Mehmet Cansev

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. Alzheimers 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.

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 Alzheimers 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 Alzheimers disease.

Oral administration of circulating precursors for membrane phosphatides can promote the synthesis of new brain synapses.

Although cognitive performance in humans and experimental animals can be improved by administering omega‐3 fatty acid docosahexaenoic acid (DHA), the neurochemical mechanisms underlying this effect remain uncertain. In general, nutrients or drugs that modify brain function or behavior do so by affecting synaptic transmission, usually by changing the quantities of particular neurotransmitters present within synaptic clefts or by acting directly on neurotransmitter receptors or signal‐transduction molecules. We find that DHA also affects synaptic transmission in mammalian brain. Brain cells of gerbils or rats receiving this fatty acid manifest increased levels of phosphatides and of specific presynaptic or postsynaptic proteins. They also exhibit increased numbers of dendritic spines on postsynaptic neurons. These actions are markedly enhanced in animals that have also received the other two circulating precursors for phosphatidylcholine, uridine (which gives rise to brain uridine diphosphate and cytidine triphosphate) and choline (which gives rise to phosphocholine). The actions of DHA aere reproduced by eicosapentaenoic acid, another omega‐3 compound, but not by omega‐6 fatty acid arachidonic acid. Administration of circulating phosphatide precursors can also increase neurotransmitter release (acetylcholine, dopamine) and affect animal behavior. Conceivably, this treatment might have use in patients with the synaptic loss that characterizes Alzheimers disease or other neurodegenerative diseases or occurs after stroke or brain injury.

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 Alzheimers disease, could be beneficial.

Giving Uridine and/or Docosahexaenoic Acid Orally to Rat Dams during Gestation and Nursing Increases Synaptic Elements in Brains of Weanling Pups

Developing neurons synthesize substantial quantities of membrane phospholipids in producing new synapses. We investigated the effects of maternal uridine (as uridine-5′-monophosphate) and docosahexaenoic acid supplementation on pups’ brain phospholipids, synaptic proteins and dendritic spine densities. Dams consumed neither, 1 or both compounds for 10 days before parturition and 20 days while nursing. By day 21, brains of weanlings receiving both exhibited significant increases in membrane phosphatides, various pre- and postsynaptic proteins (synapsin-1, mGluR1, PSD-95), and in hippocampal dendritic spine densities. Administering these phosphatide precursors to lactating mothers or infants could be useful for treating developmental disorders characterized by deficient synapses.

A specific multi-nutrient enriched diet enhances hippocampal cholinergic transmission in aged rats

Fortasyn Connect (FC) is a specific nutrient combination designed to target synaptic dysfunction in Alzheimers disease by providing neuronal membrane precursors and other supportive nutrients. The aim of the present study was to investigate the effects of FC on hippocampal cholinergic neurotransmission in association with its effects on synaptic membrane formation in aged rats. Eighteen-month-old male Wistar rats were randomized to receive a control diet for 4 weeks or an FC-enriched diet for 4 or 6 weeks. At the end of the dietary treatments, acetylcholine (ACh) release was investigated by in vivo microdialysis in the right hippocampi. On completion of microdialysis studies, the rats were sacrificed, and the left hippocampi were obtained to determine the levels of choline, ACh, membrane phospholipids, synaptic proteins, and choline acetyltransferase. Our results revealed that supplementation with FC diet for 4 or 6 weeks, significantly enhanced basal and stimulated hippocampal ACh release and ACh tissue levels, along with levels of phospholipids. Feeding rats the FC diet for 6 weeks significantly increased the levels of choline acetyltransferase, the presynaptic marker Synapsin-1, and the postsynaptic marker PSD-95, but decreased levels of Nogo-A, a neurite outgrowth inhibitor. These data show that the FC diet enhances hippocampal cholinergic neurotransmission in aged rats and suggest that this effect is mediated by enhanced synaptic membrane formation. These data provide further insight into cellular and molecular mechanisms by which FC may support memory processes in Alzheimers disease.

