Bioinformatics of edible yellow mealworm (Tenebrio molitor) proteome reveal the cuticular proteins as promising precursors of dipeptidyl peptidase-IV inhibitors

Encapsulation of Tenebrio molitor Hydrolysate with DPP-IV Inhibitory Activity by Electrospraying and Spray-Drying

This study investigates the encapsulation of Tenebrio molitor hydrolysate exhibiting DPP-IV inhibitory activity by spray-drying and electrospraying techniques. First, we optimized the feed formulation and processing conditions required to obtain nano-microcapsules by electrospraying when using Arabic gum as an encapsulating agent and pullulan and Tween 20 as additives. The optimum formulation was also dried by spray-drying, where the removal of the additives was also assayed. Morphology analysis reveals that electrosprayed capsules have a smaller size (1.2 ± 0.5 µm vs. 12.4 ± 8.7 µm) and greater uniformity compared to those obtained by spray-drying. Regarding the surface nitrogen content and DPP-IV inhibitory activity, our results show no significant difference between the electrosprayed capsules and spray-dried capsules containing additives (IC50 of ~1.5 mg protein/mL). Therefore, it was concluded that adding additives during spray-drying allows for a similar encapsulation efficiency and reduced degradation during processing, as achieved by electrospraying technique but providing higher productivity. On the other hand, spray-dried capsules without additives displayed a higher surface nitrogen content percentage, which was mainly due to the absence of Tween 20 in the feed formulation. Consequently, these capsules presented a higher IC50 value (IC50 of 1.99 ± 0.03 mg protein/mL) due to the potential degradation of surface-exposed peptides.

Tenebrio molitor Proteins-Derived DPP-4 Inhibitory Peptides: Preparation, Identification, and Molecular Binding Mechanism

Inhibition of dipeptidyl peptidase-4 (DPP-4) is an effective way to control blood glucose in diabetic patients. Tenebrio (T.) molitor is an edible insect containing abundant protein. T. molitor protein-derived peptides can suppress the DPP-4 activity. However, the amino acid sequence and binding mechanism of these DPP-4 inhibitory peptides remain unclear. This study used the flavourzyme for T. molitor protein hydrolysis, identified the released peptides with DPP-4 inhibitory effect, and investigated the binding interactions of these peptides with DPP-4. The results showed that flavourzyme efficiently hydrolyzed the T. molitor protein, as demonstrated by the high degree of hydrolysis, disappearance of protein bands in SDS-PAGE, and changes to protein structure. The 4-h flavourzyme hydrolysates showed a good inhibitory effect on DPP-4 (IC₅₀ value of 1.64 mg/mL). The fragment of 1000-3000 Da accounted for 10.39% of the total peptides, but showed the strongest inhibitory effect on DPP-4. The peptides LPDQWDWR and APPDGGFWEWGD were identified from this fraction, and their IC₅₀ values against DPP-4 were 0.15 and 1.03 mg/mL, respectively. Molecular docking showed that these two peptides interacted with the DPP-4 active site via hydrogen bonding, hydrophobic interactions, salt bridge formation, π-cation interactions, and π-π stacking. Our findings indicated that T. molitor protein-derived peptides could be used as natural DPP-4 inhibitors.

In Silico Screening of a Bile Acid Micelle Disruption Peptide for Oral Consumptions from Edible Peptide Database

Recently, many bioactive peptides have been identified using bioinformatics tools. Previously, our group developed a method to screen dual-functional peptides that have direct intestinal delivery with porous silica gel and bile acid micelle disruption. However, newly designed peptides were not found in any storage protein. Therefore, in this study, in silico screening was performed using a 350,000 edible peptide library consisting of 4- to 7-mer independent peptides. As an initial screening, all edible peptides were applied to the random forest model to select predicted positive peptides. For a second screening, the peptides were assessed for the possibility of intestinal delivery using a 3D color map. From this approach, three novel dual-functional peptides, VYVFDE, WEFIDF, and VEEFYC were identified, and all of them were derived from storage proteins (legumin, myosin, and 11S globulin). In particular, VEEFYCS, in which a serine residue (S) is added to VEEFYC, was assumed to be released by thermolysin from the 11S-globulin derived from Ginkgo biloba by LC-MS/MS analysis. VEEFYCS was found to have suitable direct intestinal delivery and bile acid micelle disruption activity.

