Age-associated mitochondrial oxidative decay: improvement of carnitine acetyltransferase substrate–binding affinity and activity in brain by feeding old rats acetyl–L–Carnitine and/or R–alpha–Lipoic acid

Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2002; 99(4):1876-81. DOI: 10.1073/pnas.261709098
Source: PubMed


We test whether the dysfunction with age of carnitine acetyltransferase (CAT), a key mitochondrial enzyme for fuel utilization, is due to decreased binding affinity for substrate and whether this substrate, fed to old rats, restores CAT activity. The kinetics of CAT were analyzed by using the brains of young and old rats and of old rats supplemented for 7 weeks with the CAT substrate acetyl-l-carnitine (ALCAR) and/or the mitochondrial antioxidant precursor R-alpha-lipoic acid (LA). Old rats, compared with young rats, showed a decrease in CAT activity and in CAT-binding affinity for both substrates, ALCAR and CoA. Feeding ALCAR or ALCAR plus LA to old rats significantly restored CAT-binding affinity for ALCAR and CoA, and CAT activity. To explore the underlying mechanism, lipid peroxidation and total iron and copper levels were assayed; all increased in old rats. Feeding old rats LA or LA plus ALCAR inhibited lipid peroxidation but did not decrease iron and copper levels. Ex vivo oxidation of young-rat brain with Fe(II) caused loss of CAT activity and binding affinity. In vitro oxidation of purified CAT with Fe(II) inactivated the enzyme but did not alter binding affinity. However, in vitro treatment of CAT with the lipid peroxidation products malondialdehyde or 4-hydroxy-nonenal caused a decrease in CAT-binding affinity and activity, thus mimicking age-related change. Preincubation of CAT with ALCAR or CoA prevented malondialdehyde-induced dysfunction. Thus, feeding old rats high levels of key mitochondrial metabolites can ameliorate oxidative damage, enzyme activity, substrate-binding affinity, and mitochondrial dysfunction.

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Available from: David W Killilea, Jan 18, 2015
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    • "Damage to mitochondria is primarily caused by ROS generated by the mitochondria themselves [11] [12], in particular by complexes I and III of the electron respiratory chain [13]. Direct damage to mitochondrial proteins decreases their affinity for substrates or coenzymes and, thereby, decreases their function [14]. ROS represented the mechanism of mitochondrial dysfunction during inflammation . "
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    ABSTRACT: Mitochondria are critical regulator of cell metabolism; thus, mitochondrial dysfunction is associated with many metabolic disorders. Defects in oxidative phosphorylation, ROS production, or mtDNA mutations are the main causes of mitochondrial dysfunction in many pathological conditions such as IR/diabetes, metabolic syndrome, cardiovascular diseases, and cancer. Thus, targeting mitochondria has been proposed as therapeutic approach for these conditions, leading to the development of small molecules to be tested in the clinical scenario. Here we discuss therapeutic interventions to treat mitochondrial dysfunction associated with two major metabolic disorders, metabolic syndrome, and cancer. Finally, novel mechanisms of regulation of mitochondrial function are discussed, which open new scenarios for mitochondria targeting.
    The Scientific World Journal 03/2014; 2014:604685. DOI:10.1155/2014/604685 · 1.73 Impact Factor
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    • "Given that mitochondria-centered dysfunction was an essential feature of unloading, we developed a nutrient formula designed to synergistically promote mitochondrial biogenesis, improve mitochondrial dysfunction, and balance oxidative stress using compounds whose mitochondrial beneficial effects have been well documented by our laboratory and other laboratories. For example, LA plus ALCAR, cofactors located within mitochondria, have been shown to improve mitochondrial metabolism and integrity by both enhancing acetyltransferase substrate-binding affinity and activity and ameliorating oxidative stress [40] [42]. HT, a natural polyphenol compound from olive oil, activates PGC-1α-mediated mitochondrial biogenesis in retinal pigment epithelial cells, adipocytes, and muscles [24] [25] [43]; CoQ 10 , a mitochondrial electron transporter, promotes mitochondrial function when applied to Goto–Kakizaki rats [26]. "
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    ABSTRACT: We previously found that mitochondrial dysfunction occurs in disuse-induced muscle atrophy. However, the mitochondrial remodeling that occurs during reloading, an effective approach for rescuing unloading-induced atrophy, remains to be investigated. In the present study, using a rat model of 3-week hindlimb unloading plus 7-day reloading, we found that reloading protected mitochondria against dysfunction, including mitochondrial loss, abnormal mitochondrial morphology, inhibited biogenesis, and activation of mitochondria-associated apoptotic signaling. Interestingly, a combination of nutrients, including alpha-lipoic acid, acetyl-L- carnitine, hydroxytyrosol, and CoQ10, which we designed to target mitochondria, was able to efficiently rescue muscle atrophy via a reloading-like action. It is suggested that reloading ameliorates skeletal muscle atrophy through the activation of mitochondrial biogenesis and the amelioration of oxidative stress. Nutrient administration acted similarly in unloaded rats. Here, the study of mitochondrial remodeling in rats during unloading and reloading provides a more detailed picture of the pathology of muscle atrophy.
    Free Radical Biology and Medicine 01/2014; 69. DOI:10.1016/j.freeradbiomed.2014.01.003 · 5.74 Impact Factor
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    • "Additionally, acetyl L-carnitine attenuated ketamine-induced behavioral alterations and body weight decrements in preweaning rats (Boctor et al., 2008) and was found to exert efficient preventive effects in a cellular model of Parkinson's disease (Zhang et al., 2010). Beneficial effects of acetyl L-carnitine on cognitive and mitochondrial dysfunction have been shown in aging rats (Hagen et al., 2002a; Liu et al., 2002), as well. In our earlier study, we speculated that acetyl L-carnitine's reversal of ketamine-induced decrease in heart rate and ERK/MAPK activity could be mediated by calcium-modulated signaling (Kanungo et al., 2012). "
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    ABSTRACT: Ketamine, a non-competitive antagonist of N-methyl-d-aspartate (NMDA) type glutamate receptors is commonly used as a pediatric anesthetic. Multiple studies have shown ketamine to be neurotoxic, particularly when administered during the brain growth spurt. Previously, we have shown that ketamine is detrimental to motor neuron development in the zebrafish embryos. Here, using both wild type (WT) and transgenic (hb9:GFP) zebrafish embryos, we demonstrate that ketamine is neurotoxic to both motor and sensory neurons. Drug absorption studies showed that in the WT embryos, ketamine accumulation was approximately 0.4% of the original dose added to the exposure medium. The transgenic embryos express green fluorescent protein (GFP) localized in the motor neurons making them ideal for evaluating motor neuron development and toxicities in vivo. The hb9:GFP zebrafish embryos (28 h post fertilization) treated with 2 mM ketamine for 20 h demonstrated significant reductions in spinal motor neuron numbers, while co-treatment with acetyl l-carnitine proved to be neuroprotective. In whole mount immunohistochemical studies using WT embryos, a similar effect was observed for the primary sensory neurons. In the ketamine-treated WT embryos, the number of primary sensory Rohon-Beard (RB) neurons was significantly reduced compared to those in controls. However, acetyl l-carnitine co-treatment prevented ketamine-induced adverse effects on the RB neurons. These results suggest that acetyl l-carnitine protects both motor and sensory neurons from ketamine-induced neurotoxicity.
    Neurotoxicology and Teratology 07/2013; 39. DOI:10.1016/ · 2.76 Impact Factor
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