Division of Experimental Medicine, University Hospital Center, Charleroi, Belgium.
Department of Biostatistics, University Hospital of Liège, Liège, Belgium.
Nutrition. 2019 Nov-Dec;67-68:110517. doi: 10.1016/j.nut.2019.05.009. Epub 2019 Jun 12.
Dietary and energetic restrictions are endowed with protection against experimental injuries. However, a drop in cell energetic status under a critical threshold may prevent protection, as previously observed for livers isolated from rat donors undergoing 18-h fasting versus feeding. The aim of this study was to further explore, in the latter model, links between nutritional status, energy availability, and protection through lengthening of rat fasting to 24 h and withdrawal of energy sources from perfusions.
Energy-free perfused ex vivo livers from fed, 18-h-fasted, and 24-h-fasted rats were studied during 135 min for cytolysis (potassium, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase releases in perfusates), cell deaths (activated caspase-3 [apoptosis], LC3 II/actin and p62/actin ratios [autophagy]), glycogen stores, glucose, and lactate production.
Cytolysis was significantly increased by 18-h and 24-h fasting versus feeding but unexpectedly the increase was less for 24-h fasting than it was for 18-h fasting. Apoptotic marker caspase 3 significantly increased under fed and 18-h fasting but not 24-h fasting conditions. Autophagic marker LC3 II/actin significantly increased during perfusion in the 24-h fasted group but neither fed nor 18-h fasted groups. Autophagic induction also was supported by a drop in the p62/actin ratio. Under perfusion with 3-methyladenine, a standard autophagy inhibitor, protection and enhanced autophagy provided by 24-h but not 18-h fasting were lost without affecting apoptosis.
Liver protections are obviously influenced by nutritional status in a way that is parallel to hepatic energy mobilization capacities (glycogen plus autophagy) with a decreased order of protection: Fed >24-h fasted >18-h fasted >24-h fasted + 3-methyladenine livers. By showing that autophagy induction limits starvation-induced cytolysis, the present work supports the emerging view that autophagy inducers might improve health benefits of diet restriction.
饮食和能量限制具有防止实验性损伤的作用。然而，细胞能量状态下降到临界阈值以下可能会阻止保护，正如先前观察到的，从接受 18 小时禁食和喂养的大鼠供体中分离的肝脏。本研究的目的是进一步探索在后一种模型中，营养状况、能量供应与保护之间的联系，方法是延长大鼠禁食时间至 24 小时，并从灌注中去除能量来源，对喂食、18 小时禁食和 24 小时禁食的大鼠离体能量自由灌注肝脏进行 135 分钟的研究，以研究细胞溶解（灌流液中钾、天冬氨酸氨基转移酶、丙氨酸氨基转移酶和乳酸脱氢酶释放）、细胞死亡（活化的 caspase-3 [凋亡]、LC3 II/肌动蛋白和 p62/肌动蛋白比值 [自噬]）、糖原储存、葡萄糖和乳酸生成。
与喂食相比，18 小时和 24 小时禁食显著增加了细胞溶解，但出乎意料的是，24 小时禁食的增加程度低于 18 小时禁食。在喂食和 18 小时禁食条件下，凋亡标志物 caspase 3 显著增加，但在 24 小时禁食条件下没有增加。在 24 小时禁食组的灌注过程中，自噬标志物 LC3 II/肌动蛋白显著增加，而在喂食和 18 小时禁食组中均未增加。自噬诱导也支持 p62/肌动蛋白比值的下降。在 3-甲基腺嘌呤（一种标准的自噬抑制剂）灌注下，24 小时禁食而不是 18 小时禁食提供的保护和增强的自噬丧失，而不影响凋亡。
肝脏保护显然受到营养状况的影响，这种影响与肝能量动员能力（糖原加自噬）平行，保护作用依次减弱：Fed>24-h 禁食>18-h 禁食>24-h 禁食+3-甲基腺嘌呤肝脏。通过显示自噬诱导可限制饥饿诱导的细胞溶解，本工作支持自噬诱导剂可能改善饮食限制的健康益处的新观点。
