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PubMed2003

Glucosamine: a review of its use in the management of osteoarthritis.

UNLABELLED: Glucosamine occurs naturally in all human tissues. It stimulates the synthesis of glycosaminoglycan, proteoglycan and hyaluronic acid, although the precise mechanism of action remains to be established. Formulated as glucosamine sulphate (Dona) and various others), glucosamine has been evaluated for its efficacy in relieving the symptoms of osteoarthritis and its disease-modifying potential. In two large randomised, double-blind, multicentre studies in patients with osteoarthritis, oral or intramuscular glucosamine for 4-6 weeks was associated with a greater decrease in symptom severity (as assessed by the Lequesne index) than placebo. In addition, there was a greater proportion of responders (defined as patients with a >or=3-point reduction in the Lequesne index, along with a positive overall assessment by the investigator) at the end of the treatment period with glucosamine than with placebo. In two large 4-week trials, oral glucosamine produced similar improvements to ibuprofen in the Lequesne index in one study and in articular pain scores in the other study. In a smaller 8-week comparative trial, oral glucosamine therapy achieved a significantly greater improvement in articular pain score than ibuprofen, and the investigators rated treatment efficacy as 'good' in a significantly greater proportion of glucosamine than ibuprofen recipients. In comparison with piroxicam, glucosamine significantly improved arthritic symptoms after 12 weeks of therapy and remained effective 8 weeks after treatment was discontinued. Beneficial effects of long-term oral glucosamine therapy in preventing joint space narrowing and improving symptoms were shown in two 3-year placebo-controlled trials in a total of 414 patients with osteoarthritis. Statistically significant differences favouring glucosamine were noted in the per-protocol and intention-to-treat analyses for the primary endpoints for both joint structural changes and symptom modification. Glucosamine has a tolerability profile similar to that of placebo and is better tolerated than ibuprofen or piroxicam. In particular, glucosamine recipients had a markedly lower incidence of gastrointestinal disturbances than those receiving ibuprofen. Other adverse events reported in both glucosamine and ibuprofen recipients were pruritus or skin reactions, flushing and fatigue. In general, a lower incidence of withdrawal from clinical trials was reported for glucosamine recipients than either ibuprofen or piroxicam recipients. CONCLUSION: In short-term clinical trials, glucosamine provided effective symptomatic relief for patients with osteoarthritis of the knee. In addition, glucosamine has shown promising results in modifying the progression of arthritis over a 3-year period. Glucosamine may therefore prove to be a useful treatment option for osteoarthritis.

Adult↗

PubMed2005

Glucosamine therapy for treating osteoarthritis.

BACKGROUND: Osteoarthritis (OA) is the most common form of arthritis, and it is often associated with significant disability and an impaired quality of life. OBJECTIVES: To review all randomized controlled trials (RCTs) evaluating the effectiveness and toxicity of glucosamine in OA. SEARCH STRATEGY: We searched MEDLINE, PREMEDLINE, EMBASE, AMED, ACP Journal Club, DARE, CDSR, and the CCTR. We also wrote letters to content experts, and hand searched reference lists of identified RCTs and pertinent review articles. All searches were updated in January 2005. SELECTION CRITERIA: Relevant studies met the following criteria: 1) RCTs evaluating the effectiveness and safety of glucosamine in OA, 2) Both placebo controlled and comparative studies were eligible, 3) Both single blinded and double blinded studies were eligible. DATA COLLECTION AND ANALYSIS: Data abstraction was performed independently by two investigators and the results were compared for degree of agreement. Gotzsche's method and a validated tool (Jadad 1996) were used to score the quality of the RCTs. Continuous outcome measures were pooled using standardized mean differences (SMD) as the measure of effect size. Dichotomous outcome measures were pooled using relative risk ratios (RR). MAIN RESULTS: Analysis restricted to eight studies with adequate allocation concealment failed to show benefit of glucosamine for pain and WOMAC function. Collectively, the 20 analyzed RCTs found glucosamine favoured placebo with a 28% (change from baseline) improvement in pain (SMD -0.61, 95% CI -0.95, -0.28) and a 21% (change from baseline) improvement in function using the Lequesne index (SMD -0.51 95% CI -0.96, -0.05). However, the results are not uniformly positive, and the reasons for this remain unexplained. WOMAC pain, function and stiffness outcomes did not reach statistical significance. In the 10 RCTs in which the Rotta preparation of glucosamine was compared to placebo, glucosamine was found to be superior for pain (SMD -1.31, 95% CI -1.99, -0.64) and function using the Lequesne index (SMD -0.51, 95% CI -0.96, -0.05). Pooled results for pain (SMD -0.15, 95% CI -0.35, 0.05) and function using the WOMAC index (SMD 0.03, 95% CI -0.18, 0.25) in those RCTs in which a non-Rotta preparation of glucosamine was compared to placebo did not reach statistical significance. In the four RCTs in which the Rotta preparation of glucosamine was compared to an NSAID, glucosamine was superior in two, and equivalent in two. Two RCTs using the Rotta preparation showed that glucosamine was able to slow radiological progression of OA of the knee over a three year period (SMD 0.24, 95% CI 0.04, 0.43). Glucosamine was as safe as placebo in terms of the number of subjects reporting adverse reactions (RR=0.97, 95% CI, 0.88, 1.08). AUTHORS' CONCLUSIONS: This update includes 20 studies with 2570 patients. Pooled results from studies using a non-Rotta preparation or adequate allocation concealment failed to show benefit in pain and WOMAC function while those studies evaluating the Rotta preparation show that glucosamine was superior to placebo in the treatment of pain and functional impairment resulting from symptomatic OA. WOMAC outcomes of pain, stiffness and function did not show a superiority of glucosamine over placebo for both Rotta and non-Rotta preparations of glucosamine. Glucosamine was as safe as placebo.

