Naringenin is a flavonoid found in grapefruit. Most readers of ergo-log will recognise naringenin as the substance that sabotages glucose uptake in fat cells. [Biochem Biophys Res Commun. 2003 May 30;305(2):229-34.] That same naringenin actually stimulates the uptake of glucose in muscle cells, write health scientists from Brock University, Canada, in Biochemical and Biophysical Research Communications. [We read every number. Religiously. We are fans.]
The diagram shows the structure of naringenin, which is remarkably similar to that of quercetin. Remove 2 hydroxyl groups from quercetin and you've got naringenin. Because naringenin's structure resembles that of resveratrol, and because the researchers had previously discovered that resveratrol induces muscle cells to absorb more glucose [Biochem Biophys Res Commun. 2008 Sep 12; 374(1): 117-22.] the Canadians wanted to know whether naringenin does the same. The researchers are looking for ways of lessening the damaging effects of diabetes-2 through diet.
The Canadians exposed young and fully-grown muscles cells of rats to naringenin in test tubes. Young muscle cells did not react, adult ones did. This indicates that naringenin enhances the activity of GLUT4, a glucose transporter. Fully-grown muscle cells synthesise it; young muscles cells don't.
The figure below shows that as the naringenin concentration rises, the muscle cells take up more glucose. The figure underneath shows that the glucose uptake rises, the longer the exposure to 75 micromols naringenin.