Blockade Of Fatty Acid Oxidation Research Articles

Fatty acid synthesis and oxidation regulate human endoderm differentiation by mediating SMAD3 nuclear localization via acetylation.

Metabolic remodeling is one of the earliest events that occur during cell differentiation. Here, we define fatty acid metabolism as a key player in definitive endoderm differentiation from human embryonic stem cells. Fatty acid β-oxidation is enhanced while lipogenesis is decreased, and this is due to the phosphorylation of lipogenic enzyme acetyl-CoA carboxylase by AMPK. More importantly, inhibition of fatty acid synthesis by either its inhibitors or AMPK agonist significantly promotes human endoderm differentiation, while blockade of fatty acid oxidation impairs differentiation. Mechanistically, reduced de novo fatty acid synthesis and enhanced fatty acid β-oxidation both contribute to the accumulation of intracellular acetyl-CoA, which guarantees the acetylation of SMAD3 and further causes nuclear localization to promote endoderm differentiation. Thus, our current study identifies a fatty acid synthesis/oxidation shift during early differentiation and presents an instructive role for fatty acid metabolism in regulating human endoderm differentiation.

CPT2 K79 acetylation regulates platelet life span

AbstractThe short life span of platelets is a major challenge to platelet transfusion services because of the lack of effective intervention. Here, we found that the accumulation of long-chain acylcarnitines (LCACs) is responsible for mitochondrial damage and platelet storage lesion. Further studies showed that the blockade of fatty acid oxidation and the activation of AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase/carnitine palmitoyltransferase 1 (CPT1) pathways that promote fatty acid metabolism are important reasons for the accumulation of LCACs. The excessive accumulation of LCACs can cause mitochondrial damage and a short life span of stored platelets. The mechanism study elucidated that NAD+ exhaustion and the subsequent decrease in sirtuin 3 (Sirt3) activity caused an increase in the level of CPT2 K79 acetylation, which is the primary cause of the blockade of fatty acid oxidation and the accumulation of LCACs. Blocking LCAC generation with the inhibitors of AMPK or CPT1, the agonists of Sirt3, and antioxidants tremendously retarded platelet storage lesion in vitro and prolonged the survival of stored platelets in vivo posttransfusion with single or combined use. In summary, we discovered that CPT2 acetylation attenuates fatty acid oxidation and exacerbates platelet storage lesion and may serve as a new target for improving platelet storage quality.

Glucocorticoid receptor modulates myeloid-derived suppressor cell function via mitochondrial metabolism in immune thrombocytopenia.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature cells and natural inhibitors of adaptive immunity. Intracellular metabolic changes in MDSCs exert a direct immunological influence on their suppressive activity. Our previous study demonstrated that high-dose dexamethasone (HD-DXM) corrected the functional impairment of MDSCs in immune thrombocytopenia (ITP); however, the MDSC population was not restored in nonresponders, and the mechanism remained unclear. In this study, altered mitochondrial physiology and reduced mitochondrial gene transcription were detected in MDSCs from HD-DXM nonresponders, accompanied by decreased levels of carnitine palmitoyltransferase-1 (CPT-1), a rate-limiting enzyme in fatty acid oxidation (FAO). Blockade of FAO with a CPT-1 inhibitor abolished the immunosuppressive function of MDSCs in HD-DXM responders. We also report that MDSCs from ITP patients had lower expression of the glucocorticoid receptor (GR), which can translocate into mitochondria to regulate the transcription of mitochondrial DNA (mtDNA) as well as the level of oxidative phosphorylation. It was confirmed that the expression of CPT-1 and mtDNA-encoded genes was downregulated in GR-siRNA-treated murine MDSCs. Finally, by establishing murine models of active and passive ITP via adoptive transfer of DXM-modulated MDSCs, we confirmed that GR-silenced MDSCs failed to alleviate thrombocytopenia in mice with ITP. In conclusion, our study indicated that impaired aerobic metabolism in MDSCs participates in the pathogenesis of glucocorticoid resistance in ITP and that intact control of MDSC metabolism by GR contributes to the homeostatic regulation of immunosuppressive cell function.

Chemical Proteomics Identifies SLC25A20 as a Functional Target of the Ingenol Class of Actinic Keratosis Drugs.