Peripheral administration of CDP-choline and its cholinergic metabolites increases serum insulin: Muscarinic and nicotinic acetylcholine receptors are both involved in their actions

The present study was designed to test the effects of CDP-choline and its metabolites on serum insulin concentrations in rats and to investigate the involvements of cholinergic and adrenergic receptors in the effect. Intraperitoneal (i.p.) administration of CDP-choline (200-600 micromol/kg) increased serum insulin in a dose- and time-related manner. Equivalent doses (200-600 micromol/kg; i.p.) of phosphocholine or choline also increased serum insulin dose-dependently. Serum-free choline concentrations increased several-fold following i.p. administration of CDP-choline, phosphocholine or choline itself. In contrast, equivalent doses of cytidine monophosphate and cytidine failed to alter serum insulin concentrations. The increases in serum insulin induced by i.p. 600 micromol/kg of CDP-choline, phosphocholine or choline were abolished by pretreatment with the ganglionic nicotinic acetylcholine receptor antagonist hexamethonium (15 mg/kg; i.p.), or by the muscarinic receptor antagonist atropine methylnitrate (2 mg/kg; i.p.). Pretreatment with prazosin (0.5 mg/kg; i.p.), an alpha(1)-adrenoceptor antagonist, or yohimbine (5 mg/kg, i.p.), an alpha(2)-adrenoceptor antagonist, enhanced slightly the increases in serum insulin in response to 600 micromol/kg of CDP-choline, phosphocholine and choline. Serum insulin also increased following central administration of choline; the effect was blocked by intracerebroventricularly injected atropine, mecamylamine or hemicholinium-3 (HC-3). It is concluded that CDP-choline or its cholinergic metabolites phosphocholine and choline increases circulating insulin concentrations by increasing muscarinic and nicotinic cholinergic neurotransmission in the insulin secreting beta-cells.

Serum butyrylcholinesterase and paraoxonase 1 in a canine model of endotoxemia: effects of choline administration.

Butyrylcholinesterase (BChE) and paraoxonase 1 (PON1) are two serum enzymes synthesized by the liver that are related with inflammation. The main objectives of this study were to determine changes in serum BChE and PON1 by using a canine model of endotoxemia, and to evaluate whether choline alters BChE and PON1 activities during inflammation. For this purpose, a total of 20 mongrel dogs were divided into four groups: control, choline (C), lipopolysaccharide (LPS), and LPS+C. Dogs in the control group were injected with 0.9% NaCl (0.2 ml/kg, i.v.). Dogs in C and LPS+C groups received choline chloride (20 mg/kg, i.v., three times with 4 h intervals). Endotoxin was injected (0.02 mg/kg, i.v., once) to the dogs of LPS and LPS+C groups. Statistically significant decreases in BChE and PON1 activities in LPS group were detected 24 and 48 h post injection, respectively. No statistically significant changes in BChE and PON1 activities at different times were detected in control, C, or LPS+C groups. In conclusion, the data obtained in present study revealed a decrease in serum BChE and PON1 activities in dogs during experimentally induced endotoxemia and that choline administration attenuates these changes.

Choline Or Cdp-choline Alters Serum Lipid Responses To Endotoxin In Dogs And Rats: Involvement Of The Peripheral Nicotinic Acetylcholine Receptors

We showed previously that choline administration protects dogs from endotoxin-induced multiple organ injury and platelet dysfunctions. Because sepsis/endotoxemia is associated with alterations in lipid metabolism, we have investigated whether choline or cytidine-5&vprime;-diphosphate choline, a choline donor, alters serum lipid responses to endotoxin in dogs and rats. In response to endotoxin, serum concentrations of triglycerides, choline-containing phospholipids, total cholesterol, and high-density lipoprotein cholesterol increased in a dose- and time-related manner. Administration of choline (20 mg/kg i.v. in dogs or 90 mg/kg i.p. in rats) or cytidine-5&vprime;-diphosphate choline (70 mg/kg i.v. in dogs) 5 min before and 4 and 8 h after endotoxin blocked or attenuated the increases in serum triglycerides, total cholesterol, and nonesterified fatty acids. Endotoxin-induced elevations in serum phospholipid levels did not change in rats and were enhanced in dogs by choline. In rats, serum lipid response to endotoxin was accompanied by severalfold elevations in serum levels of hepatorenal injury markers; their elevations were also blocked by choline. Pretreatment with hexamethonium blocked cholines effects on serum lipids and hepatorenal injury markers. Pretreatment with atropine blocked endotoxin-induced elevations in serum lipid and hepatorenal injury markers, but failed to alter cholines actions on these parameters. Choline treatment improved survival rate of rats in lethal endotoxin shock. In conclusion, these data show that choline treatment alters serum lipid responses to endotoxin and prevents hepatorenal injury during endotoxemia through a nicotinic acetylcholine receptor-mediated mechanism. Hence, choline and choline-containing compounds may have a therapeutic potential in the treatment of endotoxemia/sepsis.

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

Abstract 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 μmol/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 α-adrenoceptor antagonist phentolamine or by the α2-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 α2-adrenoceptors.