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PubMed1974

Lipids of putative relevance to virulence in Mycobacterium tuberculosis: phthiocerol dimycocerosate and the attenuation indicator lipid.

Lipid compositions of 40 patient isolates of Mycobacterium tuberculosis derived from Madras, Burma, Rangoon, and East Africa were studied, and two major populations of tubercle bacilli were distinguished. Nearly all of the strains previously designated as attenuated for the guinea pig (D. A. Mitchison) are characterized by a specific phenolic phthiocerol diester which is identified with the aglycone moieties of mycosides A and B (and probably G). This lipid (AI) was not seen in any of the more virulent strains. Thus, presence of AI may be taken as definitive for attenuation (P << 0.001). Phthiocerol dimycoserosate (DIM), a companion substance, is ubiquitous for the series of 40 strains. However, a dramatic attenuation found in a DIM-less H37Rv mutant may support a role for this substance in the virulent state. Since mycosides A, G, and B seem to be restricted to certain chromogenic and bovine species, respectively, we speculate that lysogenization or transduction of fully virulent M. tuberculosis may have provided the genetic determinants for attenuation and AI synthesis, and thus led to the two classes of tubercle bacilli.

Africa, Eastern↗
PubMed2004

Effects of Western, Vegetarian, and Japanese dietary fat model diets with or without green tea extract on the plasma lipids and glucose, and liver lipids in mice. A long-term feeding experiment.

BACKGROUND/AIMS: The purpose of this study was to investigate the long-term effects of three model diets containing different fats, with or without a small amount of green tea extract (GTE), on plasma lipids and glucose, and liver lipids in mice. METHODS: Male mice (2 months old) fed 10% fat diets with Western (W), Vegetarian (V), and Japanese (J) fat compositions with or without 0.03% GTE for 7 months. RESULTS: The concentrations of plasma and liver total cholesterol in animals fed the W diet were not significantly different from those fed the J diet. Plasma triacylglycerol (TG) concentrations were significantly different from one another in the following order: V > J > W diet groups. GTE supplementation significantly reduced plasma and liver TG content only in V diet group. Plasma glucose (Glu) concentrations were in the following order: W > V > J diet groups, and the GTE supplementation reduced the concentration of Glu in each diet group. The ratios of plasma n-6 to n-3 fatty acids were in the following order: V > W > J diet groups, regardless of GTE supplementation. CONCLUSION: These findings show the possibility that Japanese eating habits combined with drinking green tea might be a factor in preventing the onset of non-insulin-dependent diabetes mellitus.

Animals↗
PubMed2006

Diacylglycerol-enriched structured lipids containing CLA and capric acid alter body fat mass and lipid metabolism in rats.

OBJECTIVE: The present study compared the effect of corn oil, diacylglycerol (DG) oil, and DG-enriched structured lipids (SL-DG) produced from corn oil, capric and conjugated linoleic acid on adiposity in rats fed an AIN-76 diet (5% fat) for 6 weeks. METHODS: The plasma and hepatic lipids, adipose tissue weight, and enzyme activities related to fatty acid metabolism were determined. RESULTS: The weights of the epididymal white adipose tissue (WAT), perirenal WAT, and interscapular WAT were significantly lower in the SL-DG group than in the DG group. Reduction of fat mass in the SL-DG group was related to suppressing fatty acid synthase activities and enhancing beta-oxidation activity in perirenal WAT. The plasma leptin was lower in the SL-DG group than in the DG group, plus a lower plasma TG level was accompanied by an increase in adipocyte LPL activity. Meanwhile the SL-DG supplement lowered the plasma and hepatic cholesterol level. In addition, the hepatic HMG-CoA reductase and ACAT activities were significantly lower in the SL-DG group than in the other groups. CONCLUSION: The DG-enriched SL used in this study was effective in enhancing triglyceride metabolism in adipose tissue, especially as regards reducing the abdominal fat mass and cholesterol metabolism in the liver.

Adipose Tissue↗
PubMed1980

Effect of undernutrition on lipid metabolism of brain. In vivo incorporation of labelled acetate and palmitate into lipids.

Albino rats were malnourished from neonatal to weanling stage by increasing the litter size. The in vivo incorporation of (1-(14)C)-acetate, (1-(14)C)-palmitate into the lipid classes was examined in the animals. A stimulated incorporation of the label was observed in total lipids, phospholipids, cholesterol, cerebrosides and sulfatides of the brain of malnourished animals compared to controls.

