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PubMed2006

Clinical inquiries: Do glucosamine and chondroitin worsen blood sugar control in diabetes?

Despite theoretical risks based on animal models given high intravenous doses, glucosamine/chondroitin (1500 mg/1200 mg daily) does not adversely affect short-term glycemic control for patients whose diabetes is well-controlled, or for those without diabetes or glucose intolerance (SOR: A, consistent, good-quality patient-oriented evidence). Some preliminary evidence suggests that glucosamine may worsen glucose intolerance for patients with untreated or undiagnosed glucose intolerance or diabetes (SOR: C, extrapolation from disease-oriented evidence). Long-term effects are unknown; however, no compelling theoretical or incidental data suggest that long-term results should be different (SOR: C, expert opinion). Further studies are required to clarify the effects of glucosamine on patients with poorly controlled diabetes or glucose intolerance.

Blood Glucose↗

PubMed2006

Single dose pharmacokinetics and bioavailability of butyryl glucosamine in the rat.

PURPOSE: To study single dose pharmacokinetics and bioavailability of the synthetic glucosamine analogue, N-butyryl glucosamine (GLcNBu) after different routes of administration, and also the effect of food following oral doses of GLcNBu in the rat, and stability and absorption of GLcNBu across the rat everted intestine. METHOD: GLcNBu was administered intravenously (i.v.), intraperitoneally (i.p.) and orally. Effect of food was studied following oral administration only. Single doses of 223 mg/kg were administered in all cases. Serial blood samples were collected from the jugular vein for GLcNBu determination. Everted excised rat intestine segments were suspended in Tris buffer at 37 degrees C and samples collected from both serosal and mucosal sides. GLcNBu was measured using HPLC. RESULT: Following i.v. administration, the terminal half-life was 0.29 -/+ 0.06 h, volume of distribution at steady state was 2.1 -/+ 0.26 L/kg and total body clearance was 5.23 -/+ 1.44 L/h/kg. Bioavailability was less than 17% and 100% following oral and i.p. doses respectively. GLcNBu was rapidly absorbed after oral doses (Tmax, 29-40 min). Food had no significant effect on the pharmacokinetics of GLcNBu. There was no evidence of breakdown of GLcNBu in the presence of everted intestine. The mucosal to serosal transport of GLcNBu was about 20% after 2 h incubation. CONCLUSION: GLcNBu has rapid but low absorption and is widely distributed and efficiently cleared. The gut rather than liver is mainly responsible for the low bioavailability of GLcNBu. Limited absorption of GLcNBu suggests a transport dependent absorption. Food does not significantly affect the bioavailability of GLcNBu.

Administration, Oral↗

PubMed1990

Characterization of novel sequences containing 3-O-sulfated glucosamine in glomerular basement membrane heparan sulfate and localization of sulfated disaccharides to a peripheral domain.

Fragmentation of the heparan sulfate chains from bovine glomerular basement membrane (GBM) by hydrazine/nitrous acid treatment followed by NaB3H4-reduction yielded a mixture of six sulfated disaccharides containing D-glucuronic (GlcUA) or L-iduronic acid (IdUA) and terminating in 2,5-anhydro[3H]mannitol (AnManH2), in addition to the nonsulfated component GlcUA beta 1----4AnManH2. Among these products two novel disaccharide units were identified as IdUA alpha 1----4AnManH2(3-SO4) and IdUA(2-SO4)alpha 1----4AnManH2(3-SO4); these accounted for 22% of the total sulfated species indicating that there are 2-3 residues of 3-O-sulfated glucosamine/heparan sulfate chain. The disulfated disaccharide was shown through its release by direct nitrous acid treatment to be situated in a GlcNSO3-IdUA(2-SO4)-GlcNSO3(3-SO4) sequence which is distinct from that in which 3-O-sulfated glucosamine is located in the antithrombin-binding region of heparins. Analyses of heparan sulfate from lens capsule, a nonvascular basement membrane, indicated the absence of sequences containing 3-O-sulfated glucosamine, although otherwise the sulfated disaccharides produced by hydrazine/nitrous acid/Na-B3H4 treatment (GlcUA beta 1----4AnManH2(6-SO4), IdUA alpha 1----4AnManH2(6-SO4), IdUA(2-SO4)alpha 1----4AnManH2 and IdUA(2-SO4)alpha 1----4AnManH2(6-SO4] were the same as from GBM. Examination of the GBM heparan sulfate domains after nitrous acid treatment indicated that the O- as well as N-sulfate groups are clustered in an iduronic acid-rich 10-disaccharide peripheral segment, while the internal region (approximately 20 disaccharides) is composed primarily of repeating GlcUA beta 1----4GlcNAc units. The localization of chain diversity to the outer region may facilitate interactions of the heparan sulfate with other macromolecular components.

