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Scott KA, Tan Y, Johnson DN, Elsaafien K, Baumer-Harrison C, Eikenberry SA, Sa JM, de Lartigue G, de Kloet AD, Krause EG. Mechanosensation of the heart and gut elicits hypometabolism and vigilance in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.29.547073. [PMID: 37425814 PMCID: PMC10327188 DOI: 10.1101/2023.06.29.547073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Interoception broadly refers to awareness of one's internal milieu. Vagal sensory afferents monitor the internal milieu and maintain homeostasis by engaging brain circuits that alter physiology and behavior. While the importance of the body-to-brain communication that underlies interoception is implicit, the vagal afferents and corresponding brain circuits that shape perception of the viscera are largely unknown. Here, we use mice to parse neural circuits subserving interoception of the heart and gut. We determine vagal sensory afferents expressing the oxytocin receptor, hereafter referred to as NDGOxtr, send projections to the aortic arch or stomach and duodenum with molecular and structural features indicative of mechanosensation. Chemogenetic excitation of NDGOxtr significantly decreases food and water consumption, and remarkably, produces a torpor-like phenotype characterized by reductions in cardiac output, body temperature, and energy expenditure. Chemogenetic excitation of NDGOxtr also creates patterns of brain activity associated with augmented hypothalamic-pituitary-adrenal axis activity and behavioral indices of vigilance. Recurrent excitation of NDGOxtr suppresses food intake and lowers body mass, indicating that mechanosensation of the heart and gut can exert enduring effects on energy balance. These findings suggest that the sensation of vascular stretch and gastrointestinal distention may have profound effects on whole body metabolism and mental health.
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Affiliation(s)
- Karen A. Scott
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Yalun Tan
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Dominique N. Johnson
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Khalid Elsaafien
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Caitlin Baumer-Harrison
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Sophia A. Eikenberry
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Jessica M. Sa
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | | | - Annette D. de Kloet
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Eric G. Krause
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
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Feeding circuit development and early-life influences on future feeding behaviour. Nat Rev Neurosci 2019; 19:302-316. [PMID: 29662204 DOI: 10.1038/nrn.2018.23] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A wide range of maternal exposures - undernutrition, obesity, diabetes, stress and infection - are associated with an increased risk of metabolic disease in offspring. Developmental influences can cause persistent structural changes in hypothalamic circuits regulating food intake in the service of energy balance. The physiological relevance of these alterations has been called into question because maternal impacts on daily caloric intake do not persist to adulthood. Recent behavioural and epidemiological studies in humans provide evidence that the relative contribution of appetitive traits related to satiety, reward and the emotional aspects of food intake regulation changes across the lifespan. This Opinion article outlines a neurodevelopmental framework to explore the possibility that crosstalk between developing circuits regulating different modalities of food intake shapes future behavioural responses to environmental challenges.
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Clyburn C, Howe CA, Arnold AC, Lang CH, Travagli RA, Browning KN. Perinatal high-fat diet alters development of GABA A receptor subunits in dorsal motor nucleus of vagus. Am J Physiol Gastrointest Liver Physiol 2019; 317:G40-G50. [PMID: 31042399 PMCID: PMC6689732 DOI: 10.1152/ajpgi.00079.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 04/22/2019] [Accepted: 04/29/2019] [Indexed: 01/31/2023]
Abstract
Perinatal high-fat diet (pHFD) exposure increases the inhibition of dorsal motor nucleus of the vagus (DMV) neurons, potentially contributing to the dysregulation of gastric functions. The aim of this study was to test the hypothesis that pHFD increases the inhibition of DMV neurons by disrupting GABAA receptor subunit development. In vivo gastric recordings were made from adult anesthetized Sprague-Dawley rats fed a control or pHFD (14 or 60% kcal from fat, respectively) from embryonic day 13 (E13) to postnatal day 42 (P42), and response to brainstem microinjection of benzodiazepines was assessed. Whole cell patch clamp recordings from DMV neurons assessed the functional expression of GABAA α subunits, whereas mRNA and protein expression were measured via qPCR and Western blotting, respectively. pHFD decreased basal antrum and corpus motility, whereas brainstem microinjection of L838,417 (positive allosteric modulator of α2/3 subunit-containing GABAA receptors) produced a larger decrease in gastric tone and motility. GABAergic miniature inhibitory postsynaptic currents in pHFD DMV neurons were responsive to L838,417 throughout development, unlike control DMV neurons, which were responsive only at early postnatal timepoints. Brainstem mRNA and protein expression of the GABAA α1,2, and 3 subunits, however, did not differ between control and pHFD rats. This study suggests that pHFD exposure arrests the development of synaptic GABAA α2/3 receptor subunits on DMV neurons and that functional synaptic expression is maintained into adulthood, although cellular localization may differ. The tonic activation of slower GABAA α2/3 subunit-containing receptors implies that such developmental changes may contribute to the observed decreased gastric motility. NEW & NOTEWORTHY Vagal neurocircuits involved in the control of gastric functions, satiation, and food intake are subject to significant developmental regulation postnatally, with immature GABAA receptors expressing slower α2/3-subunits, whereas mature GABAA receptor express faster α1-subunits. After perinatal high-fat diet exposure, this developmental regulation of dorsal motor nucleus of the vagus (DMV) neurons is disrupted, increasing their tonic GABAergic inhibition, decreasing efferent output, and potentially decreasing gastric motility.
