August 25, 2014
Latinos with type 2 diabetes have a significantly higher risk of developing severe diabetic retinopathy – the leading cause of blindness in working-age adults in the United States – if they also have many Native American ancestors, researchers report in the journal Investigative Ophthalmology & Visual Science.
“Our findings present a strong case that the high prevalence of diabetic retinopathy in Latinos is due in part to genes of Native American origin,” said Xiaoyi Gao, associate professor of ophthalmology and visual sciences at the University of Illinois at Chicago and a corresponding author on the study.
Diabetic retinopathy is a complication of diabetes that affects blood vessels in the retina. Latinos are almost twice as likely to be diagnosed with diabetes than non-Hispanic Whites and have a higher prevalence of diabetic retinopathy. While several lifestyle and dietary factors have been blamed for higher rates of diabetes among Latinos, Gao and his colleagues wanted to see if genetic ancestry was associated with the development of diabetic retinopathy.
Latinos are a diverse group of populations with varying blends of Native American, African and European ancestry. Gao and his colleagues analyzed DNA from participants in the Los Angeles Latino Eye Study (LALES), the largest population-based study of ophthalmic diseases in Latinos. That study’s principal investigator is Dr. Rohit Varma, chair of ophthalmology at the University of Southern California Keck School of Medicine, and a corresponding author on the diabetic retinopathy study.
The researchers estimated the proportion of Native American, European and African genetic ancestry of 135 LALES participants with type 2 diabetes and severe diabetic retinopathy and 809 participants with type 2 diabetes without severe diabetic retinopathy. Based on their analysis, the researchers determined that roughly half the genetic material was of Native American origin for participants with severe diabetic retinopathy, compared to only 45 percent for those without severe diabetic retinopathy.
Participants with more than 50 percent Native American genetic ancestry had an 87 percent higher chance of having vision-threatening diabetic retinopathy compared to those with less than 50 percent Native American ancestry.
The association between Native American ancestry and diabetic retinopathy remained significant after the researchers adjusted for other known risk factors for diabetic retinopathy, including age, sex, duration of diabetes, glycosylated hemoglobin levels (a measure of glucose control) and socio-economic factors.
“Our next steps will be to try to narrow down which genes among those with greater Native American origin might be contributing to boosting the risk for developing severe diabetic retinopathy,” Gao said.
W. James Gauderman, Paul Marjoram, and Mina Torres from the University of Southern California; and Yii-Der I. Chen, Kent Taylor, and Dr. Jerome Rotter from the Los Angeles Biomedical Research Institute at Harbor-UCLA, are co-authors on the paper.
This research was supported by grants U10EY011753, R01EY02265 and P30EY001792 from the National Institutes of Health and a grant from Research to Prevent Blindness, a grant from the National Center for Advancing Translational Sciences, Clinical Translational Science Institute grant UL1TR000124 and grant DK063491 from the National Institute of Diabetes and Digestive and Kidney Disease Diabetes Research Center.
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