Linxi Yuan

Background: Lactoferrin (LF) is a multifunctional glycoprotein that can regulate lipid metabolism, lower cholesterol, reduce body weight, and prevent atherosclerosis. Bile acid (BA) metabolism plays an important role in removing excess cholesterol from the body. However, studies on the effects of LF on BA metabolism are limited and inconsistent. Methods: Male C57BL/6J mice aged 6–8 weeks were fed with a normal diet (control group), high-fat/high-cholesterol diet containing cholate (HFCCD group), or HFCCD and 1.0% LF in drinking water (LF group) for 8 weeks. Serum and hepatic lipid profiles, and glucose tolerance were measured. Fecal BA composition was determined through ultra-high performance liquid chromatography–tandem mass spectrometry. The gene expression of BA synthase in the liver and farnesoid X receptor (FXR)-mediated BA negative feedback regulation pathway in the liver and ileum were analyzed via RNA analysis. Results: HFCCD resulted in abnormal cholesterol levels in the serum and liver. LF intervention significantly increased the serum high-density lipoprotein cholesterol level by 24.9% and decreased the hepatic total cholesterol content by 26%. LF treatment significantly increased the BA content per gram by 109.8%, the total amount of BA excretion by 153.5% and conjugated BAs by 87.6% in the feces. Furthermore, LF upregulated the expression of the hepatic sterol 12α-hydroxylase (CYP8B1) gene, which expresses important enzymes in the classical pathway of BA synthesis, and the bile acid-CoA amino acid N-acetyltransferase (BAAT) gene, which is responsible for the formation of conjugated BAs. The FXR-mediated pathways in the enterohepatic axis, including FXR, fibroblast growth factor 15, and fibroblast growth factor receptor 4, were inhibited by LF. Conclusions: LF ameliorated hepatic cholesterol deposition in mice fed with a high-fat and high cholesterol diet containing cholate. LF elevated the conjugated BA level, inhibited the ileum FXR and FXR-mediated enterohepatic axis, and increased BA synthesis and excretion.

The present study investigated the beneficial role of selenium (Se) in protecting oilseed rape (Brassica napus L.) plants from cadmium (Cd+2) and lead (Pb+2) toxicity. Exogenous Se markedly reduced Cd and Pb concentration in both roots and shoots. Supplementation of the medium with Se (5, 10 and 15 mg kg-1) alleviated the negative effect of Cd and Pb on growth and led to a decrease in oxidative damages caused by Cd and Pb. Furthermore, Se enhanced superoxide free radicals (O2-), hydrogen peroxide (H2O2) and lipid peroxidation, as indicated by malondialdehyde (MDA) accumulation, but decreased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. Meanwhile, the presence of Cd and Pb in the medium affected Se speciation in shoots. The results suggest that Se could alleviate Cd and Pb toxicity by preventing oxidative stress in oilseed rape plant.

Selenium (Se) has important benefits for crop growth and stress tolerance at low concentrations. However, there is very little information on antimicrobial effect of selenium against the economically important fungus Botrytis cinerea. In the present study, using sodium selenite as Se source, we investigated the effect of Se salts on spore germination and mycelial growth of the fungal pathogen in vitro and gray mould control in harvested tomato fruit. Se treatment at 24 mg/L significantly inhibited spore germination of the fungal pathogen and effectively controlled gray mould in harvested tomato fruit. Se treatment at 24 mg/L seems to induce the generation of intracellular reactive oxygen species in the fungal spores. The membrane integrity damage was observed with fluorescence microscopy following staining with propidium iodide after treatment of the spores with Se. These results suggest that Se has the potential for controlling gray mould rot of tomato fruits and might be useful in integrated control against gray mould disease of postharvest fruits and vegetables caused by B. cinerea. The mechanisms by which Se decreased gray mould decay of tomato fruit may be directly related to the severe damage to the conidia plasma membrane and loss of cytoplasmic materials from the hyphae.

