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Michael NJ, Watt MJ. Long Chain Fatty Acids Differentially Regulate Sub-populations of Arcuate POMC and NPY Neurons. Neuroscience 2020; 451:164-173. [PMID: 33002557 DOI: 10.1016/j.neuroscience.2020.09.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 09/09/2020] [Accepted: 09/21/2020] [Indexed: 02/07/2023]
Abstract
Long chain fatty acids (LCFAs) have been suggested to influence the activity of hypothalamic neurons, however, limited studies have attempted to identify the neurochemical phenotype of these neurons. We aimed to determine if physiological levels of LCFAs alter the electrical excitability of pro-opiomelanocortin (POMC) and neuropeptide Y (NPY) neurons in the arcuate nucleus of the hypothalamus. We utilised whole-cell patch-clamp electrophysiology on brain slice preparations from genetic mouse models where green fluorescent protein was expressed in either POMC or NPY expressing cells. All animals had undergone an overnight fast to replicate conditions in which fatty acids would usually increase. Bath application of LCFAs were found to predominantly inhibit POMC neurons and predominantly excite NPY neurons. Differences between oleic and palmitic acid were not observed. These results suggest that LCFAs in the cerebrospinal fluid exert an underlying orexigenic tone to key hypothalamic neurons known to regulate energy homeostasis.
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Affiliation(s)
- Natalie J Michael
- Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton 3800, VIC, Australia; Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City G1V4G5, Québec, Canada.
| | - Matthew J Watt
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne 3010, VIC, Australia
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Bacterial fatty acid metabolism in modern antibiotic discovery. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:1300-1309. [PMID: 27668701 DOI: 10.1016/j.bbalip.2016.09.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/12/2016] [Accepted: 09/19/2016] [Indexed: 12/28/2022]
Abstract
Bacterial fatty acid synthesis is essential for many pathogens and different from the mammalian counterpart. These features make bacterial fatty acid synthesis a desirable target for antibiotic discovery. The structural divergence of the conserved enzymes and the presence of different isozymes catalyzing the same reactions in the pathway make bacterial fatty acid synthesis a narrow spectrum target rather than the traditional broad spectrum target. Furthermore, bacterial fatty acid synthesis inhibitors are single-targeting, rather than multi-targeting like traditional monotherapeutic, broad-spectrum antibiotics. The single-targeting nature of bacterial fatty acid synthesis inhibitors makes overcoming fast-developing, target-based resistance a necessary consideration for antibiotic development. Target-based resistance can be overcome through multi-targeting inhibitors, a cocktail of single-targeting inhibitors, or by making the single targeting inhibitor sufficiently high affinity through a pathogen selective approach such that target-based mutants are still susceptible to therapeutic concentrations of drug. Many of the pathogens requiring new antibiotic treatment options encode for essential bacterial fatty acid synthesis enzymes. This review will evaluate the most promising targets in bacterial fatty acid metabolism for antibiotic therapeutics development and review the potential and challenges in advancing each of these targets to the clinic and circumventing target-based resistance. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Dridi S, Decuypere E, Buyse J. Cerulenin upregulates heat shock protein-70 gene expression in chicken muscle. Poult Sci 2013; 92:2745-53. [PMID: 24046423 DOI: 10.3382/ps.2013-03242] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Lines of evidence suggested that systems involved in the regulation of the stress responses and energy homeostasis are highly integrated. Because cerulenin, the natural antibiotic product of the fungus Cephalosporium ceruleans and a broad-spectrum fatty acid synthesis (FAS) inhibitor, has been shown to affect food intake and energy balance, and because the biomarker of stress Hsp-70 gene was found to interact directly with fatty acids, we hypothesized that cerulenin may regulate Hsp-70 gene expression. Therefore, the present study was undertaken to examine this issue. Cerulenin administration significantly (P < 0.05) decreased food intake and induced Hsp-70 mRNA levels in muscle, but not in liver or hypothalamus of 2-wk-old broiler chickens. These changes were accompanied by an unpregulation of muscle uncoupling protein and carnitine palmitoyltransferase 1 mRNA levels. This result indicated that the regulation of Hsp-70 gene expression in normal chickens, as estimated by oxidative stress indices [TBA reacting substances, ferric reducing/antioxidant power, and ceruloplasmin oxidase activity] levels, is tissue-specific. In attempt to discriminate between the effect of cerulenin and cerulenin-reduced food intake on Hsp-70 gene expression, we also evaluated the effect of food deprivation on the same cellular responses. Food deprivation for 16 h did not affect Hsp-70 gene expression in all tissues examined, indicating that the effect of cerulenin is independent of the inhibition of food intake. To ascertain whether the effect of cerulenin is direct or indirect, we carried out in vitro studies. Cerulenin treatment did not affect Hsp-70 gene expression in Leghorn male hepatoma and quail myoblast cell lines, suggesting that the observed effect in vivo may be mediated through the central nervous system.
