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PubMed2005

Glucosamine-induced activation of glycogen biosynthesis in isolated adipocytes. Evidence for a rapid allosteric control mechanism within the hexosamine biosynthesis pathway.

Enhanced flux through the hexosamine biosynthesis pathway (HBP) induces insulin resistance and facilitates lipid storage through the up-regulation of enzyme mRNA levels. Both actions occur over several hours and require gene expression. We now identify a regulatory arm of the HBP that involves rapid allosteric activation of glycogen synthase (GS) and stimulation of glycogen biosynthesis (GBS). When insulin-pretreated adipocytes were exposed to 2 mM GlcN, incorporation of [14C]glucose into glycogen doubled by 10 min (t(1/2) of <5 min), whereas UDP-glucose levels were concomitantly decreased during this time (t(1/2) of 1.4 min; >90% depletion). Stimulation of GBS and depletion of UDP-glucose both correlated with an early and rapid rise in the levels of glucosamine-6-phosphate (GlcN-6-P), a known activator of GS. The lowering of GlcN-6-P levels by removing extracellular GlcN (>80% reduction by 45 min) was accompanied by the restoration of UDP-glucose levels. Prolonged GlcN treatment (20 min to 2 h) inhibited GBS, which corresponded to a massive intracellular accumulation of GlcN-6-P (t(1/2) of approximately 32 min; >1,400 nmol/g). From these data, we conclude the following. 1) GlcN treatment elevated intracellular GlcN-6-P levels within minutes, resulting in allosteric activation of GS, stimulation of GBS, and a reduction in steady-state levels of UDP-glucose due to increased precursor utilization. 2) Prolonged treatment with high concentrations of GlcN caused massive accumulation of GlcN-6-P that adversely affected cellular metabolism and reduced GBS. 3) The biphasic actions of GlcN on GBS may explain many of the discrepant reports on the role of the HBP in glycogen metabolism.

Adipocytes↗
PubMed2005

Distinct substrate specificities of bacterial heparinases against N-unsubstituted glucosamine residues in heparan sulfate.

The rare N-unsubstituted glucosamine (GlcNH(3)(+)) residues in heparan sulfate have important biological and pathophysiological roles. In this study, four GlcNH(3)(+)-containing disaccharides were obtained from partially de-N-sulfated forms of heparin and the N-sulfated K5 polysaccharide by digestion with combined heparinases I, II, and III. These were identified as DeltaHexA-GlcNH(3)(+),DeltaHexA-GlcNH(3)(+)(6S),DeltaHexA(2S)-GlcNH(3)(+), and DeltaHexA(2S)-GlcNH(3)(+)(6S). Digestions with individual enzymes revealed that heparinase I did not cleave at GlcNH(3)(+) residues; however, heparinases II and III showed selective and distinct activities. Heparinase II generated DeltaHexA-GlcNH(3)(+)(6S),DeltaHexA(2S)-GlcNH(3)(+), and DeltaHexA(2S)-GlcNH(3)(+)(6S) disaccharides, whereas heparinase III yielded only the DeltaHexA-GlcNH(3)(+) unit. Thus, the action of heparinase II requires O-sulfation, whereas heparinase III acts only on the corresponding non-sulfated unit. These striking distinctions in substrate specificities of heparinases could be used to isolate oligosaccharides with novel sequences of GlcNH(3)(+) residues. Finally, heparinases were used to identify and quantify GlcNH(3)(+)-containing disaccharides in native bovine kidney and porcine intestinal mucosal heparan sulfates. The relatively high content of O-sulfated GlcNH(3)(+)-disaccharides in kidney HS raises questions about how these sequences are generated.

Chromatography, High Pressure Liquid↗
PubMed1998

The effects of glucosamine and chondroitin sulfate on osteoarthritis of the TMJ: a preliminary report of 50 patients.

The signs and symptoms of osteoarthritis are common complaints seen in patients suffering with chronic temporomandibular disorders (TMD), specifically, internal derangements with a diagnosis of osteoarthritis. With or without the complaints of pain and swelling, joint noises are bothersome and annoying to both the patient and at times, to those seated close to the patient during mealtime. In fact, many patients are driven to seek care by family members because of his or her TMJ noises. For years in veterinarian medicine, glucosamine and chondroitin sulfates have been used to treat symptoms of osteoarthritis. Recently, the use of these two supplements has been recommended for human beings as well. Reports of decreased joint noises, pain and swelling after the administration of therapeutic doses of these supplements have sparked an interest in their possible use in the treatment of osteoarthritis.

