Glucosamine and O-GlcNAcylation: a novel immunometabolic therapeutic target for OA and chronic, low-grade systemic inflammation?

O-GlcNAcylation in ischemic diseases

Protein glycosylation is an extensively studied field, with the most studied forms being oxygen or nitrogen-linked N-acetylglucosamine (O-GlcNAc or N-GlcNAc) glycosylation. Particular residues on proteins are targeted by O-GlcNAcylation, which is among the most intricate post-translational modifications. Significantly contributing to an organism's proteome, it influences numerous factors affecting protein stability, function, and subcellular localization. It also modifies the cellular function of target proteins that have crucial responsibilities in controlling pathways related to the central nervous system, cardiovascular homeostasis, and other organ functions. Under conditions of acute stress, changes in the levels of O-GlcNAcylation of these proteins may have a defensive function. Nevertheless, deviant O-GlcNAcylation nullifies this safeguard and stimulates the advancement of several ailments, the prognosis of which relies on the cellular milieu. Hence, this review provides a concise overview of the function and comprehension of O-GlcNAcylation in ischemia diseases, aiming to facilitate the discovery of new therapeutic targets for efficient treatment, particularly in patients with diabetes.

O-GlcNAcylation: a pro-survival response to acute stress in the cardiovascular and central nervous systems

O-GlcNAcylation is a unique monosaccharide modification that is ubiquitously present in numerous nucleoplasmic and mitochondrial proteins. The hexosamine biosynthesis pathway (HBP), which is a key branch of glycolysis, provides the unique sugar donor UDP-GlcNAc for the O-GlcNAc modification. Thus, HBP/O-GlcNAcylation can act as a nutrient sensor to perceive changes in nutrient levels and trigger O-GlcNAc modifications of functional proteins in cellular (patho-)physiology, thereby regulating diverse metabolic processes. An imbalance in O-GlcNAcylation has been shown to be a pathogenic contributor to dysfunction in metabolic diseases, including type 2 diabetes, cancer, and neurodegeneration. However, under acute stress conditions, protein O-GlcNAc modification exhibits rapid and transient upregulation, which is strongly correlated with stress tolerance and cell survival. In this context, we discuss the metabolic, pharmacological and genetic modulation of HBP/O-GlcNAc modification in the biological system, the beneficial role of O-GlcNAcylation in regulating stress tolerance for cardioprotection, and neuroprotection, which is a novel and rapidly growing field. Current evidence suggests that transient activation of the O-GlcNAc modification represents a potent pro-survival signalling pathway and may provide a promising strategy for stress-related disorder therapy.

Systemic osteoarthritis: the difficulty of categorically naming a continuous condition

Osteoarthritis (OA) is a disease with systemic implications that go beyond joint problems. Its pathogenic mechanisms involve a variety of systemic conditions that contribute to joint damage. These include metabolic dysfunction, chronic low-grade inflammation, neuroplastic pain, and the influence of the central nervous system in the development of neuropathic pain. Besides, OA can negatively affect other aspects of health, such as quality of life, reduced physical activity, social isolation, depression, and anxiety. OA can be considered a complex system in which pathological interactions involve not only obesity and metabolic dysfunction, but also fragility syndrome, sarcopenia, neurological complications, and systemic energy redistribution. Complex systems are composed of multiple interacting and dynamic parts and exhibit emergent properties that cannot be fully explained by examining their individual components. Chronic low-grade inflammation is characteristic of OA, occurring both in the affected joint, and systemically, mainly due to adipose tissue inflammation in obese patients. Obesity is a key factor in the progression of OA, so primary treatment should focus on its control, while maintaining muscle health. The chronic inflammation could lead to changes in energy distribution among the affected joint tissues. Therefore, OA should be approached as a systemic disease, considering individual patient factors, such as genetics, inflammatory response, and lifestyle. Medical care should be more holistic and personalized. Consideration of a name change, such as "systemic OA", could help to move away from the perception of a disease focused only on the joints.

