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PubMed1984

[Effects of 3,4,5-trimethoxy-N-(3-piperidyl) benzamide (KU-54) on the incorporation (excretion) of 14C-glucosamine in the gastric mucosa and the liver of rats].

Effects of KU-54 on the biosynthesis of glycoprotein in the gastric mucosa and the liver, as measured by the rate of incorporation of 14C-glucosamine, were investigated in rats under various conditions after a single administration of 14C-glucosamine of (9.88 microCi/animal, ip). 14C-glucosamine was incorporated with relative ease in the acid-insoluble fraction of the gastric mucosa. KU-54 at 100 mg/kg was orally administered twice daily for 5 days in rats (though it was given once on the 5th day) before injection of 14C-glucosamine. The rate of 14C-glucosamine incorporation into the acid-insoluble fraction of the gastric mucosa was significantly increased by KU-54, but that of the hepatic tissue was not increased. In addition, hydrocortisone (20 mg/kg) also produced a drop of incorporation of 14C-glucosamine in the gastric mucosa, but oral KU-54 at 100 mg/kg twice daily for 5 days (though it was given once on the 5th day) significantly inhibited the drop of incorporation of 14C-glucosamine in the gastric mucosa, but that in the hepatic tissue was not inhibited. Therefore, the effects of KU-54 were greater in the gastric mucosa than in the hepatic tissue. On the 5th day of the ulcer produced by acetic acid in rats, the specific radioactivity in the mucosa of the margin of the ulcer increased significantly compared with that in the normal (non-ulcerative) mucosa, but this phenomenon was not affected by KU-54.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1981

Double-blind clinical evaluation of intra-articular glucosamine in outpatients with gonarthrosis.

Fifty-four outpatients with gonarthrosis participated in a double-blind clinical test with the aim of evaluating the efficacy and tolerance of intra-articular glucosamine in comparison with a 0.9% NaCl placebo. Each patient had one intra-articular injection per week for five consecutive weeks. Pain, active and passive mobility of the joint, swelling, and generalized and local intolerance symptoms were recorded before beginning the treatment, and four weeks after the last injection. glucosamine reduced pain to a significantly greater extent than did placebo, and resulted in significantly more pain-free patients. The angle of joint flexion substantially increased after glucosamine treatment. Active mobility increased with both treatments, with a more favorable trend after glucosamine administration. Knee swelling did not decrease significantly after glucosamine, whereas it worsened (although no significantly) after placebo. There were no local or general intolerance symptoms during and after treatment. Glucosamine administration was able to accelerate the recovery of arthrosic patients, with no resulting side effects, and to partially restore articular function. In addition, the clinical recovery did not fade after treatment ended, but lasted for the following month, at least. These features are a definite improvement over antirheumatic drugs, the major drawbacks of which are action of short duration and side effects. Glucosamine therapy therefore deserves a selected place in the management of osteoarthrosis.

Adult↗

PubMed1982

The formation of lipid-linked oligosaccharides in Madin-Darby canine kidney cells. Changes in oligosaccharide profiles induced by glucosamine.

Glucosamine inhibits the incorporation of [2-3H]mannose into lipid-linked oligosaccharides and into glycoproteins in influenza virus-infected MDCK cells. Fifty per cent inhibition of these components requires about 2 mM glucosamine. The oligosaccharide portions of the lipid-linked oligosaccharides in cells inhibited with glucosamine were compared to that of normal cells by chromatography on Bio-Gel P-4 columns. In uninhibited cells, the major oligosaccharide formed from [2-3H]mannose was the Glc3Man9GlcNAc2 species as demonstrated by the products of endoglucosaminidase H and alpha-mannosidase digestion. At low concentrations of glucosamine (approximately 2 mM) or in short term incubations (1 to 2 h), the large oligosaccharide disappeared and was replaced by a Man7GlcNAc2 species. This was also characterized by various enzymatic treatments as well as its migration rate on Bio-Gel P-4 as compared to known oligosaccharides. At still higher glucosamine concentrations or longer incubation times, the Man7GlcNAc2 species also disappeared and was replaced by a Man3GlcNAc2 species. The effect of glucosamine was reversible such that when the cells were washed free of this inhibitor, they resumed the synthesis of the Glc3Man9GlcNAc2 species and the other two oligosaccharides disappeared. These smaller oligosaccharides were not observed when glucosamine was replaced by either 5 mM galactosamine or 5 mM N-acetylglucosamine.

