Choline Administration Elevates Brain Phosphorylcholine Concentrations

Abstract: The phosphorylcholine concentration of rat brain rises and falls in response to parallel changes in the concentration of circulating choline. A single oral dose of choline chloride (20 mmol/kg) elevated whole-brain concentrations of both choline and phosphorylcholine 5 h after administration; a greater proportion of exogenously administered choline was retained by the brain in its phosphorylated form than as the free arnine. Striatal phosphorylcholine concentrations were elevated within 2 h of choline administration and continued to be significantly greater than control values for up to 34 h after treatment. The response of striatal choline levels to exogenous choline was of shorter duration than that of phosphorylcholine and was correlated with a significant increase in striatal acetylcholine concentrations. The consumption of a choline-free diet for 7 days lowered both serum choline and striatal phosphorylcholine concentrations, but had no effect on striatal choline or acetylcholine. These results suggest that choline kinase is unsaturated by its substrate in vivo and may thus serve to modulate the response of brain choline concentrations to alterations in the supply of circulating choline.     

Effects of amiridin and tacrine, drugs effective in Alzheimer's disease, on the activity of monoamine oxidase A and B]

In vitro comparative studies of effects of amiridin (9-amino-2, 3, 5, 6, 7, 8-hexahydro-1H-cyclopentane (b) choline monohydrate hydrochloride) and tacrine physostigmine and piracetam on monoamine oxidase A (MAO-A) and B (MAO-B) activity in the rat brain were carried out. Piracetam (1 x 10(-4)-1 x 10(-3) M) dose-dependently increased MAO-A and MAO-B activity. At all concentrations used (1 x 10(-7)-5 x 10(-4) M) physostigmine had no effect on MAO-A and MAO-B activity. Amiridin was found to inhibit MAO-B activity at 5 x 10(-4) M concentration only. Tacrine inhibited MAO-A activity at 5 x 10(-4) M concentration. The therapeutical effects of amiridin and tacrine in treatment of Alzheimer disease were not related to their action on MAO-A and -B activity.     

Acetylcholinesterase inhibitors neostigmine and physostigmine inhibit induction of alpha-amylase activity during seed germination in barley, Hordeum vulgare var. Jyoti

Acetylcholine (ACh) is an important neurotransmitter whose non-neuronal biological roles are being widely accepted. ACh and components of its metabolism are present in plants. ACh and some inhibitors of acetylcholinesterase (AChE) share structural similarity (quaternary ammonium group) with some inhibitors of biosynthesis of a plant hormone, gibberellic acid (GA); e.g., 2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) inhibits GA biosynthesis as well as AChE. The present study explores the possibility that ACh and antiAChE may inhibit GA biosynthesis. Seeds of barley var. Jyoti were germinated in the presence of ACh, its breakdown products - choline and acetate, and two antiAChE - neostigmine and physostigmine (all 10(-5) M). Alpha amylase activity in germinating seeds was measured as a reliable indicator of the level of GA biosynthesis. Alpha amylase activity in barley seeds was significantly reduced after 72 h of treatment with antiChE but not by ACh or its breakdown products. Since germinating barley seeds contain AChE, much of the ACh may have been broken down before its uptake. Quaternary ammonium antiChE neostigmine was more effective (50% inhibition at 10(-5) M) as compared to tertiary ammonium physostigmine (15% inhibition at 10(-5) M). ACh, choline, acetate, neostigmine and physostigmine (all 10(-5) M) did not affect formation of starch-iodine complex or activity of alpha-amylase per se. Our results indicate that quaternary ammonium inhibitors of AChE may inhibit GA biosynthesis.     

The physostigmine depolarization potentiating effect of salicylate in frog skeletal muscle.

