MTORC1-Regulated Metabolism Controlled by TSC2 Limits Cardiac Reperfusion Injury

2021 ◽  
Author(s):  
Christian U Oeing ◽  
Seungho Jun ◽  
Sumita Mishra ◽  
Brittany Dunkerly-Eyring ◽  
Anna Chen ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Ex Vivo ◽  
Heart Function ◽  
Acid Oxidation ◽  
Chain Acyl ◽  
Myocardial Substrate ◽  
Gain Loss ◽  
Whole Heart ◽  
Mtorc1 Activation

Rationale: The mechanistic target of rapamycin complex-1 (mTORC1) controls metabolism and protein homeostasis, and is activated following ischemic reperfusion (IR) injury and by ischemic preconditioning (IPC). However, studies vary as to whether this activation is beneficial or detrimental, and its influence on metabolism after IR is little studied. A limitation of prior investigations is their use of broad gain/loss of mTORC1 function, mostly applied prior to ischemic stress. This can be circumvented by regulating one serine (S1365) on tuberous sclerosis complex (TSC2) to achieve bi-directional mTORC1 modulation but only with TCS2-regulated co-stimulation. Objective: We tested the hypothesis that reduced TSC2 S1365 phosphorylation protects the myocardium against IR and IPC by amplifying mTORC1 activity to favor glycolytic metabolism. Methods and Results: Mice with either S1365A (TSC2 SA ; phospho-null) or S1365E (TSC2 SE ; phosphomimetic) knock-in mutations were studied ex vivo and in vivo. In response to IR, hearts from TSC2 SA mice had amplified mTORC1 activation and improved heart function compared to WT and TSC2 SE hearts. The magnitude of protection matched IPC. IPC requited less S1365 phosphorylation, as TSC2 SE hearts gained no benefit and failed to activate mTORC1 with IPC. IR metabolism was altered in TSC2 SA , with increased mitochondrial oxygen consumption rate and glycolytic capacity (stressed/maximal extracellular acidification) after myocyte hypoxia-reperfusion. In whole heart, lactate increased and long-chain acyl-carnitine levels declined during ischemia. The relative IR protection in TSC2 SA was lost by lowering glucose in the perfusate by 36%. Adding fatty acid (palmitate) compensated for reduced glucose in WT and TSC2 SE but not TSC2 SA which had the worst post-IR function under these conditions. Conclusions: TSC2-S1365 phosphorylation status regulates myocardial substrate utilization, and its decline activates mTORC1 biasing metabolism away from fatty acid oxidation to glycolysis to confer protection against IR. This pathway is also engaged and reduced TSC2 S1365 phosphorylation required for effective IPC.

Profiling substrate fluxes in the isolated working mouse heart using 13C-labeled substrates: focusing on the origin and fate of pyruvate and citrate carbons

2004 ◽  
Vol 286 (4) ◽  
pp. H1461-H1470 ◽  
Author(s):  
Maya Khairallah ◽  
François Labarthe ◽  
Bertrand Bouchard ◽  
Gawiyou Danialou ◽  
Basil J. Petrof ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Ex Vivo ◽  
Heart Function ◽  
Acid Oxidation ◽  
Mouse Heart ◽  
Relative Contribution ◽  
Cardiac Functions ◽  
Lactate And Pyruvate

The availability of genetically modified mice requires the development of methods to assess heart function and metabolism in the intact beating organ. With the use of radioactive substrates and ex vivo perfusion of the mouse heart in the working mode, previous studies have documented glucose and fatty acid oxidation pathways. This study was aimed at characterizing the metabolism of other potentially important exogenous carbohydrate sources, namely, lactate and pyruvate. This was achieved by using 13C-labeling methods. The mouse heart perfusion setup and buffer composition were optimized to reproduce conditions close to the in vivo milieu in terms of workload, cardiac functions, and substrate-hormone supply to the heart (11 mM glucose, 0.8 nM insulin, 50 μM carnitine, 1.5 mM lactate, 0.2 mM pyruvate, 5 nM epinephrine, 0.7 mM oleate, and 3% albumin). The use of three differentially 13C-labeled carbohydrates and a 13C-labeled long-chain fatty acid allowed the quantitative assessment of the metabolic origin and fate of tissue pyruvate as well as the relative contribution of substrates feeding acetyl-CoA (pyruvate and fatty acids) and oxaloacetate (pyruvate) for mitochondrial citrate synthesis. Beyond concurring with the notion that the mouse heart preferentially uses fatty acids for energy production (63.5 ± 3.9%) and regulates its fuel selection according to the Randle cycle, our study reports for the first time in the mouse heart the following findings. First, exogenous lactate is the major carbohydrate contributing to pyruvate formation (42.0 ± 2.3%). Second, lactate and pyruvate are constantly being taken up and released by the heart, supporting the concept of compartmentation of lactate and glucose metabolism. Finally, mitochondrial anaplerotic pyruvate carboxylation and citrate efflux represent 4.9 ± 1.8 and 0.8 ± 0.1%, respectively, of the citric acid cycle flux and are modulated by substrate supply. The described 13C-labeling strategy combined with an experimental setup that enables continuous monitoring of physiological parameters offers a unique model to clarify the link between metabolic alterations, cardiac dysfunction, and disease development.

