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Diabetic nephropathy (DN) is a primary diabetic complication ascribed to the pathological changes in renal microvessels. This study investigated the nuclear factor erythroid 2‐related factor 2 (Nrf2)/Kelch ECH associating protein (Keap1)/antioxidant response element (ARE) signaling pathway impact of chitooligosaccharides (COS) with a certain degree of polymerization (DP) on DN mouse models and high glucose‐damaged human kidney 2 (HK‐2) cells. The findings indicated that COS effectively reduced the renal function indexes (uric acid [UA], urinary albumin excretion rate [UAER], urine albumin‐to‐creatinine ratio [UACR], blood urea nitrogen [BUN], and creatinine [Cre]) of DN mice. It increased (p <.05) the superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), and catalase (CAT) antioxidant enzyme activity in the serum and kidneys, and decreased (p <.05) the malondialdehyde (MDA) content. The mechanistic investigation showed that COS significantly increased (p <.05) Nrf2 and downstream target gene (GCLM, GCLC, HO‐1, and NQO‐1) expression, and substantially decreased (p <.05) Keap1 expression. The protein level was consistent with the messenger RNA (mRNA) level in in vitro and in vivo models. The docking data indicated that COS and Keap1 protein binding included six hydrogen bond formation processes (Gly364, Arg415, Arg483, His436, Ser431, and Arg380). The COS intervention mechanism may be related to the Nrf2/Keap1/ARE antioxidant pathway. Therefore, it provides a scientific basis for COS application in developing special medical food for DN patients. [ABSTRACT FROM AUTHOR]

Summary: Chitooligosaccharides (COS) with different degree of polymerisation (DP) have different physiological activities such as anti‐tumour and anti‐hyperlipidemia activities. However, the digestive process might lead to the change of DP of COS as well as cause the change of physiological activities in vivo. In this study, two in vitro digestion models (static and dynamic) were used to investigate digestion behaviours of COS and the influencing factors during digestion with or without food matrix. The results showed that COS with DP 2–5 were indigestible and COS with DP 6–10 degraded with time during gastric and intestinal digestion. Pepsin, pancreatin and lipase were the main factors leading to degradation. Food matrix could protect COS with DP 6–10 from degradation during gastric digestion. However, the degradation of COS with DP 6–10 accelerated and the degradation of COS with DP 5 occurred during intestinal digestion with food matrix due to pancreatin, lipase and bile salt. [ABSTRACT FROM AUTHOR]

Chitooligosaccharides (COS) are multi-functional foods and nutrients and environmentally friendly biological abiotic-resistance inducing agents for plants. In the current study, the effects and possible mechanisms of COS on improving the cold resistance of rice (II YOU 1259) seedlings were investigated. Compared with the control, a COS pre-soaking treatment enhanced photosynthesis, reduced oxidation damage and led to accumulation of more osmotic regulation substances under chilling treatment. In addition, a novel Deg/HtrA family serine endopeptidase (DegQ) gene, related to COS enhanced rice cold resistance, was identified. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that transcription of DegQ and psbA (D1 protein encoding gene) were up-regulated in a time-dependent manner by COS treatment under cold stress. With increasing expression of the D1 protein, chlorophyll b content was enhanced correspondingly. The current results suggest that COS could enhance cold stress tolerance of rice by repairing the photodamaged photosystem II, altering osmotic regulation and reducing oxidation damage. [ABSTRACT FROM AUTHOR]

• The effect of COS on the microecology of NAFLD patients were evaluated. • Treated with COS, the microbial beta diversity of NAFLD patients was shifted. • The target microorganisms of COS were determined. • The differential metabolites of COS were related to the changes of microorganisms. Chitobiose (OC)and chitotriose (TOC)were used to simulate the in vitro fermentation of feces samples from nonalcoholic fatty liver disease (NAFLD) patients to evaluate their effects on gut microorganisms and metabolites. The results indicated that OC and TOC shifted the gut microbial community of NAFLD patients to that of healthy volunteers. Specifically, OC and TOC increased the relative abundance of Fusobacteria, while reducing Actinobacteria and the ratio of Firmicutes to Bacteroidetes. OC's targeted bacteria were Fusobacterium , Clostridium sensu stricto 13 and Parabacteroides , while TOC's targeted bacteria were Clostridium sensu stricto 1 , Enterococcus. The content of total short-chain fatty acids, propionic acid and butyric acid in the OC and TOC groups increased significantly, which was closely related to the increase in the abundance of the targeted flora. Although the non-targeted metabolites of OC and TOC had a high degree of similarity in the positive ion mode and a large difference in the negative ion mode. The up-regulated metabolites of the OC and TOC groups include bile acids (7-ketodeoxycholic acid, docosahexaenoic acid ethyl ester, deoxycholic acid, cholic acid), amino acids (succinyl proline, cys-tyr, L-β-leucine), antibiotics (fortimicin FU-10, kanoamine), and down-regulated metabolites include xanthine, hypoxanthine, L-glutamic acid, acetophenone, etc. The biomarker metabolites of OC and TOC may reveal the probiotic effect on gut microecological health on the biosynthesis of amino acids, butyric and bile acid metabolism pathways. The results can be helpful for the further development of COS as a functional food. [ABSTRACT FROM AUTHOR]