1) The frog's sartorius muscle was depolarized depending on the degree of concentration 2--4 times more intensely by physostigmine salicylate than by physostigmine sulphate. 2) In normal Ringer's solution, 1 mM physostigmine salicylate decreased the sensitivity of the membrane to potassium depolarization by about 90%. Under similar experimental conditions, physostigmine sulphate and Na salicylate, respectively, decrease the sensitivity of the membrane to potassium depolarization by about 30%. 3) The difference manifested in the depolarizing effect of salicylate and other physostigmine salts (chloride, sulphate, phosphate, formiate, acetate, monochloracetate, benzoate and para-oxy-benzoate) is expressed already at 1 mM concentration (about 10-fold), if the muscle had been equilibrated in chloride-free glucuronate or sulphate milieu. 4) The depolarization develops slowly. It takes 30--60 minutes for the new steady state to develop even in the superficial sartorius fibres. If depolarization has reached its maximum on an average 100 mV, the membrane potential remains unchanged for hours. 5) Depolarization ensues at an unchanged degree in the presence of Na-free (choline) Ringer as well as in the presence of 2X10(-8) g/ml tetrodotoxin; therefore, it is not a Na-dependent process. 6) Under the influence of 1 mM physostigmine salicylate the membrane's resistance to the inward potassium current increased about twofold, while the increase was only 15% to the outward potassium current. It is assumed that the salicylate anion is characteristically capable of potentiating the decreasing effect of physostigmine on potassium permeability, though the role of the metabolic effect of salicylate cannot be excluded.     

Effect of Choline Chloride on the Lipid Content and Composition in the Leaves of Principal Magnetically-Oriented Radish Types

The effects of radish seed treatment with choline chloride on the number and weight of leaves, the weight of roots, as well as the content and composition of polar and neutral lipids and their component fatty acids in the leaves of principal magnetically-oriented types (MOTs) of radish (cv. Rosovo-krasnyi s belym konchikom), that is, North–South (NS) and West–East (WE) ones, were investigated. It was shown that seed treatment with 1% choline chloride increased the proportion of WE MOT in plant population. In spring and in autumn, this treatment increased the weight of roots of the NS MOT plants, but did not affect this index in the WE MOT plants. In the spring NS MOT plants, choline chloride treatment did not change the absolute content of polar lipids as compared to the control, but in autumn, this index increased. Meanwhile, in the WE MOT plants, it increased in spring and did not change in autumn. In the spring NS MOT plants, the content of neutral lipids increased, but in the autumn plants, it did not change. At the same time, in the WE MOT plants, this index decreased both in spring and in autumn. Seed treatment with choline chloride resulted in a substantial increase in the total content of phospholipids, in particular, that of phosphatidylcholine and phosphatidylethanolamine, in the NS and WE MOT plants sampled both in spring and in autumn. In addition, the ratio of unsaturated to saturated fatty acids, as well as that of linolenic to linoleic fatty acids, somewhat increased in the NS MOT leaf lipids, but decreased in the WE MOT ones. Presowing treatment of radish seeds with choline chloride variously and sometimes oppositely affected the content and composition in the NS and WE MOT leaf lipids. This seems to be caused by different response of these MOTs to the environmental factors.     

Plasma concentrations of choline in man following choline chloride

Plasma choline levels were measured in patients being treated with choline chloride for movement disorders. Following single doses of 5 g given orally in aqueous solution, plasma concentrations rose to a peak within four hours and then rapidly declined. The degree of increase was variable both between and within patients. During chronic treatment, plasma choline concentrations tended to rise as the dose increased, although the relationship was not strong. The highest concentrations attained by patients were always at a dose of 16 or 20 g daily. Following chronic treatment, the disappearance of choline from plasma was rapid, with most patients reaching baseline by four days. Choline chloride is generally given in four divided doses, which seems reasonable in the early stages of treatment. Most therapeutic effect is seen when patients are treated with daily doses in the 12 to 20 g range, doses likely to produce substantial increases in plasma choline concentration. However, the relationship of plasma choline concentration to clinical efficacy may be tenuous. Following discontinuation of treatment, clinical improvement tends to persist long after plasma choline has returned to baseline concentrations.     

