Exploring Reversible Redox Behavior in the 6H-BaFeO3-δ (0 < δ < 0.4) System: Impact of Fe3+/Fe4+ Ratio on CO Oxidation.

This work is devoted to evaluating the relationship between the oxygen content and catalytic activity in the CO oxidation process of the 6H-type BaFeO3-δ system. Strong evidence is provided about the improvement of catalytic performance with increasing Fe average oxidation state, thus suggesting the involvement of lattice oxygen in the catalytic process. The compositional and structural changes taking place in both the anionic and cationic sublattices of the catalysts during redox cycles have been determined by temperature-resolved neutron diffraction. The obtained results evidence a structural transition from hexagonal (P63/mmc) to orthorhombic (Cmcm) symmetry. This transition is linked to octahedra distortion when the Fe3+ concentration exceeds 40% (δ values higher than 0.2). The topotactical character of the redox process is maintained in the δ range 0 < δ < 0.4. This suggests that the cationic framework is only subjected to slight structural modifications during the oxygen exchange process occurring during the catalytic cycle.

Can dynamic in vitro digestion systems mimic the physiological reality?

During the last decade, there has been a growing interest in understanding the fate of food during digestion in the gastrointestinal tract in order to strengthen the possible effects of food on human health. Ideally, food digestion should be studied in vivo on humans but this is not always ethically and financially possible. Therefore simple static in vitro digestion models mimicking the gastrointestinal tract have been proposed as alternatives to in vivo experiments but these models are quite basic and hardly recreate the complexity of the digestive tract. In contrast, dynamic models that allow pH regulation, flow of the food and injection in real time of digestive enzymes in the different compartments of the gastrointestinal tract are more promising to accurately mimic the digestive process. Most of the systems developed so far have been compared for their performances to in vivo data obtained on animals and/or humans. The objective of this article is to review the validation towards in vivo data of some of the dynamic digestion systems currently available in order to determine what aspects of food digestion they are able to mimic. Eight dynamic digestion systems are presented as well as their validation towards in vivo data. Advantages and limits of each simulator is discussed. This is the result of a cooperative international effort made by some of the scientists involved in Infogest, an international network on food digestion.

Correlation between in vitro and in vivo data on food digestion. What can we predict with static in vitro digestion models?

During the last decade, there has been a growing interest in understanding food's digestive fate in order to strengthen the possible effects of food on human health. Ideally, food digestion should be studied in vivo on humans but this is not always ethically and financially possible. Therefore, simple in vitro digestion models mimicking the gastrointestinal tract have been proposed as alternatives to in vivo experiments. Thus, it is no surprise that these models are increasingly used by the scientific community, although their various limitations to fully mirror the complexity of the digestive tract. Therefore, the objective of this article was to call upon the collective experiences of scientists involved in Infogest (an international network on food digestion) to review and reflect on the applications of in vitro digestion models, the parameters assessed in such studies and the physiological relevance of the data generated when compared to in vivo data. The authors provide a comprehensive review in vitro and in vivo digestion studies investigating the digestion of macronutrients (i.e., proteins, lipids, and carbohydrates) as well as studies of the bioaccessibility and bioavailability of micronutrients and phytochemicals. The main conclusion is that evidences show that despite the simplicity of in vitro models they are often very useful in predicting outcomes of the digestion in vivo. However, this has relies on the complexity of in vitro models and their tuning toward answering specific questions related to human digestion physiology, which leaves a vast room for future studies and improvements.

Effect of processing on polyamine content and bioactive peptides released after in vitro gastrointestinal digestion of infant formulas.

This study examined the influence of processing on polyamines and peptide release after the digestion of a commercial infant formula designed for children during the first months of life. Polyamine oxidase activity was not suppressed during the manufacturing process, which implicates that polyamine concentrations were reduced over time and during infant formula self-life. In gel electrophoresis, in vitro gastrointestinal digestion of samples with reduced amount of enzymes and time of digestion shows an increase in protein digestibility, reflected in the increase in nonprotein nitrogen after digestion and the disappearance of ß-lactoglobulin and α-lactalbumin bands in gel electrophoresis. Depending on the sample, between 22 and 87 peptides were identified after gastrointestinal digestion. A peptide from ß-casein f(98-105) with the sequence VKEAMAPK and antioxidant activity appeared in all of the samples. Other peptides with antioxidant, immunomodulatory, and antimicrobial activities were frequently found, which could have an effect on infant health. The present study confirms that the infant formula manufacturing process determines the polyamine content and peptidic profile after digestion of the infant formula. Because compositional dissimilarity between human milk and infant formula in polyamines and proteins could be responsible for some of the differences in health reported between breast-fed and formula-fed children, these changes must be taken into consideration because they may have a great effect on infant nutrition and development.

