Major plasma lipids and fatty acids in four HDL mammals

Lipid classes and their fatty acids were compared in plasma from four mammals: a laboratory rodent, the mouse; two domestic animals, the cat and dog; and a wild animal, the South American armadillo, Chaetophractus villosus. In all, the most abundant lipoprotein was high-density lipoprotein (HDL). In the total lipid of plasma, phospholipids (PL) predominated in all four species, in correlation with the proportion of HDL, both being largest in dogs. The major PL was phosphatidylcholine (PC), followed by sphingomyelin (SM) and lysophosphatidylcholine. The total plasma lipid from the four species contained long-chain n-6 polyunsaturated fatty acids as the predominant acyl groups, followed by comparable proportions of total saturated and monoenoic fatty acids and small percentages of n-3 PUFA. The percentages of these four major groups of fatty acids in PC, SM, triacylglycerols and cholesterol esters were similar among species, but showed significant differences in the ratios between major individual fatty acids composing these groups.     

Effect of exercise and medium-chain fatty acids on postprandial lipemia.

The purpose of this study was to evaluate the effect of medium-chain triglycerides (MCT) with and without exercise on postprandial lipemia (PPL). Subjects were 25 young men and women. Each subject performed three trials: 1) control (fat meal only, 1.5 g fat/kg) 2) MCT (substitution of MCT oil, 30% of fat calories), and 3) MCT + Ex (exercise 12 h before the MCT meal). Before each trial, the subject underwent consistent dietary preparation. Blood was collected on 2 separate days for baseline measurements of postheparin lipases and, in each trial, at 0 h (premeal), at 2, 4, 6, and 8 h after the fat meal for triglycerides and cholesterol ester transfer protein (CETP), and at 8 h for postheparin lipoprotein lipase (LPL) and hepatic lipase activities (HL). ANOVA indicated that the partial substitution of MCT oil to the fat meal did not affect the PPL response. However, the PPL was significantly lower after the MCT + Ex trial vs. the other trials. LPL activity was significantly elevated after all trials compared with baseline, whereas HL was lower in the MCT + Ex trial only. CETP mass was significantly lower at 4 and 8 h than 0 h during all trials but relatively higher in the MCT + Ex trial vs. the nonexercise trials. These results suggest that MCT does not affect the TG response to a fat meal. LPL and CETP are affected by a fat meal with or without exercise, but HL is affected only when exercise is included.     

Effect of carbohydrate or carbohydrate plus medium-chain triglyceride ingestion on cycling time trial performance.

This study examined the effectiveness of ingesting a carbohydrate or carbohydrate + medium-chain triglycerides (MCT) on metabolism and cycling performance. Eight endurance-trained men [peak O(2) uptake = 4.71 +/- 0.09 (SE) l/min] completed 35 kJ/kg as quickly as possible [time trial (TT)] while consuming 250 ml/15 min of either a 6% (wt/vol) carbohydrate solution (C), a 6% carbohydrate + 4.2% MCT solution (C+M), or a sweet placebo (P). Time to complete the set amount of work was reduced in both C and C+M compared with P by 7 and 5%, respectively (C: 166 +/- 7 min; C+M: 169 +/- 7 min; P: 178 +/- 11 min; P < 0.01). Plasma glucose concentration was maintained at or above resting values throughout both C and C+M trials but decreased (P < 0.05) below resting values in P at the completion of the TT. The estimated rate of carbohydrate oxidation was not different during the first 90 min of exercise but thereafter was reduced (P < 0.05) in P and was maintained in both C and C+M. These data demonstrate that carbohydrate ingestion during exercise improves 100-km TT performance compared with a sweet placebo, but the addition of MCT does not provide any further performance enhancement.     