Acetates↗
PubMed2006

Lipid transport, dietary fats, and endogenous lipid synthesis: hypotheses on saturation and competition processes.

Plasma lipid concentrations are the net result of the balance between two opposite processes: the loading, i.e. the entry of new lipids into the plasma compartment through the ingestion (diet) and/or endogenous synthesis, and the unloading, i.e. energy utilization, incorporation into cell membranes, and storage. Even though many fatty acids are thought to be synthesized in the body, it appears as nearly all circulating fatty acids are, in fact, derived from the diet. In view of the wide dietary availabilty of such nutrients, the need to conserve energy likely minimizes endogenous synthesis. Consequently, the possibility exists to alter circulating the profile of fatty acids, including the "non essential" ones by dietary manipulations. In turn, a theory on the dietary vs endogenous contribution to circulating fatty acids, including those known as non-essential, is discussed based on critical interpretation of original data.

Adult↗
PubMed1992

Faecal lipid excretion levels in normal Japanese females on an unrestricted diet and a fat-restricted diet measured by simultaneous analysis of faecal lipids.

Faecal lipid excretion was determined in 16 females on an unrestricted diet and on a fat-restricted diet using a chromatographic method for the simultaneous analysis of faecal lipids. The fat-restricted diet reduced the total quantity of faeces and the amounts of fatty acids, neutral sterols and bile acids excreted were almost halved compared with when on an unrestricted diet. This indicates that dietary fat, fibre and cholesterol affect the amount of faecal bile acid, neutral sterol and fatty acid excretion. The amount of cholesterol/animal sterols excreted and the percentage of primary bile acids were, however, similar for both the fat-restricted and unrestricted diets.

Adult↗
PubMed2003

A quantitative analysis of apolipoprotein binding to SR-BI: multiple binding sites for lipid-free and lipid-associated apolipoproteins.

Competitive binding experiments were performed using Y1-BS1 adrenal cells to provide information about the interaction of HDL apolipoproteins with scavenger receptor class B, type I (SR-BI). Exchangeable apolipoproteins apolipoprotein A-I (apoA-I), apoA-II, apoE-2, apoE-3, and apoE-4 as phospholipid complexes bind like HDL3 to SR-BI via their multiple amphipathic alpha-helices; the concentrations required to reduce the binding of HDL3 to SR-BI by 50% (IC50) were similar and in the range of 35-50 microgram protein/ml. In the case of apoA-I, peptides corresponding to segments 1-85, 44-65, 44-87, 149-243, and 209-241 all had the same IC50 as each other (P = 0.86), showing that a specific amino acid sequence in apoA-I is not responsible for the interaction with SR-BI. The distribution of charged residues in the amphipathic alpha-helix affects the interaction, with class A and Y helices binding better than class G* helices. Synthetic alpha-helical peptides composed of either l or d amino acids can bind equally to the receptor. Association with phospholipid increases the amount of apolipoprotein binding to SR-BI without altering the affinity of binding. Lipid-free apolipoproteins compete only partially with the binding of HDL to SR-BI, whereas lipidated apolipoproteins compete fully. These results are consistent with the existence of more than one type of apolipoprotein binding site on SR-BI.

Animals↗
PubMed1990

Effects of tamoxifen treatment on plasma lipids and lipoprotein lipid composition.

Concern has been raised that long term treatment with the antiestrogen tamoxifen might predispose women to the rapid development of cardiovascular disease. Since estrogen-induced changes in plasma lipids confer protection to females from coronary heart disease, we have examined the impact of tamoxifen on lipoprotein levels and composition on eight posmenopausal women. After 3 months of tamoxifen treatment (10 mg, twice daily), no significant changes were observed in either whole plasma triglyceride (pre-Rx, 137 +/- 59; post-Rx, 157 +/- 110 mg/dL) or cholesterol (pre-Rx, 193 +/- 23; post-Rx, 204 +/- 14 mg/dL); plasma free (unesterified) cholesterol (FC), however, fell significantly (pre-Rx, 66.5 +/- 6.5; post-Rx, 59.6 +/- 4.6 mg/dL; P less than 0.05). Since plasma lecithin (L) was unchanged, the FC/L ratio declined significantly to levels observed in healthy menstruating women (pre-Rx, 95 +/- 0.16; post-Rx, 0.74 +/- 0.12 molar ratio; P less than 0.025). In low density lipoprotein (LDL), the concentrations of cholesterol and FC and the FC/L ratio all fell significantly (P less than 0.025, P less than 0.05, and P less than 0.025, respectively). Despite a tendency for high density lipoprotein2 cholesterol (HDL2-C) to increase (pre-Rx, 9.7 +/- 3.6; post-Rx, and 14.4 +/- 13.3 mg/dL; P less than 0.4) and phosphoinositol to fall, there were few clear-cut alterations in either HDL2 or HDL3 surface or core lipid composition. The combination of reduced HDL3 lysolecithin (P less than 0.025) associated with a posttreatment trend toward increased triglyceride/cholesterol esters ratios in both HDL subfractions are findings consistent with tamoxifen-induced inhibition of hepatic lipase. These changes in lipoprotein composition together with the fall in LDL cholesterol and increase in sex hormone-binding globulin (P less than 0.005) indicate that tamoxifen acts as an estrogen agonist on the liver. Since elevated LDL cholesterol levels and qualitatively altered lipoproteins enriched in FC are both associated with increased coronary risk, the improvement noted in these parameters after tamoxifen should allay to some degree anxiety about its use with regard to cardiovascular risk.

