Evaluation of the effect of N-acetyl-glucosamine administration on biomarkers for cartilage metabolism in healthy individuals: a randomized double-blind placebo-controlled clinical study

Background: A randomized double-blind placebo-controlled clinical study was conducted to evaluate the chondroprotective action of N-acetyl-glucosamine (GlcNAc) supplement on healthy individuals without arthritis.Methods: Healthy subjects (n=120, 54.3 ± 8.1 years (mean ± SD)) without arthritis were randomly assigned to receive 500 mg GlcNAc (n=60, GlcNAc group) or a placebo (n=60, placebo group) once a day for 16 weeks, and cartilage metabolism was evaluated by analyzing type II collagen degradation (C2C) and type II collagen synthesis (PIICP) markers, and the ratio of type II collagen degradation to type II collagen synthesis (C2C/PIICP).Results: Among 120 eligible subjects, 114 subjects completed the study. First, all the subjects with a body mass index of ≥25 kg/m2 and Kellgren and Lawrence grade of ≥1 were analyzed. However, the changes in the C2C and PIICP levels and the C2C/PIICP ratios from the baseline were not significantly different between the placebo and GlcNAc groups during 16 weeks and 8 weeks after the intervention. Next, to make the effect of GlcNAc even clearer, the subjects with body mass index of <25 kg/m2 and Kellgren and Lawrence grade of 0 were analyzed. The changes in the C2C levels from the baseline were significantly decreased in the GlcNAc group compared with the placebo group at 8 and 12 weeks during the intervention. In contrast, the changes in the PIICP levels from the baseline levels were almost constant during and after the intervention in both groups. Based on these findings, the changes in the C2C/CIICP ratios from the baseline slightly decreased in the GlcNAc group compared to the placebo group at 8 and 12 weeks during the intervention. Furthermore, no test supplement-related adverse events were observed during and after the intervention.Conclusions: These observations suggest that oral administration of GlcNAc at a dose of 500 mg/day exerts a chondroprotective effect in subjects without arthritis. This effect was achieved by improving cartilage metabolism (reducing type II collagen degradation), without causing apparent adverse effects.