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Quinpirole ameliorates nigral dopaminergic neuron damage in Parkinson's disease mouse model through activating GHS-R1a/D 2R heterodimers. Acta Pharmacol Sin 2023:10.1038/s41401-023-01063-0. [PMID: 36899113 PMCID: PMC10374575 DOI: 10.1038/s41401-023-01063-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 02/12/2023] [Indexed: 03/12/2023] Open
Abstract
Growth hormone secretagogue receptor 1a (GHS-R1a) is an important G protein-coupled receptor (GPCR) that regulates a variety of functions by binding to ghrelin. It has been shown that the dimerization of GHS-R1a with other receptors also affects ingestion, energy metabolism, learning and memory. Dopamine type 2 receptor (D2R) is a GPCR mainly distributed in the ventral tegmental area (VTA), substantia nigra (SN), striatum and other brain regions. In this study we investigated the existence and function of GHS-R1a/D2R heterodimers in nigral dopaminergic neurons in Parkinson's disease (PD) models in vitro and in vivo. By conducting immunofluorescence staining, FRET and BRET analyses, we confirmed that GHS-R1a and D2R could form heterodimers in PC-12 cells and in the nigral dopaminergic neurons of wild-type mice. This process was inhibited by MPP+ or MPTP treatment. Application of QNP (10 μM) alone significantly increased the viability of MPP+-treated PC-12 cells, and administration of quinpirole (QNP, 1 mg/kg, i.p. once before and twice after MPTP injection) significantly alleviated motor deficits in MPTP-induced PD mice model; the beneficial effects of QNP were abolished by GHS-R1a knockdown. We revealed that the GHS-R1a/D2R heterodimers could increase the protein levels of tyrosine hydroxylase in the SN of MPTP-induced PD mice model through the cAMP response element binding protein (CREB) signaling pathway, ultimately promoting dopamine synthesis and release. These results demonstrate a protective role for GHS-R1a/D2R heterodimers in dopaminergic neurons, providing evidence for the involvement of GHS-R1a in PD pathogenesis independent of ghrelin.
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Daimon CM, Hentges ST. Inhibition of POMC neurons in mice undergoing activity-based anorexia selectively blunts food anticipatory activity without affecting body weight or food intake. Am J Physiol Regul Integr Comp Physiol 2022; 322:R219-R227. [PMID: 35043681 PMCID: PMC8858678 DOI: 10.1152/ajpregu.00313.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anorexia nervosa (AN) is a debilitating eating disorder characterized by severely restricted eating and significant body weight loss. In addition, many individuals also report engaging in excessive exercise. Previous research using the activity-based anorexia (ABA) model has implicated the hypothalamic proopiomelanocortin (POMC) system. Using the ABA model, Pomc mRNA has been shown to be transiently elevated in both male and female rodents undergoing ABA. In addition, the POMC peptide β-endorphin appears to contribute to food anticipatory activity (FAA), a characteristic of ABA, as both deletion and antagonism of the µ opioid receptor (MOR) that β-endorphin targets, results in decreased FAA. The role of β-endorphin in reduced food intake in ABA is unknown and POMC neurons release multiple transmitters in addition to β-endorphin. In the current study, we set out to determine whether targeted inhibition of POMC neurons themselves rather than their peptide products would lessen the severity of ABA. Inhibition of POMC neurons during ABA via chemogenetic Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology resulted in reduced FAA in both male and female mice with no significant changes in body weight or food intake. The selective reduction in FAA persisted even in the face of concurrent chemogenetic inhibition of additional cell types in the hypothalamic arcuate nucleus. The results suggest that POMC neurons could be contributing preferentially to excessive exercise habits in patients with AN. Furthermore, the results also suggest that metabolic control during ABA appears to take place via a POMC neuron-independent mechanism.
