Publications by authors named "Caitlin M Daimon"

24 Publications

  • Page 1 of 1

β-endorphin differentially contributes to food anticipatory activity in male and female mice undergoing activity-based anorexia.

Physiol Rep 2021 Mar;9(5):e14788

Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.

Anorexia nervosa (AN) has a lifetime prevalence of up to 4% and a high mortality rate (~5-10%), yet little is known regarding the etiology of this disease. In an attempt to fill the gaps in knowledge, activity-based anorexia (ABA) in rodents has been a widely used model as it mimics several key features of AN including severely restricted food intake and excessive exercise. Using this model, a role for the hypothalamic proopiomelanocortin (POMC) system has been implicated in the development of ABA as Pomc mRNA is elevated in female rats undergoing the ABA paradigm. Since the Pomc gene product α-MSH potently inhibits food intake, it could be that elevated α-MSH might promote ABA. However, the α-MSH receptor antagonist SHU9119 does not protect against the development of ABA. Interestingly, it has also been shown that female mice lacking the mu opioid receptor (MOR), the primary receptor activated by the Pomc-gene-derived opioid β-endorphin, display blunted food anticipatory behavior (FAA), a key feature of ABA. Thus, we hypothesized that the elevation in Pomc mRNA observed during ABA may lead to increased β-endorphin concentrations and MOR activation to promote ABA. Further, given the known sex differences in AN and ABA, we hypothesized that MORs may contribute differentially in male and female mice. Using wild-type and MOR knockout mice of both sexes, a MOR antagonist and careful analysis of food anticipatory behavior and β-endorphin levels, we found 1) increased Pomc mRNA levels in both female and male mice that underwent ABA, 2) increased β-endorphin in female mice that underwent ABA, and 3) blunted FAA in both sexes in response to MOR genetic deletion yet blunted FAA only in males in response to MOR antagonism. The results presented provide support for both hypotheses and suggest that it may be the β-endorphin resulting from increased Pomc transcription that supports the development of some features of ABA.
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http://dx.doi.org/10.14814/phy2.14788DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7931805PMC
March 2021

Altered learning, memory, and social behavior in type 1 taste receptor subunit 3 knock-out mice are associated with neuronal dysfunction.

J Biol Chem 2017 07 18;292(27):11508-11530. Epub 2017 May 18.

the Receptor Pharmacology Unit, NIA, National Institutes of Health, Baltimore, Maryland 21224,

The type 1 taste receptor member 3 (T1R3) is a G protein-coupled receptor involved in sweet-taste perception. Besides the tongue, the T1R3 receptor is highly expressed in brain areas implicated in cognition, including the hippocampus and cortex. As cognitive decline is often preceded by significant metabolic or endocrinological dysfunctions regulated by the sweet-taste perception system, we hypothesized that a disruption of the sweet-taste perception in the brain could have a key role in the development of cognitive dysfunction. To assess the importance of the sweet-taste receptors in the brain, we conducted transcriptomic and proteomic analyses of cortical and hippocampal tissues isolated from T1R3 knock-out (T1R3KO) mice. The effect of an impaired sweet-taste perception system on cognition functions were examined by analyzing synaptic integrity and performing animal behavior on T1R3KO mice. Although T1R3KO mice did not present a metabolically disrupted phenotype, bioinformatic interpretation of the high-dimensionality data indicated a strong neurodegenerative signature associated with significant alterations in pathways involved in neuritogenesis, dendritic growth, and synaptogenesis. Furthermore, a significantly reduced dendritic spine density was observed in T1R3KO mice together with alterations in learning and memory functions as well as sociability deficits. Taken together our data suggest that the sweet-taste receptor system plays an important neurotrophic role in the extralingual central nervous tissue that underpins synaptic function, memory acquisition, and social behavior.
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http://dx.doi.org/10.1074/jbc.M116.773820DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5500814PMC
July 2017

Genomic deletion of GIT2 induces a premature age-related thymic dysfunction and systemic immune system disruption.

Aging (Albany NY) 2017 03;9(3):706-740

Receptor Pharmacology Unit, Laboratory of Neurosciences, National Institute on Aging (NIA), National Institutes of Health (NIH), Baltimore, MD 21224, USA.

