Plasma Unesterified Fatty Acids Research Articles

Fluorimetric determination of plasma unesterified fatty acid

A reliable and simple method is described for the determination of plasma unesterified fatty acid. The method involves extraction by Dole's reagent, washing with dilute sulphuric acid and determination by the decrease of fluorescence of a dilute solution of 7-hydroxy-4-methylcoumarin. Results on rat and human plasma are in good agreement with those obtained by titration.

Lipids of Plasmodium lophurae, and of Erythrocytes and Plasmas of Normal and P. lophurae-Infected Pekin Ducklings

A lipid analysis was performed on the avian malaria parasite Plasmodium lophurae, freed from duckling erythrocytes by immune hemolysis, and on the erythrocytes and plasmas of normal and P. lophurae-infected ducklings. Major lipids of normal erythrocytes were: phosphatidylcholine (40% of total lipids), phosphatidylethanolamine (20%), cholesterol (20%), sphingomyelin (11%), and glycosphingolipids (5%). Major fatty acids of erythrocyte total phospholipids (74% of total lipids) were 16:0 (22%), 18:2 (n-6) (21%), 18.1 (n-7, n-9) (18%), 18:0 (9%), 20:4 (n-6) (9%), 22:6 (n-3) (5%). Erythrocyte phosphatidylcholine was greater than 90% the diacyl form, while phosphatidylethanolamine was approximately 44% alkoxy forms and phosphatidylinositol approximately 11% alkoxy forms. Major fatty aldehydes of phosphatidylethanolamine were 16:0 (47%), 18:1 (23%), 18:0 (14%), and 14:0 (12%). The lipid composition of P. lophurae (plus the parasitophorous vacuole membrane) was qualitatively and quantitatively different from that of the duckling erythrocyte in a number of respects. Major lipids were phosphatidylcholine (40%), phosphatidylethanolamine (36%), cholesterol (8%), phosphatidylinostol (4%), 1,2-diacylglycerols (3%), sphingomyelin (2%), and glycosphingolipids (2%). Diphosphatidylglycerol (approximately 1%) was also detected. The major fatty acids of parasite total phospholipids (86% of total lipids) were more saturated than those of the erythrocyte, and octadecenoic acids were notably elevated: 18:1 (33%), 16:0 (26%), 18:0 (16%), 18:2 (12%), 20:4 (3%), and 22:6 (3%). Parasite phosphatidylcholine and phosphatidylethanolamine were greater than 93% the diacyl form and phosphatidylinositol was approximately 25% alkoxy forms. Major fatty aldehydes of the phosphatidylethanolamine were 14:0 (62%), unidentified long chain forms (24%), 16:0 (7%), 18:0 (4%), 18:1 (3%). The lipid composition of the infected erythrocyte reflected the separate contributions of the erythrocyte and parasite. The major lipids of normal duckling plasma were phosphatidylcholine (33%), triacylglycerols (22%), cholesterol esters (20%), cholesterol (12%), phosphatidylethanolamine (5%), and sphingomyelin (2%). The fatty acids of plasma total lipids were 18:1 (26%), 16:0 (26%), 18:2 (12%), 20:4 (12%), 18:0 (9%), 22:6 (3%). Plasma phosphoglycerides were remarkably lower in C18 unsaturated fatty acids and higher in 20:4 than the erythrocyte phosphoglycerides. Infection of ducklings with P. lophurae caused increases in plasma unesterified fatty acids, triacylglycerols and cholesterol esters, and a notable rise in the 18:1 content of all fatty acid-containing plasma neutral lipids. These findings are compared with those reported for other species of Plasmodium infecting other avian and mammalian hosts.

Effect of aminophylline on tryptophan and other aromatic amino acids in plasma, brain and other tissues and on brain 5-hydroxytryptamine metabolism.

