Optimizing preparation of low-NaCl protein gels from goose meat and understanding synergistic effects of pH/NaCl in improving gel characteristics.

This study explored the feasibility of partially substituting NaCl with MgCl2 in preparing gel products from goose meat. Furthermore, the effects of synergistic interaction between different pH levels and NaCl concentrations on the structure and characteristics of the gels were explored by analyzing their secondary structure, microstructure, and water-distribution properties. The results showed that NaCl could be partially substituted by MgCl2, with the optimal preparation conditions: NaCl (0.83 mol/L), pH (7.3), MgCl2 (0.04 mol/L), heating temperature (79 °C), heating time (20 min), and solid-liquid ratio (1:3). Furthermore, the pH had a more significant impact on the gels' structure and characteristics than did NaCl concentration. Thus, our optimized method can reduce the usage of NaCl in the gel products while at the same time improving the characteristics of gel products under low-NaCl conditions by lowering pH, laying a solid theoretical foundation for producing low-NaCl protein gel products from goose meat.

Immune dysfunction mediated by the competitive endogenous RNA network in fetal side placental tissue of polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS), a common endocrine and metabolic disorder affecting women in their reproductive years. Emerging evidence suggests that the maternal-fetal immune system is crucial for proper pregnancy. However, whether immune function is altered at the end of pregnancy in PCOS women and the underlying molecular mechanisms is currently unexplored. Herein, the basic maternal immune system was investigated (n = 136 in the control group; n = 103 in the PCOS group), and whole-transcriptome sequencing was carried out to quantify the mRNAs, miRNAs, and lncRNAs expression levels in fetal side placental tissue of women with PCOS. GO, KEGG, and GSEA analysis were employed for functional enrichment analysis. The process of identifying hub genes was conducted utilizing the protein-protein interaction network. CIBERSORT and Connectivity Map were deployed to determine immune cell infiltration and predict potential drugs, respectively. A network of mRNA-miRNA-lncRNA was constructed and then validated by qRT-PCR. First, red blood cell count, neutrophil count, lymphocyte count, hypersensitive C-reactive protein, and procalcitonin were significantly elevated, while placental growth factor was hindered in PCOS women. We identified 308 DEmRNAs, 77 DEmiRNAs, and 332 DElncRNAs in PCOS samples. Functional enrichment analysis revealed that there were significant changes observed in terms of the immune system, especially the chemokine pathway. Eight genes, including FOS, JUN, EGR1, CXCL10, CXCR1, CXCR2, CXCL11, and CXCL8, were considered as hub genes. Furthermore, the degree of infiltration of neutrophils was dramatically decreased in PCOS tissues. In total, 57 ceRNA events were finally obtained, and immune-related ceRNA networks were validated. Some potential drug candidates, such as enalapril and RS-100329, could have a function in PCOS therapy. This study represents the inaugural attempt to evaluate the immune system at the end of pregnancy and placental ceRNA networks in PCOS, indicating alterations in the chemokine pathway, which may impact fetal and placental growth, and provides new therapy targets.

Three-axis angle measurement method based on an optical wedge.

A three-axis angle measurement method is proposed using an optical wedge as a reflector. In this paper, the mathematical model of three-axis angle solving corresponding to the method is derived, and it is verified and corrected by establishing an optical simulation model, and, finally, the feasibility and measurement accuracy of the method are verified by using a principle prototype. The experimental results show that the RMS values of the measurement errors of pitch angle α, yaw angle ß, and roll angle γ are 6.27 ' ' , 4.35 ' ' , and 17.68 ' ' , respectively, within the measurement range of ±2∘, and the measurement accuracy is insensitive to the measurement distance.

Sweet taste receptors play roles in artificial sweetener-induced enhanced urine output in mice.