Adolescent↗
PubMed2005

Evaluation of the physicochemical stability and skin permeation of glucosamine sulfate.

Glucosamine sulfate (GS) is known to stop the degenerative process of osteoarthritis. Because most of the GS formulation on the market is in the oral form, an alternative formulation such as a transdermal delivery system (TDS) is necessary in order to increase patient compliance. As the initial step to develop a TDS of GS, the physicochemical stability and permeation study in rat skin were examined. Evaluation of the stability of GS at different pHs showed the compound to be most stable at pH 5.0. The degradation rate constant at 25 degrees C was estimated to be 5.93 x 10(-6) hr(-1) (t90 approximately 2.03 years) in a pH 5 buffer solution. Due to its hydrophilic characteristic, low skin permeability was expected of GS. However, the skin permeation rate was determined to be 13.27 microg/cm2/hr at 5% concentration. Results of this study suggest the possibility of developing GS into a transdermal delivery system.

Administration, Cutaneous↗
PubMed1977

Pathogenesis of Shigella diarrhea. VII. Evidence for a cell membrane toxin receptor involving beta1 leads to 4-linked N-acetyl-D-glucosamine oligomers.

The binding of ShigeUa dysenteriae 1 cytotoxin to HeLa cells in culture and to isolated rat liver cell membranes was studied by means of an indirect consumption assay of toxicity from the medium, or by determination of cytotoxicity to the HeLa cell monolayer. Both liver cell membranes and HeLa cells removed toxicity from the medium during incubation, in contrast to WI-38 and Y-1 mouse adrenal tumor cells, both of which neither bound nor were affected by the toxin. Uptake of toxin was directly related to concentration of membranes added, time,and temperature, and indirectly related to the ionic strength of the buffer used. The chemical nature of the membrane receptor was characterized by using three principal approaches: (a) enzymatic sensitivity; (b) competitive inhibition and (c) receptor blockade studies. The receptor was destroyed by proteolytic enzymes, phospholipases (which markedly altered the gross appearance of the membrane preparation) and by lysozyme, but not by a variety of other enzymes. Of 28 carbohydrate and glycoprotein haptens studied, including cholera toxin and ganglioside, only the chitin oligosaccharide lysozyme substrates, per N-acetylated chitotriose, chitotetraose, and chitopentaose were effective competitive inhibitors. Greatest inhibition was found with the trimer, N, N', N" triacetyl chitotriose. Of three lectins studied as possible receptor blockers, including phytohemagglutinin, concanavalin A, and wheat germ agglutinin, only the latter, which is known to possess specific binding affinity for N, N', N" triacetyl chitotriose, was able to block toxin uptake. Evidence from all three approaches indicate, therefore, existence of a glycoprotein toxin receptor on mammalian cells, with involvement of oligomeric beta1{arrow}4-1inked N-acetyl glucosamine in the receptor. This receptor is clearly distinct from the G(M1) ganglioside thought to be involved in the binding of cholera toxin to the cell membrane of a variety of cell types susceptible to its action.

Acetylglucosamine↗
PubMed2004

Assessment of therapeutic tumor response using 99mtc-ethylenedicysteine-glucosamine.

PURPOSE: The aim of this study was to evaluate 99mTc-ethylenedicysteine-glucosamine (EC-DG) for the assessment of tumor growth. METHOD: To evaluate whether 99mTc-EC-DG is involved in cell nuclei activity, in vitro thymidine incorporation, and cell-cycle assays of EC-DG were conducted using lung and breast cancer cells. Biodistribution of 99mTc-EC-DG in lung tumor-bearing mice (0.5-4 hours, 1 Ci/mouse, i. v.) was used to estimate the radiation-absorbed dose. Autoradiograms of 99mTc-EC-DG and 18F-FDG were compared in nude mice bearing uterine sarcoma. Rabbits inoculated with VX-2 cells were imaged with 99mTc-EC-DG and 99mTc-EC. For therapeutic assessment studies, scintigraphic imaging studies with 99mTc-EC-DG in mammary tumor-bearing rats were conducted at various days after treatment with paclitaxel and cisplatin. The imaging findings were correlated immunohistochemical assays (mRNA expression, apoptosis, and cell-cycle changes in tumor), and flow cytometry analysis was performed. RESULTS: In vitro cellular uptake assays indicated that cell nuclei activity could be assessed by 99mTc-EC-DG. Scintigraphy and autoradiograms in animal models demonstrated that the tumor could be clearly visualized by 99mTc-EC-DG. The efficacy of paclitaxel and cisplatin treatment in rodent models could be assessed using tumor/muscle ratios. Immunohistochemical staining indicated a reduced expression of bFGF and an increased apoptosis and cell-cycle changes after paclitaxel and cisplatin treatment. CONCLUSION: 99mTc-EC-DG is involved in cell nuclei activity and could assess the therapeutic tumor response.

