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Lack of a direct metabolic effect of fructose, 1,6-diphosphate in ischemic myocardium
Insights
Fructose 1,6-diphosphate (FdP) did not directly protect ischemic myocardium in a canine model. Studies showed FdP infusion did not improve high-energy phosphate levels or prevent lactate accumulation in ischemic heart tissue.
Area of Science:
- Cardiovascular Physiology
- Metabolic Biochemistry
Background:
- Fructose 1,6-diphosphate (FdP) is suggested to protect ischemic myocardium.
- The direct cardiac action of FdP in ischemia remains unclear.
Purpose of the Study:
- To investigate the direct protective effects of Fructose 1,6-diphosphate on the heart during ischemia.
- To determine if FdP influences myocardial energy metabolism and contractility directly.
Main Methods:
- A canine model with bilaterally reduced coronary perfusion was utilized.
- Fructose 1,6-diphosphate (FdP) or saline was infused into separate coronary arteries.
- Myocardial biopsies were analyzed for ATP, phosphocreatine (PC), and lactate; contractility was measured.
Main Results:
- Ischemic tissue treated with FdP showed no significant difference in ATP and phosphocreatine levels compared to saline-treated ischemic tissue.
- Lactate levels were similarly elevated in both ischemic groups.
- FdP infusion directly into the coronary artery depressed myocardial contractility under both ischemic and non-ischemic conditions.
Conclusions:
- Fructose 1,6-diphosphate does not exert a direct protective effect on the myocardium during ischemia.
- The observed depression of contractility suggests FdP may have detrimental direct cardiac effects.
- Potential protective actions of FdP in ischemia, if they exist, are not mediated by direct interaction with cardiac tissue.
Abstract:
Fructose 1,6-diphosphate (FdP) reportedly protects ischemic myocardium. To determine whether this is a direct action on the heart, we used a canine model in which two coronary arteries were perfused at identical but reduced rates. Into one artery we infused FdP (total doses of 400 mg or 1.8 g) while the other received 0.9% NaCl. After 1 h, biopsies were taken from a normal region and the two ischemic regions and were analyzed for ATP, phosphocreatine (PC), and lactate content. In the 0.9% NaCl-treated ischemic tissue, ATP and PC fell to half the nonischemic levels. The FdP-treated tissue exhibited high-energy phosphate levels similar to the 0.9% NaCl-treated tissue with no significant differences between the two ischemic areas. Lactate levels in both ischemic areas were elevated threefold above nonischemic levels. Contractility studies showed that infusion of FdP directly into the coronary artery depressed contractility in both nonischemic and ischemic conditions. Our data show that, if FdP does have a protective action in ischemia, it is not through a direct action on the heart.