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Affiliation(s)
- Caitlin M. Daimon
- Department of Biomedical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - Shane T. Hentges
- Department of Biomedical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado
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Iijima M, Takemi S, Aizawa S, Sakai T, Sakata I. The suppressive effect of REVERBs on ghrelin and GOAT transcription in gastric ghrelin-producing cells. Neuropeptides 2021; 90:102187. [PMID: 34450431 DOI: 10.1016/j.npep.2021.102187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/05/2021] [Accepted: 08/19/2021] [Indexed: 11/30/2022]
Abstract
Ghrelin is a multifunctional gut peptide with a unique structure, which is modified by a medium chain fatty acid at the third serine by ghrelin O-acyl transferase (GOAT). It is well known that the major source of plasma ghrelin is the stomach, but the transcriptional regulation of gastric ghrelin and GOAT is incompletely understood. Here, we studied the involvement of the nuclear receptors REV-ERBα and REV-ERBβ on ghrelin and GOAT gene expression in vivo and in vitro. Reverse-transcriptase polymerase chain reaction analysis showed that REV-ERBα and REV-ERBβ mRNAs were expressed in the stomach and a stomach-derived ghrelin cell line (SG-1 cells). In vivo experiments with mice revealed the circadian rhythm of ghrelin, GOAT, and REV-ERBs. The peak expression of ghrelin and GOAT mRNAs occurred at Zeitgeber time (ZT) 4, whereas that of REV-ERBα and REV-ERBβ was observed at ZT8 and ZT12, respectively. Treatment of SG-1 cells with SR9009, a REV-ERB agonist, led to a significant reduction in ghrelin and GOAT mRNA levels. Overexpression of REV-ERBα and REV-ERBβ decreased ghrelin and GOAT mRNA levels in SG-1 cells. In contrast, small-interfering RNA (siRNA)-mediated double-knockdown of REV-ERBα and REV-ERBβ in SG-1 cells led to the upregulation in the expression of ghrelin and GOAT mRNAs. These results suggest that REV-ERBs suppress ghrelin and GOAT mRNA expression.
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Affiliation(s)
- Mio Iijima
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Shota Takemi
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Sayaka Aizawa
- Department of Biology, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan
| | - Takafumi Sakai
- Professor emeritus, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Ichiro Sakata
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan; Area of Life-NanoBio, Division of Strategy Research, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan.
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Abstract
Feeding, which is essential for all animals, is regulated by homeostatic mechanisms. In addition, food consumption is temporally coordinated by the brain over the circadian (~24 h) cycle. A network of circadian clocks set daily windows during which food consumption can occur. These daily windows mostly overlap with the active phase. Brain clocks that ensure the circadian control of food intake include a master light-entrainable clock in the suprachiasmatic nuclei of the hypothalamus and secondary clocks in hypothalamic and brainstem regions. Metabolic hormones, circulating nutrients and visceral neural inputs transmit rhythmic cues that permit (via close and reciprocal molecular interactions that link metabolic processes and circadian clockwork) brain and peripheral organs to be synchronized to feeding time. As a consequence of these complex interactions, growing evidence shows that chronodisruption and mistimed eating have deleterious effects on metabolic health. Conversely, eating, even eating an unbalanced diet, during the normal active phase reduces metabolic disturbances. Therefore, in addition to energy intake and dietary composition, appropriately timed meal patterns are critical to prevent circadian desynchronization and limit metabolic risks. This Review provides insight into the dual modulation of food intake by homeostatic and circadian processes, describes the mechanisms regulating feeding time and highlights the beneficial effects of correctly timed eating, as opposed to the negative metabolic consequences of mistimed eating.
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Affiliation(s)
- Etienne Challet
- Circadian clocks and metabolism team, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg, France.
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Wu CS, Bongmba OYN, Lee JH, Tuchaai E, Zhou Y, Li DP, Xue B, Chen Z, Sun Y. Ghrelin receptor in agouti-related peptide neurones regulates metabolic adaptation to calorie restriction. J Neuroendocrinol 2019; 31:e12763. [PMID: 31251830 PMCID: PMC7233797 DOI: 10.1111/jne.12763] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 06/24/2019] [Accepted: 06/25/2019] [Indexed: 12/16/2022]
Abstract
Ghrelin is a gut hormone that signals to the hypothalamus to stimulate growth hormone release, increase food intake and promote fat deposition. The ghrelin receptor, also known as growth hormone secretagogue receptor (GHS-R), is highly expressed in the brain, with the highest expression in agouti-related peptide (AgRP) neurones in the hypothalamus. Compelling evidence indicates that ghrelin serves as a survival hormone with respect to maintaining blood glucose and body weight during nutritional deficiencies. Recent studies have demonstrated that AgRP neurones are involved in metabolic and behavioural adaptation to an energy deficit to improve survival. In the present study, we used a neuronal subtype-specific GHS-R knockout mouse (AgRP-Cre;Ghsrf/f ) to investigate the role of GHS-R in hypothalamic AgRP neurones in metabolic and behavioural adaptation to hypocaloric restricted feeding. We subjected the mice to a restricted feeding regimen of 40% mild calorie restriction (CR), with one-quarter of food allotment given in the beginning of the light cycle and three-quarters given at the beginning of the dark cycle, to mimic normal mouse intake pattern. The CR-fed AgRP-Cre;Ghsrf/f mice exhibited reductions in body weight, fat mass and blood glucose. Metabolic profiling of these CR-fed AgRP-Cre;Ghsrf/f mice showed a trend toward reduced basal metabolic rate, significantly reduced core body temperature and a decreased expression of thermogenic genes in brown adipose tissue. This suggests a metabolic reset to a lower threshold. Significantly increased physical activity, a trend toward increased food anticipatory behaviour and altered fuel preferences were also observed in these mice. In addition, these CR-fed AgRP-Cre;Ghsrf/f mice exhibited a decreased counter-regulatory response, showing impaired hepatic glucose production. Lastly, hypothalamic gene expression in AgRP-Cre;Ghsrf/f mice revealed increased AgRP expression and a decreased expression of genes in β-oxidation pathways. In summary, our data suggest that GHS-R in AgRP neurones is a key component of the neurocircuitry involved in metabolic adaptation to calorie restriction.
