Effect of glucosamine supplementation on fasting and non-fasting plasma glucose and serum insulin concentrations in healthy individuals

Imaging of sugar-based contrast agents using their hydroxyl proton exchange properties

The ability of CEST MRI to detect the presence of millimolar concentrations of non-metallic contrast agents has made it possible to study, non-invasively, important biological molecules such as proteins and sugars, as well as drugs already approved for clinical use. Here, we review efforts to use sugar and sugar polymers as exogenous contrast agents, which is possible based on the exchange of their hydroxyl protons with water protons. While this capability has raised early enthusiasm, for instance about the possibility of imaging D-glucose metabolism with MRI in a way analogous to PET, experience over the past decade has shown that this is not trivial. On the other hand, many studies have confirmed the possibility of imaging a large variety of sugar analogues, each with potentially interesting applications to assess tissue physiology. Some promising applications are the study of (i) sugar delivery and transport to assess blood-brain barrier integrity and (ii) sugar uptake by cells for their characterization (e.g., cancer versus healthy), as well as (iii) clearance of sugars to assess tissue drainage-for instance, through the glymphatic system. To judge these opportunities and their challenges, especially in the clinic, it is necessary to understand the technical aspects of detecting the presence of rapidly exchanging protons through the water signal in MRI, especially as a function of magnetic field strength. We expect that novel approaches in terms of MRI detection (both saturation transfer and relaxation based), MRI data analysis, and sugar design will push this young field forward in the next decade.

Glucosamine Use, Inflammation, and Genetic Susceptibility, and Incidence of Type 2 Diabetes: A Prospective Study in UK Biobank

OBJECTIVE

Glucosamine is a widely used supplement typically taken for osteoarthritis and joint pain. Emerging evidence suggests potential links of glucosamine with glucose metabolism, inflammation, and cardiometabolic risk. We prospectively analyzed the association of habitual glucosamine use with risk of type 2 diabetes (T2D) and assessed whether genetic susceptibility and inflammation status might modify the association.

RESEARCH DESIGN AND METHODS

This study analyzed 404,508 participants from the UK Biobank who were free of diabetes, cancer, or cardiovascular disease at baseline and completed the questionnaire on supplement use. Cox proportional hazards models were used to evaluate the association between habitual use of glucosamine and risk of incident T2D.

RESULTS

During a median of 8.1 years of follow-up, 7,228 incident cases of T2D were documented. Glucosamine use was associated with a significantly lower risk of T2D (hazard ratio 0.83, 95% CI 0.78-0.89) after adjustment for age, sex, BMI, race, center, Townsend deprivation index, lifestyle factors, history of disease, and other supplement use. This inverse association was more pronounced in participants with a higher blood level of baseline C-reactive protein than in those with a lower level of this inflammation marker (P-interaction = 0.02). A genetic risk score for T2D did not modify this association (P-interaction = 0.99).

CONCLUSIONS

Our findings indicate that glucosamine use is associated with a lower risk of incident T2D.

[Experience of using the chondroprotector Sustagard Artro (sashe) in the treatment of lower back pain]

AIM

To compare the efficacy of oral administration of the chondroprotector (CP) Sustagard Artro and nonsteroidal anti-inflammatory drugs (NSAIDs) in reducing lower back pain and to assess the level of blood glucose in patients taking CP.

MATERIAL AND METHODS

Sixty patients with spondylarthrosis (SA) were studied. Patients were randomized into the CP group (n=30), which received Sustagard Artro (1 sachet once a day for 6 weeks), and the NSAIDs group (n=30) treated with injectable forms of different groups of NSAIDs for 3-7 days. Pain intensity was evaluated by the numerical rating scale (NRS) and the Oswestry disability index (ODI).

RESULTS

The reduction in the severity of pain on NRS was similar in both groups: 5.73±1.74 before treatment and 1.43±0.33 after treatment in the CP group; 6.03±0.93 and 1.17±0.97 in the NSAIDs group, respectively. No significant difference in the efficacy was observed between two groups on ODI: 34.66% at baseline and 1.86% after 6 weeks in the CP group; 37.47% and 2.27% in the NSAIDs group, respectively. Changes in the level of glucose were within the upper limit of normal in the CP group.

CONCLUSION

Oral administration of CP (Sustagard Artro, sashe) reduces pain syndrome as effectively as NSAIDs.

