Oxidative changes during ice storage of rainbow trout (Oncorhynchus mykiss) fed different ratios of marine and vegetable feed ingredients

Effect of three unsaturated fatty acids on the protein oxidation and structure of myofibrillar proteins from rainbow trout (Oncorhynchus mykiss)

In this study, the impact of three unsaturated fatty acids (Oleic acid: OA, Eicosapentaenoic acid: EPA, Docosahexaenoic acid: DHA) on the oxidation and structure of rainbow trout myofibrillar protein (MP) was explored. The findings revealed a notable increase in carbonyl content (P < 0.05) and a significant decrease in total sulfhydryl content (P < 0.05) of MP with the concentration increase of the three unsaturated fatty acids. Endogenous fluorescence spectroscopy and surface hydrophobicity analyses showed that unsaturated fatty acids can cause unfolding and exposure of hydrophobic groups in MP. In addition, SDS-PAGE showed that disulfide bonds were associated with MP cross-linking and aggregate size induced by unsaturated fatty acids. Overall, three unsaturated fatty acid treatments facilitated the oxidation of myofibrillar proteins, and the extent of protein oxidation was closely associated with the concentration of unsaturated fatty acids.

Protective Effect of Orbitides from Linseed (Linum usitatissimum L.) against Ultraviolet B-induced Photoaging in Zebrafish

Excessive ultraviolet (UV) exposure is the primary environmental factor that contributes to skin aging. Orbitides have been considered as important functional components in linseed, and they are complex and multiple. In this study, linseed orbitides (LOs) were divided into oxidized linseed orbitides (OLOs) and reduced linseed orbitides (RLOs) and used to investigate protection against ultraviolet B-induced photoaging in zebrafish. First, the results of the zebrafish embryo acute toxicity test showed that the OLOs had obvious embryo toxicity compared with RLOs. And RLOs had better effect in ultraviolet B-treated zebrafish, which may significantly reduce the reactive oxygen species levels and inhibit the degradation of collagen. Besides, we also found that RLOs could effectively inhibit the oxidation of proteins and lipids and regulate the activity of antioxidant enzymes. Furthermore, neutrophil recruitment to the dorsal and caudal fin regions was observed in UVB-treated zebrafish, and RLOs effectively alleviated this migration. In conclusion, RLOs have strong photoprotective effects and potential to be used as antiphotoaging ingredients.

Effects of Dietary Protein and Lipid Levels on Growth, Metabolism, Antioxidative Capacity, and Fillet Quality of Adult Triploid Rainbow Trout Farmed in Net Cage

The research is aimed at investigating the effects of dietary protein and lipid levels on adult triploid rainbow trout growth performance, feed utilization, digestive and metabolic enzyme activities, antioxidative capacity, and fillet quality. Nine diets containing three dietary protein levels (DP) (300, 350, and 400 g kg^-1) and three dietary lipid levels (DL) (200, 250, and 300 g kg^-1) were prepared using a 3 × 3 factorial design. In freshwater cages, 13,500 adult female triploid rainbow trout (3.2 ± 0.1 kg) were cultured for 77 days. Triplicate cages (500 fish per cage) were used as repetitions of each experimental diet. The findings revealed that as DP increased to 400 g kg^-1 and DL raised to 300 g kg^-1, the weight gain ratio (WGR) elevated significantly (P < 0.05). However, when DP ≥ 350 g kg^-1, WGR was similar in the DL250 and DL300 groups. As DP raised to 350 g kg^-1, the feed conversion ratio (FCR) notably decreased (P < 0.05). In the DP350DL300 group, lipids had a protein-sparing impact. High DP diet (400 g kg^-1) generally improved fish health status by increasing antioxidant capacity in the liver and intestine. A high DL diet (300 g kg^-1) showed no harmful effect on hepatic health based on plasma levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and antioxidant capacity in the liver. For fillet quality, a high DP diet could increase fillet yield, improve fillet hardness, springiness, and water-holding capacity values, and inhibit the production of off-flavors caused by n-6 fatty acids. A high DL diet could increase odor intensity, and EPA, DHA, and n-3 fatty acid concentrations decrease the thrombogenicity index value. The maximum fillet redness value was discovered in the DP400DL300 group. Overall, for adult triploid rainbow trout (≥3 kg), the minimum recommended DP and DL according to growth performance were 400 and 250 g kg^-1, respectively; DP and DL based on feed utilization were 350 and 200 g kg^-1, respectively; DP and DL based on fillet quality were 400 and 300 g kg^-1, respectively.

