Genetic difference in the way some African-Americans process glucose may explain why they are disproportionately susceptible to diabetes and heart disease, scientists at UNC-Chapel Hill report today.
While it has long been understood that some diseases run in families, the UNC-CH finding 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 UNC-CH 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 role of diabetes
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.
In North Carolina and across the nation, type 2 diabetes is on the rise in all populations, the result of obesity and inactivity. But it hits African-Americans disproportionately. More than 13percent of blacks in North Carolina have diabetes, while 8.7 percent of whites have it, state data show.
A similar disparity is found in heart disease among men.
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.
Broader view wanted
Joseph Graves Jr., a molecular biologist and dean of biological sciences at N.C. A&T State University in Greensboro, said he does not question the genetic findings, but he 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.
Ministry unsurprised
Such insights could help those working to erase the disparities.
Barbara Lee, a clinical social worker in Pitt County who is director of an intervention to help blacks with diabetes and heart disease, said the hereditary nature of the diseases has long been evident.
"It does exist disproportionately in the African-American communities," Lee said, noting that her organization, Cornerstone Ministries, is working with black churches to help their members become more active and eat healthier.
The group won a $360,000 grant three years ago that was renewed in July by the state's Health and Wellness Trust Fund. Its mission is to tackle the health disparities of diabetes and heart disease - one of the primary goals of the trust fund.
The UNC-CH team is now studying interventions that could be specific to the different groups, based on their genetic makeup.
"The standard approach in medicine is to treat every patient the same, in terms of drug therapies and interventions," Patterson said. "But we know that every patient is not the same. Understanding genetics will help us understand what the patient needs."
