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BackgroundsAs a systemic skeletal dysfunction, osteoporosis (OP) is characterized by low bone mass and bone microarchitectural damage. The global incidences of OP are high.MethodsData were retrieved from databases like Gene Expression Omnibus (GEO), GeneCards, Search Tool for the Retrieval of Interacting Genes/Proteins (STRING), Gene Expression Profiling Interactive Analysis (GEPIA2), and other databases. R software (version 4.1.1) was used to identify differentially expressed genes (DEGs) and perform functional analysis. The Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression and random forest algorithm were combined and used for screening diagnostic markers for OP. The diagnostic value was assessed by the receiver operating characteristic (ROC) curve. Molecular signature subtypes were identified using a consensus clustering approach, and prognostic analysis was performed. The level of immune cell infiltration was assessed by the Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm. The hub gene was identified using the CytoHubba algorithm. Real-time fluorescence quantitative PCR (RT-qPCR) was performed on the plasma of osteoporosis patients and control samples. The interaction network was constructed between the hub genes and miRNAs, transcription factors, RNA binding proteins, and drugs.ResultsA total of 40 DEGs, eight OP-related differential genes, six OP diagnostic marker genes, four OP key diagnostic marker genes, and ten hub genes (TNF, RARRES2, FLNA, STXBP2, EGR2, MAP4K2, NFKBIA, JUNB, SPI1, CTSD) were identified. RT-qPCR results revealed a total of eight genes had significant differential expression between osteoporosis patients and control samples. Enrichment analysis showed these genes were mainly related to MAPK signaling pathways, TNF signaling pathway, apoptosis, and Salmonella infection. RT-qPCR also revealed that the MAPK signaling pathway (p38, TRAF6) and NF-kappa B signaling pathway (c-FLIP, MIP1β) were significantly different between osteoporosis patients and control samples. The analysis of immune cell infiltration revealed that monocytes, activated CD4 memory T cells, and memory and naïve B cells may be related to the occurrence and development of OP.ConclusionsWe identified six novel OP diagnostic marker genes and ten OP-hub genes. These genes can be used to improve the prognostic of OP and to identify potential relationships between the immune microenvironment and OP. Our research will provide insights into the potential therapeutic targets and pathogenesis of osteoporosis.

Antifreeze peptides are a class of small molecule protein hydrolysates that protect frozen products from cold damage under freezing or subcooling conditions. In this study, three different Pseudosciaena crocea (P. crocea) peptides were from pepsin, trypsin, and neutral protease enzymatic hydrolysis. It aimed to elect the P. crocea peptides with better activity through molecular weight, antioxidant activity, and amino acid analysis, as well as to compare the cryoprotective effects with a commercial cryoprotectant. The results showed that the untreated fillets were prone to be oxidized, and the water-holding capacity after freeze-thaw cycle decreased. However, the treatment of the trypsin hydrolysate of P. crocea protein significantly promoted the water-holding capacity level and reduced the loss of Ca2+-ATP enzyme activity and the structural integrity damage of myofibrillar protein in surimi. Moreover, compared with 4% sucrose-added fillets, trypsin hydrolysate treatment enhanced the umami of frozen fillets and reduced the unnecessary sweetness. Therefore, the trypsin hydrolysate of P. crocea protein could be used as a natural cryoprotectant for aquatic products. Hence, this study provides technical support for its use as a food additive to improve the quality of aquatic products after thawing and provides a theoretical basis and experimental foundation for the in-depth research and application of antifreeze peptides.

Putrescine is a low-molecular-weight organic compound that is widely found in pickled foods. Although the intake of biogenic amines is beneficial to humans, an excessive intake can cause discomfort. In this study, the ornithine decarboxylase gene (ODC) was involved in putrescine biosynthesis. After cloning, expression and functional verification, it was induced and expressed in E. coli BL21 (DE3). The relative molecular mass of the recombinant soluble ODC protein was 14.87 kDa. The function of ornithine decarboxylase was analyzed by determining the amino acid and putrescine content. The results show that the ODC protein could catalyze the decarboxylation of ornithine to putrescine. Then, the three-dimensional structure of the enzyme was used as a receptor for the virtual screening of inhibitors. The binding energy of tea polyphenol ligands to the receptor was the highest at −7.2 kcal mol−1. Therefore, tea polyphenols were added to marinated fish to monitor the changes in putrescine content and were found to significantly inhibit putrescine production (p < 0.05). This study lays the foundation for further research on the enzymatic properties of ODC and provides insight into an effective inhibitor for controlling the putrescine content in pickled fish.