Learning behaviour and cerebral protein kinase C, antioxidant status, lipid composition in senescence-accelerated mouse: influence of a phosphatidylcholine–vitamin B12diet
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Our objective was to determine whether dietary supplementation with phosphatidylcholine (PC) plus vitamin B 12 could afford beneficial effects on biochemical and biophysical events in the brain of senescence-accelerated mouse (SAM) substrain SAMP8. We measured learning behaviour, hippocampal protein kinase C (PKC) activity, cerebral antioxidant status, phospholipid composition and fatty acid composition in 6-month-old SAMP8 and in age-matched controls (SAM substrain SAMR1). In comparison with SAMR1, SAMP8 showed a significant elevation in total grading score of senescence (P<0·05) and a significant decline in acquisition (P<0·05). SAMP8 had a lower hippocampal PKC activity and cerebral PKC-β mRNA abundance than SAMR1. SAMP8 had increased cerebral lipid peroxide levels and proportion of sphingomyelin, and a lower proportion of 20 : 4 n -6 and 22 : 6 n -3 in cerebral phosphtidylethanolamine than SAMR1. SAMP8 fed the PC combined with vitamin B 12 diet had an increased PKC activity and a higher proportion of 22 : 6 n -3 than SAMP8 fed the control diet. These results indicate the potential benefit of PC combined with vitamin B 12 as a dietary supplement.Keywords:
Senescence
Lipid peroxide
Sphingomyelin synthesis was studied in slices of rat heart by using [Me-14C]choline, [1,2-14C]ethanolamine, S-adenosyl-L-[14C]methionine and [32P]Pi as as precursors. In the presence of both [Me-14C]choline and [32P]Pi the ratio of the specific radioactivities of 14C and 32P in phosphatidylcholine was greater than in sphingomyelin at all the times studied. This suggested that synthesis of phosphatidylcholine and sphingomyelin de novo did not involve the utilization of a common pool of cytidine diphosphate choline. In addition, studies with [1,2-14C]ethanolamine and S-adenosyl-L-[14C]methionine indicated that a quantitatively significant pool of choline, derived from these precursors, was selectively utilized for sphingomyelin formation. This pool was not represented by phosphatidylcholine formed by methylation of phosphatidylethanolamine or by other pathways.
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Phosphatidylethanolamine
Phosphocholine
Ethanolamines
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The lipid composition of membranes of erythrocytes in athletes of cyclic types of sport with qualification from first adult class to Master of Sports and persons doing no sports was analyzed. The qualitative and quantitative analysis of phospholipid fractions and fatty-acid specter of sphingomyelin and phosphatidylcholine was implemented. In athletes, amount of sphingomyelin and phosphatidylcholine and percentage content of phosphatidylcholine were significantly increased. The percentage content of kefalin was also decreased. The ratio of sphingomyelin/phosphatidylcholine was lower on 52.3%. In fatty-acid specter of sphingomyelin and phosphatidylcholine of athletes the percentage of C14:0 and C16:0 was decreased. In phosphatidylcholine increase of content of C16:1 was noted and in sphingomyelin content of C18:3 was increased. The ratio of sums of saturated fatty acids/ polyunsaturated fatty acids were lower in athletes. The study results testify significant alterations in membranes of erythrocytes caused by regular physical loads and probably favoring increase of functional activity.
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The temperature dependences of the ESR spectra from different positional isomers of sphingomyelin and of phosphatidylcholine spin-labeled in their acyl chain have been compared in mixed membranes composed of sphingolipids and glycerolipids. The purpose of the study was to identify the possible formation of sphingolipid-rich in-plane membrane domains. The principal mixtures that were studied contained sphingomyelin and the corresponding glycerolipid phosphatidylcholine, both from egg yolk. Other sphingolipids that were investigated were brain cerebrosides and brain gangliosides, in addition to sphingomyelins from brain and milk. The outer hyperfine splittings in the ESR spectra of sphingomyelin and of phosphatidylcholine spin-labeled on C-5 of the acyl chain were consistent with mixing of the sphingolipid and glycerolipid components, in fluid-phase membranes. In the gel phase of egg sphingomyelin and its mixtures with phosphatidylcholine, the outer hyperfine splittings of sphingomyelin spin-labeled at C-14 of the acyl chain of sphingomyelin are smaller than those of the corresponding sn-2 chain spin-labeled phosphatidylcholine. This is in contrast to the situation with sphingomyelin and phosphatidylcholine spin-labeled at C-5, for which the outer hyperfine splitting is always greater for the spin-labeled sphingomyelin. The behavior of the C-14 spin-labels is attributed to a different geometry of the acyl chain attachments of the sphingolipids and glycerolipids that is consistent with their respective crystal structures. The two-component ESR spectra of sphingomyelin and phosphatidylcholine spin-labeled at C-14 of the acyl chain directly demonstrate a broad two-phase region with coexisting gel and fluid domains in sphingolipid mixtures with phosphatidylcholine. Domain formation in membranes composed of sphingolipids and glycerolipids alone is related primarily to the higher chain-melting transition temperature of the sphingolipid component.