Molecular imaging of tumors by chemical exchange saturation transfer MRI of glucose analogs

Early detection of the cancerous process would benefit greatly from imaging at the cellular and molecular level. Increased glucose demand has been recognized as one of the hallmarks of cancerous cells (the "Warburg effect"), hence glucose and its analogs are commonly used for cancer imaging. One example is FDG-PET technique, that led to the use of chemical exchange saturation transfer (CEST) MRI of glucose ("glucoCEST") for tumor imaging. This technique combines high-resolution MRI obtained by conventional imaging with simultaneous molecular information obtained from the exploitation of agents with exchangeable protons from amine, amide or hydroxyl residues with the water signal. In the case of glucoCEST, these agents are based on glucose or its analogs. Recently, preclinical glucoCEST studies demonstrated the ability to increase the sensitivity of MRI to the level of metabolic activity, enabling identification of tumor staging, biologic potential, treatment planning, therapy response and local recurrence, in addition to guiding target biopsy for clinically suspected cancer. However, natural glucose limits this method because of its rapid conversion to lactic acid, leading to reduced CEST effect and short signal duration. For that reason, a variety of glucose analogs have been tested as alternatives to the original glucoCEST. This review discusses the merits of these analogs, including new data on glucose analogs heretofore not reported in the literature. This summarized preclinical data may help strengthen the translation of CEST MRI of glucose analogs into the clinic, improving cancer imaging to enable early intervention without the need for invasive techniques. The data should also broaden our knowledge of fundamental biological processes.

The Effect of Prolonged Glucosamine Usage on HbA1c Levels and New-Onset Diabetes Mellitus in Overweight and Obese Middle-Aged Women

OBJECTIVE

The aim of the present study was to evaluate the effect of a 2.5-year glucosamine sulfate intervention on hemoglobin A1c (HbA1c) levels and the incidence of new-onset diabetes mellitus over 6.5 years in middle-aged women with a body mass index ≥27 kg/m².

METHODS

In total, 407 women were randomized into either oral crystalline glucosamine sulfate or placebo. At baseline, 1 year, 2.5 years, and 6.5 years, a blood sample for the HbA1c level was drawn and questionnaires were taken. After 6.5 years there were missing data for some variables, therefore, multiple imputation was used. With the imputed data, a generalized estimating equation was performed to analyze the effect of glucosamine sulfate usage over 6.5 years. Finally, these analyses were rerun for the 2 subgroups of participants with and without high HbA1c level (≥42 mmol/mol) at baseline.

RESULTS

There was no significant effect of a 2.5-year glucosamine sulfate intervention on mean HbA1c level or on obtaining a high HbA1c level or new-onset diabetes mellitus over 6.5 years. The subgroup analyses of participants with and without high HbA1c level at baseline were also not statistically significant. However, participants with a high HbA1c level at baseline had higher odds ratios compared with the participants with a normal HbA1c at baseline.

CONCLUSIONS

There was no effect of glucosamine sulfate on mean HbA1c level nor on obtaining a high HbA1c level or new-onset diabetes mellitus over 6.5 years, especially in participants with a normal HbA1c level at baseline.

Oral Glucosamine Effect on Blood Glucose and Insulin Levels in Patients With Non-Diabetic Osteoarthritis: A Double-Blind, Placebo-Controlled Clinical Trial

Objectives

This study aims to determine the effects of oral glucosamine on glucose metabolism and insulin resistance in non-diabetic patients with osteoarthritis in Northeastern Iran.

Patients and methods

This placebo-controlled, randomized clinical trial included 40 non-diabetic patients with osteoarthritis (15 males, 25 females, mean age 63.8±7.64 years; range 49 to 80 years). Patients were randomly divided into two equal groups and treated with oral glucosamine sulfate 1500 mg a day or placebo for 90 days. Fasting blood sugar, glucose tolerance test with 75 grams glucose and serum insulin levels, and homeostatic model assessment-insulin resistance were evaluated initially and at the end of intervention.

Results

There were no significant differences between the groups in terms of blood sugar, glucose tolerance test, and insulin levels at the beginning and end of the study. In the oral glucosamine group, there were no significant changes in fasting blood sugar (94.1±7.14 mg/dL versus 93.5±9.45 mg/dL, p=0.15), glucose tolerance test (99.3±8.99 mg/dL versus 103.3±10.1 mg/dL, p=0.07), and homeostatic model assessment-insulin resistance (1.57±0.21 versus 1.48±0.21, p=0.13) after treatment. Also, placebo did not significantly affect serum glucose levels and insulin resistance.

