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

Osteoarthritis (OA) is a disease with a very long course and varied clinical expression in the initial stages, when it is really challenging to adequately measure disease outcomes both in clinical trials and in daily life.1 It is also very difficult to accurately study the efficacy of symptomatic slow-acting drugs for OA and that of non-pharmacological treatments.2 Although the efficacy of glucosamine (GlcN) in the treatment of OA is still a controversial issue3 4, recent high-quality epidemiological studies confirm previous data showing that prolonged GlcN intake, regardless of its effect on OA progression, could decrease cardiovascular disease (CVD) events, and the incidence of CVD-associated diseases.5–8 These data should be analysed keeping in mind that CVD is the main cause of death in patients with OA.9 Different authors suggest that this protective effect may be associated with the anti-inflammatory properties of GlcN,5 although the molecular basis has been only partially defined. The imbalance between the mechanical loading and its absorption by the articular cartilage is the origin of joint tissue alteration in OA. While a severe overload can deteriorate any kind of cartilage, a certain load that is physiologically well tolerated by a robust cartilage could be the origin of pathological alterations for a weakened one.9 Cartilage damage begins when the load prevails over the resistance, which in the midterm activates innate immune response in the different joint tissues, and is, at least partially, responsible for joint deterioration. Unbalanced mechanical forces and damage-associated molecular patterns turn on the innate immune system through the activation of the Toll-like receptors. Once this response is activated, a secondary wave of inflammatory mediators is released, with a robust increase in the concentration of cytokines and metalloproteases, the final effectors of cartilage destruction.9 Certainly, these mediators can …