1. Department of Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL, USA.
2. Department of Biology, University of Illinois Springfield, Springfield, IL, USA.
3. Department of Neurology and Center for Alzheimer's Disease and Related Disorders, Southern Illinois University School of Medicine, Springfield, IL, USA.
4. Joslin Diabetes Center, Section on Integrative Physiology and Metabolism, Harvard Medical School One Joslin Place, Boston, MA, USA.