The uptake of methonium compounds by isolated slices of rat cerebral cortex

Abstract— The uptakes of a series of methonium compounds, C2, C4, C6, C7, C8, C9 and C10, by isolated slices of rat cerebral cortex were measured. Analyses of the kinetics of uptake of C7, C8, C9 and C10 indicate that their initial influxes consist of two components. A Michaelis-Menten type uptake by carrier can account for the saturable fraction. C7 had the lowest affinity for the carrier, with values increasing for C8, C9 and C10, while C10 had the smallest maximum influx with values increasing for C9, C8 and C7. The unsaturable fraction corresponded to the slow continuous swelling of the tissue. The uptake of C8 was inhibited by other methonium compounds, choline, ACh, physostigmine, ouabain and morphine. C8 could be counter-transported by C7. There is evidence that the main driving force for uptake is the transmembrane potential, but the steric factor may be a restricting influence.     

Phospholipid synthesis by activated human B lymphocytes

Pokeweed mitogen- (PWM) stimulated DNA and Ig synthesis in human B cells is dependent on the presence of T cells and adherent cells, but the influence of these regulatory cells on earlier activation events is unknown. We have studied the T cell and monocyte influence on the incorporation of [methyl-14C]choline chloride into B cell phospholipids (PL) after varying periods of in vitro culture with or without pokeweed mitogen (PWM). By separating B and T cells after choline pulsing, a peak in PWM-induced PL synthesis of B cells at days 1 to 2 was revealed, whereas the T cell response was later (days 2 to 3). In the first 4 hr of culture, the purified B cell plus monocyte fraction incorporated choline four to six times faster than the T cell fraction, but PWM did not increase choline incorporation, whether these fractions were cultured separately or together. When cultures were pulsed with choline between 16 and 20 hr with or without PWM, monocytes incorporated choline six to nine times faster than T cells, and B cells were intermediate. Also at 16 to 20 hr of culture, a significant PWM-induced increase in choline incorporation by B cells was evident and was dependent on the presence of T cells and monocytes. The monocytes showed no increased choline incorporation due to PWM. Thus, the influence of regulatory cells on the PWM response in B cells is evident within the first 24 hr.     

Discoupling of excitation-contraction processes by urea treatment of frog skeletal muscle

On exposure (E) of frog semitendinosus muscle to 400 mmol/l urea (U) in sodium chloride Ringer's solution, the tension development to isoK+ solutions decreased, while in choline chloride Ringer it increased. On quick removal (R) of urea, always a block of excitation-contraction (E-C) coupling occurred accompanied by transient or persistent swelling of fibres and a similar but definite decrease of their resting membrane potential (Fig. 2). Muscle contraction could be elicited by caffeine even after UER-treatment but then only the slow tension increase (second phase of normal caffeine contraction) occurred (Fig. 3a). The fast tension increase to caffeine (first phase) could be restored if after UER-treatment 5 mmol/l mannitol (Fig. 3b), a 20 min treatment with choline chloride (Fig. 4a) or sodium isethionate (Fig. 4b) Ringer's solution of double osmolarity were applied. Caffeine contraction could not be elicited when sodium chloride Ringer's solution of double osmolarity was used under similar conditions (Fig. 5). E-C block to isoK+ solution persisted in all these experiments. E-C coupling could partially be restored by short treatment of muscle with caffeine (Figs 6a, b).     

Fewer metabolites of dietary choline reach the blood of rats after treatment with lithium

