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At least 433 records · Page 24Linked to original sources

PubMed2003

Glucosamine-induced insulin resistance is coupled to O-linked glycosylation of Munc18c.

Evidence suggests that glucosamine inhibits distal components regulating insulin-stimulated GLUT4 translocation to the plasma membrane. Here we assessed whether key membrane docking and fusion events were targeted. Consistent with a plasma membrane-localized effect, 3T3-L1 adipocytes exposed to glucosamine displayed an increase in cell-surface O-linked glycosylation and a simultaneously impaired mobilization of GLUT4 by insulin. Analysis of syntaxin 4 and SNAP23, plasma membrane-localized target receptor proteins (t-SNAREs) for the GLUT4 vesicle, showed that they were not cell-surface targets of O-linked glycosylation. However, the syntaxin 4 binding protein, Munc18c, was targeted by O-linked glycosylation. This occurred concomitantly with a block in insulin-stimulated association of syntaxin 4 with its cognate GLUT4 vesicle receptor protein (v-SNARE), VAMP2. In conclusion, our data suggest that the mechanism by which glucosamine inhibits insulin-stimulated GLUT4 translocation involves modification of Munc18c.

Adipocytes↗

PubMed1997

Glucosamine may retard atherogenesis by promoting endothelial production of heparan sulfate proteoglycans.

Heparan sulfate proteoglycans produced by vascular endothelium may function physiologically to restrain the migration, multiplication, and phenotypic transition of vascular smooth-muscle cells, and to maintain an anticoagulant luminal surface by bonding and activating antithrombin III. Thus, ample production of heparan sulfate proteoglycans may act to prevent atherosclerosis and its thrombotic complications. The ability of exogenous heparin to stimulate synthesis of heparan sulfate proteoglycans by vascular endothelium may be largely responsible for the positive outcomes of most controlled evaluations of low-dose heparin as a long-term therapy for coronary disease. Glucosamine, a biosynthetic precursor of mucopolysaccharides, can substantially enhance mucopolysaccharide production when added to cultured fibroblasts or chondrocytes; the clinical utility of oral glucosamine in osteoarthritis may reflect increased synthesis of cartilage proteoglycans. It is reasonable to speculate that exogenous glucosamine will likewise enhance heparan sulfate proteoglycans production by vascular endothelial cells, and, when administered orally in regimens comparable to those effective in osteoarthritis, will thereby act to retard atherogenesis.

Animals↗

PubMedDate not supplied

Synthesis of 6'-O-lissamine-rhodamine B-glucosamine as a novel probe for fluorescence imaging of lysosomes in breast tumors.

Lysosomes contain multiple proteases, which play a crucial role in breast cancer invasion and metastasis. Noninvasive labeling of lysosomes in breast cancer cells and solid breast tumor models is therefore useful to study lysosomal trafficking and its role in invasion. We have synthesized a novel compound, 6'-O-lissamine-rhodamine B-glucosamine, to fluorescently label lysosomes, and evaluated the compound in human breast cancer cells in cell culture or in orthotopic human breast cancer models. We demonstrated that this novel compound biosynthetically labeled lysosomal proteins following addition to cell culture medium or following intravenous injection into mouse models of breast cancer. Fluorescence from 6'-O-lissamine-rhodamine B-glucosamine colocalized with several well-established lysosomal markers, such as lysosome-associated proteins 1 and 2 (LAMP-1 and -2) and CD63. We also demonstrated the feasibility of performing in vivo fluorescence imaging of 6'-O-lissamine-rhodamine B-glucosamine to image lysosomes in human breast cancer models.

Animals↗

PubMed1987

Contribution of 3-O- and 6-O-sulfated glucosamine residues in the heparin-induced conformational change in antithrombin III.

