This study explored the efficacy of multi-elements combined with chemometrics to discriminate the geographical origins of oysters (Crassostrea ariakensi). We determined 52 elements in 166 samples from four regions along the southeast coast of China. Significant regional variations of 51 elements were revealed (P < 0.05), while the principal component analysis (PCA) provided no clear regional delineations. The training models (n = 117) established on linear discriminant analysis (LDA), partial least square discriminant analysis (PLS-DA), and random forest (RF) uniformly achieved 100% predictive accuracy. The cross-validation accuracies of the final models (n = 166) derived from LDA, PLS-DA, and RF were 100%, 100%, and 99.4%, respectively. Even with the models simplified to 8 elements (Zn, Al, K, Cd, Cu, Rb, B, and Ag), high predictive and cross-validation accuracies were maintained, underscoring the robustness and algorithm flexibility of elemental profiling for accurately identifying the geographical origins of oysters.

Fried oyster is a popular aquatic food product in East Asia, but nutrient loss during thermal processing become a significant concern. The goal of this research was to examine the impact of distinct frying techniques, including deep frying (DF), air frying (AF), and vacuum frying (VF), on the nutritional, textural and flavor characteristics of oysters. The VF method demonstrated superior retention of beneficial properties and flavor, and reduced protein and lipid oxidation compared to the DF and AF methods. Furthermore, proteomic analysis of oysters was attempted to explain the molecular mechanisms governing the influence of key differential proteins. 20 major differential proteins, including actin-2 protein, tryptophan 2,3-dioxygenase and 1-alph, involved in oyster protein oxidation were identified, annotated and analyzed to elucidate their influence mechanisms. This research provides a deeper understanding of intricate interactions between frying techniques and oyster biochemistry, which offers valuable implications for enhancing food quality in seafood industry.

The cytochrome P450 (CYP) gene superfamily plays a significant role in various physiological processes, producing different compounds such as hormones, fatty acids, and biomolecules. However, little information is known their roles during gonad development in Pacific oyster (Crassostrea gigas). In this study, total of 116 CgCYP (Crassostrea gigas cytochrome P450) genes were identified and their expression pattern was analyzed for the first time. The relative molecular weights of these CgCYP genes ranged from 63.52 to 113.41 kDa, and the length of encoded amino acids ranged from 103 to 993. And total 26 cis-acting elements of these CgCYP genes were identified. GO and KEGG enrichment analysis showed some CgCYP genes are essential for the metabolism of male and female sex hormones. Additionally, expression anslysis showed 69 CgCYP genes were over-expressed in early gonad development and triploid infertile individuals. More importantly, expression levels of CgCYP1, CgCYP15, CgCYP34, CgCYP46, CgCYP69, CgCYP87, CgCYP88, and CgCYP103, were found to be significantly higher in female gonad, suggesting their important roles in female gonad development. The results of this study will provide a better understanding of the CgCYP genes in the gonad development of Pacific oyster.

This study exposed adult Sydney rock oysters, of either sex or both, to the synthetic estrogen 17α-ethinylestradiol (EE2) at 50 ng/L for 21 days, followed by an examination of developmental endpoints and transcriptomic responses in unexposed larvae. Reduced survival was observed at 1 day post-fertilisation (dpf) in larvae from bi-parental exposure (FTMT). Motile larvae at 2 dpf were fewer from maternal (FTMC), paternal (FCMT), and FTMT exposures. Additionally, shell length at 7 dpf decreased in larvae from FTMC and FTMT parents. RNA sequencing (RNA-seq) revealed 1064 differentially expressed genes (DEGs) in 1-dpf larvae from FTMT parents, while fewer DEGs were detected in larvae from FTMC and FCMT parents, with 258 and 7, respectively. GO and KEGG analyses showed significant enrichment of DEGs in diverse terms and pathways, with limited overlap among treatment groups. IPA results indicated potential inhibition of pathways regulating energy production, larval development, transcription, and detoxification of reactive oxygen species in FTMT larvae. qRT-PCR validation confirmed significant downregulation of selected DEGs involved in these pathways and relevant biological processes, as identified in the RNA-seq dataset. Overall, our results suggest that the intergenerational toxicity of EE2 is primarily maternally transmitted, with bi-parental exposure amplifying these effects.

Cypermethrin (CP) is a neurotoxic insecticide found accumulated in oysters, one of the most commonly consumed seafoods, posing potential health risks to the human body. We designed a gastrointestinal tracing method allowing for accurate quantification of the propulsion of chyme and further established the mouse in vivo digestion model to explore the behavior of CP in the digestion of raw, steamed, and roasted oysters. The results showed that bioaccumulation of CP in oysters may be accompanied by the biotransformation of CP. Thermal processing decreased both the CP content in oysters and its bioaccessibility. The small intestine is the main site for CP digestion and absorption. The cis-isomers of CP might finally accumulate in the body at a higher ratio and further become the predominant configuration for toxic effects. Taken together, the study contributes to the risk assessment of the dietary exposure of CP from aquatic products.