Choline is an important precursor for the biosynthesis of acetylcholine, phosphatidylcholine and sphingomyelin. It is also a major source of labile methyl groups. Lithium is an important component of the treatment of bipolar affective illness, and it inhibits choline transport across membranes. We studied the effect of lithium treatment upon the appearance in blood, liver and intestine of metabolites formed from dietary choline. Rats were treated for 9 days with 2 mEq/kg lithium carbonate or water. Animals were fasted overnight, and on the 10th day were fed with a solution containing radiolabeled choline chloride. The lithium-treated groups also received 2.0 mEq/kg lithium as part of this solution. After an oral dose of 1 ml of a 1 mM choline solution, the lithium-treated animals had significantly lower levels of choline-derived radiolabel in blood than did controls at 30, 60, 120, and 180 minutes (47% (+/- 5%; SEM), 51% (+/- 7%), 59% (+/- 4%) and 74% (+/- 9%), respectively). We observed similar decreases of the accumulation in blood, at 180 minutes after the dose, of choline-derived radiolabel when choline was administered at lower or higher concentrations. After an oral treatment containing 0.1, 1 or 10 mM choline, lithium treated animals accumulated 69% (+/- 6%; SEM), 66% (+/- 11%) and 72% (+/- 7%) as much radiolabel in serum as did controls. Most of the radiolabel found in blood at 180 minutes was in metabolites of choline which are formed within liver (betaine and phosphatidylcholine). The diminished accumulation of radiolabel in serum after lithium treatment was not due to increased accumulation of label by erythrocytes, liver or gut wall. We suggest that lithium influences the release by liver of betaine and phosphatidylcholine.     

Choline administration: central effect mediated by stimulation of acetylcholine synthesis.

Oral administration of either choline or physostigmine to rats stimulated the metabolism of dopamine in brain. Treatment of rats with an acetylcholine receptor blocker (atropine) or an inhibitor of acetylcholine synthesis [4-(1-naphthylvinyl) pyridine] antagonized the choline-induced increase in dopamine metabolism. In contrast to its effect on the choline-induced increase in dopamine metabolism, 4-(1-naphthylvinyl) pryridine did not prevent the increase induced by physostigmine. These results indicate that oral administration of choline augments central cholinergic function, and suggest that the mechanism involves stimulation of the rate of synthesis and release of acetylcholine.     

Acetylcholine in the posterior hypothalamic nucleus is involved in the elevated blood pressure in the spontaneously hypertensive rat

Intravenous injection of physostigmine, 40 and 80 ug/kg, in unanesthetized normotensive rats increased systolic blood pressure (SBP) by 21 +/- 3 and 42 +/- 7 mmHg. This pressor response was 80% inhibited by intracerebroventricular (icv) injection of hemicholinium-3 (HC-3), 20 ug. Simultaneous icv injection of HC-3 and choline (365 ug) prevented the inhibition of the pressor response by HC-3. In spontaneously hypertensive rats, injection of HC-3 either icv (20 ug) or bilaterally into the posterior hypothalamic nuclei (1 ug) decreased SBP by about 40 mmHg. The effect of intrahypothalamic HC-3 was completely blocked by simultaneous injection of choline (24.3 ug) into the same site. The hypotensive effect of icv HC-3 was completely blocked by icv choline (243 ug) and was inhibited up to 60% by injections of choline (24.3 ug) into the posterior hypothalamic nuclei.     

Lifelong choline supplementation ameliorates Alzheimer’s disease pathology and associated cognitive deficits by attenuating microglia activation

Currently, there are no effective therapies to ameliorate the pathological progression of Alzheimer's disease (AD). Evidence suggests that environmental factors may contribute to AD. Notably, dietary nutrients are suggested to play a key role in mediating mechanisms associated with brain function. Choline is a B‐like vitamin nutrient found in common foods that is important in various cell functions. It serves as a methyl donor and as a precursor for production of cell membranes. Choline is also the precursor for acetylcholine, a neurotransmitter which activates the alpha7 nicotinic acetylcholine receptor (α7nAchR), and also acts as an agonist for the Sigma‐1 R (σ1R). These receptors regulate CNS immune response, and their dysregulation contributes to AD pathogenesis. Here, we tested whether dietary choline supplementation throughout life reduces AD‐like pathology and rescues memory deficits in the APP/PS1 mouse model of AD. We exposed female APP/PS1 and NonTg mice to either a control choline (1.1 g/kg choline chloride) or a choline‐supplemented diet (5.0 g/kg choline chloride) from 2.5 to 10 months of age. Mice were tested in the Morris water maze to assess spatial memory followed by neuropathological evaluation. Lifelong choline supplementation significantly reduced amyloid‐β plaque load and improved spatial memory in APP/PS1 mice. Mechanistically, these changes were linked to a decrease of the amyloidogenic processing of APP, reductions in disease‐associated microglial activation, and a downregulation of the α7nAch and σ1 receptors. Our results demonstrate that lifelong choline supplementation produces profound benefits and suggest that simply modifying diet throughout life may reduce AD pathology.     

