Several clinical studies demonstrated that glucosamine sulfate (GS) is effective in controlling osteoarthritis (OA), showing a structure-modifying action. However, little is known about the molecular mechanism(s) by which GS exerts such action and about the effects of GS at a tissue level on osteoarthritic cartilage and other joint structures. Here we provide mechanistic evidence suggesting that in vitro GS attenuates NF-κB activation at concentrations in the range of those observed after GS administration to volunteers and patients, thus strengthening previous findings. Furthermore, we describe the effects of GS at a tissue level on the progression of the disease in a relevant model of spontaneous OA, the STR/ort mouse. In this model, the administration of GS at human corresponding doses was associated with a significant decrease of OA scores. Histomorphometry showed that the lesion surface was also significantly decreased, while the number of viable chondrocytes within the matrix was significantly increased. GS improved the course of OA in the STR/Ort mouse, by delaying cartilage breakdown as assessed histologically and histomorphometrically.

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.

Growing evidence suggests that galectin-3 (Gal-3) is instrumental in orchestrating innate immune response and microglia activation following different brain pathologies. However, its role remains controversial. We recently showed that a readily available natural product glucosamine may act as a strong modulator of Gal-3. Glucosamine is a naturally occurring sugar and a precursor in the synthesis of glycosylated proteins. It is often used as a supplement to treat symptoms of various inflammatory conditions. Our recent work suggests that by increasing the synthesis and availability of Gal-3 ligands and/or by regulating its expression levels, glucosamine may significantly modulate Gal-3 signaling. Because evidence suggests that Gal-3 might be differentially regulated after ischemic injury in the brains of female mice, here we examined and compared the immunomodulatory potential of glucosamine in male and female stroke. The mice were subjected to transient middle cerebral artery occlusion (MCAO), followed by different reperfusion periods. The short-term 5 days treatment with glucosamine (150 ​mg/kg i.p.) was initiated 2 ​hrs after stroke. To visualize the effects of glucosamine treatment on post-stroke inflammation, we took advantage of a transgenic mouse model bearing the dual reporter system luciferase/GFP under transcriptional control of a murine TLR2 promoter (TLR2-luc-GFP) allowing in vivo bioluminescence imaging of innate immune response and microglial activation. We report that after stroke, both, male and female mice strongly up-regulate the TLR2 bioluminescence signals from activated microglia, however, the observed in vivo immunomodulatory effects of glucosamine after stroke were sex-dependent. Analysis of cytokine profiles at protein level, in glucosamine-treated male mice 72hsr after stroke, revealed down regulation of pro-inflammatory cytokines, an increase in levels of anti-inflammatory cytokines including IL-4, IL13 and colony stimulating factors MCFC and GM-CSF and a significant decrease in the size of ischemic lesion in male mice. Conversely, in female mice glucosamine markedly increases the pro-inflammatory signaling and exacerbates ischemic injury. Analysis of the downstream signaling target of glucosamine/Gal-3 revealed that glucosamine administration restored PPAR-γ activity in male but not in female mice 3 days following MCAO. Together, our results suggest that glucosamine acts as a fine tuner of post-ischemic inflammation in a sex dependent-manner and may have therapeutic potential after stroke in males. Based on our results propose that targeting immune system after stroke may require adapted sex-specific therapeutic approaches.

Glucosamine (GLU) is a natural compound found in cartilage, and supplementation with glucosamine has been shown to improve joint heath and has been linked to reduced mortality rates. GLU is poorly absorbed and may exhibit functional properties in the gut. The purpose of this study was to examine the impact of glucosamine on gastrointestinal function as well as changes in fecal microbiota and metabolome. Healthy males (n = 6) and females (n = 5) (33.4 ± 7.7 years, 174.1 ± 12.0 cm, 76.5 ± 12.9 kg, 25.2 ± 3.1 kg/m2, n = 11) completed two supplementation protocols that each spanned three weeks separated by a washout period that lasted two weeks. In a randomized, double-blind, placebo-controlled, crossover fashion, participants ingested a daily dose of GLU hydrochloride (3000 mg GlucosaGreen®, TSI Group Ltd., Missoula, MT, USA) or maltodextrin placebo. Study participants completed bowel habit and gastrointestinal symptoms questionnaires in addition to providing a stool sample that was analyzed for fecal microbiota and metabolome at baseline and after the completion of each supplementation period. GLU significantly reduced stomach bloating and showed a trend towards reducing constipation and hard stools. Phylogenetic diversity (Faith's PD) and proportions of Pseudomonadaceae, Peptococcaceae, and Bacillaceae were significantly reduced following GLU consumption. GLU supplementation significantly reduced individual, total branched-chain, and total amino acid excretion, with no glucosamine being detected in any of the fecal samples. GLU had no effect on fecal short-chain fatty acids levels. GLU supplementation provided functional gut health benefits and induced fecal microbiota and metabolome changes.

The inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis, are caused in part by aberrant immune responses to resident intestinal bacteria. Certain dietary components, including carbohydrates, are associated with IBDs and alter intestinal bacterial composition. However, the effects of luminal carbohydrates on the composition and colitogenic potential of intestinal bacteria are incompletely understood. We hypothesize that carbohydrate metabolism by resident proinflammatory intestinal bacteria enhances their growth and worsens intestinal inflammation.

Glucosamine sulphate (GS) can be used as background therapy in people affected by knee osteoarthritis (OA). Knowledge regarding the efficacy and safety of GS is of importance since its use worldwide is increasing. Therefore, the present study aimed to map and grade the diverse health outcomes associated with GS using an umbrella review approach.

Accelerated atherosclerosis is one of the major vascular complications of diabetes. Factors including hyperglycemia and hyperinsulinemia may contribute to accelerated vascular disease. Among the several mechanisms proposed to explain the link between hyperglycemia and vascular dysfunction is the hexosamine pathway, where glucose is converted to glucosamine. Although some animal experiments suggest that glucosamine may mediate insulin resistance, it is not clear whether glucosamine is the mediator of vascular complications associated with hyperglycemia. Several processes may contribute to diabetic atherosclerosis including decreased vascular heparin sulfate proteoglycans (HSPG), increased endothelial permeability and increased smooth muscle cell (SMC) proliferation. In this study, we determined the effects of glucose and glucosamine on endothelial cells and SMCs in vitro and on atherosclerosis in apoE null mice. Incubation of endothelial cells with glucosamine, but not glucose, significantly increased matrix HSPG (perlecan) containing heparin-like sequences. Increased HSPG in endothelial cells was associated with decreased protein transport across endothelial cell monolayers and decreased monocyte binding to subendothelial matrix. Glucose increased SMC proliferation, whereas glucosamine significantly inhibited SMC growth. The antiproliferative effect of glucosamine was mediated via induction of perlecan HSPG. We tested if glucosamine affects atherosclerosis development in apoE-null mice. Glucosamine significantly reduced the atherosclerotic lesion in aortic root. (P < 0.05) These data suggest that macrovascular disease associated with hyperglycemia is unlikely due to glucosamine. In fact, glucosamine by increasing HSPG showed atheroprotective effects.

Phosphorylated glucosamine (glucosamine-6-phosphate, PGlc) was synthesized using methanesulfonic acid, phosphorus pentoxide (P(2)O(5)), NH(2)NH(2) and DMF. Its inhibitory effect on lipid accumulation in cultured 3T3-L1 adipocytes was investigated by measuring triglyceride contents and Oil Red O staining. In order to understand the mechanism by which lipid accumulation in adipocytes is decreased by PGlc, we examined the expression levels of several genes and proteins associated with adipogenesis and lipolysis using reverse transcription polymerase chain reaction, real-time polymerase chain reaction and Western blot analysis. Treatment with PGlc significantly reduced lipid accumulation during adipocyte differentiation and induced down-regulation of peroxisome proliferator-activated receptor-gamma, sterol regulatory element binding protein 1 and CCAAT/enhancer binding protein-alpha in a dose-dependent manner. Moreover, treatment with PGlc during adipocyte differentiation induced significant up-regulation of preadipocyte factor 1 mRNA and down-regulation of such adipocyte-specific gene promoters as adipocyte fatty acid binding protein, fatty acid synthase, lipoprotein lipase and leptin. According to the lipolytic response, PGlc up-regulated hormone-sensitive lipase mRNA expression and suppressed the expression levels of tumor necrosis factor-alpha mRNA compared with fully differentiated adipose tissue. These results suggest that the inhibitory effect of PGlc on adipocyte differentiation might be mediated through the down-regulation of adipogenic transcription factors, such as peroxisome proliferator-activated receptor-gamma, sterol regulatory element binding protein 1 and CCAAT/enhancer binding protein-alpha, which are related to the downstream adipocyte-specific gene promoters.