Conclusion

Oral glucosamine with routine dosage was safe in our non-diabetic patients with osteoarthritis and had no significant effect on glucose metabolism and insulin resistance.

Glucosamine and N-acetyl glucosamine as new CEST MRI agents for molecular imaging of tumors

The efficacy of glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc) as agents for chemical exchange saturation transfer (CEST) magnetic resonance molecular imaging of tumors is demonstrated. Both agents reflect the metabolic activity and malignancy of the tumors. The method was tested in two types of tumors implanted orthotopically in mice: 4T1 (mouse mammary cancer cells) and MCF7 (human mammary cancer cells). 4T1 is a more aggressive type of tumor than MCF7 and exhibited a larger CEST effect. Two methods of administration of the agents, intravenous (IV) and oral (PO), gave similar results. The CEST MRI observation of lung metastasis was confirmed by histology. The potential of the clinical application of CEST MRI with these agents for cancer diagnosis is strengthened by their lack of toxicity as can be indicated from their wide use as food supplements.

Glucosamine induces REDD1 to suppress insulin action in retinal Müller cells

Resistance to insulin action is a key cause of diabetic complications, yet much remains unknown about the molecular mechanisms that contribute to the defect. Glucose-induced insulin resistance in peripheral tissues such as the retina is mediated in part by the hexosamine biosynthetic pathway (HBP). Glucosamine (GAM), a leading dietary supplement marketed to relieve the discomfort of osteoarthritis, is metabolized by the HBP, and in doing so bypasses the rate-limiting enzyme of the pathway. Thus, exogenous GAM consumption potentially exacerbates the resistance to insulin action observed with diabetes-induced hyperglycemia. In the present study, we evaluated the effect of GAM on insulin action in retinal Müller cells in culture. Addition of GAM to Müller cell culture repressed insulin-induced activation of the Akt/mTORC1 signaling pathway. However, the effect was not recapitulated by chemical inhibition to promote protein O-GlcNAcylation, nor was blockade of O-GlcNAcylation sufficient to prevent the effects of GAM. Instead, GAM induced ER stress and subsequent expression of the protein Regulated in DNA Damage and Development (REDD1), which was necessary for GAM to repress insulin-stimulated phosphorylation of Akt on Thr308. Overall, the findings support a model whereby GAM promotes ER stress in retinal Müller cells, resulting in elevated REDD1 expression and thus resistance to insulin action.

Oral glucosamine sulfate supplementation does not induce endoplasmic reticulum stress or activate the unfolded protein response in circulating leukocytes of human subjects

Glucosamine sulfate is a dietary supplement that is marketed as a treatment for osteoarthritis. Recent evidence from animal and cell culture models have suggested that glucosamine treatment can promote the misfolding of proteins and the activation of the unfolded protein response (UPR). We investigated whether glucosamine sulfate supplementation activates the UPR in circulating leukocytes of human subjects. Cultured Thp1 human monocytes were exposed to increasing concentrations of glucosamine (0, 0.25, 1.0, 4.0 mmol · L(-1)) for 18 h. We observed a dose-dependent increase in intracellular glucosamine levels as well as the activation of UPR. To test the effect of glucosamine sulfate supplementation in humans, 14 healthy human subjects took 1500 mg · day(-1) glucosamine sulfate for 14 days. Metabolic parameters and blood samples were collected before and after supplementation. In humans, glucosamine sulfate supplementation did not alter metabolic parameters including lipid levels and glucose tolerance. Further, glucosamine sulfate supplementation did not affect intracellular glucosamine levels or activate the UPR in the leukocytes of human subjects. Our results indicate that in healthy human subjects, the recommended dose of glucosamine sulfate (1500 mg · day(-1)) for 14 days does not significantly alter intracellular glucosamine levels and does not activate the UPR in circulating leukocytes.