A mass spectrometry-based high-throughput screening method for engineering fatty acid synthases with improved production of medium-chain fatty acids

Microbial cell factories have been extensively engineered to produce free fatty acids (FFAs) as key components of crucial nutrients, soaps, industrial chemicals, and fuels. However, our ability to control the composition of microbially synthesized FFAs is still limited, particularly, for producing medium-chain fatty acids (MCFAs). This is mainly due to the lack of high-throughput approaches for FFA analysis to engineer enzymes with desirable product specificity. Here we report a mass spectrometry (MS)-based method for rapid profiling of MCFAs in Saccharomyces cerevisiae by using membrane lipids as a proxy. In particular, matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) MS was used to detect shorter acyl chain phosphatidylcholines from membrane lipids and a higher m/z peak ratio at 730 and 758 was used as an indication for improved MCFA production. This colony-based method can be performed at a rate of ~2 s per sample, representing a substantial improvement over gas chromatography-MS (typically >30 min per sample) as the gold standard method for FFA detection. To demonstrate the power of this method, we performed site-saturation mutagenesis of the yeast fatty acid synthase and identified nine missense mutations that resulted in improved MCFA production relative to the wild-type strain. Colony-based MALDI-ToF MS screening provides an effective approach for engineering microbial fatty acid compositions in a high-throughput manner.     

Polyunsaturated fatty acids in plasma and erythrocyte membrane lipids of diabetic children

While insulin is a potent activator of essential fatty acid metabolism, portal hypoinsulinemia is common in Type 1 diabetes. Fatty acids were determined by high-resolution capillary gas-liquid chromatography in plasma and erythrocyte membrane lipids in diabetic children (n = 40) and in age-matched healthy controls (n = 40). In plasma phospholipids, values of linoleic acid (23.00 [2.35] vs. 18.13 [2.54], % by wt, median [range from the first to the third quartile], P<0.000l) and alpha-linolenic acid (0.12 [0.06] vs. 0.07 [0.07], P<0.05) were significantly higher in diabetic children than in controls. In contrast, values of arachidonic acid (10.73 [2.34] vs. 11.53 [2.50], P<0.05) and docosahexaenoic acid (2.23 [0.63] vs. 2.77 [0.98], P<0.01) were significantly lower in diabetic children than in controls. Reduced availability of long-chain polyunsaturates in diabetic children suggests that an enhanced dietary supply of long-chain polyunsaturates may be beneficial.     

Effects of dietary monounsaturated fatty acids on plasma lipids in humans

In order to test whether monounsaturated fatty acids (MUFA, M) would lower plasma cholesterol and/or triglycerides (TG), 14 young men were studied in a metabolism ward. They were given two experimental diets with the same P/S ratio (P: polyunsaturated; S:saturated fatty acids) but different P + M/S ratios in composition of dietary fatty acids. Six men were in experiment I. In two groups of three, each group was given either the high or the low P + M/S ratio diet for 6 weeks. In experiment II, two groups of four men were subjected to a 3-week cross-over feeding trial (total of 6 weeks). We found in the crossover study that when the dietary P/S ratio was fixed at 1.0, those subjects given a diet with the higher P + M/S ratio of 4.5 showed significantly higher plasma total TG, very low density lipoprotein (VLDL)-TG, low density lipoprotein (LDL)-TG, and LDL-cholesterol than when given a diet with a lower P + M/S ratio of 1.5. Plasma total cholesterol, apoprotein A-I, and apoprotein B-100 were not significantly different between the two dietary periods. Plasma fatty acid patterns showed a significantly higher plasma MUFA level during the period of a higher P + M/S diet. In contrast to some recent reports, our studies indicate that a large amount of dietary MUFA may raise some fractions of plasma lipids in humans.     

Effects of highly purified structured lipids containing medium-chain fatty acids and linoleic acid on lipid profiles in rats

The purpose of this study is to examine the effects of highly purified structured lipids on serum and liver lipid profiles in rats. We also investigated in vitro hydrolysis of lipid emulsions by porcine pancreas. Hydrolysis rates of medium chain (M)-linoleic (L)-medium chain (M) types were 2 to 3 times higher than those of L-M-L types. The diet containing structured lipids or corn oil was administered to rats for 4 weeks. There were no significant differences in growth and food efficiency. Serum cholesterol levels were significantly lower (P<0.05) in the 2-octanoyl-1,3-dilinoleoyl-glycerol, 2-linoleoyl-1,3-didecanoyl-glycerol, and 2-decanoyl-1,3-dilinoleoyl-glycerol groups than in the corn-oil group. Serum triglyceride levels were significantly lower (P<0.05) in rats fed L-M-L types than those in the other groups. Serum non-esterified fatty acid (NEFA) and beta-hydroxybutylate levels were significantly higher (P<0.01) in rats fed M-L-M types than those of the other groups. These results indicate that the feeding of highly purified L-M-L types could effectively improve serum and liver lipid profiles and that M-L-M types may be a preferable substrate for the pancreas and contribute to energy supply in rats.     