This study investigated the intervention effects of chitooligosaccharides (COS) on retinol metabolism and included comparisons of the retinol level, retinol binding protein 4 (RBP4) content, key genes, and protein expression between mice on a COS‐enriched diet and a normal diet. The results showed that COS markedly decreased the retinol and RBP4 concentrations in the serum and liver. Furthermore, COS suppressed the mRNA and protein expression of RBP4, cellular retinol binding protein 1 (CRBP1), lecithin: retinol acyltransferase (LRAT) and cytochrome P45026A1 (CYP26A1). In addition, COS inhibited the mRNA expression of stimulated by retinoic acid 6 (STRA6). However, the protein expression of STRA6 was not significantly decreased. Thus, COS reduced the retinol concentration in the serum and disrupted the metabolism of retinol. The intervention mechanism of COS on retinol metabolism may be attributed to the modulation of RBP4, CRBP1, LRAT, STRA6, and CYP26A1 expression at the mRNA and protein levels. Practical applications: Chitooligosaccharides (COS), known to be the degradation products of chitosan, have been found to induce pinkeye in industrial workers who participate in the manufacturing of COS. Meanwhile, 5% population with COS dietary supplement also have similar phenomenon. The aim of this study is to explore the possible mechanism underlay of this potential risk. The results of this study showed that high exposure to COS during manufacture influences retinol metabolism and leads to a decrease in retinol content, ultimately causing pinkeye. These findings provide new evidence for understanding COS‐induced retinol metabolism alteration and drawing attention toward the prevention of potential risk in high‐exposure populations. [ABSTRACT FROM AUTHOR]

Chitooligosaccharides (COS) is a kind of functional carbohydrates with great application potential as its various biological functions in food, cosmetics, and pharmaceutical fields. Exploring the relationship between structure and function of chitosanase is essential for the controllable preparation of chitooligosaccharides with the specific degree of polymerization (DP). GsCsn46A is a cold-adapted glycosyl hydrolase (GH) family 46 chitosanase with application potential for the controllable preparation of chitooligosaccharides. Here, we present two complex structures with substrate chitopentaose and chitotetraose of GsCsn46A, respectively. The overall structure of GsCsn46A contains nine α-helices and two β-strands that folds into two globular domains with the substrate between them. The unique binding positions of both chitopentaose and chitotetraose revealed two novel sugar residues in the negatively-numbered subsites of GH family 46 chitosanases. The structure–function analysis of GsCsn46A uncovers the substrate binding and catalysis mechanism of GH family 46 chitosanases. Structural basis mutagenesis in GsCsn46A indicated that altering interactions near +3 subsite would help produce hydrolysis products with higher DP. Specifically, the mutant N21W of GsCsn46A nearly eliminated the ability of hydrolyzing chitotetraose after long-time degradation. • Two complex structures with substrate chitopentaose and chitotetraose of GsCsn46A were determined, respectively. • Two novel sugar residues, −5 sugar residue and −4 subsite in negatively-numbered subsites of GsCsn46A were first reported. • The mutant N21W of GsCsn46A nearly abolished hydrolysis ability towards chitotetraose. [ABSTRACT FROM AUTHOR]

