1. Department of Surgery, University of Michigan , Ann Arbor, MI 48109 , USA
2. Veterans Affairs Ann Arbor Healthcare System, Research Service , Ann Arbor, MI 48105 , USA
3. Molecular and Integrative Physiology, University of Michigan , Ann Arbor, MI 48109 , USA
4. Novo Nordisk Inc. , Copenhagen , Denmark
5. Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Michigan , Ann Arbor, MI 48109 , USA