Effects of L-carnitine and its acetyl and propionyl esters on ATP and PCr levels of isolated rat hearts perfused without fatty acids and investigated by means of 31P-NMR spectroscopy

Advances in small-molecule therapy for managing angina pectoris in the elderly

Introduction: As our population ages, the prevalence of angina is growing, leading to increased morbidity and decreased quality of life. The management of angina in the elderly is challenging due to drug intolerance and/or drug resistance as well as frailty. Over the past decades, many new therapeutic small molecules have been investigated for the management of angina. Although none of these studies have specifically focused on the therapies for the elderly, they offer promising new avenues for the treatment of angina in the elderly. Areas covered: Herein, the authors provide a review of the recently published literature on the use of small-molecule therapies for angina management in the elderly and provide a brief overview of these therapies. Expert opinion: A variety of therapeutic classes of existing and newer small molecules are emerging for the management of angina in the elderly. An individualized approach to the management of angina in this growing population is critical for good outcomes. Many small molecules are in their initial stages of clinical use, and further research should be conducted on their utility, especially in the elderly.

Neuroprotective effects of L-carnitine against oxygen-glucose deprivation in rat primary cortical neurons

Purpose

Hypoxic-ischemic encephalopathy is an important cause of neonatal mortality, as this brain injury disrupts normal mitochondrial respiratory activity. Carnitine plays an essential role in mitochondrial fatty acid transport and modulates excess acyl coenzyme A levels. In this study, we investigated whether treatment of primary cultures of rat cortical neurons with L-carnitine was able to prevent neurotoxicity resulting from oxygen-glucose deprivation (OGD).

Methods

Cortical neurons were prepared from Sprague-Dawley rat embryos. L-Carnitine was applied to cultures just prior to OGD and subsequent reoxygenation. The numbers of cells that stained with acridine orange (AO) and propidium iodide (PI) were counted, and lactate dehydrogenase (LDH) activity and reactive oxygen species (ROS) levels were measured. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the terminal uridine deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay were performed to evaluate the effect of L-carnitine (1 µM, 10 µM, and 100 µM) on OGD-induced neurotoxicity.

Results

Treatment of primary cultures of rat cortical neurons with L-carnitine significantly reduced cell necrosis and prevented apoptosis after OGD. L-Carnitine application significantly reduced the number of cells that died, as assessed by the PI/AO ratio, and also reduced ROS release in the OGD groups treated with 10 µM and 100 µM of L-carnitine compared with the untreated OGD group (P<0.05). The application of L-carnitine at 100 µM significantly decreased cytotoxicity, LDH release, and inhibited apoptosis compared to the untreated OGD group (P<0.05).

Conclusion

L-Carnitine has neuroprotective benefits against OGD in rat primary cortical neurons in vitro.

Pharmacological effects and clinical applications of propionyl-L-carnitine

Propionyl-L-carnitine (PLC) is a naturally occurring derivative of carnitine that plays an important role in the metabolism of both carbohydrates and lipids, leading to an increase of ATP generation. PLC, however, is not only a metabolic drug; it is also a potent antiradical agent and thus may protect tissues from oxidative damage. PLC has been demonstrated to exert a protective effect in different models of both cardiac and endothelial dysfunction, to prevent the progression of atherosclerosis, and, more recently, to improve some of the cardiometabolic alterations that frequently accompany insulin resistance. As a result, most of the clinical trials conducted in humans highlight PLC as a potential treatment option in cardiovascular diseases such as peripheral arterial disease, chronic heart failure, or stable angina, especially when type 2 diabetes mellitus or hyperglycemia (i.e., patients on hemodialysis) are also present. The aim of this review is to summarize the pharmacological effects and possible therapeutic applications of PLC, including the most recent findings to date.

Critical update for the clinical use of L-carnitine analogs in cardiometabolic disorders

Acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC) are two naturally occurring carnitine derivates formed by carnitine acetyltransferase. The beneficial cardiovascular effects of ALC and PLC have been extensively evaluated in animals and humans during the last 20 years. For instance, many clinical trials have suggested ALC and PLC as potential strategies in the management of peripheral arterial disease, heart and cerebral ischemia, and congestive heart failure. As a result, several experts have already aimed to revise the clinical evidence supporting the therapeutic use of ALC and PLC. On the basis of their conclusions, our aim was a critical review of the effectiveness of ALC and PLC in the treatment of cardiovascular diseases. Type 2 diabetes mellitus is an independent risk factor for the development of cardiovascular disease. Therefore we also describe recent studies that have addressed the emerging use of ALC and PLC amelioration of the insulin resistant state and its related morbidities.

