Green tea catechins protect cattle and human cartilage from arthritis. (Photo by Vincent Boiteau)
Joint diseases such as arthritis are huge problems in the developed world. In the US, they account for more disabilities than cancer or heart disease.
We know that arthritis is associated with varying degrees of inflammation of the joints. Inflammation is accompanied by a loss of the connective tissue of the joint, especially the layer of cartilage covering the ends of bone. When enough damage has accumulated, the joint becomes dysfunctional and needs replacing surgically.
Treating the inflammation will only fix a part of the problem, however. Some studies have reported that the destruction of connective tissue may continue even when inflammation is suppressed, which suggests that ongoing loss of cartilage and inflammation are two separate processes. None of the traditional treatments for arthritis preserve cartilage from being destroyed and may in fact even increase the rate of loss.
Fortunately, green tea may be of help here. Adcocks et al. studied the effects of green tea catechins on the integrity of joint structure and function. Based on the results it seems that in addition to reducing inflammation associated with arthritis, green tea contains catechins that may protect from cartilage breakdown as well.
The authors studied the effects of green tea on cartilage breakdown in vitro by treating cartilage from both humans and cattle with cytokines or all-trans-retinoic acid (Ret), which are known to cause breakdown of cartilage proteoglycan. The cytokines used were recombinant human interleukin-1-alpha & beta (IL-1a & IL-1b) and recombinant human tumor necrosis factor-alpha (TNF). They then treated the cartilages with different catechins from green tea to see whether this breakdown was prevented.
Green tea catechins and breakdown of bovine cartilage
Epigallocatechin gallate (EGCG), the main catechin found in green tea, effectively prevented the TNF-stimulated breakdown of nasal cartilage from cattle. The effect was dose-dependent: with every ten-fold increase in EGCG concentration, the percentage of inhibition doubled. EGCG did not prevent cartilage breakdown caused by Ret or IL-1a, however.
In contrast, two other green tea catechins, epicatechin gallate (ECG) and epicatechin (EC), inhibited breakdown caused by IL-1a but not Ret or TNF. Epigallocatechin (EGC) was ineffective in preventing nasal cartilage breakdown. EGCG, ECG or EGC all decreased loss of type II collagen resulting from IL-1a by 50% or more.
In bovine articular cartilage, EGCG and ECG prevented cartilage breakdown from IL-1a, Ret and TNF. EC and EGC, on the other hand, had no effect.
Green tea catechins, osteoarthritis and rheumatic arthritis
The authors also tested the effect of green tea catechins on cartilage from humans suffering from osteoarthritis (OA) or rheumatic arthritis (RA). Osteoarthritis, also referred to as degenerative joint disease or wear-and-tear arthritis, is caused by a deterioration of cartilage and overgrowth of bone usually due to injury or aging. Rheumatic arthritis, on the other hand, is a chronic inflammation of the connective tissues of joints, which eventually leads to loss cartilage. The cause of RA is less clear.
The catechins of green tea were effective against both types of arthritis. ECG and EGCG inhibited the proteoglycan breakdown of human cartilage treated with IL-1b or TNF. The same effect was seen regardless of whether the cartilage was from OA or RA sufferers. The catechins also inhibited the breakdown of treated cartilage from humans not suffering from arthritis.
Comparing the results in human and bovine cartilages, it seems that EGCG and ECG are the most effective catechins in terms of arthritis. EGCG prevented cartilage loss from TNF in all cases, while ECG was effective against IL-1.
Arthritis is associated with inflammation and deterioration of cartilage, which seem to be two separate processes. Since reducing inflammation may not prevent the loss of cartilage in patients suffering from arthritis, finding ways to inhibit cartilage breakdown is important.
In addition to being anti-inflammatory, green tea catechins protect cartilage from breakdown caused by proinflammatory cytokines in vitro. Catechins were also effective in reducing the loss of type II collagen. Whether drinking green tea provides sufficient levels of catechins to treat arthritis in humans remains to be seen.
For more information on green tea, see these posts:
Green Tea Enhances Abdominal Fat Loss from Exercise
Peak Increase in Antioxidants Occurs 20-40 Minutes After Drinking Green Tea
Green Tea Reverses the Effect of DHT in Prostate Cancer Cells
Caffeine and Polyphenol Contents of Green Tea, Black Tea, Oolong Tea & Pu-Erh Tea