A Novel Tetrapeptide Ala-Phe-Phe-Pro (AFFP) Derived from Antarctic Krill Prevents Scopolamine-Induced Memory Disorder by Balancing Lipid Metabolism of Mice Hippocampus.

Memory impairment is a serious problem with organismal aging and increased social pressure. The tetrapeptide Ala-Phe-Phe-Pro (AFFP) is a synthetic analogue of Antarctic krill derived from the memory-improving Antarctic krill peptide Ser-Ser-Asp-Ala-Phe-Phe-Pro-Phe-Arg (SSDAFFPFR) after digestion and absorption. The objective of this research was to assess the neuroprotective effects of AFFP by reducing oxidative stress and controlling lipid metabolism in the brains of mice with memory impairment caused by scopolamine. The 1H Nuclear magnetic resonance spectroscopy results showed that AFFP had three active hydrogen sites that could contribute to its antioxidant properties. The findings from in vivo tests demonstrated that AFFP greatly enhanced the mice's behavioral performance in the passive avoidance, novel object recognition, and eight-arm maze experiments. AFFP reduced oxidative stress by enhancing superoxide dismutase activity and malondialdehyde levels in mice serum, thereby decreasing reactive oxygen species level in the mice hippocampus. In addition, AFFP increased the unsaturated lipid content to balance the unsaturated lipid level against the neurotoxicity of the mice hippocampus. Our findings suggest that AFFP emerges as a potential dietary intervention for the prevention of memory impairment disorders.

Characterisation of a casein-/whey protein concentrate-Antarctic krill oil emulsion system and improvement of its storage stability.

AIMS: To develop Antarctic krill oil emulsions with casein and whey protein concentrate (WPC) and study their physicochemical properties and storage stability. METHODS: Emulsions were prepared by homogenisation and ultrasonication. The properties of the emulsions were investigated via ultraviolet ray spectroscopy, dynamic light scattering, confocal laser scanning microscope, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, Fourier transform infra-red spectrometer, and fluorescence spectrum. Shelf life was predicted by the Arrhenius model. RESULTS: Casein- and WPC-krill oil emulsions were well formed; the mean particle diameters were less than 128.19 ± 0.64 nm and 158 ± 1.56 nm, the polymer dispersity indices were less than 0.26 ± 0.01 and 0.27 ± 0.01, and the zeta potential were around -46.88 ± 5.02 mV and -33.51 ± 2.68 mV, respectively. Shelf life was predicted to be 32.67 ± 1.55 days and 29.62 ± 0.65 days (40 °C), 27.69 ± 1.15 days and 23.58 ± 0.14 days (50 °C), 24.02 ± 0.15 days and 20.1 ± 0.08 days (60 °C). CONCLUSION: The prepared krill oil emulsions have great potential to become a new krill oil supplement.

Digestive and Absorptive Properties of the Antarctic Krill Tripeptide Phe-Pro-Phe (FPF) and Its Auxiliary Memory-Enhancing Effect.

Aging and stress have contributed to the development of memory disorders. Phe-Pro-Phe (FPF) was identified with high stability by mass spectrometry from simulated gastrointestinal digestion and everted gut sac products of the Antarctic krill peptide Ser-Ser-Asp-Ala-Phe-Phe-Pro-Phe-Arg (SSDAFFPFR) which was found to have a positive impact on memory enhancement. This study investigated the digestive stability, absorption, and memory-enhancing effects of FPF using nuclear magnetic resonance spectroscopy, simulated gastrointestinal digestion, in vivo fluorescence distribution analysis, mouse behavioral experiments, acetylcholine function, Nissl staining, immunofluorescence, and immunohistochemistry. FPF crossed the blood-brain barrier into the brain after digestion, significantly reduced shock time, working memory errors, and reference memory errors, and increased the recognition index. Additionally, FPF elevated ACh content; Nissl body counts; and CREB, SYN, and PSD-95 expression levels, while reducing AChE activity (P < 0.05). This implies that FPF prevents scopolamine-induced memory impairment and provides a basis for future research on memory disorders.

Advances in encapsulation systems of Antarctic krill oil: From extraction to encapsulation, and future direction.

