Carrier mediated blood-brain barrier transport of choline and certain choline analogs

MFSD7c functions as a transporter of choline at the blood-brain barrier

Mutations in the orphan transporter MFSD7c (also known as Flvcr2), are linked to Fowler syndrome. Here, we used Mfsd7c knockout (Mfsd7c-/-) mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics analysis and detected differential changes of metabolites in the brains and livers of Mfsd7c-/-embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the level of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch clamp analysis showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c was shown to be conserved in vertebrates, but not in yeasts. We demonstrated that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. We also showed that several missense mutations identified in patients exhibiting Fowler syndrome had abolished or reduced choline transport activity. Mice lacking Mfsd7c in endothelial cells of the central nervous system suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c was required for exporting choline derived from lysophosphatidylcholine in the brain. Collectively, our work identifies MFSD7c as a choline exporter at the BBB and provides a foundation for future work to reveal the disease mechanisms of Fowler syndrome.

Fermented soybean foods (natto) ameliorate age-related cognitive decline by hippocampal TAAR1-mediated activation of the CaMKII/CREB/BDNF signaling pathway in senescence-accelerated mouse prone 8 (SAMP8)

Natto is a traditional fermented soybean-based food that has been an integral part of Japanese cuisine for several centuries. Although there have been extensive studies on the cognitive benefits of soybeans, only limited studies have examined the effects of natto on cognitive function. This study investigated the potential cognitive benefits of natto in senescence-accelerated mouse-prone 8 (SAMP8) mice. After 12 weeks of oral administering natto fermented for 18 h, the spatial learning and memory performance were improved compared with those in SAMP8 control mice. Furthermore, activation of the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element-binding protein (CREB) signaling and N-methyl-D-aspartate receptor (NMDAR)-calcium/calmodulin-dependent protein kinase II (CaMKII) cascade was observed in the hippocampus of SAMP8 mice that were fed natto. Additionally, natto administration upregulated trace amine-associated receptor 1 (TAAR1) as a modulator of NMDAR. These findings suggest that natto ameliorates cognitive decline by activating the TAAR1-mediated CaMKII/CREB/BDNF signaling pathway in the hippocampus of SAMP8 mice.

Hemodialysis-Related Acute Brain Injury Demonstrated by Application of Intradialytic Magnetic Resonance Imaging and Spectroscopy

SIGNIFICANCE STATEMENT

Hemodialysis (HD) results in reduced brain blood flow, and HD-related circulatory stress and regional ischemia are associated with brain injury over time. However, studies to date have not provided definitive direct evidence of acute brain injury during a HD treatment session. Using intradialytic magnetic resonance imaging (MRI) and spectroscopy to examine HD-associated changes in brain structure and neurochemistry, the authors found that multiple white (WM) tracts had diffusion imaging changes characteristic of cytotoxic edema, a consequence of ischemic insult and a precursor to fixed structural WM injury. Spectroscopy showed decreases in prefrontal N -acetyl aspartate (NAA) and choline concentrations consistent with energy deficit and perfusion anomaly. This suggests that one HD session can cause brain injury and that studies of interventions that mitigate this treatment's effects on the brain are warranted.

BACKGROUND

Hemodialysis (HD) treatment-related hemodynamic stress results in recurrent ischemic injury to organs such as the heart and brain. Short-term reduction in brain blood flow and long-term white matter changes have been reported, but the basis of HD-induced brain injury is neither well-recognized nor understood, although progressive cognitive impairment is common.

METHODS

We used neurocognitive assessments, intradialytic anatomical magnetic resonance imaging, diffusion tensor imaging, and proton magnetic resonance spectroscopy to examine the nature of acute HD-associated brain injury and associated changes in brain structure and neurochemistry relevant to ischemia. Data acquired before HD and during the last 60 minutes of HD (during maximal circulatory stress) were analyzed to assess the acute effects of HD on the brain.

RESULTS

We studied 17 patients (mean age 63±13 years; 58.8% were male, 76.5% were White, 17.6% were Black, and 5.9% were of Indigenous ethnicity). We found intradialytic changes, including the development of multiple regions of white matter exhibiting increased fractional anisotropy with associated decreases in mean diffusivity and radial diffusivity-characteristic features of cytotoxic edema (with increase in global brain volumes). We also observed decreases in proton magnetic resonance spectroscopy-measured N -acetyl aspartate and choline concentrations during HD, indicative of regional ischemia.

CONCLUSIONS

This study demonstrates for the first time that significant intradialytic changes in brain tissue volume, diffusion metrics, and brain metabolite concentrations consistent with ischemic injury occur in a single dialysis session. These findings raise the possibility that HD might have long-term neurological consequences. Further study is needed to establish an association between intradialytic magnetic resonance imaging findings of brain injury and cognitive impairment and to understand the chronic effects of HD-induced brain injury.

CLINICAL TRIALS INFORMATION

NCT03342183 .

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Blood-brain barrier delivery for lysosomal storage disorders with IgG-lysosomal enzyme fusion proteins

The majority of lysosomal storage diseases affect the brain. Treatment of the brain with intravenous enzyme replacement therapy is not successful, because the recombinant lysosomal enzymes do not cross the blood-brain barrier (BBB). Biologic drugs, including lysosomal enzymes, can be re-engineered for BBB delivery as IgG-enzyme fusion proteins. The IgG domain of the fusion protein is a monoclonal antibody directed against an endogenous receptor-mediated transporter at the BBB, such as the insulin receptor or the transferrin receptor. This receptor transports the IgG across the BBB, in parallel with the endogenous receptor ligand, and the IgG acts as a molecular Trojan horse to ferry into brain the lysosomal enzyme genetically fused to the IgG. The IgG-enzyme fusion protein is bi-functional and retains both high affinity binding for the BBB receptor, and high lysosomal enzyme activity. IgG-lysosomal enzymes are presently in clinical trials for treatment of the brain in Mucopolysaccharidosis.

