We previously demonstrated that sources of diet such as fish can enhance the HbA1c-lowering effects of DPP-4i (J Diabet Investig 2012:3(5):464-467). In our retrospective studies, we also reported that DPP-4i treatments are more effective in type 2 diabetic patients with high plasma levels of EPA and DHA, polyunsaturated fatty acids that are rich in fish (J Diabet Investig 2012:3(5):464-467; J Diabet Investig 2012:3(6):498-502). In the course of analyzing the mechanism, we found that ingestion of fish prior to rice enhanced secretion of GLP-1 (Yabe D et al. Late breaking poster presentation in ADA 2014, manuscript in preparation). Further investigation of the ideal dietary content for combination with DPP-4i could be helpful in enhancing DPP-4i efficacy for more patients.