Palmitic Acid-1 Research Articles

Incorporation of palmitic acid-1- 14C into lipids of pharate adult tissues of Bombyx mori

Incorporation of palmitic acid-1- 14C into pharate adult tissues and their lipid components of Bombyx mori was investigated. Rapid incorporation of radioactivity took place predominantly in fat body and haemolymph lipids, and partially in ovarian lipids immediately after the injection at the middle stage of pharate adult development. The major parts of the radioactivities in fat body, haemolymph and ovary were distributed in triglycerides and phospholipids, diglycerides, and triglycerides, respectively. The patterns of time course of incorporation of radioactivity into lipid components of pharate adult tissues suggest that the major form of lipid released from fat body may be diglycerides and the diglycerides in haemolymph are probably the main source of ovarian triglycerides.

Metabolism of palmitate in the adult Pieris brassicae

The rôle of palmitic acid in adult lipids and its degradation during adult life (after the pupal-adult ecdysis) was studied in Pieris brassicae. The present findings support the view that there is sexual dimorphism in the metabolism of the fatty acids used for energy. Palmitic acid-1- 14C is lost at approximately equal rates in both sexes during adult life. The females, however, synthesize more palmitate. The males utilize more fat during flight, apparently by oxidizing more oleate. The label is retained longer in the lipids of the thorax than those of the abdomen. During 9 days the specific activity of the neutral fraction of the female abdomen decreased to one-seventh but that of the thorax only by 50%. In the flight muscles diglycerides and free fatty acids were the major neutral lipids incorporating palmitate, whereas in the abdomen triglycerides contained most of the label. The distribution of the label in phospholipids suggests that phosphatidyl cholines are metabolically more labile than phosphatidyl ethanolamines or sphingomyelins.

Studies on the ethanol-induced decrease of fatty acid oxidation in rat and human liver slices

In order to elucidate the mechanisms involved in the acute ethanol-induced liver triglyceride accumulation, the oxidation, esterification and β-keto acid formation have been studied in rat and human liver slices after incubation with albumin bound, long chain fatty acids (palmitic. oleic and linoleic acids). The addition of alcohol to rat and human liver slices depressed the formation of 14CO 2 from palmitic acid-1- 14C, oleic acid-1- 14C and linoleic acid-1- 14C. The esterification to triglycerides and phospholipids was increased and the formation of β-keto acids was decreased by alcohol. Addition of 4-methylpyrazole, an inhibitor of liver alcohol dehydrogenase, almost prevented the alcohol effect on the lipid metabolism of the liver slices. The oxidation of alcohol is thus obligatory for the decreased β-oxidation of fatty acids, the increased esterification and for the decreased formation of β-keto acids. The results suggest that ethanol oxidation inhibits β-oxidation of fatty acids and that this primary effect leads to accumulation of liver triglycerides by increased esterification of plasma free fatty acids.

Formation of 1-O-2′-hydroxyalkyl glycerophosphatides from 1,2-heptadecanediol in myelinating brain

1,2-Heptadecanediol-2-(14)C was administered intracerebrally to 18-day-old rats, and its incorporation, after 8 hr, into the individual aliphatic moieties of the ethanolamine glycerophosphatides was determined. Much of the radioactivity was found in a lipid fraction identified as 1-O-2'-hydroxyheptadecyl glycerol. Evidence is presented that a major portion of the precursor was incorporated into 1-O-2'-hydroxyheptadecyl-2-acyl ethanolamine phosphatides. Some of the diol administered was degraded to palmitic acid. The palmitic acid-1-(14)C derived from 1,2-heptadecanediol-2-(14)C apparently served as precursor for stearic and oleic acids, which were found as acyl groups, and for the biosynthesis of the corresponding O-alkyl and O-alk-1-enyl glycerols. The data presented prove that biological dehydration of 1-O-2'-hydroxyalkyl glycerophosphatides to the corresponding plasmalogens does not occur in myelinating brain.