Adult↗

PubMed2000

The effects of glucosamine derivatives on equine articular cartilage degradation in explant culture.

OBJECTIVE: To determine whether glucosamine-3-sulfate, glucose-3-sulfate (control) and N-acetyl glucosamine inhibit experimentally induced degradation of equine articular cartilage explants similar to glucosamine HCl. DESIGN: Articular cartilage was obtained from the antebrachio-carpal and middle joints of horses (2-8 years old) killed for reasons unrelated to lameness. Cartilage discs were harvested from the weight-bearing region of the articular surface and cultured. Media were exchanged daily and the recovered media stored at 4 degrees C. On days 1 and 2 lipopolysaccharide (LPS, 10 microg/ml) was added to induce cartilage degradation. To evaluate the effects of different sources of glucosamine (on an equal molar basis), varying concentrations of glucosamine HCl (0.25, 2.5, or 25 mg/ml), glucosamine-3-sulfate (0.304, 3.04, or 30.4 mg/ml), or N-acetyl-glucosamine (0.256, 2.56, or 25.6 mg/ml) were added to the cultures. The glucose-3-sulfate control was added at 0.3075, 3.075 or 30.75 mg/ml. Nitric oxide and proteoglycan released into conditioned media and tissue proteoglycan synthesis and total tissue PG content were measured as indicators of cartilage metabolism. RESULTS: Glucosamine-3-sulfate consistently inhibited cartilage degradation in a manner similar to glucosamine HCl, while the effects of N-acetyl-glucosamine were highly variable and did not inhibit cartilage degradation. Glucose-3-sulfate did not inhibit cartilage degradation. CONCLUSION: Our results indicate that glucosamine sulfate also has the potential to prevent or reduce articular cartilage degradation similar to glucosamine HCl in vitro. The amine group at the carbon-2 position appears important for the effectiveness of the glucosamine derivative. The therapeutic value of N-acetyl-glucosamine remains questionable.

Acetylglucosamine↗

PubMed2004

Randomized, double-blind, placebo-controlled glucosamine discontinuation trial in knee osteoarthritis.

OBJECTIVE: To assess the efficacy of glucosamine sulfate in knee osteoarthritis (OA). METHODS: A 4-center, 6-month, randomized, double-blind, placebo-controlled glucosamine discontinuation trial was conducted in 137 current users of glucosamine with knee OA who had experienced at least moderate improvement in knee pain after starting glucosamine. Study medication dosage was equivalent to the dosage of glucosamine taken prior to the study (maximum 1,500 mg/day). Followup continued for 6 months or until disease flare, whichever occurred first. The primary outcome was the proportion of disease flares in the glucosamine and placebo groups using an intent-to-treat analysis. Secondary outcomes included time to disease flare; analgesic medication use; severity of disease flare; and change in pain, stiffness, function and quality of life in the glucosamine and placebo groups. RESULTS: Disease flare was seen in 28 (42%) of 66 placebo patients and 32 (45%) of 71 glucosamine patients (difference -3%; 95% confidence interval [95% CI] -19, 14; P = 0.76). In the Cox regression analysis, after adjustment for sex, study site, and OA radiographic severity, time to disease flare was not significantly different in the glucosamine compared with placebo group (hazard ratio of flare = 0.8; 95% CI 0.5, 1.4; P = 0.45). At final study visit, acetaminophen was used in 27% and 21% of placebo and glucosamine patients, respectively (P = 0.40), nonsteroidal antiinflammatory drugs were used in 29% and 30% (P = 0.92), and both were used in 20% and 21% (P = 0.84). No differences were found in severity of disease flare or other secondary outcomes between placebo and glucosamine patients. CONCLUSION: In patients with knee OA with at least moderate subjective improvement with prior glucosamine use, this study provides no evidence of symptomatic benefit from continued use of glucosamine sulfate.

Adult↗

PubMed1975

Inhibitory effect of D-glucosamine on glycolysis in bovine retina.