Effects of ethanol-and choline-treated astrocytes on hippocampal neuron neurite outgrowth in vitro

Exposure to ethanol in utero can result in Fetal Alcohol Spectrum Disorders, which may cause long-lasting cognitive and behavioral abnormalities. Preclinical studies indicate that choline ameliorates the behavioral effects of developmental alcohol exposure in rodents, and clinical studies on the effectiveness of choline, administered early in pregnancy, showed that the adverse effects of heavy prenatal alcohol exposure on postnatal growth, and cognition in human infants were mitigated. However, little is known on the mechanisms behind the effects of choline. We have previously reported that astrocyte pre-treatment with 75 mM ethanol, in vitro, reduces neurite outgrowth in hippocampal neurons co-cultured with the pre-treated astrocytes. Our in vitro system allows us to study the effects of chemicals on astrocyte functions, able to modulate neuronal development. The main objective was to test the hypothesis that choline can ameliorate the astrocyte-mediated effects of ethanol on neurite growth. In this study, we exposed primary rat cortical astrocytes to ethanol, choline, ethanol plus choline, or control conditions for 24 h. Culture media was then removed, replaced with fresh media containing no ethanol or choline treatments and primary rat hippocampal neurons were plated on top of the astrocyte monolayer and cultured for 16 h. Neurons were then stained for β-III Tubulin and neurite outgrowth was measured. Astrocyte exposure to ethanol (25, 50, and 75 mM) decreases neurite outgrowth in co-cultured hippocampal pyramidal neurons, while astrocyte treatment with choline had no effect. Astrocyte treatment with ethanol and choline in combination, however, prevented the effect of ethanol, leading to levels of neurite outgrowth similar the control condition. Choline prevents the inhibitory effect of ethanol-treated astrocytes on neurite outgrowth while not altering normal neuronal development. These results suggest a new, astrocyte-mediated mechanism by which choline ameliorates the effects of developmental alcohol exposure.

Attenuation of neurological deficit by a novel ethanolamine derivative in rats after brain trauma

Objectives: To prove that our novel ethanolamine derivative (FDES) can normalize overall movement and exploratory activity of rats with traumatic brain injury (TBI) owing to its peculiar properties.

Materials and methods: TBI was modeled using controlled cortical impact injury (CCI) model method. The resulting neurological deficit, efficacy of the novel agent and other reference agents used were assayed in tests which evaluated overall movements and exploratory behavior of the rats. Finally, scopolamine in equimolar dose was used to estimate the role of cholinergic system in the efficacy of our agent. The tests included: limb-placing, open field, elevated plus maze, cylinder, and beam walking tests.

Results: Intraperitoneal administration of FDES at a dose of 10 mg/kg led to improvement of fore- and hind-limb functions of rats with traumatic brain injury as was shown in “Limb placing”, “Open field” “Cylinder” and “Beam walking” tests. The new agent had no effects on traumatized rats behavior in the “Elevated Plus Maze” test. Simultaneous co-administration of scopolamine with FDES reduced the beneficial effects of the latter in rats with trauma.

Conclusion: The neuroprotective effects of new agent were manifested in the reduction of motor deficiencies, and exploratory activity in the CCI model rats. In comparison with choline alfoscerate and citicoline, FDES showed more beneficial effects as were observed in most of the tests, and did not negatively influence the traumatized rats psychologically. Notably, it is possible that the neuroprotective influence of the new agent is mediated by its actions on the cholinergic system.

Plasma Betaine Is Positively Associated with Developmental Outcomes in Healthy Toddlers at Age 2 Years Who Are Not Meeting the Recommended Adequate Intake for Dietary Choline

Background

Choline is an important nutrient during development. However, there are limited data on dietary choline intake and status in toddlers and the relation to neurodevelopmental outcomes.

Objective

This study assessed dietary choline intake and status in healthy toddlers at ages 1 and 2 y and determined the relation to neurodevelopmental outcomes.

Methods

This is a secondary analysis of data from healthy toddlers enrolled in a double-blind, randomized controlled trial of long-chain polyunsaturated fatty acid supplementation between ages 1 and 2 y. Dietary intakes of betaine and choline were estimated by 3-d food records; plasma free choline, betaine, and dimethylglycine were quantified by liquid chromatography-tandem mass spectrometry. Developmental outcomes were assessed at age 2 y with the use of the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III), Cognitive and Language composites, and the Beery-Buktenica Developmental Test of Visual-Motor Integration (Beery-VMI).

Results

The mean ± SD daily intake for total choline at age 1 y was 174 ± 56.2 mg/d and increased (P < 0.001) to 205 ± 67.5 mg/d at age 2 y. At ages 1 and 2 y, 71.8% and 55.8%, respectively, of toddlers did not meet the recommended 200-mg/d Adequate Intake (AI) for dietary choline. At age 1 y, mean ± SD plasma free choline, betaine, and dimethylglycine concentrations were 10.4 ± 3.3, 41.1 ± 15.4, and 4.1 ± 1.9 µmol/L, respectively. Plasma free choline (8.5 ± 2.3 µmol/L) and dimethylglycine (3.2 ± 1.3 µmol/L) concentrations were lower (P < 0.001) at age 2 y. Plasma betaine concentrations were positively associated with the Beery-VMI (β = 0.270; 95% CI: 0.026, 0.513; P = 0.03) at age 2 y.

Conclusions

These findings suggest that most toddlers are not meeting the recommended AI for dietary choline and that higher plasma betaine concentrations are associated with better visual-motor development at age 2 y. Further work is required to investigate choline metabolism and its role in neurodevelopment in toddlers. The trial is registered at clinicaltrials.gov as NCT01263912.

High yield one-pot production of [18F]FCH via a modified TRACERlab FxFN module

INTRODUCTION

[¹⁸F]Fluoromethylcholine ([¹⁸F]FCH) is a potent tumors imaging agent. In order to fulfill the demand of pre-clinical and clinical studies, we have developed an automated high yield one-pot synthesis of this potent tumors imaging agent.

METHODS

[¹⁸F]FCH was synthesized using a modified TRACERlab Fx_FN module. Briefly, dibromomethane (10% in CH₃CN) was fluorinated with K[¹⁸F]/K _2.2.2 in a glassy carbon reaction vessel at 120°C for about 5min to generate [¹⁸F]fluorobromomethane ([¹⁸F]FBM). The resulting [¹⁸F]FBM was then bubbling (He, 700mL/min) through four Sep-Pak® Silica Plus Long cartridges to react with dimethylaminoethanol (10% DMAE in 0.3mL DMSO) which was pre-loaded on Sep-Pak® C₁₈ Plus Short cartridge. The [¹⁸F]FCH was purified by solid-phase extraction (SPE) using one Sep-Pak® C₁₈ Plus Short and one Sep-Pak® CM Plus Short in series. The quality of [¹⁸F]FCH synthesized by this method was verified by HPLC and TLC as compared to authentic sample.

RESULTS

Using this improved one-pot method, the RCY of [¹⁸F]FCH was 18.8 ± 2.1% (EOB, n = 27) in a synthesis time of 49 ± 5min from EOB. The radiochemical purity of [¹⁸F]FCH was greater than 90% and the residual DMAE concentration in the final product was less than 10ppm.

CONCLUSIONS

This optimized method could fulfill the demand of [¹⁸F]FCH for both pre-clinical and clinical studies, especially for nearby study sites without a cyclotron.

