Osteoarthritis pain inversely correlates with histidine and glutamine following CSF and serum profiling

Background Osteoarthritis is a leading cause of pain and disability, yet the biological processes linking peripheral joint pathology with central pain mechanisms and wider symptom burden remain poorly defined. Methods We performed an integrated metabolomic and inflammatory analysis of cerebrospinal fluid and serum obtained from patients with osteoarthritis ( n = 81) and healthy pain-free controls ( n = 70). Proton nuclear magnetic resonance spectroscopy was used for metabolomic profiling, alongside targeted protein assays for inflammatory mediators. Orthogonal partial least squares discriminant analysis was applied to assess separation between groups and to determine diagnostic accuracy. Associations between metabolites and clinical outcomes, including pain intensity, disability and sleep disturbance, were examined, with adjustment for age and BMI. Results Clear separation between osteoarthritis and healthy pain-free control participants was observed in both biofluids, with classification accuracies of 87% for serum and 89% for cerebrospinal fluid. Reduced serum histidine, glutamine, albumin (lysyl) and lysine distinguished osteoarthritis from healthy controls. In cerebrospinal fluid, osteoarthritis was characterised by higher lactate and glutamate and lower glucose and glutamine compared to controls. Combining metabolomic data with inflammatory proteins increased diagnostic accuracy to 90% and remained significant after matching for age and BMI. Reductions in serum histidine and glutamine were consistent across subgroups, including stratification by pain severity. These metabolites correlated inversely with pain intensity, disability, sleep disturbance and overall symptom impact, and were more markedly altered in women, who also reported greater symptom burden. Conclusions Osteoarthritis is associated with a distinct pattern of peripheral and central metabolic disturbance. Histidine and glutamine emerge as promising biomarkers related to pain and clinical severity, highlighting metabolic pathways as potential targets for improved stratification and intervention in osteoarthritis pain.