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Effect of cyclosporine on plasma lipids and modification with dietary fish oil.

Hyperlipidemia is an identified risk factor for atherosclerosis in patients following renal transplantation that may be related to previous uremia and various drugs including steroids. Recent evidence has suggested that treatment with cyclosporine may be an independent risk factor for development of hyperlipidemia in some patients. Twenty-four Sprague Dawley rats were given CsA at 30 mg/kg by gavage for 28 days in 1 ml of olive oil or fish oil vehicle, and compared with controls receiving just vehicle. Increases of both triglyceride (233.6%) and cholesterol (50.9%) were observed in olive oil/CsA animals (P less than .01), with no significant change noted with either vehicle alone. An increase of triglyceride from baseline was observed with fish oil/CsA (119%) (P less than .01) but was significantly less than the increase with olive oil/CsA animals (P less than .05). No increase in cholesterol was found in CsA-treated rats using the fish oil vehicle. The mechanisms leading to hyperlipidemia with four weeks of CsA administration in these rats are unknown, but may be related to altered hepatic synthesis. CsA levels were lower in fish oil-treated animals, possibly explaining the difference noted in lipid levels--or, alternatively, reduction of plasma lipoproteins may have altered drug kinetics and CsA binding. This work emphasizes a need for further study of lipids in CsA-treated patients, and advises some caution in the use of lipoprotein-reducing agents in patients using CsA without consideration of the possible effect on free drug levels.

Animals↗

[Specific features of lipid atherogenic modification in patients with ischemic heart disease and diabetes mellitus].

A comparative study of the effect of concomitant compensated diabetes mellitus (DM) on plasma oxidation in patients with ischemic heart disease (IHD) with stable angina of effort (functional class II-III) in 28 anginal patients with IHD, arterial hypertension and DM, 67 anginal patients with IHD and hypertension, 57 anginal patients with IHD and 28 donors. Lipoproteins oxidation was studied by enzymic methods. A significant effect of the type of DM on dynamics of plasma oxidation in IHD patients was found. This may be an additional prognostic criterion of IHD progression in DM patients.

Arteriosclerosis↗

Program on the Surgical Control of the Hyperlipidemias (POSCH): design and methodology. POSCH Group.

The Program on the Surgical Control of the Hyperlipidemias (POSCH) is a prospective, randomized, controlled, multi-center, secondary, atherosclerosis intervention trial. POSCH addresses the therapeutic arm of the lipid-atherosclerosis theory, i.e. whether lowering of plasma cholesterol is directly related to a reduction in atherosclerosis risk. In this trial, lipid modification is accomplished by the partial ileal bypass operation. Between 1975 and 1983, 838 patients were randomized into this study. All patients were between 30 and 64 years of age, had survived one and only one electrocardiogram and enzyme-documented myocardial infarction, and had a total plasma cholesterol of at least 220 mg/dl or a low density lipoprotein (LDL)-cholesterol of at least 140 mg/dl if the total plasma cholesterol was between 200 and 219 mg/dl after a minimum of 6 weeks of dietary fat and cholesterol restriction. The primary response variable in POSCH is overall mortality. Secondary endpoints include fatal and non-fatal myocardial infarctions, serial electrocardiographic changes, and, most importantly, sequential coronary arteriography changes. The minimum follow-up is currently planned to be 7 years. Study analyses will be made primarily on the "intention to treat" basis. This paper is the first detailed presentation of POSCH design and methodology. Included are descriptions of study design, implementation, and data collection, including data processing, quality assurance/quality surveillance, and patient safety monitoring. POSCH seeks to demonstrate a significant reduction in overall mortality by lipid modification and to validate the use of coronary arteriographic change as a surrogate endpoint for change in coronary heart disease risk.

Adult↗

Thematic review series: lipid posttranslational modifications. geranylgeranylation of Rab GTPases.

Rab GTPases require special machinery for protein prenylation, which include Rab escort protein (REP) and Rab geranylgeranyl transferase (RGGT). The current model of Rab geranylgeranylation proposes that REP binds Rab and presents it to RGGT. After geranylgeranylation of Rab C-terminal cysteines, REP delivers the prenylated protein to membranes. The REP-like protein Rab GDP dissociation inhibitor (RabGDI) then recycles the prenylated Rab between the membrane and the cytosol. The recent solution of crystal structures of the Rab prenylation machinery has helped to refine this model and provided further insights. The hydrophobic prenyl binding pocket of RGGT and geranylgeranyl transferase type-I (GGT-I) differs from that of farnesyl transferase (FT). A bulky tryptophan residue in FT restricts the size of the pocket, whereas in RGGT and GGT-I, this position is occupied by smaller residues. A highly conserved phenylalanine in REP, which is absent in RabGDI, is critical for the formation of the REP:RGGT complex. Finally, a geranylgeranyl binding site conserved in REP and RabGDI has been identified within helical domain II. The postprenylation events, including the specific targeting of Rabs to target membranes and the requirement for single versus double geranylgeranylation by different Rabs, remain obscure and should be the subject of future studies.

Adaptor Proteins, Signal Transducing↗

Plasma cholesterol: an influencing factor in red blood cell oxygen release and cellular oxygen availability.

BACKGROUND: A fairly immediate reduction in angina pectoris symptoms after cholesterol lowering has been described. Our previous findings in rabbits and in a four-patient human pilot study indicated the existence of an RBC membrane barrier to oxygen (O2) transport in the presence of hypercholesterolemia. Our current objective was to determine whether, and to what extent, the plasma cholesterol concentration is an influencing factor in RBC O2 release and cellular O2 availability. STUDY DESIGN: In an unique O2 diffusion analysis system, blood samples from 100 patients referred for lipid modification were analyzed. After 1 to 2 minutes of mixing in our diffusion analysis system, the next 1 to 2 minutes of circulation is comparable with 1 to 2 seconds of myocardial capillary flow. RBC O2 diffusion was defined by the depletion rate of total O2 content in blood from full O2 saturation (98%) to desaturation (approximately 60%). Relative tissue O2 availability was defined as the percentage decrease in O2 availability between the high-cholesterol group and the low-cholesterol group. RESULTS: The 100 patients were divided almost equally into two groups on the basis of plasma cholesterol ranges of 175 to 229 mg/dL (n=49) and 230 to 299 mg/dL (n = 51). The mean cholesterol concentrations and percentage increases in the high-cholesterol group over the low-cholesterol group were: for plasma, 206 +/- 0.3 and 256 +/- 0.4 mg/dL, 24.3% (p < 0.001); for RBCs, 93 +/- 0.2 and 106 +/- 0.2mg/dL, 14.0% (p < 0.001); and for RBC membranes, 41 +/- 0.1 and 54 +/- 0.2mg/dL, 31.7% (p < 0.001). The blood O2 diffusion curves were distinctly different between the high- and the low-cholesterol groups (p < 0.05). Blood O2 diffusion, defined by the blood O2 diffusion curves, was inversely proportional to the plasma, RBC, and RBC-membrane cholesterol concentrations. The relative tissue O2 availability, after a circulation period of more than 3 minutes in the diffusion system, showed a decrease of 17.5% (p < 0.05) between the plasma cholesterol groups. In comparing the two plasma cholesterol concentration extremes of less than 200mg/dL (n= 14) and greater than 275 mg/dL (n= 11) after a circulation period of more than 3 minutes in the diffusion system, we found a decrease in relative tissue O2 availability of 35.8% (p < 0.05). CONCLUSIONS: The plasma cholesterol concentration may be an influencing factor in RBC-membrane cholesterol content, which, in turn, may regulate RBC-membrane O2 transport, RBC O2 release, and cellular O2 availability. The implications of this work include the addition of angina pectoris control to the indications for appropriate lipid modification and the development of an in vitro blood stress test to replace patient cardiac stress testing.

Cholesterol↗

Protein modification by lipid peroxidation products: formation of malondialdehyde-derived N(epsilon)-(2-propenol)lysine in proteins.

Malondialdehyde (MDA), a naturally occurring dialdehyde produced in the membrane lipid peroxidation, is known to react with lysine residues of proteins, but the MDA-lysine adducts generated in the proteins have not been characterized adequately. In the present study, we provide evidence that the enaminal-type MDA-lysine adduct, N(epsilon)-(2-propenal)lysine, is formed in human low-density lipoprotein (LDL) upon reaction with MDA or Cu2+. We found that the incubation of N(alpha)-acetyllysine with MDA generated N(alpha)-acetyl-N(epsilon)-(2-propenal)lysine as the predominant product. In addition, a polyclonal antiserum raised against the MDA-modified protein was found to contain antibody populations that could be purified by affinity gel prepared by covalent attachment of N(alpha)-acetyl-N(epsilon)-(2-propenal)lysine. It was concluded that the affinity-purified anti-N(epsilon)-(2-propenal) lysine antibody was highly specific to the enaminal derivative of both lysine residues and phosphatidylethanolamine, based on the observations that (i) MDA was the only aldehyde which generated immunoreactive materials in proteins; (ii) among structurally defined MDA-lysine adducts tested, the antibody recognized the enaminal adduct only; and (iii) immunoreactivity to N-(2-propenal)serine was still significant but much weaker than its reactivity to N-(2-propenal)ethanolamine. Furthermore, analysis of antibody recognition sites with a variety of N-(2-propenal)alkylamines revealed that the mono-specific antibody recognized the N-2-propenal-N-ethyl moiety [-(CH2)2-NH-CH=CH-CHO] of enaminal adducts. Determination by a competitive enzyme-linked immunosorbent assay demonstrated that N(epsilon)-(2-propenal)lysine accounted for 33.7 and 3.1% of the lysine residues that disappeared during in vitro incubation of LDL with MDA and Cu2+, respectively. These results suggest that N(epsilon)-(2-propenal)lysine represents a major form of MDA covalently attached to proteins.

Antibodies, Monoclonal↗

Lipid mediated modification of rat heart allograft survival.

The effect on allograft survival of intravenous fat emulsions that differed in the ratio of functionally important n-3 and n-6 fatty acids was studied in a heterotopic cardiac transplant model in rats. Twenty percent fat emulsions were administered by continuous infusion at a dosage of 9 g fat/kg body weight per day, starting immediately after transplantation and continuing until complete rejection. The n-6 and n-3 fatty acids represent 75%, 43%, 60%, and 59% of all fatty acids in safflower oil, fish oil, soybean oil, and a 1:1 mixture of safflower and fish oil, respectively. The n-6 fatty acids predominate in safflower oil (370/1) and soybean oil (6.5/1), while the n-3 fatty acids dominate in the fish oil (7.6/1). The 1:1 mixture of safflower and fish oil has the balanced composition (n-6/n-3 = 2.1/1) recommended by Kinsella and served as oil-treated controls. Continuous infusion of safflower oil, fish oil, and soybean oil prolonged graft survival time to 13.3, 12.3, and 10.4 days, respectively, compared to 6.8 days in the oil-treated controls (P < 0.01 for all comparisons). Another control group infused with saline rejected the allografts after 7.8 days (P = NS compared to oil-treated controls; P < 0.01 for all other comparisons). The data suggest that intravenous administration of polyunsaturated fat emulsions results in an immunosuppressive effect that seems to be dependent on the n-3/n-6 fatty acid ratio of the fat emulsion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Tight junctions and the experimental modifications of lipid content.

Tight junctions (TJs) are cell-to-cell contacts made of strands, which appear as ridges on P faces and complementary furrows on E faces on freeze fracture replicas. Evidences and opinions on whether these strands are composed of either membrane-bound proteins or lipid micelles are somewhat varied. In the present work we alter the lipid composition of Madin-Darby canine kidney monolayers using a novel approach, while studying (i) their transepithelial electrical resistance, a parameter that depends on the degree of sealing of the TJs; (ii) the apical-to-basolateral flux of 4 kD fluorescent dextran (JDEX), that reflects the permeability of the intercellular spaces; (iii) the ability of TJs to restrict apical-to-basolateral diffusion of membrane lipids; and (iv) the pattern of distribution of endogenous and transfected occludin, the sole membrane protein presently known to form part of the TJs. We show that changing the total composition of phospholipids, sphingolipids, cholesterol and the content of fatty acids, does not alter TER nor the structure of the strands. Interestingly, enrichment with linoleic acid increases the JDEX by 631%. The fact that this increase is not reflected in a decrease of TER, suggests that junctional strands do not act as simple resistive elements but may contain mobile translocating mechanisms.

Animals↗

Induction, by adriamycin and mitomycin C, of modifications in lipid composition, size distribution, membrane fluidity and permeability of cultured RDM4 lymphoma cells.

Adriamycin and mitomycin C were previously found to modulate the sensitivity of lymphoma cells to lysis by certain effectors of immunity and this modulation was dependent on drug concentration. In the present studies, RDM4 lymphoma cells were treated with different concentrations of the two drugs for 24 h in culture. These treatments resulted in changes in the lipid composition, membrane fluidity, cell size distribution, and permeability to 51CrO4, Trypan blue, Acridine orange and trimethylaminodiphenylhexatriene (TMA-DPH) of the cells. Changes in some of these parameters, as a function of drug concentration, resulted in dose-response curves which were bell-like shaped, hence paradoxical similarities between non-drug-treated cells and cells treated with higher drug concentrations were observed.

Animals↗

Modification of lipid phase behavior with membrane-bound cryoprotectants.

Several derivatives of cholesterol containing oxyethylene headgroups with and without a terminal galactose have been synthesized in order to examine the effects of immobilizing a cryoprotectant at a membrane surface. In this work, we have studied the ability of the triethoxycholesterol (TEC) and triethoxycholesterol galactose (TEC-Gal) derivatives to modulate the phase behavior of phosphatidylcholine and phosphatidylethanolamine membranes. Methods of fluorescence polarization, 31P-NMR and freeze-fracture electron microscopy were employed to monitor these changes in lipid phase behavior. Fluorescence polarization data demonstrated the ability of the derivatives to fluidize gel state and rigidify liquid-crystalline state phosphatidylcholines in a manner similar to that observed for cholesterol. Unlike cholesterol, however, the Tm of dipalmitoylphosphatidylcholine (DPPC) was reduced in a concentration-dependent manner with each of the derivatives. Freeze-fracture electron microscopy and 31P-NMR of DOPE dispersions indicate an increase in the lamellar to hexagonal phase-transition temperature on the order of 10-20 C degrees above room temperature for mixtures with 20 mol% of the derivatives. These results are discussed in terms of the properties exhibited by compounds such as carbohydrates, which are known to serve as cryoprotectants for synthetic and biological membranes.

1,2-Dipalmitoylphosphatidylcholine↗

The modification of lipid composition in L-M cultured cells supplemented with elaidate. Increased formation of fatty alcohols.

Supplementation of culture medium with elaidic acid (40 micrograms/ml) resulted in the incorporation of this acid into 50% of the acyl groups of phospholipids in L-M cells; elaidate was esterified at both the sn-1 and the sn-2 positions of phosphatidylcholine and phosphatidylethanolamine. In addition, elaidate supplementation of L-M cells induces the accumulation of free fatty alcohols, alkyldiacylglycerols and wax esters/cholesterol esters. The concentration of intracellular free fatty alcohols increased as a function of the concentration of elaidic acid in the growth medium and the duration of exposure. However, the concentration of alcohol-containing lipids, total alkyl and alk-1-enyl lipids, was only slightly decreased. This decrease was much less than the increase in the level of free fatty alcohols. Therefore, we conclude that when elaidic acid is supplemented to L-M cells in culture, a net increase in the production of free fatty alcohols occurs.

Animals↗

Decreased activity of the phosphate carrier and modification of lipids in cardiac mitochondria from senescent rats.

