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PubMed1989

Lecithin intake and serum cholesterol.

To find out whether the consumption of lecithin has a more beneficial effect on serum cholesterol than does the consumption of equivalent amounts of polyunsaturated oils, we scrutinized 24 studies on the effect of supplementary lecithin intakes ranging from 1 to 54 mg/d. Most of the studies lacked an appropriate control group, had a small sample size, or had changes in intake of other foods because of increased energy intake from lecithin. In only four trials were attempts made to balance fatty acid intakes of control and experimental groups. There is no evidence for a specific effect of lecithin on serum cholesterol independent of its linoleic acid content or secondary changes in food intake. The observed lecithin-induced hypocholesterolemic effects found in various studies were artifacts caused by the design and the manner of data analysis, were mediated by other dietary changes, or were due to the linoleic acid present in lecithin.

Cholesterol↗
PubMed1976

Properties of liposomal membranes composed of short-chain lecithins.

Permeability properties of multilamellar liposomes prepared from synthetic, saturated short-chain (C8, C10, C12) lecithins (3-sn-phosphatidyl choline) were studied. Dioctanoyllecithin, didecanoyllecithin, and dilauroyllecithin form "stable" bilayers which are practically impermeable to glucose when prepared with proportions of more than 1.2, 0.75, and 0.6 of cholesterol (molar ratio to phospholipid), respectively. Dioctanoyllecithin liposomes were rather leaky above 30 degrees, even when a proportion of 1.5 of cholesterol (molar ratio to lecithin) was incorporated. Judging from their sensitivities to temperature, Triton X-100, serum albumin, and other reagents, short-chain lecithin bilayers show characteristic properties, different from those of both saturated long-chain lecithins (dipalmitoyllecithin and dimyristoyllecithin) and lecithins having unsaturated fatty acid residues (egg lecithin and dioleoyllecithin).

Anti-Bacterial Agents↗
PubMed1976

Interaction of apoprotein from porcine high-density lipoprotein with dimyristoly lecithin. 2. Nature of lipid-protein interaction.

The detailed molecular structure of the complex formed by the apoprotein from porcine high density lipoprotein and dimyristoly phosphatidylcholine (lecithin) has been investigated by a range of physical techniques. The complex, an oblate ellipsoid with major axis 11.0 nm and minor axis 5.5 nm (see the accompanying paper), is comprised of a section of lecithin bilayer with apoprotein at the surface. The main site of interaction between protein and lipid is in the lipid glycerophosphorylcholine group region; as with native high density lipoprotein the surface of the particle consists of a mosaic of lecithin polar groups and protein. The formation of this mosaic reduces the cooperativity of the lecithin chain motions and changes the curvature of the lipid-water interface, as compared to a bilayer. Otherwise, there are no major changes in lecithin motions indicating that no strong binding of lipid to protein occurs. The interaction involves the intercalation of amphipathic, 60% alpha-helical, apoprotein molecules among the lecithin molecules so that the protein residues at the lipid-water interface. The apoprotein has a high affinity for the lipid-water interface but specific lipid-protein interactions are not involved.

Amino Acid Sequence↗
PubMed1978

Protection by unsaturated lecithin against the imidazole antimycotics, clotrimazole and miconazole.

The activity of egg lecithin in preventing the antifungal action of the two imidazole antimycotics, clotrimazole and miconazole, was confirmed. However, addition of this phospholipid could not relieve an existing imidazole inhibition. Compared with egg lecithin, reduced egg lecithin showed no such protective effect. The addition of egg lecithin to an aqueous suspension of the imidazole drugs changed the absorption profile of the imidazole, suggesting a low solubility and, consequently, a lower effective concentration; however, the addition of reduced egg lecithin did not produce any change in the adsorption. These results indicate that the preventive effect of egg lecithin on imidazole inhibition may be a consequence of preferential in vitro interaction of the drug with unsaturated phospholipid to form a hydrophobic complex.

Absorption↗
PubMed1977

Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids.

Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different enviroments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.

Animals↗
PubMed1978

Chylomicron composition during duodenal triglyceride and lecithin infusion.

