Egg Lecithin Research Articles

PH-responsive polymer core-shell nanospheres for drug delivery

Stimuli-responsive polymer nanoparticles are playing an increasingly more important role in drug delivery applications. However, limited knowledge has been accumulated about processes which use stimuli-responsive polymer nanospheres (matrix nanoparticles whose entire mass is solid) to carry and deliver hydrophobic therapeutics in aqueous solution. In this research, pyrene was selected as a model hydrophobic drug and a pyrene-loaded core-shell structured nanosphere named poly(DEAEMA)-poly(PEGMA) was designed as a drug carrier where DEAEMA and PEGMA represent 2-(diethylamino)ethyl methacrylate and poly(ethylene glycol) methacrylate, respectively. The pyrene-loaded core-shell nanospheres were prepared via an in situ two-step semibatch emulsion polymerization method. The particle size of the core-shell nanosphere can be well controlled through adjusting the level of surfactant used in the polymerization where an average particle diameter of below 100 nm was readily achieved. The surfactant was removed via a dialysis operation after polymerization. Egg lecithin vesicles (liposome) were prepared to mimic the membrane of a cell and to receive the released pyrene from the nanosphere carriers. The in vitro release profiles of pyrene toward different pH liposome vesicles were recorded as a function of time at 37 °C. It was found that release of pyrene from the core-shell polymer matrix can be triggered by a change in the environmental pH. In particular the pyrene-loaded nanospheres are capable of responding to a narrow window of pH change from pH = 5, 6, to 7 and can achieve a significant pyrene release of above 80% within 90 h. The rate of release increased with a decrease in pH. A first-order kinetic model was proposed to describe the rate of release with respect to the concentration of pyrene in the polymer matrix. The first-order rate constant of release k was thus determined as 0.049 h−1 for pH = 5; 0.043 h−1 for pH = 6; and 0.035 h−1 for pH = 7 at 37 °C. The release of pyrene was considered to follow a diffusion-controlled mechanism. The synthesis and encapsulation process developed herein provides a new approach to prepare smart nanoparticles for efficient delivery of hydrophobic drugs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4440–4450

Permeability of Fluid-Phase Phospholipid Bilayers: Assessment and Useful Correlations for Permeability Screening and Other Applications

Permeability data (P(lip/w) ) for liquid crystalline phospholipid bilayers composed of egg lecithin and dimyristoylphosphatidylcholine (DMPC) are analyzed in terms of a mathematical model that accounts for free surface area and chain-ordering effects in the bilayer as well as size and lipophilicity of the permeating species. Free surface area and chain ordering are largely determined by temperature and cholesterol content of the membrane, molecular size is represented by molecular weight, and lipophilicity of the barrier region is represented by the 1,9-decadiene/water partition coefficient, following earlier work by Xiang, Anderson, and coworkers. A correlating variable χ = MW(n) σ/(1 -σ) is used to link the results from different membrane systems, where different values of n are tried, and σ denotes a reduced phospholipid density. The group (1 -σ)/σ is a measure of free surface area, but can also be interpreted in terms of free volume. A single exponential function of χ is developed that is able to correlate 39 observations of P(lip/w) for different compounds in egg lecithin at low density, and 22 observations for acetic acid in DMPC at higher densities, spanning nine orders of magnitude to within an rms error for log 10 P(lip/w) of 0.20. The best fit found for n = 0.87 ultimately makes χ much closer to the ratio of molecular to free volumes than surface areas. The results serve as a starting point for estimating passive permeability of cell membranes to nonionized solutes as a function of temperature and cholesterol content of the membrane.

Influence of Drug Lipophilicity on Drug Release from Sclera After Iontophoretic Delivery of Mixed Micellar Carrier System to Human Sclera

Mixed micelles prepared using sodium taurocholate (TA) and egg lecithin (LE) were previously found to be an effective carrier for sustained release of a poorly water-soluble drug in transscleral iontophoretic delivery. The objectives of the present study were to investigate the effects of drug lipophilicity upon micellar carrier solubilization potential and drug release profiles from the sclera after iontophoretic delivery of model lipophilic drugs dexamethasone (DEX), triamcinolone acetonide (TRIAM), and β-estradiol (E2β) with a mixed micellar carrier system of TA-LE (1:1 mole ratio). In this study, the micellar carrier system was characterized for drug solubilization. The micelles encapsulating these drugs were evaluated for transscleral passive and 2-mA iontophoretic delivery (both cathodal and anodal) and drug release from excised human sclera in vitro. The results show that drug solubility enhancement of the micellar carrier system increased with increasing drug lipophilicity. The more lipophilic drugs E2β and TRIAM displayed slower drug release from the sclera compared with the less lipophilic drug DEX after iontophoretic drug delivery with the mixed micelles. These results suggest that the combination of transscleral iontophoresis and micellar carriers is more effective in sustaining transscleral delivery of the more lipophilic drugs studied in this investigation.