Myocardial substrate metabolism influences left ventricular energetics in vivo

2000 ◽  
Vol 278 (4) ◽  
pp. H1345-H1351 ◽  
Author(s):  
Christian Korvald ◽  
Odd Petter Elvenes ◽  
Truls Myrmel
Keyword(s):  
Fatty Acid ◽  
Coronary Flow ◽  
Left Ventricular Pressure ◽  
Random Order ◽  
Left Ventricular ◽  
Acid Oxidation ◽  
Left Ventricular Volumes ◽  
Acid Consumption ◽  
Myocardial Substrate

The myocardial oxygen consumption (MV˙o 2) to left ventricular pressure-volume area (PVA) relationship is assumed unaltered by substrates, despite varying phosphate-to-oxygen ratios and possible excess MV˙o 2 associated with fatty acid consumption. The validity of this assumption was tested in vivo. Left ventricular volumes and pressures were assessed with a combined conductance-pressure catheter in eight anesthetized pigs. MV˙o 2 was calculated from coronary flow and arterial-coronary sinus O2 differences. Metabolism was altered by glucose-insulin-potassium (GIK) or Intralipid-heparin (IH) infusions in random order and monitored with [14C]glucose and [3H]oleate tracers. Profound shifts in glucose and fatty acid oxidation were observed. Contractility, coronary flow, and slope of the MV˙o 2-PVA relationship were unchanged during GIK and IH infusions. MV˙o 2 at zero PVA (unloaded MV˙o 2) was 0.16 ± 0.13 J ⋅ beat− 1 ⋅ 100 g− 1 higher during IH compared with GIK infusion ( P = 0.001), a 48% increase. The study demonstrates a marked energetic advantage of glucose oxidation in the myocardium, profoundly affecting the MV˙o 2-PVA relationship. This may in part explain the “oxygen-wasting” effect of lipid-enhancing interventions such as adrenergic drugs and ischemia.

scholarly journals Overexpression of Nudt7 decreases bile acid levels and peroxisomal fatty acid oxidation in the liver

2019 ◽  
Vol 60 (5) ◽  
pp. 1005-1019 ◽  
Author(s):  
Stephanie A. Shumar ◽  
Evan W. Kerr ◽  
Paolo Fagone ◽  
Aniello M. Infante ◽  
Roberta Leonardi
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
Bile Acid ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Nudix Hydrolase ◽  
Peroxisomal Fatty Acid Oxidation ◽  
Chain Acyl ◽  
Peroxisomal Fatty Acid

Lipid metabolism requires CoA, an essential cofactor found in multiple subcellular compartments, including the peroxisomes. In the liver, CoA levels are dynamically adjusted between the fed and fasted states. Elevated CoA levels in the fasted state are driven by increased synthesis; however, this also correlates with decreased expression of Nudix hydrolase (Nudt)7, the major CoA-degrading enzyme in the liver. Nudt7 resides in the peroxisomes, and we overexpressed this enzyme in mouse livers to determine its effect on the size and composition of the hepatic CoA pool in the fed and fasted states. Nudt7 overexpression did not change total CoA levels, but decreased the concentration of short-chain acyl-CoAs and choloyl-CoA in fasted livers, when endogenous Nudt7 activity was lowest. The effect on these acyl-CoAs correlated with a significant decrease in the hepatic bile acid content and in the rate of peroxisomal fatty acid oxidation, as estimated by targeted and untargeted metabolomics, combined with the measurement of fatty acid oxidation in intact hepatocytes. Identification of the CoA species and metabolic pathways affected by the overexpression on Nudt7 in vivo supports the conclusion that the nutritionally driven modulation of Nudt7 activity could contribute to the regulation of the peroxisomal CoA pool and peroxisomal lipid metabolism.

scholarly journals In vivo reprogramming of pathogenic lung TNFR2+ cDC2s by IFNβ inhibits HDM-induced asthma