Sweet taste receptors found in oral and extra oral tissues play important roles in the regulation of many physiological functions. Studies have shown that urine volume increases during the lifetime exposure to artificial sweeteners. However, the detailed molecular mechanism and the general effects of different artificial sweeteners exposure on urine volume remain unclear. In this study, we investigated the relationship between urinary excretion and the sweet taste receptor expression in mice after three artificial sweeteners exposure in a higher or lower concentration via animal behavioral studies, western blotting, and real-time quantitative PCR experiment in rodent model. Our results showed that high dose of acesulfame potassium and saccharin can significantly enhance the urine output and there was a positive correlation between K+ and urination volume. The acesulfame potassium administration assay of T1R3 knockout mice showed that artificial sweeteners may affect the urine output directly through the sweet taste signaling pathway. The expression of T1R3 encoding gene can be up-regulated specifically in bladder but not in kidney or other organs we tested. Through our study, the sweet taste receptors, distributing in many tissues as bladder, were indicated to function in the enhanced urine output. Different effects of long-term exposure to the three artificial sweeteners were shown and acesulfame potassium increased urine output even at a very low concentration.

The effective compounds and mechanisms of Cang-Fu-Dao-Tan Formula in treating polycystic ovary syndrome based on UPLC/Q-TOF-MS/MS, network pharmacology and molecular experiments.

BACKGROUND: Polycystic ovary syndrome (PCOS), as a common endocrine disease in reproductive-age women, which is characterized by both reproductive and metabolic disorders. Cang-Fu-Dao-Tan Formula (CFDTF) is an effective and relatively safe treatment for PCOS. However, the underlying mechanism is poorly understood. PURPOSE: To explore the effective compounds and mechanisms of CFDTF in treating PCOS based on UPLC/Q-TOF-MS/MS, network pharmacology and molecular experiments. METHODS: The UPLC/Q-TOF-MS/MS and TCMSP, SwissTargetPrediction databases were used to identify the active ingredients of CFDTF. Then GeneCards, Disgenet, Drugbank databases were used to obtain the PCOS related targets. Based above, the Drug-component-target (D-C-T) network and protein-protein-interaction (PPI) network were built to analysis the key targets. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis were performed to find the potential mechanisms. Finally, molecular docking analysis, molecular dynamics (MD) simulations and molecular experiments were used to confirm the interactions among the active compounds, targets and explore the potential mechanisms. RESULTS: A total of 20 compounds were identified by UPLC/Q-TOF-MS/MS, and 136 active compounds by TCMSP from CFDTF. After removing the duplicate results, there were 370 targets related to both CFDTF and PCOS, among which, MAPK3, AKT1, RELA, EGF, TP53 and MYC were proved to have high interactions with the components. The mechanisms of CFDTF against PCOS were related to PI3K-Akt, mTOR, MAPK signaling pathways, and the in vitro experiments proved that the CFDTF positively regulated the cell proliferation and inhibited the apoptosis levels in PCOS cell model. CONCLUSIONS: The combination of UPLC/Q-TOF-MS/MS, systematic network pharmacology and molecular experiments identified that the quercetin, hesperidin, and glycyrrhizin disaccharide are the TOP 3 effective compounds of CFDTF in treating PCOS and the potential mechanisms may involve in regulating proliferation and apoptosis of granulosa cells.

Dietary Cholesterol Requirements of Large Red Swamp Crayfish (Procambarus clarkii).

To investigate the dietary cholesterol requirements of large red swamp crayfish (Procambarus clarkii), crayfish (initial body weight: 13.49 ± 0.22 g) were hand-fed six diets containing 2.47 (C0), 4.27 (C1), 6.80 (C2), 8.77 (C3), 11.74 (C4), and 14.24 (C5) g/kg cholesterol. After 8 weeks of feeding, the maximum weight gain rate and specific growth rate occurred in group C4. The lowest feed conversion ratio was observed in group C3. Total flesh percentage increased significantly by 15.33% in group C2 compared to group C0. The increase in dietary cholesterol resulted in significant quadratic trends in concentrations of crude protein and lipid in muscle and whole body; cholesterol and free fatty acid in hemolymph, hepatopancreas, and muscle; activities of lipase and amylase in hepatopancreas and intestine; and total antioxidant capacity and catalase activity in hepatopancreas. Group C3 experienced a noteworthy increase in hemolymph glucose and total protein content compared to group C0. Additionally, malondialdehyde content and superoxide dismutase activity in hepatopancreas displayed significant linear and quadratic trends. The optimal dietary cholesterol level for large P. clarkii is between 7.42 and 10.93 g/kg, as revealed by the quadratic regression analysis.

