Little known type of cholesterol may pose the greatest heart disease risk

Aug 20, 2009
A little known type of cholesterol, oxycholesterol, may pose the greatest heart disease risk, researchers say. Shown is a diagram of a heart attack. Credit: Wikimedia Commons

Health-conscious people know that high levels of total cholesterol and LDL cholesterol (the so-called "bad" cholesterol) can increase the risk of heart attacks. Now scientists are reporting that another form of cholesterol called oxycholesterol — virtually unknown to the public — may be the most serious cardiovascular health threat of all.

Scientists from China presented one of the first studies on the cholesterol-boosting effects of oxycholesterol here today at the 238th National Meeting of the American Chemical Society. The researchers hope their findings raise public awareness about oxycholesterol, including foods with the highest levels of the substance and other foods that can combat oxycholesterol's effects.

"Total cholesterol, low-density lipoprotein cholesterol (LDL), and the heart-healthy high-density cholesterol (HDL) are still important health issues," says study leader Zhen-Yu Chen, Ph.D., of Chinese University of Hong Kong. "But the public should recognize that oxycholesterol is also important and cannot be ignored. Our work demonstrated that oxycholesterol boosts total cholesterol levels and promotes atherosclerosis ["hardening of the arteries"] more than non-oxidized cholesterol."

Fried and processed food, particularly fast-food, contains high amounts of oxycholesterol. Avoiding these foods and eating a diet that is rich in antioxidants, such as fresh fruits and vegetables, may help reduce its levels in the body, the researchers note.

Scientists have known for years that a reaction between fats and oxygen, a process termed oxidation, produces oxycholesterol in the body. Oxidation occurs, for instance, when fat-containing foods are heated, as in frying chicken or grilling burgers or steaks. Food manufacturers produce oxycholesterol intentionally in the form of oxidized oils such as and partially-hydrogenated vegetable oils. When added to processed foods, those substances improve texture, taste and stability. Until now, however, much of the research focused on oxycholesterol's effects in damaging cells, DNA, and its biochemical effects in contributing to atherosclerosis. Chen believes this is one of the first studies on oxycholesterol's effects in raising blood cholesterol levels compared to non-oxidized cholesterol.

In the new study, Chen's group measured the effects of a diet high in oxycholesterol on hamsters, often used as surrogates for humans in such research. Blood cholesterol in hamsters fed oxycholesterol rose up to 22 percent more than hamsters eating non-oxidized cholesterol. The oxycholesterol group showed greater deposition of cholesterol in the lining of their arteries and a tendency to develop larger deposits of . These fatty deposits, called atherosclerotic plaques, increase the risk for heart attack and stroke.

Most importantly, according to Chen, oxycholesterol had undesirable effects on "artery function." Oxycholesterol reduced the elasticity of arteries, impairing their ability to expand and carry more blood. That expansion can allow more blood to flow through arteries that are partially blocked by plaques, potentially reducing the risk that a clot will form and cause a heart attack or stroke.

But a healthy diet rich in antioxidants can counter these effects, Chen said, noting that these substances may block the oxidation process that forms oxycholesterol. Good sources of antioxidants include fruits, veggies, beans, and certain herbs and spices. Healthy alternatives to fast-food, which also boosts oxycholesterol, include whole grains, fresh fruits and , seeds, and nuts.

Scientists do not know whether the popular anti-cholesterol drugs called statins lower oxycholesterol, Chen said.

Source: American Chemical Society (news : web)