Physiological effects of oral glucosamine on joint health: current status and consensus on future research priorities

The aim of this paper was to provide an overview of the current knowledge and understanding of the potential beneficial physiological effects of glucosamine (GlcN) on joint health. The objective was to reach a consensus on four critical questions and to provide recommendations for future research priorities. To this end, nine scientists from Europe and the United States were selected according to their expertise in this particular field and were invited to participate in the Hohenheim conference held in August 2011. Each expert was asked to address a question that had previously been posed by the chairman of the conference. Based on a systematic review of the literature and the collection of recent data, the experts documented the effects of GlcN on cartilage ageing, metabolic/kinetic and maintenance of joint health as well as reduction of risk of OA development. After extensive debate and discussion the expert panel addressed each question and a general consensus statement was developed, agreeing on the current state-of-the-art and future areas for basic and clinical studies. This paper summarizes the available evidence for beneficial effects of GlcN on joint health and proposes new insight into the design of future clinical trials aimed at identifying beneficial physiological effect of GlcN on joint tissues.

Role of glucosamine in the treatment for osteoarthritis

Over the last 20 years, several studies have investigated the ability of glucosamine sulfate to improve the symptoms (pain and function) and to delay the structural progression of osteoarthritis. There is now a large, convergent body of evidence that glucosamine sulfate, given at a daily oral dose of 1,500 mg, is able to significantly reduce the symptoms of osteoarthritis in the lower limbs. This dose of glucosamine sulfate has also been shown, in two independent studies, to prevent the joint space narrowing observed at the femorotibial compartment in patients with mild-to-moderate knee osteoarthritis. This effect also translated into a 50 % reduction in the incidence of osteoarthritis-related surgery of the lower limbs during a 5-year period following the withdrawal of the treatment. Some discrepancies have been described between the results of studies performed with a patent-protected formulation of glucosamine sulfate distributed as a drug and those having used glucosamine preparations purchased from global suppliers, packaged, and sold over-the-counter as nutritional supplements.

Effect of a dietary supplement containing glucosamine hydrochloride, chondroitin sulfate and quercetin glycosides on symptomatic knee osteoarthritis: a randomized, double-blind, placebo-controlled study

BACKGROUND

Oral glucosamine and chondroitin sulfate, alone and in combination, have been used worldwide for the treatment of osteoarthritis (OA), but their efficacy is controversial. This clinical study was aimed at investigating the potential of a dietary supplement containing glucosamine and chondroitin sulfate in combination with derivatives of quercetin, a naturally occurring flavonoid, (GCQ supplement) for knee OA care.

RESULTS

A randomized, double-blind, placebo-controlled study was conducted in 40 Japanese subjects with symptomatic knee OA. Subjects were randomly assigned to GCQ supplement (1200 mg glucosamine hydrochloride, 60 mg chondroitin sulfate and 45 mg quercetin glycosides per day) or placebo and the treatment and follow-up were continued for 16 weeks. The results of symptomatic efficacy assessment based on Japanese Orthopaedic Association criteria showed that scores for two of the four symptom/function subscales, as well as the aggregate scores, were significantly improved at week 16 or earlier in the GCQ group compared to the placebo group. Moreover, analyses of cartilage metabolism biomarkers showed a trend of improvement in type II collagen synthesis/degradation balance in the GCQ group during follow-up.

CONCLUSION

GCQ supplement was thought to be more effective than placebo in decreasing the intensity of knee OA-associated clinical symptoms.

Crystalline glucosamine sulfate in the treatment of osteoarthritis: evidence of long-term cardiovascular safety from clinical trials

BACKGROUND AND OBJECTIVE

Glucosamine is a safe and common treatment for osteoarthritis. Even so, literature data on the cardiovascular safety of glucosamine are limited. The objective of this paper is to investigate the long-term effects of crystalline glucosamine sulfate (CGS) on key measures of cardiovascular risk in patients with osteoarthritis.

METHODS

We analyzed safety data from two long-term (6-month and 3-year, respectively) randomized controlled trials of CGS. Mean changes in blood pressure, lipids, and glucose were calculated for all patients randomized to CGS or placebo in either study and for subgroups with abnormally elevated baseline values. Shift tables were used to analyze transitions from normal to abnormal levels, or vice versa.

RESULTS

This analysis on 428 osteoarthritis patients includes data from subjects who had, on average, high normal blood pressure or high cholesterol at baseline. There were no significant changes in mean blood pressure after 6 months on CGS (systolic: -5±15 mmHg; diastolic: -5±10 mmHg) or placebo (systolic: -7±14 mmHg; diastolic: -4±10 mmHg). Subgroup analysis did not show significant effects in subjects with hypertension. Likewise, blood lipids (total/LDL cholesterol) and blood glucose did not change over 3 years and 6 months of treatment, respectively, even in hypercholesterolemic or hyperglycemic subjects. The proportions of patients whose blood pressure or cholesterol levels shifted from normal to abnormal, or vice versa, were comparable in the CGS and placebo groups.