The nano drug delivery system (NDDS) has been extensively investigated for cancer treatment because of its ability to enhance drug efficacy. However, there are only a few studies attempting NDDS for AZD9291 (Osimertinib). Here, we encapsulated AZD9291 in chitooligosaccharides (COS)-modified poly (lactic- co -glycolic acid) (PLGA) nanoparticles. COS, a cationic polymer, was used to develop positively charged nanoparticles with good biological affinity. The prepared AZD-PLGA-COS NPs exhibited a smaller particle size (176.6 ± 0.4 nm), a positively charged surface (+18.65 ± 0.38 mV), and an increased cellular uptake. The IC 50 of H1975 cells was reduced by 45.90%, and the expression of p-EGFR, PARP, Bak, caspase-9, Bax, and Bcl-2 was regulated to promote cellular apoptosis. Furthermore, COS was found to inhibit the expression of immune checkpoint PD-L1. This study suggests that COS-modified PLGA nanoparticles with low toxicity and high encapsulation efficiency (EE) could potentially enhance drug efficacy. Unlabelled Image • AZD-PLGA-COS nanoparticles (NPs) were successfully prepared. • Modification of NPs with increased EE and a high positive charge. • AZD-PLGA-COS NPs enhanced the efficacy of the drug by promoting the cellular uptake. • COS inhibited PD-L1, thus, indicating its immunomodulatory potential. [ABSTRACT FROM AUTHOR]

Chitooligosaccharides (COS) are hydrolytic products of chitosan that are essential in functional food, medicine, and other fields due to their biological activities. Commercial COS are often prepared by the hydrolysis of chitosan by chitosanase. In this study, a glycoside hydrolase family 46 cluster B chitosanase from Bacillus amyloliquefaciens (BaCsn46B) was efficiently expressed in Pichia pastoris. The recombinant enzyme was secreted into the culture medium that reached a total extracellular protein concentration of 4.5 g/L with an activity of 8907.2 U/mL in a high cell density fermenter (5 L). The molecular mass of deglycosylated BaCsn46B was 29.0 kDa. Purified BaCsn46B exhibited excellent enzymatic properties, which had high specific activity (2380.5 U/mg) under optimal reaction conditions (55 °C and pH 6.5). BaCsn46B hydrolyzed chitosan yielded a series of COS with different degrees of polymerization by endo-type cleavage. The end hydrolytic products of BaCsn46B were chitobiose and chitotriose, while no monosaccharide yield was evident in the hydrolytic reaction. The excellent secreted expression level and hydrolytic performance make the enzyme a desirable biocatalyst for the industrial preparation of COS. • A high-activity chitosanase from B.amyloliquefaciens (BaCsn46B) was identified. • Eight surface amino acid residues affected the catalytic specificity of BaCsn46B. • BaCsn46B hydrolyzed chitosan to yield various of chitooligosaccharides. • BaCsn46B could be used for chitooligosaccharide large-scale preparation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The diffusion behavior of COS molecules within PEEK, PES, PSF, PVDF and PPTA membranes was investigated by MS. • The mechanism of interactions among the polymer chains, COS with different DP and water was first studied. • The mechanism of differences in the diffusion behavior of COS with different DP in polymeric membranes was elucidated. • Compared with other materials, PPTA was more beneficial to the precise separation of COS with different DP. The membrane separation technology with the advantage of cost-benefit, energy-efficient and ease to scale up, is promising to realize the industrialized separation of chitooligosaccharides (COS) to meet the industrial demands. While COS with different degree of polymerization (DP) have similar molecular size and physicochemical properties which hinders the precise separation of COS by the commercial membranes. Herein, molecular dynamics simulations were performed to explore the diffusion behavior of COS within PEEK, PES, PSF, PVDF and PPTA membranes, to provide a theoretical basis for the screening and development of novel polymeric membrane materials for precise separation of COS. The interaction among the COS, water, and the polymer chains were investigated by calculating diffusion coefficient, interaction energy, hydrogen bonding and radial distribution function. And the diffusion process of the COS within the five polymeric membranes was investigated. Results showed that the diffusion behavior of the COS within the polymeric membranes depended on the interactions among the polymer chain, COS and water, which determined by the DP of COS and the structural properties of the polymer chain. Compared with other four kinds of materials, the interaction between PPTA chain and COS molecules repressed the decline trend of the difference between the diffusion coefficients of COS with adjacent DP as the DP of COS increased, making PPTA the most beneficial to the precise separation of the COS with different DP. [ABSTRACT FROM AUTHOR]

