Anti-Tumor Activity of an Enzymatically Synthesized α-1,6 Branched α-1,4-Glucan, Glycogen

Normal and abnormal glycogen structure - A review

Glycogen, a complex branched glucose polymer, is found in animals and bacteria, where it serves as an energy storage molecule. It has linear (1 → 4)-α glycosidic bonds between anhydroglucose monomer units, with branch points connected by (1 → 6)-α bonds. Individual glycogen molecules are referred to as β particles. In organs like the liver and heart, these β particles can bind into larger aggregate α particles, which exhibit a rosette-like morphology. The mechanisms and bonding underlying the aggregation process are not fully understood. For example, mammalian liver glycogen has been observed to be molecularly fragile under certain conditions, such as glycogen from diabetic livers fragmenting when exposed to dimethyl sulfoxide (DMSO), while glycogen from healthy livers is much less fragile; this indicates some difference, as yet unknown, in the bonding between β particles in healthy and diabetic glycogen. This fragility may have implications for blood sugar regulation, especially in pathological conditions such as diabetes.

Characterization and applications of biomacromolecule structurally similar to glycogen as a dispersion aid and skin protection agent

Glycogen is a naturally occurring or metabolically synthesized biological macromolecule found in a wide range of living organisms, including animals, microorganisms, and even plants. However, naturally sourced glycogen poses challenges for industrial use. This study focused on a biological macromolecule referred to as glycogen-like particles (GLPs), detailing the production methods and biological properties of these particles. In vitro enzymatic production of GLPs was successfully achieved. GLPs synthesized through a simultaneous enzymatic reaction using sucrose had significant changes in their structure and functionality based on the branching enzyme (BE) to amylosucrase (ASase) ratio. As this ratio increased, the GLPs developed higher molecular weights and greater density, solubility, and branching degree while reducing size and turbidity. Structural changes in these enzymes were not observed beyond a critical BE/ASase ratio. Uniformly dispersed curcumin powder was generated in 50 % (w/v) aqueous GLP solution, and the GLPs were non-toxic to human skin keratinocytes at a concentration of 2.5 mg/mL. GLPs with lower branching inhibited tyrosinase activity and melanin synthesis, while those with more long chains displayed effective UV-blocking. By manipulating the BE/ASase ratio, GLPs were shown to display diverse chemical structures and physical characteristics, suggesting their potential application in the food and cosmetics industries.

Advanced dendritic glucan-derived biomaterials: From molecular structure to versatile applications

There is considerable interest in the development of advanced biomaterials with improved or novel functionality for diversified applications. Dendritic glucans, such as phytoglycogen and glycogen, are abundant biomaterials with highly branched three-dimensional globular architectures, which endow them with unique structural and functional attributes, including small size, large specific surface area, high water solubility, low viscosity, high water retention, and the availability of numerous modifiable surface groups. Dendritic glucans can be synthesized by in vivo biocatalysis reactions using glucosyl-1-phosphate as a substrate, which can be obtained from plant, animal, or microbial sources. They can also be synthesized by in vitro methods using sucrose or starch as a substrate, which may be more suitable for large-scale industrial production. The large numbers of hydroxyl groups on the surfaces of dendritic glucan provide a platform for diverse derivatizations, including nonreducing end, hydroxyl functionalization, molecular degradation, and conjugation modifications. Due to their unique physicochemical and functional attributes, dendritic glucans have been widely applied in the food, pharmaceutical, biomedical, cosmetic, and chemical industries. For instance, they have been used as delivery systems, adsorbents, tissue engineering scaffolds, biosensors, and bioelectronic components. This article reviews progress in the design, synthesis, and application of dendritic glucans over the past several decades.

Application of natural polysaccharides and their novel dosage forms in gynecological cancers: therapeutic implications from the diversity potential of natural compounds