Animals↗
PubMed1989

The uptake of [3H] glucosamine-labelled glycoconjugates into the perivitelline space of preimplantation mouse embryos.

Autoradiography has been used to follow the synthesis and migration of labelled glycoconjugates into fertilized and unfertilized mouse eggs. Adult female mice were paired individually with males and injected with 100 microCi [3H] glucosamine, either when they were paired with males or at the time a vaginal plug was first detected. The mice were killed at intervals after the injection of label and 5-microns and semi-thin sections of the oviducts were processed for autoradiography. Labelled glycoconjugates passed rapidly into the perivitelline space of fertilized and unfertilized mouse eggs. There was a positive correlation between the density of label within the zona pellucida and the perivitelline space. Labelled glycoconjugates were maintained within the perivitelline space of many developing embryos for at least 48 h despite very low levels of label within the oviduct by this time. Other 2-cell embryos were only lightly labelled. It is suggested that labelled glycoconjugates may be derived from secretions of the cumulus cells which surround the egg at ovulation rather than from oviductal secretions.

Animals↗
PubMed1995

Importance of 6-O-sulfate groups of glucosamine residues in heparin for activation of FGF-1 and FGF-2.

Treatment of the pyridinium salts of heparin with N-methyltrimethylsilyl-trifluoroacetamide (MTSTFA) in pyridine for 2 h at various temperatures caused specific 6-O-desulfations from trisulfated disaccharide units to various degrees without detectable depolymerization or other chemical changes. In order to assess the importance of 6-O-sulfate groups in N-sulfated glucosamine (GlcNS) residues to promote FGF-1 and FGF-2 activities, various 6-O-desulfated (6-O-DS-) heparins were quantitatively examined for activity as enhancers or inhibitors of specific FGF-1- and FGF-2-induced proliferation of BALB/c3T3 clone A31 (A31) cells and the chlorate-treated cells. The present results suggested that a high content of 6-O-sulfate groups in GlcNS residues was required for activation of FGF-1, but not FGF-2. However, complete 6-O-desulfation of trisulfated disaccharide units in heparin resulted in loss of the ability to activate FGF-2, although the desulfated product bound strongly to FGF-2.

Animals↗
PubMed1978

Glucosamine-containing sphingoglycolipids from sheep erythrocytes.

Glucosamine-containing sphingoglycolipids were isolated from sheep erythrocyte membranes, and the presence of glycolipids with long carbohydrate chains was demonstrated. The purification of highly polar glycolipids was achieved by high-performance liquid chromatography of acetylated samples followed by deacetylation with sodium methoxide. Their structures were elucidated by conventional methylation studies, oxidation with chromium trioxide and the direct measurement of permethylated glycolipids by GC-MS. Forssman-active glycolipid2 was a major component of sheep erythrocytes and lacto-N-neotetraosylceramide (LcnOse4Cer) was found to be one of the components. The amount of tetraglycosylceramide was only 5% of that of Forssman-active glycolipid. Three highly polar glycolipid components with ten to twelve carbohydrate residues were also found in sheep erythrocytes.

Acetylation↗
PubMed1982

A simple method for the determination of glucosamine and galactosamine using cellulose acetate electrophoresis.

A new electrophoretic method is presented for the determination of glucosamine and galactosamine. The technique is quite simple and rapid, it involves cellulose acetate electrophoresis in borate buffer (200 V, 15 min) and silver nitrate staining. Hexosamine samples of 0.36-1.80 micrograms were separated and stained within 30 min. This method was applied for the hexosamine analysis of glycosaminoglycans.

Animals↗
PubMed2006

Glucosamine supplementation during in vitro maturation inhibits subsequent embryo development: possible role of the hexosamine pathway as a regulator of developmental competence.

