Green Tea Helps Protect Against Alzheimer's Disease

A compound found in green tea may help protect the brain from Alzheimer’s disease (AD) according to findings of researchers at the University of South Florida (USF) in Tampa published in the September 21 2005 issue of the Journal of Neuroscience.

Jun Tan, MD, PhD and colleagues gave daily injections of epigallocatechin-3-gallate (EGCG), an antioxidant component of green tea, to mice bred to develop neurodegenerative disease. After two months, the team observed a decrease in beta-amyloid containing plaques of up to 54 percent. Experimentation with mouse neuronal cell cultures produced similar findings.

Dr Tan, who is the director of the Neuroimmunology Laboratory at the Silver Child Development Center, at USF's Department of Psychiatry, stated, "The findings suggest that a concentrated component of green tea can decrease brain beta-amyloid plaque formation. If beta-amyloid pathology in this Alzheimer's mouse model is representative of Alzheimer's disease pathology in humans, EGCG dietary supplementation may be effective in preventing and treating the disease."

Although other flavonoids in green tea help protect against free radical damage, in this study they were actually found to oppose the action of EGCG in preventing amyloid build-up. Report coauthor Doug Shytle explained, "This finding suggests that green tea extract selectively concentrating EGCG would be needed to override the counteractive effect of other flavonoids found in green tea. A new generation of dietary supplements containing pure EGCG may lead to the greatest benefit for treating Alzheimer's disease."

Dr Tan added that humans would need 1500 to 1600 milligrams EGCG to mimic the dose found to benefit the mice in the current study. This dosage has already been found to be safe in human studies. The authors conclude, "These data raise the possibility that EGCG dietary supplementation may provide effective prophylaxis for Alzheimer's Disease."

For Medical Professionals

If only it were so easy; it tastes good and it's good for you. This week, Rezai-Zadeh et al. report that a component of green tea modulated amyloid precursor protein (APP) processing in a mouse model of Alzheimer's disease in vitro and in vivo.

Epigallocatechin-3-gallate (EGCG), the main polyphenolic component of green tea, reduced -amyloid (A) production in neurons cultured from APP-overexpressing mice (Tg APP_SW). Notably, EGCG was more effective than whole green tea extract. -secretase and -secretase process APP by parallel amyloidogenic and nonamyloidogenic pathways, respectively. EGCG boosted activity of the latter pathway, indicated by increased -C-terminal fragment and soluble APP-. Tumor necrosis factor (TNF)- converting enzyme (TACE), a candidate -secretase, increased after EGCG treatment, and -secretase activity was reduced by TNF- protease inhibitor-1 (TAPI-1), a selective TACE inhibitor. Treatment of Tg APP_SW mice at 12 months of age with EGCG (provided as intraperitoneal injections, not by teacup) also promoted -secretase activity.

After 2 months of treatment, A-containing plaques were significantly reduced.

Source:

Green Tea Epigallocatechin-3-Gallate (EGCG) Modulates Amyloid Precursor Protein...
Rezai-Zadeh et al. J. Neurosci..2005; 25: 8807-8814.

Key concepts: green tea, Alzheimer's disease