AMP-activated protein kinase regulation of fatty acid oxidation in the ischaemic heart

2003 ◽  
Vol 31 (1) ◽  
pp. 207-212 ◽  
Author(s):  
T.A. Hopkins ◽  
J.R.B. Dyck ◽  
G.D. Lopaschuk
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Acid Oxidation ◽  
Oxidation Rates ◽  
Ischaemic Damage ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

The heart relies predominantly on a balance between fatty acids and glucose to generate its energy supply. There is an important interaction between the metabolic pathways of these two substrates in the heart. When circulating levels of fatty acids are high, fatty acid oxidation can dominate over glucose oxidation as a source of energy through feedback inhibition of the glucose oxidation pathway. Following an ischaemic episode, fatty acid oxidation rates increase further, resulting in an uncoupling between glycolysis and glucose oxidation. This uncoupling results in an increased proton production, which worsens ischaemic damage. Since high rates of fatty acid oxidation can contribute to ischaemic damage by inhibiting glucose oxidation, it is important to maintain proper control of fatty acid oxidation both during and following ischaemia. An important molecule that controls myocardial fatty acid oxidation is malonyl-CoA, which inhibits uptake of fatty acids into the mitochondria. The levels of malonyl-CoA in the heart are controlled both by its synthesis and degradation. Three enzymes, namely AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC) and malonyl-CoA decarboxylase (MCD), appear to be extremely important in this process. AMPK causes phosphorylation and inhibition of ACC, which reduces the production of malonyl-CoA. In addition, it is suggested that AMPK also phosphorylates and activates MCD, promoting degradation of malonyl-CoA levels. As a result malonyl-CoA levels can be dramatically altered by activation of AMPK. In ischaemia, AMPK is rapidly activated and inhibits ACC, subsequently decreasing malonyl-CoA levels and increasing fatty acid oxidation rates. The consequence of this is a decrease in glucose oxidation rates. In addition to altering malonyl-CoA levels, AMPK can also increase glycolytic rates, resulting in an increased uncoupling of glycolysis from glucose oxidation and an enhanced production of protons and lactate. This decreases cardiac efficiency and contributes to the severity of ischaemic damage. Decreasing the ischaemic-induced activation of AMPK or preventing the downstream decrease in malonyl-CoA levels may be a therapeutic approach to treating ischaemic heart disease.

Effect of phosphorylation by AMP-activated protein kinase on palmitoyl-CoA inhibition of skeletal muscle acetyl-CoA carboxylase

2005 ◽  
Vol 98 (4) ◽  
pp. 1221-1227 ◽  
Author(s):  
D. S. Rubink ◽  
W. W. Winder
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Oxidation Rates ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

AMP-activated protein kinase (AMPK) has previously been demonstrated to phosphorylate and inactivate skeletal muscle acetyl-CoA carboxylase (ACC), the enzyme responsible for synthesis of malonyl-CoA, an inhibitor of carnitine palmitoyltransferase 1 and fatty acid oxidation. Contraction-induced activation of AMPK with subsequent phosphorylation/inactivation of ACC has been postulated to be responsible in part for the increase in fatty acid oxidation that occurs in muscle during exercise. These studies were designed to answer the question: Does phosphorylation of ACC by AMPK make palmitoyl-CoA a more effective inhibitor of ACC? Purified rat muscle ACC was subjected to phosphorylation by AMPK. Activity was determined on nonphosphorylated and phosphorylated ACC preparations at acetyl-CoA concentrations ranging from 2 to 500 μM and at palmitoyl-CoA concentrations ranging from 0 to 100 μM. Phosphorylation resulted in a significant decline in the substrate saturation curve at all palmitoyl-CoA concentrations. The inhibitor constant for palmitoyl-CoA inhibition of ACC was reduced from 1.7 ± 0.25 to 0.85 ± 0.13 μM as a consequence of phosphorylation. At 0.5 mM citrate, ACC activity was reduced to 13% of control values in response to the combination of phosphorylation and 10 μM palmitoyl-CoA. Skeletal muscle ACC is more potently inhibited by palmitoyl-CoA after having been phosphorylated by AMPK. This may contribute to low-muscle malonyl-CoA values and increasing fatty acid oxidation rates during long-term exercise when plasma fatty acid concentrations are elevated.

Regulation of fatty acid oxidation and glucose metabolism in rat soleus muscle: effects of AICAR

2001 ◽  
Vol 281 (2) ◽  
pp. E335-E340 ◽  
Author(s):  
Virendar K. Kaushik ◽  
Martin E. Young ◽  
David J. Dean ◽  
Theodore G. Kurowski ◽  
Asish K. Saha ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Protein Kinase ◽  
Glucose Uptake ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Acid Oxidation ◽  
Malonyl Coa ◽  
Rat Soleus Muscle ◽  
Amp Activated Protein Kinase ◽  
Fasted Rats

Previous studies have shown that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a cell-permeable activator of AMP-activated protein kinase, increases the rate of fatty acid oxidation in skeletal muscle of fed rats. The present study investigated the mechanism by which this occurs and, in particular, whether changes in the activity of malonyl-CoA decarboxylase (MCD) and the β-isoform of acetyl-CoA carboxylase (ACCβ) are involved. In addition, the relationship between changes in fatty acid oxidation induced by AICAR and its effects on glucose uptake and metabolism was examined. In incubated soleus muscles isolated from fed rats, AICAR (2 mM) increased fatty acid oxidation (90%) and decreased ACCβ activity (40%) and malonyl-CoA concentration (50%); however, MCD activity was not significantly altered. In soleus muscles from overnight-fasted rats, AICAR decreased ACCβ activity (40%), as it did in fed rats; however, it had no effect on the already high rate of fatty acid oxidation or the low malonyl-CoA concentration. In keeping with its effect on fatty acid oxidation, AICAR decreased glucose oxidation by 44% in fed rats but did not decrease glucose oxidation in fasted rats. It had no effect on glucose oxidation when fatty acid oxidation was inhibited by 2-bromopalmitate. Surprisingly, AICAR did not significantly increase glucose uptake or assayable AMP-activated protein kinase activity in incubated soleus muscles from fed or fasted rats. These results indicate that, in incubated rat soleus muscle, 1) AICAR does not activate MCD or stimulate glucose uptake as it does in extensor digitorum longus and epitrochlearis muscles, 2) the ability of AICAR to increase fatty acid oxidation and diminish glucose oxidation and malonyl-CoA concentration is dependent on the nutritional status of the rat, and 3) the ability of AICAR to diminish assayable ACC activity is independent of nutritional state.

Isoproterenol stimulates 5′-AMP-activated protein kinase and fatty acid oxidation in neonatal hearts

2010 ◽  
Vol 299 (4) ◽  
pp. H1135-H1145 ◽  
Author(s):  
Jagdip S. Jaswal ◽  
Chad R. Lund ◽  
Wendy Keung ◽  
Donna L. Beker ◽  
Ivan M. Rebeyka ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Energy Demand ◽  
Glucose Oxidation ◽  
Acid Oxidation ◽  
Acetyl Coa ◽  
Lactate Oxidation ◽  
Major Energy Source ◽  
Amp Activated Protein Kinase

Isoproterenol increases phosphorylation of LKB, 5′-AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC), enzymes involved in regulating fatty acid oxidation. However, inotropic stimulation selectively increases glucose oxidation in adult hearts. In the neonatal heart, fatty acid oxidation becomes a major energy source, while glucose oxidation remains low. This study tested the hypothesis that increased energy demand imposed by isoproterenol originates from fatty acid oxidation, secondary to increased LKB, AMPK, and ACC phosphorylation. Isolated working hearts from 7-day-old rabbits were perfused with Krebs solution (0.4 mM palmitate, 11 mM glucose, 0.5 mM lactate, and 100 mU/l insulin) with or without isoproterenol (300 nM). Isoproterenol increased myocardial O2 consumption (in J·g dry wt−1·min−1; 11.0 ± 1.4, n = 8 vs. 7.5 ± 0.8, n = 6, P < 0.05), and the phosphorylation of LKB (in arbitrary density units; 0.87 ± 0.09, n = 6 vs. 0.59 ± 0.08, n = 6, P < 0.05), AMPK (0.82 ± 0.08, n = 6 vs. 0.51 ± 0.06, n = 6, P < 0.05), and ACC-β (1.47 ± 0.14, n = 6 vs. 0.97 ± 0.07, n = 6, P < 0.05), with a concomitant decrease in malonyl-CoA levels (in nmol/g dry wt; 0.9 ± 0.9, n = 8 vs. 7.5 ± 1.3, n = 8, P < 0.05) and increase in palmitate oxidation (in nmol·g dry wt−1·min−1; 272 ± 45, n = 8 vs. 114 ± 9, n = 6, P < 0.05). Glucose and lactate oxidation were increased (in nmol·g dry wt−1·min−1; 253 ± 75, n = 8 vs. 63 ± 15, n = 9, P < 0.05 and 246 ± 43, n = 8 vs. 82 ± 11, n = 6, P < 0.05, respectively), independent of alterations in pyruvate dehydrogenase phosphorylation, but occurred secondary to a decrease in acetyl-CoA content and acetyl-CoA-to-free CoA ratio. As acetyl-CoA levels decrease in response to isoproterenol, despite an acceleration of the rates of palmitate and carbohydrate oxidation, these data suggest net rates of acetyl-CoA utilization exceed the net rates of acetyl-CoA generation.

