Effect of phosphomonoesters, phosphodiesters, and phosphocreatine on glutamate uptake by synaptic vesicles

Altered phospholipid and high-energy phosphate metabolism in the basal ganglia and thalamus of severe obsessive compulsive patients with treatment resistance: A phosphorus 31 nuclear magnetic resonance spectroscopy study

INTRODUCTION

Cerebral metabolism in obsessive-compulsive-disorder(OCD) has been the subject of numerous studies using proton magnetic resonance spectroscopy(MRS). Despite heterogeneous results, some studies have unraveled membrane turnover and energy metabolism abnormalities in different brain regions, suggesting that alterations in these processes may contribute to the pathophysiology. So far, no authors have explored phospholipids and high-energy phosphate metabolism using ³¹P-MRS, which allows in vivo quantification of phosphorus metabolites that are considered to be related to membrane turnover and energy metabolism.

MATERIALS AND METHODS

The aim of our study was to describe and compare brain metabolic changes using ³¹P-MRS in the striatum and the thalamus, between 23 severe OCD patients and 22 healthy controls. All subject underwent a clinical examination and a same ³¹P-MRS protocol.

RESULTS

Significantly, increased concentrations of PC, PDE,PME,GPC,PME/PCr,PDE/PCr were found in patients compared to controls in the striatum and the thalamus. PCr and tATP were decreased in the striatum. Finally, significant correlations were found in the striatum and the thalamus between illness duration and some specific measured parameters.

CONCLUSION

Our results showed significant modifications of the membrane and energy metabolism in the basal ganglia of severe OCD patients and suggests a link between energetic buffer and serotonin metabolism disorder.

Creatine target engagement with brain bioenergetics: a dose-ranging phosphorus-31 magnetic resonance spectroscopy study of adolescent females with SSRI-resistant depression

Major depressive disorder (MDD) often begins during adolescence and is projected to become the leading cause of global disease burden by the year 2030. Yet, approximately 40 % of depressed adolescents fail to respond to standard antidepressant treatment with a selective serotonin reuptake inhibitor (SSRI). Converging evidence suggests that depression is related to brain mitochondrial dysfunction. Our previous studies of MDD in adult and adolescent females suggest that augmentation of SSRI pharmacotherapy with creatine monohydrate (CM) may improve MDD outcomes. Neuroimaging with phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) can measure the high-energy phosphorus metabolites in vivo that reflect mitochondrial function. These include phosphocreatine (PCr), a substrate for the creatine kinase reaction that produces adenosine triphosphate. As part of the National Institute of Mental Health’s experimental medicine initiative, we conducted a placebo-controlled dose-ranging study of adjunctive CM for adolescent females with SSRI-resistant MDD. Participants were randomized to receive placebo or CM 2, 4 or 10 g daily for 8 weeks. Pre- and post-treatment ³¹P-MRS scans were used to measure frontal lobe PCr, to assess CM’s target engagement with cerebral energy metabolism. Mean frontal lobe PCr increased by 4.6, 4.1 and 9.1 % in the 2, 4 and 10 g groups, respectively; in the placebo group, PCr fell by 0.7 %. There was no group difference in adverse events, weight gain or serum creatinine. Regression analysis of PCr and depression scores across the entire sample showed that frontal lobe PCr was inversely correlated with depression scores (p = 0.02). These results suggest that CM achieves target engagement with brain bioenergetics and that the target is correlated with a clinical signal. Further study of CM as a treatment for adolescent females with SSRI-resistant MDD is warranted.

Neurotoxicity of glutamate uptake inhibition in vivo: correlation with succinate dehydrogenase activity and prevention by energy substrates

Impairment of glutamate uptake or the reverse action of its transporters has been suggested as the mechanism responsible for the increased glutamate extracellular levels associated with ischemic neuronal damage. In previous studies we have shown that glutamate uptake inhibition by L-trans-pyrrolidine-2,4-dicarboxylate (PDC) in the rat striatum and hippocampus in vivo does not induce neuronal death despite the notable increase in the extracellular levels of glutamate and aspartate. However, PDC intracerebral administration leads to neuronal death in rats chronically injected with the mitochondrial toxin 3-nitropropionic acid (3-NP), an inhibitor of succinate dehydrogenase (SDH). In the present study we have determined the time course of inhibition of SDH activity in the striatum of rats acutely injected with a single dose of 3-NP (20 mg/kg), and studied its relation to PDC neurotoxicity. PDC induced larger lesions when administered during maximum inhibition of SDH activity while smaller lesions were found when it was injected during recovery of enzyme activity. We also studied the neuroprotective effect of different energy substrates such as creatine, pyruvate, and the ketone bodies beta-hydroxybutyrate and acetoacetate in this experimental model. Our results show partial protection with all compounds except for beta-hydroxybutyrate that showed no protection, while MK-801 completely prevented PDC-induced neuronal damage. We believe that the present results might be of relevance for the understanding of the mechanisms responsible for ischemic neuronal death and its prevention.

Molecular insights into neurodevelopmental and neurodegenerative diseases

Magnetic resonance spectroscopy (MRS) is a non-invasive physical technique that is routinely used to determine the quantity and structure of organic molecules in solution. Technical advances that have expanded the usefulness of this technique include: (1) high resolution MRS to identify and quantify individual molecules present in complex mixtures of tissue extracts; (2) in vivo MRS techniques to non-invasively monitor metabolites in humans; (3) structure determination of proteins of moderate size; and (4) improved structure characterization of solids and liquid crystals, such as the detection of phase changes in membranes. The focus of this review is on the first two technical advances mentioned above. The strengths of MRS as a research tool to investigate molecular alterations in disease states include ease of sample preparation, minimum sample manipulation, avoidance of the preparation of derivatives, and the ability to analyze an unfractionated sample. The strengths of MRS in the clinic are its ability to measure neuronal metabolite levels non-invasively in humans and its potential for disease diagnosis, monitoring disease progression, and assessing the efficacy of experimental therapies.