Recent research has proposed that GIT2 (G protein-coupled receptor kinase interacting protein 2) acts as an integrator of the aging process through regulation of 'neurometabolic' integrity. One of the commonly accepted hallmarks of the aging process is thymic involution. At a relatively young age, 12 months old, GIT2 mice present a prematurely distorted thymic structure and dysfunction compared to age-matched 12 month-old wild-type control (C57BL/6) mice. Disruption of thymic structure in GIT2 (GIT2KO) mice was associated with a significant reduction in the expression of the cortical thymic marker, (cytokeratin 8). Double positive (CD4CD8) and single positive CD4 T cells were also markedly reduced in 12 month-old GIT2KO mice compared to age-matched control wild-type mice. Coincident with this premature thymic disruption in GIT2KO mice was the unique generation of a novel cervical 'organ', . 'parathymic lobes'. These novel organs did not exhibit classical peripheral lymph node-like characteristics but expressed high levels of T cell progenitors that were reflexively reduced in GIT2KO thymi. Using signaling pathway analysis of GIT2KO thymus and parathymic lobe transcriptomic data we found that the molecular signaling functions lost in the dysfunctional GIT2KO thymus were selectively reinstated in the novel parathymic lobe - suggestive of a compensatory effect for the premature thymic disruption. Broader inspection of high-dimensionality transcriptomic data from GIT2KO lymph nodes, spleen, thymus and parathymic lobes revealed a systemic alteration of multiple proteins (Dbp, Tef, Per1, Per2, Fbxl3, Ddit4, Sin3a) involved in the multidimensional control of cell cycle clock regulation, cell senescence, cellular metabolism and DNA damage. Altered cell clock regulation across both immune and non-immune tissues therefore may be responsible for the premature 'aging' phenotype of GIT2KO mice.
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http://dx.doi.org/10.18632/aging.101185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5391227PMC
March 2017

GIT2 Acts as a Systems-Level Coordinator of Neurometabolic Activity and Pathophysiological Aging.

Front Endocrinol (Lausanne) 2015 18;6:191. Epub 2016 Jan 18.

Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA; Translational Neurobiology Group, VIB Department of Molecular Genetics, University of Antwerp, Antwerp, Belgium; Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.

Aging represents one of the most complicated and highly integrated somatic processes. Healthy aging is suggested to rely upon the coherent regulation of hormonal and neuronal communication between the central nervous system and peripheral tissues. The hypothalamus is one of the main structures in the body responsible for sustaining an efficient interaction between energy balance and neurological activity and therefore likely coordinates multiple systems in the aging process. We previously identified, in hypothalamic and peripheral tissues, the G protein-coupled receptor kinase interacting protein 2 (GIT2) as a stress response and aging regulator. As metabolic status profoundly affects aging trajectories, we investigated the role of GIT2 in regulating metabolic activity. We found that genomic deletion of GIT2 alters hypothalamic transcriptomic signatures related to diabetes and metabolic pathways. Deletion of GIT2 reduced whole animal respiratory exchange ratios away from those related to primary glucose usage for energy homeostasis. GIT2 knockout (GIT2KO) mice demonstrated lower insulin secretion levels, disruption of pancreatic islet beta cell mass, elevated plasma glucose, and insulin resistance. High-dimensionality transcriptomic signatures from islets isolated from GIT2KO mice indicated a disruption of beta cell development. Additionally, GIT2 expression was prematurely elevated in pancreatic and hypothalamic tissues from diabetic-state mice (db/db), compared to age-matched wild type (WT) controls, further supporting the role of GIT2 in metabolic regulation and aging. We also found that the physical interaction of pancreatic GIT2 with the insulin receptor and insulin receptor substrate 2 was diminished in db/db mice compared to WT mice. Therefore, GIT2 appears to exert a multidimensional "keystone" role in regulating the aging process by coordinating somatic responses to energy deficits.
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http://dx.doi.org/10.3389/fendo.2015.00191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4716144PMC
February 2016

Hippocampal Transcriptomic and Proteomic Alterations in the BTBR Mouse Model of Autism Spectrum Disorder.

Front Physiol 2015 24;6:324. Epub 2015 Nov 24.

Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health Baltimore, MD, USA ; Translational Neurobiology Group, VIB Department of Molecular Genetics, University of Antwerp Antwerp, Belgium ; Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp Antwerpen, Belgium.

Autism spectrum disorders (ASD) are complex heterogeneous neurodevelopmental disorders of an unclear etiology, and no cure currently exists. Prior studies have demonstrated that the black and tan, brachyury (BTBR) T+ Itpr3tf/J mouse strain displays a behavioral phenotype with ASD-like features. BTBR T+ Itpr3tf/J mice (referred to simply as BTBR) display deficits in social functioning, lack of communication ability, and engagement in stereotyped behavior. Despite extensive behavioral phenotypic characterization, little is known about the genes and proteins responsible for the presentation of the ASD-like phenotype in the BTBR mouse model. In this study, we employed bioinformatics techniques to gain a wide-scale understanding of the transcriptomic and proteomic changes associated with the ASD-like phenotype in BTBR mice. We found a number of genes and proteins to be significantly altered in BTBR mice compared to C57BL/6J (B6) control mice controls such as BDNF, Shank3, and ERK1, which are highly relevant to prior investigations of ASD. Furthermore, we identified distinct functional pathways altered in BTBR mice compared to B6 controls that have been previously shown to be altered in both mouse models of ASD, some human clinical populations, and have been suggested as a possible etiological mechanism of ASD, including "axon guidance" and "regulation of actin cytoskeleton." In addition, our wide-scale bioinformatics approach also discovered several previously unidentified genes and proteins associated with the ASD phenotype in BTBR mice, such as Caskin1, suggesting that bioinformatics could be an avenue by which novel therapeutic targets for ASD are uncovered. As a result, we believe that informed use of synergistic bioinformatics applications represents an invaluable tool for elucidating the etiology of complex disorders like ASD.
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http://dx.doi.org/10.3389/fphys.2015.00324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4656818PMC
December 2015

Nuclear GIT2 is an ATM substrate and promotes DNA repair.

