Nutritional supplementation with mixed essential amino acids enhances myocyte survival, preserving mitochondrial functional capacity during ischemia-reperfusion injury.
In patients undergoing coronary surgery, the uptake of amino acids, which has been shown to correlate with oxygen consumption, is a mechanism of cardiac adaptation to the iatrogenic ischemia-reperfusion injury associated with cardioplegic arrest. Based on these premises, we sought to determine whether oral supplementation with mixed amino acids may protect the rat heart exposed to ischemia-reperfusion and to address whether this hypothesized cardioprotection is achieved, at least in part, through preservation of the energy-producing properties of mitochondria. Sprague-Dawley rats were fed (by enteral route) a liquid diet, with or without mixed essential amino acids (daily dose of 1 g/kg) for 30 days. Hearts from anesthetized rats were perfused by the Langendorff method and randomized to 3 groups. The control group was perfused with buffer for 60 minutes; the ischemia-reperfusion control and the amino acid-treated groups were exposed to 35 minutes of ischemia, followed by 60 or 120 minutes of reperfusion. Amino acid supplements minimized infarct size (22 +/- 1.8% vs 33 +/- 2.5%; p <0.05) and occurrence of cardiomyocyte apoptosis, as assessed by co-localization of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and caspase-3-positive staining (p <0.01). Long-term treatment with amino acids also reduced the proportion of cardiomyocytes exhibiting immunostaining for cleaved caspase-9 (p <0.01) but was ineffective on processing of caspase-8. Similar results were obtained in the whole heart by caspase activity assays (p <0.01). The lessened activation of caspase-9 detected in amino acid-treated hearts paralleled a strong reduction in mitochondrial release of cytochrome c. Adenosine triphosphate (ATP) content and rate of ATP production in isolated mitochondria were reduced by >75% in control hearts after 2 hours of reperfusion (p <0.05 vs control hearts); these values returned toward those of the control group in hearts supplemented with amino acids (p <0.01). Finally, the oxygen consumption rate in myocardial skinned bundles was markedly reduced in ischemia-reperfusion control hearts and almost normalized in amino acid-treated hearts (approximately 20% and 93% of the value for normoxic hearts; p <0.01). These results suggest that oral amino acid supplementation attenuates the extent of ischemia-reperfusion injury in the rat heart, through preservation of the mitochondria-generated production of high-energy phosphates.
Scarabelli
Tiziano M
TM
Division of Cardiology, St. John Hospital and Medical Center, Wayne State University, Detroit, Michigan, USA. tiziano.scarabelli@stjohn.org
Pasini
Evasio
E
Stephanou
Anastasis
A
Chen-Scarabelli
Carol
C
Saravolatz
Louis
L
Knight
Richard A
RA
Latchman
David S
DS
Gardin
Julius M
JM
D000601:Amino Acids, Essential / Q000008:administration & dosage*; D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism; D010101:Oxygen Consumption; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000178:diet therapy* / Q000473:pathology
D000601:Amino Acids, Essential; D004044:Dietary Proteins