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PubMed2002

Rapid thermogravimetric measurements of boiling points and vapor pressure of saturated medium- and long-chain triglycerides.

In developing compositional models for biomass-based diesel fuel extenders, volatility properties of medium- and long-chain saturated triglycerides are essential to predict the impact of low levels of these compounds in mixtures with short-chain triglycerides. A thermogravimetric analysis (TGA) method for rapid measurement of boiling points and vapor pressure was used to obtain data for four pure medium- and long-chain triglycerides. Normal boiling points at 1 atm and the temperature dependence of vapor pressure from 760 mm down to 25 mm Hg were obtained for trilaurin (C12:0), trimyristin (C14:0), tripalmitin (C16:0), and tristearin (C18:0). The data showed good agreement with the Clausius-Clapeyron model for temperature dependence of vapor pressure up to 1 atm pressure. The results of this study were consistent with those obtained using differential scanning calorimetry (DSC) and with data previously reported for reduced pressure.

Pressure↗
PubMed2004

Reactivity of triglycerides and fatty acids of rapeseed oil in supercritical alcohols.

A catalyst-free biodiesel production method with supercritical methanol has been developed that allows a simple process and high yield because of simultaneous transesterification of triglycerides and methyl esterification of fatty acids. From these lines of evidence, we expected that similar results would be attained with the use of various alcohols by the supercritical treatment. However, it still remains unclear which type of reaction, transesterification or alkyl esterification, is faster. This parameter would be important in designing the optimum reaction conditions of the supercritical alcohol method. Therefore, we studied the effect of transesterification of triglycerides and esterification of fatty acids in rapeseed oil. Reaction temperature was set at 300 degrees C, and methanol, ethanol, 1-propanol, 1-butanol or 1-octanol was used as the reactant. The results showed that transesterification of triglycerides (rapeseed oil) was slower in reaction rates than alkyl esterification of fatty acids for any of the alcohols employed. Furthermore, saturated fatty acids such as palmitic and stearic acids had slightly lower reactivity than that of the unsaturated fatty acids; oleic, linoleic and linolenic.

Alcohols↗
PubMed2000

Puberty-associated differences in total cholesterol and triglyceride levels according to sex in French children aged 10-13 years.

PURPOSE: To assess the relationships between lipid levels and sexual maturity, independently of age-related differences, and to investigate possible differences related to sexual maturity across the percentiles of the lipid distributions. METHODS: Fasting serum total cholesterol and triglyceride concentrations were measured in 6577 boys and 6605 girls, aged from 10 to 13 years, with different Tanner stages. The total cholesterol and triglyceride mean and percentile levels were estimated according to age and Tanner stage by ordinary least squares and percentile regression models, separately in both sexes. RESULTS: In boys and girls, total cholesterol levels were significantly associated with pubertal stage after controlling for age. At age 12, the estimated mean levels in boys varied from 4.82 mmol/L for Tanner 1 to 4.41 for Tanner 5. The corresponding values were 5.05 and 4.62 mmol/L in girls, for whom the association with maturity was stronger in the upper than in the lower percentiles (p < 0.0001); between the extreme Tanner stages, the 95th percentiles of total cholesterol differed by 0.80 mmol/L, in comparison to 0.19 mmol/L for the 5th percentiles. Therefore, 1. 8% of girls and 0.7% of boys were classified differently whether Tanner stage was used or not to assess hypercholesterolemia (concentrations in the upper 5% of the distributions). Triglycerides were positively related to sexual maturity independently of age, but the discrepancies between classifications were lower; 1.1% in girls and 0.4% in boys. CONCLUSIONS: Our findings emphasize the importance of sexual maturity, even for a given age, for interpreting lipid levels in children.

Adolescent↗
PubMed2004

Triglyceride and coronary heart disease mortality in a 24-year follow-up study in Xi'an, China.