ATPase activity of human ABCG1 is stimulated by cholesterol and sphingomyelin

ATP-binding cassette protein G1 (ABCG1) is important for the formation of HDL. However, the biochemical properties of ABCG1 have not been reported, and the mechanism of how ABCG1 is involved in HDL formation remains unclear. We established a procedure to express and purify human ABCG1 using the suspension-adapted human cell FreeStyle293-F. ABCG1, fused at the C terminus with green fluorescent protein and Flag-peptide, was solubilized with n-dodecyl-β-D-maltoside and purified via a single round of Flag-M2 antibody affinity chromatography. The purified ABCG1 was reconstituted in liposome of various lipid compositions, and the ATPase activity was analyzed. ABCG1 reconstituted in egg lecithin showed ATPase activity (150 nmol/min/mg), which was inhibited by beryllium fluoride. The ATPase activity of ABCG1, reconstituted in phosphatidylserine liposome, was stimulated by cholesterol and choline phospholipids (especially sphingomyelin), and the affinity for cholesterol was increased by the addition of sphingomyelin. These results suggest that ABCG1 is an active lipid transporter and possesses different binding sites for cholesterol and sphingomyelin, which may be synergistically coupled.

Electrochemical Impedance Investigation of the Binding Properties of Phloretin to Egg Lecithin Liposomes

Immobilization of egg lecithin liposomes on Octadecanethiol (ODT) modified gold electrodes has been studied. The changes of the resistance of the layer with deposited liposomes, occurred under stimulation by different concentration of phloretin were measured with electrochemical impedance spectroscopy (EIS) and were used for the calculation of association constants. The binding constants Kb was obtained to be (7.571±0.821)×105 L•mol-1, indicated that high affinity existed between phloretin and liposomes.

New 1,3-diarylureas linked by CC Suzuki coupling to the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate moiety: Synthesis and fluorescence studies in solution and in lipid membranes

► Six new 1,3-diarylurea derivatives in the thieno[3,2- b ]pyridine series were synthesized. ► The fluorescence properties of the new compounds were studied in solution and in lipid membranes. ► The compounds were incorporated in lipid membranes of DPPC, DPPG, egg lecithin and DODAB. ► These compounds are useful to monitor changes in fluidity of lipid membranes. New six fluorescent 1,3-diarylureas linked by C C Suzuki coupling to the 6-position of the methyl 3-aminothieno[3,2- b ]pyridine-2-carboxylate moiety were prepared by reaction of the amino groups on the ortho or meta positions relative to the C C bond of the Suzuki coupling products, with different para -substituted arylisocyanates (H, OMe, CN), in high to excellent yields. The fluorescence properties of the 1,3-diarylureas in solution and in lipid membranes of egg yolk phosphatidylcholine (Egg-PC), dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) or dioctadecyldimethylammonium bromide (DODAB), with or without cholesterol (Ch), were studied. The six 1,3-diarylureas have reasonable fluorescence quantum yields in several solvents (0.02 ≤ Φ F ≤ 0.69) and present a moderately solvent sensitive emission, but are not fluorescent in alcohols and water. The compounds bearing the arylurea moiety in the meta position relative to the C C bond, especially with the OMe and CN substituents, present the better solvatochromic properties. Incorporation of the six compounds in lipid membranes indicates that all the compounds are deeply located in the hydrophobic region of the lipid bilayers, feeling the transition between the rigid gel phase and fluid phases.

