Quantitating heart lipids: comparison of results obtained using the Iatroscan method with those from phosphorus and gas chromatographic techniques

Dietary canolol protects the heart against the deleterious effects induced by the association of rapeseed oil, vitamin E and coenzyme Q10 in the context of a high-fat diet

Background

Obesity progressively leads to cardiac failure. Omega-3 polyunsaturated fatty acids (PUFA) have been shown to have cardio-protective effects in numerous pathological situations. It is not known whether rapeseed oil, which contains α-linolenic acid (ALA), has a similar protective effect. Omega-3 PUFAs are sensitive to attack by reactive oxygen species (ROS), and lipid peroxidation products could damage cardiac cells. We thus tested whether dietary refined rapeseed oil (RSO) associated with or without different antioxidants (vitamin E, coenzyme Q10 and canolol) is cardio-protective in a situation of abdominal obesity.

Methods

Sixty male Wistar rats were subdivided into 5 groups. Each group was fed a specific diet for 11 weeks: a low-fat diet (3% of lipids, C diet) with compositionally-balanced PUFAs; a high-fat diet rich in palm oil (30% of lipids, PS diet); the PS diet in which 40% of lipids were replaced by RSO (R diet); the R diet supplemented with coenzyme Q10 (CoQ10) and vitamin E (RTC diet); and the RTC diet supplemented with canolol (RTCC diet). At the end of the diet period, the rats were sacrificed and the heart was collected and immediately frozen. Fatty acid composition of cardiac phospholipids was then determined. Several features of cardiac function (fibrosis, inflammation, oxidative stress, apoptosis, metabolism, mitochondrial biogenesis) were also estimated.

Results

Abdominal obesity reduced cardiac oxidative stress and apoptosis rate by increasing the proportion of arachidonic acid (AA) in membrane phospholipids. Dietary RSO had the same effect, though it normalized the proportion of AA. Adding vitamin E and CoQ10 in the RSO-rich high fat diet had a deleterious effect, increasing fibrosis by increasing angiotensin-2 receptor-1b (Ag2R-1b) mRNA expression. Overexpression of these receptors triggers coronary vasoconstriction, which probably induced ischemia. Canolol supplementation counteracted this deleterious effect by reducing coronary vasoconstriction.

Conclusion

Canolol was found to counteract the fibrotic effects of vitamin E + CoQ10 on cardiac fibrosis in the context of a high-fat diet enriched with RSO. This effect occurred through a restoration of cardiac Ag2R-1b mRNA expression and decreased ischemia.

Effect of diet on animal performance, lipid composition of subcutaneous adipose and liver tissue of beef cattle

Two trials were carried out with Brahman beef cattle to study animal performance and carcass characteristics as well as fatty acid composition of subcutaneous adipose and hepatic tissue, as influence by length of grain feeding period or a pasturing regimen. In trial 1, steers were allotted to three feedlot finishing periods (76, 104 and 146 days) after being backgrounded on pasture. Steers fed 76 days had greater average daily gains (P < 0·05) than steers fed 146 and 104 days, respectively. Carcasses of steers slaughtered after 146 days on feed had higher (P < 0·05) marbling scores, quality grades, fat over ribeye, quality yield and per cent kidney, pelvic and heart (KPH) fat than steers fed for 104 and 76 days. The proprortions of certain fatty acid of subcutaneous fat and liver tissue were influenced by the length of grain feeding. There was a marked increased in the proportion of oleic acid in both tissues as the steers remained longer in the feedlot and a higher percentage of total saturated fatty acids at 76 days than at the other two times. Quantitative separation of hepatic lipid classes by the Iatroscan revealed that phosphatidylcholine and phosphatidylethanolamine were the main components of the phospholipids. Presents as minor components were cardiolipin and sphingomyelin. No differences (P > 0.·05) in these individual subclasses of liver lipids or in triglycerides were observed between the feedlot groups. Liver polyunsaturated fatty acids (PUFA) were higher (P < 0·001) at 104 than 76 days. In trial 2, steers fed a concentrate diet gained faster (P < 0·05) than the pasture group after 138 days. Marbling scores, yield grade, quality grade, fat over ribeye and per cent KPH were higher (P < 0·01) for the concentrate group while fat color scores were higher (P < 0·01) for the pasture group. Liver fatty acid analysis of summed ω6 PUFAs of triglyceride, phosphatidylcholine, phosphatidylethanolamine were higher for the feedlot than the pasture group. Linoleic acid was higher (P < 0·05) in the TG and PC liver subclass of the feedlot animals while higher (P < 0·05) linolenic acid occurred in the pasture group.