Contribution of labor related gene subtype classification on heterogeneity of polycystic ovary syndrome.

OBJECTIVE: As one of the most common endocrine disorders in women of reproductive age, polycystic ovary syndrome (PCOS) is highly heterogeneous with varied clinical features and diverse gestational complications among individuals. The patients with PCOS have 2-fold higher risk of preterm labor which is associated with substantial infant morbidity and mortality and great socioeconomic cost. The study was designated to identify molecular subtypes and the related hub genes to facilitate the susceptibility assessment of preterm labor in women with PCOS. METHODS: Four mRNA datasets (GSE84958, GSE5090, GSE43264 and GSE98421) were obtained from Gene Expression Omnibus database. Twenty-eight candidate genes related to preterm labor or labor were yielded from the researches and our unpublished data. Then, we utilized unsupervised clustering to identify molecular subtypes in PCOS based on the expression of above candidate genes. Key modules were generated with weighted gene co-expression network analysis R package, and their hub genes were generated with CytoHubba. The probable biological function and mechanism were explored through Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis. In addition, STRING and Cytoscape software were used to identify the protein-protein interaction (PPI) network, and the molecular complex detection (MCODE) was used to identify the hub genes. Then the overlapping hub genes were predicted. RESULTS: Two molecular subtypes were found in women with PCOS based on the expression similarity of preterm labor or labor-related genes, in which two modules were highlighted. The key modules and PPI network have five overlapping five hub genes, two of which, GTF2F2 and MYO6 gene, were further confirmed by the comparison between clustering subgroups according to the expression of hub genes. CONCLUSIONS: Distinct PCOS molecular subtypes were identified with preterm labor or labor-related genes, which might uncover the potential mechanism underlying heterogeneity of clinical pregnancy complications in women with PCOS.

The Association Between Polycystic Ovary Syndrome and Metabolic Syndrome in Adolescents: a Systematic Review and Meta-analysis.

The association between polycystic ovary syndrome (PCOS) and metabolic syndrome (MetS) is not widely recognized or properly assessed in adolescents. The aim of this study was to conduct a systematic review and meta-analysis to provide reliable results concerning MetS development in adolescents with PCOS. We searched studies published in PubMed, Medline, and Web of Science from January 2010 to December 2020. The quality of studies was assessed by the Newcastle-Ottawa Scale (NOS), and the data analysis was performed with Stata 14.0. Twelve articles were finally included in the systematic review and meta-analysis. The results suggested that adolescents with PCOS have more than three times the odds of having MetS than controls (OR 3.32, 95% CI [2.14, 5.14]). Obese adolescents with PCOS also had a higher risk of MetS than those with obesity but without PCOS (OR 3.97, 95% CI [1.49, 10.53]). Compared to those without PCOS, systolic blood pressure was higher in adolescents with PCOS (weighted mean difference (WMD) 3.85, 95% CI [1.73, 5.97]), while diastolic blood pressure was higher only in girls with PCOS who had a normal weight (WMD 3.52, 95% CI [1.57, 5.48]). The levels of triglycerides were higher in obese adolescents with PCOS than in those with obesity but without PCOS (WMD 27.84, 95% CI [10.16, 45.51]). PCOS could increase the frequency of MetS by influencing blood pressure and lipid metabolism independent of obesity as early as the adolescent period. Thus, clinicians should perform early interventions in adolescents with PCOS and follow up the relevant indicators of MetS to decrease the risk of poor long-term prognosis.