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Affiliation(s)
- Sami Dridi
- Department of Poultry Science, Center of Excellence for Poultry Science, University of Arkansas, Fayetteville 72701; and
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Guyenet SJ, Nguyen HT, Hwang BH, Schwartz MW, Baskin DG, Thaler JP. High-fat diet feeding causes rapid, non-apoptotic cleavage of caspase-3 in astrocytes. Brain Res 2013; 1512:97-105. [PMID: 23548599 DOI: 10.1016/j.brainres.2013.03.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 03/07/2013] [Accepted: 03/13/2013] [Indexed: 12/27/2022]
Abstract
Astrocytes respond to multiple forms of central nervous system (CNS) injury by entering a reactive state characterized by morphological changes and a specific pattern of altered protein expression. Termed astrogliosis, this response has been shown to strongly influence the injury response and functional recovery of CNS tissues. This pattern of CNS inflammation and injury associated with astrogliosis has recently been found to occur in the energy homeostasis centers of the hypothalamus during diet-induced obesity (DIO) in rodent models, but the characterization of the astrocyte response remains incomplete. Here, we report that astrocytes in the mediobasal hypothalamus respond robustly and rapidly to purified high-fat diet (HFD) feeding by cleaving caspase-3, a protease whose cleavage is often associated with apoptosis. Although obesity develops in HFD-fed rats by day 14, caspase-3 cleavage occurs by day 3, prior to the development of obesity, suggesting the possibility that it could play a causal role in the hypothalamic neuropathology and fat gain observed in DIO. Caspase-3 cleavage is not associated with an increase in the rate of apoptosis, as determined by TUNEL staining, suggesting it plays a non-apoptotic role analogous to the response to excitotoxic neuron injury. Our results indicate that astrocytes in the mediobasal hypothalamus respond rapidly and robustly to HFD feeding, activating caspase-3 in the absence of apoptosis, a process that has the potential to influence the course of DIO.
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Affiliation(s)
- Stephan J Guyenet
- Department of Medicine, Division of Metabolism, Endocrinology and Nutrition, Diabetes and Obesity Center of Excellence, University of Washington, UW Medicine at South Lake Union, 850 Republican Street, Box 358055, Seattle, WA 98109, USA.
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Guyenet SJ, Matsen ME, Morton GJ, Kaiyala KJ, Schwartz MW. Rapid glutamate release in the mediobasal hypothalamus accompanies feeding and is exaggerated by an obesogenic food. Mol Metab 2013; 2:116-22. [PMID: 24199157 DOI: 10.1016/j.molmet.2013.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 02/02/2013] [Accepted: 02/04/2013] [Indexed: 10/27/2022] Open
Abstract
The mediobasal hypothalamus (MBH) plays a central role in the regulation of food intake and energy balance. Although the excitatory neurotransmitter glutamate is implicated in energy balance regulation by the MBH, the hypothesis that feeding elicits local glutamate release remains untested. To test this hypothesis, we employed a glutamate biosensor that measures glutamate concentrations at 1-s intervals in conscious, freely behaving rats. Results indicate that feeding is associated with an increase of MBH glutamate concentration that occurs within 1-2 s of oral contact with a food pellet, and the glutamate response to a palatable high-fat pellet is greatly exaggerated relative to chow. In contrast, glutamate responses were not observed during water ingestion or other observed behaviors. These findings indicate that feeding is associated with rapid release of glutamate in the MBH, that this release is exaggerated with an obesogenic food, and that this response is likely stimulated by orosensory factors.