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User comments : 2

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deatopmg
1 / 5 (1) Aug 20, 2009
It has been hypothesized for 10's of years that 5,6-epoxycholesterol ("oxidized cholesterol") is a bad actor in CHD. This finally confirms it. Even more active cholesterol derivatives though are the 2 cholestenals generated when cholesterol is oxidized by the ozone generated by microphages in vivo in response to an artial infection.
SJG
5 / 5 (1) Aug 21, 2009
Staprans and colleagues at the VA Medical Center in San Francisco published in a series of paper between 1993 to 2000 in American Heart Association's publication Arteriosclerosis, Thrombosis, and Vascular biology, showed that the consumption of oxysterols increases the development of atherogenic oxidized LDLs in the blood stream which, in turn, accelerates the development of atherosclerosis. Staprans found that rabbits consuming a diet enriched in these oxidized cholesterols resulted in a 100% increase in fatty streak lesions (the early stage of atherosclerosis) in the aorta with increased levels of oxysterols in the atherosclerotic plaques itself.
Overly processed foods that are exposed to air and heat can enrich harmful oxysterols or oxidized cholesterol -- specifically, 7 beta-hydroxycholesterol, 7-ketocholesterol, 5 beta, 6 beta-epoxycholesterols and 5 beta,6 beta-epoxycholesterols -- the culprits found in cholesterol-rich diets that are associated with atherosclerosis
She went on to show that advanced atherosclerotic lesions in diseased humans also showed significantly higher levels of these same oxidized cholesterol that were feed to rabbits. Collectively, her studies suggest that western diets containing high concentrations of oxidized cholesterol products increase the serum levels of oxidized cholesterol-rich LDLs which, in turn, concentrate in atherosclerotic plaques.
Origo Biosciences has shown that naturally-occurring anti-cholesterol antibodies may serve an %u2018immuno-housekeeping%u2019 or protective role by facilitating the clearance of oxidized cholesterol-rich particles in both the blood stream and in the gut.
Nearly a half a century ago, researchers showed that production of cholesterol antibodies and the immunologic clearance of LDL might be a useful strategy to reduce serum cholesterol levels and dietary-induced aortic atherosclerosis. A series of independent reports over the past decade have subsequently correlated high levels of anticholesterol antibodies with a significant reduction of both diet-induced hypercholesterolemia and atherosclerotic lesions. Human subjects with peripheral atherosclerosis and cerebrovascular disease reportedly have low levels of circulating cholesterol antibodies.
A report many years ago by Green and colleagues in the Journal of Immunology showed that anticholesterol antibodies from atherosclerosis-protected animals preferentially binds to human LDL or 'bad cholesterol.' And more recent studies by Origo Biosciences found that anticholesterol antibodies and a monoclonal antibody exhibited binding activity four times higher for oxidized cholesterol LDL than for the native non-oxidized LDLs. The source of oxidized cholesterol in LDLs originates as cholesterol-rich micelles -- cholesterol carries in the gut -- through the introduction of processed foods. Hence, gut micelles rich in oxidized cholesterols become an attractive target for anticholesterol antibodies. Interestingly, Origo Biosciences found these antibodies are in certain sources of dairy.
The idea of looking for 'anticholesterol-active milk and whey' that block the uptake of dietary cholesterol originates from a simple observation and unlikely source. The Masai of Africa are nearly free of hypercholesterolemia and atherosclerosis, despite the Masai%u2019s diet that is rich in high-fat meat and that includes the consumption of enormous quantities of milk. It is tempting to conclude that their remedy for preventing cardiovascular disease is their consumption of cow milk containing these highly protective cholesterol antibodies.
Origo Biosciences evaluated over 70 sources of bovine milk, whey, and colostrum where the vast majority showed negligible levels of anticholesterol activity. However, the selective few that did exhibit anticholesterol activity, the levels approximated those previously observed in protected cholesterol-vaccinated animals.
It is interesting to note that a number of reports over the past 25 years have shown that consumption of some sources of antibodies, found as a naturally occurring minor component in milk, whey, and colostrum, can be a remedy in reducing cardiovascular disease. Unfortunately, all of these studies were unclear as how ingestion of antibodies from these sources reduced cholesterol levels.
Origo Biosciences intends to certify 'Anticholesterol active whey' for cholesterol-lowering foods, beverages, and supplement powders. If the cholesterol inhibitor activity observed in these studies is indicative of what we should expect to see in humans, then Origo Biosciences' certified %u2018anticholesterol active whey%u2019 (or milk and colostrum) may present a viable and highly functional ingredient for a variety of foods, beverages, and supplements that can be offered to a board audience to prevent the absorption of dietary sources of oxidized cholesterol in the gut.

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