Oral administration of chitooligosaccharides (COS) has been reported to alleviate colitis in mice. However, the mechanism of action of COS with specific polymerization degree on gut inflammation and metabolism remains unclear. This study aimed to investigate the effects of chitobiose (COS2), chitotetraose (COS4), and chitohexaose (COS6) on colitis, and to elucidate their underlying mechanisms. COS2, COS4, and COS6 were able to significantly alleviate colonic injury and inflammation levels. COS6 has the best anti-inflammatory effect. Furthermore, COS6 could down-regulate the level of indoleamine-2,3-dioxygenase1 (IDO1) and restore the levels of indole, indoleacetic-3-acid (IAA), and indole-3-carbaldehyde (I3A) in the cecum of chronic colitis mice (p < 0.05), thereby regulating tryptophan metabolism. In the aromatic hydrocarbon receptor-IL-22 (AHR-IL-22) pathway, although there were differences between chronic colitis and acute colitis mice, COS intervention could restore the AHR-IL-22 pathway to normal, promote the expression of MUC2, and repair the intestinal mucosal barrier. In conclusion, the results of this study suggested that COS had a good inhibitory effect on IDO1 under inflammation and the changes of AHR and IL-22 levels at different stages of disease development. This provides new insights into the potential use of COS as a functional food for improving intestinal inflammation and metabolism. [Display omitted] • Dosage and polymerization of chitooligosaccharides affect its activity in colitis. • Colonic aryl hydrocarbon receptor during acute colitis and remission periods varied. • Chitohexaose exhibited the most potent anti-inflammatory effect. • Chitohexaose significantly enhanced the production of intestinal indole-3-carbaldehyde. • The correlation between chitooligosaccharides dosage and polymerization-gut metabolism-colitis was established. [ABSTRACT FROM AUTHOR]

Abstract Chitooligosaccharides are widely used in functional food, medicaments and agriculture. Controllable conversion of chitosan to chitooligosaccharides with desired degree of polymerization (DP) is of great value. Herein, a novel glycoside hydrolase family 46 chitosanase (BaCsn46A) was cloned and expressed from Bacillus amyloliquefaciens. BaCsn46A exhibited good enzymatic properties with high specific activity (1031.2 U/mg) under optimal hydrolysis conditions of pH 6.0 and 50 °C. BaCsn46A is an endo-type chitosanase, which could be utilized to yield abundant chitooligosaccharides. Furthermore, the preparation of high degree of polymerization chitooligosaccharides (DP 5–10) was investigated by BaCsn46A in an enzymatic reactor with a subsequent series of membranes. The maximum concentration of total chitooligosaccharides (DP 2–10) was 28.11 g/L (93.70% yield). The proportion of high degree of polymerization chitooligosaccharides (DP 5–10) occupied 56.17% (w/w) of total chitooligosaccharides. This study provided a cleaner production process for the controllable preparation of chitooligosaccharides with specific degree of polymerization. Graphical abstract Image 1 Highlights • A high-activity chitosanase from B.amyloliquefaciens (BaCsn46A) was identified. • BaCsn46A could be used for controllable producing chitooligosaccharides in membrane reactor. • High degree polymerized chitooligosaccharides was accumulated by enzyme-membrane coupling process. • This study provided a cleaner production process for controllable producing chitooligosaccharides. [ABSTRACT FROM AUTHOR]

AZD9291 can prolong the survival of patients with non-small cell lung cancer. Unfortunately, resistance to AZD9291 is inevitable and hinders effectiveness. Studies showed the combination of Cyclosporin A (CsA) and AZD9291 could increase the efficacy of AZD9291, but the delivery efficiency of free drugs was limited. A chitooligosaccharide (COS) -based nanoparticle with enhanced delivery efficiency and endocytosis was constructed in this study. The results showed that this pH/redox cascade responsive nanoparticles improved therapeutic effect. The system is small and the surface charge changed from negative to positive according to the weakly acidic tumor microenvironment. After endocytosis, the nanoparticles decomposed and released AZD9291 and CsA in redox-rich cytoplasm. Experiments in vitro and in vivo proved that the nanoparticles overcame the biological barrier and significantly enhanced the anti-tumor effect of AZD9291. The novel multifunctional nanoparticle provides a way to overcome the drug resistance and the possibility of clinical application. [Display omitted] [ABSTRACT FROM AUTHOR]

