Some answers about blacks' higher rates of diabetes, heart disease

Genetic difference in the way some African-Americans process glucose might help explain why they are disproportionately susceptible to diabetes and heart disease.

While it has long been understood that some diseases run in families, a finding by the University of North Carolina-Chapel Hill adds clarity to the genetic causes and is certain to spark debate over the notion of an inherent, racially based predisposition to disease.

"There's no doubt that this is a controversial issue," said Dr. Cam Patterson, chief of the division of cardiology at UNC-Chapel Hill School of Medicine and co-author of the study, published in the online journal PloS One. "But it's a big mistake to overlook the differences in genes and populations and ethnicities that are going to have an impact on health."

Patterson said the team was surprised by its discovery, which was made when the scientists began building a database for common molecular traits among people who have heart problems. One genetic marker, associated with poor glucose metabolism, showed up repeatedly.

"It really mystified us," Patterson said.

When the scientists checked which patients had this trait, they discovered the racial connection. A similar genetic finding shows up in a database of heart disease patients throughout West Africa, Patterson said.

The link between glucose metabolism and heart disease is diabetes, which causes heart problems. People with diabetes cannot properly process the sugars from food into energy, and the buildup of glucose in the bloodstream damages organs, including the heart.

Type 2 diabetes is on the rise in all populations, the result of obesity and inactivity. But it hits African-Americans disproportionately.

Patterson said the genetic finding likely stems from geography, harkening back thousands of years when humans uniquely adapted to the food and microorganisms in their environments. Northern Europeans, science has shown, have different genetic tendencies than Southern Italians.

Joseph Graves, a molecular biologist and dean of biological sciences at North Carolina A&T State University in Greensboro, said he does not question the genetic findings, but said they do not explain why blacks have higher rates of diabetes or heart disease.

Instead, he noted, African-Americans are disproportionately poor. As a result, they have less access to healthy foods, make fewer doctor visits and are exposed to more environmental toxins - all of which add up to higher disease rates.

"They're assigning causality to a gene that isn't simply the gene," Graves said. "And they're not doing a sufficient job of explaining how environmental differences, which result from our social history, are playing a role in making people sick."

Graves, who published a book in 2002 about biological theories of race, said there is no genetic basis for race written into the DNA codes of humans, but he concurred that geographic history can create inherited differences between people.

To the extent that there is no so-called race gene, the UNC-CH findings add to a growing number of studies that are finding molecular differences that predispose disease on people linked by their geographic histories. Earlier this year, a Wake Forest University team reported on a genetic link among African-Americans to a form of kidney disease.

Such insights could help those working to erase the disparities.