Liposomes for Topical Use: A Physico-Chemical Comparison of Vesicles Prepared from Egg or Soy Lecithin

Developments in nanotechnology and in the formulation of liposomal systems provide the opportunity for cosmetic dermatology to design novel delivery systems. Determination of their physico-chemical parameters has importance when developing a nano-delivery system. The present study highlights some technological aspects/characteristics of liposomes formulated from egg or soy lecithins for topical use. Alterations in the pH, viscosity, surface tension, and microscopic/macroscopic appearance of these vesicular systems were investigated. The chemical composition of the two types of lecithin was checked by mass spectrometry. Caffeine, as a model molecule, was encapsulated into multilamellar vesicles prepared from the two types of lecithin: then zeta potential, membrane fluidity, and encapsulation efficiency were compared. According to our observations, samples prepared from the two lecithins altered the pH in opposite directions: egg lecithin increased it while soy lecithin decreased it with increased lipid concentration. Our EPR spectroscopic results showed that the binding of caffeine did not change the membrane fluidity in the temperature range of possible topical use (measured between 2 and 50 °C). Combining our results on encapsulation efficiency for caffeine (about 30% for both lecithins) with those on membrane fluidity data, we concluded that the interaction of caffeine with the liposomal membrane does not change the rotational motion of the lipid molecules close to the head group region. In conclusion, topical use of egg lecithin for liposomal formulations can be preferred if there are no differences in the physico-chemical properties due to the encapsulated drugs, because the physiological effects of egg lecithin vesicles on skin are significantly better than that of soy lecithin liposomes.

An Investigation into Some Effective Factors on Encapsulation Efficiency of Alpha-Tocopherol in MLVs and the Release Profile from the Corresponding Liposomal Gel.

Vitamin E (α-tocopherol) is a natural antioxidant very useful for preventing the harmful effects of UV sun rays as skin aging and cancers. In this study, different MLV formulations were made using egg lecithin and varying molar ratios of α-tocopherol and/or cholesterol, and their encapsulation efficiencies were determined. The best liposomal product was incorporated into a carbomer 980 gel. The resulting preparation was then studied with regard to the rheology and release profile using r(2) values and Korsmeyer-Peppas equation. The encapsulation efficiency was dramatically decreased when using α-tocopherol at molar ratios of 1:10 or more, which is suggested to be due to the defect in regular linear structure of the bilayer membrane. Addition of cholesterol to formulations caused a decrease in encapsulation efficiency directly related to its molar ratio, which is due to the condensation of the bilayer membrane as well as competition of cholesterol with α-tocopherol. The liposomal gel showed a yield value of 78.5 ± 1.8 Pa and a plastic viscosity of 27.35 ± 2.3 cp. The release showed a two-phase pattern with the zero-order model being the best fitted model for the first phase. However, the "n" and r(2) values suggested a minor contribution of Higuchi model due to some diffusion of α-tocopherol from the outermost bilayers of the MLVs to the gel. The second phase showed a non-Fickian release indicating a more prominent role for diffusion. This combinational release profile provides a high initial concentration of α-tocopherol followed by a slow release throughout a 10 h period.

Suitability of polymer materials for production of pulmonary microparticles using a PGSS supercritical fluid technique: Thermodynamic behaviour of fatty acids, PEGs and PEG-fatty acids

The thermodynamic behaviour of selected polymeric components for preparation of controlled release microparticles using supercritical carbon dioxide (scCO(2)) processing was investigated. The polymeric materials selected were egg lecithin (a model for the lung surfactant phospholipid), poly(ethyleneglycol) (PEG) of different molecular weights, fatty acids (C18, C16, and C14), and physical blends of PEGs and fatty acids. In addition a range of PEG-stearates was also assessed. Analysis of thermodynamic behaviour was performed by differential scanning calorimetry (DSC) and by assessment of their interaction with scCO(2) in a high-pressure variable volume view cell. The key criterion was to demonstrate a strong interaction with scCO(2) and to show liquefaction of the polymeric material at acceptable processing temperatures and pressures. Positive results should then indicate the suitability of these materials for processing by the Particle from Gas Saturated Solutions (PGSS) technique using scCO(2) to create microparticles for pulmonary administration. It was found that the materials tested interacted with scCO(2) and showed a sufficient lowering of their melting temperature (T(m)) to make them suitable for use in the PGSS microparticle production rig. Fatty acids of low T(m) were shown to act as a plasticising agent and to lower the T(m) of PEG further during interaction with scCO(2).