Conversion of Palmitic acid-1- 14C to 14C0 2 and incorporation into lipids by tissues from hyperthermic hamsters during incubation at 7, 17, 27, and 37 °C

Conversion of Palmitic acid-1- 14C to 14C0 2 and incorporation into lipids by tissues from hyperthermic hamsters during incubation at 7, 17, 27, and 37 °C

Lecithin Biosynthesis in Cigarette Smoking Dogs

The effects of acute exposure to cigarette smoke on the synthesis of lecithins in lung, pulmonary surfactant, heart, and liver were studied in anesthetized dogs after intravenous injection of³²PO₄, cholinemethyl-³H and either methionine-methyl-¹⁴C, ethanolamine-1-2-¹⁴C, or palmitic acid1-¹⁴C. Control dogs and dogs exposed to heavy doses of smoke were anesthetized and ventilated with a positive pressure respirator through an endotracheal tube for 90 to 220 minutes after isotope injection. The pool size of lecithins was not changed by smoking, but statistically significant decreases in choline and phosphate incorporation were observed in the lecithins of lung and pulmonary surfactant and in the linoleoyl lecithin of the heart. No significant differences were noted in terms of isotope incorporation in liver, the phosphatidyl ethanolamines of any tissues, or in surface activity of lung extracts.

Lecithin biosynthesis in cigarette smoking dogs

The effects of acute exposure to cigarette smoke on the synthesis of lecithins in lung, pulmonary surfactant, heart, and liver were studied in anesthetized dogs after intravenous injection of³²PO₄, cholinemethyl-³H and either methionine-methyl-¹⁴C, ethanolamine-1-2-¹⁴C, or palmitic acid1-¹⁴C. Control dogs and dogs exposed to heavy doses of smoke were anesthetized and ventilated with a positive pressure respirator through an endotracheal tube for 90 to 220 minutes after isotope injection. The pool size of lecithins was not changed by smoking, but statistically significant decreases in choline and phosphate incorporation were observed in the lecithins of lung and pulmonary surfactant and in the linoleoyl lecithin of the heart. No significant differences were noted in terms of isotope incorporation in liver, the phosphatidyl ethanolamines of any tissues, or in surface activity of lung extracts.

Epoxy acids in the lipid polymer, cutin and their role in the biosynthesis of cutin

In apple skin slices oleic acid-1- 14C was incorporated specifically into 18-hydroxyoleic acid, 10,18-dihydroxystearic acid and 9,10, 18-trihydroxystearic acid of cutin, whereas stearic acid-1- 14C was not converted into these acids. Palmitic acid-1- 14C, but neither palmitoleic acid-10- 14C nor palmitelaidic acid-10- 14C, was converted into 16-hydroxypalmitic acid and 10,16-dihydroxypalmitic acid. Based on this tracer evidence a pathway for the biosynthesis of hydroxy C 18 acids is proposed which involves hydration of the double bond of ω-hydroxyoleic acid and epoxidation followed by hydration. The proposed epoxy intermediate was identified in cutin by LiAlD 4 treatment followed by mass spectrometry.

Biosynthesis of a lipid polymer, cutin: The structural component of plant cuticle

Cutin, the lipid polymer of plant cuticle, when treated with LiAlH 4 in tetrahydrofuran gave better than 95% conversion into reduced monomers which were separated by thin-layer chromatography into fatty alcohols, alkanediols, alkanetriols and alkanetetraols. The major component from Vicia faba leaf cutin was identified by TLC, GLC, NMR, IR and mass spectrometry to be hexadecan-1,7, 16-triol, most probably derived from 10, 16-dihydroxy palmitic acid of the cutin. Palmitic acid-1- 14C was readily incorporated into this component and lesser amounts into monohydroxy acids and fatty acids of the cutin. Experimental evidence suggests the reaction sequence palmitic acid → 16-hydroxy palmitic acid → 10, 16-dihydroxy-palmitic acid → cutin. Palmitoleic acid-10- 14C was not incorporated into dihydroxy palmitic acid suggesting the noninvolvement of epoxide intermediate. Acetate-1- 14C, oleic acid-1- 14C and stearate-1- 14C also labeled the cutin.