The effects of n-3 and n-6 polyunsaturated fatty acids on plasma lipids and fatty acids of treated phenylketonuric children

Dietary-treated phenylketonuric patients (PKUs) display low levels of long-chain polyunsaturated fatty acids (PUFA) in plasma lipids. In a 6-month clinical trial we observed a decrease of triglycerides and an increase of n-3 long-chain PUFA in plasma of PKUs supplemented with fish oil, while no major differences in respect to the baseline values were found in a group supplemented with blackcurrant oil. A more complete source of long-chain PUFA of both the n-6 and n-3 series should be investigated for dietary supplementation of PKU patients.     

Age-associated changes in rat plasma lipids, platelet fatty acids and prostacyclin release

The effect of age on plasma lipids, platelet fatty acids and prostacyclin release was studied in the rat. The contents of arachidonic acid, cholesterol, bile acids and free fatty acids in the plasma of aged rats (15 months old) were higher than those of young rats (3 months old). No significant differences in fatty acid composition of platelet lipids and release of prostacyclin from aortas between young and aged rats were observed. The data suggest that plasma lipids may play a more important role in the development of cardiovascular disease with increasing age than prostaglandins do.     

Biosynthesis of medium-chain fatty acids by mammary epithelial cells from virgin rats.

Epithelial cells were isolated from the undifferentiated mammary glands of mature virgin female rats, and their lipogenic characteristics were studied. These cells synthesized predominantly medium-chain fatty acids, albeit at a low rate. In contrast, whole tissue from mammary glands of virgin rats synthesized predominantly long-chain fatty acids at a relatively higher rate, indicating that the lipogenic activity is dominated by the adipocyte component of the gland. Enzyme assays revealed that thioesterase II, the enzyme which regulates production of medium-chain fatty acids by the fatty acid synthetase, was present at a high activity in the undifferentiated mammary epithelial cells of virgin rats. Immunohistochemical studies confirmed this observation and showed that the regulatory enzyme was present exclusively in the epithelial cells lining the alveolar and ductal elements of the undifferentiated gland. This study demonstrates that the potential to elaborate tissue-specific medium-chain fatty acids is already expressed in the undifferentiated tissue of virgin rats and is not acquired as a result of the differentiation associated with the lactogenic phase of development. In this species mammary epithelial cells apparently synthesize predominantly medium-chain fatty acids at all stages of development, and only the overall rate of synthesis is increased on induction of the fatty acid synthetase during lactogenesis.     

Silver ion chromatography of lipids and fatty acids

Silver ion chromatography as applied to the analysis of lipids is reviewed. Thin-layer, column, high-performance liquid and supercritical fluid chromatography in the silver ion mode are included. The lipid types covered are fatty acids, triacylglycerols and complex lipids. Separations are divided into those according to number, geometry and position of double bonds, as well as acyl positional isomers for triacylglycerols. The mechanism of silver ion chromatography is discussed in relation to recent studies using silver ion high-performance liquid chromatographic methodology.     

Bone lipids and fatty acids of Peru fish

The neurocranium of the vieja, Pimelometopon darwini, and the cojinoba, Seriolella violacea, contained 29.5 and 26% lipid (as percent dry weight), mostly as triacylglycerol. The anchoveta, Engraulis ringens; sardina, Sardinops sagax sagax; doncella, Halichoeres dispilis; and mackerel, Scomber japonicus, contained less lipid in the neurocranium (3.3–18.4%). Polyunsaturated fatty acids, dominated by 20:5 and 22:6, were highest for S. violacea (10.6–56.1%) and P. darwini (12.2–28.9%). Lower levels of polyunsaturated fatty acids were found in E. ringens. The major monosaturated fatty acids in all Peruvian fish included 16:1n7, 18:1n9 + 11, and 18:n7, whereas the major saturated fatty acids were 14:0 and 16:0 with lesser amounts of 18:0.     