Antarctic krill oil (AKO) is highly sought after by consumers and the food industry due to its richness in a variety of nutrients and physiological activities. However, current extraction methods are not sufficient to better extract AKO and its nutrients, and AKO is susceptible to lipid oxidation during processing and storage, leading to nutrient loss and the formation of off-flavors and toxic compounds. The development of various extraction methods and encapsulation systems for AKO to improve oil yield, nutritional value, antioxidant capacity, and bioavailability has become a research hotspot. This review summarizes the research progress of AKO from extraction to encapsulation system construction. The AKO extraction mechanism, technical parameters, oil yield and composition of solvent extraction, aqueous enzymatic extraction, supercritical/subcritical extraction, and three-liquid-phase salting-out extraction system are described in detail. The principles, choice of emulsifier/wall materials, preparation methods, advantages and disadvantages of four common encapsulation systems for AKO, namely micro/nanoemulsions, microcapsules, liposomes and nanostructured lipid carriers, are summarized. These four encapsulation systems are characterized by high encapsulation efficiency, low production cost, high bioavailability and high antioxidant capacity. Depending on the unique advantages and conditions of different encapsulation methods, as well as consumer demand for health and nutrition, different products can be developed. However, existing AKO encapsulation systems lack relevant studies on digestive absorption and targeted release, and the single product category of commercially available products limits consumer choice. In conjunction with clinical studies of AKO encapsulation systems, the development of encapsulation systems for special populations should be a future research direction.

Effects of whaling and krill fishing on the whale-krill predation dynamics: bifurcations in a harvested predator-prey model with Holling type I functional response.

In the Antarctic, the whale population had been reduced dramatically due to the unregulated whaling. It was expected that Antarctic krill, the main prey of whales, would grow significantly as a consequence and exploratory krill fishing was practiced in some areas. However, it was found that there has been a substantial decline in abundance of krill since the end of whaling, which is the phenomenon of krill paradox. In this paper, to study the krill-whale interaction we revisit a harvested predator-prey model with Holling I functional response. We find that the model admits at most two positive equilibria. When the two positive equilibria are located in the region { ( N , P ) | 0 ≤ N < 2 N c , P ≥ 0 } , the model exhibits degenerate Bogdanov-Takens bifurcation with codimension up to 3 and Hopf bifurcation with codimension up to 2 by rigorous bifurcation analysis. When the two positive equilibria are located in the region { ( N , P ) | N > 2 N c , P ≥ 0 } , the model has no complex bifurcation phenomenon. When there is one positive equilibrium on each side of N = 2 N c , the model undergoes Hopf bifurcation with codimension up to 2. Moreover, numerical simulation reveals that the model not only can exhibit the krill paradox phenomenon but also has three limit cycles, with the outmost one crosses the line N = 2 N c under some specific parameter conditions.

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season.

Among large cetaceans in the Southern Hemisphere, fin whales were the most heavily exploited in terms of numbers taken during the period of intense industrial whaling. Recent studies suggest that, whilst some humpback whale populations in the Southern Hemisphere appears to have almost completely recovered to their estimated pre-whaling abundance, much less is known about the status of Southern Hemisphere fin whales. Circumpolar estimates in the 1990s suggest an abundance of about 5500 animals south of 60° S, while the IDCR/SOWER-2000 survey for the Scotia Sea and Antarctic Peninsula areas estimated 4670 fin whales within this region in the year 2000. More recent studies in smaller regions indicate higher densities, suggesting that previous estimates are overly conservative and/or that fin whales are undergoing a substantial increase. Here we report findings from a recent multi-vessel single-platform sightings survey carried out as part of the 2019 Area 48 Survey for Antarctic krill. While fin whales were encountered throughout the entire survey area, which covered the majority of CCAMLR Management Area 48, they were particularly abundant around the South Orkney Islands and the eastern Bransfield Strait. Large feeding aggregations were also encountered within the central Scotia Sea between South Orkney Islands and South Georgia. Distance sampling analyses suggest an average fin whale density throughout the Scotia Sea of 0.0256 ( CV = 0.149 ) whales per km2, which agrees well with recent density estimates reported from smaller sub-regions within the Scotia Sea. Design-based distance sampling analyses resulted in an estimated total fin whale abundance of 53,873 (CV = 0.15, 95% CI 40,233-72,138), while a density surface model resulted in a slightly lower estimate of 50,837 (CV: 0.136, 95% CI 38,966-66,324). These estimates are at least an order of magnitude greater than the previous estimate from the same region based on the IDCR/SOWER-2000 data, suggesting that fin whales are undergoing a substantial abundance increase in the South Atlantic. This may have important implications for the assessment of cetacean population trends, but also for CCAMLRs spatial overlap analysis process and efforts to implement a Feedback Management system for Antarctic krill. Our abundance estimate suggests an annual summer krill consumption by fin whales in the Antarctic Peninsula and Scotia Sea area of 7.97 (95% CI 4.94-11.91) million tonnes, which would represent around 20 times the total krill catch taken by the commercial fishery in Area 48 in the same season, or about 12.7% of the 2019 summer krill standing stock estimated from data collected during the same survey. This highlights the crucial importance of including cetacean krill predators in assessment and management efforts for living marine resources in the Southern Ocean, and particularly stresses the urgent need for a re-appraisal of abundance, distribution and ecological role of Southern Hemisphere fin whales.