Cancer is one of the most lethal diseases. Globally, the number of cancers is nearly 10 million per year. Gynecological cancers (for instance, ovarian, cervical, and endometrial), relying on hidden diseases, misdiagnoses, and high recurrence rates, have seriously affected women's health. Traditional chemotherapy, hormone therapy, targeted therapy, and immunotherapy effectively improve the prognosis of gynecological cancer patients. However, with the emergence of adverse reactions and drug resistance, leading to the occurrence of complications and poor compliance of patients, we have to focus on the new treatment direction of gynecological cancers. Because of the potential effects of natural drugs in regulating immune function, protecting against oxidative damage, and improving the energy metabolism of the body, natural compounds represented by polysaccharides have also attracted extensive attention in recent years. More and more studies have shown that polysaccharides are effective in the treatment of various tumors and in reducing the burden of metastasis. In this review, we focus on the positive role of natural polysaccharides in the treatment of gynecologic cancer, the molecular mechanisms, and the available evidence, and discuss the potential use of new dosage forms derived from polysaccharides in gynecologic cancer. This study covers the most comprehensive discussion on applying natural polysaccharides and their novel preparations in gynecological cancers. By providing complete and valuable sources of information, we hope to promote more effective treatment solutions for clinical diagnosis and treatment of gynecological cancers.

Production of branched glucan polymer by a novel thermostable branching enzyme of Bifidobacterium thermophilum via one-pot biosynthesis containing a dual enzyme system

Glycogen-like particles (GLPs) are applied in food, pharmaceutical, and cosmetics. The large-scale production of GLPs is limited by their complicated multi-step enzymic processes. In this study, GLPs were produced in a one-pot dual-enzyme system using Bifidobacterium thermophilum branching enzyme (BtBE) and Neisseria polysaccharea amylosucrase (NpAS). BtBE showed excellent thermal stability (half-life of 1732.9 h at 50 °C). Substrate concentration was the most influential factor during GLPs production in this system: GLPs yield and [sucrose]_ini decreased from 42.4 % to 17.4 % and 0.3 to 1.0 M, respectively. Molecular weight and apparent density of GLPs decreased significantly with increasing [sucrose]_ini. Regardless of the [sucrose]_ini, the DP 6 of branch chain length was predominantly occupied. GLP digestibility increased with increasing [sucrose]_ini, indicating that the degree of GLP hydrolysis may be negatively related to its apparent density. This one-pot biosynthesis of GLPs using a dual-enzyme system could be useful for the development of industrial processes.

Designing starch derivatives with desired structures and functional properties via rearrangements of glycosidic linkages by starch-active transglycosylases

Modification of starch by transglycosylases from glycoside hydrolase families has attracted much attention recently; these enzymes can produce starch derivatives with novel properties, i.e. processability and functionality, employing highly efficient and safe methods. Starch-active transglycosylases cleave starches and transfer linear fragments to acceptors introducing α-1,4 and/or linear/branched α-1,6 glucosidic linkages, resulting in starch derivatives with excellent properties such as complexing and resistance to digestion characteristics, and also may be endowed with new properties such as thermo-reversible gel formation. This review summarizes the effects of variations in glycosidic linkage composition on structure and properties of modified starches. Starch-active transglycosylases are classified into 4 groups that form compounds: (1) in cyclic with α-1,4 glucosidic linkages, (2) with linear chains of α-1,4 glucosidic linkages, (3) with branched α-1,6 glucosidic linkages, and (4) with linear chains of α-1,6 glucosidic linkages. We discuss potential processability and functionality of starch derivatives with different linkage combinations and structures. The changes in properties caused by rearrangements of glycosidic linkages provide guidance for design of starch derivatives with desired structures and properties, which promotes the development of new starch products and starch processing for the food industry.

Multiple Fingerprint-Activity Relationship Assessment of Immunomodulatory Polysaccharides from Ganoderma lucidum Based on Chemometric Methods

Polysaccharides with molecular weights ranging from 1.75 × 10³ to 1.14 × 10⁴ g/mol were obtained from the fruit bodies of Ganoderma lucidum. The multiple fingerprints and macrophage immunostimulatory activity of these fractions were analyzed as well as the fingerprint-activity relationship. The correlation analysis of molecular weight and immune activity demonstrated that polysaccharides with molecular weights of 4.27 × 10³~5.27 × 10³ and 1 × 10⁴~1.14 × 10⁴ g/mol were the main active fractions. Moreover, the results showed that galactose, mannose, and glucuronic acid were positively related to immunostimulatory activity. Additionally, partial least-squares regression and grey correlation degree analyses indicated that three peaks (P2, P3, P8) in the oligosaccharide fragment fingerprint significantly affected the immune activity of the polysaccharides. Hence, these ingredients associated with activity could be considered as markers to assess Ganoderma lucidum polysaccharides and their related products, and the study also provides a reference for research on the spectrum-effect relationship of polysaccharides in the future.

