Abstract
Background: A low level of serum magnesium ion (Mg2+) is associated with type 2 diabetes mellitus (T2D). However, the molecular mechanism of Mg2+ deficiency has not been fully clarified. The current study sought to assesses the effect of reactive oxygen species on the expression of Mg2+ channels and miRNA. Methods: The expression of Mg2+ channels and miRNA were examined by real-time polymerase chain reaction. Intracellular Mg2+ concentration was measured by Magnesium Green fluorescence measurement. Results: The mRNA level of transient receptor potential melastatin 6 (TRPM6), which functions as Mg2+ influx channel in the distal convoluted tubule (DCT) of the kidney, was decreased by glycated albumin (GA), but not by insulin in rat renal tubule-derived NRK-52E cells. The mRNA levels of TRPM7, a homologue of TRPM6, and CNNM2, a Mg2+ efflux transporter located at the basolateral membrane of DCT, were changed by neither GA nor insulin. The generation of reactive oxygen species (ROS) was increased by GA. Hydrogen peroxide (H2O2) dose-dependently decreased TRPM6 mRNA, but it inversely increased the reporter activity of TRPM6. H2O2 accelerated the degradation of TRPM6 mRNA in actinomycin D assay without affecting TRPM7 and CNNM2 mRNA expressions. Nine miRNAs were considered as candidates for the regulator of stability of TRPM6 mRNA. Among them, miR-24-3p expression was increased by H2O2. The H2O2-induced reduction of TRPM6 mRNA was rescued by miR-24-3p siRNA. Magnesium Green fluorescence measurement showed that Mg2+ influx is suppressed by H2O2, which was rescued by an antioxidant and miR-24-3p siRNA. Conclusions: We suggest that GA decreases TRPM6 expression mediated by the elevation of ROS and miR-24-3p in renal tubular epithelial cells of T2D.
Highlights
The body content of magnesium is controlled by the absorption in the intestine and reabsorption in the kidney
We suggest that glycated albumin (GA) decreases transient receptor potential melastatin 6 (TRPM6) expression mediated by the elevation of reactive oxygen species (ROS) and miR-24-3p in renal tubular epithelial cells of type 2 diabetes mellitus (T2D)
We revealed that epidermal growth factor (EGF) increases the transcriptional activity of TRPM6 mediated through the activation of a mitogen-activated protein kinase kinase (MEK) and extracellular signalregulated kinase (ERK), so-called MEK/ERK signaling pathway using rat renal tubular NRK-52E and human embryonic kidney 293 (HEK293) cells [12,13]
Summary
The body content of magnesium is controlled by the absorption in the intestine and reabsorption in the kidney. Transient receptor potential melastatin 6 (TRPM6) is located at the apical membrane of DCT, a main site of active renal Mg2+ reabsorption [3], and may facilitate Mg2+ influx from the lumen to the cells. CNNM2, a Mg2+ efflux transporter located at the basolateral membrane, is considered to transport Mg2+ from the cells to the blood in the DCT, but it is controversial [4,5]. Results: The mRNA level of transient receptor potential melastatin 6 (TRPM6), which functions as Mg2+ influx channel in the distal convoluted tubule (DCT) of the kidney, was decreased by glycated albumin (GA), but not by insulin in rat renal tubule-derived NRK-52E cells. The mRNA levels of TRPM7, a homologue of TRPM6, and CNNM2, a Mg2+ efflux transporter located at the basolateral membrane of DCT, were changed by neither GA nor insulin
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