Phospholipid Fatty Acyl Chain Research Articles

Overexpression of lysophospholipid acyltransferase, LPLAT10/LPCAT4/LPEAT2, in the mouse liver increases glucose-stimulated insulin secretion.

Postprandial hyperglycemia is an early indicator of impaired glucose tolerance that leads to type 2 diabetes mellitus (T2DM). Alterations in the fatty acid composition of phospholipids have been implicated in diseases such as T2DM and nonalcoholic fatty liver disease. Lysophospholipid acyltransferase 10 (LPLAT10, also called LPCAT4 and LPEAT2) plays a role in remodeling fatty acyl chains of phospholipids; however, its relationship with metabolic diseases has not been fully elucidated. LPLAT10 expression is low in the liver, the main organ that regulates metabolism, under normal conditions. Here, we investigated whether overexpression of LPLAT10 in the liver leads to improved glucose metabolism. For overexpression, we generated an LPLAT10-expressing adenovirus (Ad) vector (Ad-LPLAT10) using an improved Ad vector. Postprandial hyperglycemia was suppressed by the induction of glucose-stimulated insulin secretion in Ad-LPLAT10-treated mice compared with that in control Ad vector-treated mice. Hepatic and serum levels of phosphatidylcholine 40:7, containing C18:1 and C22:6, were increased in Ad-LPLAT10-treated mice. Serum from Ad-LPLAT10-treated mice showed increased glucose-stimulated insulin secretion in mouse insulinoma MIN6 cells. These results indicate that changes in hepatic phosphatidylcholine species due to liver-specific LPLAT10 overexpression affect the pancreas and increase glucose-stimulated insulin secretion. Our findings highlight LPLAT10 as a potential novel therapeutic target for T2DM.

Role of biomembrane phospholipid fatty acyl chains in membrane protein function.

Role of biomembrane phospholipid fatty acyl chains in membrane protein function.

Interaction between soybean oleosome-associated proteins and phospholipid bilayer and its influence on environmental stability of luteolin-loaded liposomes

Soybean oleosome-associated protein (SOP) plays a vital role in stabilizing soy oleosomes owing to its unique amphipathic topological structure. Inspired by the structure of natural oleosomes, in the current study, SOP-decorated liposomes (SOP-Lips) were proposed as a vehicle for improving phospholipid bilayer membrane stability. The micro morphology, size, encapsulation efficiency, and retention rate of SOP-Lips were characterized, the interactions between SOP and the phospholipid bilayer and their effects on the protein and lipid bilayer structures were evaluated. When the liposomes/SOP mass ratio was 1: 0.2 and 1: 0.4, the SOP-Lips exhibited spherical morphology and favorable dispersibility. The quartz crystal microbalance with dissipation monitoring (QCM-D) result suggested that most of SOP bound to liposomes in a tightly integrated way. Spectroscopy analysis indicated that the aromatic amino acids in the protein were exposed to a more hydrophobic microenvironment due to the interactions between the SOP and liposomes. There was an increase in α-helix and decrease in β-sheet and random curl contents in SOP upon exposure to liposomes. The decoration of SOP to liposomes could decrease membrane fluidity and enhance lateral packing of the phospholipid fatty acyl chain. The SOP coating increased the pH, ionic strength and temperature stability of luteolin liposomes (LUT-Lips). In the simulated digestion, SOP-decorated luteolin liposomes (SOP-LUT-Lips) showed a delayed release effect compared with LUT-Lips, suggesting that the inclusion of SOP resulted in a more digestion-resistant structure. This work provides a viable strategy for using SOP-Lips as a delivery system for nutraceuticals in functional food, dietary supplements and pharmaceuticals. • Soybean oleosome-associated protein (SOP) decorated liposomes were constructed. • SOP interacted with liposomes through hydrogen bonding and hydrophobic interaction. • SOP decreased phospholipid membrane fluidity and enhanced the bilayer orderness. • Inclusion of SOP increased the load efficiency of luteolin in liposomes. • SOP modified liposomes exhibited sustained luteolin release profile.