Antiviral activity of casein and αs2 casein hydrolysates against the infectious haematopoietic necrosis virus, a rhabdovirus from salmonid fish.

Salmonid fish viruses, such as infectious haematopoietic necrosis virus (IHNV), are responsible for serious losses in the rainbow trout and salmon-farming industries, and they have been the subject of intense research in the field of aquaculture. Thus, the aim of this work is to study the antiviral effect of milk-derived proteins as bovine caseins or casein-derived peptides at different stages during the course of IHNV infection. The results indicate that the 3-h fraction of casein and α(S2) -casein hydrolysates reduced the yield of infectious IHNV in a dose-dependent manner and impaired the production of IHNV-specific antigens. Hydrolysates of total casein and α(S2) -casein target the initial and later stages of viral infection, as demonstrated by the reduction in the infective titre observed throughout multiple stages and cycles. In vivo, more than 50% protection was observed in the casein-treated fish, and the kidney sections exhibited none of the histopathological characteristics of IHNV infection. The active fractions from casein were identified, as well as one of the individual IHNV-inhibiting peptides. Further studies will be required to determine which other peptides possess this activity. These findings provide a basis for future investigations on the efficacy of these compounds in treating other viral diseases in farmed fish and to elucidate the underlying molecular mechanisms of action. However, the present results provide convincing evidence in support of a role for several milk casein fractions as suitable candidates to prevent and treat some fish viral infections.

Static in vitro digestion model adapted to the general older adult population: an INFOGEST international consensus.

Understanding the mechanisms of food digestion is of paramount importance to determine the effect foods have on human health. Significant knowledge on the fate of food during digestion has been generated in healthy adults due to the development of physiologically-relevant in vitro digestion models. However, it appears that the performance of the oro-gastrointestinal tract is affected by ageing and that a model simulating the digestive conditions found in a younger adult (<65 years) is not relevant for an older adult (>65 years). The objectives of the present paper were: (1) to conduct an exhaustive literature search to find data on the physiological parameters of the older adult oro-gastrointestinal tract, (2) to define the parameters of an in vitro digestion model adapted to the older adult. International experts have discussed all the parameters during a dedicated workshop organized within the INFOGEST network. Data on food bolus properties collected in the older adult were gathered, including food particle size found in older adult boluses. In the stomach and small intestine, data suggest that significant physiological changes are observed between younger and older adults. In the latter, the rate of gastric emptying is slowed down, the pH of the stomach content is higher, the amount of secretions and thus the hydrolytic activities of gastric and intestinal digestive enzymes are reduced and the concentration of bile salts lower. The consensus in vitro digestion model of the older adult proposed here will allow significant progress to be made in understanding the fate of food in this specific population, facilitating the development of foods adapted to their nutritional needs. Nevertheless, better foundational data when available and further refinement of the parameters will be needed to implement the proposed model in the future.

Identification of a novel recurrent gain on 20q13 in chronic lymphocytic leukemia by array CGH and gene expression profiling.

BACKGROUND: The presence of genetic changes is a hallmark of chronic lymphocytic leukemia (CLL). The most common cytogenetic abnormalities with independent prognostic significance in CLL are 13q14, ATM and TP53 deletions and trisomy 12. However, CLL displays a great genetic and biological heterogeneity. The aim of this study was to analyze the genomic imbalances in CLL cytogenetic subsets from both genomic and gene expression perspectives to identify new recurrent alterations. PATIENTS AND METHODS: The genomic imbalances and expression levels of 67 patients were analyzed. The novel recurrent abnormalities detected with bacterial artificial chromosome array were confirmed by FISH and oligonucleotide microarrays. In all cases, gene expression profiling was assessed. RESULTS: Copy number alterations were identified in 75% of cases. Overall, the results confirmed FISH studies for the regions frequently involved in CLL and also defined a new recurrent gain on chromosome 20q13.12, in 19% (13/67) of the CLL patients. Oligonucleotide expression correlated with the regions of loss or gain of genomic material, suggesting that the changes in gene expression are related to alterations in copy number. CONCLUSION: Our study demonstrates the presence of a recurrent gain in 20q13.12 associated with overexpression of the genes located in this region, in CLL cytogenetic subgroups.