Physicochemical characteristics and gel-forming properties of mandarin fish (Siniperca chuatsi) protein during the fish fermentation with Lactobacillus sake SMF-L5: The formation of garlic-cloves shaped protein gel.

Mandarin fish (Siniperca chuatsi) during fermentation presents a unique elastic texture. In this investigation, the physicochemical and gel-forming properties of fish proteins were evaluated to explain the formation of elastic characteristics. During fermentation, the combined effects of acidification by Lactobacillus sake SMF-L5, increased sodium chloride, and decreased moisture content in the fish protein generated a suitable microenvironment for gelation. The mass transfer of sodium chloride was accompanied by NMR relaxation of the immobilized water. The ripening fermented fish had a functionally available MHC, a higher fractal dimension, and a stable α-helical structure. Also, it exhibited excellent gel-forming performances, mainly including garlic-cloves shaped protein gel, stronger springiness, and enhanced L* and whiteness. Correlation analysis showed that the gel's physical properties were differently related to the protein's physicochemical characteristics except for total free amino acids. These results could lay a theoretical foundation for the gel formation mechanism of fermented mandarin fish.

Metabolic differences in women with premature ovarian insufficiency: a systematic review and meta-analysis.

OBJECTIVE: This review aimed to investigate the metabolic profile of women with premature ovarian insufficiency (POI) compared relative to women with normal ovarian functioning. METHODS: A systematic search of PubMed, EMBASE, and the Web of Science for observational studies published up until the 6th of July 2021 that compared the metabolic profile of POI women with a healthy control group were assessed. Mean differences (MD) and 95% confidence interval (CI) were pooled using the fixed or random effect models. RESULTS: A total of 21 studies involving 1573 women with POI and 1762 control women were included. POI patients presented significantly higher waist circumference, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, and fasting glucose. Additionally, POI patients had marginally higher insulin level. However, the differences in systolic, and diastolic blood pressure were non-significant relative to the control group. CONCLUSIONS: POI is associated with alterations in certain metabolic parameters compared to control women. This finding highlights the importance of early screening and the lifelong management of metabolic health for women with POI.

A network pharmacology approach to explore active compounds and pharmacological mechanisms of a patented Chinese herbal medicine in the treatment of endometriosis.

OBJECTIVE: Endometriosis is a common benign disease in women of reproductive age. Qu's formula (QUF) is a patented Chinese herbal medicine for treating endometriosis that has been proven to be effective in treating and preventing the recurrence of endometriosis. This study is aimed to discover its molecular mechanism and to explore the potential drug targets. METHODS: A QUF target and endometriosis-related gene set was identified by the Traditional Chinese Medicine Systems Pharmacology (TCMSP) and Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM) databases and five disease-gene databases. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed, and a protein-protein interaction (PPI) network was established to discover the potential mechanism. MalaCards was searched for targets and signaling pathways related to endometriosis, and the search results were also used to identify the key factors in QUF. Molecular docking was performed to visualize the interactions between the effective molecules and proteins encoded by critical genes. Cell experiments and molecular dynamics (MD) simulations were used to further validate the therapeutic effects of the active compounds in QUF on endometriosis. RESULTS: A compound-target network with 117 nodes (94 genes and 23 active compounds) and 224 edges was generated. The results of GO and KEGG analyses indicated that QUF could act by regulating the immune response, apoptosis and proliferation, oxidative stress, and angiogenesis. VEGFA, CXCL8, CCL2, IL1B and PTGS2 were selected for molecular docking analysis from two critical subnetworks with high correlation scores in MalaCards, and the active compounds of QUF had binding potential and high affinity for them. The mRNA expression levels of CCL2, IL1B and PTGS2 significantly decreased after treatment with quercetin. MD simulations showed that the combinations of quercetin and these proteins were relatively stable. CONCLUSION: The network pharmacological strategy integrates molecular docking to unravel the molecular mechanism by which QUF protects against endometriosis. Our findings not only confirm the clinical effectiveness of QUF but also provide a foundation for further experimental study.

