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Maxwell ND, Smiley CE, Sadek AT, Loyo-Rosado FZ, Giles DC, Macht VA, Woodruff JL, Taylor DL, Wilson SP, Fadel JR, Reagan LP, Grillo CA. Leptin activation of dorsal raphe neurons inhibits feeding behavior. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.538086. [PMID: 37162932 PMCID: PMC10168215 DOI: 10.1101/2023.04.24.538086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Leptin is a homeostatic regulatory element that signals the presence of energy stores -in the form of adipocytes-which ultimately reduces food intake and increases energy expenditure. Similarly, serotonin (5-HT), a signaling molecule found in both the central and peripheral nervous systems, also regulates food intake. Here we use a combination of pharmacological manipulations, optogenetics, retrograde tracing, and in situ hybridization, combined with behavioral endpoints to physiologically and anatomically identify a novel leptin-mediated pathway between 5-HT neurons in the dorsal raphe nucleus (DRN) and hypothalamic arcuate nucleus (ARC) that controls food intake. In this study, we show that microinjecting leptin directly into the DRN reduces food intake in male Sprague-Dawley rats. This effect is mediated by leptin-receptor expressing neurons in the DRN as selective optogenetic activation of these neurons at either their ARC terminals or DRN cell bodies also reduces food intake. Anatomically, we identified a unique population of serotonergic raphe neurons expressing leptin receptors that send projections to the ARC. Finally, by utilizing in vivo microdialysis and high-performance liquid chromatography, we show that leptin administration to the DRN increases 5-HT efflux into the ARC. Overall, this study identifies a novel circuit for leptin-mediated control of food intake through a DRN-ARC pathway, utilizing 5-HT as a mechanism to control feeding behavior. Characterization of this new pathway creates opportunities for understanding how the brain controls eating behavior, as well as opens alternative routes for the treatment of eating disorders. Significance Leptin and serotonin both play a vital role in the regulation of food intake, yet there is still uncertainty in how these two molecules interact to control appetite. The purpose of this study is to further understand the anatomical and functional connections between leptin receptor expressing neurons in the dorsal raphe nucleus, the main source of serotonin, and the arcuate nucleus of the hypothalamus, and how serotonin plays a role in this pathway to reduce food intake. Insight gained from this study will contribute to a more thorough understanding of the networks that regulate food intake, and open alternative avenues for the development of treatments for obesity and eating disorders.
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Administration of small-molecule guanabenz acetate attenuates fatty liver and hyperglycemia associated with obesity. Sci Rep 2020; 10:13671. [PMID: 32792584 PMCID: PMC7426972 DOI: 10.1038/s41598-020-70689-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 07/27/2020] [Indexed: 12/13/2022] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive accumulation of hepatic triglycerides (TG) and hyperglycemia arising due to persistent insulin resistance, and is profoundly linked to obesity. However, there is currently no established treatment for NAFLD in obese human subjects. We previously isolated Helz2, the expression of which was upregulated in human and mouse NAFLD, and its deletion activated the hepatic expression of functional leptin receptor long form (Leprb) and suppressed NAFLD development and body weight (BW) gain in obese mice. A high-throughput assay of small-molecule drugs revealed that guanabenz acetate (Ga), originally used to treat hypertension, possesses a high affinity constant against HELZ2, and its administration activates LEPRB expression in HepG2 cells in vitro. The chronic oral administration of Ga shows the selective leptin sensitization in the liver via upregulation of hepatic Leprb expression, which affects expression of genes involved in lipogenesis and fatty acid β-oxidation and diminishes hepatocyte hypertrophy with droplets enriched in TG in high-fat diet-induced obese mice. This activity significantly improves insulin resistance to decrease hyperglycemia and hepatocyte and adipocyte weights, resulting in BW reduction without reducing food intake. Regarding drug repositioning, Ga has the potential to effectively treat NAFLD and hyperglycemia in obese patients.
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Mouse Genetic Analysis of Bone Marrow Stem Cell Niches: Technological Pitfalls, Challenges, and Translational Considerations. Stem Cell Reports 2017; 9:1343-1358. [PMID: 29056332 PMCID: PMC5829346 DOI: 10.1016/j.stemcr.2017.09.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 09/18/2017] [Accepted: 09/19/2017] [Indexed: 01/08/2023] Open
Abstract
The development of mouse genetic tools has made a significant contribution to the understanding of skeletal and hematopoietic stem cell niches in bone marrow (BM). However, many experimental designs (e.g., selections of marker genes, target vector constructions, and choices of reporter murine strains) have unavoidable technological limitations and bias, which lead to experimental discrepancies, data reproducibility issues, and frequent data misinterpretation. Consequently, there are a number of conflicting views relating to fundamental biological questions, including origins and locations of skeletal and hematopoietic stem cells in the BM. In this report, we systematically unravel complicated data interpretations via comprehensive analyses of technological benefits, pitfalls, and challenges in frequently used mouse models and discuss their translational relevance to human stem cell biology. Particularly, we emphasize the important roles of using large human genomic data-informatics in facilitating genetic analyses of mouse models and resolving existing controversies in mouse and human BM stem cell biology.
