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Exploring the Genetics of Antioxidants

By Joanna Cosgrove | September 1, 2009

Study of turmeric's artery protecting abilities examined on the genetic level.

Recent research has revealed that turmeric is more than just a popular spice in curried Indian cuisine. Researchers from the Centre de Clermont-Ferrand/Thiex in Saint Genes Champanelle, France, set out to uncover the compound(s) responsible for turmeric's ability to protect arteries from fatty buildup. Thanks to cutting edge genetic technology, the team discovered not only the compound, but also the mechanism behind the compound's protective actions.

Curcumin is a polyphenol and the principal compound of turmeric, a member of the ginger family. The powdered stem of this plant is used as a condiment and a yellow dye. Polyphenols are naturally occurring antioxidants found in plant foods that can help protect against plaque buildup in arteries.

The research team, led by Dragan Milenkovic, PhD, a research scientist at the Centre, explained to attendees of the American Heart Association's Basic Cardiovascular Sciences Conference 2009, held in Lake Las Vegas this summer, that curcumin may limit oxidative stress and inflammation.

The study took a two-pronged approach. A preliminary laboratory model administered a daily curcumin supplement to mice for 16 weeks. The mice were found to have a 26% lower level of fat deposits in the aortic root compared to a control group. This reduction was not related to the effect on blood fats or antioxidant capacity.

When the laboratory model concluded, researchers then isolated RNA (ribonucleic acid) samples from the aorta to identify curcumin-induced changes in gene expression. In this phase of the study, researchers found altered expression of 2252 genes involved in cellular signaling and adhesion, immune function and inflammation, as well as metabolic processes like fat metabolism and oxidative changes.

Though Dr. Milenkovic was unavailable for comment, he told HealthDay News that his team employed a "microarray approach."

"We have slides with samples of all the genes and we compared the expression of each gene to see which of them had their activity modified by exposure to curcumin," he said.

The researcher reported that many of the differentially expressed genes have important cardiovascular functions and pathologies. Dietary curcumin weakens the deposits of fats in the aortic root in mice, and the researchers said they identified biological pathways affected by curcumin that are of interest as the potential target of this polyphenol at the molecular level.

In a related development, another French research team (also based at the Centre de Clermont-Ferrand/Thiex) reported a similar study on hesperidin, a prominent antioxidant component of orange juice. The research was conducted on 24 human male test subjects who exhibited cardiovascular risk factors but were otherwise healthy. Spanning three one-month periods, the men were dosed either 500 milliliters of orange juice (containing 292 milligrams of hesperidin), 500 milliliters of an energy drink, or 500 milliliters of the same drink enriched with 292 milligrams of hesperidin.

In this study, the researchers discovered "a trend toward improved blood pressure and better function of the endothelium" in the men who consumed hesperidin, either in orange juice or as a supplement. Genetic studies found that hesperidin affected activity of 1820 genes from white blood cells.

Although both research studies demonstrated positive effects, Dr. Milenkovic said that while nutritional doses of curcumin or hesperidin could be beneficial for the health, he warned that dietary supplements of the two ingredients could pose danger at high doses.

Dr. Thomas Force, professor of medicine at Thomas Jefferson University, and a spokesman for the American Heart Association, commented that although nutritional supplements based on the two ingredients studied might be a logical extension of the research, neither of the two studies denoted concrete information about the preventive value of the nutrients.

"Most of the literature is not at a very mechanistic level or picks out one specific protein that is regulated. These studies do provide a more global approach to how these compounds may function to do what they are purported to do," Dr. Force said, noting that more research is needed beyond the preliminary findings to form the basis of dietary recommendations.

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