Animals↗

PubMed1988

[Regulation of glucosamine synthetase activity by cholesterol and hydrocortisone].

The effects of cholesterol and hydrocortisone (cortisol) on the activity of purified glucosamine synthetase from rat liver was studied in vitro. It was found that the enzyme activity is increased by cholesterol and inhibited by hydrocortisone. These steroids block the allosteric effect of vitamin K1 on the enzyme. There is evidence testifying to the allosteric type of cholesterol and hydrocortisone effects on glucosamine synthetase.

Animals↗

PubMed1983

Fatty acyl derivatives of glucosamine 1-phosphate in Escherichia coli and their relation to lipid A. Complete structure of A diacyl GlcN-1-P found in a phosphatidylglycerol-deficient mutant.

We have determined the complete structure of a glycolipid (designated lipid X) previously found to accumulate in certain Escherichia coli mutants defective in phosphatidylglycerol synthesis (Nishijima, M., and Raetz, C.R.H. (1979) J. Biol. Chem. 254, 7837-7844). Based on fast atom bombardment mass spectrometry and proton nuclear magnetic resonance studies, this substance is an acylated metabolite of glucosamine 1-phosphate. Lipid X of E. coli has a Mr = 711.87 as the free acid (C34H66NO12P) and contains two beta-hydroxymyristate moieties, one attached as an amide at the 2 position and the other as an ester at the 3 position of the sugar. It has free hydroxyl groups at the 4 and 6 positions, and the anomeric configuration is alpha. The structure of lipid X from E. coli closely resembles the reducing end subunit of lipid A, and it might represent a very early precursor in the biosynthesis of lipid A. To our knowledge, fatty acyl derivatives of glucosamine 1-phosphate have not been reported previously.

Escherichia coli↗

PubMed1984

16,16-Dimethyl prostaglandin E2 stimulates galactose and glucosamine but not serine incorporation in rat gastric mucous cells.

It has been suggested that the cytoprotective effect of prostaglandins could be mediated by an increased mucus glycoprotein secretion in the stomach. In the rat we studied the mucus glycoprotein synthesis after an in vivo treatment with 16,16-dimethyl prostaglandin E2 (10 micrograms/kg X day subcutaneously) for 1 h or 7 days. The incorporation rate of [3H]galactose, [3H]glucosamine, and [3H]serine was determined by light microscopic autoradiography in the ex vivo vascularly perfused stomach. Prostaglandin increased the rate of [3H]galactose and [3H]glucosamine incorporation twofold to fourfold in the fundic surface mucous cells; but the total protein synthesis as measured by [3H]serine incorporation was not increased. Analyses of purified mucus glycoprotein did not show an effect on carbohydrate composition, oligosaccharide chain size, nor on buoyant density, after prostaglandin treatment. The present study reveals that 16,16-dimethyl prostaglandin E2 stimulates the mucus glycoprotein synthesis in the fundic mucous cells. This effect may well be one of the mechanisms by which prostaglandin protects the stomach against noxious agents.

16,16-Dimethylprostaglandin E2↗

PubMed1983

Degradation of [6-3H]- and [1-14C]glucosamine-labeled asialo-alpha 1-acid glycoprotein by the perfused rat liver.

We studied the degradation and metabolism of radioactive glucosamine-labeled asialo-alpha 1-acid glycoprotein by the perfused rat liver. Removal of 130 micrograms of the protein from the perfusate occurred with a T 1/2 of 10.3 min. Radioactivity associated initially with the microsomal fraction of the tissue homogenate and was then transferred to the lysosomes where hydrolysis of N-acetylglucosamine residues took place. Radioactivity left the lysosomal-rich fraction of the homogenate with a T 1/2 of 50 min. Final accumulation of radioactivity was in the supernatant and greater than 80% of this material was found to be UDP-N-acetylhexosamines. In those studies, 10 mumol of unlabeled glucosamine had been added to the perfusate to expand the intracellular pool of UDP-GlcNAc and prevent further metabolism of any radioactive N-acetylglucosamine released by the lysosomes. When this procedure was not done, greater than one-third of the lysosomally derived N-acetylglucosamine was reused by the liver to form new radioactive glycoproteins secreted into the perfusate. Overall hydrolysis of N-acetylglucosamine from the glycoprotein substrate was greater than 80% during 2 h of perfusion. However, leupeptin, a thiol cathepsin inhibitor, decreased the release of amino sugar by 50%, even though this compound had no effect on the activity of any lysosomal glycosidase in vitro. Large glycopeptides of molecular weight 35,000 accumulated in the lysosomes due to leupeptin. From these studies, we conclude that efficient digestion of the carbohydrate component of this glycoprotein in situ requires the concerted activity of both lysosomal glycosidases and proteases.