Nintedanib ameliorates osteoarthritis in mice by inhibiting synovial inflammation and fibrosis caused by M1 polarization of synovial macrophages via the MAPK/PI3K-AKT pathway

Synovial inflammation and fibrosis are important pathological changes associated with osteoarthritis (OA). Herein, we investigated if nintedanib, a drug specific for pulmonary fibrosis, plays a positive role in osteoarthritic synovial inflammation and fibrosis. We assessed the effect of nintedanib on osteoarthritic synovial inflammation and fibrosis in a mouse model of OA created by destabilization of the medial meniscus and a macrophage M1 polarization model created by stimulating RAW264.7 cells with lipopolysaccharide. Histological staining showed that daily gavage administration of nintedanib significantly alleviated articular cartilage degeneration, reduced the OARSI score, upregulated matrix metalloproteinase-13 and downregulated collagen II expression, and significantly reduced the synovial score and synovial fibrosis in a mouse OA model. In addition, immunofluorescence staining showed that nintedanib significantly decreased the number of M1 macrophages in the synovium of a mouse model of OA. In vitro results showed that nintedanib downregulated the phosphorylation levels of ERK, JNK, p38, PI3K, and AKT while inhibiting the expression of macrophage M1 polarization marker proteins (CD86, CD80, and iNOS). In conclusion, this study suggests that nintedanib is a potential candidate for OA treatment. The mechanisms of action of nintedanib include the inhibition of M1 polarization in OA synovial macrophages via the MAPK/PI3K-AKT pathway, inhibition of synovial inflammation and fibrosis, and reduction of articular cartilage degeneration.

Effectiveness and Safety of Glucosamine in Osteoarthritis: A Systematic Review

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.

Effects of Modified Glucosamine on the Chondrogenic Potential of Circulating Stem Cells under Experimental Inflammation

Glucosamine (GlcN) is a glycosaminoglycan (GAGs) constituent in connective tissues. It is naturally produced by our body or consumed from diets. In the last decade, in vitro and in vivo trials have demonstrated that the administration of GlcN or its derivates has a protective effect on cartilage when the balance between catabolic and anabolic processes is disrupted and cells are no longer able to fully compensate for the loss of collagen and proteoglycans. To date, these benefits are still controversial because the mechanism of action of GlcN is not yet well clarified. In this study, we have characterized the biological activities of an amino acid (AA) derivate of GlcN, called DCF001, in the growth and chondrogenic induction of circulating multipotent stem cells (CMCs) after priming with tumor necrosis factor-alpha (TNFα), a pleiotropic cytokine commonly expressed in chronic inflammatory joint diseases. In the present work, stem cells were isolated from the human peripheral blood of healthy donors. After priming with TNFα (10 ng/mL) for 3 h, cultures were treated for 24 h with DCF001 (1 μg/mL) dissolved in a proliferative (PM) or chondrogenic (CM) medium. Cell proliferation was analyzed using a Corning^® Cell Counter and trypan blue exclusion technique. To evaluate the potentialities of DCF001 in counteracting the inflammatory response to TNFα, we measured the amount of extracellular ATP (eATP) and the expression of adenosine-generating enzymes CD39/CD73, TNFα receptors, and NF-κB inhibitor IκBα using flow cytometry. Finally, total RNA was extracted to perform a gene expression study of some chondrogenic differentiation markers (COL2A1, RUNX2, and MMP13). Our analysis has shed light on the ability of DCF001 to (a) regulate the expression of CD39, CD73, and TNF receptors; (b) modulate eATP under differentiative induction; (c) enhance the inhibitory activity of IκBα, reducing its phosphorylation after TNFα stimulation; and (d) preserve the chondrogenic potentialities of stem cells. Although preliminary, these results suggest that DCF001 could be a valuable supplement for ameliorating the outcome of cartilage repair interventions, enhancing the efficacy of endogenous stem cells under inflammatory stimuli.

Glucosamine as a Treatment for Osteoarthritis: What If It's True?

No disease-modifying treatments are currently available for osteoarthritis (OA). While many therapeutic approaches are now being investigated it is ethical to resort to alternative solutions as that we already possess. There are many reasons for thinking that, at sufficiently high doses, glucosamine (GlcN) sulphate possesses a clinically relevant effect on OA pain. Wide inter-individual variations in the symptomatic effects of GlcN are explained by the extreme variability of its bioavailability. In studies evaluating its structure-modifying effect, GlcN was more effective than placebo in reducing the rate of joint space narrowing in patients with knee OA. More recent data suggest that GlcN may be effective in the primary prevention of OA in sportsmen. There is no controversy concerning the safety of GlcN which does not differ to that of placebo. Several studies have recently revealed an unexpected effect of GlcN on cardiovascular mortality. After adjusting for confounding factors, the regular consumption of GlcN correlated with a 27% reduction in mortality and a 58% reduction in deaths from cardiovascular causes. These data confirm animal studies demonstrating a protective effect of GlcN against cancer and cardiovascular diseases due to modulation of the O-GlcNAcylation pathway. Disorders in O-GlcNAcylation are involved in diabetes, obesity and cancers, which all feature chronic low-grade inflammation (CLGI). By regulating CLGI, GlcN may be beneficial to the symptoms of OA, its outcome and to that of the concomitant chronic pathologies, making GlcN as a valuable candidate for the treatment of OA in patients with metabolic syndrome, diabetes or cardiovascular diseases.

Risk of ischaemic stroke among new users of glucosamine and chondroitin sulphate: a nested case–control study

Background:

Several studies have reported that the use of chondroitin sulphate (CS) and glucosamine may reduce the risk of acute myocardial infarction. Although it is thought that this potential benefit could be extended to ischaemic stroke (IS), the evidence is scarce.

Objective:

To test the hypothesis that the use of prescription glucosamine or CS reduces the risk of IS.

Design:

Case–control study nested in an open cohort.

Methods:

Patients aged 40–99 years registered in a Spanish primary healthcare database (BIFAP) during the 2002–2015 study period. From this cohort, we identified incident cases of IS, applying a case-finding algorithm and specific validation procedures, and randomly sampled five controls per case, individually matched with cases by exact age, gender and index date. Adjusted odds ratios (AORs) and 95% confidence interval (CI) were computed through a conditional logistic regression. Only new users of glucosamine or CS were considered.

Results:

A total of 13,952 incident cases of IS and 69,199 controls were included. Of them, 106 cases (0.76%) and 803 controls (1.16%) were current users of glucosamine or CS at index date, yielding an AOR of 0.66 (95% CI: 0.54–0.82) (for glucosamine, AOR: 0.55; 95% CI: 0.39–0.77; and for CS, AOR: 0.77; 95% CI: 0.60–0.99). The reduced risk among current users was observed in both sexes (men, AOR: 0.69; 95% CI: 0.49–0.98; women, AOR: 0.65; 95% CI: 0.50–0.85), in individuals above and below 70 years of age (AOR: 0.69; 95% CI: 0.53–0.89 and AOR: 0.59; 95% CI: 0.41–0.85, respectively), in individuals with vascular risk factors (AOR: 0.53; 95% CI: 0.39–0.74) and among current/recent users of nonsteroidal anti-inflammatory drugs (NSAIDs) (AOR: 0.71; 95% CI: 0.55–0.92). Regarding duration, the reduced risk was observed in short-term users (<365 days, AOR: 0.61; 95% CI: 0.48–0.78) while faded and became nonsignificant in long-term users (>364 days AOR: 0.86; 95% CI: 0.57–1.31).

Conclusions:

Our results support a protective effect of prescription CS and glucosamine in IS, which was observed even in patients at vascular risk.

Mini abstract

Our aim was to analyse whether the use of glucosamine or chondroitin sulphate (CS) reduces the risk of ischaemic stroke (IS). We detected a significant decrease.

Osteoarthritis Progression: Mitigation and Rehabilitation Strategies

Osteoarthritis is the most common form of arthritis and is a substantial burden for patients with the disease. Currently, there is no cure for osteoarthritis, but many emerging therapies have been developed to aid in the mitigation of disease progression. When osteoarthritis reaches the end-stage of disease many patients undergo total joint arthroplasty to improve quality of life, yet some experience persistent pain and mobility limitations for extended periods following surgery. This review highlights recent therapeutic advancements in osteoarthritis treatment consisting of pharmacologics, nutraceuticals, biologics, and exercise while emphasizing the current state of post-arthroplasty rehabilitation.

Risk of acute myocardial infarction among new users of chondroitin sulfate: A nested case-control study

Objective

To test the hypothesis that the use of chondroitin sulfate (CS) or glucosamine reduces the risk of acute myocardial infarction (AMI).

Design

Case-control study nested in a primary cohort of patients aged 40 to 99 years, using the database BIFAP during the 2002–2015 study period. From this cohort, we identified incident cases of AMI and randomly selected five controls per case, matched by exact age, gender, and index date. Adjusted odds ratios (AOR) and 95% confidence interval (CI) were computed through a conditional logistic regression. Only new users of CS or glucosamine were considered.