Recovery of Fatty Acid and Volatile Flavor Compound Composition in Farmed Tiger Puffer (Takifugu rubripes) with a Fish Oil-Finishing Strategy

Booming fish farming results in a relative shortage of fish oil (FO) supply, meaning that alternative oils are increasingly used in fish feeds, which leads to reduction of long-chain polyunsaturated fatty acids (LC-PUFAs) and other relevant changes in fish products. This study investigated the efficacy of an FO-finishing strategy in recovering the muscle quality of farmed tiger puffer. An eight-week feeding trial (growing-out period) was conducted with five experimental diets, in which graded levels (0 (control), 25, 50, 75, and 100%) of added FO were replaced by poultry oil (PO). Following the growing-out period was a four-week FO-finishing period, during which fish in all groups were fed the control diet. Dietary PO significantly decreased the muscle LC-PUFA content, whereas in general, the FO-finishing strategy recovered it to a level comparable with that of the group fed FO continuously. The recovery efficiency of EPA was higher than that of DHA. Dietary PO also led to changes of volatile flavor compounds in the muscle, such as butanol, pentenal, and hexenal, whereas the FO-finishing strategy mitigated the changes. In conclusion, the FO-finishing strategy is promising in recovering the LC-PUFA and volatile-flavor-compound composition in farmed tiger puffer after the feeding of PO-based diets.

Recent advances on characterization of protein oxidation in aquatic products: A comprehensive review

In addition to microbial spoilage and lipid peroxidation, protein oxidation is increasingly recognized as a major cause for quality deterioration of muscle-based foods. Although protein oxidation in muscle-based foods has attracted tremendous interest in the past decade, specific oxidative pathways and underlying mechanisms of protein oxidation in aquatic products remain largely unexplored. The present review covers the aspects of the origin and site-specific nature of protein oxidation, progress on the characterization of protein oxidation, oxidized proteins in aquatic products, and impact of protein oxidation on protein functionalities. Compared to meat protein oxidation, aquatic proteins demonstrate a less extent of oxidation on aromatic amino acids and are more susceptible to be indirectly oxidized by lipid peroxidation products. Different from traditional measurement of protein carbonyls and thiols, proteomics-based strategy better characterizes the targeted oxidation sites within proteins. The future trends using more robust and accurate targeted proteomics, such as parallel reaction monitoring strategy, to characterize protein oxidation in aquatic products are also given.

Protein oxidation marker, α-amino adipic acid, impairs proteome of differentiated human enterocytes: Underlying toxicological mechanisms

Protein oxidation and oxidative stress are involved in a variety of health disorders such as colorectal adenomas, inflammatory bowel's disease, neurological disorders and aging, among others. In particular, the specific final oxidation product from lysine, the α-amino adipic acid (α-AA), has been found in processed meat products and emphasized as a reliable marker of type II diabetes and obesity. Currently, the underlying mechanisms of the biological impairments caused by α-AA are unknown. To elucidate the molecular basis of the toxicological effect of α-AA, differentiated human enterocytes were exposed to dietary concentrations of α-AA (200 μM) and analyzed by flow cytometry, protein oxidation and proteomics using a Nanoliquid Chromatography-Orbitrap MS/MS. Cell viability was significantly affected by α-AA (p < 0.05). The proteomic study revealed that α-AA was able to alter cell homeostasis through impairment of the Na⁺/K⁺-ATPase pump, energetic metabolism, and antioxidant response, among other biological processes. These results show the importance of dietary oxidized amino acids in intestinal cell physiology and open the door to further studies to reveal the impact of protein oxidation products in pathological conditions.

Protein carbonylation in food and nutrition: a concise update

Protein oxidation is a topic of indisputable scientific interest given the impact of oxidized proteins on food quality and safety. Carbonylation is regarded as one of the most notable post-translational modifications in proteins and yet, this reaction and its consequences are poorly understood. From a mechanistic perspective, primary protein carbonyls (i.e. α-aminoadipic and γ-glutamic semialdehydes) have been linked to radical-mediated oxidative stress, but recent studies emphasize the role alternative carbonylation pathways linked to the Maillard reaction. Secondary protein carbonyls are introduced in proteins via covalent linkage of lipid carbonyls (i.e. protein-bound malondialdehyde). The high reactivity of protein carbonyls in foods and other biological systems indicates the intricate chemistry of these species and urges further research to provide insight into these molecular mechanisms and pathways. In particular, protein carbonyls are involved in the formation of aberrant and dysfunctional protein aggregates, undergo further oxidation to yield carboxylic acids of biological relevance and establish interactions with other biomolecules such as oxidizing lipids and phytochemicals. From a methodological perspective, the routine dinitrophenylhydrazine (DNPH) method is criticized not only for the lack of accuracy and consistency but also authors typically perform a poor interpretation of DNPH results, which leads to misleading conclusions. From a practical perspective, the biological relevance of protein carbonyls in the field of food science and nutrition is still a topic of debate. Though the implication of carbonylation on impaired protein functionality and poor protein digestibility is generally recognized, the underlying mechanism of such connections requires further clarification. From a medical perspective, protein carbonyls are highlighted as markers of protein oxidation, oxidative stress and disease. Yet, the specific role of specific protein carbonyls in the onset of particular biological impairments needs further investigations. Recent studies indicates that regardless of the origin (in vivo or dietary) protein carbonyls may act as signalling molecules which activate not only the endogenous antioxidant defences but also implicate the immune system. The present paper concisely reviews the most recent advances in this topic to identify, when applicable, potential fields of interest for future studies.