PURPOSE: To study whether serum triglyceride (TG) was associated with coronary heart disease (CHD) mortality. METHODS: A cohort analytic study carried out in a machinery factory in Xi'an, China on 1696 subjects aged 35 years or above (1124 men and 572 women) examined in 1976 and followed up till 2000. RESULTS: At baseline, the mean serum total cholesterol (TC) and triglyceride (TG) was 4.64 and 1.16 mmol/L in men, 4.62 and 1.10 mmol/L in women, respectively. Three hundred six (239 men, 67 women) had died within 37,781 person-years of follow-up, with 49 CHD deaths (36 male, 13 female). The relative risk (95% confidence interval) of CHD mortality per mmol/L increase in TG was 2.13 (1.46-3.17) after adjusting for age, marital status, occupation, education, systolic blood pressure and TC. Dose-response relationship between TG levels by tertiles and CHD risk was found. Stratified analyses showed TG was an independent predictor for CHD mortality in subjects with lower or higher TC. CONCLUSIONS: Chinese had lower levels of TC and TG than Western populations. This study provides new evidence that TG is an independent risk factor of CHD in subjects with lower or higher TC levels, and supports the lowering of cut-off value for elevated triglyceride.

Adult↗
PubMed2004

Serum triglycerides are a predictive factor for the development and the progression of renal and retinal complications in patients with type 1 diabetes.

OBJECTIVES: It is controversial that serum lipIds affect the development and progression of microvascular complications in patients with type 1 diabetes. METHODS: We prospectively followed 297 patients with type 1 diabetes without end-stage renal disease for 7 Years (range: 2-10). Serum lipIds were measured at baseline (total and HDL-cholesterol, triglycerIdes and calculated LDL-cholesterol, Lipoprotein (a)). The primary end-point was the occurrence of a renal event and the secondary end-point was the occurrence of a retinal event, defined as the progression to a higher stage of diabetic nephropathy or retinopathy, respectively. RESULTS: Serum triglycerIde (TG) levels were higher in patients who progressed in nephropathy than in those who dId not [median 1.21 (range 0.41-2.96) vs 0.91 (0.31-11.07) mmol/l; p=0.0037] and in those who developed retinal events than in those who dId not [1.05 (0.46-8.27) vs 0.87 mmol/l (0.31-11.07); p=0.0302], both in the whole cohort and in patients with normoalbuminuria at baseline. After adjustment for systolic blood pressure (SBP), diabetes duration, gender, stage of complications at baseline and glycohemoglobin (HbA1c), the relative risk for progression was 2.01 (95% CI: 1.07-3.77) for nephropathy and 2.30 (95% CI: 1.03-5.12) for retinopathy for patients having serum TG in the highest tertile, compared to the others. This result persisted when only patients with normoalbuminuria were consIdered. CONCLUSION: High triglycerIde levels are an independent predictive factor of both renal and retinal complications in patients with type 1 diabetes.

Adult↗
PubMed1990

Genetic variance and heritability of serum cholesterol and triglycerides among Chinese twin neonates.

In order to examine the genetic variance and heritability of serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides, a total of 349 pairs of same-sexed twin neonates born in four major general teaching hospitals in Taipei City were studied. Based on the placental pattern and 12 red blood cell antigens, 271 monozygotic (MZ) and 78 dizygotic (DZ) twin pairs were identified. There was a significant genetic variance for total cholesterol, HDL-C, LDL-C, and triglycerides both unadjusted and adjusted for sex, gestational age and placentation. The unadjusted heritability of total cholesterol, HDL-C, LDL-C, and triglycerides was 0.59, 0.30, 0.25 and 0.75, respectively; while the corresponding adjusted heritability was 0.74, 0.38, 0.31, and 0.49, respectively. Intrapair variance of serum lipids was not significantly different between monochorionic and dichorionic MZ twins.

China↗
PubMed1976

Genetics of plasma cholesterol and triglycerides: a study of adult male twins.

Fasting plasma triglycerides and cholesterol, as well as cholesterol in very low density, low density and high density lipoproteins, were measured in 250 MZ and 264 DZ adult male twin pairs. A new method was used to choose an estimate of genetic variance. This includes an estimate of genetic variance for use when the total variances of MZ and DZ twins are unequal. DZ twins had greater total variance for cholesterol. When genetic variance was estimated by subtracting the within-MZ-sets mean square from the within-DZ-sets mean square, all of the lipids had significant estimates of genetic variance; however, when genetic variance was estimated by a method designed to correct bias due to unequal total variances of MZ and DZ twins, only triglycerides had significant genetic variance. The heritability of plasma triglycerides was calculated to be 0.68.

Adult↗
PubMed1990

Local control of the onset of mammary extraction of plasma triglycerides during lactogenesis in the goat.