Results

A total of 23,585 incident cases of AMI and 117,405 controls were included. Of them, 89 cases (0.38%) and 757 controls (0.64%) were current users of CS at index date, yielding an AOR of 0.57 (95%CI: 0.46–0.72). The reduced risk among current users was observed in both short-term (<365 days, AOR = 0.58; 95%CI: 0.45–0.75) and long-term users (>364 days AOR = 0.56; 95%CI:0.36–0.87), in both sexes (men, AOR = 0.52; 95%CI:0.38–0.70; women, AOR = 0.65; 95%CI:0.46–0.91), in individuals over or under 70 years of age (AOR = 0.54; 95%CI:0.38–0.77, and AOR = 0.61; 95%CI:0.45–0.82, respectively) and in individuals at intermediate (AOR = 0.65; 95%CI:0.48–0.91) and high cardiovascular risk (AOR = 0.48; 95%CI:0.27–0.83), but not in those at low risk (AOR = 1.11; 95%CI:0.48–2.56). In contrast, the current use of glucosamine was not associated with either increased or decreased risk of AMI (AOR = 0.86; 95%CI:0.66–1.08).

Conclusions

Our results support a cardioprotective effect of CS, while glucosamine seems to be neutral. The protection was remarkable among subgroups at high cardiovascular risk.

Glucosamine promotes seizure activity via activation of the PI3K/Akt pathway in epileptic rats

CONTEXT

Glucosamine is an amino monosaccharide with a small molecular weight and has a protective effect against various neurological diseases including multiple sclerosis and encephalomyelitis. Interestingly, low-dose glucosamine has exhibited anti-epilepsy activity. Recent studies have shown that the activation of the protein kinase B (Akt) signaling pathway may promote epilepsy. Glucosamine can increase the level of Akt phosphorylation in the brain tissue, which may aggravate epilepsy. Hence, we speculate that a higher dose of glucosamine may aggravate epilepsy via AKT signaling.

OBJECTIVE

To investigate the effect of glucosamine on the behavior and electrophysiology of epileptic rats through PI3K/Akt pathway.

METHODS

Glucose (2.0 g/kg) and glucosamine (0, 0.5, 1.0, and 2.0 g/kg) were added to 2 mL of drinking water, respectively. An acute seizure rat model of lithium-pilocarpine and PTZ-kindling were constructed to observe the effects of different doses of glucosamine on epileptic behavior and hippocampal electrical activity. Meanwhile, the changes in Akt were detected by western blot.

RESULTS

Epileptic seizures were induced by a single dose of pilocarpine or PTZ and 2.0 g/kg of glucosamine significantly prolonged the duration and severity of epileptic seizures, enhanced hippocampal electrical activity energy density, and increased phosphorylated AKT levels. A glucosamine dose of 2.0 g/kg also significantly increased the total onset energy density. Furthermore, 2.0 g/kg glucosamine facilitated the development of the chronic PTZ-kindling process.

CONCLUSIONS

Glucosamine may exacerbate acute and chronic epileptic seizures via activation of the PI3K/Akt pathway in rats with experimental epilepsy.

Synovial Fibrosis Involvement in Osteoarthritis

Bone changes have always been the focus of research on osteoarthritis, but the number of studies on synovitis has increased only over the last 10 years. Our current understanding is that the mechanism of osteoarthritis involves all the tissues that make up the joints, including nerve sprouting, pannus formation, and extracellular matrix environmental changes in the synovium. These factors together determine synovial fibrosis and may be closely associated with the clinical symptoms of pain, hyperalgesia, and stiffness in osteoarthritis. In this review, we summarize the consensus of clinical work, the potential pathological mechanisms, the possible therapeutic targets, and the available therapeutic strategies for synovial fibrosis in osteoarthritis to gain insight and provide a foundation for further study.

The second phase of brain trauma can be controlled by nutraceuticals that suppress DAMP-mediated microglial activation

INTRODUCTION

A delayed second wave of brain trauma is mediated in large part by microglia that are activated to a pro-inflammatory M1 phenotype by DAMP proteins released by dying neurons. These microglia can promote apoptosis or necrosis in neighboring neurons by producing a range of pro-inflammatory cytokines and the deadly oxidant peroxynitrite. This second wave could therefore be mitigated with agents that blunt the post-traumatic M1 activation of microglia and that preferentially promote a pro-healing M2 phenotype.