Animals↗

PubMed2002

Glucosamine sulfate use and delay of progression of knee osteoarthritis: a 3-year, randomized, placebo-controlled, double-blind study.

BACKGROUND: Conventional symptomatic treatments for osteoarthritis do not favorably affect disease progression. The aim of this randomized, placebo-controlled trial was to determine whether long-term (3-year) treatment with glucosamine sulfate can modify the progression of joint structure and symptom changes in knee osteoarthritis, as previously suggested. METHODS: Two hundred two patients with knee osteoarthritis (using American College of Rheumatology criteria) were randomized to receive oral glucosamine sulfate, 1500 mg once a day, or placebo. Changes in radiographic minimum joint space width were measured in the medial compartment of the tibiofemoral joint, and symptoms were assessed using the algo-functional indexes of Lequesne and WOMAC (Western Ontario and McMaster Universities). RESULTS: Osteoarthritis was of mild to moderate severity at enrollment, with average joint space widths of slightly less than 4 mm and a Lequesne index score of less than 9 points. Progressive joint space narrowing with placebo use was -0.19 mm (95% confidence interval, -0.29 to -0.09 mm) after 3 years. Conversely, there was no average change with glucosamine sulfate use (0.04 mm; 95% confidence interval, -0.06 to 0.14 mm), with a significant difference between groups (P =.001). Fewer patients treated with glucosamine sulfate experienced predefined severe narrowings (>0.5 mm): 5% vs 14% (P =.05). Symptoms improved modestly with placebo use but as much as 20% to 25% with glucosamine sulfate use, with significant final differences on the Lequesne index and the WOMAC total index and pain, function, and stiffness subscales. Safety was good and without differences between groups. CONCLUSION: Long-term treatment with glucosamine sulfate retarded the progression of knee osteoarthritis, possibly determining disease modification.

Administration, Oral↗

PubMed2003

Structural and symptomatic efficacy of glucosamine and chondroitin in knee osteoarthritis: a comprehensive meta-analysis.

OBJECTIVE: To assess the structural and symptomatic efficacy of oral glucosamine sulfate and chondroitin sulfate in knee osteoarthritis through independent meta-analyses of their effects on joint space narrowing, Lequesne Index, Western Ontario MacMaster University Osteoarthritis Index (WOMAC), visual analog scale for pain, mobility, safety, and response to treatment. METHODS: An exhaustive systematic research of randomized, placebo-controlled clinical trials published or performed between January 1980 and March 2002 that assessed the efficacy of oral glucosamine or chondroitin on gonarthrosis was performed using MEDLINE, PREMEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Current Contents, BIOSIS Previews, HealthSTAR, EBM Reviews, manual review of the literature and congressional abstracts, and direct contact with the authors and manufacturers of glucosamine and chondroitin. Inclusion, quality scoring, and data abstraction were performed systematically by 2 independent reviewers who were blinded to sources and authors. Conservative approaches were used for clear assessment of potential efficacy. RESULTS: Our results demonstrated a highly significant efficacy of glucosamine on all outcomes, including joint space narrowing and WOMAC. Chondroitin was found to be effective on Lequesne Index, visual analog scale pain, mobility, and responding status. Safety was excellent for both compounds. CONCLUSIONS: Our study demonstrates the structural efficacy of glucosamine and indistinguishable symptomatic efficacies for both compounds. Regarding the relatively sparse data on glucosamine and joint space narrowing and the absence of data on structural effects of chondroitin, further studies are needed to investigate the relationship among time, dose, patient baseline characteristics, and structural efficacy for an accurate, disease-modifying characterization of these 2 compounds.

