1. Research Service, Richmond Veterans Affairs Medical Center, Central Virginia Veterans Affairs Health Care System, Richmond, VA 23249, USA
2. Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond VA 23298, USA
3. Department of Biology, Virginia Commonwealth University, Richmond, VA 23298, USA
4. Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
5. Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA