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PubMed1991

Palmitic acid as an excipient in implants for sustained release of insulin.

Sustained-release implants for insulin can be made by compressing a powder admixture with palmitic acid as the excipient. At less than 20%, insulin does not disperse uniformly in the admixture. The size distribution of the excipient particles obtained after grinding for 15 min does not affect the sustained release action. When tested in a 33 d period, an 1/8-size piece (approximately 25 mg) implant cut from a pellet disc containing 20% insulin which is 13 mm in diameter and 1.5 mm thick released 0.12-0.17 mg insulin/d in diabetic Wistar rats. The 1/8-size piece containing 20% insulin or a rod of similar weight with a diameter of 3 mm, which can be inserted by a trocar, was optimal for the implant to provide a service-life of 49 +/- 7 d. The service-life decreased with progressive reduction in implant size. The implant functioned just as well subcutaneously or intraperitoneally and was eroded subcutaneously by 33.6-53.1% in 33 d. The glycosylated haemoglobin contents of diabetic animals on implant therapy which had a blood glucose level of 4.7 +/- 2.5 mmol/l were in a range of 6.2-8.9% compared to the control value of greater than 13% with chronic hyperglycemia. The overall results indicated that the implant was a promising alternative to daily insulin injections.

Animals↗

PubMed1993

Dietary palmitic acid raises plasma LDL cholesterol relative to oleic acid only at a high intake of cholesterol.

Using a crossover design, the effects of exchanging up to 10% dietary energy (%en) between oleic (18:1) and palmitic acid (16:0) on plasma lipoprotein metabolism was investigated in 12 normocholesterolemic cebus monkeys, both in the absence and presence of dietary cholesterol (0.3%, w/w). In all the purified diets, which contained 33%en as fat blends, myristic acid (14:0) and linoleic acid (18:2) were held constant at 0.3%en and 3.7%en, respectively. Cholesterol-free diets containing either high 18:1 (19%en), roughly equivalent levels of 16:0 and 18:1 (12 and 15%en, respectively), or a high level of 16:0 (18%en), generated similar values for total plasma cholesterol (TC), HDL-C and LDL-C. Plasma triacylglycerol concentrations (TG) were significantly higher when monkeys were fed the 16: 0-rich diet than when fed the 18: 1-rich diet (75 +/- 6 vs. 52 +/- 8 mg/dl; P < 0.05). LDL and HDL kinetic parameters (assessed after simultaneous injection of homologous 131I-LDL and 125I-HDL) revealed no significant differences between the 18: 1-rich or 16: 0-rich diets. By contrast, with added dietary cholesterol (0.78 mg/kcal) the 16: 0-rich diet resulted in significantly higher TC (318 +/- 20 vs. 299 +/- 20 mg/dl; P < 0.05) and LDL-C (136 +/- 10 vs. 117 +/- 10 mg/dl; P < 0.05) in comparison to the 18: 1-rich diet. HDL-C was unaffected (159 +/- 8 vs. 156 +/- 5 mg/dl), but plasma TG concentrations also tended to be higher (70 +/- 8 vs. 60 +/- 6 mg/dl, P < 0.08). Kinetic studies revealed that the higher LDL-C concentration was associated with an elevated pool size of LDL apo B (40 +/- 2 vs. 34 +/- 2 mg/kg body weight; P < 0.005), the latter attributed to decreased FCR (1.06 +/- 0.07 vs. 1.27 +/- 0.12 pools/day; P < 0.04) with no effect on the transport rate of LDL apo B (41 +/- 2 vs. 42 +/- 3 mg/kg body weight per day). HDL kinetic parameters were comparable during the 16: 0 and 18: 1 dietary periods, but dietary cholesterol caused an increase in apo A-I pool size and transport rate without impacting FCR. In this study a palmitic acid-rich diet failed to alter plasma or LDL-C when compared to an oleic acid-rich diet, unless the diet also contained cholesterol. In the latter case, 16: 0 increased LDL-C, which reflected a decrease in the efficiency of LDL apo B removal.