Abstract 1627: Metabolic links between obesity and ferroptosis in a murine model of breast cancer

Abstract Background Obesity is an established risk factor for post-menopausal triple negative breast cancer (TNBC). Multiple aspects of fatty acid metabolism, including fatty acid synthesis, are upregulated in white adipose tissue during obesity development. The enzyme pyruvate carboxylase (PC), a supportive player in fatty acid synthesis, is relied upon for metastasis of murine TNBC particularly in models of obesity- further elucidating the importance of fatty acid metabolism to breast cancer progression in those with obesity. Ferroptosis, a method of cell death induced by peroxidation of phospholipid fatty acyl chains, is a recently discovered and rapidly developing mechanistic target in multiple cancer types. While several cancers, including breast cancer, are sensitive to ferroptosis induced by different mechanisms, the metabolic vulnerabilities and consequent therapeutic potential of ferroptosis are just beginning to be explored. This study aims to determine whether obesity-driven reprogramming of fatty acid metabolism exacerbates breast cancer progression via altered sensitivity to ferroptosis Methods The relationship between obesity, breast cancer and lipid peroxidation was investigated in vitro via proliferation assays, qPCR, Western blot and flow cytometry using multiple murine models of breast cancer treated with erastin and RSL3. PC was suppressed using shRNA introduced via lentiviral transduction. In vivo tumor growth in lean and obese mice was determined following treatment with erastin, RSL3, or a vehicle control. Results In vitro data reveals that TNBC cells are highly sensitive to treatment with the ferroptosis-inducing molecules erastin and RSL3. Erastin treatment transcriptionally induces PC expression in several murine models of TNBC in vitro. Suppression of PC at baseline (without ferroptosis induction) is sufficient to induce transcription of glutathione peroxidase-4 (a critical regulator of ferroptosis). While Affymetrix array data of untreated metastatic M-WntLung primary tumors showed a decrease in PC and associated genes in tumors from obese mice relative to lean mice, treatment with erastin increased PC expression specifically in tumors from obese mice. Tumors from obese mice relative to control mice have an altered response to treatment with the ferroptosis inducing molecules erastin and RSL3. Conclusion These data indicate that obesity-associated dysregulation of lipid metabolism and regulation of PC may be key determinants of sensitivity to induction of ferroptosis. Future work will delineate the relationship between breast cancer, ferroptosis, and fatty acid metabolism utilizing in vivo models to determine whether ferroptosis-specific mechanisms are exacerbated with PC suppression to further impede obesity-exacerbated tumor growth. Citation Format: Emily Devericks, Michael F. Coleman, Hannah Malian, Violet Kiesel, Dorothy Teegarden, Stephen D. Hursting. Metabolic links between obesity and ferroptosis in a murine model of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1627.

Fusion peptide from SARS-2 spike transforms into a wedge inserted in a bilayer leaflet, and thins the opposite leaflet

Activation of SARS-CoV-2 Spike deploys its fusion peptide to a membrane of the host cell to infect it. NMR in solution demonstrates that this fusion peptide transforms from intrinsic disorder in solution into a wedge-shaped structure inserted in bilayered micelles. According to NOEs and proximity to a nitroxide spin label deep in the membrane mimic, the globular fold of three helices contrasts the open, extended conformations observed in compact prefusion states. In the hydrophobic, narrow end of the wedge, helices 1 and 2 contact the fatty acyl chains of phospholipids.