Association between circadian rhythm disruption and polycystic ovary syndrome.

OBJECTIVE: To explore the association of circadian rhythm disruption with polycystic ovary syndrome (PCOS) and the potential underlying mechanism in ovarian granulosa cells (GCs). DESIGN: Multicenter questionnaire-based survey, in vivo and ex vivo studies. SETTING: Twelve hospitals in China, animal research center, and research laboratory of a women's hospital. PATIENTS/ANIMALS: A total of 436 PCOS case subjects and 715 control subjects were recruited for the survey. In vivo and ex vivo studies were conducted in PCOS-model rats and on ovarian GCs collected from women with PCOS and control subjects. INTERVENTION(S): The PCOS rat model was established with the use of testosterone propionate. MAIN OUTCOME MEASURE(S): Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), RNA sequencing, rhythmicity analysis, functional enrichment analysis. RESULT(S): There was a significant correlation between night shift work and PCOS. PCOS-model rats presented distinct differences in the circadian variation of corticotropin-releasing hormone, adrenocorticotropic hormone, prolactin, and a 4-h phase delay in thyrotropic hormone levels. The motif enrichment analysis of ATAC-seq revealed the absence of clock-related transcription factors in specific peaks of PCOS group, and RNA sequencing ex vivo at various time points over 24 hours demonstrated the differential rhythmic expression patterns of women with PCOS. Kyoto Encyclopedia of Genes and Genomes analysis further highlighted metabolic dysfunction, including both carbohydrate and amino acid metabolism and the tricarboxylic acid cycle. CONCLUSION(S): There is a significant association of night shift work with PCOS, and genome-wide chronodisruption exists in ovarian GCs.

Molecular mechanisms underlying altered neurobehavioural development of female offspring of mothers with polycystic ovary syndrome: FOS-mediated regulation of neurotrophins in placenta.

BACKGROUND: This study explored the mechanisms underlying altered neurobehavioural development of female offspring born to mothers with polycystic ovary syndrome (PCOS). METHODS: In total, 20 women with PCOS and 32 healthy women who underwent caesarean deliveries with a single female foetus were recruited. Infants were assessed with Dubowitz scoring. Swan71 cell line with stable FOS overexpression was used to verify the regulatory effects of FOS on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) expression. Learning and memory in female first-generation (F1) and second-generation (F2) offspring in a rat model of PCOS was tested using the Morris water maze at puberty and adulthood. Transcriptome analysis of pubertal hippocampi and hypothalami of female F1 offspring was conducted. FINDINGS: Total score and behaviour subscales of Dubowitz scoring were significantly lower in female infants of women with PCOS. FOS and NGF protein levels were downregulated in placental villi of the PCOS group. FOS played a key role in BDNF inhibition and enhancing NGF in Swan71 cells. PCOS female F1 rats exhibited lower target crossing times during puberty when compared to controls. Transcriptome analysis revealed significant changes in hippocampal and hypothalamic neuronal pathways in female F1 rats at puberty. INTERPRETATION: FOS regulation of neurotrophins in the placenta negatively affects neurobehavioural development of female offspring of PCOS mothers. FUNDING: This study was funded by the National Key R&D Program of China (2018YFC1004900 to F.Q. and F.W.) and the National Natural Science Foundation of China (81874480 to F.Q.; 81873837 to F.W.).

Establishment and Analysis of a Combined Diagnostic Model of Polycystic Ovary Syndrome with Random Forest and Artificial Neural Network.