Quantitative analysis of biological membrane lipids at the low picomole level by nano-electrospray ionization tandem mass spectrometry

Nano-electrospray tandem mass spectrometry allows qualitative and quantitative analysis of complex membrane lipid mixtures at the subpicomole level. We have exploited this technique to selectively detect individual classes of phospholipids from unprocessed total cellular lipid extracts by either precursor ion or neutral loss scanning. This way phosphatidylcholine, sphingomyelin, phosphatidylinositol and -phosphates, phosphatidylethanolamine, phosphatidylserine, phosphatidylglycerol, phosphatidic acid, and their plasmalogen analogues can be detected. The optimized ionization and fragmentation conditions described together with the principle of internal standardization by nonnatural analogues allow the rapid and quantitative determination of membrane lipid compositions down to sample amounts of 1000 cells.

Methods for the analysis of triacylglycerols

This article discusses the methods most commonly employed in the analysis of the triacylglycerols (TAGs) in natural fats and considers the main advantages and disadvantages of each and the techniques for optimising analytical conditions. Complete analysis of the composition of a natural fat calls for a method of extracting and purifying the triglyceride fraction, normally by preparatory thin-layer and column chromatography. Determination of the individual components of triglyceride mixtures still entails certain difficulties, namely, the separation and identification of the TAGs in natural fats. High-performance liquid chromatography (HPLC) offers significant advantages over gas and thin-layer chromatography. Many workers have developed non-aqueous, reversed-phase HPLC systems capable of successfully resolving complex mixtures of TAGs, and combining reversed-phase (RP) HPLC and argentation chromatography may improve the results. Identification of the TAGs separated by HPLC becomes an extremely complex task if many different fatty acids are involved and if the sn-stereoscopic positions on the glycerol are to be determined. Enzymatic analysis and chiral-phase chromatography are capable of localising fatty acids on the TAG molecule. In closing, some of the most interesting biomedical applications of TAG analysis are summarised.

Chromatographic separation of cholesterol in foods

Based on the current literature and on experience gained in the laboratory, a simplified procedure using direct saponification (0.4 M potassium hydroxide in ethanol and heating at 60 degrees C for 1 h) is the most appropriate method for the determination of total cholesterol in foods. Extraction of the unsaponifiable matter with hexane is efficient and no extra clean-up is required before quantification. An internal standard, 5 alpha-cholestane or epicoprostanol, should be added to the sample prior to saponification and, together with reference standards, carried through the entire procedure to ensure accurate results. A significant improvement in cholesterol methodology has been achieved by decreasing the sample size and performing all the sample preparation steps in a single tube. The method has the advantages of elimination of an initial solvent extraction for total lipids and errors resulting from multiple extractions, transfers, filtration and wash steps after saponification. The resulting hexane extract, which contains a variety of sterols and fat soluble vitamins, requires an efficient capillary column for complete resolution of cholesterol from the other compounds present. The development of fused-silica capillary columns using cross-linked and bonded liquid phases has provided high thermal stability, inertness and separation efficiency and, together with automated cold on-column gas chromatographic injection systems, has resulted in reproducible cholesterol determinations in either underivatized or derivatized form. If free cholesterol and its esters need to be determined separately, they are initially extracted with other lipids with chloroform-methanol followed by their separation by column or thin-layer chromatography and subsequently analysed by gas or liquid chromatography. Although capillary gas chromatography offers superior efficiency in separation, the inherent benefits of liquid chromatography makes it a potential alternative. Isotope dilution mass spectrometry has been widely accepted as a reliable analytical method for highly accurate determination of cholesterol in serum and several definitive methods have been reported. The combination of capillary gas chromatography with mass spectrometry has become an excellent approach for the determination of cholesterol in complex mixtures of sterols and tocopherols, providing high resolution with positive identification. When used to determine cholesterol in multi-component foods, spectrophotometric methods have been documented to overestimate significantly the amount of cholesterol owing to the presence of other interfering substances. A re-evaluation of food products should be undertaken using the more specific chromatographic methods to accumulate data that will more accurately reflect the true cholesterol content.

Thin-layer chromatography-flame ionization detection Iatroscan system

The thin-layer chromatography-flame ionization detection (TLC-FID) Iatroscan system is a technique which is still being evolved. Quantification with the TLC-FID system relies heavily on the accurate setting up and calibration of the instrument. An appreciation of the factors that influence the analysis can eliminate significant errors. At least a few of the numerous operating variables need to be fixed to obtain coherent results from different laboratories. Hydrogenation of the sample is recommended in order to improve quantification with the Iatroscan system. The improved reproducibility obtained with automatic sample spotters compared with manual spotting indicates that autosampling is highly advisable.