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Affiliation(s)
- Stephan J Guyenet
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington, UW Medicine at South Lake Union, 850 Republican Street, Box 358055, Seattle, WA 98109, USA
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Poplawski MM, Mastaitis JW, Yang XJ, Mobbs CV. Hypothalamic responses to fasting indicate metabolic reprogramming away from glycolysis toward lipid oxidation. Endocrinology 2010; 151:5206-17. [PMID: 20881243 PMCID: PMC2954726 DOI: 10.1210/en.2010-0702] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nutrient-sensitive hypothalamic neurons regulate energy balance and glucose homeostasis, but the molecular mechanisms mediating hypothalamic responses to nutritional state remain incompletely characterized. To address these mechanisms, the present studies used quantitative PCR to characterize the expression of a panel of genes the hypothalamic expression by nutritional status of which had been suggested by DNA microarray studies. Although these genes regulate a variety of function, the most prominent set regulate intermediary metabolism, and the overall pattern clearly indicated that a 48-h fast produced a metabolic reprogramming away from glucose metabolism and toward the utilization of alternative fuels, particularly lipid metabolism. This general reprogramming of intermediary metabolism by fasting was observed both in cortex and hypothalamus but most prominently in hypothalamus. The effect of fasting on the expression of these genes may be mediated by reduction in plasma glucose or glucose metabolism, rather than leptin, because they were generally recapitulated by hypoglycemia even in the presence of elevated insulin and in vitro by low glucose but were not recapitulated in ob/ob mice. These studies suggest that fasting reduces glucose metabolism and thus minimizes the production of hypothalamic malonyl-coenzyme A. However, because the reprogramming of glucose metabolism by fasting was also observed in cortex, this apparent substrate competition may mediate more general responses to nutritional deprivation, including those responsible for the protective effects of dietary restriction. The present studies also provide a large panel of novel glucose-regulated genes that can be used as markers of glucose action to address mechanisms mediating hypothalamic responses to nutritional state.
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Affiliation(s)
- Michal M Poplawski
- Fishberg Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Kim ER, Mizuno TM. Xenin delays gastric emptying rate and activates the brainstem in mice. Neurosci Lett 2010; 481:59-63. [PMID: 20599589 DOI: 10.1016/j.neulet.2010.06.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2010] [Revised: 05/24/2010] [Accepted: 06/21/2010] [Indexed: 11/15/2022]
Abstract
Xenin, a 25-amino acid gastrointestinal peptide, inhibits feeding by acting through the central nervous system. Gastrointestinal hormones reduce food intake partly by activating the brainstem and inhibiting gastric emptying. Therefore, we hypothesized that xenin delays gastric emptying through the activation of the brainstem cells. To address this hypothesis, we examined the effect of intraperitoneal (i.p.) injection of xenin on gastric emptying rate and brainstem Fos expression in mice. Gastric emptying rate was reduced by about 93% in xenin-treated mice compared to saline-treated control mice. The i.p. xenin injection significantly increased Fos-immunoreactive cells in the nucleus of the solitary tract (NTS) of the brainstem, but not area postrema (AP) and dorsal motor nucleus of the vagus (DMV). These findings support the hypothesis that xenin-induced anorexia is at least partly due to delayed gastric emptying and the activation of the NTS cells.
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Affiliation(s)
- Eun Ran Kim
- Department of Physiology, University of Manitoba, Winnipeg, MB R3E0J9, Canada
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Stolarczyk E, Guissard C, Michau A, Even PC, Grosfeld A, Serradas P, Lorsignol A, Pénicaud L, Brot-Laroche E, Leturque A, Le Gall M. Detection of extracellular glucose by GLUT2 contributes to hypothalamic control of food intake. Am J Physiol Endocrinol Metab 2010; 298:E1078-87. [PMID: 20179244 DOI: 10.1152/ajpendo.00737.2009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The sugar transporter GLUT2, present in several tissues of the gut-brain axis, has been reported to be involved in the control of food intake. GLUT2 is a sugar transporter sustaining energy production in the cell, but it can also function as a receptor for extracellular glucose. A glucose-signaling pathway is indeed triggered, independently of glucose metabolism, through its large cytoplasmic loop domain. However, the contribution of the receptor function over the transporter function of GLUT2 in the control of food intake remains to be determined. Thus, we generated transgenic mice that express a GLUT2-loop domain, blocking the detection of glucose but leaving GLUT2-dependent glucose transport unaffected. Inhibiting GLUT2-mediated glucose detection augmented daily food intake by a mechanism that increased the meal size but not the number of meals. Peripheral hormones (ghrelin, insulin, leptin) were unaffected, leading to a focus on central aspects of feeding behavior. We found defects in c-Fos activation by glucose in the arcuate nucleus and changes in the amounts of TRH and orexin neuropeptide mRNA, which are relevant to poorly controlled meal size. Our data provide evidence that glucose detection by GLUT2 contributes to the control of food intake by the hypothalamus. The sugar transporter receptor, i.e., "transceptor" GLUT2, may constitute a drug target to treat eating disorders and associated metabolic diseases, particularly by modulating its receptor function without affecting vital sugar provision by its transporter function.
