CDPcholine and CDPethanolamine prevent the release of free fatty acids during brain ischemia

Mitigating Traumatic Brain Injury: A Narrative Review of Supplementation and Dietary Protocols

Traumatic brain injuries (TBIs) constitute a significant public health issue and a major source of disability and death in the United States and worldwide. TBIs are strongly associated with high morbidity and mortality rates, resulting in a host of negative health outcomes and long-term complications and placing a heavy financial burden on healthcare systems. One promising avenue for the prevention and treatment of brain injuries is the design of TBI-specific supplementation and dietary protocols centred around nutraceuticals and biochemical compounds whose mechanisms of action have been shown to interfere with, and potentially alleviate, some of the neurophysiological processes triggered by TBI. For example, evidence suggests that creatine monohydrate and omega-3 fatty acids (DHA and EPA) help decrease inflammation, reduce neural damage and maintain adequate energy supply to the brain following injury. Similarly, melatonin supplementation may improve some of the sleep disturbances often experienced post-TBI. The scope of this narrative review is to summarise the available literature on the neuroprotective effects of selected nutrients in the context of TBI-related outcomes and provide an evidence-based overview of supplementation and dietary protocols that may be considered in individuals affected by-or at high risk for-concussion and more severe head traumas. Prophylactic and/or therapeutic compounds under investigation include creatine monohydrate, omega-3 fatty acids, BCAAs, riboflavin, choline, magnesium, berry anthocyanins, Boswellia serrata, enzogenol, N-Acetylcysteine and melatonin. Results from this analysis are also placed in the context of assessing and addressing important health-related and physiological parameters in the peri-impact period such as premorbid nutrient and metabolic health status, blood glucose regulation and thermoregulation following injury, caffeine consumption and sleep behaviours. As clinical evidence in this research field is rapidly emerging, a comprehensive approach including appropriate nutritional interventions has the potential to mitigate some of the physical, neurological, and emotional damage inflicted by TBIs, promote timely and effective recovery, and inform policymakers in the development of prevention strategies.

[Molecular and clinical aspects of the effect of cytidyndiphosphocholine on cognitive functions]

OBJECTIVE

Systematization of the array of publications on cytidyldiphosphocholine (CDP-choline).

MATERIAL AND METHODS

Systematic computer analysis of all currently available publications on CDP-choline (1750 publications in PUBMED) using the topological theory of big data analysis.

RESULTS

CDP-choline is essential for acetylcholine biosynthesis, phospholipid metabolism, and DNA methylation. The article describes the effects of CDP-choline on acetylcholinergic and other types of neurotransmission, anti-inflammatory, neuroprotective and neurotrophic effects of CDP-choline. Also, the paper presents the effects of the molecule on lipid metabolism and gene expression within the post-genomic paradigm (in particular, an increase in the expression of nicotinic and muscarinic acetylcholine receptors). The results of fundamental and clinical studies of CDP-choline in the treatment of cognitive impairments associated with cerebral ischemia and neurodegeneration are presented.

CONCLUSION

The pharmacological effects of CDP-choline are mediated through multiple molecular mechanisms that contribute to the nootropic action of this molecule.

[Phospholipids metabolism disorders in acute stroke]

The disturbances of cerebral circulation results in the violation of phospholipid metabolism. Activation of lipid peroxidation and protein kinase C and release of intracellular calcium leads to disruption of the homeostasis of phosphatidylcholine. The use of cytidine-5-diphosphocholine, which is used as an intermediate compound in the biosynthesis of phospholipids of the cell membrane, helps to stabilize cell membranes, and reduce the formation of free radicals.

In vivo protective effect of Uridine, a pyrimidine nucleoside, on genotoxicity induced by Levodopa/Carbidopa in mice