Portable Sensor for the Detection of Choline and Its Derivatives Based on Silica Isoporous Membrane and Gellified Nanointerfaces

A portable amperometric ion sensor was fabricated by integrating silica isoporous membrane (SIM) and organogel composed of polyvinyl chloride and 1,2-dichloroethane (PVC-DCE) on a 3D-printed polymer chip. The detection of ionic species in aqueous samples could be accomplished by adding a microliter of sample droplet to the sensor and by identifying the ion-transfer potential and current magnitude at the water/organogel interface array templated by SIM. Thanks to the ultrasmall channel size (2-3 nm in diameter), high channel density (4 × 10⁸ μm^-2), and ultrathin thickness (80 nm) of SIM, the ensemble of nanoscopic water/organogel (nano-W/Gel) interface array behaved like a microinterface with two back-to-back hemispherical mass diffusion zones. So, the heterogeneous ion-transfer across the nano-W/Gel interface array generated a steady-state sigmoidal current wave. The detection of choline (Ch) and its derivatives, including acetylcholine (ACh), benzoylcholine (BCh), and atropine (AP), in aqueous samples was examined with this portable sensor. Using differential pulse stripping voltammetry (DPSV), the quantification of these analytes was achieved with a limit of detection (LOD) down to 1 μM. Moreover, the portable ion sensor was insensitive to various potential interferents that might coexist in vivo, owing to size-/charge-based selectivity and antifouling capacity of SIM. With this priority, the portable ion sensor was able to quantitatively determine Ch and its derivatives in diluted urine and blood samples. The LODs for Ch, ACh, AP, and BCh in urine were 1.12, 1.30, 1.08, and 0.99 μM, and those for blood samples were 3.61, 3.38, 2.32, and 1.81 μM, respectively.

Convection-Enhanced and Local Delivery of Targeted Cytotoxins in the Treatment of Malignant Gliomas

Despite advances in our knowledge about the genesis, molecular biology, and natural history of malignant gliomas and the use of a multi-disciplinary approach to their treatment, patients harboring this diagnosis continue to face a grim prognosis. At the time of diagnosis, patients typically undergo surgery for the establishment of a histologic diagnosis, the reduction of tumor burden, and the relief of mass effect, with the maintenance of the patient's neurological function in mind. This is followed by the administration of adjuvant therapeutics, including radiation therapy and chemotherapy.

Many investigational agents with laboratory evidence of efficacy against malignant gliomas have not met their promise in the clinical setting, largely due to the barriers that they must overcome to reach the tumor at a therapeutically meaningful concentration for a durable period of time. The relevant aspects of the blood-brain barrier, blood-tumor barrier, and blood-cerebrospinal fluid barrier, as they pertain to the delivery of agents to the tumor, will be discussed along with the strategies devised to circumvent them. This discussion will be followed by a description of agents currently in preclinical and clinical development, many of which are the result of intense ongoing research into the molecular biology of gliomas.

Blood-brain barrier endogenous transporters as therapeutic targets: a new model for small molecule CNS drug discovery

INTRODUCTION

The blood-brain barrier (BBB) limits the uptake of most drugs by brain, and the traditional approach to the BBB problem is the use of medicinal chemistry to increase drug lipid solubility, and increase lipid-mediated transport across the BBB. This review advocates a new model to CNS drug discovery of BBB-penetrating small molecules, whereby drug candidates are screened for carrier-mediated transport (CMT) across the BBB.

AREAS COVERED

CMT systems are expressed by genes within the Solute Carrier (SLC) Transporter Gene Family, which now totals > 400 transporter genes. Emphasis is placed on reconciliation of the substrate transporter profile (STP) of BBB transport in vivo with the STP of the cloned SLC transporter in vitro. This reconciliation is crucial to the identification, from sometimes a large number of candidates, of the respective SLC transporter that is responsible for BBB transport in vivo for a given class of nutrients.

EXPERT OPINION

Dual track screening of a small molecule library for drugs that have the dual properties of affinity for a neural cell drug receptor target, and affinity for a BBB CMT transporter target, can lead to a revolution in how small molecule drugs are identified in CNS drug discovery programs.

Evidence for altered metabolic pathways during environmental stress: (1)H-NMR spectroscopy based metabolomics and clinical studies on subjects of sea-voyage and Antarctic-stay

The Antarctic context is an analogue of space travel, with close similarity in ambience of extreme climate, isolation, constrained living spaces, disrupted sleep cycles, and environmental stress. The present study examined the impact of the harsh habitat of Antarctica on human physiology and its metabolic pathways, by analyzing human serum samples, using (1)H-NMR spectroscopy for identification of metabolites; and quantifying other physiological and clinical parameters for correlation between expression data and metabolite data. Sera from seven adult males (of median age 36years) who participated in this study, from the 28th Indian Expeditionary group to the Antarctica station Maitri, were collected in chronological sequence. These included: i) baseline control; ii) during ship journey; iii) at Antarctica, in the months of March, May, August and November; to enable study of temporal evolution of monitored physiological states. 29 metabolites in serum were identified from the 400MHz (1)H-NMR spectra. Out of these, 19 metabolites showed significant variations in levels, during the ship journey and the stay at Maitri, compared to the base-line levels. Further biochemical analysis also supported these results, indicating that the ship journey, and the long-term Antarctic exposure, affected kidney and liver functioning. Our metabolite data highlights for the first time the effect of environmental stress on the patho-physiology of the human system. Multivariate analysis tools were employed for this metabonomics study, using (1)H-NMR spectroscopy.

A fully-automated one-pot synthesis of [18F]fluoromethylcholine with reduced dimethylaminoethanol contamination via [18F]fluoromethyl tosylate

INTRODUCTION

A novel one-pot method for preparing [(18)F]fluoromethylcholine ([(18)F]FCH) via in situ generation of [(18)F]fluoromethyl tosylate ([(18)F]FCH2OTs), and subsequent [(18)F]fluoromethylation of dimethylaminoethanol (DMAE), has been developed.

METHODS

[(18)F]FCH was prepared using a GE TRACERlab FXFN, although the method should be readily adaptable to any other fluorine-(18) synthesis module. Initially ditosylmethane was fluorinated to generate [(18)F]FCH2OTs. DMAE was then added and the reaction was heated at 120 °C for 10 min to generate [(18)F]FCH. After this time, reaction solvent was evaporated, and the crude reaction mixture was purified by solid-phase extraction using C(18)-Plus and CM-Light Sep-Pak cartridges to provide [(18)F]FCH formulated in USP saline. The formulated product was passed through a 0.22 µm filter into a sterile dose vial, and submitted for quality control testing. Total synthesis time was 1.25 h from end-of-bombardment.

RESULTS

Typical non-decay-corrected yields of [(18)F]FCH prepared using this method were 91 mCi (7% non-decay corrected based upon ~1.3 Ci [(18)F]fluoride), and doses passed all other quality control (QC) tests.