1 Aminophylline and other methylxanthines increase brain tryptophan and hence 5-hydroxytryptamine turnover. The mechanism of this effect of aminophylline was investigated. 2 At lower doses (greater than 100 mg/kg i.p.) the brain tryptophan increase could be explained by the lipolytic action of the drug, i.e. increased plasma unesterified fatty acid freeing plasma tryptophan from protein binding so that it became available to the brain. 3 Plasma unesterified fatty acid did not increase when aminophylline (109 mg/kg i.p.) was given to nicotinamide-treated rats but as both plasma total and free tryptophan rose, a tryptophan increase in the brain still occurred. 4 The rise in brain tryptophan concentration following the injection of a higher dose of the drug (150 mg/kg i.p.) could no longer be explained by a rise of plasma free tryptophan as the ratio of brain tryptophan to plasma free tryptophan rose considerably. Plasma total tryptophan fell and the plasma insulin concentration rose. 5 The increase of brain tryptophan concentration after injection of 150 mg/kg aminophylline appeared specific for this amino acid as brain tyrosine and phenyllanine did not increase. However as their plasma concentrations fell the brain/plasma ratio for all three amino acids rose. 6 The higher dose of aminophylline increased the muscle concentration of tryptophan but that of tyrosine fell and that of phenylalanine remained unaltered. The liver concentrations were not affected. 7 The aminophylline-induced increase of the ratio of brain tryptophan of plasma free tryptophan no longer occurred when the drug was given to animals injected with the beta-adrenoreceptor blocking agent propranolol or the diabetogenic agent streptozotocin. 8 The changes in brain tryptophan upon aminophylline injection may be explained by (a) increased availability of plasma tryptophan to the brain due to increased lipolysis and (b) increased effectiveness of uptake of tryptophan by the brain due to increased insulin secretion.

Control of brain tryptophan concentration in rats on a high fat diet.

SYNTHESIS in the brain of the neurotransmitter 5-hydroxytryptamine (5-HT) is influenced by the concentration of its precursor tryptophan1,2. Much attention has therefore been paid to the determinants of brain tryptophan concentration. Evidence suggests that plasma free tryptophan is an important influence on brain tryptophan3,4 and that both concentrations increase when plasma unesterified fatty acids (UFA) rise3,5,6 and release plasma tryptophan from albumin7,8. Other results, however, disagree. Thus feeding rats for 2 h with high fat diets apparently led to large increases in serum UFA and free tryptophan but not brain tryptophan9,10,11. We now present evidence suggesting that the latter findings may have been due to in vitro lipolysis during either the preparation of serum or its dialysis at 37 °C for 3.5 h to separate free tryptophan9. Here we describe work in which precautions were taken to avoid in vitro changes and which is consistent with a relationship between plasma free tryptophan and brain tryptophan concentrations.

Rapid effects of environmental disturbance on rat plasma unesterified fatty acid and tryptophan concentrations and their prevention by antilopolytic drugs.

1 Changes of plasma unesterified fatty acid (UFA) and tryptophan concentration in group-housed rats following removal of their cage-mates and the effects of antilipolytic drugs on these changes were investigated. 2 Removal of group-housed 24 h fasted rats but not fed rats from cages resulted in increased plasma UFA concentration in the remaining rats which was associated with significant increases of the proportion of free tryptophan but significant falls of total tryptophan concentration. These rapid changes were not associated with brain tryptophan changes. Plasma tyrosine concentration was unaffected. 3 The fall of plasma tryptophan did not appear to be due to passage into red cells as erythrocyte tryptophan concentration remained unchanged. 4 Plasma UFA concentrations correlated positively and significantly with corticosterone concentrations which were also increased following removal of cage-mates. 5 Plasma UFA increases and tryptophan changes in the fasting rats were both prevented by nicotinic acid or propranolol. Corticosterone concentration was increased by nicotinic acid but unaffected by propranolol. 6 The possible importance of these rapid changes of plasma tryptophan and of their prevention by antilipolytic drugs is discussed.

Effect of electroconvulsive therapy on plasma unesterified fatty acid and free tryptophan concentrations in man.

Effect of electroconvulsive therapy on plasma unesterified fatty acid and free tryptophan concentrations in man.

Effects on plasma and brain tryptophan in the rat of drugs and hormones that influence the concentration of unesterified fatty acid in the plasma.