Analysis of Variance↗

PubMed1976

Palmitic acid-1-14C incorporation and turnover in lung phospholipids of rats treated with chlorphentermine, RMI 10.393 and Ro 4-4318.

The effects of 3 lipidosis-inducing drugs on the incorporation and turnover of palmitic acid-1-14C in lung phospholipids was studied. In rats treated with 1 dose of chlorphentermine or RMI 10.393, the incorporation of palmitate-1-14C into most lung phospholipid fractions was moderately decreased, but markedly lowered after 1 dose of Ro 4-4318. Eight doses of chlorphentermine and RMI 10.393 strongly inhibited the incorporation of palmitate-1-14C into lung phospholipids, whereas with 8 doses of Ro 4-4318 the incorporation was highly increased. Thirty hours after the last of 3 injections of the labeled palmitic acid the turnover of most lung phospholipids was considerably lower in chlorphentermine- and RMI 10.393-treated rats than in controls. Ro 4-4318, however, induced a highly increased turnover of most phospholipids. After 54 h, this effect had practically disappeared. Our studies showed that phospholipid storage after treatment with chlorphentermine and RMI 10.393 is mainly due to decreased degradation of phospholipids, whereas increased synthesis accounts for the effect of Ro 4-4318.

Amitriptyline↗

PubMed1979

Conformational changes associated with complex formation between a mycobacterial polymethylpolysaccharide and palmitic acid.

The anomeric proton magnetic resonances of Mycobacterium smegmatis 3-O-methylmannose polysaccharide have chemical shifts intermediate betwen those of nonaglucoamylose and alpha-cyclodextrin, and on addition of palmitic acid most of these resonances are shifted upfield toward that of the cyclodextrin. This suggests that the methylated polysaccharide could have a conformation with some secondary structure intermediate between those of the two reference compounds, and that it forms a tightened coil upon addition of the lipid which yields an inclusion complex with the polysaccharide. The change in chemical shift is linear with lipid concentration, which indicates that the complex undergoes rapid exchange with free polysaccharide. The changes in proton chemical shifts of the polysaccharide and of the palmitic acid are consistent with the fatty acid being inserted in the coiled polysaccharide with its carboxyl group near the methyl aglycon.

Chemical Phenomena↗

PubMed2004

Mono-thioesters and di-thioesters by lipase-catalyzed reactions of alpha,omega-alkanedithiols with palmitic acid or its methyl ester.

1- S-Mono-palmitoyl-hexanedithiol and 1- S-mono-palmitoyl-octanedithiol were prepared in high yield (80-90%) by solvent-free lipase-catalyzed thioesterification of palmitic acid with the corresponding alpha,omega-alkanedithiols in vacuo. Similarly, 1,6-di- S-palmitoyl-hexanedithiol and 1,8-di- S-palmitoyl-octanedithiol were prepared in moderate yield (50-60%) by solvent-free lipase-catalyzed thioesterification of palmitic acid with 1- S-Mono-palmitoyl-hexanedithiol and 1- S-mono-palmitoyl-octanedithiol, respectively. An immobilized lipase preparation from Rhizomucor miehei (Lipozyme RM IM) was more effective than a lipase B preparation from Candida antarctica (Novozym 435) or a lipase preparation from Thermomyces lanuginosus (Lipozyme TL IM). Lipase-catalyzed transthioesterifications of methyl palmitate with alpha,omega-alkanedithiols using the same enzymes were less effective than thioesterification for the preparation of the corresponding 1- S-mono-palmitoyl thioesters.

Ascomycota↗

PubMed2006

Differential effects of dietary intake of palmitic acid and oleic acid on oxygen consumption during and after exercise.