2021 ◽  
Vol 6 (61) ◽  
pp. eabi8472
Author(s):  
Samira Mansouri ◽  
Himanshu Gogoi ◽  
Mauricio Pipkin ◽  
Tiago N. Machuca ◽  
Amir M. Emtiazjoo ◽  
...  
Keyword(s):  
Steady State ◽  
Fatty Acid ◽  
Asthma Exacerbation ◽  
Human Lung ◽  
Ex Vivo ◽  
Acid Oxidation ◽  
Eosinophilic Asthma ◽  
Dust Mite ◽  
Tolerogenic Dcs

Asthma is a common inflammatory lung disease with no known cure. Previously, we uncovered a lung TNFR2+ conventional DC2 subset (cDC2s) that induces regulatory T cells (Tregs) maintaining lung tolerance at steady state but promotes TH2 response during house dust mite (HDM)–induced asthma. Lung IFNβ is essential for TNFR2+ cDC2s–mediated lung tolerance. Here, we showed that exogenous IFNβ reprogrammed TH2-promoting pathogenic TNFR2+ cDC2s back to tolerogenic DCs, alleviating eosinophilic asthma and preventing asthma exacerbation. Mechanistically, inhaled IFNβ, not IFNα, activated ERK2 signaling in pathogenic lung TNFR2+ cDC2s, leading to enhanced fatty acid oxidation (FAO) and lung Treg induction. Last, human IFNβ reprogrammed pathogenic human lung TNFR2+ cDC2s from patients with emphysema ex vivo. Thus, we identified an IFNβ-specific ERK2-FAO pathway that might be harnessed for DC therapy.

scholarly journals Reduced Cardiac Efficiency and Altered Substrate Metabolism Precedes the Onset of Hyperglycemia and Contractile Dysfunction in Two Mouse Models of Insulin Resistance and Obesity

Endocrinology ◽  
2005 ◽  
Vol 146 (12) ◽  
pp. 5341-5349 ◽  
Author(s):  
Jonathan Buchanan ◽  
Pradip K. Mazumder ◽  
Ping Hu ◽  
Gopa Chakrabarti ◽  
Matthew W. Roberts ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Mouse Models ◽  
Acid Oxidation ◽  
Contractile Dysfunction ◽  
Oxidation Rates ◽  
Myocardial Substrate ◽  
Old Mice

Hyperglycemia is associated with altered myocardial substrate use, a condition that has been hypothesized to contribute to impaired cardiac performance. The goals of this study were to determine whether changes in cardiac metabolism, gene expression, and function precede or follow the onset of hyperglycemia in two mouse models of obesity, insulin resistance, and diabetes (ob/ob and db/db mice). Ob/ob and db/db mice were studied at 4, 8, and 15 wk of age. Four-week-old mice of both strains were normoglycemic but hyperinsulinemic. Hyperglycemia develops in db/db mice between 4 and 8 wk of age and in ob/ob mice between 8 and 15 wk. In isolated working hearts, rates of glucose oxidation were reduced by 28–37% at 4 wk and declined no further at 15 wk in both strains. Fatty acid oxidation rates and myocardial oxygen consumption were increased in 4-wk-old mice of both strains. Fatty acid oxidation rates progressively increased in db/db mice in parallel with the earlier onset and greater duration of hyperglycemia. In vivo, cardiac catheterization revealed significantly increased left ventricular contractility and relaxation (positive and negative dP/dt) in both strains at 4 wk of age. dP/dt declined over time in db/db mice but remained elevated in ob/ob mice at 15 wk of age. Increased β-myosin heavy chain isoform expression was present in 4-wk-old mice and persisted in 15-wk-old mice. Increased expression of peroxisomal proliferator-activated receptor-α regulated genes was observed only at 15 wk in both strains. These data indicate that altered myocardial substrate use and reduced myocardial efficiency are early abnormalities in the hearts of obese mice and precede the onset of hyperglycemia. Obesity per se does not cause contractile dysfunction in vivo, but loss of the hypercontractile phenotype of obesity and up-regulation of peroxisomal proliferator-activated receptor-α regulated genes occur later and are most pronounced in the presence of longstanding hyperglycemia.