Molecular Mechanisms of Iron Transport and Homeostasis Regulated by Antarctic Krill-Derived Heptapeptide-Iron Complex.

In this study, the molecular mechanisms of iron transport and homeostasis regulated by the Antarctic krill-derived heptapeptide-iron (LVDDHFL-iron) complex were explored. LVDDHFL-iron significantly increased the hemoglobin, serum iron, total iron binding capacity levels, and iron contents in the liver and spleen to normal levels, regulated the gene expressions of iron homeostasis, and enhanced in vivo antioxidant capacity in iron-deficiency anemia mice (P < 0.05). The results revealed that iron ions within LVDDHFL-iron can be transported via the heme transporter and divalent metal transporter-1, and the absorption of LVDDHFL-iron involved receptor-mediated endocytosis. We also found that the transport of LVDDHFL-iron across cells via phagocytosis was facilitated by the up-regulation of the high mobility group protein, heat shock protein ß, and V-type proton ATPase subunit, accompanied by the regulatory mechanism of autophagy. These findings provided deeper understandings of the mechanism of LVDDHFL-iron facilitating iron absorption.

Rich microbial and depolymerising diversity in Antarctic krill gut.

With almost a quadrillion individuals, the Antarctic krill processes five million tons of organic carbon every day during austral summer. This high carbon flux requires a broad range of hydrolytic enzymes to decompose the diverse food-derived biopolymers. While krill itself possesses numerous such enzymes, it is unclear, to what extent the endogenous microbiota contribute to the hydrolytic potential of the gut environment. Here we applied amplicon sequencing, shotgun metagenomics, cultivation, and physiological assays to characterize the krill gut microbiota. The broad bacterial diversity (273 families, 919 genera, and 2,309 species) also included a complex potentially anaerobic sub-community. Plate-based assays with 198 isolated pure cultures revealed widespread capacities to utilize lipids (e.g., tributyrin), followed by proteins (casein) and to a lesser extent by polysaccharides (e.g., alginate and chitin). While most isolates affiliated with the genera Pseudoalteromonas and Psychrobacter, also Rubritalea spp. (Verrucomicrobia) were observed. The krill gut microbiota growing on marine broth agar plates possess 13,012 predicted hydrolyses; 15-fold more than previously predicted from a transcriptome-proteome compendium of krill. Cultivation-independent and -dependent approaches indicated members of the families Flavobacteriaceae and Pseudoalteromonadaceae to dominate the capacities for lipid/protein hydrolysis and to provide a plethora of carbohydrate-active enzymes, sulfatases, and laminarin- or porphyrin-depolymerizing hydrolases. Notably, also the potential to hydrolyze plastics such as polyethylene terephthalate and polylactatide was observed, affiliating mostly with Moraxellaceae. Overall, this study shows extensive microbial diversity in the krill gut, and suggests that the microbiota likely play a significant role in the nutrient acquisition of the krill by enriching its hydrolytic enzyme repertoire.IMPORTANCEThe Antarctic krill (Euphausia superba) is a keystone species of the Antarctic marine food web, connecting the productivity of phyto- and zooplankton with the nutrition of the higher trophic levels. Accordingly, krill significantly contributes to biomass turnover, requiring the decomposition of seasonally varying plankton-derived biopolymers. This study highlights the likely role of the krill gut microbiota in this ecosystem function by revealing the great number of diverse hydrolases that microbes contribute to the krill gut environment. The here resolved repertoire of hydrolytic enzymes could contribute to the overall nutritional resilience of krill and to the general organic matter cycling under changing environmental conditions in the Antarctic sea water. Furthermore, the krill gut microbiome could serve as a valuable resource of cold-adapted hydrolytic enzymes for diverse biotechnological applications.

Mechanism of color change in Antarctic krill oil during storage.

