Role of ketone bodies in perinatal myocardial energy metabolism.

Metabolic changes at around the time of birth are crucial for life. Here we review the energy utilization in the myocardium, emphasizing ketone body metabolism. Before birth, glucose and lactate are the major energy substrates for the myocardium. Long-chain fatty acids (LCFA) are normally not available as an energy substrate for the fetal heart; however, when LCFA are supplied artificially in near-term fetal lambs, they are readily oxidized. Hence the myocardium has no limitation to its ability to use LCFA before birth. After birth, lactate remains an important energy source for the myocardium, whereas the contribution of glucose to myocardial energy production decreases despite an increase in the supply of glucose. The oxidation of ketone bodies increases after birth in relation to an increase in supply. However, ketone bodies account for only 7% of left ventricular oxygen consumption. The supply and contribution of LCFA to the myocardium increases after birth; the oxidation of LCFA accounts for most of the left ventricular oxygen consumption. Hence the role of ketone bodies in myocardial metabolism is limited. However, there are interesting observations on interference between the uptake of different substrates and the release of ketone bodies, which might have consequences for our interpretation of ketone body utilization.