Polycystic ovary syndrome (PCOS) is one of the most common metabolic and reproductive endocrinopathies. However, few studies have tried to develop a diagnostic model based on gene biomarkers. In this study, we applied a computational method by combining two machine learning algorithms, including random forest (RF) and artificial neural network (ANN), to identify gene biomarkers and construct diagnostic model. We collected gene expression data from Gene Expression Omnibus (GEO) database containing 76 PCOS samples and 57 normal samples; five datasets were utilized, including one dataset for screening differentially expressed genes (DEGs), two training datasets, and two validation datasets. Firstly, based on RF, 12 key genes in 264 DEGs were identified to be vital for classification of PCOS and normal samples. Moreover, the weights of these key genes were calculated using ANN with microarray and RNA-seq training dataset, respectively. Furthermore, the diagnostic models for two types of datasets were developed and named neuralPCOS. Finally, two validation datasets were used to test and compare the performance of neuralPCOS with other two set of marker genes by area under curve (AUC). Our model achieved an AUC of 0.7273 in microarray dataset, and 0.6488 in RNA-seq dataset. To conclude, we uncovered gene biomarkers and developed a novel diagnostic model of PCOS, which would be helpful for diagnosis.

Artificial sweeteners affect the glucose transport rate in the Caco-2/NCI-H716 co-culture model.

BACKGROUND: Artificial sweeteners have been used widely as substitutes for sugar for several decades. In recent years they have been reported to be harmful to human health - especially to glucose absorption. However, as conclusions from previous studies using a single Caco-2 cell model were not consistent, further studies with a more suitable cell model are needed. RESULTS: We established a co-culture model with enterocyte Caco-2 and enteroendocrine NCI-H716 cell lines cultured in transwell inserts. The effects of artificial sweeteners, enhancing the glucose transport rate, lasted for 60 min and then began to diminish. Most importantly, different artificial sweeteners with the same sweetness intensity had similar effects on glucose transport. The sodium / glucose co-transporter member 1 (SGLT1) mRNA expression levels increased significantly with an initial glucose concentration of 20 mM, while glucose transporter 2 (GLUT2) mRNA expression significantly increased with initial glucose concentrations of 20 mM and 60 mM. CONCLUSION: Based on the Caco-2/NCI-H716 co-culture model, SGLT1 and GLUT2 mediated the enhancing effects of artificial sweeteners on glucose transport, depending on the sweetness intensity and initial glucose concentration.

Influence of peptide characteristics on their stability, intestinal transport, and in vitro bioavailability: A review.

In recent years, large amounts of peptides have been purified and characterized from food protein hydrolysates. Many of these peptides have been demonstrated to be of potential application as health-improving ingredients against plenty of disease conditions, such as cancer, inflammation, and cardiovascular disease. The real efficacy of functional application of these peptides depends on their stability, transport, and bioavailability in target tissues, which in turn depends on the peptides characteristics. Therefore, the characteristic-function parameters are crucial for peptides using as functional agents. This review article intends to summarize the effects of peptide characteristics, including molecular weight, charge and hydrophobicity, on their stability, intestinal transport, and in vitro bioavailability. PRACTICAL APPLICATIONS: In the near future, bioactive peptides will play important roles in the area of functional foods and pharmacy. However, the gastrointestinal digestion and transport usually restrict their bioavailability in vivo. Understanding the relationships between peptide characteristics and their digestion stability, bioavailability may provide guidance and theoretical basis for the further application of bioactive peptides.

A 4-miRNA signature act as a novel prognostic biomarker in patients with Sarcoma.

BACKGROUND: A sarcoma is a rare form of cancer that can develop throughout the body and has a poor prognosis. Micro RNA may be used as molecular markers in sarcoma patients to predict patient outcomes. METHODS: In this study, miRNA expression data of sarcoma tissues samples were downloaded from The Cancer Genome Atlas (TCGA) database. The univariable cox regression and log likelihood were performed to screen the miRNAs related with prognosis. The Cox proportional hazard regression model was used to establish a multi-gene prognostic model based on the expression value of the miRNAs. The survival curve was created by the KM method. The interaction network and function annotation of the target genes were analyzed to investigate the mechanism of the key miRNAs. RESULTS: Hsa-miR-190b, hsa-miR-3170, hsa-miR-4762, hsa-miR-18a were identified and used to establish the prediction model. The target genes of the 4 miRNAs were involved in cancer signaling pathways as revealed by KEGG. Cox regression analysis showed that the prognostic model of miRNA was an independent influencing factor in Sarcoma patients (P<0.05). Survival analysis confirmed that the overall survival rate of sarcoma patients with low risk scores was significantly higher than those with high risk scores (P<0.01). CONCLUSIONS: The miRNA prognosis model established in this study can be used to predict the prognosis of Sarcoma patients, and these 4 miRNAs may involve in cancer signaling pathways by regulating these target genes.