Mol Cell Biol 2015 Apr 20;35(7):1081-96. Epub 2015 Jan 20.

Receptor Pharmacology Unit, National Institute on Aging, Baltimore, Maryland, USA VIB Department of Molecular Genetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium

Insults to nuclear DNA induce multiple response pathways to mitigate the deleterious effects of damage and mediate effective DNA repair. G-protein-coupled receptor kinase-interacting protein 2 (GIT2) regulates receptor internalization, focal adhesion dynamics, cell migration, and responses to oxidative stress. Here we demonstrate that GIT2 coordinates the levels of proteins in the DNA damage response (DDR). Cellular sensitivity to irradiation-induced DNA damage was highly associated with GIT2 expression levels. GIT2 is phosphorylated by ATM kinase and forms complexes with multiple DDR-associated factors in response to DNA damage. The targeting of GIT2 to DNA double-strand breaks was rapid and, in part, dependent upon the presence of H2AX, ATM, and MRE11 but was independent of MDC1 and RNF8. GIT2 likely promotes DNA repair through multiple mechanisms, including stabilization of BRCA1 in repair complexes; upregulation of repair proteins, including HMGN1 and RFC1; and regulation of poly(ADP-ribose) polymerase activity. Furthermore, GIT2-knockout mice demonstrated a greater susceptibility to DNA damage than their wild-type littermates. These results suggest that GIT2 plays an important role in MRE11/ATM/H2AX-mediated DNA damage responses.
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http://dx.doi.org/10.1128/MCB.01432-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4355538PMC
April 2015

Amitriptyline improves motor function via enhanced neurotrophin signaling and mitochondrial functions in the murine N171-82Q Huntington disease model.

J Biol Chem 2015 Jan 11;290(5):2728-43. Epub 2014 Dec 11.

Receptor Pharmacology Unit, the VIB Department of Molecular Genetics, Institute Born-Bunge Laboratory of Neurogenetics, University of Antwerp, 2000 Antwerp, Belgium

Huntington disease (HD) is a neurodegenerative disorder characterized by progressive motor impairment and cognitive alterations. Hereditary HD is primarily caused by the expansion of a CAG trinucleotide repeat in the huntingtin (Htt) gene, which results in the production of mutant huntingtin protein (mHTT) with an expanded amino-terminal polyglutamine (poly(Q)) stretch. Besides pathological mHTT aggregation, reduced brain-derived neurotrophic factor (BDNF) levels, impaired neurotrophin signaling, and compromised mitochondrial functions also contribute to the deleterious progressive etiology of HD. As a well tolerated Food and Drug Administration-approved antidepressant, amitriptyline (AMI) has shown efficacy in treating neurodegenerative murine models via potentiation of BDNF levels and amelioration of alterations in neurotrophin signaling pathways. In this study, we observed profound improvements in the motor coordination of AMI-treated N171-82Q HD model mice. The beneficial effects of AMI treatment were associated with its ability to reduce mHTT aggregation, potentiation of the BDNF-TrkB signaling system, and support of mitochondrial integrity and functionality. Our study not only provides preclinical evidence for the therapeutic potency of AMI in treating HD, but it also represents an important example of the usefulness of additional pharmacogenomic profiling of pre-existing drugs for novel therapeutic effects with often intractable pathological scenarios.
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http://dx.doi.org/10.1074/jbc.M114.588608DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4317004PMC
January 2015

The effects of aging on the BTBR mouse model of autism spectrum disorder.

Front Aging Neurosci 2014 1;6:225. Epub 2014 Sep 1.

Receptor Pharmacology Unit, Laboratory of Neurosciences, National Institute on Aging Baltimore, MD, USA ; VIB-Department of Molecular Genetics, University of Antwerp Antwerp, Belgium.