The role of 3-O- and 6-O-sulfated glucosamine residues within the heparin octasaccharide critical for biological activity, iduronic acid----N-acetylglucosamine 6-O-sulfate----glucuronic acid----N-sulfated glucosamine 3,6-di-O-sulfate----iduronic acid 2-O-sulfate----N-sulfated glucosamine 6-O-sulfate----iduronic acid 2-O-sulfate----anhydromannitol 6-O-sulfate, was determined by comparing its ability to bind antithrombin, induce a conformational change in this protease inhibitor as monitored by the enhancement of intrinsic fluorescence, and accelerate (at saturation) the interaction of this protein with human factor Xa. The octasaccharide produced a maximum 48% increase in intrinsic fluorescence at 37 degrees C and a rate of factor Xa inhibition of 6 X 10(5) M-1 s-1 as measured by stopped-flow fluorometry at 25 degrees C. The basal rate of the antithrombin-factor Xa interaction observed in the absence of oligosaccharide was 2 X 10(3) M-1 s-1. The synthetic pentasaccharide, consisting of residues 2-6, produced fluorescence enhancement and rate of inhibition equal to those of the octasaccharide. However, a similar pentasaccharide, identical in all respects except that it lacked the 3-O-sulfate on residue 4, produced less than a 5% fluorescence enhancement and a rate of factor Xa inhibition of 8 X 10(3) M-1 s-1. The tetrasaccharide consisting of residues 2-5 produced a 35% fluorescence enhancement and a rate of factor Xa inhibition of 3 X 10(5) M-1 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2003

Structural identification of nonvolatile dimerization products of glucosamine by gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and nuclear magnetic resonance analysis.

The degradation profile of glucosamine bulk form stressed at 100 degrees C for 2 h in an aqueous solution was studied. Column chromatography of acetylated product mixture led to isolation of two pure compounds (1b and 2b) and a mixture of at least three isomers (3b). 1a and 2a were identified as 5-(hydroxymethyl)-2-furaldehyde (5-HMF) and 2-(tetrahydroxybutyl)-5-(3',4'-dihydroxy-1'-trans-butenyl)pyrazine, respectively, by utilizing a variety of analytical techniques, such as GC-MS, LC-MS, on-line UV spectrum, (1)H and (13)C NMR, and DEPT, as well as (1)H-(1)H COSY. 3a was identified as 2-(tetrahydroxybutyl)-5-(2',3',4'-trihydroxybutyl)pyrazine, commonly known as deoxyfructosazine. In addition, glucosamine solid dosage form was exposed to 40 degrees C/75% relative humility for 10 weeks. Methanol extract of glucosamine solid dosage form was analyzed after acetylation by LC-MS, resulting in degradants 3b and 4b. 3a and 4a were, therefore, determined as deoxyfructosazine and 2,5-bis(tetrahydroxybutyl)pyrazine (fructosazine), respectively. Furthermore, the mechanisms of formation of identified degradation products are proposed and briefly discussed.

Chromatography, High Pressure Liquid↗

PubMed1976

Glucosamine metabolism in regenerating rat liver.

1. Glycoprotein synthesis was investigated with [1-14C]glucosamine in vivo. [14C]Glucosamine was administered intravenously 24h after hepatectomy to rats. 2. Incorporation into the acid-soluble fraction was maximum at 15 min after injection both in sham-operated and hepatectomized rats. 3. Enhancement of incorporation into UDP-N-acetylhexosamine in regenerating liver was observed. However, its specific activity was lower, because of a greater enhancement of synthesis de novo of the amino sugar. 4. In the liver acid-insoluble fraction, maximum incorporation of [14C]glucosamine was at 30 min in sham-operated rats and 2 h in hepatectomized rats respectively. 5. In sham-operated rats, incorporation into the plasma acid-insoluble fraction followed that of the liver acid-insoluble fraction, but hepatectomy resulted in a rapid enchancement of incorporation into plasma. 6. It is concluded that synthesis of liver glycoproteins is stimulated after partial hepatectomy and that glycoproteins synthesized are released rapidly into the plasma.

Animals↗

PubMed2000

Efficacy of a combination of FCHG49 glucosamine hydrochloride, TRH122 low molecular weight sodium chondroitin sulfate and manganese ascorbate in the management of knee osteoarthritis.

OBJECTIVES: The objective of this study was to evaluate the oral combination of glucosamine HCl, sodium chondroitin sulfate and manganese ascorbate for the treatment of osteoarthritis (OA) of the knee. DESIGN: A randomized placebo-controlled study design was implemented. We recruited 93 patients with OA of the knee from a single center. The intervention group received 1000 mg FCHG49 glucosamine HCl, 800 mg TRH122 low molecular weight sodium chondroitin sulfate and 152 mg manganese ascorbate twice daily (Cosamin DS). Patients were evaluated initially and then every 2 months for 6 months. The primary outcome was the Lesquene Index of severity of osteoarthritis of the knee (ISK). RESULTS: Patients with radiographically mild or moderate OA (N=72) in the intervention group showed significant improvement in the ISK at 4 and 6 months (P=0.003 and P=0.04, respectively). The response rate to the medication was 52% vs a 28% response rate to placebo. Patients with radiographically severe osteoarthritis (N=21) did not show significant improvements in the ISK. There was a 17% incidence of adverse events in the intervention group and 19% in the placebo group. CONCLUSIONS: The studied combination of glucosamine HCl, sodium chondroitin sulfate and manganese ascorbate was found to be effective for the treatment of radiographically mild to moderate OA of the knee as measured by the ISK. This is the first U.S. study of these agents.