Growth response and fatty acid composition of rainbow trout (Oncorhynchus mykiss) fry fed diets containing different levels of soybean and egg lecithin

We investigated the effect of soybean and chicken egg lecithin on the growth performance, fatty acid profile and body composition of rainbow trout fry. Seven isonitrogenous and isolipidic diets were prepared by replacing 0, 2, 4 and 6 % soybean and egg lecithin instead of soybean oil in diets. Trout fry with initial average weight 120 ± 4.08 mg were randomly distributed in twenty-one 90-L tanks. Triplicate groups (165 fish per tank) of fry were fed to visual satiation at six meals per day for 40 days. Incorporation of 2 and 4 % egg lecithin led to increase in final weight, specific growth rate and weight gain compared with control group. Also, 4 % soybean lecithin had moderate effects on growth performance of fry. The fatty acid compositions of fry were influenced by dietary fatty acid. Fish fed egg lecithin showed higher amount of monounsaturated fatty acid than soybean lecithin and control groups. Fry fed soybean lecithin had significantly higher levels of polyunsaturated and n-6 fatty acid than egg lecithin and control groups. Soybean and egg lecithin induced higher amount of highly unsaturated fatty acid in lecithin groups compared with control group. The lipid and ash content of whole-body tissues were positively affected by percentages of soybean and egg lecithin in the diets. So 6 % soybean and egg lecithin induced higher amounts of lipid and ash body content. The results of our study indicated that dietary egg lecithin had growth-promoting effect, and rainbow trout fry had moderate lecithin requirement (at least 2 % as fed).

Colloidal catalysts based on iron(III) oxides. 2. Peculiarities of catalyzed oxidation of palm oil

The catalytic activity of an iron(III)-oxide-based colloidal catalyst with respect to oxidation of palm oil with atmospheric oxygen at 60°C is investigated. In a microheterogeneous system of palm oil containing phospholipids and large amounts of α-tocopherol and β-carotene, oxidation in the presence of the catalyst proceeds by a latent radical mechanism. This mechanism manifests itself as oxygen uptake against a background of almost constant concentrations of natural antioxidants, i.e., α-tocopherol and β-carotene. Using a model reaction of oxidation of an individual natural olefin, limonene, it is shown that, in the presence of the catalyst and trace amounts of hydroperoxide, oxidation of the hydrocarbon occurs through the chain free-radical mechanism. The presence of a phospholipid (egg lecithin) dramatically decelerates the catalytic oxidation of limonene and makes the process proceed through the latent radical mechanism, the rate of which is unaffected by oil-soluble inhibitors.

Interaction of antitumoral fluorescent heteroaromatic compounds, a benzothienopyrrole and two thienoindoles, with DNA and lipid membranes

► The fluorescence properties of a benzothienopyrrole and two thienoindoles were studied. ► The compounds were incorporated in lipid membranes of DPPC, DPPG, egg lecithin and DODAB. ► All compounds exhibited a growth inhibitory effect on three human tumor cell lines. ► The benzothienopyrrole showed a higher affinity to DNA than the two thienoindoles. Three tricyclic compounds, a benzothieno[2,3- b ]pyrrole 1 , a thieno[3,2- f ]indole 2 and a thieno[2,3- e ]indole 3 , early synthesized by us, were evaluated for their capacity to inhibit the in vitro growth of three human tumor cell lines, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer) and it was found that compound 1 is the most potent presenting the lowest GI 50 values (7.9–14.1 μM). The photophysical properties of the three compounds (absorption and fluorescence) were studied in different solvents and in lipid membranes of dipalmitoyl phosphatidylcholine (DPPC), dioctadecyldimethylammonium bromide (DODAB), phosphatidylcholine from egg yolk (egg lecithin, Egg-PC) and dipalmitoyl phosphatidylglycerol (DPPG), considering future drug delivery applications using liposomes. Fluorescence measurements indicate that all the compounds incorporated in lipid membranes are mainly located in the lipid bilayer. Compounds 1 and 3 clearly detect the gel to liquid-crystalline phase transition, while compound 2 feels a more hydrated environment in DPPG and DODAB vesicles. Due to the antitumoral properties of the three fluorescent compounds, interactions with salmon sperm DNA were investigated using fluorescence techniques which allowed the determination of binding constants ( K i ) and binding site sizes ( n ) for each compound. When compared with the thienoindoles 2 and 3 , the benzothienopyrrole 1 showed the highest affinity to DNA. Quenching experiments with iodide ion showed that intercalation is the preferred mode of binding of the three compounds to the DNA molecule.