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder characterized by alterations in social functioning, communicative abilities, and engagement in repetitive or restrictive behaviors. The process of aging in individuals with autism and related neurodevelopmental disorders is not well understood, despite the fact that the number of individuals with ASD aged 65 and older is projected to increase by over half a million individuals in the next 20 years. To elucidate the effects of aging in the context of a modified central nervous system, we investigated the effects of age on the BTBR T + tf/j mouse, a well characterized and widely used mouse model that displays an ASD-like phenotype. We found that a reduction in social behavior persists into old age in male BTBR T + tf/j mice. We employed quantitative proteomics to discover potential alterations in signaling systems that could regulate aging in the BTBR mice. Unbiased proteomic analysis of hippocampal and cortical tissue of BTBR mice compared to age-matched wild-type controls revealed a significant decrease in brain derived neurotrophic factor and significant increases in multiple synaptic markers (spinophilin, Synapsin I, PSD 95, NeuN), as well as distinct changes in functional pathways related to these proteins, including "Neural synaptic plasticity regulation" and "Neurotransmitter secretion regulation." Taken together, these results contribute to our understanding of the effects of aging on an ASD-like mouse model in regards to both behavior and protein alterations, though additional studies are needed to fully understand the complex interplay underlying aging in mouse models displaying an ASD-like phenotype.
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http://dx.doi.org/10.3389/fnagi.2014.00225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4150363PMC
September 2014

Metabolic and hormonal signatures in pre-manifest and manifest Huntington's disease patients.

Front Physiol 2014 23;5:231. Epub 2014 Jun 23.

Metabolism Unit, National Institute on Aging, National Institutes of Health Baltimore, MD, USA.

Huntington's disease (HD) is an inherited neurodegenerative disorder typified by involuntary body movements, and psychiatric and cognitive abnormalities. Many HD patients also exhibit metabolic changes including progressive weight loss and appetite dysfunction. Here we have investigated metabolic function in pre-manifest and manifest HD subjects to establish an HD subject metabolic hormonal plasma signature. Individuals at risk for HD who have had predictive genetic testing showing the cytosine-adenine-guanine (CAG) expansion causative of HD, but who do not yet present signs and symptoms sufficient for the diagnosis of manifest HD are said to be "pre-manifest." Pre-manifest and manifest HD patients, as well as both familial and non-familial controls, were evaluated for multiple peripheral metabolism signals including circulating levels of hormones, growth factors, lipids, and cytokines. Both pre-manifest and manifest HD subjects exhibited significantly reduced levels of circulating growth factors, including growth hormone and prolactin. HD-related changes in the levels of metabolic hormones such as ghrelin, glucagon, and amylin were also observed. Total cholesterol, HDL-C, and LDL-C were significantly decreased in HD subjects. C-reactive protein was significantly elevated in pre-manifest HD subjects. The observation of metabolic alterations, even in subjects considered to be in the pre-manifest stage of HD, suggests that in addition, and prior, to overt neuronal damage, HD affects metabolic hormone secretion and energy regulation, which may shed light on pathogenesis, and provide opportunities for biomarker development.
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http://dx.doi.org/10.3389/fphys.2014.00231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4066441PMC
July 2014

Stress-dependent opioid and adrenergic modulation of newly retrieved fear memory.

Neurobiol Learn Mem 2014 Mar 27;109:1-6. Epub 2013 Nov 27.

Department of Anatomy & Cell Biology, Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA 19140, USA. Electronic address:

Recent studies on the effect of stress on modulation of fear memory in our laboratory have uncovered endogenous opioid and adrenergic based modulation systems, working in concert, that limit the strengthening or weakening of newly acquired fear memory during consolidation under conditions of mild or intense stress, respectively. The present study sought to determine if similar stress-dependent modulation, mediated by endogenous opioid and adrenergic systems, occurs during reconsolidation of newly retrieved fear memory. Rats underwent contextual fear conditioning followed 24h later by reactivation of fear memory; a retention test was administered the next day. Stress was manipulated by varying duration of recall of fear memory during reactivation. In the first experiment, vehicle or the opioid-receptor blocker naloxone was administered immediately after varied durations (30 or 120 s) of reactivation. The results indicate that (1) reactivation, in the absence of drug, has a marked effect on freezing behavior-as duration of reactivation increases from 30 to 120 s, freezing behavior and presumably fear-induced stress increases and (2) naloxone, administered immediately after 30 s (mild stress) or 120 s (intense stress) of reactivation, enhances or impairs retention, respectively, the next day. In the second experiment, naloxone and the ß-adrenergic blocker propranolol were administered either separately or in combination immediately after 120 s (intense stress) reactivation. The results indicate that separate administration of propranolol and naloxone impairs retention, while the combined administration fails to do so. Taken together the results of the two experiments are consistent with a protective mechanism, mediated by endogenous opioid and adrenergic systems working in concert, that limits enhancement and impairment of newly retrieved fear memory during reactivation in a stress-dependent manner.
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http://dx.doi.org/10.1016/j.nlm.2013.11.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3943532PMC
March 2014

The role of Thyrotropin Releasing Hormone in aging and neurodegenerative diseases.

Am J Alzheimers Dis (Columbia) 2013 ;1(1)

Metabolism Unit, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224.