Machine learning screening of bile acid-binding peptides in a peptide database derived from food proteins

Bioactive peptides (BPs) are protein fragments that exhibit a wide variety of physicochemical properties, such as basic, acidic, hydrophobic, and hydrophilic properties; thus, they have the potential to interact with a variety of biomolecules, whereas neither carbohydrates nor fatty acids have such diverse properties. Therefore, BP is considered to be a new generation of biologically active regulators. Recently, some BPs that have shown positive benefits in humans have been screened from edible proteins. In the present study, a new BP screening method was developed using BIOPEP-UWM and machine learning. Training data were initially obtained using high-throughput techniques, and positive and negative datasets were generated. The predictive model was generated by calculating the explanatory variables of the peptides. To understand both site-specific and global characteristics, amino acid features (for site-specific characteristics) and peptide global features (for global characteristics) were generated. The constructed models were applied to the peptide database generated using BIOPEP-UWM, and bioactivity was predicted to explore candidate bile acid-binding peptides. Using this strategy, seven novel bile acid-binding peptides (VFWM, QRIFW, RVWVQ, LIRYTK, NGDEPL, PTFTRKL, and KISQRYQ) were identified. Our novel screening method can be easily applied to industrial applications using whole edible proteins. The proposed approach would be useful for identifying bile acid-binding peptides, as well as other BPs, as long as a large amount of training data can be obtained.

Antidiabetic Food-Derived Peptides for Functional Feeding: Production, Functionality and In Vivo Evidences

Bioactive peptides released from the enzymatic hydrolysis of food proteins are currently a trending topic in the scientific community. Their potential as antidiabetic agents, by regulating the glycemic index, and thus to be employed in food formulation, is one of the most important functions of these peptides. In this review, we aimed to summarize the whole process that must be considered when talking about including these molecules as a bioactive ingredient. In this regard, at first, the production, purification and identification of bioactive peptides is summed up. The detailed metabolic pathways described included carbohydrate hydrolases (glucosidase and amylase) and dipeptidyl-peptidase IV inhibition, due to their importance in the food-derived peptides research field. Then, their characterization, concerning bioavailability in vitro and in situ, stability and functionality in food matrices, and ultimately, the in vivo evidence (from invertebrate animals to humans), was described. The future applicability that these molecules have due to their biological potential as functional ingredients makes them an important field of research, which could help the world population avoid suffering from several diseases, such as diabetes.

Evaluation of Tenebrio molitor protein as a source of peptides for modulating physiological processes

The increasing world population has led to the need to search for new protein sources, such as insects, the harvesting of which can be economical and environmentally sustainable. This study explores the biological activities (angiotensin-converting enzyme (ACE) inhibition, antioxidant capacity, and dipeptidyl peptidase IV (DPP-IV) inhibition) of Tenebrio molitor hydrolysates produced by a set of food-grade proteases, namely subtilisin, trypsin, ficin and flavourzyme, and the degree of hydrolysis (DH), ranging from 5% to 20%. Trypsin hydrolysates exhibited the highest ACE inhibitory activity at a DH of 10% (IC₅₀ 0.27 mg mL^-1) in the experimental series, which was attributed to the release of short peptides containing Arg or Lys residues in the C terminus, and described as the ACE-inhibition feature. The levels of in vitro antioxidant activities were comparable to those reported for insect species. Subtilisin and trypsin hydrolysates at a DH of 10% displayed optimal DPPH scavenging and ferric reducing activities, which was attributed to the presence of 5-10-residue active peptides, as reported in the literature. Iron chelating activity was significantly favoured by increasing the DH, attaining a minimal IC₅₀ of 0.8 mg mL^-1 at a DH of 20% regardless of the enzymatic treatment. Similarly, in vitro antidiabetic activity was significantly improved by extensive hydrolysis, and, more specifically, the presence of di- and tripeptides. In this regard, the combined treatment of subtilisin-flavourzyme at a DH of 20% showed maximal DPP-IV inhibition (IC₅₀ 2.62 mg mL^-1). To our knowledge, this is the first study evaluating the DPP-IV activity of Tenebrio molitor hydrolysates obtained from these commercial proteases. We conclude that Tenebrio molitor hydrolysates produced with food-grade proteases are a valuable source of active peptides that can be used as functional ingredients in food and nutraceutical preparations.