Overexpression of acyl-CoA synthetase-1 increases lipid deposition in hepatic (HepG2) cells and rodent liver in vivo

2006 ◽  
Vol 291 (4) ◽  
pp. E737-E744 ◽  
Author(s):  
Heidi A. Parkes ◽  
Elaine Preston ◽  
Donna Wilks ◽  
Mercedes Ballesteros ◽  
Lee Carpenter ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Hepg2 Cells ◽  
Hepatoma Cell ◽  
Acid Oxidation ◽  
Hepatoma Cell Line ◽  
Human Hepatoma Cell ◽  
Chain Acyl

Accumulation of intracellular lipid in obesity is associated with metabolic disease in many tissues including liver. Storage of fatty acid as triglyceride (TG) requires the activation of fatty acids to long-chain acyl-CoAs (LC-CoA) by the enzyme acyl-CoA synthetase (ACSL). There are five known isoforms of ACSL (ACSL1, -3, -4, -5, -6), which vary in their tissue specificity and affinity for fatty acid substrates. To investigate the role of ACSL1 in the regulation of lipid metabolism, we used adenoviral-mediated gene transfer to overexpress ACSL1 in the human hepatoma cell-line HepG2 and in liver of rodents. Infection of HepG2 cells with the adenoviral construct AdACSL1 increased ACSL activity >10-fold compared with controls after 24 h. HepG2 cells overexpressing ACSL1 had a 40% higher triglyceride (TG) content (93 ± 3 vs. 67 ± 2 nmol/mg protein in controls, P < 0.05) after 24-h exposure to 1 mM oleate. Furthermore, ACSL1 overexpression produced a 60% increase in cellular LCA-CoA content (160 ± 6 vs. 100 ± 6 nmol/g protein in controls, P < 0.05) and increased [14C]oleate incorporation into TG without significantly altering fatty acid oxidation. In mice, AdACSL1 administration increased ACSL1 mRNA and protein more than fivefold over controls at 4 days postinfection. ACSL1 overexpression caused a twofold increase in TG content in mouse liver (39 ± 4 vs. 20 ± 2 μmol/g wet wt in controls, P < 0.05), and overexpression in rat liver increased [1-14C]palmitate clearance into liver TG. These in vitro and in vivo results suggest a pivotal role for ACSL1 in regulating TG synthesis in liver.

Abstract 12117: The Cardioprotection of Trimetazidine Against Ischemic Injury is Mediated by AMPK and ERK Signaling Pathway

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Zhenling Liu ◽  
Yina Ma ◽  
Michelle Kuznicki ◽  
Xingchi Chen ◽  
Wanqing Sun ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Ex Vivo ◽  
Ischemic Injury ◽  
Erk Signaling ◽  
Acid Oxidation ◽  
Ampk Signaling ◽  
Heart Perfusion

Introduction: Trimetazidine (TMZ) is an anti-anginal drug that has been widely used in Europe and Asia. The TMZ can optimize energy metabolism via inhibition of long-chain 3-ketoacyl CoA thiolase (3-KAT) in the heart, with subsequent decrease in fatty acid oxidation and stimulation of glucose oxidation. However, the mechanism by which TMZ aids in cardioprotection against ischemic injury has not been characterized. Hypothesis: AMP-activated protein kinase (AMPK) is an energy sensor that control ATP supply from substrate metabolism and protect heart from energy stress. TMZ changes the cardiac AMP/ATP ratio via modulating fatty acid oxidation, thereby it may trigger AMPK signaling cascade that contribute to protection heart from ischemia/reperfusion (I/R) injury. Methods: The mouse in vivo regional ischemia and reperfusion by the ligation of the left anterior descending coronary artery (LAD) were used for determination of myocardial infarction. The infarct size was compared between C57BL/6J WT mice and AMPK kinase dead (KD) transgenic mice with or without TMZ treatment. The ex vivo working heart perfusion system was used to monitor the effect of TMZ on glucose oxidation and fatty acid oxidation in the heart. Results: TMZ treatment significantly stimulates cardiac AMPK and extracellular signal-regulated kinase (ERK) signaling pathways (p<0.05 vs. vehicle group). The administration of TMZ reduces myocardial infarction size in WT C57BL/6J hearts, the reduction of myocardial infarction size by TMZ in AMPK KD hearts was significantly impaired versus WT hearts (p<0.05). Intriguingly, the administration of ERK inhibitor, PD 98059, to AMPK KD mice abolished the cardioprotection of TMZ against I/R injury. The ex vivo working heart perfusion data demonstrated that TMZ treatment significantly activates AMPK signaling and modulating the substrate metabolism by shifting fatty acid oxidation to glucose oxidation during reperfusion, leading to reduction of oxidative stress in the I/R hearts. Conclusions: Both AMPK and ERK signaling pathways mediate the cardioprotection of TMZ against ischemic injury. The metabolic benefits of TMZ for angina patients could be due to the activation of energy sensor AMPK in the heart by TMZ administration.

