Treatment of C2C12 muscle cells with metformin or the NR4A1 ligand 1,1-bis(3′-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) induced NR4A1 and Glut4 messenger RNA and protein expression. Similar results were observed with buttressed (3- or 3,5-substituted) analogs of DIM-C-pPhOH, including 1,1-bis(3′-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (DIM-C-pPhOH-3-Cl-5-OCH 3), and the buttressed analogs were more potent than DIM-C-pPhOH NR4A1 agonists. Metformin and the bis-indole substituted analogs also induced expression of several glycolytic genes and Rab4, which has previously been linked to enhancing cell membrane accumulation of Glut4 and overall glucose uptake in C2C12 cells, and these responses were also observed after treatment with metformin and the NR4A1 ligands. The role of NR4A1 in mediating the responses induced by the bis-indoles and metformin was determined by knockdown of NR4A1, and this resulted in attenuating the gene and protein expression and enhanced glucose uptake responses induced by these compounds. Our results demonstrate that the bis-indole-derived NR4A1 ligands represent a class of drugs that enhance glucose uptake in C2C12 muscle cells, and we also show that the effects of metformin in this cell line are NR4A1-dependent.
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