Administration, Oral↗

PubMed2001

Interleukin-1beta down-regulates the expression of glucuronosyltransferase I, a key enzyme priming glycosaminoglycan biosynthesis: influence of glucosamine on interleukin-1beta-mediated effects in rat chondrocytes.

OBJECTIVE: To assess the variations of galactose-beta-1,3-glucuronosyltransferase I (GlcAT-I) expression related to the decrease in proteoglycan synthesis mediated by interleukin-1beta (IL-1beta) in rat chondrocytes, and to evaluate the influence of glucosamine on the effects elicited by this proinflammatory cytokine. METHODS: Rat articular chondrocytes in primary monolayer cultures or encapsulated into alginate beads were treated with recombinant IL-1beta in the absence or presence (1.0-4.5 gm/liter) of glucosamine. Variations of GlcAT-I and expression of stromelysin 1 (matrix metalloproteinase 3 [MMP-3]) messenger RNA (mRNA) were evaluated by quantitative multistandard reverse transcriptase-polymerase chain reaction. In vitro enzymatic activity of GlcAT-I was measured by thin-layer chromatography, with radiolabeled UDP-glucuronic acid and a digalactoside derivative as substrates. Proteoglycan synthesis was determined by ex vivo incorporation of Na2-35SO4. Nitric oxide synthase and cyclooxygenase activities were monitored by the evaluation of nitrite (NO2-) and prostaglandin E2 (PGE2) produced in the culture medium, respectively. RESULTS: IL-1beta treatment resulted in a marked inhibition of GlcAT-I mRNA expression and in vitro catalytic activity, together with a decrease in proteoglycan synthesis. In addition, glucosamine was able to prevent, in a dose-dependent manner, the inhibitory effects of IL-1beta. In the same way, the amino sugar reduced NO2- and PGE2 production induced by IL-1beta. Finally, the up-regulation of stromelysin 1 (MMP-3) mRNA expression by IL-1beta was fully prevented by glucosamine. CONCLUSION: The results of this study suggest that the deleterious effect of IL-1beta on the anabolism of proteoglycan could involve the repression of GlcAT-I, a key enzyme in the biosynthesis of glycosaminoglycan. Glucosamine was highly effective in preventing these IL-1beta-mediated suppressive effects. The amino sugar also prevented the production of inflammatory mediators induced by the cytokine. This action could account for a possible beneficial effect of glucosamine on osteoarthritic articular cartilage.

Animals↗

PubMed2002

The bioavailability and pharmacokinetics of glucosamine hydrochloride and low molecular weight chondroitin sulfate after single and multiple doses to beagle dogs.

OBJECTIVE: The purpose of this study was to determine the oral bioavailability and pharmacokinetics of a glucosamine (GL) and the disaccharides of chondroitin sulfate (CS) after single and multiple-dosing of a GL/CS combination (Cosamin, Cosequin). METHODS: Male beagle dogs (n = 8, 12 kg) received the following treatments: (1) IV GL (500 mg)/CS (400 mg), (2) p.o. GL (1500 mg)/CS (1200 mg), (3) p.o. GL (2000 mg)/CS (1600 mg), (4) p.o. GL (1500 mg)/CS (1200 mg) QD for days 1-7 and p.o. GL (3000 mg)/CS (2400 mg) from days 8 to 14. Blood samples were collected over 24 h and glucosamine and the disaccharides of chondroitin sulfate were determined. Pharmacokinetic analysis was performed on glucosamine and total chondroitin sulfate disaccharides and parameters were compared across treatments using ANOVA with post hoc analysis. RESULT: After the IV administration, glucosamine declined rapidly in a bi-exponential fashion with a mean (+/- S.D.) elimination t(1/2) of 0.52 (0.25) h. GL absorption was relatively fast (C(max) = 8.95 microg/ml, and T(max) 1.5 h after 1500 mg dose) and the mean bioavailability of glucosamine after single dosing was approximately 12%. The extent of absorption of chondroitin sulfate as indicated by the mean C(max) (21.5 microg/ml) and mean AUC (187 microg/ml h) of total disaccharides after dosing (1600 mg) provides evidence that chondroitin sulfate is absorbed orally. The bioavailability of CS ranged from 4.8 to 5.0% after single dosing and 200-278% upon multiple dosing. CONCLUSION: The results of this study show that both glucosamine and chondroitin sulfate (measured as total disaccharides) are bioavailable after oral dosing. In addition, the low molecular weight chondroitin sulfate used in this study displays significant accumulation upon multiple dosing.