1. The effects of glucosamine concentration on the size of the lactate pool, on the levels of ATP, ADP, AMP and on the radioactivity incorporation from [1-14-C] glucosamine into lactate, N-acetylglucosamine and glucosamine-6-P were studied using whole bovine retinas. 2. The radioactive lactate, evaluated in relation to glucosamine molarity, after a modest initial increase, diminishes significantly. On the contrary the N-acetyl [1-14-C] glucosamine, the [1-14-C] glucosamine-6-P and, consequently, also the [1-14-C] glucosamine-6-P/[-14-C] lactate ratio increase with glucosamine molarity. 3. The retinal content of ATP shows a modest increment after incubation with low concentrations of D-glucosamine (0.5--2.0 mM) and a remarkable fall at higher concentrations. 4. Using retinal homogenates D-glucosamine clearly lowers the lactate production from glucose, glucose-6-P and fructose-1, 6-P2. 5. D-Glucosamine acts as an inhibitor of retinal glyceraldehyde-3-P dehydrogenase and lactate dehydrogenase by decreasing the initial velocity of these reactions. 6. It is concluded that D-glucosamine causes a reduction in the lactate production, by inhibiting two enzymes of the glycolytic pathway: glyceraldehyde-3-P dehydrogenase and lactate dehydrogenase. The fall in the adenine nucleotides content is a consequence of a dephosphorylation of ATP for the phosphorylation of glucosamine without concomitant resynthesis of ATP "via glycolysis".

Acetylglucosamine↗

PubMed1999

Effect of glucosamine hydrochloride in the treatment of pain of osteoarthritis of the knee.

OBJECTIVE: Glucosamine products have been used extensively for the management of pain in osteoarthritis (OA). We investigated the efficacy of the hydrochloride salt of glucosamine on pain and disability in knee OA. METHODS: At Week -2, subjects were examined, randomized, and instructed to take only prescribed acetaminophen for pain. At Week 0 patients were examined, prescribed acetaminophen, and either placebo or glucosamine hydrochloride (glucosamine). At Week 4 the prescriptions for acetaminophen and placebo or glucosamine were renewed. At Weeks 4 and 8, patients returned diaries and unused medications, and were examined. The WOMAC questionnaire was administered at Weeks -2, 0, and 8. After completing the randomized 8 week trial, subjects were offered known glucosamine hydrochloride capsules in an 8 week open label trial, with followup telephone survey after the 8 week open label trial. RESULTS: The primary endpoint (statistically significant difference in WOMAC pain score between Week 0 and Week 8) was not met. However, positive trends were noted for the glucosamine group in 23 of 24 WOMAC questions. A significant difference was noted from Week 5 through Week 8 in the knee examination (p = 0.026) and in the response to a daily diary pain question (p = 0.018). However, responding to the question, "Are you better than at the start of the trial?", 40% of placebo and only 49% of glucosamine subjects answered in the affirmative (p = 0.58). At the end of the randomized trial, 34% of placebo and 47% of glucosamine subjects believed that they had been given glucosamine. After the end of the 8 week open label trial, 77% of the subjects were still taking glucosamine, although now obliged to pay for commercially available products. CONCLUSION: There was no significant difference in pain reduction between the glucosamine hydrochloride and placebo groups as measured by WOMAC. However, the secondary endpoints of cumulative pain reduction as measured by daily diary and knee examination were favorable, suggesting that glucosamine hydrochloride benefits some patients with knee OA.

Aged↗

PubMed2004

Glucosamine, a naturally occurring amino monosaccharide, suppresses the ADP-mediated platelet activation in humans.

OBJECTIVE: To evaluate the anti-thrombotic action of glucosamine, a naturally occurring amino monosaccharide, platelets were stimulated with ADP in the presence of glucosamine, and its effects on platelet functions were examined. MATERIALS AND METHODS: Human platelet-rich plasma was stimulated with 2.5 microM ADP in the presence of glucosamine (0.01 approximately 1 mM) or other aminosugars (N-acetyl-glucosamine, galactosamine or N-acetyl-galactosamine, 1 mM), and platelet aggregation was monitored. Furthermore, the effects of glucosamine on the thromboxane A2 production, release of granule contents, intracellular calcium mobilization and phosphorylation of Syk (a 72 kD protein tyrosine kinase) were evaluated following ADP-stimulation. In addition, the binding of [3H] ADP to its receptors was examined. RESULTS: Glucosamine (>0.01 mM) dose-dependently suppressed platelet aggregation in response to ADP (p < 0.05), whereas N-acetyl-glucosamine, galactosamine or N-acetyl-galactosamine (1 mM) did not affect the ADP-induced platelet aggregation. Furthermore, glucosamine (>0.1 mM) inhibited the extracellular release of granule contents (ATP and platelet factor 4) and production of thromboxane A2 from ADP-stimulated platelets (p < 0.05). Moreover, glucosamine significantly repressed the intracellular calcium mobilization at >0.1 mM and phosphorylation of Syk at >0.01 mM upon ADP-stimulation (p < 0.05). In addition, glucosamine (>0.1 mM) inhibited the binding of ADP to its receptors (p < 0.05). CONCLUSION: Glucosamine is able to suppress platelet aggregation, release of granule constituents, thromboxane A2 production, calcium mobilization and phosphorylation of Syk possibly via the inhibition of ADP-binding to the receptors. Glucosamine could be expected as a novel anti-platelet agent for thrombotic disorders due to its suppressive actions on platelets.

