Effects of acute systemic 3-nitropropionic acid administration on rat activity and acoustic startle

Spontaneous activity, acoustic startle, and prepulse inhibition (PPI) of acoustic startle were measured in male Sprague–Dawley rats 3–5 h after 0, 10, 15, or 20 mg/kg i.p. 3-nitropropionic acid (3-NP), a mitochondrial toxin. Mean activity was significantly influenced by the 3-NP dose due to decreased activity for 20 mg/kg. Mean startle amplitude was not significantly affected by the 3-NP dose. Means of PPI for prepulses 6 and 12 dBA above background were smaller than means for respective 0 mg/kg doses, but the main effect of 3-NP dose did not reach statistical significance in ANOVA. The changes in measured exploratory-type activity and, possibly, in startle PPI parallel the occurrence of clinical signs exhibited at 3–5 h after 3-NP injection. Neural processing involved in these quantitative behavioral endpoints seems to be affected as energy stores are depleted and degenerative processes are beginning.     

Effect of docosahexaenoic acid and furan fatty acids on cytokinesis block micronucleus cytome assay biomarkers in astrocytoma cell lines under conditions of oxidative stress

Fatty acids from fish such as docosahexaenoic acid (DHA) are associated with improved brain function, whereas furan fatty acids (FFAs) also found in fish oil at low levels (1%) are thought to have antioxidant properties. Understanding their effects in astrocytes is important as these cells are responsible for maintaining healthy neurons via lipid homeostasis and distribution within the brain, and their decline with aging is a possible cause of dementia. We investigated the cytotoxic and genotoxic effects of DHA and FFA using the cytokinesis‐block micronucleus cytome assay in in vitro cultures of U87MG (APOE ?3/?3) and U118MG (APOE ?2/?4) astrocytoma cell lines with and without a hydrogen peroxide (H₂O₂, 100 µM) challenge. U118MG was found to be more sensitive to the cytostatic, cytotoxic (i.e., apoptosis), and DNA damaging effects [micronuclei (MNi), nucleoplasmic bridges (NPBs), and nuclear buds (NBUDs)] of H₂O₂ (P < 0.01 and P < 0.001) when compared with U87MG. DHA at 100 µg/mL significantly affected cytostasis (P < 0.05) and increased DNA damage in the form of NPBs and MNi (P < 0.05) in both cell lines, whereas it decreased necrosis (P = 0.0251) in U87MG. Significant DHA–H₂O₂ interactions were observed for decreased necrosis (P = 0.0033) and DNA damage biomarkers (P < 0.0001) in the U87MG cell line and increased cytostasis (P < 0.0001) in the U118MG cell line. The effects of FFA also varied between the cell lines, with significant effects observed in decreased cytostasis (P = 0.0022) in the U87MG cell line, whereas increasing cytostasis (P = 0.0144) in the U118MG cell line. Overall, FFA exerted minimal effects on DNA damage biomarkers. Environ. Mol. Mutagen. 55:573–590, 2014. © 2014 Wiley Periodicals, Inc.     

Effect of free fatty acid on the rat lateral hypothalamic neurons

The glucose-sensitive neurons in the rat lateral hypothalamic area which are inhibited by glucose microapplications through one of multibarreled micropipettes were facilitated by microapplication of free fatty acids (FFA). This was a specific effect and was not obtained from a majority of neurons which were insensitive to glucose. The specific effect may be generated by an inactivation of the Na-pump. It may be suggested that when the rat is in energy deficit and FFA is consequently released into the blood stream, the specific chemosensitive neuron might this event and lead the animal to eat.     

The influence of free fatty acids on glycogen recovery in rat heart after exercise

Summary Glycogen supercompensation is the term used to denote the abnormally high levels of glycogen found in the heart shortly after an exercise-induced reduction of the substrate. Using rats, we tested whether this condition was linked to the use of plasma free fatty acids (FFA), which normally rise with exercise. Before a 1-h swim, animals received an injection of either saline (S) or nicotinic acid (NA). The nicotinic acid treatment dramatically suppressed the rise in plasma FFA observed in the S-group. Exercise caused a significant but similar reduction (35–38%) of the myocardial glycogen content in both groups. After 1 h of recovery in the S-group, myocardial glycogen reached a value of 30.3±1.7 Μmol·g⁻¹ or 113% of that measured before the exercise began. In contrast, the value for hearts from the NA-group with reduced FFA levels was 24.0±1.9 Μmol·g⁻¹ or only 91% of that measured before exercise. After 2 h the values were 33.8±1.4 and 29.0±1.9 Μmol·g⁻¹ respectively. These data indicate that glycogen repletion in rat heart after exercise is related to the amount of FFA present in the plasma. We suggest that carbohydrate metabolism is diverted towards synthesis and storage as a result of the glycolytic inhibition exerted by the increased use of fat as an energy source as previously observed in hearts from fasted or diabetic animals. This work was supported by a grant from the Utah Heart Association and the Deseret Gym Corporation     

Dose-response effects of free fatty acids on amino acid metabolism and ureagenesis

Aim: Free fatty acids (FFAs) are important fuels and have vital protein‐sparing effects, particularly during conditions of metabolic stress and fasting. However, it is uncertain whether these beneficial effects are evident throughout the physiological range or only occur at very high FFA concentrations. It is also unclear whether secondary alterations in hormone levels and ketogenesis play a role. We therefore aimed at describing dose–response relationships between amino acid metabolism and circulating FFA concentrations at clamped hormone levels. Methods: Eight healthy men were studied on four occasions (6 h basal, 2 h glucose clamp). Endogenous lipolysis was blocked with acipimox and Intralipid was infused at varying rates (0, 3, 6 or 12 μL kg^?1 min^?1) to obtain four different levels of circulating FFAs. Endogenous growth hormone, insulin and glucagon secretion was blocked by somatostatin (300 μg h^?1) and replaced exogenously. 15N‐phenylalanine, 2H4‐tyrosine and 13C‐urea were infused continuously to assess protein turnover and ureagenesis. Results: We obtained four distinct levels of FFA concentrations ranging from 0.03 to 2.1 mmol L^?1 and 3‐hydroxybutyrate concentrations from 10 to 360 μmol L^?1. Whole‐body phenylalanine turnover and phenylalanine‐to‐tyrosine degradation decreased with increasing FFA levels as did insulin‐stimulated forearm fluxes of phenylalanine. Phenylalanine, tyrosine and urea concentrations also decreased progressively, whereas urea turnover was unperturbed. Conclusion: Circulating FFAs decrease amino acid concentrations and inhibit whole‐body phenylalanine fluxes and phenylalanine‐to‐tyrosine conversion. Our data cover FFA concentrations from 0 to 2 mmol L^?1 and indicate that FFAs exert their protein conserving effects in the upper physiological range (>1.5 mmol L^?1).     

Striatal dopamine in the response of brain and liver unsaturated and saturated free fatty acids following administration of C75 in CD-1 mice

In order to clarify the mechanism of action of cerulenin analog, C75, known to suppress feeding behavior, food intake was measured in adult CD-1 male mice n = 5 per group, treated i.p. with 10 and 20 mg/kg of C75. Animals in both treatment groups had significantly lower 24 h food consumption rate relative to the control group injected with vehicle. Striatal monoamine neurotransmitters and striatal as well as liver long chain free fatty acids concentrations were subsequently evaluated in another group treated i.p. with 20 mg/kg C75. Acute exposure to C75 at 20 mg/kg led to approximately 50% increase in the striatal dopamine levels and a decrease in dopamine turnover for up to 24 h following the injection. The concentration of serotonin remained unchanged. Concentration of saturated fatty acids in the liver and striatum did not change, while striatal unsaturated myristoleic acid (cis-9-tetradecenoic acid) levels were significantly higher as early as 2 h post-injection and remained elevated at 24 h post-injection. These preliminary data suggest a central regulatory role of unsaturated fatty acids under dopaminergic control in the C75-induced anorexia. Pharmacological alterations in fatty acid metabolism may prove beneficial in the treatment of obesity.     

Elevated free fatty acid levels inhibit glucose phosphorylation in slow-twitch rat skeletal muscle

The effect of increased free fatty acid concentrations on glucose metabolism in rat skeletal muscle was investigated at several different steps in glucose metabolism including glucose transport, glucose phosphorylation, glucose oxidation and glycogen synthesis. In isolated soleus (slow-twitch) muscles, insulin-stimulated (100 μml^-1) glucose phosphorylation, but not glucose transport, was inhibited by 26 and 22% in the presence of 1.0 and 2.0 mM oleate, respectively (P< 0.01). Regardless of oleate concentration (0.3 or 2.0 mM), insulin-stimulated glucose 6-phosphate levels were elevated to the same extent over the non-insulin-stimulated levels in soleus muscles {P < 0.01). Insulin-stimulated glucose oxidation was inhibited by 44% in soleus muscles exposed to 2.0 mM oleate (P < 0.05), whereas the rate of glucose incorporation into glycogen was not altered. In insulin-stimulated epitrochlearis (fast-twitch) muscles, elevated concentrations of oleate had no effect on the rates of glucose transport or glucose phosphorylation, or on the level of glucose 6-phosphate. These data suggest that increased free fatty acid availability decreases glucose utilization by selectively inhibiting glucose phosphorylation and oxidation in slow-twitch, but not fast-twitch skeletal muscle.     

Detection of free fatty acids following a conditioned taste aversion in rats

A gustatory transduction mechanism for free fatty acids (FFAs) has been described in isolated rat taste receptor cells; however, the ability of behaving rats to detect FFAs has not been characterized. Through conditioned taste aversion (CTA) methodology, this study defines the ability of rats to detect and avoid the two principal FFA components of corn oil, linoleic and oleic acid. Following taste aversion conditioning, rats avoided both linoleic and oleic acid at greater than or equal to 66 muM and failed to avoid either 44 muM linoleic or oleic acid. Rats demonstrated generalized avoidances between 88 muM linoleic and oleic acid irrespective of presenting the FFAs as either unesterified acids dissolved in 5 mM ethanol or aqueous sodium salts, sodium linoleate and sodium oleate. Following a CTA to linoleic acid, rats did not show generalized avoidance of NaCl or ethanol, two potentially concomitant tastants in the oral cavity. A CTA to linoleic or oleic acid did produce a generalized avoidance to the other FFA. These results support the ability of rats to detect linoleic and oleic acid (>44 muM) and suggest that the two FFAs share common orosensory properties. Furthermore, it is unlikely that the detection of the FFAs is due to an enhancement of other concomitant tastants such as saliva or the delivery solution.     

Delayed cell migration in the developing rat brain following maternal omega 3 alpha linolenic acid dietary deficiency

Diminished levels of docosahexaenoic acid (DHA, 22:6n-3), the major polyunsaturated fatty acid (FA) synthesized from alpha linolenic acid (ALA, 18:3n-3), have been implicated in changes in neurotransmitter production, ion channel disruption and impairments of a variety of cognitive, behavioral and motor functions in the perinatal and adult mammal. Neuronal migration in the cortex and hippocampus of newborn and postnatal rats after ALA-deficiency, beginning on the 2nd day after conception and continuing for three weeks, was investigated. A marked decrease in the migration of bromodeoxyuridine⁽⁺⁾/neuronal nuclei⁽⁺⁾/neurofilament⁽⁺⁾ and glia fibrillary acidic protein^(–) neuronal cells to the dense cortical plate was accompanied by a corresponding abundance of non-migrating cells in several regions such as cortical layers IV–VI, corpus callosum and the sub-ventricular zone of ALA-deficient newborns. Similarly, a delayed migration of cells to CA1 and dentate gyrus areas was noticed while most cells were retained in the subicular area adjacent to the hippocampus. The reversibility of delay in migration in the hippocampus and cortex, after one and two weeks respectively, may be attributed to a temporary reelin disorganization or partial deficiency. Transient obstruction of neuronal cell migration may have long-lasting consequences on the organization of neuronal assemblies, on the connection between neurons (lateral connections) and acquisition of function in the adult brain.     

JCL roundtable: Omega-3 fatty acids and cardiovascular outcomes

The Reduction of Cardiovascular Events with Icosapent Ethyl–Intervention Trial (REDUCE-IT) in 2018 demonstrated the value of an omega-3 fatty acid formulation, icosapent ethyl (eicosapentaenoic acid ethyl ester) for preventive treatment of atherosclerotic cardiovascular disease (ASCVD). This JCL Roundtable discussion brings together three experts to explore the origins and implications of REDUCE-IT and more broadly omega-3 fatty acids for mitigation of ASCVD risk. REDUCE-IT achieved a highly significant 25% reduction of major adverse cardiovascular events. It is the first trial of a triglyceride-lowering drug to gain unequivocal success in high-risk patients treated intensively with statins. It corroborates positive results from an earlier major trial using eicosapentaenoic acid (EPA) ethyl ester, the Japan EPA Lipid Intervention Study (JELIS), which included hypercholesterolemic subjects treated with low-dose statin mostly in primary prevention. Together these studies mark a new avenue for preventive treatment of ASCVD. Omega-3 fatty acids also show some promise, though less decisively, for reducing inflammation and cardiovascular mortality in a broader context.     

Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart Study

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Influence of osmolality,short chain fatty acids and deoxycholic acid on mucus secretion in the rat colon

Mucus secretion into the rat colon has been measured in situ using a single perfusion technique. Protein, sialic acid and hexose concentrations in the perfusion solution were found to give reliable estimates of mucus output if samples were homogenized prior to analysis. Mucus output as indicated by an increase in the concentration of mucus constituents was higher when the solution was hypotonic (270 mosm·kg^–1) or hypertonic (370 mosm·kg^–1) than when isotonic solutions (320 mosm·kg^–1) were used. The proportion of hexoses and sialic acid to protein was 23 and 14% at low, 23 and 11% at high osmolality, and 21 and 13% when isotonic solutions were used. Deoxycholic acid (DCA, 4 mmol·l^–1) increased the net secretion of mucus constituents 3 fold, whereas short chain fatty acids (SCFA) had no effect. Mucus composition during all treatments did not change significantly, even when stimulated with DCA.When mucus was released from the epithelial surface by previous perfusion with a DCA containing solution, net water and SCFA absorption rates and mucus output were significantly lowered for 2 to 3 h. However, no correlation between mucus secretion and SCFA absorption was found, indicating that a role for mucus as a diffusion barrier to SCFA is unlikely.Mucus output, which indicates the amount of mucus released from the epithelial surface, probably depends on the direction of net water movement, which follows the osmotic gradient between colon lumen and blood.     

A high n-6 polyunsaturated fatty acid diet reduces muscarinic M2/M4 receptor binding in the rat brain

The aim of this study was to examine the influence of different fat diets on muscarinic acetylcholine receptor binding. Nineteen male Sprague–Dawley rats were divided into four groups and fed a diet of either high saturated fat, n-6 polyunsaturated fatty acid (PUFA), n-3 PUFA or low fat (control) for 8 weeks. Using quantitative autoradiography, [³H]pirenzepine binding to muscarinic M1/M4 receptors and [³H]AF-DX384 binding to M2/M4 receptors were measured throughout the brain in all four groups. The main findings were that compared to the low fat control group, M2/M4 receptor binding was significantly reduced in the dorsolateral, dorsomedial and ventromedial parts of the caudate putamen (61–64%, p < 0.05), anterior cingulate cortex (59%, p < 0.01), dentate gyrus and CA1–3 fields of the hippocampus (32–43%, p < 0.01) of rats on a high n-6 PUFA diet; however, no differences in M1/M4 receptor binding densities between the four groups were observed. These results suggest that a diet high in n-6 PUFA, but not of n-3 PUFAs or saturated fat, may selectively alter M2/M4 receptor-mediated signal transduction in the rat brain.     

Induction of apoptosis signal-regulating kinase 1 and oxidative stress mediate age-dependent vulnerability to 3-nitropropionic acid in the mouse striatum

The mitochondrial toxin, 3-nitropropionic acid (3-NP), produces age-dependent oxidative stress and selective striatal damage, which may simulate Huntington's disease starting in middle age. Recent reports showed that apoptosis signal-regulating kinase 1 (Ask1) activated by oxidative stress triggers a cell death signaling pathway. 3-NP was injected to the striatum in C57BL/6J mice. We have confirmed that striatal lesion volume and DNA fragmentation were age-dependent after 3-NP treatment. In the non-injured striatum of the middle-aged group, the protein levels of Ask1 and its active form, phosphorylated Ask1 (pAsk1), were significantly higher than in the young group. Ask1 increased more in the 3-NP injured striatum of the middle-aged group than in the non-injured striatum, and subsequently the activity of pAsk1 was significantly higher than in the young group. However, middle-aged SOD1Tg mice showed significant reductions of Ask1 and pAsk1 in the injured and the non-injured striatum compared to the middle-aged group. In particular, apoptosis signal transduction and cell death were significantly inhibited by the reduction of Ask1 expression using siRNA. Present results suggest that age-related upregulation of Ask1 and oxidative stress may mediate age-dependent striatal vulnerability to 3-NP.     

Effect of n-3 fatty acids on free tryptophan and exercise fatigue

Free tryptophan (Trp), which is augmented by liberated free fatty acids (FFA) from adipose tissue, can induce mental fatigue via serotonin during exercise. Since an attenuation in FFA has been observed with omega-3 fatty acid (n-3fa) use, our purpose was to examine the effect of n-3fa supplementation on free Trp availability and exercise fatigue. Ten recreationally trained men (n=5) and women (n=5), with maximal oxygen consumption (O_2max)of 51.6 (3.0) and 44.3 (1.4) ml kg^–1 min^–1, respectively, were studied on two occasions following an overnight fast, before and after n-3fa supplementation (4 g day^–1 for 4 weeks). The exercise trials consisted of a 75-min treadmill run at 60% O_2max followed immediately by a high-intensity incremental bout to fatigue. Measurements included exercise monitors, plasma volume (PV), triglycerides (TG), FFA, glycerol, lactate, and glucose. Free Trp and branched-chain amino acids (BCAA) were measured and correlated with time to fatigue; all blood variables were corrected for PV. Free Trp, lactate, glucose, FFA, and glycerol were not significantly different between trials, but TG (P<0.001) and the free Trp/BCAA ratio were significantly lower after n-3fa use [1.76 (0.18)×10^-2 g ml^–1] versus before supplementation [2.17 (0.22), P=0.033]. There was a non-significant increase in time to fatigue after supplementation [10.2 (0.3) min] versus before n-3fa use [9.7 (0.2), P=0.068], and a tendency for higher BCAA levels after supplementation, P=0.068. However, neither free Trp nor the free Trp/BCAA ratio significantly predicted time to fatigue. In conclusion, n-3fa supplementation did not diminish free Trp concentrations or significantly improve endurance performance during a maximal bout of exercise.     

Analysis of rapid oscillations of glucose and free fatty acids in plasma

Summary The authors analyzed rapid oscillations of blood sugar (GL) and free fatty acid levels (FFA) in serum of healthy subjects. They investigated a series of blood samples taken under conditions of absolute rest from the cubital vein at 15-s intervals for a period of 6 min. In addition to common statistical parameters, they calculated the course of autocorrelation and cross-correlation functions and periodograms. The magnitude of oscillations is significantly higher than the error of the biochemical methods. In some sequences periodicities were detected which were statistically significant in 23.8% of GL and in 38.1% of FFA. 24-point series of GL collected in parallel from both arms correlate in 36.3% positively, in 27.3% negatively, and in 36.4% they do not correlate. Series of FFA and GL collected simultaneously from one site correlate mutually in almost all instances either positively or negatively, frequently with a time shift. The oscillations may be due to (a) feedback regulations of the levels of the two metabolites, (b) permanent mutual interaction between the FFA and glucose level and (c) an uneven concentration of the two metabolites in different parts of the circulation. The above factors may combine, and the list of possible factors may not be complete.     

Chronic n-3 polyunsaturated fatty acid diet-deficiency acts on dopamine metabolism in the rat frontal cortex: a microdialysis study

The effects of -linolenic acid diet deficiency on rat dopaminergic metabolism were investigated in the frontal cortex of male 2–3 month-old rats using the microdialysis method. Increased basal levels of dopamine metabolites were observed in the frontal cortex of awake deficient rats, without modification of dopamine levels. Moreover, using KCl perfusion which releases newly synthesized dopamine, no difference was observed in anaesthetized deficient rats versus control rats. In addition, a decrease in dopamine release was observed in anaesthetized deficient rats versus control rats after tyramine stimulation, which is known to induce release of dopamine from vesicular stores. A working model is proposed which suggests that a chronic n-3 polyunsatured fatty acids (PUFA) deficiency may lead to modifications in the internalization of dopamine in the storage pool in the frontal cortex.     

3-硝基丙酸预处理对脑缺血耐受模型GLUT1和GLUT3表达的影响

目的: 探讨3-硝基丙酸(3-NPA)预处理对大鼠局灶性脑缺血半暗带区不同再灌注时点GLUT1和GLUT3 mRNA及蛋白水平表达的影响。方法: 雄性SD大鼠40只,随机分为假手术组(sham组,n=4)、预处理对照组(3-NPA组,n=4)、大脑中动脉缺血组(M组,n=16)、3-NPA 预处理组(IPC组,n=16)。M组和IPC组按再灌注时间(4 h、12 h、24 h及48 h)不同又分为4个亚组,每组动物4只。将大鼠在相应时点断头取脑,取缺血侧(左侧)冠状面中间1/3皮质,分别采用RT-PCR和Western blotting方法检测GLUT1、GLUT3 mRNA和蛋白水平表达情况。结果: IPC组GLUT1 mRNA表达在缺血再灌注后4 h开始升高,48 h最大,显著高于sham组和M组相应时点。IPC组GLUT3 mRNA表达在24 h增高,48 h最高,与M组相应时点24 h、48 h及sham组比较显著增高。IPC组比M组的GLUT1蛋白、GLUT3蛋白表达增高,有显著差异(F=5.848,P<0.05;F=6.295,P<0.05),尤以缺血再灌注后48 h两者差异最明显。结论: 3-NPA预处理能诱导脑缺血耐受,其机制可能是上调GLUT1和GLUT3 mRNA及蛋白表达水平,维持脑组织的能量供给。