Separation and quantitation of phospholipids in animal tissues by Iatroscan TLC/FID

A procedure has been developed to separate and quantitate phospholipids, including phosphatidylinositol and phosphatidylserine, from animal tissues by means of the Iatroscan TLC/FID technique. The method is based on the use of 0.01 M oxalic acid impregnated Chromarods-SII and stepwise resolution of the phospholipids in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospho (N,N-dimethylethanolamine) as internal standard. To remove the neutral lipids, the rods are initially developed in a non-polar solvent mixture followed by partial scanning. Next, the rods are impregnated with oxalic acid, developed twice in CHCl3/CH3OH/CH3COOH/HCOOH/H2O (80:35:2:1:3, v/v/v/v/v) and partially scanned for measuring lysophosphatidylcholine, sphingomyelin and phosphatidylcholine. The subsequent step involves double development in CHCl3/CH3OH/30% NH4OH (60:35:0.9, v/v/v) to resolve cardiolipin, internal standard, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidic acid. For each phospholipid a linear calibration curve with a highly significant correlation coefficient was obtained. However, the calibration lines extrapolated to negative intercepts on the ordinate, indicating declining sensitivity at low phospholipid loads.

Separation and quantification of heart and liver phospholipid classes by high-performance liquid chromatography using a new light-scattering detector

This work describes a one-step separation of rat tissue phospholipid classes by high-performance liquid chromatography (HPLC) using a silica column and a new light-scattering detector (LSD). Complete separation of phosphatidylcholine, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylserine, sphingomyelin, lysophosphatidylethanolamine, and lysophosphatidylcholine was obtained. Direct quantification was achieved after detector calibration for each phospholipid class. The detector response was shown to be linear within the ranges used. The LSD results agreed well with those obtained by phospholipid phosphorus assay. The present method was applied to rat heart and rat liver phospholipid analysis.

Myocardial changes in newborn piglets fed sow milk or milk replacer diets containing different levels of erucic acid

This study was undertaken to determine whether the neonate was more susceptible to the effects of dietary erucic acid (22:1n-9) than the adult. Newborn piglets were used to assess the safety of different levels of 22:1n-9 on lipid and histological changes in the heart. Newborn piglets showed no myocardial lipidosis as assessed by oil red 0 staining, but lipidosis appeared with consumption of sow milk and disappeared by seven days of age. Milk replacer diets containing soybean oil, or rapeseed oil mixtures with up to 5% 22:1n-9 in the oil, or 1.25% in the diet, gave trace myocardial lipidosis. Rapeseed oil mixtures with 7 to 42.9% 22:1n-9 showed definite myocardial lipidosis in newborn piglets, which correlated to dietary 22:1n-9, showing a maximum after one week on diet. The severity of the lipidosis was greater than observed previously with weaned pigs. There were no significant differences among diets in cardiac lipid classes except for triacylglycerol (TAG), which increased in piglets fed a rapeseed oil with 42.9% 22:1n-9. TAG showed the highest incorporation of 22:1n-9, the concentration of 22:1n-9 in TAG was similar to that present in the dietary oil. Among the cardiac phospholipids, sphingomyelin and phosphatidylserine had the highest, and diphosphatidylglycerol (DPG) the lowest level of 22:1n-9. The low content of 22:1n-9 in DPG of newborn piglets is not observed in weaned pigs and rats fed high erucic acid rapeseed oil. The relative concentration of saturated fatty acids was lowered in all cardiac phospholipids of piglets fed rapeseed oils, possibly due to the low content of saturated fatty acids in rapeseed oils. The results suggest that piglets fed up to 750 mg 22:1n-9/kg body weight/day showed no adverse nutritional or cardiac effects.

Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37-1200 days (liver) and 331-1200 days (heart)

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerol, free cholesterol, free fatty acids and phospholipids, as well as the fatty acid patterns of total lipids, were measured in liver homogenates of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. The same parameters were measured in the apex of the heart in female and male rats aged 331-1213 days. 3. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 4. The lipid fractions in liver showed a positive linear regression vs age, whereas all lipids in rat heart showed a negative regression vs age in both sexes. 5. The significance of regression vs age of fatty acids was much less than that in the lipid fractions of liver and heart of these animals.

Influence of excess dietary copper on lipid composition of calf tissues

Lipid composition of calf liver, heart, and skeletal muscle was measured, as affected by control Cu (10 ppm in DM), high Cu (1000 ppm), or high Cu plus high Zn (1000 ppm) in milk replacer. High dietary Cu increased all lipid classes in liver, some in the heart, and decreased all lipid classes except cholesterol in muscle. Zinc inhibited many of the changes in tissue lipid classes by excess copper. High Cu intake increased fatty acid unsaturation (palmitoleic, oleic, linoleic acids) and decreased stearic acid in phosphatidylcholine and phosphatidylethanolamine of liver and heart. Excess Cu tended to have an opposite effect in changing fatty acid concentrations in liver and muscle. Activities of various desaturases and elongases were estimated in liver, heart, and muscle using ratios of fatty acid precursors to products in combined phosphatidylcholine and phosphatidylethanolamine. High Cu intake frequently altered activities of these enzymes in all three tissues with additional high Zn usually coregulating activity in the direction opposite to Cu.