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Affiliation(s)
- Courtney Clyburn
- Department of Neural and Behavioral Sciences, Penn State College of Medicine , Hershey, Pennsylvania
| | - Caitlin A Howe
- Department of Neural and Behavioral Sciences, Penn State College of Medicine , Hershey, Pennsylvania
| | - Amy C Arnold
- Department of Neural and Behavioral Sciences, Penn State College of Medicine , Hershey, Pennsylvania
| | - Charles H Lang
- Department of Cellular and Molecular Physiology, Penn State College of Medicine , Hershey, Pennsylvania
| | - R Alberto Travagli
- Department of Neural and Behavioral Sciences, Penn State College of Medicine , Hershey, Pennsylvania
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine , Hershey, Pennsylvania
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McMenamin CA, Clyburn C, Browning KN. High-Fat Diet During the Perinatal Period Induces Loss of Myenteric Nitrergic Neurons and Increases Enteric Glial Density, Prior to the Development of Obesity. Neuroscience 2019; 393:369-380. [PMID: 30454864 DOI: 10.1016/j.neuroscience.2018.09.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 09/19/2018] [Accepted: 09/24/2018] [Indexed: 02/07/2023]
Abstract
Diet-induced obesity induces peripheral inflammation accompanied by a loss of myenteric neurons. Few studies, however, have investigated the effects of a high-fat diet (HFD) on either the development of myenteric neurons or prior to the occurrence of obesity. The present study assessed the effects of maternal HFD on the density and neurochemical phenotype of myenteric ganglia in the upper gastrointestinal tract. Sprague-Dawley rats were fed either a control or HFD (14% or 60% kcal from fat, respectively) from embryonic day 13; the fundus, corpus and duodenum were fixed thereafter at postnatal 2, 4, 6 and 12 weeks of age for subsequent immunohistochemical studies. While myenteric ganglion size did not differ throughout the study, HFD exposure decreased the number of nitrergic neurons by 6 weeks of age in all regions. This decrease was accompanied by a loss of PGP-immunoreactive neurons, suggesting a decline in myenteric neuronal number. HFD also increased myenteric plexus glial cell density in all regions by 4 weeks of age. These changes occurred in the absence of an increase in serum or gastric inflammatory markers. The present study suggests that exposure to a HFD during the perinatal time period results in glial proliferation and loss of inhibitory nitrergic neurons prior to the onset of obesity, suggesting that dietary alterations may affect gastrointestinal functions independently of increased adiposity or glycemic dysregulation.
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Affiliation(s)
- Caitlin A McMenamin
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Courtney Clyburn
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, United States.
