Metabolic therapy for heart disease: impact of trimetazidine

Trimetazidine therapy for diabetic mouse hearts subjected to ex vivo acute heart failure

Acute heart failure (AHF) is the most common primary diagnosis for hospitalized heart diseases in Africa. As increased fatty acid β-oxidation (FAO) during heart failure triggers detrimental effects on the myocardium, we hypothesized that trimetazidine (TMZ) (partial FAO inhibitor) offers cardioprotection under normal and obese-related diabetic conditions. Hearts were isolated from 12-14-week-old obese male and female diabetic (db/db) mice versus lean non-diabetic littermates (db/+) controls. The Langendorff retrograde isolated heart perfusion system was employed to establish an ex vivo AHF model: a) Stabilization phase-Krebs Henseleit buffer (10 mM glucose) at 100 mmHg (25 min); b) Critical Acute Heart Failure (CAHF) phase-(1.2 mM palmitic acid, 2.5 mM glucose) at 20 mmHg (25 min); and c) Recovery Acute Heart Failure phase (RAHF)-(1.2 mM palmitic acid, 10 mM glucose) at 100 mmHg (25 min). Treated groups received 5 μM TMZ in the perfusate during either the CAHF or RAHF stage for the full duration of each respective phase. Both lean and obese males benefited from TMZ treatment administered during the RAHF phase. Sex differences were observed only in lean groups where the phases of the estrous cycle influenced therapy; only the lean follicular female group responded to TMZ treatment during the CAHF phase. Lean luteal females rather displayed an inherent cardioprotection (without treatments) that was lost with obesity. However, TMZ treatment initiated during RAHF was beneficial for obese luteal females. TMZ treatment triggered significant recovery for male and obese female hearts when administered during RAHF. There were no differences between lean and obese male hearts, while lean females displayed a functional recovery advantage over lean males. Thus TMZ emerges as a worthy therapeutic target to consider for AHF treatment in normal and obese-diabetic individuals (for both sexes), but only when administered during the recovery phase and not during the very acute stages.

The Role of Ivabradine and Trimetazidine in the New ESC HF Guidelines

The prevalence of heart failure (HF) is increasing, representing a major cause of death and disability, and a growing financial burden on healthcare systems. Despite the use of effective treatments with both drugs and devices, mortality remains high. There is therefore a need for new and effective therapeutic agents. Ivabradine is a specific sinus node inhibiting agent that was approved in 2005 by the European Medicines Agency, alone or in combination with a beta-blocker. Trimetazidine is a cytoprotective, anti-ischaemic agent established in the treatment of angina pectoris. In the 2012 European Society of Cardiology (ESC) guidelines for diagnosis and treatment of HF, ivabradine was recommended in symptomatic HF patients who are in sinus rhythm with left ventricular ejection fraction ≤35 % and heart rate higher than 70 beats per minute, despite optimal medical therapy, including maximally tolerated dose of beta-blocker. The role of trimetazidine in this setting was not mentioned. In the 2016 ESC guidelines, recommendations for ivabradine are unchanged but trimetazidine is included for the treatment of angina pectoris with HF. This article discusses the need for new therapeutic options in HF and reviews clinical evidence in support of these two therapeutic options.

Mitochondria and cardioprotection

Major factors linking mitochondrial dysfunction with myocardial injury are analyzed along with protective mechanisms elicited by endogenous processes and pharmacological treatments. In particular, a reduced rate of ATP hydrolysis and a slight increase in ROS formation appear to represent the prevailing components of self-defense mechanisms, especially in the case of ischemic preconditioning. These protective processes are activated by signaling pathways, which converge on mitochondria activating the mitochondrial K(ATP) channels and/or inhibiting the mitochondrial permeability transition pore. These pathways can also be stimulated by pharmacological treatments. Another major goal for cardioprotection is decreasing the burst in mitochondrial ROS formation that characterizes post-ischemic reperfusion. Finally, mitochondrial targets for therapeutic intervention may include the switch of substrate being utilized, because inhibition of fatty acid oxidation is associated with cardioprotective effects.