Effect of Starch Primers on the Fine Structure of Enzymatically Synthesized Glycogen-like Glucan

Glycogen-like glucan (GnG) is a unique hyperbranched polysaccharide nanoparticle which is drawing increasing attention due to its biodegradability and abundant short branches that can be functionalized. Because starch and GnG are both composed of glucose residues and have similar glucosidic bonds, GnG could be fabricated by sucrose phosphorylase, α-glucan phosphorylase, and branching enzymes from starch primers and sucrose. In this study, high-amylose starch, normal starch, and waxy corn starch were used as primers to synthesize GnG, and their impact on the fine structure of GnG was investigated. Structural analysis indicated that with increasing content of amylopectin in the starch primer, the proportion of short chains in GnG decreased, and the degree of β-amylolysis and α-amylolysis was enhanced. Amylose in the primer contributed to a compact and homogeneous structure of GnG, while amylopectin triggered the formation of branch points with a more open distribution. These findings provide a new strategy for regulating the fine structure of GnG.

Identification of Polysaccharides From Dipsacus asperoides and Their Effects on Osteoblast Proliferation and Differentiation in a High-Glucose Environment

Polysaccharides (DAI-1 and DAI-2) from Dipsacus asperoides (D. asperoides) were obtained using mixed-bed ion exchange resin and Sephadex G-50 column chromatography following which their properties, structures, and activities were investigated. The results showed that DAI-1 and DAI-2 were homogeneous in nature, with glucose the only constituent, and had molecular masses of 17 and 4 kDa, respectively. Methylation analysis indicated that the backbones of DAI-1 and DAI-2 were mainly composed of (1→6)-linked glucose residues. DAI-1 possessed a small number of side chains and a branch point of (1→3, 6)-glucose, while DAI-2 lacked branching. Activity assays demonstrated that exposing osteoblasts to different DAI-1 concentrations (25, 50, or 100 μg/mL) in a high-glucose environment induced cell proliferation and led to a significant increase in bone morphogenetic protein 2 (BMP-2) and runt-related transcription factor 2 (Runx2) expressions at both the mRNA and protein levels. Moreover, DAI-1 treatment significantly increased alkaline phosphatase (ALP) and osteocalcin (OCN) activities in osteoblasts. Combined, our results suggested that DAI-1 may promote osteoblast proliferation and differentiation in a high-glucose environment.

Controlling the Fine Structure of Glycogen-like Glucan by Rational Enzymatic Synthesis

Glycogen-like glucan (GnG), a hyperbranched glucose polymer, has been receiving increasing attention to generate synthetic polymers and nanoparticles. Importantly, different branching patterns strongly influence the functionality of GnG. To uncover ways of obtaining different GnG branching patterns, a series of GnG with radius from 22.03 to 27.06 nm were synthesized using sucrose phosphorylase, α-glucan phosphorylase (GP), and branching enzyme (BE). Adjusting the relative activity ratio of GP and BE (GP/BE) made the molecular weight (MW) distribution of intermediate GnG products follow two different paths. At a low GP/BE, the GnG developed from "small to large" during the synthetic process, with the MW increasing from 6.15 × 10⁶ to 1.21 × 10⁷ g/mol, and possessed a compact structure. By contrast, a high GP/BE caused the "large to small" model, with the MW reduction of GnG from 1.62 × 10⁷ to 1.21 × 10⁷ g/mol, and created a loose external structure. The higher GP activity promoted the elongation of external chains and restrained chain transfer by the BE to the inner zone of GnG, which would modulate the loose-tight structure of GnG. These findings provide new useful insights into the construction of structurally well-defined nanoparticles.

Enzymatically synthesized glycogen inhibited degranulation and inflammatory responses through stimulation of intestine

The patients of type I allergic diseases were increased in the developed countries. Recently, many studies have focused on food factors with anti-allergic activities. Enzymatically synthesized glycogen, a polysaccharide with a multi-branched α-1,4 and α-1,6 linkages, is a commercially available product from natural plant starch, and has immunostimulation activity. However, effect of enzymatically synthesized glycogen on the anti-allergic activity was unclear yet. In this study, we investigated that enzymatically synthesized glycogen inhibited allergic and inflammatory responses using a co-culture system consisting of Caco-2 and RBL-2H3 cells. Enzymatically synthesized glycogen inhibited antigen-induced β-hexosaminidase release and production of TNF-α and IL-6 in RBL-2H3 cells in the co-culture system. Furthermore, enzymatically synthesized glycogen inhibited antigen-induced phosphorylation of tyrosine kinases, phospholipase C γ1/2, mitogen-activated protein kinases and Akt. Anti-allergic and anti-inflammatory activities of enzymatically synthesized glycogen were indirect action through stimulating Caco-2 cells, but not by the direct interaction with RBL-2H3 cells, because enzymatically synthesized glycogen did not permeate Caco-2 cells. These findings suggest that enzymatically synthesized glycogen is an effective food ingredient for prevention of type I allergy through stimulating the intestinal cells.