CONCLUSION

A one-pot liquid-phase synthesis of [(18)F]FCH has been developed. Doses contain extremely low levels of residual DMAE (31.6 µg/10 mL dose or ~3 ppm) and passed all other requisite QC testing, confirming their suitability for use in clinical imaging studies.

Extracellular matrix formation enhances the ability of Streptococcus pneumoniae to cause invasive disease

During infection, pneumococci exist mainly in sessile biofilms rather than in planktonic form, except during sepsis. However, relatively little is known about how biofilms contribute to pneumococcal pathogenesis. Here, we carried out a biofilm assay on opaque and transparent variants of a clinical serotype 19F strain WCH159. After 4 days incubation, scanning electron microscopy revealed that opaque biofilm bacteria produced an extracellular matrix, whereas the transparent variant did not. The opaque biofilm-derived bacteria translocated from the nasopharynx to the lungs and brain of mice, and showed 100-fold greater in vitro adherence to A549 cells than transparent bacteria. Microarray analysis of planktonic and sessile bacteria from transparent and opaque variants showed differential gene expression in two operons: the lic operon, which is involved in choline uptake, and in the two-component system, ciaRH. Mutants of these genes did not form an extracellular matrix, could not translocate from the nasopharynx to the lungs or the brain, and adhered poorly to A549 cells. We conclude that only the opaque phenotype is able to form extracellular matrix, and that the lic operon and ciaRH contribute to this process. We propose that during infection, extracellular matrix formation enhances the ability of pneumococci to cause invasive disease.

Choline and betaine in health and disease

Choline is an essential nutrient, but is also formed by de novo synthesis. Choline and its derivatives serve as components of structural lipoproteins, blood and membrane lipids, and as a precursor of the neurotransmitter acetylcholine. Pre-and postnatal choline availability is important for neurodevelopment in rodents. Choline is oxidized to betaine that serves as an osmoregulator and is a substrate in the betaine-homocysteine methyltransferase reaction, which links choline and betaine to the folate-dependent one-carbon metabolism. Choline and betaine are important sources of one-carbon units, in particular, during folate deficiency. Choline or betaine supplementation in humans reduces concentration of total homocysteine (tHcy), and plasma betaine is a strong predictor of plasma tHcy in individuals with low plasma concentration of folate and other B vitamins (B₂, B₆, and B₁₂) in combination TT genotype of the methylenetetrahydrofolate reductase 677 C->T polymorphism. The link to one-carbon metabolism and the recent availability of food composition data have motivated studies on choline and betaine as risk factors of chronic diseases previously studied in relation to folate and homocysteine status. High intake and plasma level of choline in the mother seems to afford reduced risk of neural tube defects. Intake of choline and betaine shows no consistent relation to cancer or cardiovascular risk or risk factors, whereas an unfavorable cardiovascular risk factor profile was associated with high choline and low betaine concentrations in plasma. Thus, choline and betaine showed opposite relations with key components of metabolic syndrome, suggesting a disruption of mitochondrial choline oxidation to betaine as part of the mitochondrial dysfunction in metabolic syndrome.

Nutritional modifiers of aging brain function: use of uridine and other phosphatide precursors to increase formation of brain synapses

Brain phosphatide synthesis requires three circulating compounds: docosahexaenoic acid (DHA), uridine, and choline. Oral administration of these phosphatide precursors to experimental animals increases the levels of phosphatides and synaptic proteins in the brain and per brain cell as well as the numbers of dendritic spines on hippocampal neurons. Arachidonic acid fails to reproduce these effects of DHA. If similar increases occur in human brain, administration of these compounds to patients with diseases that cause loss of brain synapses, such as Alzheimer's disease, could be beneficial.

Biodistribution and radiation dosimetry of [(11)C]choline: a comparison between rat and human data

PURPOSE

Methyl-(11)C-choline ([(11)C]choline) is a radiopharmaceutical used for oncological PET studies. We investigated the biodistribution and biokinetics of [(11)C]choline and provide estimates of radiation doses in humans.

METHODS

The distribution of [(11)C]choline was evaluated ex vivo in healthy rats (n=9) by measuring the radioactivity of excised organs, and in vivo in tumour-bearing rats (n=4) by PET. In addition to estimates of human radiation doses extrapolated from rat data, more accurate human radiation doses were calculated on the basis of PET imaging of patients with rheumatoid arthritis (n=6) primarily participating in a synovitis imaging project with [(11)C]choline. Dynamic data were acquired from the thorax and abdomen after injection of 423+/-11 MBq (mean+/-SD) of tracer. Following PET imaging, the radioactivity in voided urine was measured. The experimental human data were used for residence time estimations. Radiation doses were calculated with OLINDA/EXM.

RESULTS

In rats, the radioactivity distributed mainly to the kidneys, lungs, liver and adrenal gland. The effective dose in a human adult of about 70 kg was 0.0044 mSv/MBq, which is equivalent to 2.0 mSv from 460 MBq of [(11)C]choline PET. The highest absorbed doses in humans were 0.021 mGy/MBq in the kidneys, 0.020 mGy/MBq in the liver and 0.029 mGy/MBq in the pancreas. Only 2.0% of injected radioactivity was excreted in the urine during the 1.5 h after injection.

CONCLUSION

The absorbed radiation doses after administration of 460 MBq of [(11)C]choline were low. Except for the pancreas, biodistribution in the rat was in accordance with that in humans, but rat data may underestimate the effective dose, suggesting that clinical measurements are needed for a more detailed estimation. The observed effective doses suggest the feasibility of [(11)C]choline PET for human studies.

Nutrition and Alzheimer's disease: pre-clinical concepts

Alzheimer's disease (AD) is a progressive condition characterized by neurodegeneration and the dense deposition of proteins in the brain. There is no cure for AD and current treatments usually only provide a temporary reduction of symptoms. There is thus a strong unmet need for effective preventative and therapeutic strategies and the potential role for nutrition in such strategies is rapidly gaining interest. An Alzheimer's brain contains fewer synapses and reduced levels of synaptic proteins and membrane phosphatides. Brain membrane phosphatide synthesis requires at least three dietary precursors: polyunsaturated fatty acids, uridine monophosphate (UMP) and choline. Animal studies have shown that administration of these nutrients increases the level of phosphatides, specific pre- or post-synaptic proteins and the number of dendritic spines - a requirement for new synapse formation. These effects are markedly enhanced when animals receive all three compounds together. This multi-nutrient approach in animals has also been shown to decrease amyloid beta protein (Abeta) plaque burden, improve learning and memory through increased cholinergic neurotransmission and have a neuroprotective effect in several mouse models of AD. Whether these potential therapeutic effects of a multi-nutrient approach observed in animal models can also be replicated in a clinical setting warrants further investigation.