1 The effects on tryptophan distribution and metabolism of drugs altering plasma unesterified fatty acid (UFA) concentration were investigated in the rat.2 UFA and plasma free (i.e. ultrafilterable) tryptophan altered in the same direction.3 Catecholamines and L-DOPA increased both plasma UFA and free tryptophan. L-DOPA also increased brain tryptophan and 5-hydroxyindoleacetic acid (5-HIAA) but decreased brain 5-hydroxytryptamine (5-HT).4 Aminophylline increased plasma UFA and free tryptophan and also brain tryptophan, 5-HT and 5-HIAA. Food deprivation had qualitatively similar effects.5 Insulin decreased plasma UFA and free tryptophan in both fed and food-deprived rats. However, while in fed rats these changes were associated with small decreases of brain indoles, in food-deprived animals small increases occurred.6 Nicotinic acid had only small effects in fed rats but it opposed both the UFA and indole changes in food-deprived animals. Total plasma tryptophan increased in nicotinic acid treated, food-deprived rats.7 There was a tendency towards inverse relations between changes of plasma free and total tryptophan.8 The results suggest that drugs which influence plasma UFA through actions on cyclic AMP thereby alter the binding of tryptophan to plasma protein and that this leads to altered distribution and metabolism of tryptophan.

Plasma and brain tryptophan changes in experimental acute hepatic failure.

AbstractAn experimental model for acute hepatic failure in man was obtained in pigs by hepatic devascularization. After operation, liver function was grossly impaired, movements became inco‐ordinated and coma ensued. Most animals died 5½–8½ h after operation. Plasma unesteritied fatty acid and free (but not total) tryptophan concentrations rose markedly after operation and correlated significantly with each other. Brain tryptophan concentration increased and correlated significantly with plasma free tryptophan concentration. Increased tryptophan was found in the four brain regions studied (hypothalamus, thalamus, caudate and cortex) and was associated with raised 5‐hydroxytryptamine turnover as indicated by raised 5‐hydroxyindolylacetic acid concentration. Results are discussed in relation to altered tryptophan metabolism in human hepatic coma and to investigations of the influence of plasma unesterified fatty acid and free tryptophan changes on brain tryptophan metabolism in the rat.

Lipoprotein lipase activity in the adipose tissue of rats adapted to controlled feeding schedules.

1. The relationships between nutritional state, lipoprotein lipase activity in epididymal fat-pads, and the concentrations of glucose, insulin and unesterified fatty acids in the plasma were studied in rats that had been adapted for 3 weeks to one of two controlled feeding schedules. In one of these, rats had access to food for 14h during each 24h period, and in the other, they had access to food for 14h during each 48h period. Groups of animals were killed at different times during the 14h when they had access to food and during the following period when they were deprived of food. 2. Low lipoprotein lipase activity, low concentrations of plasma glucose and insulin and high concentrations of plasma unesterified fatty acids were found in rats deprived of food for 34h. Feeding resulted in increases in lipoprotein lipase activity and in the concentrations of glucose and insulin in the plasma. Enzyme activity continued to increase during the first 6-9h of the feeding period. 3. After adapted rats had been deprived of food for 12-16h there was a marked and unexpected increase in lipoprotein lipase activity; this occurred even when the rats were kept in an isolated environment. 4. The findings suggest that factors other than the absolute concentrations of insulin and glucose in the blood can exert a considerable influence on lipoprotein lipase activity in the epididymal fat-pad of a rat.

Effect of Intraventricular Noradrenaline and Acetylcholine on Plasma Unesterified Fatty Acid Concentration in Sheep

Noradrenaline (3 µ g/kg) injected into a lateral cerebral ventricle of sheep exposed to –15 °C caused a fall in plasma unesterified fatty acid (UFA) concentration. Acetylcholine with

Dopamine and Mast Cells in the Adipose Tissue of the Ox and the Effect of Noradrenaline and Dopamine Infusions on the Plasma Unesterified Fatty Acids

SUMMARY The catecholamines of ox adipose tissue were extracted and separated using thin layer chromatography. The predominant catecholamine present has the same R f value as standard dopamine. Using a formaldehyde fluorescence technique it was shown that the tissue mast cells of ox adipose tissue contained a primary catecholamine which was thought to be dopamine. Using acridine orange stain the same cells were then shown to contain heparin. Intravenous infusion of 1 μg./kg. body weight)min. of noradrenaline caused an increase in the plasma unesterified fatty acids (UFA) from 8·2 to 36·0 mg./100 ml. and infusion of dopamine (5 μg./kg. body weight/min.) caused a rise in plasma UFA from 5·4 to 11·1 mg./100 ml. The action of bothnoradrenaline and dopamine on plasma UFA could be blocked by the β-blocking agent propranolol.

The effect of intraventricular noradrenaline on plasma unesterified fatty acid concentration in the ox

1. Injecting noradrenaline (3 μg/kg body wt) into a lateral ventricle of the brain of oxen exposed to cold environmental conditions (−1°C and wind speed 120 m/min) resulted in a fall in plasma unesterified fatty acid concentration, oxygen consumption and rectal temperature. 2. This effect on oxygen consumption and rectal temperature was not apparent in animals given intraventricular noradrenaline together with a simultaneous intravenous infusion of noradrenaline (0.3 μg/kg min). In these circumstances the plasma unesterified fatty acid concentration was raised. 3. It is concluded that intraventricular injection of noradrenaline results in inhibition of fat mobilization, which may in turn inhibit heat production of oxen in a cold environment.

The relationship between plasma lipid composition and milk fat secretion in cows given diets containing soybean oil.

SummaryThe effects on the composition of the plasma lipids of the isocaloric replacement of starch in a low-fat concentrate mixture by 8 % soybean oil were investigated in a feeding experiment with 6 cows in mid-lactation. Two high-fat concentrate mixtures were given: in one, the soybean oil was incorporated into the diet by the inclusion of the appropriate amount of coarsely ground soybeans; in the other, the soybean oil was incorporated directly in the concentrate mixture. The concentrate mixtures were given with a high-roughage diet that supplied daily 5·5kg hay and 2·7kg of sugar-beet pulp.When the cows were given the 2 high-fat diets there were increases in the concentrations of total plasma fatty acids and in the concentrations of fatty acids circulating in the plasma as phospholipids and cholesteryl esters. There were increases in the concentrations of plasma unesterified fatty acids and triglyceride fatty acids when the cows were given the diet containing soybeans but there were decreases in the concentrations of these 2 fractions when the cows were given the diet containing soybean oil.The inclusion of soybeans in the diet increased the concentration of 18:0 in the plasma triglycerides and unesterified fatty acids whilst the inclusion of soybean oil in the diet increased the concentrations of 18:0 and 18:1 but decreased the concentration of 18:2 in the plasma unesterified fatty acids.When the cows were given the 2 high-fat diets there were decreases in the concentrations of 16:0 and 16:1 and increases in the concentration of 18:2 in the plasma cholesteryl esters. The inclusion of soybeans in the diet also reduced the concentrations of 18:1 and 20:3 in the plasma cholesteryl esters but increased the concentrations of 18:0 and 18:2 in the plasma phospholipids.The major fatty acid circulating in the plasma of the cows was 18:2 (46·4–55·3%) on all diets but only about 1% (0·40–1·04%) of the total plasma 18:2 occurred in the plasma triglycerides.The results are discussed in relation to the changes in the composition of the milk fatty acids produced by the cows when they were given the experimental diets.

Cancer and lipid depletion.

AbstractHyperlipemia developing in tumor‐bearing animals concomitant with depletion of carcass lipid prompted study of human cancers. Gross lipemia when liver function is normal is infrequent in human cancer. Mean serum triglycerides and unesterified fatty acids (UFA) are higher than in normal individuals, but no greater than in patients undergoing severe fat depletion from causes other than cancer. Total plasma fatty acids and cholesterol concentrations in human cancer are normal. An in vivo rat assay for fat‐mobilizing substances in the urine and plasma of cancer patients was negative. The mobilization of carcass lipid in human cancer appears to be in response to an energy deficit created by actively synthesizing tumor tissue. There is no significant difference between nonneoplastic surgery and resective surgery for cancer in regard to mobilization of fat for energy substrates. Even though humans with malignancies deplete their fat stores, they are still able to respond to surgical stress by mobilizing fat from storage depots and transiently elevating plasma UFA.

