NEW YORK (GenomeWeb News) – The apparent genetic risk for type 2 diabetes seems to vary between human populations from different parts of the world, new research suggests, with populations in Africa and East Asia showing particularly pronounced differences in T2D susceptibility.
A pair of papers appearing online yesterday — both led by investigators at Stanford University — outline the approaches and analyses used to reach that conclusion.
For the first study, published in PLOS Genetics, researchers trolled through data on more than 1,000 individuals from around the world who'd been genotyped for the Human Genome Diversity Panel project. Patterns in that data revealed geography or population-related differentiation in the genetic risk associated with certain diseases.
"We demonstrated that differences in genetic risk for multiple diseases go well beyond what is expected by genetic drift," the study authors noted. "In addition, using a human population phylogenetic tree allowed us to elucidate a substructure of worldwide relationships."
In the East Asian population, for instance, the team saw diminished genetic risk for both T2D and pancreatic cancer. On the other hand, individuals of African ancestry appeared to be more apt to carry T2D risk alleles, results of the analysis suggest, pointing to possible migration-related shifts in genetic susceptibility to T2D.
For their PLOS Genetics analysis, the researchers used data for 1,043 individuals genotyped for the HGDP to delve into the genetic risk associated with more than 100 diseases, including T2D.
Because the individuals hailed from 51 different populations around the world, the group was able to get a glimpse at relationships between these genetic risk contributors and human migration and population patterns.
From that data, investigators saw at least 11 conditions for which risk variant profiles differed across human populations, researchers reported, including ulcerative colitis, bladder cancer, lupus, and inflammatory bowel disease.
For T2D, that genetic differentiation appeared to correspond with population patterns stemming from human migrations out of Africa and into other parts of the world. For instance, the analysis indicated that genetic risk for T2D dips in East Asian populations but tends to be elevated in populations from Africa — particularly the Mandinka population, which appeared to be at highest genetic risk of T2D.
"East Asians definitely get diabetes," Stanford University's Atul Butte, senior author on the study, said in a statement.
Nevertheless, he added, it's possible that there are population-specific differences in the risk alleles and genetic pathways involved, potentially producing somewhat distinct forms of the disease.
Those involved in the study noted that additional, follow-up research is needed, including whole-genome sequencing analysis, which can offer a look at larger structural variants contributing to disease risk in different populations, for instance.
But if findings from the current analysis hold in future studies, that may ultimately prompt a shift in researchers' understanding of T2D and the factors contributing to it.
"Other fields of medicine have undergone a radical rethinking in disease taxonomy," Butte said in a statement, "but this has not happened yet for diabetes, one of the world's public health menaces."
"If these are separate diseases at a molecular level, we need to try to understand that," he added.
A related study in the journal Diabetes Care, also by Stanford's Butte and his colleagues, touched on the consequences of such genetic differences. That work highlighted apparent clinical differences in T2D-related traits — particularly in insulin resistance and insulin response — in African, East Asian, and Caucasian populations.
More generally, Butte and his colleagues put together a so-called "Genetic Risk World Map" to tie together the information generated from their study of disease risk genetics in the context of human migration. The resource is available online through a Stanford website.