Cartilage and bone metabolism (type II collagen degradation) is increased by endurance exercise with intense joint loading. Interestingly, glucosamine-containing diet exhibits a chondroprotective action on osteoarthritis by inhibiting type II collagen degradation and improves the symptoms. Thus, in the present study, we evaluated the effect of glucosamine on cartilage metabolism in collegiate soccer players and professional rugby players with intense joint loading.
In soccer and rugby players, the urine level of type II collagen degradation maker CTX-II was significantly increased compared with non-athlete control, indicating that cartilage metabolism (type II collagen degradation) is increased in these athletes. In contrast, the urine level of type II collagen synthesis maker CPII was almost the same as in non-athletes. Based on these findings, the CTX-II/CPII ratios were higher in soccer and rugby players than non-athletes, suggesting that type II collagen degradation is relatively increased compared with type II collagen synthesis in these athletes. Importantly, the administration of glucosamine significantly decreased the CTX-II levels in soccer and rugby players; however, the CTX-II level returned to almost the pre-administration level after withdrawal of glucosamine administration. In contrast, the CPII level was not essentially changed during the test period. Based on these findings, the CTX-II/CPII ratios were reduced by glucosamine administration, and returned to the pre-administration level after withdrawal of glucosamine.
Together these observations suggest that glucosamine exhibits a chondroprotective action on endurance athletes, such as soccer and rugby players by preventing type II collagen degradation but maintaining type II collagen synthesis. However, the effect is transient and disappears after withdrawal of the administration.