In five untreated goats, mammary extraction of plasma triglycerides increased at parturition. In five goats that had as much secretion as possible regularly removed from one mammary gland beginning on d 143 of gestation, the change of triglyceride extraction occurred several d before parturition in the emptied gland but at parturition in the contralateral control gland. The experimentally induced early increase of extraction of plasma triglycerides preceded the increase of prostaglandin F alpha concentration in mammary secretion at parturition, and occurred despite abnormally high concentrations of progesterone in the secretion.

Animals↗
PubMed2000

Use of relationships between retention behaviors and chemical structures in subcritical fluid chromatography with CO2/modifier mixtures for the identification of triglycerides.

Satisfactory separations of vegetable oil triglycerides (TG) differing in fatty acid composition are obtained by subcritical fluid chromatography (SubFC) with octadecyl packed columns and CO2/modifier mobile phases. However, the identification of TG can be sometimes difficult due to the small retention differences between the compounds. A method of TG identification in SubFC was achieved, which does not require calculation of retention pattern but uses the differences in retention behavior related to TG structure and to the nature of the subcritical mobile phases. These retention differences were produced by the variation of either outlet pressure or modifier percentage or of temperature. Whatever the column aging, this method allows the determination of the triglyceride total chain length and double bond number. Among numerous structures, these two criteria restrict the structural hypothesis at worst to three or four possibilities and sometimes only to one. The validity of this relative identification method was confirmed by electronic impact mass spectrometry of triglyceride fractions collected from the analysis of a peanut oil. The analysis of concentrated fractions is favored by the spontaneous elimination after the pressure regulator of carbon dioxide, the main fluid of the subcritical mobile phase.

Carbon Dioxide↗
PubMed1995

Cutinase from Fusarium solani pisi hydrolyzing triglyceride analogues. Effect of acyl chain length and position in the substrate molecule on activity and enantioselectivity.

Triglyceride analogues were synthesized in which one of the primary acyl ester functions has been replaced by an alkyl group and the secondary acyl ester bond has been replaced by an acyl amino bond. The chain length at either position was varied, and both (R)- and (S)-enantiomers of each compound were synthesized. These pseudo triglycerides contain only one hydrolyzable ester bond, and they are ideally suited to studying the influence of the chain length at the 1-, 2-, and 3-position on lipase activity and on stereopreference. These substrates were used to characterize cutinase from Fusarium solani pisi. Our results show that the activity of cutinase is very sensitive to the length and distribution of the acyl chains and that the highest activities are found when the chains at positions 1 and 3 contain three or four carbon atoms. The enzyme preferentially hydrolyzes the (R)-enantiomers, but this preference is strongly dependent on the acyl chain length distribution, with (R) over (S) activity ratios varying from about 30 to 1. This enantioselectivity was found in three different assay systems: a mixed micellar, a reverse micellar, and a monolayer study. Our data suggest that at least two alkyl chains of the pseudo triglycerides must be fixed during hydrolysis. Therefore, these substrates were used to characterize mutants of cutinase with mutations in putative lipid binding domains. Two mutants (A85F and A85W) have increased activities. The results obtained with these mutants suggest an interaction of the acyl chain of the scissile ester bond with a surface loop, comprising residues 80-90, in the enzyme-substrate complex.

Carboxylic Ester Hydrolases↗
PubMed1991

Protein disulfide isomerase appears necessary to maintain the catalytically active structure of the microsomal triglyceride transfer protein.

Protein disulfide isomerase (PDI) is a component of the microsomal triglyceride transfer protein (MTP) complex. This study was initiated to help elucidate the role of PDI in MTP. The 88-kDa polypeptide of MTP (88K) was dissociated from PDI by using chaotropic agents (NaClO4 and KSCN), low concentrations of a denaturant (guanidine hydrochloride) or a nondenaturing detergent (octyl glucoside). As assessed by fluorescence and circular dichroism spectroscopy, these three different approaches appeared to dissociate the components of MTP under mild, nondenaturing conditions. The dissociating agents were diluted or removed by dialysis, and the free PDI and 88K were further characterized. In all cases, the dissociation coincided with the loss of triglyceride transfer activity. The free 88-kDa polypeptide readily aggregated, suggesting that it is a hydrophobic peptide. Even in the presence of chaotropic agents, when 88K was not aggregated, transfer activity was not expressed. These results suggest that the association of PDI with 88K is necessary to maintain the catalytically active form of the triglyceride transfer protein and prevent the aggregation of 88K.

