HIGH-RATES OF FATTY-ACID OXIDATION DURING REPERFUSION OF ISCHEMIC HEARTS ARE ASSOCIATED WITH A DECREASE IN MALONYL-COA LEVELS DUE TO AN INCREASE IN 5'-AMP-ACTIVATED PROTEIN-KINASE INHIBITION OF ACETYL-COA CARBOXYLASE
N. Kudo et al., HIGH-RATES OF FATTY-ACID OXIDATION DURING REPERFUSION OF ISCHEMIC HEARTS ARE ASSOCIATED WITH A DECREASE IN MALONYL-COA LEVELS DUE TO AN INCREASE IN 5'-AMP-ACTIVATED PROTEIN-KINASE INHIBITION OF ACETYL-COA CARBOXYLASE, The Journal of biological chemistry, 270(29), 1995, pp. 17513-17520
We determined whether high fatty acid oxidation rates during aerobic r
eperfusion of ischemic hearts could be explained by a decrease in malo
nyl-CoA levels, which would relieve inhibition of carnitine palmitoylt
ransferase 1, the rate limiting enzyme involved in mitochondrial uptak
e of fatty acids. Isolated working rat hearts perfused with 1.2 mM pal
mitate were subjected to 30 min of global ischemia, followed by 60 min
of aerobic reperfusion. Fatty acid oxidation rates during reperfusion
were 136% higher than rates seen in aerobically perfused control hear
ts, despite the fact that cardiac work recovered to only 16% of pre-is
chemic values. Neither the activity of carnitine palmitoyltransferase
1, or the IC50 value of malonyl-CoA for carnitine palmitoyl transferas
e 1 were altered in mitochondria isolated from aerobic, ischemic, or r
eperfused ischemic hearts. Levels of malonyl-CoA were extremely low at
the end of reperfusion compared to levels seen in aerobic controls, a
s was the activity of acetyl-CoA carboxylase, the enzyme which produce
s malonyl-CoA. The activity of 5'-AMP activated protein kinase, which
has been shown to phosphorylate and inactivate acetyl CoA carboxylase
in other tissues, was significantly increased at the end of ischemia,
and remained elevated throughout reperfusion. These results suggest th
at accumulation of 5'-AMP during ischemia results in an activation of
AMP-activated protein kinase, which phosphorylates and inactivates ACC
during reperfusion. The subsequent decrease in malonyl-CoA levels wil
l result in accelerated fatty acid oxidation rates during reperfusion
of ischemic hearts.