2D HILIC‐ELSD/UPLC‐Q‐TOF‐MS Method for Acquiring Phospholipid Profiles and the Application in Caenorhabditis elegans

AbstractPhospholipids are the main constituent of cellular membranes and have recently been identified to have diagnostic value as biomarkers for many diseases. Accordingly, much emphasis is now laid on developing optimal analytical techniques for the phospholipid profiles of various biological samples. In the present study, different classes of phospholipids are first separated by optimized hydrophilic interaction chromatography with evaporative light scattering detector (HILIC‐ELSD). The phospholipids in each class are then identified by ultraperformance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (UPLC‐Q‐TOF‐MS). Validation results confirm that this approach meets the requirements of quantitative analysis. Finally, the approach is adopted to analyze the phospholipid profiles in Caenorhabditis elegans. A total of 111 phospholipid species is identified according to the mass fragments. Major fatty acyl chains in phospholipids are found to be formed by oleic acid (C18:1), arachidonic acid (C20:4), and eicosapentaenoic acid (C20:5). Overall, this study improves current knowledge on analytical techniques of the phospholipid composition in C. elegans and provides a basis for future lipidomics research.Practical applications: Phospholipids reportedly play a crucial role in the development of many diseases. Until now, only a small portion of phospholipids in Caenorhabditis elegans has been reported by using one‐dimensional analysis strategy. The offline 2D liquid chromatography method developed in this study identifies 111 phospholipid species in Caenorhabditis elegans. The obtained phospholipid profiles complement the lipid database of Caenorhabditis elegans. The study also provides the basis for the future development of a 2D online approach.

Fusion Peptide of SARS-CoV-2 Spike Rearranges into a Wedge Inserted in Bilayered Micelles.

The receptor binding and proteolysis of Spike of SARS-CoV-2 release its S2 subunit to rearrange and catalyze viral-cell fusion. This deploys the fusion peptide for insertion into the cell membranes targeted. We show that this fusion peptide transforms from intrinsic disorder in solution into a wedge-shaped structure inserted in bilayered micelles, according to chemical shifts, 15N NMR relaxation, and NOEs. The globular fold of three helices contrasts the open, extended forms of this region observed in the electron density of compact prefusion states. In the hydrophobic, narrow end of the wedge, helices 1 and 2 contact the fatty acyl chains of phospholipids, according to NOEs and proximity to a nitroxide spin label deep in the membrane mimic. The polar end of the wedge may engage and displace lipid head groups and bind Ca2+ ions for membrane fusion. Polar helix 3 protrudes from the bilayer where it might be accessible to antibodies.

Role of Lipid Composition in the Interaction and Activity of the Antimicrobial Compound Fengycin with Complex Membrane Models.

Fengycins are compounds produced by bacteria of the Bacillus genus with strong antifungal activity. In this work, lipids extracted from fungal and oomycetal molds were used to assess the ability of fengycin to bind and insert into complex membrane models prepared as Langmuir lipid monolayers. In addition, fengycin-induced leakage in liposomes prepared from these complex lipid extracts was also evaluated. Fengycin's ability to bind and incorporate into these membranes seemed to be mainly related to ergosterol content. Other membrane characteristics such as phospholipid fatty acyl chain length played a more peripheral role. A high ergosterol concentration appeared to allow other membrane characteristics generally associated with fengycin binding and/or insertion, such as higher proportion of phosphatidylcholine head groups or increased fatty acyl unsaturation, to be present without adversely affecting membrane integrity. Increased membrane leakage was also generally associated with the presence of low or no ergosterol. Leakage was also correlated with the previously reported biological activity of fengycin on these molds.

The Potential of α-Spinasterol to Mimic the Membrane Properties of Natural Cholesterol.

Sterols play a unique role for the structural and dynamical organization of membranes. The current study reports data on the membrane properties of the phytosterol (3β,5α,22E)-stigmasta-7,22-dien-3-β-ol (α-spinasterol), which represents an important component of argan oil and have not been investigated so far in molecular detail. In particular, the impact of α-spinasterol on the structure and organization of lipid membranes was investigated and compared with those of cholesterol. Various membrane parameters such as the molecular packing of the phospholipid fatty acyl chains, the membrane permeability toward polar molecules, and the formation of lateral membrane domains were studied. The experiments were performed on lipid vesicles using methods of NMR spectroscopy and fluorescence spectroscopy and microscopy. The results show that α-spinasterol resembles the membrane behavior of cholesterol to some degree.