The diterpenoid ester ingenol mebutate (IngMeb) is the active ingredient in the topical drug Picato, a first-in-class treatment for the precancerous skin condition actinic keratosis. IngMeb is proposed to exert its therapeutic effects through a dual mode of action involving (i) induction of cell death that is associated with mitochondrial dysfunction followed by (ii) stimulation of a local inflammatory response, at least partially driven by protein kinase C (PKC) activation. Although this therapeutic model has been well characterized, the complete set of molecular targets responsible for mediating IngMeb activity remains ill-defined. Here, we have synthesized a photoreactive, clickable analogue of IngMeb and used this probe in quantitative proteomic experiments to map several protein targets of IngMeb in human cancer cell lines and primary human keratinocytes. Prominent among these targets was the mitochondrial carnitine-acylcarnitine translocase SLC25A20, which we show is inhibited in cells by IngMeb and the more stable analogue ingenol disoxate (IngDsx), but not by the canonical PKC agonist 12-O-tetradecanoylphorbol-13-acetate (TPA). SLC25A20 blockade by IngMeb and IngDsx leads to a buildup of cellular acylcarnitines and blockade of fatty acid oxidation (FAO), pointing to a possible mechanism for IngMeb-mediated perturbations in mitochondrial function.

December 2016 at a glance: cardiac metabolism, myocarditis, right ventricular function and prognostic markers.

December 2016 at a glance: cardiac metabolism, myocarditis, right ventricular function and prognostic markers.

Phospholipase D1-regulated autophagy supplies free fatty acids to counter nutrient stress in cancer cells.

Cancer cells utilize flexible metabolic programs to maintain viability and proliferation under stress conditions including nutrient deprivation. Here we report that phospholipase D1 (PLD1) participates in the regulation of metabolic plasticity in cancer cells. PLD1 activity is required for cancer cell survival during prolonged glucose deprivation. Blocking PLD1 sensitizes cancer cells to glycolysis inhibition by 2-deoxy-D-glucose (2-DG) and results in decreased autophagic flux, enlarged lysosomes, and increased lysosomal pH. Mechanistically, PLD1-regulated autophagy hydrolyzes bulk membrane phospholipids to supply fatty acids (FAs) for oxidation in mitochondria. In low glucose cultures, the blockade of fatty acid oxidation (FAO) by PLD1 inhibition suppresses adenosine triphosphate (ATP) production and increases reactive oxygen species (ROS), leading to cancer cell death. In summary, our findings reveal a novel role of PLD1 in sustaining cancer cell survival during metabolic stress, and suggest PLD1 as a potential target for anticancer metabolism therapy.

Excessive fatty acid oxidation induces muscle atrophy in cancer cachexia.

Cachexia is a devastating muscle-wasting syndrome that occurs in patients who have chronic diseases. It is most commonly observed in individuals with advanced cancer, presenting in 80% of these patients, and it is one of the primary causes of morbidity and mortality associated with cancer. Additionally, although many people with cachexia show hypermetabolism, the causative role of metabolism in muscle atrophy has been unclear. To understand the molecular basis of cachexia-associated muscle atrophy, it is necessary to develop accurate models of the condition. By using transcriptomics and cytokine profiling of human muscle stem cell-based models and human cancer-induced cachexia models in mice, we found that cachectic cancer cells secreted many inflammatory factors that rapidly led to high levels of fatty acid metabolism and to the activation of a p38 stress-response signature in skeletal muscles, before manifestation of cachectic muscle atrophy occurred. Metabolomics profiling revealed that factors secreted by cachectic cancer cells rapidly induce excessive fatty acid oxidation in human myotubes, which leads to oxidative stress, p38 activation and impaired muscle growth. Pharmacological blockade of fatty acid oxidation not only rescued human myotubes, but also improved muscle mass and body weight in cancer cachexia models in vivo. Therefore, fatty acid-induced oxidative stress could be targeted to prevent cancer-induced cachexia.

Metabolism: Growth in the fat lane.

Analysis of endothelial cells, which are involved in blood-vessel formation, unexpectedly reveals that proliferation in this cell type depends on fatty-acid oxidation to support DNA synthesis. See Article p.192 Peter Carmeliet and colleagues identify a crucial role for the oxidation of fatty acids in endothelial cells during angiogenesis. They show that fatty acids provide the carbons for the de novo synthesis of nucleotides, and hence fatty acid oxidation stimulates vessel sprouting by increasing endothelial cell proliferation. Pharmacological blockade of fatty acid oxidation can reduce pathological angiogenesis in a mouse model of retinopathy of prematurity.