Thyrotropin releasing hormone (TRH) is primarily known as the central regulator of the hypothalamic-pituitary-thyroid (HPT) axis. However, TRH also exerts a variety of central nervous system effects independent from its activity in the HPT axis. With advancing age, decreases in TRH synthesis, expression, and activity have been demonstrated. Associated with this emerging evidence suggests that TRH is implicated in neurodegenerative diseases of aging, including Alzheimer's disease and Parkinson's disease. TRH and its synthetic analogs have been recognized as trophic factors in neurons of the diencephalon and spinal cord, and as neuroprotectants against oxidative stress, glutamate toxicity, caspase-induced cell death, DNA fragmentation, and inflammation. In this review, we will provide an overview of some of the roles of TRH, outside of the HPT axis, associated with pathological aging and neurodegeneration and we shall discuss the potential of TRH and TRH analogs for the treatment of neurodegenerative diseases.
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http://dx.doi.org/10.7726/ajad.2013.1003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3817016PMC
January 2013

Altered lipid and salt taste responsivity in ghrelin and GOAT null mice.

PLoS One 2013 4;8(10):e76553. Epub 2013 Oct 4.

Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.

Taste perception plays an important role in regulating food preference, eating behavior and energy homeostasis. Taste perception is modulated by a variety of factors, including gastric hormones such as ghrelin. Ghrelin can regulate growth hormone release, food intake, adiposity, and energy metabolism. Octanoylation of ghrelin by ghrelin O-acyltransferase (GOAT) is a specific post-translational modification which is essential for many biological activities of ghrelin. Ghrelin and GOAT are both widely expressed in many organs including the gustatory system. In the current study, overall metabolic profiles were assessed in wild-type (WT), ghrelin knockout (ghrelin(-/-)), and GOAT knockout (GOAT(-/-)) mice. Ghrelin(-/-) mice exhibited decreased food intake, increased plasma triglycerides and increased ketone bodies compared to WT mice while demonstrating WT-like body weight, fat composition and glucose control. In contrast GOAT(-/-) mice exhibited reduced body weight, adiposity, resting glucose and insulin levels compared to WT mice. Brief access taste behavioral tests were performed to determine taste responsivity in WT, ghrelin(-/-) and GOAT(-/-) mice. Ghrelin and GOAT null mice possessed reduced lipid taste responsivity. Furthermore, we found that salty taste responsivity was attenuated in ghrelin(-/-) mice, yet potentiated in GOAT(-/-) mice compared to WT mice. Expression of the potential lipid taste regulators Cd36 and Gpr120 were reduced in the taste buds of ghrelin and GOAT null mice, while the salt-sensitive ENaC subunit was increased in GOAT(-/-) mice compared with WT mice. The altered expression of Cd36, Gpr120 and ENaC may be responsible for the altered lipid and salt taste perception in ghrelin(-/-) and GOAT(-/-) mice. The data presented in the current study potentially implicates ghrelin signaling activity in the modulation of both lipid and salt taste modalities.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076553PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3790684PMC
May 2014

Longitudinal analysis of calorie restriction on rat taste bud morphology and expression of sweet taste modulators.

J Gerontol A Biol Sci Med Sci 2014 May 28;69(5):532-44. Epub 2013 Sep 28.

*These authors contributed equally to this work.

Calorie restriction (CR) is a lifestyle intervention employed to reduce body weight and improve metabolic functions primarily via reduction of ingested carbohydrates and fats. Taste perception is highly related to functional metabolic status and body adiposity. We have previously shown that sweet taste perception diminishes with age; however, relatively little is known about the effects of various lengths of CR upon taste cell morphology and function. We investigated the effects of CR on taste bud morphology and expression of sweet taste-related modulators in 5-, 17-, and 30-month-old rats. In ad libitum (AL) and CR rats, we consistently found the following parameters altered significantly with advancing age: reduction of taste bud size and taste cell numbers per taste bud and reduced expression of sonic hedgehog, type 1 taste receptor 3 (T1r3), α-gustducin, and glucagon-like peptide-1 (GLP-1). In the oldest rats, CR affected a significant reduction of tongue T1r3, GLP-1, and α-gustducin expression compared with age-matched AL rats. Leptin receptor immunopositive cells were elevated in 17- and 30-month-old CR rats compared with age-matched AL rats. These alterations of sweet taste-related modulators, specifically during advanced aging, suggest that sweet taste perception may be altered in response to different lengths of CR.
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http://dx.doi.org/10.1093/gerona/glt129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991138PMC
May 2014

Long-term artificial sweetener acesulfame potassium treatment alters neurometabolic functions in C57BL/6J mice.

PLoS One 2013 7;8(8):e70257. Epub 2013 Aug 7.

Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland, United States of America.