CONCLUSIONS

Long-term use of CGS did not affect blood pressure, lipids, or glucose in patients with osteoarthritis. These findings further support the cardiovascular safety of CGS.

The effect of glucosamine on glucose metabolism in humans: a systematic review of the literature

OBJECTIVE

Glucosamine is commonly used for the treatment of osteoarthritis. It is available as an over the counter preparation and also as a prescription pharmaceutical. There is concern from animal experiments that glucosamine may alter glucose metabolism through the hexosamine biosynthetic pathway. The objective of this systematic review is to determine if exogenous glucosamine adversely affects glucose metabolism in humans. This review does not separate out the effects on glucose metabolism of the various glucosamine preparations.

METHOD

An English-language literature search of MEDLINE, EMBASE and EBM Reviews (1950-February 2009) was conducted. The bibliographies of selected papers were manually searched for additional references. Two reviewers independently analyzed studies for quality and content using a standardized data extraction form.

RESULTS

Eleven studies were included. Six studies were randomized controlled trials and the remaining five were prospective studies with or without controls. Four of the studies found decreased insulin sensitivity or increased fasting glucose in subjects taking glucosamine. Three of these were clinical studies using oral glucosamine. Studies that included subjects with baseline impaired glucose tolerance or insulin resistance were more likely to detect an effect on glucose metabolism than studies without such subjects.

CONCLUSION

Clinical studies, including three using oral glucosamine, have provided mixed evidence about the effect of exogenous glucosamine on glucose metabolism in humans. Therefore, more studies are needed, particularly including subjects at high risk for impairments in glucose homeostasis, before a definite conclusion can be made.

A comprehensive review of oral glucosamine use and effects on glucose metabolism in normal and diabetic individuals

Glucosamine (GlcN) is a widely utilized dietary supplement that is used to promote joint health. Reports that oral GlcN supplementation at usual doses adversely affects glucose metabolism in subjects with impaired glucose tolerance have raised concerns that GlcN should be contraindicated in individuals with diabetes and those at risk for developing it. This review addresses its potential, when used at typical doses, to affect glucose metabolism and insulin sensitivity in healthy individuals and those with diabetes or 'pre-diabetes'. Publicly available scientific information and data on GlcN were systematically compiled using the electronic search tool, Dialog , and reviewed with special emphasis on human studies. In long-term clinical trials, including those containing subjects with type 2 diabetes or 'pre-diabetes', GlcN produced a non-significant lowering of fasting blood glucose concentrations in all groups of subjects treated for periods of up to 3 years. Owing to limitations in study design, conclusions based on studies that report adverse affects of GlcN on insulin sensitivity and glucose tolerance in pre-diabetic subjects are suspect. However, no definitive long-term studies of GlcN use for individuals with pre-diabetes are available. Nevertheless, based on available evidence, we conclude that GlcN has no effect on fasting blood glucose levels, glucose metabolism, or insulin sensitivity at any oral dose level in healthy subjects, individuals with diabetes, or those with impaired glucose tolerance.

Modern management of mild-to-moderate joint pain due to osteoarthritis: a holistic approach

Osteoarthritis (OA) is the most common form of arthritis and it is often associated with significant disability and impaired quality of life. Once thought to be caused by an age-related 'wearing out' of articular cartilage, it is now recognized to be a dynamic process in which cartilage degradation alternates with repair. Several expert guidelines for the management of OA exist, which concur in their recommendations for a stepwise approach to the employment of pharmacological agents and the introduction of suggestions to extend the use of agents such as topical non-steroidal anti-inflammatory drugs, especially for mild-to-moderate forms of the disease. They also emphasize the importance of non-pharmacological measures, such as nutraceuticals, education, diet, exercise and the use of aids in improving signs and symptoms and slowing progression. In many countries, effective medicinal and nutraceutical agents are available 'over-the-counter'. This review explains the modern approach to the management of mild-to-moderate osteoarthritic pain.

