1. Department of Gastroenterology and Hepatology, Sapporo Medical University, Sapporo, Japan
2. Department of Gastroenterology, Otaru General Hospital, Otaru, Japan
3. Department of Gastroenterology, Sapporo Shirakaba-dai Hospital, Sapporo, Japan
4. Center for Translational Research, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan