Study Identifies BMI-Associated Loci in Individuals of African Descent

The United States has a weight problem: according to the CDC, more than one-third of American adults are obese. Moreover, as of 2010 one-third of children were either overweight or obese, with the rates of obesity doubling in children and tripling in adolescents in the past thirty years. And some groups are more inclined to be obese than others, with non-hispanic blacks 51 percent more likely than whites to be obese, for example.

A recently published study may help researchers better understand why some populations are more susceptible to obesity than others. Struan Grant, PhD, associate director of The Children’s Hospital of Philadelphia’s Center for Applied Genomics (CAG), co-authored a study that discovered new loci associated with body mass index (BMI) in adults of African ancestry.

Previous genome-wide association studies had identified 36 BMI-associated loci. While those studies mainly investigated individuals of European descent, in the current study the researchers conducted a meta-analysis to determine whether more than 3.2 million single nucleotide polymorphisms were associated with BMI in men and women of African ancestry. In all, more than 70,000 men and women of African descent were studied.

In addition to Dr. Grant, Children’s Hospital’s Hakon Hakonarson, M.D., PhD, director of CAG, Brendan Keating, PhD, CAG lead clinical data analyst and Faculty member in UPenn Pediatrics and Surgery, and CAG bioinformatics specialist Jonathan Bradfield, also contributed and co-authored the study. More than 200 researchers representing over 50 institutions, including the Broad Institute, the National Human Genome Research Institute, and Johns Hopkins University, took part in the investigation. The study was published online recently in Nature Genetics.

The research group discovered two new loci — 5q33 and 7p15 — associated with BMI in people of African ancestry, while a third, 6q16, was found to be suggestive of an association. “These findings provide strong support for shared BMI loci across populations, as well as for the utility of studying ancestrally diverse populations,” the researchers say.

“Our sizeable genetic database of African American children played a crucial role in this study, lending further support to the loci initially detected in the adult cohorts” Dr. Grant added.

Children’s Hospital researchers have been associated with a number of previous investigations related to the current study, including one that identified genes associated with childhood obesity.

Last year CHOP investigators, as part of the Early Growth Genetics Consortium, helped identify two new gene variants that increase the risk of childhood obesity. After performing a meta-analysis of 14 previous studies, the study’s authors identified two novel loci and the suggestion of an association for two other gene variants, none of which had previously been implicated in obesity. CAG’s Struan Grant was the senior author of the study while Jonathan Bradfield acted as co-first author, which was published in Nature Genetics.

The current study’s findings, meanwhile, “demonstrate the importance of conducting genetic studies in diverse populations to identify new susceptibility loci for common traits,” the investigators note.