New Mechanism for Berries' Potential Brain Benefits Uncovered

From Medscape Medical News
Megan Brooks

August 31, 2010 — US scientists say they have uncovered a new mechanism by which berries may protect the aging brain.

In cultured mouse hippocampal cells, they found that extracts of blueberries, strawberries, and acai berries induce autophagy, a mechanism by which toxic debris are sequestered in the brain. Studies have shown that this "housekeeping" function in the brain declines considerably with age, which can lead to the buildup of proteins linked to age-related mental decline and memory loss.

Shibu Poulose, PhD, from the US Department of Agriculture–Agricultural Research Service Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts, presented the preliminary findings at the 240th National Meeting of the American Chemical Society in Boston.

Berries and Walnuts

Natural polyphenols in berries and other fruits, vegetables, and nuts are known to enhance brain health via their antioxidant and anti-inflammatory properties. "There are many publications using animal models both from our lab and elsewhere reporting effects of berries and walnuts on memory, motor skills, and other behavior," Dr. Poulose noted in an email to Medscape Medical News.

For example, in a prior study, Dr. Poulose and Dr. Joseph showed that aging laboratory rats maintained for 2 months on diets containing 2% high-antioxidant strawberry, blueberry, or blackberry extract showed a reversal of age-related deficits in nerve function and behavior involving learning and memory.

"We have reported berries and walnuts exert powerful antioxidant and anti-inflammatory effects on the brain cells as well as regions of the brain in rats," Dr. Poulose noted.

The new research suggests that the benefits of berries on the aging brain extend beyond the antioxidant and anti-inflammatory effects to cellular toxic clearance through induction of autophagy in the brain.

They found that a blueberry, strawberry, and acai berry extract added to cultured HT22 hippocampal neuronal cells and BV2 microglial cells inhibited mammalian target of rapamycin, a protein that negatively regulates autophagy, and increased levels of proteins that facilitate the autophagic process to clear toxic proteins.

"Our research suggests that the polyphenolics in berries have a rescuing effect," Dr. Poulose noted in a written statement from the meeting. "They seem to restore the normal housekeeping function. These findings are the first to show these effects of berries."

A New Mechanism

Reached for outside comment, Joseph A. Vinson, PhD, professor of chemistry at the University of Scranton in Pennsylvania, who was not involved in the study, noted that this is "a mechanistic study and it uncovers a new mechanism."

The study, he said, provides "a hint as to how berries can be good for you," but much more study is needed. "It's possible that this mechanism operates when you consume berries but until such a mechanism is found in vivo, I wouldn't get too excited," Dr. Vinson noted in a telephone interview with Medscape Medical News.

On the other hand, Dr. Vinson added, "I do think that berries have a biological effect." He cautioned, however, that the concentration used in the study is "incredibly high, so the question is: if the concentration were diluted a lot, would it have an effect?"

The study was funded in part by the Wild Blueberry Association of North America, US Highbush Blueberry Council, California Strawberry Commission, California Walnut Commission, and American Institute for Biosocial and Medical Research Life Sciences Inc. The study authors and Dr. Vinson have disclosed no relevant financial relationships.

240th National Meeting of the American Chemical Society. Presented August 23, 2010.