Glucose concentration during cumulus-oocyte complex (COC) maturation influences several functions, including progression of oocyte meiosis, oocyte developmental competence, and cumulus mucification. Glucosamine (GlcN) is an alternative hexose substrate, specifically metabolized through the hexosamine biosynthesis pathway, which provides the intermediates for extracellular matrix formation during cumulus cell mucification. The aim of this study was to determine the influence of GlcN on meiotic progression and oocyte developmental competence following in vitro maturation (IVM). The presence of GlcN during bovine IVM did not affect the completion of nuclear maturation and early cleavage, but severely perturbed blastocyst development. This effect was subsequently shown to be dose-dependent and was also observed for porcine oocytes matured in vitro. Hexosamine biosynthesis upregulation using GlcN supplementation is well known to increase O-linked glycosylation of many intracellular signaling molecules, the best-characterized being the phosphoinositol-3-kinase (PI3K) signaling pathway. We observed extensive O-linked glycosylation in bovine cumulus cells, but not oocytes, following IVM in either the presence or the absence of GlcN. Inhibition of O-linked glycosylation significantly reversed the effect of GlcN-induced reduction in developmental competence, but inhibition of PI3K signaling had no effect. Our data are the first to link hexosamine biosynthesis, involved in cumulus cell mucification, to oocyte developmental competence during in vitro maturation.

Animals↗
PubMed2001

Determining the efficacy of glucosamine and chondroitin for osteoarthritis.

Glucosamine sulfate and chondroitin sulfate are being used by many patients for the treatment of osteoarthritis. Despite a number of studies supporting efficacy of these agents for palliation of joint pain in patients with osteoarthritis, the American College of Rheumatology Subcommittee on Osteoarthritis believes that it is too early to issue recommendations for use. Currently, the National Institute of Arthritis and Musculoskeletal and Skin Diseases in collaboration with the National Center for Complementary and Alternative Medicine have begun a pivotal study to thoroughly evaluate these agents.

Chondroitin↗
PubMed2005

A novel short-root gene encodes a glucosamine-6-phosphate acetyltransferase required for maintaining normal root cell shape in rice.

Glycosylation is a posttranslational modification occurring in many secreted and membrane-associated proteins in eukaryotes. It plays important roles in both physiological and pathological processes. Most of these protein modifications depend on UDP-N-acetylglucosamine. In this study, a T-DNA insertional rice (Oryza sativa) mutant exhibiting a temperature-sensitive defect in root elongation was isolated. Genetic and molecular analysis indicated that the mutated phenotype was caused by loss of function of a gene encoding a glucosamine-6-P acetyltransferase (designated OsGNA1), which is involved in de novo UDP-N-acetylglucosamine biosynthesis. The aberrant root morphology of the gna1 mutant includes shortening of roots, disruption of microtubules, and shrinkage of cells in the root elongation zone. Our observations support the idea that protein glycosylation plays a key role in cell metabolism, microtubule stabilization, and cell shape in rice roots.

Acetyltransferases↗
PubMed2001

N-acetylglucosamine and glucosamine-containing arabinogalactan proteins control somatic embryogenesis.

In plants, complete embryos can develop not only from the zygote, but also from somatic cells in tissue culture. How somatic cells undergo the change in fate to become embryogenic is largely unknown. Proteins, secreted into the culture medium such as endochitinases and arabinogalactan proteins (AGPs) are required for somatic embryogenesis. Here we show that carrot (Daucus carota) AGPs can contain glucosamine and N-acetyl-D-glucosaminyl and are sensitive to endochitinase cleavage. To determine the relevance of this observation for embryogenesis, an assay was developed based on the enzymatic removal of the cell wall from cultured cells. The resulting protoplasts had a reduced capacity for somatic embryogenesis, which could be partially restored by adding endochitinases to the protoplasts. AGPs from culture medium or from immature seeds could fully restore or even increase embryogenesis. AGPs pretreated with chitinases were more active than untreated molecules and required an intact carbohydrate constituent for activity. AGPs were only capable of promoting embryogenesis from protoplasts in a short period preceding cell wall reformation. Apart from the increase in embryogenesis, AGPs can reinitiate cell division in a subpopulation of otherwise non-dividing protoplasts. These results show that chitinase-modified AGPs are extracellular matrix molecules able to control or maintain plant cell fate.

Acetylglucosamine↗
PubMed1981

Incorporation of D-(3H)glucosamine into normal and psoriatic epidermal glycoconjugates.

