Modification of the fatty acid composition of Ehrlich ascites tumor cell plasma membranes

Effects of Lipids on Cancer Therapy

The fatty acid composition of cancer cell membranes can change substantially when the cells are exposed to different types of fat. Such change occurs when tumors are grown in animals fed high-fat diets that differ in degree of unsaturation or during culture in media supplemented with various fatty acids. Certain physical and functional properties of the membrane are modified when the polyunsaturated fatty acid content is increased, and the cells become more sensitive to hyperthermia or treatment with doxorubicin. These findings suggest a potential role for lipid nutrition in cancer therapy. By altering the properties of the membrane lipids, changes in the dietary fat intake may provide a new approach for enhancing the effectiveness of certain antineoplastic therapies.

The role of fatty acid unsaturation in minimizing biophysical changes on the structure and local effects of bilayer membranes

Studying the effects of saturated and unsaturated fatty acids on biological and model (liposomes) membranes could provide insight into the contribution of biophysical effects on the cytotoxicity observed with saturated fatty acids. In vitro experiments suggest that unsaturated fatty acids, such as oleate and linoleate, are less toxic, and have less impact on the membrane fluidity. To understand and assess the biophysical changes in the presence of the different fatty acids, we performed computational analyses of model liposomes with palmitate, oleate, and linoleate. The computational results indicate that the unsaturated fatty acid chain serves as a membrane stabilizer by preventing changes to the membrane fluidity. Based on a Voronoi tessellation analysis, unsaturated fatty acids have structural properties that can reduce the lipid ordering within the model membranes. In addition, hydrogen bond analysis indicates a more uniform level of membrane hydration in the presence of oleate and linoleate as compared to palmitate. Altogether, these observations from the computational studies provide a possible mechanism by which unsaturated fatty acids minimize biophysical changes and protect the cellular membrane and structure. To corroborate our findings, we also performed a liposomal leakage study to assess how the different fatty acids alter the membrane integrity of liposomes. This showed that palmitate, a saturated fatty acid, caused greater destabilization of liposomes (more "leaky") than oleate, an unsaturated fatty acid.

Experimental and computational studies investigating trehalose protection of HepG2 cells from palmitate-induced toxicity

Understanding the mechanism of saturated fatty acid-induced hepatocyte toxicity may provide insight into cures for diseases such as obesity-associated cirrhosis. Trehalose, a nonreducing disaccharide shown to protect proteins and cellular membranes from inactivation or denaturation caused by different stress conditions, also protects hepatocytes from palmitate-induced toxicity. Our results suggest that trehalose serves as a free radical scavenger and alleviates damage from hydrogen peroxide secreted by the compromised cells. We also observe that trehalose protects HepG2 cells by interacting with the plasma membrane to counteract the changes in membrane fluidity induced by palmitate. The experimental results are supported by molecular dynamics simulations of model cell membranes that closely reflect the experimental conditions. Simulations were performed to understand the specific interactions between lipid bilayers, palmitate, and trehalose. The simulations results reveal the early stages of how palmitate induces biophysical changes to the cellular membrane and the role of trehalose in protecting the membrane structure.

Influence of lipid diets on the number of metastases and ganglioside content of H59 variant tumors

We investigated the influence of the fatty acid composition of the diet on the number of hepatic metastases and the ganglioside profile of the primary tumor and metastases. C57BL/6 female mice were fed different diets containing either no fats (TEK) or 8% of fish oil (POL), linseed oil (LIN), safflower oil (SAF) or beef tallow (BT) and were injected subcutaneously in the dorsum with H59 cells, a variant of the Lewis lung carcinoma (3LLc) that metastasizes preferentially to the liver. The omega3 polyunsaturated fatty acid (PUFA)-rich diets (LIN and POL) elicited more metastases than the omega6 PUFA-rich (SAF), fat-free (TEK), or saturated fats (BT) diets. However, dietary fat did not influence the ganglioside composition of either the primary tumors or the metastases, at least in the glucidic part. However, comparison of diets with low (TEK, SAF, and BT) and high (LIN and POL) number of metastases showed that the levels of G3 (which could be a second band of GM2) were greater in metastases of the latter group. This study showed that the H59 hepatic metastases contained more GM2 than the s.c. tumors, irrespective of diet or the number of metastases produced. The small differences in the ganglioside profiles observed in this study could have resulted from the limitations of the HPTLC method. A detailed analysis of the lipid chains, as well as glycolipids other than gangliosides, could give more information on changes resulting from different lipid diets.