Enzymatically synthesized glycogen protects inflammation induced by urban particulate matter in normal human epidermal keratinocytes

Urban particulate matters (PM) exposure is significantly correlated with extrinsic skin aging signs and skin cancer incidence. PM contains polycyclic aromatic hydrocarbons, and they act as the agonists of aryl hydrocarbon receptor (AhR). Activation of AhR promotes generation of intracellular reactive oxygen species (ROS) and inflammation. Enzymatically synthesized glycogen (ESG), which is synthesized from starch, possesses various functions, such as anti-tumor, anti-obesity and antioxidant. However, the effects of ESG on PM-induced skin inflammation remain unclear. In this study, we investigated whether ESG has a protective effect on PM-induced oxidative stress and inflammation in human epidermal keratinocytes. ESG inhibited PM-induced expression of inflammatory cytokines IL6, TNFA and PTGS2. ESG also inhibited PM-induced phosphorylation of MAPKs and ROS accumulation. However, ESG had no effect on PM-induced expression of CYP1A1, one of the target proteins of AhR. On the other hand, ESG increased nuclear translocation of Nrf2 and expression of antioxidant proteins, HO-1 and NQO1. These results suggest that ESG suppressed PM-induced inflammation by decreasing ROS accumulation through the Nrf2 pathway.

Enzymatically synthesized glycogen prevents ultraviolet B-induced cell damage in normal human epidermal keratinocytes

Enzymatically synthesized glycogen is a product from starch. Enzymatically synthesized glycogen has been reported to possess various health beneficial effects such as anti-oxidative and anti-inflammatory effects. In this study, we investigated the effect of enzymatically synthesized glycogen on ultraviolet B-induced oxidative stress and apoptosis in normal human epidermal keratinocytes. Treatment with enzymatically synthesized glycogen suppressed ultraviolet B-induced reactive oxygen species, caspase-3 activity, and DNA fragmentation in normal human epidermal keratinocytes. Furthermore, enzymatically synthesized glycogen increased in the expression level of heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, and NF-E2-related factor 2, a transcriptional factor for heme oxygenase-1 and NAD(P)H: quinone oxidoreductase 1. Although enzymatically synthesized glycogen did not increase in its mRNA expression level of NF-E2-related factor 2, enzymatically synthesized glycogen retained its protein degradation. Knockdown of heme oxygenase-1 and NAD(P)H: quinone oxidoreductase 1 canceled enzymatically synthesized glycogen-suppressed reactive oxygen species accumulation in normal human epidermal keratinocytes. It is, therefore, concluded that enzymatically synthesized glycogen inhibited ultraviolet B-induced oxidative stress through increasing the expression level of heme oxygenase-1 and NAD(P)H: quinone oxidoreductase 1 through the NF-E2-related factor 2 pathway in normal human epidermal keratinocytes.

Glycogen as a Building Block for Advanced Biological Materials

Biological nanoparticles found in living systems possess distinct molecular architectures and diverse functions. Glycogen is a unique biological polysaccharide nanoparticle fabricated by nature through a bottom-up approach. The biocatalytic synthesis of glycogen has evolved over time to form a nanometer-sized dendrimer-like structure (20-150 nm) with a highly branched surface and a dense core. This makes glycogen markedly different from other natural linear or branched polysaccharides and particularly attractive as a platform for biomedical applications. Glycogen is inherently biodegradable, nontoxic, and can be functionalized with diverse surface and internal motifs for enhanced biofunctional properties. Recently, there has been growing interest in glycogen as a natural alternative to synthetic polymers and nanoparticles in a range of applications. Herein, the recent literature on glycogen in the material-based sciences, including its use as a constituent in biodegradable hydrogels and fibers, drug delivery vectors, tumor targeting and penetrating nanoparticles, immunomodulators, vaccine adjuvants, and contrast agents, is reviewed. The various methods of chemical functionalization and physical assembly of glycogen nanoparticles into multicomponent nanodevices, which advance glycogen toward a functional therapeutic nanoparticle from nature and back again, are discussed in detail.