Antarctic krill oil (AKO) is reddish-orange in color but undergoes changes during storage. To investigate the color deterioration and potential mechanisms involved, the changes in color, endogenous components (astaxanthin, fatty acids, and phospholipids), and reaction products (aldehydes, α-dicarbonyl compounds, and pyrroles) of AKO upon storage were determined. Although the visual color of AKO tended to darken upon storage, the colorimetric analysis and ultraviolet-visible spectrum analysis both indicated a fading in red and yellow due to the oxidative degradation of astaxanthin. During storage of AKO, lipid oxidation led to the formation of carbonyl compounds such as aldehydes and α-dicarbonyls. In addition, phosphatidylethanolamines (PEs) exhibited a faster loss rate than phosphatidylcholines. Moreover, hydrophobic pyrroles, the Maillard-like reaction products associated with primary amine groups in PEs accumulated. Therefore, it is suggested that the Maillard-like reaction between PEs and carbonyl compounds formed by lipid oxidation contributed to color darkening of AKO during storage.

Phospholipid-rich krill oil promotes intestinal health by strengthening beneficial gut microbial interactions in an infectious colitis model.

Krill oil (KO) is rich in bioactive ingredients including phospholipids, omega-3 fatty acids, and astaxanthin. While health benefits and roles of KO in modulating lipid metabolism are well documented, its ability to alleviate symptoms related to infectious colitis and modulate gut microbial interactions is still largely unknown. Here we used a multi-omics approach, including transcriptome, microbiome, and metabolome analyses, to understand how KO mediates gut microbial interactions and promotes epithelial healing in an infectious colitis model. KO reversed the infection-induced intestinal hyperplasia to baseline. KO dampened intestinal inflammation via multiple targets, mediating several proinflammatory pathways, including IL17 signaling, and reducing luminal histamine levels. KO supplementation enriched butyrate-producing bacteria, including Roseburia and Clostridium, and strengthened beneficial microbial interactions in the gut microbial community. Supplementation with phospholipid-rich KO also increased microbial phylogenetic diversity. KO enhanced mucosal barrier function by increasing the production of Muc6 and the antimicrobial peptide, Leap2. KO played an active role during epithelial healing by inhibiting the expression of granzyme K while increasing the expression of a colitis protective factor, Dclk1. Together, our findings demonstrate that KO rich in omega-3 phospholipids can play a protective role in infectious colitis and should be considered a dietary option for promoting gut health.

Preparation and characterization of Antarctic krill oil/quercetin co-loaded liposomes and their protective effect on oleic acid-induced steatosis and oxidative stress in vitro.

This study aims to introduce a new liposome to co-load Antarctic krill oil (AKO) and quercetin (QC) as a new delivery formulation to enrich the application of AKO and QC. The stability of liposomes could be increased by adding an appropriate quantity of soy lecithin (SL). Changes in the composition of the phospholipid membrane were strongly correlated with the stability and release capacity of loaded nutrients. SL2@QC/AKO-lips displayed a nearly spherical shape with higher oxidative stability and controlled the in vitro release performance of QC in simulated digestion. Moreover, in vitro studies indicated that new liposomes had no adverse effects on cell viability and could combine the physiological functions of AKO and QC to protect the HepG2 cells from oleic acid-induced steatosis and oxidative stress. The findings demonstrated that the AKO and QC co-loaded liposomes prepared with the addition of an appropriate quantity of SL had excellent loading efficiency of AKO/QC and good oxidative stability, security and functional activity.

At second glance: The importance of strict quality control - A case study on microplastic in the Southern Ocean key species Antarctic krill, Euphausia superba.

The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of microplastic (MP), by testing different sample volumes, extraction approaches, and applying hyperspectral imaging Fourier-transform infrared spectroscopy (µFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide.

Cloning and Characterization of Chitin Deacetylase from Euphausia superba.

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba (EsCDA-9k), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of EsCDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of EsCDA-9k showed a 67.32% homology with Penaeus monodon. Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co2+, Fe3+, Ca2+, and Na+, while it was inhibited by Zn2+, Ba2+, Mg2+, and EDTA. Molecular simulation of EsCDA-9k was conducted based on sequence alignment and homology modeling. The EsCDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba. The characterization and function study of EsCDA-9k will serve as an important reference point for future application.

Dietary antarctic krill improves antioxidant capacity, immunity and reduces lipid accumulation, insights from physiological and transcriptomic analysis of Plectropomus leopardus.