Reductive and oxidative biosynthesis of plasmalogens in myelinating brain

Palmitic acid-1-(14)C and hexadecanol-1-(14)C were administered intracerebrally to 18-day-old rats. Incorporation of radioactivity into the constituent alkyl, alk-1-enyl, and 1-acyl moieties, as well as into the 2-acyl moieties, of the ethanolamine phosphatides of brain was determined after 1, 2, 3, 6, and 22 hr. Incorporation of radioactivity from hexadecanol into both alkyl ethers and alk-1-enyl ethers proceeded at a rate more than 10 times higher than from palmitic acid. Hexadecanol was rapidly oxidized to fatty acids which were incorporated into the acyl moieties of the ethanolamine phosphatides. When palmitic acid was used as a precursor, labeled long-chain alcohols could be isolated from the lipid extract. As labeled long-chain aldehydes could not be detected in any of the lipid extracts, alcohols appear to be key intermediates for the biosynthesis of both alkyl and alk-1-enyl glycerophosphatides.

Palmitic acid-1- 14 C oxidation by skeletal muscle mitochondria of dystrophic mice.

Cofactor requirements for the oxidation of palmitate-1-14C by 600 × g supernatant fraction of mouse skeletal muscle homogenate and by skeletal muscle mitochondria are described. Optimal oxidation of palmitate-1-14C by skeletal muscle mitochondria requires the presence of carnitine, ATP, CoA, and a Krebs cycle intermediate (e.g. succinate). Succinate, malate, alpha-ketoglutarate, and oxaloacetate are all equally effective in supporting the oxidation, but isocitrate is less effective. The oxidation of palmitate-1-14C by 600 × g supernatant fraction of muscle homogenate as well as by skeletal muscle mitochondria from dystrophic mice is significantly decreased compared with that of the normal littermate controls. The present results, together with the previous findings, suggest that the decrease in oxidation of palmitate-1-14C by the dystrophic muscle preparations is most likely due to a defect in one or more of the steps of the Krebs cycle.

The effect of heparin on the metabolism of triglycerides by the liver

The output of triglyceride by the perfused rat liver was depressed by heparin (Upjohn) added to the medium in vitro. The impairment in output of triglyceride by the liver which resulted from fasting, alloxan diabetes, and from poisoning of the animal with carbon tetrachloride was observed whether or not heparin was used as an anticoagulant. The output of triglyceride by the liver was inhibited significantly by crystalline heparin (Sigma) only at the smallest concentration (0.42 USP units/ml perfusate) of heparin added to the medium. The release of lipolytic activity by the liver was stimulated as the concentration of heparin in the medium was increased; the maximal effect was obtained at a concentration of 42 units heparin/ml perfusate. Paradoxically, as the lipolytic activity in the medium increased, the inhibition of output of triglyceride by heparin diminished. The uptake and utilization by the liver of chylomicra labeled with palmitic acid-1- 14C was accelerated by crystalline heparin, presumably as a result of the increased lipolytic activity. There was, however, a real, albeit smaller, utilization of chylomicron triglyceride when heparin was omitted from the medium. One can surmise from these observations that the output of triglyceride into the very low density lipoprotein (VLDL) by the liver and the uptake of either chylomicron triglyceride or the VLDL-triglyceride occur by different cellular mechanisms, since heparin appears to affect each of these processes in diverse manners.

The biosynthesis of phospholipids in the lobsters, Homarus americanus

1. 1. The ability of intact lobster to synthesize phospholipids from radioisotopically labeled precursors was examined. 2. 2. There was incorporation of 32P-disodium phosphate, glycerol-1,3- 14C, choline-methyl- 14C, phosphorylcholine-methyl- 14C, ethanolamine-1-2- 14C, phosphorylethanolamine-1-2- 14C and S- adenosyl- l-methionine-methyl- 14C into lobster phospholipids in vivo. 3. 3. Live lobsters induced incorporated fatty acids into phospholipids. Acetic acid-1- 14C, palmitic acid-1- 14C, palmitoleic acid-10- 14C, oleic acid-1- 14C and linoleic acid-1- 14C were incorporated more actively into phosphatidylcholine than into phosphatidylethanolamine, but the converse was found with myristic acid-1- 14C or stearic acid-1- 14C. 4. 4. The results suggest that the lobster, Homarus americanus, can synthesize phospholipids by pathways established for vertebrates.

Localization of the oxidative defect in phytanic acid degradation in patients with Refsum's disease.