Our previous studies suggest that diets varying in palmitic acid (PA) and oleic acid (OA) content may affect energy expenditure and fat oxidation differentially. We hypothesized that, compared with a high-OA diet, a high-PA diet would lead to lower oxygen consumption during exercise and lower excess postexercise oxygen consumption (EPOC). Adults were randomized to 1 of 2 liquid diets (28 days): HI PA (fat, 40% of energy; PA, 16.8%; OA, 16.4%) (n = 10) or HI OA (fat, 40%; PA, 1.7%; OA, 31.4%) (n = 9). On day 29, the rates of oxygen consumption (V o(2)) and carbon dioxide production were measured during and for 270 minutes after 80 minutes of cycling (60% V o(2 peak)). There was no group difference (HI OA vs HI PA, mean +/- SEM) in fat-free mass (53.8 +/- 4.7 vs 56.9 +/- 3.0 kg), V o(2 peak) (40.7 +/- 2.3 vs 36.6 +/- 3.2 mL/kg per minute), and work during exercise (101 +/- 12 vs 101 +/- 10 W). V o(2) (L/min) during exercise (1.99 +/- 0.22 vs 1.85 +/- 0.19) was significantly different (P = .05) only when corrected for fat-free mass, with which it significantly correlated (r = 0.86; P < .001). During 60 to 270 minutes postexercise, the average EPOC was 9.7% +/- 4.9% of preexercise V o(2) in OA, whereas there was no EPOC present in PA (P = .06 between diets). In conclusion, a high-PA diet appears to lower V o(2) during and after exercise compared with a high-OA diet.

Adolescent↗

PubMed1995

Palmitic acid is absorbed as sn-2 monopalmitin from milk and formula with rearranged triacylglycerols and results in increased plasma triglyceride sn-2 and cholesteryl ester palmitate in piglets.

Milk fatty acids contain 20-30% palmitic acid (16:0), with approximately 70% of the 16:0 esterified to the sn-2 position of the milk triacylglycerol. Formulae containing vegetable and oleo oils contain different amounts of 16:0, but all have unsaturated fatty acids esterified to the triacylglycerol sn-2 position. Intraluminal triacylglycerol hydrolysis by endogenous lipases produces sn-2 monoacylglycerols and free fatty acids, which are absorbed and re-esterified in the enterocyte for secretion to plasma. The extent of absorption and re-esterification of sn-2 monoacylglycerols from milk or formula fats in infants is unknown. This was studied by feeding piglets sow milk or formulae containing similar total saturated fat, 18:1, 18:2(n-6) and 18:3(n-3) with unsaturated fatty acids at the sn-2 position or with rearranged triacylglycerols containing approximately 30% 16:0, with 70% 16:0 in fatty acids at the sn-2 position. Feeding milk or 16:0 on the sn-2 position of formula with rearranged triacylglycerols resulted in higher 16:0 esterified to the plasma triacylglycerol sn-2 position and in cholesteryl esters than feeding formulae with 0.4 to 4.4% 16:0 in the sn-2 position fatty acids. The absorption of 16:0 as monopalmitin from milk and any metabolic importance in human infants has yet to be determined.

Animals↗

PubMed1988

Aggregation-related association of lipid with the cytoskeleton of rabbit and human platelets prelabeled with [3H]palmitic acid. Similar effects of adenosine diphosphate- and thrombin-induced aggregation.

To investigate the association of lipid with the cytoskeleton of platelets during aggregation, rabbit and human platelets were isolated and labeled with [3H]palmitic acid; lipid extraction showed approximately 80% in phospholipid. Limited aggregation was induced with ADP or thrombin, and the cytoskeleton was isolated after lysis with 1% Triton X-100, 5 mM EGTA. Cytoskeleton from unactivated platelets had approximately 0.03% of the total label in the platelets, but after aggregation with ADP (2 microM) or thrombin (0.1 U/ml) for 20-30 s, 1.5-8% of the label was with the cytoskeleton. Fibrinogen enhanced aggregation and the association of label with the cytoskeleton; incorporation of label increased exponentially as aggregation proceeded, decreased exponentially during deaggregation, and appeared to be related to the number of sites of contact. Inhibitors that increase cyclic AMP inhibited aggregation and cytoskeletal labeling, but aspirin had no effect. Some experiments were done with DNase I and Ca2+ in the Triton X-100 lysis medium to cause actin depolymerization, under conditions in which the Ca2+-dependent protease activity was inhibited. This greatly reduced the association of label with the cytoskeleton at early time points, but when aggregation had proceeded further, a large proportion of the label was not dissociated by this treatment. These findings, electron microscopy, and the enrichment of the cytoskeleton of aggregated platelets with only some of the membrane proteins that were labeled by the 125I-lactoperoxidase method, indicated that with limited aggregation, the 3H-labeled lipid was mainly associated with the cytoskeleton and not with trapped membrane fragments resulting from incomplete lysis. Since the pattern of cytoskeleton labeling ([3H]palmitate) and the selective association of some membrane proteins with the cytoskeleton/lipid complex was the same with ADP and thrombin, the reactions must be dependent on aggregation and not on events associated with the release of granule contents.