Osteoporosis is a major public health problem with an urgent need for safe and effective therapeutic interventions. The process of shell formation in oysters is similar to that of bone formation in mammals, and oyster extracts have been proven to exert osteoprotective effects. Oyster mantle is the most crucial organ regulating shell formation, in which exosomes play an important role. However, the effects of oyster mantle-derived exosomes (OMEs) on mammalian osteoporosis and the underlying mechanisms remain unknown. The OMEs investigated herein was found to carry abundant osteogenic cargos. They could also survive hostile gastrointestinal conditions and accumulate in the bones following oral administration. Moreover, they promoted osteoblastic differentiation and inhibited osteoclastic differentiation simultaneously. Further mechanistic examination revealed that OMEs likely promoted osteogenic activity by activating PI3K/Akt/β-catenin pathway in osteoblasts and blunted osteoclastic activity by inhibiting NF-κB pathway in osteoclasts. These favorable pro-osteogenic effects of OMEs were also corroborated in a rat femur defect model. Importantly, oral administration of OMEs effectively attenuated bone loss and improved the bone microstructure in ovariectomy-induced osteoporotic mice, and demonstrating excellent biosafety. The mechanistic insights from our data support that OMEs possess promising therapeutic potential against osteoporosis.

The molluscan family Ostreidae, commonly known as oysters, is an important molluscan group due to its economic and ecological importance. In recent years, an abundance of genomic data of Ostreidae species has been generated and available in public domain. However, there is still a lack of a high-efficiency database platform to store and distribute these data with comprehensive tools. In this study, we developed an oyster genome database (OysterDB) to consolidate oyster genomic data. This database includes eight oyster genomes and 208,923 protein-coding gene annotations. Bioinformatic tools, such as BLAST and JBrowse, are integrated into the database to provide a user-friendly platform for homologous sequence searching, visualization of genomes, and screen for candidate gene information. Moreover, OysterDB will be continuously updated with ever-growing oyster genomic resources and facilitate future studies for comparative and functional genomic analysis of oysters ( http://oysterdb.com.cn/ ).

Hot air drying (HAD) is an extensive method used on oysters and it causes the most intuitive change, a color change. However, the mechanism of color change remains unclear. This study showed that oysters underwent browning during the HAD process. The colorimetric parameter L* decreased while a* and b* increased, all of which were well described by the first-order color kinetic model. Mechanistically, the HDA process induced the oxidative browning of phenols and the generation of Maillard reaction products (5-hydroxymethylfurfural and hydrophilic pyrrole). Meanwhile, the HAD process caused lipid oxidation, leading to the reduction of phosphatidylethanolamine and the generation of reactive carbonyl compounds (aldehydes and α-dicarbonyl compounds). Moreover, the accumulation of hydrophobic pyrroles, a lipid-induced Maillard-like reaction product, was observed. These results suggest that, in addition to phenolic oxidation, sugar- and amino acid-mediated non-enzymatic browning reactions, lipid-mediated Maillard-like reactions play important roles in oyster darkening during the HAD process.

The traceability of geographic origin is essential for guaranteeing the quality, safety, and protection of oyster brands. However, the current outcomes of traceability lack credibility as they do not adequately explain the model\'s predictions. Consequently, we conducted a study to evaluate the efficacy of utilizing explainable machine learning combined with mineral elements analysis. The study findings revealed that 18 elements have the ability to determine regional orientation. Simultaneously, individuals should pay closer attention to the potential risks associated with oyster consumption due to the regional differences in essential and toxic elements they contain. Light gradient boosting machine (LightGBM) model exhibited indistinguishable performance, achieving flawless accuracy, precision, recall, F1 score and AUC, with values of 96.77%, 96.43%, 98.53%, 97.32% and 0.998, respectively. The SHapley Additive exPlanations (SHAP) method was used to evaluate the output of the LightGBM model, revealing differences in feature interactions among oysters from different provinces. Specifically, the features Na, Zn, V, Mg, and K were found to have a significant impact on the predictive process of the model. Consistent with existing research, the use of explainable machine learning techniques can provide insights into the complex connections between important product attributes and relevant geographical information.

There is growing evidence that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contaminates the marine environment and is bioaccumulated in filter-feeding shellfish. Previous study shows the Pacific oyster tissues can bioaccumulate the SARS-CoV-2, and the oyster heat shock protein 70 (oHSP70) may play as the primary attachment receptor to bind SARS-CoV-2\'s recombinant spike protein S1 subunit (rS1). However, detailed information about the interaction between rS1 and oHSP70 is still unknown. In this study, we confirmed that the affinity of recombinant oHSP70 (roHSP70) for rS1 (KD = 20.4 nM) is comparable to the receptor-binding affinity of rACE2 for rS1 (KD = 16.7 nM) by surface plasmon resonance (SPR)-based Biacore and further validated by enzyme-linked immunosorbent assay (ELISA). Three truncated proteins (roHSP70-N/C/M) and five mutated proteins (p.I229del, p.D457del, p.V491_K495del, p.K556I, and p.ΣroHSP70) were constructed according to the molecular docking results. All three truncated proteins have significantly lower affinity for rS1 than the full-length roHSP70, indicating that all three segments of roHSP70 are involved in binding to rS1. Further, the results of SPR and ELISA showed that all five mutant proteins had significantly lower affinity for rS1 than roHSP70, suggesting that amino acids at these sites are involved in binding to rS1. This study provides a preliminary theoretical basis for the bioaccumulation of SARS-CoV-2 in oyster tissues or using roHSP70 as the capture unit to selectively enrich virus particles for detection.