Short communication: Production of antihypertensive peptide HLPLP by enzymatic hydrolysis: optimization by response surface methodology.

This study evaluates the potential ability of proteolytic enzymes to release the antihypertensive peptide HLPLP, ß-casein f(134-138), from caseinate. Corolase PP (Röhm GmbH & Co. KG, Darmstadt, Germany) was found as the most appropriate enzyme to produce this peptide. The optimization of the main experimental variables involved in the process [concentration of Corolase PP, concentration of Peptidase 433P (Biocatalysts Ltd., Parc Nantgarw, UK), and the hydrolysis time on the HLPLP concentration, expressed as area of peak] were studied using a central composite face design. The optimum conditions to obtain the maximum concentration of HLPLP provided by the statistical program were a concentration of Corolase PP of 60 mg/g of protein and hydrolysis time of 24h. The use of the Peptidase 433P did not increase the amount of the active peptide. The obtained hydrolysate might be used as functional ingredient with antihypertensive properties.

Peptidomic data in porcine duodenal effluents after oral administration of micellar casein.

The data in this article are related to the research publication "Digestion of micellar casein in duodenum cannulated pigs. Correlation between in vitro simulated gastric digestion and in vivo data" (Miralles et al., Food Chemistry, 2021, 343, 128428). Pig duodenum effluents were collected with a T-shaped cannula 15 min before and during digestion over 150 min after casein intake. The casein degradation profile of individual pigs during digestion is presented. All identified peptide sequences at different digestion times for six subjects are provided. The peptide profile of digests in the form of heat maps is shown for αs1-, αs2-, ß- and κ-casein. The sum of amino acids belonging to peptides released from ß- and αs1-casein has been used to determine correlation coefficients and range the inter-individual variability. Finally, the global amino acid composition, isoelectric point and sequence length of all released peptides has been determined.

Digestion of micellar casein in duodenum cannulated pigs. Correlation between in vitro simulated gastric digestion and in vivo data.

Correlation and validation of the results of simulated gastrointestinal digestion of food compounds towards in vivo data is essential. The objective of this work was to monitor the digestion of milk micellar casein in the porcine upper intestinal tract and to match the outcome with the gastric in vitro digestion following the Infogest harmonized protocol. In pig duodenum, small amounts of intact caseins were present in all samples, while caseins were observed up to 60 min of gastric in vitro digestion. The peptide profile generated after in vitro and in vivo digestion showed clear similarities with specific overrepresented regions rich in proline and other hydrophobic residues. The statistical comparison of the in vivo and in vitro peptidome resulted in satisfactory correlation coefficients, up to 0.8. Therefore, the in vitro protocol used was a robust and simple model that provides a similar peptide profile than that found in porcine duodenum.

Beta-lactoglobulin as source of bioactive peptides.

Beta-lactoglobulin (beta-Lg) is currently an important source of biologically active peptides. These peptides are inactive within the sequence of the precursor protein, but they can be released by in vivo or in vitro enzymatic proteolysis. Once released, these peptides play important roles in the human health, including antihypertensive, antioxidant and antimicrobial activities as well as opioid-like features and ability to decrease the body-cholesterol levels. Bioactive peptides derived from beta-Lg are currently a point of intensive research. Their structure, biological significance and mechanism of action are briefly presented and discussed in this review.

Synergistic effect between different milk-derived peptides and proteins.

Antimicrobial peptides derived from food proteins constitute a new field in the combined use of antimicrobial agents in food. The best examples of milk-derived peptides are those constituted by bovine lactoferricin [lactoferrin f(17-41)] (LFcin-B) and bovine alpha(s2)-casein f(183-207). The aim of this work was to study if the antimicrobial activity of a natural compound employed in food preservation, nisin, could be enhanced by combination with the aforementioned milk-derived peptides. Furthermore, the possibility of a synergistic effect between these peptides and bovine lactoferrin (LF) against Escherichia coli and Staphylococcus epidermidis was also studied. Finally, the most active combinations were assayed against the foodborne pathogens Listeria monocytogenes and Salmonella choleraesuis. Results showed a synergistic effect when LFcin-B was combined with bovine LF against E. coli. In the same way, the combination of LFcin-B with bovine LF was synergistic against Staph. epidermidis. Bovine LF and nisin increased their antimicrobial activity when they were assayed together with bovine alpha(s2)-casein f(183-207). It is important to note the synergistic effect among LFcin-B and bovine LF, because both compounds might be simultaneously in the suckling gastrointestinal tract and could, therefore, have a protective effect on it. The other synergistic effect high-lighted is that between alpha(s2)-casein f(183-207) and nisin against L. monocytogenes because of the ability of L. monocytogenes to develop resistance to nisin.