Adenosine Diphosphate↗

PubMed2004

Effect of glucosamine on apolipoprotein AI mRNA stabilization and expression in HepG2 cells.

Previously published studies suggest that an alteration in hexosamine flux induces a state of insulin resistance in muscle, liver, and other cell types. Glucosamine also alters the expression of several genes through an effect on transcription factors such as Sp1. Since the anti-atherogenic protein apolipoprotein AI (apoAI) is positively regulated by insulin, at least partly through its effect on Sp1, we investigated the effect of glucosamine on apoAI gene expression in the hepatocyte cell line, HepG2. By 24 hours of treatment with 0.1, 1, or 3 mmol/L glucosamine, the amount of apoAI protein secreted into the culture media increased 1.8-fold, 5.5-fold, and 2.3-fold, respectively. The decline in apoAI secretion at the highest glucosamine levels may be due to toxicity since the percentage of cells able to exclude trypan blue was lower in this group than in control cells (98.5% +/- 1.5% in control cells v 89.2% +/- 2.1% in cells treated with 3 mmol/L glucosamine, P <.01). ApoAI mRNA levels increased 2.4-fold in hepatocytes treated with 1 mmol/L glucosamine for 24 hours (1,158.1 +/- 78.8 v 482.2 +/- 24.3 arbitrary integrator units [AIU], P <.02), suggesting that the increase in apoAI protein secretion was due, at least partly, to an increase in apoAI mRNA levels. However, glucosamine had no effect on apoAI gene transcription rate as measured by nuclear runoff analysis (3,155 +/- 46.0 in control cells v 3,181 +/- 30.0 AIU in glucosamine-treated cells). Similarly, apoAI promoter activity measured in HepG2 cell transfected with an apoAI reporter plasmid containing the full-length apoAI promoter including an insulin-responsive Sp1 binding site did not change with glucosamine addition. In this assay, the chloramphenicol acetyltransferase (CAT) activity was 12.4% +/- 3.1%, 10.1% +/- 2.4%, 9.8% +/- 2.0%, 9.7% +/- 2.2%, and 11.9% +/- 2.9% in cells treated with 0, 0.03, 0.1, 0.3, and 1 mmol/L glucosamine, respectively. The apoAI mRNA turnover studies showed that 1 mmol/L glucosamine treatment of HepG2 cells was associated with increased apoAI mRNA half-life, from 7.6 to 16.6 hours. These findings suggest that increases in apoAI gene expression by glucosamine occur primarily through stabilizing apoAI mRNA.

Apolipoprotein A-I↗

PubMed1999

Nutraceuticals as therapeutic agents in osteoarthritis. The role of glucosamine, chondroitin sulfate, and collagen hydrolysate.

There are a sufficient number of short-term studies with these agents suggesting efficacy equal to that seen in the symptomatic treatment of OA using NSAIDs. Two recent meta-analyses by McAlindon and colleagues and Towheed et al reviewed clinical trials of glucosamine and chondroitin in the treatment of osteoarthritis. The study by McAlindon and co-workers included all double-blind placebo-controlled trials of greater than 4 weeks' duration, testing oral or parenteral glucosamine or chondroitin for treatment of hip or knee osteoarthritis. Thirteen trials (six with glucosamine, seven with chondroitin) met eligibility criteria. The authors used global pain score or the Lequesne index in the index joint as the primary outcome measure and considered the trial positive if improvement in the treatment group was equal to or greater than 25% compared with the placebo group, and was significant (P < or = .05). All 13 studies reviewed were classified as positive, demonstrating large effects, compared with placebo (39.5% [S.D. 21.9] for glucosamine, 40.2% [S.D. 6.4] for chondroitin). The authors concluded that clinical trials of these two agents showed substantial benefit in the treatment of osteoarthritis but provided insufficient information about study design and conduct to allow definitive evaluation. Towheed and colleagues reviewed nine randomized, controlled trials of glucosamine sulfate in osteoarthritis. In seven of the randomized controlled trials, in which they compared glucosamine with placebo, glucosamine was always superior. In two randomized controlled trials comparing glucosamine to ibuprofen, glucosamine was superior in one and equivalent in one. Methodologic problems, including lack of standardized case definition of osteoarthritis and lack of standardized outcome assessment led the authors to conclude that further studies are needed to determine if route of administration is important and whether the therapeutic effect is site specific. A meta-analysis of chondroitin sulfate trials has also been published. Of the 12 published trials, 4 randomized double-blind placebo or NSAID-controlled trials with 227 patients on chondroitin sulfate were entered into the analysis. All four studies showed chondroitin sulfate to be superior to placebo, with respect to Lequesne index, visual analog scale for pain and medication consumption. Significant changes (P < or = .05) were seen in those treated from day 60 to the study endpoints (150 to 180 days). Pooled data demonstrated at least 50% improvement in the study variables in the chondroitin treated group. Discrepancies in some of the study findings reported in the literature may relate to the composition of the nutritional supplements used. Studies in the United States have revealed that a number of preparations claiming to contain certain doses of glucosamine or chondroitin sulfate have significantly less (or none) of the dosages described. Accordingly, it is essential that studies performed with these agents use preparations that are carefully defined in manufacture. The amounts generally administered are glucosamine, 1500 mg, and chondroitin sulfate, 1200 mg, daily. Although glucosamine has been described as effective when used alone, it is probably reasonable to use the combination pending further studies. The average cost is approximately $30 to $45 per month. In the interim, what should physicians tell their patients when they ask whether these agents are effective, or whether they should or should not take them? The authors emphasize that these agents are not FDA-evaluated or recommended for the treatment of OA. They are available as health food supplements, and the number of studies of toxicity, particularly with respect to long-term evaluations, is limited. The pros and cons of these agents and the published data are described so that patients can make a reasonably informed decision as to whether they wish to proceed with use of these agents in therapy. (ABSTRACT TRUNCATED)

