Role of Lysine Acetylation in the Control of Cardiac Energy Metabolism

• Author / Creator

  Abu Alrub, Osama Y

• Cardiac Fatty acids β-oxidation (FAO) markedly increases during maturation and become the major source of energy for the adult heart. However, excessive rates of FAO can compromise cardiac function in obesity, diabetes, and heart failure. Lysine acetylation has recently been identified as a potentially important pathway involved in the control of energy metabolism. In mitochondria, this post-translational acetylation is catalyzed by general control of amino acid synthesis 5-like 1 (GCN5L1), while SIRT3 is a major deacetylase. Despite the fact that a number of FAO enzymes can be acetylated, whether this post-translational modification activates or inhibits FAO enzymes is a matter of debate. We therefore examined the role of lysine acetylation on cardiac FAO during maturation (1-day, 7-day, and 21-day old rabbit), and in hearts from high fat (HF) diet-induced obese mice, and abdominal aortic constriction (AAC)-induced HF obese mice. Cardiac FAO rates were significantly increased during maturation. Activities of the FAO enzymes, long chain acyl CoA dehydrogenase (LCAD) and β-hydroxyacyl CoA dehydrogenase (β-HAD) were increased in hearts from 7-, and 21-day vs 1-day old rabbits, and were associated with LCAD and β-HAD hyperacetylation. Increased overall myocardial protein acetylation during maturation was associated with increased mitochondrial acetyltransferase GCN5L1 expression, while expression of the mitochondrial deacetylase, SIRT3, did not change. Increased expression of the nuclear deacetylase SIRT1 and a decrease in cardiac SIRT6 expression during maturation was accompanied by decreased acetylation of peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α) and increased ATP production. Acetylation of the glycolytic enzymes hexokinase (HK) and phosphoglycerate mutase (PGM) were increased; scenarios consistent with the decrease in glycolytic activity seen in 7-, and 21-day vs. 1-day old hearts. High FAO rates in isolated working hearts from diet-induced obese mice was found to be positively correlated with an increase in activity of the FAO enzymes, LCAD and β-HAD. An increase in LCAD and β-HAD acetylation was also observed, which was associated with a decrease in SIRT3 expression and no change in the expression of GCN5L1. To further examine the role of acetylation in regulating FAO, we used SIRT3 KO mice to investigate the role of lysine acetylation on cardiac FAO. Although cardiac work was similar, cardiac FAO rates were increased in SIRT3 KO versus WT mice (422±29 vs 291±17 nmol.g dry wt-1.min-1, respectively, p<0.05). This was accompanied by a decrease in glucose oxidation rates in SIRT3 KO versus WT mice (1262±121 vs 1983±174 nmol.g dry wt-1.min-1, respectively, p<0.05). Cardiac lysine acetylation was increased in SIRT3 KO mice compared to WT mice, which included an increased acetylation and activity of LCAD and β-HAD. Obesity and heart failure were induced in mice by feeding a HF diet (60% kcal from fat) for 4 weeks and producing an AAC. At 4 wk post-AAC, mice were either switched to a low-fat (LF) diet (4% kcal from fat; HF AAC LF) or maintained on a HF Diet (HF AAC HF) for a further 10 wk period. After 18 weeks, HF AAC HF mice weighed significantly higher than HF AAC LF mice. Cardiac hypertrophy evident in HF AAC HF mice was associated with SIRT1 mediated inhibition of FoxO1 while activation of FoxO1 and AMPK blunted this effect in HF AAC LF mice. In isolated working hearts, insulin stimulated glucose oxidation rates were also significantly increased in HF AAC LF hearts, compared to HF AAC HF hearts. Activity of the fatty acid β-oxidation enzyme, LCAD was significantly increased in hearts from HF AAC HF vs HF AAC LF mice, and was associated with LCAD hyperacetylation. Heart failure observed in vivo by echocardiography in HF AAC HF was significantly improved in HF AAC LF mice. These results suggest a key regulatory role of acetylation in controlling cardiac energy metabolism. However, we conclude that lysine acetylation increases, rather than decreases, FAO in the heart.

• Subjects / Keywords

  • Obesity
  • Heart Failure
  • Lysine acetylation
  • Sirtuins
  • SIRT3
  • Heart
  • Energy Metabolism

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3G15TK4X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.