Use of phosphatide precursors to promote synaptogenesis

New brain synapses form when a postsynaptic structure, the dendritic spine, interacts with a presynaptic terminal. Brain synapses and dendritic spines, membrane-rich structures, are depleted in Alzheimer's disease, as are some circulating compounds needed for synthesizing phosphatides, the major constituents of synaptic membranes. Animals given three of these compounds, all nutrients-uridine, the omega-3 polyunsaturated fatty acid docosahexaenoic acid, and choline-develop increased levels of brain phosphatides and of proteins that are concentrated within synaptic membranes (e.g., PSD-95, synapsin-1), improved cognition, and enhanced neurotransmitter release. The nutrients work by increasing the substrate-saturation of low-affinity enzymes that synthesize the phosphatides. Moreover, uridine and its nucleotide metabolites activate brain P2Y receptors, which control neuronal differentiation and synaptic protein synthesis. A preparation containing these compounds is being tested for treating Alzheimer's disease.

Getting into the brain: approaches to enhance brain drug delivery

Being the most delicate organ of the body, the brain is protected against potentially toxic substances by the blood-brain barrier (BBB), which restricts the entry of most pharmaceuticals into the brain. The developmental process for new drugs for the treatment of CNS disorders has not kept pace with progress in molecular neurosciences because most of the new drugs discovered are unable to cross the BBB. The clinical failure of CNS drug delivery may be attributed largely to a lack of appropriate drug delivery systems. Localized and controlled delivery of drugs at their desired site of action is preferred because it reduces toxicity and increases treatment efficiency. The present review provides an insight into some of the recent advances made in the field of brain drug delivery.The various strategies that have been explored to increase drug delivery into the brain include (i) chemical delivery systems, such as lipid-mediated transport, the prodrug approach and the lock-in system; (ii) biological delivery systems, in which pharmaceuticals are re-engineered to cross the BBB via specific endogenous transporters localized within the brain capillary endothelium; (iii) disruption of the BBB, for example by modification of tight junctions, which causes a controlled and transient increase in the permeability of brain capillaries; (iv) the use of molecular Trojan horses, such as peptidomimetic monoclonal antibodies to transport large molecules (e.g. antibodies, recombinant proteins, nonviral gene medicines or RNA interference drugs) across the BBB; and (v) particulate drug carrier systems. Receptor-mediated transport systems exist for certain endogenous peptides, such as insulin and transferrin, enabling these molecules to cross the BBB in vivo.The use of polymers for local drug delivery has greatly expanded the spectrum of drugs available for the treatment of brain diseases, such as malignant tumours and Alzheimer's disease. In addition, various drug delivery systems (e.g. liposomes, microspheres, nanoparticles, nanogels and bionanocapsules) have been used to enhance drug delivery to the brain. Recently, microchips and biodegradable polymers have become important in brain tumour therapy.The intense search for alternative routes of drug delivery (e.g. intranasal drug delivery, convection-enhanced diffusion and intrathecal/intraventricular drug delivery systems) has been driven by the need to overcome the physiological barriers of the brain and to achieve high drug concentrations within the brain. For more than 30 years, considerable efforts have been made to enhance the delivery of therapeutic molecules across the vascular barriers of the CNS. The current challenge is to develop drug delivery strategies that will allow the passage of drug molecules through the BBB in a safe and effective manner.

Effects of adult-onset choline deprivation on the activities of acetylcholinesterase, (Na+,K+)- and Mg2+-ATPase in crucial rat brain regions

Choline (Ch) plays an important role in brain neurotransmission, while Ch-deprivation (CD) has been linked to various pathophysiological states. Prolonged ingestion of Ch-deficient diet (CDD) is known to produce CD causing a reduction of rat brain acetylcholine (ACh) levels, as well as memory and growth disorders. The aim of this study was to investigate the effect of a 2-month adult-onset CD on the activities of acetylcholinesterase (AChE), (Na+,K+)- and Mg2+-ATPase in crucial brain regions of male rats. Adult rats were divided into two groups (control and CD). The CD group was fed with CDD for 2-months. At the end of the second month, rats were sacrificed by decapitation and the brain regions were rapidly removed. Enzyme activities were measured spectrophotometrically in the homogenated frontal cortex, hippocampus, hypothalamus, cerebellum, and pons. In CD rats, AChE activity was found statistically significantly increased in the hippocampus and the cerebellum (+28%, P<0.001 and +46%, P<0.001, respectively, as compared to control), while it was found unaltered in the other three regions (frontal cortex, hypothalamus and pons). (Na+,K+)-ATPase activity was found increased by CD in the frontal cortex (+30%, P<0.001), decreased in both hippocampus and hypothalamus (-68%, P<0.001 and -51%, P<0.001, respectively), and unaltered in both cerebellum and pons. No statistically significant changes were observed in the activities of Mg2+-ATPase in the frontal cortex and the hypothalamus, while statistically significant increases were recorded in the hippocampus (+21%, P<0.01), the cerebellum (+85%, P<0.001) and the pons (+19%, P<0.05), as compared to control levels. Our data suggest that adult-onset CD can have significant effects on the examined brain parameters in the examined crucial brain regions, as well as that CD is a metabolic disorder towards which different and brain region specific neurophysiological responses seem to occur. Following a 2-month adult-onset CD, the activity of AChE was found to be increased in the hippocampus and the cerebellum and unaltered in the other three regions (frontal cortex, hypothalamus and pons), while Na+,K+-ATPase activity was found to be increased in the frontal cortex, decreased in both hippocampus and hypothalamus, and unaltered in both cerebellum and pons. Moreover, Mg2+-ATPase activity was found to be unaltered in the frontal cortex and the hypothalamus, and increased in the hippocampus, the cerebellum and the pons. The observed differentially affected activities of AChE, (Na+,K+)-ATPase and Mg2+-ATPase (induced by CD) could result in modulations of cholinergic neurotransmission, neural excitability, metabolic energy production, Mg2+ homeostasis and protein synthesis (that might have a variety of neurophysiological consequences depending on the brain region in which they seem to occur).