Animals↗
PubMed1992

An NMR investigation of the changes in plasma membrane triglyceride and phospholipid precursors during the activation of T-lymphocytes.

Two-dimensional 1H-NMR spectroscopy was used to quantify the level of isotropically tumbling plasma membrane triglyceride and the intracellular concentrations of water-soluble phospholipid precursors during the activation of thymic T-lymphocytes. The concentration of "mobile" triglyceride in the plasma membrane was seen to increase 25-fold during 72 h of activation of murine thymic T-lymphocytes with ionomycin and phorbol myristate acetate. This is the first unequivocal demonstration of such a dramatic increase in mobile plasma membrane triglyceride during T-lymphocyte activation and leads to the suggestion that immune cell activation is associated with increased plasma membrane fluidity. The intracellular concentrations of choline- and ethanolamine-based phospholipid precursors were shown to increase during the early stages of T-lymphocyte activation and then remain at levels above those in resting cells. This may facilitate de novo phospholipid biosynthesis, which is presumably necessary since cell volume, and hence the plasma membrane surface area, was demonstrated to increase significantly during thymocyte activation.

Animals↗
PubMed1983

Triolein-cholesteryl oleate-cholesterol-lecithin emulsions: structural models of triglyceride-rich lipoproteins.

The organization of lipids within emulsions composed of triolein (TO), cholesteryl oleate (CO), cholesterol (C), and egg yolk phosphatidylcholine (L) was examined. CO was substituted for TO in a series of emulsions to obtain TO:CO ratios comparable to the triglyceride:cholesterol ester ratios observed in subfractions of triglyceride-rich lipoproteins. The weight fraction of TO in the surface phase (0.02-0.05) was independent of the TO content of the emulsions. However, the weight fraction of CO in the surface phase depended upon the percentage of CO in the emulsions and was less than 0.004 even when 13.7% CO was present in the emulsion. When CO was substituted for TO, the percent of the total particle C which was carried in the droplet oil phase was increased. The interparticle equilibration of lipids was studied in subfractions of sonicated emulsions with particle sizes comparable to triglyceride-rich lipoproteins. The TO:CO ratios of the subfractions of a given emulsion were constant and independent of size, but the C:L ratio decreased in particles of smaller diameter. However, the surface C:L ratio was the same in all particles from a given emulsion. The size dependence of the C:L ratios was attributed to the partitioning of C into the oil cores of the emulsions. Because large droplets have the greatest core:surface mass ratios, more of their total particle C is carried in the core.

Chemical Phenomena↗
PubMed2003

Structure of triglyceride-rich human low-density lipoproteins according to cryoelectron microscopy.

Low-density lipoprotein (LDL) particles from normolipidemic individuals contain a cholesteryl ester-rich core that undergoes a thermal transition from a liquid crystalline to an isotropic liquid phase between 20 and 35 degrees C. LDL from hypertriglyceridemic patients or prepared in vitro by the exchange of very low-density lipoprotein for LDL cholesteryl esters is triglyceride-rich, does not have a thermal transition above 0 degrees C, and exhibits impaired binding to the LDL receptor on normal human skin fibroblasts. Cryoelectron microscopy of LDL quick-frozen from 10 (core-frozen) and 40 degrees C (core-melted) revealed ellipsoidal particles with internal striations and round particles devoid of striations, respectively. Cryoelectron microscopy of triglyceride-rich LDL prepared in vitro revealed particles similar to the core-melted normolipidemic LDL, i.e., round particles without striations. These data suggest that the LDL core in the liquid crystalline phase is characterized by the appearance of striations, whereas LDL with a core that is an isotropic liquid lacks striations. It is suggested that freezing the LDL core into a liquid crystalline phase imposes structural constraints that force LDL from a sphere without partitions to an ellipsoid with partitions. We further suggest that the striation-defined lamellae are a structural feature of a liquid crystalline neutral lipid core that is a determinant of normal binding to the LDL receptor and that conversion of the neutral lipid core of LDL to the isotropic liquid phase via an increase in the temperature or via the addition of triglyceride partially ablates the receptor binding determinants on the LDL surface. This effect is likely achieved through changes in the conformation of apo-B-100. These data suggest that the physical state of the LDL core determines particle shape, surface structure, and metabolic fate.

Binding Sites↗
PubMed2004

Inhibitory effect of natural phenolic lipids upon NAD-dependent dehydrogenases and on triglyceride accumulation in 3T3-L1 cells in culture.

