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Retinoid X receptor α overexpression alleviates mitochondrial dysfunction-induced insulin resistance through transcriptional regulation of insulin receptor substrate 1.

Lee SE, Koo YD, Lee JS, Kwak SH, Jung HS, Cho YM, Park YJ, Chung SS, Park KS - Mol. Cells (2015)

Bottom Line: RXRα overexpression also increased IRS1 transcription and mitochondrial function.Because RXRα overexpression, knock-down, or activation by LG1506 regulated IRS1 transcription mostly independently of mitochondrial function, it is likely that RXRα directly regulates IRS1 transcription.Consistent with the hypothesis, we showed that RXRα bound to the IRS1 promoter as a heterodimer with peroxisome proliferator-activated receptor δ (PPARδ).

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul 110-744, Korea.

ABSTRACT
Mitochondrial dysfunction is associated with insulin resistance and diabetes. We previously showed that retinoid X receptor α (RXRα) played an important role in transcriptional regulation of oxidative phosphorylation (OXPHOS) genes in cells with mitochondrial dysfunction caused by mitochondrial DNA mutation. In this study, we investigated whether mitochondrial dysfunction induced by incubation with OXPHOS inhibitors affects insulin receptor substrate 1 (IRS1) mRNA and protein levels and whether RXRα activation or overexpression can restore IRS1 expression. Both IRS1 and RXRα protein levels were significantly reduced when C2C12 myotubes were treated with the OXPHOS complex inhibitors, rotenone and antimycin A. The addition of RXRα agonists, 9-cis retinoic acid (9cRA) and LG1506, increased IRS1 transcription and protein levels and restored mitochondrial function, which ultimately improved insulin signaling. RXRα overexpression also increased IRS1 transcription and mitochondrial function. Because RXRα overexpression, knock-down, or activation by LG1506 regulated IRS1 transcription mostly independently of mitochondrial function, it is likely that RXRα directly regulates IRS1 transcription. Consistent with the hypothesis, we showed that RXRα bound to the IRS1 promoter as a heterodimer with peroxisome proliferator-activated receptor δ (PPARδ). These results suggest that RXRα overexpression or activation alleviates insulin resistance by increasing IRS1 expression.

No MeSH data available.


Related in: MedlinePlus

RXRα agonists restore mitochondrial function and IRS transcription impaired by rotenone. C2C12 myoblasts were differentiated to myotubes and treated with rotenone (3 μM) or antimycin A (10 μM) for 24 h. (A) Cells were lysed and then Western blot analyses were performed with the specific antibodies. (B) Total RNAs were isolated and real time quantitative PCR was performed. The mRNA levels of each gene were normalized by that of GAPDH. The value of Veh was set to 1 and the others were expressed as the relatives to that. The data are the means ± SEM of 3 experiments. *, P < 0.05 vs. Veh. (C-F) C2C12 myotubes were treated with rotenone (3 μM) for 24 h and then the media was replaced to the fresh media containing DMSO (Veh), 9cRA (5 μM) or LG1506 (2 μM) for 18 h. (C) Cells were lysed and ATP contents were measured (n = 6). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (D) Cell lysates were subjected to Western blot analysis. (E) The IRS1 mRNA levels were measured by real time PCR (n = 5). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (F) Insulin (100 nM) was added 15 min before harvesting. Cell lysates were subjected to the Western blot analysis.
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f1-molce-38-4-356: RXRα agonists restore mitochondrial function and IRS transcription impaired by rotenone. C2C12 myoblasts were differentiated to myotubes and treated with rotenone (3 μM) or antimycin A (10 μM) for 24 h. (A) Cells were lysed and then Western blot analyses were performed with the specific antibodies. (B) Total RNAs were isolated and real time quantitative PCR was performed. The mRNA levels of each gene were normalized by that of GAPDH. The value of Veh was set to 1 and the others were expressed as the relatives to that. The data are the means ± SEM of 3 experiments. *, P < 0.05 vs. Veh. (C-F) C2C12 myotubes were treated with rotenone (3 μM) for 24 h and then the media was replaced to the fresh media containing DMSO (Veh), 9cRA (5 μM) or LG1506 (2 μM) for 18 h. (C) Cells were lysed and ATP contents were measured (n = 6). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (D) Cell lysates were subjected to Western blot analysis. (E) The IRS1 mRNA levels were measured by real time PCR (n = 5). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (F) Insulin (100 nM) was added 15 min before harvesting. Cell lysates were subjected to the Western blot analysis.

Mentions: We first determined whether IRS1 and RXRα protein levels were affected by mitochondrial dysfunction. C2C2 myoblasts were differentiated to myotubes, and then treated with the OXPHOS complex inhibitors rotenone (complex I inhibitor) and antimycin A (complex III inhibitor) for 24 h. Both IRS1 and RXRα protein levels were markedly decreased after treatments (Fig. 1A). Real time quantitative PCR was used to determine whether the reduction of IRS1 and RXRα proteins was due to decreased mRNA levels. Both IRS1 and RXRα mRNA levels were significantly reduced following treatment with rotenone or antimycin A (Fig. 1B), suggesting that IRS1 and RXRα transcription are suppressed in the setting of mitochondrial dysfunction.


