Metabolic alterations in a rat model of takotsubo syndrome

Cardiovasc Res. 2022 Jun 29;118(8):1932-1946. doi: 10.1093/cvr/cvab081.

Abstract

Aims: Cardiac energetic impairment is a major finding in takotsubo patients. We investigate specific metabolic adaptations to direct future therapies.

Methods and results: An isoprenaline-injection female rat model (vs. sham) was studied at Day 3; recovery assessed at Day 7. Substrate uptake, metabolism, inflammation, and remodelling were investigated by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography, metabolomics, quantitative PCR, and western blot (WB). Isolated cardiomyocytes were patch-clamped during stress protocols for redox states of NAD(P)H/FAD or [Ca2+]c, [Ca2+]m, and sarcomere length. Mitochondrial respiration was assessed by seahorse/Clark electrode (glycolytic and β-oxidation substrates). Cardiac 18F-FDG metabolic rate was increased in takotsubo (P = 0.006), as was the expression of GLUT4-RNA/GLUT1/HK2-RNA and HK activity (all P < 0.05), with concomitant accumulation of glucose- and fructose-6-phosphates (P > 0.0001). Both lactate and pyruvate were lower (P < 0.05) despite increases in LDH-RNA and PDH (P < 0.05 both). β-Oxidation enzymes CPT1b-RNA and 3-ketoacyl-CoA thiolase were increased (P < 0.01) but malonyl-CoA (CPT-1 regulator) was upregulated (P = 0.01) with decreased fatty acids and acyl-carnitines levels (P = 0.0001-0.02). Krebs cycle intermediates α-ketoglutarate and succinyl-carnitine were reduced (P < 0.05) as was cellular ATP reporter dihydroorotate (P = 0.003). Mitochondrial Ca2+ uptake during high workload was impaired on Day 3 (P < 0.0001), inducing the oxidation of NAD(P)H and FAD (P = 0.03) but resolved by Day 7. There were no differences in mitochondrial respiratory function, sarcomere shortening, or [Ca2+] transients of isolated cardiomyocytes, implying preserved integrity of both mitochondria and cardiomyocyte. Inflammation and remodelling were upregulated-increased CD68-RNA, collagen RNA/protein, and skeletal actin RNA (all P < 0.05).

Conclusion: Dysregulation of glucose and lipid metabolic pathways with decreases in final glycolytic and β-oxidation metabolites and reduced availability of Krebs intermediates characterizes takotsubo myocardium. The energetic deficit accompanies defective Ca2+ handling, inflammation, and upregulation of remodelling pathways, with the preservation of sarcomeric and mitochondrial integrity.

Keywords: Energetics; Heart failure; Inflammation; Metabolism; Remodelling; Takotsubo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Fatty Acids / metabolism
  • Female
  • Flavin-Adenine Dinucleotide / metabolism
  • Fluorodeoxyglucose F18
  • Glucose / metabolism
  • Inflammation / metabolism
  • Malonyl Coenzyme A / metabolism
  • Myocardium / metabolism
  • NAD / metabolism
  • Oxidation-Reduction
  • RNA / metabolism
  • Rats
  • Takotsubo Cardiomyopathy* / metabolism

Substances

  • Fatty Acids
  • NAD
  • Fluorodeoxyglucose F18
  • Flavin-Adenine Dinucleotide
  • Malonyl Coenzyme A
  • RNA
  • Glucose
  • Calcium