Dietary supplementation with acetyl-l-carnitine in seizure treatment of pentylenetetrazole kindled mice

In spite of the availability of new antiepileptic drugs a considerable number of epilepsy patients still have pharmacoresistant seizures, and thus there is a need for novel approaches. Acetyl-l-carnitine (ALCAR), which delivers acetyl units to mitochondria for acetyl-CoA production, has been shown to improve brain energy homeostasis and protects against various neurotoxic insults. To our knowledge, this is the first study of ALCAR's effect on metabolism in pentylenetetrazole (PTZ) kindled mice. ALCAR or the commonly used antiepileptic drug valproate, was added to the drinking water of mice for 25days, and animals were injected with PTZ or saline three times a week during the last 21days. In order to investigate ALCAR's effects on glucose metabolism, mice were injected with [1-(13)C]glucose 15min prior to microwave fixation. Brain extracts from cortex and the hippocampal formation (HF) were studied using (1)H and (13)C NMR spectroscopy and HPLC. PTZ kindling caused glucose hypometabolism, evidenced by a reduction in both glycolysis and TCA cycle turnover in both brain regions investigated. Glutamatergic and GABAergic neurons were affected in cortex and HF, but the amount of glutamate was only reduced in HF. Slight astrocytic involvement could be detected in the cortex. Interestingly, the dopamine content was increased in the HF. ALCAR attenuated the PTZ induced reduction in [3-(13)C]alanine and the increase in dopamine in the HF. However, TCA cycle metabolism was not different from that seen in PTZ kindled animals. In conclusion, even though ALCAR did not delay the kindling process, it did show some promising ameliorative effects, worthy of further investigation.     

Chronic acetyl-L-carnitine alters brain energy metabolism and increases noradrenaline and serotonin content in healthy mice

Acetyl-L-carnitine (ALCAR), the short-chain ester of carnitine, is a common dietary supplement readily available in health food stores, claimed to improve energy levels and muscle strength. ALCAR has numerous effects on brain and muscle metabolism, protects against neurotoxic insults and may be an effective treatment for certain forms of depression. However, little is known about the effect of chronic ALCAR supplementation on the brain metabolism of healthy mice. Here, we investigated ALCAR's effect on cerebral energy and neurotransmitter metabolism after supplementing the drinking water of mice with ALCAR for 25 days, providing a daily dose of about 0.5 g/kg. Thereafter the animals were injected with [1-(13)C]glucose, and (13)C incorporation into and levels of various metabolites were quantified in extracts of the hippocampal formation (HF) and cortex using (1)H- and (13)C-nuclear magnetic resonance (NMR) spectroscopy and high performance liquid chromatography (HPLC). Increased glucose levels were detected in both regions together with a decreased amount of [3-(13)C]lactate, but no alterations in incorporation of (13)C derived from [1-(13)C]glucose into the amino acids glutamate, GABA and glutamine. These findings are consistent with decreased metabolism of glucose to lactate but not via the TCA cycle. Higher amounts of the sum of adenosine nucleotides, phosphocreatine and the phosphocreatine/creatine ratio found in the cortex of ALCAR-treated mice are indicative of increased energy levels. Furthermore, ALCAR supplementation increased the levels of the neurotransmitters noradrenaline in the HF and serotonin in cortex, consistent with ALCAR's potential efficacy for depressive symptoms. Other ALCAR-induced changes observed included reduced amounts of GABA in the HF and increased myo-inositol. In conclusion, chronic ALCAR supplementation decreased glucose metabolism to lactate, resulted in increased energy metabolite and altered monoamine neurotransmitter levels in the mouse brain.     

l-carnitine supplementation as a potential antioxidant therapy for inherited neurometabolic disorders

