Can Exercise Improve African Americans' Cholesterol?
Kwame Osei, MD, FACE, FACP
Kwame Osei, MD, FACE, FACP
Endocrinologist, Ohio State University Medical Center
|ADA Research Funding|
Clinical Translational Award
When it comes to diabetes and its complications, African Americans face tough realities. Three quarters of African Americans are overweight. When they develop diabetes, they have more complications than average: African Americans have significantly higher rates of cardiovascular disease and kidney failure. They have amputations as a result of diabetic complications at two to four times the rate of whites. And African Americans are twice as likely to die of diabetes as whites.
Kwame Osei, MD, FACE, FACP, a physician at Ohio State University Medical Center, has spent 25 years studying the reasons why. Different groups of people and ethnicities develop diabetes and its associated complications differently, it turns out.
Biological differences help explain why some groups of people are harder hit than others. Blacks are more insulin resistant than whites, for example. And Osei has noticed another big difference: cholesterol. A type of fat that circulates in the body, cholesterol comes in two varieties: high density, or HDL, and low density, or LDL. HDL cholesterol is known as "good" cholesterol, and it plays an important role in reducing the risk of heart disease by keeping the walls of the arteries healthy and by removing artery-clogging LDL, or "bad" cholesterol, from the bloodstream.
Considering the high levels of heart disease in African Americans, you would think they might lack HDL cholesterol, at least compared with whites. But the opposite is true. "When you look at blacks, in Africa or here, they have higher HDL compared to Caucasians," Osei says.
Based on their high levels of "good" cholesterol, "African Americans shouldn't suffer from cardiovascular disease," says Osei. But, paradoxically, they do—at rates nearly double those of whites. "HDL is supposed to be the good guy, and LDL the bad guy. But African Americans don't seem to be protected by the HDL they have," Osei says. "So we asked the question: Does HDL have the same function in blacks as it does in white people?"
The short answer is no. A key HDL protein, the enzyme paraoxonase, "is 50 percent less functional in blacks," Osei says. "They have the quantity, but not the quality." Whatever the benefits of paraoxonase—research has shown it may be an antioxidant—African Americans aren't getting as much of a boost from it as whites, neutralizing their HDL cholesterol head start.
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Osei thinks the problem may be genetic. "We've compared the same parameters with African Americans and Ghanaians in Ghana. This phenomenon is something intrinsic to people with African ancestry," he says.
With the help of a grant from the American Diabetes Association, Osei is looking for ways to reactivate this enzyme and get HDL functioning again in African Americans. He's in the middle of a three-year experiment to see if weight loss through diet or exercise can improve HDL functionality.
To find out, Osei is gathering 100 people—a total of 50 African Americans and 50 whites, all overweight or obese and matched roughly for age and gender. By the end of the experiment, all the participants will have gone on a six-month Slim-Fast diet, restricting their calories to between 1,200 and 1,600 a day while they work out several times each week.
The early results have been dramatic. Some of the participants lost 30 pounds in six months, with Osei and his team measuring their insulin resistance and the functionality of their HDL at regular intervals along the way. When the results are analyzed later this year, Osei hopes to have evidence that weight loss and exercise can give HDL some of its kick back.
If it does, Osei hopes to repeat the study, but this time without the weight loss. If the HDL still works better, it will be a sign that exercise (and not weight loss) makes the difference. "In the real world, we know exercise is your best shot," Osei says. "Ultimately, we're trying to find out if African Americans can improve the quantity and the quality of their HDL through exercise."
The results could resound beyond the United States. Osei, who earned his MD at the University of Ghana Medical School in Accra, says that when he was in medical school 30 years ago, type 2 diabetes affected fewer than 1 percent of Africans. Today, that number has risen to nearly 7 percent (it is 12.6 percent among African Americans), a dramatic increase that's worth paying attention to. Understanding how to help people with African ancestry on both sides of the Atlantic avoid cardiovascular disease and diabetes may save a lot of lives.