Animals↗

PubMed2001

Glutamine metabolism to glucosamine is necessary for glutamine inhibition of endothelial nitric oxide synthesis.

L-Glutamine is a physiological inhibitor of endothelial NO synthesis. The present study was conducted to test the hypothesis that metabolism of glutamine to glucosamine is necessary for glutamine inhibition of endothelial NO generation. Bovine venular endothelial cells were cultured for 24 h in the presence of 0, 0.1, 0.5 or 2 mM D-glucosamine, or of 0.2 or 2 mM L-glutamine with or without 20 microM 6-diazo-5-oxo-L-norleucine (DON) or with 100 microM azaserine. Both DON and azaserine are inhibitors of L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) (EC 2.6.1.16), the first and rate controlling enzyme in glucosamine synthesis. Glucosamine at 0.1, 0.5 and 2 mM decreased NO production by 34, 45 and 56% respectively compared with controls where glucosamine was lacking. DON (20 microM) and azaserine (100 microM) blocked glucosamine synthesis and prevented the inhibition of NO generation by glutamine. Neither glutamine nor glucosamine had an effect on NO synthase (NOS) activity, arginine transport or cellular tetrahydrobiopterin and Ca(2+) levels. However, both glutamine and glucosamine inhibited pentose cycle activity and decreased cellular NADPH concentrations; these effects of glutamine were abolished by DON or azaserine. Restoration of cellular NADPH levels by the addition of 1 mM citrate also prevented the inhibiting effect of glutamine or glucosamine on NO synthesis. A further increase in cellular NADPH levels by the addition of 5 mM citrate resulted in greater production of NO. Collectively, our results demonstrate that the metabolism of glutamine to glucosamine is necessary for the inhibition of endothelial NO generation by glutamine. Glucosamine reduces the cellular availability of NADPH (an essential cofactor for NOS) by inhibiting pentose cycle activity, and this may be a metabolic basis for the inhibition of endothelial NO synthesis by glucosamine.

Animals↗

PubMed1992

Glucosamine-induced desensitization of beta-cell responses: possible involvement of impaired information flow in the phosphoinositide cycle.

The influence of glucosamine on beta-cell response characteristics of collagenase-isolated rat islets was determined. Groups of islets were incubated for 2 h with myo-[2-3H]inositol to label their phosphoinositide (PI) pools. Also included in some experiments was glucosamine (0.1-10 mM). Subsequently, these islets were perifused, and their responses to 10 mM glucose, 10 mM alpha-ketoisocaproate (KIC), and 1 microM of the phorbol ester phorbol 12-myristate 13-acetate were assessed. Increases in PI hydrolysis were monitored during the perfusion by measuring fractional efflux rates of [3H]inositol. The accumulation of inositol phosphates after the perifusion was also determined. In other experiments, the use of 10 mM glucose was measured after a 2-h exposure to 5 or 10 mM glucosamine. Finally, the ability of glucosamine itself to augment release and activate PI hydrolysis was assessed. The following observations were made. 1) A prior 2-h exposure to 5-10 mM glucosamine resulted in parallel dose-dependent impairments in 10 mM glucose-induced insulin release and PI hydrolysis. 2) Glucosamine (5-10 mM) also impaired the subsequent response to alpha-ketoisocaproate (KIC). Parallel deficits in KIC-induced PI hydrolysis were noted under conditions where insulin secretion was impaired. 3) Under several conditions where glucosamine impaired glucose-induced secretion, it had no adverse effect on phorbol 12-myristate 13-acetate-induced release. 4) The desensitizing effect of 10 mM glucosamine on 10 mM glucose-induced release and PI hydrolysis developed within 30 min of exposure to it. 5) Glucosamine (5-10 mM) preexposure had no adverse effect on the use of 10 mM glucose by desensitized islets. 6) Short term (5-min) exposure to glucosamine (10 mM) alone stimulated PI hydrolysis, while a 30-min exposure to the same level of the hexosamine depressed it. 7) In the presence of 0.25 microM forskolin, 10 mM glucosamine also had a transient stimulatory effect on insulin release. These findings support the concept that the acute and chronic effects of glucosamine on the beta-cell result at least in part from its ability to influence PI hydrolysis in islets.

