title: Depletion of mitochondrial DNA causes impaired glucose utilization and insulin resistance in L6 GLUT4myc myocytes.
abstract: Mitochondrial dysfunction contributes to a number of human diseases, such as hyperlipidemia, obesity, and diabetes. The mutation and reduction of mitochondrial DNA (mtDNA) have been suggested as factors in the pathogenesis of diabetes. To elucidate the association of cellular mtDNA content and insulin resistance, we produced L6 GLUT4myc myocytes depleted of mtDNA by long term treatment with ethidium bromide. L6 GLUT4myc cells cultured with 0.2 mug/ml ethidium bromide (termed depleted cells) revealed a marked decrease in cellular mtDNA and ATP content, concomitant with a lack of mRNAs encoded by mtDNA. Interestingly, the mtDNA-depleted cells showed a drastic decrease in basal and insulin-stimulated glucose uptake, indicating that L6 GLUT4myc cells develop impaired glucose utilization and insulin resistance. The repletion of mtDNA normalized basal and insulin-stimulated glucose uptake. The mRNA level and expression of insulin receptor substrate (IRS)-1 associated with insulin signaling were decreased by 76 and 90% in the depleted cells, respectively. The plasma membrane (PM) GLUT4 in the basal state was decreased, and the insulin-stimulated GLUT4 translocation to the PM was drastically reduced by mtDNA depletion. Moreover, insulin-stimulated phosphorylation of IRS-1 and Akt2/protein kinase B were drastically reduced in the depleted cells. Those changes returned to control levels after mtDNA repletion. Taken together, our data suggest that PM GLUT4 content and insulin signal pathway intermediates are modulated by the alteration of cellular mtDNA content, and the reductions in the expression of IRS-1 and insulin-stimulated phosphorylation of IRS-1 and Akt2/protein kinase B are associated with insulin resistance in the mtDNA-depleted L6 GLUT4myc myocytes.
authors.affiliation: Department of Biochemistry, College of Medicine, Dongguk University, Kyungju 780-714, Korea.
authors.forename: Seung Y
authors.initials: SY
authors.lastname: Park
authors.forename: Guem H
authors.initials: GH
authors.lastname: Choi
authors.forename: Hyo I
authors.initials: HI
authors.lastname: Choi
authors.forename: Jiwon
authors.initials: J
authors.lastname: Ryu
authors.forename: Chan Y
authors.initials: CY
authors.lastname: Jung
authors.forename: Wan
authors.initials: W
authors.lastname: Lee
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004272:DNA, Mitochondrial / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism; D004996:Ethidium / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D032342:Muscle Cells / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D012313:RNA / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D000255:Adenosine Triphosphate; D017931:DNA Primers; D004272:DNA, Mitochondrial; D003847:Deoxyglucose; D004996:Ethidium; D005947:Glucose; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D012313:RNA; C526292:IRS1 protein, human; C526296:Irs1 protein, rat; C495692:SLC2A4 protein, human; C495694:Slc2a4 protein, rat; C494921:AKT2 protein, human; C494923:Akt2 protein, rat