Brain-derived neurotrophic factor (BDNF) is an important factor for memory consolidation and cognitive function. Protein kinase A (PKA) signaling interacts significantly with BDNF-provoked downstream signaling. Glucosamine (GLN), a common dietary supplement, has been demonstrated to perform a variety of beneficial physiological functions. In the current study, an in vivo model of 7-week-old C57BL/6 mice receiving daily intraperitoneal injection of GLN (0, 3, 10 and 30 mg/animal) was subjected to the novel object recognition test in order to determine cognitive performance. GLN significantly increased cognitive function. In the hippocampus GLN elevated tissue cAMP concentrations and CREB phosphorylation, and upregulated the expression of BDNF, CREB5 and the BDNF receptor TrkB, but it reduced PDE4B expression. With the in vitro model in the HT22 hippocampal cell line, GLN exposure significantly increased protein and mRNA levels of BDNF and CREB5 and induced cAMP responsive element (CRE) reporter activity; the GLN-mediated BDNF expression and CRE reporter induction were suppressed by PKA inhibitor H89. Our current findings suggest that GLN can exert a cognition-enhancing function and this may act at least in part by upregulating the BDNF levels via a cAMP/PKA/CREB-dependent pathway.

Glucosamine, the intermediate metabolite of the hexosamine biosynthesis pathway (HBP), is widely used as a supplementary drug in patients with osteoarthritis. However, its consequences in such patients concomitantly suffering from diabetic nephropathy is unknown.

The extent of glycation and conformational changes of horse myoglobin (Mb) upon glycation with N-acetyl-glucosamine (GlcNAc), glucose (Glc) and glucosamine (GlcN) were investigated. Among tested sugars, the rate of glycation with GlcN was the most rapid as shown by MALDI and ESI mass spectrometries. Protein oxidation, as evaluated by the amount of carbonyl groups present on Mb, was found to increase exponentially in Mb-Glc conjugates over time, whereas in Mb-GlcN mixtures the carbonyl groups decreased significantly after maximum at 3 days of the reaction. The reaction between GlcN and Mb resulted in a significantly higher amount of α-dicarbonyl compounds, mostly glucosone and 3-deoxyglucosone, ranging from and 27 to 332 mg/L and from 14 to 304 mg/L, respectively. Already at 0.5 days, tertiary structural changes of Mb-GlcN conjugate were observed by altered tryptophan fluorescence. A reduction of metmyoglobin to deoxy-and oxymyoglobin forms was observed on the first day of reaction, coinciding with the greatest amount of glucosone produced. In contrast to native α-helical myoglobin, 41% of the glycated protein sequence was transformed into a β-sheet conformation, as determined by circular dichroism spectropolarimetry. Transmission electron microscopy demonstrated that Mb glycation with GlcN causes the formation of amorphous or fibrous aggregates, started already at 3 reaction days. These aggregates bind to an amyloid-specific dye thioflavin T. With the aid of α-dicarbonyl compounds and advanced products of reaction, this study suggests that the Mb glycation with GlcN induces the unfolding of an initially globular protein structure into amyloid fibrils comprised of a β-sheet structure.