Actin Cytoskeleton↗

PubMed1994

[Uncoupling effect of dicarbonic analogs of stearic and palmitic acids in heart mitochondria].

The uncoupling effect of 2-hexadecylmalonic acid (HDMA) and 2-tetradecylmalonic acid (TDMA), the dicarboxylic derivatives of stearic and palmitic acids, have been studied in heart mitochondria. The effects of these compounds and related fatty acids on the induced by ascorbate oxidation with PMS (or TMPD) in the presence of oligomycin, phosphate and rotenone have been compared. It was found that both HDMA and TDMA uncoupled mitochondria with a similar efficiency as did the corresponding fatty acids, while the uncoupling effect of low concentrations of HDMA and TDMA were almost completely suppressed by carboxyatractylate.

Animals↗

PubMed1990

Inhibition of the receptor-mediated endocytosis of diferric transferrin is associated with the covalent modification of the transferrin receptor with palmitic acid.

The human transferrin receptor is post-translationally modified by the covalent attachment of palmitic acid to Cys62 and Cys67 via a thio-ester bond. To investigate the role of the acylation of the transferrin receptor, Cys62 and Cys67 were substituted with serine and alanine residues. The properties of the mutant receptors were compared with wild-type receptors after expression in Chinese hamster ovary cells that lack endogenous transferrin receptors. Rapid incorporation of [3H]palmitate into the wild-type transferrin receptor was observed, but the mutant receptors were found to be palmitoylation-defective. The kinetics of endocytosis and recycling of the wild-type and mutant receptors were compared. It was observed that the rate of endocytosis of the palmitoylation-defective transferrin receptors was significantly greater than the rate measured for the wild-type transferrin receptor. In contrast, the mutation of Cys62 and Cys67 was found to have no significant effect on the rate of transferrin receptor recycling. Consistent with these observations, it was found that cells expressing palmitoylation-defective transferrin receptors exhibited an increased rate of accumulation of [59Fe]diferric transferrin. Together, these data indicate that the palmitoylation of the transferrin receptor is associated with an inhibition of the rate of transferrin receptor endocytosis. Addition of insulin to cultured cells causes an increase in the palmitoylation of cell surface transferrin receptors and a decrease in the rate of transferrin receptor internalization. It was observed that the effect of insulin to inhibit the endocytosis of the acylation-defective [Ala62 Ala67]transferrin receptor was attenuated in comparison with the wild-type receptor. The decreased effectiveness of insulin to inhibit the internalization of the acylation-defective transferrin receptor is consistent with the hypothesis that palmitoylation represents a potential mechanism for the regulation of transferrin receptor endocytosis.

Acylation↗

PubMed1988

Deuterium nuclear magnetic resonance investigation of bacteriophage M13 coat protein in dimyristoylphosphatidylcholine liposomes using palmitic acid as a probe.

The effect of incorporation of various amounts of M13 bacteriophage coat protein on the bilayer order and acyl chain motion in dimyristoylphosphatidylcholine (DMPC) liposomes has been investigated using deuterium NMR of specifically deuterated palmitic acid as a bilayer probe, phosphorus NMR and additional spin-label electron spin resonance (ESR). The secondary structure of the M13 coat protein in these bilayers was determined from circular dichroism spectra. Phosphorus NMR spectra of the mixed liposomes are characteristic for DMPC organized in bilayers, also after incorporation of various levels of M13 protein. Circular dichroism spectra of the coat protein indicate that the protein conformation is predominantly a beta-structure (more than 75%). Various incorporation levels of M13 coat protein do not affect the order of the deuterium-labelled positions along the acyl chain at the carbon-2, 9 and 16 positions. In contrast, the spin-spin relaxation times decrease at higher protein levels, especially at the carbon-16 position. The spin-label ESR spectra of the same system using 14-doxylstearic acid as a label show a second, motionally restricted component, that is not observed by deuterium NMR. The NMR and ESR results are consistent with a model in which the fatty acid molecules are in a fast two-site exchange (at a rate of approx. 10(7) Hz) between the sites in the bulk of the lipid bilayer and the motionally restricted sites on the coat protein.

