Study Finds African-American Gene Risks for IBD

Inflammatory bowel disease affects the gut, causing symptoms such as abdominal cramps, blocked bowels, fever, extreme weight loss and anemia.

African-Americans have unique genetic risks for inflammatory bowel disease that are traceable to their African heritage, according to research published this month in the journal Gastroenterology. The finding is a significant step toward tailoring potential therapies to patients with the debilitating, chronic disorder.

Inflammatory bowel disease (IBD), which comprises Crohn's disease and ulcerative colitis, affects more than 3 million people in the U.S., according to the federal Centers for Disease Control and Prevention. Symptoms include abdominal cramps, blocked bowels, fever, extreme weight loss and anemia. Although treatments may relieve symptoms, there is no cure.

"The hope for genetic advances is that we will be able to develop new therapies and more personalized approaches for IBD," said Dermot McGovern, MD, PhD, FRCP(Lon), co-senior author of the multicenter study and director of Cedars-Sinai Precision Health, a new initiative promoting personalized medicine. "These benefits should be available to all sections of society. This study extends these possible advances to the African-American population, who may be at risk for more severe forms of these diseases."

The research constitutes the first genome-wide association study of IBD in African-Americans, said McGovern, professor of Medicine and Biomedical Sciences, the Joshua L. and Lisa Z. Greer Chair in Inflammatory Bowel Disease Genetics and director of Translational Medicine in the F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute at Cedars-Sinai.

Dermot McGovern, MD, PhD, FRCP(Lon)

Genome-wide association studies search for genetic variations that occur more frequently in people with a specific disease than in healthy people. The goal is to identify inherited risk factors for a disease and create potential therapies to target these factors.

In the new study, genome-wide scans were performed for 2,345 African-Americans with IBD and 5,002 African-Americans without the disease. These scans identified two locations of genes on chromosomes that were uniquely associated with ulcerative colitis in African-Americans and were inherited from their African ancestors.

In addition, the study indicated that nearly half of the gene locations found to be associated with IBD in previous studies of European populations also had some influence on IBD development in African-Americans. "This finding supports shared pathogenic mechanisms across different ethnicities," the investigators concluded.

The research was conducted at 35 institutions in the U.S. and Canada. It builds on a multicenter study in 2015 that was the first large-scale evaluation of gene locations associated with IBD in African-Americans, according to McGovern. He was co-senior author for that study as well, also published in Gastroenterology. Both studies were co-led by Cedars-Sinai, Emory University in Atlanta and the Johns Hopkins University School of Medicine in Baltimore.

The investigators in the latest study emphasized that there is a pressing need to conduct more IBD research among African-Americans.

"It is clear that further studies with larger sample sizes in the African-American population are needed to identify additional population-specific variants and novel gene locations, as well as to more fully characterize the role of risk variants established in other populations on the development of IBD in African-Americans," they wrote.

Other Cedars-Sinai contributors to the study, besides McGovern, were Stephan R. Targan, MD, professor of Medicine, the Feintech Family Chair in Inflammatory Bowel Disease and director of the F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute; Zhenqiu Liu, PhD, associate professor of Medicine and director of Bioinformatics at the Samuel Oschin Comprehensive Cancer Institute; and Talin Haritunians, PhD, a research scientist in McGovern's laboratory.