Resveratrol has already been shown to offer heart benefits
TUESDAY, Oct. 2 (HealthDay News) -- Chinese researchers have outlined the molecular chain of activity that makes resveratrol, a chemical found in the skin of red grapes and in red wine, a promising candidate for treatment of diabetes and other conditions.
The study focused on how resveratrol improved the sensitivity of mice to insulin, an effect that could lead to new treatments for type 2 diabetes, in which human cells lose their sensitivity to insulin.
And U.S. experts said the chemical's effect on a number of different tissues could eventually lead to such dreamed-of medications as an effective diet pill.
The study, by researchers at the Chinese Academy of Sciences in Shanghai, showed that resveratrol activates an enzyme called SIRT1. This enzyme, in turn, suppresses the activity of a molecule called PTP1B, which ordinarily works to decrease insulin activity. SIRT1 levels were reduced in the animals' insulin-resistant cells. Increasing SIRT1 activity with resveratrol improved insulin sensitivity by acting on PTP1B.
The study is published in the October issue of Cell Metabolism.
"When you suppress PTP1B, insulin activity improves," said Young-Bum Kim, an assistant professor of medicine at Beth Israel Deaconess Medical Center in Boston, one author of an accompanying editorial in the journal.
"SIRT1 has a variety of functions in the body," Kim said. "Now we can move on to other tissues, such as the brain. It is possible that regulating the hypothalamus with SIRT1 can prevent diet-induced obesity."
That is clearly a long-term goal, said Janice M. Zabolotny, an instructor in medicine at Beth Israel Deaconess, and the other author of the editorial.
"But it can make animals want less food and lower body weight," she said. "By activating SIRT1, you could block the expression of PTP1B and get the same hopeful benefit."
But clearly, "further studies are needed by other researchers and on different tissues in animals," Zabolotny said.
One striking finding was that much lower levels of resveratrol than in previous trials were able to increase the animals' sensitivity to insulin.
"This paper is different from previous reports in that lower doses were effective," Zabolotny said. "The reason for the difference is unclear."
A statement by Qiwei Zhai, lead author of the report, recommended caution to resveratrol enthusiasts, noting that those who have been drinking red wine might "think about drinking less."
Previous studies had indicated that a human would have to drink about 120 liters of red wine in a day to get the benefit seen in animals. The new results reduce that amount to a still-substantial three liters.
"An even better option may be to find other natural foods enriched with resveratrol or foods supplemented with resveratrol," Zhai said.
To learn more about resveratrol, visit Oregon State University.
SOURCES: Young-Bum Kim, Ph.D., assistant professor of medicine, and Janice M. Zabolotny, Ph.D., instructor in medicine, Beth Israel Deaconess Medical Center, Boston; October 2007, Cell Metabolism
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