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Affiliation(s)
- Chia-Shan Wu
- Department of Nutrition and Food Science, Texas A&M University, College Station, TX, 77843, USA
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Odelia Y. N. Bongmba
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Jong Han Lee
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
- College of Pharmacy, Gachon University, Incheon, 21936, Korea
| | - Ellie Tuchaai
- Department of Nutrition and Food Science, Texas A&M University, College Station, TX, 77843, USA
| | - Yu Zhou
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - De-Pei Li
- Center for precision medicine, School of Medicine, University of Missouri. Columbia, MO 65212, USA
| | - Bingzhong Xue
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA
| | - Zheng Chen
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, TX 77030, USA
| | - Yuxiang Sun
- Department of Nutrition and Food Science, Texas A&M University, College Station, TX, 77843, USA
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
- To whom correspondence should be addressed: Dr. Yuxiang Sun, mailing address: Department of Nutrition and Food Science, Texas A&M University, 214C Cater-Mattil, 2253 TAMU, College Station, TX 77843. Phone: 979-862-9143;
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Baldini G, Phelan KD. The melanocortin pathway and control of appetite-progress and therapeutic implications. J Endocrinol 2019; 241:R1-R33. [PMID: 30812013 PMCID: PMC6500576 DOI: 10.1530/joe-18-0596] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 01/22/2019] [Indexed: 12/19/2022]
Abstract
The initial discovery that ob/ob mice become obese because of a recessive mutation of the leptin gene has been crucial to discover the melanocortin pathway to control appetite. In the melanocortin pathway, the fed state is signaled by abundance of circulating hormones such as leptin and insulin, which bind to receptors expressed at the surface of pro-opiomelanocortin (POMC) neurons to promote processing of POMC to the mature hormone α-melanocyte-stimulating hormone (α-MSH). The α-MSH released by POMC neurons then signals to decrease energy intake by binding to melanocortin-4 receptor (MC4R) expressed by MC4R neurons to the paraventricular nucleus (PVN). Conversely, in the 'starved state' activity of agouti-related neuropeptide (AgRP) and of neuropeptide Y (NPY)-expressing neurons is increased by decreased levels of circulating leptin and insulin and by the orexigenic hormone ghrelin to promote food intake. This initial understanding of the melanocortin pathway has recently been implemented by the description of the complex neuronal circuit that controls the activity of POMC, AgRP/NPY and MC4R neurons and downstream signaling by these neurons. This review summarizes the progress done on the melanocortin pathway and describes how obesity alters this pathway to disrupt energy homeostasis. We also describe progress on how leptin and insulin receptors signal in POMC neurons, how MC4R signals and how altered expression and traffic of MC4R change the acute signaling and desensitization properties of the receptor. We also describe how the discovery of the melanocortin pathway has led to the use of melanocortin agonists to treat obesity derived from genetic disorders.
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Affiliation(s)
- Giulia Baldini
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Kevin D. Phelan
- Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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Stutz B, Nasrallah C, Nigro M, Curry D, Liu ZW, Gao XB, Elsworth JD, Mintz L, Horvath TL. Dopamine neuronal protection in the mouse Substantia nigra by GHSR is independent of electric activity. Mol Metab 2019; 24:120-138. [PMID: 30833218 PMCID: PMC6531791 DOI: 10.1016/j.molmet.2019.02.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Revised: 02/15/2019] [Accepted: 02/16/2019] [Indexed: 12/25/2022] Open
Abstract
Objective Dopamine neurons in the Substantia nigra (SN) play crucial roles in control of voluntary movement. Extensive degeneration of this neuronal population is the cause of Parkinson's disease (PD). Many factors have been linked to SN DA neuronal survival, including neuronal pacemaker activity (responsible for maintaining basal firing and DA tone) and mitochondrial function. Dln-101, a naturally occurring splice variant of the human ghrelin gene, targets the ghrelin receptor (GHSR) present in the SN DA cells. Ghrelin activation of GHSR has been shown to protect SN DA neurons against 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) treatment. We decided to compare the actions of Dln-101 with ghrelin and identify the mechanisms associated with neuronal survival. Methods Histologial, biochemical, and behavioral parameters were used to evaluate neuroprotection. Inflammation and redox balance of SN DA cells were evaluated using histologial and real-time PCR analysis. Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology was used to modulate SN DA neuron electrical activity and associated survival. Mitochondrial dynamics in SN DA cells was evaluated using electron microscopy data. Results Here, we report that the human isoform displays an equivalent neuroprotective factor. However, while exogenous administration of mouse ghrelin electrically activates SN DA neurons increasing dopamine output, as well as locomotion, the human isoform significantly suppressed dopamine output, with an associated decrease in animal motor behavior. Investigating the mechanisms by which GHSR mediates neuroprotection, we found that dopamine cell-selective control of electrical activity is neither sufficient nor necessary to promote SN DA neuron survival, including that associated with GHSR activation. We found that Dln101 pre-treatment diminished MPTP-induced mitochondrial aberrations in SN DA neurons and that the effect of Dln101 to protect dopamine cells was dependent on mitofusin 2, a protein involved in the process of mitochondrial fusion and tethering of the mitochondria to the endoplasmic reticulum. Conclusions Taken together, these observations unmasked a complex role of GHSR in dopamine neuronal protection independent on electric activity of these cells and revealed a crucial role for mitochondrial dynamics in some aspects of this process. Dln101 is a human splice-variant of the ghrelin gene with different expression pattern. Ghrelin and Dln101 display equivalent levels of neuroprotection of SN DA cells. Modulation of electrical activity of SN DA cells is not relevant for neuroprotection. Mitochondrial fusion protein 2 (MFN 2) blocks DLN101-induced mitochondrial fusion in SN DA neurons and prevents DLN101-induced neuroprotection.
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Affiliation(s)
- Bernardo Stutz
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, USA.
| | - Carole Nasrallah
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, USA; Interdepartmental Neuroscience Program, USA
| | - Mariana Nigro
- Department of Obstetrics, Gynecology and Reproductive Sciences, USA
| | | | - Zhong-Wu Liu
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, USA
| | - Xiao-Bing Gao
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, USA
| | | | | | - Tamas L Horvath
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, USA; Interdepartmental Neuroscience Program, USA; Department of Obstetrics, Gynecology and Reproductive Sciences, USA; Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, 1078, Hungary.
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Reichenbach A, Mequinion M, Bayliss JA, Lockie SH, Lemus MB, Mynatt RL, Stark R, Andrews ZB. Carnitine Acetyltransferase in AgRP Neurons Is Required for the Homeostatic Adaptation to Restricted Feeding in Male Mice. Endocrinology 2018; 159:2473-2483. [PMID: 29697769 PMCID: PMC6692886 DOI: 10.1210/en.2018-00131] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 04/19/2018] [Indexed: 12/14/2022]
Abstract
Behavioral adaptation to periods of varying food availability is crucial for survival, and agouti-related protein (AgRP) neurons have been associated with entrainment to temporal restricted feeding. We have shown that carnitine acetyltransferase (Crat) in AgRP neurons enables metabolic flexibility and appropriate nutrient partitioning. In this study, by restricting food availability to 3 h/d during the light phase, we examined whether Crat is a component of a food-entrainable oscillator (FEO) that helps link behavior to food availability. AgRP Crat knockout (KO) mice consumed less food and regained less body weight but maintained blood glucose levels during the 25-day restricted feeding protocol. Importantly, we observed no difference in meal latency, food anticipatory activity (FAA), or brown adipose tissue temperature during the first 13 days of restricted feeding. However, as the restricted feeding paradigm progressed, we noticed an increased FAA in AgRP Crat KO mice. The delayed increase in FAA, which developed during the last 12 days of restricted feeding, corresponded with elevated plasma levels of corticosterone and nonesterified fatty acids, indicating it resulted from greater energy debt incurred by KO mice over the course of the experiment. These experiments highlight the importance of Crat in AgRP neurons in regulating feeding behavior and body weight gain during restricted feeding but not in synchronizing behavior to food availability. Thus, Crat within AgRP neurons forms a component of the homeostatic response to restricted feeding but is not likely to be a molecular component of FEO.