Animals↗

PubMed1983

Distributions of 35S-sulfate and 3H-glucosamine in the angular region of the hamster: light and electron microscopic autoradiography.

The distribution of 35S-sulfate and 3H-glucosamine in the angular region of the hamster was studied by light and electron microscopic autoradiography following intraperitoneal injection of these compounds to hamsters. Exposed silver grains of 35S-sulfate were concentrated in the trabecular meshwork, sclera, and cornea, and grains of 3H-glucosamine were localized in the trabecular region. The radioactivity of both isotopes was observed in the Golgi apparatuses of the endothelial cells of the angular aqueous plexus and the trabecular meshwork. The grains were noted over the entire cytoplasm, except for the nucleus, and then were incorporated into the amorphous substance and collagen fibers in the region adjacent to the angular aqueous sinus. These results suggest that endothelial cells in the angular region synthesize and secrete the sulfated glycosaminoglycans and hyaluronic acid.

Animals↗

PubMed1982

Incorporation in vitro of [3H]glucosamine or [3H]glucose and [35S]SO42- into rat gastric mucosa. Presence of N-acetylhexosamine mono- and disulfates and galactose monosulfate in glycoprotein.

Rat gastric mucosa segments incorporate [3H]glucosamine and [35S]sulfate into glycosaminoglycans and glycoproteins. After 6-h incubation, the order of radioactivity incorporated from both precursors was glycoproteins greater than heparan sulfate greater than chondroitin sulfate. Pulse-chase studies indicate that much of the tissue-bound radioactivity was extruded into the medium by the 6th hour of incubation. The glycoprotein fraction was electrophoretically polydisperse and its subfractions exhibited a wide range of 3H/35S. Mild acid hydrolysis of the glycoprotein fraction afforded sulfated hexosamine fractions which migrated like N-acetylhexosamine mono- and disulfates by paper chromatography and by paper electrophoresis and exhibited 3H/35S which was in accord with the presence of mono- and disulfated compounds. The ratio of the monosulfated to the disulfated species was about 7 to 1. In separate studies, both of these compounds were found in the glycoprotein fraction elaborated into the medium, the glycoprotein from the combined tissue plus medium, and in the sulfated oligosaccharide isolated from the latter by reductive alkaline cleavage. Subsequent acid hydrolysis and paper chromatographic examination of the sugars liberated from each of these compounds revealed the presence of glucosamine as the principal amino sugar. The results of a periodate oxidation study of the N-acetylhexosamine monosulfate were in accord with N-acetylhexosamine 6-sulfate being the principal compound. About 20% of the 3H in the N-acetylhexosamine monosulfate and 10% of the 3H in the disulfated compound were found associated with galactosamine. Separate incorporation studies with [35S] sulfate and [3H]glucose not only confirmed the presence of N-acetylhexosamine mono- and disulfates in the glycoprotein fraction but also demonstrated the presence of galactose monosulfate therein.

Animals↗

PubMed1993

Radioautographic study on the aging change of 3H-glucosamine uptake in mouse ileum.

The changes of the localization of incorporated glucosamine in mice ilea due to aging were studied by light microscopic radioautography in 10 groups of mice from fetus (19th day of embryo) to senescent (postnatal 2 years). After intraperitoneal injection of 6-3H-D-glucosamine the ilea of respective age groups were taken out and processed for light microscopic radioautography. The numbers of silver grains were counted at each part of ileal mucosal cells. The results show that the silver grains of columnar epithelial cells were localized mainly on brush border and Golgi region, and the grains of goblet cells were localized on Golgi region and mucous granules. Comparing the intestinal villi and crypts, the uptake of columnar epithelial cells and villi goblet cells was higher than these cells in crypt. The number of grains in respective age groups increased from perinatal to mature adults due to aging.

Aging↗

PubMedDate not supplied

[The effect of the amino sugar glucosamine on the endogenous intoxication processes in pulmonary edema in rats].