Analysis of Variance↗

PubMed1999

Glucosamine infusion in rats rapidly impairs insulin stimulation of phosphoinositide 3-kinase but does not alter activation of Akt/protein kinase B in skeletal muscle.

Glucosamine, a metabolite of glucose via the hexosamine biosynthetic pathway, potently induces insulin resistance in skeletal muscle by impairing insulin-induced GLUT4 translocation to the plasma membrane. Activation of phosphoinositide (PI) 3-kinase is necessary for insulin-stimulated GLUT4 translocation, and the serine/threonine kinase Akt/protein kinase B (PKB) is a downstream mediator of some actions of PI 3-kinase. To determine whether glucosamine-induced insulin resistance could be due to impaired signaling, we measured insulin receptor substrate (IRS)-1 and insulin receptor tyrosine phosphorylation; PI 3-kinase activity associated with IRS-1, IRS-2, and phosphotyrosine; and Akt activity and phosphorylation in skeletal muscle of rats infused for 2 h with glucosamine (6.0 mg x kg(-1) x min(-1)) or saline. Euglycemic-hyperinsulinemic clamp studies (12 mU x kg(-1) x min(-1) insulin) in awake rats showed that glucosamine infusion resulted in rapid induction of insulin resistance, with a 33% decrease in glucose infusion rate (P < 0.01). Tissues were harvested after saline alone (basal), 1 min after an insulin bolus (10 U/kg), or after 2 h of insulin clamp in saline- and glucosamine-infused rats. After 1 min of insulin stimulation, phosphorylation of IRS-1 and insulin receptor increased 6- to 8-fold in saline-infused rats and 7- to 10-fold in glucosamine-infused rats. In saline-infused rats, 1 min of insulin stimulation increased PI 3-kinase activity associated with IRS-1, IRS-2, or phosphotyrosine 7.6-, 6.4-, and 10-fold, respectively. In glucosamine-infused rats treated for 1 min with insulin, PI 3-kinase activity associated with IRS-1 was reduced 28% (P < 0.01) and that associated with phosphotyrosine was reduced 43% (P < 0.01). Insulin for 1 min stimulated Akt/PKB activity approximately 5-fold in both saline- and glucosamine-infused rats; insulin-induced hyperphosphorylation of Akt/PKB was not different between groups. Glucosamine infusion alone had no effect on tyrosine phosphorylation of the insulin receptor or IRS-1 or on stimulation of PI 3-kinase or Akt/PKB activity. However, 2 h of insulin clamp reduced PI 3-kinase activity associated with IRS-1, IRS-2, or phosphotyrosine to <30% of that seen with 1 min of insulin. No effect of glucosamine was seen on these signaling events when compared with 2 h of insulin clamp without glucosamine. Our data show that 1) glucosamine infusion in rats is associated with an impairment in the early activation of PI 3-kinase by insulin in skeletal muscle, 2) this insulin-resistant state does not involve alterations in the activation of Akt/PKB, and 3) prolonged insulin infusion under clamp conditions results in a blunting of the PI 3-kinase response to insulin.

Animals↗

PubMed1995

Effects of glucosamine on insulin-stimulated glucose metabolism in rat soleus muscle.