Archaeosomes and Tetraether Lipid Liposome

Archaea have phytanyl ether lipids which is one of the characteristics that separates them from bacteria and eukaryotes. Some archaea have also unique membrane spanning tetrae- ther lipids (T EL); in Sulfolobus and Ihermoplasma species these TELmake up the majority of total membrane lipids. Archaeal lipids are able to form stable liposomal structures, both from membrane factions, mainly the polar membrane fraction, i.e. archaeosomes, or from highly purified TEL (tetraether lipid liposomes). Liposomes of the main polar lipid (MPL) from thermoacidophilic archaeon Ihermoplasma acidophilum were thoroughly inevstigat- ed. Archaeosomes and TEL liposomes exhibit extremely low proton permeability and high stability at low pH, which makes them suitable to delivery of therapeutics and vaccines via the gastro-inetestinal route. Liposomes from egg lecithin can be stabilized by incorporation of 11-12 mole% MPL. MPL liposomes show long-term shelf stability even at high tempera- tures without conservation. The size of MPL liposomes between 100 nm (unilamellar) and several gm (multilamellar) depends mainly on the method of preparation. Toxicity and mutagenicity have not been detected in toxicological screening. This is a review report on the lipid from archaea to be developed as an alternative to conventional liposome for vari- ous industrial applications, especially for pharmaceutical industry.

Structure and properties of complexes formed by cationic polymers and anionic cholesterol-containing liposomes

The adsorption of the synthetic polycation poly(N-ethyl-4-vinylpyridinium bromide) on the surface of three-component lipid vesicles (liposomes) formed from a mixture of anionic cardiolipin, electroneutral egg lecithin, and nonionic cholesterol is studied via laser microelectropheresis, dynamic light scattering, conductometry, fluorescence spectroscopy, and UV spectroscopy. The incorporation of cholesterol into the liposomal membrane increases its microviscosity; however, the membrane remains liquid-crystalline. Simultaneously, an increase in the fraction of cholesterol causes the formation of defects in liposome membranes during their binding with poly(N-ethyl-4-vinylpyridium bromide) and makes complexation irreversible. The results of this study are of interest for predicting the behavior of polyelectrolytes and biologically active structures formed on their basis on the surface of cells and the reaction of the cellular membrane to the adsorbed polymer.

Diffusion of Chlorin-p6 Across Phosphatidyl Choline Liposome Bilayer Probed by Second Harmonic Generation

We have investigated the diffusion of the photosensitizer Chlorin-p(6) (Cp(6)) across a egg lecithin lipid bilayer at different pH by the Second Harmonic Generation (SHG) method. Cp(6) has three ionizable carboxylic acid groups, and consequently, neutral and several ionic forms of Cp(6) are expected to be present in the pH range 3-8. The absorption spectra of Cp(6) get considerably modified in the presence of liposomes as the pH is decreased indicating that the drug liposome binding is pH dependent. The first pK(a) of interconversion (D-C) has been identified at pH ~7.0 by fluorescence measurement in an earlier work. In this work, the second pK(a) of interconversion (C-B) has been identified at pH ~4.8 by the hyper-Rayleigh scattering method. At acidic pH (3, 4, and 5), where species A, B, and C are dominant, the addition of liposomes to a Cp(6) solution generates an instantaneous rise (less than 1 s) in the second harmonic (SH) signal followed by decays whose time constants ranged from ten to hundreds of seconds. The instantaneous rise is attributed to the adsorption of Cp(6) to the outer lipid bilayer, and the decay is attributed to the diffusion of the neutral and charged (A and B) species of the drug. The observed fast and slow time constants for diffusion in the pH range 3-5 are attributed to the neutral (A) and ionic form (B) of Cp(6), respectively. At pH 6, the intensity of the generated SH signals on the addition of liposome reduced, and at physiological pH, it was too weak to be detected. These results are consistent with previous studies that show that the interaction between Cp(6) and egg-PC liposomes is pH dependent. At lower pH due to the presence of the hydrophobic species (A and B) of Cp(6), its interaction with liposomes is strong, and at higher pH, the abundance of the negatively charged hydrophilic species (C and D) decreases the interaction with the like charged liposomes. We have also studied the effect of increasing the bilayer rigidity by decreasing the temperature of the medium or by incorporating 50 mol % cholesterol in the lipid bilayer and observed that lowering of temperature has more profound effect on the diffusion rates. The characteristics of the SH signal changed significantly when liposomes incorporating 50 mol % cholesterol were used at a low (3 °C) temperature. Under these conditions, the SH signal consisted of an instantaneous (<1s) followed by a slower rise (10-90s), and then, it decayed on a much longer time scale. This slow rise of the SH signal at pH 3 and 4 may be attributed to the temperature dependent adsorption of the anionic species (B) of Cp(6) with the liposomes. Further investigations are required in order to understand clearly the pH dependent diffusion of this drug across lipid bilayers.