Parkinson's disease (PD) is a common neurodegenerative disorder that affects millions of people all over the world. Motor symptoms of PD are most commonly controlled by L-3,4-dihydroxyphenylalanine (Levodopa, L-DOPA), a precursor of dopamine, plus a peripherally-acting aromatic-L-amino-acid decarboxylase (dopa decarboxylase) inhibitor, such as carbidopa. However, chronic treatment with a combination of Levodopa plus carbidopa has been demonstrated to cause a major complication, namely abnormal involuntary movements. On the other hand, the effect of this treatment on bone marrow cells is unknown. Therefore, in this study, we aimed to investigate possible genotoxic effects of Levodopa and Carbidopa using male Balb/C mice. Our results showed that Levodopa alone or in combination with carbidopa caused genotoxicity in in vivo micronucleus test (mouse bone marrow) and Comet assay (blood cells). Furthermore, we showed that simultaneous administration of uridine, a pyrimidine nucleoside, reversed the genotoxic effect of Levodopa and Carbidopa in both assays. Our data show for the first time that Levodopa plus carbidopa combination causes genotoxicity which is reversed by uridine treatment. These findings might enhance our understanding for the complications of a common Parkinson's treatment and confer benefit in terms of reducing a possible genotoxic effect of this treatment.

Neuroprotective properties of citicoline: facts, doubts and unresolved issues

Citicoline is the generic name of the pharmaceutical substance that chemically is cytidine-5'-diphosphocholine (CDP-choline), which is identical to the natural intracellular precursor of phospholipid phosphatidylcholine. Following injection or ingestion, citicoline is believed to undergo quick hydrolysis and dephosphorylation to yield cytidine and choline, which then enter the brain separately and are used to resynthesize CDP-choline inside brain cells. Neuroprotective activity of citicoline has been repeatedly shown in preclinical models of brain ischaemia and trauma, but two recent, large, pivotal clinical trials have revealed no benefits in ischaemic stroke and traumatic brain injury. However, the substance seems to be beneficial in some slowly advancing neurodegenerative disorders such as glaucoma and mild vascular cognitive impairment. This paper critically discusses issues related to the clinical pharmacology of citicoline, including its pharmacokinetics/biotransformation and pharmacodynamics/mode of action. It is concluded that at present, there is no adequate description of the mechanism(s) of the pharmacological actions of this substance. The possibility should be considered and tested that, in spite of apparently fast catabolism, the intact citicoline molecule or the phosphorylated intermediate products of its hydrolysis, cytidine monophosphate and phosphocholine, are pharmacologically active.

Cytidine-5'-diphosphocholine affects CTP-phosphocholine cytidylyltransferase and lyso-phosphatidylcholine after transient brain ischemia

Cytidine-5'-diphosphocholine (CDP-choline, also referred as citicoline), the key intermediate in phosphatidylcholine (PtdCho) synthesis, provided significant benefit in experimental central nervous system (CNS) injury including cerebral ischemia. CDP-choline is synthesized by CTP:phosphocholine cytidylyltransferase (CCT), the key rate-limiting enzyme in PtdCho synthesis. Phospholipase A(2) (PLA(2)) hydrolyzes PtdCho to produce free fatty acids and lyso-PtdCho, an inhibitor of CCT. We investigated the status of CCT and lyso-PtdCho after 10-min transient brain ischemia in gerbils with reperfusion up to 2 days. Ischemia with no reperfusion resulted in loss of CCT activity in cytosol (408 +/- 8 pmol/min/mg protein compared to sham 695 +/- 45; P < 0.01) and membrane (383 +/- 61 compared to sham 532 +/- 54; P < 0.05). CCT activity remained low over 24-hr reperfusion, and returned to sham levels at Day 2 in membrane but remained low in cytosol. CDP-choline significantly increased CCT activity in cytosol at 1 hr reperfusion (saline, 339 +/- 35 compared to CDP-choline, 430 +/- 70; P < 0.05) and in membrane at 6 hr (saline, 381 +/- 32 compared to CDP-choline, 489 +/- 50; P < 0.01) and 24 hr (saline, 417 +/- 24 compared to CDP-choline, 594 +/- 45; P < 0.01), but had no effect on CCT activity at Day 2. Lyso-PtdCho increased at 1-hr reperfusion (219 +/- 5 nmol/g tissue compared to sham, 92 +/- 8; P < 0.01), and remained elevated over 2 days. CDP-choline attenuated lyso-PtdCho levels at 1-hr reperfusion (162 +/- 21, P < 0.01 compared to saline). These data indicate that PtdCho synthesis is impaired after brain ischemia, and CDP-choline may increase PtdCho levels by attenuating the loss of CCT activity and lyso-PtdCho formation.