In SilicoStudy of 1, 4 Alpha Glucan Branching Enzyme and Substrate Docking Studies

Background:

The 1,4-alpha-glucan branching protein (GlgB) plays an important role in the glycogen biosynthesis and the deficiency in this enzyme has resulted in Glycogen storage disease and accumulation of an amylopectin-like polysaccharide. Consequently, this enzyme was considered a special topic in clinical and biotechnological research. One of the newly introduced GlgB belongs to the Neisseria sp. HMSC071A01 (Ref.Seq. WP_049335546). For in silico analysis, the 3D molecular modeling of this enzyme was conducted in the I-TASSER web server.

Methods:

For a better evaluation, the important characteristics of this enzyme such as functional properties, metabolic pathway and activity were investigated in the TargetP software. Additionally, the phylogenetic tree and secondary structure of this enzyme were studied by Mafft and Prabi software, respectively. Finally, the binding site properties (the maltoheptaose as substrate) were studied using the AutoDock Vina.

Results:

By drawing the phylogenetic tree, the closest species were the taxonomic group of Betaproteobacteria. The results showed that the structure of this enzyme had 34.45% of the alpha helix and 45.45% of the random coil. Our analysis predicted that this enzyme has a potential signal peptide in the protein sequence.

Conclusion:

By these analyses, a new understanding was developed related to the sequence and structure of this enzyme. Our findings can further be used in some fields of clinical and industrial biotechnology.

Rhizopus nigricans polysaccharide activated macrophages and suppressed tumor growth in CT26 tumor-bearing mice

In this study, a homogeneous polysaccharide (RPS-1) was extracted from liquid-cultured mycelia of Rhizopus nigricans. The weight-average molecular weight of RPS-1 was 1.617 × 10⁷ g/mol and structural characterization indicated that RPS-1 was a non-starch glucan which consisted of a backbone structure of (1→4)-linked α-d-glucopyranosyl residues substituted at the O-6 position with α-d-glucopyranosyl branches. RPS-1 stimulated the production of nitric oxide and tumor necrosis factor-α by triggering phosphorylation of mitogen-activated protein kinases and nuclear translocation of nuclear factor kappa B p65 in RAW 264.7 macrophage cells. Moreover, intragastric administration of RPS-1 improved the immune function of CT26 tumor-bearing mice and significantly inhibited the growth of transplanted tumor. In combination with 5-FU, RPS-1 enhanced antitumor activity of 5-FU and alleviated its toxicity on immune system. These findings suggested that RPS-1 has the potential for the development of functional foods and dietary supplements.

Enzymatically synthesized glycogen inhibits colitis through decreasing oxidative stress

Inflammatory bowel diseases are a group of chronic inflammation conditions of the gastrointestinal tract. Disruption of the mucosal immune response causes accumulation of oxidative stress, resulting in the induction of inflammatory bowel disease. In this study, we investigated the effect of enzymatically synthesized glycogen (ESG), which is produced from starch, on dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in C57BL/6 mice. Oral administration of ESG suppressed DSS- and TNBS-induced shortening of large intestine in female mice and significant decreased DSS-induced oxidative stress and TNBS-induced pro-inflammatory cytokine expression in the large intestine. ESG increase in the expression levels of heme oxygenase-1 (HO-1) and NF-E2-related factor-2 (Nrf2), a transcription factor for HO-1 expressed in the large intestine. Furthermore, ESG-induced HO-1 and Nrf2 were expressed mainly in intestinal macrophages. ESG is considered to be metabolized to resistant glycogen (RG) during digestion with α-amylase in vivo. In mouse macrophage RAW264.7 cells, RG, but not ESG decreased 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced reactive oxygen species (ROS). Knockdown of Nrf2 inhibited RG-induced HO-1 expression and negated the decrease in AAPH-induced ROS brought about by RG. RG up-regulated the protein stability of Nrf2 to decrease the formation of Nrf2-Keap1 complexes. RG-induced phosphorylation of Nrf2 at Ser40 was suppressed by ERK1/2 and JNK inhibitors. Our data indicate that ESG, digested with α-amylase to RG, suppresses DSS- and TNBS-induced colitis by increasing the expression of HO-1 in the large intestine of mice. Furthermore, we demonstrate that RG induces HO-1 expression by promoting phosphorylation of Nrf2 at Ser40 through activation of the ERK1/2 and JNK cascade in macrophages.

