Mexicans and other Latin Americans have a higher risk of diabetes because of a Neanderthal gene mutation, researchers say.
These findings could uncover new targets for diabetes drugs, investigators added.
An international team of researchers focused on Type 2 diabetes, the most common form of the disease, accounting for 90 percent to 95 percent of diabetes cases in humans. In Type 2 diabetes, the body either does not generate enough insulin or its cells ignore the molecule. Insulin is a hormone the body needs in order to use sugar for energy.
The scientists investigated the genetic basis of Type 2 diabetes in Mexican and other Latin American populations, where the disease is roughly twice as common as it is in white, non-Hispanic populations in the United States. [Salud! 8 Ways Hispanic People Are Healthier]
The research team, known as the Slim Initiative in Genomic Medicine for the Americas (SIGMA) Type 2 Diabetes Consortium, performed the largest and most comprehensive genetic study to date of Type 2 diabetes in Mexican and Mexican-American populations. This involved analyzing the genomes of more than 8,200 Mexicans and other Latin Americans, including more than 3,800 people with Type 2 diabetes and more than 4,300 without the condition.
The investigators discovered a risk gene for Type 2 diabetes known as SLC16A11 that had gone undetected in previous research. People who carry the higher-risk mutation of the gene, which is active in the liver, are 25 percent more likely to have diabetes than those who lack the mutation, and people who inherited copies of this gene variant from both parents are 50 percent more likely to have diabetes.
The higher-risk version of this gene is seen in up to half of people who have recent Native American ancestry, including Latin Americans. The fact that this gene mutation is more common in Latin Americans could account for as much as 20 percent of their increased levels of Type 2 diabetes.
The researchers noted changing levels of the protein that the gene encodes could alter the amount of a specific type of fat, one that prior studies have linked to the risk of diabetes.
"What is most exciting to me, and has the greatest long-term implication, is a new clue about the biology of Type 2 diabetes,"study co-authorDavid Altshuler, professor of genetics and medicine at Massachusetts General Hospital and the Broad Institute, told LiveScience.
"If we can come to understand the biological function of SLC16A11, and how changing its sequence increases risk of Type 2 diabetes, then we may in the long run be able to develop improved prevention or treatment," Altshuler added.
Roots of diabetes
Although this gene variant is common among people with recent Native American ancestry and is also found in about 20 percent of East Asians, only 2 percent of Europeans have it, and no known Africans carry SLC16A11. This pattern is somewhat unusual; modern humans arose in Africa, so nearly all common human genetic variants are found in African populations. [Top 10 Mysteries of the First Humans]
To uncover the roots of this odd pattern, the researchers investigated ancient human DNA and found the high-risk mutation of this gene was apparently inherited from Neanderthals, the closest extinct relatives of modern humans. Recent analysis of Neanderthal DNA revealed the ancestors of modern humans interbred with Neanderthals; the first high-quality genome sequence from a Neanderthal suggests about 1.5 percent to 2.1 percent of the DNA of modern humans living outside Africa is Neanderthal in origin. In contrast, Neanderthal DNA is much less common among modern Africans, matching these latest findings.
The scientists are now using their findings "to design new studies that aim to understand how this variant influences metabolism and disease," study co-authorTeresa Tusie-Luna, principal investigator at the National University of Mexico's Biomedical Research Institute, said in a statement.
These insights could "illuminate new pathways to target with drugs and a deeper understanding of the disease," study co-author José Florez, from the Broad Institute and Harvard Medical School, said in a statement.
The researchers cautioned that Type 2 diabetes is a complex disease influenced by multiple genes and by environment and behavior. "Our finding is only one piece in a large and complex puzzle," Altshuler said. "Any clinical translation of this finding will take many years. It is still in the research phase, and any health benefits will take time."
The scientists detailed their findings online Dec. 25 in the journal Nature.