Effects of adrenaline on ketogenesis from long- and medium-chain fatty acids in starved rats.

1. Injection of adrenaline into 24 h-starved rats caused a 69% decrease in blood [ketone-body] (3-hydroxybutyrate plus acetoacetate), accompanied by a decreased [3-hydroxybutyrate]/[acetoacetate] ratio. Blood [glucose] and [lactate] increased, but [alanine] was unchanged. 2. Adrenaline also decreased [ketone-body] after intragastric feeding of both long- and medium-chain triacylglycerol. The latter decrease was observed after suppression of lipolysis with 5-methylpyrazole-3-carboxylic acid, indicating that the antiketogenic action of adrenaline was not dependent on the chain length of the precursor fatty acid. 3. The actions of adrenaline to decrease blood [ketone-body] and to increase blood [glucose] were not observed after administration of 3-mercaptopicolinate, an inhibitor of gluconeogenesis. This suggests that these effects of the hormone are related. 4. The possible clinical significance of the results is discussed with reference to the restricted ketosis often observed after surgical or orthopaedic injury.     

One-step quantitative extraction of medium-chain and long-chain fatty acids from aqueous samples

Medium-chain (C(6) and longer) fatty acids, as well as 12-hydroxystearic and long-chain fatty acids, can be quantitatively extracted into toluene and titrated in the toluene phase with tetrabutylammonium hydroxide. The method may be useful in determinations of fecal and serum fatty acids and of the products of lipolysis.     

Determination of volatile fatty acids in plasma after ethanolic extraction

1. A new rapid micro-method for measuring plasma volatile fatty acids is described. The volatile fatty acids are extracted from plasma with ethanol in the presence of a known quantity of internal standard (sodium isobutyrate). After evaporation of the ethanolic solution of the sodium salts, the residue is dissolved in a dilute solution of orthophosphoric acid to permit analysis by g.l.c. 2. A technique of g.l.c. analysis is described which permits the separation of all the volatile fatty acids from the other plasma constituents at temperatures below 100 degrees C in 5 min. 3. Steam-distillation techniques are unsatisfactory when the acetic acid concentrations in the plasma are below 0.2mm. Heating of a number of plasma constituents in acid conditions gives rise to acetic acid. 4. The binding of volatile fatty acids to plasma proteins was studied; this binding is negligible for acetic acid, but increases with the length of the fatty acid carbon chain. 5. The limits of use of the method and the physiological implications are discussed.     

Effect of long- and medium-chain fatty acids on insulin secretion from pieces of rat pancreas.

The effect of fatty acids on insulin secretion in vitro was investigated. Pieces of pancreas from fed rats were incubated for 15 or 90 min at low (0.6 mg/ml) and high (3.0 mg/ml) glucose concentrations with and without either sodium octanoate or sodium oleate. A highly significant difference in insulin secretion between low and high glucose concentrations indicated viability and responsiveness of the incubated tissue. No statistically significant effect of octanoate or oleate on insulin secretion was found at either low or high glucose concentration. Thus, no support was found for the concept that medium- and long-chain free fatty acids are insulin secretagogues.     

Changes in liver microsome lipids and plasma fatty acids induced by dietary orotate in the weanling rat.

1. Dietary orotate produced a decrease in total plasma fatty acids which was reflected in low values of saturated, monounsaturated and polyunsaturated fatty acids longer than 18 carbon atoms of the n-6 series. The relative content of saturated fatty acids in microsomes of animals fed orotate was also decreased. 2. Rat liver delta-9 desaturase activity was lower in the group fed orotate. However, delta-6 desaturase activity did not show significant differences between the groups. 3. Microsomal cholesterol content was lower in rats fed orotate than in controls but phospholipid phosphorus contents were similar. These results suggest a direct effect of dietary orotate on the key enzymes which regulates cholesterol liver metabolism.