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Affiliation(s)
- Emilie Stolarczyk
- Unité Mixte de Recherche (UMR) S872, Centre de Recherche des Cordeliers, 15 rue de l'Ecole de médecine, Paris, F-75006 France
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Leckstrom A, Kim ER, Wong D, Mizuno TM. Xenin, a gastrointestinal peptide, regulates feeding independent of the melanocortin signaling pathway. Diabetes 2009; 58:87-94. [PMID: 18984739 PMCID: PMC2606897 DOI: 10.2337/db08-0260] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE Xenin, a 25-amino acid peptide, was initially isolated from human gastric mucosa. Plasma levels of xenin rise after a meal in humans, and administration of xenin inhibits feeding in rats and chicks. However, little is known about the mechanism by which xenin regulates food intake. Signaling pathways including leptin and melanocortins play a pivotal role in the regulation of energy balance. Therefore, we addressed the hypothesis that xenin functions as a satiety factor by acting through the melanocortin system or by interacting with leptin. RESEARCH DESIGN AND METHODS The effect of intracerebroventricular and intraperitoneal administration of xenin on food intake was examined in wild-type, agouti, and ob/ob mice. The effect of intracerebroventricular injection of SHU9119, a melanocortin receptor antagonist, on xenin-induced anorexia was also examined in wild-type mice. To determine whether the hypothalamus mediates the anorectic effect of xenin, we examined the effect of intraperitoneal xenin on hypothalamic Fos expression. RESULTS Both intracerebroventricular and intraperitoneal administration of xenin inhibited fasting-induced hyperphagia in wild-type mice in a dose-dependent manner. The intraperitoneal injection of xenin also reduced nocturnal intake in ad libitum-fed wild-type mice. The intraperitoneal injection of xenin increased Fos immunoreactivity in hypothalamic nuclei, including the paraventricular nucleus and the arcuate nucleus. Xenin reduced food intake in agouti and ob/ob mice. SHU9119 did not block xenin-induced anorexia. CONCLUSIONS Our data suggest that xenin reduces food intake partly by acting through the hypothalamus but via signaling pathways that are independent of those used by leptin or melanocortins.
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Affiliation(s)
- Arnold Leckstrom
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
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Proulx K, Cota D, Woods SC, Seeley RJ. Fatty acid synthase inhibitors modulate energy balance via mammalian target of rapamycin complex 1 signaling in the central nervous system. Diabetes 2008; 57:3231-8. [PMID: 18776140 PMCID: PMC2584128 DOI: 10.2337/db07-1690] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 09/01/2008] [Indexed: 01/11/2023]
Abstract
OBJECTIVE Evidence links the hypothalamic fatty acid synthase (FAS) pathway to the regulation of food intake and body weight. This includes pharmacological inhibitors that potently reduce feeding and body weight. The mammalian target of rapamycin (mTOR) is an intracellular fuel sensor whose activity in the hypothalamus is also linked to the regulation of energy balance. The purpose of these experiments was to determine whether hypothalamic mTOR complex 1 (mTORC1) signaling is involved in mediating the effects of FAS inhibitors. RESEARCH DESIGN AND METHODS We measured the hypothalamic phosphorylation of two downstream targets of mTORC1, S6 kinase 1 (S6K1) and S6 ribosomal protein (S6), after administration of the FAS inhibitors C75 and cerulenin in rats. We evaluated food intake in response to FAS inhibitors in rats pretreated with the mTOR inhibitor rapamycin and in mice lacking functional S6K1 (S6K1(-/-)). Food intake and phosphorylation of S6K1 and S6 were also determined after C75 injection in rats maintained on a ketogenic diet. RESULTS C75 and cerulenin increased phosphorylation of S6K1 and S6, and their anorexic action was reduced in rapamycin-treated rats and in S6K1(-/-) mice. Consistent with our previous findings, C75 was ineffective at reducing caloric intake in ketotic rats. Under ketosis, C75 was also less efficient at stimulating mTORC1 signaling. CONCLUSIONS These findings collectively indicate an important interaction between the FAS and mTORC1 pathways in the central nervous system for regulating energy balance, possibly via modulation of neuronal glucose utilization.