Effect of ions on the efflux of acetylcholine from peripheral nerve

The nerves from the walking leg of lobster released acetylcholine (ACh) even when the ends were tied off, although this release was significantly increased when the nerve endings were not tied. The resting nerves were kept in sea water containing physostigmine. In absence of physostigmine no ACh was found in the surrounding fluid. Removal of Ca from the sea water reduced the release of ACh, while increased concentrations of Ca had no significant effect. Removal of Mg++ or increased Mg++ concentrations in the presence of normal Ca++ concentrations increased the release of ACh. Increased K+ concentrations had a stimulating action on the efflux of ACh. Increased or reduced Na+ concentrations had only slight effects on the release of ACh in resting lobster nerve. During the 4 hr observation period the excised nerves were still able to synthesize ACh. The choline acetylase activity was stimulated by increased concentrations of Mg++ and K+. The effects of ions on the release of ACh are similar to those reported at the junction.     

Endogenous acetylcholine release and labelled acetylcholine formation from [3H]choline in the myenteric plexus of the guinea-pig ileum.

The spontaneous release of acetylcholine (ACh) from the guinea-pig myenteric plexus - longitudinal muscle preparation superfused at a constant rate in the presence of physostigmine was 10 nmol-g-1-h-1. This release was decreased to one-third by tetradotoxin or by MnCl2 and increased 2.5 times by 0.1 Hz and 20 times by 16 Hz stimulation. The formation of [3H]ACh from [3H]choline increased from 3 to 33 nmol-g(-1)-h(-1) when the concentration of [3H]choline was increased from 1 muM to 50 muM. The rate of [3H]ACh formation was not affected by tetrodotoxin, MnCl2, or physostigmine in the absence of stimulation. It was increased by 50% by 0.1 Hz and by 100% by 16 Hz stimulation during the first 9 min of exposure to [3H]choline but not subsequently. The myenteric plexus - longitudinal muscle preparation contains 200 nmol/g choline. Results suggest that the apparent small [3H]ACh formation from low concentrations of [3H]choline is due to the dilution of [3H]choline by endogenous choline. The major part of [3H]ACh formation appears to be due to the intracellular turnover of ACh while the evoked release of [3H]ACh appears to originate from a small pool.     

Effect of triiodothyronine administration on the plasma TSH and prolactin responses to TRH in patients with hypothalamic-pituitary insufficiency.

A study was carried out in 10 patients with multiple pituitary hormone deficiencies to determine the response of thyroid-stimulating hormone (TSH) and prolactin (PRL) to thyrotropin-releasing hormone (TRH) and their suppressibility by treatment with triiodothyronine (T3) given at a dose of 60 microgram/day for 1 week. In 3 patients the basal tsh values were normal and in 7 patients, 2 of whom had not received regular thyroid replacement therapy, they were elevated. The response of TSH to TRH was normal in 6 patients and exaggerated in 4 (of these, 1 patient had not received previous substitution therapy and 2 had received only irregular treatment). The basal and stimulated levels of TSH were markedly suppressed by the treatment with T3. The basal PRL levels were normal in 7 and slightly elevated in 3 patients. The response of PRL to TRH stimulation was exaggerated in 2, normal in 6 and absent in 2 patients. The basal PRL levels were not suppressible by T3 treatment but in 4 patients this treatment reduced the PRL response to TRH stimulation. From these findings the following conclusions are drawn: (1) T3 suppresses TSH at the pituitary level, and (2) the hyperreactivity of TSH to TRH and the low set point of suppressibility are probably due to a lack of TRH in the type of patients studied.     