In recent years increasing evidence has emerged suggesting that oxidative stress is involved in the pathophysiology of a number of inherited metabolic disorders. However the clinical use of classical antioxidants in these diseases has been poorly evaluated and so far no benefit has been demonstrated. l-Carnitine is an endogenous substance that acts as a carrier for fatty acids across the inner mitochondrial membrane necessary for subsequent beta-oxidation and ATP production. Besides its important role in the metabolism of lipids, l-carnitine is also a potent antioxidant (free radical scavenger) and thus may protect tissues from oxidative damage. This review addresses recent findings obtained from patients with some inherited neurometabolic diseases showing that l-carnitine may be involved in the reduction of oxidative damage observed in these disorders. For some of these diseases, reduced concentrations of l-carnitine may occur due to the combination of this compound to the accumulating toxic metabolites, especially organic acids, or as a result of protein restricted diets. Thus, l-carnitine supplementation may be useful not only to prevent tissue deficiency of this element, but also to avoid oxidative damage secondary to increased production of reactive species in these diseases. Considering the ability of l-carnitine to easily cross the blood–brain barrier, l-carnitine supplementation may also be beneficial in preventing neurological damage derived from oxidative injury. However further studies are required to better explore this potential.     

Neurite outgrowth in PC12 cells stimulated by acetyl-l-carnitine arginine amide

Senescence of the central nervous system is characterized by a progressive loss of neurons that can result in physiological and behavioral impairments. Reduction in the levels of central neurotrophic factors or of neurotrophin receptors may be one of the causes of the onset of these degenerative events. Thus, a proper therapeutic approach would be to increase support to degenerating neurons with trophic factors or to stimulate endogenous neurotrophic activity. Here we report that acetyl-l-carnitine arginine amide (ST-857) is able to stimulate neurite outgrowth in rat pheochromocytoma PC12 cells in a manner similar to that elicited by nerve growth factor (NGF). Neurite induction by ST-857 requires de novo mRNA synthesis and is independent of the action of several common trophic factors. The integrity of the molecular structure of ST-857 is essential for its activity, as the single moieties of the molecule have no effect on PC12 cells, whether they are tested separately or together. Also, minor chemical modifications of ST-857, such as the presence of the arginine moiety at a position other than the amino one, completely abolish its neuritogenic effect. Lastly, the presence of ST-857 in the culture medium competes with the high affinity NGF binding in a dose dependent fashion. These results, although preliminary, are suggestive of a possible role for ST-857 in the development of therapeutic strategies to counteract degenerative diseases of the CNS.     

Functional relevance of carnitine transporter OCTN2 to brain distribution of l-carnitine and acetyl-l-carnitine across the blood–brain barrier

Transport of L-[3H]carnitine and acetyl-L-[3H]carnitine at the blood-brain barrier (BBB) was examined by using in vivo and in vitro models. In vivo brain uptake of acetyl-L-[3H]carnitine, determined by a rat brain perfusion technique, was decreased in the presence of unlabeled acetyl-L-carnitine and in the absence of sodium ions. Similar transport properties for L-[3H]carnitine and/or acetyl-L-[3H]carnitine were observed in primary cultured brain capillary endothelial cells (BCECs) of rat, mouse, human, porcine and bovine, and immortalized rat BCECs, RBEC1. Uptakes of L-[3H]carnitine and acetyl-L-[3H]carnitine by RBEC1 were sodium ion-dependent, saturable with K(m) values of 33.1 +/- 11.4 microM and 31.3 +/- 11.6 microM, respectively, and inhibited by carnitine analogs. These transport properties are consistent with those of carnitine transport by OCTN2. OCTN2 was confirmed to be expressed in rat and human BCECs by an RT-PCR method. Furthermore, the uptake of acetyl-L-[3H]carnitine by the BCECs of juvenile visceral steatosis (jvs) mouse, in which OCTN2 is functionally defective owing to a genetical missense mutation of one amino acid residue, was reduced. The brain distributions of L-[3H]carnitine and acetyl-L-[3H]carnitine in jvs mice were slightly lower than those of wild-type mice at 4 h after intravenous administration. These results suggest that OCTN2 is involved in transport of L-carnitine and acetyl-L-carnitine from the circulating blood to the brain across the BBB.