TY - JOUR
T1 - Inhibition of SNAT5 induces incretin-responsive state from incretin-unresponsive state in pancreatic B-cells
T2 - Study of B-cell spheroid clusters as a model
AU - Hashim, Mahira
AU - Yokoi, Norihide
AU - Takahashi, Harumi
AU - Gheni, Ghupurjan
AU - Okechi, Oduori S.
AU - Hayami, Tomohide
AU - Murao, Naoya
AU - Hidaka, Shihomi
AU - Minami, Kohtaro
AU - Mizoguchi, Akira
AU - Seino, Susumu
N1 - Funding Information:
Acknowledgments. The authors thank Yasuhiro Minami (Kobe University) for his support and encouragement throughout this study; Ritsuko Hoshikawa, Chihiro Seki, Akiko Kanagawa, Niina Ota, Ayako Kawabata, and Haruyo Maeda (Kobe University) for their excellent technical assistance in this study; and Christopher M. Carmean (Kobe University) for his valuable comments and suggestions. Funding. This study was supported by grants-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan, MSD K.K., and the Kobayashi Foundation. M.H. was supported by a scholarship from Honjo International Scholarship Foundation and by a student fellowship from Novo Nordisk A/S. Duality of Interest. No potential conflicts of interest relevant to this article were reported. Author Contributions. M.H., N.Y., H.T., G.G., O.S.O., T.H., N.M., S.H., K.M., A.M., and S.S. reviewed the manuscript and participated in discussion of the results. M.H., N.Y., G.G., O.S.O., T.H., N.M., S.H., and A.M. performed experiments. M.H., N.Y., and S.S. designed the study, analyzed data, discussed the data, and wrote the manuscript. H.T. and K.M. contributed to analysis and discussion of the data and edited the manuscript. S.S. conceived the project. S.S. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Prior Presentation. Parts of this study were presented in abstract form at the 52nd Annual Meeting of the European Association for the Study of Diabetes, Munich, Germany, 12–16 September 2016, and at the 53rd Annual Meeting of the European Association for the Study of Diabetes, Lisbon, Portugal, 11–15 September 2017.
Publisher Copyright:
© 2018 by the American Diabetes Association.
PY - 2018/9/1
Y1 - 2018/9/1
N2 - B-Cell-b-cell interactions are required for normal regulation of insulin secretion. We previously found that formation of spheroid clusters (called K20-SC) from MIN6-K20 clonal b-cells lacking incretin-induced insulin secretion (IIIS) under monolayer culture (called K20-MC) drastically induced incretin responsiveness. Here we investigated the mechanism by which an incretin-unresponsive state transforms to an incretin-responsive state using K20-SC as a model. Glutamate production by glucose through the malate-aspartate shuttle and cAMP signaling, both of which are critical for IIIS, were enhanced in K20-SC. SC formed from b-cells deficient for aspartate aminotransferase 1, a critical enzyme in the malate-aspartate shuttle, exhibited reduced IIIS. Expression of the sodium-coupled neutral amino acid transporter 5 (SNAT5), which is involved in glutamine transport, was downregulated in K20-SC and pancreatic islets of normal mice but was upregulated in K20-MC and islets of rodent models of obesity and diabetes, both of which exhibit impaired IIIS. Inhibition of SNAT5 significantly increased cellular glutamate content and improved IIIS in islets of these models and in K20-MC. These results suggest that suppression of SNAT5 activity, which results in increased glutamate production, and enhancement of cAMP signaling endows incretin-unresponsive b-cells with incretin responsiveness.
AB - B-Cell-b-cell interactions are required for normal regulation of insulin secretion. We previously found that formation of spheroid clusters (called K20-SC) from MIN6-K20 clonal b-cells lacking incretin-induced insulin secretion (IIIS) under monolayer culture (called K20-MC) drastically induced incretin responsiveness. Here we investigated the mechanism by which an incretin-unresponsive state transforms to an incretin-responsive state using K20-SC as a model. Glutamate production by glucose through the malate-aspartate shuttle and cAMP signaling, both of which are critical for IIIS, were enhanced in K20-SC. SC formed from b-cells deficient for aspartate aminotransferase 1, a critical enzyme in the malate-aspartate shuttle, exhibited reduced IIIS. Expression of the sodium-coupled neutral amino acid transporter 5 (SNAT5), which is involved in glutamine transport, was downregulated in K20-SC and pancreatic islets of normal mice but was upregulated in K20-MC and islets of rodent models of obesity and diabetes, both of which exhibit impaired IIIS. Inhibition of SNAT5 significantly increased cellular glutamate content and improved IIIS in islets of these models and in K20-MC. These results suggest that suppression of SNAT5 activity, which results in increased glutamate production, and enhancement of cAMP signaling endows incretin-unresponsive b-cells with incretin responsiveness.
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U2 - 10.2337/db17-1486
DO - 10.2337/db17-1486
M3 - Article
C2 - 29954738
AN - SCOPUS:85052680053
VL - 67
SP - 1795
EP - 1806
JO - Diabetes
JF - Diabetes
SN - 0012-1797
IS - 9
ER -