Glucosamine and chondroitin for osteoarthritis

Osteoarthritis (OA) is a common, chronic disease that most frequently affects the knees and is a major cause of disability in the elderly. It is characterized by progressive cartilage loss, accompanied by secondary changes such as osteophyte formation and calcium deposition. Inflammatory processes are also involved, leading to stiffness and pain, for which patients seek treatment. Conventional treatment includes analgesics or non-steroidal anti-inflammatory drugs, however life-style changes should also be recommended, such as weight reduction and specific exercises. Glucosamine and chondroitin, classed as over-the-counter supplements or nutraceuticals, are regularly self-administered by patients with OA. Both agents are produced endogenously in the human body and are essential components of cartilage. This review discusses the evidence that supports the use of these agents either alone or in combination for pain relief and as disease-modifying agents in OA.

Dietary supplements commonly used for prevention

The use of complimentary and alternative medicine is on the rise. This article reviews some of the commonly used herbal supplements and others focusing mainly on disease prevention. A summary table of medical conditions is provided, and when possible, a summary of efficacy and safety is provided to facilitate decision making.

Effects of short-term cinnamon ingestion on in vivo glucose tolerance

AIMS

Various spices display insulin-potentiating activity in vitro, and in particular, cinnamon spice and its phenolic extracts have been shown to exhibit these capabilities. In vivo study shows that cinnamon may have beneficial effects on glucose homeostasis; therefore the aim of this study was to further investigate this phenomenon in humans.

METHODS

Seven lean healthy male volunteers, aged 26 +/- 1 years, body mass index 24.5 +/- 0.3 kg/m(2) (mean +/- s.e.m.), underwent three oral glucose tolerance tests (OGTT) supplemented with either a 5 g placebo (OGTT(control)), 5 g of cinnamon (OGTT(cin)), or 5 g of cinnamon taken 12 h before (OGTT(cin12hpre)) in a randomized-crossover design.

RESULTS

Cinnamon ingestion reduced total plasma glucose responses (AUC) to oral glucose ingestion [-13% and -10% for OGTT(cin) (p < 0.05) and OGTT(cin12hpre) (p < 0.05), respectively], as well as improving insulin sensitivity as assessed by insulin sensitivity index measures based on Matsuda's model in both OGTT(cin) (p < 0.05) and OGTT(cin12hpre) (p < 0.05) trials compared with OGTT(control).

CONCLUSIONS

These data illustrate that cinnamon spice supplementation may be important to in vivo glycaemic control and insulin sensitivity in humans, and not only are its effects immediate, they also appear to be sustained for 12 h.

Oral glucosamine in doses used to treat osteoarthritis worsens insulin resistance

BACKGROUND

Glucosamine is used to treat osteoarthritis. In animals, the compound is known to cause insulin resistance, the underlying abnormality in type 2 diabetes mellitus. Insulin resistance in humans taking oral glucosamine in doses used for osteoarthritis has not been studied.

METHODS

Volunteer human subjects (n = 38) without known abnormality of glucose homeostasis had fasting serum glucose, insulin, and lipids determined before and after taking 1500 mg glucosamine by mouth every day for 6 weeks. Fasting insulin and glucose were used to calculate homeostasis model assessment (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI). Vascular elasticity was measured by pulse wave analysis. The paired Student's t test was used to compare baseline with posttreatment values. Pearson's correlation was used to determine the relation of baseline HOMA-IR with changes in other variables.

RESULTS

We found a rise in HOMA-IR after 6 weeks of glucosamine (2.8 versus 3.2, P < 0.04). The fall in HOMA-IR among the subjects was statistically related to a higher baseline HOMA-IR by Pearson's correlation(P < 0.01). A rise in serum triglycerides and a rise in LDL cholesterol were statistically related to baseline HOMA-IR. Small artery elasticity fell, and the decrease was higher in those with the highest baseline HOMA-IR.

CONCLUSIONS

Notwithstanding its efficacy remaining in question, glucosamine is widely used as treatment for osteoarthritis, which is a condition associated with both obesity and type 2 diabetes mellitus. Our data indicate that persons with underlying poorer insulin sensitivity are at risk for worsening insulin resistance and vascular function with the use of glucosamine in doses used to treat osteoarthritis.