Protein degradation and peptide release from milk proteins in human jejunum. Comparison with in vitro gastrointestinal simulation.

Human jejunal digests after oral ingestion of casein and whey protein were collected by a nasogastric tube and protein degradation and peptide release was compared with that found in the digests of the same substrates using a standardised protocol. No intact casein was detected in the jejunal nor in the in vitro samples taken during the intestinal phase, while ß-lactoglobulin was found in one hour-jejunal samples in agreement with the in vitro digestion. In vivo and in vitro digests showed comparable peptide profiles and high number of common sequences. A selective precipitation step was used to strengthen the identification of phosphorylated peptides. Most of the sequences found in jejunum, some of them not previously described, were also identified in the simulated digests. Common resistant regions to digestion were identified, revealing that the in vitro protocol constitutes a good approximation to the physiological gastrointestinal digestion of milk proteins.

Antihypertensive effect of peptides obtained from Enterococcus faecalis-fermented milk in rats.

Previous studies have demonstrated that milk fermented with Enterococcus faecalis decreases the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of spontaneously hypertensive rats. In this study, we evaluated the antihypertensive activity of the following peptide sequences: LHLPLP, LHLPLPL, LVYPFPGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV. These peptides isolated from E. faecalis-fermented milk showed in vitro angiotensin I-converting enzyme-inhibitory activity. Because the most potent angiotensin I-converting enzyme-inhibitory sequences were LHLPLP and LVYPFPGPIPNSLPQ-NIPP, we administered different doses of these peptides to spontaneously hypertensive rats. High doses of the remaining sequences were also administered to these animals. Water served as a negative control and captopril as a positive control. All products were administered orally. The SBP and DBP were measured before administration and also at 2, 4, 6, 8, and 24 h after administration. Before administration of the different products, spontaneously hypertensive rats showed SBP and DBP values of 218 +/- 2.5 and 157 +/- 5.9 mmHg, respectively (n = 30). The sequences LHLPLP, LVYPF-PGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV caused clear and significant decreases in SBP, DBP, or both in the animals. In particular, the antihypertensive effect could be clearly established when 2 or 3 mg/kg of LHLPLP was administered. These 2 doses of LHLPLP showed similar antihypertensive properties. Four hours after administration of captopril or the highest doses of the different peptides, the decreases in the SBP and the DBP (mmHg) were as follows: captopril (SBP = 52 +/- 5.8, DBP = 38.8 +/- 3.8), 3 mg/kg of LHLPLP (SBP = 25.3 +/- 8.2, DBP = 29.5 +/- 7.6), 6 mg/kg of LVYPFPGPIP-NSLPQNIPP (SBP = 14.9 +/- 3.7, DBP = 8.7 +/- 4.4), 10 mg/kg of LHLPLPL (SBP = 7.7 +/- 4.1, DBP = 9.4 +/- 3.1), 10 mg/kg of VLGPVRGPFP (SBP = 16.2 +/- 5.8, DBP = 21.64 +/- 3.2), and 10 mg/kg of VRGPFPIIV (SBP = 16.05 +/- 2.74, DBP = 9.19 +/- 3.49). The results obtained suggest that the sequences LHLPLP, LVYPFPGPIPNSLPQ-NIPP, VLGPVRGPFP, and VRGPFPIIV could be responsible, at least in part, for the antihypertensive properties described for E. faecalis-fermented milk.

Determination of the antihypertensive peptide LHLPLP in fermented milk by high-performance liquid chromatography-mass spectrometry.

Among different lactic acid bacteria isolated from raw milk, 4 Enterococcus faecalis strains have stood out as producers of fermented milk with potent antihypertensive activity. The peptide beta-casein f(133-138), LHLPLP, was identified as one of the major peptides responsible for the activity of these fermented milk products. A simple method was developed to quantify this peptide in fermented milk using high-performance liquid chromatography coupled in line with mass spectrometry. This procedure does not require any previous sample fractionation or extraction, and direct analysis of the water-soluble extract obtained from the fermented milk can be performed. Validation studies showed sufficient specificity, reproducibility, linearity, and recovery, demonstrating that this method can be used for the routine quantification of LHLPLP during the production of fermented milk products. The developed method was readily applied to quantify the peptide LHLPLP under different fermentation conditions and with different aromatized products.

Emergence of low noise frustrated states in E/I balanced neural networks.