Integrin-Dependent Akt1 Activation Regulates PGC-1 Expression and Fatty Acid Oxidation

Background: Poly-N-acetyl glucosamine nanofibers derived from a marine diatom have been used to increase cutaneous wound healing. These nanofibers exert their activity by specifically activating integrins, which makes them a useful tool for dissecting integrin-mediated pathways. We have shown that short-fiber poly-N-acetyl glucosamine nanofiber (sNAG) treatment of endothelial cells results in increased cell motility and metabolic rate in the absence of increased cell proliferation. Results: Using a Seahorse Bioanalyzer to measure oxygen consumption in real time, we show that sNAG treatment increases oxygen consumption rates, correlated with an integrin-dependent activation of Akt1. Akt1 activation leads to an increase in the expression of the transcriptional coactivator, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). This is not due to increased mitochondrial biogenesis, but is associated with an increase in the expression of pyruvate dehydrogenase kinase 4 (PDK4), suggesting regulation of fatty acid oxidation. Blockade of fatty acid oxidation with etomoxir, an O-carnitine palmitoyltransferase-1 inhibitor, blocks the sNAG-dependent increased oxygen consumption. ³H-palmitate uptake experiments indicate a PDK4-dependent increase in fatty acid oxidation, which is required for nanofiber-induced cell motility. Conclusions: Our findings imply a linear pathway whereby an integrin-dependent activation of Akt1 leads to increased PGC-1α and PDK4 expression resulting in increased energy production by fatty acid oxidation.

NPAS2 deletion impairs responses to restricted feeding but not to metabolic challenges

Neuronal PAS domain protein 2 ( Npas2) is a clock gene expressed widely in brain and peripheral tissues. NPAS2 is responsive to cellular metabolic state and mutation of this gene impairs adaptation to restricted feeding schedules, suggesting that NPAS2 is required for effective control of a food-entrainable oscillator. However, an alternative possibility, that NPAS2 is required for detection of metabolic cues signaling energy deficiency or for arousal of appropriate behavioral responses to such cues, as not been directly examined. Therefore, we examined the effect of targeted disruption of Npas2 on responses to several acute and chronic metabolic challenges. We found that under normal light–dark and ad libitum feeding conditions, Npas2 knockout (KO) mice did not differ from wild-type (WT) controls with respect to diurnal feeding or blood glucose levels, body weight or size or body composition. Furthermore, feeding responses to overnight food deprivation, insulin- or 2-deoxy- d-glucose (2DG)-induced glucoprivation, mercaptoacetate (MA)-induced blockade of fatty acid oxidation and cold exposure did not differ by genotype. However, KO mice lost more weight than WT during overnight food deprivation and when placed on a 4-h restricted feeding schedule, even though food intake did not differ between groups. Thus, it appears that NPAS2 is not required for detection of or behavioral responses to a variety of acute or chronic metabolic deficits, but is more likely to be involved in effective synchronization of feeding behavior with scheduled food availability.

Simultaneous Silencing ofNpyandDbhExpression in Hindbrain A1/C1 Catecholamine Cells Suppresses Glucoprivic Feeding

Previous data have strongly implicated hindbrain catecholamine/neuropeptide Y (NPY) coexpressing neurons as key mediators of the glucoprivic feeding response. Catecholamine/NPY cell bodies are concentrated in the A1 and caudal C1 cell cluster (A1/C1) in the ventrolateral medulla, a region highly sensitive to glucoprivic challenge. To further investigate the importance of this catecholamine subpopulation in glucoregulation, we used small interfering RNA (siRNA) technology to produce a targeted gene knockdown of NPY and dopamine-beta-hydroxylase (DBH), a catecholamine biosynthetic enzyme. Unilateral injection of NPY siRNA and DBH siRNA (0.02 nmol each) both significantly inhibited expression of the targeted genes up to 2 d, as revealed by real-time PCR, and reduced protein expression up to 8 d, as revealed by immunohistochemistry, compared with the control nontargeting siRNA (ntRNA) side. Subsequently, targeted siRNA or control ntRNA was injected bilaterally into A1/C1 and responses to 2-deoxy-D-glucose (2DG; 200 mg/kg)-induced glucoprivation were tested 3-7 d later. Silencing of either Npy or Dbh alone did not reduce glucoprivic feeding or hyperglycemic responses, compared with responses of ntRNA-injected controls. In contrast, simultaneous silencing of both Npy and Dbh reduced 2DG-induced feeding by 61%. Neither the hyperglycemic response to 2DG nor feeding elicited by mercaptoacetate (68 mg/kg)-induced blockade of fatty acid oxidation ("lipoprivic feeding") was reduced by simultaneous silencing of these two genes. These results suggest that catecholamines and NPY act conjointly to control glucoprivic feeding and that the crucial NPY/catecholamine coexpressing neurons are concentrated in the A1/C1 cell group.

Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steatosis

Nonalcoholic steatohepatitis (NASH) is a common feature of the metabolic syndrome and toxic reactions to pharmacological drugs. Tamoxifen, (TMX) a widely used anti-breast cancer drug, can induce NASH and changes in plasma cholesterol levels through mechanisms that are unclear. We studied primary actions of TMX using a short-term treatment (5 days) that induces microvesicular hepatic steatosis and marked hypercholesterolemia in male rats. Using a combined approach of gene expression profiling and NMR-based metabolite analysis, we found that TMX-treated livers have increased saturated fatty acid content despite changes in gene expression, indicating decreased de novo lipogenesis and increased fatty acid oxidation. Our results show that TMX predominantly down-regulates FAS expression and activity as indicated by the accumulation of malonyl-CoA, a known inhibitor of mitochondrial beta-oxidation. In the face of a continued supply of exogenous free fatty acids, the blockade of fatty acid oxidation produced by elevated malonyl-CoA is likely to be the major factor leading to steatosis. Use of a combination of metabolomic and transcriptomic analysis has allowed us to identify mechanisms underlying important metabolic side effects of a widely prescribed drug. Given the broader importance of hepatic steatosis, the novel molecular mechanism revealed in this study should be examined in other forms of steatosis and nonalcoholic steatohepatitis.

Hindbrain catecholamine neurons mediate consummatory responses to glucoprivation

Previous work using the retrogradely transported immunotoxin, saporin (SAP) conjugated to a monoclonal antibody against dopamine-β-hydroxylase (DBH; DSAP), to selectively lesion norepinephrine (NE) and epinephrine (E) neurons projecting to the medial hypothalamus, demonstrated the essential role of these neurons for appetitive ingestive responses to glucoprivation. Here, we again utilized this lesion to assess the importance of these same neurons for the consummatory phase of glucoprivic feeding. To test consummatory responses, milk was infused intraorally through a chronic cheek fistula until rejected. Appetitive responses were tested in the same rats using pelleted food. Feeding responses to insulin-induced hypoglycemia, 2-deoxy- d-glucose (2DG)-induced blockade of glucose utilization, mercaptoacetate (MA)-induced blockade of fatty acid oxidation, 0.9% saline, and 18-h food deprivation were assessed. Unlike unconjugated SAP controls, the DSAP rats did not increase their food intake in response to glucoprivic challenges in either the pelleted food or the intraoral feeding tests. However, the DSAP rats did not differ from SAPs in their ingestive responses to food deprivation and blockade of fatty acid oxidation. The selective impairment of glucoprivic feeding responses indicates that DSAP did not impair the underlying circuitry required for either appetitive or consummatory ingestive responding but eliminated the mechanism for control of this circuitry specifically by glucoprivation. Results suggest that both appetitive and consummatory responses to glucoprivation are controlled and coordinated by multilevel terminations of the same catecholamine neurons.

Blockade of fatty acid oxidation mimics phase II-phase III transition in a fasting bird, the king penguin.

This study tests the hypothesis that the metabolic and endocrine shift characterizing the phase II-phase III transition during prolonged fasting is related to a decrease in fatty acid (FA) oxidation. Changes in plasma concentrations of various metabolites and hormones and in lipolytic fluxes, as determined by continuous infusion of [2-(3)H]glycerol and [1-(14)C]palmitate, were examined in vivo in spontaneously fasting king penguins in the phase II status (large fat stores, protein sparing) before, during, and after treatment with mercaptoacetate (MA), an inhibitor of FA oxidation. MA induced a 7-fold decrease in plasma beta-hydroxybutyrate and a 2- to 2.5-fold increase in plasma nonesterified fatty acids (NEFA), glycerol, and triacylglycerols. MA also stimulated lipolytic fluxes, increasing the rate of appearance of NEFA and glycerol by 60-90%. This stimulation might be partly mediated by a doubling of circulating glucagon, with plasma insulin remaining unchanged. Plasma glucose level was unaffected by MA treatment. Plasma uric acid increased 4-fold, indicating a marked acceleration of body protein breakdown, possibly mediated by a 2.5-fold increase in circulating corticosterone. Strong similarities between these changes and those observed at the phase II-phase III transition in fasting penguins support the view that entrance into phase III, and especially the end of protein sparing, is related to decreased FA oxidation, rather than reduced NEFA availability. MA could be therefore a useful tool for understanding mechanisms underlying the phase II-phase III transition in spontaneously fasting birds and the associated stimulation of feeding behavior.

