It is commonly accepted that brain phospholipids are highly enriched with long-chain polyunsaturated fatty acids (PUFAs). However, the evidence for this remains unclear. We used HPLC-MS to analyze the content and composition of phospholipids in rat brain and compared it to the heart, kidney, and liver. Phospholipids typically contain one PUFA, such as 18:2, 20:4, or 22:6, and one saturated fatty acid, such as 16:0 or 18:0. However, we found that brain phospholipids containing monounsaturated fatty acids in the place of PUFAs are highly elevated compared to phospholipids in the heart, kidney, and liver. The relative content of phospholipid containing PUFAs is ~ 60% in the brain, whereas it is over 90% in other tissues. The most abundant species of phosphatidylcholine (PC) is PC(16:0/18:1) in the brain, whereas PC(18:0/20:4) and PC(16:0/20:4) are predominated in other tissues. Moreover, several major species of plasmanyl and plasmenyl phosphatidylethanolamine are found to contain monounsaturated fatty acid in the brain only. Overall, our data clearly show that brain phospholipids are the least enriched with PUFAs of the four major organs, challenging the common belief that the brain is highly enriched with PUFAs.
BackgroundCardiac arrest (CA) has been a leading cause of death for many decades. Despite years of research, we still do not understand how each organ responds to the reintroduction of blood flow after prolonged CA. Following changes in metabolites of individual organs after CA and resuscitation gives context to the efficiency and limitations of current resuscitation protocols.Methods and ResultsAdult male Sprague–Dawley rats were arbitrarily assigned into 3 groups: control, 20 minutes of CA, or 20 minutes of CA followed by 30 minutes of cardiopulmonary bypass resuscitation. The rats were euthanized by decapitation to harvest brain, heart, kidney, and liver tissues. The obtained tissue samples were analyzed by ultra‐high‐performance liquid chromatography–high‐accuracy mass spectrometry for comprehensive metabolomics evaluation. After resuscitation, the brain showed decreased glycolysis metabolites and fatty acids and increased amino acids compared with control. Similarly, the heart displayed alterations mostly in amino acids. The kidney showed decreased amino acid and fatty acid pools with severely increased tricarboxylic acid cycle metabolites following resuscitation, while the liver showed minimal alterations with slight changes in the lipid pool. Each tissue has a distinct pattern of metabolite changes after ischemia/reperfusion. Furthermore, resuscitation worsens the metabolic dysregulation in the brain and kidney, while it normalizes metabolism in the heart.ConclusionsDeveloping metabolic profiles using a global metabolome analysis identifies the variable nature of metabolites in individual organs after CA and reperfusion, establishing a stark contrast between the normalized heart and liver and the exacerbated brain and kidney, only after the reestablishment of blood circulation.
Cardiac arrest induces whole-body ischemia, which causes damage to multiple organs. Understanding how each organ responds to ischemia/reperfusion is important to develop better resuscitation strategies. Because direct measurement of organ function is not practicable in most animal models, we attempt to use mitochondrial respiration to test efficacy of resuscitation on the brain, heart, kidney, and liver following prolonged cardiac arrest. Male Sprague-Dawley rats are subjected to asphyxia-induced cardiac arrest for 30 min or 45 min, or 30 min cardiac arrest followed by 60 min cardiopulmonary bypass resuscitation. Mitochondria are isolated from brain, heart, kidney, and liver tissues and examined for respiration activity. Following cardiac arrest, a time-dependent decrease in state-3 respiration is observed in mitochondria from all four tissues. Following 60 min resuscitation, the respiration activity of brain mitochondria varies greatly in different animals. The activity after resuscitation remains the same in heart mitochondria and significantly increases in kidney and liver mitochondria. The result shows that inhibition of state-3 respiration is a good marker to evaluate the efficacy of resuscitation for each organ. The resulting state-3 respiration of brain and heart mitochondria following resuscitation reenforces the need for developing better strategies to resuscitate these critical organs following prolonged cardiac arrest.
BackgroundThe concept that resuscitation from cardiac arrest (CA) results in a metabolic injury is broadly accepted, yet patients never receive this diagnosis. We sought to find evidence of metabolic injuries after CA by measuring O2 consumption and CO2 production (VCO 2) in a rodent model. In addition, we tested the effect of inspired 100% O2 on the metabolism.Methods and ResultsRats were anesthetized and randomized into 3 groups: resuscitation from 10‐minute asphyxia with inhaled 100% O2 (CA–fraction of inspired O2 [FIO2] 1.0), with 30% O2 (CA‐FIO 2 0.3), and sham with 30% O2 (sham‐FIO 2 0.3). Animals were resuscitated with manual cardiopulmonary resuscitation. The volume of extracted O2 (VO 2) and VCO 2 were measured for a 2‐hour period after resuscitation. The respiratory quotient (RQ) was RQ=VCO 2/VO 2. VCO 2 was elevated in CA‐FIO 2 1.0 and CA‐FIO 2 0.3 when compared with sham‐FIO 2 0.3 in minutes 5 to 40 after resuscitation (CA‐FIO 2 1.0: 16.7±2.2, P<0.01; CA‐FIO 2 0.3: 17.4±1.4, P<0.01; versus sham‐FIO 2 0.3: 13.6±1.1 mL/kg per minute), and then returned to normal. VO 2 in CA‐FIO 2 1.0 and CA‐FIO 2 0.3 increased gradually and was significantly higher than sham‐FIO 2 0.3 2 hours after resuscitation (CA‐FIO 2 1.0: 28.7±6.7, P<0.01; CA‐FIO 2 0.3: 24.4±2.3, P<0.01; versus sham‐FIO 2 0.3: 15.8±2.4 mL/kg per minute). The RQ of CA animals persistently decreased (CA‐FIO 2 1.0: 0.54±0.12 versus CA‐FIO 2 0.3: 0.68±0.05 versus sham‐FIO 2 0.3: 0.93±0.11, P<0.01 overall).Conclusions CA altered cellular metabolism resulting in increased VO 2 with normal VCO 2. Normal VCO 2 suggests that the postresuscitation Krebs cycle is operating at a presumably healthy rate. Increased VO 2 in the face of normal VCO 2 suggests a significant alteration in O2 utilization in postresuscitation. Several RQ values fell well outside the normally cited range of 0.7 to 1.0. Higher FIO 2 may increase VO 2, leading to even lower RQ values.
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