Planar chromatographic techniques in biomedicine: current status

In planar chromatography (PLC), the solvent flows through a layer either by means of capillary forces [conventional thin-layer chromatography (TLC)] or by a forced-flow system (over-pressured layer chromatography). Phases and instrumentation currently available are briefly examined. The main applications in biomedicine are reviewed. Although silica gel TLC plates still predominate, interest in other phases is increasing. Unique detection features such as immunostaining are emphasized. Although gas chromatography and high-performance liquid chromatography have superseded TLC in the analysis of carbohydrates, amino acids and indole derivatives, interest in PLC continues to be high in lipid analysis.

Testing a short-term feeding trial to assess compositional and histopathological changes in hearts of rats fed vegetable oils

Male, female and castrated rats, three wk of age, were fed a low-fat diet for 14 wk followed by high-fat diets (20% by weight) for one wk containing graded levels of erucic acid from 1 to 50%, to evaluate the effect of short-term feeding and interaction of male sex hormones on formation of heart lesions. Some rats within each group were returned to the low-fat diet for one wk after the test period. For comparison, one group of three-wk-old male rats was fed the high fat 50% erucic acid diet for 15 wk. Erucic acid depressed growth rate and food consumption and increased cardiac lipidosis and triglycerides proportional to the erucic acid content of the diet. There were no sex differences, and the effects disappeared once rats were returned to the low-fat diet for one week. There was a significance (P less than 0.05) in the incidence of myocardial necrosis among male rats fed increased levels of erucic acid for one week, but the response was not linear to the increase in dietary erucic acid. Furthermore, the response was much less than in males fed the 50% erucic acid diet continually for 15 weeks. These results suggest that the short-term model is not a suitable substitute for the long-term feeding trial to test the cardiopathogenicity of a vegetable oil. The significantly lower incidence in myocardial lesions in female and castrated male rats compared with male rats suggests involvement of sex hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration of thin-layer chromatography with flame ionization detection for the analysis of natural lipid samples

Thin-layer chromatography coupled with flame ionization detection has been used to develop a method to quantitate fish lipids. Quantitation of fractionated lipid classes is usually accomplished through calibration with standards. Our work shows that various standards within a class, such as triglycerides or free fatty acids give substantially different responses to the detector. A method has been developed in which a composite sample of salmon lipid is prepared with an internal standard. This technique eliminates the variable detector response observed for compounds within a class and provides more accurate quantitation of oils from which the calibration samples were prepared. The lipid classes quantitated were triglycerides, free fatty acids, phosphatidylethanolamine and phosphatidylcholine.

Neutral lipid storage disease with ichthyosis: lipid content and metabolism of fibroblasts

Neutral lipid storage disease with ichthyosis is a newly recognized heritable disorder characterized by widespread cellular triglyceride storage. Lipid metabolism in fibroblasts cultured from three affected family members was studied. The stored lipid is triglyceride composed of an unremarkable fatty acid profile and derived from both exogenously-supplied and endogenously-synthesized fatty acids. Lipid storage could not be corrected by prolonged culture in lipid-depleted media. Acetyl CoA carboxylase activity and beta-oxidation of palmitate were both normal. Taken together, these studies exclude a primary defect of fatty acid uptake, over-synthesis or impaired beta-oxidation. Moreover, triacylglycerol lipase activity of homogenates of fibroblasts from patients with NLSDI examined over the range of pH 3.5-8.5 was normal.

Lipids and their constituents

Many tissues, cells and body fluids possess characteristic lipid composition that can be readily recognized without full resolution and quantitation of individual molecular species. Various chromatographic methods have been adopted for this purpose and are extensively employed in biomedical research. Although lipid profiles are known to change with disease and lipid profiling holds considerable potential for clinical diagnosis, few routines have been established for this purpose. This is partly due to the laborious nature of the simpler methods and the high cost of automated systems. A combination of thin-layer or liquid chromatography with universal detection systems promises to provide more attractive analytical routines for clinical application in the future. At present thin-layer chromatography is the simplest and most rapid qualitative assay for both neutral and polar lipids. Low-temperature gas chromatography is still the method of choice for fatty acid analyses, while high-temperature gas chromatography is eminently suited for quantitative analysis of intact neutral lipids. The availability of the flame ionization and mass detectors now makes high-performance liquid chromatography more useful for profiling both neutral and polar lipids. Combinations of gas or liquid chromatography with mass spectrometry must remain of specialized interest only because of the prohibitive costs of operation.