Membrane stabilizer: citicoline

Brain ischaemia leads to a cascade of biochemical events, many of which ultimately cause cell membrane injury. Therefore, measures aimed at protecting neuronal membranes could be useful treatment strategies following stroke. Citicoline (cytidine-5-diphosphocholine; CDP-choline) is a naturally occurring nucleotide derivative that may reduce central nervous system (CNS) ischaemic injury by stabilizing cell membranes and reducing free radical generation. Several animal models of ischaemic stroke or hypoxia have shown beneficial effects of citicoline treatment. Randomized clinical stroke treatment trials performed outside of the United States (US) have shown promising results but several recent US trials have failed to support the use of citicoline following middle cerebral artery (MCA) stroke. It remains possible that more specific subgroups of patients may benefit from this well tolerated therapy, but these subgroups have yet to be determined. In addition, there remains the possibility that efficacy may be seen when citicoline is administered in combination with other neuroprotectants with complementary mechanisms of action.

Synergistic effects of citicoline and MK-801 in temporary experimental focal ischemia in rats

BACKGROUND AND PURPOSE

Citicoline, a naturally occurring precursor of phosphatidylcholine, is neuroprotective and is currently being assessed in clinical trials. To evaluate potential synergistic neuroprotective effects of prolonged citicoline treatment and early N-methyl-D-aspartate (NMDA) antagonist therapy, suboptimal treatment regimens of citicoline and MK-801 were tested alone and in combination in a rat model of temporary focal ischemia.

METHODS

Four groups of Sprague-Dawley rats (n = 12 per group) underwent 90 minutes of temporary middle cerebral artery occlusion (MCAO) with the suture model. Animals were randomly and blindly assigned to one of four treatment groups: (1) saline, vehicle; (2) MK-801, 0.5 mg/kg IV bolus at 60 minutes after MCAO followed by saline 1 mL/kg IP daily for 7 days; (3) saline IV at 60 minutes after MCAO followed by citicoline 250 mg/kg IP daily for 7 days; or (4) both MK-801 and citicoline (daily for 7 days) active treatment. Triphenyltetrazolium chloride staining was used to assess postmortem infarct volume. Neurological scores were determined daily.

RESULTS

Premature mortality between days 2 and 4 was 33.3% in group 1, 41.7% in groups 2 and 3, and 25.0% in group 4. Mean corrected infarct volume was significantly reduced in group 4 compared with the others (175.2 +/- 89.3 mm3 in group 1, 179.1 +/- 78.5 mm3 in group 2, 163.9 +/- 73.7 mm3 in group 3, and 84.7 +/- 56.8 mm3 in group 4 [P < .02, ANOVA and P < .05, Scheffé's test for group 1 versus group 4]). Mean infarct volume in animals dying prematurely was significantly (P < .05, Student's t test) larger in group 1 than those surviving for 7 days (247.2 +/- 89.5 versus 139.2 +/- 68.2 mm3), but there was no significant difference in infarct volume in groups 2, 3, and 4 between animals dying prematurely and those surviving for 7 days.

CONCLUSIONS

These results demonstrate synergistic neuroprotective effects of citicoline and an NMDA antagonist in temporary experimental focal ischemia.

The effects of prolonged treatment with citicoline in temporary experimental focal ischemia

Potential therapeutic effects of cytidine 5-diphosphocholine (citicoline), a key intermediary in the biosynthesis of the membrane phospholipid, phosphatidylcholine, are presumably related to enhanced phospholipid synthesis in the ischemic brain. We evaluated prolonged citicoline treatment in a temporary focal ischemia model. Using the suture occlusion model, we induced 2 hours of temporary ischemia in 30 Sprague-Dawley rats. The rats were randomly and blindly assigned to receive intraperitoneally 500 mg/kg citicoline (HD), 100 mg/kg citicoline (LD) or physiologic saline as the control group once daily for 7 days (n = 10 per group) beginning at the time of reperfusion. Neurological scoring (0-5 scale) was performed daily. After elective sacrifice on day 7, or earlier if death occurred prematurely, the brains underwent 2,3,5-triphenyltetrazolium chloride (TTC) staining for calculation of corrected infarct and edema volume. The mean corrected infarct volume in the HD group was 125 +/- 45.2 mm3 (mean +/- SD), significantly smaller than controls, 243.5 +/- 88.6 mm3 (p < 0.01, Scheffe's-test). The LD group infarct volume was 200.2 +/- 62.8 mm3 (N.S.). The mean amount of brain edema in the HD group was 46.4 +/- 45.6 mm3 was smaller than the controls, 92.3 +/- 54.4 mm3 and the LD group, 84.9 +/- 71.7 mm3 (N.S.). Mortality before day 7 in the HD was 30% while it was 50% in the two other groups. The neurologic score on day 7 was 2.5 +/- 1.8 in the HD group, 3.3 +/- 1.8 in the LD group and 3.4 +/- 1.7 in controls (N.S.). These results demonstrate that extended high dose citicoline treatment significantly reduced infarct volume in this temporary focal ischemia model and that there was a trend toward reducing brain edema and mortality. These effects may be related to membrane stabilization and inhibition of free fatty acid release.