Metabolic and behavioral responses in pre-weanling rats following alteration of maternal diet

In rat pups, blockade of fatty acid oxidation by administration of 2-mercaptoacetate (MA) produces an increase in independent ingestion by 12 days of age. In contrast, administration of methyl palmoxirate (MP) fails to increase intake or to alter oxidation of fatty acids in young rats due to the high proportion of medium chain triglycerides (MCT) in rat milk. In the present experiments, the composition of rat milk was altered by placing dams on a high fat (HF) diet to examine the development of ingestive responding in rat pups following administration of MP. Following delivery of MP (0.5–10 mg/kg), pups were placed in a cage inside an incubator for 1, 3, or 6 h, and then received an intake test consuming a commercial half-and-half milk diet from the floor of test containers. Blood was collected from additional groups of pups for measurement of β-hydroxybutyrate (βHBA) and glucose levels. The results demonstrated that administration of MP produced significant reductions in βHBA levels after 3 h in 12- and 15-day-old pups, but behavioral responses were noted only in pups aged 15 days. Similar results were obtained following administration of MA to pups reared by dams on HF diets; physiological responses were observed at 12 and 15 days of age, but behavioral responses were not observed after administration of MA until 15 days of age. Taken together, these results suggest that (1) changes in fatty acid oxidation may represent an early metabolic signal that can influence intake in rat pups and (2) alteration of the dam's diet produces physiological and behavioral changes in the pups.

Effects of metabolic inhibitors on ingestive behavior and physiology in preweanling rat pups

We have previously demonstrated that administration of 2-Mercaptoacetate (MA) stimulates independent intake after 1h in 12 and 15-day-old rat pups, but not younger pups. MA also produces decreases in β-HBA levels, consistent with the development of a role of altered fatty acid oxidation in modulating independent ingestion in rat pups by 12 days of age. The present experiments extended investigations of the role of changes in energy utilization in young rats by investigating the duration of the effects of altered fatty acid oxidation and the effects of combined blockade of fatty acid oxidation and glucose utilization. Pups were tested at 9, 12 or 15 days of age 3 or 6h following administration of a dose of 0, 11·4, 22·8, 45·6 or 91·2mg/kg MA. In pups aged 12 and 15 days, moderate doses of MA stimulated intake 3h, but not 6h, following administration. Administration of the highest dose of MA produced significant decreases in β-HBA levels in pups at all ages when tested after 3h, but not after 6h. In the second set of experiments, behavioral and physiological responses to administration of MA (0, 11·4 or 22·.8mg/kg) combined with 2-Deoxyglucose (2-DG: 0, 100 or 200mg/kg) were investigated in pups aged 6, 9, 12 or 15 days of age. The results demonstrated that while administration of 2-DG produced physiological responses, intake was not stimulated at any age by 2-DG alone or in combination with MA. In fact, in 12 and 15-day-old pups, administration of 2-DG blocked the stimulatory effects of administration of MA. Therefore, while altered utilization of glucose does not appear to be an effective stimulus for increased independent ingestion in pups at this age, altered fatty acid oxidation may be an early metabolic modulator of intake.

Do NSAIDs contribute to acute fatty liver of pregnancy?

Acute fatty liver of pregnancy (AFLP) and the childhood encephalopathy known as Reye’s syndrome are both characterised by microvesicular steatosis. Mothers with AFLP are frequently heterozygous for a mutation which reduces the activity of the trifunctional protein (TP) of fatty-acid oxidation. Several lines of evidence suggest that blockade of fatty-acid oxidation may also be the underlying cause of Reye’s syndrome, and epidemiological studies have identified aspirin taken during a viral illness as a contributing factor to the development of the disease. The hypotheses are presented:• that children with Reye’s syndrome may also be heterozygous for TP mutation, and• that inhibition of the residual long-chain fatty-acid oxidation by NSAIDs including aspirin precipitates the similar symptoms observed in patients with Reye’s syndrome and AFLP.Identification of NSAIDs as candidates for the unidentified factor which precipitates AFLP suggests that avoidance of NSAIDs during pregnancy may lead to a reduction in the incidence of this life-threatening disease.

Behavioral specificity of effects of 2-Mercaptoacetate on independent ingestion in developing rats

Blockade of fatty acid oxidation in rat pups using 2-Mercaptoacetate (MA) produces increases in independent ingestion by 12 days of age. In the present experiments, the behavioral specificity of the effects of MA on ingestion were examined. In the first experiment, administration of MA to pups aged 9 and 12 days of age failed to increase intake of an oral infusion of a milk diet. In the second experiment, administration of MA did enhance intake of a milk diet in a short-term test of consuming from the floor of a test container and the level of gastric fill appeared to determine intake during the test. Finally, administration of MA did not affect intake of water in 9- or 12-day-old pups. These results suggest that MA produces increases in intake through specific effects on selective ingestive responses and not through nonspecific behavioral arousal.

Development of independent ingestive responding to blockade of fatty acid oxidation in rats.

The present studies examined the development of ingestive responsiveness to blockade of fatty acid oxidation in rat pups using 2-mercaptoacetate (MA), an inhibitor of mitochondrial acyl-coenzyme A dehydrogenases, or methyl palmoxirate (MP), an inhibitor of carnitine palmitoyltransferase I (CPT-I). Rat pups aged 6, 9, 12, or 15 days of age received an intraperitoneal injection of 0, 100, 200, 400, or 800 mumol/kg MA, and intake of a commercial half-and-half or 15% glucose diet from the floor of test containers was assessed in a 30-min test beginning 1 h after administration of MA. The results demonstrate that, although no dose of MA affected intake of either diet in pups 9 days or younger, low doses of MA increased intake and the highest dose suppressed intake of both diets in pups 12 days of age or older. Physiological measurements indicated that levels of beta-hydroxybutyrate were significantly lower following doses of 400 or 800 mumol/kg MA in 9-, 12-, and 15-day-old pups and that gastric emptying was inhibited in 12 and 15 day olds by 800 mumol/kg MA. Intake of a commercial half-and-half diet from the floor of test containers was also assessed in 12- to 18-day-old rat pups 6.5 h after they received a gavage load of 0, 1.25, 2.5, 5, or 10 mg/kg MP. Unlike MA, MP did not increase intake of a commercial half-and-half diet in rat pups 12 or 15-18 days of age; instead, the highest dose of MP suppressed intake in 15- to 18-day-old pups. The failure of MP to enhance intake in pups at the ages tested is likely related to composition of dam's milk; rat milk is high in medium-chain fatty acids that do not require CPT-I for entry into mitochondria. Thus it is likely that MP does not significantly block fatty acid oxidation in pups at the ages tested. On the other hand, blockade of fatty acid oxidation produced by MA significantly affects intake by 12 days of age, suggesting it may be the first metabolic signal that influences intake in rat pups.

Feeding induced by pharmacological blockade of fatty acid metabolism is selectively attenuated by hindbrain injections of the galanin receptor antagonist, M40.

Galanin has been shown to stimulate feeding when injected intracranially in rats. Lesion and Fos studies have shown that the neural pathway for feeding stimulated by mercaptoacetate (MA)-induced blockade of fatty acid oxidation includes several structures rich in galanin cell bodies or terminals. In the present experiment, we examined the role of hindbrain galanin in feeding stimulated by MA. We found that galanin (1 nmol) stimulates feeding when injected in the nucleus of the solitary tract (NTS), a site that is crucial for MA-induced feeding, or into the fourth ventricle (4V, 1 or 5 nmol) and that NTS or 4V injections of the galanin receptor antagonist, M40 (1.5 or 5 nmol), completely blocked feeding induced by MA (68 mg/kg). The effect of the M40 appeared to be specific for MA-induced feeding, since M40 did not significantly attenuate either feeding induced by the antimetabolic glucose analog, 2-deoxy-D-glucose (2DG, 100 or 200 mg/kg), or deprivation-induced water intake. Results suggest that feeding induced by decreased fatty acid oxidation relies upon galaninergic terminals in the hindbrain. Furthermore, results indicate that hindbrain neurons involved in MA-induced feeding differ neurochemically from those important for 2DG-induced feeding.