The rate of oxidation of phytanic acid-U-(14)C to (14)CO(2) in three patients with Refsum's disease was less than 5% of that found in normal volunteers. In contrast, the rate of oxidation of alpha-hydroxyphytanic acid-U-(14)C and of pristanic acid-U-(14)C to (14)CO(2), studied in two patients, while somewhat less than that in normal controls, was not grossly impaired. These studies support the conclusion that the defect in phytanic acid oxidation in Refsum's disease is located in the first step of phytanic acid degradation, that is, in the alpha oxidation step leading to formation of alpha-hydroxyphytanic acid. The initial rate of disappearance of plasma free fatty acid radioactivity after intravenous injection of phytanic acid-U-(14)C (t(1/2) = 5.9 min) was slower than that seen with pristanic acid-U-(14)C (t(1/2) = 2.7 min) or palmitic acid-1-(14)C (t(1/2) = 2.5 min). There were no differences between patients and normal controls in these initial rates of free fatty acid disappearance for any of the three substrates tested. There was no detectable lipid radioactivity found in the plasma 7 days after the injection of palmitic acid-1-(14)C or pristanic acid-U-(14)C in either patients or controls. After injection of phytanic acid-U-(14)C, however, the two patients showed only a very slow decline in plasma lipid radioactivity (estimated t(1/2) = 35 days), in contrast to the normals who had no detectable radioactivity after 2 days. Incorporation of radioactivity from phytanic acid-U-(14)C into the major lipid ester classes of plasma was studied in one of the patients; triglycerides accounted for by far the largest fraction of the total present between 1 and 4 hr.

Plasma free fatty acid and triglyceride turnover in obesity

The turnover rate of plasma free fatty acids and of triglyceride in plasma very low density lipoprotein was studied in 15 obese subjects with a constant infusion of palmitic acid-1- 14C. The plasma FFA turnover rate was significantly correlated with the plasma FFA concentration. The FFA turnover rate was also significantly related to fat mass, to fat mass as a percentage of total body weight and especially to per cent desirable weight. Since it was not related to body weight, it is evident that the plasma FFA turnover rate is related to the degree of adiposity as distinct from total body weight. The plasma triglyceride levels were on the average higher than normal in these obese subjects. The turnover rate of triglyceride in very low density lipoproteins was significantly correlated with the triglyceride concentration, and showed that increased formation was a major factor in the development of the hypertriglyceridemia.

The incorporation of acetate and palmitate into lipids by human platelets

The optimal conditions for the incorporation of acetate-1-(14)C and palmitic acid-1-(14)C into platelet lipids have been described. In buffer incubations with acetate there was a sharp pH optimum at 6.8; in plasma incubations, there was a broad pH optimum between 6.8-7.4. Maximal incorporation of acetate occurred at a final concentration of 1.5 mmoles/liter. In buffer, no labeled lipids were released from platelets into the medium. In plasma, 40% of newly formed lipids was recovered in the plasma. 75% of the incorporated acetate could be recovered in ceramide, lecithin, and free fatty acids. Platelet fatty acids were formed both by de novo synthesis and chain elongation. The fatty acids formed by de novo synthesis exchanged with plasma free fatty acids. In buffer incubations no turnover of newly labeled lipids occurred, but in the plasma incubations exchange of newly labeled lecithin with plasma lipids was demonstrable. Palmitic acid-1-(14)C added to plasma was incorporated into platelet lipids. The distribution among the lipid classes of palmitate taken up from plasma was the same as that of palmitate formed intracellularly by de novo synthesis.

Metabolism of chylomicrons by the isolated rat liver

Isolated livers perfused with washed corn oil chylomicrons labeled in vivo with palmitic acid-1-(14)C removed a large proportion of the chylomicrons. Slices from these livers oxidized chylomicron fatty acid esters to both carbon dioxide and acetoacetate. The liver slices also generated free fatty acids from chylomicron lipids and converted chylomicron triglycerides to phospholipids. Similar activities were observed in rat liver slices prepared shortly after the intravenous administration of chylomicrons to intact rats. The observed chylomicron uptake and lipid conversions were similar in livers from both fed and fasted rats. Fasting increased the oxidation of chylomicron fatty acid esters by livers labeled in vivo and by perfusion. In livers removed from intact rats given labeled chylomicrons, the triglyceride-(14)C to phospholipid-(14)C ratio was high, a finding unexpected if the liver had acquired this (14)C by removal of circulating fatty acids formed by extrahepatic lipolysis. These results demonstrate the ability of the liver to remove and utilize chylomicrons directly and suggest that direct removal accounts for a significant portion of the chylomicron fatty acids utilized by the liver of intact rats.