Equilibrated diet restores the effects of early age choline-deficient feeding on rat brain antioxidant status and enzyme activities: the role of homocysteine, L-phenylalanine and L-alanine

Choline is an essential nutrient that seems to be involved in a wide variety of metabolic reactions and functions, that affect the developing brain. The aim of this study was to: (a)examine the effects of early age choline deficient diet (CDD) administration on the total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), (Na(+),K(+))-ATPase and Mg(2+)-ATPase in the rat brain, (b)investigate the effect of feeding restoration into an equilibrated diet on the above parameters, and (c)study the role of homocysteine (Hcy), L: -phenylalanine (Phe) and L: -alanine (Ala) in certain of the above effects. Male and female Wistar rats were continuously kept off choline (Ch) during their gestational period of life, as well as during the first 6 weeks of their post-gestational life. The animals were sacrificed by decapitation and their whole brains were rapidly removed and homogenated. Their enzyme activities were measured spectrophotometrically. Moreover, in vitro experiments were conducted in order to estimate the effects of Hcy (0.3 mM), Phe (1.2 mM) and/or Ala (1.2 mM) on the above parameters. The administration of CDD led to a statistically significant decrease of the rat brain TAS (-29%, p < 0.001) and to a significant increase of both AChE (+20%, p < 0.001) and (Na(+),K(+))-ATPase (+35%, p < 0.001) activities. Mg(2+)-ATPase activity was found unaltered. Equilibrated diet, administered to early age CDD-treated rats of both sexes for an additional period of 18 weeks, restored the above parameters to control levels. Moreover, the in vitro experiments showed that Hcy could simulate these changes (at least under the examined in vitro conditions), while both Phe and Ala act protectively against the CDD-induced effects on the examined rat brain enzyme activities. The effects of early age CDD-feeding on the examined parameters are proved to be reversible through restoration to equilibrated diet, while our data suggest a role for Hcy (as a causative parameter for the CDD-induced effects) and a possible protective role for Phe and Ala (in reversing the observed CDD-induced effects).

Active targeting of brain tumors using nanocarriers

The delivery of drugs to brain tumors is limited by the presence of the blood-brain barrier (BBB) separating the blood from the cerebral parenchyma. An understanding of the specific mechanisms of the brain capillary endothelium has led to the development of various strategies to enhance the penetration of drugs into the brain tissue. Active targeting is a non-invasive approach, which consists in transporting drugs to target organs using site-specific ligands. Drug-loaded nanocarriers capable of recognizing brain capillary endothelial cells and cerebral tumoral cells have shown promising potential in oncology. Endogenous and chimeric ligands binding to carriers or receptors of the BBB have been directly or indirectly conjugated to nanocarriers. This review indexes the main targeted colloidal systems used for drug delivery to the brain. Their pharmacological behavior and their therapeutic effect are discussed.

Chronic administration of docosahexaenoic acid or eicosapentaenoic acid, but not arachidonic acid, alone or in combination with uridine, increases brain phosphatide and synaptic protein levels in gerbils

Synthesis of phosphatidylcholine, the most abundant brain membrane phosphatide, requires three circulating precursors: choline; a pyrimidine (e.g. uridine); and a polyunsaturated fatty acid. Supplementing a choline-containing diet with the uridine source uridine-5'-monophosphate (UMP) or, especially, with UMP plus the omega-3 fatty acid docosahexaenoic acid (given by gavage), produces substantial increases in membrane phosphatide and synaptic protein levels within gerbil brain. We now compare the effects of various polyunsaturated fatty acids, given alone or with UMP, on these synaptic membrane constituents. Gerbils received, daily for 4 weeks, a diet containing choline chloride with or without UMP and/or, by gavage, an omega-3 (docosahexaenoic or eicosapentaenoic acid) or omega-6 (arachidonic acid) fatty acid. Both of the omega-3 fatty acids elevated major brain phosphatide levels (by 18-28%, and 21-27%) and giving UMP along with them enhanced their effects significantly. Arachidonic acid, given alone or with UMP, was without effect. After UMP plus docosahexaenoic acid treatment, total brain phospholipid levels and those of each individual phosphatide increased significantly in all brain regions examined (cortex, striatum, hippocampus, brain stem, and cerebellum). The increases in brain phosphatides in gerbils receiving an omega-3 (but not omega-6) fatty acid, with or without UMP, were accompanied by parallel elevations in levels of pre- and post-synaptic proteins (syntaxin-3, PSD-95 and synapsin-1) but not in those of a ubiquitous structural protein, beta-tubulin. Hence administering omega-3 polyunsaturated fatty acids can enhance synaptic membrane levels in gerbils, and may do so in patients with neurodegenerative diseases, especially when given with a uridine source, while the omega-6 polyunsaturated fatty acid arachidonic acid is ineffective.

The Use of Microdialysis for the Study of Drug Kinetics: Central Nervous System Pharmacokinetics of Diphenhydramine in Fetal, Newborn, and Adult Sheep

The central nervous system (CNS) pharmacokinetics of the H(1) receptor antagonist diphenhydramine (DPHM) were studied in 100- and 120-day-old fetuses, 10- and 30-day-old newborn lambs, and adult sheep using in vivo microdialysis. DPHM was administered i.v. at five infusion rates, with each step lasting 7 h. In all ages, cerebrospinal fluid (CSF) and extracellular fluid (ECF) concentrations were very similar to each other, which suggests that DPHM between these two compartments is transferred by passive diffusion. In addition, the brain-to-plasma concentration ratios were >or=3 in all age groups, suggesting the existence of a transport process for DPHM into the brain. Both brain and plasma DPHM concentrations increased in a linear fashion over the dose range studied. However, the ECF/unbound plasma and CSF/unbound plasma DPHM concentration ratios were significantly higher in the fetus and lambs (approximately 5 to 6) than in the adult (approximately 3). The factors f(CSF) and f(ECF), the ratios of DPHM areas under the curves (AUCs) in CSF and ECF to the plasma DPHM AUC, respectively, decreased with age, indicating that DPHM is more efficiently removed from the brain with increasing age. The extent of plasma protein binding of the drug increased with age. This study provides evidence for a transporter-mediated mechanism for the influx of DPHM into the brain and also for an efflux transporter for the drug, whose activity increases with age. Moreover, the higher brain DPHM levels in the fetus and lamb compared with the adult may explain the greater CNS effects of the drug at these ages.

Effects of gestational and lactational choline deprivation on brain antioxidant status, acetylcholinesterase, (Na+,K+)- and Mg2+-ATPase activities in offspring rats

BACKGROUND

Choline plays an important role in brain development. Choline-deficient diet (CDD) is known to produce (among other effects) a decrease in acetylcholine in rat brains. The aim of our study was to investigate how CDD administration during gestation and lactation could affect total antioxidant status (TAS) and activities of acetylcholinesterase (AChE), (Na(+),K(+))- and Mg(2+)-ATPase in the brains of both male and female newborn and suckling (21-day-old) rats.

METHODS

Three different experiments were performed. Whole brains were obtained from: (a) newborn rats following gestational CDD (experiment I); (b) 21-day-old rats following gestational but not lactational CDD (experiment II); and (c) 21-day-old rats following gestational and lactational CDD (experiment III). Enzyme activities and TAS were measured spectrophotometrically.