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Affiliation(s)
- Alex Reichenbach
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Mathieu Mequinion
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Jacqueline A Bayliss
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Sarah H Lockie
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Moyra B Lemus
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Randall L Mynatt
- Gene Nutrient Interactions Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana
- Transgenic Core Facility, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana
| | - Romana Stark
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Zane B Andrews
- Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Physiology, Monash University, Clayton, Victoria, Australia
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Thomas MA, Xue B. Mechanisms for AgRP neuron-mediated regulation of appetitive behaviors in rodents. Physiol Behav 2017; 190:34-42. [PMID: 29031550 DOI: 10.1016/j.physbeh.2017.10.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Revised: 08/29/2017] [Accepted: 10/06/2017] [Indexed: 12/19/2022]
Abstract
The obesity epidemic is a major health and economic burden facing both developed and developing countries worldwide. Interrogation of the central and peripheral mechanisms regulating ingestive behaviors have primarily focused on food intake, and in the process uncovered a detailed neuroanatomical framework controlling this behavior. However, these studies have largely ignored the behaviors that bring animals, including humans, in contact with food. It is therefore useful to dichotomize ingestive behaviors as appetitive (motivation to find and store food) and consummatory (consumption of food once found), and utilize an animal model that naturally displays these behaviors. Recent advances in genetics have facilitated the identification of several neuronal populations critical for regulating ingestive behaviors in mice, and novel functions of these neurons and neuropeptides in regulating appetitive behaviors in Siberian hamsters, a natural model of food foraging and food hoarding, have been identified. To this end, hypothalamic agouti-related protein/neuropeptide Y expressing neurons (AgRP neurons) have emerged as a critical regulator of ingestive behaviors. Recent studies by Dr. Timothy Bartness and others have identified several discrete mechanisms through which peripheral endocrine signals regulate AgRP neurons to control food foraging, food hoarding, and food intake. We review here recent advances in our understanding of the neuroendocrine control of ingestive behaviors in Siberian hamsters and other laboratory rodents, and identify novel mechanisms through which AgRP neurons mediate appetitive and consummatory behaviors.
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Affiliation(s)
- M Alex Thomas
- Department of Biology, Georgia State University, Atlanta, GA 30302, USA; Center for Obesity Reversal, Georgia State University, Atlanta, GA 30302, USA
| | - Bingzhong Xue
- Department of Biology, Georgia State University, Atlanta, GA 30302, USA; Center for Obesity Reversal, Georgia State University, Atlanta, GA 30302, USA; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, USA.
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10
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The Role of Ghrelin and Ghrelin Signaling in Aging. Int J Mol Sci 2017; 18:ijms18071511. [PMID: 28704966 PMCID: PMC5536001 DOI: 10.3390/ijms18071511] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 07/04/2017] [Accepted: 07/07/2017] [Indexed: 01/20/2023] Open
Abstract
With our aging society, more people hope for a long and healthy life. In recent years, researchers have focused on healthy longevity factors. In particular, calorie restriction delays aging, reduces mortality, and extends life. Ghrelin, which is secreted during fasting, is well known as an orexigenic peptide. Because ghrelin is increased by caloric restriction, ghrelin may play an important role in the mechanism of longevity mediated by calorie restriction. In this review, we will discuss the role of orexigenic peptides with a particular focus on ghrelin. We conclude that the ghrelin-growth hormone secretagogue-R signaling pathway may play an important role in the anti-aging mechanism.
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Butler AA, Girardet C, Mavrikaki M, Trevaskis JL, Macarthur H, Marks DL, Farr SA. A Life without Hunger: The Ups (and Downs) to Modulating Melanocortin-3 Receptor Signaling. Front Neurosci 2017; 11:128. [PMID: 28360832 PMCID: PMC5352694 DOI: 10.3389/fnins.2017.00128] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/01/2017] [Indexed: 11/13/2022] Open
Abstract
Melanocortin neurons conserve body mass in hyper- or hypo-caloric conditions by conveying signals from nutrient sensors into areas of the brain governing appetite and metabolism. In mice, melanocortin-3 receptor (MC3R) deletion alters nutrient partitioning independently of hyperphagia, promoting accumulation of fat over muscle mass. Enhanced rhythms in insulin and insulin-responsive metabolic genes during hypocaloric feeding suggest partial insulin resistance and enhanced lipogenesis. However, exactly where and how MC3Rs affect metabolic control to alter nutrient partitioning is not known. The behavioral phenotypes exhibited by MC3R-deficient mice suggest a contextual role in appetite control. The impact of MC3R-deficiency on feeding behavior when food is freely available is minor. However, homeostatic responses to hypocaloric conditioning involving increased expression of appetite-stimulating (orexigenic) neuropeptides, binge-feeding, food anticipatory activity (FAA), entrainment to nutrient availability and enhanced feeding-related motivational responses are compromised with MC3R-deficiency. Rescuing Mc3r transcription in hypothalamic and limbic neurons improves appetitive responses during hypocaloric conditioning while having minor effects on nutrient partitioning, suggesting orexigenic functions. Rescuing hypothalamic MC3Rs also restores responses of fasting-responsive hypothalamic orexigenic neurons in hypocaloric conditions, suggesting actions that sensitize fasting-responsive neurons to signals from nutrient sensors. MC3R signaling in ventromedial hypothalamic SF1(+ve) neurons improves metabolic control, but does not restore appetitive responses or nutrient partitioning. In summary, desensitization of fasting-responsive orexigenic neurons may underlie attenuated appetitive responses of MC3R-deficient mice in hypocaloric situations. Further studies are needed to identify the specific location(s) of MC3Rs controlling appetitive responses and partitioning of nutrients between fat and lean tissues.