In lymph fistula rats infused intraduodenally with trioleoylglycerol emulsions, the secretion of triglyceride was enhanced and that of total and esterified cholesterol in chylomicrons was strikingly reduced when lecithin was added at 4-5 times the biliary lecithin secretion rate. During continued triglyceride secretion in the presence of lecithin, the phospholipid: unesterified cholesterol ratio of the chylomicrons increased significantly in contrast to lecithin-free emulsions. Bile-diverted lymph fistula rats secreted significantly less esterified and total cholesterol in lymph chylomicrons than controls, and the difference was magnified by lecithin administration. Cholesterol appears to become relatively unavailable for incorportion into chylomicrons when lecithin is administered at high rates.

Animals↗
PubMed1978

Surfactant lecithin fatty acid composition and its relationship to the infantile respiratory distress syndrome.

In order to evaluate the role of surfactant lecithin composition in the development of the infantile respiratory distress syndrome (IRDS) we have examined lecithin fatty acid composition from gastric aspirates obtained at the time of delivery from 14 full term healthy infants, 9 control premature infants without respiratory distress, and 16 premature infants who developed IRDS. The latter had significantly reduced concentrations of palmitic acid (48.4 +/- 1.8% vs. 65.3 +/- 1.5% in fullterm and 59.5 +/- 0.8% in control premature infants, P less than 0.001). None of the infants in whom palmitic acid was more than 60% of total lecithin fatty acids developed IRDS, whereas 10 of 11 infants with values below 50% did develop this complication. Lecithin from gastric aspirate was shown to be similar in fatty acid composition to lecithins from tracheal washings and amniotic fluid. Palmitic acid concentrations in lecithins of serial tracheal washings paralleled the clinical course of eight infants with IRDS.

Fatty Acids↗
PubMed2006

Effect of lecithin coating on the pulmonary absorption of furosemide in rats.

The effect of lecithin coating on the pulmonary absorption of furosemide after application by metered dose inhalers (MDI) containing HFA 227 was evaluated in rats. The plasma concentration of furosemide after application of lecithin-coated furosemide was higher than that after application of the un-coated form. Since the disposition in the lung 2 min after application of un-coated furosemide was significantly lower than that after application of the coated form and the adsorption to a polyethylene tube used for the application of the un-coated form was significantly higher than that of the coated form, the higher plasma concentration after application of lecithin-coated furosemide could be partly related to the efficient delivery of the furosemide particles to the lung. The permeation-enhancing effect of the lecithin coating was investigated using Calu-3 cell monolayers. The cumulative amount of furosemide permeated over 2 h from a suspension containing lecithin-coated furosemide through the monolayers was significantly higher than that from a conventional furosemide suspension. This enhancing effect could also contribute to the high plasma concentration of furosemide in rats. The lecithin-coated furosemide will be useful for the formulation of MDI offering high bioavailability.

Animals↗
PubMed1976

Further study on the turnover calculation of lung lecithins.

Using the data reported previously by Moriya and Kanoh, the metabolic turnover of rat lung lecithins was calculated on the basis of the new assumption that the formation rate (Va) of lecithins from diacylglycerols did not equal the disappearance rate (Vb) of lecithins because of the presence of precursors other than diacylglycerols. The ratio of Va/Vb was almost the same in dienoic lecithin as that for total lecithins, whereas a very low ratio was found in saturated and hexaenoic species. The turnover time of lung lecithins estimated was markedly shorter than those determined in much later experimental periods after administration of labeled precursors. The reason for this discrepancy was discussed.

Animals↗
PubMed1975

Studies in cholestasis of pregnancy. V. Gallbladder disease, liver function tests, serum lipids and fatty acid composition of serum lecithin in the non-pregnant state.

Women from an earlier series of cholestasis of pregnancy (CP) were called for a retrospective study to consider presence of gallstones in the gallbladder (evaluated by cholecystography), liver function tests, serum lipids and lipoproteins and the relative fatty acid composition of serum lecithin (as determined by GLC). The attendance in the retrospective study was 60%. Estimated on the total series (assuming that none of the non-responders would have a positive X-ray), the incidence of gallbladder disease was 23.7%. Among women with previous cholestasis of pregnancy and with a positive X-ray finding no characteristic changes in liver function tests or serum lipids were revealed. The women with positive X-ray had, however, a lower alpha-lipoprotein cholesterol than women with negative X-ray. A characteristic finding among women with positive X-ray was furthermore the low relative content of palmitic acid (16:0) in serum lecithin. Also women with negative X-ray had a lower relative content of palmitic acid than controls. It is suggested that the low palmitic acid content is expressive of an influence on liver lecithin synthesis pathways and that the serum lecithin fatty acid composition reflects similar changes in bile lecithin. The "basic defect" in CP influencing liver lecithin synthesis might be the primary cause for disturbed cholesterol solubility in bile and of the frequent occurrence of gallstones in CP.

