Conflict of interest
Chunmei Yang, Guanya Guo, Bo Li, Linhua Zheng, Ruiqing Sun, Xiufang Wang, Juan Deng, Gui Jia, Xia Zhou, Lina Cui, Changcun Guo, Xinmin Zhou, Patrick S. C. Leung, M. Eric Gershwin, Yulong Shang and Ying Han declared that there are no conflicts of interest.