Effect of hydrazine on plasma free fatty acid transport

Effects of intravenously injected hydrazine (1.15–1.20 μoles/kg) on plasma free fatty acid (FFA) transport were studied in one-day fasted, anesthetized rats. Two hours after hydrazine injection, blood glucose levels were depressed, and plasma FFA concentration and pool size were elevated to twice the control level. When, at this time, the plasma free fatty acid pool was labeled with palmitic or oleic acid-1- 14C, its fractional turnover rate appeared to be little affected by hydrazine. However, an increase was observed in the fraction of the labeled fatty acids which, on leaving the blood, appeared in the liver. The chief component of plasma FFA transport to the liver was accelerated to more than twice the rate in control rats.

CLINICAL STUDY ON LIPID METABOLISM. EFFECT OF GLUCOSE AND INSULIN ON NEFA METABOLISM.

The lipid metabolism, especially Nefa oxidation to expired CO2 and transfer to plasma triglycerides was investigated by using palmitic acid-1 -C14 with reference to glucose metabolism in arteriosclerotic, diabetic, hyperlipemic and control subjects. 1 ) In a fasting state, Nefa oxidation in the cells of an arteriosclerotic subject was twice as much as that in the control subject and transfer of Nefa into plasma triglycerides was 3 times in the arteriosclerotic, 2 or 3 times in the hyperlipemic, 2 times in the diabetic subject as much as that in the control subject. The Nefa oxidation rate in the cells of an arteriosclerotic subject was most increased to reach to 4 times and in the diabetics 2 times as much as that in the control subject. Rate of Nefa transfer to plasma triglycerides increased in both arteriosclerotic and diabetic subjects to 6 or 4 times as much as that in the normal subject. 2) Glucose loading increased the Nefa oxidation in the control, diabetic and male hyperlipemic subject, while decreased in an arteriosclerotic and a female hyperlipemic subject. By glucose loading the transfer of Nefa into plasma triglycerides was only slightly changed in the control, arteriosclerotic and diabetic subject, while was increased in the male hyperlipemic subject. By glucose loading the rate of Nefa oxidation in the cell was increased in the control and diabetic subject, while decreased in the arteriosclerotic subject ; then the rates became to almost same in all cases. The rate of Nefa transfer into plasma triglycerides in the arteriosclerotic and diabetic subject was decreased, while in the control subject was increased a little by glucose loading. 3) The Nefa oxidation was markedly or a little depressed in the control or arteriosclerotic subject respectively and unchanged in a diabetic subject by insulin administration. Insulin de-pressed the Nefa transfer into plasma triglycerides in the control and arteriosclerotic subject. By insulin administration, the rate of Nefa oxidation was unchanged in the arteriosclerotic and depressed in the control and diabetic subject ; especially, in the diabetic subject was most influenced. 4) In an arteriosclerotic subject, the accelerated Nefa oxidation in a fasting state was decreased to half by glucose administration and unchanged by insulin loading. Then, available glucose seems to be insufficient in the cells of arteriosclerosis. In a diabetic subject, Nefa oxidation was not increased in a fasting state and increased by glucose loading and unchanged by insulin loading. Then, insulin seems to be insufficient in the cell of diabetes mellitus. In a control subject, Nefa oxidation was accelerated by glucose loading and depressed by insulin loading. In an arteriosclerotic subject, Nefa transfer into plasma triglycerides was markedly accelerated in a fasting state ; this Nefa transfer was changed a little by glucose and decreased by insulin loading. In arteriosclerotic subjects, it would be suggested that disturbances in lipid metabolism may be partly caused by the deficiency of glucose metabolism. In a diabetic subject, Nefa transfer was moderately accelerated in a fasting state and slightly changed by glucose or insulin loading. In diabetes mellitus, glucose seems to have the direct influence, while insulin, the indirect influence through glucose metabolism, on lipid metabolism. In a control subject, Nefa transfer was slightly increased by glucose and markedly decreased by insulin loading.