Understanding microsecond-timescale dynamics is crucial to establish three-dimensional (3D) structure-activity relationships in sugars but has been intractable to experiments and simulations. As a consequence, whether arguably the most important chemical scaffold in glycobiology, N-acetyl-d-glucosamine (GlcNAc), deviates from a rigid (4)C(1) chair is unknown. Here, conformer populations and exchange kinetics were quantified from the longest aqueous carbohydrate simulations to date (0.2 ms total) of GlcNAc, four derivatives from heparan sulfate and their methylglycosides. Unmodified GlcNAc took 3-5 μs to reach a conformational equilibrium, which comprised a metastable (4)C(1) chair that underwent (4)C(1) ↔ (1)C(4) transitions at a predicted forward rate of 0.8 μs(-1) with an average (1)C(4)-chair lifetime of 3 ns. These predictions agree with high-resolution crystallography and nuclear magnetic resonance but not with the hypothesis that GlcNAc is a rigid (4)C(1) chair, concluded from previous experimental analyses and non-aqueous modeling. The methylglycoside was calculated to have a slower forward rate (0.3 μs(-1)) and a more stable (4)C(1) conformer (0.2 kcal mol(-1)), suggesting that pivotal 3D intermediates (particularly (2)S(O), (1)S(5) and B(2,5)) increased in energy, and water was implicated as a major cause. Sulfonation (N-, 3-O and 6-O) significantly augmented this effect by blocking pseudorotation, but did not alter the rotational preferences of hydroyxl or hydroxymethyl groups. We therefore propose that GlcNAc undergoes puckering exchange that is dependent on polymerization and sulfo substituents. Our analyses, and 3D model of the equilibrium GlcNAc conformer in water, can be used as dictionary data and present new opportunities to rationally modify puckering and carbohydrate bioactivity, with diverse applications from improving crop yields to disease amelioration.

In this work, glucose transporter-1 (GLUT-1) and glutathione (GSH) over-expression in liver cancer was utilized to design a reduction-responsive and active targeting drug delivery system AG-PEG-SS-PCL (APSP) for the delivery of sorafenib (SF). The SF-APSP micelles were prepared using the thin film hydration method and characterized by various techniques. In vitro release experiments showed that the cumulative release of SF-APSP micelles in the simulated tumor microenvironment (pH 7.4 with GSH) reached 94.76 ± 1.78% at 48 h, while it was only 20.32 ± 1.67% in the normal physiological environment (pH 7.4 without GSH). The in vitro study revealed that glucosamine (AG) enhanced the antitumor effects of SF, and SF-APSP micelles inhibited proliferation by targeting HepG2 cells and suppressing cyclin D1 expression. The in vivo antitumor efficacy study further confirmed that the SF-APSP micelles had excellent antitumor effects and better tolerance against nude mouse with HepG2 cells than other treatment groups. All in all, these results indicated that SF-APSP micelles could be a promising drug delivery system for anti-hepatoma treatment.

Recent studies have reported that glucosamine (GlcN) showed therapeutic effects in allergic diseases such as asthma and rhinitis, and its mechanisms include the suppression of T helper type 2 immune responses and the nuclear factor-κB pathway.

We have reported that the glucosamine suppressed the proliferation of the human prostate carcinoma cell line DU145 through inhibition of STAT3 signaling. DU145 cells autonomously express IL-6 and the IL-6/STAT3 signaling is activated. IL-6 receptor subunits are subject to N-glycosylation, a posttranslational modification which is important for protein stability and function. We speculated that the inhibition of STAT3 phosphorylation by glucosamine might be a functional consequence of the reduced N-glycosylation of gp130.

Osteoarthritis (OA) and osteoporosis (OP) are common among older women, especially postmenopausal women. Glucosamine (GlcN) is a common medication for OA, but it may induce insulin resistance and β-cell dysfunction, especially if ovarian hormones are lacking. Raloxifene (RLX) is a selective estrogen receptor modulator and also an OP drug. Previously, we found that estrogen could improve GlcN-induced insulin resistance in ovariectomized (OVX) rats. Here, we further hypothesized that RLX, similarly to estrogen, can ameliorate GlcN-induced insulin resistance in OVX rats. We used GlcN to induce insulin resistance in OVX rats as a model for evaluating the protective effects of RLX in vivo. We used a pancreatic β-cell line, MIN-6, to study the mechanisms underlying the effect of RLX in GlcN-induced β-cell dysfunction in vitro. Increases in fasting plasma glucose, insulin, and homeostasis model assessments of insulin resistance in OVX Sprague Dawley rats treated with GlcN were reversed by RLX treatment (n = 8 in each group). Skeletal muscle GLUT-4 increased, liver PEPCK decreased, pancreatic islet hypertrophy, and β-cell apoptosis in OVX rats treated with GlcN was ameliorated by RLX. The negative effects of GlcN on insulin secretion and cell viability in MIN-6 cells were related to the upregulation of reticulum (ER) stress-associated proteins (C/EBP homologous protein, phospho-extracellular signal-regulated kinase, phospho-c-JunN-terminal kinase), the expression of which was reduced by RLX. Pretreatment with estrogen receptor antagonists reversed the protective effects of RLX. GlcN can induce insulin resistance, β-cell dysfunction, and apoptosis in OVX rats and increase ER stress-related proteins in β-cells, whereas RLX can reverse these adverse effects. The effects of RLX act mainly through estrogen receptor α; therefore, RLX may be a candidate drug for postmenopausal women with OA and OP.

