A rapid LC-ESI-MS/MS method for the quantitation of choline, an active metabolite of citicoline: Application to in vivo pharmacokinetic and bioequivalence study in Indian healthy male volunteers.

A rapid, simple, and sensitive high performance liquid chromatography-tandem mass spectrometry method (LC-ESI-MS/MS) was developed and validated for the determination and pharmacokinetic investigation of choline (CL), active metabolite of citicoline in human plasma using metformin (MF) as IS. The chromatographic separation was performed on a reversed-phase Phenomenx Gemini C18 column with a mobile phase of methanol:water (containing 10mM ammonium formate) (9:1, v/v). The calibration curves were linear over the range of 0.05-5µg/ml. The validated LC-ESI-MS/MS method was successfully applied for the evaluation of pharmacokinetic parameters and bioequivalence study of test and reference control release (CR) tablet preparation of citicoline 1000mg after a single oral administration to all 12 healthy male volunteers.

Peripheral administration of CDP-choline, phosphocholine or choline increases plasma adrenaline and noradrenaline concentrations.

1 Intraperitoneal (i.p.) injection of 200-600 mumol/kg of cytidine-5'-diphosphocholine (CDP-choline) increased plasma adrenaline and noradrenaline concentrations dose- and time-dependently. 2 CDP-choline treatment caused several-fold increases in plasma concentrations of CDP-choline and its metabolites phosphocholine, choline, cytidine monophosphate (CMP) and cytidine. 3 Equivalent doses (200-600 mumol/kg; i.p.) of phosphocholine or choline, but not CMP or cytidine, increased plasma adrenaline and noradrenaline dose-dependently. 4 CDP-choline, phosphocholine and choline (600 mumol/kg; i.p.) augmented the increases in plasma adrenaline and noradrenaline in response to graded haemorrhage. 5 The increases in plasma adrenaline and noradrenaline induced by i.p. 600 mumol/kg of CDP-choline, phosphocholine or choline were abolished by pre-treatment with hexamethonium (15 mg/kg; i.p.), but not atropine (2 mg/kg; i.p.). 6 At 320-32 000 mum concentrations, choline, but not CDP-choline or phosphocholine, evoked catecholamine secretion from perfused adrenal gland. Choline (3200 mum)-induced catecholamine secretion was attenuated by the presence of 1 mum of hexamethonium or mecamylamine, but not atropine, in the perfusion medium. 7 Intracerebroventricular (i.c.v.) injection of choline (0.5-1.5 mumol) also increased plasma adrenaline and noradrenaline dose- and time-dependently. Pre-treatment with mecamylamine (50 mug; i.c.v.) or hexamethonium (15 mg/kg; i.p.), but not atropine (10 mug; i.c.v.), prevented i.c.v. choline (1.5 mumol)-induced elevations in plasma adrenaline and noradrenaline. 8 It is concluded that i.p. administration of CDP-choline or its cholinergic metabolites phosphocholine and choline increases plasma adrenaline and noradrenaline concentrations by enhancing nicotinic cholinergic neurotransmission in the sympatho-adrenal system. Central choline also activates the sympatho-adrenal system by increasing central nicotinic cholinergic neurotransmission.

Intraperitoneal administration of CDP-choline and its cholinergic and pyrimidinergic metabolites induce hyperglycemia in rats: involvement of the sympathoadrenal system.

CDP-choline is an endogenous metabolite in phosphatidylcholine biosynthesis. Exogenous administration of CDP-choline has been shown to affect brain metabolism and to exhibit neuroprotective actions. On the other hand, little is known regarding its peripheral actions. Intraperitoneal administration of CDP-choline (200-600 micromol/kg) induced a dose- and time-dependent hyperglycemia in rats. Hyperglycemic response to CDP-choline was associated with several-fold elevations in serum concentrations of CDP-choline and its metabolites. Intraperitoneal administration of phosphocholine, choline, cytidine, cytidine monophosphate, cytidine diphosphate, cytidine triphosphate, uridine, uridine monophosphate, uridine diphosphate and uridine triphosphate also produced significant hyperglycemia. Pretreatment with atropine methyl nitrate failed to alter the hyperglycemic responses to CDP-choline and its metabolites whereas hexamethonium, the ganglionic nicotinic receptor antagonist which blocks nicotinic cholinergic neurotransmission at the autonomic ganglionic level, blocked completely the hyperglycemia induced by CDP-choline, phosphocholine and choline, and attenuated the hyperglycemic response to cytidine monophosphate and cytidine. Increased blood glucose following CDP-choline, phosphocholine and choline was accompanied by elevated plasma catecholamine concentrations. Hyperglycemia elicited by CDP-choline and its metabolites was entirely blocked either by pretreatment with a nonselective -adrenoceptor antagonist phentolamine or by the 2-adrenoceptor antagonist, yohimbine. Hyperglycemic responses to CDP-choline, choline, cytidine monophosphate and cytidine were not affected by chemical sympathectomy, but were prevented by bilateral adrenalectomy. Phosphocholine-induced hyperglycemia was attenuated by bilateral adrenalectomy or by chemical sympathectomy. These data show that CDP-choline and its metabolites induce hyperglycemia which is mediated by activation of ganglionic nicotinic receptors and stimulation of catecholamine release that subsequently activates 2-adrenoceptors.

