1. Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
2. Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
3. Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23284, USA
4. McGuire Veterans Affairs Medical Center, Research Division, Richmond, VA 23249, USA