The effects of glycosamine aminosugar on the processes of endotoxicosis and lipid peroxidation were thoroughly studied in rats with toxic pulmonary edema. There was a glycosamine-induced decrease in markers of endotoxicosis, such as medium-weight molecular peptides and malonic dialdehyde in serum and lung tissue. Administration of exogenous glucosamine resulted in its incorporation into the membranes of target organs, connective tissue and normalized the levels of endogenous N-acetyl-glucosamine, which finally determined antitoxic and antioxidative properties in this aminosugar.

Ammonium Chloride↗

PubMed1991

Ecdysteroid-stimulated synthesis and secretion of an N-acetyl-D-glucosamine-rich glycopeptide in a lepidopteran cell line derived from imaginal discs.

Hormone-regulated processing of N-acetyl-D-glucosamine was studied in an insect cell line derived from imaginal wing discs of the Indian meal moth, Plodia interpunctella (Hübner). The cell line, IAL-PID2, responded to treatment with 20-hydroxyecdysone with increased incorporation of GlcNAc into glycoproteins. Cycloheximide and tunicamycin counteracted the action of the hormone. In particular, treatment with 20-hydroxyecdysone resulted in the secretion of a 5,000 dalton N-acetyl-D-glucosamine-rich glycopeptide by the IAL-PID2 cells. Accumulation of this peptide was prevented by the use of teflubenzuron, a potent chitin synthesis inhibitor. A glycopeptide of similar molecular weight was observed in imaginal discs of P. interpunctella treated with 20-hydroxyecdysone in vitro, under conditions that induce chitin synthesis. Although the function of the 5,000 dalton glycopeptide is not known, we believe that the PID2 cell line is a promising model for molecular analysis of ecdysteroid-regulated processing of aminosugars by epidermal cells during insect development.

Acetylglucosamine↗

PubMed2001

Allosteric transition and substrate binding are entropy-driven in glucosamine-6-phosphate deaminase from Escherichia coli.

Glucosamine-6P-deaminase (EC 3.5.99.6, formerly glucosamine-6-phosphate isomerase, EC 5.3.1.10) from Escherichia coli is an attractive experimental model for the study of allosteric transitions because it is both kinetically and structurally well-known, and follows rapid equilibrium random kinetics, so that the kinetic K(m) values are true thermodynamic equilibrium constants. The enzyme is a typical allosteric K-system activated by N-acetylglucosamine 6-P and displays an allosteric behavior that can be well described by the Monod-Wyman-Changeux model. This thermodynamic study based on the temperature dependence of allosteric parameters derived from this model shows that substrate binding and allosteric transition are both entropy-driven processes in E. coli GlcN6P deaminase. The analysis of this result in the light of the crystallographic structure of the enzyme implicates the active-site lid as the structural motif that could contribute significantly to this entropic component of the allosteric transition because of the remarkable change in its crystallographic B factors.

Acetylglucosamine↗

PubMed2000

Crystal structure of N-acyl-D-glucosamine 2-epimerase from porcine kidney at 2.0 A resolution.

The X-ray crystallographic structure of N-acyl-d-glucosamine 2-epimerase (AGE) from porcine kidney, which has been identified to be a renin-binding protein (RnBP), was determined by the multiple isomorphous replacement method and refined at 2.0 A resolution with a final R-factor of 16.9 % for 15 to 2.0 A resolution data. The refined structure of AGE comprised 804 amino acid residues (one dimer) and 145 water molecules. The dimer of AGE had an asymmetric unit with approximate dimensions 46 Ax48 Ax96 A. The AGE monomer is composed of an alpha(6)/alpha(6)-barrel, the structure of which is found in glucoamylase and cellulase. One side of the AGE alpha(6)/alpha(6)-barrel structure comprises long loops containing five short beta-sheets, and contributes to the formation of a deep cleft shaped like a funnel. The putative active-site pocket and a possible binding site for the substrate N-acetyl-d-glucosamine (GlcNAc) were found in the cleft. The other side of the alpha(6)/alpha(6)-barrel comprises short loops and contributes to the dimer formation. At the dimer interface, which is composed of the short loops and alpha-helices of the subunits, five strong ion-pair interactions were observed, which play a major role in the dimer assembly. This completely ruled out the previously accepted hypothesis that the formation of the RnBP homodimer and RnBP-renin heterodimer requires the leucine zipper motif present in RnBP.