The protective effect of L-carnitine on ischemia-reperfusion heart

To investigate the protective effect of L-carnitine on myocardial ischemia-reperfusion injury in rat heart,all harvested isolated hearts were perfused on Langendorff apparatus with oxygenized K-H solution for 20 min. The hearts were then exposed to ischemia for 30 min. Following the ischemia the hearts were re-perfused with K-H solution for 120 min to serve as the control group A. Either 5 or 10 mmol/L of L-carnitine was added into the K-H solution for 20 min at the beginning of reperfusion to generate group B and group C, respectively. The derivatives of the intraventricular pressure curve (DP/DT), left ventricular developed pressure (LVDP), and coronary flux were monitored during the entire experiment. The levels of ATP, hepatin, malondialdehyde (MDA), and superoxide dismutase (SOD) in tissue, and lactic dehydrogenase (LDH), creatine phosphate kinase (CPK), malondialdehyde (MDA), and superoxide dismutase (SOD) concentration in the coronary efflux were all measured. Compared with the control group, the treatment with L-carnitine resulted in better results, i. e., higher DP/DTmax and LVDP. At the same time, ventricular fibrillation was reduced, and the levels of ATP, hepatin and SOD were all elevated. However, the concentrations of MDA, CPK and LDH were all reduced. In conclusion, L-carnitine has a protective effect on ischemia-reperfusion injury, which is partly due to its prevention of energy loss and its antioxidant activity.

The use of levo-carnitine in children with renal disease: a review and a call for future studies

Carnitine is an amino acid derivative that has a key role in the regulation of fatty acid metabolism and ATP formation. Carnitine deficiency has been described in various conditions, including chronic kidney disease (CKD) and end stage renal disease (ESRD). The deficiency of this micronutrient is postulated to lead to adverse effects across multiple organ systems. There is a paucity of information on carnitine deficiency and its effects in the pediatric CKD and ESRD populations. Currently, there is no evidence supporting the routine use of carnitine supplementation in children with ESRD. In this article, we review the pathophysiology, pharmacokinetics and the potential effects of levo-carnitine supplementation with a focus on the pediatric CKD and ESRD populations. Finally, potential future directions of research are discussed.

Dobutamine alters carnitine metabolism in the neonatal piglet heart

The use of inotropic agents to support the neonatal heart after sepsis or hypoxia increases cardiac energy demand. Carnitine plays a vital role in energy, fuel metabolism. To test the hypothesis that inotropic agents affect carnitine metabolism, hearts from sow-fed piglets were isolated and perfused with an oxygenated buffer containing glucose and palmitate. Increasing dosages of dobutamine (DOB 2.5–15 µg/Kg body wt per min, 0.007–0.044 µmol/kg per min) or saline vehicle (SAL) were administered. Heart rate (HR), left ventricular systolic (LVSP) and end diastolic pressures (LVEDP) were measured. Left ventricular developed pressure (LVDP = LVSP - LVEDP) and pressure-rate product (LVDP × HR) were calculated. Coronary effluent was collected to measure flow and metabolites. Heart tissue samples were collected for metabolite analysis. Results: DOB increased HR, LVEDP and the pressure-rate product [LVDP × HR]. Mean lactate production increased in DOB, but not in SAL control hearts, and was correlated with heart acylcarnitine, but not with coronary flow. Tissue acylcarnitine levels were higher in the DOB than in the SAL group. Plasma total carnitine was correlated with [LVDP × HR] and LVDP, but not with HR. The findings demonstrate that DOB alters myocardial carnitine metabolism and suggest that carnitine status may affect cardiac response to inotropic agents.Key words: carnitine, dobutamine, neonate, swine, isolated perfused heart.