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McMenamin CA, Travagli RA, Browning KN. Perinatal high fat diet increases inhibition of dorsal motor nucleus of the vagus neurons regulating gastric functions. Neurogastroenterol Motil 2018; 30:10.1111/nmo.13150. [PMID: 28762595 PMCID: PMC5739938 DOI: 10.1111/nmo.13150] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/07/2017] [Indexed: 01/02/2023]
Abstract
BACKGROUND Previous studies suggest an increased inhibition of dorsal motor nucleus of the vagus (DMV) neurons following exposure to a perinatal high fat diet (PNHFD); the underlying neural mechanisms, however, remain unknown. This study assessed the effects of PNHFD on inhibitory synaptic inputs to DMV neurons and the vagally dependent control of gastric tone and motility. METHODS Whole-cell patch clamp recordings were made from DMV neurons in thin brainstem slices from Sprague-Dawley rats fed either a control diet or HFD (14 or 60% kcal from fat, respectively) from embryonic day 13 onwards; gastric tone and motility were recorded in in vivo anesthetized rats. KEY RESULTS The non-selective GABAA antagonist, BIC (10 μmol L-1 ), induced comparable inward currents in PNHFD and control DMV neurons, but a larger current in PNHFD neurons at higher concentrations (50 μmol L-1 ). Differences were not apparent in neuronal responses to the phasic GABAA antagonist, gabazine (GBZ), the extrasynaptic GABAA agonist, THIP, the GABA transport blocker, nipecotic acid, or the gliotoxin, fluoroacetate, suggesting that PNHFD altered inhibitory transmission but not GABAA receptor density or function, GABA uptake or glial modulation of synaptic strength. Similarly, the increase in gastric motility and tone following brainstem microinjection of low doses of BIC (1-10 pmoles) and GBZ (0.01-0.1 pmoles) were unchanged in PNHFD rats while higher doses of BIC (25 pmoles) induced a significantly larger increase in gastric tone compared to control. CONCLUSIONS AND INFERENCES These studies suggest that exposure to PNHFD increases the tonic inhibition of DMV neurons, possibly contributing to dysregulated vagal control of gastric functions.
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Affiliation(s)
| | | | - Kirsteen N. Browning
- Address for correspondence: Kirsteen N Browning, PhD, Department of Neural and Behavioral Science, Penn State College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, Tel: 717 531 8267,
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Reduced intestinal brain-derived neurotrophic factor increases vagal sensory innervation of the intestine and enhances satiation. J Neurosci 2014; 34:10379-93. [PMID: 25080597 DOI: 10.1523/jneurosci.1042-14.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is produced by developing and mature gastrointestinal (GI) tissues that are heavily innervated by autonomic neurons and may therefore control their development or function. To begin investigating this hypothesis, we compared the morphology, distribution, and density of intraganglionic laminar endings (IGLEs), the predominant vagal GI afferent, in mice with reduced intestinal BDNF (INT-BDNF(-/-)) and controls. Contrary to expectations of reduced development, IGLE density and longitudinal axon bundle number in the intestine of INT-BDNF(-/-) mice were increased, but stomach IGLEs were normal. INT-BDNF(-/-) mice also exhibited increased vagal sensory neuron numbers, suggesting that their survival was enhanced. To determine whether increased intestinal IGLE density or other changes to gut innervation in INT-BDNF(-/-) mice altered feeding behavior, meal pattern and microstructural analyses were performed. INT-BDNF(-/-) mice ate meals of much shorter duration than controls, resulting in reduced meal size. Increased suppression of feeding in INT-BDNF(-/-) mice during the late phase of a scheduled meal suggested that increased satiation signaling contributed to reduced meal duration and size. Furthermore, INT-BDNF(-/-) mice demonstrated increases in total daily intermeal interval and satiety ratio, suggesting that satiety signaling was augmented. Compensatory responses maintained normal daily food intake and body weight in INT-BDNF(-/-) mice. These findings suggest a target organ-derived neurotrophin suppresses development of that organ's sensory innervation and sensory neuron survival and demonstrate a role for BDNF produced by peripheral tissues in short-term controls of feeding, likely through its regulation of development or function of gut innervation, possibly including augmented intestinal IGLE innervation.
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Spencer SJ. Perinatal programming of neuroendocrine mechanisms connecting feeding behavior and stress. Front Neurosci 2013; 7:109. [PMID: 23785312 PMCID: PMC3683620 DOI: 10.3389/fnins.2013.00109] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 05/31/2013] [Indexed: 01/24/2023] Open
Abstract
Feeding behavior is closely regulated by neuroendocrine mechanisms that can be influenced by stressful life events. However, the feeding response to stress varies among individuals with some increasing and others decreasing food intake after stress. In addition to the impact of acute lifestyle and genetic backgrounds, the early life environment can have a life-long influence on neuroendocrine mechanisms connecting stress to feeding behavior and may partially explain these opposing feeding responses to stress. In this review I will discuss the perinatal programming of adult hypothalamic stress and feeding circuitry. Specifically I will address how early life (prenatal and postnatal) nutrition, early life stress, and the early life hormonal profile can program the hypothalamic-pituitary-adrenal (HPA) axis, the endocrine arm of the body's response to stress long-term and how these changes can, in turn, influence the hypothalamic circuitry responsible for regulating feeding behavior. Thus, over- or under-feeding and/or stressful events during critical windows of early development can alter glucocorticoid (GC) regulation of the HPA axis, leading to changes in the GC influence on energy storage and changes in GC negative feedback on HPA axis-derived satiety signals such as corticotropin-releasing-hormone. Furthermore, peripheral hormones controlling satiety, such as leptin and insulin are altered by early life events, and can be influenced, in early life and adulthood, by stress. Importantly, these neuroendocrine signals act as trophic factors during development to stimulate connectivity throughout the hypothalamus. The interplay between these neuroendocrine signals, the perinatal environment, and activation of the stress circuitry in adulthood thus strongly influences feeding behavior and may explain why individuals have unique feeding responses to similar stressors.