Formulation optimization of prostaglandin E1-loaded lipid emulsion: Enhanced stability and reduced biodegradation

The purpose of this study is to develop a new formulation for prostaglandin E1 (PGE1)-loaded lipid emulsion (Lipo-PGE1) with improved stability and reduced biodegradation. High-pressure homogenization was used to prepare the Lipo-PGE1, and high-performance liquid chromatography and accelerated test were used to evaluate its physicochemical stability. A tissue homogenate incubation test was firstly established and validated to assess its biodegradation. The factors influencing the stability of Lipo-PGE1, including oil phase, emulsifier, pH value, and drug concentration were systematically investigated. The optimized formulation consisting of poloxamer188 1.5% (w/v), egg lecithin 0.5% (w/v), soybean oil 10.0% (w/v), oleic acid 0.24% (w/v), and glycerol 2.2% (w/v), with the pH value at 4.0, was defined and characterized. When compared with the currently available commercial product of Lipo-PGE1, the degradation percentage of this optimized Lipo-PGE1 reduced by 47.1% after sterilization, the drug remaining percentage increased by 13.9% after storage at 4°C over 6 months. Also, a significant reduction in biodegradation of the optimized Lipo-PGE1 in comparison with the commercial Lipo-PGE1 was observed by a tissue homogenate incubation test. Overall, we provided a novel formulation for Lipo-PGE1 with a better physicochemical stability and a less biodegradation than the currently available commercial product of Lipo-PGE1, indicating its potential superiority in clinical application.

Sustained release micellar carrier systems for iontophoretic transport of dexamethasone across human sclera

A challenge in ocular drug delivery is to maintain the therapeutic concentration of a drug at the site of action in the eye. The objective of the present study was to investigate the feasibility of micellar carrier systems for sustained drug delivery in transscleral iontophoresis in vitro. Simple and mixed micelles prepared using sodium taurocholate (TA) alone or with egg lecithin (LE) were the carrier systems studied. Dexamethasone (DEX), a poorly water soluble corticosteroid, was the model drug. The micellar carrier systems were first characterized for their solubilization and encapsulation of the drug. Passive and 2-mA iontophoretic (both cathodal and anodal) transport experiments were conducted using these micellar carrier systems in side-by-side diffusion cells with excised human sclera in vitro. Drug release studies were performed after the transport experiments. Saturated DEX solution without the micellar carriers was used as a control. It was found that the solubilization capacity of the micellar carrier systems increased as the total lipid concentration of the systems increased. Drug release from the sclera was significantly prolonged with the micellar carrier systems as compared to the control after passive and iontophoretic delivery. Less than ~20% of DEX was released from the sclera in approximately 2h after cathodal iontophoretic delivery of the micellar carrier systems, whereas more than ~50% of DEX was released from the control in the same time period under the same condition. Micellar carrier systems can be a suitable transscleral drug delivery system for poorly water soluble drugs by enhancing their aqueous solubilities and providing sustained drug delivery. These micellar carrier systems can be efficiently delivered into and across the sclera by iontophoresis for drug delivery.

Effect of dietary phospholipid sources and levels on growth performance, enzymes activity, cholecystokinin and lipoprotein fractions of rainbow trout (Oncorhynchus mykiss) fry

This study was conducted to evaluate the effect of soybean lecithin (SBL) and chicken egg lecithin (EGL) on growth performance; pancreatic and intestine enzymes, cholecystokinin (CCK) and lipoprotein fractions of rainbow trout, Oncorhynchus mykiss (Walbaum) fry. Seven isonitrogenic and isolipidic diets were prepared by replacing 0 (as a control), 2%, 4% and 6% soybean and chicken egg lecithin instead of soybean oil in diets. Trout fry with initial average weight of 120 ± 4.08 mg, were randomly distributed in 21 90 L tanks. Triplicate groups (165 fish for each tank) of fry were fed each diet to visual satiation at six meals per day for 40 days. Dietary supplements of 2% and 4% chicken egg lecithin led to increase in fry final weight, weight gain and specific growth rate suggesting that moderate PL levels are needed during this stage of rainbow trout. Also 2% chicken egg lecithin caused significantly higher activity of amylase, lipase, phospholipase A2, alkaline phosphatase (AP), aminopeptidase-N (AN) and lower activity of leucine alanine peptidase (leu-ala) in the digestive tract of fry than those in control group. Furthermore, fry fed 2% chicken egg lecithin had a higher ratio of AN/leu-ala and AP/leu-ala than that in the control group. Chicken egg lecithin increased significantly cholecystokinin (CCK) and chylomicron fractions of fry compared to control group. It is noteworthy that soybean lecithin had moderate effect on final growth, weight gain and specific growth rate of fry and induced significantly higher activity of amylase, lipase, phospholipase A2 and secretion of CCK compared to control group. The results of this study indicate that dietary supplementation 2% chicken egg lecithin indirectly through some biochemical parameters improves growth performance of rainbow trout fry.