Reactive Carbonyl Species Scavengers-Novel Therapeutic Approaches for Chronic Diseases.

To summarize recent evidence supporting the use of reactive carbonyl species scavengers in the prevention and treatment of disease. The newly developed 2-aminomethylphenol class of scavengers shows great promise in preclinical trials for a number of diverse conditions including neurodegenerative diseases and cardiovascular disease. In addition, new studies with the thiol-based and imidazole-based scavengers have found new applications outside of adjunctive therapy for chemotherapeutics. Reactive oxygen species (ROS) generated by cells and tissues act as signaling molecules and as cytotoxic agents to defend against pathogens, but ROS also cause collateral damage to vital cellular components. The polyunsaturated fatty acyl chains of phospholipids in the cell membranes are particularly vulnerable to damaging peroxidation by ROS. Evidence suggests that the breakdown of these peroxidized lipids to reactive carbonyls species plays a critical role in many chronic diseases. Antioxidants that abrogate ROS-induced formation of reactive carbonyl species also abrogate normal ROS signaling and thus exert both beneficial and adverse functional effects. The use of scavengers of reactive dicarbonyl species represent an alternative therapeutic strategy to potentially mitigate the adverse effects of ROS without abrogating normal signaling by ROS. In this review, we focus on three classes of reactive carbonyl species scavengers: thiol-based scavengers (2-mercaptoethanesulfonate and amifostine), imidazole-based scavengers (carnosine and its analogs), and 2-aminomethylphenols-based scavengers (pyridoxamine, 2-hydroxybenzylamine, and 5'-O-pentyl-pyridoxamine) that are either undergoing pre-clinical studies, advancing to clinical trials, or are already in clinical use.

Cholesterol in the rod outer segment: A complex role in a “simple” system

The rod outer segment (ROS) of retinal photoreceptor cells consists of disk membranes surrounded by the plasma membrane. It is a relatively uncomplicated system in which to investigate cholesterol distribution and its functional consequences in biologically relevant membranes. The light sensitive protein, rhodopsin is the major protein in both membranes, but the lipid compositions are significantly different in the disk and plasma membranes. Cholesterol is high in the ROS plasma membrane. Disk membranes are synthesized at the base of the ROS and are also high in cholesterol. However, cholesterol is rapidly depleted as the disks are apically displaced. During this apical displacement the disk phospholipid fatty acyl chains become progressively more unsaturated, which creates an environment unfavorable to cholesterol. Membrane cholesterol has functional consequences. The high cholesterol found in the plasma membrane and in newly synthesized disks inhibits the activation of rhodopsin. As disks are apically displaced and cholesterol is depleted rhodopsin becomes more responsive to light. This effect of cholesterol on rhodopsin activation has been shown in both native and reconstituted membranes. The modulation of activity can be at least partially explained by the effect of cholesterol on bulk lipid properties. Cholesterol decreases the partial free volume of the hydrocarbon region of the bilayer and thereby inhibits rhodopsin conformational changes required for activation. However, cholesterol binds to rhodopsin and may directly affect the protein also. Furthermore, cholesterol stabilizes rhodopsin to thermal denaturation. The membrane must provide an environment that allows rhodopsin conformational changes required for activation while also stabilizing the protein to thermal denaturation. Cholesterol thus plays a complex role in modulating the activity and stability of rhodopsin, which have implications for other G-protein coupled receptors.

Daily and Seasonal Rhythms in Human Mucosa Phospholipid Fatty Acid Composition.