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Affiliation(s)
- Karine Proulx
- From the Department of Psychiatry, University of Cincinnati, Genome Research Institute, Cincinnati, Ohio
| | - Daniela Cota
- From the Department of Psychiatry, University of Cincinnati, Genome Research Institute, Cincinnati, Ohio
| | - Stephen C. Woods
- From the Department of Psychiatry, University of Cincinnati, Genome Research Institute, Cincinnati, Ohio
| | - Randy J. Seeley
- From the Department of Psychiatry, University of Cincinnati, Genome Research Institute, Cincinnati, Ohio
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Wang Y, Zhang SY, Ma XF, Tian WX. Potent inhibition of fatty acid synthase by parasitic loranthus [Taxillus chinensis(DC.) Danser] and its constituent avicularin. J Enzyme Inhib Med Chem 2008; 21:87-93. [PMID: 16570511 DOI: 10.1080/14756360500472829] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
The medicinal herb parasitic loranthus in a screen was found to inhibit fatty acid synthase (EC 2.3.1.85, FAS) and reduce body weight of rats in our previous study. Now we have determined the inhibitory characteristics and kinetic parameters of extracts of parasitic loranthus [Taxillus chinensis (DC.) Danser]. The parasitic loranthus extracts (PLE) inhibits FAS reversibly and irreversibly and with an IC50 value of 0.48 microg/ml, appears to be the most potent inhibitor reported to date. PLE contains various potent inhibitors and may react with different sites on FAS. The irreversible inhibition exhibits a time-dependent biphasic process including a speedy fast-phase during the initial several minutes. The fast-phase inhibition seems to be caused by some potent but low-concentration component(s) in the extracts. In addition, we have found that avicularin existing in this herb can potently inhibit FAS. This glycosylated flavonoid and quercetin play an effective role in inhibiting FAS by parasitic loranthus.
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Affiliation(s)
- Yan Wang
- Department of Biology, Graduate University of Chinese Academy of Sciences, Beijing 100049, China
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Vázquez MJ, Leavens W, Liu R, Rodríguez B, Read M, Richards S, Winegar D, Domínguez JM. Discovery of GSK837149A, an inhibitor of human fatty acid synthase targeting the beta-ketoacyl reductase reaction. FEBS J 2008; 275:1556-1567. [PMID: 18312417 DOI: 10.1111/j.1742-4658.2008.06314.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
GSK837149A has been identified as a selective inhibitor of human fatty acid synthase (FAS). The compound was first isolated as a minor impurity in a sample found to be active against the enzyme in a high-throughput screening campaign. The structure of this compound was confirmed by NMR and MS studies, and evaluation of the newly synthesized molecule confirmed its activity against FAS. The compound and other analogs synthesized, all being symmetrical structures containing a bisulfonamide urea, act by inhibiting the beta-ketoacyl reductase activity of the enzyme. GSK837149A inhibits FAS in a reversible mode, with a K(i) value of approximately 30 nm, and it possibly binds to the enzyme-ketoacyl-ACP complex. Although initial results suggest that cell penetration for these compounds is impaired, they still can be regarded as useful tools with which to probe and explore the beta-ketoacyl reductase active site in FAS, helping in the design of new inhibitors.
