Stress causes heart-damaging fats to stay in blood longer

Catherine Stoney says the study shows one way that stress can contribute to heart disease.   By Kevin Fitzsimons

By Jeff Graaabmeier, Research Communications

A new study has found the first evidence that short periods of psychological stress can cause the body to take longer to clear heart-damaging fats from the bloodstream.

Researchers at Ohio State tested how quickly triglycerides -- a type of fat linked to heart disease -- cleared out of the bloodstream of volunteers during a stress-inducing test compared to a session in which the volunteers rested.

The results showed that, in all cases, stress caused triglycerides to stay in the bloodstream longer.

The findings suggest one reason why stress has been linked to heart disease, said Catherine Stoney, co-author of the study and professor of psychology at Ohio State.

"If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time," Stoney said. "That means it may be more likely to be deposited in the arteries, where it can contribute to heart disease."

The study appears in the current issue of the journal Psychophysiology.

Seventy healthy, nonsmoking middle-aged volunteers -- half men and half women -- participated in the study. Half were between the ages of 40 and 48 and half were between 54 and 61. The two age groups allowed the researchers to consider both premenopausal and postmenopausal women during the project.

Each of the volunteers was tested twice, with both sessions occurring within three days of each other. In both sessions, an intravenous tube was inserted into the veins of the volunteers. A solution containing triglycerides -- the equivalent of about 100 calories -- was then intravenously administered. The procedure replicated what would happen in a person's bloodstream hours after they ate a meal containing fat, Stoney said.

In one session, the volunteers simply rested and their triglyceride level was checked continuously for 40 minutes. In the other session, the volunteers were administered the triglyceride solution and then given 40 minutes of stressful tests. The tests included having to prepare and give a videotaped speech, a difficult word problem task, a psychomotor task consisting of drawing mirror images, and a task where they had to quickly and accurately subtract two-digit numbers from four-digit numbers. Again, their triglyceride level was monitored continuously for 40 minutes.

In all 70 volunteers, triglyceride levels declined more quickly in the restful session than in the session during which they completed the stressful tests, Stoney said. Overall, triglyceride levels declined an average of 2.8 percent a minute in the stress-inducing test session, compared to a quicker 3.2 percent per minute in the resting session.

In some people, the difference between the stressful and restful sessions was quite dramatic, Stoney said, while in others the differences in triglyceride levels were small. This reflects individual differences in how people metabolize fat. But it was significant that stress had negative effects in all the volunteers, she said.

"During stress, people are not metabolizing fat as rapidly and efficiently," Stoney said.

The study found that during the nonstress session, women cleared triglycerides out of their bloodstreams more quickly than did men. These findings were consistent with other research, Stoney said. However, the research found no difference in how quickly men and women cleared triglycerides during stress. Because reproductive hormones might affect how triglycerides are cleared, the researchers separated pre- and naturally postmenopausal women. However, they found no differences in how these groups responded. In an additional analysis, the researchers also compared postmenopausal women who were taking hormone replacement therapy with those who were not. Again, they found no differences.

Stoney conducted the study with Shelia West, a former Ohio State postdoctoral student now at Pennsylvania State University; Joel Hughes, a former Ohio State graduate student now at Duke University; Lisa Lentino, a former Ohio State graduate student now at the Veteran's Administration Hospital in Bedford, Mass.; current Ohio State graduate student Montenique Finney; James Falko, emeritus faculty in endocrinology at Ohio State; and Linda Bausserman of The Miriam Hospital at Brown University.

The work was supported in part by grants from the National Institutes of Health.

Stoney and her colleagues are continuing their work examining how stress affects blood chemicals linked to heart disease. For a new study, the researchers are looking for volunteers to test whether vitamin supplements affect stress responses. Volunteers should be healthy, between 30 and 45 years of age and not already taking vitamins or dietary supplements. People will be asked to participate for about six weeks, and need to be able to come to a lab for testing three times during that period. Those who are interested should call Lisa or Laura at 688-3895.

The Office of University Relations produces articles about faculty research to distribute to the national media. Among the most recent stories:

Chemists make first-ever compounds of noble gases and uranium

Ohio State chemists and their colleagues at the University of Virginia have created the first-ever compounds of uranium bonded to atoms of three so-called "noble gases" -- argon, krypton and xenon. In the last 40 years, scientists have been able to form compounds from noble gases only a handful of times. These chemical outcasts were once thought incapable of forming bonds with other elements, and until the 1960s were considered completely inert. The chemists published their results in the journal Science.

The same technique that created these uranium compounds might be used to link noble gases to other metals, said Bruce Bursten, professor and chair of chemistry.

The chemists created their first noble gas compound by chance, while studying a molecule with the formula CUO. This molecule is formed from the reaction of uranium atoms with carbon monoxide, and frozen atoms of the noble gas argon were supposed to form a protective "cage" around the CUO to preserve the molecules for study. Instead, the chemists noticed that the argon and CUO appeared to interact. Computer simulations explained that the CUO molecules were bonding to the argon atoms.

www.osu.edu/researchnews/archive/noblegas.htm