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Londraville RL, Prokop JW, Duff RJ, Liu Q, Tuttle M. On the Molecular Evolution of Leptin, Leptin Receptor, and Endospanin. Front Endocrinol (Lausanne) 2017; 8:58. [PMID: 28443063 PMCID: PMC5385356 DOI: 10.3389/fendo.2017.00058] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 03/15/2017] [Indexed: 12/16/2022] Open
Abstract
Over a decade passed between Friedman's discovery of the mammalian leptin gene (1) and its cloning in fish (2) and amphibians (3). Since 2005, the concept of gene synteny conservation (vs. gene sequence homology) was instrumental in identifying leptin genes in dozens of species, and we now have leptin genes from all major classes of vertebrates. This database of LEP (leptin), LEPR (leptin receptor), and LEPROT (endospanin) genes has allowed protein structure modeling, stoichiometry predictions, and even functional predictions of leptin function for most vertebrate classes. Here, we apply functional genomics to model hundreds of LEP, LEPR, and LEPROT proteins from both vertebrates and invertebrates. We identify conserved structural motifs in each of the three leptin signaling proteins and demonstrate Drosophila Dome protein's conservation with vertebrate leptin receptors. We model endospanin structure for the first time and identify endospanin paralogs in invertebrate genomes. Finally, we argue that leptin is not an adipostat in fishes and discuss emerging knockout models in fishes.
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Affiliation(s)
- Richard Lyle Londraville
- Program in Integrative Bioscience, Department of Biology, University of Akron, Akron, OH, USA
- *Correspondence: Richard Lyle Londraville,
| | | | - Robert Joel Duff
- Program in Integrative Bioscience, Department of Biology, University of Akron, Akron, OH, USA
| | - Qin Liu
- Program in Integrative Bioscience, Department of Biology, University of Akron, Akron, OH, USA
| | - Matthew Tuttle
- Program in Integrative Bioscience, Department of Biology, University of Akron, Akron, OH, USA
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Londraville RL, Macotela Y, Duff RJ, Easterling MR, Liu Q, Crespi EJ. Comparative endocrinology of leptin: assessing function in a phylogenetic context. Gen Comp Endocrinol 2014; 203:146-57. [PMID: 24525452 PMCID: PMC4128956 DOI: 10.1016/j.ygcen.2014.02.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 01/31/2014] [Accepted: 02/03/2014] [Indexed: 12/11/2022]
Abstract
As we approach the end of two decades of leptin research, the comparative biology of leptin is just beginning. We now have several leptin orthologs described from nearly every major clade among vertebrates, and are moving beyond gene descriptions to functional studies. Even at this early stage, it is clear that non-mammals display clear functional similarities and differences with their better-studied mammalian counterparts. This review assesses what we know about leptin function in mammals and non-mammals, and gives examples of how these data can inform leptin biology in humans.
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Affiliation(s)
- Richard L Londraville
- Department of Biology and Program in Integrated Biosciences, University of Akron, Akron, OH, USA.
| | - Yazmin Macotela
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico
| | - Robert J Duff
- Department of Biology and Program in Integrated Biosciences, University of Akron, Akron, OH, USA
| | - Marietta R Easterling
- School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
| | - Qin Liu
- Department of Biology and Program in Integrated Biosciences, University of Akron, Akron, OH, USA
| | - Erica J Crespi
- School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
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Ball HC, Holmes RK, Londraville RL, Thewissen JGM, Duff RJ. Leptin in whales: validation and measurement of mRNA expression by absolute quantitative real-time PCR. PLoS One 2013; 8:e54277. [PMID: 23342116 PMCID: PMC3546977 DOI: 10.1371/journal.pone.0054277] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 12/10/2012] [Indexed: 12/17/2022] Open
Abstract
Leptin is the primary hormone in mammals that regulates adipose stores. Arctic adapted cetaceans maintain enormous adipose depots, suggesting possible modifications of leptin or receptor function. Determining expression of these genes is the first step to understanding the extreme physiology of these animals, and the uniqueness of these animals presents special challenges in estimating and comparing expression levels of mRNA transcripts. Here, we compare expression of two model genes, leptin and leptin-receptor gene-related product (OB-RGRP), using two quantitative real-time PCR (qPCR) methods: "relative" and "absolute". To assess the expression of leptin and OB-RGRP in cetacean tissues, we first examined how relative expression of those genes might differ when normalized to four common endogenous control genes. We performed relative expression qPCR assays measuring the amplification of these two model target genes relative to amplification of 18S ribosomal RNA (18S), ubiquitously expressed transcript (Uxt), ribosomal protein 9 (Rs9) and ribosomal protein 15 (Rs15) endogenous controls. Results demonstrated significant differences in the expression of both genes when different control genes were employed; emphasizing a limitation of relative qPCR assays, especially in studies where differences in physiology and/or a lack of knowledge regarding levels and patterns of expression of common control genes may possibly affect data interpretation. To validate the absolute quantitative qPCR methods, we evaluated the effects of plasmid structure, the purity of the plasmid standard preparation and the influence of type of qPCR "background" material on qPCR amplification efficiencies and copy number determination of both model genes, in multiple tissues from one male bowhead whale. Results indicate that linear plasmids are more reliable than circular plasmid standards, no significant differences in copy number estimation based upon background material used, and that the use of ethanol precipitated, linearized plasmid preparation produce the most reliable results.