Noradrenaline treatment of rats stimulates H2O2 generation in liver mitochondria.

Treatment of rats with noradrenaline stimulated H2O2 generation in liver mitochondria using succinate, choline or glycerol 1-phosphate as substrate. The dehydrogenase activity with either succinate or choline as substrate showed no change, whereas that with glycerol 1-phosphate increased. The effect was obtained with noradrenaline, but not with dihydroxyphenylserine. Phenoxybenzamine and yohimbine, but not propranolol, prevented the response to noradrenaline treatment. Phenylephrine could stimulate H2O2 generation, whereas isoprenaline had only a marginal effect. Theophylline treatment slightly decreased the generation of H2O2 in liver mitochondria, but treatment with pargyline, Ro4-1284 and dibutyryl cyclic AMP had little effect. These studies showed that noradrenaline might possibly be acting through the alpha 2-adrenergic system.     

Choliae esterases and choline acetyltransferase in the seeds ofAllium altaicum (Pall.) Reyse

In the seeds ofAllium altaicun (Pall.)Reyse a set of enzymes was found, metabolizing choline esters, composed of active choline esterases and choline acetyltransferase. Choline esterase cleaving acetylcholine occurs in five isoenzymes. The enzyme preparation hydrolyses strongly acetylthiocholine and sinapine, but weakly butyrylthiocholine (20%) in comparison with acetylthiocholine. The hydrolysis of the substrates mentioned is inhibited by physostigmine and neostigmine, but it is not inhibited by the specific inhibitor of acetylcholine esterase (BW 284 C51). In addition to hydrolytic activity a strong catalytic activity of choline acetyltransferase was also observed during the synthesis of sinapine from sinapic acid and choline. The detection of the mentioned enzymes in some representatives of theAllium genus indicates that choline esterases are more widely distributed in monocotyledons than previously assumed.     

Dietary choline affects response to acetylcholine by isolated urinary bladder

Age-related increases occur in the response of isolated urinary bladders to the parasympathetic neurotransmitter acetylcholine (ACh). Experiments were carried out to determine whether long-term elevation or diminution in the amount of ingested choline can also affect the response of the urinary bladder to ACh. Female C57BL/6J mice were maintained on a choline-deficient chow and on drinking water supplemented with either 0, 1.5, or 4.0 mg/ml choline chloride from 8 to 20 months of age. Isolated bladders from choline deficient animals showed a 46% increase in the maximum response to ACh as compared to those from normal choline animals, while bladders from animals on choline enriched diets showed a 15% decrease in maximum contractile response. Radioligand binding experiments suggested that the functional changes result from alterations in the density of muscarinic receptors in the bladder. The results are consistent with the hypothesis that muscarinic receptors are down-regulated to compensate for increased parasympathetic activity associated with choline-enriched diets and up-regulated to compensate for decreased parasympathetic activity associated with choline-deficient diets.     

Naturally occurring antibodies to liposomes. II. Specificity and electrophoretic pattern of rabbit antibodies reacting with sphingomyelin-containing liposomes

Sera obtained from rabbits after immunization with a variety of unrelated antigens contain antibodies that induce complement- (C) mediated lysis of sphingomyelin-containing liposomes in the absence of the relevant antigen from the membrane. Absorption or inhibition with dimyristoyl-phosphatidyl choline-containing liposomes were less effective than with sphingomyelin-containing liposomes in decreasing or abolishing C-dependent lysis of target-liposomes. Phosphoryl choline chloride inhibited the C-dependent lysis mediated by these antibodies, but only when used in high molar excess and in the presence of low antibody concentrations. Purified anti-liposome antibodies displayed an isoelectric focusing pattern consistent with a polyclonal response. The findings confirm the antibody nature of the anti-liposome activity of rabbit sera and indicate that their predominant specificity is directed against conformations of the phospholipid molecule in which the polar (phosphoryl choline) group does not have a major contribution.