Increase In Fatty Acid Content Research Articles

Vitamin E reduces the reactive oxygen species production in dominant follicle during the negative energy balance in cattle.

In the postpartum period, there is an increase in non-esterified fatty acids (NEFA) in both serum and follicular fluid (FF) of cattle. The increase in fatty acid concentration results in increased production of reactive oxygen species (ROS) that can compromise bovine fertility. The objectives of this study were to characterize the lipid profile found in the FF of cows experiencing induced negative energy balance (NEB) and to evaluate the effect of α-tocopherol in the prevention of oxidative stress in the serum and FF of cows. Twenty-nine beef cows were divided into groups: (1) control; (2) Fasting for 24 days; and (3) Fasting + VitE. Between D0 and D4 blood samples were taken to assess concentrations of NEFA, ROS production, total antioxidant capacity (FRAP), lipid peroxidation, and α-tocopherol (vitamin E). On D4, follicular aspiration was performed for analysis of FF from the dominant follicle. Our results demonstrate that fasting was effective in causing increased fat mobilization in animals. The increase in serum concentration of C18:1c9 was reflected in the FF of fasting cows. Serum α-tocopherol concentration was higher in the control and Fasting + VitE groups compared to the Fasting group. In FF, there was an increase of α-tocopherol in the Fasting + VitE group in comparison to Fasting cows. There was an increase in ROS production in the serum of fasting cows. ROS production in FF was higher in the Fasting compared to the Fasting + VitE group. Vitamin E has beneficial effects in reducing ROS production in the dominant follicle of cows in NEB.

Impact of cooking on the content of nutritionally important fatty acids in muscle from lambs raised to have divergent intramuscular fatty acid compositions

The effect of sous vide cooking or grilling longissimus thoracis et lumborum (LTL) on the intramuscular fatty acid concentrations of lambs raised at pasture (Pasture), fed a cereal concentrate-based diet (Concentrate) or fed a cereal concentrate-based diet with a protected linseed oil supplement (Linseed) was assessed using GC-FID. Sous vide and grilling led to significant increases in fatty acid concentrations, particularly in the Pasture group. The apparent retention values were generally higher in the Pasture group. Concentrate, Linseed and Pasture groups had 16.7–19.9 mg, 25.8–28.7 mg, and 38.8–42.9 mg eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) in 100 g cooked meat, respectively. The EPA+DHA in the Pasture group met the requirements for a nutrient claim as a “source of n-3 fatty acids” set by the European Commission and as a “good source of n-3 fatty acids” set by the Food Standards Australia and New Zealand.

In Vivo Yarrowia lipolytica Fermented Biomass Feed Supplementation for Shrimp and Its Effects Upon Frozen Meat Storage

ABSTRACT In this work, Macrobrachium rosenbergii were supplemented (0%, 3%, 5%, 10%) with fermented biomass of Yarrowia lipolytica in the feed for 50 days, and subsequently, analyses of the fresh carcass were carried out, and a frozen meat storage test was carried out at − 18 ºC during 0, 3, 6, and 9 months of storage. Regarding fresh meat, an increase in humidity and pH was observed. Total lipid content (5 and 10% groups), thiobarbituric acid reactive substances (TBARS) (10% group), and total volatile basic nitrogen (TVB-N) (3 and 5% groups) also increased, while a reduction in titratable acidity (5 and 10% groups) was observed. Furthermore, increased fatty acid (FA) content was observed predominantly in mono- and polyunsaturated FAs in all groups. Significant rises in TBARS and TVB-N were observed during the storage over time. There was an increase in FA concentrations up to 6 months compared to the initial time and decreased at 9 months. The Y. lipolytica biomass at 3 and 5% can be added to the feed to supplement the shrimp diet since these concentrations improved body composition by increasing the content of mono- and polyunsaturated FAs and has not affected the quality parameters of meat during storage.