BACKGROUND: Due to its enormous biomass, Antarctic krill (Euphausia superba) plays a crucial role in the Antarctic Ocean ecosystem. In recent years, Antarctic krill has found extensive application in aquaculture, emerging as a sustainable source of aquafeed with ideal nutritional profiles. However, a comprehensive study focused on the detailed effects of dietary Antarctic krill on aquaculture animals, especially farmed marine fishes, is yet to be demonstrated. RESULTS: In this study, a comparative experiment was performed using juvenile P. leopardus, fed with diets supplemented with Antarctic krill (the krill group) or without Antarctic krill (the control group). Histological observation revealed that dietary Antarctic krill could reduce lipid accumulation in the liver while the intestine exhibited no obvious changes. Enzyme activity measurements demonstrated that dietary Antarctic krill had an inhibitory effect on oxidative stress in both the intestine and the liver. By comparative transcriptome analysis, a total of 1,597 and 1,161 differentially expressed genes (DEGs) were identified in the intestine and liver, respectively. Functional analysis of the DEGs showed multiple enriched terms significantly related to cholesterol metabolism, antioxidants, and immunity. Furthermore, the expression profiles of representative DEGs, such as dhcr7, apoa4, sc5d, and scarf1, were validated by qRT-PCR and fluorescence in situ hybridization. Finally, a comparative transcriptome analysis was performed to demonstrate the biased effects of dietary Antarctic krill and astaxanthin on the liver of P. leopardus. CONCLUSIONS: Our study demonstrated that dietary Antarctic krill could reduce lipid accumulation in the liver of P. leopardus, enhance antioxidant capacities in both the intestine and liver, and exhibit molecular-level improvements in lipid metabolism, immunity, and antioxidants. It will contribute to understanding the protective effects of Antarctic krill in P. leopardus and provide insights into aquaculture nutritional strategies.

Submesoscale coupling of krill and whales revealed by aggregative Lagrangian coherent structures.

In the marine environment, dynamic physical processes shape biological productivity and predator-prey interactions across multiple scales. Identifying pathways of physical-biological coupling is fundamental to understand the functioning of marine ecosystems yet it is challenging because the interactions are difficult to measure. We examined submesoscale (less than 100 km) surface current features using remote sensing techniques alongside ship-based surveys of krill and baleen whale distributions in the California Current System. We found that aggregative surface current features, represented by Lagrangian coherent structures (LCS) integrated over temporal scales between 2 and 10 days, were associated with increased (a) krill density (up to 2.6 times more dense), (b) baleen whale presence (up to 8.3 times more likely) and (c) subsurface seawater density (at depths up to 10 m). The link between physical oceanography, krill density and krill-predator distributions suggests that LCS are important features that drive the flux of energy and nutrients across trophic levels. Our results may help inform dynamic management strategies aimed at reducing large whales ship strikes and help assess the potential impacts of environmental change on this critical ecosystem.

Characterization of oxylipins in Antarctic krill oil (Euphausia superba) during storage based on RPLC-MS/MS analysis.

Antarctic krill oil (AKO) is rich in polyunsaturated fatty acids (PUFAs), but is prone to oxidative degradation, resulting in the formation of oxylipins, which compromise AKO quality. Herein, we used reversed-phase-high performance liquid chromatography-tandem mass spectrometry (RPLC-MS/MS) to perform qualitative and semi-quantitative analyses of oxylipins in AKO during storage. A total of 27 oxylipins were identified. A notable decrease in epoxy oxylipins (from 41.8 % to 26.9 % of the total oxylipins) was observed, whereas the content of dihydro oxylipins initially increased and then decreased with 48 h, as a pivotal point for AKO quality decline during storage. We suspected that the ratio of dihydroxyl and epoxy oxylipins could be a novel oxidative index to evaluate the oxidation of AKO. Statistical analysis allowed the identification of five oxylipins which showed unique correlations with various indexes. The findings discussed herein provide important new insights into mechanisms of oxidation occurring in AKO during storage.

Based on hydrogen and disulfide-mediated bonds, l-lysine and l-arginine enhanced the gel properties of low-salt mixed shrimp surimi (Antarctic krill and Pacific white shrimp).

This study delved into the effects of l-lysine (Lys) and l-arginine (Arg) on the gel properties and intermolecular interactions of low-salt (NaCl, 1 g/100 g) mixed shrimp surimi (Antarctic krill and Pacific white shrimp). The addition of Lys and Arg improved the gel strength and water holding capacity of low-salt gels, which were superior to the properties of STPP and high-salt (NaCl, 2.25 g/100 g) gels. These results can be attributed to the role of Lys and Arg in enhancing hydrogen and disulfide bonds within the low-salt gel system, promoting the solubilization of myofibrillar proteins (MP) and consequently increasing the number of MP molecules participating in gel formation. Antarctic krill MP did not show gel-forming ability and exerted a diluting effect on low-salt mixed shrimp surimi gels. Molecular docking analysis indicated the stable binding of Lys and Arg to myosin.

