Age-related increase in 4-hydroxynonenal adduction to rat heart alpha-ketoglutarate dehydrogenase does not cause loss of its catalytic activity.
4-hydroxynonenal (HNE), a product of omega-6 polyunsaturated fatty acid peroxidation, impairs mitochondrial respiration in vitro by adducting the alpha-ketoglutarate dehydrogenase complex (KGDC) and inhibiting its activity. The present study seeks to define whether aging increases HNE adduction to rat heart KGDC, and whether such adduction impacts KGDC activity. We found that hearts from old rats exhibit significantly (p< or =0.01) higher HNE-modified mitochondrial proteins when compared with those from young rats. Among these proteins, dihydrolipoamide succinyltransferase, the E2k component of KGDC, was most markedly modified (p< or =0.01) by HNE with age. As opposed to that seen in vitro, no significant change in electrophoretic mobility or impairment in enzyme activity was observed. On the contrary, KGDC activity increased onefold (p< or =0.01) in old rats, suggesting that the aging myocardium is not affected by HNE adduction or compensates for such damage. Further analysis revealed that heightened KGDC activity was not due to increased protein content or gene expression, but correlates with a lower Km for alpha-ketoglutarate. Thus, contrary to that observed in vitro, the measurement of HNE-KGDC adduct in rat heart is more relevant as a marker of age-related protein oxidation than a factor of mitochondrial dysfunction.
Linus Pauling Institute and Department of Biochemistry and Biophysics, Oregon State University, 571 Weniger Hall, Corvallis, OR 97331, USA.
Régis
R
Moreau
Shi-Hua D
SH
Heath
Catalin E
CE
Doneanu
J Gordon
JG
Lindsay
Tory M
TM
Hagen
D000217:Acyltransferases / Q000032:analysis / Q000737:chemistry; D000284:Administration, Oral; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002384:Catalysis; D003402:Creatine Kinase / Q000032:analysis / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D008058:Dihydrolipoamide Dehydrogenase / Q000032:analysis / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000737:chemistry; D015870:Gene Expression; D007655:Ketoglutarate Dehydrogenase Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008929:Mitochondria, Heart / Q000737:chemistry / Q000201:enzymology; D008969:Molecular Sequence Data; D009206:Myocardium / Q000737:chemistry / Q000201:enzymology*; D051381:Rats; D011916:Rats, Inbred F344; D012709:Serum Albumin / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013552:Swine; D008063:Thioctic Acid / Q000494:pharmacology
D000447:Aldehydes; D003432:Cross-Linking Reagents; D004791:Enzyme Inhibitors; D012709:Serum Albumin; D008063:Thioctic Acid; D007655:Ketoglutarate Dehydrogenase Complex; D008058:Dihydrolipoamide Dehydrogenase; D000217:Acyltransferases; C021515:dihydrolipoamide succinyltransferase; D003402:Creatine Kinase; C027576:4-hydroxy-2-nonenal