AICA riboside increases AMP-activated protein kinase, fatty acid oxidation, and glucose uptake in rat muscle

1997 ◽  
Vol 273 (6) ◽  
pp. E1107-E1112 ◽  
Author(s):  
G. F. Merrill ◽  
E. J. Kurth ◽  
D. G. Hardie ◽  
W. W. Winder
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Glucose Uptake ◽  
Fatty Acid Oxidation ◽  
Fold Increase ◽  
Acid Oxidation ◽  
Acetyl Coa Carboxylase ◽  
Malonyl Coa ◽  
Amp Activated Protein Kinase

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) has previously been reported to be taken up into cells and phosphorylated to form ZMP, an analog of 5′-AMP. This study was designed to determine whether AICAR can activate AMP-activated protein kinase (AMPK) in skeletal muscle with consequent phosphorylation of acetyl-CoA carboxylase (ACC), decrease in malonyl-CoA, and increase in fatty acid oxidation. Rat hindlimbs were perfused with Krebs-Henseleit bicarbonate containing 4% bovine serum albumin, washed bovine red blood cells, 200 μU/ml insulin, and 10 mM glucose with or without AICAR (0.5–2.0 mM). Perfusion with medium containing AICAR was found to activate AMPK in skeletal muscle, inactivate ACC, and decrease malonyl-CoA. Hindlimbs perfused with 2 mM AICAR for 45 min exhibited a 2.8-fold increase in fatty acid oxidation and a significant increase in glucose uptake. No difference was observed in oxygen uptake in AICAR vs. control hindlimb. These results provide evidence that decreases in muscle content of malonyl-CoA can increase the rate of fatty acid oxidation.

Triacylglycerol turnover in isolated working hearts of acutely diabetic rats

1994 ◽  
Vol 72 (10) ◽  
pp. 1110-1119 ◽  
Author(s):  
Maruf Saddik ◽  
Gary D. Lopaschuk
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Acid Oxidation ◽  
Atp Production ◽  
Oxidation Rates ◽  
Rat Hearts

Although myocardial triacylglycerol may be a potentially important source of fatty acids for β-oxidation in diabetes, few studies have measured triacylglycerol turnover directly in hearts from diabetic animals. In this study, myocardial triacylglycerol turnover was directly measured in isolated working hearts from streptozotocin-induced acutely diabetic rats. Hearts were initially perfused in the presence of 1.2 mM [14C]palmitate and 11 mM glucose for 1 h (pulse) to label the endogenous lipid pools, followed by a 10-min washout perfusion. Hearts were then perfused for another hour (chase) with buffer containing 11 mM glucose ± 1.2 mM [3H]palmitate. During the chase, both 14CO2 and 3H2O production (measures of endogenous and exogenous fatty acid oxidation, respectively) were determined. A second series of hearts were perfused using the same protocol, except that unlabeled palmitate was used during the pulse and 11 mM [14C(U),5-3H]glucose ± unlabeled palmitate was present during the chase. Both glycolysis (3H2O production) and glucose oxidation (14CO2 production) rates were measured in this series. Myocardial triacylglycerol levels were significantly higher in the diabetic rat hearts (77.5 ± 4.6 vs. 33.7 ± 4.1 μmol fatty acid/g dry mass in control hearts). In diabetic rat hearts chased with 1.2 mM palmitate, triacylglycerol lipolysis was increased, although endogenous [14C]palmitate oxidation rates were similar to control hearts and contributed 10.1% of overall ATP production. The majority of fatty acids derived from triacylglycerol lipolysis were released into the perfusate. In the absence of palmitate, both triacylglycerol lipolysis and endogenous [14C]palmitate oxidation rates were significantly increased in diabetic rat hearts, compared with control. Under these conditions, triacylglycerol fatty acid oxidation contributed 70% of steady-state ATP production in diabetic rat hearts, compared with 34% in control hearts. These results demonstrate that in diabetic rat hearts myocardial triacylglycerol lipolysis is significantly increased and can readily be used as a source of fatty acids for mitochondrial β-oxidation.Key words: heart, triacylglycerols, fatty acid oxidation, glucose oxidation, glycolysis.

scholarly journals Hearts lacking plasma membrane KATP channels display changes in basal aerobic metabolic substrate preference and AMPK activity

2017 ◽  
Vol 313 (3) ◽  
pp. H469-H478 ◽  
Author(s):  
Nermeen Youssef ◽  
Scott Campbell ◽  
Amy Barr ◽  
Manoj Gandhi ◽  
Beth Hunter ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Metabolic Stress ◽  
Cardiac Metabolism ◽  
Acid Oxidation ◽  
Metabolic Substrate ◽  
Amp Activated Protein Kinase