Simultaneous quantification of tin and lead species in Antarctic krill and fish by interfacing high-performance liquid chromatography with inductively coupled plasma mass spectrometry based on strong cation-exchange and Amphion columns.

Tin and lead are a global concern considering their species-dependent toxicity, bioavailability and transformation. Simultaneous speciation analysis of tin and lead is challenging for a large food capacity containing unstable species. Herein, we developed two sensitive methods for rapid quantification of tin and lead species in Antarctic seafood by high-performance liquid chromatography and inductively coupled plasma mass spectrometry based on strong cation-exchange and Amphion columns. Inorganic tin and lead, four organotin and two organolead compounds can be analysed in 16 min on a 10-cm Amphion II column (mobile phase: 4 mM sodium dodecyl benzene sulfonate at pH 2.0) with 0.02-0.24 µg L-1 detection limits. The method was applied to Antarctic krill and fish, demonstrating the presence of any tin and lead species down to µg kg-1 level. Overall, the proposed methods are sensitive, efficient and environment-friendly for routine speciation analysis of tin and lead in food samples.

Foam-templated oleogels constructed by whey protein isolate and xanthan gum: Multiple-effect delivery vehicle for Antarctic krill oil.

To address the limitations of Antarctic krill oil (AKO) such as easy oxidation, unacceptable fishy flavor and low bioaccessibility of astaxanthin in it, a multiple-effect delivery vehicle for AKO is needed. In this study, whey protein isolate (WPI) and xanthan gum (XG) were utilized to construct AKO into oleogels by generating foam-templates. The effects of the concentration of XG on the properties of foam, cryogel and the corresponding oleogels were investigated, and the formation mechanism of oleogel was discussed from the perspective of the correlation between foam-cryogel-oleogel. The results demonstrated that with the increase of the concentration of XG, the foam stability was improved, the cryogel after freeze drying had a more uniform network structure and superior oil absorption ability, and the corresponding oleogel had excellent oil holding ability after oil absorption. The AKO oleogels showed superior oxidative stability compared with AKO. The in vitro digestion experiments demonstrated that the bioaccessibility of the astaxanthin in this oleogel was also considerably higher than that in AKO. In addition, this oleogel had masking effect on the odor-presenting substances in AKO, while retaining other flavors of AKO. The foam-templated oleogel can be considered as a multiple-effect vehicle for AKO to facilitate its application in food products. This study provides theoretical basis and data support for the development and utilization of novel vehicle for AKO, broadening the application of AKO in the field of food science.

Long-Term Krill Oil Administration Alleviated Early Mild Cognitive Impairment in APP/PS1 Mice.

SCOPE: Alzheimer's disease is an age-dependent neurodegenerative disorder. Mounting studies focus on the improvement of advanced cognitive impairment by dietary nutrients. Krill oil (KO), a rich source of DHA/EPA and astaxanthin, is effective in improving cognitive function. The study mainly investigates the protective effects of long-term KO administration on early cognitive impairment. METHODS AND RESULTS: Results show that 2 months KO administration (50 and 100 mg kg-1 BW) can dramatically promote learning and memory abilities. Mechanism studies demonstrate that KO reduces amyloid ß concentration by regulating the amyloidogenic pathway, inhibits neuro-inflammation via regulating TLR4-NLRP3 signaling pathway, and prevents neuron injure. KO supplementation also enhances gut barrier integrity, reduces serum lipopolysaccharide leakage, and alters the gut microbiota by reducing Helicobacteraceae, Lactobacillaceae proportion, increasing Dubosiella and Akkermansia relative abundance. Particularly, a significant increase of isovaleric acid, propionic acid, and acetic acid levels is observed after KO supplementation. Correlation analysis shows that short-chain fatty acids (SCFAs), gut microbiota, and cognitive function are strongly correlated. CONCLUSIONS: The results reveal that KO relieves early mild cognitive impairment possibly for its role in mediating the gut microbiome-SCFAs-brain axis. Thus, KO may provide potential intervention strategies to prevent cognitive impairment in the early stages through the microbiota-gut-brain axis.