Phosphocreatine restores high-energy phosphates in ischemic myocardium: implication for off-pump cardiac revascularization

BACKGROUND

High-energy phosphate metabolism is altered in the ischemic myocardium. We investigated the effects of in vivo administration of phosphocreatine (PCr) in a transient ischemic rat model to emulate off-pump myocardial revascularization.

STUDY DESIGN

Rats received either PCr (100 mg/kg) or saline intravenously 1 hour before surgery. Regional ischemia was maintained for 12 minutes by ligation of the left anterior descending artery and compared with sham-operated animals. Cardiac tissue was studied for ATP, PCr, and inorganic phosphate (Pi) using (31)P-cryo-NMR. Results were compared by ANOVA.

RESULTS

Levels of ATP were significantly (p < 0.01) lower in the ischemic hearts compared with controls; Pi and PCr remained unchanged. The PCr/Pi ratio was altered in ischemic hearts, reflecting an increased energy demand. PCr administration significantly (p < 0.01) elevated the content of PCr and ATP in both normal and ischemic hearts.

CONCLUSIONS

PCr restores high-energy phosphates and attenuates metabolic stress during periods of myocardial ischemia in the rat. Preconditioning with PCr may serve as a useful adjunct to off-pump coronary revascularization.

Protection of the retina from ischemia-reperfusion injury by L-carnitine in guinea pigs

PURPOSE

To investigate the efficacy of L-carnitine in preventing retinal injury followed by ischemia-reperfusion.

METHODS

The eyes of 34 guinea pigs were used in this experiment. The guinea pigs were divided into two groups: the first group (n=17) was given L-carnitine intraperitoneally (500 mg/kg) and second group (n=17) received the same dose of saline solution. Under general anesthesia, peritomy was performed. Retro-orbital tissues were ligated for 90 minutes and ischemia was induced, followed by 4 hours of reperfusion. One of the enucleated eye was stained with hematoxylin and eosin (H&E) and retinal thicknesses were evaluated. Thiobarbituric acid reactive substances (TBARS) levels were determined in the retina of the other eye.

RESULTS

Mean TBARS levels in retinal tissue were found lower in L-carnitine group (2.77 +/- 0.55 microM) than in the control group (6.57 +/- 1.19 microM), (p<0.01). On the other hand, mean retinal thickness was found to be increased in the control group (47.47 +/- 5.62 microm) when compared to the L-carnitine group (26.52 +/- 4.65 microm), (p<0.01). In correlation analysis, significantly positive relationships were found between retinal TBARS level and retinal thickness both in the control and L-carnitine groups (r=0.981, p<0.01 and r= 0.967, p<0.01 respectively).

CONCLUSIONS

L-carnitine is effective in preventing retinal injury followed by ischemia-reperfusion.

L-carnitine reduces malondialdehyde concentrations in isolated rat hearts in dependence on perfusion conditions

The study investigated the influence of L-carnitine on the formation of malondialdehyde, an indicator of lipid peroxidation, in isolated Langendorff rat hearts. Earlier investigations of hemodynamic parameters and the recovery of ATP and creatine phosphate, carried out by means of 31P-NMR spectroscopy, had demonstrated that, depending on the composition of the perfusates (content of glucose, fatty acids, and carnitine), quite strong differences may occur in the reperfusion period after ischemia. In order to determine a possible relationship between these differences and the addition of carnitine, the study investigated whether carnitine penetrated into the tissue during the experiments, and whether it was able to reduce the concentration of detrimental substances. The concentrations of free and total carnitine as well as the malondialdehyde content as an indicator of ischemia/reperfusion damage were determined in different parts of the cardiac tissue as follows: After the Langendorff-experiments the hearts were dissected, homogenized and reconditioned; then carnitine and malondialdehyde were determined. The study included 63 hearts, which were divided into 8 different perfusion groups. Carnitine concentrations in heart tissue perfused with L-carnitine were much higher than those of the controls. Since exogenous L-carnitine and formed esters could be found in the tissue after the experiment, they must have permeated the cellular membrane rapidly. The concentrations of malondialdehyde behaved in an inverted way; as expected they were lower in carnitine-perfused hearts. The favourable effects of L-carnitine, expressed both by improved cardiac dynamics and ATP and CrP recovery in the reperfusion period, are obviously due to the fact that L-carnitine reduces ischemic damage.