Inhibition of L‐carnitine biosynthesis and transport by methyl‐γ‐butyrobetaine decreases fatty acid oxidation and protects against myocardial infarction

Abstract

BACKGROUND AND PURPOSEThe important pathological consequences of ischaemic heart disease arise from the detrimental effects of the accumulation of long-chain acylcarnitines in the case of acute ischaemia-reperfusion. The aim of this study is to test whether decreasing the L-carnitine content represents an effective strategy to decrease accumulation of long-chain acylcarnitines and to reduce fatty acid oxidation in order to protect the heart against acute ischaemia-reperfusion injury. KEY RESULTSIn this study, we used a novel compound, 4-[ethyl(dimethyl)ammonio]butanoate (Methyl-GBB), which inhibits γ-butyrobetaine dioxygenase (IC50 3 μM) and organic cation transporter 2 (OCTN2, IC50 3 μM), and, in turn, decreases levels of L-carnitine and acylcarnitines in heart tissue. Methyl-GBB reduced both mitochondrial and peroxisomal palmitate oxidation rates by 44 and 53% respectively. In isolated hearts treated with Methyl-GBB, uptake and oxidation rates of labelled palmitate were decreased by 40%, while glucose oxidation was increased twofold. Methyl-GBB (5 or 20 mg·kg ) attenuated the infarct size by 45% and improved 24 h survival of rats by 20-30%. CONCLUSIONS AND IMPLICATIONSReduction of L-carnitine and long-chain acylcarnitine content by the inhibition of OCTN2 represents an effective strategy to protect the heart against ischaemia-reperfusion-induced damage. Methyl-GBB treatment exerted cardioprotective effects and increased survival by limiting long-chain fatty acid oxidation and facilitating glucose metabolism. AbbreviationsAAR, area at risk; ACOX, acyl-CoA oxidase 1; ACSL, long-chain fatty acid CoA synthetase; AN, area of necrosis; BBOX, γ-butyrobetaine dioxygenase; CD36, fatty acid translocase; CPT I, carnitine palmitoyltransferase I; FABP, fatty acid binding protein; FAO, fatty acid oxidation; HR, heart rate; IHD, ischaemic heart disease; IS, infarct size; KH, Krebs-Henseleit; LAD, left anterior descending coronary artery; LCFA, long-chain fatty acids; LV, left ventricle; LVDP, left ventricle developed pressure; IntroductionIschaemic heart disease (IHD) is a major medical problem causing disability and death for millions of people annually (Lavie et al., 2009). The important pathological consequences of IHD arise from the detrimental effects of the accumulation of long-chain fatty acids (LCFAs) in the case of acute ischaemia-reperfusion (Wang and Lopaschuk, 2007;Liepinsh et al., 2013b). Therefore, pharmacological intervention that targets LCFA accumulation has been suggested for the development of novel treatment strategies to improve the clinical outcomes of patients with IHD (Horowitz et al., 2010;Lopaschuk et al., 2010). The main advantages of reduced LCFA oxidation are the reduction of energy waste through mitochondrial uncoupling induced by LCFA overload as well as the reduction of direct damage by LCFA metabolites on glucose metabolism and insulin signalling (Zhang et al., 2011). In addition, pharmacological manipulation of energy metabolism does not directly influence the haemodynamic parameters of th...

Methyl-γ-butyrobetaine decreases levels of acylcarnitines and attenuates the development of atherosclerosis

“…In our experimental setup, treatment of apoE −/− mice with methyl-GBB significantly decreased pools of L-carnitine but we did not observe any signs of muscle weakness or elevations of ALT and AST. Very recently it has been shown, that 2-week treatment with methyl-GBB at the dose 20 mg/kg decreased L-carnitine pools in heart tissues by 95%, but the systolic function and anatomical parameters of the left ventricle was unchanged [16]. Thus, we conclude that the decrease of L-carnitine pools may not be the main factor that determines the development of organ dysfunction and it could be a matter of pharmacological properties of the studied substance.…”

“…In a previous study, methyl-GBB administration displayed marked cardioprotective effects [16], which were based on the regulation of energy metabolism pathways and the reduction of L-carnitine and long-chain acylcarnitine content in heart tissues. In this study, the effects of methyl-GBB treatment on the development of atherosclerosis in an apoE −/− mice were studied.…”

“…This could lead to a depletion of ATP levels and development of ventricular dysfunction, which was observed after prolonged administration of pivalate [2]. On the contrary, treatment with methyl-GBB not only inhibited fatty acid metabolism, but also facilitated glucose metabolism in heart tissues [16], thus, preserving ATP pools and heart function.…”

“…The newly synthesised compounds effectively decreased the L-carnitine pools in the plasma and heart tissues and possessed marked cardioprotective activities [15,16]. The best cardioprotective effect in the rat experimental heart infarction model was observed after treatment with 4-[ethyl(dimethyl)ammonio]butanoate (methyl-GBB), a methyl-derivative of GBB that effectively inhibits GBB dioxygenase (IC 50 2.8 μM) and organic cation transporter 2 (IC 50 3.0 μM) [16].…”

Combination of vitamin E and L-carnitine is superior in protection against isoproterenol-induced cardiac injury: histopathological evidence

“…Liepinsh et al reported that long-term decrease in L-carnitine is important for the energy metabolism regulation and treatment of atherosclerosis and heart diseases [18]. On the other hand, Zambrano et al reported that arterial hypertension-related cardiac fibrosis could be inhibited by L-carnitine through modulation of Peroxisome Proliferator Activated Receptor-γ expression [35].…”