Cardiac ATP-sensitive K+ (KATP) channels couple changes in cellular metabolism to membrane excitability and are activated during metabolic stress, although under basal aerobic conditions, KATP channels are thought to be predominately closed. Despite intense research into the roles of KATP channels during metabolic stress, their contribution to aerobic basal cardiac metabolism has not been previously investigated. Hearts from Kir6.2+/+ and Kir6.2−/− mice were perfused in working mode, and rates of glycolysis, fatty acid oxidation, and glucose oxidation were measured. Changes in activation/expression of proteins regulating metabolism were probed by Western blot analysis. Despite cardiac mechanical function and metabolic efficiency being similar in both groups, hearts from Kir6.2−/− mice displayed an approximately twofold increase in fatty acid oxidation and a 0.45-fold reduction in glycolytic rates but similar glucose oxidation rates compared with hearts from Kir6.2+/+ mice. Kir6.2−/− hearts also possessed elevated levels of activated AMP-activated protein kinase (AMPK), higher glycogen content, and reduced mitochondrial density. Moreover, activation of AMPK by isoproterenol or diazoxide was significantly blunted in Kir6.2−/− hearts. These data indicate that KATP channel ablation alters aerobic basal cardiac metabolism. The observed increase in fatty acid oxidation and decreased glycolysis before any metabolic insult may contribute to the poor recovery observed in Kir6.2−/− hearts in response to exercise or ischemia-reperfusion injury. Therefore, KATP channels may play an important role in the regulation of cardiac metabolism through AMPK signaling. NEW & NOTEWORTHY In this study, we show that genetic ablation of plasma membrane ATP-sensitive K+ channels results in pronounced changes in cardiac metabolic substrate preference and AMP-activated protein kinase activity. These results suggest that ATP-sensitive K+ channels may play a novel role in regulating metabolism in addition to their well-documented effects on ionic homeostasis during periods of stress.

Malonyl-CoA decarboxylase inhibition suppresses fatty acid oxidation and reduces lactate production during demand-induced ischemia

2005 ◽  
Vol 289 (6) ◽  
pp. H2304-H2309 ◽  
Author(s):  
William C. Stanley ◽  
Eric E. Morgan ◽  
Hazel Huang ◽  
Tracy A. McElfresh ◽  
Joseph P. Sterk ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Glucose Oxidation ◽  
Contractile Function ◽  
Lactate Production ◽  
Specific Inhibitor ◽  
Acid Oxidation ◽  
Malonyl Coa ◽  
Cpt I

The rate of cardiac fatty acid oxidation is regulated by the activity of carnitine palmitoyltransferase-I (CPT-I), which is inhibited by malonyl-CoA. We tested the hypothesis that the activity of the enzyme responsible for malonyl-CoA degradation, malonyl-CoA decarboxlyase (MCD), regulates myocardial malonyl-CoA content and the rate of fatty acid oxidation during demand-induced ischemia in vivo. The myocardial content of malonyl-CoA was increased in anesthetized pigs using a specific inhibitor of MCD (CBM-301106), which we hypothesized would result in inhibition of CPT-I, reduction in fatty acid oxidation, a reciprocal activation of glucose oxidation, and diminished lactate production during demand-induced ischemia. Under normal-flow conditions, treatment with the MCD inhibitor significantly reduced oxidation of exogenous fatty acids by 82%, shifted the relationship between arterial fatty acids and fatty acid oxidation downward, and increased glucose oxidation by 50%. Ischemia was induced by a 20% flow reduction and β-adrenergic stimulation, which resulted in myocardial lactate production. During ischemia MCD inhibition elevated malonyl-CoA content fourfold, reduced free fatty acid oxidation rate by 87%, and resulted in a 50% decrease in lactate production. Moreover, fatty acid oxidation during ischemia was inversely related to the tissue malonyl-CoA content ( r = −0.63). There were no differences between groups in myocardial ATP content, the activity of pyruvate dehydrogenase, or myocardial contractile function during ischemia. Thus modulation of MCD activity is an effective means of regulating myocardial fatty acid oxidation under normal and ischemic conditions and reducing lactate production during demand-induced ischemia.

scholarly journals Fatty acids stimulate AMP-activated protein kinase and enhance fatty acid oxidation in L6 myotubes

2006 ◽  
Vol 574 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Matthew J. Watt ◽  
Gregory R. Steinberg ◽  
Zhi-Ping Chen ◽  
Bruce E. Kemp ◽  
Mark A. Febbraio
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
L6 Myotubes ◽  
Amp Activated Protein Kinase
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