The Effect of Intravenous Infusion of Dopamine on the Unesterified Fatty Acids of Sheep Plasma

Intravenous infusion of 5 μg./kg. min, dopamine for 25 min, in sheep caused a rise in plasma unesterified fatty acids from 10.5 mg. to 16.6 mg./100 ml. plasma. The percentage of oleic acid in the total plasma unesterified fatty acids increased during dopamine infusion from 30.8 to 36.4% and the percentage of stearic acid decreased from 43.5 to 38.2%.

The Effects of the Intravenous Administration of Noradrenalin on the Composition of the Plasma Lipids of Sheep

SUMMARY The plasma lipid composition was determined in sheep after they had been given intravenous infusions of isotonic saline or isotonic saline containing noradrenalin. The noradrenalin was infused over a period of 1 hr. at the rate of 2 µg./kg. bodyweight/min. The administration of noradrenalin resulted in a marked increase in the concentration of unesterified fatty acids in the plasma, and in the concentration oj oleic acid in the plasma unesterified fatty acids. Noradrenalin administration had no effect on the concentrations of cholesteryl esters, triglycerides or phospholipids in the plasma or on the fatty acid composition of these plasma lipids.

The relationships between dietary fatty acids, plasma lipid composition and milk fat secretion in the cow

SummaryThe effects of the isocaloric replacement of starch in a low-fat concentrate mixture by either 5 or 10% ‘stearic acid’ (85% pure) or by 10% ‘palmitic acid’ (85% pure) on the composition of the plasma lipids were investigated in a feeding experiment with 12 cows in mid-lactation. The concentrate mixtures were given with a high roughage diet that supplied daily 4·4 kg of hay and 2·7 kg of sugar-beet pulp. A study was made of the relationships between the compositions of the plasma and milk lipids.The inclusion of 10% ‘stearic acid’ or 10% ‘palmitic acid’ in the concentrate mixture increased the concentration of total plasma fatty acids. Irrespective of dietary treatment, about 40% of the total plasma fatty acids occurred in the cholesteryl ester fraction, 54% in the phospholipid fraction, 3% in the triglyceride fraction and 3% in the unesterified fatty acid fraction. There was a positive curvilinear relationship between the concentration of unesterified fatty acids in the plasma and the yield of total milk fatty acids.In the plasma triglycerides, the concentrations of 16:0 and 16:1 were decreased and the concentration of 18:0 was increased when the concentrate mixture contained ‘stearic acid’; the concentration of 16:0 was increased and the concentrations of 18:0, 18:1 and 18:2 were decreased when the concentrate mixture contained ‘palmitic acid’. Similar changes were observed in the compositions of the plasma unesterified fatty acids when the cows were given the different diets.In the plasma cholesteryl esters, the concentration of 16:0 was decreased and the concentrations of 18:3 and 20:4 were increased when the concentrate mixture contained stearic acid; the concentrations of 16:1, 18:3 and 20:4 were increased and the concentration of 18:2 was decreased when the diet was supplemented with palmitic acid. The addition of stearic acid to the diet increased the concentration of 18:0, 18:1 and 18:3 in the plasma phospholipids but decreased the concentrations of 16:0, 18:2, 20:3 and 20:4. When the diet contained palmitic acid the concentrations of 16:0, 16:1, 18:1 and 18:3 in the plasma phospholipids were increased but the concentrations of 18:0, 18:2 and 20:3 were decreased.The major fatty acid circulating in the plasma of the cows was 18:2, which accounted for about 45% of the total plasma fatty acids. Only about 0·7% of the total plasma 18:2 occurred in the plasma triglycerides.The results are discussed in relation to the changes in the composition of the milk fatty acids produced by the cows when they were given the experimental diets.