With the prevalence of obesity, artificial, non-nutritive sweeteners have been widely used as dietary supplements that provide sweet taste without excessive caloric load. In order to better understand the overall actions of artificial sweeteners, especially when they are chronically used, we investigated the peripheral and central nervous system effects of protracted exposure to a widely used artificial sweetener, acesulfame K (ACK). We found that extended ACK exposure (40 weeks) in normal C57BL/6J mice demonstrated a moderate and limited influence on metabolic homeostasis, including altering fasting insulin and leptin levels, pancreatic islet size and lipid levels, without affecting insulin sensitivity and bodyweight. Interestingly, impaired cognitive memory functions (evaluated by Morris Water Maze and Novel Objective Preference tests) were found in ACK-treated C57BL/6J mice, while no differences in motor function and anxiety levels were detected. The generation of an ACK-induced neurological phenotype was associated with metabolic dysregulation (glycolysis inhibition and functional ATP depletion) and neurosynaptic abnormalities (dysregulation of TrkB-mediated BDNF and Akt/Erk-mediated cell growth/survival pathway) in hippocampal neurons. Our data suggest that chronic use of ACK could affect cognitive functions, potentially via altering neuro-metabolic functions in male C57BL/6J mice.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0070257PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3737213PMC
August 2014

Plurigon: three dimensional visualization and classification of high-dimensionality data.

Front Physiol 2013 22;4:190. Epub 2013 Jul 22.

Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health Baltimore, MD, USA.

High-dimensionality data is rapidly becoming the norm for biomedical sciences and many other analytical disciplines. Not only is the collection and processing time for such data becoming problematic, but it has become increasingly difficult to form a comprehensive appreciation of high-dimensionality data. Though data analysis methods for coping with multivariate data are well-documented in technical fields such as computer science, little effort is currently being expended to condense data vectors that exist beyond the realm of physical space into an easily interpretable and aesthetic form. To address this important need, we have developed Plurigon, a data visualization and classification tool for the integration of high-dimensionality visualization algorithms with a user-friendly, interactive graphical interface. Unlike existing data visualization methods, which are focused on an ensemble of data points, Plurigon places a strong emphasis upon the visualization of a single data point and its determining characteristics. Multivariate data vectors are represented in the form of a deformed sphere with a distinct topology of hills, valleys, plateaus, peaks, and crevices. The gestalt structure of the resultant Plurigon object generates an easily-appreciable model. User interaction with the Plurigon is extensive; zoom, rotation, axial and vector display, feature extraction, and anaglyph stereoscopy are currently supported. With Plurigon and its ability to analyze high-complexity data, we hope to see a unification of biomedical and computational sciences as well as practical applications in a wide array of scientific disciplines. Increased accessibility to the analysis of high-dimensionality data may increase the number of new discoveries and breakthroughs, ranging from drug screening to disease diagnosis to medical literature mining.
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http://dx.doi.org/10.3389/fphys.2013.00190DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3717481PMC
July 2013

Textrous!: extracting semantic textual meaning from gene sets.

PLoS One 2013 30;8(4):e62665. Epub 2013 Apr 30.

Receptor Pharmacology Unit, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.

The un-biased and reproducible interpretation of high-content gene sets from large-scale genomic experiments is crucial to the understanding of biological themes, validation of experimental data, and the eventual development of plans for future experimentation. To derive biomedically-relevant information from simple gene lists, a mathematical association to scientific language and meaningful words or sentences is crucial. Unfortunately, existing software for deriving meaningful and easily-appreciable scientific textual 'tokens' from large gene sets either rely on controlled vocabularies (Medical Subject Headings, Gene Ontology, BioCarta) or employ Boolean text searching and co-occurrence models that are incapable of detecting indirect links in the literature. As an improvement to existing web-based informatic tools, we have developed Textrous!, a web-based framework for the extraction of biomedical semantic meaning from a given input gene set of arbitrary length. Textrous! employs natural language processing techniques, including latent semantic indexing (LSI), sentence splitting, word tokenization, parts-of-speech tagging, and noun-phrase chunking, to mine MEDLINE abstracts, PubMed Central articles, articles from the Online Mendelian Inheritance in Man (OMIM), and Mammalian Phenotype annotation obtained from Jackson Laboratories. Textrous! has the ability to generate meaningful output data with even very small input datasets, using two different text extraction methodologies (collective and individual) for the selecting, ranking, clustering, and visualization of English words obtained from the user data. Textrous!, therefore, is able to facilitate the output of quantitatively significant and easily appreciable semantic words and phrases linked to both individual gene and batch genomic data.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062665PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3639949PMC
November 2013

BRET Biosensor Analysis of Receptor Tyrosine Kinase Functionality.

Front Endocrinol (Lausanne) 2013 9;4:46. Epub 2013 Apr 9.

Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health Baltimore, MD, USA.

