Selenomethionine Modulates Insulin Secretion in the MIN6-K8 Mouse Insulinoma Cell Line

Selenium is an essential trace element that has gained interest for its potential role in glucose homeostasis. The purpose of the present study was to investigate the impact of selenium supplementation as selenomethionine (SeMet) on insulin secretion in MIN6-K8 cells, a model of pancreatic -cells. We found that 40 μM and 80 μM SeMet significantly enhanced percent insulin secretion at low (2.8 mM), intermediate (11.7 mM), and high (16.7 mM) glucose stimulation. SeMet also increased tolbutamide- or KCl-induced percent insulin secretion at 40 μM and 80 μM. Ca2+ influx was only reduced with 80 μM SeMet. RNA-sequencing showed that 40 μM SeMet supplementation upregulated expression of selenoprotein H (SelH) and thioredoxin reductase 1 (Txnrd 1) and downregulated expression of glutathione peroxidase 3 (Gpx3), selenoprotein O (SelO), and selenoprotein P (SelP). Gpx3 knockdown increased both percent and total insulin release with high glucose stimulation. SelP knockdown increased insulin release at high glucose. In conclusion, high SeMet supplementation augments insulin secretion, while reductions in Gpx3 and SelP expression, from SeMet supplementation or via silencing, augment -cell function in the MIN6-K8 cell line. These studies support a putative role for selenium and selenoproteins in the regulation of glucose homeostasis and diabetes risk.