1. A comparative study of the effects of aging on the transport of phosphate and on the lipid composition in cardiac mitochondria isolated from young and aged rats was carried out. 2. Mitochondria from aged rats (26 month old) translocate phosphate much more slowly than do mitochondria from young control rats (4 month old). 3. Kinetic analysis of the phosphate transport show that only the Vmax of this process is decreased while there is no change in the Km value. 4. There is no appreciable difference in either the respiratory control ratios or in the ADP/O ratios between mitochondria from young and aged rats. 5. The heart mitochondrial lipid composition is altered in aged rats; in particular, the cholesterol/phospholipid molar ratio increases and the content of cardiolipin decreases with aging.

Aging↗

Modification of lipid composition of erythrocyte membranes in chronic alcoholism.

The lipid composition and microviscosity of erythrocyte membranes have been studied in chronic alcoholics with macrocytosis and minimal liver dysfunction. The findings have been compared with those obtained in subjects with macrocytosis not related to ethanol abuse. In all instances, macrocytosis was accompanied by an increased microviscosity of erythrocyte membranes, together with an increase of the cholesterol/phospholipid and of saturated/unsaturated fatty acids ratio. Both microviscosity and saturated/unsaturated ratio were significantly higher in alcoholics compared to subjects with macrocytosis not related to ethanol abuse. These findings confirm that altered lipid composition and fluidity of erythrocyte membrane may be observed in chronic alcoholics with minimal liver dysfunction, possibly due to the "stabilising" properties of ethanol - among a number of drugs- on biological membranes.

Adult↗

Age-dependent modification of lipid composition and lipid structural order parameter of rat peritoneal macrophage membranes.

The effect of aging on the lipid composition and fluidity of rat peritoneal macrophage membranes has been determined using young (3 months), mature (12 months) and aged (24 months) Wistar rats. In the aged animals, total phospholipid decreased significantly (P < 0.05), whereas cholesterol increased (P < 0.01), with an age-dependent increase in the molar ratio of cholesterol/phospholipid. The most marked change in phospholipid content was the significant (P < 0.001) age-dependent increase of phosphatidylserine and cardiolipin and the significant decrease of phosphatidylcholine and phosphatidylinositol. During aging there was a considerable decrease in arachidonic acid and docosapentanoic acid (about 50% in both cases). In contrast, an increase in the levels of oleic, linoleic and docosahexanoic acid was observed. Steady-state fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene as the probe was used to estimate the lipid structural order parameter of macrophage membranes. There was a highly significant (P < 0.001) age-dependent increase in the lipid structural order parameter, which correlated well with the increased molar ratio of cholesterol/phospholipid in the membranes isolated from aged animals. The data suggests alteration in membrane lipid-protein interactions in aging, and are consistent with the hypothesis of the aging process.

Aging↗

Modification of lipid acyl groups by serum deprivation does not affect phorbol ester-induced differentiation of human leukemia cells.

12-O-Tetradecanoylphorbol-13-acetate (TPA), a potent tumor promoter, can induce differentiation of human promyelocytic leukemia cells grown in a serum-free environment. Removal of serum produces altered acyl group composition of cellular phospholipids, most notably, marked decreases in the polyunsaturated fatty acid content. Although higher amounts of TPA are required to induce differentiation in serum-free cell populations, induction assessed by morphological and enzymatic markers in similar to the "macrophage-like' differentiated state reported for cells grown in a serum-rich medium.

Cell Differentiation↗

Modification of lipid composition of neuroblastoma C1300 N18 cells with liposomes alters the cholesterol content.

Cell incubation with lecithin-cholesterol liposomes (1:1 mol/mol) caused enhancement of the cholesterol content. The level of cholesterol esters of total and phospholipid unsaturated fatty acids increased in cholesterol enriched cells. Simultaneously the amount of saturated fatty acids decreased and lysophosphatidylcholine appeared in the cells. On the contrary, cell incubation with lecithin liposomes resulted in cholesterol depletion. This effect was accompanied by a decrease of cholesterol esters, of total and phospholipid unsaturated fatty acids. The content of saturated fatty acids was raised in cells with reduced amount of cholesterol. The quantity of N-acylphosphatidylethanolamine and N-acylethanolamine, lipids newly found in neuroblastoma cells, also changed in cells with modified content of cholesterol. The physiological role of cell response to the changes of cholesterol level is discussed.

Cell Line↗