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4.22.2013

Researchers Identify “Obesity Genes” Among People of African Ancestry

An international team of researchers, including three from the Miller School, has discovered new regions of the human genome that influence obesity in people of African ancestry, as well as others.

Published in the journal Nature Genetics, their study, “A meta-analysis identifies new loci associated with mass index in individuals of African ancestry,” is based on the largest genomic search for “obesity genes” in people of African ancestry. Although there are notable racial and ethnic disparities in the prevalence of obesity in the United States — where 50 percent of African American adults are classified as obese, compared with 35 percent of non-Hispanic whites — the study notes large genome-wide studies of Body Mass Index (BMI) are lacking.

Contributing to the study from the Miller School were Jennifer J. Hu, Ph.D., Associate Director for Cancer Prevention and Control at Sylvester Comprehensive Cancer Center and professor of epidemiology and public health; Evadnie Rampersaud, Ph.D., research assistant professor of human genetics and Director of the Division of Genetic Epidemiology at the John P. Hussman Institute for Human Genomics; and Jorge L. Rodriguez Gil, B.S., research assistant at Sylvester.

“These findings demonstrate the importance of conducting genetic studies in diverse populations to identify new susceptibility loci for common BMI traits,” Hu said.

Led by the University of North Carolina’s Gillings School of Global Public Health and the Keck School of Medicine of the University of Southern California, the researchers analyzed the genetic makeup of more than 70,000 men and women of African ancestry, and identified three new genetic variants, or single nucleotide polymorphisms (SNPs), associated with BMI and obesity. “This observation,” the study says, “suggests that the biologically functional alleles are ancient and likely arose before migrations out of Africa.”

But the researchers also found that the same SNPs common to people of African ancestry appear among those with no known African ancestry.

“It’s an important finding,” said co-principal investigator Kari North, Ph.D., associate professor of epidemiology at the Gillings School. “It provides substantial evidence that genes can influence obesity, and that this genetic predisposition is likely shared across populations. This research also opens the door for more genetic studies in this area, and to examine other potential shared traits in diverse populations.”

Another co-principal investigator, Christopher Haiman, Ph.D., professor of preventive medicine at the Keck School, emphasized that, while having these risk SNPs does not mean the individual will have a higher BMI or become obese, “it does signal a predisposition.”

“Just to be clear, these genes account for a very small fraction of the differences in BMI noted between individuals in the population,” Haiman said. “Poor diet and reduced physical activity continue to be the main driving forces for obesity.”

Hu noted the significant impact of the findings on the South Florida community, particularly Miami-Dade County, where more than 67 percent of adults are obese or overweight.

“Future genomic studies in Hispanic populations will be important to identify new BMI loci in this underserved minority population,” Hu said.

In addition to researchers at institutions across the U.S., investigators from Nigeria, Barbados, Canada and Germany also contributed to the study.

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