Grapefruit’s sour taste holds a sweet promise for diabetics

New joint research by scientists at the Hebrew University of Jerusalem and Harvard University’s Massachusetts General Hospital (MGH) has demonstrated the mechanism by which a single compound in grapefruit controls fat and glucose metabolism, replacing multiple drugs. Naringenin, an antioxidant derived from the sour flavor of grapefruits and other citrus fruits, may cause the liver to break down fat while increasing sensitivity to insulin – a process that naturally occurs during long periods of fasting.

The US-Israeli team reports that naringenin activates a family of small proteins called nuclear receptors, causing the liver to break down fatty acids. In fact, the compound seems to mimic the actions of other drugs, such as the lipid-lowering fenofibrate and the anti-diabetic rosiglitazone, offering the advantages of both. If the results of this study extend to human patients, this dietary supplement could become a staple in the treatment of hyperlipidemia, type-2 diabetes and perhaps metabolic syndrome, the precursor of diabetes. The report appeared two weeks ago in the online journal PLoS (Public Library of Science) One.

“It’s a fascinating find,” says senior author Dr. Yaakov Nahmias of HU. “We show the mechanism by which naringenin increases two important pharmaceutical targets, PPAR alpha and PPAy, while blocking a third, LXR alpha. The results are similar to those induced by long periods of fasting.” The liver is the main organ responsible for the regulation of carbohydrate and lipid levels. Following a meal, the blood is flushed with sugars, which activate LXR alpha, causing the liver to create fatty acids for long-term storage. During fasting, the process is reversed; fatty acids are released by fat cells, activate PPAR alpha in the liver, and are broken down to ketones. A similar process, involving PPARy, increases sensitivity to insulin.

“It is a process which is similar to the Atkins diet, without many of the side effects,” says Dr. Martin Yarmush, director of the MGH Center for Engineering in Medicine and one of the paper’s authors.
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