By Emily Dickson, MS
As a quick refresher, cartilage has two main components: 1) Chondrocytes, i.e. the master builder and regulator cells, and 2) the extracellular matrix, which contains collagen and proteoglycans.
Proteoglycans are made up of a core protein and a glycosaminoglycan side chain. I know these are weird words, but I’m sure you have heard of chondroitin sulfate (CS); you may even have some form of CS in your home or barn already. CS is the primary glycosaminoglycan in cartilage.
The really cool thing about proteoglycans is that they act as shock absorbers and compressive strength for the joint. No wonder we all seem to be crazy about supplementing with chondroitin--It makes sense we would want to provide as much cushion to our horses’ joints as possible.
For reference, glucosamine, another common joint supplement ingredient, also occurs naturally in the body, and acts as a building block for proteoglycans and hyaluronic acid. Both are important, but CS is actually a glycosaminoglycan (building block) in cartilage, while glucosamine which is basically food for the joint.
Hopefully you are starting to see how this is all related.
The reason the cartilage proteoglycan network is a big deal is because it is constantly regenerating, unlike collagen which has very limited abilities. And we know for sure that a healthy level of exercise actually stimulates proteoglycan synthesis. The adage “a body in motion stays in motion” may not be too far off after all.
Within the joint, a substance called CS-846 (chondroitin-sulfate 846) has been measured in experiments to characterize what happens to the proteoglycan network during exercise and different stages of life.
Research has found that CS-846 is highest in fetal and newborn cartilage and gradually declines with age, indicating that proteoglycan synthesis is greatest in early development. CS-846 levels have also been shown to be elevated after joint injury or trauma, which also makes sense. Synthesis here indicates the joint’s effort to repair itself.