Radioiodinated diacylglycerol analogue: a potential imaging agent for single-photon emission tomographic investigations of cerebral ischaemia

Phospholipid metabolism is closely related to membrane perturbation in cerebral ischaemia. We investigated in vivo topographical lipid metabolism using an iodine-123-labelled diacylglycerol analogue, (1-(15-(4-iodine-123-iodophenyl)-pentadecanoyl)-2-stearoyl-rac-gly cerol) (123I-labelled DAG), in a middle cerebral artery (MCA) occlusion model with the aim of positive imaging of ischaemic insult. Sprague-Dawley rats underwent coagulation of the MCA to induce permanent occlusion. MCA occlusion times prior to injection of 123I-labelled DAG ranged from 15 min to 14 days. Each rat was injected with 11-37 MBq of 123I-labelled DAG via a tail vein. After 30 min, in vivo autoradiographs were reconstructed. Scanning of the living rat brain in this MCA occlusion model was performed using a gamma camera with a pinhole collimator. Cerebral infarctions were recognized in the frontal cortex, the parietal cortex and the lateral portion of the caudate-putamen by 2,3,5-triphenyltetrazolium hydrochloride staining. In infarcted regions (region 1), 123I-labelled DAG incorporation showed a slight decrease up to 12 h; it then increased up to 6 days and decreased thereafter. In peri-infarcted regions (region 2), the incorporation showed almost no change up to 12 h, then increased up to 5-6 days and decreased thereafter. In other regions (region 3), the incorporation showed no change. Lipid analysis showed that 123I-labelled DAG was metabolized to 15-(4-iodine-123-iodophenyl)-pentadecanoic acid by DAG lipase and to 123I-labelled phosphatidylcholine. Scanning of the ischaemic region showed higher accumulation than on the non-lesioned side. We established a method to visualize ischaemic foci as positive images. The early changes in 123I-labelled DAG incorporation were closely related to DAG lipase, which degraded the accumulated intrinsic DAG, and increased 123I-labelled DAG incorporation in the chronic stage involves several aspects of neural destruction in the process of autolysis. It is concluded that the reported method could have a clinical future.

Metabolism and actions of CDP-choline as an endogenous compound and administered exogenously as citicoline

CDP-choline, supplied exogenously as citicoline, has beneficial physiological actions on cellular function that have been extensively studied and characterized in numerous model systems. As the product of the rate-limiting step in the synthesis of phosphatidylcholine from choline, CDP-choline and its hydrolysis products (cytidine and choline) play important roles in generation of phospholipids involved in membrane formation and repair. They also contribute to such critical metabolic functions as formation of nucleic acids, proteins, and acetylcholine. Orally-administered citicoline is hydrolyzed in the intestine, absorbed rapidly as choline and cytidine, resynthesized in liver and other tissues, and subsequently mobilized in CDP-choline synthetic pathways. Citicoline is efficiently utilized in brain cells for membrane lipid synthesis where it not only increases phospholipid synthesis but also inhibits phospholipid degradation. Exogenously administered citicoline prevents, reduces, or reverses effects of ischemia and/or hypoxia in most animal and cellular models studied, and acts in head trauma models to decrease and limit nerve cell membrane damage, restore intracellular regulatory enzyme sensitivity and function, and limit edema. Thus, considerable accumulated evidence supports use of citicoline to enhance membrane maintenance, membrane repair, and neuronal function in conditions such as ischemic and traumatic injuries. Beneficial effects of exogenous citicoline also have been postulated and/or reported in experimental models for dyskinesia, Parkinson's disease, cardiovascular disease, aging, Alzheimer's disease, learning and memory, and cholinergic stimulation.