Aged↗

PubMed2000

Sulfated glycosaminoglycans and glucosamine may synergize in promoting synovial hyaluronic acid synthesis.

High-molecular-weight hyaluronic acid (HA) produced by the synovium may function physiologically to aid preservation of cartilage structure and prevent arthritic pain; both the size and concentration of HA in synovial fluid are diminished in osteoarthritis (OA). Glucosamine therapy for OA can be expected to increase synovial HA production by providing rate-limiting substrate. In addition, certain sulfated glycosaminoglycans and polysaccharides - including chondroitin sulfate (CS), dermatan sulfate, and pentosan polysulfate - stimulate synovial HA production, apparently owing to a hormone-like effect triggered by the binding of these polymers to membrane proteins of synovial cells. Surprisingly, a significant proportion of orally administered CS is absorbed as intact polymers - apparently by pinocytosis. These considerations may rationalize clinical studies concluding that oral CS provides slow-onset but durable pain relief and functional improvement in OA. The possibility that oral glucosamine and CS may interact in a complementary or synergistic fashion to improve synovial fluid HA content in OA should be assessed in clinical studies, and the potential of adjunctive CS administration to improve the clinical response achievable with optimal intakes of glucosamine should likewise be evaluated. In light of the fact that the synovium virtually functions as a 'placenta' for cartilage, focusing on synovium as the target for therapeutic intervention in OA may be a rational strategy.

Administration, Oral↗

PubMed1978

The effect of cyclic nucleotides on the incorporation of 3H-glucosamine into hyaluronate in bone organ culture.

Addition of dibutyryl cyclic AMP or parathyroid hormone to bone organ cultures markedly increased the incorporation of 3H-glucosamine into non-dialyzable macromolecules. Other cyclic nucleotides or their dibutyryl derivatives did not stimulate glucosamine incorporation. DEAE-cellulose chromatography of the papain-digested calvaria and culture medium resolved the labeled material into four peaks. A four-fold increase in radioactivity was observed in peak III. Previous studies of peak III have identified the labeled material as hyaluronic acid. The results suggest that the parathyroid hormone stimulated increase in glucosamine incorporation is mediated via the adenylate cyclase-cyclic AMP system, and that the increased amount of radioactivity is due to an increased amount of hyaluronic acid. Turnover studied of the labeled material suggest that the release of proteoglycans into the culture medium is not inhibited in the cultures treated with dibutyryl cyclic AMP. The role of hyaluronate in this experimental system remains to be elucidated.

Animals↗

PubMed1980

Evidence for a 3-O-sulfated D-glucosamine residue in the antithrombin-binding sequence of heparin.

An octasaccharide with high affinity for antithrombin was isolated after partial deaminative cleavage of heparin with nitrous acid. After conversion of the 2,5-anhydro-D-mannose end group to anhydro[1-3H]mannitol, labeled pentasaccharide was released from the octasaccharide by periodate-alkali treatment. Incubation of the pentasaccharide with a recently discovered 3,O-sulfatase from human urine resulted in desulfation, suggesting the occurrence of a 3-sulfate group on the terminal glucosamine residue. The same glucosamine residue was recovered as a 2,5-anhydro[1-3H]mannitol derivative by a procedure involving deamination of the octasaccharide with nitrous acid, reduction of the products with sodium boro[3H]hydride, isolation of 3H-labeled tetrasaccharide by gel chromatography, and release of the labeled end-group by periodate-alkali treatment. Paper electrophoresis indicated disulfated anhydro[3H]mannitol, presumably sulfated at C3 and C6, as a major component, along with smaller amounts of monosulfated (presumably 3-sulfated) anhydro[3H]mannitol. Similar treatment of an analogous tetrasaccharide derived from heparin with low affinity for antithrombin failed to produce any disulfated anhydromannitol. These results suggest that 3-sulfated glucosamine is a unique component of high-affinity heparin, located at a specific position in the antithrombin-binding sequence of the molecule.

Animals↗

PubMed2002

Location of N-unsubstituted glucosamine residues in heparan sulfate.

Functional properties of heparan sulfate (HS) are generally ascribed to the sulfation pattern of the polysaccharide. However, recently reported functional implications of rare N-unsubstituted glucosamine (GlcNH(2)) residues in native HS prompted our structural characterization of sequences around such residues. HS preparations were cleaved with nitrous acid at either N-sulfated or N-unsubstituted glucosamine units followed by reduction with NaB(3)H(4). The labeled products were characterized following complementary deamination steps. The proportion of GlcNH(2) units varied from 0.7-4% of total glucosamine in different HS preparations. The GlcNH(2) units occurred largely clustered at the polysaccharide-protein linkage region in intestinal HS, also more peripherally in aortic HS. They were preferentially located within N-acetylated domains, or in transition sequences between N-acetylated and N-sulfated domains, only 20-30% of the adjacent upstream and downstream disaccharide units being N-sulfated. The nearest downstream (toward the polysaccharide-protein linkage) hexuronic acid was invariably GlcUA, whereas the upstream neighbor could be either GlcUA or IdoUA. The highly sulfated but N-unsubstituted disaccharide unit, -IdoUA2S-GlcNH(2)6S-, was detected in human renal and porcine intestinal HS, but not in HS from human aorta. These results are interpreted in terms of a biosynthetic mechanism, whereby GlcNH(2) residues are formed through regulated, incomplete action of an N-deacetylase/N-sulfotransferase enzyme.

Animals↗

PubMed1975

Effect of X-irradiation on 3-H-glucosamine uptake by human embryo fibroblasts.

The incorporation of 3-H-glucosamine into unirradiated and X-irradiated (905 rad) cultures of human embryo fibroblasts was studied by light microscopic, autoradiographic and biochemical methods in pulse-chase experiments. The precursor was 3-H-glucosamine. In unirradiated cells the grains appeared in various subcellular regions in a particular order: at first over the Golgi complex, then over the whole cytoplasm and finally at least some of the labelled macromolecules emerged from the cell. The radioactivity emerging from the cell appeared to be protein bound. Due to the effect of irradiation, the uptake of 3-H-glucosamine by the interphase cells was considerably decreased. The amount of radioactivity per cell indicated both the inhibition of cytoplasmic segregation and migration of labelled macromolecules from the cell. In the mitotic figures appearing after the release from radiation-induced mitotic block (approximately 30 hours after irradiation), the grain counts were still considerably lower than the controls. The functional and structural radiation injury of the Golgi-complex was suggested by the less well-defined sequence of localization of radioactive macromolecules than in control cells.

Autoradiography↗

PubMed1976

Glucosamine resistance in yeast. I. A preliminary genetic analysis.

Mutants of the yeast Saccaromyces cerevisiae which can grow on glycerol medium in the presence of 0.05% D (+) glucosamine have been isolated. Genetic analysis of 13 of these glucosamine resistant (GR) mutants demonstrated two modes of inheritance. One group of mutants (GR 5, 6, 7, 8, 9 and 10) gave results characteristic of non-Mendelian inheritance and it is suggested that these mutants represent one or more new mitochondial loci. Four of the remaining mutants showed clear-cut Mendelian inheritance. These mutants fell into two complementation groups and subsequent mapping experiments demonstrated that two independent loci, gay 1 and gay 2, unlinked to each other or to the centromeres of chromosomes I, II, IV, VIII or IX, were responsible for conferring glucosamine resistance in these mutants.

Chromosome Mapping↗

PubMed1976

Inhibition of Echovirus-12 multiplication by N-carbobenzoxy-D-glucosamine.

The glucosamine derivative, N-carbobenzoxy-D-glucosamine (NCBZG) inhibits the multiplication of Echovirus-12 and the synthesis of both virus RNA and protein at a stage in the virus growth cycle after attachment and penetration. However, the compound does not inhibit virus multiplication after the appearance of progeny virus nor after virus RNA has accumulated. Incorporation of radioactive glucosamine and choline into infected and uninfected cultures is inhibited by NCBZG as is the virus-induced increase in choline incorporation. The compound also prevents the appearance of radioactive choline in isolated membranous structures. The compound did not alter significantly the cellular RNA or protein synthesis, plating efficiency of the cells, their growth over a period of several days, nor the virus-directed inhibition of cellular RNA and protein. These findings suggest that the compound inhibits virus multiplication by its effect on the initiation of biosynthesis which appears to require membrane synthesis.