Administration, Oral↗

PubMed2006

Liquid chromatography with electrospray ionization mass spectrometry method for the assay of glucosamine sulfate in human plasma: validation and application to a pharmacokinetic study.

A liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed and validated for the assay of glucosamine sulfate in human plasma. Plasma proteins were precipitated by acetonitrile, followed by vortex mixing and centrifugation. The supernatant was transferred and derivatized with phenyl iso-thiocyanate in acetonitrile at 60 degrees C for 40 min. Chromatographic separation was performed on a C(18) column (Inertsil ODS-3 150 x 2.1 mm i.d., 5 microm, JP) with a mobile phase gradient consisting of 0.2% acetic acid (aqueous) and methanol at a flow-rate of 0.3 mL/min. MS detection using electrospray ionization (ESI) as an interface was used in single ion monitoring mode to determine positive ions at m/z 297. This method was shown to be selective and sensitive for glucosamine sulfate. The limit of detection was 35 ng/mL for glucosamine sulfate in plasma and the linear range was 0.1-20 microg/mL in plasma with a correlation coefficient (r) of 0.9991. The relative standard deviations (RSDs) of intra-day and inter-day assays were 8.7-11.4 and 9.8-12.6%, respectively. Extraction recoveries of glucosamine sulfate in plasma were greater than 73%. This method proved to be simple, reproducible and feasible for pharmacokinetic studies of glucosamine sulfate in healthy volunteers after a single oral administration (1500 mg). The pharmacokinetic parameters and relative bioavailabilities were investigated for both domestic glucosamine sulfate tablet and capsule preparations compared with an imported capsule product.

Area Under Curve↗

PubMed2005

Synergistic antiinflammatory effects of pinitol and glucosamine in rats.

This study evaluated the antiinflammatory activities of pinitol and glucosamine either alone or in combination against carrageenan- and cotton pellet-induced acute and subacute inflammation in rats. Five groups were included in each of the acute and subacute inflammation studies: the vehicle control group, positive control group (aminopyrine 100 mg/kg), pinitol group (20 mg/kg), glucosamine group (25 mg/kg) and a pinitol (20 mg/kg) and glucosamine (25 mg/kg) combination group. When 20 mg/kg of pinitol was administered to the rats, paw edema induced by the carrageenan injection was significantly suppressed and the level of granuloma formation induced by the cotton pellet implantation was slightly reduced. When 25 mg/kg of glucosamine was administered, paw edema caused by the acute inflammation was slightly reduced and the level of granuloma formation caused by the subacute inflammation was strongly suppressed. Although the combined application of pinitol and glucosamine did not have an additional antiinflammatory effect on the paw edema caused by acute inflammation, it did have an increased antiinflammatory effect on the formation of granuloma induced by subacute inflammation. Therefore, pinitol and glucosamine have an antiinflammatory effect on acute and subacute conditions. Moreover, a synergistic antiinflammatory effect against subacute inflammation was observed when the two chemicals were administered in combination.

Animals↗

PubMed1981

Oxidation of glucosamine by human polymorphonuclear leukocytes.

When exposed to a phagocytic stimulus (opsonized zymosan), human polymorphonuclear leukocytes (PMNs) produced 14CO2 from [1-14C]glucosamine at a rate 10-25% of that produced from glucose under the same conditions. The production of CO2 from glucosamine by intact PMNs was inhibited by glucose and dependent upon activation of the hexosemonophosphate shunt (HMPS). However, the metabolic pathways for the oxidation of glucose and glucosamine by PMNs are not identical. This is suggested by the fact that glucose-6-phosphate dehydrogenase, the initiating enzyme for the HMPS, did not utilize glucosamine-6-phosphate as a substrate. In addition, glucosamine was not oxidized by sonically disrupted PMNs whereas oxidation of glucose by the same preparation was increased sevenfold over intact cells. Taken together, the data suggest that PMNs oxidize glucosamine by converting it to a compound compatible with the enzymes of the HMPS. This conversion requires intact PMNs and/or an as yet unidentified cofactor.