Elevated erythrocyte CDP-choline levels associated with beta-thalassaemia in patients with transfusion independent anaemia.

The accumulation of CDP-ethanolamine as well as CDP-choline in a small cohort of patients with normal UMPH1 and no defined cause for their anaemia suggested a defect in both phosphotransferases. Here we report 10 patients with transfusion independent beta-thalassaemia; 8 being pure heterozygotes and 2 heterozygotes also for Hb E. Mean CDP-choline (86.xxx +/- 48 microM) and CDP-ethanolamine (34.6 microM +/- 34.5 microM), mean control <3 microM. Elevated CDP-choline in patients with no defined cause for their haemolytic anaemia was previously suggested as a possible indicator of CDP-choline phosphotransferase deficiency. Here we associate it with transfusion independent beta-thalassaemia.

Effect of oral CDP-choline on plasma choline and uridine levels in humans.

Twelve mildly hypertensive but otherwise normal fasting subjects received each of four treatments in random order: CDP-choline (citicoline; 500, 2000, and 4000 mg) or a placebo orally at 8:00 a.m. on four different treatment days. Eleven plasma samples from each subject, obtained just prior to treatment (8:00 a.m.) and 1-12 hr thereafter, were assayed for choline, cytidine, and uridine. Fasting terminated at noon with consumption of a light lunch that contained about 100 mg choline. Plasma choline exhibited dose-related increases in peak values and areas under the curves (AUCs), remaining significantly elevated, after each of the three doses, for 5, 8, and 10 hr, respectively. Plasma uridine was elevated significantly for 5-6 hr after all three doses, increasing by as much as 70-90% after the 500 mg dose, and by 100-120% after the 2000 mg dose. No further increase was noted when the dose was raised from 2000 to 4000 mg. Plasma cytidine was not reliably detectable, since it was less than twice blank, or less than 100 nM, at all of the doses. Uridine is known to enter the brain and to be converted to UTP; moreover, we found that uridine was converted directly to CTP in neuron-derived PC-12 cells. Hence, it seems likely that the circulating substrates through which oral citicoline increases membrane phosphatide synthesis in the brains of humans involve uridine and choline, and not cytidine and choline as in rats.

A family with chronic haemolysis and selective accumulation of erythrocyte CDP-choline.

In this paper, we report a family with compensated chronic haemolysis where the only erythrocyte abnormality detected was an increased level of erythrocyte CDP-choline. Using 31P-NMR spectroscopy and enzymatic analysis the possibility of a pyrimidine 5'-nucleotidase deficiency was excluded. Thus, this family represents the first evidence for a hereditary haemolytic anaemia where the inferred enzymatic defect is located to choline phosphotransferase, the enzyme catalysing the final step in lecithin synthesis. The family history indicates an autosomal dominant mode of transmission with incomplete penetrance.

[Preparation, properties and therapeutic potential of cytidine diphosphocholine incorporated into liposomes]. / Preparazione, proprietà e potenzialità terapeutiche della citidin-difosfocolina associata a liposomi.

Cytidine diphosphocholine (CDC) was incorporated into unilamellar egg lecithin liposomes with a yield of 23% and subsequently administered to rats by intracardiac injection. Unlike free CDC, 0.2% of which was absorbed by the brain, 21% of the CDC-liposomes was absorbed by the brain, while their relative distribution among brain phospholipids was similar. The changes in blood concentration and brain content of CDC, with and without liposomes, were measured at different times after administration. The CDC-liposome association significantly increased, unlike CDC alone, the levels of dopamine catabolites in the striatum of rats treated with haloperidol (0.15 mg/Kg/die) after 5 days of intravenous administration (20 mg/Kg/die).

Detection of pyrimidine 5'-nucleotidase deficiency using 1H- or 31P-nuclear magnetic resonance.

We describe here a further Japanese family with pyrimidine 5'-nucleotidase (P5'N) deficiency diagnosed using a nuclear magnetic resonance (NMR) spectrum, in Kumamoto prefecture where two families having the disease have been reported before. The specific spectra in 1H-NMR of P5'N deficient erythrocytes were due to three methyl protons of CDP-choline at 3.22 ppm and to H-2, H-8 and ribose-1' of pyrimidine nucleotide phosphate(s) in the lower fields (at 5.82 and 8.00 ppm). The other specificities in 31P-NMR spectra were due to CDP-choline, CDP-ethanolamine and UDP-glucose. Those spectra were not detected in other types of hemolytic anemia.

Abnormal erythrocyte pyrimidine nucleotides in uremic subjects.