Intracellular accumulation of glucosamine metabolites (which can be achieved by pre-incubation of cells with glucosamine) during hyperglycaemia may decrease the rate of insulin-mediated glucose transport in cells. Soleus muscle preparations were pre-incubated in the presence or absence of glucosamine in media that contained glutamine (Dulbecco's modified Eagle medium, DMEM; Medium 199, M199) or devoid of glutamine (Krebs-Henseleit's buffer, KHB). Subsequently, muscles were transferred to fresh media, in the absence of glucosamine, but with various concentrations of insulin and the rates of 2-deoxyglucose transport or intracellular glucose metabolism were measured. Glucosamine pre-exposure decreased both insulin-stimulated (1000 microU/ml) glucose transport and phosphorylation. The percentage decreases for 3H-2-deoxyglucose transport after pre-incubation with 40 mM glucosamine compared with untreated muscles were: DMEM, 48%; KHB, 50%; M199, 29%. The percentage decreases for 3H-2-deoxyglucose-6-phosphate accumulation were: DMEM, 53%; KHB 60%; M199, 37%. In DMEM and KHB, glucosamine pre-treatment of soleus muscle preparations markedly decreased the rate of lactate release and stimulated the rate of 14C-glucose incorporation into glycogen. Thus, a distinct shift of glucosyl units from glycolysis to glycogenesis occurred with low and high insulin concentrations. For the latter (1000 microU of insulin/ml) the ratio of moles of glucose converted to lactate divided by moles of glucose incorporated into glycogen in muscles pre-incubated in the absence or presence of glucosamine (40 mM) was, respectively: DMEM, 4.34 + 0.52 vs 1.55 + 0.06, P < 0.001; KHB, 2.80 + 0.44 vs 0.76 + 0.03, P < 0.005). Glycogen synthesis was not stimulated in muscles pre-exposed to glucosamine in M199. In muscles pre-incubated to glucosamine and incubated in DMEM or KHB, there was a marked shift of glucose transported into the cell from glycolysis to glycogenesis. Thus, glucosamine or its metabolites had distinct effects on intracellular glucose handling.

Animals↗

PubMed2006

The effect of glucosamine concentration on the development and sex ratio of bovine embryos.

Glucosamine is a component of hyaluronic acid and an alternative substrate to glucose for the extracellular matrix synthesis of COCs. Its addition to an IVM medium reduces the glucose consumption of bovine COCs. Glucosamine is also metabolized to UDP-N-acetyl glucosamine (UDP-GlcNAc) via the hexosamine biosynthesis pathway and is utilized for O-linked glycosylation by the X-linked enzyme, O-linked GlcNAc transferase (OGT). Moreover, the inactivation of the second X chromosome in female embryos is influential in producing the sex ratio bias observed in vitro when embryos are cultured in the presence of glucose above 2.5mM. Accordingly, the aim of this study is to examine whether the presence of glucosamine during maturation or embryo culture causes a sex ratio bias in bovine blastocysts. Glucosamine was added to the medium in three different embryo developmental periods: in vitro maturation, the one-cell to eight-cell stage (before the maternal-zygotic transition, MZT), and the eight-cell to blastocyst stage (after MZT). When glucosamine was added during in vitro maturation, the developmental competence of oocytes was severely compromised. However, the sex ratio of embryos was not influenced. When glucosamine was added to embryo culture medium during development from one-cell to eight-cell stage (before MZT), it affected neither the development nor the sex ratio of bovine embryos. Finally, when glucosamine was added after MZT, the development rate of embryos was severely decreased, and the sex ratio was skewed toward males. Moreover, an inhibitor of OGT, benzyl-2-acetamido-2-deoxy-alpha-D-galactopyranoside (BADGP), negated the effect of glucosamine on the sex ratio when it was added to embryo culture medium from the eight-cell to blastocyst stage (after MZT). These results suggest that, like glucose, the supplementation of glucosamine into the medium skewed the sex ratio to males and that OGT, an X-linked enzyme, was involved in this phenomenon. Moreover, this effect of glucosamine was limited only to when it was present in the embryo culture medium after MZT.

Animals↗

PubMed2006

The lack of effect of glucosamine sulphate on aggrecan mRNA expression and (35)S-sulphate incorporation in bovine primary chondrocytes.

Glucosamine and glucosamine sulphate have been promoted as a disease-modifying agent to improve the clinical symptoms of osteoarthritis. The precise mechanism of the action of the suggested positive effect of glucosamine or glucosamine sulphate on cartilage proteoglycans is not known, since the level of glucosamine in plasma remains very low after oral administration of glucosamine sulphate. We examined whether exogenous hexosamines or their sulphated forms would increase steady-state levels of aggrecan and hyaluronan synthase (HAS) or glycosaminoglycan synthesis using Northern blot and (35)S-sulphate incorporation analyses. Total RNA was extracted from bovine primary chondrocytes which were cultured either in 1 mM concentration of glucosamine, galactosamine, mannosamine, glucosamine 3-sulphate, glucosamine 6-sulphate or galactosamine 6-sulphate for 0, 4, 8 and 24 h, or in three different concentrations (control, 100 microM and 1 mM) of glucosamine sulphate salt or glucose for 24 or 72 h. Northern blot assay showed that neither hexosamines nor glucosamine sulphate salt stimulated aggrecan and HAS-2 mRNA expression. Glycosaminoglycan synthesis remained at a control level in the treated cultures, with the exception of mannosamine which inhibited (35)S-sulphate incorporation in low-glucose DMEM treatment. In our culture conditions, hexosamines or their sulphated forms did not increase aggrecan expression or (35)S-sulphate incorporation.

Aggrecans↗

PubMed2005

Glucosamine effects in humans: a review of effects on glucose metabolism, side effects, safety considerations and efficacy.