Inhibitory effects of docosahexaenoic acid on colon carcinoma 26 metastasis to the lung

Unsaturated fatty acids, including n-3 polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (C22:6, DHA) and eicosapentaenoic acid (C20:5, EPA), and a series of n-6 PUFAs were investigated for their anti-tumour and antimetastatic effects in a subcutaneous (s.c.) implanted highly metastatic colon carcinoma 26 (Co 26Lu) model. EPA and DHA exerted significant inhibitory effects on tumour growth at the implantation site and significantly decreased the numbers of lung metastatic nodules. Oleic acid also significantly inhibited lung metastatic nodules. Treatment with arachidonic acid showed a tendency for reduction in colonization. However, treatment with high doses of fatty acids, especially linoleic acid, increased the numbers of lung metastatic nodules. DHA and EPA only inhibited lung colonizations when administered together with the tumour cells, suggesting that their incorporation is necessary for an influence to be exerted. Chromatography confirmed that contents of fatty acids in both tumour tissues and plasma were indeed affected by the treatments. Tumour cells pretreated with fatty acids in vivo, in particular DHA, also showed a low potential for lung colony formation when transferred to new hosts. Thus, DHA treatment exerted marked antimetastatic activity associated with pronounced change in the fatty acid component of tumour cells. The results indicate that uptake of DHA into tumour cells results in altered tumour cell membrane characteristics and a decreased ability to metastasize.

Effect of fish oil on glucose metabolism in the interleukin-1 alpha-treated rat

Fish oil has been demonstrated to ameliorate many of the responses to infection. This study was conducted to determine whether fish oil feeding could modify the alterations of glucose metabolism induced by interleukin-1 alpha (IL-1 alpha) infusion in the rat. Male Sprague-Dawley rats were pair-fed for 5 weeks on two experimental diets in which the source of fat was either fish oil or soybean oil and provided 20% of calories; the diets were isonitrogenous and isocaloric. After 5 weeks of feeding, rats from both diet regimens were further divided into two subgroups to receive a 3-hour infusion of either 0.1% albumin in saline or 0.1% albumin in saline containing IL-1 alpha. A total of 20 micrograms/kg IL-1 alpha was administered, and half the dose of IL-1 alpha was given as a bolus and the remaining portion (10 micrograms/kg) was continuously infused into the jugular vein. During the last 2 hours of IL-1 alpha infusion, a primed constant infusion of D-(6-3H)glucose and D-(U-14C)glucose was combined to determine the effects of IL-1 alpha and diet on glucose kinetics. Plasma levels of glucose and insulin, energy expenditure, and respiratory quotient were also measured. IL-1 alpha significantly increased concentrations of plasma insulin and the percentage of glucose carbon recycling, confirming previous findings. Concentrations of glucose and insulin with IL-1 alpha treatment were significantly higher in soybean oil- fed animals compared with fish oil-fed animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of effect of topical iodostearic acid on cervical intraepithelial neoplasia II-III

Stearic and iodostearic acid inhibit growth of a cervical carcinoma cell line in vitro. This study was performed to determine if iodostearic acid would induce regression of cervical intraepithelial neoplasia (CIN). Women with histologically-proven CIN II or III were randomised into two groups. Those in the first group were given pessaries composed of iodostearic acid in polyethylene glycol (PEG) base. Women in the second group were given pessaries containing only the PEG base. One pessary was inserted into the vagina nightly for 30 nights, and each woman then had the CIN lesion removed by CO2 laser cone excision. There was no difference in the histology of the cone biopsies between the groups, demonstrating that this regime of iodostearic acid has no useful role in the treatment of CIN II-III.

Food use and health effects of soybean and sunflower oils

This review provides a scientific assessment of current knowledge of health effects of soybean oil (SBO) and sunflower oil (SFO). SBO and SFO both contain high levels of polyunsaturated fatty acids (PUFA) (60.8 and 69%, respectively), with a PUFA:saturated fat ratio of 4.0 for SBO and 6.4 for SFO. SFO contains 69% C18:2n-6 and less than 0.1% C18:3n-3, while SBO contains 54% C18:2n-6 and 7.2% C18:3n-3. Thus, SFO and SBO each provide adequate amounts of C18:2n-6, but of the two, SBO provides C18:3n-3 with a C18:2n-6:C18:3n-3 ratio of 7.1. Epidemiological evidence has suggested an inverse relationship between the consumption of diets high in vegetable fat and blood pressure, although clinical findings have been inconclusive. Recent dietary guidelines suggest the desirability of decreasing consumption of total and saturated fat and cholesterol, an objective that can be achieved by substituting such oils as SFO and SBO for animal fats. Such changes have consistently resulted in decreased total and low-density-lipoprotein cholesterol, which is thought to be favorable with respect to decreasing risk of cardiovascular disease. Also, decreases in high-density-lipoprotein cholesterol have raised some concern. Use of vegetable oils such as SFO and SBO increases C18:2n-6, decreases C20:4n-6, and slightly elevated C20:5n-3 and C22:6n-3 in platelets, changes that slightly inhibit platelet generation of thromboxane and ex vivo aggregation. Whether chronic use of these oils will effectively block thrombosis at sites of vascular injury, inhibit pathologic platelet vascular interactions associated with atherosclerosis, or reduce the incidence of acute vascular occlusion in the coronary or cerebral circulation is uncertain. Linoleic acid is needed for normal immune response, and essential fatty acid (EFA) deficiency impairs B and T cell-mediated responses. SBO and SFO can provide adequate linoleic acid for maintenance of the immune response. Excess linoleic acid has supported tumor growth in animals, an effect not verified by data from diverse human studies of risk, incidence, or progression of cancers of the breast and colon. Areas yet to be investigated include the differential effects of n-6- and n-3-containing oil on tumor development in humans and whether shorter-chain n-3 PUFA of plant origin such as found in SBO will modulate these actions of linoleic acid, as has been shown for the longer-chain n-3 PUFA of marine oils.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of butyrate on lipid metabolism, survival, and differentiation of colon cancer cells