Ascorbic Acid↗

PubMed1993

Inhibition of Glossina morsitans midgut trypsin activity by D-glucosamine.

The effect of the amino sugar D-glucosamine on trypsin in crude midgut homogenates of Glossina morsitans morsitans was studied in vitro. The results showed that the midgut trypsin was specifically and competitively inhibited by D-Glucosamine. Glucose, fructose, mannose, inositol, galactose, galactosamine, N-acetyl-D-glucosamine, and methyl-alpha-D-glucosamine were ineffective as inhibitors, even at concentrations exceeding 600 mM. D-glucosamine also had a similar inhibitory effect on bovine pancreatic trypsin. In both cases, the inhibition was incomplete as shown by nonlinear Dixon plots. The Michaelis and inhibition constants estimated for the midgut trypsin were 41 +/- 2 microM and 68 +/- 3 mM, respectively. These results suggest that the susceptibility of tsetse flies to trypanosome infection, which is associated with high midgut glucosamine levels, could be due to inhibition of trypsin or trypsin-like enzymes by this sugar.

Animals↗

PubMed1980

Glucosamine metabolism of herpes simplex virus infected cells. Inhibition of glycosylation by tunicamycin and 2-deoxy-D-glucose.

The formation of glucosamine-containing cell surface glycoproteins of herpes simplex virus (HSV) infected BMK cells was studied. Tunicamycin (TM) and 2-deoxy-D-glucose (DG) were used as inhibitors. With both inhibitors the multiplication of HSV was inhibited. DG markedly reduced cellular uptake of radioactively labelled glucosamine while TM interfered with the processing of glucosamine into TCA-insoluble material. Gel filtration chromatography on Sephadex G50 gel of cell surface material released by trypsin and further prepared by digestion with pronase indicated that TM and DG reduced the apparent high molecular weights of virus induced surface glycoproteins. In presence of DG the accumulation of a class of glucosamine-containing heterosaccharides (MW less than 3000) not present on DG-free HSV infected cells was observed. In TM treated cells virtually all surface heterosaccharides with molecular weights exceeding 3000 and containing glucosamine disappeared. Moreover, a component compatible with a lipid-linked oligosaccharide present in DG treated cells was not observed in HSV infected TM treated cells. The results exemplifies some different steps in glucosamine metabolism of virus induced cell surface glycoproteins differently affected by tunicamycin and 2-deoxy-D-glucose.

Animals↗

PubMed2005

Systemically administered glucosamine-kynurenic acid, but not pure kynurenic acid, is effective in decreasing the evoked activity in area CA1 of the rat hippocampus.

The metabolism of tryptophan along the kynurenine pathway yields several neuroactive intermediates, including kynurenic acid, which is one of the few known endogenous N-methyl-d-aspartate receptor inhibitors; in parallel with this, it is an alpha7 nicotinic acetylcholinergic receptor antagonist. On the basis of these properties, kynurenic acid might therefore come into consideration as a therapeutic agent in certain neurobiological disorders. However, the use of kynurenic acid as a neuroprotective agent is practically excluded because kynurenic acid hardly crosses the blood-brain barrier. We recently synthetized a new compound, glucosamine-kynurenic acid, which is presumed to cross the blood-brain barrier more easily. In this study, the effects of systemically administered kynurenic acid and glucosamine-kynurenic acid on CA3 stimulation-evoked population spike activity in region CA1 of the rat hippocampus were compared. The effect of kynurenic acid or glucosamine-kynurenic acid was augmented by probenecid (200 mg/kg), which inhibits kynurenic acid excretion from the cerebrospinal fluid. The results showed that, while kynurenic acid administered i.p. or i.v. in doses of 17, 34, 68 or 136 micromol/kg did not cause any observable change in the animals, 136 micromol/kg glucosamine-kynurenic acid (either i.p. or i.v.) resulted in the sudden death of all the animals. The dose of 68 micromol/kg i.v., but not i.p., resulted in a sudden stoppage of breath, but the animals could be reanimated. As small a dose of glucosamine-kynurenic acid as 17 micromol/kg i.p. resulted in a reduction in population spike amplitudes; this effect was further augmented by probenecid, whereas neither 17 micromol/kg nor higher doses of pure kynurenic acid had a similar effect. The results presented here suggest that glucosamine-kynurenic acid passes the blood-brain barrier much more readily than does kynurenic acid.