Glucosamine regulates differentiation of a chondrogenic cell line, ATDC5

Osteoarthritis (OA) is a slowly progressing chronic joint disease. Glucosamine (GlcN) is a saccharide that is widely used to relieve symptoms associated with OA. However, the mechanism of the effects of GlcN on articular cartilage remains unclear. We studied the effects of GlcN and its analogues, including chitin derivatives included in health supplements containing GlcN, on a chondrogenic cell line, ATDC5. We examined the effects of these saccharides on the proliferation and differentiation of ATDC5 cells. Glucosamine analogues, such as N-acetyl glucosamine and chitobiose, did not affect the proliferation or differentiation of ATDC5 cells. While GlcN did not affect the proliferation of ATDC5 cells, it inhibited their differentiation. Next, we examined whether GlcN affects mineralization and glycosaminoglycan (GAG) production by ATDC5 cells. Mineralization was markedly inhibited by addition of GlcN to the cell culture medium. Moreover, GlcN induced the formation of sulfated GAG in ATDC5. We also analyzed the mRNA levels in ATDC5 cells. GlcN reduced the mRNA levels of Smad2, Smad4 and MGP. GlcN might inhibit expression of MGP mRNA and induce the production of chondroitin sulfate in ATDC5 cells. The mechanism by which GlcN inhibits mineralization may be by regulating the expression of mRNA for the Smad2 and Smad4 chondrogenic master genes.

The reverse glucosamine sulfate pathway: application in knee osteoarthritis

Glucosamine is a natural amino sugar and a normal constituent of glycosaminoglycans in the cartilage matrix and synovial fluid of joints. Crystalline glucosamine sulfate salt has been approved as a medicinal product for the treatment of osteoarthritis in several European countries. Nevertheless, although it has been prescribed for more than 10 years, it is only due to the research in the last 5 years that the scientific basis underlying its beneficial effects are starting to be clarified. In randomised, double-blind, placebo-controlled trials, this compound clinically controls pain and produces beneficial effects in patients with knee osteoarthritis, possibly delaying the appearance of long-term structural changes in the joint (i.e., it has a structure-modifying effect). Furthermore, it has an excellent toxicity profile. Despite the different lines of investigation that have been followed, the mechanism of action of glucosamine sulfate still remains to be clearly defined. However, the activity of glucosamine sulfate has recently been related to its capacity to downregulate the catabolic effects of pro-inflammatory molecules, such as IL-1, which are present in osteoarthritic cartilage.

Risk assessment for glucosamine and chondroitin sulfate

Glucosamine and chondroitin sulfate are two popular dietary ingredients present in dietary supplements intended to support joint health. A large body of human and animal research suggests that oral intakes of these ingredients, either alone or in combination, reduces joint pain and improves mobility in persons with osteoarthritis. The increased awareness and use of these ingredients in dietary supplements warrant a comprehensive review of their safety. Systematic evaluation of the research designs and data do not provide a basis for risk assessment and the usual safe upper level of intake (UL) derived from it unless the newer methods described as the observed safe level (OSL) or highest observed intake (HOI) are utilized. The OSL risk assessment method indicates that the evidence strongly supports safety at intakes up to 2000 mg/d for glucosamine, and 1200 mg/d for chondroitin sulfate, and these levels are identified as the respective OSL. These values represent the highest levels tested in human clinical trials. The complete absence of adverse effects at these levels supports a confident conclusion of their long-term safety.

Oral glucosamine for 6 weeks at standard doses does not cause or worsen insulin resistance or endothelial dysfunction in lean or obese subjects

Glucosamine is a popular nutritional supplement used to treat osteoarthritis. Intravenous administration of glucosamine causes insulin resistance and endothelial dysfunction. However, rigorous clinical studies evaluating the safety of oral glucosamine with respect to metabolic and cardiovascular pathophysiology are lacking. Therefore, we conducted a randomized, placebo-controlled, double-blind, crossover trial of oral glucosamine at standard doses (500 mg p.o. t.i.d.) in lean (n = 20) and obese (n = 20) subjects. Glucosamine or placebo treatment for 6 weeks was followed by a 1-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by hyperinsulinemic-isoglycemic glucose clamp (SI(Clamp)) and endothelial function evaluated by brachial artery blood flow (BAF; Doppler ultrasound) and forearm skeletal muscle microvascular recruitment (ultrasound with microbubble contrast) before and during steady-state hyperinsulinemia. Plasma glucosamine pharmacokinetics after oral dosing were determined in each subject using a high-performance liquid chromatography method. As expected, at baseline, obese subjects had insulin resistance and endothelial dysfunction when compared with lean subjects (SI(Clamp) [median {25th-75th percentile}] = 4.3 [2.9-5.3] vs. 7.3 [5.7-11.3], P < 0.0001; insulin-stimulated changes in BAF [% over basal] = 12 [-6 to 84] vs. 39 [2-108], P < 0.04). When compared with placebo, glucosamine did not cause insulin resistance or endothelial dysfunction in lean subjects or significantly worsen these findings in obese subjects. The half-life of plasma glucosamine after oral dosing was approximately 150 min, with no significant changes in steady-state glucosamine levels detectable after 6 weeks of therapy. We conclude that oral glucosamine at standard doses for 6 weeks does not cause or significantly worsen insulin resistance or endothelial dysfunction in lean or obese subjects.

