The Journal of Nutrition Biochemical, Molecular, and Genetic Mechanisms Insulin Modulates the Na+/Mg2+ Exchanger

Background: Magnesium deficiency is a common complication of diabetes with an unclear molecular background. Objective: Our aim was to investigate the effect of the insulin (INS)-signaling pathway (ISP) on the regulation of Mg2+ efflux (Mg2+E) conducted by solute carrier family 41, member A1 (SLC41A1; activated by protein kinase A) in transgenic human embryonic kidney (HEK) 293 cells. Methods: HEK293 cells overexpressing SLC41A1 were loaded with the Mg2+ fluorescent indicator mag-fura-2 and Mg2+. Measurements of Mg2+E were conducted in Mg2+-free buffer by using fast-filter fluorescence spectrometry. We examined the effects of INS, inhibitors of ISP or p38 mitogen-activated protein kinase (p38 MAPK), an activator of adenylate cyclase (ADC), and their combinations on SLC41A1-attributed Mg2+E. Results: The application of 400 mU/mL INS inhibited SLC41A1-mediated Mg2+E by up to 50.6 % compared with INS-untreated cells (P < 0.001). Moreover, INS evoked the early onset ofMg2+ release from intracellular stores. The application of 0.1 mM wortmannin or 10 mM zardaverine (both ISP inhibitors) restored SLC41A1 Mg2+E capacity in the presence of INS to the same levels seen in INS-untreated cells. The simultaneous application of 10 mM forskolin, and ADC activator, and INS resulted in a reduction of Mg2+E of up to 59 % compared with untreated cells (P < 0.001), which was comparable to that seen in cells treated with INS alone. Inhibition of p38 MAPK with 10 mM SB 202190 (SB) in the absence of INS resulted in