Quercetine tegen hart- en vaatziektes*
In veel eerdere studies over de bioactieve stof quercetine en de kans op hart- en vaatziektes werd veelal in het laboratoriumtests quercetine zelf gebruikt. Doch omdat veel quercetine eenmaal in het lichaam bijna direct wordt afgebroken in metabolieten is in deze studie getest met quercetine en die metabolieten. Ook nu blijkt dat quercetine en de in het lichaam gevormde metabolieten de ontstekingsreacties die leiden tot hart- en vaatziektes duidelijk kunnen verminderen. Wat ook bleek was dat de vermindering afhankelijk was van de hoeveelheid quercetine. Veel quercetine had veel minder effect dan lagere waarden. De meest effectieve waarden zijn te vergelijken met het eten van 100-200 gram
uien.
Quercetin Found to Prevent Cardiovascular Disease
Quercetin appears to provide protection against cardiovascular disease even though the body breaks it down before it enters the blood, according to a new study conducted by researchers at the Institute of Food Research and published in the journal "Atherosclerosis."
While many studies have linked quercetin - a flavonoid that naturally occurs in onions, apples, tea and wine - to a reduced risk of cardiovascular disease, they have usually tested the chemical's direct effects on cells. But because the intestines and liver break down quercetin rapidly, the chemical never actually reaches the blood when consumed in
food.
"We tested compounds that are actually found in the blood, rather than the flavonoid in food before it is eaten, as only these compounds will actually come into contact with human tissues and have an effect on arterial health," lead researcher Paul Kroon said.
Yet when tested on the cells lining human blood vessels, both quercetin and its metabolites (which are produced as the body breaks it down) were found to reduce the inflammation that can lead to cardiovascular
disease.
"The effect is more subtle than laboratory experiments using [quercetin]," Kroon said. "But we can confirm that eating quercetin-rich foods may help prevent chronic inflammation leading to cardiovascular disease, because the metabolites still have an effect on the cells lining the blood vessels."
Lower doses of quercetin metabolites actually appeared to provide a greater protective benefit than higher doses. The most effective dose was achieved from the equivalent of eating 100 to 200 grams (3.5 to 7 ounces) of onions, the researchers
said.
In addition to its cardiovascular and general anti-inflammatory benefits, quercetin has been linked to a decreased risk or increased recovery from cancer, allergies, cataracts, prostatitis and respiratory diseases including asthma and bronchitis.
Comparative effects of quercetin and its predominant human metabolites on adhesion molecule expression in activated human vascular endothelial cells
Sandra Triboloa, Federica Lodiab, Carol Connora, Sunita Suric, Vincent G. Wilsonc, Moira A. Taylorc, Paul W. Needsa, Paul A. Kroona, David A. Hughesa
Abstract
Adhesion of circulating monocytes to vascular endothelial cells, a critical step in both inflammation and atherosclerosis, is mediated by cross-linkage of adhesion molecules expressed on the surface of both cell types. Dietary flavonoids have been shown to have anti-inflammatory properties, decreasing the expression of cell adhesion molecules, such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on endothelial cells. However, flavonoids are efficiently metabolised during absorption and the forms reaching the systemic circulation are glucuronidated, sulphated and methylated. Most previous in vitro studies of the effects of flavonoids have used the parent compounds at concentrations far higher than those physiologically achievable. We investigated the ability of quercetin and its human metabolites, at physiological concentrations (2μmol/L and 10μmol/L), to attenuate the inflammation-induced upregulated expression of VCAM-1, ICAM-1 and of the chemokine, monocyte chemoattractant protein-1 (MCP-1), in human umbilical vein endothelial cells (HUVECs), at the protein and transcript levels. Quercetin treatment reduced the inflammation-induced over-expression of VCAM-1 and ICAM-1 (protein and transcript) in HUVECs. Quercetin also inhibited MCP-1 gene expression. However, quercetin 3′-sulfate, quercetin 3-glucuronide and 3′-methylquercetin 3-glucuronide (isorhamnetin 3-glucuronide) generally exhibited either a reduced ability to inhibit the expression of these molecules compared with the parent aglycone or had no effect. However, all three metabolites inhibited VCAM-1 cell surface expression at 2μmol/L. These results indicate that both quercetin and its metabolites, at physiological concentrations, can inhibit the expression of key molecules involved in monocyte recruitment during the early stages of
atherosclerosis. (Juni
2008)
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