AREAS COVERED

The literature on nutraceuticals that might have clinical potential in this regard.

EXPERT OPINION

The chief signaling pathway whereby DAMPs promote M1 microglial activation involves activation of toll-like receptor 4 (TLR4), NADPH oxidase, NF-kappaB, and the stress activated kinases JNK and p38. The green tea catechin EGCG can suppress TLR4 expression. Phycocyanobilin can inhibit NOX2-dependent NADPH oxidase, ferulate and melatonin can oppose pro-inflammatory signal modulation by NADPH oxidase-derived oxidants. Long-chain omega-3 fatty acids, the soy isoflavone genistein, the AMPK activator berberine, glucosamine, and ketone bodies can down-regulate NF-kappaB activation. Vitamin D activity can oppose JNK/p38 activation. A sophisticated program of nutraceutical supplementation may have important potential for mitigating the second phase of neuronal death and aiding subsequent healing.

Human osteoclasts/osteoblasts 3D dynamic co‑culture system to study the beneficial effects of glucosamine on bone microenvironment

Glucosamine (GlcN) functions as a building block of the cartilage matrix, and its multifaceted roles in promoting joint health have been extensively investigated. However, the role of GlcN in osteogenesis and bone tissue is poorly understood, mainly due to the lack of adequate experimental models. As a result, the benefit of GlcN application in bone disorders remains controversial. In order to further elucidate the pharmacological relevance and potential therapeutic/nutraceutic efficacy of GlcN, the effect of GlcN treatment was investigated in human primary osteoclasts (hOCs) and osteoblasts (hOBs) that were cultured with two‑dimensional (2D) traditional methods or co‑cultured in a 3D dynamic system more closely resembling the in vivo bone microenvironment. Under these conditions, osteoclastogenesis was supported by hOBs and sizeable self‑assembling aggregates were obtained. The differentiated hOCs were evaluated using tartrate‑resistant acid phosphatase assays and osteogenic differentiation was monitored by analyzing mineral matrix deposition via Alizarin Red staining, with expression of specific osteogenic markers determined via reverse transcription‑quantitative PCR. It was found that crystalline GlcN sulfate was effective in decreasing osteoclastic cell differentiation and function. hOCs isolated from patients with OA were more sensitive compared with those from healthy donors. Additionally, GlcN exhibited anabolic effects on hOCs both in 2D conventional cell culture and in hOC/hOB 3D dynamic co‑culture. The present study demonstrated for the first time the effectiveness of a 3D dynamic co‑culture system for characterizing the spectrum of action of GlcN on the bone microenvironment, which may pave the way for more fully determining the potential applications of a compound such as GlcN, which is positioned between pharmaceuticals and nutraceuticals. Based on the present findings, it is hypothesized that GlcN may have potential benefits in the treatment of osteopenic diseases such as osteoporosis, as well as in bone maintenance.

Glucosamine sulphate: an umbrella review of health outcomes

Background and Aims:

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.

Methods:

Medline, Cinahl and Embase databases were searched until 1 April 2020. An umbrella review of systematic reviews and meta-analyses of randomized controlled trials (RCTs) was carried out. The evidence from the RCTs was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) tool.

Results:

From 140 articles returned, 11 systematic reviews, for a total of 21 outcomes (37 RCTs; 3949 participants; almost all using 1500 mg/day), were included. No systematic reviews/meta-analyses of observational studies were included. Regarding the findings of the meta-analyses, 9/17 outcomes were statistically significant, indicating that GS is more effective than placebo. A high certainty of evidence, as assessed by GRADE, supported the use of GS (versus placebo) in improving the Lequesne Index, joint space width change, joint space width change after 3 years of follow up, joint space narrowing and OA progression. No difference in terms of adverse effects was found between GS and placebo. In systematic reviews, GS was associated with a better glucose profile and a better physical function performance than placebo.

Conclusion:

GS, when used as a prescription drug (i.e. crystalline glucosamine sulphate) at 1500 mg daily dosage, can positively affect the cartilage structure, reduce pain, improve function and glucose metabolism in people with knee OA, without having a greater incidence of adverse effects than placebo.