RESULTS

In choline-deprived (CD) newborn rats, TAS and AChE and Na(+),K(+)-ATPase activities were significantly reduced by 23%, 24% and 50%, respectively, in the brains of both sexes. Gestational CDD caused only a decrease in TAS (-27%, p<0.001) in suckling rat brains in both sexes. No changes were observed for the other enzyme activities. Moreover, gestational and lactational CDD also led only to a decrease in TAS (-24%, p<0.001) in the suckling rat brains of both sexes. Mg(2+)-ATPase activities showed no changes after any of the experimental procedures.

CONCLUSIONS

Our data suggest that the lower enzyme activities in newborn CD brains were restored to normal after 21 days of either normal or CDD lactation, possibly due to novel synaptogenesis, endogenous neuroregulation, and/or to other substances acquired by lactation. The increase in homocysteine concentration due to choline deficiency reported in the literature may be the cause of the low antioxidant capacity observed in offspring rat brains. Brain Na(+),K(+)-ATPase inhibition (induced by CDD) could result in modulations of neural excitability, metabolic energy production and neurotransmission.

Blood-brain barrier delivery

Neuropharmaceutics is the largest potential growth sector of the pharmaceutical industry. However, this growth is blocked by the problem of the blood-brain barrier (BBB). Essentially 100% of large-molecule drugs and >98% of small-molecule drugs do not cross the BBB. The BBB can be traversed because there are multiple endogenous transporters within this barrier. Therefore, brain drug development programs of the future need to be re-configured so that drugs are formulated to enable transport into the brain via endogenous BBB transporters.

Choline: critical role during fetal development and dietary requirements in adults

Choline is an essential nutrient needed for the structural integrity and signaling functions of cell membranes; for normal cholinergic neurotransmission; for normal muscle function; for lipid transport from liver; and it is the major source of methyl groups in the diet. Choline is critical during fetal development, when it influences stem cell proliferation and apoptosis, thereby altering brain and spinal cord structure and function and influencing risk for neural tube defects and lifelong memory function. Choline is derived not only from the diet, but from de novo synthesis as well. Though many foods contain choline, there is at least a twofold variation in dietary intake in humans. When deprived of dietary choline, most men and postmenopausal women developed signs of organ dysfunction (fatty liver or muscle damage), while less than half of premenopausal women developed such signs. Aside from gender differences, there is significant variation in the dietary requirement for choline that can be explained by very common genetic polymorphisms.

Nicotine Exposure Does not Alter Plasma to Brain Choline Transfer

Acute and chronic nicotine exposure in rats is associated with an increase in brain acetylcholine (ACh) transmission. The acquisition of choline for neuronal ACh synthesis occurs primarily via two pathways; first, free choline is transported from the blood across the blood-brain barrier (BBB) and/or second, from synaptic choline generated by either hydrolysis of non-bound ACh or membrane phosphatidylcholine catabolism. To determine if nicotine-induced cholinergic demand is associated with increased choline transport rates into brain, we measured BBB choline transport in naïve and S-(-) nicotine exposed rats (acute and chronic, 4.5 mg/kg/d for 1, 14, 21 and 28 d; osmotic minipumps) using the in situ rat brain perfusion technique. No significant changes in choline uptake after acute or chronic nicotine exposure were observed in whole brain or cortex. Of considerable interest was a significant decrease in regional brain choline uptake measured in the hippocampus after chronic nicotine exposure (28 d). Our data suggest that the increased ACh transmission observed after nicotine exposure does not correlate with increased blood-to-brain transfer of choline. Considering these data and previous literature reports, we propose that the additional free choline required under conditions of nicotine exposure (for ACh synthesis) is primarily recruited from membrane phospholipid metabolism.

Synaptic proteins and phospholipids are increased in gerbil brain by administering uridine plus docosahexaenoic acid orally

The synthesis of brain phosphatidylcholine may utilize three circulating precursors: choline; a pyrimidine (e.g., uridine, converted via UTP to brain CTP); and a PUFA (e.g., docosahexaenoic acid); phosphatidylethanolamine may utilize two of these, a pyrimidine and a PUFA. We observe that consuming these precursors can substantially increase membrane phosphatide and synaptic protein levels in gerbil brains. (Pyrimidine metabolism in gerbils, but not rats, resembles that in humans.) Animals received, daily for 4 weeks, a diet containing choline chloride and UMP (a uridine source) and/or DHA by gavage. Brain phosphatidylcholine rose by 13-22% with uridine and choline alone, or DHA alone, or by 45% with the combination, phosphatidylethanolamine and the other phosphatides increasing by 39-74%. Smaller elevations occurred after 1-3 weeks. The combination also increased the vesicular protein Synapsin-1 by 41%, the postsynaptic protein PSD-95 by 38% and the neurite neurofibrillar proteins NF-70 and NF-M by up to 102% and 48%, respectively. However, it had no effect on the cytoskeletal protein beta-tubulin. Hence, the quantity of synaptic membrane probably increased. The precursors act by enhancing the substrate saturation of enzymes that initiate their incorporation into phosphatidylcholine and phosphatidylethanolamine and by UTP-mediated activation of P2Y receptors. Alzheimer's disease brains contain fewer and smaller synapses and reduced levels of synaptic proteins, membrane phosphatides, choline and DHA. The three phosphatide precursors might thus be useful in treating this disease.

The blood-brain barrier: bottleneck in brain drug development

The blood-brain barrier (BBB) is formed by the brain capillary endothelium and excludes from the brain approximately 100% of large-molecule neurotherapeutics and more than 98% of all small-molecule drugs. Despite the importance of the BBB to the neurotherapeutics mission, the BBB receives insufficient attention in either academic neuroscience or industry programs. The combination of so little effort in developing solutions to the BBB problem, and the minimal BBB transport of the majority of all potential CNS drugs, leads predictably to the present situation in neurotherapeutics, which is that there are few effective treatments for the majority of CNS disorders. This situation can be reversed by an accelerated effort to develop a knowledge base in the fundamental transport properties of the BBB, and the molecular and cellular biology of the brain capillary endothelium. This provides the platform for CNS drug delivery programs, which should be developed in parallel with traditional CNS drug discovery efforts in the molecular neurosciences.

Donepezil, tacrine and alpha-phenyl-n-tert-butyl nitrone (PBN) inhibit choline transport by conditionally immortalized rat brain capillary endothelial cell lines (TR-BBB)

In the present study, we have characterized the choline transport system and examined the influence of various amine drugs on the choline transporter using a conditionally immortalized rat brain capillary endothelial cell line (TR-BBB) in vitro. The cell-to-medium (C/M) ratio of [3H]choline in TR-BBB cells increased time-dependently. The initial uptake rate of [3H]choline was concentration-dependent with a Michaelis-Menten value, Km, of 26.2 +/- 2.7 microM. The [3H]choline uptake into TR-BBB was Na+-independent, but was membrane potential-dependent. The [3H]choline uptake was susceptible to inhibition by hemicholinium-3, and tetraethylammonium (TEA), which are organic cation transporter substrates. Also, the uptake of [3H]choline was competitively inhibited with Ki values of 274 microM, 251 microM and 180 microM in the presence of donepezil hydrochloride, tacrine and alpha-phenyl-n-tert-butyl nitrone (PBN), respectively. These characteristics of choline transport are consistent with those of the organic cation transporter (OCT). OCT2 mRNA was expressed in TR-BBB cells, while the expression of OCT3 or choline transporter (CHT) was not detected. Accordingly, these results suggest that OCT2 is a candidate for choline transport at the BBB and may influence the BBB permeability of amine drugs.