Alkylresorcinols are phenolic lipids present at levels of 0.03-0.15% in wheat and rye grains and almost 10 times higher in respective bran products. Despite numerous studies on the influence of dietary fibers on the regulation of energy metabolism, this issue still remains controversial. The objective of our current studies was to investigate whether 5-n-alk(en)ylresorcinols, natural phenolic components of high fiber human diets, may be considered as natural regulators of excessive fat accumulation. Our studies revealed that 5-n-alk(en)ylresorcinols isolated from wheat and rye bran inhibit glycerol-3-phosphate dehydrogenase, the key enzyme in triglyceride synthesis in adipocytes, specifically and effectively. Further in vitro studies showed that these compounds also prevent triglyceride accumulation in 3T3-L1 cells. The most effective compound in both systems was 5-n-heneicosylresorcinol. The results indicate that the potential to prevent triglyceride accumulation increases with the hydrophobicity of the phenolic inhibitor.

3T3-L1 Cells↗
PubMed2004

Cluster analysis for the systematic grouping of genuine cocoa butter and cocoa butter equivalent samples based on triglyceride patterns.

The triglyceride profile of cocoa butters (CBs) from different geographical origins, varieties, growing seasons, and a number of cocoa butter equivalents (CBEs) was determined by capillary gas liquid chromatography. Hierarchical cluster analysis was applied to the five main triglycerides of the samples for the ability to find natural groupings among (a) CBs of various provenance and (b) CBE samples of different types. The samples were clustered using Ward's method, and the similarity values of the linkages were represented by dendrograms. The five triglycerides contained adequate information to obtain a meaningful sample differentiation. This information can be used to assess the purity and the origin of the CB sample examined.

Chromatography, Gas↗
PubMed1999

Comparative study on the triglyceride composition of almond kernel oil. A new basis for cultivar chemometric characterization.

Nine triglycerides (LLL, OLL, PLL, OLO, PLO, PLP, OOO, POO, and SOO; triglycerides are abbreviated using L, O, P, and S for linoleoyl, oleoyl, palmitoyl, and stearoyl fat acid radicals, respectively) in the almond kernel of 19 different cultivars have been determined by high-performance liquid chromatography. Multivariate techniques have been applied to the data from 114 chromatographic determinations. Principal component analysis efficiently reduces the number of variables so that the first two principal components explain 84.4% of the total variance. The classification obtained by the application of cluster analysis to triglyceride composition differentiates the American cultivar Texas from the rest of the cultivars. The Italian cultivars are grouped. The cultivars Achaak, Del Cid, Malagueña, Desmayo Largueta, and Chellaston form another group, and the largest group includes most of the Spanish cultivars. Discriminant analysis provides convenient functions to describe the four groups previously established by cluster analysis. The calculated classification functions correctly assign samples from the testing set to their respective groups.

Fatty Acids↗
PubMed2004

Microemulsification of triglyceride sebum and the role of interfacial structure on bicontinuous phase behavior.

A unique triblock surfactant is reported that allows for the efficient microemulsification of triglycerides. Unlike the results of all previous efforts, these triglyceride microemulsions can be formed without the use of cosurfactants or dilution with co-oils and follow the classical patterns of surfactant phase behavior exhibited by mixtures of water, alkane oils, and nonionic oligoethylene glycol surfactants, i.e., progression from oil/water emulsions to one-phase microemulsions to water/oil emulsions with increasing temperature. Lamellar phases that usually dominate the aqueous phase behavior of surfactant/triglyceride mixtures are suppressed, allowing for the formation of single-phase microemulsions containing equal amounts of triglyceride and water. These isotropic and low-viscous fluids are particularly useful for cleansing and delivery of functional ingredients in skin care products. The effects of mixing a variety of typical skin care ingredients and components of sebum (skin oil) were also explored. Fatty acids significantly reduce the average microemulsion temperature, while other ingredients and oils, which do not partition at the oil/water interface, have less impact on the phase behavior. In all cases, one-phase microemulsions containing equal amounts of oil and water can be formed even at high additive concentrations. Indeed, partial replacement oftriglyceride with any of the additives examined consistently reduced the amount of surfactant necessary to form single-phase microemulsions. However, the greatest boost in surfactant efficiency was found with the addition of medium molecular weight amphiphilic block copolymers.

Emulsions↗