Gut Microbiota Control the Bioavailability and Metabolism of Organoarsenicals of Seaweeds in Mice after Oral Ingestion.

Edible seaweed consumption is an essential route of human exposure to complex organoarsenicals, including arsenosugars and arsenosugar phospholipids. However, the effects of gut microbiota on the metabolism and bioavailability of arsenosugars in vivo are unknown. Herein, two nori and two kelp samples with phosphate arsenosugar and sulfonate arsenosugar, respectively, as the predominant arsenic species, were administered to normal mice and gut microbiota-disrupted mice treated with the broad-spectrum antibiotic cefoperazone for 4 weeks. Following exposure, the community structures of the gut microbiota, total arsenic concentrations, and arsenic species in excreta and tissues were analyzed. Total arsenic excreted in feces and urine did not differ significantly between normal and antibiotic-treated mice fed with kelp samples. However, the total urinary arsenic of normal mice fed with nori samples was significantly higher (p < 0.05) (urinary arsenic excretion factor, 34-38 vs 5-7%), and the fecal total arsenic was significantly lower than in antibiotic-treated mice. Arsenic speciation analysis revealed that most phosphate arsenosugars in nori were converted to arsenobetaine (53.5-74.5%) when passing through the gastrointestinal tract, whereas a large portion of sulfonate arsenosugar in kelp was resistant to speciation changes and was excreted in feces intact (64.1-64.5%). Normal mice exhibited greater oral bioavailability of phosphate arsenosugar from nori than sulfonate arsenosugar from kelp (34-38 vs 6-9%). Our work provides insights into organoarsenical metabolism and their bioavailability in the mammalian gut.

Insights into Cryoprotective Roles of Carrageenan Oligosaccharides in Peeled Whiteleg Shrimp (Litopenaeus vannamei) during Frozen Storage.

The cryoprotective effects of carrageenan oligosaccharides on peeled whiteleg shrimp were investigated and compared with sodium pyrophosphate treatment during frozen storage, primarily the interaction mechanisms between oligosaccharides and shrimp myosin. Data revealed significant profitable effects on water-holding capacity and textural variables in oligosaccharide-treated shrimp compared to the control. Chemical analyses showed that these saccharides maintained a higher myofibrillar protein content and Ca2+-ATPase activity in frozen shrimp. Additionally, the hematoxylin and eosin staining results indicated that the saccharides significantly slowed the damage to muscle tissue structures. The assumption was that water replacement hypothesis played a leading role in cryoprotection of frozen shrimp. Furthermore, the homology modeling and molecular dynamics simulations confirmed that the saccharides substituted water molecules around the shrimp myosin surface by forming hydrogen bonds with polar residues of amino acids, thereby stabilizing the structures in the absence of water, leading to an increase in protein stability during frozen storage.

Cryoprotective roles of trehalose and alginate oligosaccharides during frozen storage of peeled shrimp (Litopenaeus vannamei).

Cryoprotective saccharides are widely accepted additives that reduce thawing loss, maintain texture, and retard protein denaturation in the frozen seafood. The present study aimed to investigate the roles of trehalose and alginate oligosaccharides on cryoprotection of frozen shrimp, primarily focusing on the interactions between myosin and saccharide molecules using a molecular dynamics (MD) simulation analysis. The results indicated that soaking in the trehalose and alginate oligosaccharides solutions markedly reduced thawing and cooking losses in frozen shrimp, with respective values decreasing to 6.02%, 8.14%, and 5.99%, 8.19% after 9weeks of storage, which were significantly lower than that of fresh water treatment (9.75% and 15.09%). Our assumption was that water replacement played a leading role in cryoprotection, as shown in previous experimental results and reports. Furthermore, homology modeling and MD simulations confirmed that trehalose and alginate oligosaccharides substituted the water molecules around the myosin surface by forming hydrogen bonds with polar residues of amino acids, thereby stabilizing the structures in the absence of water during frozen storage. These conditions affected the flexibility of particular amino acid residues, enhanced the residue cross correlations within the two chains of myosin, and also increased the total interaction energy between myosin and water/saccharide molecules, thereby leading to an increase in protein stability. Finally, by comparing the experimental results to that of MD simulation, significant positive correlation existed between saccharides and the stabilization of myosin in shrimp muscle. The findings of the present study may help better understand the cryoprotective mechanisms of saccharides in frozen shrimp, and the two saccharides may be potentially used as alternative additives in seafood to maintain better quality during frozen storage.