Like their owners, dogs and cats are more and more affected by overweight and obesity-related problems and interest in functional pet foods is growing sharply. Through numerous studies, fish protein hydrolysates have proved their worth to prevent and manage obesity-related comorbidities like diabetes. In this work, a human in vitro static simulated gastrointestinal digestion model was adapted to the dog which allowed us to demonstrate the promising effects of a tilapia byproduct hydrolysate on the regulation of food intake and glucose metabolism. Promising effects on intestinal hormones secretion and dipeptidyl peptidase IV (DPP-IV) inhibitory activity were evidenced. We identify new bioactive peptides able to stimulate cholecystokinin (CCK) and glucagon-like peptide 1 (GLP-1) secretions, and to inhibit the DPP-IV activity after a transport study through a Caco-2 cell monolayer.

The exploration of certain microbial resources such as beneficial endophytic microorganisms is considered a promising strategy for the discovery of new antimicrobial compounds for the pharmaceutical industries and agriculture. Thirty-one endophytic bacterial strains affiliated with Bacillus, Janthinobacterium, Yokenella, Enterobacter, Pseudomonas, Serratia, and Microbacterium were previously isolated from vetiver (Chrysopogon zizanioides (L.) Roberty) roots. These endophytes showed antifungal activity against Fusarium graminearum and could be a source of antimicrobial metabolites. In this study, in particular, using high-throughput screening, we analyzed their antagonistic activities and those of their cell-free culture supernatants against three species of Fusarium plant pathogens, a bacterial strain of Escherichia coli, and a yeast strain of Saccharomyces cerevisiae, as well as their capacity to produce lipopeptides. The results showed that the culture supernatants of four strains close to B. subtilis species exhibited antimicrobial activities against Fusarium species and E. coli. Using mass spectrometry analyses, we identified two groups of lipopeptides (surfactins and plipastatins) in their culture supernatants. Whole-genome sequencing confirmed that these bacteria possess NRPS gene clusters for surfactin and plipastatin. In vitro tests confirmed the inhibitory effect of plipastatin alone or in combination with surfactin against the three Fusarium species.

Bovine cruor, a slaughterhouse waste, was mainly composed of hemoglobin, a protein rich in antibacterial and antioxidant peptides after its hydrolysis. In the current context of food safety, such bioactive peptides derived from enzymatic hydrolysis of hemoglobin represent potential promising preservatives for the food sector. In this work, the hemoglobin hydrolysis to produce bioactive peptides was performed in a regulated pH medium without the use of chemical solvents and by an eco-efficient process: electrodialysis with bipolar membrane (EDBM). Bipolar/monopolar (anionic or cationic) configuration using the H⁺ and OH⁻ generated by the bipolar membranes to regulate the pH was investigated. The aim of this study was to present and identify the bioactive peptides produced by EDBM in comparison with conventional hydrolysis and to identify their biological activity. The use of the EDBM for the enzymatic hydrolysis of hemoglobin has allowed for the production and identification of 17 bioactive peptides. Hydrolysates obtained by EDBM showed an excellent antimicrobial activity against six strains, antioxidant activity measured by four different tests and for the first time anti-fungal activities against five yeasts and mold strains. Consequently, this enzymatic hydrolysis carried out in regulated pH medium with bipolar membranes could provide bioactive peptides presenting antibacterial, antifungal and antioxidant interest.

Dipeptidyl-peptidase IV (DPP-IV) plays an essential role in glucose metabolism by inactivating incretins. In this context, food-protein-derived DPP-IV inhibitors are promising glycemic regulators which may act by preventing the onset of type 2 diabetes in personalized nutrition. In this study, the DPP-IV-inhibitory potential of seven proteins from diverse origins was compared for the first time in vitro and in vivo in rat plasma after the intestinal barrier (IB) passage of the indigested proteins. The DPP-IV-inhibitory potentials of bovine hemoglobin, caseins, chicken ovalbumin, fish gelatin, and pea proteins were determined in rat plasma thirty minutes after oral administration. In parallel, these proteins, together with bovine whey and gluten proteins, were digested using the harmonized INFOGEST protocol adapted for proteins. The DPP-IV half-maximal inhibitory concentration (IC₅₀) was determined in situ using Caco-2 cells. The DPP-IV-inhibitory activity was also measured after IB passage using a Caco2/HT29-MTX mixed-cell model. The peptide profiles were analyzed using reversed-phase high-performance liquid chromatography tandem mass spectrometry (RP-HPLC-MS/MS) with MS data bioinformatics management, and the IC₅₀ of the identified peptides was predicted in silico. The in vitro and in vivo DPP-IV-inhibitory activity of the proteins differed according to their origin. Vegetable proteins and hemoglobin yielded the highest DPP-IV-inhibitory activity in vivo. However, no correlation was found between the in vivo and in vitro results. This may be partially explained by the differences between the peptidome analysis and the in silico predictions, as well as the study complexity.