Selenium (Se) is an essential trace element for humans and animals but at high concentrations, Se becomes toxic to organisms due to Se replacing sulfur in proteins. Selenium biofortification is an agricultural process that increases the accumulation of Se in crops, through plant breeding, genetic engineering, or use of Se fertilizers. Selenium phytoremediation is a green biotechnology to clean up Se-contaminated environments, primarily through phytoextraction and phytovolatilization. By integrating Se phytoremediation and biofortification technologies, Se-enriched plant materials harvested from Se phytoremediation can be used as Se-enriched green manures or other supplementary sources of Se for producing Se-biofortified agricultural products. Earlier studies primarily aimed at enhancing efficacy of phytoremediation and biofortification of Se based on natural variation in progenitor or identification of unique plant species. In this review, we discuss promising approaches to improve biofortification and phytoremediation of Se using knowledge acquired from model crops. We also explored the feasibility of applying biotechnologies such as inoculation of microbial strains for improving the efficiency of biofortification and phytoremediation of Se. The key research and practical challenges that remain in improving biofortification and phytoremediation of Se have been highlighted, and the future development and uses of Se-biofortified agricultural products in China has also been discussed.

An ancient wood layer dated at about 5600 yr BP by accelerator mass spectrometry (AMS) ¹⁴C was discovered in an intertidal zone of the East China Sea. Extensive and horizontally stratified sediments with black color on the top and yellowish-red at the bottom, and some nodule-cemented concretions with brown surface and black inclusions occurred in this intertidal zone. Microscale analysis methods were employed to study the microscale characterization and trace element distribution in the stratified sediments and concretions. Light microscopy, scanning electron microscopy (SEM) and backscattered electron imaging (BSE) revealed the presence of different coatings on the sand grains. The main mineral compositions of the coatings were ferrihydrite and goethite in the yellowish-red parts, and birnessite in the black parts using X-ray powder diffraction (XRD). SEM observations showed that bacteriogenic products and bacterial remnants extensively occurred in the coatings, indicating that bacteria likely played an important role in the formation of ferromanganese coatings. Post-Archean Australian Shale (PAAS)-normalized middle rare earth element (MREE) enrichment patterns of the coatings indicated that they were caused by two sub-sequential processes: (1) preferentially release of Fe-Mn from the beach rocks by fermentation of ancient woods and colloidal flocculation in the mixing water zone and (2) preferential adsorption of MREE by Fe-Mn oxyhydroxides from the seawater. The chemical results indicated that the coatings were enriched with Sc, V, Cr, Co, Ni, Cu, Zn, Ba, especially with respect to Co, Ni. The findings of the present study provide an insight in the microscale features of ferromanganese coatings and the Fe-Mn biogeochemical cycling during the degradation of buried organic matter in intertidal zones or shallow coasts.

A novel selenium- (Se-) hyperaccumulating plant,Cardamine hupingshanesis, accumulating Se as a form of SeCys₂, was discovered in Enshi, Hubei, China, which could not be explained by present selenocysteine methyltransferase (SMT) theory. However, it is interesting to investigate if rhizosphere bacteria play some roles during SeCys₂accumulation. Here, one Se-tolerant rhizosphere strain,Microbacterium oxydans, was isolated fromC. hupingshanesis. Phylogenetic analysis and 16S rRNA gene sequences determined the strain as a kind of Gram positive bacillus and belonged to the familyBrevibacterium frigoritolerans. Furthermore, Se tolerance test indicated the strain could grow in extreme high Se level of 15.0 mg Se L⁻¹. When exposed to 1.5 mg Se L⁻¹, SeCys₂was the predominant Se species in the bacteria, consistent with the Se species inC. hupingshanesis. This coincidence might reveal that this strain played some positive effect in SeCys₂accumulation ofC. hupingshanesis. Moreover, when exposed to 1.5 mg Se L⁻¹or 15.0 mg Se L⁻¹, As absorption diminished in the logarithmic phase. In contrast, As absorption increased when exposed to 7.5 mg Se L⁻¹, indicating As metabolism processes could be affected by Se on this strain. The present study provided a sight on the role of rhizosphere bacteria during Se accumulation for Se-hyperaccumulating plant.