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At least 883 records · Page 49Linked to original sources
PubMed2000

High glucose and glucosamine induce insulin resistance via different mechanisms in 3T3-L1 adipocytes.

Sustained hyperglycemia induces insulin resistance, but the mechanism is still incompletely understood. Glucosamine (GlcN) has been extensively used to model the role of the hexosamine synthesis pathway (HSP) in glucose-induced insulin resistance. 3T3-L1 adipocytes were preincubated for 18 h in media +/- 0.6 nmol/l insulin containing either low glucose (5 mmol/l), low glucose plus GlcN (0.1-2.5 mmol/l), or high glucose (25 mmol/l). Basal and acute insulin-stimulated (100 nmol/l) glucose transport was measured after re-equilibration in serum and insulin-free media. Preincubation with high glucose or GlcN (1-2.5 mmol/l) inhibited basal and acute insulin-stimulated glucose transport only if insulin was present during preincubation. However, only preincubation with GlcN plus insulin inhibited insulin-stimulated GLUT4 translocation. GLUT4 and GLUT1 protein expression were not affected. GlcN (2.5 mmol/l) increased cellular UDP-N-acetylhexosamines (UDP-HexNAc) by 400 and 900% without or with insulin, respectively. High glucose plus insulin increased UDP-HexNAc by 30%. GlcN depleted UDP-hexoses, whereas high glucose plus insulin increased them. Preincubation with 0.5 mmol/l GlcN plus insulin maximally increased UDP-HexNAc without affecting insulin-stimulated or basal glucose transport. GlcN plus insulin (but not high glucose plus insulin) caused marked GlcN dose-dependent accumulation of GlcN-6-phosphate, which correlated with insulin resistance of glucose transport (r = 0.935). GlcN plus insulin (but not high glucose plus insulin) decreased ATP (10-30%) and UTP (>50%). GTP was not measured, but GDP increased. Neither high glucose plus insulin nor GlcN plus insulin prevented acute insulin stimulation (approximately 20-fold) of insulin receptor substrate 1-associated phosphatidylinositol (PI)-3 kinase. We have come to the following conclusions. 1) Chronic exposure to high glucose or GlcN in the presence of low insulin caused insulin resistance of glucose transport by different mechanisms. 2) GlcN inhibited GLUT4 translocation, whereas high glucose impaired GLUT4 "intrinsic activity" or membrane intercalation. 3) Both agents may act distally to PI-3 kinase. 4) GlcN has metabolic effects not shared by high glucose. GlcN may not model HSP appropriately, at least in 3T3-L1 adipocytes.

3T3 Cells↗
PubMed2005

Effects of glucosamine hydrochloride and chondroitin sulphate, alone and in combination, on normal and interleukin-1 conditioned equine articular cartilage explant metabolism.

REASONS FOR PERFORMING STUDY: Clinical trials in human and veterinary literature have documented the benefits of oral nutraceutical joint supplements containing glucosamine (GU) and chondroitin sulphate (CS) to treat mild to moderate osteoarthritis, but the effects of these components have not yet been conclusively determined. OBJECTIVES: To assess varying dosages of GU and CS on normal and interleukin-1alpha (IL-1) conditioned equine cartilage explants and rationalise the use of these products. HYPOTHESIS: Treatment would not be detrimental to cartilage metabolism and higher dosages and the combination of GU and CS would be more beneficial than lower dosages and. GU or CS alone. METHODS: Articular cartilage explants collected from the femoral trochlea and condyles were cultured in normal and IL-1 conditioned media. Treatment groups included 0, 12.5, 25,125 and 250 microg/ml concentrations of GU alone, CS alone, or GU+CS in combination. Glycosaminoglycan (GAG) synthesis and total GAG content in the explants and media were analysed. RESULTS: There were no detrimental effects of GU, CS or GU+CS on cartilage metabolism. High dosages of GU+CS reduced total GAG release into the media (degradation). CONCLUSIONS: Our results suggests that GU+CS may prevent cartilage GAG degradation. POTENTIAL RELEVANCE: The combination of GU and CS may be more effective in preventing or treating osteoarthritis in horses than either product alone.

Animals↗
PubMed1992

Exploring the hexokinase glucose binding site through correlation analysis and molecular modeling of glucosamine inhibitors.

A series of N-substituted glucosamines has been designed, synthesized, and tested as inhibitors of yeast hexokinase. All derivatives exhibited competitive inhibition kinetics with respect to glucose. Quantitative structure-activity relationships were derived from the resulting inhibition data. The most significant equation demonstrated the existence of highly specific steric effects for the seven meta-substituted benzoylglucosamines included in the relationship. Molecular modeling of potential complexes between the inhibitors and the hexokinase substrate binding site strongly suggests that the steric effects arise from potential contacts with two amino acid residues lying in the region occupied by the amide substituents.