Antitumor activity of orally administered maitake α-glucan by stimulating antitumor immune response in murine tumor

Maitake α-glucan, YM-2A, isolated from Grifola frondosa, has been characterized as a highly α-1,6-branched α-1,4 glucan. YM-2A has been shown to possess an anti-virus effect in mice; however, it does not directly inhibit growth of the virus in vitro, indicating that the anti-virus effect of YM-2A might be associated with modulation of the host immune system. In this study, we found that oral administration of YM-2A could inhibit tumor growth and improve survival rate in two distinct mouse models of colon-26 carcinoma and B16 melanoma. Orally administered YM-2A enhanced antitumor immune response by increasing INF-γ-expressing CD4⁺ and CD8⁺ cells in the spleen and INF-γ-expressing CD8⁺ cells in tumor-draining lymph nodes. In vitro study showed that YM-2A directly activated splenic CD11b⁺ myeloid cells, peritoneal macrophages and bone marrow-derived dendritic cells, but did not affect splenic CD11b^- lymphocytes or colon-26 tumor cells. YM-2A is more slowly digested by pancreatic α-amylase than are amylopectin and rabbit liver glycogen, and orally administered YM-2A enhanced the expression of MHC class II and CD86 on dendritic cells and the expression of MHC class II on macrophages in Peyer’s patches. Furthermore, in vitro stimulation of YM-2A increased the expression of pro-inflammatory cytokines in Peyer’s patch CD11c⁺ cells. These results suggest that orally administered YM-2A can activate dendritic cells and macrophages in Peyer’s patches, inducing systemic antitumor T-cell response. Thus, YM-2A might be a candidate for an oral therapeutic agent in cancer immunotherapy.

Qualitative and Quantitative Analyses of Glycogen in Human Milk

Identification as well as a detailed analysis of glycogen in human milk has not been shown yet. The present study confirmed that glycogen is contained in human milk by qualitative and quantitative analyses. High-performance anion exchange chromatography (HPAEC) and high-performance size exclusion chromatography with a multiangle laser light scattering detector (HPSEC-MALLS) were used for qualitative analysis of glycogen in human milk. Quantitative analysis was carried out by using samples obtained from the individual milks. The result revealed that the concentration of human milk glycogen varied depending on the mother's condition-such as the period postpartum and inflammation. The amounts of glycogen in human milk collected at 0 and 1-2 months postpartum were higher than in milk collected at 3-14 months postpartum. In the milk from mothers with severe mastitis, the concentration of glycogen was about 40 times higher than that in normal milk.

Immunostimulatory properties and antitumor activities of glucans (Review)

New foods and natural biological modulators have recently become of scientific interest in the investigation of the value of traditional medical therapeutics. Glucans have an important part in this renewed interest. These fungal wall components are claimed to be useful for various medical purposes and they are obtained from medicinal mushrooms commonly used in traditional Oriental medicine. The immunotherapeutic properties of fungi extracts have been reported, including the enhancement of anticancer immunity responses. These properties are principally related to the stimulation of cells of the innate immune system. The discovery of specific receptors for glucans on dendritic cells (dectin-1), as well as interactions with other receptors, mainly expressed by innate immune cells (e.g., Toll-like receptors, complement receptor-3), have raised new attention toward these products as suitable therapeutic agents. We briefly review the characteristics of the glucans from mycelial walls as modulators of the immunity and their possible use as antitumor treatments.

Amphiphilic polysaccharide nanoballs: a new building block for nanogel biomedical engineering and artificial chaperones

Enzymatically synthesized glycogen (ESG), a highly branched (1→4)(1→6)-linked α-glucan, is a new monodisperse spherical hyperbranched nanoparticle (molecular weight, 10(6)-10(7); diameter, 20-30 nm), polysaccharide nanoball. Amphiphilic ESG nanoballs were synthesized by introducing a cholesterol group to enzymatically synthesized glycogen (CHESG). CHESG assembled into a structure containing a few molecules to form cluster nanogels (approximately 35 nm in diameter) in water. The cluster nanogels were dissociated by the addition of cyclodextrin (CD) to form a supramolecular CHESG-CD nanocomplex due to complexation with the cholesterol group and CD. The CHESG nanogel showed high capacity for complexation with proteins, and the CHESG-CD nanocomplex showed high chaperone-like activity for thermal stabilization of enzymes. CHESG has great potential to become a new building block for nanogel biomedical engineering and to act as an artificial chaperone for protein engineering.