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Affiliation(s)
- María Jesús Vázquez
- GlaxoSmithKline R&D, Biological Reagents and Assay Development Department, Centro de Investigación Básica, Tres Cantos, Spain
| | - William Leavens
- GlaxoSmithKline R&D, Analytical Chemistry Department, Medicines Research Center, Stevenage, UK
| | - Ronggang Liu
- GlaxoSmithKline R&D, Cardiovascular and Urogenital Centre of Excellence for Drug Discovery, King of Prussia, PA, USA
| | - Beatriz Rodríguez
- GlaxoSmithKline R&D, Biological Reagents and Assay Development Department, Centro de Investigación Básica, Tres Cantos, Spain
| | - Martin Read
- GlaxoSmithKline R&D, Analytical Chemistry Department, Medicines Research Center, Stevenage, UK
| | - Stephen Richards
- GlaxoSmithKline R&D, Analytical Chemistry Department, Medicines Research Center, Stevenage, UK
| | - Deborah Winegar
- GlaxoSmithKline R&D, Metabolic Centre of Excellence for Drug Discovery, Research Triangle Park, Durham, NC, USA
| | - Juan Manuel Domínguez
- GlaxoSmithKline R&D, Biological Reagents and Assay Development Department, Centro de Investigación Básica, Tres Cantos, Spain
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Wolfgang MJ, Lane MD. Control of energy homeostasis: role of enzymes and intermediates of fatty acid metabolism in the central nervous system. Annu Rev Nutr 2006; 26:23-44. [PMID: 16704352 DOI: 10.1146/annurev.nutr.25.050304.092532] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The regulation of energy homeostasis is critical for normal physiology and survival. Energy flux must be rigorously monitored and adjusted to ensure that fuel intake and expenditure remain within acceptable limits. The central nervous system (CNS) is, in large part, responsible for conducting this energy-monitoring function and for integrating the numerous inputs. It has become evident that neurons of the CNS monitor and respond to levels of metabolic intermediates that reflect peripheral energy status. Intermediates in the fatty acid biosynthetic pathway have been implicated as hypothalamic signaling mediators that sense and respond to changes in circulating fuels. Genetic and pharmacologic manipulation of the enzymes of fatty acid metabolism have led to the hypothesis that neuronal metabolic intermediates affect neural outputs that modify both feeding behavior and energy expenditure. This review focuses on the regulatory roles of these enzymes and intermediates in the regulation of food intake and energy balance.
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Affiliation(s)
- Michael J Wolfgang
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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Hentges ST, Low MJ, Williams JT. Differential regulation of synaptic inputs by constitutively released endocannabinoids and exogenous cannabinoids. J Neurosci 2006; 25:9746-51. [PMID: 16237178 PMCID: PMC6725733 DOI: 10.1523/jneurosci.2769-05.2005] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Endocannabinoid release from a single neuron has been shown to cause presynaptic inhibition of transmitter release at many different sites. Here, we demonstrate that hypothalamic proopiomelanocortin (POMC) neurons release endocannabinoids continuously under basal conditions, unlike other release sites at which endocannabinoid production must be stimulated. The basal endocannabinoid release selectively inhibited GABA release onto POMC neurons, although exogenous administration of cannabinoid agonists also inhibited glutamate release. The CB1 cannabinoid receptor antagonist AM 251 [N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide] blocked endocannabinoid-mediated inhibition of GABA release without affecting excitatory synaptic currents, whereas the CB1 receptor agonist WIN 55,212-2 [R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrol [1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate] inhibited both inhibitory and excitatory synaptic currents in POMC neurons. These data demonstrate that endogenously released cannabinoids and exogenously applied CB1 receptor agonists can have markedly different effects on synaptic inputs. Furthermore, the data suggest a novel form of endocannabinoid-mediated retrograde inhibition, whereby the regulation of a subset of inputs requires either the removal of tonic presynaptic inhibition caused by endocannabinoids or the engagement of a mechanism that actively inhibits endocannabinoid production.
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Affiliation(s)
- Shane T Hentges
- Vollum Institute, Oregon Health and Science University, Portland, Oregon 97329, USA.
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Wang R, Cruciani-Guglielmacci C, Migrenne S, Magnan C, Cotero VE, Routh VH. Effects of Oleic Acid on Distinct Populations of Neurons in the Hypothalamic Arcuate Nucleus Are Dependent on Extracellular Glucose Levels. J Neurophysiol 2006; 95:1491-8. [PMID: 16306178 DOI: 10.1152/jn.00697.2005] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pharmacological manipulation of fatty acid metabolism in the hypothalamic arcuate nucleus (ARC) alters energy balance and glucose homeostasis. Thus, we tested the hypotheses that distinctive populations of ARC neurons are oleic acid (OA) sensors that exhibit a glucose dependency, independent of whether some of these OA sensors are also glucose-sensing neurons. We used patch-clamp recordings to investigate the effects of OA on ARC neurons in brain slices from 14- to 21-day-old Sprague–Dawley (SD) rats. Additionally, we recorded spontaneous discharge rate in ARC neurons in 8-wk-old fed and fasted SD rats in vivo. Patch-clamp studies showed that in 2.5 mM glucose 12 of 94 (13%) ARC neurons were excited by 2 μM OA (OA-excited or OAE neurons), whereas six of 94 (6%) were inhibited (OA-inhibited2.5or OAI2.5neurons). In contrast, in 0.1 mM glucose, OA inhibited six of 20 (30%) ARC neurons (OAI0.1neurons); none was excited. None of the OAI0.1neurons responded to OA in 2.5 mM glucose. Thus OAI2.5and OAI0.1neurons are distinct. Similarly, in seven of 20 fed rats (35%) the overall response was OAE-like, whereas in three of 20 (15%) it was OAI-like. In contrast, in fasted rats only OAI-like response were observed (three of 15; 20%). There was minimal overlap between OA-sensing neurons and glucose-sensing neurons. In conclusion, OA regulated three distinct subpopulations of ARC neurons in a glucose-dependent fashion. These data suggest that an interaction between glucose and fatty acids regulates OA sensing in ARC neurons.
