studies are required as the specific role of food protein-derived DPP-IV inhibitory peptides in the regulation of glycaemia in humans remains to be fully elucidated. PRACTICAL APPLICATIONS: This review provides recent information on dipeptidyl peptidase IV (DPP-IV) inhibitory peptides arising from food protein hydrolysates. Small animal studies have demonstrated that food protein hydrolysates with in vitro DPP-IV inhibitory properties also display antidiabetic activity. DPP-IV inhibitory peptides may be used as food ingredients to improve glycemic regulation in Type 2 diabetics. Therefore, the development of potent DPP-IV inhibitory hydrolysates containing bioavailable peptides in humans is of significant interest. This may help in the formulation of foods containing physiologically relevant doses of bioactive hydrolysates/peptides. Acquisition of detailed knowledge of DPP-IV inhibitory peptide features via the utilization of in silico tools may help to optimize the release of potent DPP-IV inhibitory peptides during enzymatic hydrolysis of food proteins. This review provides information on features within the primary sequences of potent DPP-IV inhibitory peptides and current in silico strategies which may be used to inform on the targeted enzymatic hydrolysis of food proteins.

Rapid Identification of Dipeptidyl Peptidase-IV (DPP-IV) Inhibitory Peptides from Ruditapes philippinarum Hydrolysate

Dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides were rapidly identified from Ruditapes philippinarum hydrolysate. The hydrolysate was fractionated by ethanol precipitation and preparative reverse phase high-performance liquid chromatography (RP-HPLC). The fraction which showed the highest DPP-IV inhibitory activity was then analyzed by a high-throughput nano-liquid chromatography electrospray ionization tandem mass spectrometry (nano-LC ESI-MS/MS) method, and the sequences of peptides were identified based on the MS/MS spectra against the Mollusca protein data from the UniProt database. In total, 50 peptides were identified. Furthermore, molecular docking was used to identify potential DPP-IV inhibitors from the identified peptides. Docking results suggested that four peptides: FAGDDAPR, LAPSTM, FAGDDAPRA, and FLMESH, could bind pockets of DPP-IV through hydrogen bonds, π-π bonds, and charge interactions. The four peptides were chemically synthesized and tested for DPP-IV inhibitory activity. The results showed that they possessed DPP-IV inhibitory activity with IC₅₀ values of 168.72 μM, 140.82 μM, 393.30 μM, and >500 μM, respectively. These results indicate that R. philippinarum-derived peptides may have potential as functional food ingredients for the prevention of diabetes.

Identification of novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides in camel milk protein hydrolysates

Nine novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides (FLQY, FQLGASPY, ILDKEGIDY, ILELA, LLQLEAIR, LPVP, LQALHQGQIV, MPVQA and SPVVPF) were identified in camel milk proteins hydrolysed with trypsin. This was achieved using a sequential approach combining liquid chromatography tandem mass spectrometry (LC-MS/MS), qualitative/quantitative structure activity relationship (QSAR) and confirmatory studies with synthetic peptides. The most potent camel milk protein-derived DPP-IV inhibitory peptides, LPVP and MPVQA, had DPP-IV half maximal inhibitory concentrations (IC₅₀) of 87.0 ± 3.2 and 93.3 ± 8.0 µM, respectively. DPP-IV inhibitory peptide sequences identified within camel and bovine milk protein hydrolysates generated under the same hydrolysis conditions differ. This was linked to differences in enzyme selectivity for peptide bond cleavage of camel and bovine milk proteins as well as dissimilarities in their amino acid sequences. Camel milk proteins contain novel DPP-IV inhibitory peptides which may play a role in the regulation of glycaemia in humans.