Improving the Biological Value of Olive and Soybean Oil Blends with Olive Leaf Extract Obtained by Ultrasound-Assisted Extraction towards the Preparation of a Sauce Product

French sauce from different blends of soybean and olive oils was prepared and the oxidative stability of the optimum sauce sample, enriched with various amounts of olive leaf polyphenolic extract (OLE) (obtained via ultrasound-assisted extraction), was investigated over 90 days of storage. The microbiological and sensory properties of the samples containing the optimum amounts of OLE, as a substitution for synthetic preservatives, were studied. According to the results, the addition of olive oil at higher levels (75% and 100%) could affect the physicochemical properties of the sauce as compared to the control sample. It was also found that the addition of olive oil (up to 50%) would not significantly impact the sauce properties. Regarding the OLE enrichment in the samples, it was found that high levels of OLE could improve the oxidative stability of the samples. It was also found that OLE could be used as a preservative instead of commercial ones. Overall, this study suggests the potential use of olive oil and olive leaf extract in the preparation of French sauce to boost its nutritional value and its stability.

Noxious effects of selected food-occurring oxidized amino acids on differentiated CACO-2 intestinal human cells

The harmful effects of food-occurring oxidized amino acids, namely, aminoadipic acid (AAA), dityrosine (DTYR), L-kynurenine (KN), kynurenic acid (KA) and 3-nitrotyrosine (3NT), were studied on differentiated CACO-2 cells by flow cytometry and quantification of glutathione (GSH), and allysine. Cells were exposed to food-relevant doses (200 μM) of each compound for 4 or 72h and compared to a control (no stimulated cells). All oxidized amino acids induced apoptosis and results indicated that underlying mechanisms depended on the chemical nature of the species. AAA, KN and KA caused ROS generation and severe oxidative stress in 96%, 98% and 89% of exposed cells (77% in control cells), leading to significant GSH depletion and allysine accretion (1.5, 1.5 and 1.6 nmol allysine/mg protein, respectively at 4h; control: 0.22 nmol/mg protein; p < 0.05). DTYR and 3NT induced significant apoptosis to 29% and 25% of cells (control: 16%; p < 0.05) and necrosis to 28% and 26% of cells (control: 23%) at 72h by ROS-independent mechanisms. KN and KA were found to induce a cycle arrest effect on CACO-2 cells. These findings emphasize the potential harmful effects of the intake of oxidized proteins and amino acids and urge the necessity of carrying out further molecular studies.

Influence of essential oils in diet and life-stage on gut microbiota and fillet quality of rainbow trout (Oncorhynchus mykiss)

Developing fish farming to meet the demands of food security and sustainability in the 21st century will require new farming systems and improved feeds. Diet and microbe interactions in the gut is an important variable with the potential to make a significant impact on future fish farming diets and production systems. It was monitored the gut microbiota of farmed rainbow trout using 16S rRNA profiling over 51 weeks during standard rearing conditions and feeding diet with supplementation of an essential oils (MixOil) mixture from plants (at a concentration in diet of 200 mg/kg). Gut microbiota 16S rRNA profiling indicated that the fish gut was dominated by Actinobacteria, Proteobacteria, Bacteroidetes and Firmicutes. Although the dietary supplementation with MixOil had no impact on either the composition or architecture of gut microbiota, significant changes in alpha and beta diversity and relative abundance of groups of gut bacteria were evident during growth stages on test feeds, especially upon prolonged growth on finishing feed. Fish fillet quality to guarantee palatability and safety for human consumption was also evaluated. Significant differences within the gut microbiota of juvenile and adult trout under the same rearing conditions were observed, The addition of essential oil blend affected some physicochemical characteristics of trout fillets, including their resistance to oxidative damage and their weight loss (as liquid loss and water holding capacity) during the first period of storage, that are two important parameters related to product shelf life and susceptibility to spoilage. The results highlighted the need for further studies concern dietary microbiome modulation at different life stages and its influence on animal health, growth performance and final product quality.

