The way that glucosamine works is a very complicated process. In a nutshell, cartilage consists of several different cells, one of which is chondrocytes. Chondrocytes are responsible for synthesizing new cartilage. Through normal wear, cartilage is constantly being broken down and replaced. When a dog has hip dysplasia or ages, the chondrocytes do not have the building blocks available to them to build enough new cartilage to keep up with the breakdown of the old cartilage. Glucosamine provides the building blocks to synthesize new cartilage. Glucosamine is the building block necessary for the production of the substances called glycosaminoglycans. The glycosaminoglycans are combined with hyaluronic acid to make the substance proteoglycans. The proteoglycans and collagen are the main structures of cartilage.
Chondroitin also is one of the products necessary for the synthesis of glycosaminoglycans. But it probably plays a more important role by combating and neutralizing destructive enzymes in the joint. There is always a low level of destructive enzymes found in the joint, but when injury or abnormal wear occurs, the destructive enzymes and agents increase accelerating cartilage destruction. When chondroitin is added to the diet it helps to reduce the level of these destructive enzymes.
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