MicroRNA-7 Regulates the mTOR Pathway and Proliferation in Adult Pancreatic β-Cells

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Abstract
Elucidating the mechanism underlying the poor proliferative capacity of adult pancreatic β-cells is critical to regenerative therapeutic approaches for diabetes. Here, we show that the microRNA (miR)-7/7ab family member miR-7a is enriched in mouse adult pancreatic islets compared with miR-7b. Remarkably, miR-7a targets five components of the mTOR signaling pathway. Further, inhibition of miR-7a activates mTOR signaling and promotes adult β-cell replication in mouse primary islets, which can be reversed by the treatment with a well-known mTOR inhibitor, rapamycin. These data suggest that miR-7 acts as a brake on adult β-cell proliferation. Most importantly, this miR-7–mTOR proliferation axis is conserved in primary human β-cells, implicating miR-7 as a therapeutic target for diabetes.