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Affiliation(s)
- Andrew A Butler
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine St. Louis, MO, USA
| | - Clemence Girardet
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine St. Louis, MO, USA
| | - Maria Mavrikaki
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine St. Louis, MO, USA
| | - James L Trevaskis
- In vivo Pharmacology, Cardiovascular and Metabolic Disease, Medimmune Gaithersburg, MD, USA
| | - Heather Macarthur
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine St. Louis, MO, USA
| | - Daniel L Marks
- Papé Family Pediatric Research Institute, Oregon Health and Science University Portland, OR, USA
| | - Susan A Farr
- Department of Internal Medicine, Division of Geriatrics, Saint Louis University School of MedicineSt. Louis, MO, USA; VA Medical CenterSt. Louis, MO, USA
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Melanocortin-3 receptors expressed in Nkx2.1(+ve) neurons are sufficient for controlling appetitive responses to hypocaloric conditioning. Sci Rep 2017; 7:44444. [PMID: 28294152 PMCID: PMC5353610 DOI: 10.1038/srep44444] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 02/08/2017] [Indexed: 01/12/2023] Open
Abstract
Melanocortin-3 receptors (MC3R) have a contextual role in appetite control that is amplified with hypocaloric conditioning. C57BL/6J (B6) mice subjected to hypocaloric feeding schedules (HFS) exhibit compulsive behavioral responses involving food anticipatory activity (FAA) and caloric loading following food access. These homeostatic responses to calorie-poor environs are attenuated in B6 mice in which Mc3r transcription is suppressed by a lox-stop-lox sequence in the 5'UTR (Mc3rTB/TB). Here, we report that optimization of caloric loading in B6 mice subject to HFS, characterized by increased meal size and duration, is not observed in Mc3rTB/TB mice. Analysis of hypothalamic and neuroendocrine responses to HFS throughout the light-dark cycle suggests uncoupling of hypothalamic responses involving appetite-stimulating fasting-responsive hypothalamic neurons expressing agouti-related peptide (AgRP) and neuropeptide Y (Npy). Rescuing Mc3rs expression in Nkx2.1(+ve) neurons is sufficient to restore normal hypothalamic responses to negative energy balance. In addition, Mc3rs expressed in Nkx2.1(+ve) neurons are also sufficient to restore FAA and caloric loading of B6 mice subjected to HFS. In summary, MC3Rs expressed in Nkx2.1(+ve) neurons are sufficient to coordinate hypothalamic response and expression of compulsive behavioral responses involving meal anticipation and consumption of large meals during situations of prolonged negative energy balance.
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You P, Hu H, Chen Y, Zhao Y, Yang Y, Wang T, Xing R, Shao Y, Zhang W, Li D, Chen H, Liu M. Effects of Melanocortin 3 and 4 Receptor Deficiency on Energy Homeostasis in Rats. Sci Rep 2016; 6:34938. [PMID: 27713523 PMCID: PMC5054679 DOI: 10.1038/srep34938] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 09/20/2016] [Indexed: 01/08/2023] Open
Abstract
Melanocortin-3 and 4 receptors (MC3R and MC4R) can regulate energy homeostasis, but their respective roles especially the functions of MC3R need more exploration. Here Mc3r and Mc4r single and double knockout (DKO) rats were generated using CRISPR-Cas9 system. Metabolic phenotypes were examined and data were compared systematically. Mc3r KO rats displayed hypophagia and decreased body weight, while Mc4r KO and DKO exhibited hyperphagia and increased body weight. All three mutants showed increased white adipose tissue mass and adipocyte size. Interestingly, although Mc3r KO did not show a significant elevation in lipids as seen in Mc4r KO, DKO displayed even higher lipid levels than Mc4r KO. DKO also showed more severe glucose intolerance and hyperglycaemia than Mc4r KO. These data demonstrated MC3R deficiency caused a reduction of food intake and body weight, whereas at the same time exhibited additive effects on top of MC4R deficiency on lipid and glucose metabolism. This is the first phenotypic analysis and systematic comparison of Mc3r KO, Mc4r KO and DKO rats on a homogenous genetic background. These mutant rats will be important in defining the complicated signalling pathways of MC3R and MC4R. Both Mc4r KO and DKO are good models for obesity and diabetes research.
