N-Acetylglucosamine ameliorates knee osteoarthritis by enhancing UDP-GlcNAc conversion and chondrocyte DNA repair capacity

Abstract

Background: Knee osteoarthritis (KOA) is a degenerative joint disease characterized by progressive cartilage degradation and synovial inflammation, while current therapies offer only symptomatic relief. This study aimed to determine whether N-acetylglucosamine (GlcNAc) is superior to glucosamine hydrochloride (GlcN{middle dot}HCl) in slowing the progression of KOA and to elucidate the underlying mechanisms involved. Methods: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to assess serum concentrations of UDP-GlcNAc to conduct a comprehensive evaluation of the pharmacokinetics and pharmacodynamics associated with both GlcNAc and GlcN{middle dot}HCl. Using a destabilization of the medial meniscus (DMM) rat model, we performed micro-computed tomography and histopathological assessments to evaluate structural changes in the joint tissues. Additionally, we conducted bulk RNA sequencing, flow cytometry and ELISA to validate the efficacy of GlcNAc in anti-inflammatory immunoregulation and DNA repair in knee cartilage. Results: GlcNAc achieved higher peak serum concentrations and more efficient conversion to UDP-GlcNAc than GlcN{middle dot}HCl, with UDP-GlcNAc levels 4.57 times higher at 9 hours after administration. GlcNAc significantly attenuated KOA-like pathological changes, downregulated catabolic markers Mmp3 and Adamts4, decreased pain-related neural markers Pgp9.5 and Ngf, and alleviated pain sensitivity. RNA-seq identified 4,395 downregulated DEGs in DMM rats, of which GlcNAc upregulated 2,808 compared to only 391 by GlcN{middle dot}HCl. GlcNAc promoted DNA repair and adaptive immune cell differentiation pathways, and decreased serum IL-1{beta}, IL-6, and IL-17. Four candidate DNA repair genes, Hist1h2an, Poli, Ube2t, and Hells, were identified as significantly upregulated by GlcNAc, with GSEA confirming homologous recombination repair pathway enrichment. Conclusion: This study shows GlcNAc outperforms GlcN{middle dot}HCl in rat DMM knee osteoarthritis via multiple mechanisms, including 4.57-fold higher UDP-GlcNAc conversion, reduced cartilage degeneration, immune rebalancing, and DNA repair activation, supporting GlcNAc as a promising KOA candidate warranting further clinical study.