Argonaute2 mediates compensatory expansion of the pancreatic ß-cell

Pancreatic ß-cells adapt to compensate for the increased metabolic demand during insulin resistance. While the microRNA pathway has an essential role in the expansion of ß-cell mass, the extent of its contribution is unclear. Here we show that miR-184 is silenced in the pancreatic islets of several insulin-resistant mouse models and in the islets of type-2 diabetic human subjects. Reduction of miR-184 promotes the expression of its target Argonaute2 (Ago2), a component of the microRNA-induced silencing complex. While over-expression of Ago2 increased ß-cell proliferation, conditional deletion decreased ß-cell number. Moreover, restored expression of miR-184 in leptin-deficient ob/ob mice decreased Ago2 and prevented compensatory ß-cell expansion. Loss of Ago2 expression during insulin resistance blocked ß-cell growth and relieved the regulation of miR-375-targeted genes including the growth suppressor Cadm1. This study identifies the regulation of Ago2 by miR-184 as an essential component of the compensatory response to promote proliferation during insulin resistance. MIN6 cells were transfected with Doxycyline responsive plasmids including the tetO-184 construct in biological triplicates for every time point. The conditions included untransfected control (CTR, induced), Transfected Control (TC, uninduced) along the time points of miR-184 overexpression in 16, 24, 48, and 72 hours of doxycycline treatment.