Metabolic alterations in a rat model of takotsubo syndrome

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 (versus sham) was studied at day-3; recovery assessed at day-7. Substrate uptake, metabolism, inflammation and remodelling were investigated by 18F-FDG-PET, metabolomics, qPCR and 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 were 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 3KAT 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 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 Dys-regulation of glucose and lipid metabolic pathways with decreases in final glycolytic and β-oxidation metabolites and reduced availability of Krebs intermediates characterises takotsubo myocardium. The energetic deficit accompanies defective Ca2+ handling, inflammation and upregulation of remodelling pathways, with preservation of sarcomeric and mitochondrial integrity. Translational Perspective The simultaneous dysregulation in the glycolytic and beta-oxidation pathways which underlies the energetic deficit of the takotsubo heart supports further testing of currently available metabolic modulators as possible candidates for successful therapy, as well as targeting the inflammatory and remodelling pathways.

Takotsubo Syndrome: Translational Implications and Pathomechanisms

“…ISO significantly increased the levels of reactive oxygen species (ROS) in the setting of TTS, leading to the injury of myocardial cells, mitochondrial dysfunction, acute Ca 2+ overload, TLR4/NF-κB signaling alterations, dysregulation of the glucose and lipid metabolic pathways represented by decreases in the final glycolytic and β-oxidation metabolites and reduced availability of Krebs cycle intermediates. It was shown that icariin, an antioxidant and anti-inflammatory agent, prevented ISO-induced TTS-like cardiac dysfunction in rats by suppressing the TLR4/NF-κB pathway and long-term inhibition of PI3K/AKT/mTOR expression and by reducing the mitochondrial ROS and oxidative stress-induced apoptosis, which provides new insights into the protective effect against myocardial dysfunction in TTS rats [197][198][199][200][201].…”

“…The animal models of TTS are mainly based on monkeys, rabbits, rats and mice, which can be used to simulate TTS to a certain extent through immobilization, repeated intravenous infusion of an epinephrine overdose, vagal stimulation, intraperitoneally isoprenaline and other methods [152][153][154][182][183][184][185][186][187][188][190][191][192][193][194][195][197][198][199][200][201][202][203][204][205][206]. Many live-stranded cetaceans and terrestrial wildlife experienced capture myopathy, which was similar to TTS [207,208].…”

Takotsubo Cardiomyopathy: Current Treatment

“…It is conceivable that a diverse variety of pathophysiologic entities (ACS, AMI, Prinzmetal’s angina, and TTS) could lead to the same pathophysiologic/pathoanatomic/pathohistologic outcome, i.e., that of “ischemic/reperfusion injury” [ 4 ], and thus therapies previously proposed for ACS and AMI [ 8 , 9 , 116 ], deserve a trial in patients with TTS [ 10 , 11 ]. Accordingly, it has been recently proposed that large doses of insulin infusions, in connection with careful monitoring to prevent hypoglycemia and hypokalemia, via concomitant infusions of dextrose and potassium supplementation, in conjunction with intravenous use of short-, or ultrashort-acting β-blockers (e.g., esmolol or landiolol) [ 39 ] ( Figure 7 ) perhaps have beneficial therapeutic effects in patients with TTS [ 10 , 11 ], addressing specifically the devastating metabolic impairment (glucose and lipid pathways dysregulation, leading to decreased final glycolytic and β-oxydation metabolites and reduced availability of Krebs intermediates), noted in TTS [ 117 , 118 ]. This proposal is based on previous literature of animal models of stress cardiomyopathy, recently summarized [ 10 ], and limited experience in patients with neurogenic cardiomyopathy and TTS [ 37 , 38 , 119 , 120 , 121 , 122 ] ( Figure 8 ).…”

Genetic and Epigenetic Factors of Takotsubo Syndrome: A Systematic Review

“…Currently, it has also been demonstrated that Takotsubo myocardium is characterized by a dysregulation of glucose and lipid metabolic pathways. In turn, this energetic deficit determines a malfunctioning Ca 2+ metabolism, inflammation, and overexpression of remodeling pathways [ 16 ]. Cotemporally, it has been shown that an increase in reactive oxygen species (ROS) followed by the downstream cascade’s effects characteristic TTS development [ 17 ], probably as a consequence of the above-mentioned dysregulation.…”