1. Center for American Indian Health Research, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190, USA
2. Section of Diabetes and Endocrinology, Department of Pediatrics, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
3. The Cherokee Nation, P.O. Box 948, Tahlequah, OK 74465, USA