Effects of oral glucosamine sulphate on serum glucose and insulin during an oral glucose tolerance test of subjects with osteoarthritis

BACKGROUND

and objective: Glucosamine is suggested to affect glucose transport and insulin resistance. The effects of oral glucosamine on serum glucose and insulin levels at the initiation and throughout the duration of a 3-h oral glucose tolerance test were examined.

METHODS

Sera from 16 patients with osteoarthritis, but with no other diagnosed medical condition who had fasted overnight, were obtained every 15-30 min during the 3 h of continued fasting and during the 3 h after ingestion of 75 g of glucose with or without ingestion of 1500 mg of glucosamine sulphate. Glucose was analysed by high-performance liquid chromatography using a Metrohm-Peak 817 Bioscan, and the area under the curve (AUC) for glucose was calculated. Insulin was measured by radioimmunoassay every 30 min for 2 h.

RESULTS

Three participants who were found to have previously undiagnosed abnormalities of glucose tolerance demonstrated significant (p = 0.04) incremental elevations in glucose levels after ingestion of glucosamine sulphate. The other 13 participants also had mean incremental elevations that were not significant (p = 0.20). Glucosamine sulphate ingestion had no effect on insulin levels.

CONCLUSION

The results suggest that glucosamine ingestion may affect glucose levels and consequent glucose uptake in patients who have untreated diabetes or glucose intolerance.

Effect of glucosamine on glucose control

OBJECTIVE

To review the literature regarding the effect of glucosamine on glucose control.

DATA SOURCES

English-language articles on the effects of administration of exogenous glucosamine on glucose control were identified through a search of MEDLINE (1966-March 2006), EMBASE (1988-March 2006), and International Pharmaceutical Abstracts (1970-March 2006) databases using the search terms glucosamine, blood glucose, and diabetes mellitus. Abstracts of articles were then reviewed to determine relevance to the topic. Bibliographies of selected articles were screened for other pertinent references.

DATA SYNTHESIS

Theoretically, glucosamine may alter glucose metabolism. Insulin resistance has been noted following intravenous administration of glucosamine in animal studies; however, these findings have not been confirmed in humans. Alterations in glucose control have not been documented in long-term efficacy studies using oral glucosamine for osteoarthritis or in trials of short duration conducted in healthy or diabetic subjects. The long-term effects of glucosamine in patients with diabetes have yet to be established in well-controlled trials.

CONCLUSIONS

Small, short-term studies suggest that glucosamine may be used in selected patients without affecting glucose control; however, data in patients with diabetes mellitus are limited, and close monitoring for potential changes in glucose control is recommended.

Nutritional factors and osteoarthritis: recent developments

PURPOSE OF REVIEW

The role of nutrition and nutritional supplements in the development and progression of osteoarthritis is now a topic of considerable public, industry, and academic interest. This review focuses on how the evidence for a role of nutritional factors or nutritional supplements in the management of knee osteoarthritis has been changed by recent research.

RECENT FINDINGS

Recent studies include clinical trials of weight loss and exercise as interventions for osteoarthritis of the knee, the elucidation of mechanisms of oxidative stress on the chondrocyte genome, further study of vitamin C supplementation in an animal with spontaneous osteoarthritis, and further clinical and pharmacodynamic evaluations of glucosamine and chondroitin sulfate. Perplexing findings among these studies include the deleterious effects of vitamin C on osteoarthritis in the Hartley guinea pig, the low levels of glucosamine achieved in serum after an oral dose, recent negative clinical studies of glucosamine, and the heterogeneity of results among glucosamine trials.

SUMMARY

With an intensification of research in this field come new clinical and basic science data, sometimes with surprising results. These confirm the considerable potential for a role of nutritional interventions for osteoarthritis, but they emphasize the need for systematic scientific evaluation of the claims made for such products.

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.

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.