Tampa, FL (Sept. 21, 2005) -- Researchers at the University of South(USF) have found that green tea may offer another potential healthbenefit -- protecting the brain against the ravages of Alzheimer'sdisease.
In an article published Sept. 21 in the Journal of Neuroscience, USFresearchers report that a component of green tea preventedAlzheimer's-like damage in the brains of mice genetically programmed todevelop the neurodegenerative disease process. The component, calledepigallocatechin-3-gallate (EGCG), is a major antioxidant in green teaand has been widely studied for its reported protection against certaincancers.
Now the USF team provides the first evidence that EGCGdecreases production of the Alzheimer's-related protein, beta-amyloid,which can accumulate abnormally in the brain and lead to nerve damageand memory loss. This reduction in beta-amyloid was observed both incell cultures and a mouse model for Alzheimer's disease. EGCG appearsto block the initial process by which the Alzheimer's-related proteinis formed in brain cells.
After treating Alzheimer's mice for several months with dailyinjections of pure EGCG, the researchers observed a dramatic decrease-- as much as 54 percent -- of brain-clogging Alzheimer's plaques.
"The findings suggest that a concentrated component of greentea can decrease brain beta-amyloid plaque formation," said seniorstudy author Jun Tan, PhD, MD, director of the NeuroimmunologyLaboratory at the Silver Child Development Center, USF Department ofPsychiatry. "If beta-amyloid pathology in this Alzheimer's mouse modelis representative of Alzheimer's disease pathology in humans, EGCGdietary supplementation may be effective in preventing and treating thedisease."
Green tea contains many antioxidants, including those known asflavonoids that can protect against free radical damage to the brain.However, Dr. Tan and colleagues demonstrated that other flavinoids ingreen tea actually oppose naturally-occurring EGCG's ability to preventthe harmful build-up of beta-amyloid. Thus, Dr. Tan said, drinkinggreen tea alone would not likely have a beneficial effect through thesame mechanism that EGCG works.
"This finding suggests that green tea extract selectivelyconcentrating EGCG would be needed to override the counteractive effectof other flavinoids found in green tea," said study co-author DougShytle, PhD. "A new generation of dietary supplements containing pureEGCG may lead to the greatest benefit for treating Alzheimer'sdisease." Dr. Tan said humans would likely need 1500 to 1600 mg of EGCGdaily to approximate the injection dosage that benefited theAlzheimer's mice. That dosage has already been studied in healthy humanvolunteers and was found to be safe and well tolerated.
The USF researchers plan to study whether multiple oral dosesof EGCG can improve memory loss in Alzheimer's mice as well as reducingtheir Alzheimer's plaque burden. "If those studies show clear cognitivebenefits," Dr. Tan said, "we believe clinical trials of EGCG to treatAlzheimer's disease would be warranted."
Kavon Rezai-Zedah, a PhD candidate in the USF Department ofMedical Microbiology and Immunology was first author of the study.Other authors were Nan Sun, MS; Takashi Mori, PhD, Huayan Hou, MD;Deborah Jeanniton, BS; Jared Ehrhart; PhD candidate; Kirk Townsend,PhD; Jin Zeng, MS; David Morgan, PhD; John Hardy, PhD; and TerrenceTown, PhD.
The study was supported by the Johnnie B. Byrd Sr. Alzheimer'sCenter & Research Institute, USF College of Medicine facultystart-up funds, the National Institute of Neurological Disorders andStroke and the Alzheimer's Association.
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