Capsid↗

PubMed1992

Palmitic acid conjugation of a protein antigen enhances major histocompatibility complex class II-restricted presentation to T cells.

The effect on antigenicity of covalent attachment of lipid groups to a protein antigen was investigated. Coupling of palmitic acid to ovalbumin (OVA) enhanced major histocompatibility complex (MHC) class II-restricted presentation to most OVA-specific murine T-cell clones in vitro. The enhanced antigenicity of palmitoylated antigen was localized to the level of presentation of the synthetic peptide epitope, OVA 323-339. T-cell responses to palmitoylated antigen were more difficult to block with anti-MHC class II antibodies than responses to native antigen. However, T-cell proliferation to palmitoyl (p)-OVA and native (n)-OVA were blocked equally by anti-CD4 antibodies. Taken together, the results suggest that lipid conjugation of a protein antigen leads to the formation of a lipopeptide T-cell epitope with increased affinity of binding to MHC class II and/or T-cell receptor (TcR). These results have implications for the design of synthetic peptide vaccines.

Adjuvants, Immunologic↗

PubMed1994

Titration of numbers of human-derived Mycobacterium leprae required to progressively oxidize 14C-palmitic acid and release 14CO2.

Mycobacterium leprae was isolated from skin-punch biopsies of 2 untreated lepromatous leprosy patients. The bacteria were enumerated, diluted 10-fold and cultured in Middlebrook 7H9 medium supplemented with albumin, dextrose, catalase and 14C-palmitic acid. The cultures were incubated at 33 degrees C in a modified Buddemeyer radiorespiratory detection vessel. Those cultures containing at least 10(7) mycobacteria demonstrated a progressive evolution of 14CO2.

Carbon Dioxide↗

PubMed1969

Effect of DL-ethionine on the intestinal absorption and transport of palmitic acid-1-14C and tripalmitin-14C. Role of intramucosal factors in the uptake of luminal lipids.

The effect of DL-ethionine on the uptake and transport of lipid by the rat small intestine was investigated. A cottonseed oil emulsion containing (14)C-labeled tripalmitin or palmitic acid was administered intragastrically to rats pretreated with DL-ethionine, DL-ethionine plus methionine, or saline, and the rats were sacrificed 2, 4, and 6 hr later. Lipids from the plasma, the stomach, the colon, the luminal contents of the small intestine, and the wall of the small intestine were extracted, fractionated, and their radioactivity assayed. Ethionine markedly inhibited the uptake of lipids by the small intestine. This inhibition was not related to impairment of intraluminal lipolysis since analagous inhibitions were observed when palmitic acid or predigested triglyceride (TG), obtained through a jejunal fistula from normal animals, was administered instead of tripalmitin. Ethionine also inhibited the transport of lipid from the wall of the small intestine. A significant fraction of the administered lipid remained in the wall of the small intestine, and only a small fraction was transported to the blood stream. Although most of the wall radioactivity was in the form of TG, significant proportions were also found in the free fatty acid (FFA) and partial glyceride fractions, indicating a marked inhibition of mucosal reesterification to TG. The degree of inhibition of mucosal reesterification and the degree of inhibition of transport of wall lipids were directly related to the degree of inhibition of uptake of luminal radioactivity. This relationship suggests that the rate of reesterification, the level of mucosal FFA, and the rate of transport of intramucosal TG may be of importance in determining the extent of uptake of intraluminal lipid by the mucosal cells. Since a significant fraction of the wall radioactivity was in the form of TG, the decreased transport of wall lipids was attributed to an impairment of chylomicron completion due to inhibition of either the synthesis of chylomicron apoprotein or the association of preformed TG with the protein moiety of chylomicrons. Experiments with labeled amino acids support the first possibility.