Cell Line↗

PubMed2006

Purification, crystallization and preliminary X-ray analysis of the glucosamine-6-phosphate N-acetyltransferase from human liver.

Glucosamine-6-phosphate N-acetyltransferase from human liver, which catalyzes the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to the primary amine of D-glucosamine 6-phosphate to form N-acetyl-D-glucosamine 6-phosphate, was expressed in a soluble form from Escherichia coli strain BL21 (DE3). The protein was purified to homogeneity using Ni(2+)-chelating chromatography followed by size-exclusion chromatography. Crystals of the protein were obtained by the hanging-drop vapour-diffusion method and diffracted to 2.6 A resolution. The crystals belonged to space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 50.08, c = 142.88 A.

Amino Acid Sequence↗

PubMedDate not supplied

Fungicidal activity of latex sap from Carica papaya and antifungal effect of D(+)-glucosamine on Candida albicans growth.

Carica papaya latex sap inhibits the growth of Candida albicans when added to a culture during the exponential growth phase. Approximately 60% was achieved. This fungistatic effect is the result of cell wall degradation due to a lack of polysaccharidic constituents in the outermost layers of the fungal cell wall and release of cell debris into the culture medium. When C. albicans was cultured on medium supplemented with D(+)-glucosamine, an inhibitor of N-acetyl-beta-D-glucosaminidase, growth was inhibited (34%) in a similar manner. Addition of D(+)-glucosamine during the exponential growth phase also had a fungistatic effect (26%). The modes of action of C. papaya latex and of D(+)-glucosamine in cell wall breakdown are discussed.

Acetylglucosaminidase↗

PubMed1981

Competitive inhibition of rat brain hexokinase by 2-deoxyglucose, glucosamine, and metrizamide.

The effects of metrizamide on the kinetics of rat brain hexokinase were compared in vitro with those of 2-deoxyglucose and glucosamine. Although metrizamide, 2-deoxyglucose, and glucosamine are known to be competitive inhibitors of approximately equal potency for glucose of yeast hexokinase (Ki approximately 0.7 mM for all three), metrizamide is a much weaker competitive inhibitor (Ki about 20 mM) of rat brain hexokinase than either 2-deoxyglucose or glucosamine (Ki about 0.3 mM for both). This indicates a greater active site specificity of rat brain hexokinase than of yeast hexokinase. Rat brain hexokinase activity is enhanced approximately threefold in the presence of 0.05, 0.2, and 0.8 mg/ml bovine serum albumin, while yeast hexokinase is only enhanced by 50% under these conditions. Despite the high Ki value for metrizamide, interference with glucose metabolism may occur whenever metrizamide is present in much higher concentrations than glucose. Myelography in humans is one such situation.

Animals↗

PubMed1987

Glycosylation process in gonadotrophs: a quantitative electron microscope autoradiographic study with labeled glucosamine.

Incorporation of [3H]glucosamine into dispersed anterior pituitary cells was studied by electron microscope autoradiography. Gonadotrophs were examined to determine the intracellular route and kinetic patterns of glycosylation. Studies were performed with cells from; (a) normal adult male rats; (b) rats orchidectomized 3 wk earlier; and (c) orchidectomized rats treated with tunicamycin. Our results show that incorporation of [3H]glucosamine first occurs in the rough endoplasmic reticulum (RER), then proceeds in the Golgi elements (where peripheral carbohydrates are attached). Treatment with tunicamycin results in a decrease in labeling of these 2 organelles. Comparison of the kinetic patterns in normal and castrated male rats shows that the accumulation of labeled glycosylated proteins in granules reaches a plateau within 2 hr post-pulse in normal rats, and rises during a 6-hr chase in castrated rats. However, because of the necessity for a rather long 15 min pulse, we cannot exclude the possibility that incorporation of glucosamine during the pulse may occur concomitantly in the RER and the Golgi saccules, to be followed by rapid transfer to the secretory granules.

Animals↗