Reduced activity of mtTFA decreases the transcription in mitochondria isolated from diabetic rat heart.
To evaluate abnormalities in the mitochondrial transcription factor A (mtTFA) function as a cause of mitochondrial dysfunction in diabetes, we measured the mRNA contents of the proteins consisting of the mitochondrial respiratory chain as well as transcriptional and translational activities in the mitochondria isolated from controls and streptozotocin-induced diabetic rat hearts. Using Northern blot analysis, we found 40% reduced mRNA contents of mitochondrial-encoded cytochrome b and ATP synthase subunit 6 in diabetic rat hearts compared with control rats (P < 0.05). These abnormalities were completely recovered by insulin treatment. Furthermore, the mitochondrial activities of transcription and translation were decreased significantly in mitochondria isolated from diabetic rats by 60% (P < 0.01) and 71% (P < 0.01), respectively, compared with control rats. The insulin treatment also completely normalized these abnormalities in diabetic rats. Consistently, gel retardation assay showed a reduced binding of mtTFA to the D-loop of mitochondrial DNA in diabetic rats, although there was no difference in the mtTFA mRNA and protein content between the two groups. On the basis of these findings, a reduced binding activity of mtTFA to the D-loop region in the hearts of diabetic rats may contribute to the decreased mitochondrial protein synthesis.
Kanazawa
Akio
A
Department of Biochemistry, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Nishio
Yoshihiko
Y
Kashiwagi
Atsunori
A
Inagaki
Hidetoshi
H
Kikkawa
Ryuichi
R
Horiike
Kihachiro
K
D000818:Animals; D001665:Binding Sites; D001786:Blood Glucose / Q000032:analysis; D015152:Blotting, Northern; D003573:Cytochrome b Group / Q000235:genetics; D004268:DNA-Binding Proteins; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D007328:Insulin / Q000627:therapeutic use; D015227:Lipid Peroxidation; D008297:Male; D008929:Mitochondria, Heart / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014284:Triiodothyronine / Q000494:pharmacology
D001786:Blood Glucose; D003573:Cytochrome b Group; D004268:DNA-Binding Proteins; D007328:Insulin; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; C489030:Tfam protein, rat; D014157:Transcription Factors; C422562:mitochondrial transcription factor A; D014284:Triiodothyronine; D006861:Hydrogen Peroxide; C412204:ATP synthase subunit 6; D025261:Mitochondrial Proton-Translocating ATPases