Human evolution seems to be paradoxically increasing the susceptibility to type 1 diabetes, new research concludes.
A study by researchers at the Stanford University School of Medicine finds that gene variants associated with an increased risk for type 1 and rheumatoid arthritis may supply previously unknown benefits and thus persist through the selective process.
“At first we were completely shocked because, without insulin treatment, type-1 diabetes will kill you as a child,” said senior study author Atul Butte in a release announcing the findings. “Everything we’ve been taught about evolution would indicate that we should be evolving away from developing it. But instead, we’ve been evolving toward it.”
Among the potential benefits are protections against certain viruses and bacteria, though it is not yet clear if these protections come from disease-associated mutations or from neighboring genes associated with diabetes.
The researchers analyzed the genetic variants called single nucleotide polymorphisms associated with type 1 diabetes, finding that 80 of them have been increasing in prevalence recently — indicating they have survived selection. Of those 80, 58 are associated with an increased risk of diabetes, while 22 appear protective.
Type 2 diabetes SNPs were also analyzed but no such paradox resulted.
The SNPs may be defying evolution because in some parts of the world the associated triggers for diabetes are never activated, so only the protective effects manifest themselves, Butte said.
The research was published Tuesday in the journal Public Library of Science ONE.
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