• Adsorption behaviors of COS 2–6 were studied. • pH and ionic strength marked affect the adsorption behaviors of COS 2–6. • Adsorption equilibrium capacities decrease with the increase of COS DP. • COS 2–6 adsorption kinetic data fit to the pseudo-second-order kinetic model. • Adsorption rate-limiting steps are liquid-film and intra-practical diffusion both. Physiological activities of chitooligosaccharides (COSs) are related to their intrinsic structure and purities of products. However, the efficient preparation method of COSs with a specific degree of polymerization (DP) is still lacking, which limits the in-depth research and application of COSs. This work focused on the adsorption characters of COSs on the ion-exchange resin. Static adsorption experiments were conducted to study the effects of initial solution pH and ionic strength on the adsorption behaviors of chitobiose, chitotriose, chitotetraose, chitopentaose, and chitohexaose (COS 2–6). The adsorption equilibrium, thermodynamics, and kinetics of adsorption were investigated, and the molecular dynamics method was used to calculate the interaction energy of COS 2–6 with the resin and the diffusion coefficients of COS 2–6 in solution. The results show that the adsorption equilibrium data of COS 2–6 are satisfied with the Langmuir model, while the adsorption equilibrium capacities decrease with the increase of COSs DP. The COS 2–6 adsorption kinetic data are well fitted to the pseudo-second-order kinetic model. Liquid-film diffusion and intra-practical diffusion are both the adsorption rate-limiting steps. Thermodynamic parameters show that the adsorptions of COS 2–6 on HX-7 resin are spontaneous and feasible. With the increase of DP, the diffusion coefficients of COS 2–6 in solution decrease while the interaction force with resin become stronger, thus leading to more favorable adsorption. [ABSTRACT FROM AUTHOR]

Consumption of chitooligosaccharides (COS) prevents intestinal microecological disorder. The mechanisms for the effects of different COS on the gut microbiota are currently unclear. This study examined the impact of COS with different degrees of polymerization (DPs) on the gut microbial community and metabolic profile. COS significantly promoted the growth of Bacteroidetes, and inhibited that of Proteobacteria, which were significantly correlated with DPs. COS3 and COS2 enriched the butyrate production in microbial communities composed of Clostridium and Parabacteroides. Microbial communities enriched by DPs 4–6 COS displayed increased diversity in differential metabolite function. Several biomarkers were distinguished significantly, including unsaturated fatty acids, bile acids, indoles and amines, which are mainly related to processes such as fatty acid synthesis and decomposition, bile acid modification, and tryptophan metabolism. The results display the relationship among COS structure-gut microbes-metabolomics, providing a new perspective for COS as a functional food to improve intestinal health. [Display omitted] • Functional microorganisms are enriched in GlcN and DPs 2–6 COS at the genus and species levels. • The promotion of Bacteroidetes growth and the inhibition of Proteobacteria growth by COS are closely related to the DPs. • COS2 and COS3 enrich butyric acid-producing Clostridium. • The prebiotic effect of DPs 4–6 COS on intestinal microbes is more significant than that of others. • Relationships among COS structure-gut microbiota-metabolite profile are established. [ABSTRACT FROM AUTHOR]

• High-degree-polymerized COS were obtained by enzyme-membrane coupling reactor. • COS treatment of C33A cells induced ROS production and decreased the MMP. • COS treatment induced cell apoptosis and regulated apoptotic-related proteins. • COS treatment increased the levels of autophagy markers. Gynecological cancers are the most commonly diagnosed forms of cancer among the female population. Chitooligosaccharides (COS)—hydrolysis products from chitosan—display high bioavailability, high water solubility, and low molecular weight properties. Here, we investigated the influence of COS on 11 gynecological tumor cell types, and subsequently elucidated molecular mechanisms through which the observed inhibition occurred. Initially, we used a controllable enzyme-membrane coupling reactor system to obtain COS with a high degree of polymerization; the yield of high-degree-polymerized COS (DP 5–12) obtained with this reactor system accounted for ∼75% yields (w/w). Using these COS materials, cell line assays showed that COS elicited the most significant anti-tumor activity against C33A cells, with anti-tumor mechanisms related to oxidative stress, as well as activation of intrinsic mitochondrial apoptosis and autophagic signaling. Thus, we provide experimental evidence to demonstrate how the enzyme-membrane coupling reactor system can generate COS that exert bioactivity against gynecological cancers. [ABSTRACT FROM AUTHOR]