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Affiliation(s)
- R Wang
- Department of Pharmacology and Physiology, New Jersey Medical School, 185 S. Orange Ave, PO Box 1709, Newark, NJ 07101-1709, USA
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Dridi S, Ververken C, Hillgartner FB, Arckens L, Lutgarde A, Van der Gucht E, Cnops L, Decuypere E, Buyse J. FAS inhibitor cerulenin reduces food intake and melanocortin receptor gene expression without modulating the other (an)orexigenic neuropeptides in chickens. Am J Physiol Regul Integr Comp Physiol 2006; 291:R138-47. [PMID: 16455759 DOI: 10.1152/ajpregu.00899.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cerulenin, a natural fatty acid synthase (FAS) inhibitor, and its synthetic analog C75 are hypothesized to alter the metabolism of neurons in the hypothalamus that regulate ingestive behavior to cause a profound decrease of food intake and an increase in metabolic rate, leading to body weight loss. The bulk of data exclusively originates from mammals (rodents); however, such effects are currently lacking in nonmammalian species. We have, therefore, addressed this issue in broiler chickens because this species is selected for high growth rate and high food intake and is prone to obesity. First, we demonstrate that FAS messenger and protein are expressed in the hypothalamus of chickens. FAS immunoreactivity was detected in a number of brain regions, including the nucleus paraventricularis magnocellularis and the nucleus infundibuli hypothalami, the avian equivalent of the mammalian arcuate nucleus, suggesting that FAS may be involved in the regulation of food intake. Second, we show that hypothalamic FAS gene expression was significantly (P < 0.05) decreased by overnight fasting similar to that in liver, indicating that hypothalamic FAS gene is regulated by energy status in chickens. Finally, to investigate the physiological consequences of in vivo inhibition of fatty acid synthesis on food intake, we administered cerulenin by intravenous injections (15 mg/kg) to 2-wk-old broiler chickens. Cerulenin administration significantly reduced food intake by 23 to 34% (P < 0.05 to P < 0.0001) and downregulated FAS and melanocortin receptors 1, 4, and 5 gene expression (P < 0.05). However, the known orexigenic (neuropeptide Y, agouti gene-related peptide, orexin, and orexin receptor) and anorexigenic (pro-opiomelanocortin and corticotropin-releasing hormone) neuropeptide mRNA levels remained unchanged after cerulenin treatment. These results suggest that the catabolic effect of cerulenin in chickens may be mediated through the melanocortin system rather than the other neuropeptides known to be involved in food intake regulation.
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Affiliation(s)
- Sami Dridi
- Laboratory of Physiology and Immunology of Domestic Animals, Catholic University of Leuven, Heverlee, Belgium.
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López M, Tovar S, Vázquez MJ, Nogueiras R, Señarís R, Diéguez C. Sensing the fat: fatty acid metabolism in the hypothalamus and the melanocortin system. Peptides 2005; 26:1753-8. [PMID: 15979207 DOI: 10.1016/j.peptides.2004.11.025] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Accepted: 11/15/2004] [Indexed: 11/28/2022]
Abstract
Recent evidence has demonstrated that circulating long chain fatty acids act as nutrient abundance signals in the hypothalamus. Moreover, pharmacological inhibition of fatty acid synthase (FAS) results in profound decrease in food intake and body weight in rodents. These anorectic actions are mediated by the modulation of hypothalamic neuropeptide systems, such as melanocortins. In this review, we summarize what is known about lipid sensing and fatty acid metabolism in the hypothalamus. Understanding these molecular mechanisms could provide new pharmacological targets for the treatment of obesity and appetite disorders, as well as novel concepts in the nutritional design.