Animals↗

PubMed1978

Uptake and utilization of 1-14C palmitic acid by heart cells treated with fresh or thermally oxidized fats.

The effects of fractions isolated from thermally oxidized corn oil or olive oil on the metabolic activity of heart endothelial and muscle cells were studied. Rat heart cells in culture, exposed to thermally oxidized fat components, took up more exogenous 1-14C-palmitic acid and incorporated more of it into the cell triacylglycerol fraction than when the cells were treated with fresh fats. Particularly with the heated corn oil compared to fresh corn oil, much less of the radioactivity from the labeled palmitic acid was deposited in the phospholipid fraction. Also, with heated corn oil when the incubation period was extended beyond 12 hr, there was a decline in the radioactivity retained in the triacylglycerol fraction of the heart muscle cells. When the fresh fats were compared for 14C-radioactivity incorporation into the heart cells, the olive oil gave much higher values, indicating a distinct difference in response to the proportion of fatty acids supplied.

Animals↗

PubMed1999

[Utilization of glucose, valine, glycerin and palmitic acid by energy and anabolic pathways of metabolism in rats].

Possibility of evaluation of nutrients use by energy and anabolic ways by measurement in blood of radioactivity of water formed from labelled by tritium precursors was studied. The experiment was made on rats, which consecutively with interval 1.5-2 weeks were given intravenous indicative amount of 3H2(2,3)-valine, 1-14C-glucose, 6-3H-glucose, 3H2(1,3)-glycerin and 3H2(9,10)-palmitic acid. Half-time of glucose in blood was 46 min, glycerin--16 min, valine and palmitic acid--24 min. Plastic and energy characteristics of these substances were studied. The proposed approach to the evaluation of plastic and energy functions of nutrients can be useful for development of specialized products for enteral and parenteral feeding.

Animals↗

PubMed1990

Differential induction of peroxisomal oxidation of palmitic acid and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid in rat liver.

The effect of feeding rats 20% partially hydrogenated marine oil (PHMO), 20% soybean oil, or clofibrate on the conversion of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid to cholic acid was studied in light mitochondrial (L) fractions prepared from liver. 20% PHMO gave a doubling both of the specific and of the total activity of the cholic acid formation compared to those found in the L-fraction from animals given standard pellets. 20% soybean oil induced the specific and the total activity to a lesser extent, 1.4- and 1.2-fold, respectively. The specific and total activity of the peroxisomal beta-oxidation of palmitic acid were induced 2.4- and 2.7-fold, respectively, by PHMO feeding. Soybean oil gave a smaller increase, 2-fold, in both specific and total activity. Clofibrate, a known peroxisomal proliferator, induced the specific and total activity of the peroxisomal fatty acid beta-oxidation 5.2- and 5.7-fold, respectively, whereas the specific activity of the cholic acid formation remained unchanged compared to standard pellet feeding. The same pattern was found in the postnuclear supernatants (E-fractions), excluding the possibility that different treatments caused different distributions of organelles between the fractions. This differential induction of two similar peroxisomal reaction sequences suggests that at least two mechanisms for peroxisomal induction exist.

Acyl-CoA Oxidase↗

PubMed1986

[Lecithin /sphingomyelin ratio and palmitic acid percentage in the diagnosis and prediction of idiopathic respiratory distress syndrome].

The L/S ratio of gastric aspirate was determined in the first day of life in 47 patients with IRDS and in 87 without IRDS. In 97.7% of those without IRDS the gastric L/S ratio was greater than 3.5. Ninety three percent (93%) of the patients with IRDS had a gastric L/S ratio less than 3.5. In these cases the palmitic percentage was 49.1 +/- 11.5 been in normal full term infants 69.4 +/- 5.2 (p less than 0.01). The use of a biochemical score including the L/S ratio and the palmitic acid percentage in patients with IRDS could differentiate survivors and non survivors.

Amniotic Fluid↗