Action Potentials↗

PubMed2002

Glucosamine modulates IL-1-induced activation of rat chondrocytes at a receptor level, and by inhibiting the NF-kappa B pathway.

We recently reported that glucosamine reversed the decrease in proteoglycan synthesis and in UDP-glucuronosyltransferase I mRNA expression induced by interleukin-1 beta (IL-1 beta) [Arthritis Rheum. 44 (2001) 351-360]. In the present work, we show that glucosamine does not exert the same effects when chondrocytes were stimulated with reactive oxygen species (ROS). In order to better understand its mechanism of action, we determined if glucosamine could prevent the binding of IL-1 beta to its cellular receptors or could interfere with its signaling pathway at a post-receptor level. Addition of glucosamine to rat chondrocytes treated with IL-1 beta or with ROS decreased the activation of the nuclear factor kappa B, but not the activator protein-1. After treatment with IL-1 beta, glucosamine increased the expression of mRNA encoding the type II IL-1 beta receptor. These results emphasize the potential role of two regulating proteins of the IL-1 beta signaling pathway that could account for the beneficial effect of glucosamine in osteoarthritis.

Animals↗

PubMed2002

GLUT2 is a high affinity glucosamine transporter.

When expressed in Xenopus oocytes, GLUT1, 2 and 4 transport glucosamine with V(max) values that are three- to four-fold lower than for glucose. The K(m)s for glucosamine and glucose of GLUT1 and GLUT4 were similar. In contrast, GLUT2 had a much higher apparent affinity for glucosamine than for glucose (K(m)=0.8+/-0.1 mM vs. approximately 17-20 mM). Glucosamine transport by GLUT2 was confirmed in mammalian cells and, using hepatocytes from control or GLUT2-null mice, HgCl(2)-inhibitable glucosamine uptake by liver was shown to be exclusively through GLUT2. These data have implications for glucosamine effects on impaired glucose metabolism and for structure-function studies of transporter sugar binding sites.

Animals↗

PubMed1994

Glucosamine sulfate in osteoarthritis of the knee.

Glucosamine sulfate is a drug used for the treatment of osteoarthritis (OA), based on its pharmacological and metabolic activities on the cartilage and chondrocytes, complemented by mild anti-inflammatory properties and a favorable pharmacokinetic profile. The aim of this study was to define the activity and safety of glucosamine sulfate on the symptoms of patients with OA, using a multicenter, randomized, placebo-controlled, double-blind, parallel-group study design. The study included 252 outpatients with OA of the knee (Lequesne's criteria), radiological stage between I and III, and Lequesne's severity index of at least 4 points and symptoms for at least 6 months. Patients were treated with either placebo or oral glucosamine sulfate 500 mg t.i.d. for 4 weeks, with weekly, with weekly clinic visits. Responders to treatment were defined as patients with a reduction of at least 3 points in the Lequesne's index with a positive overall assessment by the investigator. The Lequesne's index was 10.6 +/- 0.45 S.E.M. points in both groups at the start of the study. This decreased to 7.45 +/- 0.5 points in the treatment group (average 3.2) and 8.4 +/- 0.4 points in the placebo group (average 2.2) (P < 0.05, Student's t-test). The responder rate in the evaluable patients was 55% with glucosamine (N = 120) vs 38% with placebo (N = 121). These proportions were 52% vs 37% in an intention-to-treat analysis (P = 0.014 and 0.016, respectively; Fisher's Exact Test). The medications were well tolerated throughout the study, with no difference between the glucosamine and placebo treated groups. It is concluded that glucosamine sulfate may be a safe and effective symptomatic Slow Acting Drug for OA.