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Affiliation(s)
- Panpan You
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Handan Hu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Yuting Chen
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Yongliang Zhao
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Yiqing Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Tongtong Wang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Roumei Xing
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Yanjiao Shao
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Wen Zhang
- School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Dali Li
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Huaqing Chen
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China
| | - Mingyao Liu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, Shanghai 200241, China.,Institute of Biosciences and Technology, Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center, Houston, Texas 77030, USA
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Mavrikaki M, Girardet C, Kern A, Faruzzi Brantley A, Miller CA, Macarthur H, Marks DL, Butler AA. Melanocortin-3 receptors in the limbic system mediate feeding-related motivational responses during weight loss. Mol Metab 2016; 5:566-579. [PMID: 27408780 PMCID: PMC4921936 DOI: 10.1016/j.molmet.2016.05.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 04/28/2016] [Accepted: 05/04/2016] [Indexed: 12/21/2022] Open
Abstract
Objective Appetitive responses to weight loss are mediated by a nutrient-sensing neural network comprised of melanocortin neurons. The role of neural melanocortin-3 receptors (MC3R) in mediating these responses is enigmatic. Mc3r knockout mice exhibit a paradoxical phenotype of obesity and reduced feeding-related behaviors in situations of nutrient scarcity. Here we examined whether MC3Rs expressed in mesolimbic neurons regulate feeding-related motivational responses. Methods Interactions between Mc3r genotype, cognitive function and energy balance on food self-administration were assessed using operant conditioning with fixed- and progressive ratio (FR1/PR1) settings. Inhibition of Mc3r transcription by a loxP-flanked transcriptional blocker (TB) in C57BL/6JN mice (Mc3rTB/TB) was reversed in mesolimbic neurons using DAT-Cre (DAT-MC3R). Results Caloric restriction (CR) caused 10–15% weight loss and increased motivation to acquire food rewards during training sessions. c-Fos-expression in the nucleus accumbens was increased 1 h following food presentation. While exhibiting weight loss, total food self-administration, enhanced motivation to self-administer food rewards in training sessions held during CR and c-Fos-activation in the nucleus accumbens following re-feeding were all markedly attenuated in Mc3rTB/TB mice. In contrast, cognitive abilities were normal in Mc3rTB/TB mice. Total food self-administration during FR1 sessions was not rescued in DAT-MC3R mice, however enhanced motivational responses to self-administer food rewards in PR1 conditions were restored. The nutrient-partitioning phenotype observed with Mc3r-deficiency was not rescued in DAT-MC3R mice. Conclusions Mesolimbic MC3Rs mediate enhanced motivational responses during CR. However, they are insufficient to restore normal caloric loading when food is presented during CR and do not affect metabolic conditions altering nutrient partitioning. Food-related motivational responses in mice increase with caloric restriction (CR). Melanocortin-3 receptors (MC3R) are required for food-related motivational responses. MC3Rs role in food-related motivational responses depends on metabolic condition. Mesolimbic MC3Rs increase food-related motivational responses during CR.
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Affiliation(s)
- Maria Mavrikaki
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Pharmacology & Physiology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Clemence Girardet
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Pharmacology & Physiology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Andras Kern
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Alicia Faruzzi Brantley
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA; Behavioral Core, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Courtney A Miller
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Heather Macarthur
- Department of Pharmacology & Physiology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Daniel L Marks
- Papé Family Pediatric Research Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Andrew A Butler
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Pharmacology & Physiology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.
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Roles of NMDA and dopamine in food-foraging decision-making strategies of rats in the social setting. BMC Neurosci 2016; 17:3. [PMID: 26754043 PMCID: PMC4710019 DOI: 10.1186/s12868-015-0233-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 12/08/2015] [Indexed: 01/15/2023] Open
Abstract
Background
In highly complex social settings, an animal’s motivational drive to pursue an object depends not only on the intrinsic properties of the object, but also on whether the decision-making animal perceives an object as being the most desirable among others. Mimetic desire refers to a subject’s preference for objects already possessed by another subject. To date, there are no appropriate animal models for studying whether mimetic desire is at play in guiding the decision-making process. Furthermore, the neuropharmacological bases of decision-making processes are not well understood. In this study, we used an animal model (rat) to investigate a novel food-foraging paradigm for decision-making, with or without a mimetic desire paradigm. Results Faced with the choice of foraging in a competitive environment, rats preferred foraging for the desirable object, indicating the rats’ ability for decision-making. Notably, treatment with the non-competitive N-methyl-d-aspartate receptor antagonist MK-801, but not with the dopamine D1 or D2 receptor antagonists, SCH23390 and haloperidol, respectively, suppressed the food foraging preference when there was a competing resident rat in the cage. None of these three antagonists affected the food-foraging preference for palatable food. Moreover, MK-801 and SCH23390, but not haloperidol, were able to abolish the desirable environment effect on standard food-foraging activities in complex social settings. Conclusions These results highlight the concept that mimetic desire exerts a powerful influence on food-foraging decision-making in rats and, further, illustrate the various roles of the glutamatergic and dopaminergic systems in mediating these processes.