Fatty acids (FAs) can exert important physiological effects: for example, as precursors of eicosanoids, as signaling molecules, and, in particular, as parts of phospholipids, the major constituents of cell membranes. Animals can remodel cell membranes in terms of their FA composition in response to environmental conditions, and even endothermic mammals exhibit seasonal cycles in the FA makeup of membranes. Previous evidence pointed to the existence of both seasonal and daily cycles in phospholipid composition of human cell membranes. Therefore, we used a noninvasive method to collect human mucosa cells over 1 year in 20 healthy subjects, and we determined seasonal and daily rhythmicity of phospholipid FA content. Our results show that significant daily rhythms were detectable in 11 of 13 FAs and were largely synchronous among subjects. Also, these daily rhythms showed stable phase relationships between different FAs within subjects. In contrast, yearly rhythms in phospholipid FA content were statistically significant in only ~50% of subjects and were asynchronous between subjects. These results support the view that while human physiology is still dominated by geophysical sunrise and sunset, resulting in strong daily cycles, seasonal rhythms are less well defined, at least in Western societies. We suggest that the main physiological function underlying rhythms in cell membrane composition is the regulation of the activity of transmembrane proteins, such as ion pumps, which can be strongly affected by the fatty acyl chains of phospholipids in the surrounding membrane bilayer. Hence, among a multitude of other functions, cycles in membrane FA composition may be involved in generating the daily rhythm of metabolic rate. Rhythms in certain membrane FAs, namely polyunsaturated and monounsaturated FAs that are known to affect health, could be also involved in daily and seasonal rhythms of diseases and death.

Detection of liposomal cholesterol and monophosphoryl lipid A by QS-21 saponin and Limulus polyphemus amebocyte lysate

Liposomes containing cholesterol (Chol) have long been used as an important membrane system for modeling the complex interactions of Chol with adjacent phospholipids or other lipids in a membrane environment. In this study we utilize a probe composed of QS-21, a saponin molecule that recognizes liposomal Chol and causes hemolysis of erythrocytes. The interaction of QS-21 with liposomal Chol results in a stable formulation which, after injection into the tissues of an animal, lacks toxic effects of QS-21 on neighboring cells that contain Chol, such as erythrocytes. Here we have used liposomes containing different saturated phospholipid fatty acyl groups and Chol, with or without monophosphoryl lipid A (MPLA), as model membranes. QS-21 is then employed as a probe to study the interactions of liposomal lipids on the visibility of membrane Chol. We demonstrate that changes either in the mole fraction of Chol in liposomes, or with different chain lengths of phospholipid fatty acyl groups, can have a substantial impact on the detection of Chol by the QS-21. We further show that liposomal MPLA can partially inhibit detection of the liposomal Chol by QS-21. The Limulus amebocyte lysate assay is used for binding to and detection of MPLA. Previous work has demonstrated that sequestration of MPLA into the liposomal lipid bilayer can block detection by the Limulus assay, but the binding site on the MPLA to which the Limulus protein binds is unknown. Changes in liposomal Chol concentration and phospholipid fatty acyl chain length influenced the detection of the liposome-embedded MPLA.

Cellular Lipid Composition Affects Sensitivity of Plant Pathogens to Fengycin, an Antifungal Compound Produced by Bacillus subtilis Strain CU12

Fengycin is an antimicrobial cyclic lipopeptide produced by various Bacillus subtilis strains, including strain CU12. Direct effects of fengycin include membrane pore formation and efflux of cellular contents leading to cell death in sensitive microorganisms. In this study, four plant pathogens were studied in order to elucidate the role of membrane lipids in their relative sensitivity to fengycin. Inhibition of mycelial growth in these pathogens varied considerably. Analysis of membrane lipids in these microorganisms indicated that sensitivity correlated with low ergosterol content and shorter phospholipid fatty acyl chains. Sensitivity to fengycin also correlated with a lower anionic/zwitterionic phospholipid ratio. Our data suggest that decreased fluidity buffering capacity, as a result of low ergosterol content, and higher intrinsic fluidity afforded by short fatty acyl chain length may increase the sensitivity of microbial membranes to fengycin. Our results also suggest that lower content in anionic phospholipids may increase fengycin insertion into the membrane through reduced electrostatic repulsion with the negatively charged fengycin. The intrinsic membrane lipid composition may contribute, in part, to the observed level of antimicrobial activity of fengycin in various plant pathogens.