The present work was designed to study the differentiating effect of butyrate on LS174T cells after modification of their lipids with long-chain fatty acid (LCFA) supplementation. The LCFAs 18:1(n-9), 18:2(n-6), 20:4(n-6), 20:5(n-3), and 22:6(n-3) bound to added to the media of confluent cells for eight days. The fatty acid-to-albumin ratio was 3:1. The concentration of fatty acids in the media was 100 microM. On the last day, half of the flasks were treated with 2 mM butyrate. The data indicate that supplementation with polyunsaturated LCFAs having 20-22 carbon atoms resulted in a significant reduction in cell density and viability, whereas all LCFA supplementation reduced differentiation as measured by alkaline phosphatase activity. Butyrate treatment increased the density, viability, and differentiation of the tumor cells. The effect of butyrate on differentiation was mainly with cells supplemented with 18:1, 20:5, and 22:6. In the absence of LCFA supplementation, butyrate reduced the concentration of 22:5(n-6) in the cellular lipids. Also, butyrate modified the LCFAs incorporated in cells supplemented with 18:2 and 20:5, with changes occurring in 20:5(n-3), 22:5(n-3), and 22:5(n-6). Thus the present study suggests an interaction between butyrate and LCFA on differentiation and LCFA metabolism of human colon cancer cells.

Modulation of CD4 expression on lymphoma cells transplanted to mice fed (n - 3) polyunsaturated fatty acids

Groups of adult AKR mice were fed well defined fats controlled diet regimens. These consisted of either saturated (beef tallow: 'BT') or (n - 3) polyunsaturated (fish oil: 'FO') fatty acids supplementation to basal mix mouse food. In other groups, the basal mix was given without any fat supplement ('NF'). Six weeks or more after the initiation of these diet regimens, mice received intraperitoneal injection of histocompatible RDM-4 lymphoma cells. Ascites RDM-4 tumors were harvested approximately two weeks later, and some of their physicochemical properties were studied. It was repeatedly found that: (1) the tumor grew considerably faster in the FO-fed donor than in the BT- or NF-fed donors; (2) cell membrane fluidity, content of C20(n - 3) and of C22(n - 3) fatty acids were significantly higher in the FO groups than in both BT and NF groups, while the content of C20(n - 6) and 22:4(n - 6) fatty acids was concomitantly decreased; (3) expression of the CD4 cell surface marker was always significantly diminished in the FO groups, whereas other markers such as CD8, H2K, Thy-1 and LFA-1 were not affected. Similar results were obtained, whether fats constituted from 1% to 16% by weight of the food intake. Use of a recently selected line of the RDM-4 lymphoma, exhibiting higher CD4 marker expression, resulted in similar observations. On the other hand, CD4 expression on cells from lymphoid organs of healthy adult AKR mice was not detectably modulated by the dietary fats.

Effect of dietary fat on the lipid composition and utilization of short-chain fatty acids by rat colonocytes

The objective of the present studies was to examine the effect of dietary fat on the lipid composition of rat colonocytes and their utilization of short-chain fatty acids (SCFA). Rats were fed 14% beef fat, fish oil or safflower oil plus 2% corn oil in a semi-synthetic base diet for 4 wk. Colonocytes were isolated and their lipid composition was examined. Feeding beef fat and fish oil resulted in an increase in monounsaturated fatty acids and a reduction in omega-6 fatty acids. Feeding fish oil resulted in an enrichment with omega-3 fatty acids. There was no dietary influence on the amount of either cholesterol or phospholipids of colonocytes. Fish oil feeding resulted in significant increase in colonocyte free fatty acids (FFA) as compared to other diets. Dietary fat was found to have no effect on SCFA utilization by colonocytes. Colonocytes were found to utilize SCFA in the order of butyrate greater than or equal to acetate greater than or equal to propionate. The presence of acetate and propionate in the medium had no effect on the rate of butyrate utilization.

Susceptibility of RDM4 lymphoma cells to LAK-mediated lysis is decreased in tumor bearers fed fish oil high fat regimen

RDM4 lymphoma cells were grown intraperitoneally in genetically compatible AKR mice fed either regular mouse chow, or diet supplemented with either saturated fat (hydrogenated beef tallow = HBT) or unsaturated fat (fish oil = FO). It was observed that the lymphoma cells number was significantly greater in FO-fed hosts and lower in HBT-fed hosts, than in the mice fed regular chow. The tumor bearers diet did not dramatically influence the rate of DNA synthesis of RDM4 cells, as measured by [3H]thymidine uptake in culture, a few hours after harvesting from the peritoneal cavity. It was repeatedly found that FO feeding of the tumor bearers elicited an increased resistance of RDM4 cells to lysis by LAK effectors, as appraised in vitro by 51Cr release test and in vivo by the "Winn assay". Different FO percentage of the diet (16%, 8%, 4%) resulted in comparable reduction of susceptibility of RDM4 cells to lysis by LAK effectors. Lipid analysis showed that RDM4 cells grown in mice fed FO diet or HBT diet differed markedly in their fatty acid composition and that their resistance to lysis by LAK cells correlated with the quantity of oxidizable fatty acids especially of the n-6 type.

Effect of dietary lipids on plasma lipoproteins and fluidity of lymphoid cell membranes in normal and leukemic mice

Mice of the GR/A strain were fed four different isocaloric semipurified diets, enriched in either (1) saturated fatty acids (palm oil), or (2) polyunsaturated fatty acids (corn oil), or (3) palm oil plus cholesterol, or (4) a fat-poor diet containing only a minimal amount of essential fatty acids. We have studied the effects of these dietary lipids on the density profile and composition of the plasma lipoproteins and on the lipid composition and fluidity of (purified) lymphoid cell membranes in healthy mice and in mice bearing a transplanted lymphoid leukemia (GRSL). Tumor development in these mice occurred in the spleen and in ascites. While the fatty acid composition of the VLDL-triacylglycerols still strongly resembled the dietary lipids, the effects of the diets decreased in the order VLDL-triacylglycerols greater than HDL-phospholipids greater than plasma membrane phospholipids. Diet-induced differences in the latter fraction were virtually confined to the content of oleic acid and linoleic acid, and they were too small to affect the membrane fluidity, as measured by fluorescence polarization using the probe 1,6-diphenyl-1,3,5-hexatriene. Healthy mice were almost irresponsive to dietary cholesterol, but in the tumor bearers, where lipoprotein metabolism has been shown to be disturbed, the cholesterol diet caused a substantial increase in the low- and very-low density regions of both blood and ascites plasma lipoproteins. The cholesterol-rich diet also increased the cholesterol/phospholipid molar ratio and lipid structural order (decreased fluidity) in GRSL ascites cell membranes, but not in the splenic GRSL cell membranes. We conclude that the composition of plasma lipoproteins and cell membrane lipids in GR/A mice is subject to exquisite homeostatic control. However, in these low-responders to dietary lipids the development of an ascites tumor may lead to increased responsiveness to dietary cholesterol. The elevated level of membrane cholesterol thus obtained in GRSL ascites cells did not affect the expression of various cell surface antigens or tumor cell growth.

Modification of the fatty acid composition of L1210 leukemia subcellular organelles

We have examined the extent to which it is possible to modify the fatty acid composition of subcellular organelles of L1210 leukemia cells. A polyunsaturated fatty acid, docosahexaenoic acid, or a monounsaturated fatty acid, oleic acid, were added to the culture media. After 48 hr, the cells were ruptured and the subcellular fractions isolated. Fatty acid analysis revealed that nuclei, mitochondria, plasma membranes and microsomes of the cells grown in media supplemented with docosahexaenoic acid contained increased amounts of polyenoic fatty acids compared with cells grown in oleic acid. We conclude that it is possible to experimentally modify the lipids of multiple intracellular structures of L1210 cells by the addition of fatty acids to the growth media.

Ribonucleic acid efflux from isolated mouse liver nuclei is altered by diet and genotypically determined change in nuclear envelope composition

Differences in immunological abnormalities like autoimmunity, abnormal T cell proliferative disorders and accelerated ageing occur between MRL/Mp-lpr/lpr(lpr/lpr) and MRL/Mp-+/+(+/+) mice as a consequence of one gene. The present study was designed to assess the effect of these differences in genotype and diet on the composition and function of the liver nuclear envelope. Mice of both strains were fed nutritionally adequate diets differing only in fatty acid composition for 4 weeks. Phospholipid fatty acid composition of the liver nuclear envelope was determined and the effect of altering the lipid composition of the nuclear membrane on nucleoside-triphosphatase (NTPase) activity, ribonucleic acid (RNA) efflux and binding of L-triiodothyronine (L-T3) was determined. Strain of mouse and level of dietary linoleic acid exhibited significant effects on the phospholipid fatty acid composition of the nuclear envelope. Levels of 18:1(n - 9) and 18:2(n - 6) were lower and 20:4(n - 6) content was higher in nuclear envelope phospholipids of lpr/lpr mice compared with mice of the +/+ strain. Mice fed the high linoleic acid diet exhibited higher levels of 18:0, 18:2(n - 6) and 20:4(n - 6) and lower levels of 16:0 and 18:1(n - 9) in liver nuclear envelope phospholipids, compared with mice fed the low linoleic acid diet. These changes in membrane composition were reflected in alteration of NTPase activity and efflux of RNA from isolated mouse liver nuclei. Nucleoside triphosphatase activity and efflux of ribonucleic acid from isolated nuclei were significantly higher in livers of the lpr/lpr strain. NTPase activity and RNA efflux from isolated nuclei were higher in the high linoleic acid fed group compared with the low linoleic acid group. A single class of binding sites for L-T3 was present in liver nuclear envelopes of these mice and Kd values were not influenced by strain or dietary linoleic acid levels. Nuclear envelopes prepared from +/+ animals exhibited a significantly higher number of binding sites for L-T3 compared with the lpr/lpr group. These observations indicate that the single gene difference characterizing lpr/lpr mice from +/+ mice results in alterations in the composition and function of the nuclear envelope. This genetic difference also alters the response of this membrane to dietary factors known to modulate characteristics and functions of the nuclear envelope.

Membrane fatty acid composition and radiation response of Bp8 sarcoma ascites tumour cells

The radiation response of Bp8 sarcoma ascites tumour cells with differences in membrane fatty acid composition was studied. The cells were grown i.p. in NMRI mice and their membrane composition was changed in response to different dietary regimes provided to the host animals. Three diets that differed only with regard to the source of fatty acids, i.e. sunflower seed oil, coconut oil, hydrogenated lard and a fourth commercially available standard laboratory diet, were given to the mice for different lengths of time, before implantation of the tumour cells. The time course for the dietary regimes to induce different levels of changes in membrane fatty acid composition of the ascites cells was established. The evaluation of the radiosensitivity of cells with different membrane fatty acid composition was done in vitro. Cell survival, expressed by D0, varied only insignificantly between the four dietary groups, while their repair capacity (Dq and n) differed significantly. Increased repair capacity was observed for ascites cells grown in animals on diets enriched in sunflower seed oil and coconut oil, compared with cells from mice fed the hydrogenated lard diet or from cells from the control animals. The membrane fatty acid composition of the cells from the two dietary groups with increased levels of repair capacity differed extensively, and in general there was no correlation observed between radiation response and the membrane fatty acid composition of the four dietary groups studied. For two of the dietary groups, coconut oil and control, with marked differences in membrane fatty acid composition, the effects of irradiation on ascites tumour growth rate and cell cycle distribution were followed in vivo. For none of these parameters was an effect of membrane fatty acid composition on radiation response observed.

Membrane fatty acid modification in tumor cells: a potential therapeutic adjunct

The fatty acid compositions of several tumors have been modified sufficiently to alter some of their properties and functions. These modifications were produced in culture by adding specific fatty acids to the growth medium or by feeding fat-supplemented diets to tumor-bearing mice. The phospholipid fatty acid composition of the plasma membrane was modified, but there were no changes in membrane phospholipid or cholesterol content or in phospholipid head group composition. Each of the most abundant membrane phosphoglyceride fractions exhibited some degree of fatty acid modification. Electron spin resonance measurements with nitroxystearate spin probes indicated that the fatty acid modifications were sufficient to alter the physical properties of the plasma membrane. The K'm for methotrexate uptake was reduced when the L1210 leukemia cells were enriched in linoleic acid. Even when the kinetics of uptake at 37 C were not altered, such as for melphalan and phenylalanine uptake, the temperature transition of transport was modified, indicating that these transport systems also are responsive to the membrane fatty acid modifications. Enrichment with highly polyunsaturated fatty acid did not affect either the growth rate or radiosensitivity of the L1210 leukemia. However, the sensitivity of the L1210 cells to the cytotoxic effects of Adriamycin and hyperthermia was increased. These findings suggest the possibility that fatty acid modification of tumors may be a useful adjunct to certain currently available therapeutic modalities.

Variations in dietary triacylglycerol saturation alter the lipid composition and fluidity of rat intestinal plasma membranes

Rats were maintained on nutritionally complete diets enriched in unsaturated (corn oil) or saturated (butter fat) triacylglycerols. After 6 weeks, significant differences in the lipid composition and fluidity of a number of intestinal membranes were observed. The corn oil diet (enriched mainly in linoleic acid) increased the overall unsaturation of the acyl chains and enhanced the lipid fluidity, as assessed by the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene, of enterocyte microvillus and basolateral membranes and of colonocyte basolateral membranes. Concomitantly, the cholesterol content and the cholesterol/phospholipid molar ratio were increased in the microvillus but not in the basolateral membranes. The increased cholesterol in ileal microvillus membranes can result from enhanced cellular biosynthesis, since ileal slices from rats fed the unsaturated diet incorporated [14C]octanoate more rapidly into digitonin-precipitable sterol. Increased fluidity of the enterocyte microvillus and basolateral membranes, respectively, enhanced the enzyme specific activities of p-nitrophenylphosphatase and (Na+ + K+)-dependent adenosine triphosphatase. The results indicate that the lipid composition, fluidity and enzyme activities of intestinal plasma membranes can be altered by dietary means. Moreover, rat enterocytes possess regulatory mechanisms which modulate the cholesterol content of the microvillus membranes so as to mitigate changes in lipid fluidity.

Exposure to free fatty acid increases the transfer of albumin across cultured endothelial monolayers

An initial exposure to high concentrations of free fatty acid increased the transfer of albumin across cultured endothelial monolayers. The rate and amount of albumin transfer was dependent on the oleic acid concentration to which the cultures were initially exposed, with 300 microM producing the maximum transfer. The albumin transfer also increased with the increasing time of exposure to oleic acid, the maximum effect occurring during the first 24 hours. An exposure to 300 microM linoleic acid produced an even greater increase in albumin transfer than did 300 microM oleic acid. The increased albumin transfer observed when cells were exposed to high concentrations of free fatty acid was largely reversible after reincubation of the cell monolayers in free fatty acid-poor media. In parallel experiments, radioactive oleic acid incorporation into cell triglycerides increased linearly as the fatty acid concentration was raised, with cell triglyceride content increasing up to sevenfold after incubation in a medium containing 300 microM oleic acid. A significant amount of oleic acid was incorporated into phospholipids, and the fatty acid composition of the endothelial triglycerides and phospholipids was modified. All these effects of oleic occurred without altering the incorporation of leucine into the cell protein. These results indicate that exposure to high concentrations of free fatty acid can alter endothelial cell lipid composition, and that this increases the albumin transfer across endothelium. This process might permit more macromolecules to enter the arterial wall.

Difference in plasma membrane structure between two sublines of Ehrlich-Lettrè ascites tumor cells

The plasma membranes of the glycogen-free and the glycogen-containing subline of Ehrlich-Lettrè ascites cells were purified and compared with respect to their enzyme activity, chemical, lipid and protein composition, and membrane fluidity. Both membrane fractions differed in a number of parameters which are discussed as differences in the expression of malignant transformation of the two sublines. 1. The 5'-nucleotidase activity was 3-5 times higher and the sialic acid content 3-times lower in the glycogen-containing than in the glycogen-free subline. 2. Differences were also observed with respect to the phospholipid composition, that is in the relative proportions of mainly phosphatidylcholine, -inositol and -serine. 3. The fatty acid spectrum of the two sublines differed in the C-18 series and in the percentage of polyunsaturated acids, which was about 6% lower in the glycogen-containing line. 4. Measurements of fluorescence polarization (P) using 1,6-diphenyl-1,3,5-hextriene as probe generally gave higher P values, indicating a decreased membrane fluidity for the plasma membranes of the glycogen-containing subline both below and above the transition temperature at 33 degrees C. 5. Polyacrylamide gel electrophoresis revealed different protein patterns mainly in the molecular weight range of around 90 000 and in the range between 31 000 and 14 000.

Increasing the levels of ether-linked lipids in L-M cells by glyceryl ether supplementation depresses growth and choline utilization

To gain insight into the role of alkyl-linked lipids in biological systems, we added hexadecylglycerol (a precursor of complex ether-linked lipids) to medium required for the growth of L-M cells in culture. L-M fibroblasts cultured through several generations in the presence of hexadecylglycerol grow at a reduced rate. Experimental cells at their sixth passage, with 2 microgram supplement/ml, double at 50% the rate of control cell populations. Hexadecylglycerol (10 microgram/ml) added 1 day after cell passage does not retard growth; however, within 1 h it decreases the incorporation of choline into the choline glycerophosphatide fraction. Inhibition is specific for choline; ethanolamine incorporation is not affected. The inhibition of choline utilization by hexadecylglycerol-treated cells is dose-dependent and reaches a maximum 12 h after supplementation. Cellular uptake of choline is reduced (approx. 17%) but not as much as the incorporation of choline into the phospholipids (approx. 60% at 12 h). The assimilation of ether lipid precursor into cellular phospholipids was followed by incubating cells with [1-14C]hexadecylglycerol. Incorporation of radioactivity into cellular phospholipids begins to plateau after 24 h, whereas the interference of hexadecylglycerol with choline metabolism could be detected as early as 1 h. The majority of the radioactivity recovered from cells incubated with labeled hexadecylglycerol is localized in the microsomal fraction (56%), where the label was distributed as free hexadecyglycerol, alkylacyl-phospholipids and alkyldiacylglycerols. These results show that the supplementation of a glyceryl ether to L-M fibroblast growth media selectively inhibits the utilization of choline for choline glycerophospholipid biosynthesis and causes a reduction in cell growth rate when cells are continually passaged in the presence of the glyceryl ether.

Effect of dietary lipid on locomotor activity and response to psychomotor stimulants

Spontaneous locomotor activity was investigated in developing rats fed diets rich in either saturated fat (coconut oil) or polyunsaturated fat (sunflower oil). The locomotor activity response to amphetamine, methylphenidate, and atropine in the dietary groups was also measured. Rats from dams fed sunflower oil had a late developing (20 days of age) increase in basal locomotor activity when compared to rats from dams fed coconut oil and the standard laboratory diet. The locomotor activity response to d-amphetamine administered IP to 30-day-old animals was potentiated in rats exposed to coconut oil compared to the other two groups. A dose-response analysis of the effect of methylphenidate revealed no differences among the dietary groups. A low dose of atropine (2 mg/kg) decreased 1 h locomotor activity 40% below basal level in rats fed sunflower oil but increased locomotor activity 90% over basal activity in rats fed coconut oil. These results indicate that dietary lipid can have a marked effect on basal locomotor activity as well as on the response to stimulant drugs.

Manipulation of alkylglycerolipid levels in cultured cells. Fatty alcohol versus alkylglycerol supplements

Ehrlich ascites cells and monolayers of L-M cell fibroblasts were grown in medium containing either long-chain fatty alcohols or alkylglycerols. The cells were then analyzed to determine the contribution of these lipid precursors to the synthesis of complex lipids for the purpose of defining the most efficient system to elevate the levels of ether phospholipids. Label from high specific activity [1-14C]hexadecanol, [1-14C]octadecanol, and [1-14C]octadecenol was incorporated into alkyl linkages (C-18 : 1 greater than C-16 : 0 greater than C-18 : 0); however, similar labeling of acyl groups occurred. Increasing the amount of hexadecanol in the growth medium resulted in a higher percentage of 14C-labeled acyl groups than alkyl linkages at all concentrations of the alcohol supplement. Supplements of rac-[1-14C]hexadecylglycerol to the growth media were assimilated into phospholipids, which significantly increased as a function of the amounts added. Mass determinations of the alkyl ether phospholipid content in L-M cells incubated for 24 h with an alkylglycerol mixture (10.8 microgram/ml) showed an approximate 70% increase over control levels; supplementation had only a slight effect on the alk-1-enyl content. The systems described will be useful for investigating biophysical and biochemical effects of alkyl ether enrichment in membranes.

Levels of polyunsaturated fatty acids in lymphocytes of rats fed on diets varying in polyunsaturated fatty acid content

1. When weanling rats were fed on a diet containing 0.1 g/kg of the diet as polyunsaturated fatty acid, it was found that after 2 weeks the level of linoleate in the lymphocyte lipids was 56 mg/g total fatty acids, as compared with a level of 138 mg/g in rats on a normal diet (P less than 0.005). Similar levels were obtained from rats which had been fed for up to 16 weeks on the deficient diet, but in a group killed after 28 weeks on the diet level was found to be only 20 mg/g total fatty acids. The arachidonate level was found to be approximately 220 mg/g total fatty acids, regardless of whether the rats were fed on a diet deficient in linoleate for up to 16 weeks or on a normal diet. In the group of rats killed after 28 weeks on the linoleate deficient diet, however, the arachidonate level was only 60 mg/g total fatty acids. 2. Percentage values for total fatty acids are given for plasma, adipose tissue, and lymphocytes for rats on normal and experimental diets. 3. Scatter diagrams of the levels of linoleate v. arachidonate in the lymphocyte total fatty acids showed no correlation between the levels of the two acids (r 0.05), but similar plots of linoleate and oleate levels showed an inverse correlation (r -0.68).