Cation Transport Specificity at the Blood?Brain Barrier

The molecular identification, expression and cloning of membrane-bound organic cation transporters are being completed in isolated in vitro membranes. In vivo studies, where cation specificity overlaps, need to complement this work.

METHOD

Cross-inhibition of [3H]choline and [3H]thiamine brain uptake by in situ rat brain perfusion.

RESULTS

[3H]Choline brain uptake was not inhibited by thiamine at physiologic concentrations (100 nM). However, choline ranging from 100 nM to 250 microM inhibited [3H]thiamine brain uptake, though not below levels observed at thiamine concentrations of 100 nM.

CONCLUSION

(1) The molecular family of the blood-brain barrier (BBB) choline transporter may be elucidated in vitro by its interaction with physiologic thiamine levels, and (2) two cationic transporters at the BBB may be responsible for thiamine brain uptake.

A performance comparison of choline biosensors: anodic or cathodic detections of H2O2 generated by enzyme immobilized on a conducting polymer

Amperometric choline biosensors were fabricated by the covalent immobilization of an enzyme of choline oxidase (ChO) and a bi-enzyme of ChO/horseradish peroxidase (ChO/HRP) onto poly-5,2':5',2"-terthiophene-3'-carboxylic acid (poly-TTCA) modified electrodes (CPMEs). A sensor modified with ChO utilized the oxidation process of enzymatically generated H(2)O(2) in a choline solution at +0.6V. The other one modified with ChO/HRP utilized the reduction process of H(2)O(2) in a choline solution at -0.2V. Experimental parameters affecting the sensitivity of sensors, such as pH, applied potential, and temperature were optimized. A performance comparison of two sensors showed that one based on ChO/HRP/CPME had a linear range from 1.0 x 10(-6) to 8.0 x 10(-5) M and the other based on ChO/CPME from 1.0 x 10(-6) to 5.0 x 10(-5) M. The detection limits for choline employing ChO/HRP/CPME and ChO/CPME were determined to be about 1.0 x 10(-7) and 4.0 x 10(-7) M, respectively. The response time of sensors was less than 5s. Sensors showed good selectivity to interfering species. The long-term storage stability of the sensor based on ChO/HRP/CPME was longer than that based on ChO/CPME.

Oral choline increases choline metabolites in human brain

Choline, a precursor of acetylcholine and phosphatidylcholine, is largely obtained from the diet. Animal studies demonstrate increased choline metabolites in brain following oral administration. Several proton magnetic resonance spectroscopy ((1)H-MRS) reports differ as to whether similar increases are observable in human subjects. This study was designed to minimize intra-subject variance and thereby maximize the ability to determine if a significant increase in brain choline can be detected after choline ingestion. (1)H-MRS was performed continuously for 2.5 h on 11 healthy young males following choline ingestion. Nine of the original subjects returned for identical scans without choline ingestion. Following oral choline, there was a statistically significant increase in the choline signal (Cho) measured from the left putamen, representing choline-containing compounds, as measured against creatine (Cr) or N-acetylaspartate (NAA). The mean increase in Curve maxima (C(max)) is 6.2% for Cho/Cr and 3.0% for Cho/NAA. The Mean Time to C(max) (T(max)) was approximately 2 h after ingestion. A 3-6% increase in Cho by MRS likely corresponds to a 10-22% increase in phosphocholine, similar to findings in animal studies. In conclusion, a significant increase in choline-containing compounds in human brain can be detected by (1)H-MRS after choline ingestion in young subjects.

Uptake rates of 18F-fluorodeoxyglucose and 11C-choline in lung cancer and pulmonary tuberculosis: a positron emission tomography study

STUDY OBJECTIVE

The purpose of this study was to examine the uptake rates of (18)F-fluorodeoxyglucose (FDG) and (11)C-choline in patients with lung cancer, pulmonary tuberculosis, and atypical mycobacterial infection of the lung by positron emission tomography (PET) scanning with relation to their tumor size.

DESIGN

Ninety-seven patients with untreated lung cancer, 14 patients with untreated pulmonary tuberculosis, and 5 patients with untreated atypical mycobacterial infection were examined. The diagnosis of lung cancer was confirmed pathologically after biopsy and surgery. The diagnosis of tuberculosis and atypical mycobacterial infection was confirmed by bacterial culture. The uptake rates of FDG and (11)C-choline were presented quantitatively as the standardized uptake value (SUV).

SETTING

International Medical Center of Japan.

RESULTS

In lung cancer patients, the SUV of FDG increased with increasing tumor size, whereas the SUV of (11)C-choline was almost constant at around 3.5 for every tumor size. In tuberculosis patients, the SUV of FDG increased with increasing tumor size, whereas the SUV of (11)C-choline was almost constant at around 2 for every tumor size. In atypical mycobacterial infection patients, the SUV of FDG and the SUV of (11)C-choline were equally low at around < or = 2.

CONCLUSION

The differences in the SUVs of FDG and (11)C-choline in patients with lung cancer, tuberculosis, and atypical mycobacterial infection for the same tumor size (tumor size, > 1.5 cm) were distinct. In lung cancer patients, the SUVs of both FDG and (11)C-choline were high. In tuberculosis patients, the SUV of FDG was high, but the SUV of (11)C-choline was low. In atypical mycobacterial infection patients, the SUVs of both FDG and (11)C-choline were low. It may be possible to apply this principle to make a presumptive diagnosis of a solitary pulmonary nodule if it is too small to make a definitive diagnosis pathologically and bacteriologically.

The blood-brain barrier choline transporter as a brain drug delivery vector

Choline is a ubiquitous molecule, found throughout almost every tissue in the body. Given it is a charged cation, nearly every cellular membrane has a transport mechanism to meet the intracellular and membrane need for choline. The blood-brain barrier is no exception in that a carrier-mediated transport mechanism is present to deliver choline from plasma to brain. The carrier consists of an anionic binding area that attracts positively charged quaternary ammonium groups or simple cations. Recent reports have shown this vector to be efficacious in delivering quaternary ammonium analogs of nicotine to brain. Future work is being completed to determine if other cationic or positively charged therapeutics can be effectively delivered to brain via this carrier.