Genetic deletion of endothelial Caveolin‐1 is protective against metabolic disease

In metabolic disease, the endothelium is exposed to a substantial increase in fatty acid concentrations creating a pathological role for endothelial cells (ECs) as lipid metabolizing cells. One mechanism whereby lipids may enter ECs is by caveolin‐1 (Cav1)‐mediated endocytosis. Because both ECs and adipocytes both have abundant Cav1 and both can readily take up lipids, we wanted to differentiate the role of Cav1 between the two cell types. For these reasons, we used an inducible EC‐specific Cav1 knockout mouse (Cav1fl/fl/Cdh5‐CreERT2+). Using these mice, we induced Cav1 genetic deletion from endothelium at 6 weeks, and began a high fat diet (HFD; 60% fat) to induce metabolic disease at 8 weeks. Normal chow fed littermates were used as controls. All mice were examined at 20 weeks (i.e., 12 weeks of HFD). Thus, we had four cohorts: Cre+ HFD, Cre‐ HFD, Cre+ normal chow, and Cre‐ normal chow all injected with tamoxifen. All mice regardless of genotype had comparable weight gain within diet groups, and gonadal fat pad mass. Food consumption was similar between groups, and electron microscopy was used to confirm presence of caveola in adipocytes, but not endothelium. Initial experiments examining plasma lipids found HFD Cre+ mice had both increased serum cholesterol (175mg/dL) and LDL (75mg/dL) compared to HFD Cre‐ controls (cholesterol, 125mg/dL; LDL, 60mg/dL). When these mice were challenged with a bolus of insulin, the blood glucose of Cre+ HFD mice dropped significantly resembling an insulin tolerance curve from normal chow fed controls. Similarly, Cre+ HFD mice were protected from hyperglycemia after bolus glucose injections, resulting in a glucose tolerance phenotype similar to that of a normal chow fed mouse (HFD Cre+ AUC 3000 vs. HFD Cre‐ AUC 60000). There was no difference in Cre+ or Cre‐ mice on normal chow diets with serum lipids or after challenge with insulin or glucose. It isn’t clear why the insulin and glucose protection correspond with significantly increased lipids in the Cre+ HFD mice. For these reasons, we began investigating the possible mechanisms with primary cultures of Human Adipose Microvascular Endothelial Cells (HAMECs) and knocked down Cav1 with siRNA. In monolayers of HAMEC without any other cell type present, we did not observe altered lipid uptake after addition of 50µM of exogenous fatty acids with a 70% knockdown of Cav1 protein. Additionally, HAMECs seahorse assays were used to determine if there were changes in metabolic function when Cav1 was knocked down. This work provides initial evidence for the unique metabolic roles of endothelial Cav1 during periods of high lipid circulation.

The WRKY6 transcription factor affects seed oil accumulation and alters fatty acid compositions in Arabidopsis thaliana.

In rapeseed, the oil content of the seed not only supplies energy for seed germination and seedling development but also provides essential dietary nutrients for humans and livestock. Recent studies have revealed that many transcription factors (TFs) regulate the accumulation of fatty acids (FAs) during seed development. WRKY6, a WRKY6 family TF, was reported to serve a function in the plant senescence processes, pathogen defense mechanisms and abiotic stress responses. However, the precise role of WRKY6 in influencing FA accumulation in seeds is still unknown. In this study, we demonstrate that WRKY6 has a high expression level in developing seeds and plays an essential role in regulating the accumulation of FAs in developing seeds of Arabidopsis. Mutation of WRKY6 resulted in significant increase in seed size, accompanied by an increase in FA content and changes in FA composition. Ultrastructure analyses showed that the absence of WRKY6 resulted in more and higher percentage of oil body in the cell of mature seeds. Quantitative real-time PCR analysis revealed changes in the expression of several genes related to photosynthesis and FA biosynthesis in wrky6 mutants at 10 or 16 days after pollination. These results reveal a novel function of WRKY6 influencing seed oil content and FAs compositions. This gene could be used as a promising gene resource to improve FA accumulation and seed yield in Brassica napus through genetic manipulation.

GRP94 Is Involved in the Lipid Phenotype of Brain Metastatic Cells.

Metabolic adaptation may happen in response to the pressure exerted by the microenvironment and is a key step in survival of metastatic cells. Brain metastasis occurs as a consequence of the systemic dissemination of tumor cells, a fact that correlates with poor prognosis and high morbidity due to the difficulty in identifying biomarkers that allow a more targeted therapy. Previously, we performed transcriptomic analysis of human breast cancer patient samples and evaluated the differential expression of genes in brain metastasis (BrM) compared to lung, bone and liver metastasis. Our network approach identified upregulation of glucose-regulated protein 94 (GRP94) as well as proteins related to synthesis of fatty acids (FA) in BrM. Here we report that BrM cells show an increase in FA content and decreased saturation with regard to parental cells measured by Raman spectroscopy that differentiate BrM from other metastases. Moreover, BrM cells exerted a high ability to oxidize FA and compensate hypoglycemic stress due to an overexpression of proteins involved in FA synthesis and degradation (SREBP-1, LXRα, ACOT7). GRP94 ablation restored glucose dependence, down-regulated ACOT7 and SREBP-1 and decreased tumorigenicity in vivo. In conclusion, GRP94 is required for the metabolic stress survival of BrM cells, and it might act as a modulator of lipid metabolism to favor BrM progression.

Phospholipid components of the synthetic pulmonary surfactant CHF5633 probed by fluorescence spectroscopy

CHF5633 (Chiesi Farmaceutici, Italy) is a synthetic pulmonary surfactant currently under clinical development for the treatment of Respiratory Distress Syndrome in premature infants. The product is composed of phospholipids in liposomal organization, together with two peptide analogues of human surfactant proteins B and C. Phospholipids in liposomes can undergo oxidation of unsaturated lipids and hydrolysis, with formation of fatty acids and lysolipids, both affecting the physico-chemical properties of the formulation. We exploited two fluorescence probes, Prodan and ADIFAB, to evaluate the stability of the phospholipid components of CHF5633. While Prodan enters the phospholipid bilayer and probes the polarity of this environment, ADIFAB binds free fatty acids in the aqueous phase, allowing to determine their concentration. Changes of Prodan fluorescence emission indicated an increase in the polarity of the phospholipid bilayer as a function of time. This behavior is coupled with an increase in fatty acids concentration in the aqueous phase, as determined by ADIFAB, and an increase in lysolipids concentration, as determined by HPLC-MS. Prodan and ADIFAB resulted efficient probes to monitor phospholipids hydrolysis in liposomes, reporting an increased stability of CHF5633 at pH values higher than 6.5.

Effects of increased myocardial tissue concentration of myristic, palmitic and palmitoleic acids on the course of cardiac atrophy of the failing heart unloaded by heterotopic transplantation.

The present experiments were performed to evaluate if increased heart tissue concentration of fatty acids, specifically myristic, palmitic and palmitoleic acids that are believed to promote physiological heart growth, can attenuate the progression of unloading-induced cardiac atrophy in rats with healthy and failing hearts. Heterotopic abdominal heart transplantation (HT(x)) was used as a model for heart unloading. Cardiac atrophy was assessed from the ratio of the native- to-transplanted heart weight (HW). The degree of cardiac atrophy after HT(x) was determined on days 7, 14, 21 and 28 after HT(x) in recipients of either healthy or failing hearts. HT(x) of healthy hearts resulted in 23+/-3, 46+/-3, 48+/-4 and 46+/-4 % HW loss at the four time-points. HT(x) of the failing heart resulted in even greater HW losses, of 46+/-4, 58+/-3, 66+/-2 and 68+/-4 %, respectively (P<0.05). Activation of "fetal gene cardiac program" (e.g. beta myosin heavy chain gene expression) and "genes reflecting cardiac remodeling" (e.g. atrial natriuretic peptide gene expression) after HT(x) was greater in failing than in healthy hearts (P<0.05 each time). Exposure to isocaloric high sugar diet caused significant increases in fatty acid concentrations in healthy and in failing hearts. However, these increases were not associated with any change in the course of cardiac atrophy, similarly in healthy and post-HT(x) failing hearts. We conclude that increasing heart tissue concentrations of the fatty acids allegedly involved in heart growth does not attenuate the unloading-induced cardiac atrophy.

Evaluation of Major Fatty Acids Determination in Palm Oil by Gas Chromatography-Flame Ionization Detection

The fatty acid composition of palm oil is the major factor influencing its physical and chemical properties. The purpose of this research was to evaluate the analytical performance of major fatty acids (palmitic acid, stearic acid, oleic acid, and linoleic acid) analysis in palm oil. Triglycerides of palm oil were derivatized to fatty acid methyl esters (FAMEs) by using boron trifluoride (BF3) in methanol. FAMEs were determined by gas chromatography-flame ionization detection (GC-FID) using DB-23 capillary column as stationary phase. The studied parameters were instrument performance analysis, the efficiency of fatty acid derivatization, stability of derivatized analytes, accuracy, repeatability, intra-lab reproducibility, ruggedness, and method uncertainty. The evaluation results showed the instrument linearity at a working range of 5 to 40 mg/mL marked by coefficient of determination (R2) between 0.991-0.995. Instrument limits of detection (LOD) and instrument limits of quantification (LOQ) for 4 major fatty acids analysis were 26-35 µg/mLand 86-128 µg/mL, respectively. The increase of fatty acid concentration led to the decrease of derivatization efficiency in the fatty acids analysis. The result also showed that derivatized analytes were stable during 24 h storage at freeze temperature. The average recovery values by spiking method with the spiking concentration at 50 and 90 mg/g sample were at 75-94 % for stearic and linoleic acids analysis, however those for palmitic and oleic acids analysis were considered very low (&lt;40 %), due to their low derivatization efficiency. Repeatability and intra-lab reproducibility of 4 major fatty acids analysis were at acceptable ranges, 0.45-1.38 % and 1.15-2.03 %, respectively. Determination by varying the volume of derivatizing agent showed the rugged method. Uncertainty of repeatability (Ur) and uncertainty of reproducibility (Ur) were ranged at 1.84-9.02 mg/g and 1.40-10.65 mg/g, respectively. This method was considerably reliable for the analysis of less abundance fatty acids in palm oil, stearic and linoleic acids.

Increased serum serotonin improves parturient calcium homeostasis in dairy cows

Hypocalcemia in dairy cows is caused by the sudden increase in calcium demand by the mammary gland for milk production at the onset of lactation. Serotonin (5-HT) is a key factor for calcium homeostasis, modulating calcium concentration in blood. Therefore, it is hypothesized that administration of 5-hydroxy-l-tryptophan (5-HTP), a 5-HT precursor, can increase 5-HT concentrations in blood and, in turn, induce an increase in blood calcium concentration. In this study, 20 Holstein dairy cows were randomly assigned to 2 experimental groups. Both groups received a daily i.v. infusion of 1 L of either 0.9% NaCl (C group; n = 10) or 0.9% NaCl containing 1 mg of 5-HTP/kg of BW (5-HTP group, n = 10). Infusions started d 10 before the estimated parturition and ceased the day of parturition, resulting in at least 4 d of infusion (8.37 ± 0.74 d of infusion). Until parturition, blood samples were collected every morning before the infusions, after parturition samples were taken daily until d 7, and a final sample was collected on d 30. Milk yield was recorded during this period. No differences between groups were observed for blood glucose, magnesium, and β-hydroxybutyrate. Cows receiving the 5-HTP infusion showed an increase in fatty acid concentrations from d -3 to -1 before parturition. Serum 5-HT concentrations were increased at d -4 related to parturition until d 5 postpartum in the 5-HTP group compared with the C group. In addition, cows from the 5-HTP group had increased 5-HT concentrations in colostrum, but not in mature milk, on d 7 postpartum. Serum calcium concentrations decreased in both groups around parturition; however, calcium remained higher in the 5-HTP group than in controls, with a significant difference between groups on d 1 (1.62 ± 0.08 vs. 1.93 ± 0.09 mmol/L in control and 5-HTP groups, respectively) and d 2 (1.83 ± 0.06 vs. 2.07 ± 0.07 mmol/L in control and 5-HTP groups, respectively). Additionally, colostrum yield (first milking) was lower in the 5-HTP group compared with the C group, but without consequences on colostrum IgG concentrations. Milk yield did not differ between groups during the rest of the experiment. The study data were consistent with the concept that infusion of 5-HTP to dairy cows increases blood 5-HT concentrations, which in turn is a significant regulatory component in the chain of effectors that affect calcium status around parturition, hence the occurrence of clinical or subclinical hypocalcemia.

The effect of photon flux density on algal biofilm growth and internal fatty acid concentrations

Algal biofilm systems offer potential advantages over planktonic systems for growing, harvesting and processing algal biomass. To determine how feasible these systems can be, however, researchers must determine optimal biomass and lipid productivities. In this paper the effect of photon flux density (PFD) on algal biofilm biomass productivities, internal fatty acid concentrations, and overall fatty acid productivity was studied. It was determined that as PFD increased, algal biofilm biomass productivities significantly increased until they peaked i.e. at about 300μmol/m2/s, presumably due to light saturation. Increasing PFDs from 50 to 150μmol/m2/s produced statistically significant increases in fatty acid concentrations from 5% to 8%; however, increasing PFDs beyond that range did not enhance lipid accumulation. Because of significant increases in biomass productivity with increased PFD, there was also a significant increase in fatty acid productivity with increased PFD. Lastly, increasing PFD resulted in diminishing returns of biomass productivity, suggesting that photons are not being effectively utilized at higher light intensities. This finding has implications for photobioreactor design and operation with artificial lighting.

The Effect of TRANSPARENT TESTA2 on Seed Fatty Acid Biosynthesis and Tolerance to Environmental Stresses during Young Seedling Establishment in Arabidopsis

In plants, fatty acids (FAs) and FA-derived complex lipids are major carbon and energy reserves in seeds. They are essential components of cellular membranes and cellular signal or hormone molecules. Although TRANSPARENT TESTA2 (TT2) is well studied for its function in regulating proanthocyanidin biosynthesis in the seed coat, little attention has been given to its role in affecting seed FA accumulation and tolerance to environmental stresses. We demonstrate that the tt2 mutation remarkably increased the seed FA content, decreased seed weight, and altered the FA composition. The increase in FA content in the tt2 seeds was due to the relative decrease of seed coat proportion as well as the more efficient FA synthesis in the tt2 embryo. Microarray analysis revealed that tt2 mutation up-regulated a group of genes critical to FA biosynthesis and embryonic development. The mutation also altered the gene expressions that respond to stress. The microarray analysis discovered that the increase in FA accumulation of the tt2 seeds were accompanied by the significant up-regulation of FUSCA3, a transcriptional factor for embryonic development and FATTY ACID ELONGASE1, which catalyzes the elongation of FA chains. Moreover, lower seed protein accumulation during seed maturation also contributed to the increased seed FA accumulation in tt2 mutants. This study advances the understanding of the TT2 gene in seed FA accumulation and abiotic stresses during seed germination and seedling establishment.

Temporal fatty acid dynamics of the octocoral Veretillum cynomorium

The objectives of the present work were to investigate the temporal variation in the fatty acid (FA) composition of the octocoral Veretillum cynomorium, examine the effects of reproduction and environmental factors on FA variation, and establish a chemotaxonomic identification for this species. Mean oocyte size-frequency distributions showed that the majority of the oocytes had an intermediate size (Group II) before spawning (April and June). The late-vitellogenic oocytes (Group III) became absent in August and October and, during this post-spawning period, oocytes were primarily of small size (Group I). Most of the major FA, 16:0, 18:0, 20:4n-6, 20:5n-3, and the tetracosapolyenoic fatty acid (TPA), 24:6n-3, varied significantly throughout the year (p<0.01), with two peaks in August/October and February. The boost in early oogenesis, also associated with warmer temperatures, seemed to be responsible for the observed increase in FA content between June and August. The highest values of FA content were observed in February when intermediate oogenesis (Group II) was at its peak and there were considerable levels of available food in the environment. Also, the increase in food availability seemed to trigger the final stages of gametogenesis. The high quantity of 18:1n-7, odd-numbered and branched FAs, suggested the presence of a dynamic bacterial community in V. cynomorium, probably as an adaptive response to the lack of symbiotic microalgae. Although the presence of TPAs is the main feature distinguishing octocorals from other coral species, here we showed that there was no single FA clearly dominating the FA composition of V. cynomorium throughout the year. Instead, four main FAs share similar concentrations: 16:0, 20:4n-6, 20:5n-3 and 24:6n-3. The predominance of these four FAs combined with the higher amount of 24:6n-3 when compared to 24:5n-6 may serve as a chemotaxonomic feature to distinguish this octocoral species (or genus).

Differential effects of short- and long-term high-fat diet feeding on hepatic fatty acid metabolism in rats

Imbalance in the supply and utilization of fatty acids (FA) is thought to contribute to intrahepatic lipid (IHL) accumulation in obesity. The aim of this study was to determine the time course of changes in the liver capacity to oxidize and store FA in response to high-fat diet (HFD). Adult male Wistar rats were fed either normal chow or HFD for 2.5weeks (short-term) and 25weeks (long-term). Short-term HFD feeding led to a 10% higher palmitoyl-l-carnitine-driven ADP-stimulated (state 3) oxygen consumption rate in isolated liver mitochondria indicating up-regulation of β-oxidation. This adaptation was insufficient to cope with the dietary FA overload, as indicated by accumulation of long-chain acylcarnitines, depletion of free carnitine and increase in FA content in the liver, reflecting IHL accumulation. The latter was confirmed by in vivo1H magnetic resonance spectroscopy and Oil Red O staining. Long-term HFD feeding caused further up-regulation of mitochondrial β-oxidation (24% higher oxygen consumption rate in state 3 with palmitoyl-l-carnitine as substrate) and stimulation of mitochondrial biogenesis as indicated by 62% higher mitochondrial DNA copy number compared to controls. These adaptations were paralleled by a partial restoration of free carnitine levels and a decrease in long-chain acylcarnitine content. Nevertheless, there was a further increase in IHL content, accompanied by accumulation of lipid peroxidation and protein oxidation products. In conclusion, partially effective adaption of hepatic FA metabolism to long-term HFD feeding came at a price of increased oxidative stress, caused by a combination of higher FA oxidation capacity and oversupply of FA.

High fat diet induced diabetic cardiomyopathy

In response to a chronic high plasma concentration of long-chain fatty acids (FAs), the heart is forced to increase the uptake of FA at the cost of glucose. This switch in metabolic substrate uptake is accompanied by an increased presence of the FA transporter CD36 at the cardiac plasma membrane and over time results in the development of cardiac insulin resistance and ultimately diabetic cardiomyopathy. FA can interact with peroxisome proliferator-activated receptors (PPARs), which induce upregulation of the expression of enzymes necessary for their disposal through mitochondrial β-oxidation, but also stimulate FA uptake. This then leads to a further increase in FA concentration in the cytoplasm of cardiomyocytes. These metabolic changes are supposed to play an important role in the development of cardiomyopathy. Although the onset of this pathology is an increased FA utilization by the heart, the subsequent lipid overload results in an increased production of reactive oxygen species (ROS) and accumulation of lipid intermediates such as diacylglycerols (DAG) and ceramide. These compounds have a profound impact on signaling pathways, in particular insulin signaling. Over time the metabolic changes will introduce structural changes that affect cardiac contractile characteristics. The present mini-review will focus on the lipid-induced changes that link metabolic perturbation, characteristic for type 2 diabetes, with cardiac remodeling and dysfunction.

Role of prostaglandin I2 and prostaglandin E2 in the initiation of nonshivering thermogenesis during the simulation of birth in utero.

Because maximal nonshivering thermogenesis can commence only after occlusion of the umbilical cord, circulating stimulators and inhibitors were hypothesized to alter brown fat activity in the perinatal period. The roles of prostaglandin I2 (PGI2) and PGE2 in the initiation of nonshivering thermogenesis at birth were investigated. Indomethacin (45 mg bolus, 3 mg h-1 thereafter) was infused into 10 near-term fetal sheep to decrease prostanoid synthesis; 6 age-matched fetuses were infused with saline as controls. Sixteen hours later, birth was simulated in utero by sequentially cooling the fetus, ventilating its lungs with oxygen and occluding the umbilical cord. In the control fetuses, the plasma concentrations of PGI2 and PGE2 and free fatty acids, an index of nonshivering thermogenesis, were unaffected by cooling. Ventilation caused the concentration of PGI2 to increase 108% (P < 0.001) and that of PGE2 to decrease 26% (P < 0.05), while fatty acid concentrations increased 100% (P < 0.05). After cord occlusion, PGI2 concentrations remained elevated whereas PGE2 concentrations decreased a further 46% (P < 0.01), and fatty acid concentrations increased a further 100% (P < 0.05). In the indomethacin-treated fetuses, PGI2 and PGE2 concentrations decreased to 20% of the preinfusion values (P < 0.001) and did not change during the experiment. Cooling initiated a 300% increase in fatty acid concentrations (P < 0.05) and ventilation and cord occlusion induced no further significant changes. Thus, prostanoid concentrations follow changes in nonshivering thermogenic activity and support a regulatory role for PGI2 and PGE2 in the initiation of thermogenesis. Before birth, high concentrations of PGE2 favour suppression of thermogenesis, and after birth this inhibition is removed and there is stimulation by PGI2.

Acute effects of surgery on carbohydrate production and utilization in the fed rat.

1. The work utilized a model of uncomplicated abdominal surgery (laparotomy under ether anaesthesia) to delineate the effects of abdominal trauma on glucose homoeostasis in the fed rat. 2. Regulation of glucose production and utilization was investigated by observing the response to the administration of glucose, insulin plus glucose and 5-methylpyrazole 3-carboxylic acid. 3. Glucose administration suppressed hepatic glucose output as assessed by portal-venous concentration differences in control or surgically stressed rats. In contrast, glycaemia was increased and lactaemia decreased in the latter group. Portal-venous concentrations differences for lactate were unaffected. 4. Surgery increased plasma fatty acid concentrations and the antilipolytic response to glucose or glucose plus insulin was diminished. Post-operative increases in fatty acid concentrations were associated with inhibition of hepatic pyruvate dehydrogenase complex which was reversed by insulin, indicating a differential sensitivity of adipose tissue and liver to the hormone. 5. The model of surgical stress utilized, while affecting extrahepatic glucose disposal, did not elicit depletion of liver glycogen or inactivation of L-pyruvate kinase. 6. It is concluded that the initial response to uncomplicated abdominal surgery involves carbohydrate conservation rather than increased glucose production, with effects to decrease extrahepatic glucose uptake and hepatic glucose oxidation.

On the mechanism by which noradrenaline increases the activity of phosphofructokinase in isolated rat adipocytes.

We confirmed that, as reported by Sooranna & Saggerson [(1982) Biochem. J. 202, 753-758], the affinity of 6-phosphofructo-1-kinase (PFK) for fructose 6-phosphate in an adipocyte extract was increased after incubation of the cells in the presence of noradrenaline. The participation of fructose 2,6-bisphosphate in this kinetic modification could be excluded, because the noradrenaline effect persisted after extensive gel filtration of the extracts and also because the treatment did not cause any change in the concentration of fructose 2,6-bisphosphate in the adipocytes. Oleic acid was found to be another potent positive effector of PFK in an adipocyte extract, with a Ka of 10 microM. Its effect was synergistic with that of fructose 2,6-bisphosphate and AMP, and was counteracted by serum albumin. Palmitic acid had a similar effect. We conclude that the large increase in fatty acid concentration caused by noradrenaline treatment is an explanation for the activation of phosphofructokinase at low fructose 6-phosphate concentrations in an adipocyte extract.

Simulating the Diabetic Environment Modifies In Vitro Prostacyclin Synthesis

To explain the contradictory data on the secretion of prostacyclin (PGI2) in clinical and experimental diabetes, we have investigated the effect of each of the major metabolic abnormalities in uncontrolled diabetes on vascular PGI2 synthesis. An increase in fatty acid concentrations caused a dose-dependent inhibition of PGI2 synthesis by rat aortic rings in vitro; linoleic and linolenic acids were consistently the most and palmitic the least inhibitory. Glucose had a stimulatory effect between 10 and 30 mmol/L, but a progressive fall in stimulation occurred at higher concentrations. Insulin was inhibitory at 10 and 50 mU/L; however, in combination with glucose (10 mmol/L) it was significantly stimulatory (at 10 mU/L) when the aortic rings were preincubated for 2 and 4 h. A pH of 7.0 or less was significantly inhibitory, whereas ketone bodies had no significant effect on PGI2 synthesis. These data show for the first time that altered metabolic factors in uncontrolled diabetes may have different effects on vascular PGI2 synthesis. These data help explain the variability of observations related to PGI2 synthesis and secretion in diabetes, and advocate a more detailed definition of the metabolic status of patients/animals used in such experiments.

Fatty Acid Changes in Liver Produced by Protein Deficiency and by Methionine or Cystine Fed to Rats in a Protein-free Ration

Liver fatty acid changes were studied during the development of an uncomplicated protein deficiency and in protein deficiency complicated by the addition of 0.30% methionine to the protein-free diet. (Only slightly fatty livers are produced in uncomplicated protein deficiency, whereas very fatty livers are produced by including methionine or cystine in a protein-free diet.) In general the fatty acid changes in adult male rats fed either diet followed similar patterns, although the extent of the changes was different. The increase in liver fatty acids could be accounted for almost entirely by elevations in palmitate, oleate, and linoleate. When dietary fat (corn oil) was omitted, however, the contribution by linoleate was depressed almost completely, being substituted for by palmitoleate and oleate. Significant loss of all fatty acids from the phospholipid fraction occurred. The presence of methionine in the protein-free diet in general protected against the loss of fatty acids from this fraction. Palmitoleate and oleate substituted for linoleate in the phospholipid fraction when dietary corn oil was omitted. The fat in the fatty livers produced by methionine or cystine was accounted for almost entirely by marked increases in neutral lipid palmitate, oleate, and linoleate. Cystine, methionine, and valine fed in the protein-free diet increased arachidonate concentration in the neutral lipid fraction, whereas leucine depressed it almost completely. When protein repletion was begun, all fatty acids except linoleate and arachidonate returned to extremely high values in the livers of the protein-free rats and to a much less extent in livers of the rats previously fed methionine in the protein-free diet. These studies suggest the following general conclusions: An as yet unknown mechanism allows the production of fatty livers when methionine is present in a protein-free ration. If linoleate is present in the diet, it accounts for a large part of the fat; but palmitoleate and oleate can substitute for linoleate. An imbalance between fat-synthesizing systems and fat-secreting systems in the liver probably accounts for a very large, transient increase in fatty acid concentrations when protein is reintroduced into the diet of protein-deficient animals. The enzyme systems involved in producing arachidonate from linoleate appear to be sharply impaired by protein deficiency. Methionine fed in a protein-deficient diet, however, almost completely prevents this effect.