Grape Seed Extract inhibits aromatase

Supplements containing Grape Seed Extract (GSE) may well lower estradiol levels. This would make GSE an interesting supplement for athletes who want to lose weight faster or just tone up their body a bit more. Cancer researchers at the Beckman Research Institute in California demonstrated the anti-estrogenic effect of GSE in tests they did on cells.

GSE, an extract from grape seeds, consists of 75 percent proanthocyanidins. Of these, it seems likely that the procyanidin B dimers are the active ones. These are also found in red wine, and the researchers had already shown that these compounds inhibit aromatase, the enzyme that converts testosterone and androstenedione into estradiol.

This is of interest to cancer researchers because it’s estradiol that’s responsible fro the growth of many forms of breast cancer. Tumours often make their own aromatase. So it would be even better if there were naturally occurring substances that not only deactivate aromatase, but also prevent cells from making aromatase in the first place. Which of course leads to the 64 million dollar question: is GSE capable of doing this?

To answer this question, the researchers first looked at whether GSE indeed inhibits aromatase. They put increasing concentrations of the extract in test tubes with aromatase producing cells, and then measured how much estradiol was produced. The figure below shows that the more GSE there was in a test tube, the less estradiol was produced.


But how exactly does GSE work? The researchers do know which pieces of the aromatase gene [or more precisely, the exones] the cells have to read to make aromatase. Genes on the DNA are like building models. And RNA copies the components that the cells need to make a protein. The RNA then introduces the copies into the cells, where molecular ‘factories’ produce the components and put them together.

The researchers added GSE to cells and then looked at whether the cells could still read all bits of the DNA. They noticed that the extract made the cell miss bits.

When the researchers looked at why that happened, they saw that GSE sabotages two transcription factors that the cell needs to read the gene for aromatase.

If you compare DNA with an old-fashioned LP [long playing record for those of you under 40] and the rest of the cell with an equally old-fashioned record player, then a transcription factor is the needle that you place on the record to transcribe it. The metaphor doesn’t quite work, because a cell has lots of transcription factors and a record player only one, but you get the idea.

One of the transcription factors that is inhibited by GSE is an interesting one for power athletes: the glucocorticoid receptor. This is the protein that the muscle-destroying hormone cortisol attaches itself to. The figure below shows the effect of GSE on the number of glucocorticoid receptors.


Lots of phenols have a cortisol inhibiting effect. Quercetin is one of these. Natural athletes who’ve experimented with mega-doses of quercetin (500 to 1500 mg per day) notice that they lose some abdominal fat, according to Ergo-Log sources.

Of course, we’re talking here about research done with substances in test tubes. We don’t know whether humans actually make less estradiol if they take GSE. Researchers often ignore the role of digestion and metabolism. They forget that the body sometimes hardly takes up a substance at all, and the minute amounts absorbed are converted in no time at all an inactive compounds. In the case of GSE, however, the scenario might not be too bad. The body does actually absorb most substances in GSE pretty well.

Other supplements that have an anti-estrogenic effect include kelp, Ginkgo biloba, Damiana, vitamin K, fish oil, green tea and GLA.

Grape Seed Extract Is an Aromatase Inhibitor and a Suppressor of Aromatase Expression


Aromatase is the enzyme that converts androgen to estrogen. It is expressed at higher levels in breast cancer tissues than normal breast tissues. Grape seed extract (GSE) contains high levels of procyanidin dimers that have been shown in our laboratory to be potent inhibitors of aromatase. In this study, GSE was found to inhibit aromatase activity in a dose-dependent manner and reduce androgen-dependent tumor growth in an aromatase-transfected MCF-7 (MCF-7aro) breast cancer xenograft model, agreeing with our previous findings.

We have also examined the effect of GSE on aromatase expression. Reverse transcription-PCR experiments showed that treatment with 60 ?g/mL of GSE suppressed the levels of exon I.3–, exon PII–, and exon I.6–containing aromatase mRNAs in MCF-7 and SK-BR-3 cells. The levels of exon I.1–containing mRNA, however, did not change with GSE treatment. Transient transfection experiments with luciferase-aromatase promoter I.3/II or I.4 reporter vectors showed the suppression of the promoter activity in a dose-dependent manner. The GSE treatment also led to the down-regulation of two transcription factors, cyclic AMP-responsive element binding protein-1 (CREB-1) and glucocorticoid receptor (GR). CREB-1 and GR are known to up-regulate aromatase gene expression through promoters I.3/II and I.4, respectively. We believe that these results are exciting in that they show GSE to be potentially useful in the prevention/treatment of hormone-dependent breast cancer through the inhibition of aromatase activity as well as its expression. (Cancer Res 2006; 66(11): 5960-7)

Source: http://cancerres.aacrjournals.org/content/66/11/5960.abstract

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