Modulation of selenium tissue distribution and selenoprotein expression in Atlantic salmon (Salmo salar L.) fed diets with graded levels of plant ingredients

Increased substitution of marine ingredients by terrestrial plant products in aquafeeds has been proven to be suitable for Atlantic salmon farming. However, a reduction in n-3 long-chain PUFA is a consequence of this substitution. In contrast, relatively little attention has been paid to the effects of fishmeal and oil substitution on levels of micronutrients such as Se, considering fish are major sources of this mineral for human consumers. To evaluate the effects of dietary marine ingredient substitution on tissue Se distribution and the expression of Se metabolism and antioxidant enzyme genes, Atlantic salmons were fed three feeds based on commercial formulations with increasing levels of plant proteins (PP) and vegetable oil. Lipid content in flesh did not vary at any sampling point, but it was higher in the liver of 1 kg of fish fed higher PP. Fatty acid content reflected dietary input and was related to oxidation levels (thiobarbituric acid-reactive substances). Liver had the highest Se levels, followed by head kidney, whereas the lowest contents were found in brain and gill. The Se concentration of flesh decreased considerably with high levels of substitution, reducing the added value of fish consumption. Only the brain showed significant differences in glutathione peroxidase, transfer RNA selenocysteine 1-associated protein 1b and superoxide dismutase expression, whereas no significant regulation of Se-related genes was found in liver. Although Se levels in the diets satisfied the essential requirements of salmon, high PP levels led to a reduction in the supply of this essential micronutrient.

The effects of eating marine- or vegetable-fed farmed trout on the human plasma proteome profiles of healthy men

Most human intervention studies have examined the effects on a subset of risk factors, some of which may require long-term exposure. The plasma proteome may reflect the underlying changes in protein expression and activation, and this could be used to identify early risk markers. The aim of the present study was to evaluate the impact of regular fish intake on the plasma proteome. We recruited thirty healthy men aged 40 to 70 years, who were randomly allocated to a daily meal of chicken or trout raised on vegetable or marine feeds. Blood samples were collected before and after 8 weeks of intervention, and after the removal of the twelve most abundant proteins, plasma proteins were separated by two-dimensional gel electrophoresis. Protein spots < 66 kDa with a pI >4·3 visualised by silver staining were matched by two-dimensional imaging software. Within-subject changes in spots were compared between the treatment groups. Differentially affected spots were identified by matrix-assisted laser desorption ionisation-time of flight/time of flight MS and the human Swiss-Prot database. We found 23/681 abundant plasma protein spots, which were up- or down-regulated by the dietary treatment (P< 0·05, q< 0·30), and eighteen of these were identified. In each trout group, ten spots differed from those in subjects given the chicken meal, but only three of these were common, and only one spot differed between the two trout groups. In both groups, the affected plasma proteins were involved in biological processes such as regulation of vitamin A and haem transport, blood fibrinolysis and oxidative defence. Thus, regular fish intake affects the plasma proteome, and the changes may indicate novel mechanisms of effect.

Oxidative damage to poultry, pork, and beef during frozen storage through the analysis of novel protein oxidation markers

The susceptibility of meats from different animal species (beef quadriceps femoris, porcine longissimus dorsi, and chicken pectoralis major) to undergo protein oxidation during frozen storage (20 weeks/-18 °C) was studied through the analysis of novel oxidation markers. Frozen storage induced protein carbonylation (α-aminoadipic and γ-glutamic semialdehydes), carboxylation (α-aminoadipic acid), and formation of Schiff bases in meat from the three species. Major rates of protein and lipid oxidation products [thiobarbituric-acid-reactive substances (TBARS) and hexanal] were found in beef patties. Among the endogenous factors having a potential influence on the susceptibility of meat to undergo protein oxidation, heme iron seemed to play a major role. The present study illustrates the severe chemical modifications induced by oxidative stress during frozen storage of ground meat and provides original insight into the underlying mechanisms and factors.

Carbonylation of myofibrillar proteins through the maillard pathway: effect of reducing sugars and reaction temperature

Carbonylation is recognized as one of the most remarkable chemical modifications in oxidized proteins and is generally ascribed to the direct attack of free radicals to basic amino acid residues. The purpose of this work was to investigate the formation of specific carbonyls, α-aminoadipic and γ-glutamic semialdehydes (AAS and GGS, respectively), in myofibrillar proteins (MP) through a Maillard-type pathway in the presence of reducing sugars. The present study confirmed the concurrent formation of protein carbonyls and advanced glycation end-products (AGEs) during incubation (80 °C/48 h) of MP (4 mg/mL) in the presence of reducing sugars (0.5 M). Copper irons (10 μM) were found to promote the formation of protein carbonyls, and a specific inhibitor of the Maillard reaction (0.02 M pyridoxamine) blocked the carbonylation process which emphasize the occurrence of a Maillard-type pathway. The Maillard-mediated carbonylation occurred in a range of reducing sugars (0.02-0.5 M) and reaction temperatures (4-110 °C) compatible with food systems. Upcoming studies on this topic may contribute further to shed light on the complex interactions between protein oxidation and the Maillard reaction and the impact of the protein damage on food quality and human health.