Effect of norepinephrine on myocardial metabolism before and after beta receptor blockade

Cardiac beta-adrenergic receptors were stimulated by the infusion of 0.02 μg/min/kg of norepinephrine (NE) into the left circumflex coronary artery in 20 anesthetized, bilaterally vagotomized open chest dogs. NE increased myocardial extraction ratio and uptake of glucose, lactate and plasma unesterified fatty acids (FFA). The increase in metabolism was accompanied by a slight rise in peak intraventricular pressure and a significant increase in d p/d t. Mean blood pressure, coronary artery perfusion pressure, coronary flow and coronary vascular resistance were not altered. In 10 of 20 dogs treated with the beta-adrenergic receptor blocking drug, d l-propranolol, the intracoronary infusion of NE caused moderate decreases in the uptake of lactate and pyruvate, while that of glucose was not significantly altered. FFA uptake was markedly decreased from 12.7 ± 3.3 to 1.0 ± 2.3 μEq/min/100 g while the extraction ratio declined 58% from control. Myocardial glycogen concentration in 8 control dogs was found to be not significantly different from cardiac glycogen levels in dogs infused with NE before and after beta-receptor blockade. These data indicated that the myocardial uptake of FFA in dogs pretreated with propranolol was not stimulated by subsequent administration of NE, suggesting that FFA utilization by the normal heart is closely associated with the cardiac beta-adrenergic receptor. Norepinephrine dl-propranolol Myocardial carbohydrates Myocardial fatty acids Beta-adrenergic receptors

Factors affecting the polyunsaturated fatty acid content of the plasma lipids of sheep.

1. In Expt 1, four adult wether sheep were given diets of hay or dried grass in an alternating sequence of feeding treatments. Each treatment period lasted for 20 days and blood samples were taken from the sheep on the last day of each period. When the diet of hay (linoleic: linolenic acid ratio 1.40) was replaced by one of dried grass (linoleic: linolenic acid ratio 0.28), there was an increase in the concentration of linolenic acid and a decrease in the concentration of linoleic acid in the plasma cholesteryl esters and phospholipids. There was an increase in the concentration of stearic acid and a decrease in the concentration of palmitic acid in the plasma triglycerides. Dietary change did not affect the composition of the plasma unesterified fatty acids.2. In Expt 2, two adult wether sheep, each with a rumen fistula, were given daily intraruminal infusions of 60 g of ‘linolenic’ or ‘linoleic’ acids (both about 70% pure) over a period of 5 days. The infusion treatments were then reversed. Blood samples were taken at the end of each infusion period. Intraruminal infusions of ‘linolenic’ acid increased the concentration of linolenic acid in the plasma cholesteryl esters and phospholipids and increased the concentration of stearic acid in the plasma triglycerides. The infusions of ‘linoleic’ acid increased the concentration of linoleic acid in the plasma cholesteryl esters and phospholipids. No appreciable changes were observed in the composition of the plasma unesterified fatty acids.

The origin of plasma arachidonic acid in dogs

Total hepatectomy and abdominal evisceration were performed in two groups of dogs to determine if the liver is the only source of plasma arachidonic acid. Venous blood was drawn prior to surgery and hourly for 5–6 hours. Plasma lipids were fractionated by column chromatography into unesterified fatty acids, phospholipids, cholesterol esters, and triglycerides. The per cent composition of the individual fatty acids of these fractions and total esterified fatty acids were determined by gas-liquid chromatography. Hepatectomy resulted in progressive fall of the per cent composition of arachidonic acid of the unesterified fatty acid fraction only. There was no significant depression of any other fatty acid in this fraction, nor was there a change in any fatty acid including arachidonic acid in the phospholipid, cholesterol ester, and triglyceride fractions. Palmitoleic acid was significantly elevated in the unesterfied fatty acid fraction. Similar results were observed in the eviscerated group. There was no change of any fatty acid in the various lipid fractions of a group of sham operated dogs. Lipolysis of adipose tissue triglyceride supplies all fatty acids of the plasma unesterified fatty acid fraction except arachidonic acid which is virtually absent from this tissue. Thus, as the unesterified fatty acids were utilized by the peripheral tissues, all fatty acids except arachidonic acid were replenished by lipolysis of adipose tissue triglyceride. Since the liver was absent in both groups of animals, it was concluded that the liver is the source of plasma arachidonic acid in the fasting dog.