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Affiliation(s)
- Hope C. Ball
- Department of Biology, The University of Akron, Akron, Ohio, United States of America
| | - Robert K. Holmes
- Department of Biology, The University of Akron, Akron, Ohio, United States of America
| | | | - Johannes G. M. Thewissen
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, United States of America
| | - Robert Joel Duff
- Department of Biology, The University of Akron, Akron, Ohio, United States of America
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Del Bianco-Borges B, Cabral FJ, Franci CR. Co-expression of leptin and oestrogen receptors in the preoptic-hypothalamic area. J Neuroendocrinol 2010; 22:996-1003. [PMID: 20584107 DOI: 10.1111/j.1365-2826.2010.02046.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The interaction between the reproductive axis and energy balance suggests that leptin acts as a possible mediator. This hormone acts in the regulation of metabolism, feeding behaviour and reproduction. Animals homozygous for the gene 'ob' (ob/ob) are obese and infertile, and these effects are reversed after systemic administration of leptin. Thus, the present study aimed to determine: (i) whether cells that express leptin also express oestrogen receptors of type-alpha (ER-alpha) or -beta (ER-beta) in the medial preoptic area (MPOA) and in the arcuate (ARC), dorsomedial (DMH) and ventromedial hypothalamic nucleus and (ii) whether there is change in the gene and protein expression of leptin in these brain areas in ovariectomised (OVX) animals when oestrogen-primed. Wistar female rats with normal oestrous cycles or ovariectomised oestrogen-primed or vehicle (oil)-primed were utilised. To determine whether there was a co-expression, immunofluorescence was utilised for double staining. Confocal microscopy was used to confirm the co-expression. The technique of real-time polymerase chain reaction and western blotting were employed to analyse gene and protein expression, respectively. The results obtained showed co-expression of leptin and ER-alpha in the MPOA and in the DMH, as well as leptin and ER-beta in the MPOA, DMH and ARC. However, we did not detect leptin in the MPOA, ARC and DMH using western blotting and there was no statistical difference in leptin gene expression in the MPOA, DMH, ARC, pituitary or adipose tissue between OVX rats treated with oestrogen or vehicle. In conclusion, the results obtained in the present study confirm that the brain is also a source of leptin and reveal co-expression of oestrogen receptors and leptin in the same cells from areas related to reproductive function and feeding behaviour. Although these data corroborate the previous evidence obtained concerning the interaction between the action of brain leptin and reproductive function, the physiological relevance of this interaction remains uncertain and additional studies are necessary to elucidate the exact role of central leptin.
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Affiliation(s)
- B Del Bianco-Borges
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
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Hashimoto K, Ishida E, Miura A, Ozawa A, Shibusawa N, Satoh T, Okada S, Yamada M, Mori M. A liver X receptor (LXR)-β alternative splicing variant (LXRBSV) is preferentially expressed in the pituitary. Biochem Biophys Res Commun 2010; 394:548-52. [DOI: 10.1016/j.bbrc.2010.03.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 03/03/2010] [Indexed: 11/16/2022]
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Hardeland R. Neuroprotection by radical avoidance: search for suitable agents. Molecules 2009; 14:5054-102. [PMID: 20032877 PMCID: PMC6255388 DOI: 10.3390/molecules14125054] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 11/30/2009] [Accepted: 12/04/2009] [Indexed: 02/07/2023] Open
Abstract
Neurodegeneration is frequently associated with damage by free radicals. However, increases in reactive oxygen and nitrogen species, which may ultimately lead to neuronal cell death, do not necessarily reflect its primary cause, but can be a consequence of otherwise induced cellular dysfunction. Detrimental processes which promote free radical formation are initiated, e.g., by disturbances in calcium homeostasis, mitochondrial malfunction, and an age-related decline in the circadian oscillator system. Free radicals generated at high rates under pathophysiological conditions are insufficiently detoxified by scavengers. Interventions at the primary causes of dysfunction, which avoid secondary rises in radical formation, may be more efficient. The aim of such approaches should be to prevent calcium overload, to reduce mitochondrial electron dissipation, to support electron transport capacity, and to avoid circadian perturbations. L-theanine and several amphiphilic nitrones are capable of counteracting excitotoxicity and/or mitochondrial radical formation. Resveratrol seems to promote mitochondrial biogenesis. Mitochondrial effects of leptin include attenuation of electron leakage. Melatonin combines all the requirements mentioned, additionally regulates anti- and pro-oxidant enzymes and is, with few exceptions, very well tolerated. In this review, the perspectives, problems and limits of drugs are compared which may be suitable for reducing the formation of free radicals.
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Affiliation(s)
- Rüdiger Hardeland
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Berliner str. 28, D-37073 Göttingen, Germany.
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