Acknowledgements
This work was supported by grants from the Scientific Research Fund of the Ministry of Education, Science, Sports, and Culture, of Japan (No. 20591356 and No. 23591658). The authors would like to thank Professor Tatsuya Atsumi, Department of Internal Medicine II, Hokkaido University Graduate School of Medicine (Sapporo, Japan) for critical reading of this manuscript.
Conflict of interest
None.