1. Department of Internal Medicine, Yonsei University College of Medicine, Seoul 03722, Korea.
2. Institue of Gastroenterology, Yonsei University College of Medicine, Seoul 03722, Korea.
3. Yonsei Liver Center, Severance Hospital, Seoul 03722, Korea.
4. BK21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Korea.