Cholesterol, HDL↗
PubMedDate not supplied

The effect of the lipid bilayer state on fluorescence intensity of fluorescein-PE in a saturated lipid bilayer.

Fluorescein-PE is a fluorescence probe that is used as a membrane label or a sensor of surface associated processes. Fluorescein-PE fluorescence intensity depends not only on bulk pH, but also on the local electrostatic potential, which affects the local membrane interface proton concentration. The pH sensitivity and hydrophilic character of the fluorescein moiety was used to detect conformational changes at the lipid bilayer surface. When located in the dipalmitoylphosphatidylcholine (DPPC) bilayer, probe fluorescence depends on conformational changes that occur during phase transitions. Relative fluorescence intensity changes more at pretransition than at the main phase transition temperature, indicating that interface conformation affects the condition in the vicinity of the membrane. Local electrostatic potential depends on surface charge density, the local dielectric constant, salt concentration and water organisation. Initial increase in fluorescence intensity at temperatures preceding that of pretransition can be explained by the decreased value of the dielectric constant in the lipid polar headgroups region related in turn to decreased water organisation within the membrane interface. The abrupt decrease in fluorescence intensity at temperatures between 25 degrees C and 35 degrees C (DPPC pretransition) is likely to be caused by an increased value of the electrostatic potential, induced by an elevated value of the dielectric constant within the phosphate group region. Further increase in the fluorescence intensity at temperatures above that of the gel-liquid phase transition correlates with the calculated decreased surface electrostatic potential. Above the main phase transition temperature, fluorescence intensity increase at a salt concentration of 140 mM is larger than with 14 mM. This results from a sharp decline of the electrostatic potential induced by the phosphocholine dipole as a function of distance from the membrane surface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Contributions of Gaussian curvature and nonconstant lipid volume to protein deformation of lipid bilayers.

An elastic model for membrane deformations induced by integral membrane proteins is presented. An earlier theory is extended to account for nonvanishing saddle splay modulus within lipid monolayers and perturbations to lipid volume proximal to the protein. Analytical results are derived for the deformation profile surrounding a single cylindrical protein inclusion, which compare favorably to coarse-grained simulations over a range of protein sizes. Numerical results for multi-protein systems indicate that membrane-mediated interactions between inclusions are strongly affected by Gaussian curvature and display nonpairwise additivity. Implications for the aggregation of proteins are discussed.

Cell Membrane↗
PubMed1995

Long-term lipid-based total parenteral nutrition activates mononuclear cells and modulates membrane lipid composition in pigs.

In previous studies we have found lung granulomas in pigs on long-term soybean-based total parenteral nutrition (TPN). In the present study we have investigated activities and membrane lipids of cells known to participate in a granulomatous process. Pigs were given TPN with soybean emulsion for 7 weeks, controls were given saline intravenously and consumed a similar caloric load in a standard oral diet. Spontaneous nitroblue tetrazolium (NBT) reduction increased 204% in peripheral blood mononuclear cells (MNC) from TPN animals compared to controls (p < 0.05), and 161% (p = 0.05) in alveolar macrophages. The spontaneous lymphocyte mitogen response (LMR) rate in MNC increased 299% (p < 0.05). Endotoxin-stimulated procoagulant activity in MNC tended to increase in TPN animals. Acid phosphatase and lysozyme production in alveolar macrophages were not significantly changed. The serum neopterin level at the end of the observation was 7.0 nmol l-1 in TPN animals compared to 3.9 nmol l-1 in controls (p < 0.01), while interleukin-1 and tumour necrosis factor were not detectable. These findings indicated in vivo activation of peripheral blood monocytes, lymphocytes and alveolar macrophages in pigs on TPN. The membrane lipid contents of linoleic acid (18:2, n-6) increased, while arachidonic acid (20:4, n-6) tended to decrease both in MNC and lung tissue. Thus, linoleic acid conversion did not lead to accumulation of arachidonate in the cell membranes. Direct effects on monocytes, lymphocytes and alveolar macrophages of TPN particles, and altered cell membrane function, due to linoleic acid enrichment, are tentative explanations for the raised cell responses. Such cell activation may have contributed to the formation of granulomas.