Binding Sites↗
PubMed1986

Factors influencing invasion of erythrocytes by Plasmodium falciparum parasites: the effects of an N-acetyl glucosamine neoglycoprotein and an anti-glycophorin A antibody.

When schizont-infected erythrocytes were incubated with N-acetyl glucosamine coupled to bovine serum albumin (GluNAc-BSA), the number of new ring forms which appeared several hours later was reduced and the number of abnormal and unruptured schizont-infected erythrocytes was increased compared with controls, indicating that GluNAc-BSA prevents invasion by a toxic effect on schizonts rather than by receptor blockade. Invasion of erythrocytes by Plasmodium falciparum was inhibited by a monoclonal antibody against glycophorin A, but inhibition also occurred with P. knowlesi, a parasite that is known to invade independently of glycophorin A. Inhibition of invasion with anti-glycophorin A is unlikely to be related to receptor blockade and is probably related to decreased deformability of the erythrocyte membrane caused by the binding of this antibody. Previous studies suggesting that GluNAc-BSA and anti-glycophorin A antibodies inhibit invasion by receptor blockade should be reevaluated. Erythrocytes deficient in glycophorin C and band 4.1 were also resistant to invasion by both P. falciparum and P. knowlesi.

Acetylglucosamine↗
PubMedDate not supplied

Use of glucosamine and chondroitin sulfate in the management of osteoarthritis.

The goals of osteoarthritis therapy are to decrease pain and to maintain or improve joint function. The pharmacologic treatment of this condition has included the use of aspirin, acetaminophen, and nonsteroidal anti-inflammatory drugs. More recently, numerous studies have investigated the potential role of chondroprotective agents in repairing articular cartilage and decelerating the degenerative process. The reports of limited clinical experience with two of these agents, glucosamine and chondroitin sulfate, as well as the accompanying publicity in the popular media, have generated controversy. Advocates of these alternative modalities cite reports of progressive and gradual decline of joint pain and tenderness, improved mobility, sustained improvement after drug withdrawal, and a lack of significant toxicity associated with short-term use of these agents. Critics point out that in the great majority of the relevant clinical trials, sample sizes were small and follow-up was short-term.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Glucosamine, chondroitin, and manganese ascorbate for degenerative joint disease of the knee or low back: a randomized, double-blind, placebo-controlled pilot study.

OBJECTIVE: A 16-week randomized, double-blind, placebo-controlled crossover trial of a combination of glucosamine HCl (1,500 mg/day), chondroitin sulfate (1,200 mg/day), and manganese ascorbate (228 mg/day) in degenerative joint disease (DJD) of the knee or low back was conducted. METHODS: Thirty-four males from the U.S. Navy diving and special warfare community with chronic pain and radiographic DJD of the knee or low back were randomized. A summary disease score incorporated results of pain and functional questionnaires, physical examination scores, and running times. Changes were presented as a percentage of the patient's average score. RESULTS: Knee osteoarthritis symptoms were relieved as demonstrated by the summary disease score (-16.3%; p = 0.05), patient assessment of treatment effect (p = 0.02), visual analog scale for pain recorded at clinic visits (-26.6%; p = 0.05) and in a diary (-28.6%; p = 0.02), and physical examination score (-43.3%; p = 0.01). Running times did not change. The study neither demonstrated, nor excluded, a benefit for spinal DJD. Side effect frequency was similar to that at baseline. There were no hematologic effects. CONCLUSIONS: The combination therapy relieves symptoms of knee osteoarthritis. A larger data set is needed to determine the value of this therapy for spinal DJD. Short-term combination therapy appears safe in this setting.

Activities of Daily Living↗
PubMed1999

Scintigraphic evaluation of dogs with acute synovitis after treatment with glucosamine hydrochloride and chondroitin sulfate.

