Aasum E, Larsen T S
Department of Medical Physiology, University of Tromso, Norway.
Cardiovasc Res. 1997 Feb;33(2):370-7. doi: 10.1016/s0008-6363(96)00203-9.
High levels of free fatty acids have been shown to impair mechanical recovery and calcium homeostasis of isolated rat hearts following hypothermic perfusion. The objective of the present study was to investigate whether inhibition of fatty acid oxidation through activation of pyruvate dehydrogenase by millimolar concentrations of pyruvate could influence functional recovery and Ca2+ homeostasis after a hypothermic insult.
Ventricular function and myocardial calcium ([Ca]total) were measured in 3 different groups of Langendorff-perfused guinea pig hearts exposed to 40 min hypothermic (15 degrees C) perfusion, followed by 30 min rewarming at 37 degrees C. The hearts were perfused with either 11.1 mM glucose (G), glucose and 1.2 mM palmitate (GP), or glucose, palmitate and 5 mM pyruvate (GPP) as energy substrates.
All groups showed marked elevations in [Ca]total during hypothermia (from 0.6-0.7 mumol.g dry wt-1 to 9.3-12.2 mumol.g dry wt-1 at 40 min hypothermia, P < 0.05), associated with a pronounced increase in left ventricular end-diastolic pressure (LVEDP from 0-2 to 50-60 mmHg). Following rewarming, GP-perfused hearts showed significantly lower recovery of mechanical function compared to both G- and GPP-perfused hearts (% recovery of left ventricular developed pressure: 27 +/- 8 vs. 62 +/- 3 and 62 +/- 8%, respectively, P < 0.05). The reduced mechanical recovery of GP-perfused hearts was associated with elevated [Ca]total. In separate experiments we found that addition of 1.2 mM palmitate reduced glucose oxidation ([14C]glucose) from 1.77 +/- 0.28 mumol.min-1.g dry wt-1 (G-perfused hearts) to 0.15 +/- 0.04 mumol.min-1.g dry wt-1 (GP-perfused hearts, P < 0.05), implying that fatty acids had become the major substrate for oxidative phosphorylation. Fatty acid oxidation was, however, less pronounced after further addition of 5 mM pyruvate. Thus, palmitate oxidation ([3H]palmitate) was more than 40% lower in GPP-perfused than in GP-perfused hearts (0.83 +/- 0.22 vs. 1.41 +/- 0.12 mumol.min-1.g dry wt-1, P < 0.05).
The present results demonstrate impaired ventricular function and calcium homeostasis after hypothermia in guinea pig hearts perfused with fatty acids in addition to glucose, as compared to hearts perfused with glucose alone. Furthermore, we show that these unfavourable effects of fatty acids can be overcome by an exogenous supply of pyruvate.
已有研究表明，高水平的游离脂肪酸会损害低温灌注后离体大鼠心脏的机械功能恢复和钙稳态。本研究的目的是探讨通过毫摩尔浓度的丙酮酸激活丙酮酸脱氢酶来抑制脂肪酸氧化是否会影响低温损伤后的功能恢复和Ca2+稳态。
对3组Langendorff灌注的豚鼠心脏进行测量，使其暴露于40分钟的低温（15摄氏度）灌注，随后在37摄氏度复温30分钟。心脏分别用11.1 mM葡萄糖（G）、葡萄糖和1.2 mM棕榈酸（GP）或葡萄糖、棕榈酸和5 mM丙酮酸（GPP）作为能量底物进行灌注。
所有组在低温期间[Ca]总量均显著升高（低温40分钟时从0.6 - 0.7 μmol·g干重-1升至9.3 - 12.2 μmol·g干重-1，P < 0.05），同时左心室舒张末期压力显著增加（LVEDP从0 - 2 mmHg升至50 - 60 mmHg）。复温后，与G组和GPP组灌注的心脏相比，GP组灌注的心脏机械功能恢复明显较低（左心室发育压力恢复百分比：分别为27 ± 8% vs. 62 ± 3%和62 ± 8%，P < 0.05）。GP组灌注心脏机械功能恢复降低与[Ca]总量升高有关。在单独实验中，我们发现添加1.2 mM棕榈酸可使葡萄糖氧化（[14C]葡萄糖）从1.77 ± 0.28 μmol·min-1·g干重-1（G组灌注心脏）降至0.15 ± 0.04 μmol·min-1·g干重-1（GP组灌注心脏，P < 0.05），这意味着脂肪酸已成为氧化磷酸化的主要底物。然而，进一步添加5 mM丙酮酸后，脂肪酸氧化不那么明显。因此，GPP组灌注心脏中棕榈酸氧化（[3H]棕榈酸）比GP组灌注心脏低40%以上（0.83 ± 0.22 vs. 1.41 ± 0.12 μmol·min-1·g干重-1，P < 0.05）。
目前的结果表明，与仅用葡萄糖灌注的心脏相比，在葡萄糖基础上添加脂肪酸灌注的豚鼠心脏在低温后心室功能和钙稳态受损。此外，我们表明外源性供应丙酮酸可以克服脂肪酸的这些不利影响。