Cholesterol esterification by ACAT2 is essential for efficient intestinal cholesterol absorption: evidence from thoracic lymph duct cannulation

The hypothesis tested in this study was that cholesterol esterification by ACAT2 would increase cholesterol absorption efficiency by providing cholesteryl ester (CE) for incorporation into chylomicrons. The assumption was that absorption would be proportional to Acat2 gene dosage. Male ACAT2⁺/⁺, ACAT2⁺/⁻, and ACAT2⁻/⁻ mice were fed a diet containing 20% of energy as palm oil with 0.2% (w/w) cholesterol. Cholesterol absorption efficiency was measured by fecal dual-isotope and thoracic lymph duct cannulation (TLDC) methods using [³H]sitosterol and [¹⁴C]cholesterol tracers. Excellent agreement among individual mice was found for cholesterol absorption measured by both techniques. Cholesterol absorption efficiency in ACAT2⁻/⁻ mice was 16% compared with 46-47% in ACAT2⁺/⁺ and ACAT2⁺/⁻ mice. Chylomicrons from ACAT2⁺/⁺ and ACAT2⁺/⁻ mice carried ∼80% of total sterol mass as CE, whereas ACAT2⁻/⁻ chylomicrons carried >90% of sterol mass in the unesterified form. The total percentage of chylomicron mass as CE was reduced from 12% in the presence of ACAT2 to ∼1% in ACAT2⁻/⁻ mice. Altogether, the data demonstrate that ACAT2 increases cholesterol absorption efficiency by providing CE for chylomicron transport, but one copy of the Acat2 gene, providing ∼50% of ACAT2 mRNA and enzyme activity, was as effective as two copies in promoting cholesterol absorption.

Interaction of selected anthocyanins with erythrocytes and liposome membranes

Anthocyanins are one of the main flavonoid groups. They are responsible for, e.g., the color of plants and have antioxidant features and a wide spectrum of medical activity. The subject of the study was the following compounds that belong to the anthocyanins and which can be found, e.g., in strawberries and chokeberries: callistephin chloride (pelargonidin-3-O-glucoside chloride) and ideain chloride (cyanidin-3-O-galactoside chloride). The aim of the study was to determine the compounds’ antioxidant activity towards the erythrocyte membrane and changes incurred by the tested anthocyanins in the lipid phase of the erythrocyte membrane, in liposomes composed of erythrocyte lipids and in DPPC, DPPC/cholesterol and egg lecithin liposomes. In particular, we studied the effect of the two selected anthocyanins on red blood cell morphology, on packing order in the lipid hydrophilic phase, on fluidity of the hydrophobic phase, as well as on the temperature of phase transition in DPPC and DPPC/cholesterol liposomes. Fluorimetry with the Laurdan and Prodan probes indicated increased packing density in the hydrophilic phase of the membrane in the presence of anthocyanins. Using the fluorescence probes DPH and TMA-DPH, no effect was noted inside the hydrophobic phase of the membrane, as the lipid bilayer fluidity was not modified. The compounds slightly lowered the phase transition temperature of phosphatidylcholine liposomes. The study has shown that both anthocyanins are incorporated into the outer region of the erythrocyte membrane, affecting its shape and lipid packing order, which is reflected in the increasing number of echinocytes. The investigation proved that the compounds penetrate only the outer part of the external lipid layer of liposomes composed of erythrocyte lipids, DPPC, DPPC/cholesterol and egg lecithin lipids, changing its packing order. Fluorimetry studies with DPH-PA proved that the tested anthocyanins are very effective antioxidants. The antioxidant activity of the compounds was comparable with the activity of Trolox®.