Glucosamine is widely used to relieve symptoms from osteoarthritis. Its safety and effects on glucose metabolism are critically evaluated in this review. The LD50 of oral glucosamine in animals is approximately 8000 mg/kg with no adverse effects at 2700 mg/kg for 12 months. Because altered glucose metabolism can be associated with parenteral administration of large doses of glucosamine in animals and with high concentrations in in vitro studies, we critically evaluated the clinical importance of these effects. Oral administration of large doses of glucosamine in animals has no documented effects on glucose metabolism. In vitro studies demonstrating effects of glucosamine on glucose metabolism have used concentrations that are 100-200 times higher than tissue levels expected with oral glucosamine administration in humans. We reviewed clinical trial data for 3063 human subjects. Fasting plasma glucose values decreased slightly for subjects after oral glucosamine for approximately 66 weeks. There were no adverse effects of oral glucosamine administration on blood, urine or fecal parameters. Side effects were significantly less common with glucosamine than placebo or non-steroidal anti-inflammatory drugs (NSAID). In contrast to NSAID, no serious or fatal side effects have been reported for glucosamine. Our critical evaluation indicates that glucosamine is safe under current conditions of use and does not affect glucose metabolism.

Administration, Oral↗

PubMed2002

Preformulation studies and characterization of proposed chondroprotective agents: glucosamine HCl and chondroitin sulfate.

PURPOSE: Glucosamine HCl and chondroitin sulfate are proposed chondroprotective agents commonly used as dietary supplements. This study examined the physicochemical and mechanical properties of chondroitin sulfate, glucosamine HCl powder, and glucosamine HCl granulation obtained from various sources. METHODS: The particle size distributions of the materials were determined using sieve analysis and time-of-flight techniques. Polarized light microscopy was used to examine particle morphology. Powder x-ray diffraction studies, moisture sorption isotherms, deformation behavior, powder flow, and compaction characteristics were also investigated. The polarized light microscopy and x-ray diffraction patterns showed that chondroitin sulfate is amorphous while glucosamine HCl is crystalline. Particle sizes of chondroitin sulfate and glucosamine HCl varied widely, depending on their source or manufacturing technique (e.g., granulation). The studied samples of shark-derived chondroitin sulfate had a small median particle size (4 microns) compared to that derived from bovine cartilage (17 microns). Different moisture sorption profiles were obtained for the glucosamine HCl granulations studied. Glucosamine HCl granulation from Supplier I showed no observable moisture sorption, while the granulation from Supplier II showed an approximately 5% weight gain. Conversely, chondroitin sulfate was extremely hygroscopic and deliquescent. The Carr's indices for glucosamine HCl samples ranged from 12.5 to 31.5; for chondroitin sulfate the values were 25.2 and 53.6. The compression analysis showed that all chondroitin sulfate samples exhibited plastic deformation behavior, with the shark-derived chondroitin sulfate forming superior compacts when compared to the bovine. The dominant mechanism of compression of glucosamine HCl powder was brittle fracture, whereas wet granulated glucosamine HCl exhibited plastic deformation with enhanced mechanical strength. CONCLUSIONS: The physicochemical and mechanical characteristics between the various dietary supplements studied varied greatly. Data obtained from this study provide an understanding of the physicomechanical behavior of chondroitin sulfate and glucosamine HCl. Application of this knowledge would facilitate development of stable solid dosage forms containing these materials.

Animals↗

PubMed2006

Glucosamine supplementation accelerates early but not late atherosclerosis in LDL receptor-deficient mice.

Glucosamine, commonly consumed for the treatment of osteoarthritis, is classified as a nutritional supplement; however, there are few data regarding its metabolic or vascular effects. Glucosamine is a component of the hexosamine pathway, which has been implicated in the development of insulin resistance. Anecdotal reports suggest that glucosamine consumption can increase circulating cholesterol concentrations. To investigate the metabolic and vascular effects of glucosamine supplementation, we studied male and female LDL receptor-deficient mice fed a Western diet (21% fat, 0.15% cholesterol). Three groups of 6-10 mice of each gender received either no supplement, 15 mg . kg(-1) . d(-1) glucosamine (equivalent to an average human dose), or 50 mg . kg(-1) . d(-1) glucosamine added to their drinking water for 5, 10, or 20 wk. Plasma cholesterol and triglyceride concentrations increased in all mice with the addition of the Western diet. However, after 20 wk of treatment, cholesterol and triglyceride concentrations increased further in male mice consuming glucosamine compared with control groups. Glucosamine-supplemented mice had increased initiation of atherosclerosis after 5 wk; however, there was no effect on progression of atherosclerosis in either gender after longer periods of glucosamine supplementation (10 or 20 wk). Although long-term glucosamine supplementation exacerbated the hyperlipidemia in male mice, no increase in atherosclerosis occurred. Thus, glucosamine supplementation appears to be safe, with no adverse vascular consequences.

Animals↗