Animals↗

PubMed2001

Channeling of ammonia in glucosamine-6-phosphate synthase.

Glucosamine-6-phosphate synthase catalyses the first and rate-limiting step in hexosamine metabolism, converting fructose 6-phosphate into glucosamine 6-phosphate in the presence of glutamine. The crystal structure of the Escherichia coli enzyme reveals the domain organisation of the homodimeric molecule. The 18 A hydrophobic channel sequestered from the solvent connects the glutaminase and isomerase active sites, and provides a means of ammonia transfer from glutamine to sugar phosphate. The C-terminal decapeptide sandwiched between the two domains plays a central role in the transfer. Based on the structure, a mechanism of enzyme action and self-regulation is proposed. It involves large domain movements triggered by substrate binding that lead to the formation of the channel.

Ammonia↗

PubMed1992

Inhibition of superoxide anion release from human polymorphonuclear leukocytes by N-acetyl-galactosamine and N-acetyl-glucosamine.

This study shows that N-acetyl-galactosamine and N-acetyl-glucosamine can diminish the production of superoxide anion from cytochalasin-B treated PMNs stimulated with FMLP. Inhibition ranged from 80.9% to 1.8%. N-acetyl-galactosamine was superior to N-acetyl-glucosamine, but both showed their action in a dose-related fashion. The mannosamine may diminish the superoxide production, but without a statistical significance. Other sugars such as L-fucose, D-fucose and D-glucose failed to induce inhibition of superoxide generation. Previous reports showed that sugars interfere with carbohydrates lectins interaction. This study shows that aminosugars can do more than interfere with carbohydrates-lectin interaction. The mechanism is not completely known yet. The question whether aminosugars affect cell-cell interaction, regulation of respiratory burst, inflammatory mediators functions, or the glucose uptake and utilization needs further study.

Acetylgalactosamine↗

PubMed2002

Identification of the N-acetyl-D-glucosamine-inducible element in the promoter of the Trichoderma atroviride nag1 gene encoding N-acetyl-glucosaminidase.

We have investigated the regulation by N-acetyl-glucosamine of the nag1 gene of the mycoparasitic biocontrol fungus Trichoderma atroviride (= T. harzianum P1), which encodes a 73-kDa N-acetyl-beta-D-glucosaminidase. The use of translational fusions revealed that a 290-bp fragment of the 5' regulatory region of nag1 is sufficient to confer inducibility on the Aspergillus niger goxA gene. The region between positions -150 and -290, upstream of the nag1 coding region, was investigated using in vivo methylation protection analysis and electrophoretic mobility shift assays (EMSAs). Two neighbouring regions that interacted with regulatory proteins were identified, and bases essential for these interactions were determined in vitro. These data reveal protein binding to a CCCCT element at -240, a CCAGN(13)CTGG motif at -284, and a CCAAT-box which is present in the spacer of the latter motif. Evidence for the binding of a Hap2/3/5 complex to this CCAAT motif is presented. Protein binding to all three motifs was constitutive, and no differences were observed between induced and non-induced cultures. Mutation of either the CCAGN(13)CTGG or the AGGGG motif resulted in loss of inducibility of nag1 expression by N-acetyl-D-glucosamine in vivo.

Acetylglucosamine↗

PubMed1989

Evidence for vicinal thiols and their functional role in glucosamine-6-phosphate deaminase from Escherichia coli.

Methylation of glucosamine-6-phosphate isomerase deaminase (2-amino-2-deoxy-D-glucose-6-phosphate ketol-isomerase, deaminating, or glucosamine-6-phosphate deaminase, EC 5.3.1.10), from Escherichia coli produces a modified protein having two alkylated sulfhydryls per each polypeptide chain. The enzyme is still active and allosteric, but exhibits a lower homotropic cooperativity and its Vmax/Etotal is almost exactly half that of the native enzyme. Arsenite produces comparable kinetic changes that can be reversed with ethanedithiol but not with 2-thioethanol or dialysis. Thiols can be oxidized by molecular oxygen using the (1,10-phenanthroline)3-Cu(II) complex as catalyst; the enzyme obtained no longer has titrable SH groups with 5,5'-dithiobis(2-nitrobenzoic acid) and displays kinetic behavior similar to that of the other chemically modified forms of the deaminase using monofunctional or bifunctional reagents. The results reported indicate that the involved sulfhydryls are vicinal groups, and are located in a region of the molecule that moves as a whole in the allosteric transition.

Aldose-Ketose Isomerases↗