Ischemic brain damage: focus on lipids and lipid mediators

The last two decades of research have produced detailed information not only on how ischemia causes degradation of phospholipids and accumulation of potentially cytotoxic breakdown products of such lipids, but also on reactions elicited by the subsequent conversion of these products into a series of lipids, mediating an array of cellular and intercellular reactions. It now seems clear that PAF, as well as several of the cyclooxygenase and lipoxygenase products of arachidonic acid, can induce changes, particularly in the microvasculature, which jeopardize cell survival in reperfused tissue. It is equally clear that, at least following long periods of ischemia, free radicals generated in reactions that are interacting with those producing eicosanoids and PAF play a similar role. A somewhat more speculative mechanism links sustained activation and membrane translocation of PKC to delayed neuronal death following transient ischemia. All of these interactions underscore the importance of lipolytic events for cell damage in ischemia and other conditions with a compromised cellular energy metabolism.

Changes in brain striatum dopamine and acetylcholine receptors induced by chronic CDP-choline treatment of aging mice

1. Spiroperidol binding (dopamine D2 receptors) and quinuclidinyl benzilate binding (muscarinic receptors) in striata of 19-month old mice was analyzed for animals that had received chronic administration of cytidine 5'-diphosphocholine (CDP-choline) incorporated into the chow consumed (100 or 500 mg kg-1 added per day) for the 7 months before they were killed. 2. Treated animals displayed an increase in the dopamine receptor densities of 11% for those receiving 100 mg kg-1 and 18% for those receiving 500 mg kg-1 as compared to the control aged animals that had received no CDP-choline. Control animals showed, from 2 months to 19 months of life, a 28% decrease in the receptor density. No change in the affinity of the receptors for spiroperidol was found in the treated or untreated animals. 3. Muscarinic acetylcholine receptor densities were also partially recovered by the same treatment in aged animals that showed a 14% decrease of these receptors in this case. The muscarinic receptor density increased 6% for the animals that received 100 mg kg-1 and 17% for the animals that received 500 mg kg-1 without any change in the affinity of the receptor for quinuclidinyl benzilate. 4. Aged animals displayed a slight increase in brain membrane fluidity as indicated by a decrease in the polarization value of the non-polar fluorophore 1,6-diphenyl-1,3,5-hexatriene. Interestingly, in the treated animals a greater increase in membrane fluidity was determined and found to be very similar for the two doses.5. It is concluded that chronic administration of CDP-choline to aged animals promoted a partial recovery of the striatum dopamine and acetylcholine receptor function normally reduced with aging, which might be explicable in terms of mechanisms involving fluidity of the brain neuronal membrane.

Treatment of acute cerebral infarction with a choline precursor in a multicenter double-blind placebo-controlled study

A multicenter double-blind placebo-controlled study of cytidine 5'-diphosphocholine (CDP-choline) was conducted to evaluate possible clinical benefits of the drug in patients with acute, moderate to severe cerebral infarction. The patients included also suffered from moderate to mild disturbances of consciousness, and all were admitted within 14 days of the ictus. Patients were allocated randomly to treatment with either CDP-choline (1,000 mg/day i.v. once daily for 14 days) or with placebo (physiological saline). One hundred thirty-three patients received CDP-choline treatment, and 139 received placebo. The group treated with CDP-choline showed significant improvements in level of consciousness compared with the placebo-treated group, and CDP-choline was an entirely safe treatment.

Effects of CDP-choline on phospholipase A2 and cholinephosphotransferase activities following a cryogenic brain injury in the rabbit

Within the tissue surrounding the necrotic lesion, following a cryogenic injury of the brain, there is a definite activation of phospholipase A2 (at 2 and 4 hr post lesion) that accounts, at least in part, for the phospholipid breakdown. There is also an activation of cholinephosphotransferase (at 2 hr post lesion) that may correspond to an early process of phospholipid resynthesis. Oral CDP-choline in this model is able to completely inhibit the activation of phospholipase A2, but has no detectable effect on cholinephosphotransferase activity. The beneficial effect of CDP-choline might be explained by a prevention of destruction rather than by an enhancement of reconstruction of phospholipids.