Sweetness-induced activation of membrane dipole potential in STC-1 taste cells.

The biological functions of cell membranes strongly influence the binding and transport of molecular species. We developed STC-1 cell line stably expressing the sweet taste receptor (T1R2/T1R3), and explored the possible correlation between sweeteners and membrane dipole potential of STC-1 cells. In this study, sweetener-induced dipole potential activation was elucidated using a fluorescence-based measurement technique, by monitoring the voltage sensitive probe Di-8-ANEPPS using a dual wavelength ratiometric approach. It indicated that the presence of sweeteners resulted in cell membrane dipole potential change, and interaction of artificial sweeteners with taste cells resulted in a greater reduction in potential compared with natural sweeteners. Our work presents a newly developed approach using a fluorescence-based measurement technique to study sweetener-induced dipole potential activation of STC-1 cells. This new approach could be used as a complementary tool to study the function of sweet taste receptors or other GPCRs and helps to understand the basis sweetness mechanism.

Charge properties of peptides derived from casein affect their bioavailability and cytoprotection against H2O2-induced oxidative stress.

The effects of charge properties of casein peptides on absorption stability, antioxidant activity, and cytoprotection were evaluated. Alcalase hydrolysates of casein were separated into 4 fractions by cation-exchange chromatography according to charge properties. After simulated digestion and Caco-2 cell transmembrane transport, we determined the total antioxidant capacity (Trolox equivalent antioxidative capacity and oxygen radical antioxidant activity) and nitrogen content of peptide fractions to estimate available antioxidant efficacy and bioavailability (BA) of peptides. Results showed that negatively charged peptide fractions had greater BA and antioxidant activities after digestion and absorption. The peptide permeates were used to test the cytoprotective effect against H2O2-induced oxidative damage in HepG-2 cells. All peptide permeates increased cell viability, elevated catalase activity, and decreased superoxide dismutase activity. However, negatively charged peptide fractions preserved cell viability to a greater degree. Therefore, the negatively charged peptides from casein may be potential antioxidants and could be used as ingredients in functional foods and dietary supplements.

Hydrophobicity exerts different effects on bioavailability and stability of antioxidant peptide fractions from casein during simulated gastrointestinal digestion and Caco-2 cell absorption.

Alcalase-treated casein hydrolysates were separated into three hydrophobic chromatography fractions (HC-F1, HC-F2 and HC-F3) using YMC ODS C18 column. Simulated gastrointestinal (GI) digestion (stage I digestion) and Caco-2 cell absorption (stage II digestion) were sequentially applied for producing corresponding digests and adsorbates of collected peptide fractions. ANS probe and reverse-phase (RP)-HPLC were applied to detect peptide hydrophobicity, whereas trolox equivalent antioxidant capacity and oxygen radical antioxidant capacity were used to determine their antioxidant activity. Peptide nitrogen was used to evaluate bioavailability (BA) and remaining peptide content. In addition, RP-HPLC and electrospray ionization mass spectrometry were performed to obtain peptide sequences. Results showed that high hydrophobic peptide fractions (HC-F3) had excellent BA and remaining antioxidant activity, but poor digestive stability in stage I digestion. Two peptides, NTVP and IV, were identified from the adsorbate of HC-F3 to be GI-resistant peptides. Therefore, utilizing high hydrophobic peptides from casein as potential functional foods or nutraceuticals was feasible.