Fat fuels PCB damage: diet influences toxic effects leading to heart disease

Science News, Oct 16, 2004 by D. Parsell

Polychlorinated biphenyls (PCBs) have been associated with cancer for decades. Since the late 1990s, evidence has also linked the pollutants to cardiovascular disease among workers with long-term exposure to PCBs in electrical equipment. Researchers now report that experiments on mice have shown that corn oil, which is common in U.S. diets, can magnify a PCB's damage to cells lining blood vessels.

Such damage can increase the buildup of artery-clogging fat in heart disease, report Bernhard Hennig of the University of Kentucky in Louisville and his colleagues in an upcoming Environmental Health. Perspectives.

In a 4-week experiment, Hennig's team fed one group of mice a diet high in corn oil. Another group received food high in olive off. On two occasions, the scientists injected each animal with a dose of a PCB known to damage vascular tissue. Two other groups of mice followed the diets but didn't receive the injections. All the mice had been genetically altered to have a tendency to develop clogged arteries, a precursor to heart disease.

At the end of the experiment, the researchers analyzed the animals' blood and tissues. Mice that had eaten corn oil and received the PCB had the greatest amount of fat in their arteries and the worst arterial-cell damage. Their artery, walls contained large amounts of adhesion molecules, which aid the buildup of fibrous tissue and fat in plaques.

Corn oil, Hennig notes, has a high concentration of linoleic acid, which damages arteries, according to previous research. In contrast, olive oil has little linoleic acid and high concentrations of heart-friendly oleic acid.

Hennig says that the findings suggest that in people exposed to PCBs, "certain dietary fats may increase the risk of environmental insult."

In the United States, PCBs were used widely as lubricants and coatings until the government banned industrial production of the chemicals in the late 1970s. The chemicals, however, are still used in some electrical equipment. Because PCBs are slow to break down, they persist in the environment and build up in animal tissues and human breast milk.

The doses administered by Hennig's team to the mice were higher than a typical person's exposures to PCBs, but some people accumulate high concentrations of PCBs because of their occupations or locations.

The researchers say that they chose the mice used in their experiment, with a tendency to develop dogged arteries, because the condition is similar to that of people with high blood concentrations of low-density, lipoprotein cholesterol.

Calling the study "important," Margaret O. James, a toxicologist at the University of Florida in Gainesville, says that little research has examined how dietary factors influence the toxicity of pollutants.