Samples of normal, uninvolved and involved psoriatic skin were maintained for 18 h in organ culture in the presence of D-(6-3H) glucosamine which is a precursor of cell-surface associated carbohydrates in the epidermis. The total incorporation into involved psoriatic epidermis (solubilized with 8 mol/l urea, 5% sodium dodecyl sulphate, 10 mmol 2-mercaptoethanol) was less than into normal or uninvolved epidermis. This decrease was found whether specific radioactivities were expressed in terms or area, wet weight or protein content of the epidermis. Electrophoresis revealed that the major labelled component in normal and uninvolved epidermis had a high molecular weight. The labelling of this material was significantly reduced in involved psoriatic epidermis. Using pig epidermis we have shown previously that this material represents mainly extracellular glycosaminoglycans and proteoglycans. The decrease labelling (and presumable synthesis) of these extracellular carbohydrates may be related to the failure of mechanisms controlling cell proliferation and to the altered cell interactions which are found in psoriatic epidermis. Electrophoresis also showed that a non-glycosylated protein, molecular weight approximately 50,000, which was present as a singly band in both normal and uninvolved epidermis was always present as a doublet band in the involved psoriatic epidermis.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Stage-dependent toxicity of N-acetyl-glucosamine to Plasmodium falciparum.

The effects of N-acetyl-glucosamine on growth of synchronized cultures of Plasmodium falciparum were assessed by morphological observations and by measurement of parasite incorporation of 3H-hypoxanthine. Inhibition of 3H-hypoxanthine incorporation was more marked during the later stages of the erythrocytic cycle. At concentrations of the sugar below 20 mM, however, the deleterious effects were mainly a result of failure of released merozoites to invade erythrocytes, rather than a failure of schizonts to mature or release merozoites. These results are compatible with the hypothesis that a lectin-like substance on the merozoite interacts with a surface glycoprotein on the red cell and that sugar residues on this glycoprotein may be involved in this recognition.

Acetylglucosamine↗
PubMed2003

Chitin synthesis in Saccharomyces cerevisiae in response to supplementation of growth medium with glucosamine and cell wall stress.

In Saccharomyces cerevisiae most chitin is synthesized by Chs3p, which deposits chitin in the lateral cell wall and in the bud-neck region during cell division. We have recently found that addition of glucosamine (GlcN) to the growth medium leads to a three- to fourfold increase in cell wall chitin levels. We compared this result to the increases in cellular chitin levels associated with cell wall stress and with treatment of yeast with mating pheromone. Since all three phenomena lead to increases in precursors of chitin, we hypothesized that chitin synthesis is at least in part directly regulated by the size of this pool. This hypothesis was strengthened by our finding that addition of GlcN to the growth medium causes a rapid increase in chitin synthesis without any pronounced change in the expression of more than 6,000 genes monitored with Affymetrix gene expression chips. In other studies we found that the specific activity of Chs3p is higher in the total membrane fractions from cells grown in GlcN and from mutants with weakened cell walls. Sucrose gradient analysis shows that Chs3p is present in an inactive form in what may be Golgi compartments but as an active enzyme in other intracellular membrane-bound vesicles, as well as in the plasma membrane. We conclude that Chs3p-dependent chitin synthesis in S. cerevisiae is regulated both by the levels of intermediates of the UDP-GlcNAc biosynthetic pathway and by an increase in the activity of the enzyme in the plasma membrane.

Acetylglucosamine↗
PubMed1993

An artificial glycoconjugate containing the bisphosphorylated glucosamine disaccharide backbone of lipid A binds lipid A monoclonal antibodies.

Monoclonal antibodies (MAbs) against lipid A, the endotoxic component of lipopolysaccharide (LPS) of gram-negative bacteria, are presently discussed as therapeutic agents against lethal gram-negative infections; however, their binding specificities are controversial. We have isolated from the LPS of Escherichia coli J-5 the 1,4'-bisphosphorylated beta 1-->6-linked glucosamine disaccharide backbone of its lipid A moiety, which was covalently linked to bovine serum albumin. It was shown by solid-phase enzyme immunoassay that one antibody (MAb A6) bound equally well to the glycoconjugate and synthetic E. coli-type lipid A over a broad range of antigen concentrations whereas two other MAbs (IC3 and S1-15) bound better to the conjugate at low antigen concentrations and better to the lipid A when high concentrations of antigen were used. This proves in a direct way that there exist lipid A MAbs with different specificities which bind to epitopes in the hydrophilic backbone of lipid A and which do not require the presence of fatty acids.

Antibodies, Monoclonal↗