OBJECTIVE: To evaluate the effects of orally administered glucosamine hydrochloride (GlAm)-chondroitin sulfate (CS) and GlAm-CS-S-adenosyl-L-methionine (SAMe) on chemically induced synovitis in the radiocarpal joint of dogs. ANIMALS: 32 adult mixed-breed dogs. PROCEDURE: For 21 days, all dogs received a sham capsule (3 groups) or GlAm-CS (prior treatment group) in a double-blinded study. Unilateral carpal synovitis was induced by injecting the right radiocarpal joint with chymopapain and the left radiocarpal joint (control joint) with saline (0.9% NaCl) solution. Joints were injected on alternate days for 3 injections. After induction of synovitis, 2 groups receiving sham treatment were given GlAm-CS or GlAm-CS-SAMe. Another group continued to receive sham capsules (control group). Joint inflammation was quantified, using nuclear scintigraphy, before injection of joints and days 13, 20, 27, 34, 41, and 48 after injection. Lameness evaluations were performed daily. RESULTS: Dogs given GlAm-CS before induction of synovitis had significantly less scintigraphic activity in the soft-tissue phase 48 days after joint injection, significantly less uptake in the bone phase 41 and 48 days after joint injection, and significantly lower lameness scores on days 12 to 19, 23, and 24 after injection, compared with other groups. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of results of this study suggest that prior treatment with GlAm-CS for 21 days had a protective effect against chemically induced synovitis and associated bone remodeling. Prior treatment with GlAm-CS also reduced lameness in dogs with induced synovitis.

Administration, Oral↗
PubMed2001

Evaluation of glucosamine sulfate compared to ibuprofen for the treatment of temporomandibular joint osteoarthritis: a randomized double blind controlled 3 month clinical trial.

OBJECTIVE: To compare the treatment potential of glucosamine sulfate (GS) and ibuprofen in patients diagnosed with temporomandibular joint (TMJ) osteoarthritis (OA). METHODS: Forty women and 5 men received either GS (500 mg tid) or ibuprofen (400 mg tid) for 90 days in a randomized double blind study. ASSESSMENT: TMJ pain with function, pain-free, and voluntary maximum mouth opening, Brief Pain Inventory (BPI) questionnaire and masticatory muscle tenderness were performed after a one week washout and at Day 90. Acetaminophen (500 mg) dispensed for breakthrough pain was counted every 30 days to Day 120. RESULTS: In total, 176 adults were interviewed, 45 (26%) qualified, 39 (87%) completed the study (21 GS, 18 ibuprofen). Four discontinued due to stomach upset (3 ibuprofen, one GS), one due to dizziness (GS), one due to inadequate pain control (ibuprofen). Within-group analysis revealed significant improvement compared to baseline of all variables in both treatment groups but no change in acetaminophen used. Fifteen GS (71%) and 11 ibuprofen (61%) improved, with positive clinical response taken as a 20% decrease in primary outcome (TMJ pain with function). The number of patients with positive clinical response was not statistically different between groups (p = 0.73). Between-group comparison revealed that patients taking GS had a significantly greater decrease in TMJ pain with function, effect of pain, and acetaminophen used between Day 90 and 120 compared with patients taking ibuprofen. CONCLUSION: GS and ibuprofen reduce pain levels in patients with TMJ degenerative joint disease. In the subgroup that met the initial efficacy criteria, GS had a significantly greater influence in reducing pain produced during function and effect of pain with daily activities. GS has a carryover effect.

Adult↗
PubMed2002

Facilitated diffusion of glucosamine-6-phosphate synthase inhibitors enhances their antifungal activity.

N3-(4-Methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP) and 2-amino-2-deoxy-D-glucitol-6-phosphate (ADGP) are strong inhibitors of the essential fungal enzyme, glucosamine-6-phosphate synthase, but their antifungal activity is poor, due to slow penetration of these agents through the cytoplasmic membrane. In the present studies we have exploited the possibility of enhancement of ADGP and FMDP antifungal activity by improving their transport properties. It has been found that membrane-permeabilising polyene macrolides amphotericin B (AMB) and its N-methyl-N-fructosyl methyl ester derivative (MF-AME), at subinhibitory concentrations, facilitate diffusion of ADGP through the fungal cell membrane, thus allowing a decrease of its minimal inhibitory concentration (MIC). Synergistic effects have been observed for combinations of ADGP with AMB or MF-AME. Fractional inhibitory concentration (FIC) indexes, determined against a number of Candida spp., have been in the 0.18-0.81 range. Weak antifungal synergistic effects have been found for combinations of FMDP with AMB or MF-AME. ADGP can be easily encapsulated into unilamellar lipid vesicles. Liposomal preparations of ADGP demonstrated stronger antifungal activity against some fungal strains than free ADGP.

Antifungal Agents↗
PubMedDate not supplied

High performance liquid chromatographic determination of glucosamine in rat plasma.