Uremia causes major increases in the erythrocyte (RBC) purine nucleotides, presumably secondary to phosphate retention, but no previous study has been made of the pyrimidine nucleotides, normally absent from RBC. This investigation was prompted by demonstration of the abnormal presence of RBC pyrimidine nucleotides, primarily cytidine triphosphate (CTP) plus cytidine diphosphate-choline (CDP-C) and cytidine diphosphate-ethanolamine (CDP-E), in two types of congenital hemolytic anemia as well as in lead poisoning. These observations suggested an analogy to the RBC membrane dysfunction of uremia. This is a report of the identification of CDP-C and CDP-E as the predominant abnormal pyrimidine nucleotides in the RBC hemolysates of uremic subjects. High-performance liquid chromatography of hemolysates from uremic adults showed a 50% increase in purine nucleotides and the abnormal presence of pyrimidine nucleotides and diesters at approximately 10% of the concentration of the purine nucleotides. By means of UV spectra and 31P nuclear magnetic resonance, these were identified as CDP-C and CDP-E. The increased purine and abnormal pyrimidine nucleotides of uremic RBC were unrelated to the pre- or posthemodialysis state, allopurinol, levels of blood lead, copper and zinc, or RBC pyrimidine 5'-nucleotidase, the cytosolic enzyme that specifically dephosphorylates the pyrimidine nucleotides. Although the accumulation of CTP, CDP-C and CDP-E may be an epiphenomenon of phosphate retention, it also suggests a common pathway to the accelerated hemolysis of chronic renal insufficiency.

Red cell CDP (dCDP)-choline and P-choline in normal subjects and in certain hemolytic syndromes.

The concentrations of red cell CDP (dCDP)-choline and P-choline were measured and compared in normal subjects, in subjects with hemolytic anemia other than that due to pyrimidine-5'-nucleotidase deficiency, in homozygotes for the latter enzymopathy, and in a single subject with a hemolytic syndrome speculatively due to choline phosphotransferase deficiency.

Identification of cytidine diphosphodiesters in erythrocytes from a patient with pyrimidine nucleotidase deficiency.

Pyrimidine 5'-nucleotidase deficient (PND) erythrocytes contain elevated levels of pyrimidine nucleotides and relatively normal purine nucleotide levels. The composition of this nucleotide pool has been examined by others, but not all of the abnormal red cell metabolites in this disorder were identified. We have isolated and positively confirmed the identity of cytidine diphosphate (CDP)-choline and CDP-ethanolamine from PND red cells using methods including proton FT-NMR, spectroscopy, and comparative mass spectrometry. The concentrations of these and other pyrimidine nucleotidase-deficient erythrocyte nucleotides were determined using anion-exchange high performance liquid chromatography and ultraviolet (u.v.) detection. The pyrimidine diphosphodiesters appear to be the most prominent abnormal pyrimidine nucleotides in PND red cells, accounting for 55% of the total red cell pyrimidine nucleotides in this disorder. It is proposed that these abnormal phosphodiesters may be related to the accelerated hemolysis in PND.

Selective accumulation of cytosol CDP-choline as an isolated erythrocyte defect in chronic hemolysis.

Erythrocytes from a young woman with chronic hemolytic anemia were found to contain 0.31-0.45 mM CDP-choline, concentrations that are 15-25 times those in normal erythrocytes and equivalent to 20-30% of the total adenine nucleotide content. Accumulation of CDP-choline has been reported only in erythrocytes from subjects with severe (homozygous) pyrimidine nucleotidase deficiency. In the latter syndrome, however, pyrimidine nucleotidase activity is very low and a spectrum of uridine- and cytidine-containing nucleotides is present along with epiphenomena involving glutathione and ribosephosphate pyrophosphokinase. By contrast, selective accumulation of CDP-choline was the only abnormality demonstrable in proband erythrocytes. Membrane phospholipids were quantitatively and qualitatively normal, compatible with the observation that mature erythrocytes maintain membrane phospholipids largely by passive exchange with plasma components or by acylation of lysophospholipids. Although the presence of small amounts of other CDP-containing cofactors, such as CDP-ethanolamine, could not be entirely excluded, the cytidine/choline ratio closely approximated 1:1 in all studies. These data are compatible with the view that choline phosphotransferase and ethanolamine phosphotransferase are separate enzymes in erythroid cells. Selective accumulation of CDP-choline in proband erythrocytes is also compatible with an inherited deficiency of choline phosphotransferase in erythroid precursors, though this hypothesis remains unproved.

Effects of various cerebral metabolic activators on glucose metabolism of brain.

The effects of various metabolic activators on the glucose metabolism of the perfused cat brain have been investigated. (1) When the perfusion is done with the blood containing cytidine monophosphate, the glucose metabolism of the brain is enhanced, as compared to the perfusion with the blood without cytidine monophosphate. There is no marked change in the cerebral metabolic rate and in the contents of intermediate metabolite of glucose in the brain. (2) Citicoline enhances the incorporation of blood glucose into the brain and its metabolism in the brain. It increases slightly the cerebral blood flow rate and decreases the accumulation of lactate in the brain. (3) Either Pyrithioxin or Meclophenoxate has no effect on the glucose metabolism of the brain nor on the cerebral metabolic rate.