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Affiliation(s)
- Sarah J Spencer
- School of Health Sciences and Health Innovations Research Institute, RMIT University Melbourne, VIC, Australia
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Vagal afferent controls of feeding: a possible role for gastrointestinal BDNF. Clin Auton Res 2012; 23:15-31. [PMID: 22717678 DOI: 10.1007/s10286-012-0170-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 05/24/2012] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Vagal gastrointestinal (GI) afferents do not appear to contribute to long-term controls of feeding, despite downstream connections that could support such a role. This view is largely attributable to a lack of evidence for long-term effects, especially the failure of vagal afferent lesions to produce hyperphagia or obesity. AIMS Here, the possibility is evaluated that "side effects" of vagal lesion methods resulting largely from complexities of vagal organization would probably suppress long-term effects. Criteria based on knowledge of vagal organization were utilized to critique and compare vagal lesion methods and to interpret their effects on GI function, feeding and body weight. RESULTS AND CONCLUSIONS This analysis suggested that it was premature to eliminate a long-term vagal GI afferent role based on the effects of these lesions and highlighted aspects of vagal organization that must be addressed to reduce the problematic side effects of vagal lesions. The potential of "genetic" lesions that alter vagal sensory development to address these aspects, examination of the feasibility of this approach, and the properties of brain-derived neurotrophic factor (BDNF) that made it an attractive candidate for application of this approach are described. BDNF knockout from GI smooth muscle unexpectedly demonstrated substantial overeating and weight gain associated with increased meal size and frequency. The decay of eating rate during a scheduled meal was also reduced. However, meal-induced c-Fos activation was increased in the dorsal motor nucleus of the vagus, suggesting that the effect on eating rate was due to augmentation of GI reflexes by vagal afferents or other neural systems.
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Fox EA, Biddinger JE. Early postnatal overnutrition: potential roles of gastrointestinal vagal afferents and brain-derived neurotrophic factor. Physiol Behav 2012; 106:400-12. [PMID: 22712064 PMCID: PMC3517218 DOI: 10.1016/j.physbeh.2012.04.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Abnormal perinatal nutrition (APN) results in a predisposition to develop obesity and the metabolic syndrome and thus may contribute to the prevalence of these disorders. Obesity, including that which develops in organisms exposed to APN, has been associated with increased meal size. Vagal afferents of the gastrointestinal (GI) tract contribute to regulation of meal size by transmitting satiation signals from gut-to-brain. Consequently, APN could increase meal size by altering this signaling, possibly through changes in expression of factors that control vagal afferent development or function. Here two studies that addressed these possibilities are reviewed. First, meal patterns, meal microstructure, and the structure and density of vagal afferents that innervate the intestine were examined in mice that experienced early postnatal overnutrition (EPO). These studies provided little evidence for EPO effects on vagal afferents as it did not alter meal size or vagal afferent density or structure. However, these mice exhibited modest hyperphagia due to a satiety deficit. In parallel, the possibility that brain-derived neurotrophic factor (BDNF) could mediate APN effects on vagal afferent development was investigated. Brain-derived neurotrophic factor was a strong candidate because APN alters BDNF levels in some tissues and BDNF knockout disrupts development of vagal sensory innervation of the GI tract. Surprisingly, smooth muscle-specific BDNF knockout resulted in early-onset obesity and hyperphagia due to increases in meal size and frequency. Microstructure analysis revealed decreased decay of intake rate during a meal in knockouts, suggesting that the loss of vagal negative feedback contributed to their increase in meal size. However, meal-induced c-Fos activation within the dorsal vagal complex suggested this effect could be due to augmentation of vago-vagal reflexes. A model is proposed to explain how high-fat diet consumption produces increased obesity in organisms exposed to APN, and may be required to reveal effects of EPO on vagal function.
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Affiliation(s)
- Edward A Fox
- Behavioral Neurogenetics Laboratory & Ingestive Behavior Research Center, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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