Arachidonic acid, stearic acid, and diacylglycerol accumulation correlates with the loss of phosphatidylinositol 4,5-bisphosphate in cerebrum 2 seconds after electroconvulsive shock: complete reversion of changes 5 minutes after stimulation

The effects of electroconvulsive shock (750 msec, 130 V, 150 pps) on the endogenous content of rat cerebral lipids were studied 2, 5, 10, 20, 30, 60, and 300 sec after stimulation. Rapid enzyme inactivation in situ was attained by high-power head-focused microwave irradiation (6.5 kW, 2450 MHz). At 10 sec, phosphatidylinositol 4,5-bisphosphate (PIP2) mass had decreased by 249 nmol per g wet wt, mainly due to loss of arachidonate and stearate. At the same time, the stearoyl-arachidonoyl glycerol accumulated, although to a lesser extent than the loss exhibited in PIP2. Changes in phosphatidylinositol and in phosphatidylinositol 4-phosphate mass were not statistically significant. Free fatty acids and diacylglycerols accumulated to 395 nmol per g wet wt; arachidonic and stearic acids composed 322 nmol of these lipids. Hence, the reduction in content of PIP2 is sufficient to account for 80% of the increases in free fatty acid and diacylglycerol mass. Thirty-three and 12 nmol of accumulated free palmitic and docosahexaenoic acids, respectively, are not accounted for by the loss of PIP2. Sixty seconds after stimulation, PIP2 content returned to 90% of control levels, while diacylglycerol tended to remain below control levels. Free fatty acids had not returned to control levels by 60 sec, with the exception of docosahexaenoic acid. At 300 sec, PIP2, diacylglycerol, and free fatty acids had all returned to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of CDP-choline on hypocapnic neurons in culture

Neuronal cultures from chick embryo cerebral hemispheres were protected against a hypocapnic injury by adding to their growth medium 10(-6)M CDP-choline before or after the injury. The protection obtained with CDP-choline was analyzed by a morphometric analysis and showed that pretreatment of neuronal cultures with CDP-choline maintained the number of cell aggregates and of primary neuronal processes at control values after hypocapnic shock. Various experiments showed that the intact molecule was responsible for the protective action, since pretreatment with different concentrations of various nucleosides and nucleotides (up to 10(-5) M), choline, and phosphorylcholine was without protective effect. The addition of CDP-choline after the hypocapnic injury resulted in a protection of the cultures as shown by morphological observation. Incubation of neurons with radioactive choline showed that hypocapnia increased the incorporation of the label into phospholipids whereas the presence of CDP-choline reduced it. The de novo synthesis of choline was affected by neither hypocapnia nor CDP-choline treatment. The results indicate that CDP-choline may have the capacity to protect neurons under conditions of basic pH and that cellular proliferation may be stimulated by the compound.

Polyphosphoinositides as a probable source of brain free fatty acids accumulated at the onset of ischemia

The quantitative relationship between phosphoinositides and free fatty acids (FFAs) in brain ischemia was studied by measuring contents of individual fatty acids in phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), phosphatidic acid (PA), diacylglycerol (DAG), and the FFA pool. Various periods of complete ischemia (1, 3, 10, and 30 min) were produced by decapitation. Ischemia of 1-3 min caused rapid decreases in PIP2 and PIP content together with preferential production of stearic and arachidonic acids in the DAG and FFA pools. The decrement in levels of these fatty acid residues in polyphosphoinositides was sufficient to account for their increment in levels in the enlarged DAG and FFA pools. After 10 min of ischemia, levels of PIP2, PIP, and DAG approached plateau values, but levels of all FFAs continued to increase. The increases in content of DAG and FFAs at later ischemic periods could not be accounted for by the decreases in content of PIP2 and PIP, PI and PA levels showed only transient and subtle changes. These results indicate that, at the onset of ischemia, phosphodiesteric cleavage of PIP2 and PIP and subsequent deacylation by lipases are primarily responsible for the preferential increase in levels of free stearic and arachidonic acids and that, later, hydrolysis of other phospholipids plays a major role in the continuous accumulation of FFAs.

