1. Digestive Disease Center, CHA Bundang Hospital, CHA University, Seongnam 13496, Korea.
2. Department of Internal Medicine and Institute of Gastroenterology, Yonsei University College of Medicine, Seoul 03722, Korea.
3. Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul 03722, Korea.
4. Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Korea.