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Modified phosphatidylcholine and sphingomyelin containing an anthryl end group attached to one of the Fatty acyl chains were used as fluorescent probes in an investigation of the molecular organization of human high‐density lipoproteins (HDL). Monolayer experiments and NMR measurements showed the anthryl‐labeled lipids to mimic closely the corresponding host phospholipids, the fluorophores being located near to the terminal CH 3 groups of the fatty acid residues. The above fluorescent phospholipid probes made it possible for the first time to study differentially the behaviour of phosphatidylcholine and sphingomyelin in HDL. The probes were shown to interact in a different way with the apoprotein tryptophans and to be non‐randomly distributed at the surface of the globules. The probable sphingomyelin binding site of apolipoprotein A‐I was defined. Evidence was obtained suggesting the existence in high‐density lipoproteins of two slowly exchanging phospholipid pools: one strongly bound to apoproteins, and the other free or loosely bound. Fluorescence parameters characterizing the fluidity of HDL phospholipids and their interaction with the apoprotein tryptophans were found to correlate with the HDL cholesterol level. The possible significance of the obtained results for a better understanding of the relation of high‐density lipoproteins to coronary heart diseases is discussed.
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Abstract Phosphatidylcholine and sphingomyelin are the major phospholipids of the hepatocytic canalicular membrane outer leaflet. Sphingomyelin may preferentially reside with cholesterol in liquid‐ordered domains. In contrast, phosphatidylcholine is the exclusive phospholipid secreted in rat bile (enriched in hydrophilic species compared to the canalicular membrane), subsequently incorporated into bile salt‐cholesterol micelles. We determined the bile lipid composition in 95 vertebrate species (Moschetta et al., J Lipid Res. 2005, 46 , 2221–2232). Phospholipid was often virtually absent in bile of cartilaginous fish and reptiles, occurred in low relative amounts (compared to bile salts) in bony fish or birds and in high relative amounts in most mammals. Biles with low relative amounts of phospholipid often contained high proportions of sphingomyelin. Phosphatidylcholine was the predominant phospholipid in biles with high phospholipid contents. We then compared, in CaCo2 cells (without appreciable phospholipase A 2 activity), the effects of incorporating sphingomyelin, egg yolk phosphatidylcholine or lyso‐phosphatidylcholine in apical bile salt‐cholesterol micelles. Egg yolk phosphatidylcholine and (more pronounced) sphingomyelin inhibited cholesterol absorption with decreased ABC‐A1 and ‐G1 expression. Lyso‐phosphatidylcholine enhanced cholesterol absorption with increased basolateral HDL‐dependent cholesterol efflux and high expression of ABC‐A1 and ‐G1. In conclusion, sphingomyelin plays a pivotal role in protecting hepatocytes against detergent bile salts. Dietary sphingomyelin may inhibit intestinal cholesterol absorption.
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The lipid composition of membranes of erythrocytes in athletes of cyclic types of sport with qualification from first adult class to Master of Sports and persons doing no sports was analyzed. The qualitative and quantitative analysis of phospholipid fractions and fatty-acid specter of sphingomyelin and phosphatidylcholine was implemented. In athletes, amount of sphingomyelin and phosphatidylcholine and percentage content of phosphatidylcholine were significantly increased. The percentage content of kefalin was also decreased. The ratio of sphingomyelin/phosphatidylcholine was lower on 52.3%. In fatty-acid specter of sphingomyelin and phosphatidylcholine of athletes the percentage of C14:0 and C16:0 was decreased. In phosphatidylcholine increase of content of C16:1 was noted and in sphingomyelin content of C18:3 was increased. The ratio of sums of saturated fatty acids/polyunsaturated fatty acids were lower in athletes. The study results testify significant alterations in membranes of erythrocytes caused by regular physical loads and probably favoring increase of functional activity.
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Choline
Plasma lipoprotein
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