The O-linked-N-acetyl-d-glucosaminylation (O-GlcNAcylation) modulates numerous aspects of cellular processes. Akin to phosphorylation, O-GlcNAcylation is highly dynamic, reversible, and responds rapidly to extracellular demand. Despite the absolute necessity to determine post-translational sites to fully understand the role of O-GlcNAcylation, it remains a high challenge for the major reason that unmodified proteins are in excess comparing to the O-GlcNAcylated ones. Based on a click chemistry approach, O-GlcNAcylated proteins were labelled with azido-GalNAc and coupled to agarose beads. The proteome extracted from C2C12 myotubes was submitted to an intensive fractionation prior to azide-alkyne click chemistry. This combination of fractionation and click chemistry is a powerful methodology to map O-GlcNAc sites; indeed, 342 proteins were identified through the identification of 620 peptides containing one or more O-GlcNAc sites. We localized O-GlcNAc sites on proteins involved in signalling pathways or in protein modification, as well as structural proteins. Considering the recent role of O-GlcNAcylation in the modulation of sarcomere morphometry and interaction between key structural protein, we focused on proteins involved in the cytoarchitecture of skeletal muscle cells. In particular, several O-GlcNAc sites were located into protein-protein interaction domains, suggesting that O-GlcNAcylation could be strongly involved in the organization and reorganization of sarcomere and myofibrils. O-GlcNAcylation is an atypical glycosylation involved in the regulation of almost all if not all cellular processes, but its precise role remains sometimes obscure because of the ignorance of the O-GlcNAc site localization; thus, it remains indispensable to precisely map the O-GlcNAcylated sites to fully understand the role of O-GlcNAcylation on a given protein. For this purpose, we combined extensive fractionation of skeletal muscle cells proteome with click chemistry to map O-GlcNAc sites without an a priori consideration. A total of 620 peptides containing one or more O-GlcNAc sites were identified; interestingly, several of them belong to low expressed proteins, in particular proteins involved in signalling pathways. We also focused on structural proteins in view of recent data supporting the role of O-GlcNAcylation in the modulation of sarcomere cytoarchitecture; importantly, some of the O-GlcNAc sites were mapped into protein-protein interaction domains, reinforcing the involvement of O-GlcNAcylation in the organization and reorganization of sarcomere, and in larger extent, of myofibrils.

Bovine whey protein concentrate (WPC) was hydrolysed under pH-stat (ST) and non pH-controlled (free-fall, FF) conditions using Debitrase (DBT) and FlavorPro Whey (FPW). The resultant whey protein hydrolysates (WPHs) were assessed for the impact of hydrolysis conditions on the physicochemical and the in vitro antioxidant and intracellular reactive oxygen species (ROS) generation in oxidatively stressed HepG2 cells. Enzyme and hydrolysis condition dependent differences in the physicochemical properties of the hydrolysates were observed, however, the extent of hydrolysis was similar under ST and FF conditions. Significantly higher (p < 0.05) in vitro and cellular antioxidant activities were observed for the DBT compared to the FPW–WPHs. The WPHs generated under ST conditions displayed significantly higher (p < 0.05) oxygen radical absorbance capacity (ORAC) and Trolox equivalent antioxidant capacity (TEAC) values compared to the FF-WPHs. The impact of hydrolysis conditions was more pronounced in the in vitro compared to the cellular antioxidant assay. WPH peptide profiles (LC-MS/MS) were also enzyme and hydrolysis conditions dependent as illustrated in the case of β-lactoglobulin. Therefore, variation in the profiles of the peptides released may explain the observed differences in the antioxidant activity. Targeted generation of antioxidant hydrolysates needs to consider the hydrolysis conditions and the antioxidant assessment method employed.