**5. Conclusions**

In conclusion, we herein found that FAs, especially ω-3 PUFAs such as EPA and DHA, could inhibit URAT1. To gain insight into the potential SUA-lowering e ffects of certain FAs, further investigations including human studies are required.

**Author Contributions:** Conceptualization, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), and T.T.; methodology, H.S. (Hiroki Saito), Y.T. (Yu Toyoda) and H.H.; validation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda) and T.T.; formal analysis, H.S. (Hiroki Saito) and Y.T. (Yu Toyoda); investigation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), H.H., A.O.-K. and H.M.; data curation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), and T.T.; writing—original draft preparation, H.S. (Hiroki Saito) and Y.T. (Yu Toyoda); writing—review and editing, Y.T. (Yu Toyoda) and T.T.; visualization, H.S. (Hiroki Saito) and Y.T. (Yu Toyoda); supervision, Y.T. (Youichi Tsuchiya) and H.S. (Hiroshi Suzuki); project administration, T.T. and N.K.; funding acquisition, T.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by JSPS KAKENHI (grant numbers 16H01808 and 20H00568 to T.T.); T.T. has received research grants from Gout and uric acid foundation of Japan, MSD Life Science Foundation, Public Interest Incorporated Foundation, and Takeda Science Foundation. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

**Acknowledgments:** The authors thank Syuichi Segawa for his continuous encouragemen<sup>t</sup> and support for this study. Also, we would like to thank Editage (www.editage.jp) for English language editing.

**Conflicts of Interest:** H. Saito, H.H., A.O.-K., N.K., and Y.Tsuchiya were the employees of Sapporo Holdings Ltd. H.Saito, Y.Toyoda, T.T., H.H., A.O-K., and H. Suzuki have a patent pending related to the work reported in this article. The remaining authors declare no competing interests.

**Appendix A**

**Figure A1.** Chemical structures of saturated fatty acids tested in this study. (**a**) Butyric acid; (**b**) hexanoic acid; (**c**) octanoic acid; (**d**) decanoic acid; (**e**) dodecanoic acid; (**f**) myristic acid; (**g**) palmitic acid; (**h**) stearic acid.

**Figure A2.** Chemical structures of unsaturated fatty acids tested in this study. (**a**) Palmitoleic acid; (**b**) oleic acid; (**c**) linoleic acid; (**d**) α-linolenic acid (ALA); (**e**) γ-linolenic acid; (**f**) α-eleostearic acid; (**g**) eicosadienoic acid; (**h**) eicosatrienoic acid; (**i**) ω-3 eicosatetraenoic acid; (**j**) arachidonic acid (ω-6 eicosatetraenoic acid); (**k**) eicosapentaenoic acid (EPA); (**l**) henicosapentaenoic acid; (**m**) docosadienoic acid; (**n**) docosatetraenoic acid; (**o**) ω-3 docosapentaenoic acid; (**p**) ω-6 docosapentaenoic acid; (**q**) docosahexaenoic acid (DHA).

**Figure A3.** Concentration-dependent inhibition of URAT1-mediated urate transport by each fatty acid. Data are expressed as the mean ± SD; *n* = 4. (**a**) Linoleic acid; (**b**) ω-3 docosapentaenoic acid.

**Figure A4.** Biosynthetic route of fatty acids and half maximal inhibitory concentration (IC50) values of each tested fatty acid against the urate transport mediated by URAT1. The IC50 values are from Figures 2, 3 and A3. Three polyunsaturated fatty acids with substantial URAT1-inhibitory activities are indicated in red. N.D., not determined in this study; FAs, fatty acids; *des*, desaturase; *elo*, elongase. The metabolic pathway is adapted from a previous report [4], with some modifications.