We study emerging phenomena in binary neural networks where, with a probability c synaptic intensities are chosen according with a Hebbian prescription, and with probability (1-c) there is an extra random contribution to synaptic weights. This new term, randomly taken from a Gaussian bimodal distribution, balances the synaptic population in the network so that one has 80%-20% relation in E/I population ratio, mimicking the balance observed in mammals cortex. For some regions of the relevant parameters, our system depicts standard memory (at low temperature) and non-memory attractors (at high temperature). However, as c decreases and the level of the underlying noise also decreases below a certain temperature Tt, a kind of memory-frustrated state, which resembles spin-glass behavior, sharply emerges. Contrary to what occurs in Hopfield-like neural networks, the frustrated state appears here even in the limit of the loading parameter α→0. Moreover, we observed that the frustrated state in fact corresponds to two states of non-vanishing activity uncorrelated with stored memories, associated, respectively, to a high activity or Up state and to a low activity or Down state. Using a linear stability analysis, we found regions in the space of relevant parameters for locally stable steady states and demonstrated that frustrated states coexist with memory attractors below Tt. Then, multistability between memory and frustrated states is present for relatively small c, and metastability of memory attractors can emerge as c decreases even more. We studied our system using standard mean-field techniques and with Monte Carlo simulations, obtaining a perfect agreement between theory and simulations. Our study can be useful to explain the role of synapse heterogeneity on the emergence of stable Up and Down states not associated to memory attractors, and to explore the conditions to induce transitions among them, as in sleep-wake transitions.

Identification of two distinct antibacterial domains within the sequence of bovine alpha(s2)-casein.

Two distinct domains with antibacterial activity were isolated from a peptic hydrolysate of bovine alpha(s2)-casein. The digested alpha(s2)-casein was fractionated by cation-exchange chromatography, after which the peptides in the two active fractions obtained were separated by high-performance liquid chromatography and sequenced by electrospray-ionization tandem mass spectrometry. The major component in each active fraction, f(183-207) and f(164-179), was further purified and the antibacterial activity of these components was tested against several microorganisms. Depending on the target bacterial strain, these peptides exhibited minimum inhibitory concentrations between 8 and 99 microM. Peptide f(183-207) exhibited a consistently higher antibacterial activity than f(164-179), although both peptides showed a comparable hemolytic effect. A method of in situ enzymatic hydrolysis on a cation-exchange membrane to obtain a fraction enriched in the most active antibacterial domain is presented. The antibacterial and hemolytic activities are discussed in relation to the structure and hydrophobicity of the peptides.

Angiotensin-converting enzyme inhibitory activity of peptides derived from caprine kefir.

In this study, a potent angiotensin-converting enzyme (ACE)-inhibitory activity was found in a commercial kefir made from caprine milk. The low molecular mass peptides released from caseins during fermentation were mainly responsible for this activity. Sixteen peptides were identified by HPLC-tandem mass spectrometry. Two of these peptides, with sequences PYVRYL and LVYPFTGPIPN, showed potent ACE-inhibitory properties. The impact of gastrointestinal digestion on ACE-inhibitory activity of kefir peptides was also evaluated. Some of these peptides were resistant to the incubation with pepsin followed by hydrolysis with Corolase PP. The ACE-inhibitory activity after simulated digestion was similar to or slightly lower than unhydrolyzed peptides, except for peptide beta-casein f(47-52) (DKIHPF), which exhibited an activity 8 times greater after hydrolysis.

Caseinophosphopeptides released after tryptic hydrolysis versus simulated gastrointestinal digestion of a casein-derived by-product.

The production of caseinophosphopeptides from a casein-derived by-product generated during the manufacture of a functional ingredient based on antihypertensive peptides was attempted. The casein by-product was submitted to tryptic hydrolysis for 30, 60 and 120min and further precipitated with calcium chloride and ethanol at pH 4.0, 6.0 and 8.0. Identification and semi quantification of the derived products by tandem mass spectrometry revealed some qualitative and quantitative changes in the released caseinophosphopeptides over time at the different precipitation pHs. The by-product was also subjected to simulated gastrointestinal digestion. Comparison of the resulting peptides showed large sequence homology in the phosphopeptides released by tryptic hydrolysis and simulated gastrointestinal digestion. Some regions, specifically αS1-CN 43-59, αS1-CN 60-74, ß-CN 1-25 and ß-CN 30-50 showed resistance to both tryptic hydrolysis and simulated digestion. The results of the present study suggest that this casein-derived by-product can be used as a source of CPPs.