Remodeling of liver phospholipidomic profile in streptozotocin-induced diabetic rats

Lipid homeostasis in liver is known to be altered with diabetes mellitus, ultimately leading to liver damage and related complications. The present work aimed to evaluate changes in the liver phospholipid profile after 4months of uncontrolled hyperglycemia. Twenty Wistar rats were divided into two groups: control and streptozotocin-treated (T1DM). After 4months, animals were sacrificed and morphological characterization of liver was performed and related with serum markers of hepatic damage. Lipid extracts were obtained from liver and phospholipid (PL) classes were quantified. Lipid molecular species were determined by LC–MS and LC–MS/MS, and fatty acids by GC–MS. Concomitantly with signs of hepatic damage we found variations in the relative amount of phospholipid classes in T1DM, characterized by a decrease in PLs with choline head group, and by an increase in the relative content of other PL classes. A remodeling in PL fatty acyl chains was observed in T1DM liver, with a similar pattern to all the PL classes, and consisting in the reduction of 16:0 and an increase of 18:0 and 18:2 acyl chains. The observed changes in T1DM lipid profile may contribute to the altered membrane properties underlying hepatic damage, worsening the metabolic alterations that characterize T1DM.

Acclimation-induced changes in cell membrane composition and influence on cryotolerance of in vitro shoots of native plant species

Cell membranes are the primary sites of cryopreservation injury and measuring changes to membrane composition arising from cold acclimation may assist with providing a rationale for optimising cryopreservation methods. Shoot tips from two south-west Western Australian species, Grevillea scapigera and Loxocarya cinerea, and Arabidopsis thaliana (reference species) were subjected to cryopreservation using the droplet vitrification protocol. Two pre-conditioning regimes involving a constant temperature (23 °C, CT with a 12 h light/dark cycle) or an alternating temperature (AT) regime (20/10 °C with a 12 h light/dark cycle) were compared. Soluble sugars, sterols and phospholipids present in the shoot tips were analysed. Use of AT pre-conditioning (acclimation) resulted in a modest decrease in cryotolerance in A. thaliana, increased cryotolerance in G. scapigera, and increased survival in the non-frozen control explants of L. cinerea in comparison to CT pre-conditioning. Increased cryotolerance was accompanied by a higher total sugar sterol and phospholipid content, as well as an increase in strong hydrating phospholipid classes such as phosphatidylcholine. The double bond index of bound fatty acyl chains of phospholipids was greater after AT pre-conditioning, mostly due to a higher amount of monoenes in A. thaliana and trienes in G. scapigera and L. cinerea. These findings suggest that AT pre-conditioning treatments for in vitro plants can have a positive influence on cryotolerance for some plant species and this may be related to observed changes in the overall composition of cell membranes. However, alternative factors (e.g. oxidative stress) may be equally important with other species (e.g. L. cinerea).

Very-long-chain fatty acids are required for cell plate formation during cytokinesis inArabidopsis thaliana

Acyl chain length is thought to be crucial for biophysical properties of the membrane, in particular during cell division, when active vesicular fusion is necessary. In higher plants, the process of cytokinesis is unique, because the separation of the two daughter cells is carried out by de novo vesicular fusion to generate a laterally expanding cell plate. In Arabidopsis thaliana, very-long-chain fatty acid (VLCFA) depletion caused by a mutation in the microsomal elongase gene PASTICCINO2 (PAS2) or by application of the selective elongase inhibitor flufenacet altered cytokinesis. Cell plate expansion was delayed and the formation of the endomembrane tubular network altered. These defects were associated with specific aggregation of the cell plate markers YFP-Rab-A2a and KNOLLE during cytokinesis. Changes in levels of VLCFA also resulted in modification of endocytosis and sensitivity to brefeldin A. Finally, the cytokinesis impairment in pas2 cells was associated with reduced levels of very long fatty acyl chains in phospholipids. Together, our findings demonstrate that VLCFA-containing lipids are essential for endomembrane dynamics during cytokinesis.

Use of Cholesterol in Sperm Cryopreservation: Present Moment and Perspectives to Future

Sperm cryosurvival rates are not optimal for most species. Therefore, new cryopreservation strategies are needed with the objective of increasing the number of surviving sperm and the quality of those sperm after thawing. Cholesterol plays important roles in many sperm functions, including effects on membrane properties. One of these effects is to stabilize membranes at low temperatures. Thus, species that produce sperm which possess high membrane cholesterol : phospholipid ratios are more resistant to cold shock than sperm with low cholesterol : phospholipid ratios. Therefore, increasing the cholesterol content of sperm membranes may be a strategy that can improve sperm quality after freeze-thawing. In this review, information is presented related to using cyclodextrins pre-loaded with cholesterol for cryopreserving sperm from different species. The topics discussed include both in vitro and in vivo assessments of sperm quality after cryopreservation, as well as how increasing sperm cholesterol content affects other sperm functions.

Lipidome profiling of Saccharomyces cerevisiae reveals pitching rate-dependent fermentative performance

A high cell density strategy has been used in bioethanol production to shorten the fermentation period. To reveal the molecular basis of fermentative behavior in high cell density, the profiling of the phospholipids and sterols of Saccharomyces cerevisiae during fermentation at five different pitching rates (1, 5, 10, 20, and 40 g/L) was investigated. Using LC/ESI/MS(n) technology, 148 phospholipid species were detected, of which 91 species were quantified, and using the gas chromatography-time-of-flight mass spectrometry procedure, a total of 11 sterols were quantified. Phospholipid samples from different pitching rates were discriminated into three groups using principal component analysis (1, 5 g/L, and the others). The main changes in the lipid profile of yeast cells with higher pitching rates were as follows: (a) the relative contents of phosphatidylglycerol and phosphatidylserine were higher while phosphatidylinositol was lower compared with lower pitching rates, (b) the saturated and the relatively shorter fatty acyl chains of phospholipids decreased, and (c) the content of ergosterol was higher. These findings suggested a regulation of the property of the membrane at the situation of high cell density and a possible approach of self-protection of the yeast cells against the high density stresses.

Allometric scaling of fatty acyl chains in fowl liver, lung and kidney, but not in brain phospholipids

The phospholipid (PL) fatty acyl chain (FA) composition (mol%) was determined in the kidney, liver, lung and brain of 8 avian species ranging in body mass from 150g (Japanese quail, Coturnix coturnix japonica) to 19kg (turkey, Meleagris gallopavo). In all organs except the brain, docosahexaenoic acid (C22:6 n3, DHA) was found to show a negative allometric scaling (allometric exponent: B=-0.18; -0.20 and -0.24, for kidney, liver and lung, respectively). With minor inter-organ differences, smaller birds had more n3 FAs and longer FA chains in the renal, hepatic and pulmonary PLs. Comparing our results with literature data on avian skeletal muscle, liver mitochondria and kidney microsomes and divergent mammalian tissues, the present findings in the kidney, liver and lung PLs seem to be a part of a general relationship termed "membranes as metabolic pacemakers". Marked negative allometric scaling was found furthermore for the tissue malondialdehyde concentrations in all organs except the brain (B=-0.17; -0.13 and -0.05, respectively). In the liver and kidney a strong correlation was found between the tissue MDA and DHA levels, expressing the role of DHA in shaping the allometric properties of membrane lipids.