PURPOSE: A high performance liquid chromatographic method was developed for the determination of glucosamine (GlcN) in rat plasma. METHOD: Internal standard, galactosamine, was added to 100 micro L of plasma containing GlcN followed by precipitation of plasma proteins with acetonitrile. Evaporation of the decanted supernatant solution was accelerated by the addition of methanol. GlcN was derivatized by addition of a solution containing 1-naphthyl isothiocyanate. Sample cleanup included passage through an anion exchange cartridge. Analysis was accomplished by injection of 0.1 mL of the sample solution into an isocratic HPLC system consisting of a C18 column, a mobile phase of acetonitrile: water: acetic acid: triethylamine (4.5: 95.5:0.1:0.05), a flow rate of 0.9 mL/min, and a UV detector set at 254 nm. RESULTS: Galactosamine and GlcN appeared 26 and 29 min post-injection, respectively. The assay was linear over the range of 1.25-400 micro g/mL (CV<10%) with a detection limit of 0.63 microg/mL and a limit of quantification of 1.25 microg/mL. The method was applied to the determination of GlcN in rat plasma after oral administration of 350 mg/kg of GlcN hydrochloride. CONCLUSION: The present assay is specific, sensitive, precise, and accurate and is suitable for pharmacokinetic studies.

Animals↗
PubMed2001

[Spectral study on five complexes derived from D-glucosamine and their effect on DNA].

Complexes CuGlu, ZnGlu, NiGlu, Fe(III) Glu, Co(III) Glu where Glu is d-glucosamine have been synthesized. The effects of these compounds on DNA have been studied by the UV-Vis, fluorescence and SERS methods. The possible active ways of these complexes with DNA have been discussed. The results show that the adsorbed state of these complexes on silver sols are similar, and that CuGlu, Co(III) Glu have strong interactions with DNA. Their acting ways on DNA are different. It is worth to do a further research on these compounds as anticancer drugs.

Antineoplastic Agents↗
PubMed2004

Glucosamine for osteoarthritis: part II, biologic and metabolic controversies.

Glucosamine is a popular nutritional supplement, discussed in clinical offices, peer-reviewed literature, and the media. Despite its popularity, much information is still needed regarding its biological effect in-vivo and its effects on glucose metabolism. The biologic effects of other constituents such as sulfate, chondroitin sulfate, and other additives need to be investigated as well.

Dietary Supplements↗
PubMed2004

Improved borate method for the rapid distinction of glucosamine and galactosamine in an exopolysaccharide produced by Citrobacter sp.

An improved borate method for the quantitative distinction of glucosamine (GlcN) and galactosamine (GalN) in a mixture is presented which is based on the Elson-Morgan method with addition of sodium borate to differentiate colour formation by the two hexosamines. The r2 value and maximum deviation of the method based on calculations derived in this study were 0.9979 and 5.1 %, respectively. Using this method, the GlcN/GalN ratio in an exopolysaccharide (EPS) produced by Citrobacter sp. was found to change with time during the production process, with a maximum value at 9.8:1.

Borates↗
PubMed1997

[Surface-enhanced Raman spectra studies on four complexes derived from D-glucosamine and alpha-glycine and their effect on DNA].

Raman scattering of four complexes derived from d-glucosamine and alpha-glycine and their effects on DNA were studied with surface-enhanced Raman spectra (SERS). It was found that their SERS had shown little difference for their similar structural. Their interaction abilities on DNA were poor according to the change of their SERS spectrun after adding DNA to their water solution except for Co(III)GluG, which has strong effect on DNA. NiGluG's adsorptive ability on Ag sol is the strongest among other three complexes.

DNA↗
PubMed2005

Glucosamine-6-phosphate synthase, a novel target for antifungal agents. Molecular modelling studies in drug design.

Fungal infections are a growing problem in contemporary medicine, yet only a few antifungal agents are used in clinical practice. In our laboratory we proposed the enzyme L-glutamine: D-fructose-6-phosphate amidotransferase (EC 2.6.1.16) as a new target for antifungals. The structure of this enzyme consists of two domains, N-terminal and C-terminal ones, catalysing glutamine hydrolysis and sugar-phosphate isomerisation, respectively. In our laboratory a series of potent selective inhibitors of GlcN-6-P synthase have been designed and synthesised. One group of these compounds, including the most studied N3-(4-methoxyfumaroyl)-l-2,3-diaminopropanoic acid (FMDP), behave like glutamine analogs acting as active-site-directed inactivators, blocking the N-terminal, glutamine-binding domain of the enzyme. The second group of GlcN-6-P synthase inhibitors mimic the transition state of the reaction taking place in the C-terminal sugar isomerising domain. Surprisingly, in spite of the fact that glutamine is the source of nitrogen for a number of enzymes it turned out that the glutamine analogue FMDP and its derivatives are selective against GlcN-6-P synthase and they do not block other enzymes, even belonging to the same family of glutamine amidotransferases. Our molecular modelling studies of this phenomenon revealed that even within the family of related enzymes substantial differences may exist in the geometry of the active site. In the case of the glutamine amidotransferase family the glutamine binding site of GlcN-6-P synthase fits a different region of the glutamine conformational space than other amidotransferases. Detailed analysis of the interaction pattern for the best known, so far, inhibitor of the sugar isomerising domain, namely 2-amino-2-deoxy-D-glucitol-6-phosphate (ADGP), allowed us to suggest changes in the structure of the inhibitor that should improve the interaction pattern. The novel ligand was designed and synthesised. Biological experiments confirmed our predictions. The new compound named ADMP is a much better inhibitor of glucosamine-6-phosphate synthase than ADGP.