Acid Phosphatase↗
PubMed1985

Effect of lipid peroxidation on the accessibility of dansyl chloride labeling to lipids and proteins of bovine myelin.

In our previous studies we have demonstrated that bovine myelin appears highly susceptible to oxidative damage to both its lipid and protein composition. In order to determine whether these alterations would affect the accessibility of myelin components to a fluorescent probe, we have performed various labeling experiments using dansyl chloride. Results from labeling of purified bovine myelin treated with or without cumene hydroperoxide show that basic protein from treated myelin incorporated more dansyl chloride than basic protein from untreated myelin. This increase of labeling could be prevented by the addition of the antioxidant agent, butylated hydroxytoluene. This evidence suggest that lipid peroxidation may play an important role in the pathogenesis of inflammatory demyelinating diseases.

Animals↗
PubMed2003

Life style and cardiovascular risk factors in the Japanese population--from an epidemiological survey on serum lipid levels in Japan 1990 part 1: influence of life style and excess body weight on HDL-cholesterol and other lipid parameters in men.

Low HDL-cholesterol (HDL-C) has long been used as an important predictor of coronary artery disease (CAD), although HDL-C values themselves are influenced by various factors including serum triglyceride (TG) levels, obesity, and life style. In view of the importance of the metabolic syndrome as a risk factor of CAD, changes in HDL-C and other lipid parameters in the Japanese population associated with life style, especially in males, were analyzed in this study based on data obtained in an epidemiological survey carried out in 1990. Smokers had higher TG and lower HDL-C levels than non-smokers, while BMI and LDL-C were slightly decreased by smoking in middle-aged men (40-59 years old). Increases in both HDL-C and TG due to alcohol consumption were associated with an increase in BMI in younger men aged 20-39. In middle-aged men, significant increases in HDL-C were seen in every quintile of BMI, while the increase in TG levels due to alcohol was small. Middle-aged men engaged in occupations requiring greater physical activity also had higher HDL-C levels in every quintile of BMI. The influence of life style on serum lipid parameters appeared to be mostly expressed as a function of BMI in younger men, while it appeared to be independent of BMI in older men.

Adult↗
PubMedDate not supplied

Determination of lipids in infant formula powder by direct extraction methylation of lipids and fatty acid methyl esters (FAME) analysis by gas chromatography.

Fatty acid methyl esters (FAMEs) of pure triglyceride standards, oils, and fat from dry matrixes were formed by transesterification using sodium methoxide in methanol-hexane. FAMEs were produced by direct addition of sodium methoxide-hexane to samples and heating to simultaneously extract and transesterify acyl lipids. FAMEs were quantitated by capillary gas chromatography (GC) over a fatty acid concentration range of 0 to 1.7 mg/mL (r > or = 0.9997). Total fat was calculated as the sum of individual fatty acids expressed as triglyceride equivalents, in accordance with nutrition labeling guidelines. Saturated, polyunsaturated, and monounsaturated fats were calculated as sums of individual free fatty acids. Absolute recoveries determined from individual fatty acids in test samples ranged from 69.7 to 106%. Recoveries (relative to the C13:0 internal standard) for individual fatty acids in test samples ranged from 95 to 106%. Reproducibility was constant at each fatty acid level in the reaction mixture (n = 5, coefficient of variation [CV] < 2%). Absolute recovery determined from the sum of total fatty acids in standard reference material (SRM) 1846 (powdered infant formula) was 96.4%. Analysis of SRM 1846 gave results that agreed closely with the certified fat and fatty acid values. Analysis of commercial infant formula gave results that were comparable to those obtained with AOAC Method 996.01. The direct extraction methylation procedure is rapid, and the transesterification of acyl lipids to form FAMEs is complete within 15 min. Classical saponification and refluxing are not required. This method provides FAMEs free of interferences and easily quantitated by GC or confirmed by GC/mass spectrometry (MS). Unambiguous MS identification of individual FAMEs derived from pure standards, SRM 1846, and powdered infant formula product was obtained.