Adult↗
PubMed1990

Nutrient digestion, ruminal fermentation and plasma lipids in steers fed combinations of hydrogenated fat and lecithin.

Commercial soybean lecithin replaced hydrogenated fat in steer diets to determine if phospholipids enhance fatty acid digestion and microbial fermentation in ruminants. Four diets were fed in a 4 x 4 Latin square to four Angus steers with ruminal cannula. One diet contained no added fat (control) and three contained hydrogenated fat and lecithin in weight ratios of 100:0, 86:14, and 72:28. All diets with added fat had lower fatty acid digestibilities compared with the control diet with no difference due to level of lecithin. Ruminal acetate and acetate:propionate ratios were reduced by all fat supplements but reduced less for the supplements containing lecithin. Plasma triglyceride and cholesterol concentrations were increased from dietary fat but not increased as much if lecithin were present in the diet. Feeding lecithin to ruminants does not improve digestibility of hydrogenated fats that are highly saturated.

Animals↗
PubMed1998

Effect of soybean hulls, soy lecithin, and soapstock mixtures on ruminal fermentation and milk composition in dairy cows.

Two experiments were conducted to determine effects of soybean hulls, soy lecithin, and soapstock mixtures on ruminal fermentation, milk composition, and ruminal microbial populations. In Experiment 1, 20 Holstein dairy cows were assigned to one of five total mixed rations (TMR) in replicated 5 x 5 Latin squares to measure the effect of TMR on intake and milk composition. Four ruminally fistulated cows were used in a 4 x 5 Youden square to measure the effect of TMR on ruminal fermentation. The TMR consisted of 40 or 50% alfalfa and corn silages, 13% soybean hulls, and 47 or 37% of a concentrate containing either 2.25% soybean oil; 2.25% lipid from a mixture of soybean hulls, soy lecithin, and soapstock; or no added lipid. The ratios of soy lecithin to soapstock evaluated were 1:1, 2.5:1, and 4:1 (dry basis). The TMR containing soy lecithin and soapstock at ratios of 1:1 and 2.5:1 resulted in higher milk C18:2 than did the soybean oil TMR. Rate of ruminal NDF digestion of soybean hulls was reduced for the soybean oil TMR. In Experiment 2, a semi-continuous culture system was used to determine effects of soybean oil or an optimal mixture of soy lecithin and soapstock (1:1, wt/wt) on fermentation of soybean hulls and microbial populations. The TMR containing the lipid mixture increased the ratio of acetate to propionate compared with the TMR containing soybean oil and resulted in higher total protozoal counts than did the control TMR. The TMR containing mixtures of soy lecithin and soapstock at ratios of 1:1 and 2.5:1 elevated milk C18:2, and no negative effect on NDF digestion was detected, indicating some degree of ruminal protection.

Animal Feed↗
PubMed1975

Hydrocarbon chain packing and molecular motion in phospholipid bilayers formed from unsaturated lecithins. Synthesis and properties of sixteen positional isomers of 1,2-dioctadecenoyl-sn-glycero-3-phosphorylcholine.

