MCG researcher studies green tea's protective role in autoimmune disease

Main Category: Nutrition / Diet
Article Date: 14 Jun 2005 - 9:00 PDT

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Green tea seems to help protect the body from autoimmune disorders, according to a Medical College of Georgia oral biologist. Dr. Stephen Hsu, a researcher in the MCG School of Dentistry, has amassed a large bank of research helping document green tea's health benefits in everything from oral cancer to wrinkles. The benefits spring from compounds in green tea called polyphenols, which help eliminate DNA-damaging free radicals. As an added benefit, a green tea-induced protein called p57 protects healthy cells as polyphenols target cancer cells for destruction.

Dr. Hsu's most recent findings, which he will present June 17-20 in Atlanta at the Arthritis Foundation's fifth biennial Arthritis Research Conference, target autoimmune diseases. These diseases, such as type 1 diabetes, rheumatoid arthritis, lupus and Sjogren's disease, inexplicably prime the body's immune system to attack its own tissues, with often disabling and even life-threatening consequences. Adverse effects often accompany autoimmune disease treatment, which mainly focuses on the immune system.

One autoimmune disorder-the immune system's destruction of glandular cells-causes dry mouth, or xerostamia. Dry mouth occurs in about 30 percent of elderly Americans, but only in 1 percent to 2 percent of Chinese seniors. It is one of many health disparities that Dr. Hsu suspected was linked to Asians' frequent consumption of green tea.

Dr. Hsu is probing green tea's role in producing autoantigens. Autoantigens are normal molecules in the body with useful functions, but changes in their amount or location can trigger an immune response. "I wanted to know how green tea polyphenols affect the production of autoantigens," Dr. Hsu said.

He suspected a link because a polyphenol called EGCG is known to suppress inflammation, which results when the immune system mounts a defense to a real or perceived enemy. "If EGCG suppresses inflammation, it should affect the magnitude of the autoimmune response, possibly by suppressing autoantigens," Dr. Hsu said.

To test the theory, Dr. Hsu studied cells in salivary glands and skin tissue. Cells exposed to green tea showed RNA and protein levels indicating autoantigen levels were suppressed in these normal cells, but not in tumor cells. "We were so shocked," Dr. Hsu said of the finding that further highlighted green tea's role in attacking tumor cells while protecting healthy cells.

And because of the low levels of autoantigens in healthy cells, "the immune system now has considerably fewer targets to potentially attack," greatly reducing the risk of autoimmune disease, Dr. Hsu said.

Dr. Hsu, who has applied for two $1 million U.S. Department of Defense grants and a $1.25 million National Institutes of Health grant to further his research, has extended his studies to animal models. He is studying two sets of mice, both programmed to develop autoimmune disease. He is observing one set as the disease follows its natural course. "This model should develop diabetes, dry mouth and dry eyes within 12 to 30 weeks, then die quickly," Dr. Hsu said.

The other set began drinking green tea at age 3 weeks, immediately after weaning. He is anxious to determine whether green tea delays the onset of autoimmune disease or otherwise affects its course. Dr. Hsu, who has helped incorporate green tea polyphenols into everyday products such as gum and skin cream, hopes his latest research will ultimately yield a wealth of findings that can help scientists better understand and treat autoimmune disease.

The Medical College of Georgia is the state's health sciences university and includes the Schools of Allied Health Sciences, Dentistry, Graduate Studies, Medicine and Nursing. MCG is a unit of the University System of Georgia and an equal opportunity institution. http://www.mcg.edu

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