Fatty acid metabolism in hearts containing elevated levels of CoA

1986 ◽  
Vol 250 (3) ◽  
pp. H351-H359 ◽  
Author(s):  
G. D. Lopaschuk ◽  
C. A. Hansen ◽  
J. R. Neely
Keyword(s):  
Fatty Acid ◽  
Specific Activity ◽  
Pantothenic Acid ◽  
Acid Oxidation ◽  
Palmitate Oxidation ◽  
Triacylglycerol Hydrolysis ◽  
Chain Acyl ◽  
Apparent Decrease ◽  
Apparent Reduction ◽  
14Co2 Production

Palmitate metabolism was determined in isolated perfused hearts containing elevated levels of coenzyme A (CoA). CoA levels were elevated by perfusing hearts with Krebs-Henseleit buffer containing 0.1 mM cysteine, 0.2 mM dithiothreitol, 15 microM pantothenic acid, and no energy substrate. After 45 min, CoA levels had increased from 537 +/- 14 to 818 +/- 44 nmol/g dry wt. When these hearts containing high CoA were subsequently perfused as working hearts with buffer containing 11 mM glucose and 1.2 mM palmitate, long chain acyl CoA levels increased (94 +/- 5-305 +/- 6 nmol/g dry wt). Oxidation of exogenous palmitate (as measured by 14CO2 production from [U-14C]palmitate) was significantly depressed in hearts containing elevated CoA levels. This apparent reduction in fatty acid oxidation was not due to increased glucose or glycogen utilization. When the concentration of palmitate was decreased to 0.4 mM, acyl CoA levels increased much less, and the apparent rate of [14C]palmitate oxidation was unaffected by elevated CoA. Hearts containing high CoA also incorporated [14C]palmitate into triacylglycerols to a greater extent than did control hearts. To determine whether the apparent decrease in exogenous palmitate oxidation resulted from an increased utilization of unlabeled endogenous triacylglycerol fatty acid, [14C]palmitate specific activity was measured in myocardial acylcarnitine. The specific activity of this pool of fatty acid was similar in both control hearts and hearts containing elevated CoA. Thus dilution of the total cellular [14C]acyl carnitine by triacylglycerol hydrolysis was not sufficient to account for the decrease in [U-14C]palmitate oxidation. The possibility that a small pool of rapidly turning over acyl carnitine becomes dilated is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals PPARα augments heart function and cardiac fatty acid oxidation in early experimental polymicrobial sepsis

2017 ◽  
Vol 312 (2) ◽  
pp. H239-H249 ◽  
Author(s):  
Stephen W. Standage ◽  
Brock G. Bennion ◽  
Taft O. Knowles ◽  
Dolena R. Ledee ◽  
Michael A. Portman ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Mouse Models ◽  
Heart Function ◽  
Left Ventricular ◽  
Cardiac Response ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Regulatory State ◽  
Peroxisome Proliferator Activated Receptor

Children with sepsis and multisystem organ failure have downregulated leukocyte gene expression of peroxisome proliferator-activated receptor-α (PPARα), a nuclear hormone receptor transcription factor that regulates inflammation and lipid metabolism. Mouse models of sepsis have likewise demonstrated that the absence of PPARα is associated with decreased survival and organ injury, specifically of the heart. Using a clinically relevant mouse model of early sepsis, we found that heart function increases in wild-type (WT) mice over the first 24 h of sepsis, but that mice lacking PPARα ( Ppara−/−) cannot sustain the elevated heart function necessary to compensate for sepsis pathophysiology. Left ventricular shortening fraction, measured 24 h after initiation of sepsis by echocardiography, was higher in WT mice than in Ppara−/− mice. Ex vivo working heart studies demonstrated greater developed pressure, contractility, and aortic outflow in WT compared with Ppara−/− mice. Furthermore, cardiac fatty acid oxidation was increased in WT but not in Ppara−/− mice. Regulatory pathways controlling pyruvate incorporation into the citric acid cycle were inhibited by sepsis in both genotypes, but the regulatory state of enzymes controlling fatty acid oxidation appeared to be permissive in WT mice only. Mitochondrial ultrastructure was not altered in either genotype indicating that severe mitochondrial dysfunction is unlikely at this stage of sepsis. These data suggest that PPARα expression supports the hyperdynamic cardiac response early in the course of sepsis and that increased fatty acid oxidation may prevent morbidity and mortality. NEW & NOTEWORTHY In contrast to previous studies in septic shock using experimental mouse models, we are the first to demonstrate that heart function increases early in sepsis with an associated augmentation of cardiac fatty acid oxidation. Absence of peroxisome proliferator-activated receptor-α (PPARα) results in reduced cardiac performance and fatty acid oxidation in sepsis.

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