Isomers of cis-octadecenoic acid, with the double bond in each position in the hydrocarbon chain, were used to synthesize the corresponding 1,2-diacyl-sn-glycero-3phosphorylcholines (lecithins). Differential thermal analysis of the lecithins, as a function of water content, permitted evaluation of the limiting transition temperature (Tc) of each isomer. Values of Tc plotted against double bond position fell on a smooth curve with a minimum at minus 22 degrees for the dioctadec-9'-enoyl compound. The presence of a "pretransition" endotherm in differential thermal analysis of 1,2-dioctadec-15'-and 1,2-dioctadec-16'-enoyl-sn-glycero-3-phosphorylcholine implies the existence of two beta crystalline forms. This was not observed with any of the other lecithins. Enthalpy and entropy data were then obtained from differential scanning calorimetry measurements. Values of delta H were lower (7.6 plus or minus 0.1 kcal mol- minus 1) when the center of unsaturation was near the middle of the hydrocarbon chain than they were (9.6 kcal mol- minus 1) when the center of unsaturation was close to either end of the chain. However, values of delta S showed no consistent variation with double bond position. Four positional isomers of 1-octadec-cis-enoyl-2-octadecanoyl-sn-glycero-3-phosphorylcholine were synthesized. With the double bond near the middle of the chain or close to the terminal group, the Tc values of the mixed acid lecithins were higher than those of the corresponding dioctadecenoyl lecithins. 13-C nuclear magnetic resonance relaxation measurements were used to obtain information about chain motion of selected 1,2-dioctadec-cis-enoyl-sn-glycero-3-phosphorylcholines at a temperature (52 degrees) above the Tc values. Spin-lattice relaxation times of the resolved resonances indicated that location of double bonds near the middle, as compared to either end, of the hydrocarbon chain favors enhanced molecular motion along the length of the chins and especially at the terminal methyl end. In the gel state, the minimum interaction potential energy of hydrocarbon chains in bilayers formed from dioctadecenoyl lipids appears to be minimized by localization of the double bond near the middle of the chains. It is suggested that in the case of homogeneous chains the double bond primarily affects the cooperativity of interactions and has very little steric effect on van der Waals' contacts. By contrast, in bilayers of mixed lecithins, with heterogeneous chains, the steric effect may become dominant, depending on double bond position. These differences in chain packing in the gel state are promulgated beyond the phase transition to the liquid crystalline state as an enhancement of chain motion as the temperature rises above Tc.

Chromatography, Thin Layer↗
PubMed1976

Fetal lung lecithin metabolism in the glucose-intolerant Rhesus monkey pregnancy.

Fetal lung lecithin metabolism was examined in rhesus monkey gestations complicated by glucose intolerance secondary to maternal streptozotocin (STZ) administration. Fetuses of STZ-treated mothers were delivered at 85% to 89% of term and were compared to two control groups of fetuses from normal pregnancies--one group age-matched to the STZ pregnancies, and the other composed of fetuses delivered in the final 10% of gestation. In the glucose-intolerant pregnancies, two measures of fetal lung lecithin biosynthesis--the amniotic fluid lecithin-to-sphingomyelin (L/S) ratio and the rate of 14C-choline incorporation into lecithin in fetal lung slices--were significantly greater than in age-matched normal gestations and were similar to results in late-gestation controls. However, lung lecithin concentrations in the glucose-intolerant group were comparable to the age-matched controls, and both were significantly less than in the late-gestation controls. Since the gestational age, mode of delivery, and fetal acid-base status were the same in the age-matched groups, we conclude that these changes in fetal lung lecithin metabolism are due to the effects of maternal glucose intolerance.

Amniotic Fluid↗
PubMed1987

Failure of long term high-dose lecithin to retard progression of early-onset Alzheimer's disease.

We conducted a six-month, randomized, double-blind trial of lecithin therapy in early-onset Alzheimer's disease. We hypothesized that such therapy would retard the progression of the clinical and neuropsychological manifestations of this illness. Of the 73 referred patients, 37 met strict requirements for diagnosis and compliance. The 21 placebo and 16 lecithin-treated patients (mean age 63 years) had a comparable degree of severity of dementia (mean Clinical Dementia Rating 1.6). Lecithin therapy produced an increase in mean plasma choline levels from a baseline of 15.9 to 28.8 nmol/ml. Patients were evaluated by the physician using clinical assessments (CDR, Lawton ADL and other rating scales) and by the neuropsychologist who determined the outcome of therapy on a battery of tests (Mini Mental State Examination, Wepman Aphasia Screen, Verbal Fluency Test, Verbal Selective Reminding Test and Spatial Memory Test). Only 6 (37.5%) of the 16 lecithin-treated patients were considered by the neurologist to be clinically stable or improved as compared to 12 (57.1%) of the 21 patients given placebo (difference -19.6%, 95% confidence limits of -51% to 12%). The neuropsychologic scores showed no differences in the stability of the dementing process over time between the lecithin-treated (50.0%) and placebo (47.6%) groups. On the basis of these clinical and neuropsychological findings, it appears that lecithin alone has no important therapeutic effect in early-onset Alzheimer's disease.

