Bilberry Seems to Act Against Blood Sugar

Researchers who did tests in mice suggest need for human trials

WEDNESDAY, Feb. 17 (HealthDay News) -- Bilberry extract helps control blood sugar levels in mice, researchers have found.

Bilberry and other brightly colored foods such as blueberries, purple grapes, cherries and cranberries contain anthocyanins, which are thought to reduce blood sugar, improve insulin sensitivity and reduce obesity in laboratory mice.

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To study these effects further, Japanese researchers used mice genetically predisposed to develop diabetes. The mice were fed either a diet containing bilberry extract (27 grams per kilogram) or their normal diet for five weeks.

The study authors found that bilberry extract lowered blood glucose and increased insulin sensitivity in the mice. It did this by activating AMP-activated protein kinase (AMPK) in white adipose (fat) tissue, skeletal muscle and the liver, the researchers explained. AMPK stimulates fat breakdown in liver and muscle, and modulates insulin secretion by the pancreas.

The effect of AMPK was accompanied by an increase in glucose transporter 4 (which helps glucose enter cells) in white adipose tissue and skeletal muscle, and suppression of glucose production and fat content in the liver. At the same time, acetyl-CoA carboxylase (an enzyme needed for fatty acid synthesis) was inactivated and there was activation of PPARa (a protein that modulates fat metabolism), acyl-CoA oxidase (an enzyme that plays a role in fatty acid metabolism), and carnitine palmitoyltransferase-1A (an enzyme needed for the breakdown of fatty acids) in the liver.

This "overlapping and coordinated adjustment of enzymes and other factors" seen in the mice that were fed the bilberry extract might also occur in humans, the researchers said. They recommended that clinical studies be conducted to test the effects of bilberry on human health, especially in people at increased risk for type 2 diabetes.

The findings are published in the March issue of the Journal of Nutrition.

More information

The U.S. National Center for Complementary and Alternative Medicine has more about the bilberry.

-- Robert Preidt