Administration, Oral↗

PubMedDate not supplied

Effects of ammonia and glucosamine on the heterogeneity of erythropoietin glycoforms.

Recombinant human erythropoietin (EPO) is a glycoprotein produced as a therapeutic agent from mammalian cell cultures for the treatment of anemia associated with severe kidney damage. The EPO structure has a high glycan content which is essential for bioactivity but shows considerable molecular heterogeneity. The cell culture conditions that affect the heterogeneity of the glycoforms of EPO are not well understood. However, the accumulation of ammonia in culture is one factor that has been associated with an enhanced heterogeneity of glycoforms. In this report we investigate the metabolic perturbations associated with ammonia and glucosamine that may give rise to an altered pattern of EPO glycosylation. Recombinant human erythropoietin was synthesized in serum-free cultures of transfected Chinese hamster ovary (CHO) cells. The molecular heterogeneity of erythropoietin was increased by supplementation of cultures with either ammonia or glucosamine. The enhanced molecular heterogeneity was shown to be due to variable glycosylation that resulted in EPO with an enhanced molecular weight and isoelectric point range. Enzymatic removal of the glycan moiety of EPO in all cases resulted in a single molecular form with a molecular weight of 18 000, which corresponded to non-glycosylated EPO. The variable glycosylation was consistent with reduced sialylation and antennarity of the carbohydrate structures present on the three N-linked sites of EPO. In the presence of ammonia (>30 mM) the proportion of tetrasialylated and tetraantennary glycan structures were reduced by 73% and 57%, respectively, as determined by HPLC analysis. Such changes were also observed, although to a lesser extent (41% and 37%), by an increase in the glucosamine concentration (>10 mM) in the medium. The enhanced heterogeneity of the glycan structures coincided with a significant increase in the intracellular UDP-N-acetylhexosamine (UDP-GNAc) pool. The measured UDP-GNAc level was up to 2 orders of magnitude higher in the presence of either glucosamine or ammonia. However, the changes in the glycosylation profiles induced by either glucosamine or ammonia were significantly different even at the same intracellular UDP-GNAc concentration. This suggests that the enhanced EPO heterogeneity could not be mediated solely by the increased UDP-GNAc level. Glucosamine (but not ammonia) was shown to cause significant inhibition of glucose transport into the cells, which could induce a different pattern of primary metabolism.

Ammonia↗

PubMed2006

Electromigration of chitosan D-glucosamine and oligomers in dilute aqueous solutions.

The electromigration behavior of chitosan D-glucosamine and oligomers with a degree of polymerization from 1 to 6 in dilute aqueous systems containing either NaCl or KCl salt at 0.01, 0.05, and 0.1 M at pH values from 2 to 9 was evaluated. The results showed that the electromigration of the chitosan D-glucosamine and oligomers did not change by changing the type of salt in the running medium and that the pH had a significant effect on the direction of migration under an external electric field. In addition, the increase in the ionic strength of the medium caused a significant decrease on the absolute value of the electrophoretic mobility, and the highest values of the electromobility were observed in water. However, the ionic strength had no significant effect on the electrophoretic mobilities at pH 2 in comparison with the other pH values. The dimer showed the highest electrophoretic mobility in the alkaline zone of the pH. At pH values lower than the pKa of the D-glucosamine, the chitosan D-glucosamine, and oligomers migrated toward the anode, where the amine groups are protonated and carry positive charge. At higher pH values, chitosan D-glucosamine and oligomers migrated toward the anode, even though they did not carry any electric charge. The contribution of the difference in the dielectric constants between the solvent and the solute to this phenomenon was highlighted. It was shown that the glucose moiety contributes to the direction of migration of the chitosan D-glucosamine and oligomers under alkaline conditions and that the difference in the dielectric constant of glucose and the solvent accounts for the direction and the extent of electromobility.

Chitosan↗