Safety evaluation of an enzymatically-synthesized glycogen (ESG)

An enzymatically-synthesized glycogen (ESG), intended for use as a food ingredient, was investigated for potential toxicity. ESG is synthesized in vitro from short-chain amylose by the co-operative action of branching enzyme and amylomaltase. In an acute toxicity study, oral administration of ESG to Sprague-Dawley rats at a dose of 2000 mg/kg body weight did not result in any signs of toxicity. ESG did not exhibit mutagenic activity in an in vitro bacterial reverse mutation assay. In a subchronic toxicity study, increased cecal weights noted in the mid- (10%) and high-dose (30%) animals are common findings in rodents fed excess amounts of carbohydrates that increase osmotic value of the cecal contents, and thus were considered a physiological rather than toxicological response. The hematological and histopathological effects observed in the high-dose groups were of no toxicological concern as they were secondary to the physiological responses resulting from the high carbohydrate levels in the test diets. The no-observed-adverse-effect level for ESG in rats was therefore established to be 30% in the diet (equivalent to approximately 18 and 21 g/kg body weight/day for male and female rats, respectively). These results support the safety of ESG as a food ingredient for human consumption.

Safety evaluation of highly-branched cyclic dextrin and a 1,4-alpha-glucan branching enzyme from Bacillus stearothermophilus

Highly-branched cyclic dextrin (HBCD), a dextrin food ingredient presently only used in Japan, was investigated for digestibility and potential toxicity. HBCD was readily hydrolyzed in vitro to maltose and maltotriose by human salivary and porcine pancreatic alpha-amylases. Incubation of HBCD with a rat intestinal homogenate, containing digestive enzymes, resulted in the formation of maltose, maltotriose, and maltotetraose, and with longer incubation times, resulted in the formation of glucose. In an acute toxicity study, Wistar rats orally administered a single-dose of 2000mg/kg body weight of HBCD did not display mortality or any signs or symptoms of toxicity or abnormalities upon necropsy. Transient loose stools were observed, but were resolved within 24h of HBCD administration, and therefore, were not considered as compound-specific adverse effects. In the Ames assay, HBCD was non-mutagenic with or without metabolic activation. Toxicity testing of the branching enzyme (BE) involved in the synthesis of HBCD showed that the BE also was not acutely toxic when orally administered to rats and was non-mutagenic in the mouse lymphoma assay. The results of this study demonstrate that HBCD is digested to normal and safe products of carbohydrate digestion, and therefore, support the safety of HBCD for human consumption.

The augmenting activity of 6-(methylsulfinyl)hexyl isothiocyanate on cellular glutathione levels is less sensitive to thiol compounds than its cytotoxic activity

We analyzed the effects of thiol compounds on the biological activities of 6-(methylsulfinyl)hexyl isothiocyanate (6-MITC). Thiol compounds abolished the cytotoxic activity of 6-MITC, but did not abolish its activity augmenting cellular total glutathione levels and gamma-glutamylcysteine ligase gene expression. Thiol compounds might play an important role in the augmentation of several significant biological activities by overcoming the inherent limitations of 6-MITC.

Relationship between structure and immunostimulating activity of enzymatically synthesized glycogen

Glycogen acts as energy and carbon reserves in animal cells and in microorganisms. Although anti-tumor activity has recently been reported for shellfish glycogen and enzymatically synthesized glycogen, the activity of glycogen has not yet been fully clarified. We enzymatically prepared various sizes of glycogens with controlled structures to investigate the relationship between the structure and immunostimulating activity of glycogen. The results revealed that glycogens with a weight-average molecular weight (M(w)) of more than 10,000K hardly activated RAW264.7, a murine macrophage cell line, whereas glycogens of M(w) 5000K and 6500K strongly stimulated RAW264.7 in the presence of interferon-gamma (IFN-gamma), leading to augmented production of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6). Comparing the fine structure of the glycogens, the average-number of chain length, as well as the exterior and the interior chain lengths of the glycogens, had minor correlation between active and less-active glycogen derivatives. The available evidence suggests that the macrophage-stimulating activity of glycogen is strictly related to its molecular weight rather than to any fine structural property.