Chromatography, Gas↗
PubMed2000

Effect of increasing lipid loads on the ability of the endoplasmic reticulum to transport lipid to the Golgi.

We have previously shown (Mansbach, C. M. and P. J. Nevin, 1998. J. Lipid Res. 39: 963;-968) that after the development of a mass steady state with respect to triacylglycerol absorption in rats, the introduction of radiolabeled trioleoylglycerol, while maintaining the input rate of trioleoylglycerol constant at 135 micromol/h, was followed by a slow (60 min) achievement of a radiolabel steady state in the intestinal endoplasmic reticulum (ER). We hypothesized that this was due to the large input load and that the time to steady state would be shorter at lower lipid loads. Rats were infused intraduodenally with 22.5, 45, 90, or 135 micromol trioleoylglycerol/h for 6 h to obtain a mass steady state in the intestine. [(3)H]trioleoylglycerol was added to the infusate and the ER and Golgi were isolated from the proximal intestine after 5;-60 min of radiolabel infusion. The time required to reach a radiolabel steady state in the ER lengthened from 10 min at the 22.5 micromol/h infusion rate to 60 min at the 135 micromol/h rate. Similar data were obtained for the Golgi. Incubation of the ER with lipase reduced the ER;-triacylglycerol amount by 43% and increased its specific activity by 73%. The amount of [(3)H]TG-dpm in the ER was not reduced unless taurocholate, 10 mm, and colipase were added. We conclude that as the rate of triacylglycerol infusion is increased, TG movement from the ER to the Golgi progressively lengthens until finally all the triacylglycerol infused cannot be transported. A portion of this triacylglycerol is disposed on the cytoplasmic face of the ER and thus able to be attacked by lipase whereas another fraction is sequestered in the ER lumen and immune to lipase attack unless the ER membrane is solubilized.

Animals↗
PubMedDate not supplied

[Protein-lipid interactions during lipid peroxidation in photoreceptor membranes].

It has been shown that chemical modification of hydrophobic lipid phase (lipoperoxidation) of outer segments membrane discs of frog retina rods brings about weakening protein-lipid interactions in the photoreceptor membrane. As a result of this extraction of rhodopsin with anion detergent (sodium cholate) in the concentrations not exceeding the critical concentration of micelloformation increases, and spontaneous release of rhodopsin into water phase is observed. At the same time the number of phospholipid molecules extracted in lipoprotein rhodopsin complex from the membranes of outer segments decreases 3-4-fold.

Animals↗
PubMed1975

Equine serum lipids: serum lipids and glucose in Morgan and Thoroughbred horses and Shetland ponies.

Concentrations of serum phospholipids, triglycerides, total cholesterol, nonesterified fatty acids, and glucose were determined for 9 months (September, 1972, to May, 1973) in 19 fasting horses and ponies (8 Morgan horses, 7 Thoroughbred horses, and 4 Shetland Ponies). Morgan horses had higher concentrations of total lipid than did Thoroughbreds, although the relative proportions of each type of lipid were similar in the 2 breeds. Shetland Ponies had higher nonesterified fatty acid and lower glucose concentrations than did either breed of horse. In both breeds of horses, concentrations of serum triglycerides in the cold months (December to March) were lower than those in the warm months. In the Shetland Pony, there was no seasonal variation in triglycerides, but a significant increase was seen in concentration of nonesterified fatty acids in the cold months. The significance of these findings is discussed.

Animals↗
PubMedDate not supplied

Effect of exercise on the lipid content, lipid fatty acid composition and morphology of myocardial and skeletal muscles in rat.

The effect of exercise on the morphology of the myocardial and skeletal muscle, total lipid content and lipid fatty acid composition was checked in rats fed a rapeseed oil-containing diet. The graded exercise was found to reduce the growth rate of animals. Myocardial fatty degeneration was less intense and erucic acid content lower in trained rats fed a diet with 50% kcal of rapessed oil than the untrained ones. The opposite was true when rapeseed oil supplied 30% of calories. Histiocytic granulomata were more numerous in trained rats. Exercise failed to affect the accumulation of erucic acid in skeletal muscle.

Animals↗