Transport and metabolism of double-labelled CDPcholine in mammalian tissues

Double-labelled [methyl-14C,5-3H]CDPcholine has been synthesized and subjected to a pharmacokinetic analysis in several biological systems. In transport experiments with intact human erythrocytes no incorporation of radioactivity is observable. On the other hand the results obtained with perfused rat liver suggest a rapid cleavage of the pyrophosphate bridge of the molecule, followed by a rapid uptake of the hydrolytic products. The plasma half-lives of intravenously injected CDPcholine and of its metabolites have been evaluated within 60 sec range. Renal and fecal excretion of the injected radioactivity is negligible: only 2.5% of administered 14C- and 6.5% of the 3H- is excreted up to 48 hr after administration. Liver and kidney are the major CDPcholine metabolizing organs, characterized by a fast and extensive uptake of choline metabolites, followed by a slow release; conversely the rate of uptake of both 3H and 14C-labelled moieties by rat brain is significantly slower, reaching a steady-state level after 10 hr. The characterization of the labelled compounds detectable in the investigated organs provides some insights on the metabolism of the drug: the 3H-cytidine moiety in all the examined organs appears to be incorporated into the nucleic acid fraction via the cytidine nucleotide pool; the [14C]choline moiety of the molecule is in part converted, at the mitochondrial level, into betaine which accounts for about 60% of the total 14C-radioactivity associated with liver and kidney 30 min after administration; [14C]betaine in turn acts as methyl donor to homocysteine yielding [14C]methionine subsequently incorporated into proteins; the time dependent increase in labelled phospholipids is indicative of a recycling of the choline methyl-groups in this lipid fraction via CDPcholine and/or S-adenosylmethionine; the rather extensive amount of labelled methionine detectable in brain probably arises from its uptake from the blood stream, since the enzyme catalyzing the conversion of betaine into methionine is lacking in brain.

Free fatty acid content and release kinetics as manifestations of cerebral lateralization in mouse brain

Free fatty acid (FFA) content was analyzed in mouse cerebral hemispheres and cerebellum under basal and postdecapitative ischemic conditions. Total FFA content immediately after decapitation (2 s) was about two-fold higher in the left hemisphere than in the right. Marked dissimilarities between hemispheres were also apparent when FFA levels were measured during short periods of ischemia. Whereas in the right side a significant FFA release took place as early as 10 s, no accumulation was detected in the left in the 2-20 s interval. The highest rates of total fatty acid release occurred in the 20-30 s interval in both hemispheres and decreased afterwards (3 min). Individual FFA, especially stearate and arachidonate, differed in their rates of production, the right cerebral hemisphere being more active in releasing arachidonic acid. In cerebellum, FFA levels were lower and accumulation was slower than in cerebrum in both intervals. When subjected to 3 min ischemia, the same difference in FFA levels between right and left hemispheres (50%) was observed in heads kept at 20 or 30 degrees C. The differences between hemispheres are interpreted as manifestations of an inherent lateralization in the regulation of acylation-deacylation reactions of complex lipids.

The effect of CMP on the release of free fatty acids of rat brain in vitro

With CMP, phosphatidylcholine can be converted to diacylglycerols and CDPcholine by reversal of the cholinephosphotransferase that is normally used for synthesis. Incubation of homogenates of rat brains at pH 8 with 20 mM MgCl2 increased the free fatty acid (FFA) levels 30 to 117%. The FFA levels increased 62 to 212% when 4 mM CMP was included. Diacylglycerols were also produced. Hydrolysis of the diacylglycerols to FFA was markedly inhibited by inclusion of 3 mM diisopropylphosphofluoridate in the incubation mixture. The composition of the fatty acids released by CMP resembles that of phosphatidylcholine except for some polyunsaturated fatty acids. These may have been released from the ethanolamine glycerophospholipids. Most of the CMP-stimulated release of FFA was blocked by inclusion of 1 mM CDPcholine in the incubation mixture. Rat brains were labeled by intracerebral injection of [3H]oleic acid. The labeled oleic acid was released primarily from phosphatidylcholine. Thus, measurements of both mass and radioactivity confirm that the reversal of cholinephosphotransferase followed by diacylglycerol lipase can be an important pathway for the liberation of FFA from phosphatidylcholine.