Antifungal Agents↗
PubMed2005

N-acylation of glucosamine modulates chondrocyte growth, proteoglycan synthesis, and gene expression.

OBJECTIVE: To examine the effects of glucosamine (GlcN) and some N-acylated (GlcNAcyl) derivatives on the proliferation and proteoglycan (PG) synthesis of bovine articular chondrocyte (BAC); and to expand these results to human articular chondrocytes (HAC) and study the modulation of gene regulation by these compounds. METHODS: The compounds tested were: glucose (Glc), GlcN.HCl, N-acetyl GlcN (GlcNAc), and N-butyryl GlcN, (GlcNBu). GlcNBu was synthesized from GlcN and butyric anhydride. For the chondrocyte cultures, both anchorage-dependent (AD) and an anchorage-independent (AI) system (alginate beads) were evaluated. Following the various additions, BAC were assessed for total cell number, DNA, or total PG synthesis at different times. Utilizing similar conditions, human cDNA microarrays were performed for the HAC after harvesting total RNA. RESULTS: For AD cultures, the addition of GlcN.HCl (0.1-5.0 mM) to BAC or HAC cultures inhibited cell proliferation and total PG synthesis in a dose-dependent manner. For AI cultures, the inhibitory effects of GlcN.HCl on cell proliferation were less prominent, and PG synthesis increased slightly more for the GlcNAcyl than the GlcN additions. In the AD system, the addition of GlcNAc did not result in the inhibitory effect of GlcN.HCl, while GlcNBu addition resulted in an increase in BAC proliferation and PG synthesis that could not be explained by the Bu moiety alone. For the HAC, additions of 0.1 mM GlcNBu resulted in upregulation of a large number of genes, with only a few downregulated, while GlcN addition resulted in no upregulation and one downregulated gene, for preset stringency criteria. CONCLUSION: Addition of GlcNBu to BAC or HAC to AD cultures generally stimulated cell proliferation and PG synthesis, while addition of GlcN resulted in inhibition of these indicators. The inhibitory effects of the GlcN molecule appear to be related to the unsubstituted amino group. Additions of GlcNBu, but not GlcN, to HAC resulted in upregulation in the expression of a large number of genes.

Acetylation↗
PubMed1975

Autoradiographic localization of glycoprotein in human breast cancer cells maintained in organ culture after incubation with (3H)fucose or (3H)glucosamine.

Explants of nine infiltrating duct carcinomas of the human female breast, maintained in organ culture, were exposed to the glycoprotein precursors, L-[3H]furcose and [3H]glucosamine, in order to determine the cellular distribution of newly synthesized glycoprotein as revealed by autoradiography with the light and electron microscopes. Explants were incubated with a single isotope for 2 hr, at which time some of the labeled explants were removed for autoradiographic analysis while the rest were transferred to nonradioactive medium for an additional 24 hr. After exposure to label for 24 hr, autoradiography with each isotope was similar and showed strong reactions over most tumor cells. The reactions were due to clumps of silver grains over intracytoplasmic lumina within single tumor cells and silver grains over Golgi saccules, cytoplasmic vesicles, lysosome-like bodies, lateral and basal plasma membranes, and microvilli. Extracellular ductular structures were also heavily labeled. At the later sampling time, Golgi saccules often showed a reduced reaction while the reactions over other organelles and intracellular and extracellular ductular structures remained strong. The observations suggest that in our in vitro system the tumor cells are metabolically active and complete the synthesis of the carbohydrate side chains of glycoproteins within the Golgi apparatus. From there, some of the newly synthesized glycoprotein appears to migrate to plasma membranes and lysosome-like bodies. Furthermore, our data support the notion that many duct carcinomas of the breast exhibit secretory activity by showing that some newly synthesized glycoprotein also appears to become products that are secreted into intracellular and extracellular ductular structures.

Autoradiography↗