Recent studies have shown that glucosamine inhibits the proliferation of various human cancer cell lines and downregulates the activity of COX-2, HIF-1α, p70S6K, and transglutaminase 2. Because the IGF-1R/Akt pathway is a common upstream regulator of p70S6K, HIF-1α, and COX-2, we hypothesized that glucosamine inhibits cancer cell proliferation through this pathway.

Glucosamine (GlcN), a natural amino sugar in human body, was reported to exhibit anticancer activity against some tumors. In the present study, we evaluated the cytotoxicity and multi-drug resistance (MDR) reversal activity of GlcN on resistant MRP2-overexpressing ovarian cancer A2780RCIS cells. The cytotoxicity and MDR reversal activity of GlcN on cancer cells were measured by MTT assay. The effects of GlcN on MRP1 and MRP2 mRNA expression and function were evaluated by qRT-PCR and flow cytometry, respectively. The cell migration capacity of ovarian cancer cells were assessed in the presence or absence of GlcN using wound healing migration assay. Furthermore, the effects of GlcN on the mRNA expression of E-cadherin, vimentin and α-smooth muscle actin as Epithelial-Mesenchymal Transition (EMT)-related markers were evaluated by qRT-PCR. Our results indicated that glucosamine reduced the proliferation of human ovarian cancer cell lines (A2780) and its cisplatin resistant variant (A2780RCIS) in a dose-dependent manner. The IC50 values for A2780RCIS cells treated with cisplatin in the presence of different concentrations of GlcN (0, 1, 2 and 3 mM) for 72 h were 44.463 ± 1.603, 35.17 ± 0.025, 22.25 ± 0.018, 17.78 ± 0.012 μM respectively. Also GlcN decreased the expression of MRP1 and MRP2 mRNA in ovarian cancer cells. Our results further demonstrated that although GlcN had no significant effects on the expression of studied EMT-related markers in invasive A2780RCIS cells, it was able to inhibit their migration in vitro. According to these findings, GlcN could effectively enhance cisplatin cytotoxicity in resistant A2780RCIS cells.

No abstract available

Knee osteoarthritis is the most popular type of osteoarthritis that causes extreme pain in the elderly. Currently, there is no cure for osteoarthritis. To lessen clinical symptoms, glucosamine was suggested. The primary goal of our systematic review study is to evaluate the effectiveness and safety of glucosamine based on recent studies. Electronic databases such as PubMed, Scopus, and Cochrane were used to assess the randomized controlled trial (RCT). From the beginning through March 2023, the papers were checked, and if they fulfilled the inclusion criteria, they were then examined. The Western Ontario and McMaster Universities Osteoarthritis (WOMAC) and Visual Analog Scale (VAS) scales were considered the main outcome measures. A total of 15 studies were selected. Global pain was significantly decreased in comparison to placebo, as measured by the VAS index, with an overall effect size of standardized mean difference (SMD) of -7.41 ([95% CI] 14.31, 0.51). The WOMAC scale confirmed that pain, stiffness, and physical function had improved, however the effects were insufficient. A statistical update also revealed that there were no reports of serious medication interactions or significant adverse events. To summarize, glucosamine is more effective than a placebo at reducing pain in knee osteoarthritis patients. In long-term treatment, oral glucosamine sulfate 1500 mg/day is believed to be well tolerated.