Effects of postdecapitation ischemia on the metabolism of [14C]arachidonic acid and [14C]palmitic acid in the mouse brain

The effect of postdecapitation ischemia on the labeling of the free fatty acid pool and their incorporation in lipids was examined during the first 10 min after decapitation in mouse brain that had been injected intracerebrally with either [1-14C]arachidonic acid or [1-14C]palmitic acid. One min after decapitation, animals injected with labeled arachidonic acid exhibited a greatly reduced incorporation of label in brain phospholipids, diglycerides, and triglycerides. When radioactive palmitic acid was used, brain lipids exhibited considerably less inhibition of label. However, a similar degree of inhibition was observed 10 min after decapitation with both fatty acids. At this time, free arachidonic acid had decreased 84% as compared to the 24% decrease observed in the controls, and about 77% of the free palmitic acid remained in the free fatty acid fraction as compared with 30% in the controls. This decreased labeling may reflect ATP shortage that affects the fatty acid activation-reacylation reactions or the enzymes involved. Alternatively, the enhanced endogenous free arachidonic acid may compete with the radiolabeled arachidonic acid resulting in an inhibition of lipid labeling. Inhibition of label may have been greater in radiolabeled arachidonic acid than palmitic because of the larger accumulation of the former endogenous fatty acid during early ischemia.

Stimulation of free fatty acid and diacylglycerol accumulation in cerebrum and cerebellum during bicuculline-induced status epilepticus. Effect of pretreatment with alpha-methyl-p-tyrosine and p-chlorophenylalamine

The pool size and composition of free fatty acids (FFA) and diglycerides (DG) from the cerebrum and cerebellum of rats undergoing bicuculline-induced seizures were studied. A fourfold increase in cerebral FFA occurred 3-4 min after bicuculline injection; arachidonic and stearic acids were the principal fatty acids accumulated. Cerebellar FFA also increased, but to a lesser extent. An increased production of arachidonic acid took place in the cerebrum as a function of time after bicuculline injection. Other fatty acids produced were oleic, palmitic, and docosahexaenoic acids. A twofold increase in cerebral arachidonic acid was seen at the time of the first generalized tonic-clonic convulsion. However, a 13- to 17-fold increase in arachidonic acid was seen approximately 5-6 min after bicuculline injection. The rise in other FFA was much smaller. Stearoyl- and arachidonoyl-DG were also accumulated. The drug alpha-methyl-p-tyrosine was found to (a) potentiate the bicuculline-stimulated release of cerebellar FFA, and (b) inhibit by 70% the production of stearoyl- and arachidonoyl-DG in the cerebrum and cerebellum. Basal production of FFA was stimulated by p-chlorophenylalanine, but the drug had no effect on the bicuculline-induced changes. Hydrolysis of phospholipids enriched in stearoyl-arachidonoyl groups, such as phosphatidylinositol of excitable membranes, may be stimulated during seizures.

Drug action on the metabolic changes induced by acute hypoxia on synaptosomes from the cerebral cortex

The synaptosomal fractions obtained from the motor area of the cerebral cortex of normocapnic, normoxic, or hypoxic, untreated beagle dogs and of pentobarbital (Nembutal)- or cytidine diphosphate (CDP)-choline-treated dogs were incubated and analyzed for ATP, ADP, AMP, creatine phosphate, pyruvate, and lactate. The data were compared with data obtained by the surface freezing technique from the whole contralateral cortical area. The in vivo intracarotid perfusion of the drug differentially affected the content of the metabolites and their ratio. This occurred whether the evaluations were performed in the incubated synaptosomal preparations or in whole cerebral tissue, both during normoxia and after hypoxia (15 min; PaO2 = 17-19 mm Hg). Thus, intracarotid perfusion of nembutal increased the synaptosomal phosphorylation state both in normoxic and in hypoxic animals, whereas the effect on the metabolism of the contralateral cortical motor area as a whole was in all cases less than that observed in the synaptosomal fraction. Perfusion with CDP-choline increased synaptosomal phosphorylation after the hypoxic condition, but had no effect in normoxia or on the whole cortical tissue of the motor area. The possibility of obtaining a cerebral sparing action by utilizing molecules devoid of anesthetic action is suggested.