国家自然科学基金(81302160,81272447)%国家消化系统疾病临床医学研究中心基金(2015BAI13B09)%北京市医院管理局青苗人才计划(QML20150507). This study was supported by National Natural Science Foundation of China(81302160,81272447)%National Clinical Research Center for Digestive Diseases(2015BAI13B09)%Beijing Municipal Administration of Hospitals' Youth Programme(QML20150507)