Glutamic acid transport in cortical synaptosomes from essential fatty acid deficient rats

the sodium dependence of the high-affinity transport of glutamic acid in rat brain synaptosomes has been studied in animals maintained on a diet deficient in essential fatty acids (EFAD), and the results compared to similar studies with animals on a normal diet. Although the data give best fit to the same kinetic model as for control data, there are differences in the constants that describe the model. Except at low sodium concentrations, uptake is lower for the EFAD gorup. As a consequence of the differences in constants for the two groups, there are quantitative differences in the transport mechanism. The rate equation for the best fit model has been utilized to define certain functions in terms of dissociation and translocation constants, glutamate, sodium, and total carrier concentrations. These functions were calculated and utilized to compare the transport mechanism for the two groups. Although there are differences between these functions for control and EFAD animals, these differences are small and therefore of doubtful physiological significance.

Alteration of catecholamine uptake in cerebral cortex from rats fed a saturated fat diet

The transport of [3H]norepinephrine into chopped cerebral cortex of neonates was changed by feeding pregnant rats with semisynthetic diets enriched in saturated fat (coconut oil) as compared to polyunsaturated fat (sunflower oil). There was a significant decrease in the uptake of norepinephrine in neonates from dams fed coconut oil compared to neonatal pups from animals fed sunflower oil. Differences were observed on days 7, 11, 24, and 37 but not in adults which had been maintained on the diet since birth. Kinetic analysis of norepinephrine uptake on day 7 neonates demonstrated a 5-fold increase in Km and a 2-fold increase in Vmax for the coconut oil fed group as compared to control or the sunflower oil fed rats. [3H]Dopamine uptake kinetics revealed no significant difference in day 7 neonates but a doubling of the Km and Vmax in day 37 rats and in adults fed coconut oil. Lipid analysis of cerebral cortex synaptosome membrane fractions revealed significant differences in the fatty acyl composition of the phospholipid. The results indicate that the norepinephrine and dopamine transport systems can be differentially affected by dietary lipid composition in the developing rat. It is suggested that the changes may be due to alterations in membrane fluidity in the local environment of the transport system.

The effect of elaidic acid incorporation upon the lipid composition of Ehrlich Ascites tumor cells and of the host's liver

The incorporation of elaidic acid into Ehrlich ascites tumor cells (EATC) upon feeding the host an elaidic acid-rich diet has been investigated in the present study. The EATC lipids contained only one-half the concentration of elaidic acid found in the lipids of either the host livers or of livers from normal mice. On the other hand, elaidic acid incorporation into tumor cells was close to that of ascites fluid. This incorporation was mainly into phospholipids; the highest into choline phospholipids and ethanolamine phospholipids. Some changes in the EATC fatty acid composition were noted due to this incorporation. EATC phospholipids had reduced polyunsaturated fatty acids as compared with oleic acid-grown cells. The same was true with respect to ascites fluid phospholipids, but neutral lipids were not altered. Tumor development was accompanied by an increase in elaidic acid of the host's liver. Elaidic acid incorporation into tumor cells resulted in a reduction in the amount of all major lipids in the tumor. In contrast, elaidic acid had no effect on lipid composition of livers from normal mice and and-tumor bearing mice, and also had no effect upon the lipids of the ascites fluid that bathes the tumor cells. The incorporation of elaidic acid into the lipids of EATC, normal liver and host liver did not affect the relative composition of phospholipids in these tissues. The development of the tumor did result in decreases in triacylglycerols and esterified cholesterol, and increases in phospholipids and free cholesterol in the livers of host animals.

Modification of the Ehrlich ascites tumor cell nuclear lipids

The fatty acid composition of Ehrilich ascites tumor cell nuclei was differend when the tumor-bearing mice were fed diets rich in either coconut or sunflower oil. When coconut oil was fed, the monoenoic fatty acid content of many of the nuclear lipids was increased and their polyenoic fatty acid content was reduced as compared with the sunflower oil diet. By contrast, only small changes were produced in the saturated fatty acid contents of the nuclear lipids. The nuclear membrane choline phospholipid, ethanolamine phospholipid and combined serine phospholipid plus inositol phospholipid fractions exhibited statistically significant changes in fatty acid composition, but the sphingomyelins were not altered appreciably by dietary lipid modification. The fatty acid composition of the small quantity of phospholipids associated with the chromatin was much more resistant to diet-induced mosification. Except for sphingomyelin, the fatty acid composition of the chromatin phospholipids was different from that of the corresponding nuclear membrane phospholipids, containing much larger amounts of fatty acids having less than 16 carbon atoms. The fatty acid compositons of the nuclear triaclglycerols and cholesterol esters, which were associated almost entirely with the chromatin, were modified by the dietary lipid modifications. There were no changes in the DNA, RNA or lipid content of these nuclei. Therefore, this experimental system can be used to prepare mamalian nuclei that differ appreciably only in their fatty acyl composition.