Retinoid X receptor α overexpression alleviates mitochondrial dysfunction-induced insulin resistance through transcriptional regulation of insulin receptor substrate 1.

Lee SE, Koo YD, Lee JS, Kwak SH, Jung HS, Cho YM, Park YJ, Chung SS, Park KS - Mol. Cells (2015)

RXRα agonists restore mitochondrial function and IRS transcription impaired by rotenone. C2C12 myoblasts were differentiated to myotubes and treated with rotenone (3 μM) or antimycin A (10 μM) for 24 h. (A) Cells were lysed and then Western blot analyses were performed with the specific antibodies. (B) Total RNAs were isolated and real time quantitative PCR was performed. The mRNA levels of each gene were normalized by that of GAPDH. The value of Veh was set to 1 and the others were expressed as the relatives to that. The data are the means ± SEM of 3 experiments. *, P < 0.05 vs. Veh. (C-F) C2C12 myotubes were treated with rotenone (3 μM) for 24 h and then the media was replaced to the fresh media containing DMSO (Veh), 9cRA (5 μM) or LG1506 (2 μM) for 18 h. (C) Cells were lysed and ATP contents were measured (n = 6). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (D) Cell lysates were subjected to Western blot analysis. (E) The IRS1 mRNA levels were measured by real time PCR (n = 5). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (F) Insulin (100 nM) was added 15 min before harvesting. Cell lysates were subjected to the Western blot analysis.
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f1-molce-38-4-356: RXRα agonists restore mitochondrial function and IRS transcription impaired by rotenone. C2C12 myoblasts were differentiated to myotubes and treated with rotenone (3 μM) or antimycin A (10 μM) for 24 h. (A) Cells were lysed and then Western blot analyses were performed with the specific antibodies. (B) Total RNAs were isolated and real time quantitative PCR was performed. The mRNA levels of each gene were normalized by that of GAPDH. The value of Veh was set to 1 and the others were expressed as the relatives to that. The data are the means ± SEM of 3 experiments. *, P < 0.05 vs. Veh. (C-F) C2C12 myotubes were treated with rotenone (3 μM) for 24 h and then the media was replaced to the fresh media containing DMSO (Veh), 9cRA (5 μM) or LG1506 (2 μM) for 18 h. (C) Cells were lysed and ATP contents were measured (n = 6). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (D) Cell lysates were subjected to Western blot analysis. (E) The IRS1 mRNA levels were measured by real time PCR (n = 5). *, P < 0.05 vs. Veh; #, P < 0.05 vs. rotenone only. (F) Insulin (100 nM) was added 15 min before harvesting. Cell lysates were subjected to the Western blot analysis.
Mentions: We first determined whether IRS1 and RXRα protein levels were affected by mitochondrial dysfunction. C2C2 myoblasts were differentiated to myotubes, and then treated with the OXPHOS complex inhibitors rotenone (complex I inhibitor) and antimycin A (complex III inhibitor) for 24 h. Both IRS1 and RXRα protein levels were markedly decreased after treatments (Fig. 1A). Real time quantitative PCR was used to determine whether the reduction of IRS1 and RXRα proteins was due to decreased mRNA levels. Both IRS1 and RXRα mRNA levels were significantly reduced following treatment with rotenone or antimycin A (Fig. 1B), suggesting that IRS1 and RXRα transcription are suppressed in the setting of mitochondrial dysfunction.

Bottom Line: RXRα overexpression also increased IRS1 transcription and mitochondrial function.Because RXRα overexpression, knock-down, or activation by LG1506 regulated IRS1 transcription mostly independently of mitochondrial function, it is likely that RXRα directly regulates IRS1 transcription.Consistent with the hypothesis, we showed that RXRα bound to the IRS1 promoter as a heterodimer with peroxisome proliferator-activated receptor δ (PPARδ).

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul 110-744, Korea.

ABSTRACT
Mitochondrial dysfunction is associated with insulin resistance and diabetes. We previously showed that retinoid X receptor α (RXRα) played an important role in transcriptional regulation of oxidative phosphorylation (OXPHOS) genes in cells with mitochondrial dysfunction caused by mitochondrial DNA mutation. In this study, we investigated whether mitochondrial dysfunction induced by incubation with OXPHOS inhibitors affects insulin receptor substrate 1 (IRS1) mRNA and protein levels and whether RXRα activation or overexpression can restore IRS1 expression. Both IRS1 and RXRα protein levels were significantly reduced when C2C12 myotubes were treated with the OXPHOS complex inhibitors, rotenone and antimycin A. The addition of RXRα agonists, 9-cis retinoic acid (9cRA) and LG1506, increased IRS1 transcription and protein levels and restored mitochondrial function, which ultimately improved insulin signaling. RXRα overexpression also increased IRS1 transcription and mitochondrial function. Because RXRα overexpression, knock-down, or activation by LG1506 regulated IRS1 transcription mostly independently of mitochondrial function, it is likely that RXRα directly regulates IRS1 transcription. Consistent with the hypothesis, we showed that RXRα bound to the IRS1 promoter as a heterodimer with peroxisome proliferator-activated receptor δ (PPARδ). These results suggest that RXRα overexpression or activation alleviates insulin resistance by increasing IRS1 expression.

No MeSH data available.


Related in: MedlinePlus