In the present study, the effect of glucosamine administration (1.5 or 3 g/day) on cartilage and bone metabolism was investigated in bicycle racers, using cartilage‑ and bone‑specific biomarkers, including C‑terminal cross‑linked telopeptides of type II collagen (CTX‑II), C‑terminal propeptides of type II procollagen (CPII), N‑terminal telopeptides of bone‑specific type I collagen (NTx) and bone alkaline phosphatase (BAP). The results indicate that CPII (a marker of type II collagen synthesis) was not substantially changed, however, CTX‑II (a marker of type II degradation) was reduced by glucosamine administration, particularly at a dose of 3 g/day. Consistent with these observations, the ratio of CTX‑II/CPII was reduced by glucosamine administration and the effect of glucosamine was dose‑dependent. By contrast, the levels of NTx (a bone resorption marker) and BAP (a bone formation marker) were not altered by glucosamine administration. A previous study by this group reported that glucosamine exerts a chondroprotective action in soccer players by preventing type II collagen degradation but maintaining type II collagen synthesis. Together these observations indicate that glucosamine may exert a chondroprotective action by preventing type II collagen degradation in athletes of various sports, including soccer players and bicycle racers.

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