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Affiliation(s)
- Miguel López
- Department of Physiology, School of Medicine, University of Santiago de Compostela, C/S. Francisco 1, 15705 Santiago de Compostela, Spain
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Dowell P, Hu Z, Lane MD. Monitoring energy balance: metabolites of fatty acid synthesis as hypothalamic sensors. Annu Rev Biochem 2005; 74:515-34. [PMID: 15952896 DOI: 10.1146/annurev.biochem.73.011303.074027] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Because energy balance is important for survival, a system is required to monitor energy status and to make appropriate adjustments in energy intake and energy expenditure. In higher animals, a centrally located system has evolved to accomplish this task. When caloric intake exceeds expenditure, the surplus is channeled into energy storage pathways, primarily the synthesis of fatty acids, which are converted into fat and stored in adipose tissue. Thus, metabolic flux through the pathway of fatty acid synthesis, located in the lipogenic tissues, reflects the "energy status" of the animal. The enzymatic machinery of this pathway is also expressed in the brain, notably the hypothalamus. In the hypothalamus, intermediates in this pathway appear to serve as energy sensors that signal higher brain centers to produce appropriate responses, e.g., altered food intake and energy expenditure.
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Affiliation(s)
- Paul Dowell
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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Mastaitis JW, Wurmbach E, Cheng H, Sealfon SC, Mobbs CV. Acute induction of gene expression in brain and liver by insulin-induced hypoglycemia. Diabetes 2005; 54:952-8. [PMID: 15793232 DOI: 10.2337/diabetes.54.4.952] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The robust neuroendocrine counterregulatory responses induced by hypoglycemia protect the brain by restoring plasma glucose, but little is known about molecular responses to hypoglycemia that may also be neuroprotective. To clarify these mechanisms, we examined gene expression in hypothalamus, cortex, and liver 3 h after induction of mild hypoglycemia by a single injection of insulin, using cDNA microarray analysis and quantitative real-time PCR. Real-time PCR corroborated the induction of six genes (angiotensinogen, GLUT-1, inhibitor of kappaB, inhibitor of DNA binding 1 [ID-1], Ubp41, and mitogen-activated protein kinase phosphatase-1 [MKP-1]) by insulin-induced hypoglycemia in the hypothalamus: five of these six genes in cortex and three (GLUT-1, angiotensinogen, and MKP-1) in liver. The induction was due to hypoglycemia and not hyperinsulinemia, since fasting (characterized by low insulin and glucose) also induced these genes. Four of these genes (angiotensinogen, GLUT-1, ID-1, and MKP-1) have been implicated in enhancement of glucose availability, which could plausibly serve a neuroprotective role during acute hypoglycemia but, if persistent, could also cause glucose-sensing mechanisms to overestimate plasma glucose levels, potentially causing hypoglycemia-induced counterregulatory failure. Although using cDNA microarrays with more genes, or microdissection, would presumably reveal further responses to hypoglycemia, these hypoglycemia-induced genes represent useful markers to assess molecular mechanisms mediating cellular responses to hypoglycemia.
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Affiliation(s)
- Jason W Mastaitis
- Fishberg Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Abstract
Obesity in middle-aged humans is a risk factor for many age-related diseases and decreases life expectancy by about 7 years, which is roughly comparable to the combined effect of all cardiovascular disease and cancer on life span. The prevalence of obesity increases up until late middle age and decreases thereafter. Mechanisms that lead to increased obesity with age are not yet well understood, but current evidence implicates impairments in hypothalamic function, especially impairments in the ability of hypothalamic pro-opiomelanocortin neurons to sense nutritional signals. The rapid increase in the prevalence of obesity at all ages in the past decade suggests that, in the next two or three decades, diseases associated with obesity, especially diabetes, will begin to rise rapidly. Indeed, these trends suggest that for the first time in modern history, the life expectancy of people in developed societies will begin to decrease, unless the rapid increase in the prevalence of obesity can be reversed.
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Affiliation(s)
- Tooru Mizuno
- Fishberg Center for Neurobiology, Neurobiology of Aging Laboratories, Department of Geriatrics, Mt. Sinai School of Medicine, New York, NY 10029, USA
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