Alzheimer Disease↗
PubMedDate not supplied

[Enzymatic determination of lecithin concentration in the amniotic fluid for antepartal determination of fetal lung maturity].

An enzymatic method of determining the lecithin concentration in the amniotic fluid is compared with the present standard method of antepartal determination of fetal lung maturity, i.e., determination of the lecithin-sphingomyelin (L/S) ratio. A total of 320 amniotic fluid samples, of which 154 were obtained within the 72 hours preceding birth, were studied by both methods. Simultaneously with the rise in the L/S ratio in the amniotic fluid there is a rise in the enzymatically determined lecithin concentration in the last quarter of pregnancy. The critical threshold value for RDS risk of 2 for the L/S ratio corresponds to a threshold value of 5 mg/100 ml amniotic fluid for the enzymatically analyzed lecithin concentration. Established lung maturity can be demonstrated with the same degree of confidence as by using the L/S ratio. The specificity of the both methods is 91%. It is at least as easily possible to predict the likelihood of respiratory distress syndrome by determining the enzymatic lecithin concentration (11 out of 15 cases) as by means of the L/S ratio (9 out of 15). In order to improve the sensitivity (L/S ratio 60%, enzymatic lecithin determination 73%) it would be necessary to perform an additional analysis-e.g., of phosphatidylglycerol-in the amniotic fluid.

Amniocentesis↗
PubMed1967

Influence of calcium, cholesterol, and unsaturation on lecithin monolayers.

Surface pressures and potentials of mixed monolayers of dicetyl phosphate-cholesterol, dipalmitoyl lecithin-cholesterol, egg lecithin-cholesterol, and phosphatidic acid-cholesterol were measured. The surface potential is shown to be a more reliable parameter for the study of interactions in monolayers than the surface pressure. Monolayers of dicetyl phosphate-cholesterol follow the additivity rule for area/molecule whereas lecithin-cholesterol monolayers deviate from it. The reverse is true for the additivity rule with regard to surface potential/molecule. Thus, the surface potential indicates that there is no interaction (or complex formation) between lecithin and cholesterol, but that there is ion-dipole interaction between dicetyl phosphate and cholesterol, as well as between phosphatidic acid and cholesterol. The apparent condensation of mixed monolayers of lecithin when cholesterol is added is explained by a consideration of molecular cavities or vacancies caused by thermal motion of the fatty acyl chains, the size of these cavities being influenced by the length and degree of saturation (especially the proportion of monounsaturation) of the fatty acyl chains and the extent of compression of the monolayer. The cholesterol molecules occupy these cavities and therefore cause no proportional increase in area/molecule in the mixed monolayers. Monolayers are liquefied by the presence of cholesterol as well as of unsaturated fatty acyl chains; in contrast, Ca(++)tends to solidify lecithin monolayers. The available evidence suggests that cholesterol can both impart fluidity to the monolayer and occupy the molecular cavities caused by the fatty acyl chains.

Calcium↗
PubMed1967

Phase equilibria and structure of dry and hydrated egg lecithin.

The behavior of purified egg lecithin in water has been investigated in relation to the quantity of water present and the temperature. The complete binary phase diagram of egg lecithin-water is presented as well as X-ray diffraction data on selected mixtures. Dry egg lecithin is present in at least partially crystalline form until about 40 degrees C. Above this temperature it forms a "wax-like" phase up to about 88 degrees C. From 88 to 109 degrees C it forms a viscous isotropic phase which gives face-centered cubic spacings by X-ray analysis. Above 110 degrees C its texture is "neat" and the structure is assumed to be lamellar until its final melting point at 231 degrees C. Hydrated lecithin forms (except for a small zone of cubic phase at low water concentrations and high temperature) a lamellar liquid crystalline phase. This phase contains up to 45% water at 20 degrees C. Mixtures containing more water separate into two phases, the lamellar liquid crystalline phase and water. In the melting curve of hydrated lecithin a eutectic is noted at about 16% water and the cubic phase seen when less water is present disappears at this composition of the mixture. These facts, along with previous vapor pressure measurements, suggest that there is a structural change at about 16% water. X-ray diffraction studies of lecithin at 24 degrees C and calculations from these data suggest that the reason for this may be the presence of a "free water layer" when more than 16% water is present.

Eggs↗