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Vaanholt LM, Mitchell SE, Sinclair RE, Speakman JR. Mice that are resistant to diet-induced weight loss have greater food anticipatory activity and altered melanocortin-3 receptor (MC3R) and dopamine receptor 2 (D2) gene expression. Horm Behav 2015; 73:83-93. [PMID: 26122292 DOI: 10.1016/j.yhbeh.2015.06.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 06/12/2015] [Accepted: 06/13/2015] [Indexed: 11/20/2022]
Abstract
Diet-induced weight loss varies considerably between individuals, but the mechanisms driving these individual differences remain largely unknown. Here we investigated whether key neuropeptides involved in the regulation of energy balance or reward systems were differentially expressed in mice that were prone or resistant to caloric restriction (CR) induced weight loss. Mice (n=30 males and n=34 females) were fed 70% of their own baseline ad libitum intake for 25days, after which their brains were collected and expression of various neuropeptides were investigated and compared between the 10 male and 10 female mice that showed the greatest (high weight loss, HWL) or lowest weight loss (LWL) (n=40 in total). HWL mice showed a differential neuropeptide profile to LWL in both sexes, characterised by increased expression of neuropeptide Y (NPY), agouti-related peptide (AgRP), leptin receptor (ObRb), and melanocortin 3 receptor (MC3R) in the arcuate nucleus. No changes in the expression of fat mass and obesity related gene (FTO) or suppressor of cytokine signalling 3 (Socs3) were observed. Levels of dopamine D2 receptor were decreased in the nucleus accumbens in HWL compared to LWL mice. HWL mice showed a stronger increase in food anticipatory activity (FAA) in response to CR than LWL mice. These results indicate that the mice prone to diet-induced weight loss experienced greater hunger, potentially driving their elevated FAA.
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MESH Headings
- Animals
- Anticipation, Psychological/physiology
- Arcuate Nucleus of Hypothalamus/metabolism
- Caloric Restriction
- Diet, Reducing
- Energy Metabolism/genetics
- Female
- Food
- Gene Expression
- Humans
- Male
- Mice
- Mice, Obese
- Neuropeptide Y/genetics
- Neuropeptide Y/metabolism
- Obesity/diet therapy
- Obesity/genetics
- Obesity/metabolism
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptors, Dopamine D2/genetics
- Receptors, Dopamine D2/metabolism
- Receptors, Leptin/genetics
- Receptors, Leptin/metabolism
- Treatment Failure
- Weight Loss/genetics
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Affiliation(s)
- Lobke M Vaanholt
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK.
| | - Sharon E Mitchell
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
| | - Rachel E Sinclair
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK; State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
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17
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Ceccarini G, Maffei M, Vitti P, Santini F. Fuel homeostasis and locomotor behavior: role of leptin and melanocortin pathways. J Endocrinol Invest 2015; 38:125-31. [PMID: 25501840 DOI: 10.1007/s40618-014-0225-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 12/01/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND While it is now accepted that genes and their products affect food intake, the concept that locomotor behavior or the propensity for physical activity is controlled by neuro hum oral regulators is frequently underappreciated. In mammals, complex interactions have developed to allow the cross-talk between fuel homeostasis and physical activity. AIM The aim of this review is to provide a synopsis of the influence of the leptin-melanocortin pathway, a well-studied pivotal player in body weight regulation, on locomotor behaviors. CONCLUSIONS In rodents, reductions in leptin levels that physiologically occur following acute food deprivation or a reduction of the fat mass consequent to prolonged caloric restrictions are associated with a decrease in total locomotor activity and simultaneous increase in food-anticipatory activity, a locomotor behavior which reflects a foraging attitude. These actions can be prevented by leptin administration and are at least partially mediated by the neurons of the melanocortin pathway. In humans, twin studies have attributed to genetic factors approximately 50% of the variance of physical activity. An elevated number of the genes or loci which may affect physical activity are involved in body weight homeostasis. Polymorphisms of the melanocortin-4 and leptin receptors have repeatedly been associated with the level of physical activity. Unraveling the complexity of the regulation of locomotor behavior and the interconnections with the pathways involved in energy homeostasis may help explain the substantial individual variability in physical activities in humans and disentangle the harmful effects of sedentary lifestyle, which may be distinct from the detrimental effects of obesity.
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Affiliation(s)
- G Ceccarini
- Obesity Center at the Endocrine Unit, University Hospital of Pisa, Pisa, Italy.
| | - M Maffei
- Obesity Center at the Endocrine Unit, University Hospital of Pisa, Pisa, Italy
- National Research Council, Institute of Clinical Physiology, Pisa, Italy
| | - P Vitti
- Obesity Center at the Endocrine Unit, University Hospital of Pisa, Pisa, Italy
| | - F Santini
- Obesity Center at the Endocrine Unit, University Hospital of Pisa, Pisa, Italy.
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