Bioluminescence resonance energy transfer (BRET) is an improved version of earlier resonance energy transfer technologies used for the analysis of biomolecular protein interaction. BRET analysis can be applied to many transmembrane receptor classes, however the majority of the early published literature on BRET has focused on G protein-coupled receptor (GPCR) research. In contrast, there is limited scientific literature using BRET to investigate receptor tyrosine kinase (RTK) activity. This limited investigation is surprising as RTKs often employ dimerization as a key factor in their activation, as well as being important therapeutic targets in medicine, especially in the cases of cancer, diabetes, neurodegenerative, and respiratory conditions. In this review, we consider an array of studies pertinent to RTKs and other non-GPCR receptor protein-protein signaling interactions; more specifically we discuss receptor-protein interactions involved in the transmission of signaling communication. We have provided an overview of functional BRET studies associated with the RTK superfamily involving: neurotrophic receptors [e.g., tropomyosin-related kinase (Trk) and p75 neurotrophin receptor (p75NTR)]; insulinotropic receptors [e.g., insulin receptor (IR) and insulin-like growth factor receptor (IGFR)] and growth factor receptors [e.g., ErbB receptors including the EGFR, the fibroblast growth factor receptor (FGFR), the vascular endothelial growth factor receptor (VEGFR) and the c-kit and platelet-derived growth factor receptor (PDGFR)]. In addition, we review BRET-mediated studies of other tyrosine kinase-associated receptors including cytokine receptors, i.e., leptin receptor (OB-R) and the growth hormone receptor (GHR). It is clear even from the relatively sparse experimental RTK BRET evidence that there is tremendous potential for this technological application for the functional investigation of RTK biology.
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http://dx.doi.org/10.3389/fendo.2013.00046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3620488PMC
April 2013

Effective use of latent semantic indexing and computational linguistics in biological and biomedical applications.

Front Physiol 2013 30;4. Epub 2013 Jan 30.

Laboratory of Neuroscience, Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health Baltimore, MD, USA.

Text mining is rapidly becoming an essential technique for the annotation and analysis of large biological data sets. Biomedical literature currently increases at a rate of several thousand papers per week, making automated information retrieval methods the only feasible method of managing this expanding corpus. With the increasing prevalence of open-access journals and constant growth of publicly-available repositories of biomedical literature, literature mining has become much more effective with respect to the extraction of biomedically-relevant data. In recent years, text mining of popular databases such as MEDLINE has evolved from basic term-searches to more sophisticated natural language processing techniques, indexing and retrieval methods, structural analysis and integration of literature with associated metadata. In this review, we will focus on Latent Semantic Indexing (LSI), a computational linguistics technique increasingly used for a variety of biological purposes. It is noted for its ability to consistently outperform benchmark Boolean text searches and co-occurrence models at information retrieval and its power to extract indirect relationships within a data set. LSI has been used successfully to formulate new hypotheses, generate novel connections from existing data, and validate empirical data.
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http://dx.doi.org/10.3389/fphys.2013.00008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3558626PMC
February 2013

VennPlex--a novel Venn diagram program for comparing and visualizing datasets with differentially regulated datapoints.

PLoS One 2013 7;8(1):e53388. Epub 2013 Jan 7.

Metabolism Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.

With the development of increasingly large and complex genomic and proteomic data sets, an enhancement in the complexity of available Venn diagram analytical programs is becoming increasingly important. Current freely available Venn diagram programs often fail to represent extra complexity among datasets, such as regulation pattern differences between different groups. Here we describe the development of VennPlex, a program that illustrates the often diverse numerical interactions among multiple, high-complexity datasets, using up to four data sets. VennPlex includes versatile output features, where grouped data points in specific regions can be easily exported into a spreadsheet. This program is able to facilitate the analysis of two to four gene sets and their corresponding expression values in a user-friendly manner. To demonstrate its unique experimental utility we applied VennPlex to a complex paradigm, i.e. a comparison of the effect of multiple oxygen tension environments (1-20% ambient oxygen) upon gene transcription of primary rat astrocytes. VennPlex accurately dissects complex data sets reliably into easily identifiable groups for straightforward analysis and data output. This program, which is an improvement over currently available Venn diagram programs, is able to rapidly extract important datasets that represent the variety of expression patterns available within the data sets, showing potential applications in fields like genomics, proteomics, and bioinformatics.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0053388PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3538763PMC
July 2013

Altered hypothalamic protein expression in a rat model of Huntington's disease.

PLoS One 2012 18;7(10):e47240. Epub 2012 Oct 18.

Metabolism Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.

Huntington's disease (HD) is a neurodegenerative disorder, which is characterized by progressive motor impairment and cognitive alterations. Changes in energy metabolism, neuroendocrine function, body weight, euglycemia, appetite function, and circadian rhythm can also occur. It is likely that the locus of these alterations is the hypothalamus. We used the HD transgenic (tg) rat model bearing 51 CAG repeats, which exhibits similar HD symptomology as HD patients to investigate hypothalamic function. We conducted detailed hypothalamic proteome analyses and also measured circulating levels of various metabolic hormones and lipids in pre-symptomatic and symptomatic animals. Our results demonstrate that there are significant alterations in HD rat hypothalamic protein expression such as glial fibrillary acidic protein (GFAP), heat shock protein-70, the oxidative damage protein glutathione peroxidase (Gpx4), glycogen synthase1 (Gys1) and the lipid synthesis enzyme acylglycerol-3-phosphate O-acyltransferase 1 (Agpat1). In addition, there are significant alterations in various circulating metabolic hormones and lipids in pre-symptomatic animals including, insulin, leptin, triglycerides and HDL, before any motor or cognitive alterations are apparent. These early metabolic and lipid alterations are likely prodromal signs of hypothalamic dysfunction. Gaining a greater understanding of the hypothalamic and metabolic alterations that occur in HD, could lead to the development of novel therapeutics for early interventional treatment of HD.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0047240PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3475691PMC
April 2013

Aging and bone health in individuals with developmental disabilities.

Int J Endocrinol 2012 22;2012:469235. Epub 2012 Jul 22.

Metabolism Unit, National Institute on Aging, National Institutes of Health, 251 Bayview Boulevard, Suite 100, Baltimore, MD 21224, USA.

Low bone mass density (BMD), a classical age-related health issue and a known health concern for fair skinned, thin, postmenopausal Caucasian women, is found to be common among individuals with developmental/intellectual disabilities (D/IDs). It is the consensus that BMD is decreased in both men and women with D/ID. Maintaining good bone health is important for this population as fractures could potentially go undetected in nonverbal individuals, leading to increased morbidity and a further loss of independence. This paper provides a comprehensive overview of bone health of adults with D/ID, their risk of fractures, and how this compares to the general aging population. We will specifically focus on the bone health of two common developmental disabilities, Down syndrome (DS) and cerebral palsy (CP), and will discuss BMD and fracture rates in these complex populations. Gaining a greater understanding of how bone health is affected in individuals with D/ID could lead to better customized treatments for these specific populations.
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http://dx.doi.org/10.1155/2012/469235DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3408668PMC
August 2012

Euglycemic agent-mediated hypothalamic transcriptomic manipulation in the N171-82Q model of Huntington disease is related to their physiological efficacy.

J Biol Chem 2012 Sep 20;287(38):31766-82. Epub 2012 Jul 20.

Metabolism Unit, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.

Our aim was to employ novel analytical methods to investigate the therapeutic treatment of the energy regulation dysfunction occurring in a Huntington disease (HD) mouse model. HD is a neurodegenerative disorder that is characterized by progressive motor impairment and cognitive alterations. Changes in neuroendocrine function, body weight, energy metabolism, euglycemia, appetite function, and gut function can also occur. It is likely that the locus of these alterations is the hypothalamus. We determined the effects of three different euglycemic agents on HD progression using standard physiological and transcriptomic signature analyses. N171-82Q HD mice were treated with insulin, Exendin-4, and the newly developed GLP-1-Tf to determine whether these agents could improve energy regulation and delay disease progression. Blood glucose, insulin, metabolic hormone levels, and pancreatic morphology were assessed. Hypothalamic gene transcription, motor coordination, and life span were also determined. The N171-82Q mice exhibited significant alterations in hypothalamic gene transcription signatures and energy metabolism that were ameliorated, to varying degrees, by the different euglycemic agents. Exendin-4 or GLP-1-Tf (but not insulin) treatment also improved pancreatic morphology, motor coordination, and increased life span. Using hypothalamic transcription signature analyses, we found that the physiological efficacy variation of the drugs was evident in the degree of reversal of the hypothalamic HD pathological signature. Euglycemic agents targeting hypothalamic and energy regulation dysfunction in HD could potentially alter disease progression and improve quality of life in HD.
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http://dx.doi.org/10.1074/jbc.M112.387316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3442511PMC
September 2012

GIT2 acts as a potential keystone protein in functional hypothalamic networks associated with age-related phenotypic changes in rats.

PLoS One 2012 14;7(5):e36975. Epub 2012 May 14.

Receptor Pharmacology Unit, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Biomedical Research Center, Baltimore, Maryland, United States of America.

The aging process affects every tissue in the body and represents one of the most complicated and highly integrated inevitable physiological entities. The maintenance of good health during the aging process likely relies upon the coherent regulation of hormonal and neuronal communication between the central nervous system and the periphery. Evidence has demonstrated that the optimal regulation of energy usage in both these systems facilitates healthy aging. However, the proteomic effects of aging in regions of the brain vital for integrating energy balance and neuronal activity are not well understood. The hypothalamus is one of the main structures in the body responsible for sustaining an efficient interaction between energy balance and neurological activity. Therefore, a greater understanding of the effects of aging in the hypothalamus may reveal important aspects of overall organismal aging and may potentially reveal the most crucial protein factors supporting this vital signaling integration. In this study, we examined alterations in protein expression in the hypothalami of young, middle-aged, and old rats. Using novel combinatorial bioinformatics analyses, we were able to gain a better understanding of the proteomic and phenotypic changes that occur during the aging process and have potentially identified the G protein-coupled receptor/cytoskeletal-associated protein GIT2 as a vital integrator and modulator of the normal aging process.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036975PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351446PMC
October 2012